# Effect of Coconut Milk, Cow Milk, and Soybean Oil on the Surface Roughness of Milled (PICN, RNC) and 3D-Printed Hybrid Resin–Ceramic: An In Vitro Study

## TL;DR

This study found that coconut milk, cow milk, and soybean oil all increase the surface roughness of dental materials, but 3D-printed materials resist cow milk better than milled ones.

## Contribution

The study compares how different dietary substances affect the surface roughness of milled and 3D-printed hybrid resin-ceramic dental materials.

## Key findings

- All tested media increased surface roughness (Ra) across all materials.
- Cow milk roughened milled materials more than 3D-printed ones.
- Post-aging roughness remained below the bacterial adhesion threshold.

## Abstract

This in vitro study assessed the impact of coconut milk, cow milk, and soybean oil on the surface roughness (Ra) of two milled (polymer-infiltrated ceramic network (PICN), Vita Enamic (EN) and resin nanoceramic (RNC), Cerasmart (CS)) and 3D-printed (VarseoSmile Crown plus (VS)) hybrid resin–ceramic materials. Standardized rectangular specimens were prepared and subjected to cyclic immersion in the test media at 37 °C for 30 days to simulate dietary exposure. Surface roughness was measured pre- and post-aging, and statistical analysis was performed using two-way ANOVA and paired t-tests (α = 0.05). All media significantly increased Ra across all materials (p < 0.001). While coconut milk and soybean oil caused comparable roughening (Ra up to 0.155 µm), cow milk exhibited a material-specific impact. It roughened milled materials (EN and CS) (Ra: 0.147–0.154 µm) significantly more than the 3D-printed material (VS) (Ra: 0.126 µm) (p < 0.05). Notably, all post-aging Ra values remained below the clinical bacterial adhesion threshold of 0.2 µm. In conclusion, while all tested dietary media significantly degraded the surface topography of hybrid resin–ceramics, the 3D-printed hybrid resin–ceramic material demonstrated superior resistance to cow milk compared to milled alternatives. Nonetheless, plaque retention risks remain clinically acceptable for all tested materials.