Abstract:

Objective  This study aims to biomechanically analyze a mini-implant at different healing times before loading. Methods  Sixty-four mini-implants with (12±1) N·cm insertion torque were placed in the low jaw of eight beagle dogs. The test mini-implants remained in the low jaw for 0, 1, 3, and 8 weeks of bone healing and for an additional 10 weeks under a force of 0.98 N. The unloaded control implants were further divided into four groups (1, 3, 8, and 10 weeks). Maximum removal torque (MRT) testing was performed to evaluate the interfacial share strength of each group. Surface analysis of the removed implants was performed by scanning electric microscope (SEM). Results  The MRT for the loading implants at 0, 1, 3, and 8 weeks of healing were 4.10, 4.25, 2.42, and 4.42 N·cm, respectively. During the healing process, the removal torque values of the 3-week implants were significantly lower than those of the other healing groups (P<0.05). The unloaded 3-week implants also had lower removal torques (P<0.05). The implant surface of the 3-week test group showed more fibrous bone. However, the other loading implants had more lamellar-like tissue. Conclusion  A stable dangerous period occurred approximately 3 weeks after mini-implant insertion. A 3-week healing is disadvantageous to the stability of the implant. Orthodontics loading occurred immediately or after 1 week as a function of the healing time. The 8-week implant appeared to have a positive effect on peri-implant bone remodeling and implant stability.

Key words: mini-implant,  loading,  osseointegration,  removal torque