Functional appliance therapy with the bionator

Functional Appliance Therapy With the Bionator Ingrid Rudzki-Janson and Regine Noachtar Since the early 20th century, functional appliance therapy has been a significant part of orthodontic treatment, especially in Europe, where functional appliances have been used to treat many malocclusions, including some skeletal discrepancies. Although the success of functional appliance therapy as reported in numerous short-term studies from 1930 to 1975 led to an euphoric acceptance of this method, the few long-term studies, especially those comparing treated with untreated homogeneous control groups, indicated that the specific skeletal and dentoalveolar effects depended on the individual growth period and pattern of the patient. In this article, a specific functional appliance, the Bionator, is presented. Long-term follow-up studies provide indications for its use. At the present time, functional orthopedic appliance therapy has a more limited but well-defined place in our therapeutic approach. The type and character of the malocclusion determines the indications and contraindications of the functional appliance. Scientific and clinical experience has shown the importance of a differential diagnosis for each patient, which integrates etiology and morphogenesis in the individual treatment objectives for special skeletal, dentoalveolar, and functional regions. Individualization in the construction of the appliance, taking the above-mentioned factors into consideration, is essential for optimal clinical results. (Semin Orthod 1998;4: 33-45.) Copyright © 1998 by W.B. Saunders Company

unctional orthopedics is a t r e a t m e n t aimed at the correction of malocclusions and the improvem e n t of dental arch f o r m and orofacial function. Removable bimaxillary appliances are used to stimulate the muscles of mastication, as well as those of the lips and tongue. T h e main c o m p o n e n t s of these appliances are the acrylic m o n o b l o c , the inclined planes, and the wire elements, all u n d e r the guidance of the construction bite.

F

Construction of the Munich Bionator for C l a s s I I Malocclusions The core of the Munich Bionator (Fig 1) is the acrylic monobloc. Its acrylic surface is s h o r t e n e d in the

From the Department of Orthodontics, Faculty of Medicine, University of Munich, Germany. Address correspondence to [ngrid Rudzki-Janson, MD, Phi), Head of the OrthodonticDepartment, Clinicfnnenstadt, Goethestra[3e 70, D-80336 Miinchen, Germany. Copyright© 1998 by W.B. Saunders Company 1073-8746/98/0401-000558. 00/0

anterior palatal area to provide space for the Coffin spring, which produces an anterior displacement of the tongue. T h e acrylic base should be small, with the lower acrylic portions following the c o n t o u r of the tongue, e x t e n d i n g from the terminal molars on both sides and covering the lower canines and incisors. The u p p e r part extends only laterally. T h e wax construction bite is the most i m p o r t a n t e l e m e n t of the Bionator, as it d e t e r m i n e s the relative position of the j o i n e d u p p e r and lower acrylic parts of the appliance. T h e Bionator is supposed to give a three-dimensional effect; consequently the construction bite must provide three-dimensional control (Fig 2): 1. In the sagittal plane, the m a n d i b l e is positioned anteriorly no m o r e than half a p r e m o l a r width. If the patient is responding to treatment, a n o t h e r Bionator is placed after 6 to 8 m o n t h s based on a new construction bite. Additional appliances may be necessary. 2. Vertically, an edge-to-edge incisal relationship or an o p e n i n g of 2 m m between the incisors usually is r e c o m m e n d e d , d e p e n d i n g on the curve of Spee.

Seminars in Orthodontics, Vol 4, No 1 (March), 1998: pp 33-45

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34

Rudzki-Janson and Noachtar

vital role as well. Balters 1has suggested that this palatal wire stimulates the tongue muscles to provoke a reorientation that may help to correct a dysfunction in the posture of the tongue.

History and Basics

Figure 1. The Munich Bionator is based on the standard Bionator for Class II malocclusions, as developed by Balters s and modified by Ascher. 1°

