Disinfection-Induced Changes in Color Stability, Microhardness, and Surface Roughness of Conventional and CAD-CAM Occlusal Devices: An In Vitro Study

Abstract

Disinfection protocols are essential for maintaining hygiene in occlusal devices, yet they may compromise material properties, affecting clinical performance. The influence of different disinfectants across various material types remains insufficiently understood. In this study, we aimed to evaluate the effects of disinfectants, material types, and their interactions on changes in color stability (∆E), Vickers microhardness (∆VHN), and surface roughness (∆Ra) of occlusal devices, with the goal of informing evidence-based disinfection protocols for long-term maintenance.

A total of 168 specimens were fabricated from six occlusal device materials: self-cured (SC), heat-cured (HC), two milled (ML-A, ML-B), and two 3D-printed (3D-A, 3D-B) types. Specimens were aged in distilled water at 37 °C for 45 days and assigned to daily 15-minute conditions of dry storage (control) or immersion in liquid soap (LS), chlorhexidine (CHX), or denture cleanser (DC). Color stability, Vickers microhardness, and surface roughness were measured before and after immersion, and ΔE, ΔVHN, and ΔRa were calculated to determine the changes.

Two-way ANOVA evaluated the effects of disinfectant type, material type, and their interaction. One-way ANOVA with Tukey's post hoc test compared disinfectants within each material group. Significance was set at p < 0.05.

Disinfectants and material types significantly affected ΔE, ΔVHN, and ΔRa (p < 0.05). ML-A, 3D-A, and 3D-B showed greater discoloration (higher ∆E), particularly after immersion in LS and CHX. SC, 3D-A, and 3D-B materials immersed in CHX and DC demonstrated increased microhardness (higher ΔVHN), while HC, ML-A, and ML-B materials showed minimal change or slight softening. Surface roughness alterations were minimal (low ΔRa) and remained within clinically acceptable limits.

Certain disinfectants increased discoloration and microhardness in a material-dependent manner, whereas surface roughness showed no clinically relevant change. Clinicians should tailor disinfection protocols according to material type to preserve long-term performance.