Radiographic quality of primary endodontic treatment performed by undergraduate students, general dentists and endodontists: a retrospective cross-sectional study

The quality of primary endodontic treatment may be associated with operator experience and canal instrumentation method. This study evaluated the radiographic quality of root canal fillings and procedural complications in treatments performed by undergraduate students, general dentists, and endodontists. This retrospective cross-sectional study included 698 patients, 753 teeth, and 1206 root canals treated between 2018 and 2024 at a university clinic. Of the canals, 467 were treated by undergraduate students, 475 by general dentists, and 264 by endodontists. Radiographs were assessed for filling length, radiographic homogeneity, and procedural complications. Filling length was analysed using multivariable complex-samples multinomial logistic regression and radiographic homogeneity using a multivariable logistic generalized estimating equation model. Both models adjusted for instrumentation method, tooth group, dental arch, and patient-level clustering. Procedural complications were analysed descriptively. Operator group was associated with filling length ( P = 0.019). Undergraduate students had a higher relative risk of short rather than adequate fillings compared with endodontists (RRR = 3.59, 95% CI: 1.43–8.99; Holm-adjusted P = 0.019) and general dentists (RRR = 2.09, 95% CI: 1.11–3.95; Holm-adjusted P = 0.046). Instrumentation method was not independently associated with filling length ( P = 0.617). After adjustment, the odds of radiographic homogeneity were lower for undergraduate students (OR = 0.32, 95% CI: 0.17–0.62; Holm-adjusted P = 0.001) and general dentists (OR = 0.30, 95% CI: 0.16–0.57; Holm-adjusted P = 0.001) than for endodontists. Rotary instrumentation was associated with higher odds of radiographic homogeneity than hand instrumentation (OR = 1.65, 95% CI: 1.03–2.64; P = 0.036). Twenty procedural complications were identified, with no significant association with instrumentation method within any operator group. Within the limitations of this retrospective radiographic study, canals treated by undergraduate students were more likely to be short-filled than those treated by general dentists or endodontists. Radiographic homogeneity was associated with operator group and was more frequent in canals treated by endodontists. Rotary instrumentation was associated with higher radiographic homogeneity but not with filling length.