By DONALD WINSTOCK, M.B., F.D.S. St Bartholomew's Hospital and The Middlesex Hospital, London

Transcription

1 ALVEOLAR OSTECTOMY AND MENTOPLASTY IN THE TREATMENT OF MANDIBULAR PROGNATHISM By DONALD WINSTOCK, M.B., F.D.S. St Bartholomew's Hospital and The Middlesex Hospital, London THERE are basically two groups of operations currently performed for the correction of mandibular prognathism. The first consists of various osteotomies or ostectomies in the horizontal or ascending ramus, most of which have been summarised by Nordenram and Waller (I968). There are two essential features of these operations : the entire anterior part of the mandible is reduced in a posterior direction, either in the occlusal plane only or additionally in the vertical plane to correct an anterior open bite. Because of the nature of the techniques, intermaxillary fixation is employed for a period ranging from four to twelve weeks. In the second group of operations, only the tooth-bearing portion of the jaw is sectioned and retropositioned--the so-called sub-apical osteotomy (Kole, r965) or this technique is combined with ostectomy at the mandibular symphysis (Sowray and Haskell, I968). Techniques in both groups can be combined with tongue reduction (Rheinwald, I957; Egyedi, I965), or be preceded or followed by orthodontic therapy to improve the final occlusion. The method described in this paper- is based on several features of the progna&ous mandible and the desirability of avoiding intermaxillary fixation with all its attendant hazards (Winstock, I963 ; Barton, I97o) and discomforts to the patient. A study of the facial characteristics of the prognathous patient will often reveal factors which may be overlooked if one is concerned solely with the reduction of the jaw sufficient to establish a normal occlusion. For example, mandibular prognathism is not necessarily synonymous with a prominent jaw in an antero-posterior plane. The occlusion alone may be significantly pre-normal while the chin is only mildly prominent. On the other hand, pre-normal occlusion of moderate degree may be associated with a markedly prominent chin. Furthermore, a minimal pre-normal occlusion may be associated with a very long lower third of the face--the long, straight jaw seen in the patient with a long, relatively featureless face, such as flat malar eminences, thin lips and a narrow nose. If one is concerned only with the correction of the prognathism to produce a normal occlusion, the results in such cases may be rewarding from a functional standpoint, but disappointing aesthetically. Reduction of the mildly prognathous jaw to achieve a normal occlusion may result in a relatively receding chin. Where the chin prominence exceeds the occlusal defect, correction of the occlusion will still leave a protruding chin and where the chin is too long, reduction in an antero-posterior plane will leave the long chin receding, thus rendering the total facial contour even more featureless than before operation. A surgical technique has been evolved which treats the two aspects of the deformity separately at the same operation and combines a sub-apical osteotomy, usually in the first or second premolar regions, with a mento-plasty, which reduces the chin according to the need of the case.

2 ALVEOLAR OSTECTOMY AND MENTOPLASTY IN TREATMENT OF PROGNATHISM 3II Operative Technique.--Pre-operative planning on study models will determine how many teeth require removal to achieve an acceptable occlusion. Provided that the remaining premolars and molars are in a functional occlusion, even though the cusps may not contact in the ideal occlusal manner, it is not unreasonable to accept such an imperfect but functional result. There are many cases where, because of the disparity between the widths of the upper and lower dental arches, a perfect occlusion is not possible whatever surgical technique is employed although pre-operative orthodontic treatment may improve the prognosis. An acrylic cap splint is constructed to fit all the lower teeth in the corrected position, the occlusal surface of the splint being so made that it occludes with the upper teeth. The entire operation is performed intra-orally, thus obviating'the necessity for submandibular scars and possible damage to the lower branches of the facial nerve. No major artery should need ligation. The bone is sectioned just in front of or just above the mental nerve ; only in those cases where the mental foramen is unusually anterior is it necessary to dissect backwards the nerve at its exit from the foramen to allow the bone sectioning to be carried out without damage to the nerve (Fig. I Stage I). The incisive branch of the nerve is deliberately cut but this results in very limited disability--anaesthesia of the anterior gingiva and six anterior teeth. These do not behave in the same way as teeth which become devitalised following caries ; they do not discolour or develop apical abscesses. In some cases, Somewhat inexplicably these teeth regain their sensitivity and respond to thermal tests. In the typical prominent jaw, the chin eminence is planed down with burrs and chisels especially anteriorly (Fig. I, Stage 2). With the long chin, the height of the chin is reduced. Where the prognathism is mild, minimal planing of the anterior prominence is carried out. After the alveolar ostectomy and mentoplasty have been completed, the prepared splint is cemented to the teeth with a simple zinc oxide and TREATMENT OF MANDIBULAR PROGNATHISM BY ANTERIOR SUBAPICAt OSTEOTOMY AND MENTOPLASTY Stage ~ ~ FIG. I Case I. Subapical ostectomy in the first pre-molar region and reduction of the chin prominence. eugenol paste, Since the lower border of the mandible has been retained intact (the mentoplasty does not detract from this) there are no displacing forces acting on the repositioned alveolar segment and a simple splint with no intermaxillary fixation is adequate for retention of the anterior fragment. If there is a need to recontour extensively the anterior part of the jaw, especially if a significant step results in the premolar regions and at the junction of the chin and alveolar bone, bone chips from the iliac crest are invaluable in producing a good aesthetic result. In mild cases, bone chips are rarely necessary. This operation allows one to exercise some degree of flexibility in planning the final result without incurring the risks inherent in intermaxillary fixation in the presence of swelling of the jaws and face, difficulty in feeding and talking post-operatively, and with the likelihood that the patient will be able to return to work about two weeks after the operation because the appearance is neither unsightly nor jaw function markedly impaired. Removal of the splint leaves less cement to be scaled from the teeth than is the case with silver cap splints cemented with copper cement. Because the cement is so easily