3. In the transverse plane, the skeletal midlines of the mandible and the maxilla must coincide. The inclined planes in the posterior part of the appliance are trimmed as eruption facets. A combination of the force of eruption and the muscular pressure induced by the construction bite guide the premolars, and in some instances, the lower molars into a more favorable position. The acrylic capping over the lower incisors prevents their undesired protrusion and eruption. The deciduous teeth in the upper and lower buccal segments, as well as the upper first p e r m a n e n t molars, also have acrylic support occlusally; however, the lower first molar may be released to allow eruption in the early part of the treatment. As treatment progresses, the occlusal acrylic of the Bionator should be trimmed step-by-step to allow the premolars to erupt. In this way, an optimal levelling of the curve of Spee is achieved (Fig 3). The Munich Bionator features a variety of wire elements (Fig 4). Wire clasps bent into the interproxireal space (either mesial to the upper first molars or mesial or distal to the lower first molars) help achieve the objective of the construction bite in the sagittal plane. The vestibular wire is a basic feature of the Bionator. Its labial and vestibular components are known as the buccinator-lip arch. Its form supports this muscular arch to produce a negative pressure during lip closure, thereby helping the mandible find its anterior position in the appliance, with a concomitant effect on the lip and cheek musculature. In this way, the Bionator helps to normalize the muscle interplay and reduces the dysplastic influence on the surrounding dentition and bony structure. In addition, a protrusion spring on the palatal surfaces of the upper incisors either maintains their correct position or helps to protrude them, if necessary. The palatal arch, the so-called Coffin spring, plays a

The concept underlying functional orthopedic therapy is to influence the natural growth of the craniofacial complex by using the appliance as a transducer of the muscle forces against the basal parts of the jaws and the alveolar processes. Equally important is the ability of tile appliance to act as a normalizing"template" for the orofacial muscles until a normal occlusion of the teeth can take over. Roux 2 introduced the terms function, functional stimulation, and functional adaptation. Robin s observed that appliances can be used to influence muscle forces; however, it was Andresen4 who developed functional orthopedic therapy. With Hfiupl,5 the Andresen appliance ("Activator") became a part of everyday orthodontics, especially in Europe. Subsequently, various modifications of this appliance were developed, among them the cut-out activators with reduced acrylic surfaces (eg, FR-2 of Frfinkel6) and, in particular, Balters' construction of the Bionator. Ascher 7 has noted that the Bionator is built according to rules that are different from those governing treatment with an Activator. Balters 8,9 and later Ascher 1°al believed that "the equilibrium between tongue and cheeks and especially between tongue and lips, in an oral space of maximum size and optimal limits, offering functional space to the tongue, is essential for the natural health of the dental arches and their relationship to each other. Every disturbance will both deform the dentition and impede growth." According to Ascher, 7 a dental malocclusion and accompanying skeletal deformities very often are the result of abnormal function. He believed that habits, abnormal muscle activity, faulty neck posture and tongue position, incorrect breathing mode, and inadequate lip closure all constitute growth impediments. Consequently, the genetically-determined growth potential of the individual could be realized by using functional appliances. Balters I believed that the main objective of functional therapy was to normalize breathing and to achieve mouth closure. Linder-Aronsonlz has shown that breathing is an essential factor for skeletal and dentoalveolar development, especially in the maxilla. To accomplish these objectives, Baiters a3 developed the Bionator, an appliance later modified by Ascher 7 and which is less bulky then Andresen's original Activator. The modified Bionator does not impair the patient's speech and may be worn day and night. In

Functional Appliance Therapy With the Bionator

35

Figure 2. Criteria for the construction bite in the sagittal, vertical, and transverse dimensions shown on a 9-year-old boy. (A) Intraoral lateral view from the left side in centric occlusion before treatment. (B) The correctly positioned mandible using a wax bite, the basis for constructing the Bionator. (C) Extraoral profile view in centric occlusion before treatment. (D) Extraoral profile view with wax bite in place. addition, it fits loosely in the mouth and can be moved freely by the patient within the oral cavity. Although small and light, it is stable enough to withstand continuous use. Theoretically, an equilibrium between the various orofacial muscles can be achieved only if there is lip closure and the nasal airway functions properly. This equilibrium is the basis for normal development of the orofacial complex. According to the original functional orthopedic theory, a stable result can be achieved only if the muscles are not stretched by the construction bite because excessive stretching will violate the patients's physiological limits.

Functional-Appliance Mechanisms and Their Effects on Morphology and Function There are a variety of opinions concerning how functional appliances operate and how they influence the morphology and function of the orofacial complex. It is clear, however, that all aspects of the genetically-determined individual growth pattern are of utmost importance in functional orthopedics, most especially timing, potential, and direction of growth. The first aspect is the time period during which growth takes place. During the growth period, the

