The effect of force, timing, and location on bone-to-implant contact of miniscrew implants.

This study was conducted to evaluate the effect of timing and force of loading, as well as implant location, on bone-to-implant contact (BIC) of loaded and control miniscrew implants (MSI). Using seven skeletally mature male beagle dogs, 1-2 years of age, followed over a 110 day period, a randomized split-mouth design compared immediate versus delayed loading, 50 versus 25 g loading, and 25 g loads in the maxilla versus the mandible. Mobility was evaluated using a 0-3 point scale before the MSIs were prepared for histological analysis. Histomorphometric analyses were performed under light microscopy using Metamorph software on undecalcified sections. The percentage BIC was measured at three levels (coronal, middle, and apical) of the MSI. BIC was compared statistically using pairwise Wilcoxon signed-rank tests. Mobility was detected in three of the 56 (5.4 per cent) MSIs. The mobile implants were all unloaded controls and showed no BIC. All remaining stable MSIs showed some BIC. However, variation in BIC was large, ranging from 2.2 to 100 per cent. There were no significant (P > 0.05) differences in BIC associated with timing of force application, amount of force applied, or implant location. There was a tendency for less BIC at the coronal level, but the differences between levels were not statistically significant. Within the limits of this study, it is concluded that the timing and amount of force at loading and location of implant placement do not affect BIC. Moreover, it appears that only limited amounts of osseointegration are necessary to ensure implant stability.