The use of muscle forces by simple orthodontic appliances

American

Journal

of ORTHODONTICS Volume 76, Number

ORIGINAL

I

July,

1979

ARTICLES

The use of muscle forces by simple orthodontic appliances T. M. Graber, Chicago, Ill.

D.M.D., M.S.D.,

Ph.D.*

M

ost orthodontic appliances of a fixed or active removable plate type use intrinsic or stored force to move teeth. Force is exerted from within the appliance itself and dissipated against the teeth and supporting structures. This article is devoted to a.ppliances that are primarily effective because of their essential use of extrinsic force, delivered by the muscle components of the stomatognathic system. The appliances have only an occasional minor treatment objective allocated to intrinsic moving parts. Considerable variety exists in functional or muscle-motivating orthodontic appliances. Ftor purposes of classification, they may be divided into three broad groups, with each group incorporating elements that are used at least partly in the other two groups. Group I consists of inclined planes and oral shields or screens which transmit muscle force directly to the teeth. Either simple appliances, such as the cemented inclined plane, or the removable guide plane of Hotz will accomplish the same objective.’ Group II is made up largely of the original activator and its various modifications, plermitting daytime as well as nighttime wear. Such appliances are usually one-piece plastic (for example, the monobloc) with wire appurtenances that perform minor duties. They all reposition the mandible downward and forward (excelpt in Class III malocclusions), activating the attached and associated musculature. The resultant force that is created is transmitted not only to the teeth but to other structures as well. Both the maxilla and the mandible are involved. Group III also relies on mandibular positional changes, but its major operating area is in the vestibule, outside the dental arches. Supporting bone and teeth are influenced by changing the muscle balance through cheek shields and lip pads. The Frlnkel FR (function regulator) is the main appliance in this group, combining the oral-screen-like shields with activator-like mandibular guidance and muscle stimulation or activation. All three groups may be considered as interceptive appliances. The mixed-dentition period is most frequently the optimal time for therapy, though both activator and Frankel *Professor, Pediatrics, Zoller Dental Clinic; sor), Anatomy and Anthropology, University 0002.9416/79/070001+20$02.00/0

0

Chairman, Orthodontics; of Chicago.

1979 The C. V. Mosby Co.

Research

Associate

(Profes-

1

2

Am. J. Orthd.

Craber

July /,

Fig. 1. Cemented posterior appliance

TOOTH

1979

IN GROSS-SITE.

inclined-plane diagram showing appliance teeth are free to erupt with this type of appliance, works quickly, however.

used to correct a significant

anterior overbite

crossbite. is required.

Since The

appliances may be used quite successfully during pubertal growth spurt periods. For most American orthodontists, “finishing up’ ’ usually requires a period of fixed mechanotherapy to provide the best possible tooth positions and inclinations. Yet a major part of the correction of the malocclusion, particularly the sagittal problems, may be accomplished with removable appliances, and some cases have been carried completely through with them. This article will be devoted to Group I, with subsequent articles on Groups II and III to follow. Alfred Paul Roger? was among the first to recommend the use of muscles to correct malocclusion. The essence of myofunctional therapy, as well as most functional orthopedic appliances, was to use muscle activify as a primary source of force for the resolution of malocclusions. Although not entirely neglected, the effect of a change of the more passive muscle balance has been historically much less in the focus of attention. Muscle balance changes, unlike myofunctional exercises, require less volitional effort and may be active over a greater period of time. Dramatic results have been achieved. The beautiful animal model experiments of Harvold3 and McNamara and their co-worker? demonstrate the significant potential. The provocative clinical results shown by Frankel” and his disciples point up the great potential of appliances which alter orofacial muscle balance. We cannot ignore growth and development, which effects considerable change in the area in which we work. Indeed, guiding growth and development is a major part of the correction of any basal sagittal malocclusion. It is abundantly clear, however, that muscles maintaining postural and functional balance must exert an influence on these growth changes. The orthodontist can enlist these potent growth-guiding forces in the growing child. While all three functional appliance groups work by enlisting muscle activify or by virtue of changes in muscle balance, the inclined plane also makes use of the proprioceptive phenomenon, pointing up the fact that changes are under neuromuscular control. The inclined

plane

The inclined plane was first introduced by Catalan more than 150 years ago.” Now, with self-curing acrylic, such appliances can be formed either directly and cemented on

Volume 76 Number 1

Fig. 2. Oppenheim

removable Mandibular occlusal surfaces tooth in cross-bite contacts necessary to keep the force

Use

of muscle

forces

3

guideplane splint with metal insert to engage tooth or teeth in cross-bite. are covered, but the superior surface is ground away so that only the the metal incline. Periodic grinding of the buccal occlusal surfaces is on the maxillary incisors only.

