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Overbite—the dentist’s challenge
ORIGINAL ARTICLES
Overbite-the dentist’s challenge
T. M. Gräber, DDS, Kenilworth, III
Deep overbite is apparently a combination of evolu tionary skeletal change and morphogenetic pat tern, modified by a variable neurogenic component. The dentist cannot concentrate on the tooth sys tem alone in treating overbite. Harmony must be established between at least four tissue systems— tooth, muscle, bone, and nerve.
With fluoridation, the incidence of caries has been greatly reduced. It is conceivable that a preventive as effective as polio vaccine may be discovered in the near future. If caries is eliminated, with its attendant pulpal involvement and tooth loss, den tal practice orientation will have to undergo a major change. If there is no need to fill or replace teeth, what then? Most periodontal problems will remain, of course, because the likelihood that periodontal disease is a single entity is small. And malocclusion will still be common because morpho genetic pattern is the dominant etiologic factor in malocclusion. Anthropologists show that the jaws are getting smaller and that there is a developing retrusive mandibular pattern as we climb the ladder of
“civilization.” Begg,1 in his studies of Australian aboriginals, shows that many of our ancestors had an end-to-end bite, with almost no overjet. Form and function teamed together to produce a dental apparatus that was well aligned and well balanced, with harmony between the three major tissue sys tems— tooth, bone, and muscle. With diet changes and less interproximal and occlusal wear, there has been an alteration within the tooth system it self. Part of this alteration results from the differ ent functional demands being made on the tooth system by modem refined foods; part is a homeo static or adaptive response to the basal bone mod ifications of successive generations, as elucidated by the anthropologists.2 It is relatively clear that man is developing a greater amount of overjet in his dentition and a significantly deeper overbite. Two thirds of the patients now treated by ortho dontists are in the basal jaw malrelationship cate gory, with anteroposterior discrepancies mirrored in overjet and overbite.3 Excessive overbite is a vertical dysplasia, often associated with problems of overjet,4 but sufficient by itself to produce periodontal disease ramifica tions by virtue of the functional limitations im posed and the abnormal stresses created. It is the purpose of this paper to discuss the various factors contributing to the overbite prob lem so that we may understand better the role of this combined morphogenetic and functional aber ration. A discussion of some of the sequelae of overbite, such as temporomandibular joint dis1135
turbances, is given. Methods of correction and control of overbite problems are described.
The biologic continuum
Fig 1 ■ Diagrammatic representation of balance of head on vertebral column, with continuous chain of postural mus cles maintaining the balance. Even during active functions of speech, deglutition, respiration, and mastication, the postvertebra I, prevertebral, facial, masticatory, supra-, and infrahyoid muscles have active postural component, sta bilizing and counterbalancing.
Fig 2 ■ Postural resting position of mandible establishes 3 - to 4 mm interocclusal clearance between teeth. This postural vertical dimension (PVD) is relatively constant as a muscularly determined entity. When there is an abnormal occlusal vertical dimension (OVD), as in cleft palate casts on the right, interocclusal clearance is much greater and can approach 20 mm in extreme cases. Excessive inter occlusal clearance permits mandibular overclosure (see Fig 8) and concomitant aberrant functional sequelae. 1136 ■ JADA, Vol. 79, November 1969
It is imperative to recognize the dynamic consid erations in the overbite problem and to distinguish the treatment from much of restorative dentistry in which lost parts are replaced with a reasonable facsimile. The muscle and bone systems are natu rally less involved in the technology of amalgam reproductions than in the treatment of malocclu sion. Telemetry and electromyography have shown that the traditional “teeth together” cast examina tion of study models by a dentist does not give a realistic appraisal of the situation. By far the great est amount of the patient’s time each day is spent with the mandible suspended by the cradling mus culature in its postural position, with the postvertebral, prevertebral, facial, and masticatory muscles, and the supra- and infrahyoid muscles maintaining the balance of the head on the verte bral column; the postural relationship of the man dible with the associated structures must also be considered (Fig 1). This postural position is the starting point not only for mastication, but also for deglutition, respiration, and speech. Thus there are two vertical dimensions— the postural vertical dimension (PVD) which is the relationship of the mandible determined by the muscles, and the traditional occlusal vertical di mension (OVD) which is determined when the teeth are brought together in the habitual and maximum contact. It is usually the OVD that is abnormal. In other words, the tooth and bone sys tems that are largely involved in the function of mastication are not in harmony with the muscle system. The vertical dysplasia seen in the static plaster casts, with the teeth clamped together in occlusion, must be approached from the viewpoint of biology. Normally, when the mandible is in postural rest position, and the muscles are continuing to maintain the head in its proper position on the vertebral column, even while an individual is breathing and speaking and swallowing, there is a definite space between the upper and lower teeth (Fig 2). When the teeth are brought into occlusion, the mandible closes upward and for ward from postural rest to full contact. In a nor mal situation, the movement of the condyle is primarily rotary through this 3- to 4-mm distance.
Fig 3 ■ Sagittal section draw ing illu s tra tin g structu re s of tem porom andibular jo in t. There are tw o d is tin c t jo in t cavities. Lower compo n e n t fu n c tio n s p rim a rily in closure from postural rest to habitual occlusion, by con d ylar rota tio n on a rtic u la r disk. In excursive and fu n c tio n a l m ovem ents beyond postural rest position, both elements of a rticu la tio n fu n c tio n w ith rotary condylar movem ent in lower jo in t and w ith translatory movem ent also, as disk and a rtic u la r capsule are brought forw ard by external (lateral) pterygoid m us cle fibers.
BONE C A R T IL A G E L O O S E C O N N E C T IV E T IS S U E S Y N O V IA L L IN IN G CAPSULE DENSE
F IB R O U S
C O N N E C T IV E T IS S U E L A T E R A L P TE R Y G O ID M U S C L E F IB E R S
The temporomandibular joint Anatomy shows that there are in reality, two sep arate articular cavities, with the disk and associ ated ligamentous attachments separating the up per from the lower joint cavities (Fig 3). Injection of disclosing solution into the cavity between the disk and the articular eminence will show that there is no communication with the lower joint cavity between the disk and the condyle of the mandible. Although both joint cavities function in normal opening, with a translatory (gliding) movement of the disk over the articular eminence combined with a rotary action of the condyle on the disk in the lower joint cavity, there is little translation on closing from postural rest to occlu sion. As Blume5 indicates, however, when there is a deficient eruption of teeth and an excessive interocclusal clearance, with the mandible closing
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Fig 4 ■ Superimposed TMJ tracings made at PVD and OVD in cases w ith excessive interocclusal clearance. Note com bined rotary and translatory movem ent of condyle as it moves up and back, under in fluence of do m in a n t posterior te m p o ra lis m uscle activity.
