Long-term storage affects adhesion between titanium and zirconia using resin cements.

PURPOSE To determine the impact of long-term storage on adhesion between titanium and zirconia using resin cements. MATERIALS AND METHODS Titanium grade 4 blocks were adhesively fixed onto zirconia disks with four resin cements: Panavia F 2.0 (Kuraray Europe), GC G-Cem (GC Europe), RelyX Unicem (3M ESPE), and SmartCem 2 (Dentsply DeguDent). Shear bond strength was determined after storage in a water bath for 24 h, 16, 90, and 150 days at 37°C, and after 6000 cycles between 5°C and 55°C. Fracture behavior was evaluated using scanning electron microscopy. RESULTS After storage for at least 90 days and after thermocycling, GC G-Cem (16.9 MPa and 15.1 MPa, respectively) and RelyX Unicem (10.8 MPa and 15.7 MPa, respectively) achieved higher shear bond strength compared to SmartCem 2 (7.1 MPa and 4.0 MPa, respectively) and Panavia F2 (4.1 MPa and 7.4 MPa, respectively). At day 150, GC G-Cem and RelyX Unicem caused exclusively mixed fractures. SmartCem 2 and Panavia F2 showed adhesive fractures in one-third of the cases; all other fractures were of mixed type. After 24 h (GC G-Cem: 26.0, RelyX Unicem: 20.5 MPa, SmartCem 2: 16.1 MPa, Panavia F2: 23.6 MPa) and 16 days (GC G-Cem: 12.8, RelyX Unicem: 14.2 MPa, SmartCem 2: 9.8 MPa, Panavia F2: 14.7 MPa) of storage, shear bond strength was similar among the four cements. CONCLUSION Long-term storage and thermocycling differentially affects the bonding of resin cement between titanium and zirconia.

Airborne-particle Abrasion Is a Minimally Invasive Method to Pre-Treat Sclerotic, Non-Carious Cervical Dentin

Objectives: To investigate substance loss and bond strength capacity of sclerotic, non-carious cervical dentin after airborne-particle abrasion or diamond bur preparation. Methods: Fifteen non-sclerotic dentin specimens were made from crowns of extracted human incisors of which the labial surfaces had been ground with silicon carbide papers (non-sclerotic control; Group 1). Forty-five sclerotic dentin specimens (n=15/group) were made from the labial, non-carious cervical root part of extracted human incisors and underwent either no pre-treatment (sclerotic control; Group 2), pre-treatment with airborne-particle abrasion (CoJet Prep [3M ESPE] and 50 µm aluminium oxide; Group 3), or with diamond bur preparation (40 µm grit size; Group 4). Substance loss after pre-treatment was measured in Groups 3 and 4. Subsequently, Scotchbond Universal (3M ESPE) and resin composite (CeramX [DENTSPLY DeTrey]) were applied on the treated dentin surfaces. The specimens were stored at 37°C and 100% humidity for 24 h. After storage, shear bond strength (SBS) was measured and data analyzed with nonparametric ANOVA followed by Wilcoxon rank sum tests. Results: Substance loss (medians) was 19 µm in Group 3 and 113 µm in Group 4. SBS-values (MPa; medians) in Group 2 (9.24) were significantly lower than in Group 1 (13.15; p=0.0069), Group 3 (13.05; p=0.01), and Group 4 (13.02; p=0.0142). There were no significant differences in SBS between Groups 1, 3, and 4 (p≥0.8063). Conclusion: Airborne-particle abrasion and diamond bur preparation restored bond strength of Scotchbond Universal to sclerotic dentin to the level of non-sclerotic dentin, with airborne-particle abrasion being less invasive than diamond bur preparation.

Effect of zirconia surface treatments on the shear strength of zirconia/veneering ceramic composites

Aim of the investigation was to assess the effect of different surface treatments on the bond strength of veneering ceramics to zirconia. In a shear test, the influences of polishing, sandblasting, and silica-coating of the zirconia surface on bonding were assessed with five different veneering ceramics. In addition the effect of liner application was examined. With one veneering ceramic, the impact of regeneration firing of zirconia was also evaluated. Statistical analysis was performed with one-way ANOVA and post hoc Scheffé's test. Failure in every case occurred in the veneering ceramic adjacent to the interface with a thin layer of ceramic remaining on the zirconia surface, indicating that bond strength was higher than the cohesive strength of the veneering ceramic. Shear strength ranged from 23.5 +/- 3.4 MPa to 33.0 +/- 6.8 MPa without explicit correlation to the respective surface treatment. Regeneration firing significantly decreased the shear strength of both polished and sandblasted surfaces. Findings of this study revealed that bonding between veneering ceramics and zirconia might be based on chemical bonds. On this note, sandblasting was not a necessary surface pretreatment to enhance bond strength and that regeneration firing was not recommended.

