Evaluation of the bond strength between aged composite cores and luting agent

PURPOSE: The aim of this study was to evaluate effect of different surface treatment methods on the bond strength between aged composite-resin core and luting agent. MATERIALS AND METHODS: Seventy-five resin composites and also seventy-five zirconia ceramic discs were prepared. 60 composite samples were exposed to thermal aging (10,000 cycles, 5 to 55degrees C) and different surface treatment. All specimens were separated into 5 groups (n=15): 1) Intact specimens 2) Thermal aging-air polishing 3) Thermal aging- Er:YAG laser irradiation 4) Thermal aging- acid etching 5) Thermal-aging. All specimens were bonded to the zirconia discs with resin cement and fixed to universal testing machine and bond strength testing loaded to failure with a crosshead speed of 0.5 mm/min. The fractured surface was classified as adhesive failure, cohesive failure and adhesive-cohesive failure. The bond strength data was statistically compared by the Kruskal-Wallis method complemented by the Bonferroni correction Mann-Whitney U test. The probability level for statistical significance was set at alpha=.05. RESULTS: Thermal aging and different surface treatment methods have significant effect on the bond strength between composite-resin cores and luting-agent (P<.05). The mean baseline bond strength values ranged between 7.07 +/- 2.11 and 26.05 +/- 6.53 N. The highest bond strength of 26.05 +/- 6.53 N was obtained with Group 3. Group 5 showed the lowest value of bond strength. CONCLUSION: Appropriate surface treatment method should be applied to aged composite resin cores or aged-composites restorations should be replaced for the optimal bond strength and the clinical success.

Evaluation of the bond strength between aged composite cores and luting agent

PURPOSE: The aim of this study was to evaluate effect of different surface treatment methods on the bond strength between aged composite-resin core and luting agent. MATERIALS AND METHODS: Seventy-five resin composites and also seventy-five zirconia ceramic discs were prepared. 60 composite samples were exposed to thermal aging (10,000 cycles, 5 to 55degrees C) and different surface treatment. All specimens were separated into 5 groups (n=15): 1) Intact specimens 2) Thermal aging-air polishing 3) Thermal aging- Er:YAG laser irradiation 4) Thermal aging- acid etching 5) Thermal-aging. All specimens were bonded to the zirconia discs with resin cement and fixed to universal testing machine and bond strength testing loaded to failure with a crosshead speed of 0.5 mm/min. The fractured surface was classified as adhesive failure, cohesive failure and adhesive-cohesive failure. The bond strength data was statistically compared by the Kruskal-Wallis method complemented by the Bonferroni correction Mann-Whitney U test. The probability level for statistical significance was set at alpha=.05. RESULTS: Thermal aging and different surface treatment methods have significant effect on the bond strength between composite-resin cores and luting-agent (P<.05). The mean baseline bond strength values ranged between 7.07 +/- 2.11 and 26.05 +/- 6.53 N. The highest bond strength of 26.05 +/- 6.53 N was obtained with Group 3. Group 5 showed the lowest value of bond strength. CONCLUSION: Appropriate surface treatment method should be applied to aged composite resin cores or aged-composites restorations should be replaced for the optimal bond strength and the clinical success.

The effect of a diode laser and traditional irrigants on the bond strength of self-adhesive cement

PURPOSE: The purpose of this study was to compare the effect of a diode laser and traditional irrigants on the bond strength of self-adhesive cement. MATERIALS AND METHODS: Fifty-five incisors extracted due to periodontal problems were used. All teeth were instrumented using a set of rotary root canal instruments. The post spaces were enlarged for a No.14 (diameter, 1.4 mm) Snowlight (Abrasive technology, OH, USA) glass fiber reinforced composite post with matching drill. The teeth were randomly divided into 5 experimental groups of 11 teeth each. The post spaces were treated with the followings: Group 1: 5 mL 0.9% physiological saline; Group 2: 5 mL 5.25% sodium hypochlorite; Group 3: 5 mL 17% ethylene diamine tetra acetic acid (EDTA), Group 4: 37% orthophosphoric acid and Group 5: Photodynamic diode laser irradiation for 1 minute after application of light-active dye solution. Snowlight posts were luted with self-adhesive resin cement. Each root was sectioned perpendicular to its long axis to create 1 mm thick specimens. The push-out bond strength test method was used to measure bond strength. One tooth from each group was processed for scanning electron microscopic analysis. RESULTS: Bond strength values were as follow: Group 1 = 4.15 MPa; Group 2 = 3.00 MPa; Group 3 = 4.45 MPa; Group 4 = 6.96 MPa; and Group 5 = 8.93 MPa. These values were analysed using one-way ANOVA and Tukey honestly significant difference test (P.05). CONCLUSION: Orthophosphoric acid and EDTA were more effective methods for removing the smear layer than the diode laser. However, the diode laser and orthophosphoric acid were more effective at the cement dentin interface than the EDTA, Therefore, modifying the smear layer may be more effective when a self-adhesive system is used.

The effect of repeated porcelain firings on corrosion resistance of different dental alloys

PURPOSE: The aim of this study was to evaluate the effects of repeated porcelain firing process on the corrosion rates of the dental alloys. MATERIALS AND METHODS: Cr-Co, Cr-Ni and Pd-Ag alloys were used for this study. Each metal supported porcelain consisted of 30 specimens of 10 for 7, 9 and 11 firing each. Disc-shaped specimens 10 mm diameter and 3 mm thickness were formed by melting alloys with a propane-oxygen flame and casted with a centrifuge casting machine and then with the porcelain veneer fired onto the metal alloys. Corrosion tests were performed in quintuplicate for each alloy (after repeated porcelain firing) in Fusayama artificial saliva solution (pH = 5) in a low thermal-expansion borosilicate glass cell. Tamhane and Sheffe test was used to compare corrosion differences in the results after repeated firings and among 7, 9 and 11 firing for each alloy. The probability level for statistical significance was set at alpha=0.05. RESULTS: The corrosion resistance was higher (30 mV), in case of 7 times firing (Commercial). On the other hand, it was lower in case of 11 times firing (5 mV) (P<.05). CONCLUSION: Repeated firings decreased corrosion resistance of Pd-Ag, Cr-Co and Cr-Ni alloys. The Pd-Ag alloy exhibited little corrosion in in vitro tests. The Cr-Ni alloy exhibited higher corrosion resistance than Cr-Co alloys in in vitro tests.