Aim: The investigation was performed to evaluate the failure rate of immediately loaded mini-implants used for orthodontic anchorage.
Materials and Methods: 290 mini-implants of the same type (Aarhus mini-implants®, Medicon, Germany) were inserted in 186 patients and immediately loaded with super-elastic coil springs or elastic power-chains. 176 devices were inserted in the lower jaw and 114 in the upper jaw in the following sites: mandibular symphysis, mandibular alveolar process, maxillary alveolar process, retromolar area, and palate. The data was collected from an orthodontic University department and two private practices. The mini-implants were used as direct and indirect anchorage units in order to perform various dental movement. All devices that showed complete absence of mobility after 120 days of continuous load were scored as successful, those that showed mobility and had to be removed were scored as failures.
Results: 27 mini-implants failed (9.3%). Ten implants failed in the upper jaw (8.7%) and 17 in the lower jaw (9,6%).
Discussion: Many factors have been suggested as determinants for clinical failure. Inflammation of the surrounding soft tissues, bone and soft-tissues characteristics, incorrect surgical procedure and mini-implant breakage were the causes related to the failure group. The overall failure rate was similar to other investigations where a healing period had been performed, eliminating immediate loading as possible risk factor.
Conclusion: Mini-implants can be considered valuable devices for controlling anchorage in clinical practice. Only a thorough knowledge of the failure determinants can help to reduce even further tha failure rate of these devices.