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Clinical Section |
University of Rome ‘Tor Vergata’, Rome, Italy
Dr Aldo Giancotti, Via Barnaba Tortolini 5, 00197 Rome – Italy. E-mail: giancott{at}uniroma2.it
Abstract
The aim of this article is to show the use of the Balters’ Bionator in pseudo-Class III treatment. The importance of differentiating between true Class III and pseudo-Class III is emphasized. The therapeutic results of a Balters’ Bionator appliance are presented in three case reports of subjects in the mixed dentition. In this stage of development it is possible to correct an isolated problem. The use of the Bionator III in this kind of malocclusion enabled the correction of a dental malocclusion in a few months and therapeutic stability of a mesially-positioned mandible encouraging favourable skeletal growth.
Key words: Anterior crossbite, Bionator III, pseudo-Class III
Introduction
Skeletal, aesthetic, and occlusal characteristics of pseudo-Class III have been highlighted in different articles, and have been compared with normal occlusion, Class I malocclusion, or skeletal Class III malocclusion.1–
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The incidence of Class III malocclusion is variable and depends upon the different methods of classification used. Class III malocclusion in white subjects occurs in fewer than 1 per cent of the population, while frequency in the Japanese population is approximately 10 per cent.1
However, the incidence of pseudo-Class III malocclusion in a sample of 7096 Chinese children was estimated to be 2–3 per cent.
Nakasima1 has reported that the incidence of anterior crossbites has a strong ethnic distribution, particularly high in Japanese subjects and Ferguson4 has reported that an anterior crossbite could be observed in 3 per cent of patients in the United States.
Dental features, diagnosis, and aetiology
Mesio-occlusion is an anteroposterior dentoalveolar relationship characterized by a more anterior position of the mandibular dentition compared to the maxillary dentition.1 Clinically, there are two types of mesio-occlusion. The first type is considered to be a positional form, as a result of a mesial displacement of the mandible into an anterior position and has been named in a different ways (pseudo, functional or apparent...). The other form of mesio-occlusion is a true skeletal Class III. The characteristics of this malocclusion result from a combination of skeletal and dentoalveolar features.
Careful clinical evaluation of Class III malocclusion always requires checking anterior and posterior dental relationships with the mandible in centric relation. Moyers proposed the pseudo-Class III relationship as a positional malocclusion with an acquired neuromuscular reflex, and considered the hypothesis that the positional relationship in ‘apparent Class III’ may occur with an early interference with the muscular reflex of mandibular closure.5 Subjects with pseudo-Class III malocclusions mainly present with Class I or mild Class III skeletal relationships, while the mandible appears morphologically normal. However, anterior crossbite and negative overjet are constantly present due to the anterior mandibular displacement. Usually, the soft tissues tend to camouflage the skeletal discrepancy and the patient’s profile appears normal or slightly concave in centric occlusion. Different aetiological factors have been suggested in pseudo-Class III malocclusion.6
Dental factors
Functional factors
Skeletal factors
It has also been suggested that these sequelae occur more frequently in subjects with a prognathic mandible (primary cause) and the mandibular shift can be considered a functional (environmental) factor, therefore the postnatal causative factors may not be the primary cause.1
Management of pseudo-Class III malocclusion
The pseudo-Class III malocclusion involves both permanent teeth and the deciduous dentition.
Because a malocclusion may be regarded as an aesthetic problem, parents often inquire whether or not therapy might be required. Several clinicians believe in the advantages of early intervention and have suggested a number of reasons for early correction of anterior crossbite even in the deciduous dentition. The optimum period for the treatment suggested to be between the ages 6–9 years.7–10
Many practitioners however still avoid early correction of pseudo-Class III in the deciduous dentition because of poor stability of correction and unfavourable experiences with the behaviour of young patients. Patients may develop a crossbite once again during the transitional dentition, thus requiring further treatment and this may represent a possible disadvantage of treatment at early stage.
Some practitioners prefer to wait for the permanent maxillary incisors to erupt before initiating therapy due to the natural tendency of teeth to erupt in a lingual position during dental arch development. Sometimes, functional deciduous anterior crossbites occasionally correct themselves spontaneously.
White has suggested intervention in cases of pseudo-Class III malocclusion in the mixed dentition when the maxillary and mandibular incisors have erupted. 12 This allows the permanent teeth to erupt into a better position and improves the dental aesthetics.
The benefits attributed to the treatment of pseudo-Class III malocclusion in the mixed dentition are:
Use of Bionator in Pseudo-Class III malocclusion in mixed dentition
Several studies have suggested that almost 20 per cent of patients presenting with a Class III malocclusion can be treated during the mixed dentition. At this stage of development it is possible to correct an isolated problem or provide preliminary treatment.12,13 Anterior crossbite in the mixed dentition should be corrected to allow normal dental development and subsequent favourable skeletal growth.
