Do CAD/CAM restorative materials respond differently to coffee thermocycling and simulated toothbrushing?

TL;DR

This study found that dental restoration materials respond differently to coffee staining and brushing, with glass-ceramics performing better than resin-based materials.

Contribution

The study introduces a novel comparison of CAD/CAM restorative materials under combined coffee thermocycling and toothbrushing stressors.

Findings

Glass-ceramic materials showed superior color stability compared to resin-based materials after coffee thermocycling and brushing.

Resin-containing materials experienced greater surface roughness increases than glass-ceramics after mechanical aging.

Toothpaste formulation had no significant effect on color stability or surface roughness across all tested materials.

Abstract

This laboratory study aimed to investigate the effects of toothbrushing with different toothpaste formulations on the color stability and surface roughness of CAD/CAM restorative materials following coffee-staining thermocycling.

A total of 160 specimens were prepared from four restorative materials: IPS e.max CAD, CEREC Tessera, Shofu Block HC, and VITA Enamic (n = 40 each). Following initial measurements, specimens underwent thermocycling in a coffee solution (5000 cycles) to simulate staining. Each group was subsequently divided and brushed with either a whitening toothpaste containing hydrated silica and hydrogen peroxide or a non-whitening toothpaste containing hydrated silica only. A total of 10,000 brushing cycles were performed under standardized conditions. Color stability was assessed using ΔE₀₀ values, and surface roughness was quantified using the Ra parameter at baseline, after thermocycling, and after brushing. Data were analyzed using Kruskal–Wallis and Mann–Whitney U tests with the significance threshold set at p < 0.05. SEM analysis was conducted on one randomly selected specimen per group (x1000).

Statistically significant differences in color stability, as assessed by ΔE₀₀ values, were observed among the tested materials (p < 0.001). Resin-based groups, particularly Shofu Block HC, exhibited the greatest reduction in color stability after coffee thermocycling and subsequent brushing (ΔE₀₀ = 1.069, p < 0.001), whereas glass-ceramics (IPS e.max CAD and CEREC Tessera) demonstrated superior color stability (ΔE₀₀ ≤ 0.520). Surface roughness increased significantly in resin-containing materials (VITA Enamic ΔRa = 0.036; Shofu Block HC ΔRa = 0.020) compared with glass-ceramics (p < 0.001). No significant differences were detected between whitening and non-whitening toothpastes for either parameter across all groups (p > 0.05). Ra changes were also concluded by SEM.

The performance of restorative materials under staining and mechanical aging stressors is material-dependent. Glass-ceramics displayed superior color stability after coffee exposure and greater resistance to brushing-related surface degradation, whereas resin-containing materials were more vulnerable. The choice of toothpaste formulation did not significantly affect color stability or surface characteristics, suggesting that intrinsic material properties play a more critical role in long-term esthetic outcomes.

Selection of restorative materials plays a decisive role in ensuring the long-term esthetic success of dental restorations. Since intrinsic material properties strongly influence color stability and resistance to surface degradation, clinicians should carefully consider material choice during treatment planning to achieve durable and predictable outcomes.

Figures