Maxillary first premolar inclination in 8- to 11-year-old children: An observational cross-sectional study on panoramic radiographs

• Percentiles by age were computed for first premolar inclination (FPI).
• Percentiles by maturation of the mandibular second molar were computed for FPI.
• There was no difference between the distributions of these percentiles.
• Canine inclination and sector location significantly influenced FPI.
• FPI decreases progressively from 8 to 11 years of age.

IntroductionIn this study, we examined first premolar inclination in a large sample.MethodsFirst premolar inclination, canine inclination, and mesiodistal location were measured on 797 panoramic radiographs of orthodontically untreated children (ages, 8-11 years; 381 boys, 416 girls). The sample comprised 1496 premolars and 1496 canines. A linear mixed-effects model was used to determine the contribution of age, sex, canine inclination, canine sector location, second molar maturational stage (D-G), and dental arch side on premolar inclination.ResultsFirst premolar inclination values (medians and interquartile ranges) were 12.76° (8.12°-19.05°) at 8 years, 11.82° (7.87°-16.04°) at 9 years, 10.40° (6.38°-15.46°) at 10 years, and 9.03° (5.42°-12.81°) at 11 years; 13.86° (8.60°-18.78°) at stage D, 10.56° (7.39°-14.77°) at stage E, 10.43° (6.08°-15.09°) at stage F, and 8.00° (4.62°-10.74°) at stage G. The following equation was selected (Akaike information criteria = 424.99): first premolar inclination (°) = –2.211 + 2.240 (8 years) + 1.363 (9 years) + 0.955 (10 years) + 0.387 (canine inclination) + 0.902 (right side) + 2.320 (stage D) + 6.320 (sector 1) + 5.446 (sector 2) + 3.803 (sector 3). There was no difference between percentiles constructed by age and maturational stage.ConclusionsFirst premolar inclination decreases during the mixed dentition and is moderately correlated with canine inclination.