Which cleaning protocols best preserve the surface roughness and hardness of occlusal devices produced by additive, subtractive, and conventional manufacturing?

Abstract

Statement of problem: Different cleaning protocols may alter the surface integrity of occlusal devices, yet their effects on devices fabricated by additive, subtractive, and conventional methods remain unclear. Purpose: The purpose of this in vitro study was to evaluate the effects of different cleaning protocols on the surface roughness and hardness of heat-polymerized polymethylmethacrylate (PMMA), computer-aided design and computer-aided manufacturing (CAD-CAM)-milled, and 3-dimensionally (3D) printed occlusal devices. Material and methods: One hundred eighty disk-shaped specimens (Ø16×3 mm) were fabricated from 3 occlusal device materials: heat-polymerized PMMA (HP), CAD-CAM-milled (ML), and 3D printed resin (3D). After baseline surface roughness (Ra) and Vickers hardness (VHN) measurements, the specimens were divided into 6 cleaning groups (n=10): brushing with toothpaste (TP) or liquid soap (LS), immersion in chemical cleansers including effervescent denture cleansers (COR or CRP), a clove oil-based solution (EO), or distilled water (CON). TP and LS groups underwent 5000 brushing strokes, while chemical groups were subjected to 9 immersion cycles over 20 days, simulating 6 months of daily use. Ra and VHN were measured after exposure. Data were analyzed using mixed-design ANOVA and the post hoc Tukey HSD test (α=.05). Results: ML exhibited the lowest Ra and highest VHN, while 3D showed the most significant changes over time (P<.001). Brushing increased Ra and decreased VHN in most groups, except LS on ML and TP on HP (P<.001). COR reduced VHN in ML and HP, CRP affected only 3D (P<.001). EO reduced both Ra and VHN in 3D but increased Ra in the other materials (P<.05). Conclusions: ML demonstrated the best surface stability, while 3D was the most susceptible to surface changes. Immersion in CRP tablets caused minimal surface alterations in both materials, preserving the stability of milled occlusal devices and reducing the extent of surface degradation in 3D printed devices compared with other cleaning methods. © 2025 Elsevier B.V., All rights reserved.