INTRODUCTION: The single complete denture opposing all or some of the natural dentition is not an uncommon occurrence. There are several causes for the loss of teeth from the dental arches like periodontal problems, dental caries and trauma. The incidence of tooth loss is more in maxillary arch compared to mandibular arch, most of the single complete denture cases are edentulous maxilla opposing mandibular natural teeth. The single complete denture should be given for many reasons like mastication and esthetics. Several difficulties are encountered in providing a successful single complete denture treatment. Regrettably this service is envisioned as only half as difficult and time consuming as the fabrication of opposing complete dentures.

DEFINITION: Single complete denture is a prosthesis which replaces the lost natural teeth and

its associated structures functionally and esthetically as a single unit which opposes all or some of the natural teeth.

The primary consideration for continued denture success with a single conventional complete denture is the preservation of that which remains. A single complete denture may be desirable when it is to oppose any one of the following:

o Natural teeth that are sufficient in number not to necessitate a fixed or removable

partial denture.o A partially edentulous arch in which the messing teeth have been or will be

replaced by a fixed partial denture. o A partially edentulous arch in which the missing teeth have been or will be

replaced by a removable partial denture.o An existing complete denture

In the first situation the maxillary arch is usually the edentulous arch. Among the reason for this occurrence is that a maxillary compete denture is more stable, easier to retain in position and tolerated better by patients than a mandibular denture. Therefore many are less reluctant to allow the loss of the maxillary teeth and at times insist upon their removal.

Single edentulous arch :Prevalence of the condition where edentulous arch opposes a natural or restored

dentition is quite common. It has been estimated that for some patient population the mandibular canines are retained four times longer than other teeth followed by mandibular incisors. The reason for the loss of the maxillary teeth prior to the mandibular teeth are unclear and are influenced by a combination of factors. One major factor might be the profession’s perception of the ease of fabrication of maxillary dentures compared with mandibular ones and the comparative functional success of maxillary versus mandibular complete denture.

There is a qualitative and quantitative difference between natural tooth and complete denture support. The difference is one of adaptability versus invaladaptability.

Diagnosis and treatment planningThe commonly sited long term goal in prosthodontics is the preservation of that which remains. This demands an appreciation of occlusal mechanics. Carl F. Driscoll and Radi M. Masri proposed a classification system that could simplify the identification and treatment of those patients:

• Class I – Patient for whom minor or no tooth reduction is all that is needed to obtain balance.

• Class II – Patient for whom minor additions to the height of the teeth are needed to obtain balance.

• Class III – Patient for whom both reduction and additions to the teeth are required to obtain balance. The treatment of these patient involves change in the vertical dimension of occlusion.

• Class IV – Patient who presents with occlusal discrepancies that require addition to the width of the occluding surface.

• Class V – Patient who presents with combination syndrome.

PROBLEMS1. Occlusal forces :

The firmness and rigidity with which the natural teeth are retained in the bone and the magnitude of forces they can resist or deliver without any discomfort or displacement. These forces has been recorded as high as198 lbs on a single molar tooth.

This is in contrast with the forces which a complete denture, resting simply on the delicate mucosa of the ridge can resist or deliver. This force has been established as being a maximum static load of 26 lbs (Anderson and stores – 1966)

Clearly these forces by natural teeth will cause damage to the soft and hard tissues under the denture.

When one considers the great magnitude of forces involved, the unsuitability of the denture foundation to resist them, particularly due to unfavorable occlusal relationships, there is occurrence of what is described by Sharry as the “Single denture syndrome”. The patient complains of a loose or tilting denture. Examination reveals damage to the mucosa and ridge resorption. Relining temporarily cures the complaint but the cycle of trauma, resorption and looseness continues.

2. Occlusal form of the natural teeth The occlusal form of the remaining natural teeth will dictate the occlusion of the

denture. The natural teeth may be over erupted or tilted and there cusps may be high and

sharp. As a result occlusion and articulation will involve contacting of the

inclined planes of cusp in such a way that the denture will constantly be thrust or dragged horizontally on the ridge.

Because of the unstability of the denture foundation to resist there unfavarourable forces, the occurrence of single complete denture syndrome is common. Patients complain of loose, tilting dentures and soreness of the tissues underlying the dentures. Examination reveals damage to the mucosa and ridge resorption.

