In vitro evaluation of shear bond strengths of resin to densely-sintered high-purity zirconium-oxide ceramic after long-term storage and thermal cycling

STATEMENT OF PROBLEM: The few available studies on the resin bond to zirconium-oxide ceramic recommend airborne-particle abrasion and modified resin luting agents containing adhesive monomers for superior and long-term durable bond strengths. It is unknown whether this regimen can also be successfully applied to the intaglio surface of a commercial zirconia-based all-ceramic system. PURPOSE: The purpose of this study was to evaluate and compare bond strengths of different bonding/silane coupling agents and resin luting agents to zirconia ceramic before and after artificial aging. MATERIAL AND METHODS: Composite cylinders (2.9 mm x 3.0 mm) were bonded to airborne-particle-abraded intaglio surfaces of Procera AllZirkon specimens (n=80) with either Panavia F (PAN) or Rely X ARC (REL) resin luting agents after pretreatment with Clearfil SE Bond/ Porcelain Bond Activator (Group SE). In another group, Rely X ARC was used with its bonding/silane coupling agent (Single Bond/Ceramic Primer, Group SB). PAN without any bonding/silane agent (Group NO) was the control. Subgroups of 10 specimens were stored in distilled water for either 3 or 180 days before shear bond strength was tested. One hundred eighty-day-old specimens were repeatedly thermal cycled for 12,000 cycles between 5 and 60 degrees C with a 15-second dwell time. Data were analyzed with 1- and 2-way analysis of variance and the Tukey multiple comparisons test (alpha=.05). Failure modes were examined under original magnification x25. RESULTS: After 3 days, SE-REL (25.15 +/- 3.48 MPa) and SE-PAN (20.14 +/- 2.59 MPa) groups had significantly superior mean shear bond strengths (P=.0007) compared with either NO-PAN (17.36 +/- 3.05 MPa) or SB-REL (16.90 +/- 7.22 MPa). SE-PAN, NO-PAN, and SB-REL groups were not significantly different. Artificial aging significantly reduced bond strengths. After 180-day storage, SE-PAN (16.85 +/- 3.72 MPa), and SE-REL (15.45 +/- 3.79 MPa) groups demonstrated significantly higher shear bond strengths than NO-PAN (9.45 +/- 5.06 MPa) or SB-REL (1.08 +/- 1.85 MPa) groups. The modes of failure varied among 3-day groups but were 100% adhesive at the ceramic surfaces after artificial aging. CONCLUSION: Artificial aging significantly reduced bond strength. A bonding/silane coupling agent containing an adhesive phosphate monomer can achieve superior long-term shear bond strength to airborne-particle- abraded Procera AllZirkon restorations with either one of the 2 resin luting agents tested.     

Dentin and enamel bond strengths of dual-cure composite luting agents used with dual-cure dental adhesives

OBJECTIVE: The purpose of this in vitro study was to evaluate and compare dentin and enamel bond strengths obtained with dual-cure composite luting agents when used with dual-cure dental adhesives. METHODS: Human molars were ground flat to expose enamel (n=80) or dentin (n=80). Specimens in each substrate group were randomly assigned to eight treatment sub-groups, according to four adhesive-luting agent combinations and two test conditions (with or without thermocycling). Pre-polymerized composite resin posts (TPH Spectrum) were luted to either the enamel or dentin surfaces with one of the following adhesive-luting agent combinations: (1) Xeno IV Dual Cure (dual-cure self-etch adhesive) and Calibra (dual-cure luting agent); (2) Prime & Bond NT Dual Cure (dual-cure total-etch adhesive) and Calibra; (3) OptiBond All-in-One Dual Cure (dual-cure self-etch adhesive) and Nexus 2 Dual Syringe (dual-cure luting agent); (4) OptiBond Solo Plus Dual Cure (dual-cure total-etch adhesive) and Nexus 2 Dual Syringe. For each treatment sub-group, half the specimens (n=10) were tested after 24h storage in water at 37 degrees C, and the other half (n=10) were tested after thermocycling for 1800 cycles between water baths held at 5 and 55 degrees C, with a dwell time in each bath of 30s, and a transfer time of 10s. Bond strengths were measured in shear mode, and expressed in MPa. The fracture mode (adhesive, cohesive, mixed) was examined. Data were analyzed for statistical significance with a factorial ANOVA and post hoc tests. RESULTS: Mean enamel bond strengths ranged from 8.4MPa for non-thermocycled OptiBond All-in-One|Nexus 2 to 35.5MPa for non-thermocycled Prime & Bond NT|Calibra. Mean dentin bond strengths ranged from 14.5MPa for non-thermocycled OptiBond Solo Plus|Nexus 2 to 30.9MPa for thermocycled Xeno IV|Calibra. The fracture mode was predominantly adhesive for all groups. CONCLUSIONS: On enamel, the total-etch adhesives performed better than their self-etch counterparts, while in dentin, the opposite was found, i.e., the self-etch adhesives performed better than their total-etch counterparts. Thermocycling for 1800 cycles did not affect the SBS of the materials tested to dentin and enamel.     

