Reinforcement effect of intra-orifice barrier materials in teeth treated with regenerative endodontic procedure: Research article.

Background. Regenerative endodontic treatment (RET) is a clinically advanced procedure for necrotic immature teeth. However, root canal walls of these teeth are brittle especially in the cervical region and need reinforcement. This in vitro study is conducted to evaluate the effect of intra-orifice barrier materials on the fracture resistance of immature teeth treated with regenerative procedure. Methods. Forty-eight maxillary central incisors were used. Twelve intact teeth were selected for the control group. Remained teeth were prepared using peeso drills to simulate immature teeth and assigned into three groups according to the intra-orifice barrier material placed over MTA (n = 12); Composite resin (CR), ProRoot MTA and Resin-modified glass ionomer cement (RMGIC). Fracture strength test was applied using a universal testing machine. One-way ANOVA and Tukey post hoc tests were used at P = 0.05. Results. A significant difference was obtained among groups (P < 0.05). MTA showed the lowest fracture resistance (P < 0.05). However, no significant difference was found among RMGIC, CR, and control groups (P > 0.05). Conclusion. Intra-orifice restorative materials have reinforcement affect in immature teeth treated with regenerative endodontic procedure. RMGIC or CR can be regarded as a viable choice to reduce the occurrence of cervical root fracture of immature teeth treated with a regenerative therapy.

The effect of radiotherapy delivery time and obturation materials on the fracture resistance of mandibular premolars.

OBJECTIVES: This ex vivo study was performed to investigate the effect of radiotherapy (RT) delivery time on fracture resistance of mandibular premolars filled with Biodentine or gutta-percha/sealer (GPS). MATERIALS AND METHODS: Seventy-two mandibular premolars were used in this study. Randomly selected 24 teeth were kept intact for the control groups (with and without irradiation). Then, the remaining 48 teeth were randomly assigned into 4 groups (n = 12) according to RT delivery time (irradiated before or after root canal treatment) and obturation materials as follows: Group RT + GPS, Group: GPS + RT, Group RT + Biodentine and Group Biodentine + RT. The samples were either initially endodontically treated and then irradiated or initially irradiated and then endodontically treated with one of the abovementioned materials. The samples were irradiated at 2 Gy per fraction, 5 times a week for a total dose of 60 Gy in 30 fractions over 6 weeks. The roots were embedded in self-polymerizing acrylic resin. The fracture resistance was evaluated in a universal testing machine. Data was analyzed by one-way ANOVA and Games-Howell post hoc test at p < 0.05. RESULTS: Radiation therapy significantly reduced fracture resistance of intact teeth (p < 0.05). The highest fracture resistance was observed in intact/non-irradiated teeth and the lowest fracture resistance in Biodentine + RT group (p < 0.05). The effect of RT delivery time was insignificant when GPS was preferred as the root canal filling material (p > 0.05); it was significant when preferring Biodentine (p < 0.05). When RT was applied to the teeth after Biodentine obturation, the fracture resistance decreased significantly compared to the teeth that were obturated with GPS after or before RT application (p < 0.05). CONCLUSION: Both RT time and obturation materials (Biodentine or gutta-percha/sealer) affect the fracture resistance of the endodontically treated teeth. CLINICAL RELEVANCE: Endodontic treatment could be completed with both materials after RT; however, when the endodontic treatment was initially completed and the teeth were subsequently exposed to RT, it was shown that the reinforcement effect of Biodentine decreased.

The effect of different obturation methods on sealer penetration alongside apically separated rotary nickel-titanium instruments: A confocal laser scanning microscopy study.

