A Multidisciplinary Approach to the Healing of Cranial and Residual Maxillary Cleft Defects by Means of Allogenous Demineralized Osseous Implants and Polylactic Acid Casts in Dogs

Abstract

Objective The aim of this study was to evaluate the healing of artificially induced bony defects in dogs by means of demineralized allogenous bone powder (DBP) implants covered with polyhydroxy lactic acid (PLA) casts compared 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 dogs between the ages of 18 and 24 months and weighing approximately 20 kg were used as subjects. Interventions Each experimental animal had bilateral maxillary alveolar clefts created. In a later procedure, each defect was repaired with a DBP implant, half of which were covered with a PLA96 matrix. Each animal also had a circular defect created in each parietal bone that was immediately covered with DBP implants, half of which were similarly covered with a PLA96 disk. Main outcome measure Repeated technetium-99m methylene-diphosphate (99mTC MDP) uptake measurements were performed to evaluate bone metabolism during the healing period, while at relevant intervals, radiographs were taken of the healing alveolar cleft defects to register bone repair. After 1 year, the animals were euthanized for macroscopic and histologic evaluation. Results Histologically, the grafts covered with PLA96 were at a more advanced stage of healing than those without, and the cranial defects similarly were more advanced in the healing process than the alveolar defects. Uptake 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 significantly different from zero. Cranial defects covered with a PLA96-enhanced implant showed a mean maximum count rate of 275, while the plain DBP side showed 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 PLA96 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 PLA96-enhanced side was 285, while on the plain DBP side, the corresponding value was 320. Conclusion Although an advantage of the combination was established for parietal cranial defects, no advantage was seen for alveolar cleft defects in this experimental setup.