Dpto. Odontología

Objective: To assess the effects of different concentrations of 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) included in experimental ceramic primers on the degree of conversion (DC) and microshear bond strength (μSBS) of a dual-cure resin cement, and on the acidity neutralization potential of zirconia (ZrO2) in comparison to hydroxyapatite (HAp). Methods: Experimental ceramic primers were formulated using 5 wt%, 10 wt%, 20 wt%, or 40 wt% 10-MDP as an acidic functional monomer and camphorquinone (CQ)/amine or 1-phenyl-1,2- propanedione (PPD) as a photoinitiator system. Clearfil Ceramic Primer (Kuraray Dental, Tokyo, Japan) was used as the commercial control. Micro- Raman spectroscopy was used to assess the DC of uncured and light-cured resin cements applied onto primer-treated ZrO2 surfaces. The μSBS and pH of primers were assayed in a universal testing machine and by a digital pH meter (Tec-3MP; Tecnal, Piracicaba, Brazil), respectively. Statistical analysis was performed by one-way analysis of variance (ANOVA) and Tukey’s test (p<0.05). Results: DC was not affected until a concentration of 10% 10-MDP in CQ primer and 5% 10-MDP in PPD primer was reached, when compared with the positive control (p>0.05). Groups 10-MDP 5% in CQ and PPD primers showed the highest μSBS compared with the positive control (p>0.05); however, higher concentrations of 10-MDP induced significant DC and μSBS reduction (p<0.05). HAp neutralized 10-MDP primers, but ZrO2 provided higher acidity to the primers’ pH. Conclusion: 10-MDP monomer should be used in low concentrations in ZrO2 primers to avoid reduction of the polymerization and bond strength of resin cement.

This study aimed at evaluating the shear bond strength (SBS) of modern self-adhesive resin cements and resin-modified glass ionomer cements applied to di erent prosthetic substrates. Zirconia, lithium-disilicate glass-ceramic and a noble metal alloy were used as bonding substrates. They were all sand-blasted with alumina, while LD was further etched with 9.6% hydrofluoric acid (10 s). A light-curing resin-modified glass ionomer cement (3M-GIC: Ketac Cem Plus) and a self-curing resin-modified glass ionomer cement (GC-GIC: FujiCEM 2) were compared to self-adhesive resin cements (PAN: Panavia SA Universal) and (3M-RES: Rely X Unicem 2). Ten specimens for each substrate were produced and up to five cylinders of each cement were bonded to each substrate. The shear bond strength (SBS) was evaluated after 24 h or after thermocycling (TC) aging (5000 cycles). The data was statistically analysed by two-way ANOVA and Student–Newman–Keuls test ( = 0.05). Failure modes were analysed through stereoscopic microscopy. The greatest SBS was attained with PAN, whilst 3M-GIC showed the lowest SBS and failed prevalently in adhesive mode. No di erence in SBS was observed between GC-GIC and 3M-RES. After TC aging, all cements showed significant drop (p < 0.05) in SBS, but PAN showed the greatest SBS. Reliable bond strength to prosthetic substrates can be achieved with specific universal resin-luting cements and may be an alternative to glass ionomer cements when luting alloy substrates.

Purpose: To compare after five-year simulated pulpal pressure (SPP) the degradation of adhesive-dentin interfaces created using two simplified adhesives applied with different bonding strategies. Materials and Methods: A two-step self-etch (CSE: Clearfil SE Bond) adhesive was used as a control multistep adhesive. The tested experimental materials were two simplified adhesives, a one-step self-etch (CS3: Clearfil S3 Bond) and a self-priming etch-and-rinse adhesive (SB2: Adper Single-Bond 2). Half of the bonded specimens were submitted to microtensile bond strength (μTBS) testing after 24 h. The other half submitted to SPP for five years before μTBS testing. Nonfractured sticks were evaluated using transmission electron microscopy (TEM). Scanning electron microscopy (SEM) was used to evaluate silver-nitrate nanoleakage within the interface. Data were statistically analyzed by two-way ANOVA and Tukey’s test (p < 0.05). Results: Prolonged SPP induced bond-strength reduction for both SB2 and CS3. All bonding approaches showed increased nanoleakage after aging. The two simplified adhesives showed severe degradation at the resin-dentin interface. TEM revealed that the main degradation patterns for the etch-and-rinse adhesive SB2 was collagen breakdown, while polymer hydrolysis along with filler debonding was mainly observed in CS3. Conclusions: Simplified adhesives applied in etch-and-rinse mode are mainly characterized by hydrolysis and collagen degradation. In self-etch mode, simplified adhesives may principally show hydrolysis of the polymeric matrix and/or at the interface of fillers and coupling agent. The use of multistep self-etching adhesives may guarantee greater dentin bond durability compared to simplified adhesives.