In-vitro study of microtrauma following insertion of self-tapping or self-drilling miniscrew into a postmortem human mandible

Introduction The study investigated the formation of microcracks surrounding self-tapping and self-drilling miniscrews, depending on whether pilot drilling was performed beforehand. A postmortem human mandible used for measurement of microstructural damage. The null hypothesis proposed that the method of mini-implant insertion would not affect the formation or progression of microcracks in the cortical bone of the mandible. Methods On a mandible with soft tissues removed, a 50-square reference grid was applied to the bone surface. Subsequently, 20 self-tapping and 20 self-drilling miniscrews (tomas®-pin, tomas®-pin SD; Dentaurum, Ispringen, Germany) were inserted. Additional, pilot drillings without implant placement, were created. The grid was then cut into 50 bone blocks, followed by horizontal separation of 100-µm-thick cortical discs to be evaluated for periimplant microcracks and structural irregularities by light and electron microscopy. The effects of the three groups were analyzed using seperate one-way analyses of variance (ANOVA) for each variable. In addition, the non-parametric Kruskal–Wallis test was applied, due to the violations of the normality assumption. To maintain a significance level of 5%, pairwise post hoc comparisons were performed using the Bonferroni correction. Results Not significantly more microcracks were observed around self-drilling than around the self-tapping miniscrews. No significantly higher measurements for self-drilling screws were obtained in terms of maximum crack-length, accumulated crack-length, numbers of cracks and crack-width. Bone around self-tapping miniscrews exhibited slightly smoother surfaces. Microcracks were negligible after pilot drilling without screw insertion. Conclusion No significant differences in microcrack formation were observed between self-drilling and self-tapping insertion techniques. Future clinical studies may explore regional differences in microcrack distribution within the jaw.