Retentive strength and sealing ability of new self-adhesive resin cements in fiber post luting.

OBJECTIVE: To assess by means of "thin-slice" push-out test, light and scanning electron microscopy, the interfacial strength and sealing ability of new self-adhesive resin cements when used to lute fiber posts into endodontically treated teeth. METHODS: RelyX Unicem 2 Automix (3M ESPE, RUA), Maxcem Elite (Kerr, ME) and seT (SDI, S) were utilized in combination with RelyX Fiber Posts (3M ESPE). In each group 5 posted roots were used for push-out testing and 5 were processed for observations of interfacial morphology and nanoleakage under light microscope and scanning electron microscope. Five to six slices were obtained from each posted root. The statistical significance of the influence on post push-out strength of luting agent, dowel space level, and between-factor interaction was assessed using Two-Way Analysis of Variance (ANOVA) and Tukey test as needed. Differences in nanoleakage scores were also statistically evaluated (Kruskal-Wallis ANOVA) (p<0.05). RESULTS: Luting agent was a significant factor for post push-out strength. The interfacial strength achieved by RUA (9.3±2.6MPa) was significantly higher than that of ME (6.7±2.7MPa) and that of S (5.4±3.1MPa), which were comparable to each other. Dowel space level and between factor interaction were not statistically significant. Statistically comparable interfacial nanoleakage was observed in all the groups. SIGNIFICANCE: The three new self-adhesive resin cements exhibited similar sealing properties, although the post retentive ability was superior with RUA.

Effect of surface pre-treatments on the zirconia ceramic-resin cement microtensile bond strength.

OBJECTIVE: To evaluate the influence of different surface treatments on the microtensile bond strength of resin cement to zirconia ceramic. MATERIALS AND METHODS: Twelve cylinder-shaped (∅ 12×5.25 mm high) blocks of a commercial zirconium-oxide ceramic (Cercon® Zirconia, DENTSPLY) were randomly divided into 4 groups (n=3), based on the surface treatment to be performed: (1) airborne particle abrasion with 125 µm Al2O3 particles (S); (2) selective infiltration etching (SIE); (3) experimental hot etching solution applied for 30 min (ST) and (4) no treatment (C). Paradigm MZ100 blocks (3M ESPE) were cut into twelve cylinders of 4mm in thickness. Composite cylinders were bonded to conditioned ceramics using a resin cement (Calibra®, DENTSPLY), in combination with the proprietary adhesive system. After 24h bonded specimens were cut into microtensile sticks and loaded in tension until failure. Bond strength data were analyzed with Kruskall-Wallis and Dunn's Multiple Range test for multiple comparisons (p < 0.05). Failure mode distribution was recorded and the interfacial morphology of debonded specimens was analyzed using a scanning electron microscope (SEM). RESULTS: Bond strength values achieved after SIE and ST treatment were significantly higher than after S treatment and without any treatment (p < 0.05). Premature failures were mostly recorded in the S group. SIGNIFICANCE: Conditioning the high-strength ceramic surface with SIE and ST treatments yielded higher bond strengths of the resin cement than when zirconia ceramic was treated with airborne particle abrasion or left untreated.

Influence of ultrasound application on inlays luting with self-adhesive resin cements.

