Printed versus heat-polymerized resin for occlusal devices: Evaluation of physical and mechanical properties after...

To evaluate the physical and mechanical properties after brushing and microbial adhesion of printed resins (PRs) and heat-polymerized resins (HRs) for occlusal devices (ODs).

Knoop microhardness and roughness were evaluated in three measurements before and after brushing with detergent or dentifrice. Flexural strength and modulus of elasticity were assessed by 3-point bending, and the adhesion of Candida albicans and Streptococcus mutans was evaluated by colony-forming units per milliliter (CFU/mL) and metabolic activity using the XTT assay only without brushing. Flexural strength, modulus of elasticity, and microbial adhesion were analyzed using Student's t-test, while three-way repeated-measures ANOVA with post hoc Bonferroni was applied to evaluate microhardness and roughness (p < 0.05).

PR showed higher microhardness, lower microbial adhesion, and metabolic activity of C. albicans than HR (p < 0.05), which in turn showed higher flexural strength and modulus of elasticity (p < 0.05). There was no difference in the adhesion and metabolic activity of S. mutans or the roughness between the resins (p > 0.05). Brushing with detergent and dentifrice reduced HR and PR microhardness (p < 0.05); the use of detergent did not change HR and PR roughness (p = 1.00), and the use of dentifrice increased HR roughness (p < 0.001).

It was concluded that PR showed lower roughness and higher microhardness and lower microbial adhesion after brushing with dentifrice compared to HR. However, HR had higher flexural strength and modulus of elasticity than PR. The use of detergent did not promote surface changes for PR and HR after brushing.