Analysis of the correlation between mesiodistal angulation of canines and labiolingual inclination of incisors

Objective: To assess the degree of correlation between canine angulation and incisor inclination. Methods: Mesiodistal angulation of canines and labiolingual inclination of incisors were obtained by means of digital graphics software (ImageTool®) from standardized photographs of the casts of 60 patients. Incisor inclination was also assessed by lateral cephalometric radiographs. Results: Random error showed a variation of around 2° in measurements made on the casts (1.8-2.5), while systematic error, measured by the intraclass correlation test, displayed excellent reproducibility for both methods used in this study (p<0.001, r=0.84-0.96). Linear correlation tests revealed a significant positive correlation between canine angulation and incisor inclination in the maxillary arch (r=0.3, p<0.05) and even more significantly in the mandibular arch (r=0.46 to 0.51, p<0.001), when both were measured on the casts. When incisor inclination was examined by cephalometrics, correlation level was statistically insignificant for maxillary incisors (r=0.06 to 0.21, p>0.05) and varied widely in the mandibular arch (r=0.14 to 0.50). Conclusions: The introduction of changes in the angulation of canines with the aim of monitoring compensations observed in incisor inclination is warranted, especially in the lower arch.