Objective: The hypothesis to be tested is that peak-insertion torque of self-drilling micro-implants of an appropriate diameter correlates with peak-removal torque mechanically. Materials and Methods: A total of 360 self-drilling micro-implants composed of five different types were used. They (24 of each group) were inserted in three types of artificial bone with the use of a driving torque tester at a speed of 15 rpm. Insertion torque was measured during the placement, while the removal torque was measured within 3 days after insertion. Results: Most of the micro-implants in type A sheared before they were completely inserted in 40-pounds per cubic foot bone. The implants in other types were successfully inserted without implant breakage and bone fracture in all bone densities. There was a statistically significant correlation between insertion torque and removal torque (r $ 0.43543, P 5 .0001). There were significant differences in insertion and removal torque among the diameters of implants and bone densities with an increasing tendency. The torque loss rates reduced as the diameter of the implant and bone density increased. Conclusions: Micro-implants with a diameter of less than 1.3 mm are unsuitable for insertion into a bone with a density greater than 40 pounds per cubic foot mechanically when one is using a selfdrilling technique. (Angle Orthod. 2010;80:821-827.)

ObjectiveTo determine the effect of surface anodization on the interfacial strength between an orthodontic microimplant (MI) and the rabbit tibial bone, particularly in the initial phase after placement.MethodsA total of 36 MIs were driven into the tibias of 3 mature rabbits by using the self-drilling method and then removed after 6 weeks. Half the MIs were as-machined (n = 18; machined group), while the remaining had anodized surfaces (n = 18; anodized group). The peak insertion torque (PIT) and the peak removal torque (PRT) values were measured for the 2 groups of MIs. These values were then used to calculate the interfacial shear strength between the MI and cortical bone.ResultsThere were no statistical differences in terms of PIT between the 2 groups. However, mean PRT was significantly greater for the anodized implants (3.79 ± 1.39 Ncm) than for the machined ones (2.05 ± 1.07 Ncm) (p < 0.01). The interfacial strengths, converted from PRT, were calculated at 10.6 MPa and 5.74 MPa for the anodized and machined group implants, respectively.ConclusionsAnodization of orthodontic MIs may enhance their early-phase retention capability, thereby ensuring a more reliable source of absolute anchorage.

Objective: To determine the surgery site dependency of root contact during drilling for orthodontic microimplant placement and to analyze the influence of clinicians' expertise on the results. Materials and Methods: Dental arches with resin teeth were mounted on a dental phantom (P-5/3 TS, Frasaco, Germany). Drilling was conducted in six locations frequently selected for microimplant placement: between the central incisors, between the maxillary first molar and second premolar, and between the mandibular first and second molars, bilaterally. The 28 qualified dentists who participated were divided into two groups based on their clinical experience. A total of 192 drillings were performed by the experienced group and 240 by the inexperienced group. The damaged root surfaces were classified as ''moderate'' or ''severe.'' Results: Significant differences in both overall and site-dependent rates of root contacts were found between the groups. Overall rates for the experienced and inexperienced groups were 13.5% and 21.3%, respectively. For the experienced group, the incidents occurred predominantly in the lower left (34.4%) and upper right (18.8%) posterior regions. The most susceptible teeth were numbers 36 and 16. In contrast, for the inexperienced group, all four posterior regions were susceptible. Conclusions: The surgery site and clinicians' expertise had significant effects on the rate as well as the pattern of root contacts. (Angle Orthod 2010;80:130-136.)

No abstract

No abstract