Fig 5 ■ Both tem poralis and masseter m uscles are made up o f fib e r groups, capable of varying co n tra ctio n m agni tude. In normal closure from PVD to OVD, co n tra ctio n in te n sity is approxim ately equal in anterior, m iddle, and posterior tem poralis and su p e rficia l and deep m asseter m us cles (A). W ith overclosure, posterior tem poralis and deep m asseter fib e rs sta rt showing a dom inance over other fib e r groups w ith in the same m uscle (B). W ith severe overclosure, d igastric and geniohyoid m uscles also show increased ac tiv ity , team ing up w ith dom inant posterior te m p o ra lis and deep muscle fib e rs (C). A t th e same tim e, as condyle is sub jected to retruding action by th is type of m uscle a ctivity, stretch reflex is e lic ite d in lateral (external) pterygoid m us cle, w hich has fib e rs in serting in to the a rtic u la r d isk and capsule. C ontraction of lateral pterygoid p u lls a rtic u la r disk forward as condyle is being pulled upward and backward (see Fig 6). Graber: OVERBITE—DENTIST’S CHALLENGE ■ 1137
6, 8, or 10 mm from rest centric instead of the usual 3 or 4 mm, both rotary and translatory TMJ may be demonstrated (Fig 4). Posselt6 has shown that centric relation and centric occlusion are not the most posterior posi tions of the condyle within the total effective move ment pattern. As with any other joint in the body, there is a range of movement. In overclosure, there is frequently a change in the pattern of mus cle activity. The overclosure emphasizes the role of a fourth tissue system, the neurologic system, with the phenomena of proprioception and feed back mechanisms. In normal closing from postural rest to occlusion anterior, middle, and posterior temporalis muscle fibers function with about the same intensity of action, as shown by the electro myograph. This is also true of the deep and super ficial fibers of the masseter muscle. The medial pterygoid muscle also functions as a unit in nor mal closure. In overclosure, the OVD is out of harmony with the PVD and it may be shown that the posterior temporalis fibers, as well as the posterior masseter fibers, become dominant in the closing maneuver (Fig 5). With this dominant retrusive force, the posterior and superior transla-
F ig 6 ■ Condylar a c tiv ity from (1) open m outh to (2) postur al resting p o sitio n is norm ally rotary and translatory in character. From (2) PVD to (3), condylar action is norm ally rotary unless there is overclosure. Then, as Figure 5 shows, d o m in a n t posterior tem poralis m uscle a ctivity exerts up ward and backward p u ll on condyle, causing translatory a c tiv ity a fte r p o in t o f in itia l incisal contact has been passed. 1138 ■ JADA, Vol. 79, November 1969
tory movement shown in Figure 6 is a reality. As the anatomist knows, the protractor for the articular disk in the TMJ is the lateral pterygoid muscle. Fibers from this muscle insert into the disk and capsule. However, no muscle serves as an articular disk retractor. Only the integrity of the capsular ligaments, maintaining proximity of disk, condyle, and eminence, guides the posterior movement on closure. When there is overclosure and a retrusive activity of the dominant, deep masseter and posterior temporalis fibers, a stretch reflex is elicited on the external (lateral) pterygoid muscle. With stretch reflex, there is contraction, or muscle spasm. The disk is held in a forward posi tion whereas the condyle moves upward and backward because of the feedback phenomenon and posterior temporalis muscle-fiber action. The condyle, riding over the posterior periphery of the disk, then impinges on the postarticular connec tive tissue. The postarticular tissue is supplied by nerve fibers from the auriculotemporal nerve and is less well adapted to stresses of mandibular func tion. The joint structures may adapt to the deviate activity for a while (homeostasis), but with con stant stimulation of stretch reflex, forward pull of the disk, impingement on the postarticular con nective tissue, muscle spasm, and overclosure these structures may not continue to adapt indefi nitely. Proprioception cannot handle the aberrant feedback signals issued by the neural system. Ir ritation and lack of harmony of the structures is clinically observed in the form of clicking and crepitus. This condition can be mistaken for arth ritic changes and treated improperly with meniscec tomies and injections. In reality, this functional abnormality is associated with excessive overbite, homeostatic or compensatory muscular adapta tion, dominance of the posterior fibers of the temporalis muscle, retrusive condylar thrust, and the inability of the structures to adapt completely to this abnormal translatory movement through the usual neuromuscular, proprioceptive “feed back” channels. An important part of the TMJ malfunction syn drome is the neurogenic or neurologic background. It has been shown repeatedly that the mouth is not only an erotogenic zone, and an area for emo tional expression for the infant, but that it also serves to gratify tensional stresses in the adult. The widespread phenomena of bruxism and clenching show positive correlation with increasing levels of nervous excitability. So there is a psychogenic su perstructure imposed on the functional and mor
phologic abnormalities which stem from the orig inal lack of harmony of the O V D with the muscularly determined PVD. Clinical experience has shown that there is a high incidence of bruxism and clenching associ ated with overbite (Fig 7). Evidences of bruxism are seen early in the deciduous dentition of many children and the damage can be quite considerable. It is difficult to assign precise values to the neu rologic component and to the overbite and mal occlusion components. Undoubtedly they vary from individual to individual and from time to time within the same individual. There is a higher incidence of bruxism in female patients. The dam aging consequences of the cyclical, rending, noc turnal, spasmodic activity are clearly evident in the polished facets of wear on the teeth.
in the lower joint cavity. Then there should be no need for compensatory and adaptive muscle activ ity so that the anterior, middle, and posterior temporalis fibers will function at approximately the same intensity. Interceptive occlusal contacts will not exist to incite aberrant feedback phenom ena. But, since deep overbite apparently is a com bination of an evolutionary skeletal change and
Correction and control Since the deep overbite, then, is a lack of harmony of the two vertical dimensions, since it is usually the OVD that is abnormally related and responsi ble, since deep overbite means mandibular over closure, and since overclosure leads to abnormal functional patterns, what can be done about it? First, the abnormal function may take the path of bruxism and clenching; it may take the path of excessive destruction of tooth material; it may be manifested in limited excursive movement; or it may result in frank TMJ disturbances, with mus cle spasm, clicking, crepitus, pain, and even trismus. Clearly, the challenge is to establish an OVD in harmony with the PVD, eliminating occlu sal interferences at the same time. If this is done, then there will be no overclosure, and the move ment from postural rest to occlusion will be large ly a rotary action of the condyle against the disk
F ig 7 ■ Four patients w ith bruxism associated w ith exces sive overbite. All age groups are affected and show evi dence of g rin d in g and clenching. Note w earing away of canine in (A) and (B); deciduous m olar d e stru ctio n (C) and (D); severe incisor damage in an a d u lt (E) and (F); in ciso r wear and gingival recession associated w ith abnorm al fu n c tio n a l forces (G) and (H).
Fig 8 ■ Lateral cephalogram s of c le ft palate p a tie n t w ith severe growth arrest. In postural resting p o sition (PVD), note very large interocclusal space of 20 mm. Overclosure a ffe c ts anteroposterior jaw relationship, crea tin g an apparent m andibular prognathism (B). Restoration o f OVD in har mony w ith PVD by p ro sth e tic means also establishes more harm onious anteroposterior relationship, reducing seeming m an dibular protrusion (C). Graben OVERBITE—DENTIST’S CHALLENGE ■ 1139
Fig 9 ■ Use o f b ite p la te to help elim in a te excessive overbite in late deciduous d e n tition . In te r m itte n t use of b ite p la te fo r fiv e years has reduced overbite and also allowed s ig n ific a n t m andibu lar intercanine growth (A). Excessive overbite tends to c o n s tric t in ciso r segm ent in lower arch, crea tin g arch length deficie n cie s and preventing fu ll accom plishm ent of intercanine arch length increase (B) and (C).