Optical X-ray density of composite resin luting agents

This study verified the optical density of four composite resin luting agents - RelyX ARC (RY), Enforce (E), C&B Cement (CB) and Flow it (FI), at thicknesses of 2, 3, and 4 mm. The optical density of the luting agents was compared with that of enamel and dentin at the same thicknesses. Fifteen tooth crowns were embedded in PVC cylinders with self-cured acrylic resin. In addition, acrylic resin was poured into 5 PVC cylinders and four equidistant 5 mm diameter holes were prepared, with one luting material inserted in each. A laboratory cutting machine was used to prepare 4-, 3- and 2-mm thick slices of the tooth crowns and materials. Digital images were obtained with a Digora system. Three radiographs of each thickness were obtained, totalizing 135 radiographs of the crowns and 45 of the materials. Three readings were carried out on each radiograph: three in enamel, three in dentin and three in each material, totalizing 1350. According to Students t-test (p相似文献   

Comparison of the tensile bond strengths of cast metal crowns luted with resin cements

The limitation of photoactivation of dual-polymerized resin cements along the margins of metal restorations may adversely affect the mechanical properties of these cements, thus impairing the retention of restorations. The aim of this study was to assess the bond strength of cast metal crowns cemented with three dual-polymerized resin cements, using a chemically-activated resin cement and zinc phosphate as controls. Fifty nickel-chromium alloy crowns were cast and randomly assigned to five groups of equal size. Castings were cemented on their corresponding metal dies with one of the tested luting agents: Scotchbond Resin Cement, Enforce and Panavia F (dual-polymerized resin cements), Cement-It (chemically-activated resin cement) and Zinc Phosphate Cement (zinc phosphate cement). Specimens were stored in distilled water at 37 degrees C for 24 h and then loaded in tension until failure. Panavia F and Zinc Phosphate Cement provided the highest and lowest bond strength means, respectively. Scotchbond Resin Cement, Enforce and Cement-It cements exhibited similar intermediate values, but with statistically significant difference compared to the other materials (P < 0.05). Even with the restriction or absence of light activation, all tested dual-polymerized resin cements produced significantly higher bond strength than did the zinc phosphate cement and yielded similar or better results than the chemically activated cement. It should be pointed out that the findings of this study relate to a test scenario which does not mimic clinical circumstances and that further work is required to identify the clinical significance of the reported tensile bond strength differences between the different luting materials.     

In vitro evaluation of long-term bonding of Procera AllCeram alumina restorations with a modified resin luting agent

STATEMENT OF PROBLEM: Bonded densely sintered aluminum oxide ceramic restorations such as Procera AllCeram laminates rely on a strong and long-term durable resin bond. Air particle abrasion and a phosphate-modified resin luting agent have the potential to provide such bonds to aluminum oxide ceramics, but their efficacy on the Procera AllCeram intaglio surface is unknown. The inherent microroughness of this surface may influence bond strengths, because micromechanical interlocking is a main contributor for adhesion of resins to ceramic materials. PURPOSE: This study evaluated the bond strength of a phosphate-modified resin luting agent with and without silanization to an air particle-abraded Procera AllCeram intaglio surface compared with a conventional resin-bonding system before and after artificial aging. MATERIAL AND METHODS: Sixty square (10 x 10 x 2 mm) specimens of Procera AllCeram alumina ceramic with the Procera intaglio surface were air particle abraded with aluminum oxide. Composite cylinders (2.9 mm in diameter and 3.0 mm in width) were fabricated with Z-250 composite and bonded to the ceramic specimens with either Panavia 21 TC or Rely X ARC (control) and their corresponding bonding/silane coupling agents. In addition, Panavia was used without silanization as suggested in similar studies. Subgroups of 10 specimens were stored in distilled water for either 3 or 180 days before shear bond strength was tested with a universal testing machine (MPa) until fracture. The 180-day specimens were subjected to thermocycling at 2000 cycles every 30 days (12,000 cycles total). Data were analyzed with 1-way analysis of variance and Tukey's multiple comparison (alpha=.05). Failure modes were examined with a light microscope (original magnification x 25). RESULTS: Differences between short-term and long-term groups were highly significant (P=.000). Bond strength with Rely X ARC and its silane coupling agent (22.75 +/- 4 MPa) decreased significantly (P=.000) after artificial aging (3.32 +/- 3.62 MPa). Panavia 21 after silanization revealed significantly different (P=.003) early (21.42 +/- 4.3 MPa) and late (16.09 +/- 2.37 MPa) bond strengths but achieved the highest bond strength after artificial aging. Bond strengths of Panavia without silanization both early (8.06 +/- 2.1 MPa) and late (6.91 +/- 2.49 MPa) were not significantly different. Failure modes were mainly adhesive at the ceramic surface for all groups. CONCLUSION: Panavia 21 in combination with its corresponding bonding/silane coupling agent can achieve an acceptable resin bond to the air particle-abraded intaglio surface of Procera AllCeram restorations after artificial aging, which had mixed effects on the other investigated groups. The conventional resin luting agent revealed the most dramatic decrease in bond strength.     

