The objective of this study was to investigate the effect of Er:YAG laser irradiation on shear bond strength and microleakage between resin cements and yttrium-stabilized tetragonal zirconia (Y-TZP) ceramics. Eighty disc specimens of Y-TZP ceramics (6 mm × 4 mm) were prepared. The specimens were divided into two groups according to surface treatment (control and Er:YAG laser-treated). The control and lased specimens were separated into two groups for shear bond strength test (n = 20), and microleakage evaluation (n = 10). Specimens were subjected to shear bond strength test by a universal testing machine with a crosshead speed of 1 mm/min. Specimens for microleakage evaluation were then sealed with nail varnish, stained with 0.5% basic fuchsin for 24 h, sectioned, and evaluated under a stereomicroscope. The data were analyzed with one-way ANOVA and post hoc Tukey-Kramer multiple comparisons tests (α = 0.05) for shear bond strengths and a two related-samples tests (α = 0.05) for microleakage scores. Higher bond strength values were found in the laser-treated groups compared to the control groups. Microleakage scores among the groups showed that the laser-treated specimens had lower microleakage scores than those of control specimens in the adhesive-ceramic interface. Roughening surface of Y-TZP ceramic by Er:YAG laser increased the shear bond strengths of ceramic to dentin and reduced the microleakage scores.
The purpose of this study was to investigate the tensile strength of the bond between a silicone lining material and heat-cured polymethyl methacrylate (PMMA) denture base resin after Er:YAG laser treatment with different pulse durations and energy levels. PMMA test specimens were fabricated and each received one of six surface treatments: no treatment (control), and five Er:YAG laser treatments comprising (1) 100 mJ, 1 W, long pulse duration, (2) 200 mJ, 2 W, long pulse duration, (3) 200 mJ, 2 W, very short pulse duration, (4) 300 mJ, 3 W, long pulse duration, and (5) 400 mJ, 4 W, long pulse duration. The resilient liner specimens (n = 15) were processed between two PMMA blocks. The tensile strengths of the bonds between the liners and PMMA were determined using a universal testing machine at a crosshead speed of 5 mm/min. The mode of failure was characterized as cohesive, adhesive, or mixed modes. One-way ANOVA and the post hoc Tukey-Kramer multiple comparisons test were used to analyze the data (α = 0.05). There was a statistically significantly difference in tensile bond strength between laser-treated and untreated specimens (P < 0.05). The 300-mJ, 3 W, long pulse duration laser treatment produced the highest mean tensile bond strength. In addition, the long pulse duration treatments resulted in greater bond strength than very short pulse duration treatment (P < 0.05). Laser irradiation produced significant surface texture changes of the denture base material and improved the adhesion between denture base and soft lining material. In addition, different pulse durations and energy levels were found to effectively increase the strength of the bond.
Failure of the bond between the acrylic resin and resilient liner material is commonly encountered in clinical practice. The purpose of this study was to investigate the effect of different surface treatments (sandblasting, Er:YAG, Nd:YAG, and KTP lasers) on tensile bond strength of silicone-based soft denture liner. Polymethyl methacrylate test specimens were fabricated and each received one of eight surface treatments: untreated (control), sandblasted, Er:YAG laser irradiated, sandblasted + Er:YAG laser irradiated, Nd:YAG laser irradiated, sandblasted + Nd:YAG laser irradiated, KTP laser irradiated, and sandblasted + KTP laser irradiated. The resilient liner specimens (n = 15) were processed between two polymethyl methacrylate (PMMA) blocks. Bonding strength of the liners to PMMA were compared by tensile test with the use of a universal testing machine at a crosshead speed of 5 mm/min. Kruskal-Wallis and Wilcoxon tests were used to analyze the data (α = 0.05). Altering the polymethyl methacrylate surface by Er:YAG laser significantly increased the bond strengths in polymethyl methacrylate/silicone specimens, however, sandblasting before applying a lining material had a weakening effect on the bond. In addition, Nd:YAG and KTP lasers were found to be ineffective for increasing the strength of the bond.
This study evaluated the effect of various surface treatments on the tensile bond strength of a silicone-based soft denture liner to two chemically different denture base resins, heat-cured polymethyl methacrylate (PMMA), and light-activated urethane dimethacrylate or Eclipse denture base resin. PMMA test specimens were fabricated and relined with a silicone-based soft denture liner (group AC). Eclipse test specimens were prepared according to the manufacturer's recommendation. Before they were relined with a silicone-based soft denture liner, each received one of three surface treatments: untreated (control, group EC), Eclipse bonding agent applied (group EB), and laser-irradiated (group EL). Tensile bond strength tests (crosshead speed = 5 mm/min) were performed for all specimens, and the results were analyzed using the analysis of variance followed by Tukey's test (p = 0.05). Eclipse denture base and PMMA resins presented similar bond strengths to the silicone-based soft denture liner. The highest mean force was observed in group EL specimens, and the tensile bond strengths in group EL were significantly different (p < 0.05) from those in the other groups.
The two chemically different denture base polymers showed different shear bond strength values to acrylic denture teeth. Laser-irradiation of the adhesive surface was found to be ineffective on improving bond strength of acrylic denture teeth to denture base resin. Eclipse bonding agent should be used as a part of denture fabrication with the Eclipse Resin System.
The tested denture base materials adhered to the ISO standards for both cytotoxicity and water sorption. The cytotoxicity of the light-activated UDMA resin tested was statistically similar to that of the heat-activated PMMA resin; however, the UDMA resin exhibited decreased water sorption in long-term water storage.
PURPOSEThe purpose of this study was to investigate the bonding properties of denture bases to silicone-based soft denture liners immersed in isobutyl methacrylate (iBMA) and 2-hydroxyethyl methacrylate (HEMA) for various lengths of time.MATERIALS AND METHODSPolymethyl methacrylate (PMMA) test specimens were fabricated (75 mm in length, 12 mm in diameter at the thickest section, and 7 mm at the thinnest section) and then randomly assigned to five groups (n=15); untreated (Group 1), resilient liner immersed in iBMA for 1 minute (Group 2), resilient liner immersed in iBMA for 3 minutes (Group 3), resilient liner immersed in HEMA for 1 minute (Group 4), and resilient liner immersed in HEMA for 3 minutes (Group 5). The resilient liner specimens were processed between 2 PMMA blocks. Bonding strength of the liners to PMMA was compared by tensile test with a universal testing machine at a crosshead speed of 5 mm/min. Data were evaluated by 1-way ANOVA and post hoc Tukey-Kramer multiple comparisons tests (α=0.05).RESULTSThe highest mean value of force was observed in Group 3 specimens. The differences between groups were statistically significant (P<.05), except between Group 1 and Group 4 (P=.063).CONCLUSIONImmersion of silicone-based soft denture liners in iBMA for 3 minutes doubled the tensile bond strength between the silicone soft liner and PMMA denture base materials compared to the control group.
Thermocycling decreased the bond strength values in both the PMMA and UDMA groups. Regardless of types of soft liners, PMMA specimens presented lower bond strength values than UDMA specimens, both before and after thermocycling.
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