Shear bond strength of repairs in porcelain conditioned with laser

The aim of this study was to evaluate the shear bond strength of repairs in porcelain conditioned with laser. Sixty porcelain discs were made and six groups were formed (n = 10): G1: conditioning with laser with potency 760 mW; G2: conditioning with laser with potency 760 mW and application of 37% phosphoric acid for 15 s; G3: conditioning with laser with potency 900 mW; G4: conditioning with laser with potency 900 mW and application of 37% phosphoric acid for 15 s; G5: application of 37% phosphoric acid for 15 s (group control) and G6: application of 10% hydrofluoric acid for 2 min. The composite resin was insert of incremental layers at the porcelain surface aided with a metal matrix, and photoactivation for 20 s each increment. The specimens were submitted to a thermal cycling by 1000 cycles of 30 s in each bath with temperature between 5 and 55 degrees C. After the thermal cycling, specimens were submitted to the shear bond strength. The results were evaluated statistically through analysis of variance and Tukey's tests with 5% significance. The averages and standard deviation founded were: G1, 11.25 (+/- 3.10); G2, 12.32 (+/- 2.65); G3, 14.02 (+/- 2.38); G4, 13.44 (+/- 2,07); G5, 9.91 (-/+ 2,18); G6, 12.74 (+/- 2.67). The results showed that the femtosecond laser produced a shear bond strength of repairs in porcelain equal to the hydrofluoric acid and significantly superior to the use of phosphoric acid. Microsc. Res. Tech., 2012. (C) 2012 Wiley Periodicals, Inc.

Evaluation of Chemical Treatment on Zirconia Surface with Two Primer Agents and an Alkaline Solution on Bond Strength

Objectives: This study evaluated the effect of an alkaline solution and two 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-based primer agents on bond strength to zirconia (yttria-stabilized tetragonal zirconium polycrystal [Y-TZP]) through the shear bond strength (SBS) test. Materials and Methods: Sixty square-shaped Y-TZP samples were embedded in an acrylic resin mold, polished, and randomly assigned to one of six groups (n=10) according to treatment surface: group CR, no treatment (control); group NaOH, 0.5 M NaOH; group AP, Alloy Primer; group ZP, Z-Primer Plus; group NaOH-AP, 0.5 M NaOH + Alloy Primer; and group NaOH-ZP, 0.5 M NaOH + Z-Primer Plus. The resin cement (Rely X U100) was applied inside a matrix directly onto the Y-TZP surface, and it was light-cured for 40 seconds. The samples were stored in distilled water at 37 C for 24 hours prior to the test, which was performed in a universal machine at a crosshead-speed of 0.5 mm/min. The data were analyzed by one-way analysis of variance and Tukey tests (p<0.05). Light stereomicroscopy and scanning electron microscopy were used to assess the surface topography and failure mode. Results: The SBS was significantly affected by the chemical treatment (p<0.0001). The AP group displayed the best results, and the use of NaOH did not improve SBS results relative to either AP or ZP. The samples treated with Alloy Primer displayed mainly mixed failures, whereas those conditioned with Z-Primer Plus or with 0.5 M NaOH presented a balanced distribution of adhesive and mixed failure modes. Conclusions: The use of a NaOH solution may have modified the reactivity of the Y-TZP surface, whereas the employment of a MDP/6-4-vinylbenzyl-n-propyl amino-1,3,5-triazine2,4-dithione-based primer enhanced the Y-TZP bond strength.

Thermo and mechanical cycling and veneering method do not influence Y-TZP core/veneer interface bond strength

