ActiV GP Research Articles

Evaluation of Sealing Ability of Three Different Root Canal Sealers (in Vitro Study)

Aim: The aim of this study was to evaluate the apical sealing ability of three different endodontic sealers using dye penetration method. Materials and Methods: Palatal roots of forty five extracted maxillary first molars were instrumented with ProTaper rotary files to size F4. The teeth were divided into three experimental groups according to type of sealer used, group1: root obturated with AH Plus sealer and single cone technique, group2: root obturated with ActiV GP sealer and single cone technique, group3: root obturated with GuttaFlow2 sealer and single cone technique. Data was subjected to statistical analysis. P-Value

Activ GP system in endodontics: A review

The ideal endodontic obturating material must cut communication between the root canal and the periodontal tissues. It should also be nongenotoxic, non-carcinogenic, nontoxic, biocompatible with host tissues, insoluble in tissue fluids, and dimensionally stable. Because the available root canal filling materials do not have these ideal properties, Activ GP system was developed and recommended to be used as a root canal filling material. The use of a new material should be based on laboratory, biological, and clinical studies. The aim of this review was to update previously published information and present a list of articles from various highly indexed endodontic journals regarding Activ GP system, cytotoxicity, pH, solubility, anti-biofilm activity, sealing properties, resistance to fracture of dental roots obturated with Activ GP system, retreatment, and the effect of irrigating solutions on bond strength of this system.

Push-Out Bond Strength of Experimental Apatite Calcium Phosphate Based Coated Gutta-Percha.

Objectives To evaluate the push-out bond strength of experimental apatite calcium phosphate coated gutta-percha (HAGP) compared to different commercially available coated gutta-percha root obturation points. Methods Extracted teeth were selected and instrumented using ProTaper rotary files. The canals were assigned into five equal groups and obturated using matching single cone technique as follows: EndoREZ cones and EndoREZ sealer, Bioceramic Endosequence gutta-percha (BCGP) with Endosequence BC sealer, Active GP with Endosequence BC sealer (ActiV GP), conventional GP with Endosequence BC sealer, and HAGP with Endosequence BC sealer. Each root was sectioned transversally at the thickness of 1±0.1 mm to obtain 5 sections (n=25 per group). The specimens were subjected to push-out test using a Universal Test Machine at a loading speed of 0.5 mm/ min. Failure modes after push-out test was examined under stereomicroscope and the push-out data were analyzed using ANOVA and the post hoc Dunnett T3 test (p = 0.05). Results The highest mean bond strength was yielded by HAGP followed by BCGP, ActiV GP, conventional GP, and EndoREZ. There were significant differences between EndoREZ and all other groups (p<0.001). The prominent failure mode of HAGP was mixed mode, whereas EndoREZ exhibited adhesive failure mode. Conventional GP, ActiV GP, and BCGP showed cohesive failure mode. Conclusion HAGP showed promising results to be used as root canal filling material in combination with bioceramic sealer.

Evaluation of apical bacterial leakage of three different obturation systems after using two different irrigating solutions: An in vitro study

Aim: The present study aimed to compare between apical bacterial leakage of obturating systems such as EndoRez, ActiV GP and AH Plus sealers using gutta-percha, with two different irrigating materials Biopure MTAD (mixture of doxycycline, acetic acid and detergent) and 2.25% sodium hypochlorite (NaOCl). Methods: Seventy extracted human mandibular premolars with single canal were divided into two equal groups of 30 samples each according to the irrigating solution used either Biopure MTAD or 2.25% NaOCL. The other 10 teeth (5 roots positive group and 5 roots negative group) were used as control. The main groups were subdivided into 3 subgroups according to the obturation system used, EndoRez, ActiV GP or AH Plus with gutta percha. Sealing ability was assessed using Enterococcus faecalis (E. faecalis) in a double chamber leakage model. Samples were monitored weekly for periods of 1, 4 and 8 weeks to assess the turbidity of the medium in contact with the lower coronal portion of the root segment. Results: Showed statistically significant increase in the mean apical leakage with specimens irrigated with 2.25% NaOCL than Biopure MTAD in all periods, while roots obturated with EndoRez showed less statistically significant leakage than the rest of the experimental materials at 1 and 4 weeks periods while, at 8 weeks period all the experimental materials showed leakage with no statistically significance difference. Conclusion: EndoRez when used after Biopure MTAD irrigation provides better sealing with root canal dentin.