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Rudzki-Janson and Noachtar

Figure 3. (A) Bionator in place during treatment in the mixed dentition. The acrylic is trimmed to tbrm inclined planes that guide the erupting teeth into the correct position. The interocclusal space is small enough that the eruption of the lower premolars is guided by the appliance. (B) The result after all of the posterior teeth have erupted. growth of the viscerocranium corresponds to the growth of the body. Although there is only minimal skeletal growth during the prepubertal period, significant growth occurs during puberty, but with great individual variation. Two of the aims of early functional orthopedic intervention in the prepubertal period are to prevent damage to the erupting teeth and to normalize jaw development. It is assumed that later during puberty, normal growth will not be inhibited by occlusal disturbances. The next two important variables are growth potential and direction. Long!tudinal implant studies by Bj6rk, 14A5Hasund 16 and Odegaard 17 have shown that the growth potential and the direction of the viscerocranial growth are variable; however, this variation is largely correlated with the type of face. These studies also indicate that different parts of the viscerocranium have different growth patterns. It therefore is essential that an assessment of the growth potential and direction be a part of the diagnostic evaluation, because similarly appearing dental relationships may be pre-

sent in patients with different skeletal characteristics. The direction of mandibular growth may be estimated by evaluating the morphology of the mandible. Prediction of mandibular growth direction may be based on the form of the condyle and the size of the gonial angle 17 and thereby estimating the translation tendancy of the mandible. In addition, the curve of the mandible, the lower border of the mandible, the thickness of the cortical bone under the symphysis, the inclination of the symphysis (Nordeval-angle=Nangle 18 and the anterior facial height are used to estimate the rotation tendency of the mandible. The basis for prediction should be as broad as possible taking into account all factors. (Fig 5A). 17,1s The expected positional growth changes can be differentiated into rotation and translation. Hasund, 1° and Segner and Hasund 2° recommended classifying these secondary growth characteristics of the mandible using a grading system, positive values to indicate factors characteristic of a sagittal translation or an anterior rotation and negative values those factors

Figure 4. (A) Elements of the Bionator before construction of the arcylic monobloc: the palatal bar, the "Coffin spring," the protrusion spring for the incisors, the wire clasp mesial to the first upper molars, and the buccinatoMabial bow. (B) The Bionator in place in the lower arch.

Functional Appliance Therapy With the Bionator

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characteristic of a vertical translation or a posterior rotation of the m a n d i b l e (Fig 5B). Several attempts based on clinical e x p e r i e n c e and scientific investigations have a t t e m p t e d to clarify how skeletal and dentoalveolar modifications occur during t r e a t m e n t with functional appliances. At present, however, this subject still remains controversial. 21 Many clinicians are convinced that functional appliances have m o r e than j u s t a dentoalveolar impact and believe that functional appliances may affect the genetically-determined growth pattern. In addition to clinical observations and m o d e l analysis, their hypothesis is s u p p o r t e d by cephalometric studies on both h u m a n s and e x p e r i m e n t a l animals. The animal studies of M c N a m a r a 22 and Petrovic et a l y for example, show that functional appliances can influence both the skeleton and the dentition. It must be kept in mind, however, that results f r o m animal studies cannot necessarily be extrapolated to apply to humans. O t h e r clinicians reject the idea that m a n d i b u l a r growth can be stimulated. Sicher z4 and van der Linden, 25 for example, state that "a skeletal pattern c a n n o t be c h a n g e d . " They believe that a geneticallyd e t e r m i n e d growth pattern c a n n o t be altered significantly and are convinced that the clinical results of functional appliances are because of dentoalveolar modifications and natural growth adaptation. Supporters of this school of thought, however, agree that if intraoral and extraoral forces are used in combination with functional appliances, maxillary growth may be affected to some degree. 26-29 A definitive answer to the question of w h e t h e r the genetically-determined growth pattern can be modified only can be arrived at by c o n d u c t i n g studies based on differentiation of growth that compares a treated sample with a comparable h o m o g e n e o u s u n t r e a t e d group.

Recent Clinical Studies Figure 5. Positive values indicate factors characteristic of a sagittal translation or an anterior rotation. Negative values indicate factors characteristic of a vertical translation or a posterior rotation of the mandible (A). O n the left, a retrognathic facial type with vertical translation and posterior rotation of the maxilla and mandible. The incisal oveijet is reduced by dental compensation. Gro~,n_h increases mandibular length, but does not significantly reduce the sagittal discrepancy of the mandible relative to the maxilla. O n the right, an orthognathic facial type shows sagittal translation and anterior rotation for the mandible and moderate maxillary growth. The incisal overjet is easily corrected by skeletal reaction almost without any dental compensation. The sagittal discrepancy between the maxilla and mandible is reduced significandy (g).

