SEM, confocal Laser, and histological evaluation of traditional and conservative access cavities with and without 3D cleaning: an ex vivo study

Objective: The present investigation sought to compare the efficacy of a 3D Cleaning protocol comprising intrachamber sodium hypochlorite (NaOCl) preheating followed by ultrasonic activation on smear layer and debris removal, residual debris, and NaOCl penetration under different access cavity designs (traditional versus conservative). To the best of our knowledge, this is the first study to evaluate irrigant activation across access cavity designs within a single, standardised experimental framework. Materials and methods: Specimens were allocated to three primary groups according to the analytical method: Group A, scanning electron microscopy (SEM); Group B, histological analysis; and Group C, confocal laser scanning microscopy (CLSM). Each group was further subdivided into four subgroups (n = 10 per subgroup): A1/B1/C1 = traditional access without 3D Cleaning; A2/B2/C2 = traditional access with 3D Cleaning; A3/B3/C3 = conservative access without 3D Cleaning; A4/B4/C4 = conservative access with 3D Cleaning. Smear layer/debris removal, residual debris, and NaOCl penetration were assessed via SEM, histology, and CLSM, respectively. Data were analysed using the Kruskal–Wallis H test with Dunn-adjusted post hoc comparisons (α = 0.05). Results: Subgroups subjected to 3D Cleaning (A2, A4; B2, B4; C2, C4) demonstrated significantly lower smear layer/debris scores and greater NaOCl penetration compared with their respective controls (A1, A3; B1, B3; C1, C3) (p < 0.05). Histological assessment (Group B) revealed reduced residual debris in 3D Cleaning subgroups (B2, B4) relative to B1 and B3. CLSM analysis (Group C) confirmed markedly deeper irrigant penetration in C2 and C4 versus C1 and C3. With respect to access design, 3D Cleaning enhanced outcomes irrespective of approach; conservative access combined with 3D Cleaning frequently produced the most favourable results, although differences compared with traditional access plus 3D Cleaning were modest and not consistently significant (e.g., C4 vs. C2: +17 μm; 95% CI − 2.31 to + 36.31). Conclusions: A single, standardised 3D Cleaning protocol significantly improved debridement and irrigant penetration regardless of access cavity design. Conservative access combined with 3D Cleaning frequently yielded the most advantageous outcomes. Clinical relevance: Given that the protocol relies on commonly available equipment and straightforward procedures, 3D Cleaning represents a pragmatic adjunct to overcome potential cleaning limitations associated with conservative access. Nevertheless, the findings are derived from ex vivo experimentation and require validation in clinical settings.