Treatment of mandibulofacial dysostosis A case report Ane Ten Hoeve
Assen, The Netherlands
I n March, 1971, an ]l-year-old boy was referred to the orthodontic clinic at the College of Dentistry of the University of Groningen by an otorhinolaryngologist (Figs. 1 and 2). A team of physicians had made a diagnosis of a systemic disease, mandibulofacial dysostosis (Treacher-Collins syndrome). The structures involved in this illness are derived from the first branchial arch, groove, and pouch. 1 This patient presented the following characteristics of the disease : (1) anti-Mongoloid palpebral fissures, (2) malformation of the pinna, (3) frontal bossing, (4) depressed cheek bones, (5) high, narrow palatal vault, (6) retrognathic chin, (7) fishlike mouth, (8) some deafness (due to a defect in the ossicle), and (9) evidence of mental retardation. Orthodontic examination revealed a Class I subdivision malocclusion in the transitional phase of losing the posterior deciduous teeth followed by the eruption of their permanent successors (Figs. 3 to 5). There was an anterior open-bite to the extent of 10 mm. The maxillary buecal segments were in lingual cross-bite on both sides. Dentally, it was noted that the maxillary lateral incisors were pointed and the first molars showed evidence of hypocalcification. There was a history of active rickets between the ages of 4 and 5, which may explain the delay in dental eruption. An intensive radiographic evaluation was undertaken. Intraoral dental films were secured for routine caries inspection and to determine the relative eruptive positions of the remaining permanent teeth. The panographic and Lilienfeld (Waters) (Figs. 6 and 8) radiograms revealed underdevelopment and defects in the zygomatie bones. A Parma radiogram (Fig. 7) was taken to divulge any problems in the temporomandibular joint. This film also disclosed the defects in the zygomatic tubercle on the left side. It further showed that the condyles appeared to be blunted and that the rami were quite short. The anteroposterior From the Department of Orthodontics, University of Groningen, Groningen, The Netherlands. Read before the European Begg Society, Santa Margarita, Italy, M~y, 1974. 540
vozume 69
Mandibulofacial dysostosis
Number 5
541
Figs. 1 and 2.
Figs. 3 through 5.
view cephalometrically validated the presence o5 a deviation in the mandible toward the right (Fig. 9). The facial photographs also revealed a poor developmental pattern. The mandible was recessive, retrognathic, and displaced to the right. The patient had been plagued with periods of otitis media. This middle ear infection was persistent and remained chronic on the right side. To summarize, there was a severe open-bite malocclusion (Fig. 10), complicated by many osseous and developmental defects, and difficulty in proper speech pronunciation, but the swallowing pattern was quite normal. Treatment planning
The patient displayed considerable resistance to accepting orthodontic therapy. Massive maternal urging was required to convince him that treatment was
542
Te~
Hoeve
A~,~. J. Orthod. May ] 9 7 6
Fig. 6.
Figs. 7 through 9.
Ma~tdibulof acial dysostosis
V o l ~ t ~ e 69
Nu~nber 5
ANB
2,5"
/ - SN
10 6*
_* -T
11o"
M P -SN T-AP
68* 9ram
Fig. 10.
Figs. 11 through 13.
543
544
Ten Hoeve
A~l~. J. O r t h o d . May 1976
Figs. 14 through 17.
essential and could be helpful. When he did accept treatment, members of the Orthodontic Department at the University of Groningen were uncertain as to what should be done. Should the patient be treated at once ? Would it be better to attempt some minor corrective tooth movement and then transfer the patient to oral and plastic surgeons for the major corrective procedures? A f t e r many interdepartmental conferences, it was decided that a trial period of orthodontic treatment should be attempted. The prognosis was guarded and uncertain. Several theoretical considerations influenced the decision. Reitan 2 has stated that, if extrusion of teeth is a desired objective, it is best accomplished when the teeth are erupting. This is the time when the periodontium is proliferating and can better adjust to the new tooth positions. BjSrk 3 also reported that the optimum time to extrude teeth is during periods of growth. Growth also occurs at the alveolar crests at this time. Another advantage is the use of a functional appliance, such as an activator. The objective was to stimulate the growth of the right condyle in an effort to minimize the mandibular deviation. The members of the Orthodontic Department decided that the case should not be treated with only one particular system of mechanotherapy; rather, a combination of several approaches would be advisable. The initial appliance would be an activator, and thereafter the treatment would gradually work into full banded appliances. Treatment
The activator was constructed so that the molar relationship was normal and the midline harmonious (Figs. 11 to 13). No effort was made to correct the molar
Ma~tdib~tlofacial dysostosis
~ozu,~e 69 Nu~nber 5
545
Figs. 18 and 19.
