Three-dimensional analysis of the anatomical features of the proximal surfaces of primary molars after restoration with different matrix systems

Aim. The study aimed to evaluate the impact of the matrix system and filling material on the morphology of the proximal wall in Class II restorations of primary molars using an extraoral scanner and 3D analysis. Materials and methods. A lower typodont primary second molar was scanned with an extraoral scanner and used as a master model. A total of 240 standardized Class II cavities were restored on identical teeth. Different combinations between the restoration material and the matrix system were used for each group included in the study (compomer – myJuniorKit, compomer – Palodent, compomer – MyQuickMat, bulk-fill composite – myJuniorKir, bulk-fill – Palodent, Bulk-fill – MyQuickMat). After restorations, all teeth were scanned again using the same extraoral scanner. The resulting three-dimensional files were then superimposed over the initial scan (master model), to observe the differences in the proximal contour and the morphological characteristics of the proximal wall before and after cavity preparation and restoration. Additionally, changes in volume were also assessed. For this process, three reference points (vestibular, central, and lingual) were used for measurement. The software analyzed and recorded the differences in measurements (in millimeters) between the original tooth and the restoration. Results. All restored proximal surfaces showed a more convex contour compared to the original tooth. None of the matrix systems fully replicated the original morphology. The myJuniorKit matrix system demonstrated the smallest mean deviation from the master model (between 0.40 and 0.59 mm), followed by Palodent (between 0.72 and 0.79 mm) and MyQuickMat (between 0.68 and 1.79 mm), though the differences were not statistically significant (p > 0.05). Conclusion. Although no matrix system fully restored the anatomical contour of the proximal surface, the MyJuniorKit matrix system showed the least deviation. All restorations demonstrated increased convexity compared to the original tooth.