the incisors or indirectly on a plaster model and then cemented, saving chair time. Since various orthodontic texts describe the appliance’s construction and use, details will not be given here for the cemented guide plane (Fig. 1). However, it is stressed that this appliance should be limited to the simplest of cases, involving one or two teeth at most. Sufficient space is a primary prerequisite. Less cooperation from the patient is required when it is cemented. A modification of the simple cemented inclined plane is the Oppenheim splint’ (Fig. 2). When first introduced, it was made of vulcanite, with a s,mall gold inclined plane incorporated to engage the displaced incisors. The splint is fabricated with the upper premolars and molars occluding on the splint. The appliance is then activated, grinding posterior occlusal surfaces away approximately 1 mm., so that the only teeth that touch are the malposed incisors, which engage the inclined plane. The rest of the splint is out of occlusion. As the lingually malposed maxillary incisors move labially, the posterior teeth occlude again, and the acrylic must be ground off to restore inclined-plane force for the teeth in cross-bite. With this appliance, the force is minimal and is particularly desirable for teeth whose roots have not formed completely. A frequently used inclined-plane adjunct is made by merely adding an inclined plane to a removable mandibular Hawley type of retaining appliance (Fig. 3). Occlusal rests are used on the molars for stabilization. The posterior teeth may actually be covered with acrylic and gradually reduced, as with the Oppenheim splint. A, variety of clasps, described in various textbooks, may also be used. Clasps are not so important, however, since the labial arch and the acrylic offer adequate retention. This appliance has the advantage that the labial bow can be used to retract labially malposed lower incisors back into alignment. Interproximal stripping of lower incisors may assist in this process. This speledsthe correction of the anterior cross-bite. Often the cross-bite is a result of lingual malposition of the upper incisors, with a reciprocal labial movement of the opposing contiguous teeth. If acrylic is added to the occlusal surfaces of the posterior teeth, making lateral bite blocks, then the acrylic must be carefully ground away from the occlusal surface to assure that only the tooth or teeth in cross-bite are in contact with the inclined

Gruber

Fig. 3. Modified lower Hawley type of removable appliance Posterior teeth are free to erupt. The clasps and labial wire may exertion of lingual pressure on the labially malposed mandibular cross-bite.

.4m. j. Ocrhw’. July 1979

with inclined plane made of acryiic. be modified for retention and to permit incisor, assisting in correction of the

plane in the anterior region. The resultant correction is the byproduct of a combined depressing and anterior vector. The steeper the plane, the greater the anterior vector will be. Even with a steep plane, however, there is a depressing force on the incisor. All inclined planes have the characteristic of opening the bite by allowing the posterior teeth to erupt. Thus, the inclined plane is contraindicated unless there is an appreciable amount of overbite. Otherwise, even a slight opening of the bite will eliminate the stabilization of the orthodontic correction by the occlusion itself. One way to prevent eruption of the mandibular teeth, of course, is with an occlusal cover, as in the Oppenheim splint. The cemented inclined plane is best suited in deep-bite cases. It takes advantage of a larger than normal interocclusal clearance and helps to correct the deep-bite while eliminating the cross-bite. If the bite is not so deep, the Oppenheim splint or the modified mandibular Hawley appliance is a safer device. Even if the appliances are checked infrequently, little harm can be done, since the bite blocks prevent further eruption of posterior teeth. If the overbite is shallow and the use of an inclined plane is contraindicated, a maxillary plate with bite blocks on posterior teeth and springs behind the displaced maxillary incisor can be used to correct the anterior cross-bite (Fig. 4). It is not so important in the use of the upper plate that reciprocal forces are being exerted on the

Volume 76 Vumber 1

Fig. 4. Maxillary removable appliance with acrylic covering sufficiently to permit labial movement of the upper incisor recurved spring and gentle pressure. Note. the wire guard creeping up the lingual surface of the tooth in cross-bite.

occlusal surfaces to block open the bite in lingual cross-bite, This is done with a over the spring to prevent the spring from

lower, labially displaced incisors. Usually, as soon as the cross-bite is eliminated, there is some autonomous correction of the displaced mandibular incisors, under the combined forces of the occlusion and the lip, unless there is an arch length deficiency in the lower incisor segment. In deep-bite cases, the use of the maxillary active plate is not recommended, since the buccal bite-opening blocks would have to be too high. The appliance would be uncomfortable for the patient. Bite blocks tend to perpetuate a deep-bite, which is contraindicated. Regardless of the construction, all inclined-plane appliances, or any removable appliances designed to correct anterior cross-bite, must be worn continuously. If the appliance is removed during eating, this will generally force the tooth back toward the original malposition. The repeated jiggling may damage the tooth and loosen it. Contact sports or even horseback riding and skiing may mitigate against the wearing of a splint by causing undue momentary pressure. Actual fracture of an incisor by a sudden hard blow is possible. Despite the apparently cumbersome construction of both fixed and removable inclined planes, children seem to adapt well to them in 2 to 3 days. When used properly, the inclined planes, enlisting functional forces, can achieve the correction in as little as a few days. Seldom does it take any longer than 6 weeks. Sometimes, after correction, it is advisable for the patient to wear a removable inclined plane during sleeping hours to guard against the tendency to move the mandible forward and to bring the corrected incisor lingually again. If the inclined plane fails to achieve more than an end-to-end incisor relationship, an active plate with a lingual spring, as previously described, may be used. Vestibular

