Laser type effects on repair bond strength of ormocers and nanoceramic based composites

The aim of this study was to evaluate the effects of different surface treatments and different restoration materials on repair bond strength of ormocer and nanoceramic based composites. 24 (12 Admira, Voco, 12 Ceram X duo, Dentsply) thermally aged blocks (6 × 6 × 5 mm) were roughened with either bur, Er:YAG or Nd:YAG laser. In each group half of the roughened samples were repaired with composite of their respective brand; other half was repaired with composite of the other brand. All samples were subjected to microtensile bond strength test. Data were analyzed with Kruskal-Wallis and Bonferroni correction, Mann-Whitney U test (p = 0.05). For roughening methods no significant difference was found between Bur-Er:YAG (p = 0.536), however between the other groups (Bur-Nd:YAG and Er:YAG-Nd:YAG) significant difference were found (p < 0.001). For Admira as a filler material, no significant differences were found for bur, Er:YAG, Nd:YAG groups based on repair materials. For Ceram X duo as a filler material, while no significant differences were found for bur and Er:YAG groups; a significant difference was found for Nd:YAG group based on repair materials. A weak significant difference was found between the repair composite groups undergone thermocycling or not (p = 0.04). Surface roughening with Er:YAG laser can be used clinically for the repair of aged composite restorations.     

The effect of different bonding protocols on the repair microshear bond strength of water-stored CAD/CAM resin composite

This study evaluated the repair microshear bond strength (μSBS) of water stored CAD/CAM resin composite under eight different surface treatments using a silane-containing universal adhesive in etch-and-rinse and self-etching modes. In total, 48 CAD/CAM resin composite slices were prepared from Lava Ultimate CAD/CAM blocks and stored in water for 6 months. The slices were assigned into 8 main groups, according to surface treatments (no treatment, no-treatment/silane, surface grinding, surface grinding/silane, sandblasting, sandblasting/silane, silica coating and silica coating/silane). Each main group was divided according to the universal adhesive application mode (either the etch-and-rinse mode or the self-etch mode). Each slice received 6 resin composite micro-cylinders (0.8 × 1 mm). Micro-shear bond strength was run at 0.5 mm/min crosshead speed until failure. Treated surfaces were examined using SEM. Bond strength data were statistically analyzed using Two-Way ANOVA/Tukey HSD post hoc test. Only ‘surface treatment’ significantly affected the repair μSBS (p ? 0.001). Parameters ‘Adhesive application mode’ and ‘surface treatment × adhesive mode’ showed no significant effect on μSBS (p = 0.458 and p = 0.286 respectively). Regardless of the adhesive application mode, silica coating showed the highest μSBS (21.6 ± 6.8 MPa), while sandblasting/silane showed the lowest μSBS (13.0 ± 6.1 MPa). Regardless of adhesive application mode, the use of silica coating to treat the water-stored CAD/CAM resin composite surfaces is crucial to improve the repair bond strength.     

Effects of neutralizing or antioxidant agents on the consequences induced by enamel bleaching agents in immediate resin composite restorations

Purpose: Bleaching agents are claimed to impair the bonding to the tooth structure when resin composite restorations are immediately performed. This study aimed to evaluate the effect of a neutralizing solution (10% sodium bicarbonate) or an antioxidant agent (10% sodium ascorbate) on the immediate or delayed (15 days) shear bond strength (SBS) of composite restorations performed on enamel. Seventy flat buccal enamel surfaces obtained from bovine incisors were divided into seven groups (n = 10): control group, unbleached enamel, restored (3M ESPE/Adper Single Bond 2/Filtek Z350XT) (G1); bleached, immediately restored (G2); bleached, delayed restoration (G3); bleached, antioxidant (sodium ascorbate), immediately restored (G4); bleached, antioxidant, delayed restoration (G5); bleached, neutralizing (sodium bicarbonate), immediate restoration (G6); bleached, neutralizing, delayed restoration (G7). Specimens were submitted to SBS test and examined after failure using scanning electron microscopy (SEM). Results were statistically analyzed with ANOVA/Tukey’s tests (5%). Bonding to enamel immediately restored after bleaching (G2) was significantly lower than G1 (unbleached enamel; p < 0.05). Applying the antioxidant or neutralizing agent significantly improved the bonding to enamel compared with G2 (bleached, immediate restored), irrespective of the restoration time (immediate or delayed) (p < 0.05). No significance was found between the two agents when applied after bleaching, and compared with the control group, regardless of evaluation time (p > 0.05). SEM images demonstrated adhesive failures in the bleached, immediately restored group (G2). G3–G7 exhibited majority of cohesive and mixed failure patterns. 10% sodium bicarbonate or 10% sodium ascorbate neutralizes the negative immediate and delayed effects of bleaching on bond strength of enamel bleached enamel.     

