Comparative evaluation of tensile bond strength of a polyvinyl acetate-based resilient liner following various denture base surface pre-treatment methods and immersion in artificial salivary medium: An in vitro study

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.

Antifungal property of acrylic denture soft liner containing silver nanoparticles synthesized in situ

OBJECTIVES

Denture soft liner is applied to relieve pain from candida-induced denture stomatitis and promote healing, but with shortage of antifungal activity and easily harbors fungi. To overcome this problem, the in-situ method was used to synthesize silver nanoparticles (AgNPs) in acrylic soft liner to obtain antifungal effects.

METHODS

Acrylic soft-liner with various weight percentage of silver 2-ethylhexanoate (0%, 0.1 %, 0.2 %, 0.3 %) were prepared in 10 mm × 10 mm × 3 mm. After chemical polymerization, the diameter of AgNPs synthesized in situ and the degree of conversion of each group were measured. After 3, 7, and 14 days of storage in water, the antifungal rate (AFR) of in vitro direct contact antifungal assays and the antifungal test of non-cumulative extract solution were measured respectively. The release profiles of silver ions from the specimen within 14 days were also evaluated.

RESULTS

Evenly distributed AgNPs (4.7 nm-5.3 nm) were observed, and the degree of conversion had no significant difference among these groups. The AFR increased as the silver concentration rose, while decreasing with the storage time. After 14 days of water storage, the AFR of 0.2 % and 0.3 % groups still reached 63.38 % and 75.51 %, respectively. The non-cumulative extract solution had no antifungal effect.

CONCLUSIONS

Within the service life, the acrylic soft liner containing AgNPs synthesized in situ had effective control of Candida albicans through direct contact.

CLINICAL SIGNIFICANCE

This study suggests that AgNPs synthesized in situ may be an effective strategy in modifying acrylic denture soft liner to treat and prevent denture stomatitis.

Comparative evaluation of shear bond strength of two different chairside soft liners to heat processed acrylic denture base resin: An in vitro study

BACKGROUND

Chairside softliners are used more frequently than is reported and studies regarding the bond strength of chairside softliners to heat-polymerized denture base resin are few and limited. Hence, this study was conducted to comparatively evaluate the shear bond strength of two chairside soft relining materials viz., autopolymerizing plasticized acrylic resin liner and a silicone-based liner bonded to heat polymerized polymethyl methacrylate denture base resin and to analyze the mode of interfacial bond failure.

MATERIALS AND METHODS

Forty test specimens (n = 40) were prepared by bonding plasticized acrylic- and silicone-based soft liner to heat polymerized acrylic resin blocks. Twenty specimens, ten from each group, were subjected to thermal cycling and later to shear bond strength testing. The debonded specimens were then qualitatively analyzed for the mode of failure using scanning electron microscopy. The results obtained were tabulated and statistically analyzed.

RESULTS

The mean shear bond strength values obtained for acrylic-based soft liner before and after thermal cycling were 0.3365 ± 0.025 MPa and 0.3164 ± 0.04 MPa, respectively. The mean shear bond strength values obtained for silicone-based soft liner before and after thermal cycling were 0.4159 ± 0.025 MPa and 0.4335 ± 0.02 MPa, respectively. Silicone-based soft liner showed higher shear bond strength than the acrylic-based both before and after thermal cycling (P = 0.0001). Scanning electron microscopy analysis showed a predominantly mixed mode of failure with silicone-based liner and predominantly adhesive mode of failure with acrylic-based soft liner.

CONCLUSION

The silicone-based soft liner showed higher shear bond strength to heat polymerized acrylic resin than acrylic-based soft liner both before and after thermal cycling.