Effect of facial divergence and other biological factors on anchorage control and overbite in extraction cases

Objectives: To compare and quantify anchorage loss during space closure following premolar extraction in matched groups of different facial types. Materials and Methods: Variables such as facial divergency, age, sex, and crowding were considered for cephalometric analysis. Pearson's correlation coefficient was used to determine the strength of the relationship between anchorage loss and facial divergence. Multiple regression analyses were used to investigate the factors associated with variability of anchorage loss. Results: Average treatment duration was 41.90 ± 12.97 months. The mean anchorage loss was 3.30 ± 1.99 mm, 3.47 ± 1.95 mm, and 3.01 ± 2.39 mm for hypodivergent, normodivergent, and hyperdivergent patients, respectively. No significant differences in the amount of anchorage loss were found among the three facial groups and between sexes. Increasing age and crowding were significantly negatively associated with anchorage loss (P = .02 and < .001, respectively). Conclusions: Facial divergence does not significantly impact anchorage loss in orthodontic cases involving extractions. Horizontal anchorage loss decreases the mandibular plane angle, but the magnitude may not be clinically relevant. Vertical anchorage loss does not significantly change the mandibular plane angle in premolar extraction cases.