use of functional appliances in general dental practice

Journal of Contemporary Dentistry October-December 2011 | Vol 1 | Issue 2 21

IntroductionAssuming that one subscribes to the theory that movingteeth is easier than moving bones, it follows that thedegree of success in rearranging relationship of jawbones will be decided by attempting corrective stepswell before peak-growth-velocity is over. Thus, latemixed dentition may be the best period for a clinicianto aim to start correction of the commonest problem:large overjet (8-10 mm and beyond) often accompaniedby deep overbite, narrow maxillary dental arch,recessive chin and a seemingly prognathic or, betterstill, an almost normal maxillary element.Such Class II type of cases may be ideal ones for aGeneral Dentist (GD) to familiarize himself with inusing Myofunctional Appliances (also referred to asFunctional Appliances). Class III cases are as such more

difficult ones to treat and hence should be avoided atleast initially.Though functional appliances are also of a fixed variety,the authors strongly recommend use of the removabletype for their minimalistic iatrogenic-damage-potential(operator-induced-damage-potential).

Functional AppliancesThese are muscle motivating appliances, often loosefitting, which harness the natural forces of the orofacialmusculature that are transmitted to the teeth andalveolar bone through the medium of the appliance.Commonly used Functional Appliances includeAndresen's Activator12,13 (Fig.1), Balter's Bionator14

REVIEW ARTICLE

Use of Functional Use of Functional Use of Functional Use of Functional Use of Functional Appliances in General Dental PracticeAppliances in General Dental PracticeAppliances in General Dental PracticeAppliances in General Dental PracticeAppliances in General Dental Practice

Girish R. Karandikar1, Anita G. Karandikar2, Madhur Vasudev Navlani3

AbstractAlthough most malocclusions pertaining to irregularities of teeth resolve through moving teeth, occasionalmalocclusions confront us with a disharmonious inter-jaw-relationship owing to faulty size and/ or faulty antero-posterior location of the jaws or dentoalveolar regions. These malocclusions do not always respond favorably toconventional tooth moving appliances and are ideal candidates for appliances that have the capability of moldingbones as well as relocating them. Through this article, the authors outline a way that General Dentists can getenough 'food for thought' for treating such cases on their own by using simple removable appliances. Additionalreading/training may be needed to get to use the functional appliances with felicity.

Key Words: Skeletal pattern, Growth amount, Growth direction, Construction bite, Appliance manipulation

Professor and Head1

Department of OrthodonticsM.G.M. Dental College and Hospital, Navi Mumbai

Professor2

Department of OrthodonticsYMT Dental College, Kharghar, Navi Mumbai

Senior Lecturer3

Department of OrthodonticsModern Dental College & Research Centre, Indore

Address for Correspondence:Address for Correspondence:Address for Correspondence:Address for Correspondence:Address for Correspondence:Dr. Girish R. KarandikarDepartment of OrthodonticsM.G.M. Dental College and Hospital, KamotheNavi MumbaiE-mail: [email protected]

Fig.1 : Activator

(Fig.2), Frankel Appliance16,17 (Fig.3, 4), Clark's TwinBlock10 (Fig.5), etc.

22 Journal of Contemporary Dentistry October-December 2011 | Vol 1 | Issue 2

Fig.2 : Bionator

Fig.3 : Frankel's Appliance for correction of Class IIs

Fig.4 : Frankel's Appliance for correction of Class IIIs

Fig.5 : Twin Block Appliance

Fig.6 : Cephalostat, the head holding devisefor taking Lateral Cephalograms

Fig.7 : Patient's headpositioned in the Cephalostat,

Side View

Fig.8 : Position of ear-rods& Fronto-Nasal Rest,

Front View

Karandikar et.al. : Use of Functional Appliances in General Dental Practice


Why Functional:Why Functional:Why Functional:Why Functional:Why Functional:Irrespective of which functional appliance it is,functional appliances are all based on same basicprinciples (application, redirection and removal of force),that of using Function Forces & of alternating theirdirection, strength & duration. All of these appliancesare all muscle controlled even if screws & springs arebuilt in.

