Effect of mechanical loading on electrical conductivity in porcine TMJ discs.

The objective of this study was to examine the impact of mechanical loading on solute transport in porcine temporomandibular joint (TMJ) discs using the electrical conductivity method. The electrical conductivity, as well as ion diffusivity, of TMJ discs was determined under confined compression with 3 strains in 5 disc regions. The average electrical conductivity over the 5 regions (mean ± SD) at 0% strain was 3.10 ± 0.68 mS/cm, decreased to 2.76 ± 0.58 mS/cm (-11.0%) at 10% strain, and 2.38 ± 0.55 mS/cm (-22.2%) at 20% compressive strain. Correspondingly, the average relative ion diffusivity (mean ± SD) at 0% strain was 0.273 ± 0.055, decreased to 0.253 ± 0.048 (-7.3%) at 10% strain, and 0.231 ± 0.048 (-15.4%) at 20% compressive strain. These results indicated that compressive strain impeded solute transport in the TMJ disc. Furthermore, our results showed that the transport properties of TMJ discs were region-dependent. The electrical conductivity and ion diffusivity in the anterior region were significantly higher than in the posterior region. This regional difference is likely due to the significant differences of tissue hydration between these 2 regions. This study provides important insight into the electrical and solute transport behaviors in TMJ discs under mechanical loading and aids in the understanding of TMJ pathophysiology related to tissue nutrition.

Autologous TMJ disk replacement.

Several techniques have been advocated for replacement of displaced or diseased temporomandibular joint disks. Techniques are reviewed and the author's experience in managing this complex problem is presented.

A comparison of propofol with methohexital and isoflurane in two general anesthetic techniques.

The purpose of this study was to compare two general anesthetic techniques involving oral intubation for use in outpatient third molar surgery. Fifty American Society of Anesthesiologists I or II patients were randomly allocated to two groups. Group 1 received methohexital, isoflurane, nitrous oxide, and alfentanil, while group 2 received propofol, alfentanil, and nitrous oxide. An analysis of the results showed that although the technique used in group 2 cost more, had a slightly longer induction time, and produced a similar duration of apnea, it did not cause significant hypotension (as previously reported), and had a significantly better overall recovery. It was concluded that the use of propofol in the outpatient surgery setting may be a valuable addition to the oral and maxillofacial surgeon's anesthetic armamentarium.

Evaluation of biodegradable ampicillin anhydrate microcapsules for local treatment of experimental staphylococcal osteomyelitis.

Successful treatment of chronic osteomyelitis requires sustained high concentrations of antibiotics locally within the infected bone. The efficacy of biodegradable (poly-DL-lactide-co-glycolide) microspheres containing 30.7% ampicillin anhydrate for the local treatment of experimental staphylococcal osteomyelitis was evaluated in rabbits. In the initial experiment, antibiotic therapy was initiated immediately following injection of Staphylococcus aureus into the proximal tibial metaphysis. A single intramedullary injection of microencapsulated ampicillin (100 mg) prevented osteomyelitis in all seven animals tested and was as effective as a two-week course of parenteral ampicillin administration. When antibiotic therapy was delayed for seven days, osteomyelitis developed in four of eight animals treated locally with microencapsulated ampicillin and in six of eight animals that received parenteral ampicillin therapy. When antibiotic therapy was delayed for seven days and was preceded by debridement, all ten animals treated locally with microencapsulated ampicillin had sterile bone cultures. In contrast, seven of ten animals treated locally with unencapsulated ampicillin powder developed osteomyelitis. Biodegradable antibiotic-loaded microspheres may be of clinical benefit for the local treatment of chronic osteomyelitis.

A comparison of four particulate bone derivatives.