Bond strength and durability of universal adhesive agents with lithium disilicate ceramics: A shear bond strength study

The aim was to assess the shear bond strength (SBS) of lithium disilicate (LD) ceramic to resin composite with different universal adhesives, duration of ageing and silane. One hundred and twenty LD ceramic discs were processed, fired and etched (HF acid 5%) for 20 s (sec). All specimens were divided into 12 groups (n = 10), based on different combinations of, 3 different universal adhesives [Scotchbond (SB) Universal Adhesive, All-Bond (AB) Universal, and Futurabond U (FU)], silane and different duration of ageing [24 h and 3 months]. Composite resin cylinders (Tetric ceram) (3mm × 2 mm) were formed using bonding jig on ceramic and were light-cured. The specimens in groups 1–6 and 7–12 were stored in distilled water (37 °C) for 24 h and 3 months (thermocycling -5000 cycles 5–55 °C/30 s dwell time) before being subjected to bond strength testing respectively. Using universal testing machine shear bond test was performed at a crosshead speed of 1 mm/min. Failure modes and fracture patterns were assessed using stereomicroscope and scanning electron microscope. Analysis of variance was performed to analyze data. SBS was significantly higher with silane than without silane (p < 0.01), regardless of the type of adhesive or storage duration. Specimens tested at 24 h storage showed significantly higher (p < 0.01) SBS than specimens tested after 3-months. A comparison among different universal adhesives showed significantly distinct bond strength (p < 0.01). Optimal bonds to LD were achieved by application of silane. While ageing through storage had a negative impact on the SBS, it varied among different adhesives.     

Effect of adhesive type and composite viscosity on the dentin bond strength

Objectives: Evaluate the influence of composite resins viscosity and type of cure of the adhesive systems on the bond strength of composite resins submitted to artificial aging.

Methods: Dentin specimens (n = 240) were divided into 2 groups: Group GC: GrandioSO, and Group GF: GrandioSO Heavy Flow. These groups were subdivided into 6: FM: Futurabond M – light cured, FDCC: Futurabond Dual Cure – chemical cured, FDCL: Futurabond Dual Cure – light cured, CS3: Clearfil S3 – light cured, CDCC: Clearfil Dual Cure – chemical cured, and CDCL: Clearfil Dual Cure – light cured. Resin blocks were build up on the dentin surface. Half of samples on each group were cut to obtain resin/dentin sticks (1 × 1 mm). The other half was first submitted to thermomechanical aging. The dentin/resin sticks were submitted to microtensile bond strength test and the results were analyzed using three-way ANOVA and Tukey’s test (α = 5%).

Results: ANOVA showed significant influence for adhesive (p = 0.0000) and aging (p = 0.0001). No significant influence of the composite viscosity on bond strength was observed (ANOVA: p = 0.0861). For adhesive, the results of Tukey’s test (MPa) were CDCC: 13.44 (±5.13)a; FM: 14,01 (±2.71)a; CDCL: 14.51 (±4.98)a; FDCC: 18.66 (±7.13)b; CS3: 18.80 (±6.50)b; FDCL: 19.18 (±7.39)b. For aging: AGED: 14.99 (±6.32)a; NOT AGED: 17.87 (±5.97)b.

Conclusion: Composite resin viscosities did not influence on the bond strength. Type of cure of the adhesives had influence on the bond strength. Thermomechanical aging decreased the bond strength.     

The effect of MDP-based primer on shear bond strength of various cements to two different ceramic materials

