Periapical Healing Following Root Canal Treatment with Narrow (0.04) Or Wide (0.07) Preparation Tapers in Private Practice: A Retrospective Observational Cohort Study

Objective: The optimal root canal preparation taper remains a subject of debate; smaller sizes putatively favoring fracture resistance and larger, better disinfection. This study evaluated the periapical healing outcome following narrow (0.04) tapered root canal preparation compared with wider tapered preparations (0.07) during non-surgical root canal treatment (NSRCT).
Methods: Clinical and radiographic records of NSRCT completed by a single operator in an endodontic specialist practice were retrospectively reviewed. Two-hundred-and-eighty-nine teeth prepared with either a 0.04 (n=157) or 0.07 (n=132) taper, as guided by pre-operative canal size, met the inclusion criteria and were reviewed for 2 years. Loose (healed and healing) criteria was used to determine the outcome of periapical healing. Logistic regression and stratified outcome analyses were used to investigate the effect of taper and other covariates on periapical healing; the covariates analysed were sex, age, tooth type, size of radiolucency, sinus tract, periodontal defects, cracks, mishaps, number of visits, patency, quality of root filling, quality of restoration, and access cavity design—traditional or non-traditional/minimally invasive. Potential confounders were addressed using a multivariable model (odds ratios [ORs] with 95% confidence intervals [CIs]; p<0.05).
Results: The periapical healing rates of teeth treated with 0.04 (95.5%) and 0.07 (93.9%) tapers were comparable (p=0.5). The presence of iatrogenic errors (n=8) had a significant negative effect on the success rate (p=0.03).
Conclusion: In this cohort study, comparable healing rates were observed between 0.04 tapered canal preparations and wider (0.07) tapers in teeth with narrow canals. (EEJ-2025-06-094)

Keywords: Conservative root canal preparation, endodontic access cavity, endodontic outcome, minimally invasive access, periapical healing, preparation taper, root canal disinfection