King's College Hospital Dental School, London, S.E. 5.

Transcription

1 OSTECTOMY AT THE MANDIBULAR SYMPHYSIS J. H. SOWRAY, B.D.S., F.D.S.R.C.S. (Eng.), L.R.C.P., M.R.C.S. and R. HASKELL, M.B., B.S., F.D.S.R.C.S. (Eng.). King's College Hospital Dental School, London, S.E. 5. AMONG the patients referred to the oral surgeon for correction of jaw deformity some of the most difficult problems of treatment-planning arise from those in whom the deformity involves both jaws to such a degree that the treatment of only one jaw is insufficient to produce a satisfactory result. Such a case is described below. CASE HISTORY In June 1966 a 25-year-old spinster school teacher was referred regarding her appearance (Fig. I, A and c). She was a fit looking young woman with a large mandible and small under-developed maxilla. Her occlusion showed an inferior protrusion with a bilateral cross-bite which was more marked on the left side where only the second molars occluded (Fig. 2, A and B). Clinical and radiographic examination showed that this was not a bite of accommodation. It was decided to treat her with a bone graft to the maxilla and an ostectorny at the mandibular symphysis. Initially a tongue reduction was done using the technique attributed to Rheinwald by Egyedi (i965) in order to reduce the chance of subsequent relapse, and at the same time both lower first premolars were extracted. As evidenced by preand post-operative tape recordings there was no discernible difference in speech a fortnight after the tongue reduction. The second stage of treatment was carried out four weeks later when an onlay bone graft from the iliac crest was wired on to the anterior part of the maxilla around the pyriform aperture. The operation on the mandible which was performed at this time is illustrated in Fig. 3. Using an intra-oral approach, an incision was made on the vestibular aspect of the alveolus just below the mucogingival line from second molar to second molar but extending up to the crest of the ridge in the edentulous first premolar regions. This permitted a flap of labial mucoperiosteum to be rotated downwards between the mental nerves so that the symphysis of the mandible could be exposed. Using a bur, the segment of bone containing the lower six front teeth was mobilised, the horizontal cut being made below the level of the apices and also below the genial tubercles because it was thought that a considerable amount of the blood supply of this fragment would be derived from vessels entering the mandible in this region. At operation and post-operatively there was no evidence that the blood supply of this anterior fragment was inadequate. In the first premolar regions, the minimum amount ofmucoperiosteum was raised on the lingual aspect, just sufficient to insert a Howarth periosteal elevator to protect the lingual periosteum from the bur. The upper part of a body ostectomy was then performed, taking as much width of bone as possible without denuding the second premolars and canines, and care was taken to preserve the mental nerves. A segment of the lower border below the horizontal cut was then removed from the symphysis, thus separating the mandible into three parts. Originally it was planned to excise about a centimetre but as this amount is related to the size of the pieces removed from the first premolar regions it is easier to assess the correct amount at the time of operation. Examination of the post-operative models showed that about I4 mm. was removed. One of the advantages of this particular operation is the excellent view which may be obtained 97

2 9 8 BRITISH JOURNAL OF ORAL SURGERY of the operation site. This makes it extremely easy to make adjustment in the amount of bone removed and also a simple matter to get good bone apposition between the fragments. The anterior surface of the symphyseal region was smoothed with burs to produce a further slight reduction of the protrusion. The two halves of the mandible were united FIG. I A, Pre-operative profile. B, Post-operative profile. C, Pre-operative full-face appearance. D, Post-operative full-face appearance. by an interosseous wire inserted at the symphysis and a few bone chips were packed around the cuts although the latter manoeuvre was probably unnecessary since there was excellent contact between the fragments. The lower cap splint consisted of a right and a left posterior part and an anterior part and these were joined together with wires twisted around split capstan studs. Unfortunately three days after operation the lower right posterior splint became loose after passing a nasogastric tube. As a result of this the patient had to have a further

