Micro-mechanical bond strength tests for the assessment of the adhesion of GIC to dentine.

BACKGROUND: The aim of this study is to critically evaluate the bond strength (BS) of Glass-Ionomer Cements (GIC) to dentine with microtensile (µTBS) and microshear (µSBS) BS tests by assessing their rankings and failure patterns. METHODS: Samples were made on flat dentine surfaces and submitted to µTBS and µSBS. The materials used were: high viscosity GIC (Ketac™ Molar Aplicap-KM), resin-modified GIC (Fuji II-FII), nano-filled resin-modified GIC (Ketac™ N100-N100) and an etch-and-rinse adhesive system with a composite resin (Adper™ Single Bond 2 and Z100™-Z100). All tests were performed with a Universal Testing Machine (24 h water storage, crosshead speed of 1 mm/min). Debonded surfaces were examined with a stereomicroscope (×40) to identify the failure mode. The data was analyzed with two-way ANOVA (p < 0.05) and LSD test. RESULTS: Means were statistically different regarding the tests and materials, indicating that values for BS obtained for each material depend on the test performed. Failure analysis revealed that failures produced by µTBS were mainly cohesive for KM and FII. µSBS failures were mainly adhesive or mixed for all materials. For the µTBS, the rank was Z100 > FII > KM = N100, whereas for the µSBS it was Z100 = FII = KM > N100. CONCLUSION: It may be concluded that distinct micro-mechanical tests present different failure patterns and rankings depending on the material to be considered.

Microleakage of an adhesive system used as a fissure sealant.

AIM: The aim of this study was to investigate the microleakage of pit and fissure sealants in primary teeth and to determine if multi-step methods should produce better results in terms of microleakage prevention. METHODS AND MATERIALS: A total of 40 intact primary molars were randomly assigned to one of four sealant groups: resin based sealant Ultraseal XT (US - Ultradent) (Group 1, n=10); adhesive system Scotchbond Multi Purpose Plus (SBMP - 3M/ESPE) used as a sealant (Group 2, n=10); primer (SBMP) and US (Group 3, n=10); and primer, bond (SBMP) and US (Group 4, n=10). After thermocycling (x700, 5-55 degrees C) all teeth surfaces were made impermeable with the exception of the occlusal surface. Samples were immersed in 50% silver nitrate for 8 hours, sectioned longitudinally with two cuts in the central fissure pit, and then immersed in photo development solution followed by 16 hours in fluorescent light. Pictures were obtained by light microscope (x40) and the degree of microleakage was evaluated by three blinded evaluators. The data were analyzed using the Kruskal Wallis test. RESULTS: Significant statistical differences (p<.05) were observed between Groups 1-3, Groups 2-3, Groups 2-4, and Groups 3-4. Group 3 showed higher microleakage scores. CONCLUSION: The adhesive system and the resin based sealant demonstrated similar microleakage properties, suggesting the possibility that adhesives can be used in a clinical setting. Additionally, the increase in the number of clinical steps required by common application of resin based sealant, including use of primer or primer and bond, did not lead to better results in preventing microleakage. CLINICAL SIGNIFICANCE: The adhesive system can be used as a sealant without increasing the microleakage. Thus, the use of the adhesive system before the application of the sealant is not necessary to reduce the microleakage, although further research is warranted to support this conclusion.

Influence of Er,Cr:YSGG laser treatment on microtensile bond strength of adhesives to enamel.

The current trend towards minimum-intervention dentistry has introduced laser technology as an alternative technique for cavity preparation. This study assessed the null hypothesis that enamel prepared either by Er,Cr:YSGG laser or conventional diamond bur is equally receptive to adhesive procedures. The buccal and lingual surfaces of 35 sound human molars were prepared with Er,Cr:YSGG laser or a medium-grit diamond bur. One etch&rinse (OptiBond FL) and three self-etch adhesives (Adper Prompt L-Pop, Clearfil SE Bond and Clearfil S3 Bond) were applied on laser-irradiated and bur-cut enamel, followed by the application of a 5-6 mm build-up of Z100. The micro-tensile bond strength (microTBS) was determined after 24 hours of storage in water at 37 degrees C. Prepared enamel surfaces and failure patterns were evaluated using a stereomicroscope and a field-emission-gun scanning electron microscope (Feg-SEM). The pTBS to laser-irradiated enamel was significantly lower than to bur-cut enamel (p<0.05), with the exception of Clearfil S3 Bond, which bonded equally effectively to both substrates. The latter presented the highest microTBS on laser-irradiated enamel, though it was not statistically different from the microTBS of OptiBond FL. SEM analysis revealed significant morphological alterations of the laser-irradiated enamel surface, such as areas of melted and recrystalized hydroxyapatite and deep extensive micro-cracks. In conclusion, the bonding effectiveness of adhesives to laser-irradiated enamel depends not only on the structural substrate alterations induced by the laser, but also on the characteristics of the adhesive employed.