K.L.E SOCIETY`S INSTITUTE OF DENTAL SCIENCES, BANGALORE

DEPARTMENT OF PROSTHODONTICS

SEMINAR TOPIC

POLISHED SURFACE OF COMPLETE DENTURE

PRESENTED BY:

Dr Kothari Rahul Navinchand

Post graduate student

K.L.E SOCIETY`S INSTITUTE OF DENTAL SCIENCES, BANGALORE

DEPARTMENT OF PROSTHODONTICS

This is to certify that seminar was presented by Dr Kothari Rahul Navinchand titled POLISHED SURFACE OF COMPLETE DENTURE on 8/4/11.

Place :

Date:

H.O.D

Dept of Prosthodontics.

POLISHED SURFACE OF COMPLETE DENTURE

Sir Wilford Fish described three surfaces of a complete denture.

Impression surface

Occlusal surface

Polished surface

A lot has been written about the impression surface and the occlusal surface and very little attention has been paid to the polished surface.

Cameo surface: the viewable portion of a removable denture prosthesis; the portion of the surface of a denture that extends in an occlusal direction from the border of the denture and includes the facial, lingual, and palatal surface. It is the part of the denture base that is usually polished, and includes the buccal and lingual surfaces of the teeth.

Denture polished surface: the portion of the surface of a denture that extends in an occlusal direction from the border of the denture and includes the palatal surface. It is the part of the denture base that is usually polished, and it includes the buccal and lingual surfaces of the teeth

A properly designed polished surface can enhance the following characteristics in a complete denture:

Retention

Stability

Mastication

Esthetics

Phonetics

Hygiene

THE POLISHED surface of a denture is that part which lies in contact with the tongue, cheeks and lips when the teeth are closed. It consists mostly of the base material, ,but also includes the buccal, labial and lingual surfaces of the teeth themselves.

In modelling the impression surface of a denture it is only necessary to fit it to a fixed tissue which does not change its shape and which is to remain in the same relationship to the denture all the time, With the occlusal surface it is necessary to adapt a surface of out denture to the corresponding surface of the other denture, but this case the surfaces do not maintain

the same relationship w each other all the time. This is theoretically more difficult, but is accomplished by an arrangement of inclined planes on the teeth which owing to their shape press the dentures into place when the occlusal surfaces come into contact with each other.

Now in the case of the polished surface, it is necessary to adapt this surface of the denture to the movable muscular tissues of the tongue, cheeks, and lips, which not only move over the polished surface of the denture but also keep changing their own shape. In this case it will therefore be necessary to follow a method similar to the one used with, the occlusal surface. The polished surface must be modelled into a series of inclined planes each of which presents itself to the muscle with which it comes into contact, at such an angle that when the muscle moves it pushes the denture into place.

One of the important things to observe is that the, teeth, must occupy a position such that the tongue is pressed inwards just as much force as the cheek is pressed outwards. In this way the dentures occupy a dead space in the mouth and lie, during repose, in a state of equilibrium, the inward pressure of the lips and cheeks being exactly balanced by the outward pressure of the tongue.

It will be immediately clear from this that the proper position for the teeth is not necessarily on the ridge, inside the ridge or outside the ridge, but at a point where the tongue and cheek pressures balance.

As a matter of fact, in the case of the first molar, this point will always be the position occupied by the natural tooth since a tooth is guided to its position on eruption-by. just these pressures. If any of the teeth were in position when the patient first presented . himself it is of the greatest help to preserve a record of their precise position both in the buccal and lingual dimension and in the vertical dimension. This can be done by making a wax partial denture up before the teeth are extracted, then cutting the teeth off the model after taking a block to record their position and replacing them on the wax partial denture in the same relationship,. The partial denture to which the rest of the teeth have then been added is now transferred to the edentulous model after the extractions have been carried out.

If all the teeth were already lost when the patient presented, their position can only be judged by assessing anatomical probabilities. - If none of the teeth are present some information is gained by observing the tongue and cheek in repose in the slightly opened mouth, noting the position in which the artificial teeth cause least displacement of either.

This conception only deals with the dentures at rest, but it is also necessary to picture them in action chewing food, so that the relationship of the muscles to the dentures during work may also be assessed.

Consider a bolus of food to be chewed. Suppose this bolus to consist of a small pickled onion which is notoriously elusive. The difficulty will be to hold the onion securely while the teeth

crush it. This will be accomplished by the tongue pressing it outwards and the cheek (the buccinator) pressing it inwards, and these two muscles will thus grasp the morsel effectively while the teeth come down and bite it in half. it will be obvious that the triangular shape of the dentures on section is of enormous value in stabilising them during this performance. While the buccinator is pressing the food inwards, it is exerting an upward and inward force on the surface of the upper denture and a downward and inward force on the lower. In the same way the tongue is pressing the upper denture upwards and outwards and the lower downwards and outwards, Now since the forces of the buccinator and tongue exactly balance in order to hold the food still, so their inward and outward components acting on the dentures will balance and cancel out, leaving the upward lift on the upper and the downward pressure on the lower to stabilise the dentures.

In this way we are using the natural action of the muscles to hold the plates in place. If, however, the plates present convex shape on cross section, nearly all this advantage is lost. The upper plate on the lingual side still presents an inclined plane at the correct angle to the tongue, and that is why patients generally learn to manage somehow with any upper plate however it is made, but the buccal part of the polished surface of both dentures presents such an angle to the buccinator that there is no possibility of the muscle stabilising the dentures. Finally, the lingual surface of the lower overhangs the tongue so that the lower plate will definitely be raised every time the tongue comes into action.

The extension or flange on the lower plate will, however, always be tolerated if it is correctly fashioned. The reason for this is easy to understand. To return to the picture of a person biting on an onion. After biting through the onion half of it falls out into the cheek and half comes on to the tongue. While the outer half remains down in the sulcus the tongue pushes its own half back to be further crushed between the teeth, and to facilitate this the buccinator, despite the presence of the piece of food down in the sulcus, is able to oppose the tongue and hold the new morsel in place. It follows, therefore, that when the muscles of the cheek contract to hold food between the teeth they do not reduce the depth of the sulcus in the molar region as they do in the premolar and canine region but they leave enough-below the main body of the buccinator muscle which can be filled with food without interfering with the action of that muscle, just as in the monkeys there is a cheek pouch in which quite large quantities of food are temporarily stored.

The buccal extension on the outer side of the molar region of the lower denture fits into this pouch and takes up some of the room normally occupied by a food bolus, so much so that at first the patient is conscious of its presence, but he is also conscious of his control over it. He realises at once that he can use the flange to hold the plate firmly in place and quickly loses all sensation of its bulk, especially if after a week or so- it be thinned down a little.

This particular instance of the way in which the shape of the polished surface can influence the stability of a denture is only one of many, but before continuing to describe them it will be useful to discuss the muscles themselves which form the cheek and lips, since their mode of action and relationship to the dentures is the key to the whole problem.

The essential feature of the musculature of the cheek and lips is a point where eight muscles meet at the corner of the mouth. This meeting place, called in Latin the modiolus, the nave of wheel, became the eight muscles radiate from it like the spokes of a wheel from the hub, forms a distinct conical prominence at the corner of the mouth, and in lean muscular young men it can be easily seen whenever they move their lips or cheeks, defining the crescentic fold at the corners of the mouth. German anatomists call it 'Der knoten’ and if one puts the thumb inside the corner of the mouth and the finger outside on the prominence and then the lip and cheek are contracted, this modiolus feels rather like a knot.

Perhaps the two most important muscles of the group which meet in the modiolus are the buccinator and the orbicularis oris. These two muscles antagonise each other in their action. The buccinator has a crescentic origin, forming a generous curve which starts on the upper jaw along a line parallel to and above the upper molar teeth. From there it dips down along the pterygo mandibular raphe on to first the inner then crosses to the outer surface of the mandible parallel with the lower molars. From this wide sweep of its origin the fibres converge,-on to the modiolus The middle group of fibres running quite horizontally across the cheek, decussate or cross each other as they reach the modiolus and on passing through this muscle knot, the upper fibres enter the lower part of the orbicularis oris and the lower fibres enter the the upper part of the orbicularis oris.

It follows from this arrangement that the orbicularis oris, which is an oval ring of muscle round the mouth, forming the lips, takes - its origin" from the modiolus on each side, so that if one buccinator contracts, it tends to pull the orbicularis oris across to that side. It does not, however, succeed in doing this, because the modiolus is not only the point of insertion of the orbicularis oris and buccinator into each other, but is also the central point of an X-shaped muscle (M. cruciatus modioli), the outer ends of which are fixed into the bones of the skull. When, therefore, either \ the orbicularis oris or the buccinator is going to contract, this X-shaped muscle, the M. cruciatus modioli, also contracts and \ fixes the modiolus almost as firmly as if it were itself attached to bone. This form of fixation for the modiolus, however, has an enormous advantage, for it may be fixed in any one of a variety of positions either forward or backward, up or down within a considerable range depending upon the action of the M. cruciatus modioli, so that the orbicularis oris can operate from a forward point of origin if we wish to say 'Oh!' or drink soup from a spoon, or it can operate from a backward position if one should wish to say 'Ee' or to play a cornet or bite the lower lip. Whichever position the modiolus is fixed in, the orbicularis is free to carry out the delicate movements of speech for which its intricate internal structure is so beautifully adapted.

The fixing of the modiolus, however, takes place not only when the orbicularis oris comes into action, but also every time the buccinator contracts. The buccinator is thus fixed at both ends, so that when it contracts it merely humps up in the middle and pushes a pad against the molar teeth or, if they are open, between them. This is the pad which opposes the tongue in holding food in place between the molars, and it is produced by contracting the buccinator in just the same way as the biceps muscle can be humped up on one's arm if the elbow and shoulder joint are fixed and the muscle contracted.

Now since this humping-up of the buccinator muscle takes place every time we chew, and since the modiolus becomes fixed every time the buccinator contracts, it is necessary to examine the anatomy of the M. cruciatus modioli which fixes the modiolus and discuss its relation to full dentures.

This X-shaped muscle consists really of three muscles: M. zygomaticus, which takes origin from the zygomatic process; M. caninus, which arises in the canine fossa; and M. triangularis, which has a broad, often double, origin from the lower border of the mandible.

It is instructive to place a ruler along the course of the M. zygomaticus and the front part of the M. triangularis, which is in the same straight line, on one's own face. In fact, the index finger will do quite well, placing the metacarpophalangeal joint on the point of the chin and the tip of the finger on the zygoma. It will be seen that the finger crosses the lower denture just behind the corner of the mouth, in fact just where the modiolus is situated. Now, with the aid of a mirror, picture the M. caninus added to this group, pulling the modiolus forwards and inwards; and, finally, put the other finger along the other group of muscle on the other side of the face at the same time. It will be realised that the two groups of muscles together form a V shaped strap owing to the fact that the two M. zygomatici take origin widely apart on the cheek bones, and the two M. triangularis take origin close together at the point of the chin.

If. therefore, the arch of the lower denture is too wide in the premolar region, it will be squeezed in this V-shaped muscle band and will shoot up out of place. This is a Serious menace to the stability of a lower denture, perhaps its most serious menace.

The lower plate must have wide flanges on the buccal surface in the molar region. It is now clear that as we approach the premolar region there must be a very sudden narrowing of the lower denture to escape a collision with the modiolus Not only must there be flange as in the molar region, but the lower premolars themselves must be set close in on the ridge. A mere notch in the edge of the plate is not enough, the arch formed by the teeth on the denture must be narrowed in. It is the whole outer surface of the denture and the buccal surface of the teeth which must be trimmed to muscle, not merely the edge of the base.

