Evaluation of dentinal defects during root canal preparation using thermomechanically processed nickel-titanium files.

OBJECTIVE: The aim of this study was to compare the incidence of root cracks after root canal instrumentation with thermomechanically processed nickel-titanium (Ni-Ti) files with different instrumentation kinematics. MATERIALS AND METHODS: A total of 150 extracted mandibular premolars with mature apices and straight root canals were divided into five groups and used in this study. In Group 1, 30 teeth were prepared using hand K-files and assigned to control group, Group 2 was instrumented using K3XF Rotary files (SybronEndo, Glendora, CA, USA) with continuous rotary motion. The teeth in Group 3 were instrumented by ProTaper Next (Dentsply Maillefer, Ballaigues, Switzerland) rotary files which make asymmetric rotary motion, In Group 4, teeth were instrumented by RECIPROC (VDW, Munich, Germany) with reciprocation motion and in Group 5, teeth were instrumented by Twisted File (TF) Adaptive (SybronEndo, Orange, CA, USA) files that use combination of continuous rotation and reciprocation motion (n = 30/per group). All the roots were horizontally sectioned 3, 6, and 9 mm from the apex with a low speed saw under water cooling. Then, the slices were examined through a stereomicroscope to determine the presence of dentinal microcracks. RESULTS: For the apical (3-mm) and coronal (9-mm) sections, the ProTaper Next and TF Adaptive produced significantly more cracks than the hand files, RECIPROC, and K3XF (P < 0.05). There was no significant difference between the experimental groups and control group at the 6-mm level (P > 0.05). CONCLUSIONS: Within the limitations of this in vitro study, all thermal-treated Ni-Ti instruments and hand files caused microcracks in root canal dentin.

Evaluation of the Reliability of Cone-beam Computed Tomography Scanning and Electronic Apex Locator Measurements in Working Length Determination of Teeth with Large Periapical Lesions.

INTRODUCTION: This study evaluates the endodontic working-length measurements in teeth with large periapical lesions and persistent intracanal exudate by using preexisting cone-beam computed tomography (CBCT). It compares the measurements with clinical root canal lengths determined by using 2 electronic apex locators. METHODS: All patients had undergone a CBCT scan independent of the present study and needed root canal treatment of at least 1 tooth visible in the field of view. Seventy-three teeth with single roots and canals were studied. An endodontist measured each root canal length with 2 different electronic apex locators. The measurements were repeated 3 times by using a digital caliper, and the mean was recorded. This mean was compared with the root canal length as measured on CBCT sections by an oral radiologist not involved in the endodontic treatment. The CBCT measurements were taken twice for analysis of intrarater reliability. The data were statistically analyzed. RESULTS: There were no significant measurement differences between the methods used (P > .05). CONCLUSIONS: In teeth with large periapical lesions and persistent intracanal exudate, measurement of the root canal length by using CBCT was as reliable as measurements that used apex locators.

Comparison of the effect of MTAD and conventional irrigation agents on apical leakage and push-out bond strength of root canal filling.

The aim of this study was to evaluate the effect of MTAD (a mixture of tetracycline isomer, an acid, and a detergent) and conventional irrigation agents on the apical leakage and push-out bond strength of root canal filling and to correlate the apical leakage and push-out bond strength. Root canals of 120 maxillary central incisors were prepared with a ProTaper file up to F3 and distributed to six groups. Saline, 1% NaOCl, 17% EDTA, 17% EDTA/1% NaOCl, and 2% chlorhexidine (CHX) solutions were used between each file change, and 5 mL of the same irrigating solution was used for the final flush. In the MTAD group, the root canals were irrigated with 1.3% NaOCl between each file and 5 mL of MTAD for the final flush. All the root canals were filled with AH Plus sealer and gutta-percha cones. Apical leakage was evaluated using a fluid transport system. After the apical leakage test, each tooth was prepared for the push-out assessment. The statistical analysis revealed that the irrigation solutions had no effect on the apical leakage of the root canal fillings (p = 0.258). The root fillings of the groups irrigated with MTAD showed significantly lower push-out bond strength values than the other groups (p < 0.001). These commonly used irrigating solutions did not affect the apical leakage of the root canal sealer. MTAD reduced the bond strength of the root canal sealer to the root canal dentin.

The effects of different nickel-titanium instruments on dentinal microcrack formations during root canal preparation.

