|Year : 2012 | Volume
| Issue : 1 | Page : 78-84
Timely management of developing class III malocclusion
MR Yelampalli1, MR Rachala2
1 Department of Orthodontics, G. Pulla Reddy Dental College and Hospital, Kurnool, India
2 Department of Orthodontics, SVS Institute of Dental Sciences, Mahabubnagar, Andhra Pradesh, India
|Date of Web Publication||3-May-2012|
M R Rachala
Department of Orthodontics, SVS Institute of Dental Sciences, Mahabubnagar, Andhra Pradesh
| Abstract|| |
Timing of orthodontic treatment, especially for children with developing class III malocclusions, has always been somewhat controversial, and definitive treatment tends to be delayed for severe class III cases. Developing class III patients with moderate to severe anterior crossbite and deep bite may need early intervention in some selected cases. Class III malocclusion may develop in children as a result of an inherent growth abnormality, i.e. true class III malocclusion, or as a result of premature occlusal contacts causing forward functional shift of the mandible, which is known as pseudo class III malocclusion. These cases, if not treated at the initial stage of development, interfere with normal growth of the jaw bases and may result in severe facial deformities. The treatment should be carried out as early as possible for permitting normal growth of the skeletal bases. This paper deals with the selection of an appropriate appliance from the various current options available for early intervention in developing class III malocclusion through two case reports.
Keywords: Class III malocclusion, crossbite, facemask therapy, Hyrax appliance
|How to cite this article:|
Yelampalli M R, Rachala M R. Timely management of developing class III malocclusion. J Indian Soc Pedod Prev Dent 2012;30:78-84
|How to cite this URL:|
Yelampalli M R, Rachala M R. Timely management of developing class III malocclusion. J Indian Soc Pedod Prev Dent [serial online] 2012 [cited 2013 May 24];30:78-84. Available from: http://www.jisppd.com/text.asp?2012/30/1/78/95590
| Introduction|| |
The incidence of class III malocclusion is rather small in the population, but it is one of the most difficult malocclusions to treat. Class III malocclusions in children may have an underlying skeletal or dental component.  Skeletal class III malocclusions are often seen with maxillary retrognathia, mandibular prognathia, or a combination of both, of which maxillary retrognathia constitutes in majority of these patients.  Pseudo class III malocclusion is a habitual established crossbite of all anterior teeth, without any skeletal discrepancy, resulting from functional forward positioning/shift of the mandible on closure. In children with pseudo class III malocclusion, when the mandible is "guided" into a normal centric relation, a normal overjet or an edge-to-edge position of incisors can be obtained. This is an important parameter in distinguishing it from true class III malocclusion. On cephalometric analysis, pseudo class III malocclusion shows a normal SNA if diagnosed early, whereas SNB could be slightly increased because of forward positioning of the mandible. In contrast, in true class III cases, a large SNB angle or a small SNA angle may be found, depending on whether the result is due to an underdeveloped maxilla or a long mandibular base, or both. In addition, the mandibular incisors may depict a retroclination, thus lessening the incisor mandibular plane angle (IMPA). In contrast, pseudo class III cases may show a retroclination of maxillary incisors and normal lower incisors. Most true class III cases have a strong hereditary component and are a result of inherent sagittal discrepancy, the environmental factors being of little importance in their genesis. The final diagnosis of the type of class III malocclusion depends mainly on  (a) clinically establishing the dual closure pattern by asking and guiding the patient to bite in normal centric and habitual positions, (b) observing any familial tendency, (c) cephalometric parameters, and (d) incisor relationships. Both these types of malocclusions, if not treated early, may affect the normal growth and development of the skeletal bases, leading to restricted maxillary growth and may be mandibular overgrowth. ,
The case reports presented in this paper are: One pseudo class III malocclusion having anterior and posterior crossbite treated with rapid maxillary expansion by using bonded Hyrax appliance and one skeletal class III due to maxillary retrognathia treated with Petit facemask and maxillary expansion.
