12: Treatment Planning for Class II/1 Anomalies

Chapter 12

Treatment Planning for Class II/1 Anomalies

12.1 Introduction

Most matters that have come under consideration for the treatment planning of Class I anomalies can also appear in Class II/1. This also applies for abnormalities of teeth. Therefore, only insofar as the presence of a disto-occlusion would influence the treatment planning for the separate dental arches, are these mentioned again; the same approach is adopted in the following Chapters on Class II/2, and Class III anomalies and open bites.

Class II/1 anomalies with normal lip closure and regular dental arches are not necessarily unesthetic. With a marked chin, the profile in a Class II/1 anomaly can be more harmonious than in a neutro-occlusion. A correction of a mild Class II/1 anomaly does not always secure an improvement in facial appearance. In such cases it can be better not to undertake treatment.

12.2 Anatomic aspects

Class II/1 anomalies are characterized by a dorsal position of the mandibular arch relative to the maxillary arch. There is a great variation in Class II/1 anomalies,250 but it is often impracticable to indicate if the maxillary arch is advanced and/or the mandibular arch is placed back, and whether or not (and if so, which) parts of the craniofacial skeleton fall outside the norms of size, position or form. It is often a combination of minor deviations that comprise the total picture. Moreover, to seek (in such cases) where the “fault” lies has no practical value since it hardly affects the choice of treatment. Which treatment method merits preference is dictated, alongside psychological factors, by facial conformation, the situation in the dental arches, the functional aspects, the anticipated growth of the face, and the adaptability to be expected.

Also, in Class II/1 anomalies, the sizes of the apical areas can differ notably; the size of the dental arches varies as much. Class II/1 anomalies can be associated with either crowding or spacing, with double proposition/eversion or a “dished-in” profile.

As stated earlier, the primary feature of a Class II/1 anomaly is that the mandibular arch, in relation to the maxillary arch, is occluding too far dorsally. The other aspects of Class II/1 anomalies follow on from that and are secondary in nature. The maxillary arch is usually narrower than normal since the more distally occluding mandibular arch is narrower in the part with which the maxillary arch interdigitates in Class II/1 than it would have been in neutro-occlusion (Figs. 12-1A and B).

Fig. 12-1  Diagrammatic representation of the sagittal, transverse and vertical occlusion of maxillary and mandibular dental arches in different circumstances.

A  A neutro-occlusion with normal arches and a good sagittal occlusion and transverse interdigitation of the teeth in the posterior segments.

B  A disto-occlusion with an increased overjet and overbite, eversion of the maxillary incisors and a normal mandibular arch except for supraposition of the mandibular incisors. The occlusion in the posterior region is normal transversely. The width of the maxillary arch is matched to that of the mandibular arch and so is narrower in disto-occlusion than it would have been in neutro-occlusion.

C  In the correction of the posterior sagittal occlusion in a Class II/1 anomaly, the maxillary arch is widened because the teeth in the mandibular arch move to contact teeth further anteriorly in the altered jaw relation, the arch width increase is stimulated whenever the teeth make contact; in activator treatment this occurs only during the day when the appliance is not being worn. If a headgear is combined with a plate with a bite plane, then the bite plane needs to be heightened at each visit by only such a small amount that between visits the teeth will have been able to return to solid interdigitation. The degree to which the maxillary teeth are moved buccally is dependent on the improvement sagittally (rail mechanism).

D  Transverse expansion of the maxilla and retruding of the maxillary incisors without simultaneous correction of the disto-occlusion leads to a disturbance of the transverse interdigitation because the teeth in the mandible normally do not follow the expansion of the maxillary teeth.