The same rule does not apply to the upper plate, for in this case we want to lid it up so that a little extra width in the premolar region will be an advantage and enable the modiolus grasp the upper denture by the outer cusps of the premolars and hold it up. This support is very useful, especially at such moment as when suddenly saying ‘Oh!’ the patient, with teeth apart, perhaps blows air behind his plate. If such an accident happens nothing can save the plate from falling but the modiolus which fortunately will be fixed at that moment in order to let the orbicularis oris form the sound ‘Oh!’

The effect of having a relatively narrow lower and a wide upper arch in the premolar region is often to make the outer cusp of the first lower premolar articulate with the inner cusp the upper premolar, in which case the inner cusp of the lower tooth can be abolished and a lower canine used instead unless one is using a first lower premolar which is virtual single cusped tooth with a marked cingulum. In any case if lower premolar has to be pressed very far in to escape modiolus, its inner cusp can and indeed must be cut off bed! otherwise it will interfere

with the movements of the tongue and, as we shall see, tend in that way to unstabilise the denture.

It will be recalled that the main weight of the bite must be taken on the premolars, so that firm articulation of this tooth is absolutely essential. Another advantage of having the lower premolar articulate with the inner cusp of the upper, is that the pressure of the bite comes on or inside the upper ridge, and there is no risk of tipping the top plate outwards by leverage when chewing. To return to the buccinator for a moment, it will be realised that it is chiefly its middle fibres which take part in holding the food between the teeth. This must be so because the upper and lower fibres do not lie opposite the place where the food is when the teeth are closing. It is therefore clear that the middle fibres alone are those which stabilise the dentures by pressing on the flanges we have prepared for them. The lower fibres (which run outwards and forwards, not directly forwards) form the pouch for the food to collect in as it is chewed, and act independently. Their function is simply to carry the food backwards when it is ready to be swallowed, or inwards if it is to be rechewed. It is therefore in the relatively flaccid region above and especially below the central fibres of the buccinator, that the flanges are accommodated. It is not always possible to accentuate the flange over the upper molars because the attachment of the buccinator to the hamular process sometimes brings the muscle very close to the tuberosity, but it is always possible to secure a plane on this surface of the denture which looks outwards and downwards.

If necessary the second molar must be left off the plate entirely or made very narrow bucco-lingually in order to secure this result. It is extremely dangerous to the stability of an upper denture for it to present a surface to the buccinator facing outwards and upwards, because every time the muscle contracts to hold the food between the teeth it may pull the plate down. In the case of the lower denture it is always possible to extend the edge and so form a flange on the buccal surface and the only difficulty is to determine the degree of extension. This will not present any great difficulty once it is realised that the pouch is always there. If the tip of the index finger is pushed outwards and, downwards into the buccal sulcus, and the patient asked to dose the teeth and contract the buccinator, that is to tighten the - cheek, a flaccid area will at once be felt bounded below by the mandible, above by the horizontal middle fibres of the buccinators,behind by the edge of the masseter, and in front by the buccal frenum in the premolar region. It is into this pouch that the flange must be fitted by extending the outer side of the denture into it. The commonest fault is to alIow the flange to extend too far forward into the premolar region.

Before leaving the buccinator it is interesting to realise that the buccal pouch which this muscle forms for the reception of food as it is crushed by the molars is closed in front by the modiolus pressing against the premolars so that the food cannot escape at the corner of the mouth. If both upper and lower dentures were made too narrow in the first premolar region, there would be a risk in old people of the food leaking away during mastication in a quite intolerable manner. This is avoided by allowing the upper arch to be reasonably wide across the premolars but not, of course, the lower.

This combination of extreme narrowness in the premolar region with extreme width in the molar region of a lower denture is not likely to occur by accident, and that is perhaps one of the chief reasons why, if waxing up is left to technicians who have not realised the signifi-cance of the anatomical structure of the cheeks, there may be difficulty in stabilising lower dentures.

Having discussed the relationship of the buccinator and modiolus to the buccal part of the polished surface, the labial area naturally follows, since it is concerned with the orbicularis oris muscle. This muscle has a delicate marginal part under the red margin of the lips and a much stronger peripheral part. The former curls round the latter and decussates with it at the corners of the mouth, producing the pleasing eversion of the red lip margin. The significance of this arrangement is that the main pressure of the muscle against a denture is in its peripheral part, so that the incisive edge of the front teeth may be set forward almost at any angle provided a groove to accommodate the peripheral part of the muscle can be produced by inclining the necks of the teeth backwards to some extent. If aesthetic considerations render this inclination undesirable, however, the groove may be sacrificed since it is only one of the minor factors in stabilising the dentures.

There is never any need to set the lower incisors so far forward that the lower lip lifts the plate. If it is not exaggerated it x^JfL even be an advantage to have the lower teeth slightly in a position

of retrusion, and where superior protrusion was present in natural dentition it is of the utmost importance to retain the relative retrusion of the lower incisors. If the lower incisors are pushed forward in such cases in an attempt to make them reach the upper ones, they will catch the lower lip and cause it to raise the denture.

On the other hand, if the natural lower front teeth were leaning forward the orbicularis oris muscle will not interfere with their artificial successors, in that position; and unless the artificial teeth are put at this angle they will interfere with the movements of the tongue thereby becoming a source of both discomfort and instability of the denture. This naturally raises the question of giving the tongue plenty of room and we may now consider the lingual part of the polished surface.

In the upper denture the palatal surface will inevitably face inwards and downwards so that the tongue will automatically press the denture into place. The importance of allowing plenty of room for the tongue by determining the position of the front teeth is only necessary to add that in finishing the palatal surface it is sometimes necessary to give special attention to the question of speech. A hollow groove running from before backwards in the middle of the palate will cause the patient to whistle his sounds. This tendency is cured by adding wax to the middle of the palate just above the tip of the tongue at the try-in stage, and perhaps increasing the length of the central incisors. A tendency to lisp or 'slish' the sibilants is cured by adding wax at the sides of the palate. Where patients have already worn dentures it is advisable to copy the shape of the palate exactly.

The lingual surface of the lower denture is not so simple, for example it is necessary to insist that the whole of the lingual surface of the lower denture shall look inwards and upwards, there are some essenial features which are of value.

It is clear that if the extension of the posterior lingual flange can be tolerated, it will be of very crucial assistance in holding the denture down in place, for the heavy, relatively immobile base of the tongue will rest upon it. The extension of this border is not of course by any means a conception but previous writers have generally advocated placing it out under the mylohyoid ridge. It is now going to be tested that it should be turned in under the tongue so that it will be held down by that organ.

The present approach to this problem, as in the case of the buccal pouch, is also based on the anatomy of the region. When an individual puts his head back, opens his mouth widely and retracts his tongue into the pharynx, as most patients in the dental chair, the lingual surface of the mandible in the third molar region presents a precipitous appearance and falls away sheer into the darkness of the pharynx. At the same time the pouch under the buccinator is obliterated by the stretched mucous membrane of the cheek.

A denture made to the mouth in this condition will have no buccal extension at all such as we have just described, but will A have a long ‘lateral throat extension' pressed closely to the inner surface of the mandible. When, however, the patient closes his mouth, takes the tension off the cheeks and allows the tongue to come forward into its usual position, an empty buccal pouch will appear and several muscles will rise up under the lateral throat extension which will make it intolerable and a menace both to stability and comfort. This fact may be demonstrated in several ways. If the patient, whose mouth is open, is told to relax and put his tongue out and then the tongue, still protruded, be gently pulled to one side it will be seen that the precipitous appearance of the inner side of the jaw at the back is gone. There is instead a definite pouch between the tongue and the jaw bounded behind by a fold of mucous membrane where the anterior pillar of the fauces curves down on to the tongue. This we will call the 'lingual pouch/ and endeavour to describe it in some detail, since it is"Bounded all round by active muscles and yet must contain the posterior lingual corner of the denture which naturally must not interfere with the movements of these muscles.

Perhaps the most convincing way of observing the peculiarities of this region is to stand facing an edentulous patient at his right side and insert the tip of the right little finger into his right lingual pouch. Tell the patient to close his lips and rest the jaws together on the exploring finger, in complete relaxation. The terminal phalanx of the finger now lies in this pouch and can feel a springy muscular mass between the mylohyoid ridge and the ball of the finger. At the same time the finger is comfortably held down by the side of the back of the tongue resting on top of it. If the patient now draws the whole tongue back into the throat the muscle mass between the finger and the bone disappears and the mylohyoid ridge is easily felt. This is not, however, a normal position for the tongue or one into which it ever goes naturally, except perhaps in yawning. Finally ask the patient to swallow while the finger is

still in this pouch and the size and strength of this muscle mass which suddenly appears between the examining finger and the mylohyoid ridge of the bone is quite dramatic.

Equally significant is the way in which the back of the tongue holds the finger firmly down in the pouch where it is grasped between the tongue above and the mylohyoid below. It is at 'once evident that any extension of the posterior lingual border of the plate must lie in same position and not too close to the bone where it would interfere with the mylohyoid, particularly when swallowing; nor may it be turned in too much or it will irritate the under side of the tongue. The third and most difficult approach to the problem is the anatomical method. The muscles which cause most of the trouble with the posterior lingual extension are the mylohyoid and the superior constrictor of the pharynx. It is, however,only a relatively small lingual portion of this latter muscle with which we are chiefly concerned. The main body of the superior constrictor forms the side wall of the upper part of the pharynx and takes origin from the pterygomandibular raphe, that is from the same vertical line of attachment as the buccinator. The buccinator, however, spreads forwards and, lining the cheek, forms the wall bf the buccal cavity, while the superior constrictor spreads backwards and forms the wall of the nasopharynx.

This common line of origin of these two muscles stretches from the hamular process of the internal pterygoid plate to the inner edge of the alveolus of the mandible in the third molar region. In some mouths it forms a distinct fold in front of and parallel with the anterior pillar of the fauces. It is, as we know, called the pterygomandibular raphe. In any case both the hamular process and the inner edge of the alveolus may be felt and the line between is easily visualised. For instance when a J hypodermic needle is inserted for the direct .mandibular injection it goes exactly through the upper part of thus vertical line and . the resistance of the raphe to the needle, may generally be felt. The greater part of the superior constrictor muscle arises from this raphe and spreads backwards to form the wall of the nasopharynx, thereby leaving our territory at once but the lowest part of the muscle, which arises from the border of the mandible, curves or arches round and is attached to the base of the tongue, thus forming a posterior wall to the sublingual pouch. turning the posterior lingual corner of the denture in under the tongue and away from the bone. The mylohyoid is also seen producing the same effect.

The bearing of these muscles on the position of the posterior lingual corner of the denture is further clarified by looking into the sublingual pouch from the usual angle, that is through the mouth, but after the mucous membrane has been reflected and the tongue pulled to one side.

The main body of the superior constrictor (1) is seen to take origin as described from the internal pterygoid plate, the hamular process (4) and the pterygo-mandibular raphe (5). The muscle sweeps back from this line and forms the wall of the pharynx. The buccinator (G) comes forward from this line and forms the cheek, the lingual slip of the superior constrictor (2 b) takes origin from the inner border of the alveolus and arches round from the jaw to the tongue forming the posterior limit of the lingual pouch, but if the tongue were retracted into

the pharynx this mandibular part would be pulled down flat against the internal surface of the mandible as we have seen clinically.

Coming into view under this arch is the styloglossus (c). This muscle arises on the styloid process and is inserted under the superior longitudinal muscle (F) which is one of the intrinsic muscles of the tongue.