The effects of different obturation techniques on calcium silicate-based sealer penetration in the presence of apically separated rotary files were evaluated. Forty-eight extracted mandibular incisors were used. ProTaper F2 rotary files were separated at the apical thirds. Samples were divided into four groups (n = 12) according to obturation technique used: (a) cold lateral compaction (CLC); (b) single cone; (c) bulk-fill (BF) without a core material; and (d) thermoplastic injection (TI). Specimens were sectioned horizontally at 1 and 3 mm from the apex and studied using a confocal scanning laser microscope. The maximum tubule penetration depth and percentage of penetration were measured. Data were statistically analyzed using parametric and nonparametric tests with a significance level of 5%. Regarding penetration depth, a significant difference was found at 1 mm (p < .05), while no significant difference was found at 3 mm (p > .05). At the 3 mm level, all of the obturation techniques showed similar penetration depths. Regarding penetration percentage, the values of the CLC and TI groups were statistically less when compared with the BF group at 1 and 3 mm levels, respectively (p < .05). Under the limitations of this in vitro study, results suggest that the obturation technique may present a significant effect on sealer penetration.

Evaluation of fracture resistance of roots-filled with various root canal sealers at different time periods.

PURPOSE: The reinforcement effect of 3 various root canal sealers (AH 26, MTA Plus sealer and BioRoot RCS) and gutta-percha at different time periods (1 week and 1 month) were evaluated in the present study. MATERIALS AND METHODS: Single-rooted, single-canalled, cracks-free 80 mandibular premolars were decoronated to a length of 13mm. Group PC (positive control, n=10): samples were left unprepared and unfilled. Seventy samples were prepared by using the ProTaper Rotary System up to F4. Group NC (negative control, n=10): samples were left unfilled. Remaining 60 samples were assigned into 3 groups; Group 1: AH 26 + F4 gutta-percha (GP); Group 2: MTA Plus sealer + F4 GP and Group 3: BioRoot RCS + F4 GP. Filled samples were divided into subgroups according to storage time: Samples in Groups 1A, 2A, and 3A were stored for 1 week; while Groups 1B, 2B and 3B were stored for 1 month at 100% humidity to allow the complete setting of the sealers (n=10, for each). A universal testing machine at a crosshead speed of 1.0 mm/min was used for fracture testing. For each specimen, the force at the time of fracture was recorded and the data were analyzed statistically. RESULTS: The highest fracture resistance values were obtained in Group PC, while the lowest values were obtained in Group NC. Groups PC and NC were statistically different from each other and from other groups, regardless of time (p<0.05). Fracture resistance values of Group AH 26/GP were statistically different from MTA Plus sealer/GP (p<0.05) and were statistically similar with BioRoot RCS/GP , irrespective of time. Within group comparisons revealed that there were no statistically differences between samples filled with same sealer at different time periods. CONCLUSION: Root canal preparation caused decreased fracture resistance. All sealers increased the force values needed to fracture the filled samples compared to unfilled ones. Time factor had no effect on the fracture resistance values.

Effect of Calcium Hydroxide Dressing on the Dentinal Tubule Penetration of 2 Different Root Canal Sealers: A Confocal Laser Scanning Microscopic Study.

INTRODUCTION: The purpose of this study was to evaluate the effect of calcium hydroxide (Ca[OH]2) dressing on the dentinal tubule penetration of epoxy resin-based sealer (AH 26; Dentsply Maillefer, Ballaigues, Switzerland) and tricalcium silicate-based sealer (BioRoot RCS; Septodont, Saint Maurdes Fosses, France). METHODS: Fifty-two single-rooted mandibular premolars were used. Four samples were assigned as the positive control. Twenty-four samples received Ca(OH)2 labeled with rhodamine B, whereas the rest did not. Ca(OH)2 was removed with passive ultrasonic activation and copious irrigation 2 weeks later. Samples were further subdivided into 2 groups, and root canal fillings were performed with a single ProTaper F4 gutta-percha cone (Dentsply Maillefer) combined with 1 of the tested sealers labeled with fluorescein green. After 2 weeks, samples were transversely sectioned at the apical, middle, and coronal levels. The penetration depth and percentage were evaluated via imaging software. Statistical analysis was performed using Kruskal-Wallis, Siegel Castellan post hoc, and Mann-Whitney U tests at P = .05. RESULTS: The mean dentinal tubule penetration depth and percentage values were lowest in the apical third for both sealers. BioRoot RCS showed higher penetrability in all thirds compared with AH 26 (P < .05) despite Ca(OH)2 dressing remnants (P < .05). Ca(OH)2 placement resulted in a shorter dentinal tubule penetration depth with BioRoot RCS statistically in the middle and coronal thirds (P < .05), whereas it did not affect the percentage (P > .05). CONCLUSIONS: Passive ultrasonic activation and copious irrigation were insufficient in removing Ca(OH)2 from root canals. BioRoot RCS presented higher dentinal tubule penetration than AH 26 even in the presence of Ca(OH)2 residues. Ca(OH)2 remnants decreased both dentinal tubule penetration depth and the percentage of the tested sealers; however, a more drastic effect was observed for AH 26.

