Effect of water aging on microtensile bond strength of dual-cured resin cements to pre-treated sintered zirconium-oxide ceramics.

OBJECTIVES: To evaluate the hydrolytic stability of different dual-cure resin cements when luted to zirconia ceramic. METHODS: Eighteen cylinder-shaped zirconia blocks (Cercon Zirconia, Dentsply) were conditioned with: Group 1, no treatment; Group 2, sandblasting (125microm alumina-Al(2)O(3)-particles); Group 3, tribochemical silica coating (50microm silica-modified Al(2)O(3) particles). Ceramic blocks were duplicated in composite resin (Tetric Evo Ceram, Ivoclar-Vivadent). Composite disks were luted to pre-treated ceramic surfaces using: (1) Clearfil Esthetic Cement (CEC; Kuraray); (2) Rely X Unicem (RXU; 3M ESPE); (3) Calibra (CAL; Dentsply Caulk). After 24h, bonded samples were cut into microtensile sticks (1mm(2)). Half of the sticks were loaded in tension until failure (cross-head speed of 0.5mm/min). The remaining half was tested after 6 months of water storage at 37 degrees C. Data was analyzed with three-way ANOVA and Tukey's test (P<0.05). Fractographic analysis was performed by SEM. RESULTS: After 24h, bond strength of CEC to zirconia was significantly higher than that of RXU and CAL, independently from the ceramic pre-treatment (P<0.001). Using CAL, all samples failed prematurely except when luting to sandblasted surfaces. After 6 months of water aging, bond strength of CEC significantly decreased. RXU did not significantly alter bond strengths. Adhesion of sandblasted specimens luted with CAL fell over time. Micromorphological alterations were evident after water storage. SIGNIFICANCE: Resin-ceramic interfacial longevity depended on cement selection rather than on surface pre-treatments. CEC and RXU were both suitable for luting zirconia. Water aging played an important role in the durability of zirconia-to-composite chemical bonds

Bond strength of three luting agents to zirconia ceramic - influence of surface treatment and thermocycling

OBJECTIVE: This in vitro study aimed to evaluate the influence of different surface treatments, 3 luting agents and thermocycling on microtensile bond strength (µTBS) to zirconia ceramic. Material and METHODS: A total of 18 blocks (5x5x4 mm) were fabricated from zirconia ceramic (ICE Zirkonia) and duplicated into composite blocks (Alphadent). Ceramic blocks were divided into 3 groups (n=6) according to the following surface treatments: airborne-particle abrasion (AA), silica-coating, (SC) (CoJet) and silica coating followed by silane application (SCSI) (ESPE Sil). Each group was divided into 3 subgroups (n=2) according to the 3 luting agents used. Resin-modified glass-ionomer cement (RMGIC, Ketac Cem Plus), self-adhesive resin cement (UN, RelyX Unicem) and adhesive resin cement (ML, MultiLink Automix) were used for bonding composite and zirconia blocks. Each bonding assembly was cut into microbars (10 mm long and 1±0.1 mm²). Seven specimens of each subgroup were stored in water bath at 37ºC for 1 week. The other 7 specimens were stored in water bath at 37ºC for 30 days then thermocycled (TC) for 7,500 cycles. µTBS values were recorded for each specimen using a universal testing machine. Statistical analyses were performed using a 3-way ANOVA model followed by serial 1-way ANOVAs. Comparison of means was performed with Tukey's HSD test at (&#945;=0.05). RESULTS: µTBS ranged from 16.8 to 31.8 MPa after 1 week and from 7.3 to 16.4 MPa after 30 days of storage in water and thermocycling. Artificial aging significantly decreased µTBS (p<0.05). Considering surface treatment, SCSI significantly increased µTBS (p<0.05) compared to SC and AA. Resin cements (UN and ML) demonstrated significantly higher µTBS (p<0.05) compared to RMGIC cement. CONCLUSIONS: Silica coating followed by silane application together with adhesive resin cements significantly increased µTBS, while thermocycling significantly decreased µTBS

Managing the phase-down of amalgam: part II. Implications for practising arrangements and lessons from Norway

The announcement of the Minamata Convention has triggered the lead into a phase-down in the use of dental amalgam. This paper considers aspects of this development in the context of the experience of banning the use of dental amalgam in Norway. It is suggested that strong top-down leadership and joined-up working by all relevant stakeholders, including patients, may be one of the most important keys to an effective, seamless transition to the provision of preventatively orientated, patient-centred, minimally interventive operative dentistry, based on state-of-the-art selection and application of tooth-coloured restorative materials. The benefits of such a transition are considered to be an important goal for dentistry in the UK