Evaluation of apical sealing ability of ActiV GP/glass ionomer sealer as a root filling material

Introduction: The aim of this in vitro study was to assess the sealing ability of ActiV GP/glass ionomer sealer and to compare it with sealing ability of Resilon/Real Seal and gutta-percha/AH Plus. Materials and Methods: Forty-five human mandibular premolars were randomly divided into three groups (15 canals each). Each canal was instrumented to a size 40, taper 6% using K3 NiTi rotary instruments. A smear layer was removed, and the teeth were filled using single cone technique with ActiV GP, Resilon/Real Seal, or lateral condensation with gutta-percha/AH Plus. The teeth then were immersed in 2% methylene blue solution for 24 h, longitudinally sectioned and examined under a stereomicroscope to evaluate the liner leakage of the dye in each group. The data were analyzed with descriptive statistical methods and Mann–Whitney test (P = 0.05). Results: The lowest mean of leakage was recorded in gutta-percha/AH Plus group. There was a statistically significant difference between gutta-percha/AH Plus group and the two other groups; ActiV GP group and Resilon group. Conclusion: Dye penetration examination showed that ActiV GP/GI sealer had weak sealing properties, Resilon/RealSeal system did not show superior sealing properties in comparison with gutta-percha/AH Plus sealer, and lateral condensation shows better sealing properties in comparison with single cone technique.

THE EFFECT OF DIFFERENT ADHESIVE OBTURATING MATERIALS ON THE FRACTURE RESISTANCE OF ENDODONTICALLY TREATED TEETH

This study aimed to evaluate the fracture resistance of teeth obturated with different adhesive obturation systems. Seventy freshly human extracted single rooted teeth were selected. The samples were biomechanically prepared and classified according to the type of the obturating material into four groups as follows; Group 1; (21 samples) obturated with conventional gutta-percha and AD-seal sealer (META, Chungcheongbuk-do, Korea). Group 2; (21 samples) obturated with ActivGP cones and Activ GP sealer (Brasseler, Savannah, USA). Group 3; (21 samples) obturated with resilon cones and Epipheny sealer (Pentron,Wallingford,USA). Group 4; Control group (unobturated). The samples were further classified according to the observation time into: Subgroup A; (7 samples) after one week. Subgroup B; (7 samples) after one month and Subgroup C; (7 samples) after three month. Samples were loaded vertically after obturation using Universal Testing Machine until fracture. It was found that ActivGP showed the highest resistance followed by Resilon then conventional gutta-percha. It was concluded that Activ Gpobturating system can strengthen the endodontically treated teeth more than Resilon/Epipheny system.

Influence of Different Obturation Systems on the Fracture Resistance of Endodontically Treated Roots

Objective: This study aimed to compare the fracture resistance of endodontically treated roots filled by different obturation systems. Material and methods: Ninety-six upper central incisors were used and decoronated, retaining 12 mm of the roots. On the basis of obturation systems, the roots were divided into 4 groups (n=24): Group1 (COGR): control group (unprepared, unfilled), Group 2 (AVGR): ActiV GP points/ActiV GP sealer, Group3 (GPGR): Gutta percha points/AH plus sealer, and Group4 (GAGR): Gutta percha points/ActiV GP sealer. The last three groups were obturated with the single cone technique. The roots were then stored in 100% relative humidity at 37 °C for 2 weeks. A vertical compressive force was exerted with a universal testing machine until a fracture occurred. Data were statistically analyzed with one-way ANOVA. Results: Mean (SD) failure loads for groups ranged from 920.51 ± 210.37 to 1113.44 ± 489.42 N. The fracture resistance between the different study groups indicated no statistical difference. Conclusions: ActiV GP system did not exert a significant effect on the fracture resistance of endodontically treated teeth.

EFFECT OF DIFFERENT IRRIGATING PROTOCOLS ON THE BOND STRENGTH OF THE ACTIV GUTTA PERCHA ROOT CANAL OBTURATION SYSTEM (COMPARATIVE IN VITRO STUDY)