and oral screens

Using changes in muscle balance primarily, vestibular and oral screens work in an area that has been largely neglected by the orthodontist. The vestibular screen was introduced in 1912 by Newell and was actually used fairly frequently in England before World War II.8 Most recently, it has been widely advocated by Kraus,Y Hotz,’ Nerd,“, I2 and Fingeroth. I3

6

Am. .I. Orthod. July 1979

Graber

HOLE

Fig. 5. Thermoplastic burner and formed

blanks are commercially over the articulated casts

available in four sizes. with a moist towel.

LARGER

Blanks

are heated

over

a Bunsen

The vestibular screen has turned out to be a versatile and simple appliance in the early, interceptive treatment of dental arch deformities. This is particularly true when the malocclusions are caused or aggravated by faulty muscle function, producing excessive overjet. The oral screen can be used for the correction of (1) thumb-sucking, lip-biting, anld tongue-thrust, (2) mouth breathing when the airways are open, (3) mild distoclusions, with premaxillary protrusion and open-bite in the deciduous and mixed dentition, and (4) flaccid, hypotonic orofacial musculature. The simplest form of the vestibular screen or shield is a commercially manufactured polyamide or thermoplastic appliance (Fig. 5). It is particularly valuable in the early deiciduous dentition. The appliance can be used to intercept mouth breathing and some thumb-sucking or lip-sucking habits, as indicated, and to prevent the development of alveolar protrusions and open-bites. The lips exert pressure through the plastic against the anterior part of the dentition and the bony support. Since the buccal part of the screen is wide enough to keep the pressure off the posterior teeth (2 to 3 mm. clearance on each side in the first deciduous molar area), the tongue’s active function molds the posterior segments and helps to expand narrow dental arches. Thus, the anterior segment is influenced directly by the appliance through muscle pressure against the plastic, while the posterior segments are influenced by the actual keeping away of the cheek muscles, allowing tongue posture and function to expand the posterior areas. While treatment kits are available with rubber molds to permit the pouring-up of plaster models in different sizes and shapes to approximate the particular patient, duplicat.es of the patient’s own plaster study models may be used. They are articulated in occlusion, or with a slight forward positioning of the mandible, and then modified with

Fig. 6. Acrylic vestibular screen. Note small breathing holes. The screen contacts the mesial surface of the molars but stands away from the premolars and canines to allow expansion (two layers of baseplate wax provide necessary thickness between screen and teeth and alveolar bone). Earlier designs had no pressure on incisors, but current designs rest on protruding incisors in Class II, Division 1 malocclusions.

plaster added over lower incisors for the fabrication of the vestibular screen. A clear or opaque thermoplastic blank of the correct size is chosen, heated gently over a Bunsen flame, and then formed directly on the plaster model by means of a moist towel. One should remember that plaster or wax must also be added to the maxillary buccal segments to keep the screen 2 to 3 mm. away from the teeth on each side. A notched periphery of the splint blank fits the maxillary cast. If there is a low frenum, an acrylic bur may be used to deepen the midline notch. Breathing holes may be enlarged if desired. The vestibular screen is then tried in the patient’s mouth and may be modified by adding on to the margins or by cutting away and polishing. To ensure proper fit, minor changes may be made by reheating, and gentle pressures are applied where needed to ensure that the screen contacts the maxillary incisors only but stands away 3 mm. on each side from the buccal segments. The plastic portion extends as far as possible up into the mucobuccal vestibule. For an older patient, or for a child with an unusual malocclusion and arch shape, it is better to fabricate the screen especially for the individual patient. The appliance may be made of endothermic or exothermic acrylic, depending on the preference of the operator

Am. J. Orthod.

8 Graber

Fig. 7. Malocclusion corrected with vestibular have been eliminated. Also corrected was tongue-thrust and protracted tongue posture.