Development of Functional Development of Functional Development of Functional Development of Functional Development of Functional Appliances:Appliances:Appliances:Appliances:Appliances:A major reason was recognition that function had aneffect on ultimate morphologic structure of dentofacialcomplex1. Moss's Functional Matrix Theory2,contributions of Wolff on form & function, studies onresponse of bone to functional forces by Kock,Benninghof and ideas of Van Der Klauuw allcontributed in seeking to change and control thedirection of growth of the jaws in correcting imbalancein the skeletal jaw bases.

These studies and several others paved a way inproving that function plays a very important role incontrolling size & shape of bones in the membranousbones of craniofacial area and especially more so inregions of the alveolar base of jaws.

Effect of Functional Effect of Functional Effect of Functional Effect of Functional Effect of Functional Appliances:Appliances:Appliances:Appliances:Appliances:Functional Appliances are unique not solely due to theirpurported orthopedic effect influencing facial skeletonof growing child in condylar & sutural areas as claimedby several experts. They also exert an orthodontic effecton dentoalveolar area. Unlike conventional applianceswhich act on teeth using mechanical elements,functional appliances act on dentoalveolar structuresby transmitting, eliminating or guiding natural forcesproduced during various functions e.g. Swallowing,Mastication, etc.

Functional Appliances help to reset the alteredequilibrium of the orofacial musculature and often helpin elimination of oral habits whilst being an effectivepost-treatment retention appliance in certain types ofcases too.

Case Selection & Issues with Diagnosis &Treatment PlanningFunctional Analysis11 is a very important cog, in thewheel of success while using Functional Appliances.The reader is encouraged to be conversant with thenuances involved herein before attempting to treatcases.

Other important issues are:

The diagnostic criteria used to determine thegrowth pattern (both antero-posterior and vertical)in a case.

Status of lower anterior teeth (in terms ofproclination or crowding prevalent).

Judging the efficacy of the expected clinical result(clinical VTO).

Understanding the principles of, and taking aproper Construction Bite12.

Despite being seemingly easy to use, functionalappliances need proper case election criteria to befollowed and, above all, a cooperative patient toachieve the needed degree of success.

(1)(1)(1)(1)(1) Judging the Skeletal PatternJudging the Skeletal PatternJudging the Skeletal PatternJudging the Skeletal PatternJudging the Skeletal Pattern

The purpose of this step is to determine if a case belongsto the correct type in being treated with a RemovableFunctional Appliance.

This calls for routine lateral cephalometric skeletalevaluation using suitable simple analysis for judgingthe skeletal discrepancy between the upper and lowerjaws. Any standard textbook in Orthodontics 3,4 5,7,10, 12,13

will help the reader to reacquaint themselves of thesebasic facts.

If a Cephalostat (Fig.6, 7, and 8) is not available, then,a True Lateral X-ray of the Skull and Mandible takenfrom the right side with a film-to-focus distance of 5feet can be made use of.

(a) Antero-posterior Dimension:Antero-posterior Dimension:Antero-posterior Dimension:Antero-posterior Dimension:Antero-posterior Dimension: The normal ANBrelationship is about +2° with the plus signindicating that maxilla is ahead of the mandible.

Ideally, in treating Class II cases with removablefunctional appliances, the antero-posterior positionof maxilla should be more or less normal and themandible should be retro-positioned in theirrelationship to the anterior cranial base: thussetting up a large ANB value in the angularmeasurements.

Thus, all things being equal, cases with a SNAvalue that is normal or near normal for a child atthat age with a concurrent ANB value of upwardsof about +5° are ideal (as this indicates that themaxilla is normal and the mandible is retro-positioned) for intervention with a functionalappliance.

(b) VVVVVertical Dimension:ertical Dimension:ertical Dimension:ertical Dimension:ertical Dimension: For easy recall, in lateralcephalometric analysis, this information is divulgedby angular measurements FMA, GoGn-SN andMaxillo-Mandibular Plane Angle (Basal Angle). Forexample, while using FMA values, the normal is25°. When the face is more oval or long: makingthe nose-to-chin-distance increase substantially,this value increases to well beyond about 30° forthe condition to be termed as a High Angle Case.On the other hand, when the nose-to-chin-distanceshortens this angular value reduces well below 21°or so for the case to be described as a Low AngleCase.