The deep overbite that develops in a Class II/1 anomaly, unless the tongue or digit is held between the mandibular incisors and the palate and/or maxillary incisors, is also of a secondary nature. After emergence of the incisors no normal vertical support develops, especially for the mandibular incisors which continue therefore to erupt. Depending on the relationship between the lips and the maxillary incisors, the maxillary incisors also can overerupt. The extent of the proposition and eversion of the maxillary incisors is related to the extent of the disto-occlusion. The lip position and abnormal habits also have a part to play in that.389

12.3 Guidance of the development of the dentition and facial growth

With a large overjet a risk exists that the lower lip will get behind the maxillary incisors. One can try to prevent such a development by advising lip exercises in time. A good lip closure helps prevent excessive eruption of the maxillary incisors and reduces the chance of trauma to them.

It can be taken for granted that intensive, frequent and prolonged digit sucking can influence not only the position of the anterior teeth but also the morphology of the facial skeleton and worsen an existing Class II/1 anomaly. In cases with a pronounced Class II/1 anomaly it is advisable to attempt to eliminate the sucking habit before the deciduous incisors exfoliate.

Especially in Class II/1 anomalies where the lower lip might become to fall behind the maxillary incisors the importance of avoiding collapse of the mandibular arch through premature loss of deciduous teeth must be emphasized.

12.4 When to treat

In Class II/1 anomalies with a disto-occlusion of a half premolar crown width, it is reasonable to delay treatment till the second transitional period has begun. The second deciduous molars must still be present and the second permanent molars may not have yet emerged. With such a Class II/1 there is usually a normal lip relation and with guidance of facial growth and, taking advantage of the space that becomes available in the posterior segments during transition to the permanent dentition, it should be possible to complete treatment in 18 months to 2 years if cooperation is good.

If the Class II/1 anomaly is more serious, then it is advisable to begin treatment earlier, especially when the lower lip lies behind the maxillary incisors, or there is a tendency to do so.

The effect of facial orthopedic therapy decreases with age. In young children the morphology of the facial skeleton is more markedly changed in a shorter time than in older children; the adaptability of the skeletal tissues is greater.396

In practice it appears that to begin treatment sooner than advised here means that improvements obtained are usually partly lost if the therapy is ended or interrupted while the deciduous teeth are still present. One then misses the consolidation of the result achieved that would have been provided by the interdigitation of the premolars and permanent canines had they been present. If a disto-occlusion of an entire premolar crown width is corrected at an early age, by the time the second transitional period is reached it has probably relapsed half that distance. Under those circumstances, it is desirable to start a second treatment phase prior to the loss of the second deciduous molars, and not to terminate it before solid interdigitation and consolidation of premolars and permanent canines is achieved.

If one is confronted with a serious Class II/1 during the second transitional period or shortly afterwards, then it is often still possible to achieve sagittal correction by means of intensive facial orthopedic therapy (combination of headgear and functional appliance).

Individuals, whose development of the dentition and facial growth are more or less complete, will achieve little or nothing with facial orthopedic therapy. The treatment of a Class II/1 will then generally be associated with extraction of teeth in the maxilla; this is in order to move the maxillary incisors sufficiently far dorsally to reach a good sagittal contact with the mandibular incisors. In such treatment it is also occasionally necessary to extract in the mandible. In extreme cases, surgical-orthodontic treatment might be considered.

12.5 How to treat

Class II/1 anomalies can best be treated in growing individuals by means of facial orthopedic appliances.143 263 Here, use is made of the mechanisms offered by nature, which are the same as those which make facial growth (and development of the dentition) possible. Further, one should give priority to the therapy for the correction of the primary factor in the anomaly: the abnormal sagittal occlusion between the dental arches. Moreover, it is here that one should begin, since skeletal changes take the longest to accomplish and largely determine how long treatment will take. Facial orthopedic appliances can be divided into functional appliances, extra-oral traction on the maxillary complex, or a combination of both (8.6.3. to 8.6.5.)

The most well-known representative of functional appliances is the activator developed by Andresen. In principle, the activator lies loose in the mouth, with the mandible held downwards and forwards in relation to the maxilla. There are many variants of the activator, for example the Propulsor of Mühlemann, the Vorbissdoppelplatte of A.M. Schwarz, the Bionator of Balters, the Gebissformer of Bimler, the Kinetor of Stockfisch and the Funktionsregler of Fränkel 10 31 122 150 339 357 (see Fig. 8-6). Where facial orthopedic changes in a sagittal direction are concerned, there is little difference between these appliances337 and the following description of the activator can apply to them all.