T h e results of two recent studies are summarized. T h e first study 21,s° i n c l u d e d 207 Class II patients, 134 from a treated group and 73 were an u n t r e a t e d control group. Lateral cephalograms and hand-wrist radiographs were analyzed at the b e g i n n i n g and at the end of active Bionator treatment, which typically lasted 12 to 18 months. At completion of treatment, a Class I molar relationship and a vertical overbite of approximately 2 m m had b e e n achieved. Skeletal maturity was assessed in the p r e p u b e r t a l and pubertal phases by m e a n s of hand-wrist radiographs. A classification of facial type was based on the SNA angle for the maxilla and the SNB angle for the mandible. According to Bj6rk ~1 and later Hasund, 19 prognathism of the maxilla and the

Rudzki-Janson and Noachtar

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Figure 6. Individual facial types: retrognathic, orthognathic, and prognathic with a Class II malocclusion and varying inclinations of the maxilla and the mandible. mandible, as well as that of the total face, can be divided into three groups: retrognathic, orthognathic, and prognathic (Figs 6 to 8). The cephalometric values describing the inclination of the jaws and the deflection of the cranial base were noted. 10,3~-35The detailed association between the facial groups and cephalometric values for the different types of faces have been described by Segner. 36 The results of the first short-term Bionator study21,3° (Tables 1 and 2) indicate that both dentoalveolar and skeletal changes occurred in the treatment group. Dentoalveolar changes were more pronounced during the prepubertal stage (Fig 9), and skeletal changes during the pubertal stage (Fig 10). The prepubertal dentoalveolar changes mainly involved protrusion of the lower incisors and retrusion of the upper incisors. The Class II molar relationship and overjet were corrected. In contrast, the Class II molar relationship and overjet remained unchanged in the untreated group, and there were almost n o dentoalveolar changes. Skeletal effects, namely a slight increase in the size of the mandible, were insignificant in the prepubertal stage, however, during the pubertal stage,

Figure 7. Floating norms (Hasund Box) for differentiating the skeletal disharmonies and facial types. (Reprinted with permission from Segner D, Hasund A. Individualisierte Kephalometrie. (2nd ed) Hamburg: Dietmar Segner, Verlag and Vertrieb, 1994. 2°)

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Figure 8. Cephalometric measurements used in this study: SNA, SNB, ANB, NSBa, NL-NSL, ML-NSL, ML-NL, Go angle, Index, Interincisal angle, ±-NA °, T-NB°, ±-NA mm, T-NB mm. Index is the proportion of the anterior facial height. Index = N-Sp'/Sp'-Gn. ± indicates the upper incisors. T indicates the lower incisors.

39

F u n c t i o n a l A p p l i a n c e Therapy W i t h the B i o n a t o r

T a b l e 1. First Study: B i o n a t o r E f f e c t s - T r e a t e d G r o u p Prepuberty (n = 90)

Puberty (n = 44)

Variables

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SNA SNB ANB NSBa NL-NSL ML-NSL ML-NL Go-Angle Index Z -T° Z-NA° T-NB° Z-NAmm T-NBmm

79.77 75.43 4.37 132.04 6.96 33.41 26.43 125.70 81.16 130.48 20.09 23.56 3.55 3.91

79.63 75.78 3.89 131.80 7.15 33.61 26.44 125.95 80.93 131.24 19.28 25.43 2.97 4.73

0.14 - 0.35 0.48* 0.24 - 0.19 -0.20 -0.01 -0.25 0.23 - 0.76 0.81 -1.87" 0.58* -0.82*

80.16 76.10 4.10 133.30 6.81 31.31 24.50 123.31 81.46 134.09 18.60 22.99 2.55 3.41

79.82 76.43 3.41 132.94 7.24 31.78 24.53 123.40 81.34 134.45 18.33 23.16 2.59 3.82

0.34 - 0.33 0.69 0.36 - 0.43 -0.47 -0.03 -0.09 0.12" - 0.36 0.27 -0.17 -0.04 -0.41

NOTE. Mean values and mean changes of the first Bionator study showing the treatment effects (T1 = pretreatment, T2 = until class I occlusion was established). * P < .001.

t h e r e were only slight, n o n s i g n i f i c a n t d e n t o a l v e o l a r changes, b u t p r o n o u n c e d a n d significant skeletal changes. A c o m p a r i s o n o f the B i o n a t o r a n d u n t r e a t e d control groups in the p r e p u b e r t a l a n d p u b e r t a l phases revealed significant differences only in the dentoalveolar area. A c c o r d i n g to the a u t h o r s ' findings in this first study, the t r e a t m e n t results s h o w e d that this kind o f B i o n a t o r basically causes d e n t o a l v e o l a r adaptation. It did n o t increase t h e individual, genetically-determ i n e d rate o f m a n d i b u l a r growth a n d h a d n o influe n c e o n the maxilla. T h e r e d u c t i o n o f the ANB angle resulted f r o m the natural p a t t e r n o f m a n d i b u l a r growth. Because the growth in t h e maxilla was less