Figs. 20 and 21.
Figs. 22 and 23.
cross-bites at this time. It was not easy for the patient to place the activator, because of his small mouth; however, he did apply himself, and this added effort forced the mandible to shift toward the left. The activator was constructed with enough clearance to allow for extrusion of the upper and lower anterior teeth. After this functional appliance had been placed, the maxillary and mandibular incisors were banded with Begg bracket attachments. Box elastics were worn during the waking hours (Fig. 14), and four vertical elastics were worn during the sleeping hours (Fig. 15). The response was favorable, even though there was
546
-~'"- JMa~/ o,.thoa. 197(;
T en Hoet, e
Figs. 24 through 27. a tendency for the incisors to overlap slightly. The patient became more enthusiastic about orthodontic t r e a t m e n t as the i m p r o v e m e n t became obvious. The activator was worn for 4 months only (Fig. 16). The first molars were then banded and arch wires were placed. Directional elastics were prescribed to f u r t h e r reduce the midline discrepancy and to f u r t h e r correct the molar relationship. A Class I I elastic was worn on the right side and a Class I I I elastie on the left side (Fig. 17). No effort was made to correct the molar cross-bites, since this might adversely counteract f u r t h e r bite closure in the incisor area. Up to this point, the patient had been most cooperative and enthusiastic. H e suddenly found greater chewing ability, and he enjoyed eating more than ever. I n particular, he learned that he could bite into his favorite snack, Swedish crackers, on whieh he could only suck before his appliances had been placed.
VoZume 69
Number 5
Ma~tdibulofacial dysostosis
547
Figs. 28 through 31.
Figs. 32 through 35. Results
In January, 1972, the patient suddenly began to lose interest and his cooperation was faulty. He refused to wear elastics, appointments were broken, the arch wires seemed to become distorted, and there was no effort to sustain proper dental hygiene. Several conferences were held with the patient and his mother, but it was not until January, 1973, that he decided to cooperate again. In the interim,
548
Te~t Hoeve
A~)~. J. Orthod. M ay 1976
Fig. 36.
Figs. 37 through 40.
the bite reopened several millimeters. It was apparent that there had been quite a personality change. The signs of mental retardation were diminishing. His study habits improved, and he was preparing to enter high school (Figs. 18 and 19). The maxillary premolars had erupted into lingual cross-bite, and this was corrected with elastics (Figs. 20 and 21). As these teeth moved buccally, the molars also moved in a favorable direction. Arch wires were then placed on the maxillary and mandibular teeth, with vertical elastics to gain maximum interdigitation. At the same time, the molar cross-bites were completely corrected with rubber bands. Occlusal relations in June, 1973, are illustrated in Figs. 22 to 27. All interdental spaces had been eliminated and the teeth were in good alignment. The orthodontic objectives were now related to root control and root repositioning. The lateral incisors required uprighting to enhance esthetics. The premolars had
rolu.~ 69
Mandibulofacial dysostosis
2¢l~mber 5
549
Fig. 41.
Figs. 42 and 43.
been expanded and tipped so much that their root apices were positioned too far lingually. It was determined that there was sufficient bone on the buccal surfaces to move these teeth into more upright positions. In order to accomplish this root movement, a modification of the Brandt 4 lower reverse torquing complex was prescibed. In an effort to predetermine the action-reaction possibilities, this auxiliary was tested with a simple experiment upon a typodont (Figs. 28 to 30). This was made of 0.014 inch resilient wire, with four small spurs (Fig. 31) which were activated occlusally on the distal flanges of the premolar brackets. The four-spur unit was pinned gingivally to a well-formed 0.016 inch base wire. The reciprocal action on the incisors was a bit surprising. It indicated an extrusive action on the anterior segment. Since we were inexperienced with this torquing complex under these conditions, the actual force applied with the spurs was kept to a minimum (Figs. 32 to 35). The loops of the base wire, in addition to their other uses, were available for the application of elastics, thus adding to the versatility of this appliance. I f improvement for cuspal interdigitation was required, elastic bands could be placed on these loops in whatever direction desired.
550
Te~
Hocvt~
~t m. J. O r t h o d . May 1976
Figs. 44 through 46.