When the subject is eating, he opposes the tongue to the buccinator in order to hold the food between the teeth. To do this he contracts the styloglossus, the lingual slip of the superior constrictor, the mylohyoid and the superior longitudinal muscle. The styloglossus raises the tongue and pulls it outwards and does this all the more definitely because, as Quain and Garmany point out, there is often a slip of the styloglossus which takes origin not from the styloid process but from the mandible along with the lingual part of the superior constrictor (2) and is inserted with it into the tongue. When this part of the styloglossus is present it curves round with the lingual part of the superior constrictor and is practically part of that muscle, having the same action and relations. Both these muscles obviously pull the tongue up against he molar teeth. The superior longitudinal muscle of the tongue opposes the tongue to the cheek by contracting the length of the tongue and so widening it. In addition to this group, the muscles which fix the hyoid bone are also brought into play and this , includes the mylohyoid to which reference is about to be made

Another muscle which is involved to some extent in opposing the tongue to the cheek is the palatoglossus (A) (Garmany), which forms the anterior pillar of the fauces and running down from the anterior part of the soft palate on to the tongue, forms the top border of the fold which limits the lingual pouch behind. This muscle not only raises the tongue during chewing and swallowing, but also lifts the mucous membrane of the pouch and will rub it against the denture if the posterior lingual corner is extended too far back or if it is turned out under the mylohyoid ridge. Moreover it is also quite clear that if the posterior lingual corner of the denture is thus extended and kept close to the mandible it will cover the origin of the muscles we have described so that at the moment when a patient grips a piece of food between the buccinator and the tongue in order to bite it the mylohyoid, superior constrictor and styloglossus in pressing the tongue against the food, will also lift up the denture, which will then be out of place just when it is wanted..

The serious effect of this is emphasised when the size of the origin of the lingual part of the superior constrictor is observed . It is over an.inch in length and runs back along the inner border of the alveolus from the middle of the third molar socket on to the ascending ramus. Even in front of this area it is still not possible to press the lower edge of the denture close in to the bone for, as will be seen, the mylohyoid comes immediately into the picture.

Examining the anatomy of the sublingual region a little farther forward, that is at the level of the second molar, the area between the jaw and the tongue appears as a furrow formed by the mylohyoid (3) on the outer side and the hyoglossus (D) on the inner side. Deep down at the bottom of this furrow is the greater cornu of the hyoid (E). Garmany points out that the origin of the mylohyoid from the mandible goes farther back than was thought. Moreover in this posterior region it lies high up, very close to the inner edge of the alveolus, indeed in a very

resorbed jaw it takes origin almost from the top of the ridge so that it also turns the edge of the denture in under the tongue.

The attachment of the mylohyoid muscle is seen to run normally close to and parallel with the edge of the alveolus from a point half an inch behind the third molar to the anterior border of the second molar. The line of origin then dips down at an angle of 30 degrees from' the alveolar border while passing the first molar and then falls at an angle of 45 degrees to reach the symphysis below the attachment of the geniohyoglossus to the genial tubercles. The origin of the muscle therefore extends well back behind even the most extended denture and is so near the alveolar ridge through 1 out the second and third molar region as to compel our attention in fashioning the posterior lingual corner.

The downward slope of the line of origin of the mylohyoid as it is followed forward from the molars provides accommodation for the sublingual gland in its fossa. Farther forward still at the symphysis the attachment of the genioglossus forms the lingual I frenulum. When the tongue is raised the line of reflection of the mucous membrane from the inner side of the mandible is therefore horizontal as it is followed from the frenulum along over the sublingual gland to the origin of the mylohyoid in the molar ' region, and this horizontal line is always in evidence on a successful ' plaster impression when taken in the way about to be described.

To summarise the anatomy of this important region: If the finger is placed in the lingual pouch when the patient is in the act of swallowing, the tip of the finger rests against the middle of the lingual slip of the superior constrictor which, as it curves round from the jaw to the tongue, forms the posterior wall of the pouch. Entering below it and lifting it up is the styloglossus which may also have a slip reinforcing the lingual part of the superior constrictor. Just above the tip of the finger the palatoglossus is coming down on to the tongue, forming the anterior pillar of the fauces. This also forms the top border of the posterior wall of the pouch.

To the outer side, towards the jaw, the finger rests on the origin of the lingual slip of the superior constrictor and the origin If the mylohyoid, which therefore form the outer wall of the pouch and may be felt contracted during swallowing. Towards the tongue the inner wall of the pouch is formed at the back and above by the superior longitudinal muscle of the tongue, with the palatoglossus inserted into it. Immediately below and mingling with the insertion of the palatoglossus is the insertion of the lingual slip of the superior constrictor. Below this again is the insertion of the styloglossus, and under cover of this last muscle lies the hyoglossus. Farther forward the hyoglossus lies immediately under the mucous membrane.

The practical application of these observations to the shape of the lingual surface of the denture is, as will be seen, particularly satisfying because both the mechanical and anatomical approach to the subject indicate the same general pattern for the appliance.

The mechanical requirements for stability suggest that the lingual surface should look upwards and inwards. This is easily effected at the posterior lingual corner if the base is extended and the edge of the denture turned in under the tongue. The anatomical

requirements are the same. A considerable extension of the base at the back is only possible if the denture comes down over the origin of the mylohyoid and superior constrictor, but that it may safely cover the origin of these muscles provided that it is turned in under the tongue to some extent and that its back edge is curled very slightly forward so that it will not interfere with the function of these muscles. The practical problem of carrying this out is considered in the next section.

Farther forward, where the lower edge of the denture rests on the reflection of the mucous membrane over the sublingual gland, that is in the premolar region, the depth of this lower edge depends on the position of the line of reflection of the mucous membrane when the tongue is raised or extended, but in a number of cases once the depth is determined, the lower edge of the denture may be thickened here to extend over the floor of the mouth for some little distance, and thus provide an inclined plane for the anterior third of the tongue to rest upon. In this way there is no risk of a premolar overhanging the tongue.

It is not, however, possible to thicken the edge in this way in the incisor region because of the insertion of the genioglossus (Frenulum linguae) or in the first molar region because of the greater bulk of the tongue in its middle third.

The practical application of these observations to the shape of the lingual surface of the denture is, as will be seen, particularly satisfying because both the mechanical and anatomical approach to the subject indicate the same general pattern for the appliance.

The mechanical requirements for stability suggest that the lingual surface should look upwards and inwards. This is easily effected at the posterior lingual corner if the base is extended and the edge of the denture turned in under the tongue. The anatomical requirements are the same. A considerable extension of the base at the back is only possible if the denture comes down over the origin of the mylohyoid and superior constrictor, but that it may safely cover the origin of these muscles provided that it is turned in under the tongue to some extent and that its back edge is curled very slightly forward so that it will not interfere with the function of these muscles. The practical problem of carrying this out is considered in the next section.

Farther forward, where the lower edge of the denture rests on the reflection of the mucous membrane over the sublingual gland, that is in the premolar region, the depth of this lower edge depends on the position of the line of reflection of the mucous membrane when the tongue is raised or extended, but in a number of cases once the depth is determined, the lower edge of the denture may be thickened here to extend over the floor of the mouth for some little distance, and thus provide an inclined plane for the anterior third of the tongue to rest upon. In this way there is no risk of a premolar overhanging the tongue

It is not, however, possible to thicken the edge in this way in the incisor region because of the insertion of the genioglossus or in the first molar region because of the greater bulk of the tongue in its middle third.

In the Upper Denture

The labial surface will be determined by the aesthetic requirements of the case so far as the arrangement of individual teeth is concerned, but the prosthetist is not free to indulge his fancy where their position is involved. A false step here will ruin the comfort and efficiency of the denture

The buccal surface should look outwards and downward never outwards and upwards, and may often have a slight marginal beading at the top edge of its most posterior part.

The lingual surface will look inwards and downwards.

The teeth will normally be set in a rather wide arch, that is, a little outside the ridge.

In the Lower Denture

The labial surface, which is composed chiefly of the lower incisors, must be pressed back sufficiently to prevent the lower lip lifting the denture. Nevertheless in patients whose lower lip pouts somewhat, the four incisors — though never the canine - may be made to lean forward a little, provided the necks of the teeth are kept well back towards the ridge, since such patients evert the edge of the lip when the orbicularis oris contracts. The natural incisors in such patients no doubt leaned forward in this way. The lower incisors are more likely to be set too far in than too far out.

The buccal surface in the premolar region must be kept well in so that the teeth are directly over the ridge. The arch of the teeth in this region is thus very narrow to prevent the modiolus lifting the denture. In the molar region the base of the denture suddenly widens enormously to send a flange or extension out under the middle fibres of the buccinator. The polished surface in this region looks outwards and very definitely upwards, and the molar teeth may be set well out on the ridge, producing a cross-bite effect if necessary.

(iii) The lingual surface looks inwards and upwards. In the incisor region the edge is shallow and fairly thin. In the canine and premolar region the edge is fairly shallow, but very thick to accentuate the upwards inclination of the polished surface. The first molar region the edge is becoming thinner again, the polished surface more nearly vertical to provide room wide middle third of the tongue. In the second molar and retromolar region the lower edge of the denture is quite thin and flares in and down under the tongue as much as possible, the polished surface forming a shallow concavity on each side for the posterior third of the tongue to rest on.

(iv) The relationship of the teeth to the ridge varies with the degree of resorption. The incisors tend to be in front of the ridge, while in the canine and premolar region the centre of

the tooth should be exactly over the centre of the ridge. The first molar should be, if anything, a little inside the ridge, while the second molar may be put over, inside or outside the ridge, or omitted altogether, depending only upon securing the proper inclination of the lingual and buccal surfaces in this region, coupled with some suggestion of opposition to the upper second molar.

While it takes some time , to describe it, the whole picture is immediately grasped when a demonstration set of dentures is actually handled. The stereoscopic slides give a good general idea of the modelling, but it is far better for the individual prosthetist to work out the modelling for himself after giving due consideration to the anatomy of the part.

The upper denture needs very little further description. The teeth are set outside the ridge since it is the labial and buccal alveolar plate which has been resorbed most. In the labial region the appearance of the denture demands it. In the premolar region, apart from the enhanced appearance, the extra width enables the V-shaped muscles forming the modioli to grasp and support the plate, while any tendency for the plate to be tipped by leverage during mastication can be avoided by making the single-cusped lower premolars articulate only with the inner cusps of the upper premolars, which cusps are on, or even inside, the centre of the ridge.

In the molar region the effect of leverage is counter-balanced by the pressure of the dorsum of the tongue on the other side of the plate, and is not therefore of importance, while it is often necessary to set the upper molars in a fairly wide arch to avoid setting the lower molars in too narrow an arch. If the lower molars are set in so much that they overhang the tongue the lower denture will be completely unstable. On the other hand, if the upper molars are set out in too wide an arch the buccal surface of the denture will look outwards and upwards, and that is also liable to upset the denture. This danger may often be avoided by beading the top edge of the buccal surface or by using a rather narrow tooth for the second molar.

It is not possible to add flanges to the upper denture. If the sulcus is fairly deep in front, plumpers are well tolerated in the canine region because they help to hold the plate up by pressure from the orbicularis oris whichJies below them. If the sulcus is not deep enough for the plumpers to be fashioned above this muscle they will not be tolerated, unless the lower edge of the upper ridge happens to be prominent, when the orbicularis oris will press the plumper against the jaw above the prominent edge of the ridge and hook it in place. When this condition is very marked, the palate may be cut way, and it will be found that the plate is still perfectly stable.If the palate, is cut away, it is, of course, necessary to cut the palatal edges of the plate into the model very deeply along the soft tissue lying between the centre line of the palate and the ridge and the impression must be taken in composition and muscle trimmed to compress the sides.

