An Italian study has found that the length and shape of miniscrew implants used for orthodontic anchorage has an effect on their success, according to an article from Longer, and conical rather than cylindrical, screws were associated with greater success. The findings also indicate that miniscrews applied to medium-quality bone have a significantly lower failure rate than those applied to high- and low-quality bone. 

The researchers found that the method of insertion of miniscrews–pre-drilling versus drill-free–and patient skeletal type (defined according to the angle of inclination to their mandibular plane in relation to the anterior cranial base) had no effect on miniscrew success rates.

The study examined data from 144 patients, with a mean age of 24.6 years, with 324 miniscrews applied. The research team clinically evaluated the success of patients’ treatment based on the endurance and clinical usefulness of the screws over the course of patients’ orthodontic treatment.

In all, 296 applications were successful after a mean implantation duration of 13.7 months. Miniscrews of a  10-mm had the best success rate, much higher than that of 8-mm screws. 

Miniscrew diameter had no effect on the success of treatment; however, conical-shaped screws had fewer failures than cylindrical ones, although this was not a significant finding in comparison with the total mean failure rate, according to the researchers.

The researchers conclude that the causes of orthodontic miniscrew failure appear to be varied and “might also be attributable to factors that were not included as objectives of this study, such as metabolic disturbance, smoking, and specific local parafunctions.”