Objectives: The purpose of this study was to evaluate the influence of thermal and mechanical cycling and veneering technique on the shear bond strength of Y-TZP (yttrium oxide partially stabilized tetragonal zirconia polycrystal) core–veneer interfaces. Materials and methods: Cylindrical Y-TZP specimens were veneered either by layering (n = 20) or by pressing technique (n = 20). A metal ceramic group (CoCr) was used as control (n = 20). Ten specimens for each group were thermal and mechanical cycled and then all samples were subjected to shear bond strength in a universal testing machine with a 0.5 mm/min crosshead speed. Mean shear bond strength (MPa) was analysed with a 2-way analysis of variance and Tukey’s test ( p < 0.05). Failure mode was determined using stereomicroscopy and scanning electron microscopy (SEM). Results: Thermal and mechanical cycling had no influence on the shear bond strength for all groups. The CoCr group presented the highest bond strength value ( p < 0.05) (34.72 7.05 MPa). There was no significant difference between Y-TZP veneered by layering (22.46 2.08 MPa) or pressing (23.58 2.1 MPa) technique. Failure modes were predominantly adhesive for CoCr group, and cohesive within veneer for Y-TZP groups. Conclusions: Thermal and mechanical cycling, as well as the veneering technique does not affect Y-TZP core–veneer bond strength. Clinical significance: Different methods of veneering Y-TZP restorations would not influence the clinical performance of the core/veneer interfaces.

Chlorhexidine does not increase immediate bond strength of etch-and-rinse adhesive to caries-affected dentin of primary and permanent teeth

The aim of this study was to evaluate the effect of 2% chlorhexidine digluconate (CHX) on immediate bond strength of etch-and-rinse adhesive to sound (SD) and caries-affected (CAD) primary dentin compared with permanent dentin. Flat dentin surfaces from 20 primary molars (Pri) and 20 permanent molars (Perm) were assigned to 8 experimental groups (n=5) according to tooth type (Pri or Perm), dentin condition (SD or CAD - pH-cycling for 14 days) and treatment (control - C or 60 s application of 2% CHX solution after acid etching - CHX). The bonding system (Adper Single Bond 2) was applied according to manufacturer's instructions followed by resin composite application (Filtek Z250). After 24 h water storage, specimens with cross-section area of 0.8 mm² were prepared for being tested under microtensile test (1 mm/min). Data were submitted to ANOVA and Tukey's post hoc test (α=0.05). Failure mode was evaluated using a stereomicroscope at ×400. Treatment with CHX did not result in higher bond strength values than no pre-treatment (C groups), independently of tooth type. Primary teeth and caries-affected dentin showed significantly lower (p<0.05) bond strength means compared with permanent teeth and sound dentin, respectively. Predominance of adhesive/mixed failure was observed for all groups. CHX did not influence the immediate bond strength to sound or caries-affected dentin of primary and permanent teeth.

Influence of alloy microstructure on the microshear bond strength of basic alloys to a resin luting cement

The aim of this study was to evaluate the influence of microstructure and composition of basic alloys on their microshear bond strength (µSBS) to resin luting cement. The alloys used were: Supreme Cast-V (SC), Tilite Star (TS), Wiron 99 (W9), VeraBond II (VBII), VeraBond (VB), Remanium (RM) and IPS d.SIGN 30 (IPS). Five wax patterns (13mm in diameter and 4mm height) were invested, and cast in a centrifugal casting machine for each basic alloy. The specimens were embedded in resin, polished with a SiC paper and sandblasted. After cleaning the metal surfaces, six tygon tubes (0.5 mm height and 0.75 mm in diameter) were placed on each alloy surface, the resin cement (Panavia F) was inserted, and the excess was removed before light-curing. After storage (24 h/37°C), the specimens were subjected to µSBS testing (0.5 mm/min). The data were subjected to a one-way repeated measures analysis of variance and Turkey's test (α=0.05). After polishing, their microstructures were revealed with specific conditioners. The highest µSBS (mean/standard deviation in MPa) were observed in the alloys with dendritic structure, eutectic formation or precipitation: VB (30.6/1.7), TS (29.8/0.9), SC (30.6/1.7), with the exception of IPS (31.1/0.9) which showed high µSBS but no eutectic formation. The W9 (28.1/1.5), VBII (25.9/2.0) and RM (25.9/0.9) showed the lowest µSBS and no eutectic formation. It seems that alloys with eutectic formation provide the highest µSBS values when bonded to a light-cured resin luting cement.