3. Support for the denture base : In a complete denture the occlusal force must be dissipated through the denture

base to the ridge. For this reason the denture base should have the maximum extension within the functional anatomic limits. So that the forces of occlusion both vertical and horizontal will be distributed over the largest possible area of supporting structures and force / unit area kept at minimum.

In the edentulous mandible the area of support available for the denture base is relatively small when compared to maxilla and also the mucosa is thin and delicate and the underlying bone is particularly prone to resorption. For these reasons the lower complete denture opposing upper natural teeth should be normally avoided.

4. Inter maxillary relations : The principles of recording inter maxillary relation remain unchanged for single

complete denture. But when an upper complete denture is being made to occlude with lower natural

teeth, an error may be made in recording the vertical dimension, if the wax rim is trimmed to represent the incisal level of the upper anterior teeth and to be parallel with the ala tragus line as is done in conventional upper and lower complete denture construction.

The labio- lingual thickness of the wax rim, will usually not allow the lower incisor to close beyond the occlusal surface of the wax rim although previously they occluded high on the lingual of the upper incisors. Unless this fact is appreciated and allowed for an increased vertical dimension may be recorded.

To avoid this the anterior this the anterior part of the wax rim should be trimmed in such a way that it should resemble labiolingual width of the upper anterior teeth and should allow the lower anterior teeth to occlude above the occlusal plane.

Occlusal problems and fracture of denture base account for structured difficulties and may result from one or all of the following:

1. Occlusal stress on the maxillary denture and the underlying edentulous tissue from teeth and musculature accustomed to opposing natural dentition.

2. The position of the mandibular teeth which may not be properly aligned for the achievement of bilateral balance for stability.

3. Flexure of the denture base Salient considerations include:

Acceptable interocclusal distance

Stable jaw relationship with bilateral tooth contact in retruded position. Stable tooth quadrant relationships with axially directed forces Multidirectional freedom of tooth contact throughout a small range (with

in 2 mm) of mandibular movements. However when only one arch is edentulous, tooth position in the dentate arch

may preclude such objectives being reached. Unfavourable force distribution may then cause adverse tissue changes that compromise optimum function like:a) Extensive morphological changes in denture foundation b) Extreme jaw relationships c) Excessively displaceable denture bearing tissue.

Changes in the denture foundation also can occur due to long standing uncontrolled occlusal forces. Extremes of jaw relationship also make it very difficult to place the teeth in position. Excessive displaceable tissue and regular occlusal plane also cause problems.

Prior to occlusal modifications of the natural teeth it is imperative that upper and lower cast must be mounted on an articulator.

Several techniques have been described in the literature where by the necessary tooth modification are determined prior to denture construction.

1) In the method described by Swenson,The maxillary and mandibular cast are mounted on the articulator using a provisional centric relation record at an acceptable vertical dimension. After the maxillary teeth are set the lower natural teeth interfering with the placement of denture teeth are adjusted on the cast and the area is marked with pencil. The natural teeth are modified using the marked diagnostic cast as a guide. After the occlusal modification have been completed a new diagnostic cast of lower arch is made and mounted on the articulator. If more adjustments are necessary the procedure is repeated. Once the occlusal modification appear to be sufficient should be prepared for try in. This technique is simple but time consuming.

2) A second method described by Yurkstar(1968)Involves the use of a metal ‘U’ shaped occlusal template that is slightly convex on the lower surface. When placed on the occlusal surfaces of the remaining teeth the cusps to be adjusted are recognized. Those areas are marked with the pencil and the cast is then used as a guide for modifying the natural teeth.

3) A third technique was described by Bruce,The lower diagnostic cast is mounted as in the previous procedures. The necessary modifications are made on the stone cast occlusal surface. A clear acrylic resin template is fabricated over the modified stone cast. The inner surface is coated with pressure indicating paste and placed one the patients natural teeth. Interferences are readily noted through the template and are removed by reshaping the occlusal anatomy. The process is repeated until the template is seated properly.

4) Boucher et al explained another technique,That involves making the natural teeth fit to the established plane and inclines of the maxillary porcelain teeth. The casts are mounted on the articulator and porcelain teeth are arranged in the maxillary arch. The interferences are removed by movement of maxillary porcelain teeth over the mandibular stone teeth. After the denture has been processed a comparison of the natural teeth and the altered stone cast is made and the areas to be reshaped are noted. The natural teeth are ground at the areas marked on the stone cast. The occlusal surface is refined using an arch shaped layer of softened base plate wax over the lower teeth and guiding the patient to close in centric relation. Prematurities are removed by grounding the natural teeth. The procedure is repeated by right and left lateral excursion until a harmonious balanced occlsion is established.