Genesis of a VGenesis of a VGenesis of a VGenesis of a VGenesis of a Vertical Problem:ertical Problem:ertical Problem:ertical Problem:ertical Problem: Consider thefact that as a child starts to mature in the dento-facial area, the chin position is governed by growthin the dento-alveolar areas of posterior teeth. Thisis akin to creating premature contacts posteriorly,or, as in a situation created by progressive verticaleruption of teeth. Hence, the chin tends to swingdownward and backwards: making it assume aretrognathic character. This is counterbalanced bygrowth in the mandibular condylar area whichtends to make the chin go upwards and forwards:making it assume a prognathic character. Whenthe mechanism works well in unison, the result isa normal, balanced face. When growth in posterioralveolar areas radically exceeds that in the condylarregion, the result may be a High Angle Case witha longish face. If the roles are reversed, a Low AngleCase may be the outcome.All things being equal, best cases to start withFunctional Appliances are when the FMA value iswithin the normal range: between 22° to 28° or so.

(2)(2)(2)(2)(2) Status of Lower Incisor TStatus of Lower Incisor TStatus of Lower Incisor TStatus of Lower Incisor TStatus of Lower Incisor TeetheetheetheetheethSince the construction bite is taken in a protrusivemode for Class II cases, there is always a tendencyfor the lower anterior teeth to be proclined. Hence,in case selection, an important criterion is thatthe lower anterior teeth should be either 'straight'(sometimes also called as 'upright') or evenRetroclined rather than be in a state of proclination.There should also be absence of any lower incisorcrowding.

(3)(3)(3)(3)(3) Positive Clinical VTOPositive Clinical VTOPositive Clinical VTOPositive Clinical VTOPositive Clinical VTOVTO stands for Visual Treatment Objective. Inessence, this clinical test is an advance indicationof the projected/anticipated efficiency of theattained result. Since it is a very accurate way todetermine if the treatment result will make apositive effect on the personality change attempted,it is an invaluable clinical advance planning toolin clinical practice: especially since it does not needany specialised equipment.

When a patient with large overjet is to be treated witha functional appliance, the clinician needs to:

(a) Have the patient sit upright facing the clinician.Patient must be at rest with the lips in theirnormal unstrained position and the teeth in theCentric Occlusion. If the patient can be relaxedenough to give a physiological rest position, so muchthe better. Patient is now observed and preferablyphotographed from the:

The Frontal aspect The Profile view

This gives us an accurate depiction of the patient'sfacial features before treatment.

(b) Now, the patient is taught/trained to get his LowerCentral Incisor teeth in an edge-to-edgerelationship with the Upper Central Incisor teeth:a position that he will be made to assume whenbeing treated with the functional appliance. Hethen holds/maintains the teeth in the sameposition. Patent is made to drape the lips on thenewly positioned teeth with minimum possiblestrain reflected in them. Photographs are thentaken again from the:

The Frontal aspect The Profile view

This position reflects the likely looks that the patientwill exhibit at the end of treatment with FunctionalAppliance.

(c) The photographs taken in natural rest position (asin "a") are then compared with those taken in theprotrusive (as in "b").

(d) If the patient's facial features show a markedimprovement between the two sets of photographs("a" v/s "b"), the patient is said to have shown a +ve

Clinical VTO and therefore is a good candidate forbeing treated with a suitable functional appliance.

(4) Construction Bite(4) Construction Bite(4) Construction Bite(4) Construction Bite(4) Construction Bite

The case-attributes that we are contemplating ontreating with Functional Appliance shall have asignificantly large over jet. This will be attempted tobe corrected by following the well laid out principlesof registering a Construction Bite12 using modellingwax.