Influence of activation modes on diametral tensile strength of dual-curing resin cements

In metallic restorations, the polymerization of dual-curing resin cements depends exclusively on chemical activation. The effect of the lack of photoactivation on the strength of these cements has been rarely studied. This study evaluated the influence of activation modes on the diametral tensile strength (DTS) of dual-curing resin cements. Base and catalyst pastes of Panavia F, Variolink II, Scotchbond Resin Cement, Rely X and Enforce were mixed and inserted into cylindrical metal moulds (4 x 2 mm). Cements were either: 1) not exposed to light (chemical activation = self-cured groups) or 2) photoactivated through mylar strips (chemical and photo-activation = dual-cured groups) (n = 10). After a 24 h storage in 37 masculineC distilled water, specimens were subjected to compressive load in a testing machine. A self-curing resin cement (Cement-It) and a zinc phosphate cement served as controls. Comparative analyses were performed: 1) between the activation modes for each dual-curing resin cement, using Students t test; 2) among the self-cured groups of the dual-curing resin cements and the control groups, using one-way ANOVA and Tukeys test (alpha = 0.05). The dual-cured groups of Scotchbond Resin Cement (53.3 MPa), Variolink II (48.4 MPa) and Rely X (51.6 MPa) showed higher DTS than that of self-cured groups (44.6, 40.4 and 44.5 MPa respectively) (p < 0.05). For Enforce (48.5 and 47.8 MPa) and Panavia F (44.0 and 43.3 MPa), no significant difference was found between the activation modes (p > 0.05). The self-cured groups of all the dual-curing resin cements presented statistically the same DTS as that of Cement-It (44.1 MPa) (p > 0.05), and higher DTS than that of zinc phosphate (4.2 MPa). Scotchbond Resin Cement, Variolink II and Rely X depended on photoactivation to achieve maximum DTS. In the absence of light, all the dual-curing resin cements presented higher DTS than that of zinc phosphate and statistically the same as that of Cement-It (p > 0.05).     

Bond Strength of Dual-Cured Resin Cements to Human Teeth

Purpose: This study evaluated the bond strength of four commercial resin luting cements to enamel and superficial dentin, using a second‐generation laboratory composite. Materials and Methods: Forty teeth were embedded in acrylic: 20 had superficial dentin exposed; 20 had enamel exposed. Each group was divided into four subgroups (n = 5) to be bonded with Variolink II, Dual Cement, 2‐bond‐2, and Permalute System, using an inverted, truncated cone of pre‐cured Artglass that was placed over the resin cement with a load of 2 N for 2 seconds. Specimens were stored at 37°C in 100% relative humidity for 24 hours before being tested for tensile bond strength (MPa). Data were analyzed using a two‐way analysis of variance. Tukey‐Kramer intervals for comparisons among resin cements and bonding substrates were calculated at a .05 significance level. Results: Significant differences were found among resin cements. Variolink II had statistically higher bond strength values for both substrates than the rest of the cements evaluated. When bonding was to enamel, all failures were cohesive in the composite, and when bonding was to dentin, some adhesive failures occurred at the resin cement‐dentin interface. Permalute System had higher bond strengths than 2‐bond‐2 and Dual Cement when bonded to enamel. Conclusions: Variolink II and Permalute had statistically different bond strengths to enamel and dentin. Variolink II showed statistically higher values for dentin bonding than the other cements. Use of Variolink II and Permalute resulted in statistically higher bond strengths than the other two cements. CLINICAL SIGNIFICANCE Esthetic restorations, such as tooth‐colored inlays and onlays, veneers, and crowns without metal substructure, rely on bonding for success and must be cemented with a resin cement. Bond strength of the resin cement to the restoration and tooth structure affects the outcome of the restoration. Variolink II had significantly higher bond strengths to enamel and dentin than the other cements evaluated in this study.     