The study was aimed at assessing the influence of the cement manipulation and ultrasounds application on the bonding potential of self-adhesive resin cements to dentin by microtensile bond strength testing and microscopic observations of the interface. Fifty-six standardized mesio-occlusal class II cavities were prepared in extracted third molars. Class II inlays were made using the nano-hybrid resin composite Gradia Forte (GC Corp, Tokyo, Japan), following the manufacturer's instruction. The sample was randomly divided into two groups (n = 28) according to the luting technique. Half of the specimens were luted under a static seating pressure (P), while the other ones were cemented under vibration (V). The inlays were luted using the following self-adhesive resin cements: G-Cem (G, GC Corp., Tokyo, Japan) Automix (GA) and Capsule (GC); RelyX Unicem (RU, 3 M ESPE, Seefeld, Germany) Clicker (RUC) and Aplicap (RUA). Microtensile sticks and specimens for scanning electron microscope (SEM) observations were obtained from the luted teeth. The interfacial strengths measured for the cements under static pressure or ultrasonic vibration were [median (interquartile range)]: GC/V 4 (2.3-7.9); GC/P 6.8 (4.1-10.1); GA/V 3 (1.9-6.7); GA/P 1.9 (0-5.1); RUC/V 6.6 (4.6-9.8); RUC/P 4.1 (1.8-6.4); RUA/V 6.2 (2.4-10.4); RUA/P 3.4 (0-5.4). The cement formulation influenced dentin bond strength of G. RU bond strength was affected by the luting technique. SEM analysis revealed a homogeneous structure and reduced porosities for both cements as a result of ultrasonic vibration. RU benefited from the application of ultrasounds, while GC achieved higher bond strengths than GA.

Push-out bond strength of circular and oval-shaped fiber posts.

This study aimed at evaluating the post-root dentin push-out bond strength of circular and oval posts luted in oval-shaped canals with two different resin cements. Twenty extracted premolars with oval-shaped canals were selected, endodontically instrumented and obturated. The teeth were divided into two groups according to the drill used for post-space preparation and to the post shape (Ellipson oval tip + post and MTwoPF + DT Light-Post). Each group was then subdivided into two subgroups according to the cement (Gradia Core and Corecem Automix). The post-dentin bond strength was evaluated with the thin-slice push-out test. The bonded surface area was calculated for each post shape with an appropriate geometric formula in order to express the retentive strength in megapascal. Push-out strength data were analyzed with the Kruskal-Wallis ANOVA. The results showed that neither the drill-post system nor the cement significantly affected the push-out strength. The means (SD) of the push-out bond strengths in the experimental subgroups were the following: 11.79 MPa (4.77) for Gradia Core/Ellipson tip and post, 13.36 MPa (5.16) for Gradia Core/MtwoPF and DT Light-Post, 11.18 MPa (2.58) for Corecem Automix/Ellipson tip and post, and 10.91 MPa (3.89) for Corecem Automix/MtwoPF and DT Light-Post. In conclusion, circular and oval posts achieved similar retentive strengths in oval canals.

Microleakage in class II restorations: open vs closed centripetal build-up technique.

PURPOSE: This study evaluated whether a Class II restoration in a flowable resin composite has to be placed prior to (open-sandwich technique) or after (closed-sandwich technique) construction of the interproximal wall in the centripetal build-up technique in order to reduce microleakage. METHODS AND MATERIALS: Thirty non-carious molars were selected and randomly divided into two groups (n = 15). A standardized Class H preparation was made with the cervical margin 1 mm below the cementum-enamel junction. In Group 1, flowable resin composite was applied as a 1 mm base, remaining exposed at the cervical margin. In Group 2, the hybrid resin composite was applied to the interproximal wall, followed by a layer of flowable composite on the pulpal floor, away from the margins. The restorations were then subjected to 500 thermal cycles, each with a dwell time of 20 seconds at 5 degrees C and 55 degrees C. Adaptation at the cervical margin was evaluated by dye penetration and SEM analysis using the replica technique. The data were statistically analyzed using the Mann-Whitney U-test (p < 0.05). RESULTS: The centripetal open-sandwich technique led to significantly lower dye penetration than the centripetal closed-sandwich technique (p < 0.001). CONCLUSION: Flowable resin composite placed under hybrid resin composites in Group 1 provided better marginal adaptation and fewer voids. However, neither Group 1 nor Group 2 was able to completely prevent microleakage.

The effect of different surface treatments on bond strength between leucite reinforced feldspathic ceramic and composite resin.