Studies have confirmed the efficiency of the Bionator in the treatment of Class III malocclusions. Clinical experience has shown the importance of differential diagnosis and suggested that individualization of the appliance is important for good results.14 Functional orthopaedic appliance therapy is one approach to the treatment of pseudo-Class III malocclusion. The Bionator, developed by Balters is a derivative of the Activator.
His design has a palatal wire and also a wire with ‘buccinator wings’ to reduce cheek pressure, while the amount of acrylic is reduced. The Bionator can be worn both day and night.5
The reverse Bionator or Bionator III is a modified version of the traditional bionator and can be used in the treatment of Class III malocclusion. The modified Bionator differs in various characteristics from the original appliance. The lingual wire is in a different position to control the position of the tongue up to the upper first molar. The labial arch is placed in the middle of the lower teeth (Figure 1). The acrylic should be made as small as possible in order to occupy minimal space and should have a concave form to accommodate the tongue. The occlusal acrylic should be thick enough to obstruct tongue movement between the posterior segments.
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Finally the acrylic vestibular lateral shields should be positioned to allow lateral alveolar growth in order to permit expansion of the maxillary arch.
Case reports
Case report 1
A female patient, age 8 years 10 months, presented with an anterior crossbite from the upper right deciduous canine to the upper left deciduous canine and a 1-mm deviation of the mandibular midline to the right (Figure. 2). The patient had a good profile with a slight mid-face convexity and the lower lip appeared protruded (Figures 2 and 4). She was in the mixed dentition and the initial panoramic radiographs revealed that all permanent teeth were present. The upper anterior teeth were retroclined and the upper right lateral incisor was missing, while the lower anterior teeth were protrusive. The molars were in a Class I relationship. The lower arch was in the late mixed dentition and ‘E’ space was present; right and left mandibular second primary molars had exfoliated (Figure 2).
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The patient had to wear this Bionator for 16 hours a day (Figure 4
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Results.
The incisors were beyond edge-to-edge after 9 weeks, but use of the Class III Bionator was continued. Eleven months after the beginning of treatment the patient had a normal occlusion with 2-mm overjet and a Class I molar relationship. Final records showed excellent occlusal and aesthetic results, and the profile was relatively normal with a good lower lip position (Figure 5). Cephalometric tracing demonstrated a reduction of 3 mm in the Wits measurement and a retro-inclination of the lower incisors with a reduction of the angular and linear measurements (22 degrees, 3 mm to NB; Table 1).
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).
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). Cephalometric analysis revealed a Class I skeletal relationship with ANB = 2 degrees. Angular measurements of the maxilla could be considered normal, but linear measurements suggested mandibular protrusion (Wits = 5 degrees). Dental patterns revealed upper incisor retroclination (1 mm, 17 degrees to NA) and proclination of lower incisor (5 mm, 35 degrees to NB). The nasolabial angle was acute (Table 2).
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Case report 3
A 9-year-old female presented with a retruded soft-tissue profile, normal facial growth with very little protrusion of mandible (Figure 12). The patient had a bilateral Class III malocclusion, which was more pronounced on the right side, and an anterior crossbite with a 4-mm deviation of the mandibular midline to the left. The upper anterior teeth were retroclined and a minor rotation of these teeth was visible.
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Cephalometric analysis indicated a small Class III malocclusion characterized by a little mandibular protrusion (ANB = -1 degree, Wits -6 mm). The mandibular position was due to a premature of the left central incisors and subsequently mandibular displacement (Figure 13).
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It was decided to continue the therapy in order to improve and stabilize the results obtained. After 7 months a good occlusion with a Class I canine and molar relationship was obtained. The patient presented a normal overbite and overjet and the midlines were coincident (Figure 15). Final superimpositions showed improvements in the linear and angular dental values. The slight maxillary protrusion coupled with the clockwise mandibular rotation produced an overall improvement of the patient’s aesthetic appearance. A slight downward and forward mandibular growth, has occurred which will continue to be regularly monitored (Table 3).
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The various treatments suggested in the literature for the correction of anterior crossbite include several different appliances, both fixed and/or removable with heavy-intermittent forces (inclined bite-plane, tongue blade) or light-continuous forces (removable appliance with auxiliary springs).
Other alternative therapies that may correct skeletal problems in young patients have been shown to be effective, with significant changes in the cranio-facial complex, including the use of protraction headgear,15 chincap,16 and Frankel III.17,18
Turley presented the therapeutic results of orthopaedic treatment with palatal expansion and custom protraction headgear.19 Patients of 6–9 years of age can be brought to a normal occlusion in less than a year and this therapeutic approach also suggests that with proper diagnosis early Class III treatment can produce good results. Tsai suggests the use of rapid palatal expansion and standard edgewise appliance to resolve an anterior crossbite in a 7-year-old boy.20
Rabie and Gu have described a simple method for the early treatment of pseudo-Class III malocclusion in the mixed dentition with fixed appliance.21 Proclination of the upper incisors and/or retroclination of the lower incisors contribute to the correction of anterior crossbite and the elimination of mandibular displacement. The early treatment also permits us to gain space for canine eruption.
