Technical Quality of Root Canal Fillings Performed by Preclinical Dental Students: A Randomized Crossover Study

AbstractObjectives: This study aimed to evaluate the technical quality of root canal fillings (RCFs) performed by undergraduate students using different instrumentation techniques on extracted human teeth.Materials and Methods: A total of 200 permanent human teeth (72 canines, 62 maxillary first premolars, and 66 mandibular molars) were obturated by students following hand instrumentation (HI) (n = 100) or rotary instrumentation (RI) (n = 100). Overall technical quality, filling length, density, taper, iatrogenic errors, and preparation and obturation times were assessed according to instrumentation technique and tooth type. Group comparisons were analysed using generalized estimating equations (GEE), and preparation and obturation times were analysed using linear mixed models.Results: Overall, 76 of 200 teeth (38.0%) were classified as acceptable. RI significantly increased the odds of acceptable RCF quality versus HI (OR = 4.03, 95% CI: 1.54–10.53; p = 0.004), with a significant instrumentation-by-tooth-type interaction (p = 0.004). Crude proportions were higher with RI than HI (45.0% vs. 31.0%), with the largest difference in molars (47.1% vs. 18.8%; p = 0.015), while subgroup differences were not significant in canines (69.4% vs. 50.0%; p = 0.093) or premolars (13.3% vs. 21.9%; p = 0.379). RI was associated with better length and taper (p = 0.002 and p 0.001, respectively), whereas density did not differ significantly (p = 0.095). Iatrogenic errors occurred in 14.5% of teeth and were not significantly different between techniques (p = 0.159), although they were more frequent in premolars and molars than in canines. Linear mixed models showed significantly shorter preparation and obturation times with RI (both p 0.001).Conclusions: RI improved the overall technical quality of RCFs and significantly reduced preparation and obturation times compared with HI, with the greatest benefit observed in molar teeth, while the incidence of iatrogenic errors was comparable between techniques.