Fracture resistance of roots enlarged with various rotary systems and obturated with different sealers.

Background. This in vitro study compared the fracture resistance of roots instrumented either with ProTaper or One Shape rotary systems and filled with one of the silicate, epoxy resin or silicone-based sealers. Methods. Sixty single-rooted extracted mandibular premolars were decoronated to a length of 13 mm and then randomly divided into two main groups (n=30) in terms of the rotary system used for preparation. Group 1 samples were instrumented with the ProTaper Universal system up to a master apical file of #F2, while samples in group 2 were enlarged with One Shape system. The two main groups were then divided into 3 subgroups in terms of the sealer used (n=10) and filled with guttapercha (either F2 or MM-GP points) of the rotary system used and one of the sealers as follows: group 1, BioRoot RCS + ProTaper F2 gutta-percha; group 2, AH Plus + ProTaper F2 gutta-percha; group 3, GuttaFlow + ProTaper F2 gutta-percha; group 4, BioRoot RCS+ MM-GP points; group 5, AH Plus + MM-GP points; and group 6, GuttaFlow + MM-GP points. Each specimen then underwent fracture testing by using a universal testing machine at a crosshead speed of 1.0 mm/min until the root fractured. Data were statistically analyzed. Results. Two-way ANOVA showed no significant differences between the groups. One Shape instruments showed significantly better fracture resistance compared to ProTaper instruments. Statistically, no significant difference was found between AHPlus, GuttaFlow and BioRoot RCS sealers. Conclusion. It can be concluded that the rotary system used for the instrumentation of teeth has some influence on the fracture resistance, while the root canal sealers do not have such an effect.

The push-out bond strength of BIOfactor mineral trioxide aggregate, a novel root repair material.

OBJECTIVES: The aim of this in vitro study was to evaluate the push-out bond strength of a novel calcium silicate-based root repair material-BIOfactor MTA to root canal dentin in comparison with white MTA-Angelus (Angelus) and Biodentine (Septodont). MATERIALS AND METHODS: The coronal parts of 12 central incisors were removed and the roots were embedded in acrylic resin blocks. Midroot dentin of each sample was horizontally sectioned into 1.1 mm slices and 3 slices were obtained from each root. Three canal-like standardized holes having 1 mm in diameter were created parallel to the root canal on each dentin slice with a diamond bur. The holes were filled with MTA-Angelus, Biodentine, or BIOfactor MTA. Wet gauze was placed over the specimens and samples were stored in an incubator at 37°C for 7 days to allow complete setting. Then samples were subjected to the push-out test method using a universal test machine with the loading speed of 1 mm/min. Data was statistically analyzed using Friedman test and post hoc Wilcoxon signed rank test with Bonferroni correction. RESULTS: There were no significant differences among the push-out bond strength values of MTA-Angelus, Biodentine, and BIOfactor MTA (p > 0.017). Most of the specimens exhibited cohesive failure in all groups, with the highest rate found in Biodentine group. CONCLUSIONS: Based on the results of this study, MTA-Angelus, Biodentine, and BIOfactor MTA showed similar resistances to the push-out testing.

Tooth discoloration effects of calcium silicate based barrier materials used in revascularization and treatment with internal bleaching.

BACKGROUND/PURPOSE: Usage of barrier materials is an important step in revascularization procedure. One of the undesired properties of these barrier materials is to cause coronal tooth discoloration. The aim of this in vitro study was to evaluate the tooth discoloration induced by ProRoot MTA (PMTA), Biodentine, and MM-MTA, as well as the efficacy of internal bleaching on this discoloration. MATERIALS AND METHODS: Forty-two maxillary incisor teeth were prepared. Triple antibiotic paste (TAP) was placed in the root canals and incubated for 3 weeks. After removing the TAP, blood embedded spongostans were inserted into the root canals, and PMTA, Biodentine, or MM-MTA was placed over them. The teeth were incubated for 4 weeks at 37 °C; then, the internal bleaching agent was sealed for one week. The tooth color was measured throughout the study and the color change values (ΔE) of each specimen were calculated, and the data was statistically analyzed using the one-way ANOVA and Tamhane's T2 tests. RESULTS: The TAP significantly decreased the luminosity of the teeth (p < 0.05); however, no significant differences were observed between the tooth discolorations induced by the PMTA, Biodentine, and MM-MTA (p > 0.05). The teeth in the Biodentine group were more whitened than those of the PMTA and MM-MTA groups (p < 0.05). CONCLUSION: Although the PMTA, Biodentine, and MM-MTA caused similar color alterations in the teeth, more bleaching was observed on those teeth discolored using TAP + blood + Biodentine.