In patients with a marked torus palatinus an upper denture without a palate will often be more stable than one with a palate, since the latter may rock if the ridges resorb in the slightest degree. As a general rule it is better to have the buccal and labial edges of the upper denture thin everywhere except over the- second molars, where a slight thickening or rolling of the

edge is sometimes tolerated, although very often even here the edge must be thin since the buccinator may sweep round the tuberosity quite close to it.

In the premolar region the edge must always be thin to avoid the downward pressure of the anterior fibres of the buccinator and the M. incisivus superioris. These muscles must be accommodated in a notch in the edge of the plate so that just at this point the buccal surface of the upper plate looks outwards and upwards, though immediately behind this point it looks outwards and downwards again. Any plumper that may be added in the canine region must, of course, be in front of this muscle insertion.

The Lower Denture. — The polished surface of the lower denture is more important because it is very much easier to render the appliance utterly unusable if the polished surface is wrongly modelled. In the case of the upper denture the rules are few, and it is really difficult to break them provided that the teeth are correctly placed in relation to the arch. In the case of the lower denture, however, it is extremely unlikely that more than half the polished surface of the denture will be correctly modelled if the anatomy of the surrounding tissues has not been carefully considered. That is why the full lower denture is such a bete-noire in dental prosthesis.

It is impossible to fashion the polished surface correctly unless a model of the lower jaw is available in which the superior constrictor and mylohyoid muscles are raised. One way to obtain this is by taking a plaster impression with the tongue out. Once such a model is obtained it is easy to outline the base of the denture on it in such a way that by waxing up from this line to the teeth the correct modelling is obtained.

It is seen to be kept near the ridge in the incisor canine and premolar region buccally and in the incisor and first molar region lingually. On the other hand, the outline is carried freely away from the ridge behind the buccal fraenum and in the posterior lingual region. It is sometimes an advantage to cover the floor of the mouth over the sublingual gland, that is on the lingual side of the premolars, and so fashion an anterior lingual plane, but as is described below, this is not always advisable. The teeth are now set on the base with a minimum of wax such that their relation to the ridge can at all times be observed.

The incisors are generally at right-angles to the lower border of the mandible. The canines, and premolars are set exactly over the ridge labio-lingually, the centre of the tooth being over the centre of the crest . They should be placed vertically or even inclined slightly inwards so that they present

A surface to the modiolus which looks outwards and slightly upwards, the corners of the mouth will not then lift the denture. The teeth must not, of course, encroach on the tongue. The inner cusp is generally removed from the first premolar because otherwise it might do so. The remaining buccal cusp of the first premolar often articulates with the lingual cusp of the upper premolar. The molars may, however, be set slightly inside the ridge where there has been much resorption, though the greatest care must be exercised that the second molar does

not overhang the tongue. The expedient is therefore employed, of using very narrow slips of teeth in this region if there is a marked difference in the width of the upper and lower arches. This is a simple matter now that teeth are made of plastic.

Finally, the case is waxed up. Labially there is nothing more to do. Buccally round the premolars as little wax as possible is added so that the plate is kept extremely narrow in this part. On the buccal surface in the molar region the edge is thickened to about one-eighth of an inch and wax added so that a flat surface stretches from the thickened edge to the teeth. This buccal flange must be eased to the shape of the dotted line when the case is tried in if necessary, hence the use of a wax base plate and not shellac.

On the lingual side as little wax as possible is added behind the incisors, while behind the premolars a fair amount must be added to make a flat or slightly concave surface between the edge of the base and the teeth. This forms the anterior lingual plane and disappears as we pass back to the molar region.

In the second molar and retro-molar region a trace of wax is needed to make the surface smooth up to the tooth. This surface, which forms the posterior lingual rest, must be slightly concave facing inwards, upwards and forwards, and its posterior edge must be thin and rounded. If this posterior corner of the lingual surface goes down and back far enough its edge will not be noticed, and in patients with large sluggish tongues it will give an incredible degree of stability to the denture, provided, of course, that it is correctly fashioned at the point of equilibrium between the mylohyoid and superior constrictor muscles on the one part and the tongue on the other. The result is due to the fact that the heavy immobile base of the tongue rests on this deep extension, whereas if it were not there the tongue by sheer bulk would push the denture forward and dislodge it. On the other hand this posterior lingual flange must not go too far back, or the superior constrictor muscle and stylo-glossus may rub on its back edge. It can be tested in the try-in stage. The object is to get as wide a base as possible under the back of the tongue and under the middle fibres of the buccinator. This must be combined with narrow teeth, in order to give as much space as possible for tongue higher up at the level of the occlusal plane, where the tongue is widest, and in order to increase the inclined plane effect where the polished surface is in contact with tongue and cheek.

PhonemicsArticulation is usually considered to be a joining of parts; however, speech articulation takes place when any approximation or move- ment of the articulators constricts, impedes, or diverts the airstream to produce a single

sound. The single sounds that the physiologic airstream mechanism are capableof producing are varied and innumerable. Many occur as noise and are unclassified, but those that are learned as speech are called phones. Many of the phones are so similar in character that they cannot be recognized as separate sounds. These closely related phones have been combined to forn recognizable sounds and are classified as phonemes. The phoneme, then, is the unit of speech by which we distinguish one utterance from another and which, collectively make up the phonemics of a language

Each phoneme has been given a phonetic symbol, which represents its specific sound in any language. The symbols of all phonemes, together with their variants, are published by the International Phonetic Association as the j "phonetic alphabet." Knowledge of this alpha- j bet is an invaluable aid in learning different languages, and it is likely that phonetics .will be better understood when it is mastered, because to learn the alphabet, it is necessary to learn the sounds which are universal and basic to any language. Each language has its own symbols to designate the phonemes. The sound symbols for the English language are listed in the front of the dictionary under ‘pronunciation."

Speech is further classified according to sonority into surds, sonantsr and consonants. The surd is any voiceless sound and is produced by separation of the vocal folds (glottis open) with no marginal vibration. The sound is made by friction of the airstream as it passes through the appropriate cavities: initial h sound as in huh and the voiceless sibilants s, z, sh, and zh pronounced initially are examples. The sonants are voiced sounds and include all vowels and vowel like sound. They are produced by vibration of some portion of the vocal folds to establish the original sound wave, which is augmented by cavity resonation. The vowels require minimum articulation and are classified according to the tongue position- in the oral cavity (i.e., high. mid, low) and the position of the lips.. consonants are articulated speech sounds, and all require articulation to impede, constrict, divert. or stop the airstream at the proper place and time to produce the desired sound.

Consonantal Articulation

Consonants are classified according to type of articulation into stops, fricatives, affricates, and diversions of the airstream.

l. Stops are characterized by stoppage and sudden release of the airstream and require complete occlusion of the articulators involved: the plosives p and b are produced by closure of the lips to permit momentary; buildup of the airstream, followed by a sudden explosive release; the t and d are produced by the tongue contacting the hard palate to stop the airstream before suddenly releasing it; and the k sounds are produced by the tongue and soft palate closing the oral cavity at the same time the soft palate and pharynx close the nasal cavity to stop the airstream prior to plosive release.

2. The fricativesare produced by the airstream being forced through loosely closed articulators or a narrow passageway. For the labiodentals f and v, the lower lip articulates with the maxillary anterior teeth to constrict the airstream. The linguodental th is produced by

incomplete articulation of tongue tip and maxillary incisors to constrict the airstream. The sibilants z, sh, and zh are produced by the tongue blade articulating with the lateral aspects of the hard palate, permitting the airstream to be forced through the groove created in the tongue apex.

3. The affricates and ch are produced by a combination of stop and friction, accomplished by articulation of the tongue and anterior hard palate.

4. Diversion of the airstream characterized by stoppage at one point to permit escape at another. The nasal m is produced by the lips occluding to seal the oral cavity and permit emission through the nose. The nasal n is produced by articulation of the tongue and hard palate closing the oral cavity while the sound escapes through the nasal cavity. The nasal ng is produced by the tongue and soft palate closing off the oral cavity to permit nasal emission. For the lateral l, the tongue apex occludes the anterior portion of the oral cavity while the sound escapes through the lateral portion.

These few basic articulations, which have been so briefly described, are but a small part of the complex activity necessary to produce a meaningful speech sound. Articulators never act singly, but in concert to accomplish the many structural variations necessary to emit the simplest phonation. It is actually a graph of the physiology required to produce these sounds. The action of the articulators (from the glottis to the lips) can be seen by reading the chart horizontally from right to left. The type of articulation causing the least to the greatest constriction of the airstream (stricture) can be seen by reading the chart vertically from bottom to top.

A glance at the chart shows that coarticu lation is essential to producing the simplest speech sound. The vocal folds, in addition to their function as vibrators for the sonants, articulate to close off the airstream and separate to produce the voiceless sounds. The velum, in addition to articulating with the pharynx to close the nasal cavity, also approximates the pharynx to establish the proper degree of nasality to the voice. The tongue changes shape and position to pronounce the vowels and contacts various portions of the hard palate to pronounce the consonants. The lips, in addition to articulating with each other to pronounce the plosives p and b and with the teeth to pronounce the fricatives f and v, also change shape and position to pronounce the vowels.

Speech production, then, is a combined effort of the structures composing the complex physiological airstream mechanism, and failure or debility of any part thereof will adversely the quality of the product.

The Tongue

The tongue is the principal articulator for speech, and learning its position for a given sound is the key to speech learning. To assist the student in learning tongue position, the Speech clinic has a chart with a diagram of the tongue in the proper position for each given sound. To describe its role in speech, the dorsum of the tongue is divided into a back portion, which

approximates the soft palate, and a front portion, which approximates the hard palate, and the sides are referred to as the tongue blade and the apex is called the tongue tip, or apex. To pronounce a, the dorsum of the tongue is arched with the blade contacting the alveolar ridge and the tip resting behind the lower incisors. The position for e is essentially the

same, except the dorsum is arched a little higher, with the blade in heavier contact with the alveolar ridge and the tip raised slightly. To pronounce i, the tongue is pulled back with the dorsum flattened at the beginning of the sound, but raises to the e position for the completion. To pronounce u, the tongue first assumes the e position then falls back with the dorsum flattened for the second part of the sound. For the o, the tongue is in its flattest and lowest position with no palatal contact. The tongue contacts portions of the hard palate in pronouncing many of the vowels. The tongue is also the principal articulator for consonantal speech and contacts the front, middle, and back portions of the hard palate in pronouncing many of them.

The precise area of normal tongue palatal contact for a given sound must be known if it is hoped to establish normal tongue contact on the palate of the denture.

Palatograms

To learn the area of normal contact for the tongue in pronouncing the various phonemes, a series of palatograms was made on a group of dentulous subjects with normal speech who had all or most of their teeth and were chosen so as to incorporate the maximum variety of teeth occlusion, arch form, arch size, and vault depth. To accomplish this, alginate im-pressions were made for each subject, casts were poured in dental stone, and a duplicate cast was made of the maxillary master cast. Then a uniformly thin artificial palate of methyl methacrylate was constructed. To ensure uniform thickness, No. 7 Ash metal was adapted to the duplicate cast to within 3 mm of the teeth and extended posteriorly to the vibrating line. The area adjacent to the teeth including the interspaces, was carefully waxed to the same thickness as the No. 7 Ash metal and the remaining periphery was sealed to the cast. Before flasking, the teeth were trimmed flush with the wax to facilitate flasking and deflasking so that several artificial palates could be fabricated with one metal base plate. Before packing, lampblack was incorporated during mixing of the methyl methacrylate to blacken the palate for photographic contrast with the talcum powder used to make the palatogram. The palatograms that obtain in this chapter are nothing more than the area of tongue contact for a given sound displayed on an artificial palate through a medium of nonscented talcum powder.