Bond strength of glass-ceramics on the fluorosed enamel surfaces

OBJECTIVES: Effect of different adhesive luting systems on the shear bond strength of IPS Empress 2 ceramic restorations to fluorosed enamel surface was investigated. METHODS: Forty-eight ceramic discs (2 mm x 3 mm; IPS Empress 2) were fabricated. Twenty-four non-carious extracted human molar teeth with fluorosis and 24 without fluorosis were cleaned with pumice using a plastic brush and then they were divided into two main groups. The IPS Empress 2 ceramic discs were luted to the teeth of four subgroups with two different adhesive luting systems, Variolink 2/Excite DSC (etch-and-rinse) and Clearfil Esthetic Cement/ED Primer II (self-etch), thermocycling was performed 5000 times. Shear bond strengths were tested using Shimadzu Universal Testing Machine until failure. An optical microscope and image analyzer were used at 10x and 1000x magnification to analyze the surfaces for adhesive, cohesive and mixed failure percentages. Data was analyzed with one-way ANOVA and Tukey test at a significance level of p<0.05. RESULTS: Mean shear bond strength data of the groups in MPa were; Variolink 2/Excite DSC on fluorosed enamel: 18.3+/-3.08, Variolink 2/Excite DSC on non-fluorosed enamel: 18.79+/-2.65, Clearfil Esthetic Cement/ED Primer II on fluorosed enamel: 8.43+/-2.45, Clearfil Esthetic Cement/ED Primer II on non-fluorosed enamel: 13.53+/-1.68. Mixed failure was the most prevalent type of failure in moderate fluorosed and non-fluorosed teeth with etch-and-rinse dentin bonding system, and in fluorosed teeth with self-etch dentin bonding system. CONCLUSIONS: The use of an etch-and-rinse adhesive luting procedure produced higher bond strengths of glass-ceramics bonded to fluorosed and non-fluorosed enamel surfaces than the self-etch bonding system.     

Bond strength of dual-cured resin cements to human teeth

PURPOSE: This study evaluated the bond strength of four commercial resin luting cements to enamel and superficial dentin, using a second-generation laboratory composite. MATERIALS AND METHODS: Forty teeth were embedded in acrylic: 20 had superficial dentin exposed; 20 had enamel exposed. Each group was divided into four subgroups (n = 5) to be bonded with Variolink II, Dual Cement, 2-bond-2, and Permalute System, using an inverted, truncated cone of pre-cured Artglass that was placed over the resin cement with a load of 2 N for 2 seconds. Specimens were stored at 37 degrees C in 100% relative humidity for 24 hours before being tested for tensile bond strength (MPa). Data were analyzed using a two-way analysis of variance. Tukey-Kramer intervals for comparisons among resin cements and bonding substrates were calculated at a .05 significance level. RESULTS: Significant differences were found among resin cements. Variolink II had statistically higher bond strength values for both substrates than the rest of the cements evaluated. When bonding was to enamel, all failures were cohesive in the composite, and when bonding was to dentin, some adhesive failures occurred at the resin cement-dentin interface. Permalute System had higher bond strengths than 2-bond-2 and Dual Cement when bonded to enamel. CONCLUSIONS: Variolink II and Permalute had statistically different bond strengths to enamel and dentin. Variolink II showed statistically higher values for dentin bonding than the other cements. Use of Variolink II and Permalute resulted in statistically higher bond strengths than the other two cements.     

Regional measurement of resin-dentin bonding as an array

During the development of the microtensile bond-testing method, large variations in bond strengths were noted among serial sections. The reason for these variations is unknown. The purpose of this work was to determine the consistency of resin-dentin bond strengths across the occlusal surface of coronal dentin by dividing composite resin buildups into an array of 1x1 mm beams, the top half consisting of composite resin, and the bottom half consisting of dentin. Extracted human third molars had the occlusal enamel removed as a single section by means of a diamond saw. Resin composite buildups were made after the dentin was bonded with either One-Step or MacBond. After being stored in 37 degrees C water for 1 day, the teeth were vertically sectioned at 1-mm increments into slabs of bonded teeth. Each slab was further subdivided by vertical sections into 1x1x8 mm beams. Each beam was assigned an x-y coordinate and tested for tensile bond strength. Two different clinicians (A and B) performed the same procedures using One-Step in a parallel study. Using One-Step, clinician A obtained a large number of zero bonds in superficial dentin but fewer in deep dentin. This resulted in a very large standard deviation in bond strengths (mean +/- SD of 22+/-20 MPa in superficial dentin and 27+/-14 MPa in deep dentin). Clinician B obtained much higher (p<0.001) and more uniform bond strengths with One-Step (56+/-13 MPa in superficial dentin and 57+/-12 MPa in deep dentin). With MacBond, there were no zero bonds and hence less variation, with a mean of 41+/-13 MPa in superficial dentin and 27+/-12 MPa (x +/- SD) in deep dentin. When pairs of Z100 resin composite cylinders were bonded together with One-Step and then sectioned into an array, there was little variation in regional bond strength (37 +/-1 MPa). Dividing bonded resin composite buildups into an array of 20 to 30 1x1x8 mm beams allows for the evaluation of uniformity of resin-dentin bonds. The method used in this study detected local regional differences in resin-dentin bond strengths. The largest differences were shown to be related to technique rather than to material. The results indicate that resin-dentin bonds may not be as homogenous as was previously thought.     