COMBINATIONS 1) Upper single complete denture opposing complete set of lower natural teeth.2) Lower single complete denture opposing complete set of upper natural teeth. 3) Single complete denture opposing natural teeth with a removable partial denture. 4) A single complete denture opposing natural teeth with a fixed partial denture. 5) A single complete denture opposing an already existing complete denture.

Single complete denture (Maxillary) to oppose natural mandibular teeth: More frequently encountered than the single mandibular denture. The diagnostic procedure should determine that there are sufficient teeth in the

mandibular arch periodontal health acceptable, and there is no missing teeth to be replaced.

The number of mandibular teeth considered sufficient should include the first molars in jaws that have a class I or class III relation. In class II related jaws the anterior teeth and premolars bilaterally may suffice.

The occlusal forms of the natural teeth act as a guide in selecting the occlusal form for the maxillary posterior teeth.

In most situation this would be a cusp tooth. However if the natural teeth are abraded and are not restored prior to the treatment the monoplane form may be the choice for the occlusal surface of posterior teeth.

Some times the position of mandibular teeth will not allow the maxillary anterior teeth to be positioned in an esthetically acceptable manner or for balanced occlusion. This problem may be solved as follows:

Reposition of the natural teeth with orthodontic procedures

Alter the clinical crowns of the teeth by grinding or with restoration. Accept balanced occlusion with the jaws in the terminal relation and not

in the eccentric position. The mandibular posterior teeth may be mal posed or missing or the occlusal plane

may be irregular. This must be altered either by selective grinding procedures or by placing restoration.

Another problem usually with patient, who have neglected there dental care, is the prior loss of all maxillary teeth (posterior) and remaining anterior maxillary teeth that are not restorable. Mandibular teeth have not been lost for some unexplainable reason and are restorable. The mandibular arch will then present two planes of occlusion, an anterior plane and a posterior plane. The posterior teeth have extruded and inter ridge space would be less. To prepare this mouth it requires extensive restorative procedures in mandibular arch and possibly surgery in the maxillary arch.

To proceed with complete maxillary denture procedures without first preparing the environment into which the artificial teeth will be placed is to invite trouble.

Mandibular denture to oppose natural maxillary teeth : Although the mandibular arch is seldom the edentulous one, this condition does

occur. It usually happens as a result of either surgical or accidental trauma ie irradiation or accident or gunshot. The maxillary teeth are healthy and attractive.In these situation it is necessary to consider the total patient.

Three factors in particular must be carefully evaluated. 1) Preservation of the residual alveolar ridge 2) Necessity for retaining maxillary teeth 3) Mental trauma

When all factors have been evaluated and it is decided to prescribe a complete mandibular denture the patient should be well educated to the possible consequences. If this is done seriously and sincerely the treated patient will understand this consequences and help to minimize them.

1) Preservation of the residual alveolar ridge The force of jaw closure with natural teeth is greater than that with complete denture and greater the force the more the pressure which a contributing factor to bone resorption. It is not known how much force is exerted when natural teeth in one arch are opposed by a complete denture. Undoubtedly this will vary, however one cannot guess that the force will be minimal and tolerated with no deterioration of the bone.

The mandible is the movable member of the stomatognathic system therefore, it is more difficult to stabilize the mandibular denture. Also the activity of tongue may displace the denture. This denture movement increases stress and pressure on mucosa. Another factor is the minimal availability of mucosa with tightly attached submucosa for mandibular denture support.

The more concentrated the stress, the more damage to the supporting structures result. So if single factor dictating prescription of mandibular complete denture is preservation of ridge. Then such prescription should not be made. 2) Necessity for retaining maxillary teeth : The maxillary dentition may be needed to retain a prosthesis. This situation is usually associated with congenital defects such as cleft palate or stoma resulting from surgical or accidental trauma. If the cleft is not entirely closed retention for an upper complete denture may be very difficult to obtain and the addition of the obturator will increase the weight of the denture. Even if the cleft has been fully closed the prognosis for an upper complete denture is still not good because the dental arch is often small and poorly formed and the upper lip is so tight that it tends to displace the denture. For these reasons upper natural teeth must be preserved to help retain a prosthetic restoration even when it is necessary to make a lower complete denture.