The aim of this study was to determine the effect of 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-based primer on the shear bond strengths of thermally aged self-adhesive and conventional adhesive resin cements and zinc phosphate cement to zirconia and lithium disilicate substructures. Sixty zirconia (Z) and 60 lithium disilicate (L) disk specimens were cut from ceramic blocks. Each group was divided into six subgroups (n = 10). Half of the specimens of each ceramic group were treated with primer (P) and the other half was remained untreated. Three types of cement were applied: zinc phosphate cement [(ZPC) (Hoffmann Harmonic Shades)]; self-adhesive resin cement [(SAC) (RelyX U200)]; conventional adhesive resin cement [(CAC) (C&B)]. The specimens were subjected to thermal aging procedure for 1 week under 37 °C water bath. Shear bond strength (SBS) was determined using a universal testing machine at a crosshead speed of 1 mm/min. Data were analyzed with three-way (ANOVA). Pairwise comparisons and interactions between groups were analyzed by using Tukey’s simultaneous confidence intervals. There was no significant difference between the SBS values of SAC-Z (11,47 ± 0,47) and SAC-ZP (11,39 ± 0,42) (p > 0.05). However, the SBS values of SAC-L (12.34 ± 0,55) and SAC-LP (12,50 ± 0,49) were significantly higher than those of SAC-Z and SAC-ZP (p < 0.00). The use of primer significantly increased the SBS value of CAC-ZP (8,05 ± 0,55) when compared to the SBS value of CAC-Z (3,53 ± 0,41) (p < 0.00). Resin cement that contains methacrylate monomers with phosphoric ester functional groups exhibited reliable bond to zirconia. However, the use of an MDP-based primer may not further improve its bond strength.     

Removal of temporary cements following an immediate dentin hybridization approach: a comparison of mechanical and chemical methods for substrate cleaning

This study evaluated the microshear bond strength (μSBS) of a composite resin cement to a pre-hybridized dentinal substrate exposed to two kinds of temporary materials; the influence of different cleaning techniques was investigated. Dentinal surfaces were conditioned with an etch-and-rinse adhesive system to obtain an immediately-sealed (IDS) layer. Each surface was divided into quadrants and covered (1) with an eugenol-free (NE_Group) or (2) with a resin-based provisional agent (CL_Group). After storage, the temporary cement was removed by using one of the following methods: (1) Hand-scaler [S]; (2) Alumina air-abrasion [SB]; (3) Glycine-powder air-abrasion [Gly]; (4) D-Limonene chemical solvent [Or]. A new IDS layer was then created; polyethylene tubes were placed on dentin surfaces and filled with a dual-cure resin cement. A universal testing machine was used for the μSBS tests; conditioned surfaces were analyzed at SEM. Means and SD were calculated; a two-way ANOVA (a: 0.05) was performed to detect significant differences among groups. For NE groups, mean μSBS values (MPa) were: 21.6 ± 6.6 [NE_NoT]; 20.7 ± 4.5 [NE_Or]; 20.1 ± 6.6 [NE_SB]; 19.1 ± 5.3 [NE_S]; 17.8 ± 2.2 [NE_Gly]. No significant differences were found among tested treatments within NE (p: 0.5493). For CL groups, mean μSBS values (MPa) ranged from 15.8 ± 2.8 (CL_S50) to 19.4 ± 2.9 (CL_Gly). Cleaning of the substrate with glycine air-abrasion statistically improved μSBS values with respect to aluminum-oxide (CL_SB: 15.8 ± 2.8) or scaling (CL_S: 16.0 ± 2.4). The application of the IDS technique was effective for preservation of freshly-cut dentin from adverse effects of temporary materials. Glycine air-abrasion is suggested when a temporary resin cement is adopted.     

Adhesion of resin composite to enamel and dentin: a methodological assessment

This study compared the impact of four test methods on adhesion of resin composite to enamel and dentin. Human molars (N = 54) were randomly assigned to test the adhesion of resin composite material (Quadrant Universal LC) using one of the following test methods: (a) macroshear test (SBT; n = 16), (b) macrotensile test (TBT; n = 16), (c) microshear test (μSBT; n = 16) and (d) microtensile test (μTBT; n = 6). In a randomized manner, buccal or lingual surfaces of each tooth, were assigned as enamel or dentin substrates. Enamel and dentin surfaces were conditioned using an etch-and-rinse adhesive system (Syntac Classic). After storage (24 h, 37 °C), bond tests were conducted in a Universal Testing Machine (1 mm/min) and failure types were analyzed. Data were analyzed using Univariate and Tukey`s, Bonneferroni tests (α = 0.05). Two-parameter Weibull modulus, scale (m) and shape (0) were calculated. Test method (p < 0.001) and substrate type (p < 0.001) significantly affected the results. When testing adhesion of resin composite to enamel, SBT (25.9 ± 5.7)^a, TBT (17.3 ± 5.1)^a,c and μSBT (27.2 ± 6.6)^a,d test methods showed significantly higher mean bond values compared to μTBT (10.1 ± 4.4)^b (p < 0.05). Adhesion of resin composite to dentin did not show significant difference depending on the test method (12 ± 5.7–20.4 ± 4.8; p > 0.05). Only with SBT, significant difference was observed for bond values between enamel (25.9 ± 5.7) and dentin (12 ± 5.7; p < 0.05). Weibull distribution presented the highest shape values for enamel-μSBT (29.7) and dentin-μSBT (22.2) among substrate-test combinations. Regardless of the test method, cohesive failures in substrate were more frequent in enamel (19.1%) than in dentin (9.8%).     