F o u r months later the lower reverse torquing complex was removed. With the method devised by L. I ) e r m a u f ~ at the Groningen D e p a r t m e n t of Orthodontics, it was determined t h a t the premolar roots had been torqued buccally a total of 12 degrees. This was deemed significant root movement and enhanced confidence in this wire complex for increased control over roots. The models shown in Fig. 36 illustrate the condition of the teeth following completion of the buccal root torque on the premolars. These records also indicate that the molars had been expanded a total of 10 ram. In an effort to improve their stability, a torquing unit was devised to move the molar roots buecally. Twin brackets were placed on the molar bands with a rectangular s p u r between them ; this was then activated against the bracket flanges. This a r r a n g e m e n t protected the spur, which could not be ~ e l t e r e d if a buccal tube was used (Fig. 37). Note the reciprocal extrusive action on the anterior segment. Fig. 38 demonstrates how this arch wire was seated. Figs. 39 and 40 show the actual appliance that included buccal root torque. A f t e r 4 months the molar roots could be palpated beneath the cortical plate. The torquing appliance was then removed. With D e r m a u t ' s method, it was demonstrated t h a t 15 degrees of bueeal torque on the molar roots had been attained (Fig. 41). The intermolar width had been maintained during the torquing procedure. All appliances were removed in March, 1974, and a tooth positioner was
Votu,~e G9
Number
Ma~tdibulofacial dysostosis
5
551
Figs. 47 through 50. placed as a retaining device. This was Besides holding the teeth, there was stimulate as much muscular activity about 4 months, a f t e r which the boy need" to do so.
worn at night and during 4 daytime hours. the additional objective of a t t e m p t i n g to as possible. Cooperation was excellent for wore the positioner whenever he "felt the
552
Ten goeve
A m . J. Orthod.
May 1 9 7 6
Figs. 51 and 52. Posttreatment analysis
In the posttreatment analysis, it was obvious that there had been moderate improvement in facial esthetics (Figs. 42 and 43). The occlusion was acceptable, and the cuspal interdigitation in the posterior segments was good. If the canines would interlock more favorably, perhaps guided by the positioner (Figs. 44 and 45), a further improvement in the occlusion might occur. A panographic radiogram (Fig. 46) showed that the dentition had not deteriorated following 32 months of active treatment. The before- and after-treatment records (Figs. 47 to 50) illustrate the correction and the improved midline relationship. Summary
It appears that the major objectives of orthodontic treatment have been achieved. Facial esthetics is improved and occlusal relations are normal. There is evidence that the hoped-for repositioning of the mandible (Figs. 51 and 52) has occurred. The Parma radiogram (Fig. 53) revealed that during the
Ma~tdibulofacial dysostosis
V o l u b l e 69 Number 5
PRE* pO6TTRI~Al~qENT TREATMENT
R
ANB _l . SN
2,6° 10~
4° 91°
T - AP
9~
7~
553 //
L
@ Figs. 53 and 54.
Figs. 55 through 59.
first year of treatment there was significant condylar growth on the right side. The use of the activator thus appears justified, as this appliance was instrumental in correcting the mandibular deviation. Figs. 53 and 54 show the cephalometric changes over the 3-year period of treatment. This type of growth pattern is not favorable. It is a constant reminder of the uncertainty of a stable result. Figs. 55 to 60 were taken 8 months after band removal. The treatment plan followed in this case required the application of several systems of mechanotherapy. An effort was made to relate several theoretical aspects of orthodontics to the practical mechanical procedures.
554
TcH H o e u c
A~. J. Orthod. May 1976
Fig. 60. The author acknowledges the assistance in the preparation of this study to R. L. Dijkstra, P. Hartevelt, and K. J. Poel, for the photographs; to Raymond Levin, Johannesburg, South Africa, for advice on gathering the material and data; to Kees Booy~ Department of Orthodontics, University of Groningen, for aid and guidance during the treatment of this patient; and to Sidney Brandt, for assistance with the manuscript.