There are several prerequisites for making a palatogram. First, the artificial palate must be accurately adapted and refined so that it can be worn comfortably without an adhesive until speech is normal and natural. The subject who does not accommodate or who gags after a 15-minute practice speaking period should not be used, because palatograms of faulty speech would be of dubious value and gagging makes palatography impossible. Second, the subject should be trained to pronounce the sound distinctly, then to open his mouth with the tongue flat (out of contact with the palate) and not to attempt to swallow until after the palate is removed. Several trials should precede the making of the palatogram to ensure that the patient can pronounce the sound distinctly and immediately open his mouth without again contacting

the palate with the tongue. Third, the tracing medium should not be distasteful in flavor or appearance and should be of a consistency that will permit ease of application to and removal from the artificial palate. The color of the medium should contrast with the palate sufficiently to display readily the area of tongue contact. It was found that nonscented powder was the best medium for making palatograms. It can be readily applied to the dry palate with a camel's-hair brush, and the excess can be shaken off, leaving a uniform coating. Fourth, the palate must be dried thoroughly before dusting with talc, and care must be taken in inserting and removing the dusted palate to avoid finger contact, which would smudge the tracing. In pronouncing the phoneme, the moist tongue removes the talc from the contact area, leaving a clear tracing; however, this area should be outlined with a glass-marking pencil immediately after removal of the palate, because drying tends to obscure the tracing. Regular scented talc and surgical talc cannot be used, because the fillers incorporated do not permit uniform adherence to the dry palate. It was found that wetted

media on the artificial palate did not permit a clear tracing. Chalk and water, tin oxide and water, and pressure indicating paste were tried without success.

A palatographs study of the vowels re- vealed tongue palatal contact for all except o. Palatograms for a and e and drawings of pala tograms for a, e, i, and u shows the similarity of the tongue contact area on the palatograms is understandable if it is recalled that phonemes are usually composed of more than one phone and that each phone requires separate articulation. The phone e occurs singly in pronouncing the vowel e and is prevalent in a, i, and u. It occurs as the initial sound in u (ee-oo) and as the second sound of a and i (i-ee). One has only to pronounce these vowels slowly to reveal this.

The tongue palatal contact for e is registered on the palatograms of these vowels and accounts for the similarity of the tracings.

In making palatograms of consonantal articulation, it should be remembered that consonants do not occur separately, but in consort with the vowels, which alter the articulation. This is why the consonants as they usually are pronounced cannot be used in making palatograms, because the vowels included in the pronunciation involve tongue palatal contact, which would obscure the tracing of the articulation for the stop or affricate. As an example, in pronouncing t or d, the occlusive articulation is made first followed by the e. The same e follows the affricate articulation in pronouncing g or z, and a follows the affricate articulation for (j) and the occlusive

articulation for k. In pronouncing s, n, or l, the mid-vowel e precedes the articulation for the sibilant s, the nasal n, or the lateral l. To isolate these articulations on the palatogram they must be produced initially, followed by a vowel which does not involve tongue palatal contact, because it is almost impossible to produce these articulations voicelessly. The vowel o lends itself to this purpose, because in pronouncing d, the tongue naturally drops back out of contact with the palate and flattens, making it easy for the subject to open his mouth without raising the tongue. To make the palatographs study of consonantal articulation, the o was used in conjunction with the consonant to be studied, even though the combination did not result in a standard English word.

Palatal Thickness

One of the early observations of the palatographs study was that a thin, well-adapted artificial palate (about 1 mm thick) does not greatly impair speech. To test the effect of uniform additional thickness, a second palate of 2 mm added thickness was constructed for three of the group. With the thick palate in place, speech was so poor "that palatograms were not attempted. To test the areas most sensitive to thickness, base-plate wax was added to the various outlined contact areas the palate. It was found that when one layer of base-plate wax was added to the entire contact area for s, speech was awkward but not indistinct and that a second layer could be added as far forward as the mesial of the first bicuspid without further interference. Wax added beyond this point interfered distinctness of speech. The wax was re-moved from the s contact area and one layer base-plate wax was added to the anterior alveolar area (from cuspid to cuspid) in the region outlined by t, d, n, and l. This addition made speech awkward, indistinct, and difficult. Next, wax was added to the vault in increments, and it was found that the entire vault could be filled anteriorly to the tracing line for the ch and k. laterally to the tracing line for s and sh, and posteriorly to the tracing line for the k.

Tongue Palatal Patterns

In making a comparative analysis of the palatal consonants, it was found that no two subjects contacted exactly the same area in pronouncing a given consonant, but that sufficient similarity existed to constitute a pattern.

The patterns for the s and sh are of particular interest to the study because these sounds usually present the most persistent difficulty in pronunciation to the denture patient. The sh palatogram for the same subject appears directly below in the second row. The similarity of palatal contact by different subjects in pronouncing s can be seen by looking from left to right on the top row; and by reading from left to right on the bottom row, the similarity of contact in pronouncing sh is evident The distinct variation of the s and sh contact can be seen by reading from top to bottom.

Observations

Reading from left to right are palatograms of the same consonants made by different subjects, and reading from top to bottom are palatograms of different consonants made by the same subject. A glance at the chart reveals that posterior alveolar contact is made in pronouncing every one of these so-called anterior palatal consonants. A group analysis of the palatograms revealed that the tongue contacted the entire length, top, and some of the medial aspect of the posterior alveolar area in pronouncing t, d, n, and l; the entire length, top, and more of the medial aspect of the posterior alveolar area in pronouncing the affricates ch, g, and j; the entire length, top, and most or all of the medial aspect of the posterior alveolar area in pronouncing s and sh; and the back portion of the posterior alveolar area in pronouncing k. From these observations, is it not logical to conclude that the entire alveolar area should be restored to the palate of a denture if proper phonetics is to be attained?

Presently, restoration of this area is grossly neglected in denture construction. It is not uncommon to see a denture with the labial and buccal alveolar area faithfully restored in the interest of esthetics, but with the lingual alveolar area scooped out and meticulously polished in complete disregard of phonetics, Failure to reproduce this area is due in part to the early and still prevalent belief that phonetics is best served by providing maximum space for the tongue. One of my early and vivid recollections of prosthetic pedagogy was the admonishment of thickening the palate and cramping the tongue, which made little sense to me then and considerably less now, because on all the edentulous ridges that I have observed, resorption takes place on the lingual as well as' the labial and buccal.

Palatal Contour of the Denture

A few have recognized the importance palatal contour of the denture for better pho nation. Snow, as early as 1899, recommended restoring the anterior lingual alveolar area to improve phonetics, particularly the Pronounciation of s and sh, Prendergast (1935) pointed out that proper thickening of the lingual alveolar area was important for proper speech. Sears (1949) recommended making a Palatogram on cases where the median sulcus of the tongue does not coincide with the midline of the palate. He recommended grooving palate just above the median sulcus for the

patient who had little or no tongue sulcus and thickening this area for the patient who had a deep tongue sulcus, Pound (1951) was successful in improving phonetics by contouring the entire lingual aspect of the maxillary denture to simulate the normal palate. In 1958 a method for restoring the lingual alveolar area by use of palatography was published, and, in essence, that method will be presented here, together with several refinements which have been found to be advantageous.

Speech Tests

The phonetic aspect of denture construction, at least, deserves equal consideration with esthetics and mechanics and should be checked at the time of the waxed try-in when ' it is

possible to alter palatal contour to accommodate speech articulation. The trial denture evaluation should not be considered complete until a phonetic test has been made and pronunciation proved satisfactory to both the patient and the operator. Failure to conduct a speech test and make necessary corrections to improve faulty phonation at this time is negli-gence not in accord with good practice. The speech tests should be made after satisfactory esthetics, correct centric relation, proper vertical dimension, and balanced occlusion have been attained and after waxing for esthetics has been completed. Waxing of the palatal portion of the trial denturee should be confined to the area adjacent to the teeth, with just enough wax added to ensure a smooth surface between the base tray and the collars of the teeth. It is presumed that the base trays are comfortable, well-adapted, and approximate the tissues with nearly the same fidelity as anticipated for the completed denture bases. Before the speech tests are started, tbe mandibular trial denture should be secured with denture adhesive.

The first test is of random speech and is best accomplished by engaging the patient in conversation and obtaining a subjective speech analysis by asking the patient how the den-tures feel, how his speech sounds to him, and which words seem most difficult to pronounce.

The second test is of specific speech sounds. This is best accomplished by having the patient pronounce six or eight words containing the sound and then combining these words into a sentence. The following is a list of the sounds to be tested; opposite the sounds are the words to be pronounced and a sentence composed of these words:

s and sh

six, sixty, ships, sailed, Mississippi, sure, sign, sun, shine

f, d, n, locator, The locator lo

and I located, cated the tor

tornado, near, nado near To

Toledo ledo.

Joe, Joyce, Joe and Joyce

joined, George, joined George

Charles, and Charles at

Ch, f Church the church.

k

committee, The committee

convened, convened at

political, the political

convention, convention in

Connecticut Connecticut.

f and v

vivacious, Vivacious Viv-

Vivian, lived, vian lived at

five, fifty-five, five fifty-five

fifth, avenue Fifth Avenue.

In the third test, the patient is asked to read a short paragraph containing an abundance of s, sh, and ch sounds, because these sounds

are very prevalent in the English language. A paragraph of little meaningful significant which is not encountered in everyday reading is best for this test, because the patient will pronounce the words more carefully if he ponders the import of the context; e.g., "It should be pointed out to those working at precinct level in the interests of conservative con trol of these conventions and of this State convention in September, that those resolutions passed by the National Convention are in no way binding on these conventions."

If the patient can complete the speech test distinctly, with no difficulty, and if his random speech satisfies him and the operator, it would be unwise to contour the palate to solve a speech problem that does not exist If, however, problems are encountered in one ot more of the areas tested, then palatal contour is indicated and can effectively be accomplished by palatography. I have had limited success in altering a specific area of the palate; to correct a sound defect, because such alteration usually results in correcting one defect while creating another. If the palate is to be altered, the entire palate should be conjured to accommodate tongue contact for all palatal consonants. This is best accomplished; by systematically displaying each contact area with a palatogram and establishing normal tongue contact.

Palatography for Proper Palatal Contour

The only additional equipment necessary for palatography is some nonscented talc, an in-expensive soft bristle brush for dusting the talc on the palate, and a glass-marking pencil to outline the contact area. Palatograms can be easily and quickly made on the trial denture if the following steps are recalled:

Use o with the consonant to be studied, even though the combination is not a word; i.e., to study k, use ko; to study ch, use cho.

Train the patient to pronounce the sound and open the mouth without again contacting

. the palate.

Dry the palate thoroughly before dusting on nonscented talc (do not use regular or surgical talc) and shake off the excess powder.

Avoid touching the dusted palate with the fingers during insertion, but ensure that the denture is well-seated before the sound is pronounced.

Be sure the patient makes definite palatal contort- in pronouncing the sound, but avoids palatal contact after opening the mouth.

Avoid contacting the palate with the fingers when removing the denture.

Outline the contact area with a wax carver where wax is present, and with a glass- marking pencil where the base tray is exposed.