Push-out bond strength of a new post system after various post space treatments.

To assess the effect of post-space treatment with chelating agents on the push-out bond-strength of a glass fiber post-system. Fortyeight human teeth were decoronated. The roots were prepared to size 40 and obturated. The post-spaces were prepared with PeesoReamer drills. The post-spaces were irrigated with (i) NaOCl and EDTA with chlorhexidine (QMix), (ii) NaOCl and EDTA, (iii) NaOCl and Citric acid, (iv) NaOCl and saline as a control group. i-TFC glass fiber posts were then luted with i-TFC bond system. The samples were horizontally sectioned. The displacement resistance was measured. Push-out bond-strength (MPa) was calculated. Data were analyzed. NaOCl/QMix group showed highest values to dentine whereas NaOCl/Citric acid group showed lowest values. i-TFC post-system demonstrated equal bond strength values when post-space treated with either NaOCl/EDTA or NaOCl/Saline. It can be concluded that post-space could be treated with NaOCl and QMix in order to increase adhesion of i-TFC post-system to rootdentine.

Efficacy of Twisted File Adaptive, Reciproc and ProTaper Universal Retreatment instruments for root-canal-filling removal: A cone-beam computed tomography study.

The aim of this study was to evaluate the efficacy of Twisted File (TF) Adaptive, Reciproc, and ProTaper Universal Retreatment (UR) System instruments for removing root-canal-filling. Sixty single rooted teeth were decoronated, instrumented and obturated. Preoperative CBCT scans were taken and the teeth were retreated with TF Adaptive, Reciproc, ProTaper UR, or hand files (n=15). Then, the teeth were rescanned, and the percentage volume of the residual root-canal-filling material was established. The total time for retreatment was recorded, and the data was statistically analyzed. The statistical ranking of the residual filling material volume was as follows: hand file=TF Adaptive>ProTaper UR=Reciproc. The ProTaper UR and Reciproc systems required shorter periods of time for retreatment. Root canal filling was more efficiently removed by using Reciproc and ProTaper UR instruments than TF Adaptive instruments and hand files. The TF Adaptive system was advantageous over hand files with regard to operating time.

Comparison of different irrigation activation regimens and conventional irrigation techniques for the removal of modified triple antibiotic paste from root canals.

INTRODUCTION: The aim of this study was to compare the efficacy of irrigation activation regimens and conventional syringe irrigation technique in the removal of modified triple antibiotic paste (mTAP) from root canal walls. METHODS: Fifty-six extracted human mandibular premolars were prepared using ProTaper rotary files (Dentsply Maillefer, Ballaigues, Switzerland) up to size F4. The root canals were filled with mTAP medicament, and after 21 days, the roots were randomly assigned to 5 groups (n = 10) according to the irrigation regimens used: conventional syringe irrigation (CI), Self-Adjusting File (SAF; ReDent-Nova, Ra'anana, Israel), EndoVac (Discus Dental, Culver City, CA), EndoActivator (Dentsply, Tulsa, OK), and passive ultrasonic irrigation (PUI). In 3 teeth, mTAP was not removed (positive controls), and another 3 teeth were not filled with mTAP (negative controls). The roots were sectioned, and the amount of remaining medicament at each root half (n = 20) was evaluated at 30× magnification using a 4-grade scoring system. Data were evaluated using the Kruskal-Wallis and Mann-Whitney U tests. RESULTS: There were statistically significant differences among all experimental groups; of which, the CI group was the significantly least efficient in removing mTAP from the root canal (P < .05). At the apical and middle third, the PUI, SAF, EndoVac, and EndoActivator groups removed significantly more mTAP medicament than the CI group (P < .05); however, there were no significant differences between these groups (P > .05). The SAF and PUI showed significantly better performances in removing mTAP from the coronal third (P < .05). CONCLUSIONS: The use of irrigation activation regimens significantly improves the removal of mTAP from root canals when compared with CI.