Fracture Resistance of Teeth with Simulated Perforating Internal Resorption Cavities Repaired with Different Calcium Silicate-based Cements and Backfilling Materials.

INTRODUCTION: This study assessed the fracture resistance (FR) of teeth with simulated perforating internal resorption cavities repaired with different calcium silicate-based cements (CSCs) and backfilling materials. METHODS: Ninety-six mandibular premolar teeth were used. Twelve of the teeth were assigned as negative control group. Remaining roots were instrumented with rotary files, and standardized internal resorption cavities were prepared on the middle half of roots with burs. Twelve of the samples were not further interfered and were assigned as a positive control group. The apical 4 mm of the remaining 72 root canals was obturated with single-cone technique and divided into 6 groups according to CSCs used for repairing of cavities and backfilling materials as follows: MTA + MTA, MTA + gutta-percha/sealer, Biodentine + Biodentine, Biodentine + gutta-percha/sealer, MTA Plus + MTA Plus, and MTA Plus + gutta-percha/sealer. Specimens were embedded in acrylic resin and then subjected to fracture testing. The forces when the fracture occurred were analyzed with analysis of variance and Bonferroni tests at P = .05. RESULTS: No significant difference was found among CSCs irrespective of backfilling materials (P > .05). Groups MTA + gutta-percha/sealer, Biodentine + gutta-percha/sealer, and MTA Plus + gutta-percha/sealer showed significantly lower FR compared with groups MTA + MTA, Biodentine + Biodentine, and MTA Plus + MTA Plus, respectively (P < .05). The highest FR was observed in group Biodentine + Biodentine, and the lowest was in group MTA Plus + gutta-percha/sealer. FR of positive control group was statistically lower than groups completely filled with CSCs (P < .05), whereas FR of negative control group was statistically higher than the groups combined with gutta-percha and sealer (P < .05). CONCLUSIONS: The backfilling with CSCs may be a preferable material rather than gutta-percha/sealer combination for the roots with perforated internal resorptions.

Evaluation of dentinal tubule penetration depth and push-out bond strength of AH 26, BioRoot RCS, and MTA Plus root canal sealers in presence or absence of smear layer.

Background. This study compared the effect of smear layer on the penetration depth and push-out bond strength of various root canal sealers. Methods. A total of 90 extracted human mandibular premolars were assigned into 2 groups: smear layer preserved and smear layer removed. Then the roots were further divided into 3 subgroups according to the sealer tested: AH 26, BioRoot RCS and MTA Plus. Obturation was performed with gutta-percha and the relevant sealer was mixed with 0.1% rhodamine B. Three 1-mm-thick slices were obtained from the mid-third area of each root. Two slices were selected for the push-out test and the remaining slice was used to calculate the dentinal tubule penetration depth and percentage. Results. The retention of MTA Plus and BioRoot RCS was higher than that of AH 26 when the smear layer was preserved (P<0.05). BioRoot RCS showed the lowest penetration depth when the smear layer was removed (P<0.05). Conclusion. Dentinal tubule penetration of root canal sealers had a limited effect on their adhesion to root canal wall.

Influence of a glide path on the dentinal crack formation of ProTaper Next system.