To avoid overlapping the tracings and recontouring one contact area to accommodate another, a sequence of palatograms should be followed, and waxing of the palate should be accomplished in steps. First, the s and sh palatograms are made and outlined on the base trays. Where wax is present, the palatogram is outlined with the carving end of the wax spatula; where the base tray is exposed, the outline is made with a glass-marking pencil. Before waxing is commenced, the patterns for s and sh should be reviewed. The tongue contact for s is always higher and more anterior on the palate, so that the outline for the s palatogram is the high line and includes some of the anterior teeth, and the sh line is always lower and includes fewer anterior teeth. The sh line (low line) is used as a guide in waxing the posterior alveohy area, and the s line (high line) is used as a guide in waxing the anterior alveolar area. The anterior portion of the sh tracing is not waxed until last. Waxing is started around the first molar by adding enough wax to provide a 1 mm margin at the collar. Next, the low tracing line on the palate is sighted directly below this tooth, and enough wax is added to the palate to permit an even contour between this line and the margin of the molar. Then wax is added around the anterior teeth, delineated by the s tracing to provide a 1/2-mm margin at the collars. Enough wax is then added between the tracing line and teeth to present an even contour. Waxing in the bicuspid area is accomplished by using the anterior and molar regions as a guide for adding wax around these teeth to complete a smooth, even contour

between these waxed areas and the palatal tracing line. Waxing around the second molar con-sists of adding enough wax around this tooth to complete the contour between palatal tracing line and the waxed first molar area. After waxing on the other side of the palate is completed, a palatogram should be taken to check the contour. If the area is properly contoured, the tongue tracing fine should be even and about 2 mm above the original. If the tracing line rises abruptly in a specific area, that area is too thick and should be reduced until the tracing line is even. If the tracing line drops abruptly in a Specific area, that area is not thick enough and additional wax will be needed to provide an even tracing. If the entire tracing rises markedly the area has been overcontoured and should be reduced.

The photographs of the waxing procedure are of a case with considerable alveolar ridge resorption, and using the palatogram to outline the area and waxing in steps as described should aid the beginner in establishing normal tongue contact for these cases. After some ex-perience, the entire outlined areas can be waxed in one step.

The palatogram can be used effectively for any case, including the immediate denture, if the pattern for normal tongue contact is kept in mind and if sensible observation is employed.

The line on the palate outlining the palatogram represents the lowest point of tongue contact in pronouncing s, and the area between this line and the artificial tooth should be of even contour and gradual slope without excessive convexity or concavity. The amount of wax needed to complete this contour is dependent upon the extent and degree of alveolar resorption, and wax should be added evenly where necessary to compensate for alveolar deficiency. Many times it is not necessary to add wax as far down as the tracing line to complete the contour, and sometimes, as in the case of slight resorption or the immediate denture, it is not necessary to add wax at all,

because enough of the alveolar ridge remains to provide proper contour to the base tray. After lateral tongue contact for s has been established on the trial denture the speech tests should be repeated, and if speech is satisfactory, further contouring is unnecessary. However, it is usually necessary to contour the anterior aspect of the palate to facilitate proper s pronunciation.

By using the palatogram to establish normal tongue blade contact in pronouncing s ap-propriate portions of the lateral aspects of the anterior alveolar area are included in the con-tour, leaving only the region between the lateral contact areas to be considered. The area of this region, which is the most critical to proper s pronunciation, is the area midway between the lateral contacts and directly above the median sulcus of the tongue. In pronouncing s, the tongue contacts the alveolar area to occlude the lateral portion of the oral cavity and form a channel for the airstream between the median sulcus and palate. This channel narrows to a groove at the tongue apex to constrict the airstream, so that it escapes as a hiss. Normally, this jet of air exits at the incisal edges of the teeth to heard as the typical s, but on the denture where tooth arrangement has been altered to accommodate mechanics and esthetics, it is usually necessary to provide a path of exit on the palate in the area directly above the groove in the tongue apex. This is best accomplished by inserting the trial denture and instructing the patient to pronounce ess (not so) and hold it so that the groove in the tongue apex be

observed. The chair should be tilted back and slightly raised so that the operator can look up and into the oral cavity to determine the character of the groove and its proximity to the palate. It is the area directly above the groove that must be Altered according to the fault in pronunciation. If the patient whistles or hisses when pronouncing s, the area between the

Groove and denture base is excessive and will need to be thickened. For the patient with a deep groove (this is common), a slight elevation is usually required. If the patient lisps (substitutes th for s) or has a muffled, indistinct s, there is not enough space between the groove and, the denture base, and the area will need to be thinned. If the groove in the tongue is broad and shallow, a depression in the denture base may be required, and if there is no groove in the tongue, a groove on the denture base directly above the median sulcus, as remmmended by Sears, will be necessary. If the patient substitutes sh for s, the jet of air is probably escaping toward the vault and the area above the groove will need to be extended toward the tongue. This extension must be made with care, because overextension will occlude the airstream and etts will be substituted for s.

There is no simple way of correcting faulty pronunciation. The fault must be analyzed, area contoured, and the sound tested, then reanalyzed, recontoured and retested until satisfactory pronunciation is attained. The words best suited for testing are short words containing the ess sound, such as "hess ", “guess," 'less,” "mess." The time required to correct an error ins pronunciation is time well spent, because it is the commonest and most persistent oral inaccuracy of the denture patient and the one that may remain as a characteristic denture whistle to belie the denture.

Proper palatal contour is the key to proper s pronunciation, or all other pronunciation for that matter, and that the palate can be contoured to accommodate phonetics for any sensible tooth arrangement, including the bizarre Class II and severe Class III jaw relation cases. There is little doubt that the character of the airstream directed between the upper and lower incisors in pronouncing s will be affected by the relationship of these teeth at the time of exit; therefore, it is possible to soften or sharpen the s by increasing or decreasing the amount of overjet. However, the direction of exit can be controlled by palatal contour to permit considerable leeway in anterior tooth arrangement and still provide good quality to this sound.

Contour of the anterior palate is completed by adding the minimum amount of wax between the low tracing line for sh and the lateral and midpalatal contoured areas to make a smooth junction. Care should be taken not to thicken the lateral contact areas or alter the median contour. To ensure that enough wax was added to provide tongue contact for the occlusives t,d, and n, a palatogram of t, to should be made. After completing the anterior palatal contour, usually no further contouring is necessary, but the speech tests should be repeated with particular attention given to the pronunciation of ch and j, because occasionally, in contouring the midanterior alveolar region, wax builds up on the palate below and will interfere with the pronunciation of these sounds. If this happens, a palatogram should be made for ch, chd to outline the area of tongue contact so that alteration can be confined to that area.

The use of palatograms for contouring the entire alveolar area will be useful to those who adhere to the philosophy of placing the artificial teeth in the same relative position as the

dentition. If the posterior teeth are arranged near the center of the alveolar ridge and the anterior teeth arranged to occupy approximately the same position as the originals, then a palatogram on the trial denture is an aid in contouring the palate for normal contact. If, however, the philosophy of arranging teeth according to mechanical advantage is adhered to, then the palatogram would be of limited value in contouring the posterior alveolar area, because the posterior teeth will occupy a position lingual to the center of the ridge on this denture. A palatogram of the s on the trial denture in this case would reveal limited tongue contact in the molar alveolar area, progressively increasing to normal contact in the anterior region, and adding wax to simulate a natural alveolar contour in the molar area would be a grosser insult to phonetics than not adding wax to complete alveolar contour in this area on the denture with center of the ridge tooth arrangement. Phonetics is better served in these cases by keeping the posterior alveolar area as thin as possible and confining palatal contour to the anterior region. Thickening the vault to narrow the channel for the airstream, facilitates s pronunciation in this type of denture, but before wax is added to the vault, a palatogram of k, ko should be made to delineate the of posterior palatal tongue contact so that this area can be excluded from the waxing.

Satisfactory phonetics can be accomplished with a constricted posterior tooth arrangement so long as the anterior teeth are arranged to permit normal palatal contact. However, if the anterior teeth are arranged lingual to natural tooth position, they will interfere with the tongue in making palatal contact and impede or occlude the airstream after contact has been made in pronouncing s. For this reason, in cases with severe resorption, where the anterior ridge affords no clue to natural tooth position, a palatogram can advantageously be used in arranging the teeth to ensure that tongue palatal contact is not jeopardized. Considerably more leeway is permitted in arranging teeth towards the labial, because tongue contact is unhampered and the palate can be contoured to accommodate the arrangement.

Other Factors

There are other factors that can adversely j affect phonetics: increased vertical dimension encroaches on the rest position and closes the speaking space, causing tooth contact during phonation, which interferes with speech articulation and adds the embarrassing "clatter of teeth" to speech. Decreased vertical dimension permits flaccidity of the facial musculature and encourages facial collapse into the oral cavity, which muffles speech sounds diminishes the clarity of speech, Also, sh is usually substituted for s because of the collapsed lower lip and excessive space between the anterior teeth when pronouncing s. Decreased vertical dimension is accompanied by disorientation of the occlusal plane toward the maxilla or the mandible, but usually the latter. If the occlusal plane is oriented toward the mandible (too low), the tongue spreads out over the teeth and lower anterior teeth in pronouncing s, so that sh is substituted for this sound. If the occlusal plane is orientated toward the maxilla

Too high), the tongue will contact the occlusal | surfaces and incisal edges of the teeth during speech articulation, which permits lateral or anterior emission or both.

Use of Phonetics in Denture Construction

Phonetics can be used to facilitate other phases of denture construction. The use of the fricatives f and v when arranging anterior teeth, as suggested by Landa, is an aid in determining the proper position of the maxillary incisors. During the arrangement of anterior teeth, the patient is asked to repeat "five, fifty-five, five fifty-five" while the operator observes how the lower lip makes contact with the incisors. Normally, the lower lip contacts the incisal edges of these teeth in pronouncing these sounds. If the teeth have been oriented superiorly, the lower lip will contact the opposing lip instead of the teeth. If they are oriented to the lingual, the lip will contact the labial surfaces instead of the incisal edges, and if they are oriented toward the labial, the lip will contact the lingual surfaces instead of the incisal edges. The pronunciation of words ending in s to establish the closest speaking space in determining Proper vertical dimension, as advocated by Silverman, is an excellent adjunct in arriving at an occlusal mandibular position that is compatible with both the rest position and phonetics. Palatography, in addition to its use contouring the palate and arranging teeth, also be used on an existing denture to analyse defective speech.

Review of literature

FLANGE TECHNIQUE: AN ANATOMIC AND PHYSIOLOGIC APPROACHTO INCREASED RETENTION, FUNCTION, COMFORT, ANDAPPEARANCE OF DENTURES

J. Pros. Den. May-June, 1966

FLANGE TECHNIQUEThe successful application of the flange technique will depend upon the familiarity of the dentist with the basic information already given and his willingness and capability to apply it with care and discretion. The flange technique is not a completely new method of denture construction. It consists of a few additions to any acceptable complete denture technique.It can be used (1) to determine the physiologic alignment of the arch form of the anterior and posterior teeth on the occlusion rims, (2) to secure an accurate impression of the structures surrounding the trial dentures and thus determine the form of the polished surfaces of both dentures, and (3) to improve the retention, appearance, and speech on otherwise acceptable finished dentures.

TO DETERMINE A PHYSIOLOGIC ALIGNMEKT OF THE TEETHThe usual procedures of denture construction have been carried out to the point where the casts are mounted on the articulator, centric relation has been verified, the articulator guidances have been adjusted, and the teeth have been selected. It is logical and mandatory that the functions of tongue and cheeks in the posterior part of the mouth, and of the tongue and lips in the anterior region should continue as they matured with the natural teeth in place. It follows, then, that the positions of the artificial teeth should be coordinated with such physiologic activities as talking, swallowing, etc., by each individual patient.

