Retrospective Evaluation of the Survival Rate of Buccal Mini-implants and the Factors Associated with their Survival

Objective: The aim of this study is to evaluate the success rate of common mini-implants used on the buccal side of both the maxilla and mandible for orthodontic purposes. All orthodontic mini-implants placed at the University of Connecticut residency from July of 2013 till April of 2020 by various residents and faculty. The location and outcome of the implant was measured as success if the implant was stable or if it failed. Materials and Methods: Records of all mini-implants placed on the buccal aspect of both maxilla and mandible of patients receiving orthodontic treatment at the University of Connecticut Orthodontic Department from July 2013 to April 2020 were included. Both photographs and notes of the treatment were analyzed. The age, sex, malocclusion type, location of mini-implant and the dates of placement were recorded. The dates of any failures and or re-insertion at the same or different location were also recorded to the best of our abilities. The same measurements were made by 2 different operators, S.A. and L.P. The results were compared between both operators for reliability. Results: A total of 157 buccal mini-implants were placed in 65 patients during the period from July 2013 to 2020. The mean age of these patients was 29.95 ± 12.7 years (range 13-64 years). Thirty‐three patients were female (mean age: 31.6 ± 13.7 years), and twenty-two patients were male (mean age: 26.73 ± 11.1 years). No significant differences were found in relation to age. Males had a significantly higher failure rate than females 44.8% vs 25.3% respectively. The mandible had more failure rates than the maxilla, 39.1% vs 23.1% respectively. A statistically significant correlation was not found between the anterior-posterior location of the implants on the dental arches. In terms of the types of implants the failure rates were as follows: 26.9% for the buccal alveolar mini-implants, 36.4% for the infrazygomatic, and 75% for the buccal shelf mini-implants. Conclusion: Buccal-alveolar and infrazygomatic implants placed in the residency setting have a lower survival rating that shown in previous literature and the procedures are highly technique sensitive. Buccal shelf orthodontic mini-implants showed a very poor survival rate in the residency setting. Orthodontic mini-implants are more stable in female patients, and are more successful in the maxilla than the mandible. The success of mini-implants is higher when placed in patients with Class I and Class II skeletal relationships as well as when they are used for anchorage and molar protraction rather than distalization and/or intrusion as well as Class III patients.