Although there are several ways and philosophies inthe precise way of registering a construction bite, inits simplest form, the same can be broken down into:

(a) This involves training the patient to achieve themaximal protrusive relationship of the lowerincisors, and then staying at least 3 mm lessprotrusive (or, behind/distal) to this maximumprotrusive position while registering the Bite onwarm roll of horse-shoe-shaped wax.With the construction bite passively in the mouth,the patient's face should look decidedly better (asin when Clinical VTO is taken).If the patient has an overjet that is greater than 6-8 mm, often, it is necessary to advance the mandiblein two stages. However, this entirely depends upona patient's ability of giving a maximal-protrusive-posturing of lower jaw. Sometimes, it may be OKto jump even 10 mm in a one-step-bite.

Care should be taken to ensure that:

i. Upper and Lower dental midlines coincide/match



ii. While correcting the midline, there should be noposterior cross-bite created artificially by abnormalposturing of the mandible while taking theconstruction bite.

iii. The vertical separation between molars on left andright sides is equal.

iv. The vertical separation in molar region should beat least 3-4 mm.

(b) This construction bite is then used for the lab tomount the casts on a non-anatomical articulatorto fabricate the appliance using self curing acrylicresin with a salt-and-pepper technique.

(5)(5)(5)(5)(5) Appliance fabrication pre-requisites:Appliance fabrication pre-requisites:Appliance fabrication pre-requisites:Appliance fabrication pre-requisites:Appliance fabrication pre-requisites:

a) The impressions taken must be:i. Deep and should register the Labial and

Buccal vestibules in totality.ii. The lingual pouch area should also be very

well registered.iii. Made in duplicates so that another set of

casts are available to check the accuracyof fit of the fabricated appliance, etc.

b) The casts must be:i. Made out of the impressions at the soonest

so that dimensional inaccuracies do not getintroduced through syneresis andimbibitions.

ii. Made using good quality Dental Stoneiii. Without blemishes like air-bubbles or

voids.

c) Undercut Areas, especially on the lingual sideshould be blocked out with wax prior toacrylisation.

(6)(6)(6)(6)(6) Choice of Myo-functional Choice of Myo-functional Choice of Myo-functional Choice of Myo-functional Choice of Myo-functional ApplianceApplianceApplianceApplianceAppliance

Amongst the commonly used Functional Appliancesare Andresen's Activator12,13, Balter's Bionator14,Frankel Appliance16,17, Clark's Twin Block10, etc.

Generally, choice of appliance is an operator drivenissue rather than it being a case-specific one. Otherfactors like concurrent need for expansion of dentalarches; need to use extra-oral forces in tandem withthe functional appliance therapy, availability of labback-up, patient compliance etc., are some vital issueswhich determine which appliance is preferred by aclinician.All in all, the attributes of a typical Class II Division ICase to be treated well before peak growth velocity isreached should be: Mixed Dentition Phase: early, mid, or, late (in the

same preferential order of chronology). Secondpermanent molars yet to erupt.

Normal Maxilla with retro-placed mandible (asconfirmed by Lateral Cephalometric Analysis).

Normal Vertical Growth Pattern. Lower Incisors: no proclination, no crowding/

rotations. Large overjet of upper anteriors. 'V' shaped, narrow maxillary dental arch with

narrowing in cuspid region. A positive Clinical V.T.O.

Mode of Action of Functional AppliancesSeveral experts 3,4,5,6,7,8,9 have propagated proper theorieswith a scientific base: all with significant variation inviews to pin down the exact mode of action.

The authors wish to take a very simplistic model to explainto a GD the mechanism of Class II correction withFunctional Appliances.

Consider a typical case: growing child well beforeattaining peak-growth-velocity, having a large overjet,narrow maxillary dental arch with distinct constrictionin the cuspid-premolar area, deep overbite with anaccentuated curve of Spee and a near-normalmandibular dental arch with a non-contracted archform. The mandible, per say, is normal but is locatedway behind/posterior to the maxillary unit(distocclusion).

In such a situation, the narrowness of the maxillarydental arch in the cuspid-premolar area does not permitthe lower anterior teeth to go forward by translation ofthe mandible which should be occurring when growthat the mandibular condyle occurs.