Julv 1919

screen shown in Fig. 6. Open-bite the retained infantile deglutitional

and finger-sucking pattern or so-called

and the laboratory facilities available. Again, proper conformation of the plastic to the specific areas is important and may make the difference between success and failure (Fig. 6). If there is a developing distoclusion, the appliance may be made with the jaws in a more nearly normal sagittal relationship. The working or construction bite is taken directly in the patient’s mouth by moving the mandible forward 1 to 3 mm. and the bite is opened 2 mm. This is maximum for screens. Activators permit more anterior mandibular positioning and are usually preferred where a sagittal discrepancy exists. If the sagittal relationship in reasonably normal or if there is a flush terminal plane and no lower arch crowding, no anteroposterior manipulation of the casts is necessary. If overbite is normal or if there is an open-bite, the bite should not be opened before the screen is fabricated. In any event, with or without a sagittal or vertical change, the casts are mounted on a straight-line articulator to facilitate fabrication. If no articulator is available, a plaster block, built around lubricalted bases of the casts, can be used to stabilize the desired relationship prior to making the vestibular screen. As pointed out previously, the vestibular screen is constructed so that the teeth and alveolar structures either receive or are relieved of muscle pressure, depending on the malocclusion present. In the case of an open-bite, there is often no need to expand the buccal segments and the appliance is allowed to rest on the tissues. In the usual premaxillary protrusion the maxillary arch is narrow; thus, the screen is fabricated so that the intraoral forces (tongue posture and function) can act on the canine-premolar areas, enhancing expansion. For example, in a Class II, Division 1 malocclusion with protruding upper incisors, the upper and lower casts are selectively waxed, after they are mounted in the articulator, with all areas except the lower halves of the maxillary incisors covered. The buccal surfaces of the teeth and alveolar processes are covered with two layers of wax, which extend to the mesial aspects of the first permanent molars (Fig. 6). If the screen is to be made of endothermic acrylic, the wax is then invested and processed in the normal way. If exothermic or self-curing acrylic is used, the wax may be foiled and the screen made directly on the casts. Again, it is stressed that the appliance contacts only the maxillary incisors while holding the cheeks away from the buccal segments.

Volume 76 Number 1

Use of muscle

Fig. 8. Nuk-Sauger

exerciser,

and tongue-thrust. lingual bulb. Bottom

The

used

to eliminate

retained

infantile

deglutitional

appliance serves as a pacifier with a physiologically left After 6 weeks’ use. Lower right 6 years later.

pattern,

forces

9

finger-sucking,

constructed

flattened,

Finger-sucking

The sequelae of finger-sucking are well known. Narrow ma.xillary arch, unilateral cross-bite, anterior open-bite, hyperactive mentalis muscles, and hypoactive upper lip muscles, together with a tendency for the lower lip to cushion to the lingual of the maxillary incisors, are all possible when this habit persists beyond the age of 3 or 4 years. These become self-perpetuating entities when joined by the comlpensatory and adaptive

Fig. 9. Soft plastic exerciser, performs a series of prescribed

similar to vestibular screens. The patient pulls lip exercises 45 to 60 minutes each day.

against

the

ring

as he

forward tongue posture and retained infantile deglutitional thrusting patterns. The early placement of a vestibular screen will not only intercept the worsening condition but may actually correct an existing malocclusion with a Class II tendency (Fig. 7). The best time, from a patient-compliance standpoint, is 3% to 4 years of age, preferably in the early spring or early summer. In my experience, 3 to 6 months of intensive use of the vestibular screen may be all that is necessary. g-12 This demonstrates interceptive orthodontic potential. Mouth-breathing

and open-bite

To increase the usefulness of the appliance as a muscle-training device, Hotz’ recommends the addition of a wire loop to the anterior aspect of the screen. The patient then pulls the appliance forward by grasping the loop while simultaneously resisting the displacement of the screen with tightly closed lip muscles. Alternative appliances to assist in such cases are the Nuk-Sauger exerciser (Fig. 8) or specially fabricated rubber or plastic exercisers (Fig. 9). These exercises and appliances have proved useful in increasing the mobility of scar tissue structures around the mouth, particularly in cleft palate patients, as we have seen in the Craniofacial Anomalies Clinic at the University of Chicago.‘. ” Fingeroth, Kraus, and others place “breathing holes” in the labial aspect of the vestibular screen.g, i”. “r A button with a string attached is placed on the lingual surface, and the patient is instructed to perform exercises by pulling the string through the breathing hole and resisting forward displacement of the screen with contraction of perioral muscles. It is necessary to perform such exercises for % hour daily for beneficial results. Garliner’~ has also recommended similar exercises, using large convex buttons joined by a string. Lip-seal exercises play an important part in other functional appliance routines also, specifically with the Frankel function corrector. Mixed-dentition Class II, Division 1 malocclusions are often associated with excessive epipharyngeal lymphoid tissue and partial airway obstruction. Harvold and Vargervik demonstrated in primates that closing off the nasal passages and creating mouth breathing