Influence of silicoating,etching and heated glaze treatment on the surface of Y-TZP and its impact on bonding with veneering ceramic

The study aimed to investigate the influence of surface treatments of Y-TZP on its topography and their impact on shear bond strength (SBS) of Y-TZP to veneering porcelain. Thirty-four zirconia cubes (Cercon) (10 × 10 × 10 mm³) were divided randomly into 3 groups (n = 11) according to the different surface treatments, Silica Coating (SC); Hot Solution Etching (HE); and Heat Treatment after porcelain glaze and powder application (GP). Porcelain application (IPs e.max) was performed after surface treatment using a standardized technique. Porcelain application (Ceramco-3) was also performed on 10 metal cubes (I BOND 2) as controls (MC). Specimens were subjected to thermocycling (5–55 °C, 20,000 cycles) followed by SBS testing in a universal testing machine. Surface topography was assessed by scanning electron microscopy and surface roughness (Image J). SC developed significantly higher SBS (42.10 ± 5.84 MPa) of Y-TZP to veneering ceramics compared to treatment by HE (24.0 ± 6.4 MPa), GP (23.30 ± 4.72), and the MC (29.3 ± 5.4 MPa) control (p < 0.05). SBS among HE, GP and MC specimens was comparable (p > 0.05). Y-TZP specimens treated with SC and HE showed high surface roughness compared to GP. Silicoating of Y-TZP prior to veneering can potentially reduce the high failure rates of zirconia-based restorations by enhancing the chemical bond between the core and the veneer materials.     

Effect of timing for core preparation,luting cement type and root level on adhesion of fiber posts to intraradicular dentin

This study assessed the effect of timing of core preparation and luting cement on adhesion of fiber-reinforced composite (FRC) posts on different levels of intraradicular dentin when cemented with either conventional dual-polymerized or self-adhesive resin cement. Single-rooted human teeth (N = 80) were endodontically treated and randomly divided into 2 groups (n = 40) according to resin cement: (a) Conventional dual resin cement (Variolink II, V) or (b) Self-adhesive resin cement (RelyX U200, R). They were further divided into two subgroups according to timing of core preparation (n = 20): (a) immediate (i) or (b) delayed (d). FRC posts (Cytec Blanco) were cemented and the roots were sliced into discs at the coronal, middle, and apical levels. Push-out tests were then performed in a Universal Testing Machine (1 mm/min). Data (MPa) were analyzed using three-way ANOVA and Tukey’s tests considering the factors ‘core preparation time’, ‘luting cement’, and ‘root level’ (α = 0.05). Type of luting cement (p < 0.001), time of core preparation (p < 0.001), and root level (p < 0.001) significantly affected the bond strength results. R cement was more significantly affected by core preparation time (Ri: 2.91 ± 1.1; Rd: 4.83 ± 1.68) compared to V cement (Vi: 2.92 ± 1.63; Vd: 2.65 ± 1.6) (p < 0.05). Coronal region demonstrated significantly higher bond strength values than those of middle and apical third in all groups (coronal: 4 ± 1.9; middle: 3.1 ± 1.4; apical: 2.4 ± 1.1) (p < 0.05). Adhesive failure between cement and dentin was the most frequent (64%) followed by adhesive failure between cement and post (18%). Delayed core preparation can improve bond strength of FRC posts to intraradicular dentin when cemented with self-adhesive cement compared to conventional dual-polymerized resin cement.     

Effect of thermal cycling and low pressure sandblasting on the bond strength of a self-adhesive cement to Y-TZP zirconia