| Case Reports|| |
A 10-year-old girl reported with the chief complaint of irregular placement of upper lower front teeth. On extraoral examination, a concave profile was noticed, with an appearance of maxillary growth restriction. Intraoral examination revealed an early mixed dentition stage, with erupted upper and lower permanent incisors and first molars. The maxillary lateral incisors were palatally erupted. All maxillary teeth from the primary right canine to the left canine were in crossbite with the mandibular permanent incisors and from deciduous first molar to permanent molar were in partial crossbite with that of lower teeth on both sides. The molar relation on both sides was developing class III malocclusion, with reverse overjet of 2 mm and overbite of 2 mm [Figure 1]. There was no familial history of class III malocclusion. On assessment of the CR-CO discrepancy and guidance of the mandible on closure, a functional shift of the mandible was seen. The maxillary growth seemed to be restricted due to the postural shift of the mandible in a class III position. Cephalometric analysis revealed the normal maxilla (SNA 79°) with slightly greater than the normal mandible (SNB 79.5°) having hypodivergent face (GoGn-SN 28°, FMA 23°). The upper incisors were retruded (UI-NA 13°/2 mm) and the lower incisors were minimally protruded (LI-NB 26°/5 mm). Based on these findings, a diagnosis of pseudo class III malocclusion was made.
The treatment was aimed to correct the anterior and posterior crossbite, thereby allowing the normal growth of maxilla. Since the maxillary skeletal base was not at fault and fullness of the soft tissue in the anterior segment was obviously deficient, a decision was made to fabricate an expansion appliance, along with posterior bite plates, to correct the dentoalveolar relation by bringing the maxillary incisors out of crossbite, and also to expand the posterior segments for the correction of crossbite. The common type of rapid maxillary expansion (RME) appliance used currently is the Hyrax or Biederman appliance.  It is tooth borne and consists of a jack screw and an all-metal framework that is soldered to bands on the first premolars and first molars. Several studies ,, on RME with Hyrax appliances contribute to an increase in the vertical dimension. These studies reported a descent of the maxilla with opening of the bite. In addition to the downward displacement of the maxilla, dental extrusions, lateral rotation of the maxillary segments, and cuspal interferences have also been attributed to this bite opening characteristic of RME. 
The expansion appliance used in this patient was Hyrax appliance, but instead of banding to teeth it was bonded to the occlusal surfaces of the posterior teeth. The appliance was activated daily twice by 90° rotation in the morning and evening by the patient for a period of 2 weeks. A midline diastema was developed, which is an indication of active expansion [Figure 2]. Correction of overjet was seen within 2 months of the appliance delivery, following which the bite plates were sequentially trimmed to settle the occlusion. The midline diastema was closed within 4 months as a result of traction of transeptal fibers. The post-treatment results showed significant improvement in the soft tissue fullness of the maxilla and an acceptable occlusion with normal overjet and overbite [Figure 3]. Cephalometric comparison [Table 1] revealed no change in maxilla and slight downward and backward rotation of mandible with increase in lower anterior facial height [Figure 4].
|Table 1: Cephalometric comparisons of pre- and post-treatment radiographs|
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An 11-year-old boy reported to the Department of Orthodontics with the chief complaint of forward placement of lower front teeth. No familial history of similar malocclusion was noted. He had an oval, symmetrical face with decreased lower anterior face height and concave profile with flat midface. The lower lips and chin were prominent with 4 mm interlabial gap, acute nasolabial angle, and shallow mentolabial sulcus. The smile was unesthetic because of prominent display of mandibular anterior teeth. The patient was in mixed dentition, had bilateral class III molar and canine relationships, and anterior crossbite from right canine to left canine with reverse overjet of 3 mm and overbite of 4 mm [Figure 5]. Cephalometric analysis revealed a skeletal class III relationship (ANB -2°; Wits -6 mm) characterized by mild maxillary deficiency and some mandibular protrusion with hypodivergent face (GoGn-SN 24°, FMA 30°). The upper incisors were moderately protruded (UI-NA 34°/6 mm) and the lower anteriors were minimally retruded (LI-NB 24°/5 mm) representing the compensation that occurred for the underlying skeletal problems.