Shear bond strength of nanofilled flowable resins used for indirect bracket bonding

AIM: To evaluate the bond strength of brackets fixed with different materials (two light-cured nanofilled resins - Transbond Supreme LV and Flow Tain LV, a light-cured resin - Transbond XT (control) and two chemically cured resins for indirect bonding - Sondhi Rapid- Set and Custom I.Q.) using the indirect bonding technique after 10 min and 24 h, and evaluate the type of failure. METHODS: One hundred premolars were selected and randomly divided into groups (n=10) according to the material and fixation period. The brackets were bonded through the indirect technique following the manufacturer's instructions and stored in deionized water at 37°C for 10 min or 24 h. After, the specimens were submitted to a shear bond strength (SBS) test (Instron) at 0.5 mm/min and evaluated for adhesive remnant index (ARI). The data were submitted to ANOVA and Tukey's test (p<0.05) and the ARI scores were submitted to the chi-square test. RESULTS: It could be observed a significant difference among the materials (Flow Tain LV = Transbond Supreme LV = Transbond XT> Sondhi Rapid-Set > Custom I.Q.). There was no significant difference in resistance values between 10 min and 24 h, regardless of the materials. Most groups showed adhesive remaining adhered to the enamel (scores 2 and 3) without statistically significant difference (p>0.05). CONCLUSIONS: It was concluded that the light-cured nanofilled materials used in indirect bonding showed greater resistance than the chemically cured materials. The period of fixation had no influence on the resistance for different materials.

Shear bond strength of resin cements to human dentin

OBJECTIVES: The objectives of this in vitro study were (1) to assess the bond strength of the universal cement RelyX Unicem to dentin and to compare it with three conventional resin cements, (2) to test the influence of aging on their bonding capacity and (3) to test the influence of the operator on bonding quality by performing the same test in two different centers. METHODS: 160 third molars, divided into 80 for tests at the University of Zurich (Z) and 80 for tests at the University of Berne (B), were assigned to 2 x 8 subgroups of 10 teeth each. The specimens were prepared with the corresponding bonding agents and acrylic rods were luted either with RelyX Unicem (U), RelyX ARC (A), Multilink (M) or Panavia 21 (P). All specimens were stored in water for 24h (W) and half of the specimens were subjected to 1500 cycles of thermocycling (5 degrees C and 55 degrees C) (T). Bond strength was measured by means of a shear test. RESULTS: After water storage RelyX Unicem exhibited lowest bond strength (UWZ: 9.2+/-1.6 MPa, UWB: 9.9+/-1.2 MPa, AWZ: 15.3+/-6.0 MPa, AWB: 12.2+/-4.3 MPa, MWZ: 15.6+/-3.3 MPa, MWB: 12.4 MPa+/-2.4, PWZ: 13.4+/-2.9 MPa, PWB: 14.9+/-2.6 MPa). Thermocycling affected the bonding performance of all four cements. However, bond strength of RelyX Unicem was least influenced by thermocycling (UTZ: 9.4+/-2.9 MPa, UTB: 8.6+/-1.3 MPa, ATZ: 11.4+/-6.3 MPa, ATB: 13.3+/-3.7 MPa, MTZ: 15.4+/-3.1 MPa, MTB: 10.3+/-2.4 MPa, PTZ: 11.1+/-2.8 MPa, PTB: 11.3+/-2.8 MPa). SIGNIFICANCE: Although the bond strength of RelyX Unicem to dentin was lower in comparison to RelyX ARC, Multilink and Panavia 21, its bond strength was less sensitive to variations in handling and aging.

Temporary zinc oxide-eugenol cement: eugenol quantity in dentin and bond strength of resin composite

Uptake of eugenol from eugenol-containing temporary materials may reduce the adhesion of subsequent resin-based restorations. This study investigated the effect of duration of exposure to zinc oxide–eugenol (ZOE) cement on the quantity of eugenol retained in dentin and on the microtensile bond strength (μTBS) of the resin composite. The ZOE cement (IRM Caps) was applied onto the dentin of human molars (21 per group) for 1, 7, or 28 d. One half of each molar was used to determine the quantity of eugenol (by spectrofluorimetry) and the other half was used for μTBS testing. The ZOE-exposed dentin was treated with either OptiBond FL using phosphoric acid (H3PO4) or with Gluma Classic using ethylenediaminetetraacetic acid (EDTA) conditioning. One group without conditioning (for eugenol quantity) and two groups not exposed to ZOE (for eugenol quantity and μTBS testing) served as controls. The quantity of eugenol ranged between 0.33 and 2.9 nmol mg−1 of dentin (median values). No effect of the duration of exposure to ZOE was found. Conditioning with H3PO4 or EDTA significantly reduced the quantity of eugenol in dentin. Nevertheless, for OptiBond FL, exposure to ZOE significantly decreased the μTBS, regardless of the duration of exposure. For Gluma Classic, the μTBS decreased after exposure to ZOE for 7 and 28 d. OptiBond FL yielded a significantly higher μTBS than did Gluma Classic. Thus, ZOE should be avoided in cavities later to be restored with resin-based materials.

