Surface properties and biofilm formation on resins for subtractively and additively manufactured fixed dental prostheses aged in artificial saliva: Effect of material type and surface finishing.

Statement of problem: Additive manufacturing (AM) and subtractive manufacturing (SM) have been widely used for fabricating resin-based fixed dental prostheses. However, studies on the effects of material type (AM or SM resin) and surface finishing (polishing or glazing) on the surface properties and biofilm formation are lacking.

Purpose: The purpose of this in vitro study was to investigate the effects of material type and surface finishing on the surface roughness, wettability, protein adsorption, and microbial adhesion of the AM and SM resins marketed for fixed restorations under artificial saliva-aged conditions.

Material and methods: Disk-shaped specimens (∅10×2 mm) were fabricated using 3 types of resins: AM composite resin with fillers (AMC), AM resin without fillers (AMU), and SM composite resin with fillers (SMC). Each resin group was divided into 2 subgroups based on surface finishing: polished (P) and glazed (G). Therefore, 3 polished surface groups (AMCP, AMUP, and SMCP) and 3 glazed surface groups (AMCG, AMUG, and SMCG) were prepared. Specimens were then categorized according to aging condition in artificial saliva. Surface roughness (Ra and Sa), contact angle, surface free energy (SFE), protein adsorption, and microbial adhesion were measured. The data were analyzed using a nonparametric factorial analysis of variances and post hoc tests with Bonferroni correction (α=.05).

Results: When nonaged, significant interactions between material type and surface finishing were detected for Ra, contact angle, SFE, protein adsorption, and microbial adhesion (P≤.008). AMCP showed higher Ra and microbial adhesion than AMUP and SMCP, and higher contact angle and protein adsorption than SMCP (P<.001). AMCG had lower SFE than AMUG (P=.005) and higher bacterial adhesion than SMCG (P<.001). AMC had higher Sa than AMU and SMC (P≤.006). When aged, significant interactions between material type and surface finishing were detected for Ra, Sa, protein adsorption, and microbial adhesion (P≤.026). The contact angle and SFE were significantly affected only by the material type (P≤.001), as AMC exhibited higher wettability than SMC (P≤.004). AMCP had higher Ra and microbial adhesion than AMUP and SMCP (P≤.003). AMCP had higher Sa and protein adsorption than SMCP (P≤.004). AMCG showed lower Ra and higher protein adsorption than AMUG (P≤.001).

Conclusions: Both material type and surface finishing significantly affected surface properties and biofilm formation. AMCP exhibited higher surface roughness, protein adsorption, and microbial adhesion compared with SMCP. Glazing may reduce the differences in surface-biofilm interactions between AMC and SMC.