THE TECHNIQUEThe occlusal plane and the occlusal vertical dimension must be accurately maintained after the casts are mounted and the articulator is adjusted. Prepare for the patient by sealing a small metal keel into each occlusal surface of both occlusion rims. A keel* developed for this technique is a small, elongated metal ellipse one inch long and three sixteenths of an inch

wide, with a similar ellipse in the center lengthwise on the underside of the first, and at right angles to it. Its similarity to a keel on a sailing vessel prompted the name (Fig. 9). Imbed each keel flush with the occlusal surface of the occlusion rim and in the center of it, both anteroposteriorly and transversely, and, as nearly as possible, exactly opposite the one in the opposing occlusion rim. Narrow both occlusion rims buccolingually to the width of the keels, and to more or less of a knife-edge in the anterior region (Fig 10). An alternative method is to construct extra plastic bases and mount the keels on vertical columns of plastic in the same relations as just described. This method takes additional time but it may be preferred, expecially for the anterior molding or where a permanent record is desired (Fig. 11). Use of soft flange wax+ to build the occlusion rims back to slightly greater bulk than that of the resorbed structures (Fig. 12). Cut some flange wax into strips one half inch wide and place them in water at about 110” F. for five minutes to thoroughly soften them.

THE BUCCAL AND LABIAL SURFACESForm a roll of the wax long enough to extend from the tuberosity to the cuspid region and large enough in diameter to restore the estimated resorption. Remember that the ultimate object, in addition to increasing retention, is to restore the position and function of the cheek muscles by occupying, with the denture base, as much of the collapsed space above and below as did the former ridge and teeth. A roll that is slightly too large is necessary for molding purposes but an excessively large one will result in distention of the cheek, loss of time in reducing it, and extra insertions to finally trim it for comfort and function.Rub a roll of the softened wax into place on each buccal surface of both occ’lusionrims. Cover the labial surface of each occlusion rim to a contour that is slightlyfuller than that of the original occlusion rim.

THE PALATAL AND LINGUAL SURFACESAdd softened wax to the palate of the maxillary occlusion rim in the posterior region on each side in the position of the former ridge, and in the anterior region add softened wax over the rugae area, particularly at the junction of the residual ridge and the occlusion rim. Add a sufficient layer of softened wax on the surfaces of the mandibular lingual surfaces to give them a fuller contour than probably will be required by the finished denture.

MOLDING THE SOFT FLANGE WAXIf the keels were imbedded in the wax occlusion rims, soften the overlying flange wax with a bench torch to avoid softening the hard baseplate wax that supports the keels. If the keels were mounted to plastic (as in Fig. 11)) place the occlusion rims in warm water at about 110” F. for five minutes to throughly soften the flange wax. Coat the occlusal surfaces with a little petroleum jelly and insert the occlusion rims in the mouth. Direct the patient to read aloud and rapidly on some interesting subject. Reading aloud requires more strenuous muscular movement than reading quietly, and reading rapidly produces more saliva and causes more numerous swallowing actions. An interesting subject tends to draw attention away from the occlusion rims and what is being done so the movements of the tongue, lips, and cheeks will be more natural. A good alternative is to engage the patient in an animated conversation on asubject of mutual interest. Direct the patient to forcefully grin and purse the lips as a final requirement. These actions will cause the natural function of most, if not all, of the muscles involved.

ACTIONS PRODUCED BY THESE EXERCISES

The sides of the tongue press outward against the posterior lingual surfaces of the occlusion rim, especially in the act of swallowing. The middle fibers of the buccinator muscles constrict simultaneously to press inward against the buccal surfaces of the occlusion rims, and these opposing actions force the soft flange wax into the neutral space between them that was formerly occupied by the natural teeth. The modiolus tenses into a stabilizing knot and moves in various directions to aid in locating the neutral tooth zone in the buccal bicuspid regions.The tip of the tongue presses strongly against the lingual surfaces of the occlusion rims during the first part of the act of swallowing, and molds the soft wax to a contour that establishes the arch form of the teeth in the anterior lingual region.The lips do not strongly antagonize the tongue in the act of swallowing but they are particularly active in facial expression. They will mold the soft wax on the labial surfaces of the occlusion rims to appreciably assist in determining an acceptable arch form for the teeth.In subsequent stages of swallowing, the tip of the tongue presses against the rugae area first, then the body of the tongue presses against the palate and the lingual surfaces of the maxillary occlusion rim in a movement that progresses posteriorly during the act of forcing a bolus of food posteriorly into the pharynx. This action completes the molding of the soft wax in the palate. Remove the occlusion rims and trim off any excess wax that may have beenmolded over the occlusal or incisal surfaces. Then resoften the flange wax and repeat the entire procedure until wax no longer flows toward the occlusal and incisal surfaces of the occlusion rims. Then direct the patient to rinse the mouth with cold water, and remove the occlusion rims carefully to avoid distorting the wax (Fig. 13).

LABORATORY PROCEDURESThe occlusion rims may now be used in either of two ways to lay out the position of the teeth. The first is to place them on their casts and draw pencil guide lines on the casts. The second method is more accurate and should be used for patients with unfavorable situations. Remove the casts from the articulator and place the perfected occlusion rims on them. Surround each cast and occlusion rim with a wax boxing and pour in it a plaster matrix (Fig. 14). When the plaster has partly set, cut a deep groove in it in the anterior region so it can be fractured there later to make two sections which are easily removed.Remove the flange wax and keels from the occlusion rims and arrange the teeth using the plaster matrix as the guide to-tooth position. If the flange wax has been formed on plastic bases with the keels on them, simply replace them with the original wax occlusion rims, and set the teeth according to the guide formed by the plastic matrix (Fig. 15). The tooth positions can be checked at any time by assembling the matrix around the cast and the trial denture.

TO DETERMINE THE FORM OF THE POLISHED SURFACESThe second and most valuable use of this technique is to determine the form of the polished surfaces of dentures after the accuracy of the various jaw and tooth relations has been determined. Remove all excess baseplate wax from the buccal, labial, and lingual surfaces of both trial dentures. Retain only enough of the wax to hold the teeth in position (Fig. 16), and add softened flange wax over the remaining baseplate wax. Add sufficient flange wax to the buccal surfaces of the maxillary trial denture to slightly exceed the size and shape of the contours previously molded on the occlusion rims Add a slight excess of soft flange wax on the labial surface to be reduced by lip function and facial expression. Add enough soft flange wax on the palatal surface completely around the arch to enable the tongue to re-establish the lingual form of the ridges in the posterior ,region and the anterior curvature of the dental arch in the anterior region (Fig.17). Soften the flange wax that has thus been added to the maxillary trial denture slowly and evenly with a bench torch, taking care not to soften the baseplate wax supporting the teeth. Temper the soft wax quickly in water at 110” F., insert

the trial denture in the mouth, and have the patient wear it while the mandibular denture is being prepared. Remove the baseplate wax from the mandibular trial denture to make spacefor the flange wax in the same manner as the maxillary trial denture was prepared. Add flange wax on the buccal and labial surfaces by the same procedures and in comparable amounts as on the maxillary trial denture. Add an appreciable excess of flange wax beyond the usual arbitrary carving on the posterior part of the lingual surfaces of the lingual flanges. This will permit the tongue to displace the excess and shape it to accommodate all requirements of tongue positions and movements. Add a somewhat larger amount of excess of flange wax to the anterior part of the lingual surface of the lingual flange (from bicuspid to bicuspid). This is a most important surface because patients often tolerate surprisingly large extensions over the sublingual glands with comfort. These extensions can provide definitetongue rests (Fig. 17). Carefully soften the flange wax on the mandibular trial denture and insert it in the patient’s mouth. Have the patient swallow forcibly, grin broadly, pucker the lips, read aloud for a few minutes, and make other movements of the mouth. Remove the mandibular denture, resoften the flange wax on it, reinsert it, and have the patient repeat the oral and lip movements. Then hold the denture down with a finger on a molar on each side, and have the patient protrude the tongue strongly to each side, and lick his upper lip from angle to angle while his mouth is wide open. This will free the attachments of the genioglussus muscles.

The excess flange wax tends to move toward the occlusal and incisal surfaces of the teeth. If it moves toward the denture borders, it indicates that the original impressions were underextended. If the extension of the flange wax in any place around the border is small, the cast can be carefully relieved with probable success. If the extension of wax is large, a new master cast should be made. The trial dentures should now feel natural and comfortable to the patient. Chill the trial dentures in the mouth and remove them (Fig. 18). The increased size of the flanges is often surprising and yet satisfactory to the patient (Figs. 19 and 20). Reset any teeth that may have moved while the flange wax was being molded. Prepare the dentures for flasking by removing the flange wax from around the teeth. Process the dentures in such a way as to preserve the general contour established by the flange wax. Minor changes in the contour of the bases may be made around the teeth for esthetics provided the general contours are unchanged.

ADVANTAGES OF THE TECHNIQUEThe area of intimate contact of the denture bases with the underlying and adjacent structures is considerably increased by the flanges, and the retention is increased. The location of the dental arches is changed from the status of “a rule of thumb” location that is dependent upon the skill and judgment of the dentist or the estimate of the technician to a physiologically located position. Reliance is placed upon the patient for the necessary shaping of the borders and flanges. The tongue position may be established with confidence. The appearance of patients who have worn dentures for long years is improved and it is maintained for patients recently treated. The buccal and labial flanges provide complete support to the facial structures without limiting their function.The patient’s speech may be more natural because the width of the dentures in the bicuspid regions is determined by the accurate placement of the teeth in the dental arch. The anterior arch form of the teeth and the shape of the anterior part of the palate are correctly located by the molding action of the tongue. These factors may be the determining factors in the maintenance or re-establishment of correct phonation.

IMPROVEMENT OF UNSATISFACTORY DENTURES

The flange technique can be used to improve the retention of unsatisfactory dentures, or to locate the dental arches in their most favorable positions. Where only the retention is at fault, grind away the denture base material of the flanges to make space for the flange wax.Add the flange wax in the same manner as was described for adding it to a trial denture. Make a zinc oxide and eugenol reline impression. Have the patient mold the wax on the flanges as described for trial dentures. Pour a cast in the denture. Flask the denture in the bottom section of the flask. Cover the denture with a one-eighth to one-quarter inch layer of silicone release material, and complete the flasking. Pry the flask open after the stone has set. This is possible because of the elasticity of the layer of silicone. Remove the teeth from the denture and place them in their respective depressions in the silicone. Pack the mold with new denture base material, and process and finish the denture. Do the packing of the material in the flask with care to avoid increasing the occlusal vertical dimension of the denture.

CONCLUSIONThe reasoning behind the use of flanges molded by the patient on the facial, buccal, lingual, and palatal surfaces of dentures to the individual requirements of each patient is sound theoretically and physiologically. The results of the use of the flange technique are superior to the results of the discretionary methods of determining the tooth and tongue positions and the arbitrary carving of the facial, tongue, and palatal surfaces.

A STUDY OF PHONETIC CHANGES IN EDENTULOUS PATIENTS FOLLOWING COMPLETE DENTURE TREATMENT

J Prosthet. Dent. February, 1972

Speech samples were obtained from five edentulous patients, who became edentulous recently, at three periods following the use of dentures. Ten trained speech therapists assessed each patient’s speech by the method of paired comparison. Words spoken in the edentulous state were paired with words spoken at different stages of denture wear. Analysis revealed a preference by the judges for the speech sounds made following the use of dentures. The /s/, /sh/, and /t/ sounds showed improvement; however individual speech sounds developed differently. The voiced /th/ sound did not show any general improvement. Selected judgments of preference were compared to their corresponding spectrograms.

SPEECH PATTERNS OF EDENTULOUS PATIENTS AND MORPHOLOGY OF THE PALATE IN RELATION TO PHONETICS

J. Prosthet. Dent.January, 1973On the basis of analysis of the data collected, the following conclusions weremade:1. Most of the patients showed speech improvement when the dentures were first inserted.2. With increased length of time of wearing the new dentures, the speech intelligibility was improved.3. The speech of patients can be improved by experience with their new dentures.4. Individual sounds showed different levels of speech intelligibility, and this level improves with the length of denture usage.5. Acoustic distortions occurred more frequently in the s, sh, ch, zh, and j sounds than in the t, t, n, d, and 1 sounds.6. The s sound is a poor prognostic sound for intelligibility of speech.