Activators influence both the maxillary complex and the mandible in sagittal and vertical directions. Each time the patient closes (whether or not in a reflex activity) into the activator, a ventral and caudal force is applied to the structures of the mandible and a dorsal and cranial force is applied to the maxillary complex. A similar action is ascribed to the activator when the mandible is held passively forward and downward.

The result is an effect on the sutures, through which the forward growth of the maxilla is retarded. At the same time, growth at the condyles might be temporarily accelerated. The mandibular dental arch consequently comes forward in relation to the maxillary one and more than would otherwise have been the case. By cutting out the activator in the premolar/molar region so that it is free of the occlusion, provision is made for the posterior teeth to erupt further and gradually reduce the deep bite at the same time as the overjet is corrected. The teeth in the posterior segments of the maxilla are brought outwards by the rail mechanism (see Fig. 12-1C) because the activator is not worn continuously, but only during part of the day and then normally in the evening and at night. During the remaining time, the patient swallows normally and the situation is as shown in Figure 12-1C. The maxillary incisors can be retruded by the labial arch. As an accompanying effect, certainly when the mandibular incisors are not capped (or only slightly so), the mandibular incisors can protrude whether or not it is desired.

The mode of operation of the activator appears to rely on a braking effect on the normal development of the maxilla, while in the mandible it stimulates development in the natural direction. On that basis one might postulate that the effect would be greater in the mandible than on the maxilla. This is probably not the case, which is in agreement with the suggestion that the adaptability of the sutures is greater than that of the condyle.396

Some attractive aspects of the activator are that it is a relatively simple device, not particularly trying for the patient, while all the different aspects of Class II/1 anomalies are simultaneously and harmoniously corrected. It lends itself well to treatment of a Class II/1 without crowding in either arch. Moreover, it can function as a space-maintainer when deciduous molars are lost prematurely. The activator is especially suitable if one wishes, as in a case of agenesis of premolars, to permit the molars in both jaws to drift mesially while correcting the disto-occlusion. Class II/1 anomalies with an anterior open bite not due to digit sucking are unsuitable for activator treatment. This also applies in cases where the patient is unable to breathe properly through his nose, because he will not be able to keep the activator in. Then an open activator may be better tolerated (Fig. 8-6B).

In situations in which treatment must begin relatively early—such as in Class II/1 with the lower lip behind the maxillary incisors—the activator is very suitable. The patient should try to close the lips over the appliance, which stimulates use of the upper lip. Because the activator therapy is employed at a relatively early age, the number of hours it can be worn during sleep is greater, since most young children spend more time asleep. Moreover, it is felt that adaptability in younger children is relatively great. Both points can explain how an activator can achieve a significant improvement in a relatively short time. A further consideration can be that children grow more at night than during the day,380 and that facial orthopedic therapy probably profits from that. Apart from this, it should be noted that an activator is one of the few appliances that can work effectively in the absence of first permanent molars.

Extra-oral traction has been used for over a century for correction of Class II/1 anomalies. Headgears are usually fitted to maxillary first permanent molars with the object of applying a force to the maxillary complex in a dorsal (and cranial) direction. They can be used alone or in combination with plates, fixed appliances or functional appliances. Headgears can be applied to other points on the dental arch besides first molars. With the use of fixed appliances, these possibilities are more or less unlimited.

The facial orthopedic operation of a headgear rests principally on the influencing of the development of the midface, in which it exerts a force opposing the natural growth. The changes in the craniofacial skeleton are mainly the result of activity in the sutures; their adaptability being utilized.

Headgears can be distinguished according to the direction of the applied force (Fig. 12-2) and, depending on this, their effects differ. The infl/>

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Jan 2, 2015 | Posted by in Orthodontics | Comments Off on 12: Treatment Planning for Class II/1 Anomalies
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