The aim of this investigation was to assess the influence of several surface treatments on the shear bond strength (SBS) of a self-adhesive resin cement containing 10-methacryloxydecyl-dihydrogenphosphate monomer to densely sintered zirconia ceramic, before and after thermal cycles. Hundred densely sintered zirconia cylinders were divided into five groups (n = 20). Each of them received a different surface treatment: (1) control [No_T], with the zirconia surface unconditioned, (2) low pressure air abrasion [Sand_S], (50 μm, 1 bar), (3) standardized air abrasion [Sand_H], (50 μm, 2.8 bar), (4) standardized Rocatec? Plus (silica-coated alumina oxide) air abrasion (2.8 bar) and silanization [Roc_H], (5) low pressure Rocatec? Plus (silica-coated alumina oxide) air abrasion (1 bar) and silanization [Roc_S]. Five more surface-treated specimens were addressed to scanning electron microscope for qualitative observations. After specimen fabrication, subgroups of 10 bonded samples were stored in water either for 24 h (T1) or subjected to 5000 thermal cycles (T2); SBSs were determined with a universal testing machine at a crosshead speed of 1 mm/min. At T1, mean SBSs (MPa) obtained for the examined groups were: [Sand_H] 16.24 ± 2.95; [Sand_S] 16.01 ± 2.68; [Roc_H] 17.17 ± 1.64; [Roc_S] 15.92 ± 1.99. All surface treatments positively affected (p < 0.05) the initial self-adhesive cement adhesion to zirconia with respect to No_T (13.29 MPa). Artificial aging decreased the bond strength in all test groups significantly, but no spontaneous debonding was observed in [No_T]: at T2, SBS values ranged from 7.76 ± 2.37 (No_T) to 8.89 ± 1.74 (Sand_S), with no statistically significant difference between groups (p = 0.5293). Both air abrasion with alumina oxide and Rocatec? universal bonding system, used with hard or low air pressure, produced comparable effects on cement–zirconia interface before and after thermal cycles. After artificial aging, minimal differences in bond strength values between sandblasted and control groups were not of statistical significance.     

Shear bond strengths of five intraoral porcelain repair systems

In fixed prosthodontics, fracture of the porcelain veneer is not an uncommon problem under clinical conditions due to, e.g., malfunction, trauma or technical failures. To avoid time-consuming and cost-intensive renewal of the entire restoration, repair of the chipped veneer is desirable. The aim of this in vitro study was to evaluate the shear bond strengths of five intraoral porcelain repair kits based on different chemical bonding systems. 45 metal plates veneered with feldspathic porcelain were fabricated. The surface treatment was performed using five porcelain repair systems based on tribochemical silica coating (Cojet), mechanical roughening (Silistor, Cimara, Ceramic Repair) or etching (Clearfil Repair) followed by application of silane coupling agents (five specimens each). Cylinders of composite resin of Charisma and Pertac Hybrid were bonded using Cojet, Silistor, Cimara and Ceramic Repair, and of Clearfil AP-X with Clearfil Repair onto the porcelain specimens. After thermocycling (5000 cycles, 5–55°C) shear bond strength was measured according to ISO 10477 followed by assessment of the failure mode. Statistical analysis was carried out with one-way ANOVA and Bonferroni–Dunn's multiple comparisons post-hoc analysis for test groups (α = 0.05). Shear bond strengths higher than 10 MPa were found for all test groups except for Ceramic Repair with Pertac Hybrid (8.1 ±1.3 MPa), which was significantly lower than all other groups (P < 0.05). Highest shear bond strength was found for Silistor with Charisma (23.1 ± 5.8 MPa), which was significantly higher (P < 0.05) than all other groups except Cojet with Charisma (17.8 ± 3.6 MPa) and Clearfil Repair (20.3 ± 5.0 MPa). Cojet and Silistor with Charisma, Cimara, as well as with Clearfil mainly showed cohesive or mixed failure modes (cohesive and interfacial). Bond strengths of the combinations Silistor-Charisma, Clearfil Repair-Clearfil AP-X and Cojet-Charisma were superior to all other combinations used in the present tests.     

Post-treatment with high-power lasers to improve bond strength of adhesive systems to bleached dentin

To assess the effect of Er:YAG and diode lasers on the shear bond strength (SBS) of adhesive systems to bovine dentin submitted to bleaching with a high concentration agent. One hundred and twenty bovine dentin fragments were used. Fragments were distributed into 12 groups (n = 10) considering the bleaching (present or not), surface post-treatment (untreated, Er:YAG laser or diode laser) and adhesive system (total-etching or self-etching). Specimens received two applications of 38% hydrogen peroxide. Er:YAG laser (2940 nm, 200 mJ, 4 Hz) and diode laser (980 nm, 1.5 W) were applied for 15 s on bleached dentin surface. Restoration was performed with resin using split matrix. Specimens were submitted to SBS test and data (MPa) were analyzed by ANOVA and Tukey’s test (α = 0.05). SBS of bleached specimens decreased in comparison with non-bleached (p < 0.05). The highest values were obtained for the post-treatment with Er:YAG laser (p < 0.05). Total-etching adhesive was superior to self-etching system (p < 0.05). The irradiation of bleached dentin with Er:YAG laser followed by the application of the total-etching adhesive had similar SBS to unbleached dentin with no post-treatment (control) (p > 0.05). Er:YAG laser post-treatment followed by the total-etching adhesive system improve the bond strength of restorative material to bleached dentin.     