In vitro fracture strength and thermal shock resistance of metal-ceramic crowns with cast and machined AuTi frameworks

STATEMENT OF PROBLEM: AuTi alloys with 1.6% to 1.7% (wt%) Ti provide sufficient bond strength to veneering ceramics, but the strength of entire metal-ceramic restorations fabricated from these alloys is not known. However, this information is important to assess the clinical performance of such materials. PURPOSE: This in vitro study evaluated the fracture strength and thermal shock resistance of metal-ceramic crowns with AuTi frameworks produced by milling or casting. MATERIAL AND METHODS: Frameworks of the alloy Au-1.7Ti-0.1Ir (wt%) (Esteticor Vision) were produced by milling or casting (test groups). A high-gold alloy (Esteticor Special) was used as the control. The frameworks were veneered with ceramic (VMK 95). Specimens (n=7) were loaded until fracture. Loads at failure (N) were recorded and the mean values statistically evaluated using 1-way analysis of variance and a post hoc Dunnett test (alpha=.05). To assess the crazing resistance of the veneering ceramic, 6 additional crowns of each group were subjected to a thermal shock test. Fractured surfaces were documented by scanning electron microscopy. Coefficients of thermal expansion of the materials used were measured (n=2) to assess the thermal compatibility between alloys and ceramic. RESULTS: The mean fracture strength of the crowns with machined AuTi frameworks (1294 +/- 236 N) was significantly lower (P=.012) than that of the cast AuTi frameworks (1680 +/- 150 N), but statistically not different than the high-gold alloy (1449 +/- 159 N). Bonding failure to the AuTi alloy predominantly occurred at the alloy-oxide interface. For the high-gold alloy, more ceramic residues were observed. In the thermal shock test, crowns with milled AuTi frameworks showed significantly higher thermal shock resistance compared to the other groups. The coefficients of thermal expansion (Esteticor Vision cast: 14.5 microm/m.K; Esteticor Vision milled: 14.3 microm/m.K; Esteticor Special cast: 13.7 microm/m.K) did not correlate with the results of the thermal shock test. CONCLUSION: The in vitro fracture strength of crowns with milled AuTi frameworks is lower than that obtained with cast AuTi frameworks, but comparable to those crowns produced with a high-gold alloy.

Micromorphology and adhesive performance of Er:YAG laser-treated dentin of primary teeth

This study evaluated (1) the micromorphology by scanning electron microscopy (SEM) and (2) the adhesive performance by microtensile bond strength (μTBS) of diamond bur-treated dentin compared to Er:YAG laser-treated dentin of human primary teeth. (1) For qualitative SEM evaluation, dentin of 18 second primary molars (n = 3/method) was treated with either diamond bur as a control (group 1a: 40 μm diamond bur only (clinical situation); group 1b: grinding + 40 μm diamond bur) or with Er:YAG laser (group 2a (clinical situation, manufacturer's settings): 200 mJ/25 Hz (5 W) + 100 mJ/35 Hz (3.5 W) laser only; group 2b (experimental setting "high"): grinding + 400 mJ/20 Hz (8 W); group 2c (manufacturer's setting "finishing"): grinding + 100 mJ/35 Hz (3.5 W); group 2d (experimental setting "low"): grinding + 50 mJ/35 Hz (1.75 W)). (2) For evaluation of adhesive performance, 64 second primary molars were divided into four groups and treated as described for group 1b and groups 2b/c/d (n = 16/method), and μTBS of Clearfil SE/Clearfil Majesty Esthetic to dentin was measured. The SEM micrographs were qualitatively analyzed. The μTBS values were compared with a Kruskal-Wallis test. The significance level was set at α = 0.05. SEM micrographs showed the typical micromorphologies with a smear layer for the diamond bur groups and open dentin tubules for all laser-treated groups. However, in group 2d, the laser beam had insufficiently irradiated the dentin area, rendering the underlying ground surface partly visible. There were no statistically significant differences between μTBS values of the four groups (p = 0.394). This suggests that Er:YAG laser treatment of dentin of primary molars provides bond strengths similar to those obtained following diamond bur treatment.

Ceramic bonding to a machined Au-Ti alloy

Objective: To assess in vitro the bond strength of a machined surface of a Au-Ti alloy to a veneering ceramic. Method and Materials: Metal strips of the alloy Au 1.7-Ti 0.1-Ir were milled from a semiproduct fabricated by continuous casting and cold forming. For comparison, the same alloy as well as a traditional Au-Pt-Pd-In alloy were used in the as-cast state. Six samples of each group were fabricated for the crack initiation test, according to ISO 9693:1999, by preparing appropriate metal strips that were veneered with ceramic using a standard firing procedure. The crack initiation test was performed in a universal testing machine. Load at fracture was recorded. Means of bond strength were calculated for each group and the results compared by use of a 1-sided Student t test (P < .05). Fracture sites were documented by means of SEM. Results: Bond strength in the 3 groups was in the same order of magnitude. Failure mode was different for both alloys. Failure of the bonding to the Au-Ti alloy predominantly occurred at the alloy-oxide interface, no matter which fabrication process was used. On the Au-Pt-Pd-In alloy, more ceramic residues were observed. Conclusion: The machined alloy Au 1.7-Ti 0.1-Ir provides sufficient bond strength to veneering ceramics, but this has to be proven by a clinical study. (Quintessence Int 2007;38:867-872).