OBJECTIVES: The aim of this study was to evaluate the effect of different surface treatments on the microtensile bond strength between a leucite reinforced glass-ceramic and composite resin. METHODS: Leucite reinforced ceramic blocks (n=24) were constructed using the hot pressing technique. The blocks were assigned to 4 groups, which received the following surface treatments: G1: hydrofluoric (HF) acid and silane; G2: silane alone; G3: HF acid and silane then dried with warm air (100 degrees C); G4: silane alone then dried with warm air (100 degrees C). Unfilled resin was applied, followed by composite resin. Specimens were prepared and loaded in tension to determine the microtensile bond strength. Failure modes were classified by stereo- and scanning electron microscopy (SEM). Data was analysed using Kruskal-Wallis test followed by the Dunn's multiple range test. RESULTS: The groups including the warm air step (G3 and G4) achieved a significantly stronger adhesion than G1 and G2. Pre-treatment of the surface with hydrofluoric acid in G1 resulted in significantly higher bond strength than G2. Failures were mostly cohesive in the luting resin for G1, G3 and G4 and mainly adhesive at the ceramic-resin interface in G2. CONCLUSIONS: The method of application of silane to the ceramic surface can have a significant influence on the adhesion between the ceramic restoration and the resin cement. Enhancing the condensation reaction by drying the silane with a 100C warm air stream significantly improved the microtensile bond strength, possibly eliminating the need for the hydrofluoric acid etching step.

Bond strength of composite core build-up materials to fiber-reinforced posts: a microtensile comparison between conventional and wet-ethanol bonding systems.

PURPOSE: To evaluate the interfacial microtensile bond strength between a fiber-reinforced post (Rely X Post) and a core material (Multicore Flow) after placing different bonding agents. MATERIALS AND METHODS: After post surface treatment, 50 posts were divided into 5 groups. Group 1: Adper Prompt-L-Pop; group 2: SingleBond2; group 3: ScotchBond Multipurpose Plus; group 4: experimental bonding system (wet ethanol bonding technique); group 5: control group. After core reconstruction, the samples were tested with the microtensile test. Fracture type examination and SEM observation followed. Data were statistically analyzed with Kruskall-Wallis non-parametric ANOVA. RESULTS: Microtensile testing revealed significant differences (p < 0.001). There were no differences between groups 1 to 4, but there was a statistically significant difference between groups 1 to 4 and the control. Fracture type observations revealed more adhesive failures than cohesive or mixed ones. CONCLUSION: The experimental bonding technique did not improve bond strength compared to the different adhesive systems tested. However, placing a bonding agent between the post and the core seems to significantly increase microtensile bond strength.

Push-out bond strength of fiber posts luted with unfilled resin cement.

PURPOSE: The study evaluates the behavior of different adhesive systems and resin cements in fiber post placement, with the intent to clarify the possible role of unfilled resin as a luting material for fiber posts. MATERIALS AND METHODS: Two luting agents (Dual-Link and Unfilled Resin) for cementing fiber posts into root canals were applied either with All-Bond 2 or One-Step Plus, or without an adhesive system, and challenged with the push-out test. Slices of roots restored with posts were loaded until post segment extrusion in the apical-coronal direction. Failure modes were analyzed under SEM. RESULTS: Push-out strength was significantly influenced by the luting agent (p < 0.05), but not by the bonding strategy (p > 0.05). The best results were obtained in combination with Unfilled Resin with One-Step Plus. Dual-Link groups failed mainly cohesively within the cement, while Unfilled Resin demonstrated more adhesive fracture at the post interface. CONCLUSION: The results of this study support the hypothesis that adhesive unfilled resin application is essential for achieving high bond strength to radicular dentin.

Bonding potential of self-adhesive luting agents used at different temperatures to lute composite onlays.

