Investigation of the association between vertical skeletal patterns and the timing of failure of temporary anchorage devices

Abstract

Temporary anchorage devices （TADs） have become increasingly popular as orthodontic treatment measures for anchorage or distal movement of molars. However, TAD failure is a major limitation, and the aim of this study was to examine the effects of various factors on the timing of TAD failure. This study included 467 TADs implanted on the buccal side of the molar region in 197 patients undergoing orthodontic treatment. The relationship between failure and sex, age, jaw （maxilla or mandible）, side （left or right）, Frankfort mandibular plane angle （FMA）, point A-nasion-point B angle （ANB）, overbite, and overjet was examined. The time （number of days） until failure was also investigated. The failure rates were significantly higher in men compared to women （23.9％ vs. 13.6％; p-value＝0.024）, and in the mandible compared to the maxilla （28.2％ vs. 11.8％; p-value＜0.001）. A significant difference by age-group was also observed （p-value＜0.029）, with the failure rates being highest among patients aged ≥30 years （29.8％）. Approximately half （47.6％） of the maxillary failures occurred by day 120, and more than half （58.1％） of the mandibular failures occurred by day 60. Moreover, the failure rate by day 120 was higher in the maxilla when the FMA was smaller. The failure rates of TADs implanted on the buccal side of the molar region were influenced by sex, age, and location （i.e., mandible or maxilla）. Failure tended to occur more rapidly and readily in mandibular compared to maxillary implants. Moreover, when considering the vertical skeletal pattern, failure rates ＜120 days after implantation tended to increase when the FMA decreased.