OBJECTIVE: The aim of the present study was to investigate the incidence of dentinal microcracks caused by different preparation techniques. MATERIALS AND METHODS: 120 extracted human mandibular incisor teeth were divided into five experimental groups and one control group (n = 20): Group 1: Hand preparation with balanced force technique up to #25 K-file. Group 2: Preparation with only ProTaper F2 instrument in a reciprocating movement. Group 3: Preparation with Reciproc R25 instrument in a reciprocating movement. Group 4: Preparation with ProTaper instruments up to F2 instrument. Group 5: Preparation with ProTaper Next instruments up to X2 instrument. No procedure was applied to control group. The roots were sectioned horizontally at 3, 6 and 9 mm from the apex and examined. Absence or presence of dentinal microcracks was noted. RESULTS: The Chi-square test was performed to compare the appearance of cracked roots between all groups. There were no significant differences among the groups (P > 0.05). CONCLUSIONS: In conclusion, except the hand file and control group, all experimental groups showed microcrack formations.

Evaluation of the resin cement thicknesses and push-out bond strengths of circular and oval fiber posts in oval-shapes canals.

PURPOSE: The aim of this study was to evaluate whether the push-out bond strength varies between oval and circular fiber posts, and to examine the effect on the resin cement thicknesses around the posts. MATERIALS AND METHODS: Eighteen mandibular premolar roots were separated into two groups for oval and circular fiber posts systems. Post spaces were prepared and fiber posts were luted to the post spaces. Roots were cut horizontally to produce 1-mm-thick specimens. Resin cement thicknesses were determined with a metallographic optical microscope and push-out tests were done. RESULTS: No significant differences were observed in terms of push-out bond strength between the oval and circular fiber posts (P>.05) The resin cement thicknesses of the oval posts were greater than those of the circular posts group in the coronal, middle and apical specimens (P<.05). CONCLUSION: In the light of these results, it can be stated that resin cement thickness does not affect the push-out bond strength.

Effects of physical and morphological properties of roots on fracture resistance.

OBJECTIVE: The aim of this study was to determine how physical and morphological properties affect the fracture resistance of roots, and which criteria are important for root specimen standardization in fracture resistance studies. MATERIALS AND METHODS: Seventy-five freshly extracted human canine teeth were selected. Crowns were sectioned from the cement-enamel junction and the root lengths were set at 16 mm. Then they were prepared up to ProTaper F3 file. Each root was numbered and data were obtained by measuring mesiodistal and buccolingual dimensions, volume, weight, and density. Tests for fracture strength were performed using an Instron Testing Machine (Instron Corp. MA, USA). The force was applied axially, angled at 45 degrees with a constant speed of 1 mm/min. For each sample, the force at the time of fracture was recorded in Newtons. Results were evaluated statistically using linear regression analysis. RESULTS: Volume and weight of the roots had more effect than mesiodistal or buccolingual dimensions on root fracture resistance. CONCLUSIONS: In root fracture resistance studies, volume or weight of the roots must be standardized when distributing roots to groups.

In vitro fracture resistance of endodontically treated roots filled with a bonded filling material or different types of posts.

AIM: This study aimed to compare the fracture resistance of roots filled with a bonded material, fiber posts, or titanium post systems. METHODS: Canals in the first group were filled with AH Plus and gutta-percha cones, and roots in the second group were filled with Epiphany sealer and Resilon cones. The root fillings (60 roots) were removed up to 4 mm from the canal apex to obtain 10-mm-deep post spaces, and posts were cemented. The groups were as follows: AH Plus control group, Epiphany control group, AH Plus fiber post group, AH Plus titanium post group, Epiphany fiber post group, and Epiphany titanium post group. Fracture tests were performed by using an Instron testing machine. The force was applied at a 45° axial angle with a constant speed of 1 mm/min. For each sample, the force at which fracture occurred was recorded in units of newtons. Statistical analysis was carried out by using analysis of variance test. RESULTS: There was no statistically significant difference between all groups (P > .05). CONCLUSIONS: Titanium posts, fiber posts, and Epiphany root canal filling systems were found to have no reinforcing effect on endodontically treated roots.

Apical extrusion of debris using self-adjusting file, reciprocating single-file, and 2 rotary instrumentation systems.