Adhesion of orthodontic brackets to indirect laboratory-processed resin composite as a function of surface conditioning methods and artificial aging

This study compared the shear bond strength of orthodontic brackets to laboratory-processed indirect resin composites (IRC) after different surface conditioning methods and aging. Specimens made of IRC (Gradia Indirect, GC) (thickness: 2 mm; diameter: 10 mm) (N = 80) were randomly assigned to one of the following surface conditioning methods: C – Control: no treatment; AA – Air-abrasion (50 μm Al₂O₃ particles); DB – Diamond bur and HF – Etching with hydrofluoric acid (9.6%). After adhesive primer application (Transbond XT), orthodontic brackets were bonded to the conditioned IRC specimens using adhesive resin (Transbond XT). Following storage in artificial saliva for 24 h at 37 °C, the specimens were thermocycled (×1000, 5–55 °C). The IRC–bracket interface was loaded under shear in a Universal Testing Machine (0.5 mm/min). Failure types were classified using modified adhesive remnant index criteria. Data were analyzed using two-way ANOVA and Tukey`s HSD (α = 0.05). Surface conditioning method did not significantly affect the bond strength results (p = 0.2020), but aging significantly decreased the results (p = 0.04). Interaction terms were not significant (p = 0.775). In both non-aged and aged conditions, non-conditioned C group presented the lowest bond strength results (MPa) (p < 0.05). In non-aged conditions, surface conditioning with DB (8.03 ± 0.77) and HF (7.87 ± 0.64) showed significantly higher bond strength results compared to those of other groups (p < 0.05). Thermocycling significantly decreased the mean bond strength in all groups (2.24 ± 0.36–6.21 ± 0.59) (p < 0.05). The incidence of Score 5 (all adhesive resin remaining on the specimen) was the highest in HF group without (80%) and with aging (80%) followed by DB (40, 70%, respectively). C groups without and with aging showed exclusively Score 1 type (no adhesive resin on the specimen) of failures indicating the least reliable type of adhesion.     

Effect of aging type and aged unit on the repair strength of resin composite to feldspathic porcelain in testing microtensile bond strength

The aim of the present study is to investigate the effect of aging type (thermocycling vs. water storage) and aged unit (block vs. stick) on the repair strength of resin composite to feldspathic porcelain in testing microtensile bond strength (μTBS). Ceramic specimens (N = 30) (10 × 5.7 × 4.5 mm³, Vita Mark II, Vita) were obtained from CAD–CAM blocks. One surface was etched with 10% HF and silanized. An adhesive was applied and resin composite blocks were constructed incrementally on the conditioned surface. The specimens were randomly divided into five groups (n = 6): Control (C): Non-aged; BTC: Blocks were thermocycled (5–55 °C, 6000 cycles); STC: Sticks were thermocycled; BS: Blocks aged in water storage (6 months) after themocycling; SS: Blocks aged in water storage (6 months) after thermocycling. After μTBS test, failure types were classified. Data (MPa) were statistically analyzed (1-way and Dunett and 2-way ANOVA, Tukey`s) (α = 0.05). Two-parameter Weibull distribution values including the Weibull modulus, scale (m), and shape (0) values were calculated. Aging type (p = 0.009) and aged unit (p = 0.000) significantly affected the results. Interaction terms were also significant (p = 0.000). Considering the stick level, there was no significant difference between thermocycling (STC: 25.7 ± 2.3) and water storage (SS: 25.3 ± 3.8) (p > 0.05) but the results were significantly higher when blocks were thermocycled (BTC: 31.6 ± 2.9) (p < 0.05). Weibull modulus and characteristic strength was the highest in BTC (m = 4.2; σ_o: 34.4) among all other groups (m = 3–3.9; σ_o: 14.6–28.5). Adhesive failures were common and cohesive failures occurred in less than 5% in all groups. Aging protocol was detrimental on durability of repair strength of resin composite to feldspathic porcelain. Exposing the sticks to either thermocycling or water storage aging should be considered in in vitro studies.     

