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Four mandibular screw-plate locking systems were studied in sheep. Three to four centimetres angular continuity resections of the mandible were performed and the defects bridged with pre-bent angular reconstruction plates fixed with four screws in the body part and three in the ramus. Each type was used four times. Clinical and radiological examinations were carried out 1 and 2 months later. All sheep were able to eat and ruminate normally throughout the postoperative period. Radiology revealed that 6/16 plates and 5/112 screws fractured during the follow-up period. In one type, no fracture occurred. Screw fracture was confined to just one reconstruction system. Six of 16 mandibles showed slight to moderate bone resorption under the plate. The results point to the internal shortcomings of the systems tested.

Follow-up of 47 patients, treated using mandibular bilateral sagittal split osteotomy and self-reinforced poly-L-lactide acid (SR-PLLA) screws for rigid internal fixation, is presented. The focus was on clinical and radiological osteotomy healing. The average follow-up time was 2.1 years (range 0.5-5 years). Clinical recovery and radiological osteotomy healing during follow-up were uneventful. Osteolytic changes were seen around the SR-PLLA screws in 27% of cases. The majority of the screw canals remained as radiolucent shadows without bony filling.

Adult dentate patients with unilateral condylar fractures were followed up for one year after injury. Patients were interviewed about subjective complaints, and mandibular excursions and function of occlusion and temporomandibular joints (TMJs) were recorded. Radiological characteristics were assessed from panoramic and Towne's views and compared between patients with occlusal disorders and patients without. During follow up, mandibular deviation on opening towards the fractured side was more pronounced in cases with marked reduction of ramus height and condylar dislocation. This restriction of translation movement of the fractured joint was also seen radiologically in one-third of cases while in two-thirds of the fractured condyles, malpositioning was observed when compared with the healthy side. In patients (39%) having subjective symptoms such as TMJ pain, altered occlusion or ability to bite only unilaterally, and objectively verified occlusal interferences, a marked reduction of the ramus height on the fractured side was observed. In such cases nonoperative treatment of condylar fractures may be compromised.

Skeletal stability during the first year after mandibular advancement surgery and fixation using biodegradable self-reinforced poly-l-lactide (SR-PLLA) screws, without postoperative intermaxillary fixation, was studied in 25 patients by means of cephalometric measurements. The magnitude of advancement was on average, 3.88 mm at pogonion (PG) (range 1.25-6.5 mm) and 4.57 mm at B-point (range 2.75-7.5 mm). After one year a mean relapse backwards of 0.59 mm at the PG (15%) and 0.78 mm at the B-point (17%) was observed. Nineteen patients (76%) and 17 patients (68%) were stable at PG and B-point, respectively. SR-PLLA screws are considered to be comparable to other forms of rigid internal fixation for fixation of bilateral splitting osteotomies after mandibular advancement, as far as skeletal stability is concerned.

Mandibular angular ostectomy defects in 12 sheep were bridged with a titanium plate system (THORP), designed according to the screw-plate-locking principle. Two screw designs (hollow and solid) and two rough (plasma-coated, sand-blasted)-surface and one smooth (anodized)-surface structure were tested in a critical two-screw anchorage model. Fixation with two screws only per fragment was successful in only one-third of the cases. The fixation results were superior for screws with a rough surface, either sand-blasted or plasma-coated. The hollow-screw design did not seem to offer special advantages over the solid screws with identical surface structure. In the successful cases, the bone-screw contact was maintained continuously over a period of 8 weeks, and anchorage was even enhanced by reinforcement of the cancellous structures. In the unsuccessful cases, peri-implant bone resorption seemed to be related to jeopardized bone perfusion in the vicinity of the implants. It is presumed that a plating system with locked screws has the advantage that only two screws will hold a relatively short condylar process. This study proved the assumption to be questionable. However, in view of the problems related to prosthetic replacement of the temporomandibular joint, an attempt to salvage the articular portion may still be justified in selected cases, even if the chance of success is as low as 30%.

Eighteen oblique osteotomies in sheep mandibular condylar necks were fixed with self-reinforced poly-L-lactide (SR-PLLA) (n = 9) or stainless steel (n = 9) screws (core diameters 2.4, 2.7, 3.0, or 3.5 mm). No intermaxillary fixation (IMF) was applied. The follow-up periods were 6, 12, and 24 weeks, respectively, after which the sheep were killed, and the status of the condylar head was assessed radiographically and histologically. The results showed that the fixation had been adequate. Bony destruction, osteophytes, and flattening of the condylar head, however, were frequently observed in both groups, as compared with the unoperated contralateral condyle. Histologic studies revealed that the thickness of the condylar head cartilage had increased and that the boundaries of the different cell layers were irregular, as was the junction of cartilage and bone. The diameter of the screw did not seem to have any influence on the occurrence of either radiologic or histologic signs of condylar degeneration. These findings indicate that screw fixation of condylar fractures in the mandible without IMF might result in degenerative joint disease.

The results are reported on 214 patients treated for 270 mandibular fractures, using rigid internal fixation. Of these, 172 fractures (63.7%) in 131 patients had been re-evaluated at final follow-up in connection with plate and screw removal, on average 15.2 months, postoperatively. Although one-third of the patients had a history of alcohol abuse, and 86% were treated with a delay of more than 24 h (mean 3.2 days), good primary bone healing was observed in 93.9% of the patients. Infections, seen in 6.1% of the patients, were related exclusively to inadequate stability of the fracture. Malocclusion, observed in 18.2% of 159 dentate patients, was caused by incorrect plate bending and insufficient fracture reduction. Immediate postoperative dysfunction of the inferior alveolar nerve in 58.1% of the cases, and of the mandibular branch of the facial nerve in 12.7%, was followed by almost total recovery 1 year after operation. It is concluded that rigid internal fixation is a reliable method of treatment, especially indicated for patients with reduced healing capacity and poor co-operation.

