Influence of cortical thickness on the stability of mini-implants with microthreads

Abstract

The objective of this study was to assess the influence of cortical thickness and bone density on the insertion torque of a mini-implant (MI) with microthreads. Mini-implants with lengths of 6 and 8 mm in the active part were inserted into synthetic bone blocks (polyurethane resin). The density of these blocks was 20 pounds per cubic foot (pcf), simulating bone marrow, and that of blocks 1, 2, and 3-mm-thick blocks was 40 pcf, simulating cortical bone. Blocks with uniform density of 40 pcf were also used to simulate bone areas of greater density. Insertion torque was quantified with a universal testing machine (EMIC). For both MIs, increasing insertion torque was associated with increasing cortical bone thickness. For the same MI length, significant differences were observed among all assessed groups. The insertion torque of the 6-mm-long MI inserted in a 3-mm-thick cortical bone was equivalent to that of the 8-mm-long MI inserted in a 1-mm-thick cortical bone. MIs inserted in bone blocks of greater density presented insertion torque values almost twice as high as those in other groups. The shorter MI, the lower the insertion torque, and the greater the cortical bone thickness, the greater the insertion torque. To minimize fracture risk, the size of MI should be selected according to the insertion site.

Mechanical and histological evaluation of a titanium device for orthodontic anchorage, placed with or without cyanoacrylate adhesive

“…As shown in the present study, this novel mini-implant did not fracture during the shear strength test performed at different time points, despite the finding that osseointegration may increase the possibility of mini-implant fracture 14 . Although the reduced length of the device may contribute to fracture resistance, as observed by Vilani et al, 15 who reported that shorter mini-implants have a lower risk of fracture, this occurrence was not reported in the present study. The absence of fractures may be related to the mechanical properties of the titanium Grade 4, which has high strength, with minimum yield strength of 480 MPa.…”

Primary Stability of Temporary Screws after Dentary and Orthopedic Forces under Static and Dynamic Load Cycles

“…This torsional moment is analyzed in terms of the placement torque, mainly in situations where a non-osseointegration device response is planned for temporary purposes [4,5,[15][16][17][18][22][23][24][25]. In this work, torque values were measured before and after two different loads conditions with different intensities.…”

Comprehensive analysis on orthopedic drilling: A state-of-the-art review

“…Thus, it indicates that animal bone could not be employed for the prediction of heat for human bone. Similarly, Vilani et al 80 have varied the cortical bone thickness (2-3 mm) to analyze the cutting forces and torque. It was found that cutting torque increased with the increase in cortical bone thickness.…”