# A two year randomized clinical trial comparing opposing enamel wear from milled resin-matrix ceramic and direct bulk-fill composite overlays

## TL;DR

This study compared enamel wear from two dental restoration materials over two years and found no significant difference in wear between them.

## Contribution

The study provides new clinical evidence on the comparative enamel wear caused by milled resin-matrix ceramic and bulk-fill composite overlays.

## Key findings

- Mean linear wear was 0.41 ± 0.27 mm for indirect restorations and 0.20 ± 0.05 mm for direct restorations, with no significant difference.
- Volumetric wear was 0.13 ± 0.06 mm³ for indirect and 0.12 ± 0.08 mm³ for direct restorations, also with no significant difference.

## Abstract

Tooth wear has become an increasingly prevalent clinical issue. It can lead to a reduction in the vertical dimension of occlusion (VDO), heightened tooth sensitivity, and alterations in both function and esthetics due to the progressive loss of dental hard tissues. As the incidence and severity of this multifactorial condition continue to rise, there is a growing need for dentists to adopt minimally invasive approaches for diagnosis, monitoring, and management. This clinical trial was designed to evaluate the amount of enamel wear on opposing enamel in response to either indirect milled resin matrix ceramic or direct bulk-fill resin composite overlays, using intraoral digital scanning technology.

Eleven patients in each group received treatment for a total of 22 restorations. Participants were split into two groups, with R1 representing endodontically treated teeth restored with milled resin matrix ceramic overlays and R2 representing endodontically treated teeth restored with direct bulk-fill composite overlays. Using intraoral scanners and three-dimensional surface-based superimposition software, tooth enamel wear was assessed intraorally at baseline (T0), 12 months (T12), and 24 months (T24). The statistical analyses conducted included the Shapiro–Wilk test and the Mann–Whitney U test. The significance level was set at p < 0.05 across all tests.

The mean linear wear ( ± SD) for the indirect restorations was 0.41 ± 0.27 mm, compared to 0.20 ± 0.05 mm for the direct restorations; this difference was not statistically significant (p = 0.066). Similarly, the mean volumetric wear was 0.13 ± 0.06 mm³ for the indirect group and 0.12 ± 0.08 mm³ for the direct group, with no significant difference between them (p = 1).

Within the limitations of this 2-year clinical evaluation, both direct bulk-fill resin composites and milled resin matrix ceramic overlays demonstrated comparable behavior with opposing enamel in posterior teeth, with no statistically significant differences between the tested materials.

The study was registered at ClinicalTrials.gov on 29 Jan 2025 (#NCT06807125).