Acrylic resins continue to be popular in denture-base and maxillofacial prosthetic applications; the clinical longevity of such resins depends upon the polymerization technique and the exposure to the environment. This in vitro experiment compared fracture resistance of four acrylic resin materials: a representative heat-cured denture-base resin (Lucitone 199), a representative self-cured acrylic resin (Jet Denture Repair Acrylic), a cold-cured orthodontic acrylic resin (Orthocryl®), and a representative 3D-printed denture-base resin (NextDent Denture 3D+). One hundred and twenty standardized bar-shaped specimens were made and each split into four parts (n = 30 per material). Each group was further divided into three immersion conditions (n = 10): distilled water for 3 days, ethanol for 3 days, and ethanol for 10 days. Fracture resistance was then tested after immersion in a universal testing machine in a three-point bending test and the maximum fracture load was measured in Newtons. One-way analysis of variance and post hoc test by Tukey were used to analyze the data at a significance level of p < 0.05. Scanning electron microscopy was also used to investigate representative fractured surfaces in order to determine the fracture morphology. There were significant differences between the tested materials (p < 0.001). The acrylic resin with the highest fracture resistance was heat-cured and the minimum was with self-cured acrylic resin. The cold-cured orthodontic resin showed moderate performance and the 3D-printed resin was better than self-cured acrylic but still worse than heat-cured acrylic. The use of alcohol as a test material had an adverse influence on the material used and the more time the material was immersed in alcohol the more it deteriorated. The mechanical results were confirmed through SEM observations which revealed better fracture-surface integrity in the heat-cured group with more pronounced voids, microcracks, or structural discontinuities in the weaker groups. In the constraints of this in vitro experiment, heat-cured acrylic resin exhibited the most desirable fracture and solvent degradation resistance.
Hassan et al. (Tue,) studied this question.