Gastric acid challenge and surface sealant agents: Their impact on the optical and mechanical integrity of denture...

Denture base resins are subject to chemical and mechanical stressors in the oral environment that may compromise their structural integrity. Among these, exposure to acidic conditions-originating from dietary sources, medications, or gastric reflux-can adversely affect surface properties. Considering the clinical relevance of these alterations, evaluating surface roughness, hardness, and gloss is essential for understanding the performance and durability of dental materials.

The aim of this in vitro study was to assess the effect of simulated gastric acid exposure on the gloss, microhardness, and surface roughness of denture base materials fabricated by different techniques and subjected to various surface treatments.

A total of 108 disk-shaped specimens were fabricated using 3 techniques: conventional heat-polymerization, subtractive manufacturing, and additive manufacturing. Each group was subdivided according to surface treatment: conventional polishing (control), Optiglaze, or Palaseal coating agent application. The specimens were immersed in simulated gastric acid for 24 hours, simulating 2 years of clinical exposure. Gloss (GU), microhardness (VHN), and surface roughness (Ra) were measured before and after immersion, and changes (∆GU, ∆VHN, ∆Ra) were calculated. Data were analyzed using 2-way ANOVA with the Tukey post hoc test, and correlations were assessed with the Pearson test (α=.05).

Simulated gastric acid exposure resulted in decreased microhardness, increased surface roughness, and reduced gloss across all groups. The heat-polymerized and subtractive specimens exhibited significantly smaller ∆Ra and ∆VHN values than the additive group (P<.001). Gloss loss (∆GU) was greater in additive and subtractive groups compared with heat-polymerized specimens. The Optiglaze and Palaseal coating agent groups showed no significant differences in ΔRa (P=.213), ΔGU (P=.069), or ΔVHN (P=.393) and exhibited significantly lower values than the polished control group (P<.001).

The additive method demonstrated lower resistance to changes in hardness, roughness, and gloss compared with conventional heat-polymerized and subtractive methods. The surface sealant application resulted in smoother, brighter, and harder surfaces for all production techniques after exposure to simulated gastric acid compared with polishing.