7. The palatal ridge formation (palatal contour) of complete dentures will affect the acoustic distortion of affricative and fricative sounds.

THE EFFECT OF DENTURE FACTORS ON MASTICATORY PERFORMANCEPart II: Influence of the Polished Surface Contour of Denture Base

J,Pros. Den.Marc -April, 1965

Eight hundred and forty masticatory performance tests were conducted in 10 subjects to study the influence of thirteen forms of the polished surfaces of upper and lower denture bases on the masticatory effectiveness of dentures. On the average, no significant variations appeared in the ability of subjects to chew with different denture forms. However, evidence of marked improvement in masticatory performance appeared among individual subjects with different denture forms. This would suggest that polished surface denture contour may be an importantfactor influencing the efficacy of the food transporting mechanism and therebyaffecting masticatory function. Subjects with good ridges performed better than subjects with poor ridges. Results of this study verified our previous findings that denture wearers varygreatly in their ability to pulverize food.

Evaluation of the factors necessary to develop stability in mandibularDentures

J Prosthet Dent 2004;92:509-18.1. Retention is a prerequisite to stability. Some degree of retention must be present for mandibular dentures to have the quality of stability.2. In order to provide the property of retention, a border seal area must be available.3. The seal areas for mandibular dentures are the floor of the mouth and the lateral throat forms.4. The floor of the mouth and lateral throat forms make extensive movements to carry out the complex functions of the oral cavity.5. The floor of the mouth has three levels.6. The high level of the floor of the mouth accommodates for those functions of the tongue which require it to be more than moderately extended.7. The low level of the floor of the mouth accommodates for the movements of the tip of thetongue as it moves to the floor of the mouth, such as when it retrieves food.8. The normal level of the floor of the mouth, along with the corresponding position of the lateral throat form, serves to satisfy the tongue for practically all ofits functions.9. The normal tongue position places the floor of the mouth and the lateral throat forms in their normal positions.10. The floor of the mouth at its normal level appears to be approximately even with the internal oblique lines on the body of the mandible.11. The lateral throat form appears to make an angle of approximately 45 degrees downward and backward from the posterior border of the retromolar pad.12. The lingual flanges of average mandibular dentures should be extended downward one to two millimeters below the internal oblique line to make the border seal.13. The distolingual extension into the lateral throat form should extend from the retromolar pad backward and downward making an angle of approximately 45 degrees with the floor of the mouth and be continuous with the border of the lingual flange.14. A wax occlusion rim must be in place before the mandibular tray is placed in the mouth. This occlusion rim should simulate the correct occlusal plane and the proper arch arrangement.

15. Since the tongue functions primarily by touch and pressure, a wax occlusion rim simulating the occlusal plane and arch arrangement will facilitate the maintaining of a normal tongue position.16. To test a tray, it is necessary to have the tongue in a normal position in order to secure the seal. This would then serve as the starting point for testing the tongue movements.17. All procedures leading to completing a lower impression should be done with the tongue in its normal position.18. When testing the finished impression, one should keep in mind that extensive movements of the tongue can cause dislodgment.

MORPHOLOGIC COMPARISON OF TWO NEUTRAL ZONE IMPRESSION TECHNIQUES: A PILOT STUDY

J Prosthet Den 2004;92:563-8Statement of problem. Several studies have compared dentures fabricated using neutral zone and conventional techniques. However, studies comparing swallowing and phonetic techniques for assessing the location and shape of the neutral zone could not be identified in the literature.Purpose. The purpose of this pilot study was to compare the outline form of the phonetic and swallowing neutral zone impression techniques for the same subjects.Material and methods. Nine denture wearers with advanced mandibular ridge resorption were included in this study. For each subject 2 trays were prepared in autopolymerizing acrylic resin. One method used phonetics and tissue conditioner to shape the neutral zone; the second method used swallowing and modeling plastic impression compound. The resulting neutral zone impressions were leveled to the same occlusal height by gently grinding the occlusal surface on sandpaper until it corresponded with landmarks (corners of the mouth, two thirds of the height of the retromolar pads, bilaterally) noted on the cast. The impression was inverted onto graph paper, and the contour was outlined with a lead pencil. One impression was made for each subject, for each technique. The buccal contours of both neutral zones coincided at the median line. The maximum distance between the zones was measured in a buccolingual direction in the anterior, premolar, and molar regions bilaterally. When the location of the phonetic neutral zone in relation compared to the swallowing neutral zonewas buccally oriented, a plus score was given. When the phonetic neutral zone was lingually located, a minus score was given. When the 2 lines coincided, a score of 0 was given. Measurements were made from direct readings on the graph paper. Statistical analysis was performed using the Sign test (a=.05).Results. Significant differences were noted buccally in the left molar (P=.031) and right molar (P=.003) regions and also in the left and right premolar regions (P=.007), where the swallowing neutral zone was found to be located buccal to the phonetic neutral zone. Significant differences were also noted lingually, in the right premolar region (P=.015), where the swallowing neutral zone was found to be located lingual to the phoneticneutral zone. There was no significant difference between the techniques for the anterior region.Conclusion. Within the limits of this study, the phonetic neutral zone appears to be narrower posteriorly compared to the swallowing neutral zone, thus limiting premolar and molar positioning.

EXAMINATION OF DENTURE-CLEANING METHODS BASED ON THE QUANTITY OF MICROORGANISMS ADHERING TO A DENTURE.

Gerodontology. 2011 Feb 1

Examination of denture-cleaning methods based on the quantity of microorganisms adhering to a denture To investigate effective Objectives: denture-cleaning methods, we examined the relationships between the quantity of microorganisms adhering to dentures and the use of a denture brush and the frequency of use of a denture cleanser.  Subjects and Methods: Denture plaque was collected from the mucosal surface of the examined dentures, which were 142 and 80 upper and lower complete dentures, respectively, worn by 96 outpatients years) of a university hospital and 41 nursing home residents (mean age: 71.9 years). The collected microorganisms were counted in terms of (mean age: 84.8 isolated representative colonies that were cultured and identified using standard methods. The use of a denture brush, the frequency of use, and the type and soaking time of denture cleansers as denture The -cleaning methods were surveyed. Results: quantity of microorganisms was significantly lower in dentures of denture brush users than in those of non-users in the  outpatients (p<0.01, Mann-Whitney U test). The quantity of microorganisms  was significantly lower in the dentures of outpatients who used a denture cleanser daily or 3-4 times a week than in those who used one once or less per month and in the dentures of nursing home residents who used one daily than in those who used one at other frequencies  (p<0.05, Kruskal-Wallis test, followed by Dunn's Multiple Comparison test).  Within the limitations of this study, it was concluded that the use Conclusion: of a denture brush and daily use of denture cleanser should be recommended to complete dentures wearers as denture-cleaning methods that effectively reduce the quantity of microorganisms adhering to dentures.

THE POLISHED SURFACE CONTOUR: A NEW APPROACHInt J Prostbodont 1991;4:159-16J

Approximately 5 ml of a low-viscosity silicone impression material (Provil L, Bayer UK Ltd, Newbury, Berkshire, England) is mixed and applied thinly with a spatula to each denture. No adhesive is used. On the maxillary denture, the labial and buccal polished surfaces and all borders extending 3 mm onto the fitting surface are covered with the impression material (Fig la]. On the mandibular denture, all of the polished and fitting surfaces are covered (Figlb|. No material is placed on the teeth, and the denture may be held by the teeth without displacingthe impression material. Although some material may be removed during placement, its low viscosity allows it to flow in to fill such areas so that in practice such voids do not occur.The dentures are carefully placed, and the patient is given a piece of damp paper (approximately 3 X 3 cm in size) and encouraged to chew it vigorously using the lips, tongue, and cheeks, but not to swallow it. One-ply, medium-quality paper hand towel (code 2734, British Tissues Ltd, Harrow, Middlesex, Fngland] conforming to BS 1439 (1961) for wetcrepe paper is used. This has been found to produce a manageable bolus that maintains its form and does not disintegrate, leaving the patient searching for something to chew. Moistening the paper prevents it from adhering to the silicone impression material. Once the impression material has set, the dentures are removed and examined.

THE EFFECT OF THE MANDIBULAR BUCCAL DENTURE BASE SURFACE ON FOOD RETENTION

Int J Prosthodont 1992:5:457-462

Within the limitations of this study in which dentate individuals were used to evaluate the effect of different aspects of the polished surface of the buccal flange on food retention in the buccal vestibule, the following conclusions may be made: 1, The thickness of the buccal flange did not have a significant effect on the ability of the subjects to expel test particles, 2, Physiologic molding of the buccal flange did not significantly affect the ability of the subjects to expel a test bolus, 3, The slope of the flange did significantly affect the ability of subjects to expel a test bolus. There appears to be a critical angle between 600 to 700 for this slope.

PHONETICS AND TONGUE POSITION TO IMPROVE MANDIBULAR DENTURE RETENTION: A CLINICAL REPORT

J Prosthet Dent 2007;98:344-347

Fabrication of new maxillary and mandibular complete dentures for the patient proceeded, with special emphasis on retention and stability of the mandibular denture. Border molding of custom impression trays (Triad VLC Denture Base Material; Dentsply Intl, York, Pa) and making of accurate definitive impressions (Impregum; 3M ESPE, St. Paul, Minn) to capture and cover appropriate anatomical features were accomplished to enhance retention of the dentures.1-7 During border molding and making of the mandibular definitive impression, the patient was instructed to pronounce the sound “e”, as in the word “knee”, to aid in positioning the tongue and buccinator muscles to develop a peripheral seal of the mandibular denture borders. Maxillomandibular records and a trial insertion of the dentures were completed at subsequent separate appointments. At each appointment, the patient was reminded of the “challenge” to be accepted to overcome the physical and anatomical features that worked against retention and stability of the mandibular denture The patient was repeatedly informed of the important role that tongue position and facial muscles have in improving retention and stability of the new mandibular denture. On several occasions, the patient was instructed to pronounce the sound “e” to help train and coordinate the positions of the tongue and buccinator muscles. At insertion of the new maxillary and mandibular dentures, the patient initially appeared skeptical, but soon acknowledged that through the use of phonetics she was able to improve the retention and stability of her new mandibular complete denture. A clinical remount of the dentures was done to modify and refine the monoplane occlusion. Minimal adjustments of the denture base flanges and intaglio surfaces were subsequently made to the dentures at 24-hour, 72-hour, 1- week, and 2-week postinsertion appointments. At completion of treatment, the patient acknowledged that she was comfortable and pleased with the fit, retention, function, and esthetics of the new dentures.

References:1. Complete Denture Prosthodontics. 3rd edition. John J Sharry 2. Principles of Full Denture Prosthesis. 4th edition Wilfred Fish3. Boucher’s Prosthodontic Treatment for Edentulous Patients. 10th edition.

George Zarb4. Textbook of Complete Dentures. 5th edition. Arthur Rahn5. Essentials of Complete Denture Prosthodontics. Sheldon Winkler6. J Prosthet Dent 2007;98:344-3477. Int J Prosthodont 1992 :5:457-4628. Int J Prostbodont 1991;4:159-16J9. Gerodontology. 2011 Feb 110. J Prosthet Den 2004;92:563-811. J Prosthet Dent 2004;92:509-18.12. J,Pros. Den.Marc -April, 196513. J. Prosthet. Dent.January, 197314. J Prosthet. Dent. February, 197215. J. Pros. Den. May-June, 1966