Microtensile bond strength and interfacial properties of self-etching and self-adhesive resin cements used to lute composite onlays under different seating forces

PURPOSE: To evaluate strength and morphology of the interface created on enamel and dentin by Panavia F 2.0 (P, Kuraray), RelyX Unicem (RU, 3M ESPE), and Maxcem (M, Sybron-Kerr), applied under two standardized clinically realistic seating pressures. MATERIALS AND METHODS: Composite overlays (Paradigm MZ100, 3M ESPE) were luted on flat enamel or dentin surfaces of 48 extracted molars. During the initial 5-min self-curing period, a pressure of either 20 or 40 g/mm(2) was maintained on the overlay. Curing was completed by light irradiation from the top of the overlay for 20 s. Microtensile sticks and specimens for SEM observations were obtained from the luted teeth. Bond strength data from enamel and dentin (MPa) were analyzed with separate two-way ANOVAs in order to assess the effect of cement type, luting pressure, and their interactions. Tukey's test was used for post-hoc comparisons (alpha = 0.05). RESULTS: The bond strengths (MPa) to dentin were: P 20 g/mm(2) 7.5 +/- 3.7, 40 g/mm(2) 10.9 +/- 4.5; RU 20 g/mm(2) 6.8 +/- 2.6, 40 g/mm(2) 14.5 +/- 5.3; M 20 g/mm(2) 4.1 +/- 1.8, 40 g/mm(2) 5.2 +/- 1.6. The bond strengths (MPa) to enamel were: P 20 g/mm(2) 25.2 +/- 9.0, 40 g/mm(2) 30.7 +/- 8.6; RU 20 g/mm(2) 10.7 +/- 4.9, 40 g/mm(2) 11.1 +/- 5; M 20 g/mm(2) 7.3 +/- 3.1, 40 g/mm(2) 7.9 +/- .2. Cement type, luting pressure, and the interaction of these two factors had significant influences on dentin bond strength, with RU and P outperforming M. RU and P significantly benefited from the increase in luting pressure. In enamel, the type of cement was a significant factor for adhesion, with P yielding the highest and M the lowest strength. The measured bond strengths corresponded with the morphological results. CONCLUSION: Interfacial strength and adaptation of self-etching and self-adhesive dual-curing cements are enhanced if a seating force greater than finger pressure is maintained throughout the initial self-curing period.     

A bond strength study of luted castable ceramic restorations

Accurate intracoronal castings can be produced using a castable ceramic--DICOR--for which there is a need to identify a suitable luting cement. The aim of this investigation was to evaluate the bond strength of three glass-ionomer luting cements and one resin cement to treated and untreated DICOR, enamel, and dentin surfaces. Forty "cerammed" DICOR specimens were assigned to four groups: (1-3) grit-blasting and bonding to each of the three glass-ionomer cements; and (4) acid-etching, silane coating, and bonding to the resin cement. Seventy enamel specimens were assigned to seven groups: (1-3) no etching and bonding to each of the glass-ionomer cements; (4-7) acid-etching and bonding to the glass-ionomer cements and the resin cement. Seventy dentin specimens were assigned to seven groups: (1-4) bonding to each of the three glass-ionomer cements and the resin cement; (5-7) polyacrylic acid preconditioning and bonding to each of the three glass-ionomer cements. The mean resin cement bond strengths (MN/m2) to DICOR (9.4) and to etched enamel (10.7) were significantly greater (p less than 0.01) than those of the glass-ionomer cements (DICOR, 0.8-1.2; enamel, 0.4-0.9). Preconditioning of enamel and dentin significantly increased (p less than 0.05) the bond strengths to the glass-ionomer cements. The mean bond strength of the resin cement to untreated dentin (4.3) was significantly higher (p less than 0.05) than the glass-ionomer bond strengths to untreated dentin (1.0-1.7) and to preconditioned dentin (2.1-3.3). The high bond strengths achieved with the resin cement are encouraging. Selected surface treatment of DICOR, enamel, and dentin prior to luting should be clinically useful.     

Influence of light-activated and auto- and dual-polymerizing adhesive systems on bond strength of indirect composite resin to dentin