OBJECTIVES: To assess whether the bonding potential to dentin of self-adhesive resin cements was affected by their pre-cure temperature. METHODS: Composite overlays (Paradigm MZ100, 3M ESPE) were luted on 100 extracted molars with G-Cem (GC Corp.), BisCem (Bisco), Multilink Sprint (Ivoclar Vivadent), SAC-A (Kuraray Co.), XP Bond/Calibra (Detrey Dentsply). The cements were used at pre-cure temperatures that recur in their handling (4 degrees C refrigerator, 24 degrees C room and 37 degrees C intraoral), as well as following pre-heating up to 60 degrees C. Microtensile bond strengths to dentin were measured and compared with statistical tests. Scanning electron microscope observations of cement-dentin interfaces were performed. RESULTS: The bond strength of G-Cem and Calibra was not significantly affected by temperature changes from refrigerator storage to intraoral application. At any assessed pre-cure temperature the total-etch luting agent Calibra achieved a significantly stronger adhesion than the auto-adhesive cements. Limited to null adhesion was yielded by BisCem and SAC-A. The procedure of 60 degrees C pre-heating, proposed in previous studies for restorative resin composites, was of no use for the tested luting agents. Only the total-etch luting agent Calibra developed a distinct hybrid layer. The self-adhesive cements exhibited a more superficial interaction with dentin. CONCLUSIONS: Regardless of the pre-cure temperature, the bonding potential of the self-adhesive resin cements was inferior to that of the total-etch luting agent tested as control. The adhesive properties of the BisCem and SAC-A were extremely scarce.

Post space debridement in oval-shaped canals: the use of a new ultrasonic tip with oval section.

This study evaluates the effect on post space debridement in oval-shaped canals of an experimental ultrasonic tip with oval section (Satelec) compared with a circular ultrasonic tip (KaVo). Thirty teeth with an oval-shaped canal were endodontically treated and obturated and then randomly divided into 3 groups (n = 10) according to the procedure used for post space debridement: Satelec tip, Largo #2 drill + KaVo file, and Largo #2 drill + water. Debris and dentin tubules were evaluated by assigning scores to scanning electron microscope post spaces images; lower scores corresponded to fewer debris and higher number of open tubules. The Satelec group showed significantly lower debris and open tubules scores than KaVo group (p < .05) and control group (p < .05), which differed significantly between each other (p < .05). Also the debris and open tubules scores in different post space regions differed significantly among the experimental groups (p < .001). The oval ultrasonic tip resulted in a better post space debridement than a circular ultrasonic tip in oval-shaped canals.

Effect of pre-cure temperature on the bonding potential of self-etch and self-adhesive resin cements.

OBJECTIVES: To assess whether the pre-cure temperature of resin cements significantly influenced the bonding potential to dentin. METHODS: Forty extracted molars were randomly divided into 8 groups (n=5): Groups (1-4) RelyX Unicem (RU, 3 M ESPE) and Groups (5-8) Panavia F 2.0 (PF, Kuraray Co.), at pre-cure temperatures of 4, 24, 37, and 60 degrees C, respectively. Cements were used in dual-cure mode for luting composite overlays (Paradigm MZ100, 3 M ESPE) to dentin. Microtensile bond strength testing and scanning electron microscope (SEM) observations of cement-dentin interfaces were performed. RESULTS: Group 4 had to be eliminated as RU at 60 degrees C underwent such an accelerated curing that was already set at the time of dispensing. The bond strengths (MPa) measured at refrigerator, room, and intraoral temperature were, respectively: RU 5.4+/-1.7, 11.4+/-6.1, 10.6+/-4.2; PF 7.4+/-3.7, 13.9+/-6.2, 12+/-5.2. The statistical analysis revealed that both luting agents developed a significantly weaker adhesion when used at refrigerator temperature (p<0.05). No statistically significant differences in bond strength were recorded when either cement was used at 24 or 37 degrees C (p>0.05). Pre-heating of PF to 60 degrees C resulted in a significant increase in bond strength (20.7+/-9.4 MPa; p<0.05). SEM observations disclosed an enhanced potential of PF to form a hybrid layer as the temperature increased over 4 degrees C. RU exhibited a less porous and more homogeneous layer at intraoral than at refrigerated temperature. SIGNIFICANCE: It is advisable to let refrigerator-stored resin cements warm up to at least room temperature prior to clinical use. Pre-heating to 60 degrees C enhances the bonding potential of PF.

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.