Bond strength of mineral trioxide aggregate to root dentin after exposure to different irrigation solutions.

AIM: The aim of the study was to evaluate the regional push-out bond strength of mineral trioxide aggregate (MTA) after exposure to sodium hypochlorite (NaOCl), ethylenediaminetetraacetic (EDTA), and peracetic acid (PAA) irrigation solutions. MATERIALS AND METHODS: 1-mm-thick longitudinal slabs of root dentin were obtained from freshly extracted human canine teeth (n = 80). Simulated root perforation defects, 1 mm in diameter, were prepared in the coronal, middle, and apical thirds of radicular dentin. Mineral trioxide aggregate was placed into the cavities, and the specimens were stored for 1 week at 37°C. Thereafter, the specimens were randomly divided into four groups (n = 20) according to the irrigation solution applied over the repair sites: Group 1-10 ml of 5.25% NaOCl for 10 min; Group 2-10 ml of 5.25% NaOCl for 10 min, followed by 5 ml 17% EDTA for 5 min; Group 3-10 ml of 5.25% NaOCl for 10 min, followed by application of 5 ml 1% PAA for 5 min; and Group 4-no irrigation. Push-out test was performed at a crosshead speed of 1 mm/min. Debonding values were compared statistically using two-way analysis of variance and Tukey tests (P < 0.05). RESULTS: The push-out bond strength of MTA was not affected by the type of irrigation solution or location of the perforation defects (both P < 0.05). Stereomicroscopic inspection of the samples showed that the bond failure was predominantly adhesive. CONCLUSION: Exposure of repaired root perforations to 5.25% NaOCl, 17% EDTA, or 1% PAA does not alter the dislocation resistance of MTA at different locations of root dentin.

Shear bond strength between a polyester-based root canal filling material and a methacrylate-based sealer with an intermediate layer of fiber-reinforced resin-based material.

PURPOSE: To investigate the effects of an interfacial fiber-reinforced resin-based material (FRRM) application and different light-curing modes on the bond strength of a thermoplastic synthetic polymer-based root canal filling material (Resilon) to a methacrylate-based sealer (Epiphany). MATERIALS AND METHODS: One hundred Resilon disks were prepared and divided into two experimental groups: 1. application of FRRM (EverStick Net) on the Resilon surface, and 2. Resilon alone (control). Following subsequent application of the Epiphany sealer, the specimens were randomly assigned into 3 subgroups according to the curing method employed: 1. chemical curing, 2. quartz-tungsten-halogen (QTH) light, and 3. light-emitting diode (LED). The latter two groups were further subdivided to test the effects of two different polymerization modes for each light-curing unit. Cured specimens were subjected to shear bond strength testing and the failure modes were examined. The data were analyzed with three-way analysis of variance (ANOVA). RESULTS: Regardless of the curing method tested, application of FRRM at the interface significantly increased the bond strength of Resilon to Epiphany (p < 0.001). Bond strength values (MPa) were as follows (mean +/- SD): 1. chemical curing with FRRM= 3.0 +/- 0.4, without FRRM = 1.2 +/- 0.3; 2. QTH: a) standard mode with FRRM = 8.6 +/- 0.6, without FRRM = 5.5 +/- 0.9; b) ramp mode with FRRM = 8.0 +/- 1.0, without FRRM = 5.3 +/- 1.4; 3. LED: a) standard mode with FRRM = 8.8 +/- 1.1, without FRRM = 5.4 +/- 1.0; b) exponential mode with FRRM = 8.5 +/- 1.0, without FRRM = 4.6 +/- 0.6. Although light curing of specimens significantly increased the bond strength of Resilon to Epiphany (p < 0.001), the type of light-curing unit and different curing modes had no significant influence on bond strength (p = 0.852 and p = 0.776, respectively). CONCLUSION: The highest bond strength values were obtained when the FRRM was used at the interface and the sealer was light cured.

Regional push-out bond strength and coronal microleakage of Resilon after different light-curing methods.

The purpose of this study was to assess the push-out bond strength and coronal microleakage of the Epiphany (Pentron Clinical Technologies, Wallingford, CT) + Resilon (Resilon Research LLC, Madison, CT) obturation system with respect to different photoactivation methods used. Roots of human maxillary central incisors (n = 60) were prepared with 0.06 taper nickel-titanum rotary files to size 30. After application of the Epiphany sealer, the roots were obturated with Resilon cones. The specimens were randomly assigned into three groups (n = 10/group) according to the light-curing unit (LCU) used from the coronal aspect: (1) quartz-tungsten-halogen/40 seconds, (2) light-emitting diode/20 seconds, and (3) plasma arc/6 seconds. Thereafter, 2-mm thick horizontal sections (n = 3) were obtained from each specimen from the coronal to apical direction and subjected to push-out test at a crosshead-speed of 1mm/min. Failure modes were assessed quantitatively under a stereomicroscope and morphologically under a scanning electron microscope. The remaining 30 roots were used for the dye-leakage assessments. Both the type of LCU and the level of sectioning had significant effects on bond strength. The following statistical ranking was obtained for bond strength values: quartz-tungsten-halogen > light-emitting diode > plasma arc. Coronal microleakage of specimens cured with the plasma arc was significantly greater than those of other groups (p < 0.05).

