Effect of microthreads on removal torque and bone-to-implant contact

Abstract

Purpose: The objective of this study was to evaluate the effect of microthread of implant on removal torque and bone-to-implant contact

Methods: 12 miniature pigs for each experiment, total 24 animals were used. In removal torque experiment, each animal received 2 types of implants at each tibia which are treated with same surface treatment (SLA) but with difference in existence of microthread at the marginal portion. The animals were sacrificed after 4, 8, 12 weeks of healing period. Each subgroup was consists of 4 animals and tibias were extracted and removal torque was measured. In bone-to-implant contact experiment, each animal received 3 types of implants. 2 types of implants used in removal torque test and another type of implant as control. BIC experiment was conducted in mandible of the animals. P1~M1 teeth were extracted and after 4 months of healing period, 3 types of each implant at each side of mandible, total 6 implants per animal were placed. The animals were sacrificed after 2, 4, 8 weeks of healing period. Each subgroup was consists of 4 animals. Mandibles were extracted, specimen was made and BIC was analyzed by light microscopy and image analysis software program.

Results: No significant difference was found between implant with microthread and without it for removal torque test or BIC test. In removal torque experiment, removal torque value increased between 4 weeks and 8 weeks of healing period for both type of implant, but there was no significant difference between 8 weeks and 12 weeks. In BIC experiment, BIC % increased between 2 weeks and 4 weeks for every type of implant, but there was no significant difference between 4 weeks and 8weeks for all types of implant.

Conclusions: Existence of microthread was not significant factor for mechanical and histological stability. This result which seems inconsistent with previous study may due to thread pitch of the microthread and its effect on stress distribution. Further study on optimal thread pitches at the marginal portion of implant and its effect on biomechanical and histological stability are needed.