Comparison of in vivo failure of precipitation-coated hydroxyapatite temporary anchorage devices with that of uncoated temporary anchorage devices over 18 months

Introduction: The objective was to compare the stability of hydroxyapatite-coated (HA) temporary anchorage devices (TADs) with uncoated TADs. Methods: Maxillary arches of 92 patients with Class II Division 1 maloc-clusion requiring premolar extractions were randomly distributed to receive both types of Ti-6Al-4V alloy TADs by a single operator. TADs were replicas of each other except for the HA precipitation surface coating of the threaded part. TADs were placed between the roots of the first molar and the second premolar and were immediately loaded by a 300 g of force nickel-titanium spring for retraction of the anterior segment. The main outcome was the loosening of the TAD. Results: TADs of each type were placed in 92 patients. The patients were recalled monthly for 18 months; 10 TADs failed in the HA-coated group (11%), whereas 12 TADs (13%) failed in the uncoated group, with a statistically insignificant difference between the survivability of the TADs in the 2 groups (P = 0.67, log-rank). The Kaplan-Meier curve showed better survivability of the HA-coated TADs between the second and fifth months. The TADs placed on the left side (19.6%) failed significantly more than on the right side (4.3%) (P = 0.002) when placed by a right-handed operator in right-handed patients. Conclusion: The premise that the HA-coated TADs will have a lower failure rate seems incorrect.