Effects of thread depth in the neck area on peri-implant hard and soft tissues : an animal study

Abstract

Background: Implants with deep thread depth have been developed for the purpose of increasing the total implant surface area. However, the effects of implant thread depth remain controversial. The aim of this study was to examine the effects of thread depth on peri-implant tissues in terms of bone-implant contact (BIC), bone-implant volume (BIV), and hard-and soft-tissue dimensions using comprehensive analyses including micro-computed tomography (µCT). Methods: Five beagle dogs received experimental intra-mandibular implants 3 months after removal of their premolars and first molars (P2, P3, P4, and M1). Two different types of implants were installed in each animal: deep threaded (DT) and shallow threaded (ST). Resonance frequency testing were performed on the day of implantation as well as 4 weeks and 8 weeks after implantation. Intraoral radiography, micro-computed tomography (µCT), and histomorphometry were used to evaluate peri-implant tissues 4 weeks and 8 weeks after implantation. Results: There were no significant differences in resonance frequency test results between the two groups. Although radiographic analysis showed no group differences, µCT (p = 0.01) and histomorphometry (p = 0.003) revealed that the DT group had significantly lower BIC values than the ST group at 4 weeks. However, by 8 weeks, the BIC values of the two groups did not differ significantly. No significant differences in BIV or soft-tissue height were observed between the two groups at either time point. Conclusions: DT implants showed no benefits over ST implants when inserted in dog mandibles.