Volume 16 Number 1

Use of muscle forces

11

produced an “adenoidal facies” in monkeys. The mandible dropped open, posterior teeth erupted, the maxillary arch narrowed in the canine and premolar regions, and a Class II sagittal relationship was created. 3* 16,25Partial airway obstruction in man may not produce such obvious and dramatic results as this controlled experiment, but the potential does exist, with strikingly similar malocclusions associated with confirmed mouth breathing. Flaccid perioral musculature, hyperactive mentalis muscle function, narrow maxillary arch, excessive overjet, reduced interocclusal clearance, and open-bite tendencies are all possible with tonsil, adenoid, and turbinate obturation of the nasal airways, as shown by Linder-Aronson.17 Long-term studies demonstrate a spontaneous autorotation of the mandible and reduction of malocclusion characteristics when oropharyneal interference is eliminated.i7-I9 Krausg claimed that adenoid bulk actually seemed to shrink somewhat with increased nasal flow and proper respiratory physiology. Part of this may have been due to spontaneous regression of epipharyngeal lymphoid tissue, which normally occurs at from 11 to 20 years of age in most persons. His observations were supported by a study done at the Children’s Nose and Throat Clinic in Prague.15 The oral mucosa frequently becomes edematous and hypertrophic, with mouth breathing, but postpharyngeal, lymphatic, and nasal mucosa are somewhat different from gingival tissue and apparently do not respond in a like manner. In any event, if it is possible to reduce or eliminate mouth breathing, gingival hypertrophy is reduced, perioral muscle tonus may improve, and some of the selfimprovement seen in a 5-year follow-up of tonsillectomy and adenoidectomy cases by Linder-Aronsoni8 is surely possible. Vestibular screens with small breathing holes are valuable adjuncts. Holes may be gradually reduced in size as nasal breathing takes over. The use of the vestibular screen may accelerate the establishment of a normal perioral environment, together with a regimen of lip exercises, such as those recommended by Rogers’ or Franke1.j Resting on the protruding maxillary incisors, with the cheeks held away from canine and premolar areas, arch form can improve significantly and overjet may be reduced. There has been semantic and nomenclature confusion in the literature over the names of different types of screens, shields, or masks, as they are variously called. While some have made no differentiation between the terms oral and vestibular as applied to screens, Kraus’O limited the term oral screen to those appliances with the primary objective of controlling tongue function. Kraus developed the theoretical concept that, by inhibiting faulty muscle function, normal development could be achieved and malocclusions could be intercepted without the appliance actually touching the teeth. In his version of the vestibular screen, the material extended into the vestibule, in contact with the alveolar process, but did not contact the teeth at all. Subsequent clinical experience now shows that maxillary labioincisal contact of the screen is more effective in reducing excessive overjet, however.i2’ 2o Other variations of Kraus’s concept combine oral and vestibular screens (Figs. 10 and 11). This makes a “double oral screen.” A smaller lingual screen is attached to the vestibular screen with two 0.036 inch wires which run through the bite in the lateral incisor area. Such constructions can be useful in abnormal tongue posture and in tonguethrust and open-bite cases particularly. The appliance has the potential of simultaneously eliminating mouth-breathing habits, tongue-thrusting, and maxillary incisor protrusion. Selmer-Olsen,21 former head of the Orthodontic Department at the University of Oslo, has

12

Am. J. Orthod. July 1979

Graber

Fig. 10 Lingual function.

oral

screens,

designed

by Frantisek

Kraus,

to prevent

abnormal

tongue

posture

and

had great experience with functional appliances. He recommends a similar construction basis of for his version of the double screen. He writes, in support of the theorerical appliance action that: 1. The appliance prevents mouth breathing and respiration is forced through the nose, past the swollen lymphatic tissues, reducing the “exudative diathesis ,’ ’ or nasal secretions which clog the nose. The column of air thus stimulates nasal breathing. 2. The increased nasal air activity stimulates nasal tissue, the sinuses, and paranasal circulation and may have a favorable influence on growth of contiguous osseous structures. 3. Since nasal breathing is more difficult and requires more work than mouth breathing, the oral screen induces a more intensive exercise of muscles of respiration in general. (Small holes are made in the screen in the beginning for breathing but are gradually closed as the patient adapts.) 4. The double screen automatically keeps the deforming lip and tongue pressure from the upper and lower front teeth.

Volume 16 Number 1

Use of muscle forces

13

Fig. 11. Combined oral and vestibular screens (double screens) to intercept both tongue and lip and cheek activity. Screen in upper left has primarily an anterior tongue-thrust control function. Remaining views illustrate a lingual antitongue-thrust element, combined with buccal shields to stimulate arch expansion by holding away the cheeks. (Courtesy Frantisek Kraus.)