Effects of cavity disinfectants on bond strength of an etch-and-rinse adhesive to water- or ethanol-saturated sound and caries-affected dentin

Objective: To evaluate the effect of cavity disinfectants on the immediate microtensile bond strength (μTBS) of an etch-and-rinse adhesive to water- and ethanol-saturated sound and caries-affected dentin (CAD). Material and Methods: Thirty-six human molars were sectioned to expose 1/3 of the mid-coronal dentin surface. Sound (n = 18) and CAD (n = 18) specimens were divided into six groups each (n = 3): one positive control (sound), one negative control (CAD), and five experimental groups each. In the control group, dentin surfaces were bonded using an etch-and-rinse adhesive with a traditional water-wet bonding technique. In the experimental groups, ozone was applied before etching and chlorhexidine after etching. In the ethanol-wet bonding groups, acid-etched dentin surfaces were treated with ethanol. Following adhesive application and composite buildups, bonded specimens were sectioned to form sticks. Failure modes were analyzed using a stereomicroscope. Results: The water-wet bonded sound control group yielded the highest μTBS among all groups (p < 0.001). The lowest μTBS values were observed in the ozone groups (p < 0.05). The ethanol-wet bonded CAD group exhibited a higher μTBS than the water-wet bonded negative controls. Although compared to the positive control, chlorhexidine decreased the μTBS (p < 0.05), an increase with no significant difference was observed in the negative control (p > 0.05). Conclusions: The μTBS values of CAD were lower than those of sound dentin. Ethanol-wet bonding improved the μTBS of CAD. Ozone application reduced the μTBS in both sound and CAD; chlorhexidine improved the immediate μTBS after etching in CAD.     

Effect of surface conditioning methods,adhesive systems and resin composite on repair strength of dimethacrylate and silorane resin composites

This study evaluated the effect of surface conditioning methods and adhesive systems on the repair bond strength of resin composites. Specimens (FLS: Filtek LS) (N = 144) were prepared using a silicone matrix. The specimens were stored in distilled water and then were randomly divided into the twelve groups (n = 12) according to the surface conditioning method (unground or diamond bur) and adhesive system (no adhesive, LS: Filtek LS, AS: Adper Scotchbond SE Plus) and resin composite (FLS: Filtek LS; FS: Filtek Supreme). The specimens were fixed in an hourglass-shaped silicone matrix and the other half of the specimen was restored. Hourglass-shaped specimens (n = 12) were used as positive control to measure the cohesive strength of the resin composite (Filtek LS). Microtensile bond test was performed (0.5 mm/min) and failure types were analyzed. Data were analyzed using two-way analysis of variance, Tukey’s and Dunnett’s tests (α = 0.05). Adhesive protocol and resin composite significantly affected the results (p < 0.05). For the FS composite, the highest results were obtained using LS adhesive with (18.4 ± 7.7) and without (18.8 ± 4.8) bur roughening. For FLS composite, the highest results were obtained using AS adhesive with (33.2 ± 7.1) and without (25.7 ± 3.6) bur roughening. Without the use of adhesive resin, significantly lower bond strength results were observed with both LS (5 ± 2.1, 4.5 ± 1.5) and FLS (2.2 ± 1.2, 4.4 ± 1.1) for unground and diamond bur roughened groups, respectively (p < 0.0001). Cohesive strength of the FLS (52.3 ± 7.6) was significantly higher than any of the repaired groups (p < 0.0001). FS–LS combination and the groups repaired without adhesive presented more adhesive (Type I) failures.     

Shear bond strength to dentine of dental adhesives containing hydroxyapatite nano-fillers

The aim of this study was to compare the effect of hydroxyapatite (HAP) nano-rods (HAP_rods) and HAP nano-sticks (HAP_sticks) added to commercial adhesives on the macro-shear bond strength (SBS) to dentine and morphology of the adhesive–dentine interface. HAP was added to Single Bond Universal (SBU, 3M ESPE) and Te-Econom Bond (TeE; Ivoclar Vivadent), in the form of water suspensions to avoid agglomeration of nano-particles and to achieve HAP concentrations of 0.5, 1.0 and 1.5 wt%. Following a ‘total-etch’ or a ‘self-etch’ protocol, the adhesives were applied to flat dentine surface of 162 intact human, third molars (N = 6/group). Composite (Z250, 3M ESPE) was built-up using a split stainless steel mould, 3 mm in diameter. SBS was tested using a universal testing machine at 1 mm/min until fracture. Data were statistically analysed using two-way and one-way analysis of variance with Tukey’s post-test (α = 0.05). HAP_rods had no significant effect on SBS of the tested adhesives while HAP_sticks improved bond strength to dentine only of adhesives applied following the ‘total-etch’ total-etch protocol. SBS values of SBU containing 1% HAP_sticks (15.10 ± 2.96 MPa) and TeE containing 0.5% HAP_sticks applied following the total-etch protocol (12.96 ± 4.48 MPa) were higher than those of their respective control groups (10.36 ± 2.68 and 7.97 ± 3.64 MPa). Samples with higher SBS showed more ‘mixed’ failures. HAP nano-fillers may improve bond strength of total-etch adhesives without an adverse effect on adhesive dispersion on dentine and its ability to infiltrate dentinal tubules.     

