Chapter 14

Treatment Planning for Class III Anomalies

14.1 Introduction

Most matters discussed concerning Class I and abnormalities of teeth also apply to Class III, and usually complicate the situation.

A reversed overjet of incisors leads to a definite further ventral placement of the lower lip than the upper lip, which is usually considered ugly especially when associated with a long mandible and dominant chin.

In extreme abnormalities, for which facial orthopedic measures have no satisfactory remedy, it is often possible to still obtain a pleasing result by combining surgery and orthodontic treatment.

It is noted that some patients with Class III anomalies do not have a need for treatment. The fact that in its rest position the mandible has rotated caudally and the chin is consequently relatively less prominent, can be a reason to refrain from treatment. Occasionally, the Class III profile is considered a family trait to be respected and preserved.

14.2 Anatomic aspects

Class III anomalies usually exhibit an abnormal configuration of the craniofacial skeleton. The middle face can lie relatively far to dorsal, or may possess small anteroposterior dimensions. The mandible can be situated relatively far ventrally, or be too large. Further, a Class III anomaly can occasionally be complicated by an excessively large anterior lower face height and an anterior open bite.

In a Class III anomaly, it is generally easier to show where the fault lies than in a Class II/1, especially when the deviation is large. Nevertheless, also in Class III, it is seldom just one part of the craniofacial skeleton that deviates in size or position. For example, a large mandible often goes with an underdeveloped midface.

The mandible can also develop asymmetrically, growing unequally though excessively, or just growing excessively on one side. One has then laterognathism, combined with a Class III subdivision.

A Class III can increase progressively. By abnormal ventral growth of the mandible, retarded ventral development of the maxilla, or a combination of both, the sagittal occlusion of the dental arches can deviate more and more from the normal picture. In Class III anomalies the sagittal occlusion can deviate more than an entire premolar crown width. In cases with an open bite, the bite usually stays open when the anomaly progresses.

With the increase of the mesio-occlusion in cases with a deep bite in front the reverse overjet will increase, usually keeping contact between the incisors of both jaws. Further, an originally normal transverse occlusion in the posterior segments can become abnormal. Just as a reversed overjet can develop after the transition of the incisors, so the premolars can, as deciduous teeth exfoliate, move into contact in a reversed transverse occlusion.

Characteristic of Class III in an adult is eversion of the maxillary incisors and inversion of the mandibular incisors.34 The tipping of the teeth becomes more severe, the more the sagittal occlusion deviates. This adjustment of inclination compensates to some extent for the deviant mesiorelation.204 A corresponding compensation can take place transversely, being manifested in the buccolingual inclinations of the posterior teeth.

It is not simple to determine if one is dealing with a Class III anomaly that can be treated with facial orthopedic and orthodontic techniques, or with a mandible that will grow excessively and make treatment ineffective. Moreover, the mandible can increase in size after all the remaining parts of the skeleton have reached their adult dimensions.

In Class III anomalies, hereditary features can play an important role. Hence, information regarding family members is of considerable significance.

Class III malocclusions can be associated with ventral forced bites. The greater the sagittal distance between maximum occlusion and the most dorsal position of the mandible, the better the prognosis for treatment. If the ability to close dorsally is limited and if movement of the teeth in the arches would not secure normal incisor contact nor neutro-occlusion of the molars, then one is dealing with a Class III anomaly combined with a ventral forced bite. The treatment must then be directed at both aspects and, as a rule, comprised of both facial orthopedic and orthodontic techniques.

14.3 Guidance of the development of the dentition and facial growth

A progressively developing Class III anomaly cannot successfully be counteracted. Limited mesiorelation and a tendency to develop in that direction can, however, be influenced.

As noted, a ventral forced bite can for example be corrected by biting on an inclined wooden spatula or tongue blade so as to reciprocally displace the involved teeth. Also, the deciduous canines often need occlusal grinding (9.10). Further, in cases of crowding, it is possible to increase the arch perimeter in the maxilla and so develop a more favorable situation in the incisor regions.

In Class III anomalies and cases that may develop in that direction, one needs to guard against maxillary incisors moving palatally, for example as the result of premature loss of deciduous molars or through extraction of deciduous canines or permanent teeth. A possibly existing deep bite should be preserved.

14.4 When to treat

The uncertain nature of the reaction to facial orthopedic treatment mainly due to the unpredictable growth of the mandible, makes the prognosis uncertain. In Class III cases seen at an early age, the uncertainty is indeed so great that one must ask oneself if it is responsible to begin any treatment at that time. If one waits with regular checks (roentgencephalometric records and models are essential), then it may become clear how the mandible is behaving. One can then, according to what has ensued, either undertake orthodontic treatment or plan future surgery. If for any reason early treatment is preferred, then the following should be taken into consideration.

Because facial orthopedic changes in young children are easier and quicker to realize than in older patients, it is recommended that a Class III treatment begins in the deciduous dentition. If a good sagittal jaw relation has been achieved before permanent teeth emerge, then disturbances that otherwise would arise in the incisor region will be avoided. Moreover, the prognosis for favorable further facial growth is probably better when the craniofacial skeleton has been harmonized by an early age.

Treatment that is initiated in the last year at infant school (5–6 years of age) usually secures an appreciable improvement in 6 months.77 Once the desired objective is reached, one must closely follow subsequent development of the dentition and facial growth and interfere when needed. In general, one can then wait till the second transitional period and, in a relatively short time, complete the remaining corrections. If one suspects progressive Class III development, it would be appropriate to set up facial orthopedic treatment early.

Emergence of permanent incisors in a reversed overjet should be prevented or corrected as soon as possible. A mesiorelation noticed after the permanent incisors emerge can be satisfactorily corrected with facial orthopedic measures, at least if it is not a progressive mandibular development.372 This also applies, though to a lesser degree, during and after the second transitional period when the adaptability of skeletal tissues has decreased.396

In dealing with Class III anomalies, a stable result can only be spoken of after a solid interdigitation of premolars and canines is established and growth has ceased. An adequate overbite is important for a treated Class III. It can be expected that limited growth which occurs after treatment will be compensated for by dental adjustment.151 If the situation is one of a progressing overgrowth of the mandible, then the “dento-alveolar compensatory mechanism”351 will be inadequate and a reversed overjet will return.

If treatment is sought only after the development of the dentition and facial growth are largely complete, the treatment is limited to dento-alveolar movements and surgical improvements. For this reason, earlier facial orthopedic treatment is desirable. />