A Commentary on <p><b>Özen MM, Karataş E</b>.</p> <p>Effect of Cavity Design on Bacterial Reduction in Root Canals and Postoperative Pain Level: A Randomised Controlled Trial. <i>Aust Endod J.</i> 2025. <a href="https://doi.org/10.1111/aej.12976">https://doi.org/10.1111/aej.12976</a>.</p> Study design <p>A randomised controlled trial evaluated the impact of endodontic access cavity design on intra-canal bacterial reduction and postoperative pain. Patients were allocated to either the Traditional Conservative Endodontic Cavity (TEC) or Truss Endodontic Cavity (TREC) group using computer randomisation. Microbial samples were collected from the mesial root canals of lower molars at baseline and following chemo-mechanical preparation. The total number of bacteria present and the percentage reduction following instrumentation were analysed via real-time quantitative polymerase chain reaction (RT-qPCR). Samples were evaluated for bacterial load using 16S rRNA universal primers. Postoperative pain was recorded daily for 7-days using a Visual Analogue Scale (VAS).</p> Case selection <p>250 patients attended for assessment at the Endodontics Clinic of A.U. Faculty of Dentistry, Turkey. 100 patients (<i>n</i> = 50 per group) met the inclusion criteria (mainly including necrotic mandibular molars with asymptomatic apical periodontitis, where there has been complete root development), 96 patients completed the study (<i>n</i> = 48 per group).</p> Data analysis <p>Sample size calculation to achieve 95% power and 5% alpha error identified a minimum of 17 participants were required to evaluate antibacterial efficacy, with 27 participants required to evaluate postoperative pain. The statistical power was enhanced by sampling 50 patients in each of the observed groups. Blinding of operators was not possible, and information about individuals conducting the analysis was not included. Statistical analysis was performed using SPSS v20.0. Categorical variables were analysed using the Chi-square test. Normality and homogeneity of numerical data were evaluated using the Kolmogorov-Smirnov and Levene’s tests, respectively. Given the non-normal distribution of the data, intergroup comparisons of age, bacterial load, and post-operative pain levels were conducted using the Mann–Whiteny U test. To compare bacterial load and postoperative pain levels within the groups, the Wilcoxon test and Friedman test were applied, respectively. Statistical evaluations were carried out at the 95% confidence interval.</p> Results <p>Intra-canal bacterial count was significantly reduced in both groups following chemo-mechanical preparation. There was a bacterial load reduction from 6.4 × 10⁵ to 4.8 × 10⁴ (96.32%) in the TEC group and a reduction from 6.7 × 10⁵ to 5.2 × 10⁴ (92.32%) in the TREC group. This difference in the percentage of total bacterial count reduction was statistically significant between the groups (<i>p</i> &gt; 0.05). Therefore, the null hypothesis can be rejected at the 95% confidence interval. For postoperative pain, both groups demonstrated a statistically significant reduction in postoperative pain levels from day 1 to day 7. There was no statistically significant difference in pain levels between the two groups at any time point.</p> Conclusions <p>Endodontic access cavity design impacts reduction in bacterial load following chemo-mechanical preparation. The TEC allowed for greater reduction in bacterial levels compared to the TREC. This is likely due to reduced access restricting effective debridement. There are benefits to retaining more dentine with regards to improved fracture resistance following treatment, so further research is required in this area. Additionally, neither the TEC nor TREC had any impact on postoperative pain levels.</p>