STATEMENT OF PROBLEM: Clinicians must be aware of the bonding effectiveness of auto- and dual- polymerizing adhesive systems before choosing the material and technique of cementing inlay/onlays to dentin. An inadequate choice may compromise the success of indirect restorations. PURPOSE: This study compared the microtensile bond strength (MTBS) of indirect composite resin bonded to dentin by light-activated, autopolymerizing, and dual-polymerizing adhesive systems. MATERIAL AND METHODS: Occlusal dentin surfaces of 36 human third molars were exposed and flattened. Teeth were assigned to 1 of the following 6 groups (n=6) of adhesive luting systems: 2 dual-polymerizing systems (Scotchbond Multipurpose Plus/Rely X [SBMP] and Prime & Bond NT Dual Cure/Enforce [PBDC]); 1 autopolymerizing system (ED Primer/Panavia F [EDP]); and 3 light-activated systems (control groups) (Adper Single Bond/Rely X [SB], Prime & Bond NT/Enforce [PB], and Clearfil SE Bond/Panavia F [CF]). The restorative materials were applied according to manufacturer's directions. A 2-mm-thick prepolymerized composite resin (Clearfil APX) disc was cemented with the resin cements on the bonded dentin. Teeth were stored in water at 37 degrees C for 24 hours. Afterwards, teeth were sectioned both mesial-distally and buccal-lingually to obtain multiple bonded beam specimens with 0.8 mm(2) of cross-sectional area. Each specimen was tested in tension at a crosshead speed of 0.5 mm/min until failure. Data (MPa) were analyzed by 1-way analysis of variance and the Tukey post hoc test (alpha=.05). Failure patterns of tested specimens were analyzed using scanning electron microscopy. RESULTS: Mean MTBS values (MPa) for experimental groups were as follows: SBMP, 32.89 +/- 3.26(a); SB, 26.74 +/- 7.45(ab); PB, 26.11 +/- 4.48(ab); CF, 25.30 +/- 6.42(ab); EDP, 16.82 +/- 5.53(bc); PBDC, 11.20 +/- 5.89(c) (P<.001). Groups with similar lowercase letters were not significantly different. Failure pattern of fractured specimens varied according to the polymerization mode. CONCLUSION: The autopolymerizing system and one of the dual-polymerizing systems were as effective as the light-activated systems in bonding indirect composite restorations to dentin.     

Push-out bond strengths of endodontic posts bonded with different resin-based luting cements

PURPOSE: To compare the push-out bond strengths of endodontic posts bonded with different resin-based luting cements and to verify that bond strengths did not vary with cement thickness. METHODS: 48 root canals were shaped using 6% NiTi rotary files, obturated with gutta-percha and AH Plus sealer and prepared for post cementation using Panavia F, Parapost cement, SuperBond and Unicem Rely X. All roots were sectioned into 0.7 mm thick slices and digital photographs of each slice were analyzed using Scion Image to measure the surface area of the luting cement. The root slices were stressed to failure at 1 mm/minute using a push-out test. Push-out strength was calculated as the force at failure divided by the bonded surface area. Least squares linear regression analysis was used to assess the effect of cement thickness on bond strength. Fractured specimens were further observed under the SEM. RESULTS: Mean push-out bond strengths were: Panavia F (8.8 +/- 3.6 MPa), Parapost cement (9.1 +/- 4.4 MPa) SuperBond (14.6 +/- 2.9 MPa) and Rely X Unicem (12.4 +/- 3.3 MPa). The Panavia F and the Parapost cement were not significantly different from each other, but both were significantly lower (P < or = 0.05) than SuperBond and Rely X Unicem. Although there were large variations in cement thickness, the cementation of fiber posts with thicker cement layers did not affect the performance of the adhesive luting cements applied to root canal dentin.     

Push-out bond strengths of tooth-colored posts bonded with different adhesive systems

PURPOSE: To evaluate the effect of luting systems and root region on the push-out bond strengths of a glass fiber-reinforced post and a zirconia post. METHODS: Thirty-two extracted human anterior teeth (central incisors and canines) were endodontically treated with lateral condensation of gutta percha and AH26 sealer. Teeth were randomly assigned to eight groups (n = 4 per group). Two post systems from the same manufacturer (Cosmopost, a zirconia post; or FRC Postec, a glass fiber-reinforced post) were placed with a luting system (bonding agent and resin luting agent). C-Post was cemented with One-Step and Post Cement Hi-X was used as the light-polymerized adhesive control. ParaPost Fiber White cemented with ParaPost Adhesive and ParaPost Resin Cement was used as an auto-polymerized adhesive control. The roots were sectioned in equal thirds (apical, middle and cervical). A push-out test was performed in each section to measure regional bond strengths in MPa. Means were analyzed with two-way ANOVA and Duncan's post-hoc test (alpha = 0.05). RESULTS: The fiber posts ranked in the highest statistical subset regardless of the luting system: ParaPost Fiber White (self-cure control), FRC Postec bonded with Excite DSC/Variolink II, FRC Postec bonded with Syntac/Variolink II, FRC Postec bonded with Excite DSC/Experimental Self Cure Cement, and C-Post bonded with One Step/Hi-X. The zirconia post Cosmopost ranked in the lowest subsets regardless of the adhesive system used at P < 0.05. Means for the medium region of the root (5.0 +/- 0.8 MPa) were not statistically different from those obtained either in the cervical or in the apical region. Means for the cervical root region (6.2 +/- 0.9 MPa) were statistically higher than those of the apical region (4.5 +/- 1.1 MPa) at P < 0.001.     

Bonding effectiveness of adhesive luting agents to enamel and dentin.