REFERENCES 1. Gorlin, Robert J., and Pindborg, Jens J.: Syndromes of the head and neck, New York, 1964, McGraw-Hill Book Company~ Inc., pp. 346-353. 2. Reitan, Kaare: Biomechanical principles and reaction. I n Current orthodontic concepts and techniques, Philadelphia, 1969, W. B. Saunders Company, vol. ], pp. 56-159. 3. BjSrk, Arne: Facial growth in man, studied with the aid of metallic implants, Acta Odontol. Scand. 13: 9-34, 1955. 4. Brandt, Sidney: Begg course, April, 1971, University of Groningen. 5. Dermaut, L.: Personal communication, December, 1973. 116 Tuinstraat
Assen, The Netherlands
I n March, 1971, an ]l-year-old boy was referred to the orthodontic clinic at the College of Dentistry of the University of Groningen by an otorhinolaryngologist (Figs. 1 and 2). A team of physicians had made a diagnosis of a systemic disease, mandibulofacial dysostosis (Treacher-Collins syndrome). The structures involved in this illness are derived from the first branchial arch, groove, and pouch. 1 This patient presented the following characteristics of the disease : (1) anti-Mongoloid palpebral fissures, (2) malformation of the pinna, (3) frontal bossing, (4) depressed cheek bones, (5) high, narrow palatal vault, (6) retrognathic chin, (7) fishlike mouth, (8) some deafness (due to a defect in the ossicle), and (9) evidence of mental retardation. Orthodontic examination revealed a Class I subdivision malocclusion in the transitional phase of losing the posterior deciduous teeth followed by the eruption of their permanent successors (Figs. 3 to 5). There was an anterior open-bite to the extent of 10 mm. The maxillary buecal segments were in lingual cross-bite on both sides. Dentally, it was noted that the maxillary lateral incisors were pointed and the first molars showed evidence of hypocalcification. There was a history of active rickets between the ages of 4 and 5, which may explain the delay in dental eruption. An intensive radiographic evaluation was undertaken. Intraoral dental films were secured for routine caries inspection and to determine the relative eruptive positions of the remaining permanent teeth. The panographic and Lilienfeld (Waters) (Figs. 6 and 8) radiograms revealed underdevelopment and defects in the zygomatie bones. A Parma radiogram (Fig. 7) was taken to divulge any problems in the temporomandibular joint. This film also disclosed the defects in the zygomatic tubercle on the left side. It further showed that the condyles appeared to be blunted and that the rami were quite short. The anteroposterior From the Department of Orthodontics, University of Groningen, Groningen, The Netherlands. Read before the European Begg Society, Santa Margarita, Italy, M~y, 1974. 540
vozume 69
Mandibulofacial dysostosis
Number 5
541
Figs. 1 and 2.
Figs. 3 through 5.
view cephalometrically validated the presence o5 a deviation in the mandible toward the right (Fig. 9). The facial photographs also revealed a poor developmental pattern. The mandible was recessive, retrognathic, and displaced to the right. The patient had been plagued with periods of otitis media. This middle ear infection was persistent and remained chronic on the right side. To summarize, there was a severe open-bite malocclusion (Fig. 10), complicated by many osseous and developmental defects, and difficulty in proper speech pronunciation, but the swallowing pattern was quite normal. Treatment planning
The patient displayed considerable resistance to accepting orthodontic therapy. Massive maternal urging was required to convince him that treatment was
542
Te~
Hoeve
A~,~. J. Orthod. May ] 9 7 6
Fig. 6.
Figs. 7 through 9.
Ma~tdibulof acial dysostosis
V o l ~ t ~ e 69
Nu~nber 5
ANB
2,5"
/ - SN
10 6*
_* -T
11o"
M P -SN T-AP
68* 9ram
Fig. 10.
Figs. 11 through 13.
543
544
Ten Hoeve
A~l~. J. O r t h o d . May 1976
Figs. 14 through 17.
essential and could be helpful. When he did accept treatment, members of the Orthodontic Department at the University of Groningen were uncertain as to what should be done. Should the patient be treated at once ? Would it be better to attempt some minor corrective tooth movement and then transfer the patient to oral and plastic surgeons for the major corrective procedures? A f t e r many interdepartmental conferences, it was decided that a trial period of orthodontic treatment should be attempted. The prognosis was guarded and uncertain. Several theoretical considerations influenced the decision. Reitan 2 has stated that, if extrusion of teeth is a desired objective, it is best accomplished when the teeth are erupting. This is the time when the periodontium is proliferating and can better adjust to the new tooth positions. BjSrk 3 also reported that the optimum time to extrude teeth is during periods of growth. Growth also occurs at the alveolar crests at this time. Another advantage is the use of a functional appliance, such as an activator. The objective was to stimulate the growth of the right condyle in an effort to minimize the mandibular deviation. The members of the Orthodontic Department decided that the case should not be treated with only one particular system of mechanotherapy; rather, a combination of several approaches would be advisable. The initial appliance would be an activator, and thereafter the treatment would gradually work into full banded appliances. Treatment
The activator was constructed so that the molar relationship was normal and the midline harmonious (Figs. 11 to 13). No effort was made to correct the molar
Ma~tdib~tlofacial dysostosis
~ozu,~e 69 Nu~nber 5
545
Figs. 18 and 19.