p r o n o u n c e d , the b o n y profile s t r a i g h t e n e d . T h e s e conclusions were r e i n f o r c e d by factor a n a l y s i s F which also s h o w e d the h o m o g e n e i t y o f the t r e a t e d a n d u n t r e a t e d groups. T h e q u e s t i o n remains, however, as to why is t h e r e n o c o n s e n s u s in o r t h o d o n t i c s relative to the effects o f f u n c t i o n a l a p p l i a n c e therapy. T h e r e are c e p h a l o m e t ric studies t h a t indicate that f u n c t i o n a l appliances have a skeletal effect. T h e latter c o u l d be the lack o f e m p l o y i n g a p p r o p r i a t e c o n t r o l g r o u p s o r the results o f c o m p a r i s o n s o f h e t e r o g e n e o u s groups. T h e s e c o n d study r e p o r t e d h e r e 38-4° d r e w o n the first t r e a t e d g r o u p o f 134 Class II patients with retrognathic m a n d i b l e s at the b e g i n n i n g o f t r e a t m e n t . They

T a b l e 2. First Study: B i o n a t o r E f f e c t s - U n t r e a t e d G r o u p Puberty (n = 18)

Prepuberty (n = 55) Variables

T1

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T1

T2

Difference T1 - T2

SNA SNB ANB NSBa NL-NSL ML-NSL ML-NL Go-Angle Index Z-T ° Z-NA° T-NB° Z-NAmm T-NBmm

79.64 75.45 4.19 131.98 7.03 33.06 25.98 124.61 81.56 135.39 18.55 21.85 2.64 3.21

79.29 75.64 3.65 131.76 7.06 33.41 26.30 124.60 80.60 132.84 20.00 23.32 2.93 3.75

0.35 -0.19 0.54 0.22 - 0.03 -0.35 0.68 0.01 -0.04 2.55 - 1.45 - 1.45 -0.29* -0.54

80.22 75.69 4.47 133.36 6.25 32.83 26.56 125.44 79.48 133.03 20.78 21.47 3.0O 3.33

79.81 76.00 3.78 132.00 6.44 32.61 26.11 124.89 80.61 132.78 20.47 22.58 3.17 4.19

0.41 -0.31" 0.69

NOTE. Mean values and mean changes of the untreated group of the first study. *P < .00.

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Rudzki-Janson and Noachtar

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had been treated only with a Bionator (Group I) were compared with 31 of the 99 patients who had required further treatment with headgear and fixed appliances (Group II) after the Bionator phase. All patients were treated without extraction and all had a stable Class I occlusion and a harmonious profile at the end of treatment. The condyles were located in a normal position within the fossa, both in centric relation and centric occlusion. Clinical examination of these patients and mounted piaster models illustrated an apparently good treatment result. An examination of the occlusion according to the Helkimo indices41 revealed only rare interferences9 The cephalometric data were compared at four different stages: at the beginning of treatment (1), after the establishment of a Class I occlusion by =

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Figure 9. Superimposition of the cephalometric tracings showing changes during the prepubertal stage during Bionator treatment of a 9-year-old boy with Class II malocclusion and deep bite. Beginning (solid line) and end of Bionator treatment (dotted line). (A) Superimposition in the anterior cranial base structures as recommended by Bj6rk, 14 shows that the dentoalveolar changes are more pronounced than the skeletal changes. (B) Superimposition of the symphysis to evaluate the amount and direction of change in the lower incisors, to show the amount of protrusion of the lower incisors. were treated with a Bionator until a dentoalveolar Class I occlusion and a normal overbite and oveljet had been achieved. After Bionator treatment for 2 to 3 years, 99 patients (74%) required further treatment with headgear and fixed appliances due to an unstable occlusion and a variety of dental problems such as spaces, crowding, rotations, or tipping. Thirty five patients (26%) showed acceptable results, that is a stable Class I occlusion and an adequate alignment of the arches (Figs 11-14). The orthodontic treatment and retention phase for all patients lasted 4 to 5 years. Five years after retention, 28 of the 35 patients who

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B Figure 1O. Superimposition of the cephalometric tracings showing changes during Bionator treatment in the pubertal stage, shown in a 12-year-old boy with a deep bite Class II malocclusion; beginning (solid line) and end of Bionator treatment (dotted line). (A) Superimposition on stable structures of the anterior cranial base, as recommended by Bj6rk, 14 shows that the skeletal changes are more pronounced than the dentoalveolar changes. (B) Superimposition on the symphysis indicates that the lower incisors remain unchanged.