If the size of the mandible is normal and the discrepancy lies in the small maxillae, upper teeth maybe retained to avoid the problems of upper complete denture supported by a small edentulous ridge.

3) Mental trauma :Some person become depressed with the loss of teeth. This depression may lead to more complicated psychological problems. If this mental state exists when the patient loses the mandibular teeth, removal of the remaining maxillary teeth maybe more than he or she can endure mentally.

Even though the potential for the destruction of the mandibular residual ridge is great, the necessity for retaining maxillary teeth for retentive purpose and the mental trauma created by the loss of the mandibular teeth may be the deciding factors for prescribing a complete mandibular denture to oppose natural maxillary teeth.

One circumstance in which a lower complete denture opposing upper natural teeth is acceptable is for the patient with a class III jaw relationship. If the mandible is larger than normal the size and form of the supporting tissue may be adequate to resist the forces from upper natural teeth.

Proper diagnosis has to be done for a lower single complete denture against upper natured teeth.

Evical and swoop- developed useful system to determine and classify the amount of mandibular resorption. By measuring the distance from the inferior border of the mental foramen and multiplying by three. A reliable estimation of orginal height of the alveolar ridge can be obtained from this. The amount of resorption can be calculated and classified into three patterns.

Class I- approximately 2/3rd of the mandibular alveolar bone is present.Class II- approximately ½ - 2/3rd of bone is present Class III- approximately 1/3rd or less than that

Depending on the maxillary and mandibular jaw relationship as well as the resorption pattern a decision can be made concerning the retention of the remaining natural maxillary teeth.

Recommendations for retention of the remaining maxillary dentition when opposing an edentulous mandible : Resorption pattern Angle class I II IIIClass I (Mild) Consider Consider Strongly Consider

Class II (Moderate) Consider under special circumstances

Consider under special circumstances

Consider

Class III (Severe) Do not retain Do not retain Donot retain The above table should be used only as a guide other factors such as patient’s age and general health, dental and medical history and emotional condition must be taken into consideration.

The patient must be made aware of proper tongue position, necessary oral hygienic procedures and the problems involved with retention and stability of the prosthesis.

Patient should be made aware of importance of bilateral chewing. Necessary adjustments in the natural teeth should be made to get an acceptable

plane of occlusion and to direct the occlusal force vertically. Resilient liner are often very useful because of there stress breaking or stress

reducing properties may compensate for imbalance in areas subjected to functional and parefunctional pressure.

The mandibular denture is constantly monitered and soft liner replaced when it has lost its resiliency. The occlusion must be carefully checked at each recall appointment.

Complete maxillary denture to oppose a partially edentulous mandibular arch with fixed Prosthesis :

When a complete maxillary denture is to oppose a partially edentulous mandibular arch in which the missing teeth have been or will be replaced, the problems presented in this case are usually in the diagnostic procedures related to the existing restoration. At that time it must be determined if the fixed restoration are acceptable if they can be made acceptable or if they must be rejected.

When the restoration are acceptable one must then decide what occlusal concept will be persued. It must be remembered that the teeth in single complete denture are on a movable base and even though they function against natural teeth they will function as a unit.

Another consideration is the material composition of the artificial teeth to be used to complete denture.

Complete maxillary denture to oppose a partially edentulous mandibular teeth should be in acceptable state of dental health.

When there is a removable partial denture, it must be evaluated critically. The partial denture must meet the requirements of an acceptable prosthesis. The occlusal plane, tooth arrangement for occlusion, esthetics and material composition of the teeth must be such that an accepted complete denture can be constructed to oppose it. When the removable partial denture is to be supplied there should be no particular problems related to the complete denture fabrication since the treatment plan is or should be formulated for both arches at the same time.

Single complete denture to oppose an existing complete denture : In this situation this following factors must be considered.

1) Duration of existing denture 2) Was the denture an immediate insertion at the time of teeth removal

These two factors are directly related to the extent of bone resorption. The adaptation of the denture base to the bone is thoroughly investigated. Patient may not be experiencing a feeling of loss of retention because:

a) The muscles of lip, tongue, checks may have adapted to retaining the denture in place

b) Some times edema may be present but it is always not accompanied by hyperemia (these facors can be investigated by pressure indicating paste)

3) Does the denture meet the requirements of an acceptable denture. In addition to the accuracy of tissue adapatation and border extension one must evaluate the tooth position, esthetic acceptance and condition of the polished surfaces.