3 OSTECTOMY AT THE MANDIBULAR SYMPHYSIS 99 general anaesthetic so that the splint could be recemented, circumferential wires inserted and at the same time locking bars fitted. In retrospect, an error of judgement had been made in not inserting circumferential wires originally. Thirteen days post-operatively the patient was discharged from the ward and sixteen days post-operatively normal sensation was present in the patient's lower lip. In view of A FIG. 2 B The upper sets of models show the pre-operative occlusion and the lower sets show the post-operative occlusion. In addition to inward movement there is also marked distal movement of the mandibular posterior teeth. the patient's holiday, the removal of the jaw fixation was delayed until ten weeks postoperatively when rigid union was found to be established (Fig. 4)- At 3½ months post-operatively all the lower anterior teeth gave normal electric pulp test readings and reacted to ethyl chloride. Normal sensation was present in the labial mucosa. DISCUSSION This operation on the mandible may be regarded as a logical variation on other operations which have already been described. Cradock Henry (I966) and Winstanley (I965) have reported several cases in which the upper jaw has had the anterior teeth repositioned, K61e (I965) has described osteotomy of the alveolar process to retrude anterior mandibular teeth, and more recently Taylor, Mills and Brenner (I967) recorded a case in which an anterior open bite was corrected by repositioning anterior teeth in the maxilla and mandible.

4 IO0 BRITISH JOURNAL OF ORAL SURGERY FIG. 3 Diagrams showing by means of shading the sites of bone and tooth removal. The posterior fragments rotate medially and the anterior fragment is moved posteriorly. FIG. 4 Lateral skull radiographs taken pre- and post-operatively.

5 OSTECTOMY AT THE MANDIBULAR SYMPHYSIS When planning an ostectomy at the symphysis it was not known whether the rotation inwards of the two halves of the mandible would have an adverse effect upon the temporomandibular joints, but as Fig. 5 shows, if a block of bone equivalent in width to the two central incisors is removed from the symphysis then the subsequent movement of the condyle head is minimal. The patient has not IOI FIG. 5 FIG. 6 Fig. 5.--These models (which do not show the operative procedure) illustrate the minimal rotation of the condyles when approximately one centimetre of bone is removed from the symphysis. Fig. 6.--The pre- and post-operative orthopantomograms show no appreciable alteration in the position of the condyle heads. complained of any symptoms from her temporomandibular joints and it appears that she has readily adapted to the altered relationship of the articular surfaces of the condyles (Fig. 6). It is considered that the operation on the mandible which has been reported is of value where there is a severe crossbite with a small amount of protrusion and has the following advantages: I. Excellent accessibility of the operative field to permit an operation which may be extremely quick and free of technical complications.

6 IO2 BRITISH JOURNAL OF ORAL SURGERY 2. There is no difficulty in preserving the mental nerves. 3. The contact between the cut bone surfaces is maximal, without overlap, thus ensuring a rapid bony union with the restoration of the mandible to a normal anatomical configuration. 4. External scarring is avoided (Fig. I, B). 5. Unlike many operations for reducing the size of a large mandible, the width of the mandible between the angles is reduced thus improving the full-face appearance by narrowing the lower third of the face (Fig. I, c and D). SUMMARY A method of treatment of mandibular prognathism associated with severe crossbite by ostectomy at the symphysis with subapical ostectomy from canine to canine is reported and discussed. ACKNOWLEDGEMENTS We wish to thank Mr. M. A. Kettle for his specialist orthodontic advice and Mr. IV. Smith for the photographs. REFERENCES EGYZm, P. (1965). Brit. J. oral Surg., 3, 13. HENRY, T. C. (1966). Contribution in 'Oral Surgery', 4th ed. by W. H. Archer, pp Philadelphia & London: W. B. Saunders Company. KOLE, H. (1965). Oral Surg. 19, 427. TAYLOR, R. G., MILLS, P. B. & BRENNER, L. D. (I967). Oral Surg., 23, I4I. WINSTANLEY, R. P. (I965). Brit. J. oral Surg., 2, I73.