STABILITY OF TEMPORARY ANCHORAGE DEVICES IN VARYING PORCINE BONE DENSITIES

Abstract

Objectives: Human bone density varies between areas of the maxilla and mandible. Orthodontists place Temporary Anchorage Devices (TADs) in all parts, guided by bone porosity and intra-oral location. These decisions may influence TAD stability, defined as the amount of interlocking between the TAD and bone immediately after insertion. The aim of the study was to evaluate the effect of bone mineral density (BMD) on TAD stability in vitro.Methods: Porcine jawbone samples were collected from a local slaughterhouse and maintained hydrated. Samples were created by sectioning rectangular blocks of approximately 1.5×1.5×3 cm3 from different jaw locations and scanned using SkyScan 1127 with appropriate settings (16 mm pixel size, large camera, 100Kv, 100mA, 10W, 180° rotation, and 0.5Al filter). The BMD of the samples was quantified by converting the x-ray attenuation coefficients to BMD. Twenty (n=20) Rocky Mountain TADs of 1.6 mm × 8 mm were inserted perpendicular to the surface of the bone samples. To evaluate TAD stability, all TADs were subjected to a tangential force on an Instron machine until the TADs were displaced 2.5 mm. The force required to displace the TADs overtime was recorded, and the slope was calculated to determine resistance to displacement. Results: The mean BMD, resistance to displacement and yield point were 1.20 g/cm3 ± 0.12, 95.57 N/mm ± 29.14, and 29.04 N ± 10.78. Our results indicate no significant relationship between BMD and TAD resistance to displacement, and between BMD and yield point, as determined by Pearson correlation test (0.109, -0.188) and a two-tailed significance test (p = 0.647, p = 0.428), respectively. Conclusion: Data from this study design did not reveal any association between BMD and TAD stability. Changes in the study protocol such as, bone harvesting from jaw sites with lower BMD, or alterations in TAD length might provide different results.