Bond strength of a calcium silicate-based sealer tested in bulk or with different main core materials.

The aim of this study was to evaluate the influence of a calcium silicate-based sealer (iRoot SP), with or without a core material, on bond strength to radicular dentin, in comparison with various contemporary root filling systems. Root canals of freshly extracted single-rooted teeth (n = 60) were instrumented using rotary instruments. The roots were randomly assigned to one of the following experimental groups: (1) a calcium silicate-based sealer without a core material (bulk-fill); (2) a calcium silicate-based sealer + gutta-percha; (3) a calcium silicate-based sealer + Resilon; (4) a methacrylate resin-based sealer (RealSeal SE) + Resilon; (5) an epoxy resin-based sealer (AH Plus) + gutta-percha, and (6) a mineral trioxide aggregate-based endodontic sealer (MTA Fillapex) + gutta-percha. Four 1-mm-thick sections were obtained from the coronal aspect of each root (n = 40 slices/group). Push-out bond strength testing was performed at a cross-head speed of 1 mm/min, and the bond strength data were analyzed statistically by one-way analysis of variance and Tukey tests (p < 0.05). The highest and lowest debonding values were obtained for the calcium silicate-based sealer bulk-fill and mineral trioxide aggregate-based endodontic sealer + gutta-percha groups, respectively (p < 0.05). It was concluded that the calcium silicate-based sealer showed higher resistance to dislocation in the bulk-filled form than in conjunction with the tested core filling materials. When the calcium silicate-based sealer was placed in bulk, its dislocation resistance was similar to that of commonly used sealer + core root filling systems. Thus, the concept of using a calcium silicate-based sealer in bulk can be more easily advocated in clinical practice.

Effect of ethylenediaminetetraacetic acid on root fracture with respect to concentration at different time exposures.

INTRODUCTION: The objective of this study was to evaluate the effect of ethylenediaminetetraacetic acid (EDTA) on root fracture with respect to various concentrations at different time exposures. METHODS: A total of 48 mandibular incisors were selected. Eight nonprepared roots were selected as a negative control. The remaining 40 specimens were instrumented with rotary files and randomly assigned to one of the following groups for final irrigation: (1) 10 mL distilled water for 10 minutes (positive control); (2) 10 mL of 17% EDTA for 1 minute + 10 mL of 1% NaOCl for 1 minute; (3) 10 mL of 5% EDTA for 1 minute + 10 mL of 1% NaOCl for 1 minute; (4) 10 mL of 17% EDTA for 10 minutes + 10 mL of 1% NaOCl for 1 minute; (5) 10 mL of 5% EDTA for 10 minutes + 10 mL of 1% NaOCl for 1 minute. Thereafter, the root canals were filled by using AH26 root canal sealer with a single-cone technique. The specimens were loaded vertically at 1 mm/min crosshead speed until vertical root fracture occurred. Results were evaluated statistically with 1-way analysis of variance and Student's t test. RESULTS: Statistically significant differences were detected among the groups (P < .05). The highest mean fracture resistance was obtained from the group treated with 5% EDTA for 10 minutes. This is about 2 times more than the weakest mean fracture resistance, which was obtained from the 17% EDTA-10 minute group. CONCLUSIONS: The fracture resistances of endodontically treated roots were found to be differently affected by the various concentrations of EDTA at different time exposures.

Dentin moisture conditions affect the adhesion of root canal sealers.

INTRODUCTION: The purpose of this study was to evaluate the effects of intraradicular moisture conditions on the push-out bond strength of root canal sealers. METHODS: Eighty root canals were prepared using rotary instruments and, thereafter, were assigned to 4 groups with respect to the moisture condition tested: (1) ethanol (dry): excess distilled water was removed with paper points followed by dehydration with 95% ethanol, (2) paper points: the canals were blot dried with paper points with the last one appearing dry, (3) moist: the canals were dried with low vacuum by using a Luer adapter for 5 seconds followed by 1 paper point for 1 second, and (4) wet: the canals remained totally flooded. The roots were further divided into 4 subgroups according to the sealer used: (1) AH Plus (Dentsply-Tulsa Dental, Tulsa, OK), (2) iRoot SP (Innovative BioCeramix Inc, Vancouver, Canada), (3) MTA Fillapex (Angelus Indústria de Produtos Odontológicos S/A, Londrina, Brasil), and (4) Epiphany (Pentron Clinical Technologies, Wallingford, CT). Five 1-mm-thick slices were obtained from each root sample (n = 25 slices/group). Bond strengths of the test materials to root canal dentin were measured using a push-out test setup at a cross-head speed of 1 mm/min. The data were analyzed statistically by two-way analysis of variance and Tukey tests at P = .05. RESULTS: Irrespective of the moisture conditions, iRoot SP displayed the highest bond strength to root dentin. Statistical ranking of bond strength values was as follows: iRoot SP > AH Plus > Epiphany ≥ MTA Fillapex. The sealers displayed their highest and lowest bond strengths under moist (3) and wet (4) conditions, respectively. CONCLUSIONS: The degree of residual moisture significantly affects the adhesion of root canal sealers to radicular dentin. For the tested sealers, it may be advantageous to leave canals slightly moist before filling.

