A new polyisoprene-based light-curing denture soft lining material

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.

Effect of composition of experimental fluorinated soft lining materials on bond strength to denture base resin

The purpose of the present study was to investigate the effect of the composition of experimental fluorinated soft lining materials on bond strength to denture base resin. Vinylidene fluoride/hexafluoro propylene copolymer (2-6F), tridecafluorooctyl methacrylate (13FMA), methoxy diethylene glycol methacrylate (MDGMA), and silica (as filler) were used for fabrication of the experimental soft lining materials. Nine experimental soft lining materials having various compositions of 2-6F, 13FMA, and MDGMA were prepared. Shear and tensile bond strength tests were performed before and after immersion in water. The water sorption for the materials was also measured. An increase in the content of acrylic monomer, MDGMA, in the experimental materials increased the bond strength before immersion in water but reduced the bond strength after immersion in water as compared to that before immersion in water. The inclusion of fluorinated monomer (13FMA) in the materials appeared to affect water sorption.

Long-Term Soft Denture Lining Materials

Long-term soft denture lining (LTSDL) materials are used to alleviate the trauma associated with wearing complete dentures. Despite their established clinical efficacy, the use of LTSDLs has been limited due to the unfavorable effects of the oral environment on some of their mechanical and performance characteristics. The unresolved issue of LTSDL colonization by Candida albicans is particularly problematic. Silicone-based LTSDL (SLTSDL) materials, which are characterized by more stable hardness, sorption and solubility than acrylic-based LTSDLs (ALTSDLs), are currently the most commonly used LTSDLs. However, SLTSDLs are more prone to debonding from the denture base. Moreover, due to their limitations, the available methods for determining bond strength do not fully reflect the actual stability of these materials under clinical conditions. SLTSDL materials exhibit favorable viscoelastic properties compared with ALTSDLs. Furthermore, all of the lining materials exhibit an aging solution-specific tendency toward discoloration, and the available cleansers are not fully effective and can alter the mechanical properties of LTSDLs. Future studies are needed to improve the microbiological resistance of LTSDLs, as well as some of their performance characteristics.

Resilient liners: a review

Resilient liners when used intelligently are an excellent adjunct in removable prosthodontics. However, currently they have to be best considered as temporary expedients because none of the advocated permanent liners have life expectancy comparable to resin denture base. This article reviews the literature regarding their composition, functions, gelation characteristics, bond strength and influence on denture bases. It also presents their drawbacks and attempts made to extend their longevity. A Medline search was completed for the period from 1986 to 2007, along with a manual search, to identify pertinent English peer-reviewed articles and textbooks.

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

BACKGROUND AND AIM

This study was formulated to evaluate and estimate the influence of various denture base resin surface pre-treatments (chemical and mechanical and combinations) upon tensile bond strength between a poly vinyl acetate-based denture liner and a denture base resin.

MATERIALS AND METHODS

A universal testing machine was used for determining the bond strength of the liner to surface pre-treated acrylic resin blocks. The data was analyzed by one-way analysis of variance and the t-test (α =.05).

RESULTS

This study infers that denture base surface pre-treatment can improve the adhesive tensile bond strength between the liner and denture base specimens. The results of this study infer that chemical, mechanical, and mechano-chemical pre-treatments will have different effects on the bond strength of the acrylic soft resilient liner to the denture base.

CONCLUSION

Among the various methods of pre-treatment of denture base resins, it was inferred that the mechano-chemical pre-treatment method with air-borne particle abrasion followed by monomer application exhibited superior bond strength than other methods with the resilient liner. Hence, this method could be effectively used to improve bond strength between liner and denture base and thus could minimize delamination of liner from the denture base during function.

Basic evaluation on physical properties of experimental fluorinated soft lining materials

The purpose of the present study was to compare the properties required for the clinical application of soft lining materials containing a fluorinated monomer versus that of conventional materials in an effort to develop a new soft lining material with long-term stable viscoelastic properties. Four soft lining materials were examined. Two experimental materials containing dodecafluoroheptyl methacrylate (SR12F) or tridecafluorooctyl methacrylate (SR13F) were prepared. Two commercial soft lining materials, one acrylic-based and one silicone rubber-based, were selected as reference materials. Shore A hardness, viscoelastic properties, water sorption, solubility, and staining resistance were evaluated. The Shore A hardness and the displacements were analyzed with two-way analysis of variance (ANOVA) and Tukey's HSD test. The water sorption, the solubility and the color change were analyzed with one-way ANOVA and Tukey's HSD test. The significance level was set at 0.05. SR12F and SR13F showed greater viscous flow, low water sorption, low solubility, and good staining resistance compared to the commercial products. The results indicate that the soft lining materials containing fluorinated monomers might have a potentially long-term stable viscoelastic behavior.