Effect of tin-chloride pretreatment on bond strength of two adhesive systems to dentin

OBJECTIVES: To determine the effect on resin composite-to-dentin bond strength of incorporation of an acidic tin-chloride pretreatment in two adhesive systems. MATERIALS AND METHODS: Human molars were ground to expose mid-coronal dentin. For microtensile bond strength (μTBS) testing, dentin was treated with Optibond FL or Clearfil SE according to one of six protocols (n = 22/group). Group 1: Phosphoric acid etching, Optibond FL Prime, Optibond FL Adhesive (manufacturer's instructions; control); Group 2: Tin-chloride pretreatment, Optibond FL Prime, Optibond FL Adhesive; Group 3: Phosphoric acid etching, tin-chloride pretreatment, Optibond FL Prime, Optibond FL Adhesive; Group 4: Clearfil SE Primer, Clearfil SE Bond (manufacturer's instructions; control); Group 5: Phosphoric acid etching, Clearfil SE Primer, Clearfil SE Bond; and Group 6: Tin-chloride pretreatment, Clearfil SE Primer, Clearfil SE Bond. The molars were then built up with resin composite (Clearfil Majesty Esthetic). After storage (1 week, 100  % humidity, 37 °C) the μTBS was measured and failure mode was determined. Additionally, pretreated dentin surfaces were evaluated using SEM and EDX. The μTBS results were analyzed statistically by a Welch Two Sample t-test and a Kruskal-Wallis test followed by exact Wilcoxon rank sum tests with Bonferroni-Holm adjustment for multiple testing (α = 0.05). RESULTS: When Optibond FL was used, partial or total replacement of phosphoric acid with tin-chloride decreased μTBS significantly. In contrast, when Clearfil SE was used, inclusion of a tin-chloride pretreatment in the adhesive procedure increased μTBS significantly. CONCLUSIONS: Tin-chloride pretreatment had a beneficial influence on the bond promoting capacity of the MDP-containing adhesive system Clearfil SE.

Does tin pre-treatment enhance the bond strength of adhesive systems to enamel?

OBJECTIVES The study investigated the modification of composite-to-enamel bond strength by pre-treatment of enamel with a concentrated, acidic SnCl2-solution. METHODS Six groups of flat human enamel specimens (n=44 per group) were treated as follows: OB-H: H3PO4 etching, Optibond FL application (primer+adhesive; manufacturer's instructions); OB-S: SnCl2 pre-treatment, Optibond FL application (primer+adhesive); OB-HS: H3PO4 etching+SnCl2 pre-treatment, Optibond FL application (primer+adhesive); CF-N: Clearfil SE application (primer+bond; manufacturer's instructions); CF-H: H3PO4 etching, Clearfil SE application (primer+bond); CF-S: SnCl2 pre-treatment, Clearfil SE application (primer+bond). Enamel specimens were then built up with resin composite (Clearfil Majesty Esthetic) and stored (100% humidity, 37 °C, 1 week). μTBS-measurement and failure mode analysis of one-half of the specimens were performed immediately after storage, while the other half was analysed after a thermocycling procedure (8500 cycles; 5 °C and 55 °C; dwell time 30s). Additional specimens were prepared for SEM- and EDX-analysis. RESULTS Highest values were measured for OB-H before and after thermocycling, lowest values for CF-N. Compared to OB-H treatment, OB-S treatment reduced μTBS before/after thermocycling by 23%/28% and OB-HS treatment by 8%/24% (except for OB-SH before (n.s.), all p≤0.001 compared to OB-H). In the Clearfil SE treated groups pre-treatment increased μTBS significantly compared to CF-N (before/after: CF-H: +46%/+70%; CF-S: +51%/42%; all p≤0.001). CONCLUSION Pre-treatment with H3PO4 or SnCl2 markedly increased the μTBS of Clearfil SE to enamel. However, thermocycling partly reduced the gain in μTBS obtained by SnCl2 pre-treatment. CLINICAL SIGNIFICANCE The application of an acidic and highly concentrated SnCl2 solution is a good option to increase the μTBS between enamel and a resin composite mediated by an adhesive system containing the multifunctional monomer MDP.