morphogenetic pattern, as modified by a variable neurogenic component, how can it be helped? In a child with cleft palate who has had early and traumatic surgery that interferes with maxil lary growth, the interocclusal clearance may be 12, 15, or even 20 mm7 (Fig 8). Establishing a correct OVD that is harmonious with the PVD in these severe dysplasias is beyond the realm of orthodontic therapy and requires prosthetic cor rection. But in the average dental patient, the mag nitude of overbite is not as great and the objective, hopefully, is to stimulate all possible eruption of the teeth to reduce the interocclusal clearance. Fixed orthodontic appliances are capable of doing this at the right time and under proper control. However, such appliances may not be indicated for a variety of reasons particularly in the decidu ous and mixed dentitions. What else can be done? As Mathews8 has shown, the use of a palatal biteplate may be beneficial (Fig 9). When this acrylic resin and wire appliance is worn, it pre vents the posterior teeth from meeting in occlu sion. With only the lower incisors contacting the acrylic plane, it reduces the intrusive forces on the posterior teeth. If the mandible is prevented from going into a functional retrusion with dom inant posterior temporalis muscle activity, there is less likelihood of abnormal deglutitional or “reverse swallow” activity. The tongue lies lower on the floor of the mouth and spreads somewhat less laterally so that there is less chance of its pre venting eruption of the posterior teeth. Restric tions on normal growth and development are eliminated. As has been shown, overclosure may actually result in a functional retrusion of the mandible which creates a Class II malocclusion. In the nor mal course of events, with the terminal plane rela tionship of the deciduous teeth, an end-to-end cuspal relationship is already to be expected in 1140 ■ JADA, Vol. 79, November 1969
many instances.9 A functional retrusion can con vert a Class II tendency into a full Class II buccal segment relationship. By working with the nor mal processes of growth, development, and change that occur especially in the mixed dentition, the elimination of abnormal perioral muscle activity and the stimulation of eruption of posterior teeth is at least a step in the right direction. It reduces the harmful effects produced by excessive overbite and functional abnormalities. Complete success is seldom to be expected with biteplate therapy, but significant improvement may be observed. Lateral cephalograms taken before and after biteplate wear (Fig 10) show a significant antero posterior change that was achieved merely by eliminating the functional retrusion. The activator or monobloc, worn in the mixed dentition by many children— in Europe particu larly— serves a purpose similar to that of the bite plate with inclined plane; it prevents overclosure and the retrusive muscle activity tendency.10 Even the lower incisors may benefit and an appreciable intercanine dimension increase has been seen with properly chosen patients who give a high level of cooperation (Fig 9). Thus a biteplate (Fig 11) is both preventive and corrective during the child’s period of growth. If there is a habit of bruxism (and this is much more frequent than we once thought) the bite plate again serves as a valuable preventive ad junct. It prevents the “trigger area” from starting the “rending and gnashing” cycle that is so dam aging to the teeth. Any grinding that takes place is usually manifested on the flat acrylic plane be hind the maxillary incisors. Indeed, the same biteplate may be used in the adult dentition for the prevention of bruxism and clenching, with con sistently good results. In most instances, a biteplate produces only partial correction of the overbite problem. Gen-
Fig 10 ■ Tracings of lateral cephalograms o f p a tie n t before (le ft) and a fte r (rig h t) w earing biteplate fo r three and a h a lf years. Note decided reduction in interocclusal space and reduced condy lar retrusion in habitual occlusion a fte r b iteplate was worn.
Fig 11 ■ M axillary b iteplate, w ith conventional .032 inch labial bow and v e rtica l spring loops a t canines. Ball clasps are illu stra te d , b u t circu m fe re n tia l or arrow clasps work equally well (top). Drawing shows cross section o f palatal a crylic portion w ith b ite opening plane behind incisors (bottom ). A crylic portion indicated by arrow m ust be c u t away to retra ct incisors or if th e re is irrita tio n a t the g in g i val m argin. Labial bow (arrow) helps sta b ilize appliance and prevent labial m ovem ent o f incisors.
<5= Graber: OVERBITE—DENTIST’S CHALLENGE ■ 1141
CLICKING OF TH E JO IN T ON MOVEMENT LIM ITED MOVEMENT (IN C L LOCK-JAW ) PAIN IN OR ABOUT THE EARS PAIN ON MOVEMENT HEADACHE TENDERNESS ON PALPATION TIN N ITU S EXCESSIVE MOVEMENT MILD CATARRHAL DEAFNESS PAIN OVER VERTEX, OCCIPUT, OR POSTAURICULAR AREAS NEURALGIA MAX. MAND. S NECK
Fig 12 ■ TMJ disturbance sym ptom s in order o f th e ir greatest frequency, based on co m p ilatio n of results o f sev eral investigators.
erally, the vertical dysplasia is related to an ante roposterior problem such as a Class II type mal occlusion. Although the functional retrusion may be eliminated, there is still a Class II morphoge netic pattern apparent. Conventional orthodontic therapy is required, but the severity of the maloc clusion has been reduced and the appliance and time demands may be significantly less. If there is a deep overbite to start with, the wearing of a biteplate can seldom do any harm. Obviously, orthodontic consultation is strongly recommend ed beforehand and on a continuing basis if bite plate application is under the control of the gen eral practitioner.
The crutch theory After growth and development are complete, over bite correction with a biteplate is seldom possible. Only partial success may be expected and the over bite returns if the patient stops wearing the appli ance. Yet the damaging effects of an excessive overbite are quite obvious to the periodontist, in particular. Corrective lenses do not eliminate the basic visual abnormality for the person who wears glasses. They merely serve as a “crutch” through out life, allowing him to live with his defective vision. If overbite can be prevented by the wear ing of a biteplate, the same “crutch” theory may apply. Particularly in instances such as that shown in Figure 7, where the sequelae of deep overbite are excessive wear, TMJ disturbances, periodon tal involvement, bruxism, neurologic manifesta tions, and so forth, the biteplate allows the patient to live with the situation in reasonably good den tal health. Obviously, periodontal care must be concurrent and routine for optimum results. 1142 ■ JADA, Vol. 79, November 1969
If a full-mouth reconstruction is contemplated, the wearing of a biteplate initially, before any work has been done, will often determine the proper vertical dimension— from both a comfort and a physiologic viewpoint. As a diagnostic splint, the biteplate allows the dentist to use one of the best tests of all— a functional exercise— before he initiates mechanical procedures based on articu lator determinations. It must be emphasized again that harmony of four tissue systems (bone, tooth, muscle, and nerve) is absolutely essential.
Temporomandibular jo int disturbances It has been stressed that many, though not all, TMJ disturbances result from a lack of harmony of the OVD with the muscularly determined PVD. Interceptive contacts, tooth guidance, and improp er restorations are also contributing factors.11 Nev ertheless, excessive overbite, with its resultant dominant posterior temporalis muscle activity, in creased deep masseter fiber contraction, and pos sible “assists” from the digastric and geniohyoid muscles, may contribute significantly to the ob jective symptoms. The overclosure and posterior condylar thrust may elicit a stretch reflex in the lateral pterygoid muscle and stimulate reciprocal muscle spasm in other muscles associated with the stomatognathic system through the proprioceptive feedback network. The resultant clicking-crepitusmalfunction syndrome produces identifiable symp toms, as shown by Posselt6 (Fig 12). Very likely, the patient’s psychogenic superstructure and indi vidual tooth malpositions team up with the ab normal OVD to produce the net result. Myocitis may also be a factor. Clinical experience shows that these symptoms are four times more frequent in women than in men. TMJ therapy is illustrated by the following hypothetical case. Mrs. Jones, age 38, is referred by the orthopedic surgeon who had been injecting a sclerosing solu tion and cortisone into the temporomandibular joint, along with a pain killer. The question of a meniscectomy had arisen and a dental consulta tion was suggested. Mrs. Jones has a Class II, Division 2 type malocclusion (Fig 13) with ex cessive overbite and a functional retrusion; she has headaches and occasional pain radiating up over the temporal region. Palpation demonstrates clicking, crepitus, and limited motion during the opening maneuver. A stethoscopic examination of the joint area
Fig 13 ■ Deep overbite and m an d ib u la r retrusion w ith concom itant TMJ sym ptom s in a d u lt woman (a,b,d) and man (c,e,f). B ite p la te w ith fla t plane behind incisors (d) establishes OVD in harm ony w ith PVD. D om inant posterior tem poralis muscle fib e r p u ll is reduced, and fu n ctio n a l retrusion is e lim inated. C lickin g , crep itu s, and pain are greatly reduced.
