SUTURAL EXPANSION USING RIGIDLY INTEGRATED ENDOSSEOUS IMPLANTS - AN EXPERIMENTAL-STUDY IN RABBITS

Rigidly integrated implants offer great promise for orthodontic and or thopedic anchorage in the oral and midfacial regions. Rigid anchorage can be used to control unwanted tooth movement, provide abutments in e dentulous arches, and open the vertical dimension of occlusion. To eva luate the use of endosseous implants in the midface region, two flange d titanium implants were placed on either side of the midnasal suture of 18 New Zealand White rabbits. The rabbits were divided into an unlo aded control and two experimental groups. One experimental group was l oaded at 1 Newton (N) and the other at 3 N. All rabbits were euthanize d after 12 weeks of loading. Stereologic point-hit and line-intercept methods were used to analyze microradiographic and multiple fluorochro me histology of the suture. All implants remained stable during the lo ading period. The distance between the implants increased significantl y in the loaded groups compared with the control, and was significantl y higher in the 3 N group than in the 1 N group. Percent bone volume w as significantly decreased, while the percent suture volume tended to be increased in the loaded groups. Mineral apposition and bone formati on rates at the sutural surfaces were increased in the loaded groups ( P < 0.05), but did not differ between loaded groups. These results ind icate that relatively low loads (1 or 3 N) applied to rigidly integrat ed endosseous implants across an unfused suture are satisfactory for a chieving expansion under the conditions of this study. The 3 N load re sulted in slightly more expansion, but did not affect the rate of bone formation at the suture.