Functional Appliance Therapy With the Bionator

4-1

Figure 11. Study models of a patient with Class II malocclusion before treatment. (A) Before treatment. (B) After Bionator therapy, and (C) 5 years after retention. Bionator therapy (2), after the main treatment, either continuously with Bionator or with headgear and fixed appliances was completed (3) and 5 years out of retention (4). Mandibular measurements of both groups (Tables 3 and 4) indicated a continuous

increase in the size of the mandible and a decrease in both the distal skeletal jaw relationship and the gonial angle. The reaction of the mandible was significantly greater in Group I (only Bionator), indicating a reduction of maxillary prognathism probably induced

Figure 12. Profile photographs of the same patient shown in Fig 11. (A) At the beginning of treatment. (B) At the end of treatment. (C) 5 years after retention.

Rudzki-Janson and Noachtar

42

Figure 13. Lateral cephalograms of same patient as in Figures 11 a n d 12. (A) At the b e g i n n i n g of treatment. (B) After 2 years of Bionator treatment. (C) 5 years after retention. by the additional extraoral anchorage. 26,42,4s O n the other hand, the differences between Group I a n d II proved to be negligible. Regarding skeletal maturity d u r i n g the time of investigation, both groups had reached the stage of completed growth (Ru) at the comparison stage D. 44 T h e authors were interested specifically in the question as to why some of the patients r e s p o n d e d better than others. Schudy 45 stated that the vertical d i m e n s i o n was the key to a good sagittal position of the face. Therefore, the authors c o m p a r e d the two groups, using the Lavergne analysis. 46,47 Based o n a longitudinal study of subjects with metallic implants, it has b e e n shown that the sagittal development of the m a n d i b l e is closely related to the rotational pattern of face. Using cephalometric a n d other variables, the authors 46 were able to specify morphological combinations that characterized the patients with a specific rotational pattern (Fig 15).

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According to the Lavergne a n d Petrovic analysis, Group I (only Bionator treatment) consisted of those patients who had an anterior m a n d i b u l a r rotation pattern a n d a regular rotation pattern for the maxilla. The latter were classified as A1DDB, according to the classification scheme of Petrovic, Lavergne et a123,46,47 (Fig 16). The majority of the patients of Group II (those who n e e d e d additional treatment) b e l o n g e d to a rotation pattern group characterized by a regular m a n d i b u l a r rotation a n d a moderate posterior maxillary rotation a n d these were classified as R1NDB, according to the system of Petrovic, 23 Lavergne et al.46,47

.:

C/ "-'-4

i

,o.*"

Figure 14. Superimposition (following the r e c o m m e n dations of Bjork 14-15) of cephalometric tracings of same patient as in Figures 11, 12, a n d 13. At the b e g i n n i n g of treatment (solid line), at the e n d of t r e a t m e n t (hyphenated line), a n d 5 years after retention (dotted line).

4.5 %

-"x..." ,/," "W

9.5 %

Figure 15. The four m a i n combinations of facial rotation a n d their impact o n sagittal development of the mandible. The frequency of each type is given in percentages (Reprinted from Maxillary rotation during h u m a n growth: A n n u a l variation a n d correlations with m a n d i b u l a r rotation by Gasson N a n d LavergneJ from J Acta O d o n t Scand 1977; 35:13-21, by permission of Scandinavian University Press. 4s)

43

F u n c t i o n a l Appliance Therapy W i t h the Bionator

T a b l e 3. S e c o n d Study: G r o u p I: T r e a t e d Only With B i o n a t o r t Variables

SNA SNB ANB NSBa NL-NSL ML-NSL ML-NL Go-Angle Index Z-T ° L-NA° T-NB° L-NAmm T-NBmm

a

80.05 75.37 4.68 134.07 7.07 33.62 26.67 125.72 80.67 132.51 19.62 22.92 2.72 3.65

B

80.12 76.42 3.73 133.46 7.22 33.72 26.38 126.03 79.65 131.50 19.46 25.24 2.82 4.67

C

80.05 76.99 3.18 133.25 7.74 33.14 25.39 124.69 79.44 132.63 20.15 24.04 3.23 4.42

D

Difference (A - B)

Difference (B - C)

Difference (C - D)

80.91 78.18 2.72 132.08 7.28 31.46 24.19 123.08 78.13 132.98 20.72 23.59 3.88 4.60

-0.07 -1.05"** 0.96** 0.61 -0.15 -0.10 0.28 -0.32 1.02 1.00 0.16 -2.32* -0.10 -1.02"*