5. The appliance discourages both thumb-sucking and tongue-thrusting, as well as abnormal postural position of tongue and lips. 6. The appliance stimulates muscle exercise, much as chewing gum does, enhancing the tonicity and serving also as a tensional release as the patient works against the appliance. 7. The lingual pressures of the oral screen portion can retrude maxillary incisors and upright them, closing spaces at the same time. Adding gutta-percha to the lingual aspect of the labial acrylic shield or additional acrylic or finger springs may enhance favorable incisor positioning. It is stressed that the foregoing are clinical impressions and are not supported by scientific studies of controls and experimental subjects as far as tissue response to air flow is concerned. The normal postpharyngeal tissue in a nasal breather does not demonstrate hyperemia and swelling to the degree seen in maxillary labial gingival tissue. In addition to the tissue character differences between gingival and postpharyngeal areas, there is the added factor of a drying out of maxillary gingival tissue in confirmed mouth breathers during sleep. Swelling is probably due to this phenomenon as much as to any factor.” The

14

Graber

Am. .I Orthod. July 1919

Fig. 12. Half vestibular screen, covering lower arch only. The purpose is to eliminate deforming action of a hyperactive mentalis muscle and to allow the tongue to move the lower incisors forward and reduce the crowding present. (Courtesy Bedrich Neumann.)

nasopharyngeal tissues never dry out to this extent. Linder-Aronson’s studies do seem to support Selmer-Olsen’s concern over nasal obstruction and attendant malocclusion.“, ” The vestibular or oral screen should be worn by the patient every night and also during the day when possible. For example, a good time is while doing schoolwork or watching television. The patient is also instructed to perform lip exercises several times a day for a few minutes at a time, at least 30 to 4.5 minutes over a 24-hour period. The lips should be kept in contact at all times to enhance the effect of the appliance and to improve the lip seal. Frinke123 has his patients hold a piece of paper between the lips when sitting quietly or watching television (lip seal exercises). Theoretically, there is no need to check the patient in the office more often than once every 6 to 8 weeks. As soon as the patient has adjusted to the appliance, there is little to be done other than to make sure that the appliance is being worn as prescribed. From a practical point of view, however, patients are better seen every 2 weeks to motivate them and to ensure optimal cooperation from parents in seeing that the appliances are worn as much as possible. When some progress has been achieved with the use of the vestibular screen, it is advisable to reactivate it by adding acrylic on that inner portion of the appliance that is contiguous with the labial surfaces of the maxillary incisors. If this is not done, the screen may contact the border area of the mucosa and vestibule, reducing the effect on the teeth and the immediate supporting alveolar bone.

Volume 76 Number I

Use of muscle forces

0.040

BASE

15

WIRE

ACRYLIC

0.040

AUXILIARY

WIRE

Fig. 13. Lip bumper, labial portion. Wire framework can be used alone or covered with acrylic. The lip is held away from the incisors, as in the half screen (Fig. 12). The wire and acrylic element is either soldered to molar anchor crowns or inserted in buccal tubes and can be inserted and removed as directed.

As with all appliances, there are limitations. Seldom is the vestibular or oral screen the total mechanotherapy. Rather, it should be thought of in terms of an initial assault on the orthodontic problem. The screen is especially suitable in the treatment of developing malocclusions which are associated with an aberrant muscle pattern. The beneficial effect of the screen manifests itself in establishing a better muscle balance between the tongue on the inside and the buccinator mechanism on the outside. With growth and improved function, the mandible assumes a more mesial position in some cases with the guidance from the screen. The tongue may follow it, filling up the oral cavity. At the same time, the vestibular screen and prescribed exercises correct the faulty relationship of the upper and lower lips to each other, and a more nearly normal lip seal becomes possible.23 In developing distoclusions, the constructed forward position of the mandible is assumed to have an effect on the protractor and retractor muscles which are responsible for the mandibular position in the sagittal plane. Frankel claims that, in the new habitual position, the protractor muscles may shorten while the retractor muscles may be lengthened. This, together with the other favorable changes (for example, widening of the maxillary arch, rounding off of the protruding maxillary incisors, closure of spaces, and strengthening of the perioral muscles), contributes to the development of a proper functioning occlusion.23s 2s When a buccal cross-bite condition is already present, with the maxillary segments lingually malposed, the vestibular screen usually improves the maxillary intercanine width, but it may not correct the buccolingual relationship completely. In such instances, other types of removable appliance may be required, such as a split palate appliance, with an expansion screw in the center and acrylic over the maxillary occlusal surfaces.” A double screen prevents anterior tongue-thrust and should eliminate the prolonged infantile deglutitional pattern so often seen in mouth-breathing and thumb-sucking children. The

16

Am. J. Orthod. July 1979

Graber

Fig. 14. Wire and wire and plastic had a palatal the combined

lip bumpers which insert in horizontal tongue-thrust appliance cemented on the upper molars. action, intercepting both tongue-thrust and hyperactive

buccal tubes. This patient also The lateral cephalogram shows mentalis muscle activity.