substantiates the grating or grinding that may be picked up through palpation of the TMJ region.12 Palpation usually is adequate to appraise varying activity of muscle components in severe cases (posterior temporalis hyperactivity, for example), but electromyography would be required to dis cern contraction differences in the majority of pa tients. A functional analysis shows heavy facets of wear on the incisal margins of the mandibular in cisors and on the lingual surfaces of the maxillary incisors. The patient is apprehensive and nervous. When Mrs. Jones is asked to move her mandible forward so that the upper and lower incisors meet
end-to-end, and then open and close to this posi tion, there is one unlocking “pop.” Then move ment is free of the grinding and grating and popping that occurs in the habitual occlusal position. Even the stethoscope cannot demonstrate excessive joint noise. Moving the condyle forward thus es tablishes a correct relationship with the articular disk. In almost all TMJ disturbances, the same re action will be seen. It is indicative of the com bined functional retrusion and posterior tempo ralis activity, in conjunction with the stretch re reflex of the external pterygoid, that holds the disk forward. Since it is the pounding of the postGraber: OVERBITE—DENTIST’S CHALLENGE ■ 1143
Fig 14 ■ Patients who have lost OVD in posterior segments may dem onstrate increased a c tiv ity of clo sin g m uscles, w ith condyle being pulled upward and back. A ddition of a crylic resin over o cclu sal surfaces may be necessary fo r posterior support, to break up m uscle spasm tendency and estab lish new proprioceptive stim u li (a,b,c). In some cases, m andible m ust also be guided forw ard and a n te rio r guide plane placed behind m axillary incisors, to guide m andible forw ard; posterior sup p o rt is provided in te rm in a l closing position (d,e,f).
articular connective tissue which apparently in cites the pain and trismus, a splint is required to prevent overclosure, and to guide the mandible into a slightly forward position within the normal functional range, thereby preventing the elicita tion of the stretch reflex and the aberrant neuro logic feedback, muscle spasm, and clicking. A splint, similar to a Hawley biteplate (Fig 11), is constructed to be worn at all times. In addition to a combined pain killer and tranquilizer, wet 1144 ■ JADA, Vol. 79, November 1969
heat applications are prescribed for the painful joint area. A muscle massage unit is frequently beneficial when applied to masseter and tempo ralis areas. The patient is to apply heat and mas sage for 15 minutes on arising and on retiring. As with any other malfunctioning joint, limited use and maximum rest are required. Diet is kept soft or semiliquid for the first three or four days; there after, the patient may choose soft foods but the mandible is kept in its open, slightly protruded po
sition most of the time by the splint. Isometric ex ercises are sometimes prescribed after several days; the patient moves the mandible forward and brings the teeth together in forced closure for a two- to three-minute period. Mrs. Jones, if she is like most TMJ patients, will lose the objective symptoms within the first three to seven days. If she stops wearing the bite plate, however, they may return fairly soon. Hence, the biteplate is worn on a gradually re duced schedule; within two weeks, wear may be limited to sleeping hours. In most instances, the splint, together with a conservative use of heat and massage, is adequate to control the problem. Where there has been loss of posterior teeth, the condyle tends to be thrust upward and back ward in the articular fossa by the dominant poste rior temporalis activity. The flaccidity of the ar ticular capsule and ligaments may be a factor. In these instances, the modified Hawley biteplate may have to include posterior acrylic occlusal cov erage, which literally “blocks open” the bite and reduces the luxation of the condyle (Fig 14). This posterior acrylic cover for the occlusion is neces sary in only approximately 20% of the instances of TMJ disorder, however. Generally, the conven tional biteplate, with a slightly inclined plane to keep the incisal edges in proximity and the poste rior teeth apart, is adequate. If bruxism and clench ing are habitual, this biteplate serves to eliminate their deleterious effects; it suppresses the vicious cycle of neurologic feedback abnormality, at least while it is being worn. After the patient is com fortable, full-mouth reconstruction may be con templated. Or, the biteplate may be Worn on a diminishing-time basis at night. Experience has shown that this type of appliance may be worn for an indefinite period if the patient is under con tinued dental guidance for conservative tissue con trol, and if acrylic resin is added periodically and clasps are checked, and so forth. As with contact lenses, these appliances can be worn for a consid erable time with no harmful effects, if they are properly fitted and maintained. Indeed, where there has been bone loss and re sultant flaring of teeth, the biteplate serves as an essential adjunct for the periodontist. It may be used to retract incisors, close spaces, and to posi tion teeth in their best axial inclination for opti mum stress reception in the vertical direction through the long axis of the teeth. Here again, the “crutch” theory is a valid one. It should be empha sized that continued periodontal tissue control is important. Equilibration, cleaning, scaling, polish
ing, astringent packs, and so forth, enhance the establishment of the best possible dental health when a biteplate is worn.
Summary The anatomic, physiologic, and anthropologic bases for the vertical dimension problem have been discussed. The damaging effect of excessive overbite with resultant problems of bruxism, clench ing, muscle spasm, TMJ disturbances, and local ized periodontal pathology have been described. Preventive and corrective use of the biteplate in the deciduous and mixed dentition; the use of a biteplate in conjunction with conventional fixed appliance therapy; the biteplate as a diagnostic and treatment splint in TMJ disturbances; and the “crutch concept” have been described and illus trated. The dentist cannot concentrate on the tooth system alone. It is imperative that he establish and maintain the harmony of at least four tissue sys tems— tooth, muscle, bone, and nerve. Presented at the 1 0 9 th annual session of the American Dental Association, M ia m i, Fla, Oct 28, 1968. The author wishes to thank D. Blum e fo r Figure 4, J. R. Mathews and the A m e rican Journal o f O rthodontics for Figure 9, and U. Posselt and F. A. Davis fo r Figure 12. Doctor Graber is research associate (professor) a t the Zoller Dental C lin ic o f th e U nive rsity of Chicago. His ad dress is Kenilw orth D e ntal Research Foundation, 450 Green Bay Rd, Kenilw orth, III 60043.
1. Begg, P.R. Begg o rth o d o n tic theory and technique. Philadelphia, W. B. Saunders Co., 1965. 2. Hooton, E.A. E vo lu tio n and devolution of th e human face. Am er J O rthodont 32:657 Dec 1946. 3. Graber, T.M. O rth o d o n tics; p rinciples and practice, ed. 2. Philadelphia, W. B . Saunders Co., 1966. 4. Schudy, F.F. V e rtic a l growth versus anteroposterior growth as related to fu n c tio n and treatm ent. Angle Ortho do n t 34:75 A pril 1964. 5. Blume, D. A roentgenographic study of the position of the m andible in m alocclusion of the teeth. MS thesis. C hi cago, Northwestern U n ive rsity, 1947. 6. Posselt, U. The physiology o f occlusion and reh a b ilita tio n , ed. 2. Philadelphia, F. A. Davis Co., 1968. 7. Graber, T.M. C ra niofa cia l m orphology in c le ft palate and c le ft lip d e form itie s. Surg Gynec Obstet 88:359 March 1949. 8. Mathews, J.R. M a x illa ry bite plane ap p lica tio n in Class I deciduous occlusion. A m e r J O rthodont 45:721 Oct 1959. 9. Moyers, R.E. D evelopm ent o f occlusion. Dent C lin N Am er 13:523 No. 3, Ju ly 1969. 10. Schwarz, A.M., and Gratzinger, M. Removable o rtho d o n tic appliances. P hila d e lp h ia , W. B. Saunders Co., 1966. 11. Laskin, D.M. E tio lo g y of th e pain-dysfunction syn drome. JADA 79:147 J u ly 1969. 12. Graber, T.M. C u rre n t orth o d o n tic concepts and te ch niques, chapter 1. P h iladelphia, W. B. Saunders Co., 1969. Graber: OVERBITE— DENTIST’S CHALLENGE ■ 1145
Overbite-the dentist’s challenge
T. M. Gräber, DDS, Kenilworth, III
Deep overbite is apparently a combination of evolu tionary skeletal change and morphogenetic pat tern, modified by a variable neurogenic component. The dentist cannot concentrate on the tooth sys tem alone in treating overbite. Harmony must be established between at least four tissue systems— tooth, muscle, bone, and nerve.