INTRODUCTION: The purpose of this study was to evaluate the weight of debris extruded apically from teeth using different in vitro preparation techniques. METHODS: Sixty-eight extracted human mandibular premolars with single canals and similar lengths were instrumented using ProTaper F2 (25, .08; Dentsply Maillefer, Ballaigues, Switzerland), the Self-Adjusting File (1.5-mm diameter; Re-Dent Nova, Ra'anana, Israel), Revo-S SU (25, .06; MicroMega, Besancon, France), or Reciproc (R25; VDW GmbH, Munich Germany). Debris extruded during instrumentation were collected into preweighed Eppendorf tubes. The Eppendorf tubes were then stored in an incubator at 70°C for 5 days. The Eppendorf tubes were weighed to obtain the final weight of the Eppendorf tubes when the extruded debris were included. Three consecutive weights were obtained for each tube. RESULTS: There were no statistically significant differences among the groups (P = .218). The ProTaper group produced the highest mean extrusion value. The Reciproc produced less debris compared with all the other instruments (P > .05). CONCLUSIONS: All instrumentation techniques were associated with extruded debris.

Resistance to fracture of roots filled with different sealers.

The aim of this study was to compare the fracture resistance of roots filled with gutta percha (GP) and different root canal sealers.Fifty-five human maxillary central incisors were selected and randomly divided into three experimental groups (Groups 1-3) and two control groups (Groups 4 and 5). They were Group 1-15 root canals filled with an epoxy resin-based sealer (AH Plus) and GP, Group 2 -15 root canals filled with a calcium silicate-based sealer (iRoot SP) and GP, Group 3: 15 root canals filled with another calcium silicate-based sealer (MTA Fillapex) and GP, Group 4: five roots were instrumented but not filled, and Group 5: five roots were neither instrumented nor filled. Compressive loading was carried out using a universal testing machine until fracture occurred. Force applied at time of fracture was recorded as fracture strength of specimen in Newtons. There were no significant differences in fracture strength among the three experimental groups (p>0.05), whose results were significantly superior to that of Group 4 (p<0.05). In conclusion, all the root canal sealers used in the present study increased the fracture resistance of instrumented root canals.

The effect of peracetic acid on removing calcium hydroxide from the root canals.

INTRODUCTION: The goal of this study was to evaluate the efficiencies of different irrigation solutions in the removal of calcium hydroxide (CH). METHODS: Forty-eight maxillary central incisor teeth were used. Root canals were prepared with the ProTaper system (Dentsply Maillefer, Baillagues, Switzerland). Five milliliters 2% NaOCl, 5 mL 17% EDTA, and 10 mL saline were used for final irrigation. The canals were filled with CH paste. Specimens were randomly divided into 4 experimental groups (n = 10) according to irrigation protocols. Positive and negative control groups (n = 4) were used. Group 1 used 2.5 mL 17% EDTA, group 2 used 2.5 mL 2.5% NaOCl + 2.5 mL 17% EDTA, group 3 used 2.5 mL 1% peracetic acid (PAA), and group 4 used 2.5 mL 0.5% PAA. The specimens were evaluated with scanning electron microscope analysis and scored. Kruskal-Wallis and Student Newman-Keuls post hoc tests were used for statistical analysis. RESULTS: In the apical thirds, 1% PAA was superior to the other groups (P < .05); however, there were no significant differences among the other groups (P > .05). In the middle thirds, no significant differences were found among the groups (P > .05). In the coronal thirds, 1% PAA was superior to the other groups. There were significant differences among all the other groups (P < .05). CONCLUSIONS: According to the findings of the present study, 1% PAA could be recommended for the removal of CH from the root canals.

Can intra-coronally bleached teeth be bonded safely after antioxidant treatment?

The aim of this study was to compare the effects of antioxidant treatment and delayed bonding, following intra-coronal bleaching, on the shear bond strength (SBS) and bond failure site of brackets bonded to enamel. Eighty mandibular incisors were divided into four equal groups. After root canal filling, specimens in Group 1 were used as control and not bleached. For experimental groups 2 to 4, bleaching agent was placed into the rest of the cavity for a four-day period and this bleaching treatment was performed two times. In Group 2, specimens were bonded immediately after bleaching; in Group 3, specimens were bleached and then immersed in artificial saliva for 30 days before bonding; in Group 4, specimens were bleached, treated with an antioxidant agent, and then bonded. The SBS values of bonded brackets were measured in megapascal (MPa), while adhesive remnant index (ARI) scores were determined after the brackets failed. The SBS values of Group 1 (mean: 20.3+/-7.1 MPa) and Group 4 (mean: 18.2+/-6.1 MPa) were significantly higher (p>0.001) than those of Group 2 (mean: 4.9+/-3.2 MPa) and Group 3 (mean: 8.7+/-4.9 MPa). No significant differences in SBS were found between Groups 1 and 4, and between Groups 2 and 3.