The use of endodontically treated and/or fiber post-retained teeth as abutments for fixed partial dentures.

The purpose of this in vitro study was to evaluate the effect of endodontic treatment with or without fiber-post restorations on the fracture strength of abutment teeth under fixed partial dentures (FPDs). Seventy extracted premolar and canine teeth were used. Groups of fiber-post-retained and root-filled teeth were endodontically treated. The teeth were embedded in an acrylic resin perpendicular to the horizontal plane to create fixed partial dentures. The following groups were created using different abutments: (1) sound (S) canine/S premolar, (2) S canine/endodontically treated (ET) premolar, (3) ET canine/S premolar, (4) ET canine/ET premolar, (5) S canine/fiber-post-restored (FPR) premolar, (6) FPR canine/S premolar, and (7) FPR canine/FPR premolar. Each tooth was prepared for a complete-coverage full-metal crown. Impressions were taken; metal frameworks were fabricated and cemented. The samples were exposed to 5,000 cycles of thermomechanical fatigue and loaded compressively until fracture (2 mm/min). The data were statistically analyzed using (Kruskal-Wallis test, α = 0.05). No significant difference was found among the mean fracture strengths of the groups (p = 0.696). There were distinct differences in failure patterns. All of the fracture types were horizontal, and neither vertical nor non-restorable root fractures were recorded. Premolars seemed to be a critical abutment compared to canines when they were sound under FPDs. The percentage of cervical fractures was high in endodontically treated teeth when compared to post-retained groups. In case of post-debonding, the abutment fracture did not occur. When root-filled teeth are used as abutments for FPDs, fiber-post restorations or the creation of abutments from similar structures (ET/ET or FPR/FPR) results in improved conservation of root structure under loading when compared to the abutments from different structures (S/ET, ET/S, FPR/S, S/FPR).

Evaluation of gaps or voids occurring in roots filled with three different sealers.

OBJECTIVES: The purpose of this in vitro study was to evaluate gaps or voids occurring in roots filled with three different sealers. METHODS: Thirty extracted human single-rooted teeth were decoronated, instrumented using NiTi rotary instruments, divided into three groups (n=10 per group) and obturated with one of the following: Epiphany with Resilon, MetaSEAL with gutta-percha or AH Plus with gutta-percha using the match-taper single-cone technique. After storage for one week in 100% humidity at 37 degrees C, the teeth were horizontally sectioned (n=10). Photographs were taken from the coronal, median and apical parts of the roots using a stereomicroscope at 10X magnification, and the images were then transferred to a computer. The mathematical method known as the 'Affine Transformation' was used for the transformation of pixel coordinates to ground coordinates in the Netcad Software program. The mean areas (mum(2)) of the gaps between the sealer and root dentin or gutta percha/resilon and the gaps between the sealer and/or voids inside the sealer mass were measured, scored on a 0-3 scale and statistically analyzed with the Kruskal-Wallis test. RESULTS: The mean total area of gaps or voids for each sealer was 4631.80 mum(2) for the Epiphany-Resilon, 3826.80 mum(2) for the MetaSEAL-gutta-percha and 31334 mum(2) for the AH Plus-gutta-percha. The MetaSEAL-gutta-percha group showed more gap or void-free interfaces. No significant differences were found among the sealers in the scores for the gap areas (P<.05), and the MetaSEAL showed similar interfaces with Epiphany. CONCLUSIONS: No significant differences in the mean areas of gaps or voids were found among the tested resin-based sealers.