With fluoridation, the incidence of caries has been greatly reduced. It is conceivable that a preventive as effective as polio vaccine may be discovered in the near future. If caries is eliminated, with its attendant pulpal involvement and tooth loss, den tal practice orientation will have to undergo a major change. If there is no need to fill or replace teeth, what then? Most periodontal problems will remain, of course, because the likelihood that periodontal disease is a single entity is small. And malocclusion will still be common because morpho genetic pattern is the dominant etiologic factor in malocclusion. Anthropologists show that the jaws are getting smaller and that there is a developing retrusive mandibular pattern as we climb the ladder of
“civilization.” Begg,1 in his studies of Australian aboriginals, shows that many of our ancestors had an end-to-end bite, with almost no overjet. Form and function teamed together to produce a dental apparatus that was well aligned and well balanced, with harmony between the three major tissue sys tems— tooth, bone, and muscle. With diet changes and less interproximal and occlusal wear, there has been an alteration within the tooth system it self. Part of this alteration results from the differ ent functional demands being made on the tooth system by modem refined foods; part is a homeo static or adaptive response to the basal bone mod ifications of successive generations, as elucidated by the anthropologists.2 It is relatively clear that man is developing a greater amount of overjet in his dentition and a significantly deeper overbite. Two thirds of the patients now treated by ortho dontists are in the basal jaw malrelationship cate gory, with anteroposterior discrepancies mirrored in overjet and overbite.3 Excessive overbite is a vertical dysplasia, often associated with problems of overjet,4 but sufficient by itself to produce periodontal disease ramifica tions by virtue of the functional limitations im posed and the abnormal stresses created. It is the purpose of this paper to discuss the various factors contributing to the overbite prob lem so that we may understand better the role of this combined morphogenetic and functional aber ration. A discussion of some of the sequelae of overbite, such as temporomandibular joint dis1135
turbances, is given. Methods of correction and control of overbite problems are described.
The biologic continuum
Fig 1 ■ Diagrammatic representation of balance of head on vertebral column, with continuous chain of postural mus cles maintaining the balance. Even during active functions of speech, deglutition, respiration, and mastication, the postvertebra I, prevertebral, facial, masticatory, supra-, and infrahyoid muscles have active postural component, sta bilizing and counterbalancing.
Fig 2 ■ Postural resting position of mandible establishes 3 - to 4 mm interocclusal clearance between teeth. This postural vertical dimension (PVD) is relatively constant as a muscularly determined entity. When there is an abnormal occlusal vertical dimension (OVD), as in cleft palate casts on the right, interocclusal clearance is much greater and can approach 20 mm in extreme cases. Excessive inter occlusal clearance permits mandibular overclosure (see Fig 8) and concomitant aberrant functional sequelae. 1136 ■ JADA, Vol. 79, November 1969
It is imperative to recognize the dynamic consid erations in the overbite problem and to distinguish the treatment from much of restorative dentistry in which lost parts are replaced with a reasonable facsimile. The muscle and bone systems are natu rally less involved in the technology of amalgam reproductions than in the treatment of malocclu sion. Telemetry and electromyography have shown that the traditional “teeth together” cast examina tion of study models by a dentist does not give a realistic appraisal of the situation. By far the great est amount of the patient’s time each day is spent with the mandible suspended by the cradling mus culature in its postural position, with the postvertebral, prevertebral, facial, and masticatory muscles, and the supra- and infrahyoid muscles maintaining the balance of the head on the verte bral column; the postural relationship of the man dible with the associated structures must also be considered (Fig 1). This postural position is the starting point not only for mastication, but also for deglutition, respiration, and speech. Thus there are two vertical dimensions— the postural vertical dimension (PVD) which is the relationship of the mandible determined by the muscles, and the traditional occlusal vertical di mension (OVD) which is determined when the teeth are brought together in the habitual and maximum contact. It is usually the OVD that is abnormal. In other words, the tooth and bone sys tems that are largely involved in the function of mastication are not in harmony with the muscle system. The vertical dysplasia seen in the static plaster casts, with the teeth clamped together in occlusion, must be approached from the viewpoint of biology. Normally, when the mandible is in postural rest position, and the muscles are continuing to maintain the head in its proper position on the vertebral column, even while an individual is breathing and speaking and swallowing, there is a definite space between the upper and lower teeth (Fig 2). When the teeth are brought into occlusion, the mandible closes upward and for ward from postural rest to full contact. In a nor mal situation, the movement of the condyle is primarily rotary through this 3- to 4-mm distance.
Fig 3 ■ Sagittal section draw ing illu s tra tin g structu re s of tem porom andibular jo in t. There are tw o d is tin c t jo in t cavities. Lower compo n e n t fu n c tio n s p rim a rily in closure from postural rest to habitual occlusion, by con d ylar rota tio n on a rtic u la r disk. In excursive and fu n c tio n a l m ovem ents beyond postural rest position, both elements of a rticu la tio n fu n c tio n w ith rotary condylar movem ent in lower jo in t and w ith translatory movem ent also, as disk and a rtic u la r capsule are brought forw ard by external (lateral) pterygoid m us cle fibers.
BONE C A R T IL A G E L O O S E C O N N E C T IV E T IS S U E S Y N O V IA L L IN IN G CAPSULE DENSE
F IB R O U S
C O N N E C T IV E T IS S U E L A T E R A L P TE R Y G O ID M U S C L E F IB E R S
The temporomandibular joint Anatomy shows that there are in reality, two sep arate articular cavities, with the disk and associ ated ligamentous attachments separating the up per from the lower joint cavities (Fig 3). Injection of disclosing solution into the cavity between the disk and the articular eminence will show that there is no communication with the lower joint cavity between the disk and the condyle of the mandible. Although both joint cavities function in normal opening, with a translatory (gliding) movement of the disk over the articular eminence combined with a rotary action of the condyle on the disk in the lower joint cavity, there is little translation on closing from postural rest to occlu sion. As Blume5 indicates, however, when there is a deficient eruption of teeth and an excessive interocclusal clearance, with the mandible closing
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Fig 4 ■ Superimposed TMJ tracings made at PVD and OVD in cases w ith excessive interocclusal clearance. Note com bined rotary and translatory movem ent of condyle as it moves up and back, under in fluence of do m in a n t posterior te m p o ra lis m uscle activity.