tongue drops back and moves superiorly in the oral cavity, widening the maxillary intercanine dimension. Many of the oral malformations are the result of a combined tongue and lip activity, with the lip particularly exacerbating the overjet, proclining the maxillary incisors, and retroclining and crowding the mandibular incisors. The vestibular screen is an effective mechanism for reducing or eliminating hyperactive mentalis muscle activity by itself. To reduce lip hypotonicity, however, an exercise discipline must be established and maintained. 5* 2x It is estimated that about 50 percent of developing dentitions demonstrate a flush terminal plane, with the upper and lower buccal segments in an end-to-end sagittal relationship in the mixed dentition. With the loss of the deciduous molars. the differential mesial drift of the first permanent molars, using the larger leeway space in the lower arch and greater second deciduous molar width, allows for the establishment of proper interdigitation. If Harvold’s mouth-breathing experiments are valid, abnormal lip and tongue activity may convert a flush terminal plane relationship into a full-fledged Class II, Division 1 malocclusion.“, 2sThis is why some clinicians consider it important to intercept such cases in the deciduous or early mixed-dentition periods with such devices as the vestibular screen or oral mask, as it has been called by Fingeroth and Fingeroth.13 In event a full Class II malocclusion has already been established, the wearing of an oral screen, even though it has been made with a forward-positioning construction bite, is not likely to correct the anteroposterior malrelationship completely. In such cases, the orthodontist may turn to a functional appliance, such as a propulsor, activator, or Frankel appliance, for more improvement. 20. 23,25One should not hesitate to change appliances if the need is there. Vestibular and oral screens are best suited to work with abnormal lip and tongue activity. However, they may be used in conjunction with extraoral force appliances,

Volume 76 Number 1

Use of muscle forces

Fig. 15. Lip bumper. Top view shows soldered labial element. Note that acrylic mandibular incisors. Vertical loop springs are bent in wire to permit advancement shield as needed. This can be done with ordinary office pliers (middle view). Bottom wire and acrylic element attached to crowns on the lingual aspect and crossing embrasure to the labial for the anterior screen. No occlusal rest is needed, then, as left: Removable labial wire which fits into horizontal buccal tubes. Rubber tubing serves as the lip bumper and can be replaced periodically.

17

stands away from of the labial acrylic right: A soldered over at the canine in top views. Lower in anterior portion

which will reduce the basal discrepancy, allowing the oral screen to achieve its maximum potential of restoring lip tone and proper lip posture. The lip bumper Ocasionally, when there is a problem that is primarily a lower lip habit which flattens and crowds the lower anterior segment, while leaving the maxillary arch relatively normal, a lower vestibular screen can be used (Fig. 12). Lip-sucking and hyperactivity of the

18

Am. J. Onhod July 1979

Gruber

Fig. 16. Removable lip bumpers, again directed variety of clasps may be used for retention.

primarily

at the hyperactive

mentalis

muscle

activity.

A

mentalis muscle can be eliminated in a manner that is similar to the use of the lip shields which are an integral part of the Frankel appliance. Another modification of the simple vestibular screen is the combined fixed and removable appliance called the lip bumper or lip plumper. Since it is the lower lip, by virtue of the hyperactive mentalis muscle, which does the most damage, the lip bumper is usually made for the mandibular arch. 2o First permanent or second deciduous molar bands or crowns are placed, with 0.040 inch horizontal buccal tubes soldered to receive the wire or wire and acrylic assembly, or the labial screen assembly may be soldered directly on the buccal or lingual surfaces of the anchor bands or crowns (Figs. 13, 14, and 15). If buccal tubes are used, the removable bumper element may be tied in and worn continuously or used under the patient’s control as prescribed by the orthodontist. Both the wire skeleton and the combined wire and acrylic shield perform the same function of keeping the lip away from the lower incisors, preventing it from cushioning to the lingual of the maxillary incisors during posture and function. With no labial restraining lip habit, the tongue will then stimulate the lower incisors to move labially, which increases the arch length and reduces the crowding and excessive overjet. This type of combined fixed and removable muscle-anchorage appliance may be used also to upright or restrain mandibular molars in conjunction with conventional orthodontic therapy ,26or it may be used to restore space that has been lost through premature loss and mesial drift of the molar teeth. Coil-spring elements may also be used, instead of the loop stops or soldered stops at the mesial end of the molar tubes. The spring, slipped over the

Volume 16 Number 1

Fig. 17. assisted lingually.

Use of muscle forces

Denholtz appliance by open-coil springs.

used to move maxillary The upper lip activates

molars distally. The wire and the spring action as it pushes

19

acrylic element is the acrylic screen

end of the arch wire, provides a continuing and gentle force against the first permanent molars, as the labial portion of the assembly is resisted by the lower lip. An alternative is to stop the arch wire mesial to the buccal tubes and to bend in vertical loops in the arch that may be adjusted directly in the mouth with office pliers, advancing or retracting the lip bumper element. It is important to break abnormal lip habits as early as possible; the lip bumper and the vestibular screen are excellent and simple interceptive orthodontic appliances for this purpose. Removable lip bumpers, retained by Adams clasps, eyelet clasps, continuous clasps, or even cast clasps, may also be used when the patient’s compliance is assured (Fig. 16). Muscle anchorage is effective in exerting a distal force on the maxillary molars, with or without fixed orthodontic appliances. The Denholtz appliance is similar to those just described and uses a plastic shield that has been molded over the wire assembly, together with coil-spring elements at the mesial surface of the horizontal buccal tubes, to effect the the maxillary molar retropositioning (Fig. 17). Generally, however, a headgear is more effective for such purposes, inasmuch as molar bands have already been placed and a face-bow and extraoral force can deliver more continuous force.27 Thus, the mandibular lip bumper is used more often. It is also more effective, since the mentalis muscle is hyperactive, flowing into the excessive overjet, while the upper lip is hypotonic and likely to exert less force on the shield unless rigorous muscle exercises are prescribed and followed. Summary Orthodontic appliances of simple construction have been described. They are valuable in intercepting the deforming action of perioral muscle function or malfunction. The same muscles that have the deforming potential may be enlisted to correct dental malocclusions. Early interception often prevents a problem of considerably greater magnitude at a later date.