OBJECTIVES: The aim was to evaluate dentinal crack formation after root canal preparation with ProTaper Next system (PTN) with and without a glide path. MATERIALS AND METHODS: Forty-five mesial roots of mandibular first molars were selected. Fifteen teeth were left unprepared and served as controls. The experimental groups consist of mesiobuccal and mesiolingual root canals of remaining 30 teeth, which were divided into 2 groups (n = 15): Group PG/PTN, glide path was created with ProGlider (PG) and then canals were shaped with PTN system; Group PTN, glide path was not prepared and canals were shaped with PTN system only. All roots were sectioned perpendicular to the long axis at 1, 2, 3, 4, 6, and 8 mm from the apex, and the sections were observed under a stereomicroscope. The presence/absence of cracks was recorded. Data were analyzed with chi-square tests with Yates correction. RESULTS: There were no significant differences in crack formation between the PTN with and without glide path preparation. The incidence of cracks observed in PG/PTN and PTN groups was 17.8% and 28.9%, respectively. CONCLUSIONS: The creation of a glide path with ProGlider before ProTaper Next rotary system did not influence dentinal crack formation in root canals.

Antimicrobial and structural effects of different irrigation solutions on gutta-percha cones.

PURPOSE: To evaluate the alterations on the surface of gutta-percha cones (GPCs) on exposure to the different irrigation solutions and their possible antibacterial effect against Enterococcus faecalis. (E. faecalis). MATERIALS AND METHODS: Disinfection ability of different solutions (5.25% sodium hypochlorite, 2% chlorhexidine, 1% peracetic acid, and QMix) were tested with 96 GPCs and the time of exposure to each solution was 5 and 10 minutes, respectively. GPCs used in this study were contaminated with E.faecalis. After disinfection, GPCs were placed in tubes containing the medium and incubated at 37˚C for 7 days. All tubes were visually checked for turbidity at 24-hour intervals. About 92 new GPCs were analyzed by means of SEM/EDS to assess the topography and chemical elements present on their surface. The data generated was analyzed using Pearson chi-square test, p<0.05. RESULTS: There were no significant statistical differences in disinfection quality between the irrigation solutions used on GPCs contaminated with E. faecalis (p>0.05). SEM/EDS analyses showed no alteration in the superficial features of GPCs after treating with various irrigation solutions. CONCLUSION: QMix was found to be an effective agent for rapid disinfection of GPCs as well-known irrigation solutions. Irrigation solutions were found to have sterilized the GPCs after both 5 and 10 minutes of exposure.

Effects of dentin moisture on the push-out bond strength of a fiber post luted with different self-adhesive resin cements.

OBJECTIVES: This study evaluated the effects of intraradicular moisture on the pushout bond strength of a fibre post luted with several self-adhesive resin cements. MATERIALS AND METHODS: ENDODONTICALLY TREATED ROOT CANALS WERE TREATED WITH ONE OF THREE LUTING CEMENTS: (1) RelyX U100, (2) Clearfil SA, and (3) G-Cem. Roots were then divided into four subgroups according to the moisture condition tested: (I) dry: excess water removed with paper points followed by dehydration with 95% ethanol, (II) normal moisture: canals blot-dried with paper points until appearing dry, (III) moist: canals dried by low vacuum using a Luer adapter, and (IV) wet: canals remained totally flooded. Two 1-mm-thick slices were obtained from each root sample and bond strength was measured using a push-out test setup. The data were analysed using a two-way analysis of variance and the Bonferroni post hoc test with p = 0.05. RESULTS: Statistical analysis demonstrated that moisture levels had a significant effect on the bond strength of luting cements (p < 0.05), with the exception of G-Cem. RelyX U100 displayed the highest bond strength under moist conditions (III). Clearfil SA had the highest bond strength under normal moisture conditions (II). Statistical ranking of bond strength values was as follows: RelyX U100 > Clearfil SA > G-Cem. CONCLUSIONS: The degree of residual moisture significantly affected the adhesion of luting cements to radicular dentine.