Effect of Microthreads on Removal Torque and Bone-to-Implant Contact: an Experimental Study in Miniature Pigs
by: Yee-Seo Kwon, Hee Namgoong, Jung-Hoon Kim, In-Hee Cho, Myung-Duk Kim, Tae-Gwan Eom, Ki-Tae Koo
The objective of this study was to evaluate the effect of microthreads on removal torque and bone-to-implant contact (BIC).
Materials & Methods:
Twelve miniature pigs for each experiment, a total of 24 animals, were used. In the removal torque analysis, each animal received 2 types of implants in each tibia, which were treated with sandblasting and acid etching but with or without microthreads at the marginal portion. The animals were sacrificed after 4, 8, or 12 weeks of healing. Each subgroup consisted of 4 animals, and the tibias were extracted and removal torque was measured. In the BIC analysis, each animal received 3 types of implants.
Two types of implants were used for the removal torque test and another type of implant served as the control. The BIC experiment was conducted in the mandible of the animals.
The P1-M1 teeth were extracted, and after a 4-month healing period, 3 each of the 2 types of implants were placed, with one type on each side of the mandible, for a total of 6 implants per animal. The animals were sacrificed after a 2-, 4-, or 8-week healing period. Each subgroup consisted of 4 animals. The mandibles were extracted, specimens were processed, and BIC was analyzed.
Fig. 1. Design of implants used in the experiment.
Fig. 2. Cross section of implant in mandible. A: Implant group A. B: Implant Group B. C: Larger magnification of the marginal portion where the BIC measurement was performed.
No significant difference in removal torque value or BIC was found between implants with and without microthreads. The removal torque value increased between 4 and 8 weeks of healing for both types of implants, but there was no significant difference between 8 and 12 weeks. The percentage of BIC increased between 2 and 4 weeks for all types of implants, but there was no significant difference between 4 and 8 weeks.
The existence of microthreads was not a significant factor in mechanical and histological stability.
Fig. 3. Mean and standard deviation of removal torque(Ncm) at each healing period.
Fig. 4. Mean and standard deviation of BIC(%) at each healing period. BIC:bone-to-implant contact.