The therapeutic use of a Balters’ Bionator appliance is suggested in three case reports of subjects with anterior crossbite in mixed dentition. The patients all present with a convex soft-tissue profile. Pre-treatment cephalometric analysis showed an high mandibular plane angle in the first case, but the other two cases presented a normal growth with very little protrusion of the mandible.
Dental patterns revealed upper incisor retroclination and proclination of lower incisor in all cases.
The clinical examination revealed that the displacement was due to a premature contact between the upper and lower incisors.
Conclusion
The patients all wore the Bionator approximately 15 hours daily for a period of 60–90 days.
At the end of this period in all cases the correction of anterior crossbite and the elimination of the mandibular displacement were obtained, but the use of a Class III Bionator was continued for a further to maximize chances of stability.
The literature demonstrates that functional appliances work in correction of anterior crossbite. The suggested advantages of this approach are as follows:
Principal disadvantages of Bionator treatment include the following:
References
1 Nakasima A, Ichinose M, Nakata S, Genetic and environmental factors in the development of so-called pseudo-and true mesioclusions. Am J Orthod Dentofac Orthop 1986; 90: 106–116.[CrossRef][Medline]
2 Ngan P., Hu AM, Fields HW. Treatment of Class III problems begins with differential diagnosis of anterior crossbites. Pediat Dent 1997; 19: 386–395.
3 Rabie ABM, Gu Y. Diagnostic criteria for pseudo-Class III malocclusion. Am J Orthod Dentofac Orthop 2000; 11: 1–9.
4 Ferguson FS. Prevalence of labial-lingual and vertical malocclusion in the primary dentition. J Pedod 1980; 4: 187–191.
5 Moyers RE. Handbook of Orthodontics, 4th edn. Chicago: Year Book Medical Publishers, Inc; 1988.
6 Nakasima A, Ichinose M, Nakata S. Hereditary factors in the craniofacial morphology of Angle’s Class II and Class III malocclusion. Am J Orthod Dentofac Orthop 1982; 82: 150–156.
7 Chow MH. Treatment of anterior crossbite caused by occlusal interferences. Quintessence Int 1979; 2: 1–4.
8 Croll TP, Reisenberger RE. Anterior crossbite correction in the primary dentition using fixed inclined planes. I. Technique and examples. Quintessence Int 1987; 18: 847–853.[Medline]
9 Payne RC, Mueller BH, Thomas HF. Anterior crossbite in the primary dentition. J Pedod 1981; 5: 281–294.[Medline]
10 Tobias M, Album MM. Anterior crossbite correction on a cerebral palsy child: report of case. ASDC J Dent Child 1977; 44: 460–462.[Medline]
11 Turley PT. Early management of the developing Class III malocclusion. Aust Orthod J 1993; 13: 19–22.
12 White L, Hobbs NM. Early orthodontic intervention. Am J Orthod Dentofac Orthop 1998; 113: 24–28.[CrossRef][Medline]
13 Hawkins IK. Treatment planning for the mixed dentition malocclusion treatment and goals. Ann Roy Australas Coll Dent Surg 1994; 12: 160–169.
14 Garattini G, Levrini L, Crozzoli P, Levrini AQ. Skeletal and dental modifications produced by the Bionator III appliance. Am J Orthod Dentofac Orthop 1998; 114: 40–44.[CrossRef][Medline]
15 Ngan P., Hgg U, Yiu CKY, Merwin D, Wei SHY. Treatment response to maxillary expansion and protraction. Eur J Orthod 1966; 18: 151–168.
16 Allen RA, Connoly IH, Richardson A. Early treatment of Class III incisor relationship using the chincap appliance. Eur J Orthod 1993; 15: 371–376.
17 Nanda R. Protractions of maxilla in rhesus monkeys by controlled extraoral forces. Am J Orthod Dentofac Orthop 1978; 74: 121–141.
18 Turley PK. Orthopedic correction of Class III malocclusion: retention and phase II therapy. J Clin Orthod 1996; 6: 313–324.
19 Turley P. Orthopedic correction of Class III malocclusion with palatal expansion and custom protraction headgear. J Clin Orthod 1988; 22: 314–325.[Medline]
20 Tsai HH. Treatment of anterior crossbite with bilateral posterior crossbite in early mixed dentition: a case report. J Clin Pediat Dent 2000; 24: 181–186.
21 Rabie ABM, Gu Y. Management of pseudo-Class III malocclusion in southern Chinese children. Br Dent J 1999; 186: 183–187.[Medline]
Received January 10, 2002; accepted December 6, 2002
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