0.07 -0.57* 0.54* 0.21 -0.52 0.58 0.99*** 1.34"** 0.22 -1.12 -0.69 1.20 -0.41 0.25

-0.86* -1.20"* 0.47 1.17" 0.46 1.68"* 1.20"** 1.61"** 1.31 -0.36 -0.57 0.45 -0.65 -0.18

NOTE. Mean values and mean changes of the second Bionator study: Group I received only Bionator treatment. (A) Before Bionator treatment, (B) 2 years after beginning treatment, (C) end of Bionator treatment, and (D) 5 years after retention. The mean treatment time was 4 years. t ( n = 26). *P < .05. * * P < .01. ***P < .001. things as universal appliances. T h e m o r e simple an appliance, the m o r e limited is its application. This applies to the Bionator, w h i c h s h o u l d n o t be u s e d w i t h o u t a t h o r o u g h analysis o f the patient.

Conclusions T h e t r e a t m e n t effects o f B i o n a t o r t h e r a p y are primarily the result o f d e n t o a l v e o l a r adaptation. T h e M u n i c h B i o n a t o r n e i t h e r inhibits n o r stimulates skeletal growth; however, if patients are a p p r o p r i a t e l y selected

using the sensitive diagnostic criteria o f facial m o r p h o l ogy a n d growth, the B i o n a t o r can achieve stable, functional, a n d esthetically acceptable results (Figs 11 to 14). T h r e e factors m u s t b e k e p t in m i n d w h e n considering B i o n a t o r t r e a t m e n t : 1. T h e prospective patients m u s t have an orthog n a t h i c facial type (the maxillary position), a favorable growth p a t t e r n , a n d an a n t e r i o r rotation o f the m a n d i b l e a n d t h e maxilla i n d e p e n d e n t o f the i n c l i n a t i o n o f the u p p e r a n d lower jaws. Moreover,

Table 4. S e c o n d Study: G r o u p II: First Phase T r e a t m e n t With Bionator, S e c o n d Phase T r e a t m e n t With H G a n d Fixed Appliances t Variables

SNA SNB ANB NSBa NL-NSL ML-NSL ML-NL Go-Angle Index L-T ° L-NA° T-NB° L-NAmm T-NBmm

A

79.20 74.80 4.25 132.47 7.52 32.47 24.86 124.95 83.38 132.66 20.23 22.54 2.91 2.94

B

79.09 75.27 3.70 132.50 7.72 32.69 24.86 124.72 82.74 132.36 19.06 24.56 2.70 3.86

C

78.92 75.42 3.55 129.03 7.97 32.45 24.34 124.56 83.73 132.25 19.72 24.44 2.69 3.70

D

Difference (A - B)

Difference (B - CO

Difference ( C - D)

78.50 75.77 2.73 131.78 8.70 29.13 21.69 121.17 83.72 134.11 22.84 20.45 3.05 2.84

0.11 -0.47" 0.55* -0.03 -0.20 -0.22 0.00 0.23 0.63 0.30 1.17 -2.02* 0.20 - 0.92***

0.17 -0.16 0.16 3.47 -0.25 0.23 0.52 0.16 -0.99 0.11 --0.66 0.13 0.02 0.16

0.42 0.34 0.81"* -2.75 -0.73 3.33* 2.66*** 3.39*** 0.02 -1.86 -3.13 3.98** -0.36 0.86*

NOTE. Mean values and mean changes of the second Bionator study: Group II received combined treatment (Bionator, headgear, and fixed appliances). (A) Before Bionator treatment, (B) end of Bionator treatment, start of fixed appliance therapy, (C) end of treatment, (D) 5 years after retention. Mean treatment time was 4 years. t ( n = 32). *P < .05. * * P < .01. ***P< .001.

Rudzki-Janson and Noachtar

44

I

,,

t

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\

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I

I

~

tl t,,,

°,ol°,°l°,ol

..\I II..\I ,~\/ ~z " ~=

¢

0

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a

/ / ~o

/ ,I /c/c/ /~'1

\.

c/c.::~O0

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~ \

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. . . . . . . . . . . . . . . . . . . Occlusal relationship

.,

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Maxillary rotation

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J Basal growth difference

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Ilst level . . . . . . . .

