Root and canal configurations of maxillary first premolars in 22 countries using two classification systems: a multinational cross-sectional study.

This study aimed to evaluate the root and root canal morphology of maxillary first premolars (M1Ps) globally using cone-beam computed tomography (CBCT), comparing results with Vertucci's and Ahmed et al.'s classification systems. CBCT images were obtained for various purposes such as orthodontic treatment planning, tooth impaction, implant surgery, and trauma cases. M1Ps were evaluated in three planes to determine root and root canal morphology, and root bifurcation levels were assessed using integrated software. Prevalence variations between countries and overall prevalence were analyzed using meta-analysis software. A total of 6,600 patients (13,200 bilateral M1Ps) were examined. According to Vertucci's classification, Type IV (59%), Type II (12%), Type I (9%), and Type III (8%) were the most common configurations. Based on Ahmed's classification,2MP B1 P1 was the most prevalent configuration (53%), followed by 1MP1 (9%),1MP1-2-1 (8%), and 1MP2-1-1 (7%). The prevalence of 2MP B1 P1 by gender revealed a pooled prevalence of 58% in males and 50% in females. No significant difference was found across age ranges (p > 0.05). Ahmed's classification system provided a more comprehensive analysis by successfully classifying all cases, whereas Vertucci's system failed to categorize 1.8-2.7% of the cases. Significant bilateral symmetry in root morphology was noted. There are regional and gender-specific differences in the root canal morphology of M1Ps. Ahmed et al.'s classification system was more comprehensive, effectively categorizing all observed morphologies compared to Vertucci's system, which had limitations and left some morphologies unclassified.