Fig 5 ■ Both tem poralis and masseter m uscles are made up o f fib e r groups, capable of varying co n tra ctio n m agni tude. In normal closure from PVD to OVD, co n tra ctio n in te n sity is approxim ately equal in anterior, m iddle, and posterior tem poralis and su p e rficia l and deep m asseter m us cles (A). W ith overclosure, posterior tem poralis and deep m asseter fib e rs sta rt showing a dom inance over other fib e r groups w ith in the same m uscle (B). W ith severe overclosure, d igastric and geniohyoid m uscles also show increased ac tiv ity , team ing up w ith dom inant posterior te m p o ra lis and deep muscle fib e rs (C). A t th e same tim e, as condyle is sub jected to retruding action by th is type of m uscle a ctivity, stretch reflex is e lic ite d in lateral (external) pterygoid m us cle, w hich has fib e rs in serting in to the a rtic u la r d isk and capsule. C ontraction of lateral pterygoid p u lls a rtic u la r disk forward as condyle is being pulled upward and backward (see Fig 6). Graber: OVERBITE—DENTIST’S CHALLENGE ■ 1137
6, 8, or 10 mm from rest centric instead of the usual 3 or 4 mm, both rotary and translatory TMJ may be demonstrated (Fig 4). Posselt6 has shown that centric relation and centric occlusion are not the most posterior posi tions of the condyle within the total effective move ment pattern. As with any other joint in the body, there is a range of movement. In overclosure, there is frequently a change in the pattern of mus cle activity. The overclosure emphasizes the role of a fourth tissue system, the neurologic system, with the phenomena of proprioception and feed back mechanisms. In normal closing from postural rest to occlusion anterior, middle, and posterior temporalis muscle fibers function with about the same intensity of action, as shown by the electro myograph. This is also true of the deep and super ficial fibers of the masseter muscle. The medial pterygoid muscle also functions as a unit in nor mal closure. In overclosure, the OVD is out of harmony with the PVD and it may be shown that the posterior temporalis fibers, as well as the posterior masseter fibers, become dominant in the closing maneuver (Fig 5). With this dominant retrusive force, the posterior and superior transla-
F ig 6 ■ Condylar a c tiv ity from (1) open m outh to (2) postur al resting p o sitio n is norm ally rotary and translatory in character. From (2) PVD to (3), condylar action is norm ally rotary unless there is overclosure. Then, as Figure 5 shows, d o m in a n t posterior tem poralis m uscle a ctivity exerts up ward and backward p u ll on condyle, causing translatory a c tiv ity a fte r p o in t o f in itia l incisal contact has been passed. 1138 ■ JADA, Vol. 79, November 1969
tory movement shown in Figure 6 is a reality. As the anatomist knows, the protractor for the articular disk in the TMJ is the lateral pterygoid muscle. Fibers from this muscle insert into the disk and capsule. However, no muscle serves as an articular disk retractor. Only the integrity of the capsular ligaments, maintaining proximity of disk, condyle, and eminence, guides the posterior movement on closure. When there is overclosure and a retrusive activity of the dominant, deep masseter and posterior temporalis fibers, a stretch reflex is elicited on the external (lateral) pterygoid muscle. With stretch reflex, there is contraction, or muscle spasm. The disk is held in a forward posi tion whereas the condyle moves upward and backward because of the feedback phenomenon and posterior temporalis muscle-fiber action. The condyle, riding over the posterior periphery of the disk, then impinges on the postarticular connec tive tissue. The postarticular tissue is supplied by nerve fibers from the auriculotemporal nerve and is less well adapted to stresses of mandibular func tion. The joint structures may adapt to the deviate activity for a while (homeostasis), but with con stant stimulation of stretch reflex, forward pull of the disk, impingement on the postarticular con nective tissue, muscle spasm, and overclosure these structures may not continue to adapt indefi nitely. Proprioception cannot handle the aberrant feedback signals issued by the neural system. Ir ritation and lack of harmony of the structures is clinically observed in the form of clicking and crepitus. This condition can be mistaken for arth ritic changes and treated improperly with meniscec tomies and injections. In reality, this functional abnormality is associated with excessive overbite, homeostatic or compensatory muscular adapta tion, dominance of the posterior fibers of the temporalis muscle, retrusive condylar thrust, and the inability of the structures to adapt completely to this abnormal translatory movement through the usual neuromuscular, proprioceptive “feed back” channels. An important part of the TMJ malfunction syn drome is the neurogenic or neurologic background. It has been shown repeatedly that the mouth is not only an erotogenic zone, and an area for emo tional expression for the infant, but that it also serves to gratify tensional stresses in the adult. The widespread phenomena of bruxism and clenching show positive correlation with increasing levels of nervous excitability. So there is a psychogenic su perstructure imposed on the functional and mor
phologic abnormalities which stem from the orig inal lack of harmony of the O V D with the muscularly determined PVD. Clinical experience has shown that there is a high incidence of bruxism and clenching associ ated with overbite (Fig 7). Evidences of bruxism are seen early in the deciduous dentition of many children and the damage can be quite considerable. It is difficult to assign precise values to the neu rologic component and to the overbite and mal occlusion components. Undoubtedly they vary from individual to individual and from time to time within the same individual. There is a higher incidence of bruxism in female patients. The dam aging consequences of the cyclical, rending, noc turnal, spasmodic activity are clearly evident in the polished facets of wear on the teeth.
in the lower joint cavity. Then there should be no need for compensatory and adaptive muscle activ ity so that the anterior, middle, and posterior temporalis fibers will function at approximately the same intensity. Interceptive occlusal contacts will not exist to incite aberrant feedback phenom ena. But, since deep overbite apparently is a com bination of an evolutionary skeletal change and
Correction and control Since the deep overbite, then, is a lack of harmony of the two vertical dimensions, since it is usually the OVD that is abnormally related and responsi ble, since deep overbite means mandibular over closure, and since overclosure leads to abnormal functional patterns, what can be done about it? First, the abnormal function may take the path of bruxism and clenching; it may take the path of excessive destruction of tooth material; it may be manifested in limited excursive movement; or it may result in frank TMJ disturbances, with mus cle spasm, clicking, crepitus, pain, and even trismus. Clearly, the challenge is to establish an OVD in harmony with the PVD, eliminating occlu sal interferences at the same time. If this is done, then there will be no overclosure, and the move ment from postural rest to occlusion will be large ly a rotary action of the condyle against the disk
F ig 7 ■ Four patients w ith bruxism associated w ith exces sive overbite. All age groups are affected and show evi dence of g rin d in g and clenching. Note w earing away of canine in (A) and (B); deciduous m olar d e stru ctio n (C) and (D); severe incisor damage in an a d u lt (E) and (F); in ciso r wear and gingival recession associated w ith abnorm al fu n c tio n a l forces (G) and (H).
Fig 8 ■ Lateral cephalogram s of c le ft palate p a tie n t w ith severe growth arrest. In postural resting p o sition (PVD), note very large interocclusal space of 20 mm. Overclosure a ffe c ts anteroposterior jaw relationship, crea tin g an apparent m andibular prognathism (B). Restoration o f OVD in har mony w ith PVD by p ro sth e tic means also establishes more harm onious anteroposterior relationship, reducing seeming m an dibular protrusion (C). Graben OVERBITE—DENTIST’S CHALLENGE ■ 1139
Fig 9 ■ Use o f b ite p la te to help elim in a te excessive overbite in late deciduous d e n tition . In te r m itte n t use of b ite p la te fo r fiv e years has reduced overbite and also allowed s ig n ific a n t m andibu lar intercanine growth (A). Excessive overbite tends to c o n s tric t in ciso r segm ent in lower arch, crea tin g arch length deficie n cie s and preventing fu ll accom plishm ent of intercanine arch length increase (B) and (C).
