Fracture resistance of direct composite and digitally fabricated endocrowns in pulpotomized primary molars: an in vitro study

Background: Restoring extensively damaged primary molars remains challenging due to the limitations of conventional materials. Although digitally fabricated endocrowns are a potential alternative, their mechanical performance in primary teeth remains underexplored. This study aimed to compare the fracture resistance and failure modes of direct composite and digitally fabricated endocrowns in pulpotomized primary molars. Methods: Forty extracted human maxillary second primary molars were randomly allocated into four groups (n = 10): direct composite, milled resin-matrix ceramic, milled composite, and three-dimensional (3D)-printed resin. Following pulpotomy procedures, standardized endocrown preparations were performed. In the direct composite group, restorations were placed using conventional composite resin, while in the remaining groups, endocrowns were digitally fabricated through computer-aided design and computer-aided manufacturing (CAD/CAM) milling or 3D printing and adhesively cemented. Fracture resistance was evaluated using a universal testing machine until fracture occurred. Failure loads and modes were recorded. Data were analyzed using one-way analysis of variance (ANOVA), Tukey’s Honest Significance Difference (HSD), and chi-square tests (p < 0.05). Results: Fracture resistance differed significantly among groups (p < 0.05). Milled resin-matrix ceramic exhibited the highest fracture resistance (1572.42 ± 265.67 N), followed by milled composite (1494.00 ± 360.85 N), direct composite (1211.09 ± 300.76 N), and 3D-printed resin (1068.14 ± 199.67 N). The milled resin-matrix ceramic group demonstrated significantly higher fracture resistance than the direct composite and 3D-printed groups. Compared with the 3D-printed group, the milled composite group also exhibited significantly higher fracture resistance (p < 0.05). No significant differences were observed among the remaining comparisons. Failure mode distribution did not differ significantly among groups (p > 0.05). Conclusions: Resin-matrix ceramic endocrowns showed the highest fracture resistance. All tested materials exceeded average masticatory forces in children, suggesting that digitally fabricated endocrowns may serve as a minimally invasive and aesthetic restorative option for pulpotomized primary molars.

Primary molars; Endocrowns; CAD-CAM; Additive manufacturing; Fracture resistance; Composite resin; Digital dentistry

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