The use of a polydioxanone (PDS) plate for orbital reconstruction was evaluated in 20 patients with various traumatic defects of the orbital floor. The follow-up time was 9 to 45 months (mean 20.4 months). A CT scan was obtained in 13 patients. Radiographic analysis showed that in 12 of the 13 patients there was new bone in the orbital floor. Clinically, most patients had transitory postoperative diplopia (lasting for a mean of 29 days) because of overcorrection. Only 2 patients, however, suffered from persistent diplopia. In one patient, abducens nerve paresis was the cause. It is concluded that PDS is suitable for orbital floor reconstruction, at least in cases in which defects do not exceed 1-2 cm in diameter. Overcorrection seems necessary. The material is well tolerated, is totally absorbed and appears to be replaced by bone in nearly all cases.

Non-Hodgkin's lymphomas (NHL) presenting through oral symptoms are rare. Between 1976 and 1987, a total of 17 cases (7 male, 10 female) were diagnosed in our departments. The first symptom was an intraoral tumour mass in 9 cases, loosening of teeth in 2 cases and paraesthesia in another 2. Most tumours (13/17) were located in the lower jaw. In only 5 cases had the referring physician or dentist suspected malignancy. In 3 cases, the histological diagnosis was Burkitt's lymphoma. The grade of malignancy was classified as low in 4 cases, intermediate in 3 and high in 8. None of the patients was HIV-positive. Nine patients died of their disease within 1-132 months (mean 18.3 months).

Sports-related maxillofacial fractures were analysed in 80 patients, accounting for 5.6% of all patients with facial bone fractures, treated during the 5-year period 1981-1985. 55% of the patients had 1 or more mandibular fractures and 45% had midface fractures. 6% of the patients had multiple injuries. The most common causes of injury were collision and fall. Soccer and ice hockey turned out to be the most hazardous sports, although sports-related maxillofacial fractures were less severe than those related to other causes. The need for oral and facial protection among athletes involved in contact sports is discussed.

A report is given of 45 patients with fractures of the mandible treated by the method of rigid internal fixation. In a majority of cases, there were either absolute or relative contraindications for an IMF. Most of the fractures plated were body fractures of the mandible, followed by angular, and symphysis fractures. In 4 cases, the fractures, caused by gunshots, were compound ones. In these, extensive soft tissue reconstructions were also performed. In a majority of the patients, good primary healing was observed, and the mean hospitalization time was only 4.4 days. The infection rate of 13% was, however, relatively high, and a few disturbances were seen with respect to motor and sensory function of the lower lip. Slight occlusal dysharmonies were registered in 23%, on an average of 22 weeks postoperatively, but these could be adjusted with a minimum of grinding. It was concluded that bone plating is a useful method in the treatment of several different types of mandibular fractures including the severe compound ones. The method can be especially recommended in cases in which an IMF is contraindicated or should be avoided. The possibilities for decreasing the frequency of postoperative infections are discussed.

68 patients with fractures of the zygomatic complex were studied. Of these, 56 had sensory disturbances of the infraorbital nerve. 50 patients were operated on and in 42% (21) some degree of persisting hypesthesia was found. No significant difference in outcome was found between the different methods of indirect reduction used. However, in 10 out of 12 patients in which direct fixation with transosseous wiring of the infraorbital margin was performed, persisting hypesthesia was encountered. In 3 out of 4 patients where the nerve was also explored primarily, the sensation returned totally. A secondary nerve deliberation was also found to be beneficial in 4 out of 5 patients with persisting total loss of sensation.

This study comprises 30 patients with extensive oral cancer invading the mandibular bone. In each case, large segmental composite resections were performed and the mandibles primarily reconstructed, according to the principles of rigid internal fixation. All but one of the reconstructions were successful and the functional and cosmetic results were excellent or good in 12 patients. The results indicate that primary reconstruction can be performed without major complications. Bone transplantation may be omitted or postponed to a later date. The fact that tracheostomy and intermaxillary fixation can be avoided, is a major advantage for these patients.

The present report is an analysis of 93 patients (52 male; 41 female) treated in 1981-1983 for maxillofacial fractures sustained in bicycle accidents. These accidents accounted for 7.1% of all facial bone fractures treated during the same period. Most accidents were single vehicle accidents (88%) and took place during the summer months. Of the patients, 65% had mandibular fractures, 35% had midface fractures and 5% had fractures in both the middle and lower thirds of the face. Condylar fractures were by far the most common of the mandibular fractures (67%)--a result which differs from studies concerning the profile of mandibular fractures in general. The majority of the middle third fractures were zygomatic (65%). Multiple injuries were diagnosed in 38% of the cyclists and other head injuries were the most common associated injury. Mean hospitalization of the in-patients (38%) was 4.1 days and the average sick leave was 14 days. The results of the study indicate that the use of protective helmets should be strongly recommended to cyclists, although most commercially available helmets do not protect the whole facial area and especially not the chin.

Nine male patients were treated for condylar fractures of the mandible by a method involving detachment of the condylar head. Pre-operatively, all patients had severe malocclusion. Radiologically, most condyles were anteromedially displaced. Open reduction was indicated but repositioning of the condyle was impossible without ramus osteotomy followed by temporary condylectomy. On follow-up roughly 32 months after surgery no permanent complications were seen. Joint function was almost completely restored. Radiographic evaluation revealed some shortening and deformation of the condyles which had been operated. Translation and rotation movements were almost normal. The method described appears useful in those rare cases of fractures in which normal repositioning of a dislocated condyle is difficult.