morphogenetic pattern, as modified by a variable neurogenic component, how can it be helped? In a child with cleft palate who has had early and traumatic surgery that interferes with maxil lary growth, the interocclusal clearance may be 12, 15, or even 20 mm7 (Fig 8). Establishing a correct OVD that is harmonious with the PVD in these severe dysplasias is beyond the realm of orthodontic therapy and requires prosthetic cor rection. But in the average dental patient, the mag nitude of overbite is not as great and the objective, hopefully, is to stimulate all possible eruption of the teeth to reduce the interocclusal clearance. Fixed orthodontic appliances are capable of doing this at the right time and under proper control. However, such appliances may not be indicated for a variety of reasons particularly in the decidu ous and mixed dentitions. What else can be done? As Mathews8 has shown, the use of a palatal biteplate may be beneficial (Fig 9). When this acrylic resin and wire appliance is worn, it pre vents the posterior teeth from meeting in occlu sion. With only the lower incisors contacting the acrylic plane, it reduces the intrusive forces on the posterior teeth. If the mandible is prevented from going into a functional retrusion with dom inant posterior temporalis muscle activity, there is less likelihood of abnormal deglutitional or “reverse swallow” activity. The tongue lies lower on the floor of the mouth and spreads somewhat less laterally so that there is less chance of its pre venting eruption of the posterior teeth. Restric tions on normal growth and development are eliminated. As has been shown, overclosure may actually result in a functional retrusion of the mandible which creates a Class II malocclusion. In the nor mal course of events, with the terminal plane rela tionship of the deciduous teeth, an end-to-end cuspal relationship is already to be expected in 1140 ■ JADA, Vol. 79, November 1969
many instances.9 A functional retrusion can con vert a Class II tendency into a full Class II buccal segment relationship. By working with the nor mal processes of growth, development, and change that occur especially in the mixed dentition, the elimination of abnormal perioral muscle activity and the stimulation of eruption of posterior teeth is at least a step in the right direction. It reduces the harmful effects produced by excessive overbite and functional abnormalities. Complete success is seldom to be expected with biteplate therapy, but significant improvement may be observed. Lateral cephalograms taken before and after biteplate wear (Fig 10) show a significant antero posterior change that was achieved merely by eliminating the functional retrusion. The activator or monobloc, worn in the mixed dentition by many children— in Europe particu larly— serves a purpose similar to that of the bite plate with inclined plane; it prevents overclosure and the retrusive muscle activity tendency.10 Even the lower incisors may benefit and an appreciable intercanine dimension increase has been seen with properly chosen patients who give a high level of cooperation (Fig 9). Thus a biteplate (Fig 11) is both preventive and corrective during the child’s period of growth. If there is a habit of bruxism (and this is much more frequent than we once thought) the bite plate again serves as a valuable preventive ad junct. It prevents the “trigger area” from starting the “rending and gnashing” cycle that is so dam aging to the teeth. Any grinding that takes place is usually manifested on the flat acrylic plane be hind the maxillary incisors. Indeed, the same biteplate may be used in the adult dentition for the prevention of bruxism and clenching, with con sistently good results. In most instances, a biteplate produces only partial correction of the overbite problem. Gen-
Fig 10 ■ Tracings of lateral cephalograms o f p a tie n t before (le ft) and a fte r (rig h t) w earing biteplate fo r three and a h a lf years. Note decided reduction in interocclusal space and reduced condy lar retrusion in habitual occlusion a fte r b iteplate was worn.
Fig 11 ■ M axillary b iteplate, w ith conventional .032 inch labial bow and v e rtica l spring loops a t canines. Ball clasps are illu stra te d , b u t circu m fe re n tia l or arrow clasps work equally well (top). Drawing shows cross section o f palatal a crylic portion w ith b ite opening plane behind incisors (bottom ). A crylic portion indicated by arrow m ust be c u t away to retra ct incisors or if th e re is irrita tio n a t the g in g i val m argin. Labial bow (arrow) helps sta b ilize appliance and prevent labial m ovem ent o f incisors.
<5= Graber: OVERBITE—DENTIST’S CHALLENGE ■ 1141
CLICKING OF TH E JO IN T ON MOVEMENT LIM ITED MOVEMENT (IN C L LOCK-JAW ) PAIN IN OR ABOUT THE EARS PAIN ON MOVEMENT HEADACHE TENDERNESS ON PALPATION TIN N ITU S EXCESSIVE MOVEMENT MILD CATARRHAL DEAFNESS PAIN OVER VERTEX, OCCIPUT, OR POSTAURICULAR AREAS NEURALGIA MAX. MAND. S NECK
Fig 12 ■ TMJ disturbance sym ptom s in order o f th e ir greatest frequency, based on co m p ilatio n of results o f sev eral investigators.
erally, the vertical dysplasia is related to an ante roposterior problem such as a Class II type mal occlusion. Although the functional retrusion may be eliminated, there is still a Class II morphoge netic pattern apparent. Conventional orthodontic therapy is required, but the severity of the maloc clusion has been reduced and the appliance and time demands may be significantly less. If there is a deep overbite to start with, the wearing of a biteplate can seldom do any harm. Obviously, orthodontic consultation is strongly recommend ed beforehand and on a continuing basis if bite plate application is under the control of the gen eral practitioner.
The crutch theory After growth and development are complete, over bite correction with a biteplate is seldom possible. Only partial success may be expected and the over bite returns if the patient stops wearing the appli ance. Yet the damaging effects of an excessive overbite are quite obvious to the periodontist, in particular. Corrective lenses do not eliminate the basic visual abnormality for the person who wears glasses. They merely serve as a “crutch” through out life, allowing him to live with his defective vision. If overbite can be prevented by the wear ing of a biteplate, the same “crutch” theory may apply. Particularly in instances such as that shown in Figure 7, where the sequelae of deep overbite are excessive wear, TMJ disturbances, periodon tal involvement, bruxism, neurologic manifesta tions, and so forth, the biteplate allows the patient to live with the situation in reasonably good den tal health. Obviously, periodontal care must be concurrent and routine for optimum results. 1142 ■ JADA, Vol. 79, November 1969
If a full-mouth reconstruction is contemplated, the wearing of a biteplate initially, before any work has been done, will often determine the proper vertical dimension— from both a comfort and a physiologic viewpoint. As a diagnostic splint, the biteplate allows the dentist to use one of the best tests of all— a functional exercise— before he initiates mechanical procedures based on articu lator determinations. It must be emphasized again that harmony of four tissue systems (bone, tooth, muscle, and nerve) is absolutely essential.
Temporomandibular jo int disturbances It has been stressed that many, though not all, TMJ disturbances result from a lack of harmony of the OVD with the muscularly determined PVD. Interceptive contacts, tooth guidance, and improp er restorations are also contributing factors.11 Nev ertheless, excessive overbite, with its resultant dominant posterior temporalis muscle activity, in creased deep masseter fiber contraction, and pos sible “assists” from the digastric and geniohyoid muscles, may contribute significantly to the ob jective symptoms. The overclosure and posterior condylar thrust may elicit a stretch reflex in the lateral pterygoid muscle and stimulate reciprocal muscle spasm in other muscles associated with the stomatognathic system through the proprioceptive feedback network. The resultant clicking-crepitusmalfunction syndrome produces identifiable symp toms, as shown by Posselt6 (Fig 12). Very likely, the patient’s psychogenic superstructure and indi vidual tooth malpositions team up with the ab normal OVD to produce the net result. Myocitis may also be a factor. Clinical experience shows that these symptoms are four times more frequent in women than in men. TMJ therapy is illustrated by the following hypothetical case. Mrs. Jones, age 38, is referred by the orthopedic surgeon who had been injecting a sclerosing solu tion and cortisone into the temporomandibular joint, along with a pain killer. The question of a meniscectomy had arisen and a dental consulta tion was suggested. Mrs. Jones has a Class II, Division 2 type malocclusion (Fig 13) with ex cessive overbite and a functional retrusion; she has headaches and occasional pain radiating up over the temporal region. Palpation demonstrates clicking, crepitus, and limited motion during the opening maneuver. A stethoscopic examination of the joint area
Fig 13 ■ Deep overbite and m an d ib u la r retrusion w ith concom itant TMJ sym ptom s in a d u lt woman (a,b,d) and man (c,e,f). B ite p la te w ith fla t plane behind incisors (d) establishes OVD in harm ony w ith PVD. D om inant posterior tem poralis muscle fib e r p u ll is reduced, and fu n ctio n a l retrusion is e lim inated. C lickin g , crep itu s, and pain are greatly reduced.