OBJECTIVES: The bonding effectiveness of five adhesive luting agents to enamel and dentin using different application procedures was determined using a micro-tensile bond strength protocol (microTBS). METHODS: Enamel/dentin surfaces of human third molars were flattened using a high-speed diamond bur. Composite resin blocks (Paradigm, 3M ESPE) were luted using either Linkmax (LM; GC), Nexus 2 (NX; Kerr), Panavia F (PN; Kuraray), RelyX Unicem (UN; 3M ESPE) or Variolink II (VL; Ivoclar-Vivadent), strictly following manufacturers' instructions. For some luting agents, modified application procedures were also tested, resulting in four other experimental groups: Prompt L-Pop+RelyX Unicem (PLP+UN; 3M ESPE), Scotchbond Etchant+RelyX Unicem (SE+UN; 3M ESPE), Optibond Solo Plus Activator+Nexus 2 (ACT+NX; Kerr) and K-Etchant gel+Panavia-F (KE+P; Kuraray). The experimental groups were classified according to the adhesive approach in self-adhesive (UN), etch-and-rinse (ACT+NX, NX, KE+P, SE+UN and VL when bonded to enamel) and self-etch adhesive luting agents (LM, PLP+UN, PN and VL when bonded to dentin). The specimens were stored for 24h in distilled water at 37 degrees C prior to microTBS testing. The Kruskal-Wallis test was used to determine pairwise statistical differences (p<0.05) in microTBS between the experimental groups. RESULTS: When bonded to enamel, ACT+NX (15 MPa) and UN (19.6 MPa) scored significantly lower than VL (49.3 MPa), LM (49.2 MPa), PN (35.4 MPa) and SE+UN (35.2 MPa), while PLP+UN (23.5 MPa) showed a significantly lower microTBS than VL (49.3 MPa) and LM (49.2 MPa). No significant differences were noticed between VL (49.3 MPa), LM (49.2 MPa), NX (37.9 MPa), KE+PN (38.8 MPa), PN (35.4 MPa) and SE+UN (35.2 MPa). Regarding the bonding effectiveness to dentin, all luting agents bonded equally effectively (UN: 15.9 MPa; LM: 15.4 MPa; PN: 17.5 MPa; NX: 22.3 MPa), except VL (1.1 MPa), SE+UN (5.9 MPa) and ACT+NX (13.2 MPa). VL revealed an exceptionally high number of pre-testing failures, most likely due to a combined effect of not having cured the adhesive separately and an insufficiently light-cured luting agent. SIGNIFICANCE: Following a correct application procedure, the etch-and-rinse, self-etch and self-adhesive luting agents are equally effective in bonding to enamel and dentin. Several factors negatively influenced bond strength such as bonding RelyX Unicem to enamel without prior phosphoric acid etching; no separate light-curing of a light-polymerizable adhesive prior to cementation, use of a light-polymerizing adhesive converted into a dual-polymerizing adhesive, and use of a dual-cure luting agent with a low auto-polymerizable potential.     

Tensile bond strength of dual curing resin-based cements to commercially pure titanium.

OBJECTIVES: The aim of this study was to evaluate the tensile bond strength of dual curing luting resin cements to commercially pure titanium at 10 min and 24h after removal of the oxide layer. METHODS: One hundred and twenty titanium discs were obtained by casting and polishing with silicon carbide papers. The titanium discs were sandblasted with 50 microm aluminum oxide, ultrasonic cleaned and bonded in pairs with the resin-based cements Panavia F and Rely X ARC at 10 min and 24h after the sandblasting. The tensile test was performed with a crosshead speed of 0.5mm/min in an Instron Universal testing machine. RESULTS: The Rely X ARC reached the highest tensile strength value at 24h after sandblasting (18.27 MPa), but there was no statistically significant difference between the two dual curing resin cements for both times tested. All specimens showed a mixture of cohesive fracture in the resin cement and adhesive failure. However, the predominant failure mode for Panavia F was cohesive in resin cement, and the Rely X ARC exhibited a greater proportion of specimens with adhesive failure between the alloy and resin luting cement at 10 min and 24h. SIGNIFICANCE: Both cements had, statistically, the same tensile bond strength. But in the fracture mode analysis, the adhesive predominant fracture mode of Rely X ARC cement indicates a premature clinical adhesive failure. On the other hand, the cohesive predominant fracture mode of Panavia F indicates a longer clinical adhesive bond with titanium.     

