Effect of Traditional and Truss Access Cavity Designs on Residual Bacterial Levels in Mandibular First Molars: An In Vitro Confocal Microscopy Study

Aim To quantitatively compare residual bacterial levels in the pulp chambers of mandibular first molars prepared using traditional endodontic access cavities (TEC) and truss access cavities (TAC) following standardized cleaning and shaping procedures.

Methodology This in vitro experimental study included thirty extracted human mandibular first molars, randomly assigned to two groups (n = 15 each): TEC and TAC. After access cavity preparation, all specimens were inoculated with Actinomyces naeslundii and incubated for 10 days to allow biofilm formation. The distal canals were instrumented using Vortex Blue rotary files with continuous irrigation using 5.25% sodium hypochlorite at a flow rate of 1 mL/min. A final irrigation protocol consisting of 5 mL of 5.25% sodium hypochlorite, 17% ethylenediaminetetraacetic acid, and 5 mL of sterile saline was applied. Specimens were sectioned and analyzed using confocal laser scanning microscopy to quantify residual bacterial presence. Percentage bacterial reduction was calculated, and intergroup comparisons were performed using an independent two-sample t test (α = 0.05).

Results The mean (± SD) percentage of bacterial reduction was 32.7% ± 8.0 in the TEC group and 28.4% ± 4.8 in the TAC group. No statistically significant difference was observed between the groups (P = 0.08).

Conclusion Under the conditions of this in vitro study, truss access cavities demonstrated bacterial reduction comparable to traditional endodontic access cavities following cleaning and shaping. These findings suggest that truss access designs may be considered a minimally invasive alternative without compromising intracanal disinfection.