The effect of a tin-containing fluoride mouth rinse on the bond between resin composite and erosively demineralised dentin

OBJECTIVES To evaluate the effect of a tin-containing fluoride (Sn/F) mouth rinse on microtensile bond strength (μTBS) between resin composite and erosively demineralised dentin. MATERIALS AND METHODS Dentin of 120 human molars was erosively demineralised using a 10-day cyclic de- and remineralisation model. For 40 molars, the model comprised erosive demineralisation only; for another 40, the model included treatment with a NaF solution; and for yet another 40, the model included treatment with a Sn/F mouth rinse. In half of these molars (n = 20), the demineralised organic matrix was continuously removed by collagenase. Silicon carbide paper-ground, non-erosively demineralised molars served as control (n = 20). Subsequently, μTBS of Clearfil SE/Filtek Z250 to the dentin was measured, and failure mode was determined. Additionally, surfaces were evaluated using SEM and EDX. RESULTS Compared to the non-erosively demineralised control, erosive demineralisation resulted in significantly lower μTBS regardless of the removal of demineralised organic matrix. Treatment with NaF increased μTBS, but the level of μTBS obtained by the non-erosively demineralised control was only reached when the demineralised organic matrix had been removed. The Sn/F mouth rinse together with removal of demineralised organic matrix led to significantly higher µTBS than did the non-erosively demineralised control. The Sn/F mouth rinse yielded higher μTBS than did the NaF solution. CONCLUSIONS Treatment of erosively demineralised dentin with a NaF solution or a Sn/F mouth rinse increased the bond strength of resin composite. CLINICAL RELEVANCE Bond strength of resin composite to eroded dentin was not negatively influenced by treatment with a tin-containing fluoride mouth rinse.

The bonding of glass ionomer cements to caries-affected primary tooth dentin

PURPOSE The purpose of this study was to evaluate the bonding of glass ionomer cements (GICs) to sound and caries-affected dentin by microtensile bond strength (μTBS) and nanoleakage (NL) tests. METHODS Occlusal cavity preparations were made in 36 sound primary molars. Half of the specimens were submitted to a pH-cycling model to create simulated caries-affected dentin. Teeth were randomly restored with one of the three materials: (1) resin-modified GIC with nanoparticles (Ketac N100; KN); (2) resin-modified GIC (Vitremer; VI); and (3) high-viscosity GIC (Ketac Molar Easy Mix; KM). Specimens were tested using a microtensile test (1 mm/minute). One specimen from each tooth was immersed in ammoniacal silver nitrate for 24 hours and revealed after eight hours to assess interfacial NL. The μTBS means were analyzed by 2-way analysis of variance and Tukey's post hoc test. For NL, Kruskal-Wallis and Mann-Whitney tests were used (P<.05). RESULTS No difference was found between sound and caries-affected dentin (P>.05). KM showed the lowest GIC-dentin μTBS values, while VI and KN showed higher values. Infiltration of ammoniacal silver nitrate into the adhesive interface was not affected by sound or caries-affected dentin. CONCLUSION Caries-affected dentin does not jeopardize the bonding of glass ionomer cements to primary tooth dentin.

Bonding of simplified adhesive systems to caries-affected dentin of primary teeth.

PURPOSE To evaluate the bonding of simplified adhesive systems to sound and caries-affected dentin of primary teeth with microtensile (µTBS) and nanoleakage (NL) tests. MATERIALS AND METHODS Occlusal cavities were prepared in 36 sound second primary molars. Half of the specimens were submitted to pH cycling to simulate caries-affected dentin. Teeth were randomly restored with one of three materials: the etch-and-rinse adhesive system Adper Single Bond 2 (SB), the two-step self-etching adhesive system Adper SE Plus (SE), and the one-step self-etching adhesive system Adper Easy One (EASY). After storage for 24 h, specimens with cross-sectional areas of 0.8 mm2 were prepared for microtensile testing (1 mm/min). One stick from each tooth was immersed in silver nitrate solution (24 h) and allowed to develop for 8 h in order to score the nano leakage with SEM. The fracture pattern was evaluated using a stereomicroscope (400X). The µTBS means were analyzed by two-way ANOVA and Tukey's post-hoc test. For NL, the Kruskal- Wallis and Mann-Whitney tests were used (α < 0.05). RESULTS SB (35.5 ± 3.5) showed the highest µTBS value to sound dentin, followed by EASY (26.3 ± 1.9) and SE (18.2 ± 6.5) (p < 0.05). No difference among materials was observed for caries-affected dentin (SB: 17.8 ± 4.2; SE: 13.9 ± 3.2; EASY: 14.4 ± 4.2, p > 0.05). For all groups, adhesive/mixed fracture prevailed. Caries affected dentin promoted silver nitrate uptake into the adhesive interface; however, with SE, the nano leakage was more pronounced than in the other adhesive systems, even in sound dentin. CONCLUSION Caries-affected dentin negatively influences the bond strength and nano leakage of the two-step etch-and-rinse and one-step self-etching adhesive systems tested in primary teeth.

