Evaluation of primary stability of inclined orthodontic mini-implants

Abstract

The aim of this study was to investigate the initial stability of mini-implants when placed slanting or perpendicular to the bone surface, and to examine the effects of differences in tractional direction. Titanium mini-implants were inserted into rabbit nasal bones, slanting (60 degrees , 120 degrees ) or perpendicular (90 degrees ) to the bone surface. These implants were then loaded with a force of approximately 2 N, using a NiTi coil spring. The mobilities on the traction and non-traction sides were assessed using the Periotest device immediately after placement and after traction for two weeks. Then, the tissues with the mini-implants were resected, and the contact between the bone and the implant was examined by electron microscopy. There was a tendency for the mobilities of the mini-implants at 60 degrees and 120 degrees to be smaller than those at 90 degrees when measured before and after traction. The bone-implant contact lengths at 60 degrees were significantly longer than those at 90 degrees . There was no significant difference in the bone-implant contact ratio among the different angles. Correlations were evident between implant mobility and contact length or contact ratio. It is concluded that in clinical practice, implants inclined to the bone surface tend to have better primary stability.

A healing period increases mini-implant stability in growing rats

“…They used a Periotest device to assess all mini-implants before and after traction and found that mobility measurements were useful for predicting miniimplant outcomes. In addition, Inaba et al (24) found a strong correlation between the implant-bone contact ratio and PTVs (r = 0.590, P < 0.05). Thus, PTVs are an appropriate index of primary implant stability.…”

“…The mobility test is an objective, straightforward method of evaluating implantation success (20,24,25). Uemura et al (25) drilled pilot holes of various diameters in rat tibiae, inserted a mini-implant (1.2-mm diameter) in each hole, and applied an experimental traction force for 3 weeks.…”

“…In particular, mobility is thought to be an appropriate index of primary implant stability, as a previous study (24) found a strong correlation between the implant-bone contact ratio and an index of mobility.…”

“…According to Olivé et al (20), Inaba et al (24), and Uemura et al (25), the mobility test is an objective and straightforward method of evaluating the success of implantation. In particular, mobility is thought to be an appropriate index of primary implant stability, as a previous study (24) found a strong correlation between the implant-bone contact ratio and an index of mobility.…”

An in vitro study of factors affecting the primary stability of orthodontic mini-implants

“…Mini-implants inserted at 60u to 70u to the bone surface have been shown to exhibit greater primary stability than those inserted at 90u. 12,13 Predrilling reduces miniimplant insertion torque, especially with larger-diameter drills. 2,4,14 Insertion torque also decreases as the predrilling depth increases, with the reduction being most pronounced within the cortical layer.…”