The Effect of Sandblasting on Bond Strength of Soft Liners to Denture Base Resins: A Systematic Review and Meta-Analysis of In Vitro Studies

Objectives. This study aimed to evaluate the effect of sandblasting on the bond strength of denture base resin to soft liners. Materials and Methods. This report follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. PubMed, Embase, Cochrane, Scopus, and OpenGrey databases were searched for in vitro studies that compared sandblasting with no treatment in terms of the tensile, shear, and peel bond strength of resilient lining materials (acrylic-based or silicone-based) to polymethyl methacrylate denture base resin. Based on the outcome, the analysis was carried out in three groups of tensile, shear, and peel bond strength. Subgroup analysis was done for the effect of size of particles on sandblasting, blasting pressure, and type of soft liner whenever possible. Heterogeneity was evaluated among the studies, and meta-analysis was performed with random effect models ( p < .05 ). Results. After screening, 16 articles met the inclusion criteria for meta-analyses. No treatment showed significantly higher tensile ( p < 0.001 ) or peel ( p = 0.04 ) bond strength, although shear bond strength of sandblasted resin was significantly better ( p = 0.008 ). Results of subgroup analyses of particle size favored the control group in 50 µ Al2O3 particle size ( p < 0.001 ). In analyses of blasting pressure, the control group had significantly better tensile bond strength than specimens with blasting pressure ≤1 bar ( p < 0.001 ) while specimens with blasting pressure beyond 1 bar showed significantly more tensile strength than control group ( p = 0.03 ). In silicon-based liners, groups without any surface treatment had significantly higher tensile bond strength ( p < 0.001 ). Conclusion. According to the in vitro studies, sandblasting would not lead to significant increase in bond strength of soft liner to the denture base resin.

Comparative Evaluation of Compressive Bond Strength between Acrylic Denture Base and Teeth with Various Combinations of Mechanical and Chemical Treatments

Debonding and detachment of artificial teeth from the denture base is frequently encountered in prosthodontic practice. This study aims to assess the effect of modifications in the ridge-lap surface of denture teeth with various combinations of mechanical and chemical surface treatments with hydrofluoric acid on bond strength with the acrylic denture base resin and to identify the failure modes (adhesive, cohesive, or mixed). Seventy acrylic resin teeth samples were randomly divided into seven groups (n = 10): a control group (unmodified) and six treatment groups, in which various combinations of mechanical and chemical surface treatments were performed. Then, these teeth were attached to a heat-cured denture base resin block at 45° angulation. The acrylized test samples were thermocycled, and the compressive bond strength was evaluated using a universal mechanical testing machine. The results suggest that roughening with diamond burs yields the highest bond strength, whereas etching/grooving and air abrasion result in the lowest bond strength. Acid etching complemented air abrasion to improve bond strength, while negative effects were noted with acid etching in other groups. Furthermore, roughening at the neck portion of the acrylic teeth can be used by the manufacturing companies as a standard to provide higher bond strength while maintaining the esthetics of the anterior teeth.

Effect of Low Nanodiamond Concentrations and Polymerization Techniques on Physical Properties and Antifungal Activities of Denture Base Resin

Background: Denture base resin has some drawbacks. This study investigated the impact of nanodiamonds (ND) and autoclave polymerization on the surface characteristics, translucency, and Candida albicans adherence in polymethyl methacrylate (PMMA) denture base resin after thermocycling. Methods: Heat-polymerized PMMA discs (15 × 2 mm) with a total sample size n = 160 were studied. Specimens were categorized into two main groups (N = 80): conventional water-bath-polymerized PMMA (CP/PMMA) and autoclave-polymerized PMMA (AP/PMMA). Each group was subdivided according to the ND concentration into four groups (n = 20): unmodified PMMA as a control, and 0.1%, 0.25%, and 0.5% ND–PMMA. Scanning electron microscopy (SEM) was used to inspect the morphology of the ND and the ND–PMMA mixtures before heat polymerization. The specimens were exposed to thermal cycling (5000 cycles at 5 and 55 °C), then surface roughness was measured with a non-contact optical interferometric profilometer, contact angle with an automated goniometer, and translucency using a spectrophotometer. Colony-forming units (CFU) were used to determine the adherence of Candida albicans cells to the specimens. ANOVA and Tukey post hoc tests for pairwise comparison were utilized for the statistical analysis (α = 0.05). Results: Surface roughness was significantly reduced with ND addition to CP/PMMA (p ˂ 0.001), while the reduction was not statistically significant in AP/PMMA (p = 0.831). The addition of ND significantly reduced the contact angle, translucency, and Candida albicans count of CP/PMMA and AP/PMMA (p ˂ 0.001). The incorporation of ND in conjunction with autoclave polymerization of PMMA showed significant reduction in all tested properties (surface roughness, contact angle and Candida albicans adherence) except translucency (p = 0.726). Conclusions: ND addition to PMMA and autoclave polymerization improved the surface properties with respect to antifungal activities, while the translucency was adversely affected.

Non-Thermal O2 Plasma Efficacy on C. albicans and Its Effect on Denture Base Resin Color

Denture stomatitis is a disease involving C. albicans, which can affect elderly and immuno-compromised people. To avoid any recurrence of this pathology, it is necessary to treat patients regularly and disinfect dentures. However, the denture cleansers’ efficacy is not optimal and often leads to adverse color effects on the denture base resins. The aim of this study was to investigate the efficacy of a low-pressure non-thermal O2 plasma (NTP) treatment on C. albicans seeded on ProBase®Hot resin (Ivoclar Vivadent). The viability reduction of C. albicans was assessed by colony forming units (CFU) analysis and by scanning electron microscopy (SEM). The effect of repeated treatments on the resin color was evaluated by spectrophotometry. The resin samples were placed in a sealed bag in which O2 plasma was generated in low-pressure conditions. The results showed that a 120-min O2 NTP treatment led to a 6-log reduction of C. albicans viability (p < 0.05) and to yeasts’ major alterations observed by SEM. Furthermore, significant slight color changes of the resin (∆E00 = 1.33) were noted only after six plasma treatments (p < 0.05). However, the denture aesthetic was preserved, as the color changes were not perceptible and remained below the acceptability threshold (∆E00 < 4).