Can intracoronally bleached teeth be bonded safely?

INTRODUCTION: Our objective was to determine the effects of intracoronal bleaching on the shear bond strength and failure side location of metallic brackets at 2 times (bleaching immediately before bonding and 30 days before bonding). METHODS: Sixty freshly extracted mandibular incisors were randomly divided into 3 groups; each group contained 20 teeth. After finishing canal preparation and root canal filling, the root fillings were removed to a level 2 mm apical to the cementoenamel junction. Glass ionomer base (Vitrabond, 3 M Dental Products, St Paul, Minn) was placed approximately 2-mm thick. Bleaching agent (Whiteness Perfect, FGM Dental Products, Joinville, Brazil) was placed into the rest of the cavity for 4 days at 2 times. Shear bond strength of these brackets was measured in megapascals. The adhesive remnant index (ARI) scores were determined after the brackets failed. Data were analyzed with analysis of variance (ANOVA), Tukey, and chi-square tests. RESULTS: The bond strengths of the group with no bleaching (mean, 20.25 +/- 7.06 MPa) were significantly higher (P >0.001) than those of the group that had bleaching immediately before bonding (mean, 4.85 +/- 3.22 MPa) and the group that had bleaching 30 days before bonding (mean, 8.70 +/- 4.93 MPa). The results of the chi-square comparisons indicated significant differences among the 3 groups. In the group with no bleaching, there was a higher frequency of ARI scores of 2 to 4, indicating cohesive failures in the resin. In the other 2 groups, the failures were mostly adhesive at the resin-enamel interface (ARI scores of 4 and 5). CONCLUSIONS: Intracoronal bleaching with carbamide peroxide adversely affected the shear bond strength and changed the site of failure during debonding when bonding was done immediately or 30 days after bleaching.

In vitro pharmacodynamic activities of root canal sealers on Enterococcus faecalis.

AIM: The aim of this study was to evaluate the antimicrobial efficiency of different root canal sealers on Enterococcus faecalis (E. Faecalis) at different time intervals. METHODS AND MATERIALS: All sealers used were mixed according to the manufacturers' instructions then 75 mg of each sealer was added to different sterile tubes and evaluated at 20 minutes, 24 hours, 7 days, and 30 days. A time-kill assay (TKA) was used to determine the antimicrobial efficiency of the sealers. RESULTS: AH Plus and MCS were found to be bactericidal at 20 minutes and 24 hours, but only MCS was bactericidal at the seventh and thirtieth days. Epiphany and Sealapex were found to be bacteriostatic at the seventh and thirtieth days but indifferent at 20 minutes and 24-hours. MCS and AH Plus were both found to be bactericidal in freshly mixed samples, but only MCS was bactericidal at longer time periods. Epiphany Sealer and Sealapex were found to be bacteriostatic at longer time periods but indifferent at 20 minutes and 24 hours. CONCLUSION: The antibacterial effect of MCS was greater than the other sealers evaluated. CLINICAL SIGNIFICANCE: Sealers containing eugenol and epoxy resin might be preferable due to their antibacterial effect.

Evaluation of microleakage of roots filled with different techniques with a computerized fluid filtration technique.

The aim of this study was to compare the apical leakage of roots filled with different materials using a computerized fluid filtration technique. There were 36 freshly extracted human maxillary central incisors selected. After preparation and irrigation, 3 experimental groups of 10 roots were constituted. Ten roots were filled with AH Plus and gutta-percha, 10 roots were filled with Sealapex and gutta-percha, and 10 roots were filled with Epiphany sealer and Resilon cone using a single cone technique. Three roots were used as a positive control and three roots were used as a negative control group. Evaluation of the apical leakages was performed with a computerized fluid filtration technique. According to the results, the difference between group 3 and 1 and group 3 and 2 was statistically significant (p<0.05). Although group 2 leaked the most, there was no significant difference between group 1 and 2.