Bond strength of adhesives to dentin contaminated with smoker's saliva.

The purpose of this study was to determine the effects of contamination with smoker's and non-smoker's saliva on the bond strength of resin composite to superficial dentin using different adhesive systems. The interfacial structure between the resin and dentin was evaluated for each treatment using environmental scanning electron microscopy (ESEM). Freshly extracted human molars were ground with 600-grit SiC paper to expose the superficial dentin. Adhesives [One-Up-Bond-F-Plus (OUFP) and Adper-Prompt-L-Pop (APLP)] and resin composite (TPHSpectrum) were bonded to the dentin (n = 8/group, 180 total specimens) under five surface conditions: control (adhesive applied following manufacturers' instructions); saliva, then 5-s air dry, then adhesive; adhesive, saliva, 5-s air dry; adhesive, saliva, 5-s water rinse, 5-s air dry (ASW group); and adhesive, saliva, 5-s water rinse, 5-s air dry, reapply adhesive (ASWA group). After storage in water at 37 degrees C for 24 h, the specimens were debonded under tension at a speed of 0.5 mm/min. ESEM photomicrographs of the dentin/adhesive interfaces were taken. Mean bond strength ranged from 8.1 to 24.1 MPa. Fisher's protected least significant difference (P = 0.05) intervals for critical adhesive, saliva, and surface condition differences were 1.3, 1.3, and 2.1 MPa, respectively. There were no significant differences in bond strength to dentin between contamination by smoker's and nonsmoker's saliva, but bond strengths were significantly different between adhesive systems, with OUFP twice as strong as APLP under almost all conditions. After adhesive application and contamination with either smoker's or nonsmoker's saliva followed by washing and reapplication of the adhesive (ASWA group), the bond strength of both adhesive systems was the same as that of the control group.

Shear bond strength of four different esthetic brackets.

Citation only

Influence of blood contamination on bond strength of a self-etching system.

OBJECTIVES: To detect the influence of blood contamination (BC) on the bond strength (BS) of a self-etching bonding system (SES) to enamel and dentine. METHODS: 25 human molars were longitudinally sectioned on the mesio-distal axis in order to obtain 50 specimens, which were embedded in acrylic resin. At first, the specimens were ground to expose a flat surface of enamel, and a bond strength test was performed. Afterwards, the samples were ground again in order to obtain a flat surface of dentine. Ten groups (total: n=100) were assigned according to substrate (enamel and dentine), step in the bonding sequence when contamination occurred (before the acidic primer and after the bonding resin), and contamination treatment (dry or rinse and dry procedure). Fresh human blood was introduced either before or after SES application (Clearfil SE Bond) and treated with air drying, or by rinsing and drying following application. Composite resin (Filtek Z-250,3M ESPE) was applied as inverted, truncated cured cones that were debonded in tension. RESULTS: The mean tensile BS values (MPa) for enamel/dentine were 19.4/23.0 and 17.1/10.0 for rinse-and-dry treatment (contamination before and after SES, respectively); while the measurements for the dry treatment, 16.2/23.3 and 0.0/0.0 contamination before and after SES, respectively. CONCLUSIONS: It was determined that blood contamination impaired adhesion to enamel and dentine when it occurred after bond light curing. Among the tested contamination treatments, the rinse-and-dry treatment produced the highest bond strength with BC after SES application, but it was not sufficient to recover the BS in the contamination-free group.

