[Tissue response in circum-maxillary sutures after transverse palated suture expansion]

This study was carried out to investigate the histological reactions of midfacial sutures induced by transverse palatal suture expansion.

Nine mongrel dogs of 8-week old were used in the study. Six of them were used as experimental group as described in a previous paper. The additional three served as controls. In the experimental dogs, a NiTi-shape memory alloy (NiTi-SMA) arch wire was used to expand the transverse palatal suture. Tetracycline was injected intramuscularly (50 mg/kg) three days before operation and at the time of sacrifice. Tissue reactions of premaxillo-maxillary suture, transverse palatal suture, zygomatico-maxillary suture, zygomatico-temporal suture and fronto-maxillary suture were observed in undecalcified tetracycline labeled sections and decalcified histological sections.

The sutures in normal young dogs showed active bone formation. With the increase of age, the cellular components of the suture decreased. A great amount of new bone apposition was found in the bony front of expanded transverse palatal suture of the experimental dogs. Degenerative changes were found in premaxillo-maxillary suture at the expanded side while the contralateral showed active osteogenesis. Other sutures manifested both bone apposition and deposition due to the irregular interdigitations.

After expansion, a great amount of new bone formed in the transverse palatal suture and thus the hard palate was lengthened. All the circum-maxillary sutures reacted in different patterns.