The patient was diagnosed as developing skeletal class III due to mild maxillary deficiency and mandibular protrusion having hypodivergent face with compensated upper and lower anterior teeth. The Petit facemask with maxillary expansion was in this patient to correct the deficient maxilla. Petit facemask consists of two anchorage units, i.e. forehead and chin pads, interconnected by a heavy steel metal rod vertically in front of the nose and an adjustable horizontal steel framework at the occlusal level for force application. Intraoral appliance consists of Hyrax expansion screw incorporated into the acrylic splint on posterior teeth [Figure 6]. The protraction elastics were applied between the SS hooks of the splint to the facemask, directed downward at an angle of 30° to the occlusal plane. Approximately 400 g per side was recommended. The patient was instructed to wear the facemask for a minimum of 14 h/day. The treatment of phase I therapy (facemask) was completed once the anterior crossbite was corrected satisfactorily.
|Figure 6: Extraoral view of patient with Petit facemask and intraoral Hyrax appliance with acrylic splint|
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The post-treatment facial photographs showed a significant improvement in facial profile [Figure 7]. The flat midface improved because of forward movement of maxilla and the profile became mild convex due to clockwise rotation of the mandible. Post-treatment cephalometric values [Table 1] revealed positive sagittal alterations, i.e. no longer expressed a class III pattern, but approached a class I cephalometric pattern. The ANB angle increased by 4° Considering that the cephalometric measurements do not usually change in normal pattern. These changes were important as they contribute to a more expressive midface and represent the main goal of facemask therapy. Increased lower facial height by 5 mm was indicative of downward and backward rotation of the mandible [Figure 8].
| Discussion|| |
Class III malocclusions with skeletal patterns may be a result of genetic predisposition or occlusal prematurities leading to abnormal closure patterns that remained undiagnosed and worsened with time. The success of orthodontic treatment in a growing patient with a severe class III malocclusion depends on his or her individual growth and the adequate timing of the treatment. In mild to moderate skeletal Class III patients, it is difficult to decide whether to treat early or to wait until the end of growth. Moreover, to what extent the growth modification can be successful is a challenging question for many clinicians. Therefore, it is important to diagnose the degree of skeletal discrepancy in order to develop a proper treatment plan. 
The various treatment options available for the correction of developing class III malocclusions are (a) functional appliances such as Frankle III, reverse twin block (b) orthopedic appliances such as for facemask therapy and chin cup; and (c) orthodontic appliances such as removable/fixed expansion appliances or fixed orthodontic appliances with expanded upper arch wire. Treatment in all developing class III cases should be undertaken as soon as the abnormality is diagnosed to prevent it from becoming permanent and resulting in a full-blown class III malocclusion. This is especially true in girls, as a protruded mandible renders a very rigid, unpleasant facial appearance in females. 
Early management of the pseudo class III malocclusion depends on the extent of maxillary growth restriction, mandibular plane angle, the soft tissue profile, and the age of the patient. The first case described here is a developing class III malocclusion in which the skeletal bases are normal and the anterior shift of the mandible results in a dentoalveolar crossbite. The treatment of choice was expansion appliance to correct the anterior interlock, posterior crossbite and allow for normal maxillo-mandibular growth. Hyrax appliance was one such device used in a case described here and was found to be effective. Even though there is no family history of malocclusion in this case, the child needs to be kept under observation till the time she passes the third growth spurt at 18 years of age.
A combination of maxillary protraction and rapid maxillary expansion is one of the most popular orthopedic approaches for early treatment of skeletal class III patients with retrognathic maxilla. ,,,,, The facemask therapy can be started as soon as the patient can handle the appliance.  The appliance used in the second case was Petit facemask with rapid maxillary expansion. The treatment results produced by this treatment were the anterior movement of the maxilla and backward rotation of the mandible. Palatal expansion was used only to disarticulate the maxilla from the adjacent bones and move it downward and forward. Although optimal timing for phase I therapy is important, it is also necessary to know when to begin definitive phase II fixed orthodontic treatment. Starting treatment after the permanent second molars have erupted allows the clinician to evaluate post-treatment growth and to minimize the duration of fixed appliance therapy.
| Conclusion|| |
The main aim of all treatment options in developing class III malocclusions, with or without positional malrelations, is to improve the facial profile of the child and to allow the normal growth of the jaw bones. The earlier such a case presents to the clinician and is diagnosed, the simpler and faster is the treatment. The selection of an appropriate treatment option mainly depends on the extent of maxillary growth restriction; the treatment revolves around facemask in severe cases and expansion appliances in less severe cases. The patients described in this article were managed successfully by using appropriate appliances to correct the posterior crossbite, the anterior interlock, and to guide the normal unrestricted growth of the maxilla.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]