Increment thickness versus dentin bond strength of bulk fill flowables

Objectives: The aim was to investigate the influence of increment thickness on shear bond strength (SBS) to dentin of a conventional and two bulk fill flowable composites. Methods: A total of 135 specimens of ground human dentin were produced (n=15/group; 3 increment thicknesses; 3 flowable composites) and the dentin surfaces were treated with the adhesive system OptiBond FL (Kerr) according to manufacturer’s instructions. Split Teflon molds (inner diameter: 3.6 mm) of 2 mm, 4 mm, or 6 mm height allowing three increment thicknesses were clamped on the dentin surfaces and filled with either the conventional flowable Filtek Supreme XTE ((XTE); 3M ESPE) or the bulk fill flowables Filtek Bulk Fill ((FBF); 3M ESPE) or SDR ((SDR); DENTSPLY Caulk). The flowable composites were light-cured for 20 s (Demi LED; Kerr) and the specimens stored for 24 h (37°C, 100% humidity). Specimens were then subjected to a SBS-test in a universal testing machine at a cross-head speed of 1 mm/min (Zwick Z010; Zwick GmbH & Co.). SBS-values were statistically analysed with a nonparametrical ANOVA followed by exact Wilcoxon rank sum tests (α=0.05). Failure mode of the specimens was determined under a stereomicroscope at 25× magnification. Results: SBS-values (MPa) at 2 mm/4 mm/6 mm increment thicknesses (mean value [standard deviation]) were for XTE: 18.8 [2.6]/17.6 [1.6]/16.7 [3.1], for FBF: 20.6 [2.7]/17.8 [2.7]/18.7 [2.9], and for SDR: 21.7 [2.6]/18.5 [2.6]/20.3 [3.0]. For all three flowable composites, 2 mm increments yielded the highest SBS-values whereas for increments of 4 mm and 6 mm no differences were detected. All specimens presented failure modes involving cohesive failure in dentin. Conclusion: The influence of increment thickness on dentin SBS was less pronounced than expected. However, the high number of cohesive failures in dentin, reflecting the efficiency of the adhesive system, suggests a limited discriminatory power of the SBS-test.

Influence of increment thickness on microhardness and dentin bond strength of bulk fill resin composites

OBJECTIVES To investigate the influence of increment thickness on Vickers microhardness (HV) and shear bond strength (SBS) to dentin of a conventional and four bulk fill resin composites. METHODS HV and SBS were determined on specimens of the conventional resin composite Filtek Supreme XTE (XTE) and the bulk fill resin composites SDR (SDR), Filtek Bulk Fill (FBF), x-tra fil (XFIL), and Tetric EvoCeram Bulk Fill (TEBF) after 24h storage. HV was measured either as profiles at depths up to 6mm or at the bottom of 2mm/4mm/6mm thick resin composite specimens. SBS of 2mm/4mm/6mm thick resin composite increments was measured to dentin surfaces of extracted human molars treated with the adhesive system OptiBond FL, and the failure mode was stereomicroscopically determined at 40× magnification. HV profiles and failure modes were descriptively analysed whereas HV at the bottom of resin composite specimens and SBS were statistically analysed with nonparametric ANOVA followed by Wilcoxon rank sum tests (α=0.05). RESULTS HV profiles (medians at 2mm/4mm/6mm): XTE 105.6/88.8/38.3, SDR 34.0/35.5/36.9, FBF 36.4/38.7/37.1, XFIL 103.4/103.9/101.9, TEBF 63.5/59.7/51.9. HV at the bottom of resin composite specimens (medians at 2mm/4mm/6mm): XTE (p<0.0001) 105.5>85.5>31.1, SDR (p=0.10) 25.8=21.9=26.0, FBF (p=0.16) 26.6=25.3=28.9, XFIL (p=0.18) 110.5=107.2=101.9, TEBF (p<0.0001) 63.0>54.9>48.2. SBS (MPa, medians at 2mm/4mm/6mm): XTE (p<0.0001) 23.9>18.9=16.7, SDR (p=0.26) 24.6=22.7=23.4, FBF (p=0.11) 21.4=20.3=22.0, x-tra fil (p=0.55) 27.0=24.0=23.6, TEBF (p=0.11) 21.0=20.7=19.0. The predominant SBS failure mode was cohesive failure in dentin. SIGNIFICANCE At increasing increment thickness, HV and SBS decreased for the conventional resin composite but generally remained constant for the bulk fill resin composites.