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Assessment of Physical and Mechanical Properties of Auto-Polymerized Acrylic Resins Using a Custom Pressure Vessel Technique: An In Vitro Study

Year: 2025

Type: article

Abstract: Introduction: Auto-polymerized acrylic resins are essential in dentistry because of their versatility; however, their suboptimal physical and mechanical properties can limit their clinical performance. This study aimed to evaluate the impact of custom-made pressure vessel treatment on the physical, mechanical, and aesthetic properties of these resins, specifically by comparing polymerization shrinkage, assessing flexural strength, measuring water sorption, evaluating surface hardness, analyzing porosity, and determining color stability after staining. Materials and methods: This in vitro study involved 30 specimens of auto-polymerized acrylic resin, equally divided into a control group (n = 15, cured under ambient conditions) and an experimental group (n = 15, cured in a custom pressure vessel at 2.2-3.0 bar). Specimens were prepared in standardized molds, polished, and stored in distilled water to mimic oral conditions. The outcomes assessed included polymerization shrinkage (volumetric analysis), water sorption (weight change post-immersion), flexural strength (three-point bending test), surface hardness (Vickers test), porosity (scanning electron microscopy), and color stability (Commission Internationale de l'Éclairage (CIE) Lab* parameters post-coffee staining). All measurements used calibrated instruments, and data were analyzed using independent t-tests (p < 0.05) after confirming normality using the Shapiro-Wilk test. Results: The pressure-treated group exhibited significantly reduced water sorption (2.30 ± 1.11%) compared to the control group (3.47 ± 1.48%), with a mean difference of 1.17% (p = 0.021), and increased flexural strength (66.62 ± 8.67 MPa) compared to the control group (58.64 ± 10.97 MPa, p = 0.035), indicating improved material density and mechanical durability. No significant differences were found in polymerization shrinkage (p = 0.273), surface hardness (p = 0.840), or color stability, suggesting that the pressure treatment maintained the dimensional and esthetic integrity. Conclusion: Custom pressure vessel treatment enhanced the water sorption resistance and flexural strength of auto-polymerized acrylic resins without affecting their shrinkage, hardness, or color stability. These findings suggest the potential for improved durability in dental appliances, supporting the adoption of this technique in clinical practice, pending further in vivo validation.

Source: Cureus

DOI: 10.7759/cureus.96880