EFFECTS OF BUCCAL SHIELDS ON THE MAXILLARY DENTOALVEOLAR STRUCTURES AND THE MIDPALATAL SUTURE - HISTOLOGIC AND BIOMETRIC STUDIES IN RABBITS

The mechanism of the buccal shields with regard to regulating the tran sversal relationship of the maxillary dental arch is uncertain. The pe riosteal pull theory, growth at the midpalatal suture and changes in e quilibrium have all been proposed as explanatory factors. The aim of t he study was to investigate the transversal development of the dental arch and the osseous remodeling at the lateral surfaces of the maxilla ry alveolar process and in the midpalatal suture after stretching the bucca (cheek) with buccal shields in the vestibulum. Ten New Zealand w hite male rabbits 12 weeks old were used. The animals were divided int o two groups (control and experimental). Initial and final impression had been taken from the two groups and plaster models were made using biometric analysis in all animals of each group. Transversal measureme nts were taken of the distances between the maxillary right and left t eeth. Tetracycline hydrochloride and Alizarin complexone were used to label the mineralizing tissues. After the animals had been killed, the biopsies from the midpalatal suture, the alveolar wall, and the perio steum were studied under a microscope. The results from the biometric analysis showed maxillary dental arch expansion in the two groups that was significantly larger in the experimental group. Microscopically, the growth at the midpalatal suture was also significantly larger in t he experimental group, while no significant differences were found at the maxillary alveolar bone in the two groups. The conclusions drawn f rom this study are that the vestibular buccal shields bring about an i ncreased expansion of the maxillary dental arch and increased growth a t the midpalatal suture. No increased bone deposition was found at the buccal dentoalveolar wall, inducing doubts as to the accuracy of the periosteal pull theory for widening of the dental arch.