# Mechanical Performance and Marginal Integrity Evaluation of Contemporary Universal Resin Composites for Dental Restorations: An In-Vitro Study

## TL;DR

This study compares four universal resin composites for dental restorations, finding that one performs best in strength and sealing.

## Contribution

The study evaluates mechanical performance and marginal integrity of four modern universal resin composites using in-vitro methods.

## Key findings

- UC-A showed the highest flexural strength and microhardness compared to other composites.
- UC-C had the lowest mechanical performance and higher marginal leakage after thermocycling.
- Marginal integrity was best for UC-A with fewer leakage cases and narrower gaps.

## Abstract

Background: Universal resin composites are widely used for dental restorations, but differences in resin chemistry, filler composition, and polymerization can affect performance and marginal integrity.

Objective: To evaluate four modern universal resin composites in terms of their mechanical characteristics and marginal integrity.

Materials and methods: Ninety-six specimens were prepared into four groups (UC-A, UC-B, UC-C, UC-D; n = 24 each). Bar and disc shaped specimens were tested for flexural strength, Vickers’ Microhardness, and two-body wear, respectively. Extracted human molars (n = 48) with Class II cavities were restored with composites, marginal integrity using dye penetration (0-3 scoring), and gap width measurement after thermocycling (5,000 cycles). Data were analyzed with one-way ANOVA/Tukey or Kruskal-Wallis/Dunn tests (α = 0.05).

Results: UC-A exhibited the highest flexural strength (125.4 ± 7.8 MPa) and modulus (6.2 ± 0.4 GPa), significantly greater than UC-C (112.7 ± 5.9 MPa; 5.5 ± 0.4 GPa, p < 0.05). Microhardness ranged from 75.4 ± 2.2 VHN (UC-C) to 81.5 ± 2.6 VHN (UC-A, p < 0.01). Wear volume loss was lowest for UC-A (0.087 ± 0.012 mm³) and highest for UC-C (0.108 ± 0.013 mm³, p = 0.04). Marginal integrity was highest for UC-A, with 50% leakage-free restorations and gap width (45.3 ± 6.2 µm), while UC-C had more leakage (Score 3 in 8.3% of cases) and wider gaps (56.9 ± 7.1 µm, p = 0.01). UC-B and UC-D showed intermediate results.

Conclusion: UC-A demonstrated superior mechanical performance and marginal sealing, whereas UC-C performed least favorably, highlighting the influence of resin formulation.