Fracture resistance of additively or subtractively manufactured resin-based definitive crowns: Effect of restorative material, resin cement, and cyclic loading

Objective: To evaluate how restorative material, resin cement, and cyclic loading affect the fracture resistance of resin -based crowns fabricated by using additive or subtractive manufacturing. Methods: A right first molar crown standard tessellation language (STL) file was used to fabricate 120 crowns from one subtractively manufactured polymerinfiltrated ceramic network (SM) and two additively manufactured resin composites (AM -B and AM -S) (N = 40). These crowns were randomly divided into 4 groups within each material according to the dual -polymerizing resin cement to be used (RX and PN) and the aging condition (n = 10). After cementation, the crowns without cyclic loading were subjected to fracture testing, while the others were first cyclically loaded (1.7 Hz, 1.2 million cycles, and 49-N load) and then subjected to fracture testing. Data were analyzed with generalized linear model analysis ( alpha = .05). Results: Fracture resistance of the crowns was affected by material, resin cement, and cyclic loading ( P <= .030). However, none of the interactions significantly affected fracture resistance of tested crowns ( P >= .140). Among tested materials, SM had the highest fracture resistance, whereas AM -B had the lowest ( P <= .025). RX led to higher fracture resistance, and cyclic loading decreased the fracture resistance ( P <= .026). Significance: Tested materials can be considered reliable in terms of fracture resistance in short- or mid-term (5 years of intraoral simulation) when used for single molar crowns with 2 mm occlusal thickness. In the long term, polymer -infiltrated ceramic network crowns cemented with RelyX Universal may provide promising results and be less prone to complications considering higher fracture resistance values obtained.