Effect of light-emitting diode photopolymerization modes on the push-out bond strength of a methacrylate-based sealer.

INTRODUCTION: The objective of this study was to investigate and compare the effect of different light-emitting diode (LED) polymerization modes on the bond strength of a methacrylate-based sealer used with Resilon or gutta-percha. METHODS: Forty extracted single-rooted teeth were sectioned off below the cementoenamel junction, and the root canals were instrumented by using rotary instruments to ISO #30/0.06 taper. The roots were randomly assigned into 1 of the following groups for root canal obturation: (1) RealSeal + Resilon and (2) RealSeal + gutta-percha. In each group, specimens were further subgrouped according to the LED polymerization mode used to cure RealSeal: (1) standard (20 seconds of maximum intensity) and (2) exponential (5 seconds of exponential power increase, followed by 15 seconds of maximum intensity). Specimens were stored in 100% humidity for 1 week at 37 °C. Push-out test was performed at a crosshead speed of 1 mm/min on 2-mm-thick root slices obtained from coronal to apical direction. Multivariate analysis of variance and Tukey tests were used for statistical analysis of the data (P=.05). Failure modes were examined under the scanning electron microscope. RESULTS: The tested polymerization modes had no significant effect on the bond strength values (P > .05). RealSeal + gutta-percha yielded significantly greater bond strength than RealSeal + Resilon (P < .05). In all groups, the bond strength values decreased significantly from coronal to apical direction (P < .05). Adhesive failure at the sealer-dentin interface was the predominant fracture mode. CONCLUSIONS: The exponential photopolymerization mode had no significant advantage over the standard regimen in terms of dentin bond strength.

Effect of different intraorifice barriers on the fracture resistance of roots obturated with Resilon or gutta-percha.

INTRODUCTION: This study investigated and compared the root reinforcement potential of 3 different intraorifice barriers (mineral trioxide aggregate [MTA], resin-modified glass ionomer cement [Vitremer], and fiber-reinforced composite [FRC]) placed over root canals obturated with gutta-percha or Resilon. METHODS: Crowns of 80 extracted human mandibular premolars were sectioned off to obtain 14-mm-long root specimens. After preparation of root canals with nickel-titanium rotary files, the roots were obturated with either the Resilon/Epiphany system or gutta-percha + AH Plus sealer. In both obturation groups, specimens were further subgrouped with respect to the intraorifice barrier material placed after removal of 3-mm coronal portion of the root fillings: (1) MTA, (2) Vitremer, and (3) FRC. The specimens were loaded vertically at 1 mm/min crosshead speed until vertical root fracture occurred. Results were evaluated statistically with two-way analysis of variance and Tukey tests. RESULTS: Fracture resistance of roots was significantly affected by the type of intraorifice barrier (P < .05), but not by the type of obturation system used (P > .05). CONCLUSIONS: The use of Vitremer and FRC significantly improved the fracture resistance, whereas MTA did not exhibit any reinforcing effect as an intraorifice barrier.

Effects of different light-curing units and obturation techniques on the seal of the Resilon/Epiphany system.

The purpose of this study was to compare the sealing ability of a resin- and polymer-based root canal obturation system (Resilon; Resilon Research LLC, Madison, CT/Epiphany; Clinical Technologies, Wallingford, CT) used in conjunction with different light-curing units and obturation techniques. A total of 120 decrowned single-rooted human teeth were used. After preparation of the root canals with 0.06 taper nickel-titanium rotary files to size 30, the roots were randomly assigned into three experimental groups according to the obturation technique used: (1) single cone, (2) cold lateral compaction, and (3) System B + Obtura. In all groups, the specimens were randomly assigned into four subgroups according to the polymerization method that was used to cure Epiphany sealer from the coronal aspect: (1) quartz-tungsten-halogen (QTH), (2) light-emitting diode (LED), (3) plasma-arc curing (PAC), and (4) chemical cure (uncured). Leakage was measured by the fluid-filtration method at 1 day and 1 week. Statistical analysis was performed by using Kruskal-Wallis and Wilcoxon signed-rank tests at p < 0.001. Fluid conductance of all groups increased significantly within time (p < 0.001). The tested obturation techniques had no significant effect on the leakage values (p = 0.433). The following statistical ranking was obtained for fluid-filtration values: uncured > PAC > LED > QTH (p < 0.001).