Does the anatomical design in additive manufacturing influence the fracture strength and monomer release of different 3D-printed crowns?

AIM: This study evaluated the effects of occlusal anatomical design and printing orientation on the fracture strength, microhardness, and residual monomer elution of two resins used for 3D-printed crowns.

MATERIALS AND

METHODS

A total of 396 mandibular first molar crowns were 3D-printed using two resins (Group#1: n=198, Primeprint Temp, Dentsply Sirona; Group#2: n=198, OnX nanoceramic hybrid, SprintRay). In each resin group, the crowns were printed with three cuspal inclinations (90°, 120°, 150°) and three printing orientations (0°, 45°, 90°). The samples were assessed for fracture strength, microhardness, monomer elution, and SEM analysis. Statistical tests included ANOVA and Tukey's tests (⍺=0.05)

RESULTS

Printing orientation significantly influenced fracture strength, with the 0° orientation generally producing higher values than the 45° and 90° orientations in both resin groups (p < 0.05). Within the 0° printing orientation, the 90° and 120° occlusal angulations showed significantly higher fracture strength than the 150° angulation (p < 0.05). In Group #1, microhardness was not significantly affected by occlusal angulation or printing orientation (p > 0.05), whereas Group #2 showed significantly higher microhardness at the 90° occlusal angulation than at the 120° or 150° angulations, regardless of printing orientation (p < 0.05). TEGDMA and BIS-EMA were the predominant eluates from Group #1 (17.15-41.71 μM) and Group #2 (105.94-283.05 μM), respectively. Descriptive HPLC data suggested a numerical tendency toward greater monomer elution with increasing occlusal angulation (90° < 120° < 150°) in both groups. SEM analysis revealed more distinct printing-orientation-related fracture features in Group #1.

CONCLUSIONS

Fracture strength was significantly influenced by printing orientation and occlusal anatomical design, whereas descriptive HPLC data suggested a tendency toward greater residual monomer elution with increasing occlusal angulation. Microhardness was primarily material dependent, with limited influence from manufacturing parameters.

CLINICAL SIGNIFICANCE: Optimizing printing orientation and occlusal design during digital manufacturing may improve the clinical reliability of 3D-printed crowns intended for long-term provisional and definitive restorations without requiring additional materials or processing steps. These findings may guide clinicians and dental technicians in selecting fabrication strategies to enhance restoration longevity and reduce residual monomer exposure.