Early Treatment of Class III Malocclusion: Degree of Difficulty

The beginning student of orthodontics should rely on academic evidence for appropriate Class III case selection to ensure favorable treatment outcomes. As the practitioner attains experience, knowledge and expertise in orthodontics, this selection process will become more fluid. The teaching of Early Class III Malocclusion to the novice stimulated the author to a Class III literature review and a resulting publication of a New Treatment Classification of Class III Malocclusions with seven sub-types. (Table 1) The purpose of this classification was to identify Class III malocclusions within a pediatric practice that lend themselves to a more favorable treatment outcome at an earlier age (before 10 years) rather than initiating treatment at a later adolescent growth stage and also to identify the degree of difficulty of the treatment of the Class III malocclusion for the beginning student of orthodontics.¹

METHODS

Review of the current dental literature pertaining to the different clinical types of Class III malocclusions and their respective treatment protocols was performed. Various classification systems were studied and compared.² A new treatment classification system of Class III malocclusions was developed utilizing three dento-alveolar and three skeletal components combined with Cephalometric information derived from commonly used Cephalometric analyses.^{3, 4, 5} (Table 2)

RESULTS

Early Orthodontics Only

Type 1 Pseudo Class III (Dewey-Anderson Class I, Type 3)

Clinically the Class III, Type 1 resembles a Class I malocclusion with an anterior crossbite (Pseudo Class III) resulting from common dental growth and development problems.⁶ However, the molar relationship is a Class I with a tendency toward Class III up to ¼ cusp width (1-2 mm mesially). The skeletal components are characterized by normal length of both maxilla and mandible with lengths within the standard norms. The “wits” appraisal may range from +2.0mm – -2.0mm and the vertical lower facial heights are within normal range or deficient. The patient’s facial type is usually mesocephalic to brachycephalic.

Treatment is directed at the dento-alveolar problem and would consist of eliminating the anterior crossbite, arch development and maintaining a Class I molar relationship. This may be accomplished by the use of a simple guide plane in the primary dentition, a Nitanium palatal expander to control vertical combined with utility arch wires in the mixed dentition and a pre-programmed fixed appliance in the permanent dentition for case completion. A stable, excellent prognosis would be predicted. (Fig. 1)

AIRWAYS – THE KEY TO EARLY FACIAL GROWTH MALOCCLUSIONS

Type 2 Dento-Alveolar Class III

These cases have a more definite Class III molar relationship with up to ½ cusp width (3-4 mm) mesially. An anterior crossbite is usually present and a posterior crossbite frequently. The skeletal components are characterized by normal lengths of both maxilla and mandible with lengths within the Standard Normal. The “wits” appraisal may range from +2.0mm to -2.0mm. The vertical is usually within normal range with a lower mandibular plane angle of 30.0 degrees or less.

An airway problem may cause a forward posturing of the tongue manifesting a dental open bite and proclination of the lower anterior teeth: the patient’s face is usually mesocephalic or brachycephalic. Frequently these cases present as a functional Class III whereby there is an anterior slide upon closure, especially if a dental deep bite is present.

Treatment is directed at the Dento-Alveolar problem and would consist of correcting the anterior or posterior cross bite. The use of Rapid Palatal Expanders (RPE’s), Utility Arch Wires (UAW’s) and the Straight-Wire Appliance (SWA) should complete most cases. A stable, good prognosis would be predicted. (Fig. 2)

Early Orthopedics/Orthodontics Combined Type 3 Retrognathic Maxilla Class III

The most common Class III Orthopedic disharmony in the young child is a Retrognathic maxilla with normal mandibular length. These cases are more frequently seen in younger children with extensive airway problems.^{7, 8, 9}

The molars exhibit a Class III molar relationship between ½ to a full cusp mesially (4-6mm). Usually there is both posterior and anterior cross-bites with a reverse incisor relationship. The incisors may exhibit either a deep bite or open bite depending on the lower mandibular plane angle. The “wits” appraisal ranges from -2.0mm to -7.0mm. The lower mandibular plane angle may be either less than 20.0 degrees (skeletal closed bite, hypo-divergent) or greater than 30.0 degrees (skeletal open bite, hyper-divergent). Often, there is mid-facial deficiency. The faces of the patients are usually brachy-cephalic in closed bite cases and dolichocephalic in open bite cases.

Treatment is principally directed, following ENT evaluation, at the retruded maxilla and cross-bites. Treatment should be initiated before the age of 10 years according to most studies published. Banded not met during the early non-surgical phase. A poor to fair prognosis would be expected. The later the stage of child growth, with concomitant excessive vertical growth, a poorer prognosis would be predicted without surgical intervention. If treatment is delayed beyond 10 years of age, combined orthodontic and orthognathic surgery is the best option because of limited control of both horizontal and vertical mandibular growth at these later stages of child development.

DISCUSSION

Classification of the Class III malocclusion is challenging. A Class III malocclusion is not a single diagnostic entity, but rather a spectrum of protean clinical manifestation with varying clinical and Cephalometric features that predict differing biological potential. More importantly, identification of a specific Class III malocclusion in the young child leads to both early treatment of the malocclusion and correction of the underlying etiology in many of the subtypes of Class III malocclusion.

Orthodontic screening of young patients to identify potential Class III malocclusion is clinically significant because treatment timing of Class III malocclusion is critical for optimal treatment outcome. Delaying appropriate treatment beyond the late mixed dentition (10 years of age) may limit the orthopedic correction required to treat most of the Class III malocclusions. Treatment of the Class III malocclusion in the late deciduous and early mixed dentitions has been shown to be more beneficial to the child because of improved maxillary orthopedic correction, combined with controlled mandibular growth compared to treatment in the later childhood growth stages.¹²

The purpose of this classification system was to identify the degree of difficulty of the Class III malocclusion so that the beginning student may feel confident in treatment with the case selection of the subtypes 1-3. The recommendation is that subtypes 4-7 should be addressed by the advanced student. Advanced subtypes will be presented as Degree of Difficulty – Part II in a future article.

CONCLUSION

The New Classification System supports Edward H Angle’s finding: “In studying a case of malocclusion, give no thought to the methods of treatment or appliances until the case shall have been classified and all peculiarities and variations from the normal type, occlusion and facial lines have been thoroughly comprehended. Then the requirements and proper plan of treatment becomes appropriate”. (Table 3) The goals of each type of treatment whether by Growth Modification, Camouflage or Orthognathic Surgery are an interaction of skeletal and dental relationships. The purpose being to achieve optimal esthetic, functional and stable results based on when treatment is started.

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