4) Condition of opposing arch in relation to the existing denture. It should be determined if the denture opposed another complete denture a

partially edentulous arch that supported a removable partial denture or a fixed partial denture. Each of this different situations influences the arrangement size shape form and colour of the teeth used in the existing denture so it should be considered whether it can be satisfactory matched to provide satisfactory results.

5) Satisfaction of operation to institute complete denture procedures utilizing the existing dentures. Rarely is this a satisfactory solution. A most serious consideration is the fact that the dentist assumes the responsibility for both dentures as soon as he accepts the patient for treatment of the single complete denture.

Few old denture full fill the ideal requirements in all areas. Careful observation and recording of the diagnostic information must be considered before a decision is reached to fabricate a single complete denture. Also important to devote as much care as to fabrication a pair of complete dentures.

COMMON OCCLUSAL DISHARMONIES

The most common occlusal adjustments involve the anterior teeth and the last molar. Frequently natural lower incisors and cuspids are very long and there should be ground as much as is practicable. This is little contraindication to so doing because at this age there is little danger of pulpal involvement / sensitivity.

A common pattern of teeth loss involves the completely edentulous maxillary arch opposing a mandibular complement of natural teeth with missing first molar or second premolar or both. The remaining molars are often severely inclined mesially and their distal halves supra erupted. If this situation is left unaltered there would be no occlusion in protrusive and lateral excursions except for contact on the distal half of the lower molar. This would tend to push the denture forward and dislodge it.

If the molars are not severely lilted they may be reshaped by selective grinding. Stephen’s recommends that the distal half of the occlusal surface should be ground flat and the denture teeth set to occlude with only that area, leaving mesial cusps out of contact.

When more than a moderate amount of tooth reduction is found necessary, the ideal treatment is to restore the tilted molar with cast gold crowns, onlays or fixed budge if a large edentulous space exists mesial to the molars.

If a large space does exist mesial to the tilted molars another alternative treatment is to design a removable partial denture that would restore the mesial half of the molar.

If the molar are severely tilted forward and supraerupted the modification is not possible, extraction is necessary.

Another disharmony exists when insufficient mandibular teeth are left to occlude with a complete maxillary denture. Although found tolerable by many patient, this clinical situation may eventually lead to the loss of the maxillary anterior alveolar ridge along with the hyperplastic tissue change. When all the molar are missing a RPD is indicated. If all teeth remain from first molar to first molar then a RPD is usually not indicated.

Natural anterior teeth often have a large over bite and small over jet. This situation is tolerable with natural teeth because they are firmly supported in the alveolar bone and have very sensitive periodontal pressure receptors which influence the muscles of mastication so as to prevent traumatic occlusal contacts. In complete denture the periodontal receptor system are absent so that with large over bite and small overjet there is a risk of trauma to the anterior ridges. In conventional complete denture construction this problem is avoided by providing a reduced or minimal over bite and where indicated, a substantial overjet. However when lower natural teeth oppose a complete upper denture this is often difficult to do because the lower teeth previously occluded vary high on the cingula of the upper natural teeth. In these circumstances the over bite may be reduced by grinding the incisal edges of the lower anterior teeth and raising the level of upper teeth. If the lower natural incisors are inclined forward grinding their incisal edges will increase the over jet and reduce the overbite.

Methods used to achieve harmonious balanced occlusion :

Many techniques have been described but all of them basically fall into two categories. Those that dynamically equilibrate the occlusion by the use of a functionally generated path and those that statically equilibrate the occlusion using an articulator programmed to simulate the patients jaw movements.

Dynamic- Functional chew in techniques :1)Stransbury described the first functional chew in technique in 1928 for an upper complete denture opposing natural teeth. He suggested using a compound maxillary occlusal rim trimmed buccally and lingually so that the occlusion is free in lateral excursions. Carding wax is then added to the compound rim and the patient is instructed to perform eccentric chew movements. The carding wax as slowly molded to the functional movements while the compound in the central fossa act as a guide to preserve the vertical dimension. The generate occlusal rim is now removed from the mouth and stone is vibrated into the wax paths of the cusps and without separating them both are mounted on the articulator. We have now the upper cast mounted on the articulator and two lower casts. The denture teeth are set according to the lower cast of the patients teeth. After the esthetic have been approved at the try-in, the lower cast is removed and lower chew in record is secured to the articulator. All interfering spots are carefully ground until the incisal guide pin prevents further closure. Thus in centric and eccentric movements maximum bilateral balanced occlusion will have been established.

