Evaluation of Coronal Microleakage of Temporary Restorative Materials in Primary Molars with Different Cavity Designs: An In Vitro Micro-CT Analysis

Background In multi-visit primary root canal treatment, preventing coronal leakage of temporary restorative materials is particularly important. In addition, cavity design may influence the extent of microleakage. This study aimed to evaluate the coronal microleakage of different temporary restorative materials used in multi-visit root canal treatment of primary molars with Class II and Class III cavities using micro-computed tomography (micro-CT). Methods Sixty-six primary second molars with root resorption not exceeding one-third of the root length were included in the study. The teeth were divided into two main groups according to cavity design, and endodontic access cavities were prepared as Class II or Class III. Cotton pellets were placed in the pulp chambers, and each main group was further divided into three subgroups according to the temporary restorative material used: Cavit G, glass ionomer cement, and the Double Seal technique. All specimens were immersed in 50% silver nitrate solution, and microleakage was assessed using micro-CT. Data were analyzed using the Kruskal–Wallis H test, with the level of statistical significance set at p < 0.05. Results Microleakage differed significantly among the groups (Kruskal–Wallis H = 41.08, p = 0.0001). In two-surface cavities, Cavit G showed the lowest mean microleakage (0.079 ± 0.109), followed by glass ionomer cement (0.305 ± 0.199) and the Double Seal technique (1.106 ± 1.128). In three-surface cavities, the Double Seal technique showed the lowest mean microleakage (0.361 ± 0.321), followed by Cavit G (1.516 ± 1.096) and glass ionomer cement (2.144 ± 1.112). Overall, the highest microleakage was observed in the glass ionomer cement group, particularly in three-surface cavities. According to cavity design, lower microleakage values were generally observed in two-surface cavities than in three-surface cavities. Conclusions Within the limitations of this study, Cavit G and the Double Seal technique may be preferred as temporary restorative materials in multi-visit root canal treatment of primary teeth, depending on cavity type.