Are insertion torque and early osseointegration proportional? A histologic evaluation

ObjectivesThe objective of this histologic study was to determine the effect of three drilling protocols (oversized, intermediate, and undersized) on biologic responses to a single implant type at early healing periods (2weeks in vivo) in a beagle dog model. Materials and methodsTen beagle dogs were acquired and subjected to surgeries in the tibia 2weeks before euthanasia. During surgery, each dog received three Unitite implants, 4mm in diameter by 10mm in length, in bone sites drilled to 3.5, 3.75, and 4.0mm in final diameter. The insertion torque was recorded during surgery, and bone-to-implant contact (BIC), and bone area fraction occupied (BAFO) measured from the histology. Each outcome measure was compared between treatment conditions with the Wilcoxon signed-rank test. Bonferroni-corrected statistical significance was set to 95%. ResultsInsertion torque increased as an inverse function of drilling diameter, as indicated by significant differences in torque levels between each pair of conditions (P=0.005). BIC and BAFO levels were highest and statistically similar in the recommended and undersized conditions and significantly reduced in the oversized condition (P<0.01). ConclusionsReduced drilling dimensions resulted in increased insertion torque (primary stability). While BIC and BAFO were maximized when drilling the recommended diameter hole, only the oversized hole resulted in evidence of statistically reduced integration.