Figs. 20 and 21.
Figs. 22 and 23.
cross-bites at this time. It was not easy for the patient to place the activator, because of his small mouth; however, he did apply himself, and this added effort forced the mandible to shift toward the left. The activator was constructed with enough clearance to allow for extrusion of the upper and lower anterior teeth. After this functional appliance had been placed, the maxillary and mandibular incisors were banded with Begg bracket attachments. Box elastics were worn during the waking hours (Fig. 14), and four vertical elastics were worn during the sleeping hours (Fig. 15). The response was favorable, even though there was
546
-~'"- JMa~/ o,.thoa. 197(;
T en Hoet, e
Figs. 24 through 27. a tendency for the incisors to overlap slightly. The patient became more enthusiastic about orthodontic t r e a t m e n t as the i m p r o v e m e n t became obvious. The activator was worn for 4 months only (Fig. 16). The first molars were then banded and arch wires were placed. Directional elastics were prescribed to f u r t h e r reduce the midline discrepancy and to f u r t h e r correct the molar relationship. A Class I I elastic was worn on the right side and a Class I I I elastie on the left side (Fig. 17). No effort was made to correct the molar cross-bites, since this might adversely counteract f u r t h e r bite closure in the incisor area. Up to this point, the patient had been most cooperative and enthusiastic. H e suddenly found greater chewing ability, and he enjoyed eating more than ever. I n particular, he learned that he could bite into his favorite snack, Swedish crackers, on whieh he could only suck before his appliances had been placed.
VoZume 69
Number 5
Ma~tdibulofacial dysostosis
547
Figs. 28 through 31.
Figs. 32 through 35. Results
In January, 1972, the patient suddenly began to lose interest and his cooperation was faulty. He refused to wear elastics, appointments were broken, the arch wires seemed to become distorted, and there was no effort to sustain proper dental hygiene. Several conferences were held with the patient and his mother, but it was not until January, 1973, that he decided to cooperate again. In the interim,
548
Te~t Hoeve
A~)~. J. Orthod. M ay 1976
Fig. 36.
Figs. 37 through 40.
the bite reopened several millimeters. It was apparent that there had been quite a personality change. The signs of mental retardation were diminishing. His study habits improved, and he was preparing to enter high school (Figs. 18 and 19). The maxillary premolars had erupted into lingual cross-bite, and this was corrected with elastics (Figs. 20 and 21). As these teeth moved buccally, the molars also moved in a favorable direction. Arch wires were then placed on the maxillary and mandibular teeth, with vertical elastics to gain maximum interdigitation. At the same time, the molar cross-bites were completely corrected with rubber bands. Occlusal relations in June, 1973, are illustrated in Figs. 22 to 27. All interdental spaces had been eliminated and the teeth were in good alignment. The orthodontic objectives were now related to root control and root repositioning. The lateral incisors required uprighting to enhance esthetics. The premolars had
rolu.~ 69
Mandibulofacial dysostosis
2¢l~mber 5
549
Fig. 41.
Figs. 42 and 43.
been expanded and tipped so much that their root apices were positioned too far lingually. It was determined that there was sufficient bone on the buccal surfaces to move these teeth into more upright positions. In order to accomplish this root movement, a modification of the Brandt 4 lower reverse torquing complex was prescibed. In an effort to predetermine the action-reaction possibilities, this auxiliary was tested with a simple experiment upon a typodont (Figs. 28 to 30). This was made of 0.014 inch resilient wire, with four small spurs (Fig. 31) which were activated occlusally on the distal flanges of the premolar brackets. The four-spur unit was pinned gingivally to a well-formed 0.016 inch base wire. The reciprocal action on the incisors was a bit surprising. It indicated an extrusive action on the anterior segment. Since we were inexperienced with this torquing complex under these conditions, the actual force applied with the spurs was kept to a minimum (Figs. 32 to 35). The loops of the base wire, in addition to their other uses, were available for the application of elastics, thus adding to the versatility of this appliance. I f improvement for cuspal interdigitation was required, elastic bands could be placed on these loops in whatever direction desired.
550
Te~
Hocvt~
~t m. J. O r t h o d . May 1976
Figs. 44 through 46.