2nd level 3 z d !eve/ ...RelaAiv~ influence of * c o m p ~ r a t o r "

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Reiative infiuence of celi and molecular biology features

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Figure 16. M o r p h o g e n e t i c analysis o f L a v e r g n e a n d Petrovic. Based o n c e p h a t o m e t r i c values, g r o u p s with d i f f e r e n t m o r p h o l o g y were categorized. T h e y were a r r a n g e d in a n a r b o r i z a t i o n with t h r e e m a i n b r a n c h e s , e a c h o f w h i c h indicates a d i f f e r e n t p r o g n o s i s for the d e v e l o p m e n t of t h e m a n d i b l e . ( R e p r i n t e d with p e r m i s s i o n f r o m Petrovic A, S t u t z m a n n J , L a v e r g n e J . Effect o f f u n c t i o n a l a p p l i a n c e s o f t h e m a n d i b u l a r cartilage. G r a b e r TM (ed) : Physiologic p r i n c i p l e s o f f u n c t i o n a l appliances. St Louis, Mosby, 1985:38-52. 23)

t h e r e s h o u l d b e only a m o d e r a t e d i s c r e p a n c y dep e n d i n g o n t h e individual facial type a n d character. 2. A d i f f e r e n t i a t e d analysis o f t h e p o s i t i o n of the lower incisors is i m p o r t a n t for t r e a t m e n t timing. T h e individual m o r p h o l o g i c a l a n d f u n c t i o n a l t r e a t m e n t goal s h o u l d b e f o c u s e d o n individual guidelines, n o t m e a n values. 3. T h e m a i n i n d i c a t i o n for t h e B i o n a t o r is the n e e d to e l i m i n a t e any c o n t r i b u t i n g factors t h a t may cause m a l o c c l u s i o n , s u c h as p a r a f u n c t i o n s , h a b i t u a l b r e a t h i n g t h r o u g h t h e m o u t h a n d f o r c e d bites. Early d e t e c t i o n o f a f u n c t i o n a l p r o b l e m , its subsequent correction, and the maintenance of the newly e s t a b l i s h e d f u n c t i o n a l e q u i l i b r i u m are crucial. I n conclusion, t h e prerequisites for successful Bionator t r e a t m e n t i n c l u d e p a t i e n t selection b a s e d o n individual m o r p h o l o g y a n d growth, a n d t h e precise c o n s t r u c t i o n of the n e c e s s a r y appliances.

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Functional Appliance Therapy With the Bionator

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45

32. Bj6rkA. Cranial base development. AmJ Orthod 1955;41: 198-207. 33. Bj6rk A. The relationship of the jaws to the cranium. Introduction to Orthodontics. London: McGraw-Hill, 1960. 34. Quarnstr6m K, Sarngts K. R6ntgenkefalometriska studien av forandringar vid funktionskakortopedisk behandling av distalbett. Odontol Revy 1954;5:118-122. 35. Solow B. The pattern of craniofacial associations. Acta Odont Scand 1966;46 (Suppl) 36. Segner D. Floating norms as a means to describe individual skeletal patterns. EurJ Orthod 1989; 11:214-220. 37. Janson I, Uberla K_ Faktorenanalytische Auswertung einer Untersuchung fiber die Wirkungsweise des Bionators. Fortschr Kieferorthop 1979;40:494-503. 38. Euba A. Skelettale und dento-alveol/ire ~mderungen bei der kieferorthop/idischen Behandlung mit der BionatorModifikation nach Aschei: Eine kephalomeuische Studie. 1986, Diss, LMU, Munich. 39. Leibig T. Funktionelle Analyse Bionator-behandelter Patienten. 1986, Diss, LMU, Munich. 40. Janson I. Morphologische Kriterien fflr die Indikation einer Behandlung mit der Bionatormodifikation nach Ascher. Fortschr Kieferorthop 1987;48:71-86. 41. Helkimo M. Studies on function and dysfunction of the masticatory system II: Index for anamnestic and clinical dysfunction and occlusal state. Swed DentJ 1974;67:101112. 42. Poulton DT. The influence of extra-oral traction. Am J Orthod 1967;53:8-18. 43. Graber TM, Swain BE Current Orthodontic Concepts and Techniques. Philadelphia, PA, Saunders, 1975. 44. Bj6rk A. Timing of interceptive orthodontic measures based on stages of maturation. Trans Eur Orthod Soc 1972;61-74. 45. Schudy FE Vertical growth versus anteroposterior growth as related to function and treatment. Angle Orthod 1964; 34: 75-93. 46. Lavergne J, Gasson N. Analysis and classification of the rotational growth pattern without implants. BrJ Orthod 1982;9:51-56. 47. Lavergne J. Morphogenetic classification of malocclusion as a basis for growth prediction and treatment planning. BrJ Orthod 1982;9:132-145. 48. Gasson N, Lnvergne J. Maxillary rotation during human growth: Annual variation and correlations with mandibular rotation. J Acta Odont Scand 1977; 35:13-21.