VIG described as similar technique in which he recommended the use of a fin of resin placed into the central grooves of the lower posterior teeth, instead of using compound as mentioned by starsbury. The resin fin maintains the vertical dimension and also helps diagnostically locate interfering lower cusps. In eccentric movements the lower cusp tips are ground until equal contacts occur between the teeth and the resin. The fin is then built up using a soft wax and a functional path is generated.

2)Sharry mentions a simple technique of using a maxillary rim of softened wax. Lateral and protrusive chewing movements are made so that the wax is abraded generating the functional paths of the lower cusps. This is continued until the correct vertical dimension has been established.

Rudd suggests a technique similar to starsbury’s. A compound maxillary rim is formed much the same way. A thickness of recording matrix made up of 3 sheets of medium and pink base plate wax and two sheets of red counter wax in added to the buccal and lingual surface of this compound rim. He also suggests using two maxillary bases, one for recording the generated path and the other for setting the teeth. The advantage of this is to reduce the number of appointments necessary for the construction of the upper denture.

Static- Articulator equilibration technique :If the denture bases lack stability or if the patient is physically unable to perform a chew in record the articulator equilibration method is preferred.

First the upper cast is mounted on the articulator using a face bow with an orbital pointer. The lower cast is related to the upper by a centric inter occlusal record at an acceptable vertical dimension. The buccal, lingual position of the lower teeth and their relation to the upper arch is studied. A decision whether to articulate the central fossa of the denture teeth to the lower buccal cusps or lingual cusps must be made. If the denture teeth apex to be placed too far to buccal when articulated with the lower buccal cusp, they are rest to oppose the lingual cusps. Occasionally because of tipped and inclined natural teeth the buccal cusp may be used on some and lingual cusp on other. Ooncer the holding cusps have been selected the inclines of the remaining cusps are reduced and vice-versa. This allows for a cusp to fossa relationship between the upper and lower teeth.

The central fossa of the upper posterior teeth are set to articulate with the selected holding cusps of the lower natural teeth. Therefore in centric the only areas of contact on denture should be in the central fossa.

At the time of wax try in eccentric records are made and the condylar inclinations are set on the articulator. The upper posterior teeth are arranged to be as close to being balanced as is possible at this time. After the denture has been processed it is again related to the mounted lower cast with a new centric intra-occlusal record. The condlyar inclinations previously determined are reset on the articulator. Once the centric holding cusps are established by selective grinding, eccentric balance is achieved. This is simply accomplished by selectively grinding the interfering buccal and lingual cuspal inclines of the upper teeth. Once the centric contacts have been established it is advisable to use two colours of articulating paper. One colour to mark the centric contacts and other to mark the eccentric contacts. The eccentric contacts are selectively ground until a relatively continuous area of contact is noted on the buccal and lingual cuspal inclines of the upper teeth.

Types of teeth :(Occlusal materials for the single complete denture)The most important aspects is to transmit the occlusal forces vertically. This can be provided with anatomic and non anatomic teeth.

Non – anatomic teeth :If the cusps of the natural teeth have been reduced either naturally or artificially to such a degree that their occlusal surface are fairly flat, then non anatomic teeth maybe used on the denture. These teeth have flat occlusal surfaces with fissures and spillways carved into them which help to provide an effective masticating surface. Setting them against fairly flat lower teeth reduces the tendency for inclined planes to contact in centric occlusion and as a result, occlusal forces are more likely transmitted vertically only. Non anatomic teeth do not provide balanced occlusion in lateral position but a free articulation is usually obtainable.

Anatomic teeth:If the cuspal form of the lower teeth has been retained anatomic teeth can be used. These should be arranged with a cusp to fossa relation.

As the artificial teeth are usually smaller mesio-distally than their natural predecessors. Proper inter digitations should not be sacrificed simply to close the spaces because this would result in inclined plane contacts which could shift denture horizontally. A small space distal to the cuspid looks quite natural in a upper denture, spaces between the posterior teeth provide extra channel for the escape of food from the occlusal surfaces.

Artificial tooth materias :The materials available for occlusal posterior tooth forms are 1)Porcelain, 2)Acrylic teeth, 3)Gold, 4)Acrylic resin with amalgam stop,5)IPN Porcelain teeth :

Porcelain teeth wear slowly therefore the occlusal vertical dimension is maintained however they are predisposed to fracture and chipping when opposed by natural teeth and are more difficult to equilibrate. Since there surface do not mark well with articulating paper. Also they cause rapid wear of opposing natural teeth.

