Chapter 9

Possibilities and Limitations of Facial Orthopedics

9.1 Introduction

In facial-orthopedic treatment, an attempt is being made to influence the morphology of the craniofacial skeleton. The adaptability of skeletal tissues plays an important role in this. In applying any facial-orthopedic therapy, the mechanisms are called upon which are present in order to provide natural changes in the face. This is discussed and illustrated by clinical examples. To that purpose specific therapies are considered: functional therapy for Class II anomalies, and application of extraoral traction to Class II and Class III anomalies. The limits of facial-orthopedic treatment are indicated. The possibilities for increase of the apical area into the vestibule are then considered. In conclusion, the application of the system of the dentofacial complex to treatment is explained.

9.2 Orthodontics and facial orthopedics*

Orthodontic anomalies, in which there is no discrepancy in the relation between both dental arches, can be corrected by moving the teeth within the jaws orthodontically. Where there is indeed a discrepancy in the relationship between both dental arches, generally it would be recommended to attempt to correct the jaw-relationships wholly or partly by facial-orthopedic means.

Preferably treatment of an orthodontic anomaly should be undertaken in a growing individual before the replacement of the deciduous dentition by its successors is complete. One then has the possibility to take advantage of the growth potential of the face. A similar situation exists with regard to the development of the dentition. For example, if one intervenes before the second deciduous molars are exfoliated, it is often possible to benefit from use of the extra space made available in the arch as the teeth exfoliate for smaller successors (leeway space) in achieving the treatment result aimed for.

9.3 Adaptability of skeletal tissues

For both aspects, facial growth and the development of the dentition, it is reasonable to make a distinction between growth in the strict sense and the phenomenon of adaptability. Adaptability of skeletal tissues is understood to mean the ability of bony structures to change in size and shape:

Examples of the first are described extensively by Enlow as “remodeling” (see Chapter 3). Examples of the second are the changes that are manifested in the alveolar processes in both the developing and the fully erupted permanent dentition. Other examples of the second type are orthodontic tooth-movement and changes in the facial sutures and mandibular condyles that can be produced by facial-orthopedic therapy.

The adaptability described above is then, insofar as the dentition is concerned, localized in the periodontal system (and alveolar processes) and continues to exist as long as teeth are present. The adaptability of the periodontal system provides the means to maintain contact between the teeth despite interproximal abrasion, to erupt when contact is lost with an antagonist, and to obtain tooth movement, even in adults.

In the growing facial skeleton, the adaptability is primarily located in the sutures, at the condyles, and, to a lesser extent, in the periosteum. The condyles lose their adaptability with age. (Only in pathological conditions, such as in acromegaly due to a hormone disturbance, can the cartilage present at the condyles of an adult resume proliferation and result in an increase in size of the mandible.) Sutures also lose their adaptability with age, because the structures alter and bony connections form later on across the suture (ankyloses). Thus, sutures contribute nothing further to the mature face. The sutures function in a child, on the one hand, as important regions of growth, and, on the other, as essential sites for adaptation. The condyles are the most important growth areas of the facial skeleton. Because the direction in which they grow can vary, they have a great potential for adaptability. In addition, there is an extra possibility for adaptability as growth occurring at the condyles can accelerate temporarily under the influence of effects from outside the condyles. Furthermore, the periosteum plays an important part in the adaptability of the face and the rest of the body. The adaptability of the periosteum remains beyond the period of active growth, as does that of the periodontal system. There is a lifelong capacity for apposition and resorption on bone surfaces to bring about adaptive changes.

In addition, the fine cancellous bone formation that can occur in certain regions (such as the maxillary tuberositas and apically at the ends of not-yet-completed roots) can also be considered a feature of adaptability.

9.4 Growth and adaptability of the face

In Chapter 5, a diagram is presented (Fig. 5-9) illustrating the growth regions of the face according to vertical and horizontal components of growth. For the reader’s convenience, this figure is reproduced again (Fig. 9-1). In the following description of growth and adaptability in the craniofacial skeleton, this figure and its related text are used as a foundation.

The spheno-occipital synchondrosis plays a part in the vertical growth of the posterior region of the face. It contributes also to the sagittal growth, where it concerns the region adjacent to the cranium. It is accepted that the spheno-occipital synchondrosis has no adaptability. Its growth cannot be influenced by local factors, nor by those which normally are present in the growing head, nor by those which for therapeutic reasons might be applied.

The condyles can be considered as a combination of a cartilaginous growth region and an adaptability site. Because cartilage grows interstitially, it can increase a great deal in height in a short time. Through its orientation, the condyle contributes to increase both the posterior facial height and the horizontal length of the mandible. The vertical growth of the anterior part of the craniofacial skeleton is principally dependent on an increase in length of bony structures; cartilage, with its strong potential for growth, does not have a place in this, except in the nose. In the lower part of the anterior facial region, the increase in height of the skeletal framework derives from the increase in height of the alveolar process that is associated with the development of the dentition. In the upper part of the face, the vertical development of the bones occurs mainly as growth at the sutures, which through their orientation contribute not only to vertical, but also to sagittal development of the middle face.