Two pre-treatments for bonding to non-carious cervical root dentin

Purpose: To investigate the effect of airborne-particle abrasion or diamond bur preparation as pretreatment steps of non-carious cervical root dentin regarding substance loss and bond strength. Methods: 45 dentin specimens produced from crowns of extracted human incisors by grinding the labial surfaces with silicon carbide papers (control) were treated with one of three adhesive systems (Group 1A-C; A: OptiBond FL, B: Clearfil SE Bond, or C: Scotchbond Universal; n=15/adhesive system). Another 135 dentin specimens (n=15/group) produced from the labial, non-carious cervical root part of extracted human incisors were treated with one of the adhesive systems after either no pre-treatment (Group 2A-C), pre-treatment with airborne-particle abrasion (CoJet Prep and 50 µm aluminum oxide powder; Group 3A-C), or pre-treatment with diamond bur preparation (40 µm grit size; Group 4A-C). Substance loss caused by the pre-treatment was measured in Groups 3 and 4. After treatment with the adhesive systems, resin composite was applied and all specimens were stored (37°C, 100% humidity, 24 hours) until measurement of microshear bond strength (µSBS). Data were analyzed with a nonparametric ANOVA followed by Kruskal-Wallis and Wilcoxon rank sum tests (level of significance: alpha=0.05). Results: Overall substance loss was significantly lower in Group 3 (median: 19 µm) than in Group 4 (median: 113 µm; p<0.0001). There were no significant differences in µSBS between the adhesive systems (A-C) in Group 1, Group 3, and Group 4 (p>=0.133). In Group 2, OptiBond FL (Group 2A) and Clearfil SE Bond (Group 2B) yielded significantly higher µSBS than Scotchbond Universal (Group 2C; p<=0.032). For OptiBond FL and Clearfil SE Bond, there were no significant differences in µSBS between the ground crown dentin and the non-carious cervical root dentin regardless of any pre-treatment of the latter (both p=0.661). For Scotchbond Universal, the µSBS to non-carious cervical root dentin without pre-treatment was significantly lower than to ground crown dentin and to non-carious cervical root dentin pre-treated with airborne-particle abrasion or diamond bur preparation p<=0.014).

Impact of Sn/F Pre-Treatments on the Durability of Protective Coatings against Dentine Erosion/Abrasion.

For preventing erosive wear in dentine, coating with adhesives has been suggested as an alternative to fluoridation. However, clinical studies have revealed limited efficacy. As there is first evidence that Sn(2+) increases bond strength of the adhesive Clearfil SE (Kuraray), the aim of the present study was to investigate whether pre-treatment with different Sn(2+)/F(-) solutions improves the durability of Clearfil SE coatings. Dentine samples (eight groups, n=16/group) were freed of smear layer (0.5% citric acid, 10 s), treated (15 s) either with no solution (control), aminefluoride (AmF, 500 ppm F(-), pH 4.5), SnCl2 (800/1600 ppm Sn(2+); pH 1.5), SnCl2/AmF (500 ppm F(-), 800 ppm Sn(2+), pH 1.5/3.0/4.5), or Elmex Erosion Protection Rinse (EP, 500 ppm F-, 800 ppm Sn(2+), pH 4.5; GABA International), then rinsed with water (15 s) and individually covered with Clearfil SE. Subsequently the specimens were subjected to an erosion/abrasion protocol consisting of 1320 cycles of immersion in 0.5% citric acid (5 °C/55 °C; 2 min) and automated brushing (15 s, 200 g, NaF-toothpaste, RDA 80). As the coatings proved stable up to 1320 cycles, 60 modified cycles (brushing time 30 min/cycle) were added. Wear was measured profilometrically. After SnCl2/AmF, pH 4.5 or EP pre-treatment all except one coating survived. In the other groups, almost all coatings were lost and there was no significant difference to the control group. Pre-treatment with a Sn(2+)/F(-) solution at pH 4.5 seems able to improve the durability of adhesive coatings, rendering these an attractive option in preventing erosive wear in dentine.