F o u r months later the lower reverse torquing complex was removed. With the method devised by L. I ) e r m a u f ~ at the Groningen D e p a r t m e n t of Orthodontics, it was determined t h a t the premolar roots had been torqued buccally a total of 12 degrees. This was deemed significant root movement and enhanced confidence in this wire complex for increased control over roots. The models shown in Fig. 36 illustrate the condition of the teeth following completion of the buccal root torque on the premolars. These records also indicate that the molars had been expanded a total of 10 ram. In an effort to improve their stability, a torquing unit was devised to move the molar roots buecally. Twin brackets were placed on the molar bands with a rectangular s p u r between them ; this was then activated against the bracket flanges. This a r r a n g e m e n t protected the spur, which could not be ~ e l t e r e d if a buccal tube was used (Fig. 37). Note the reciprocal extrusive action on the anterior segment. Fig. 38 demonstrates how this arch wire was seated. Figs. 39 and 40 show the actual appliance that included buccal root torque. A f t e r 4 months the molar roots could be palpated beneath the cortical plate. The torquing appliance was then removed. With D e r m a u t ' s method, it was demonstrated t h a t 15 degrees of bueeal torque on the molar roots had been attained (Fig. 41). The intermolar width had been maintained during the torquing procedure. All appliances were removed in March, 1974, and a tooth positioner was
Votu,~e G9
Number
Ma~tdibulofacial dysostosis
5
551
Figs. 47 through 50. placed as a retaining device. This was Besides holding the teeth, there was stimulate as much muscular activity about 4 months, a f t e r which the boy need" to do so.
worn at night and during 4 daytime hours. the additional objective of a t t e m p t i n g to as possible. Cooperation was excellent for wore the positioner whenever he "felt the
552
Ten goeve
A m . J. Orthod.
May 1 9 7 6
Figs. 51 and 52. Posttreatment analysis
In the posttreatment analysis, it was obvious that there had been moderate improvement in facial esthetics (Figs. 42 and 43). The occlusion was acceptable, and the cuspal interdigitation in the posterior segments was good. If the canines would interlock more favorably, perhaps guided by the positioner (Figs. 44 and 45), a further improvement in the occlusion might occur. A panographic radiogram (Fig. 46) showed that the dentition had not deteriorated following 32 months of active treatment. The before- and after-treatment records (Figs. 47 to 50) illustrate the correction and the improved midline relationship. Summary
It appears that the major objectives of orthodontic treatment have been achieved. Facial esthetics is improved and occlusal relations are normal. There is evidence that the hoped-for repositioning of the mandible (Figs. 51 and 52) has occurred. The Parma radiogram (Fig. 53) revealed that during the
Ma~tdibulofacial dysostosis
V o l u b l e 69 Number 5
PRE* pO6TTRI~Al~qENT TREATMENT
R
ANB _l . SN
2,6° 10~
4° 91°
T - AP
9~
7~
553 //
L
@ Figs. 53 and 54.
Figs. 55 through 59.
first year of treatment there was significant condylar growth on the right side. The use of the activator thus appears justified, as this appliance was instrumental in correcting the mandibular deviation. Figs. 53 and 54 show the cephalometric changes over the 3-year period of treatment. This type of growth pattern is not favorable. It is a constant reminder of the uncertainty of a stable result. Figs. 55 to 60 were taken 8 months after band removal. The treatment plan followed in this case required the application of several systems of mechanotherapy. An effort was made to relate several theoretical aspects of orthodontics to the practical mechanical procedures.
554
TcH H o e u c
A~. J. Orthod. May 1976
Fig. 60. The author acknowledges the assistance in the preparation of this study to R. L. Dijkstra, P. Hartevelt, and K. J. Poel, for the photographs; to Raymond Levin, Johannesburg, South Africa, for advice on gathering the material and data; to Kees Booy~ Department of Orthodontics, University of Groningen, for aid and guidance during the treatment of this patient; and to Sidney Brandt, for assistance with the manuscript.
REFERENCES 1. Gorlin, Robert J., and Pindborg, Jens J.: Syndromes of the head and neck, New York, 1964, McGraw-Hill Book Company~ Inc., pp. 346-353. 2. Reitan, Kaare: Biomechanical principles and reaction. I n Current orthodontic concepts and techniques, Philadelphia, 1969, W. B. Saunders Company, vol. ], pp. 56-159. 3. BjSrk, Arne: Facial growth in man, studied with the aid of metallic implants, Acta Odontol. Scand. 13: 9-34, 1955. 4. Brandt, Sidney: Begg course, April, 1971, University of Groningen. 5. Dermaut, L.: Personal communication, December, 1973. 116 Tuinstraat