9.5 Adaptability and therapy

In facial-orthopedic and orthodontic therapy, the same natural mechanisms are used as those which make normal facial growth and the development of the dentition possible. The growth of cartilaginous structures can be influenced only to a limited extent—as with the mandibular condyle—or not at all—as with the synchondroses. The greatest possibility for changing the morphology of the facial skeleton rests in the sutures of the middle face. The periodontal system provides that possibility where the teeth are concerned. The assumed adaptability of the condyles and sutures, the periodontium and periosteum is illustrated in Figure 9-2A in relation to age. The height of the stippled area represents the degree of adaptability. Adjoining is Figure 9-2B, which presents the mutual relationship between growth and adaptability of the condyles and the sutures. Relative to that, it has been assumed that the growth of the condyle progresses at varying rates under hormonal control. The sutures run a more even course of growth.

It is suggested that the adaptability of sutures remains after the growth of the sutures—in the strict sense—has been completed. Although theoretically the adaptability of the sutures should operate equally in all directions, in practice, it appears not to be the case. It is easier to cause the maxillary complex to develop ventrally with the assistance of forward acting traction upon the entire maxillary arch in a young Class III patient, than to correct a Class II anomaly by supplying a dorsally acting force on the maxillary complex. In the first case (Class III), one works in the natural growth direction, while in the second situation (Class II), one is, as it were, rowing against the stream. An analogy can be made here with the extrusion and intrusion of teeth, in which a movement in the natural direction (extrusion) is easier and quicker to achieve than is the reverse movement.

The adaptability of the condyle appears to be relatively limited. This conclusion is, on one hand, based on the fact that under normal physiological conditions very little or no reduction of cartilaginous growth seems to be attainable. On the other hand is the lack of clarity that exists as to whether or not temporary stimulation of mandibular growth in humans will lead to an ultimately larger mandible than that which the individual was destined to receive in the first place. As a working hypothesis, it is maintained that one can temporarily enhance growth and influence its direction.

If the region of the teeth and the alveolar process is left out of consideration, it can be said that the adaptability of the maxillary complex is greater than that of the mandible. This is not only attributable to the greater adaptability of the sutures as such, but also to the fact that there are several of them. In addition, cancellous bone can form in the maxillary tuberositas. In the mandible, the adaptability is restricted to the possibilities already outlined—the condyles and surface remodeling. In this connection, a widening of the mandibular base in the sense that the distance between corresponding points on the right and left sides increases, is not possible to any appreciable extent. Among other related factors is that the distance between the temporomandibular joints in which the condyles are situated is determined by influences remote from the mandible itself.

9.6 Functional therapy in Class II anomalies

There are different possibilities for correction of a Class II relationship by facial orthopedics. In the scheme of this treatise, those in which so-called “functional appliances” are used come first into consideration. The manner of operation of these and where they differ from treatment methods later to be described will be explained by means of a simplified representation of the growth of the face (Fig. 9-3) comparable to Figure 9-1.

The most widely known representative of functional appliances is the activator developed by Andresen, which, in principle, rests loosely in the mouth and holds the mandible in a posture downwards and ventrally with respect to the maxilla. There are many variants of the activator, such as Mühlemann’s Propulsor, the Vorbissdoppelplatte of A. M. Schwarz, the bionator of Balters, the Gebissformer of Bimler, the Kinetor of Stockfisch, the Funktionsregler of Fränkel, and the combined appliance of Bass. As far as the facial-orthopedic changes in the sagittal plane are concerned, all these appliances work in much the same way and the remarks made here in relation to the activator generally apply to all of them.

An activator exercises an influence upon both the maxillary complex and the mandible in sagittal and vertical directions. Time and time again when the patient wearing an activator closes into it—whether or not in a reflex action—a force is generated which operates to ventral and caudal on the mandible, and to dorsal and cranial on the maxillary complex. In addition, a similar action is ascribed to the activator when, without extra muscle activity, the mandible is held in the advanced and open position used in the construction of the appliance (Figs. 9-4 and 9-5). An activator type of appliance leads to an effect on the sutures through which the growth of the maxilla ventrally will be slowed down. Simultaneously, there is the potential for a temporary favorable growth-acceleration at the condyles, resulting in the mandibular arch moving forward in relation to the maxillary arch to a larger extent than it otherwise would have done. The performance of the activator is opposed to the normal development of the maxilla, but encourages that of the mandible. On that basis, it can be suggested that the effect on the mandible will be greater than on the maxillary complex. However, this is by no means always the case, which is in agreement with the assumption that the adaptability of the sutures is greater than that of the condyles. Against this is the fact that the condyles seem to react more strongly to functional appliances when the position in which the mandible is held is regular, with intervals of some months, brought more to ventral.95 The vertical effects in the action of the activator are neither discussed in more detail here nor brought out in Figure 9-4.

In situations in which treatment preferably begins relatively early—as in pronounced Class II/I anomalies with the lower lip behind the maxillary incisors—the activator usually can be used effectively. An important advantage accompanying the use of the activator is that the patient will attempt closing his lips over the appliance, which can bring about a reactivation of the upper lip. Because activator therapy is used at a relatively early age, the time it is worn during sleep will be longer, since at that age the periods of sleep are longer. Moreover, the adaptability in younger children is suggested to be greater than that in older patients. Both points can explain how, in a relatively short time, a significant improvement can be obtained by means of this therapy.