20

Graber

Am J. Orthod. July 1979

REFERENCES I. Hotz, R.: Orthodontia in everyday practice, Berne, 1974, Hans Huber. 2. Rogers, A. P.: Exercises for the development of the muscles of the face, with a view to increase their functional activity, Dent. Cosmos 60: 857-897, 1918. 3. Harvold, E. P., and Vargervik. K.: Morphogenetic response to activator treatment, AM. J. ORIHOD. 60: 478. 1971. 4. McNamara, J. A., Carlson. D. S., Yellich, Cr. M., and Hendricksen, R. P.: Musculoskeletal adaptation following orthognathic surgery: muscle adaptation in the craniofacial region, Ann Arbor, 1978. University of Michigan. 5. Frlnkel. R.: Funktionsorthopldie und der Mundvorhof als apparative Basis, Berlin. 1967. Verlag Volk und Gesundheit. 6. Weinberger, B. W.: Orthodontics: An historical review of its origin and evolution (two vols.) St. Louis, 1926, The C. V. Mosby Company. 7. Schwarr. A. M., and Gratzinger, M.: Removable orthodontic appliances, Philadelphia, 1966. W. B. Saunders Company. 8. Schwarz, A. M.: Gebissregelung mit Platten, Vienna 1938, Verlag Urban und Schwarzenberg. 9. Kraus, F.: Prevence a naprava vyvojovych vad orofacialni soustavy. Prague. 1956, Statni Zdravotnicke nakladdatelstvi. 10. Kraus, F.: Vestibular and oral screens, Trans. Eur. Sot. Orthod., p. 317, 1956. 11. Nord, C. F. L.: Loose appliances in orthodontia, Trans. Eur. Sot. Orthod. p. 246, 1959. 12. Nord, C. F. L.: Een revolutie in die orthodontische apparatur, Ned. Tijdschr. Tandheelk. 72: 832, 1965. 13. Fingeroth, A. L., and Fingeroth, M. M.: Early treatment: Theory and therapy, Orthod. Record 1: 87-99, 1958. 14. Garlinger, D.: Myofunctional Therapy, Philadelphia, 1976, W. B. Saunders Company. 15. Rokytova, K., and Trefna, B.: Use of a vestibular screen for rehabilitation of nasal breathing in children, Cesk, Otolaryngol. 9: 293. 1960. 16. Harvold, E. P.: The role of function in the etiology and treatment of malocclusion, AM. J. ORTHOD. 54: 883, 1968. 17. Linder-Aronson, S.: Adenoids: Their effect on mode of breathing and nasal airflow and their relationship to characteristics of the facial skeleton and the dentition, Acta Oto-laryngol. (Supplement 265). Uppsala. 1970. 18. Linder-Aronson, S.: Effects of adenoidectomy on the dentition and facial skeleton over a period of tive years, Trans. Eur. Sot. Orthod. pp. 85-100, 1975. 19. Woodside, D. G., and Linder-Aronson, S.: Channelization of upper and lower face heights compared to population standard in males between 6 and 20 years, Eur. J. Orthod. 1: 25.40, 1979. 20. Graber, T. M., and Neumann, B.: Removable orthodontic appliances, Philadelphia, 1977. W. B. Saunders Company. 21. Selmer-Olsen, R.: Personal communication, May 23, 1975. 22. Graber. T. M.: Orthodontics: Principles and practice, ed. 3, Philadelphia, 1972, W. B. Saunders Company. 23. Frankel, R.: Technik und Handhabung der Funktionsregler, Berlin, 1973, Verlag Volk und Gesundheit. 24. Cole, R. M.: Early treatment of cleft lip and palate, Chicago, 1970, Northwestern University Press. 25. Harvold, E. P.: The activator in interceptive orthodontics, St. Louis, 1974, The C. V. Mosby Company. 26. Jarabak, J. R.: Technique and treatment with light-wire edgewise appliances, St. Louis, 1972, The C. V. Mosby Company, 27. Graber, T. M., and Swain, B. F.: Current orthodontic concepts and techniques, Philadelphia, 1975, W. B. Saunders Company.