Effect of cigarette smoking on the bond strength between resin cement and dental CAD/CAM ceramics

Although the effects of cigarette smoking on several dental problems have been widely studied, the association between tobacco exposure and resin-ceramic bonding is rarely reported. This study investigated the resin-ceramic adhesion (shear bond strength, SBS) and associated risk factors on three selected dental CAD/CAM ceramics using a novel model to simulate the exposure to cigarette smoking. Specimens from IPS e.max® CAD, Vitabloc® Mark II for Cerec and Zirconia Cercon were prepared and treated using silicacoating and silane. A layer of resin cement was applied on the treated ceramic surfaces and light activated. Specimens were placed in a chamber and challenged with various numbers of cigarettes (0, 1, 5, 10, and 15). Then, the specimens were subjected to SBS test and fractured surfaces were examined using scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDX) to determine the failure mode and surface composition. Overall, the mean SBS of IPS e.max^® CAD (9.6 ± 3.4 MPa), Vitabloc^® Mark II for Cerec (9.3 ± 2.5 MPa) and Zirconia Cercon (8.7 ± 3.0 MPa) did not show any statistical significant difference (p = 0.192 > 0.05), such that the adhesion of resin bonded to glass-based ceramics (IPS e.max® CAD and Vitabloc® Mark II for Cerec) decreased with cigarette smoke exposure, but increased for the resin bonded to zirconia ceramic (Zirconia Cercon). Furthermore, the number of cigarettes has a statistically significant effect on the SBS (p = 0.001), such that in general 5 cigarettes yielded the lowest mean SBS (7.6 ± 2.1 MPa). SEM-EDX analyses showed mostly adhesive failures in all experimental groups with changes in surface morphology and chemical composition after smoking challenge. Cigarette smoking produces a different effect on resin-ceramic bonding depending on ceramic type that may be due to chemical reactions in the bonding interface and changes in temperature and moisture. Further work should explore the mechanism to which cigarette smoke affects the resin-ceramic bonding and its clinical relevance.     

The shear bond strength of repaired high-viscosity bulk-fill resin composites with different adhesive systems and resin composite types

This study compared the effect of different adhesive systems and composite resins on the shear bond strength (SBS) of repaired high-viscosity bulk-fill composites(Tetric EvoCeram Bulk Fill) and investigated failure modes. One hundred twenty cylindrical bulk-fill composite blocks (diameter 5?mm) were fabricated and thermocycled for 5000 cycles (5–55?°C). Specimens were roughened by diamond bur and divided into 8 groups (n?=?15). Bulk-fill blocks were repaired with the same material or nanohybrid composite resin(Tetric EvoCeram Nanohybrid) (diameter 3?mm) using different adhesive systems:Tetric N-Bond Universal (TSE);37% phosphoric acid etching?+?Tetric N-Bond Universal (TER); Clearfil SE Bond (CSE); 37% phosphoric acid etching?+?Adper^TMSingle Bond 2(SB). After repair procedures, all specimens were thermocycled again. The shear bond strengths were measured for all specimens using a universal test machine (crosshead speed of 1?mm/min). Cohesive strengths of bulk-fill composites were measured and described as control group. Debonded surfaces were observed with a stereomicroscope under 10x magnification to determine mode of failure. The SBS data of all groups was statistically analyzed by two-way ANOVA and Bonferroni correction test (p?<?0.05). The specimens repaired with bulk-fill composites showed significantly higher SBS values (25.86?±?5.74, 27.05?±?4.93, 24.49?±?6.95MPa) than those with nanohybrid composites (20.41?±?3.70, 22.08?±?6.37, 18.74?±?6.40?MPa) for TER,CSE,SB, respectively (p?<?0.05). There were no significant differences in SBS according to the type of adhesive systems for both repair materials (p?>?0.05). The predominant mode of failure was a mixed type in the restorative material except for the ones repaired with nanohybrid composites using Adper^TMSingle Bond 2. High-viscosity bulk-fill composites could be successfully repaired with the same materials. SBS of repaired bulk-fill composites reached cohesive strength for all tested groups.