3 312 BRITISH JOURNAL OF PLASTIC SURGERY removed without discomfort to the patieat, the splint Call be removed a week or so after operation, if one wishes to check the occlusion, and then easily replaced with fresh cement. Case I (Figs. 2-5) had a severe degree of prognathism involving both the occlusion and the chin. He did not wish to have his chin reduced by the amount that would have been necessary to establish a normal occlusion. The prominence of the chin was therefore removed as described. Case 2 (Figs. 6-9) illustrates the long face with a mild degree ofpre-normal occlusion. A more radical chin reduction was carried out together with retropositioning of the anterior alveolar segment. FIG. 2 FIG. 3 FI6. 4 FIG. 5 Fig. a.--case i. Pre-operative profile showing mandibular prognathism. Fig. 3.--Case I. Post-gperative profile following subapical ostectomy involving the removal of 5 4 ] 5 and chin reduction. The chin reduction was less than would have resulted in repositioning of the anterior part of the mandible sufficient to establish a normal occlusion. This was intended to avoid a disproportion between the patient's nose and his chin. Fig. 4.--Case I. Pre-operative occlusion. Fig. 5.--Case I. Post-operative occlusion. Mandibular prognathism combined with a degree of cross-bite is shown in Case 3 (Figs. IO-I3). The excess spacing between the upper central incisors is due to the congenital absence of lateral incisors. No operation on the mandible alone could improve this.poor premaxillary appearance so, at the same operation, the central incisors were sectioned, with their surrounding bone, and repositioned to the left, thus leaving enough space for one right lateral incisor. Subsequent crowning of the central incisors and a bridge for the lateral incisor space completed the restoration to a normal dental arch. A minimal mentoplasty was performed. This patient, aged 39 years, did not wish to have her appearance altered so radically that she would not be recognisable as the same person. This is a common request made by adult patients ; the younger age group with gross jaw disprofortion seem to be more willing to acquire a new face.

4 FIG. 6 FIG. 7 ' FIG. 8 FIG. 9 Fig. 6.--Case 2. Pre-operative appearance. Mild pre-normal occlusion with a long lower third of face, Fig. 7.--Case 2. Post-operative appearance following ostectomy in first pre-molar region and great reduction in chin length. Figs. 8 and 9.--Case 2. Pre- and post-operative lateral skull X-rays. FIG. io FIG. II FIG. 12 FIG. 13 Figs. IO and II.--Case 3. Pre- and post-operative views of face. Mandibular prognathism with unilateral cross-bite, spacing between the upper central incisors and missing lateral incisors. Figs. 12 and I3.--Case 3. Pre- and post-operative occlusion following subapical ostectomy in pre-molar region in the mandible, the ]4-having been extracted, and forward and lateral osteotomy of the upper central incisors which created sufficient space for a bridge for one lateral incisor. The central incisors have been crowned.

5 314 BRITISH JOURNAL OF PLASTIC SURGERY Alveolar ostectomy and mentoplasty as a treatment for the prognathous jaw is a versatile procedure but it has its limitations. It will not influence the obtuse angle of the mandible which is sometimes a significant feature of this type of case although such an angle is not incompatible with a pleasing appearance. Many of these obtuse angles cannot be improved greatly by any other technique since the ultimate determining factor in the degree and direction of jaw reduction is the occlusal plane of the teeth and not the mere ability to square the angle of the jaw. Cases presenting with gross anterior open bites--apertognathiamcannot be corrected by this method since raising up the anterior alveolar segment would leave a space between it and :he chin and if this space were to be filled in with bone chips, the occlusion would be corrected but the length of the jaw would remain unaltered. No doubt a subsequent operation to reduce the chin length could be performed but the patient might be displeased with the appearance in the period of three months between operations. Nevertheless, this might still be a less discomforting programme than a one-stage ostectomy necessitating intermaxillary fixation. I wish to thank the X-ray and Photographic Departments, the medical artists and maxillo-facial technicians of the Middlesex and St Bartholomew's Hospitals for their invaluable asistance and Mr Peter Gordon for the restorative dentistry for Case 3. REFERENCES BARTON, P. R. and HARRIS, A. W. (I970). An investigation of the efficiency of the oral airway and a technique for improving the airway in the early post-operative period following mandibular osteotomy. British Journal of Oral Surgery, 8, EGYEDI, P. (I965). Reduction of tongue size in the surgical correction of jaw deformity. British Journal of Oral Surgery, 3, I3-2I. K6LE, H. (1965). Results, experience and problems in the operative treatment of anomalies with reverse overbite (mandibular protrusion). Oral Surgery, 19, o. NORDENRAM, A. and WALLER, A. (I968). Oral surgical correction of mandibular protrusion. British Journal of Oral Surgery, 6, RHEINWALD, U. VON. (1957). Die operative Zungenverkleinerung aus z/ihn~irztlicher indikation. Deutsche Zahn-, Mund- und Kieferheilkunde, 27, r29-i4o. SOWRAY, J. H. and HASKELL, R. (I968). Ostectomy at the mandibular symphysis. British Journal of Oral Surgery, 6, 97-1o2. WINSTOCK, D. (1963). Some complications of major oral surgery and their prevention and management. British Journal of Oral Surgery, I,