Effect of access cavity design and instrumentation on pericervical dentin thickness in molars: A cone-beam computed tomography-based pilot randomized clinical trial

To evaluate the effect of different access cavity designs and endodontic instrumentation on pericervical dentin (PCD) thickness in multirooted permanent molars using cone-beam computed tomography (CBCT).

This pilot randomized clinical trial included 120 multirooted permanent molars randomly allocated into four groups (n = 30): traditional access cavity (TradAC), conservative access cavity (ConsAC), ultraconservative (Ninja) access cavity (UltraConsAC), and truss access cavity (TrussAC). Preoperative CBCT scans were obtained to measure PCD thickness. Following access cavity preparation and root canal instrumentation, postoperative CBCT scans were acquired to evaluate changes in PCD thickness (ΔPCD). Changes in PCD thickness (ΔPCD) were calculated and compared among the groups using one-way analysis of variance and Tukey's post hoc test. Procedural time was also recorded. Statistical significance was set at P < 0.05.

All groups demonstrated a significant reduction in PCD thickness after instrumentation (P < 0.001). The TradAC group exhibited the greatest dentin loss (3.08 ± 0.92 mm; 27.7%), followed by ConsAC (1.86 ± 0.51 mm; 16.7%). TrussAC (1.23 ± 0.35 mm; 11.6%) and UltraConsAC (1.04 ± 0.25 mm; 10.3%) preserved significantly more dentin. Greater dentin reduction occurred on the buccal and distal surfaces. Procedural time differed significantly among groups (P < 0.001), with UltraConsAC requiring the longest treatment time and TradAC the shortest.

UltraConsAC and TrussAC designs preserved significantly more PCD than TradAC and ConsAC, supporting minimally invasive endodontic principles. Long-term clinical studies are required to determine whether improved dentin preservation enhances fracture resistance and long-term tooth survival.