A multidisciplinary approach to the healing of cranial and residual maxillary cleft defects by means of allogenous demineralized osseous implants andpolylactic acid casts in dogs

Objective: The aim of this study was to evaluate the healing of artificiall y induced bony defects in dogs by means of demineralized allogenous bone po wder (DBP) implants covered with polyhydroxy lactic acid (PLA) casts compar ed with DBP implants without the casts. Design: Prospective animal study. Setting: Research university. Sample: Following a pilot study in which two dogs were used, four mongrel d ogs between the ages of 18 and 24 months and weighing approximately 20 kg w ere used as subjects. Interventions: Each experimental animal had bilateral maxillary alveolar cl efts created. In a later procedure, each defect was repaired with a DBP imp lant, half of which were covered with a PLA(96) matrix. Each animal also ha d a circular defect created in each parietal bone that was immediately cove red with DBP implants, half of which were similarly covered with a PLA(96) disk. Main outcome measure: Repeated technetium-99m methylene-diphosphate ((TC)-T -99m MDP) uptake measurements were performed to evaluate bone metabolism du ring the healing period, while at relevant intervals, radiographs were take n of the healing alveolar cleft defects to register bone repair. After 1 ye ar, the animals were euthanized for macroscopic and histologic evaluation. Results: Histologically, the grafts covered with PLA(96) were at a more adv anced stage of healing than those without, and the cranial defects similarl y were more advanced in the healing process than the alveolar defects. Upta ke of 99mTC MDP into the cranial implants was at its maximal level after 1 week and then gradually decreased until, after 7 weeks, it was not signific antly different from zero. Cranial defects covered with a PLA(96)-enhanced implant showed a mean maximum count rate of 275, while the plain DBP side s howed a mean maximal count rate of 150. Alveolar defects with the plain DBP implant showed a maximum count rate in the first week; those with the PLA( 96) enhanced implant showed maximum uptake during the second week. On both sides, there was a gradual decrease to the base value in the seventh week. The mean maximum count on the PLA(96)-enhanced side was 285, while on the p lain DBP side, the corresponding value was 320. Conclusion: Although an advantage of the combination was established for pa rietal cranial defects, no advantage was seen for alveolar cleft defects in this experimental setup.