Acrylic resin teeth :Since acrylic resin teeth cause no wear of the opposing natural teeth they are the

easiest to equilibrate. They are the teeth of choice. The major disadvantage of resin teeth is there wear, which result in loss of vertical dimension. How ever wear of the occlusal surface is better than resorption of the alveolar ridge. New dentures can always be made.

Gold occlusal :The best material for an artificial occlusion opposing the natural teeth is gold. A

technique described by wallace in 1964, the denture is processed with acrylic resin teeth and is worn by t he patient for a weeks until all occlusal adjustments have been made an occlusal index of hard stone is made of the denture teeth and is extended on to the denture base posteriorly. The occlusal surfaces of the posterior denture teeth are then reduced by about 1mm and a central channel is cut posteriorly along them. The occlusal index is lubricated and repositioned firmly on the incisors and on the denture base posteriorly and inlay wax is flowed between and the teeth. The wax patterns are cast in gold and cemented with self cure acrylic resin. However their expense and the time involved in their fabrication make them impractical for most patients.

Acrylic resin with amalgam stops :This method is established by Frank R. Lauciello. After the acrylic teeth have

been balanced, occlusal preparation are made in the acrylic teeth, extending it include as much of the articulating paper tracing as is possible. Amalgam is condensed into the preparation and the articulator is gently closed, going side to side and back and forth until the incisal guide pin is again flush with the guide table. This technique is simple and much less expensive and time consuming.

Inter penetrating polymer net work (IPN)

This material minimizes the disadvantage of acrylic resin teeth and porcelain. This material consist of an unfilled, highly cross linked inter penetrating polymer network. A three year clinical study by ogle and his collegues, has determined the wear of new material to be significantly less when compared to acrylic resin teeth.

Potential complication of single dentureTwo most common adverse sequelae include:

1)Natural tooth wear Use of porcelain teeth can lead to rapid wear of opposing natural dentition. Best is to use acrylic resin denture teeth in conjunction with periodic examination

2)Denture fracture Heavy anterior occlusal contact, deep labial freni notches and high

occlusal forces due to strong mandibular elevator musculature Carefully planned occlusion, adequate denture base thickness are

necessary to prevent fracture Still if the fracture potential is high, cast metal base is the best option

Changes caused by mandibular removable partial denture apposing maxillary complete denture :

Another problem is combination syndrome. The syndrome is characterized by

a) Maxillary anterior ridge resorption b) Palatal papillary hyperplasia c) Enlargement of max. tuberositicsd) Supra eruption of lower anterior teeth e) Resorption of mand posterior ridge

Mechanics which produce the combination syndrome : The anterior part of maxilla is the weakest part of the upper arch to resist stresses and when the lower anterior natural teeth occlude the trauma is inveitable. The resorption of bone in the anterior region initiates the changes. As the anterior ridge resorption take place flabby tissue will be formed. As the flabby tissue is formed the anterior part of the upper denture moves up during function. Because it is a single unit as the anterior part moves up posteriorly it comes down. Because of this negative pressure developed posteriorly leads to papillary hyperplasia and enlargement of maxillary tuberostitics.

Posterior part of the lower ridge resoprtion is due to the upper unstable denture. As this continues the occlusal plane migrates superiorly in the anterior region and inferiorly in the posterior regions. There will be supra eruption of lower anterior teeth. The upper anterior teeth disappear under patient’s upper lip. The esthetics are poor with

the patients showing none of the upper anterior teeth and too much of the lower anterior teeth and the upper posterior teeth.

Prevention of the combination syndrome :Patients education :

The problems and how to over come those problems should be explained to the patient. the patient must be made aware of necessary oral hygiene procedures and the problems involved with retention and stability of the prosthesis.

Food should be cut into small pieces and chewed slowly. Patient should visit the dentist frequently, that time the denture and the tissues

underlying should be carefully checked and necessary correction should be done in the denture. If necessary, surgical intervention of the tissues underlying may be planned.

CONCLUSION :The problems involved in providing comport, function, proper esthetics and

retention is a vigorous challenge for practising dentist. The damage to the edentulous ridge and inability to wear the denture may be avoided by good prosthetic treatment which include adequate denture base, correct jaw relation record and proper occlusion.