Shear bond strength of resin cements to both ceramic and dentin

STATEMENT OF PROBLEM: All ceramic restorations benefit from resin cement bonding to the tooth. However, the literature is unclear on which cement, ceramic conditioning treatment, and dentin bonding agent produce the highest and longest-lasting bond strength. PURPOSE: This in vitro study evaluated immediate and 6-month shear bond strengths between a feldspathic ceramic and 4 different resin cements with the use of 6 different surface-conditioning treatments. Shear bond strengths between the 4 resin cements and dentin also were measured. MATERIAL AND METHODS: Four hundred eighty discs (10 mm in diameter and 4 mm thick) of Ceramco II porcelain were randomly divided into 6 main groups (n = 80). The ceramic specimens received 6 different surface conditioning treatments before the application of resin cement. These surface treatments were sanding with 600-grit silicon carbide paper, microetching with aluminum oxide, sanding followed by silane application, microetching followed by silane application, hydrofluoric acid-etching, and hydrofluoric acid-etching followed by silane application. Each group then was subdivided into 4 subgroups (n = 20) for the application of 1 of 4 cements: Nexus, Panavia 21, RelyX ARC, and Calibra. All cemented specimens were tested under shear loading until fracture on a universal testing machine; the load at fracture was reported in MPa as the bond strength. Bond strengths were determined at 24 hours and after 6 months of specimen storage in a saline solution. For dentin-resin cement shear bond strength testing, dentin specimens were treated with dentin bonding agents, and a thin layer of resin cement was applied according to the manufacturer's directions. Prodigy composite was bonded to the cement. Shear bond strengths were determined as above and reported in MPa at fracture. Data were analyzed with 3-way analysis of variance (P<.01). RESULTS: Hydrofluoric acid-etching followed by silane application produced bond strengths (15.0 +/- 7.4 to 21.8 +/- 5.8 MPa) in the highest statistical group with all 4 cements at both 24 hours and 6 months (P<.01). Sanding with 600-grit silicon carbide paper and microetching with aluminum oxide produced the lowest bond strengths (0.0 to 4.0 +/- 3.5 MPa). At 24 hours and 6 months, there were no significant differences among the 4 cements when hydrofluoric acid-etching was followed by silane application. Both auto- and light-polymerized dentin bonding agents bonded better to dentin than dual-polymerized bonding agents. CONCLUSION: Within the limitations of this study, hydrofluoric acid-etching followed by silane application produced the best bonds at 24 hours and 6 months with all 4 cements. Auto- and light-polymerized adhesives were associated with higher bond strengths to dentin than dual-polymerized adhesives.     

Effect of priming time on tensile bond strength to bovine teeth and morphologic structure of interfaces created by self-etching primers

PURPOSE: The purpose of this study was to investigate the effect of priming time on bovine enamel and dentin adhesion promoted by self-etching primer systems. MATERIALS AND METHODS: Two commercial self-etching primer systems, Clearfil SE Bond (SE) and Unifil Bond (UB), were used. Bovine enamel and dentin were treated with each system with various priming times (5, 20, and 60 seconds), and the tensile bond strength was measured. Scanning electron microscopic (SEM) observation was also performed to examine the effect of priming time on the morphology of the resin-tooth interface. RESULTS: The tensile bond strength to enamel ranged from 10.6 to 14.3 MPa, and no statistically significant difference was detected among products or priming times. To dentin, UB showed the statistically significantly lowest tensile bond strength when primed for 5 seconds, 6.9 +/- 1.1 MPa, but there was no significant difference between the groups primed for 20 and 60 seconds, 13.5 +/- 4.1 MPa and 13.8 +/- 4.6 MPa, respectively. SE created tensile bond strengths ranging from 13.9 to 15.7 MPa and showed no effect of priming time on dentin adhesion. SEM observation revealed that resin penetrated into both enamel and dentin more deeply with extension of priming time. CONCLUSION: Priming times longer than those recommended by the manufacturers did not influence the tensile bond strength to enamel and dentin when using two commercial self-etching primers. In contrast, a shortened priming time, 5 seconds, carried a risk of decreasing dentin adhesion, although it had no adverse effect on enamel adhesion.     

Effect of desensitizers on bond strength of adhesive luting agents to dentin

The current study investigates the influence of three dentin hypersensitivity treating agents (Gluma CPS, MS Coat and Saforide) on bond strength to dentin of two luting agents (Panavia Fluoro Cement and Super-Bond C & B). Sixty bovine dentin substrates were divided into 12 combinations of four treatment conditions (Gluma CPS, MS Coat, Saforide and control) and three adhesive systems (AD Gel sodium hypochlorite + Panavia Fluoro Cement, Panavia Fluoro Cement without AD Gel and Super-Bond C & B). After bonding the treated teeth to steel rods, 24-h tensile bond strengths were determined, and average values (n=5) were compared by analysis of variance (ANOVA). Without application of the desensitizers, bond strengths of the two groups (Super-Bond C & B, 10.2 MPa; AD Gel + Panavia, 11.5 MPa) were comparable, and they were greater than the group bonded with the Panavia material with no AD Gel conditioning (7.1 MPa). Application of the Saforide ammoniated silver fluoride desensitizer reduced bond strength of both the Super-Bond and Panavia luting agents, whereas the MS Coat polymeric agent negatively affected bond strength of the Panavia cement only. The use of the Gluma desensitizer did not affect bond strength of any of the three adhesive systems, and the bond strength of the Panavia cement with the AD Gel conditioning was not reduced by application of any of the three desensitizers. The four combinations of two desensitizers (MS Coat and Gluma CPS) and two adhesive systems (Super-Bond C & B and AD Gel + Panavia) are deemed to be applicable to fixed prosthodontic treatment.