Samples of four types of particulate bone matrix derivatives were prepared and surgically inserted into standardized critical-sized defects in calvariae of Long-Evans rats. Implantation of demineralized bone matrix (DBM), bone regenerative matrix, and two types of particulate chemosterilized, antigen-extracted, autolyzed, allogeneic (AAA) bone from endochondral (eAAA) and intramembranous (iAAA) sources will result in the regeneration of bone in orthotopic skull defects. The four preparations were tested in orthotopic, 8-mm calvarial wounds to compare the quantity of new bone that formed 28 days postimplantation. Quantitative computer imaging was used to measure roentgenographic gray levels and bone volume of new trabeculae (calcified plus osteoid). All experimental bone matrix derivatives produced more bone volume than the nontreated control wounds. Bone volume regenerated from iAAA was significantly less than eAAA and DBM-regenerated bone.

Cranial, iliac, and demineralized freeze-dried bone grafts of the mandible in dogs.

Both autogenous bone grafts and demineralized freeze-dried allogeneic bone implants were evaluated for mandibular reconstruction. Four-centimeter segmental defects of the midbody of the edentulous mandible were reconstructed in 36 dogs, with specimens recovered at 3 and 6 months and quantitatively compared for total and new bone by histomorphometric analysis. Autogenous grafts consisted of corticocancellous cranial block (CB), corticocancellous iliac block (IB), and particulate cancellous iliac marrow (PM). The allogeneic bone was demineralized and freeze-dried, and consisted of particulate cortical endochondral bone (FP), cranial cortical block (FCB), and iliac cortical block (FIB). Clinically and histomorphometrically, results appeared to indicate that (1) CB compared favorably with IB at 3 and 6 months for total bone, but IB showed a trend for more new bone formation at 6 months, a trend that may be due to the thicker cortical component of CB, which requires longer time periods to remodel than the cancellous rich IB; (2) FP failed to achieve bony union at 3 months, with inadequate rates of new bone formation; and (3) FCB and FIB compared favorably for total bone with CB and IB at 6 months, although new bone for autogenous CB and IB was 26.9% and 45.4%, while new bone for allogeneic FCB and FIB represented only 7.9% and 17.4%.

Simultaneous orthognathic surgery and cervicomental liposuction. Clinical and survey results.

Adjunctive soft tissue surgical procedures to enhance facial esthetics can be performed simultaneously with orthognathic surgery. Submental-submandibular liposuction was performed with orthognathic surgical procedures in 22 patients from April 1989 to May 1990. Patients ranged in age from 18 to 48 years. Fourteen patients had submental and eight patients had both submental and infralobular incisions. The average estimated amount of fat removed was 40 to 50 cc. In this series of patients there was a marked improvement in facial esthetics. Liposuction created greater definition of the submandibular region and a more distinct jawline, with an improved cervicomental angle. Patients appeared younger. No significant complications occurred, and patient satisfaction was high. A survey of oral and maxillofacial surgery training programs in the United States was conducted to determine experiences with liposuction. Survey results are presented. Our survey results are consistent with our clinical experiences with this procedure.

Calvarial bone regeneration using osteogenin.

This experimental study reports on the application of a partially purified noncollagenous protein extracted from cortical bone to restore craniotomy defects in Papio species (baboon). The partially purified protein (osteogenin) produced significantly more bone formation in calvarial wounds than was found in the untreated controls. There were no adverse tissue reactions from the implanted xenogeneic osteogenin.

Surgical excision of an ameloblastic odontoma in a cynomolgus monkey (Macaca fascicularis).

A surgical approach used for removal of maxillary tumors in humans was modified to excise a maxillary tumor in a cynomolgus monkey (Macaca fascicularis). This is an effective technique for excising tumors, recovering fractured canine teeth, or other health problems of the maxillary region in Macaca sp. The described approach limits facial disfigurement and enhances the probability of return to required function for future research utilization. This approach minimizes the extensive degree of post-operative intensive care.

Noma. Report of two cases.

Noma is an infectious process involving the oral cavity and occasionally other structures. It is characteristically a childhood affliction, and it never occurs in healthy persons. Conservative treatment in debriding facial lesions greatly enhances reconstructive efforts.