Development of soft denture lining materials containing fluorinated monomers

PURPOSE

To develop a new fluorine-containing soft denture lining material, the influences of fluorinated monomers on physical properties and contamination resistance were examined.

METHODS

Five experimental materials of different chemical compositions in fluorinated monomer and two plasticized acrylics (Supersoft, VertexSoft) were used to evaluate water sorption, solubility, staining resistance, Shore A hardness, and contact angle. Five specimens for each test were fabricated. The results were analyzed with one-way analysis of variance (ANOVA) and Tukey's HSD test using statistical software at p=0.05.

RESULTS

The amount of water sorption tended to decrease as the number of the fluorine atoms in fluorinated monomers increased. Similar solubility was shown regardless of the type of fluorinated monomer. The use of fluorinated monomers for immersion in coffee allowed suppression of discoloration. In beta -carotene, there were no significant differences in color changes among four experimental materials with fluorinated monomer. Shore A hardness was decreased and the contact angles tended to increase as the number of fluorine atoms in fluorinated monomers increased. When comparing the experimental materials and commercially available materials, the experimental materials containing fluorinated monomers with large numbers of fluorine atoms showed adequate clinical properties except for staining test of beta -carotene.

CONCLUSION

Monomers with a large number of fluorine atoms can be used to develop applicable soft denture lining materials in clinical practice.

Effect of microwave disinfection on the hardness and adhesion of two resilient liners

STATEMENT OF PROBLEM

Microwave irradiation has been suggested for denture disinfection. However, the effect of this procedure on the hardness and bond strength between resilient liners and denture base acrylic resin is not known.

PURPOSE

This study evaluated the effect of water storage time and microwave disinfection on the hardness and peel bond strength of 2 silicone resilient lining materials to a heat-polymerized acrylic resin.

MATERIAL AND METHODS

Acrylic resin (Lucitone 199) specimens (75 x 10 x 3 mm) were stored in water at 37 degrees C (2 or 30 days) before bonding (n = 160). The resilient lining materials (GC Reline Extra Soft and Dentusil) were bonded to the denture base and divided into the following 4 groups (n = 10): Tests performed immediately after bonding (control); specimens immersed in water (200 mL) and irradiated twice, with 650 W for 6 minutes; specimens irradiated daily for 7 total cycles of disinfection; specimens immersed in water (37 degrees C) for 7 days. Specimens were submitted to a 180-degree peel test (at a crosshead speed of 10 mm/min) and the failure values (MPa) and mode of failure were recorded. Pretreatment and posttreatment hardness measurements (Shore A) of the resilient materials were also performed. Three-way analysis of variance, followed by the Tukey HSD test, was performed (alpha = .05).

RESULTS

The analysis revealed that, for all conditions, the mean failure strengths of GC Reline Extra Soft (0.95-1.19 MPa) were significantly higher ( P < .001) than those of Dentusil (0.45-0.50 MPa). The adhesion of the liners was not adversely affected by water storage time of Lucitone 199 or microwave disinfection. All peel test failures were cohesive. There was a small but significant difference ( P < .001) between the pretreatment (34.33 Shore A) and posttreatment (38.69 Shore A) hardness measurements.

CONCLUSION

Microwave disinfection did not compromise the hardness of either resilient liners or their adhesion to the denture base resin Lucitone 199.

In vitro evaluation of the bonding of auto-polymerizing soft denture liner to cobalt-chromium alloy

This study evaluated the effects of surface pre-treatments on the bonding of auto-polymerizing silicone soft denture liner to a Co-Cr alloy denture base after cyclic thermal stressing. The bonding surfaces of Co-Cr alloy cylinders (8 mm diameter and 4 mm high) were polished with a 600-grit silicon carbide paper. The bonding surfaces received one of three pre-treatments, which included either the application of a metal primer, a metal primer after air abrasion, or a resin primer after adhesive resin coating. Tensile specimens were fabricated by polymerizing a 2-mm thickness of soft denture liner between a pair of pre-treated denture base cylinders. Failure loads were measured by tensile testing after subjecting the specimen to 0, 5, 10, 20, and 30 thousand thermal cycles. Seven specimens were fabricated for 15 groups, including three pre-treatments and five thermal cycle groups. Failure loads of resin-bonded specimens, which were formerly reported, were used as references. All data were statistically analysed by two-way anova and Bonferroni test at the 95% confidence level. Adhesive resin coating of the metal surface was effective in enhancing the failure loads up to 5000 thermal cycles. However, failure loads of all metal-bonded groups were significantly lower than those of resin-bonded groups at all thermal cycling intervals. The results of this in vitro study implied that polymerizing adhesive resin on the Co-Cr alloy might be a promising method, when the clinicians need to acquire improved bonding of an auto-polymerizing soft denture liner to Co-Cr alloy denture bases.