This is a bit like person who wears size 10 shoes tryingto get into a shoe that is size 4. The wide foot can goonly part of the way before the narrowness of the size4 shoe prevents the foot from going any further. Thus,a lot of the size 4 shoe will be unoccupied by a foot thatis normally clad in size 10 shoe. This empty space insize 4 shoe is akin to the large overjet in the narrowmaxilla that the wide foot (mandible) is unable to getto occupy due to the narrowness of the shoe's opening(narrow inter-canine-width) in maxillary dental arch.

This results in a Class II occlusion and a retrognathicprofile. The lower anterior teeth often become moreupright and sometimes even Retroclined as acompensatory effect.

Expansion of the maxillary dental arch is hence neededeither before or concurrent to use of functionalappliances for the mandible to relocate anteriorly.

Simply put, narrowness of the maxillary arch has tobe circumvented for the 'normal' growth potential ofthe mandible can be given a chance to 'catch-up' withthe maxillary growth or, 'jump' ahead to correct thebite (more like releasing the brake of a car on a slopewill allow it to move forward at a fast pace). This isoften called as 'jumping the bite'.



This circumventing is achieved through theconstruction bite. The mandibular teeth are made toassume a near edge-to-edge-relationship with themaxillary incisors: thereby taking the posterior teethout of occlusion. Maxillary teeth are thus now ready tobe expanded by a suitable method depending on thetype of functional appliance used.

The construction bite when replicated into a fabricatedappliance locks the mandible into a more protrusiveposition. The retractors muscles of the mandible (lateralpterygoids) thus get activated to try to pull the mandibleback…however, the appliance does not allow this tohappen. The pulling back impetus of the mandible istransferred through the appliance on to the maxilla asa reciprocal effect. At best, the forward and downwardgrowth of maxilla is prevented / retarded. But, themandibular condyle, owing to having been displacedout of its normal position within the glenoid fossa forthe entire time that the appliance is worn thenundergoes reorganizational changes.

If the functional appliance is worn for a sufficientlylong period (long hours every day and night and doingso continuously in excess of 6-8-10 months), the newprotrusive position of the mandible dictated by theappliance then can become the normal position for thepatient. It brings about the needed correction in bothantero-posterior and vertical dimensions.

The concept is similar to a married lady, on staying ather husband's home, over a period of time, gets toidentify and feel comfortable in her new home ratherthan her parental home ('sasural' and maika' to lapseinto colloquial).

Selective grinding (called trimming) of the acrylic ofthe functional appliance aids the condylarreorganizational changes in allowing/guidingmovements in vertical and antero-posterior directionfor the teeth.

Care to be taken in using FunctionalAppliancesWhen used early in a compliant patient, sometimesthe results seem to be attained very quickly: as seenwhen the clinician asks the patient to take off theappliance. However, when used for a shorter period oftime, this apparent correction may be just a transientphase: more due to a dual-bite created rather than apermanent correction.

Therefore, the operator and the patient both need to bepatient in getting the appliance to be used for a muchlonger period (10 months is a good ball-park-figure) forthe gains to be of a permanent nature.

In presence of a familial trait/genetic pre-dispositiontowards unfavorable growth, it is best to keep usingthe appliance for an even longer period: more like a

retention appliance. This may be done by partial use(about 9 hours daily).

It is impossible to make the reader aware of allintricacies of using a treatment philosophy. The readershould look for avenues to take Continuing EducationPrograms to hone their skills before embarking on theexciting journey to treat cases with FunctionalAppliances.

Sometimes, despite the best diagnostic skills, a properchoice of appliance exercised with adhering to all theneeded underlying principles, results are inadequate.The reason for that is best described by a simple GAKprinciple: God Alone Knows!!

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9. WOODSIDE, METAXAS, ALTUNA: The influence offunctional appliance therapy on glenoid fossa remodeling.Am. J. Orthod. Dentofacial Orthop. 1987; 92:181-198.

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12. SAMIR E. BISHARA. Textbook of Orthodontics.Saunders.2001.

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14. REEY R.W, EASTWOOD A. The passive activator: caseselection, treatment response, and corrective mechanics.Am. J. Orthod. Dentofacial Orthop. Am. J. Orthod.Dentofacial Orthop. 1978;73:378-409.

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use of functional appliances in general dental practice

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