substantiates the grating or grinding that may be picked up through palpation of the TMJ region.12 Palpation usually is adequate to appraise varying activity of muscle components in severe cases (posterior temporalis hyperactivity, for example), but electromyography would be required to dis cern contraction differences in the majority of pa tients. A functional analysis shows heavy facets of wear on the incisal margins of the mandibular in cisors and on the lingual surfaces of the maxillary incisors. The patient is apprehensive and nervous. When Mrs. Jones is asked to move her mandible forward so that the upper and lower incisors meet
end-to-end, and then open and close to this posi tion, there is one unlocking “pop.” Then move ment is free of the grinding and grating and popping that occurs in the habitual occlusal position. Even the stethoscope cannot demonstrate excessive joint noise. Moving the condyle forward thus es tablishes a correct relationship with the articular disk. In almost all TMJ disturbances, the same re action will be seen. It is indicative of the com bined functional retrusion and posterior tempo ralis activity, in conjunction with the stretch re reflex of the external pterygoid, that holds the disk forward. Since it is the pounding of the postGraber: OVERBITE—DENTIST’S CHALLENGE ■ 1143
Fig 14 ■ Patients who have lost OVD in posterior segments may dem onstrate increased a c tiv ity of clo sin g m uscles, w ith condyle being pulled upward and back. A ddition of a crylic resin over o cclu sal surfaces may be necessary fo r posterior support, to break up m uscle spasm tendency and estab lish new proprioceptive stim u li (a,b,c). In some cases, m andible m ust also be guided forw ard and a n te rio r guide plane placed behind m axillary incisors, to guide m andible forw ard; posterior sup p o rt is provided in te rm in a l closing position (d,e,f).
articular connective tissue which apparently in cites the pain and trismus, a splint is required to prevent overclosure, and to guide the mandible into a slightly forward position within the normal functional range, thereby preventing the elicita tion of the stretch reflex and the aberrant neuro logic feedback, muscle spasm, and clicking. A splint, similar to a Hawley biteplate (Fig 11), is constructed to be worn at all times. In addition to a combined pain killer and tranquilizer, wet 1144 ■ JADA, Vol. 79, November 1969
heat applications are prescribed for the painful joint area. A muscle massage unit is frequently beneficial when applied to masseter and tempo ralis areas. The patient is to apply heat and mas sage for 15 minutes on arising and on retiring. As with any other malfunctioning joint, limited use and maximum rest are required. Diet is kept soft or semiliquid for the first three or four days; there after, the patient may choose soft foods but the mandible is kept in its open, slightly protruded po
sition most of the time by the splint. Isometric ex ercises are sometimes prescribed after several days; the patient moves the mandible forward and brings the teeth together in forced closure for a two- to three-minute period. Mrs. Jones, if she is like most TMJ patients, will lose the objective symptoms within the first three to seven days. If she stops wearing the bite plate, however, they may return fairly soon. Hence, the biteplate is worn on a gradually re duced schedule; within two weeks, wear may be limited to sleeping hours. In most instances, the splint, together with a conservative use of heat and massage, is adequate to control the problem. Where there has been loss of posterior teeth, the condyle tends to be thrust upward and back ward in the articular fossa by the dominant poste rior temporalis activity. The flaccidity of the ar ticular capsule and ligaments may be a factor. In these instances, the modified Hawley biteplate may have to include posterior acrylic occlusal cov erage, which literally “blocks open” the bite and reduces the luxation of the condyle (Fig 14). This posterior acrylic cover for the occlusion is neces sary in only approximately 20% of the instances of TMJ disorder, however. Generally, the conven tional biteplate, with a slightly inclined plane to keep the incisal edges in proximity and the poste rior teeth apart, is adequate. If bruxism and clench ing are habitual, this biteplate serves to eliminate their deleterious effects; it suppresses the vicious cycle of neurologic feedback abnormality, at least while it is being worn. After the patient is com fortable, full-mouth reconstruction may be con templated. Or, the biteplate may be Worn on a diminishing-time basis at night. Experience has shown that this type of appliance may be worn for an indefinite period if the patient is under con tinued dental guidance for conservative tissue con trol, and if acrylic resin is added periodically and clasps are checked, and so forth. As with contact lenses, these appliances can be worn for a consid erable time with no harmful effects, if they are properly fitted and maintained. Indeed, where there has been bone loss and re sultant flaring of teeth, the biteplate serves as an essential adjunct for the periodontist. It may be used to retract incisors, close spaces, and to posi tion teeth in their best axial inclination for opti mum stress reception in the vertical direction through the long axis of the teeth. Here again, the “crutch” theory is a valid one. It should be empha sized that continued periodontal tissue control is important. Equilibration, cleaning, scaling, polish
ing, astringent packs, and so forth, enhance the establishment of the best possible dental health when a biteplate is worn.
Summary The anatomic, physiologic, and anthropologic bases for the vertical dimension problem have been discussed. The damaging effect of excessive overbite with resultant problems of bruxism, clench ing, muscle spasm, TMJ disturbances, and local ized periodontal pathology have been described. Preventive and corrective use of the biteplate in the deciduous and mixed dentition; the use of a biteplate in conjunction with conventional fixed appliance therapy; the biteplate as a diagnostic and treatment splint in TMJ disturbances; and the “crutch concept” have been described and illus trated. The dentist cannot concentrate on the tooth system alone. It is imperative that he establish and maintain the harmony of at least four tissue sys tems— tooth, muscle, bone, and nerve. Presented at the 1 0 9 th annual session of the American Dental Association, M ia m i, Fla, Oct 28, 1968. The author wishes to thank D. Blum e fo r Figure 4, J. R. Mathews and the A m e rican Journal o f O rthodontics for Figure 9, and U. Posselt and F. A. Davis fo r Figure 12. Doctor Graber is research associate (professor) a t the Zoller Dental C lin ic o f th e U nive rsity of Chicago. His ad dress is Kenilw orth D e ntal Research Foundation, 450 Green Bay Rd, Kenilw orth, III 60043.
1. Begg, P.R. Begg o rth o d o n tic theory and technique. Philadelphia, W. B. Saunders Co., 1965. 2. Hooton, E.A. E vo lu tio n and devolution of th e human face. Am er J O rthodont 32:657 Dec 1946. 3. Graber, T.M. O rth o d o n tics; p rinciples and practice, ed. 2. Philadelphia, W. B . Saunders Co., 1966. 4. Schudy, F.F. V e rtic a l growth versus anteroposterior growth as related to fu n c tio n and treatm ent. Angle Ortho do n t 34:75 A pril 1964. 5. Blume, D. A roentgenographic study of the position of the m andible in m alocclusion of the teeth. MS thesis. C hi cago, Northwestern U n ive rsity, 1947. 6. Posselt, U. The physiology o f occlusion and reh a b ilita tio n , ed. 2. Philadelphia, F. A. Davis Co., 1968. 7. Graber, T.M. C ra niofa cia l m orphology in c le ft palate and c le ft lip d e form itie s. Surg Gynec Obstet 88:359 March 1949. 8. Mathews, J.R. M a x illa ry bite plane ap p lica tio n in Class I deciduous occlusion. A m e r J O rthodont 45:721 Oct 1959. 9. Moyers, R.E. D evelopm ent o f occlusion. Dent C lin N Am er 13:523 No. 3, Ju ly 1969. 10. Schwarz, A.M., and Gratzinger, M. Removable o rtho d o n tic appliances. P hila d e lp h ia , W. B. Saunders Co., 1966. 11. Laskin, D.M. E tio lo g y of th e pain-dysfunction syn drome. JADA 79:147 J u ly 1969. 12. Graber, T.M. C u rre n t orth o d o n tic concepts and te ch niques, chapter 1. P h iladelphia, W. B. Saunders Co., 1969. Graber: OVERBITE— DENTIST’S CHALLENGE ■ 1145