Effect of Simulated Low-Load Functional Loading on Voids Volume and Distribution of Different Retrograde Filling Materials: A Micro-Computed Tomography Analysis

Introduction: The outcome of endodontic microsurgery depends on the integrity of the apical seal and the adaptation of root-end filling materials under functional stresses. The study aims to compare the void volumes and distribution of ProRoot MTA, ERRM, and ERRM combined with Bioceramic sealer under simulated functional loading using micro-computed tomography (micro-CT). Methods: Forty-four single-rooted mandibular premolars were prepared with 3 mm apical cavities and divided into four groups (n = 11 each): Cavit (Control), ProRoot MTA, ERRM Putty, and ERRM + BC Sealer. Samples were scanned by micro-CT to quantify internal, marginal, and total voids. Each specimen was then subjected to cyclic vertical loading of 20 N for 1,000,000 cycles in a chewing simulator, followed by post-scanning. Pre- and post-loading void volumes and distribution were analyzed and compared statistically (α = 0.05). Results: Functional loading significantly increased void volumes in all groups (p < 0.05). Control and MTA showed the highest total and marginal voids (p < 0.05), while ERRM and ERRM + BC maintained significantly lower overall and marginal voids. No difference was detected between ERRM and ERRM + BC (p > 0.05). ERRM and ERRM + BC Sealer showed relatively lower marginal-to-internal voids ratios compared to MTA. Material dislodgement occurred only in Cavit and MTA. Conclusions: ERRM and ERRM + BC sealer groups exhibited favorable marginal adaptation and significantly lower overall void volumes after low-load functional loading compared to MTA and the control. The findings indicate preserved sealing performance and suggest resistance to void formation under simulated occlusal stresses.