INTRODUCTION: Different irrigations may cause alteration in the composition of dentin, thereby affecting the adhesion of materials to dentin surfaces. OBJECTIVES: evaluate the effect of different irrigating protocols used as final rinse on the bond strength of the ActiV gutta percha. MATERIALS AND METHODS: Forty extracted single rooted lower premolars were used. Teeth were decoronated to standardize the root length to 15mm. The canals were instrumented using OneShape rotary system. Teeth were irrigated with 2.5% sodium hypochlorite then divided into four parallel groups according to the final rinse (n=10). GroupI: 10ml 17% Ethylene diaminetetraacetic acid, followed by 10ml of 2.5% NaOCL; GroupII: 10ml of 1.3%mixture of a tetracycline isomer, an acid and detergent (MTAD); GroupIII: 10ml of 2% chlorhexidine gluconate; GroupIV: 10ml 2.5% NaOCL(control). All the root canals were filled using ActiV GP. Slicing was done at the coronal and middle thirds for push-out test to measure bond strength. Then failure mode was evaluated under stereomicroscope. Data were analysed using t-test and one-way ANOVA test. RESULTS: Group III yielded significantly the highest mean push-out bond strength (2.91± 0.79 MPa), followed by group II (2.39± 0.89 MPa), then group IV (1.80± 0.61MPa) and finally group I (1.61± 0.52 MPa). The bond strength values of the middle sections were significantly higher than that of the coronal sections. The failure mode was predominantly cohesive in groups II and III and adhesive in groups I and IV. CONCLUSIONS: CHX and MTAD increased the bond strength of ActiV GP, while EDTA decreased the bond strength. The push out bond strength values were affected by the location of root segment. There was correlation between the push out bond strength values and the failure mode.

Assessment of furcal perforations in the vicinity of different root canal sealers using a cone beam computed tomography system with and without the application of artifact reduction mode: an ex vivo investigation on extracted human teeth

To investigate observer ability to diagnose exvivo simulated endodontic furcal perforations in root-filled teeth from cone beam computed tomography (CBCT) images using different artifact reduction algorithms. Our study consisted of 135 first maxillary molar teeth. In 89 teeth, furcation perforations were created using dental burs. Forty-six teeth without artificial perforations were used as controls. MTA Fillapex, Activ GP, and AH Plus were used with or without metal posts. All teeth were imaged using Planmeca ProMax 3-D Max CBCT, and four image modes were obtained as without artifact reduction and with artifact reduction in low, medium, and high modes. Images were evaluated by three observers for the presence or absence of furcation perforation using a five-point scale. Weighted kappa coefficients were calculated to assess observer agreement. Receiver operating characteristic analysis was performed. Areas under the curve (AUCs) were calculated for each image mode, observer, treatment group, and reading and were compared using Χ(2) tests, with a significance level of α=0.05. The effects on diagnosis were calculated using analysis of variance (ANOVA). Intraobserver agreements for all observers ranged from 0.857 to 0.945. Kappa coefficients among different observers ranged from 0.673 to 0.763. AUC values ranged from 0.83 to 0.92, and there were no statistically significant differences (P>.05) between different CBCT image modes. Ratings in Activ GP treatment groups with or without posts showed statistically significant differences (P<.001). All CBCT image modes performed similarly in detecting furcal perforations near different root canal sealers with or without posts.

Evaluation of root canal sealer filling quality using a single-cone technique in oval shaped canals: An In vitro Micro-CT study.

The aim of this study was to evaluate and compare the presence of voids in oval root canals filled with different root canal sealers (EndoSequence BC Sealer, Smartpaste bio, ActiV GP) and to compare those with root canals filled with AH Plus sealer using micro-CT. In total, 40 freshly extracted human single-root maxillary premolars were used. Specimens instrumented with the EndoSequence NiTi rotary instrument were assigned randomly into four groups. In each group, root canals were filled with single-cone gutta-percha and one of the tested sealers. Each specimen was then scanned using micro-CT at a voxel resolution of 13.47 μm. Proportions of sections with voids in cross-sectional images and void volumes for each sealer were calculated in the apical, middle, and coronal thirds. Differences according to root canal sealers were evaluated statistically using the Kruskal-Wallis test and the Mann-Whitney U-test at a significance level of 5%. The analysis showed a decrease in void formation in the apical third, with a significant difference between the apical and coronal thirds among bioceramic sealers, ActiV GP, and AH Plus (p < 0.05) but no significant difference between the apical and middle thirds or between the middle and coronal thirds was found for the sealers tested (p > 0.05). All root canal sealers tested resulted in voids. The bioceramic sealers (EndoSequence BC Sealer, Smartpaste bio) produced similar voids which had the fewest in the apical third of root canals among the sealers tested which can be related due to root canal anatomy variations.

Resistance to fracture of dental roots obturated with different materials.

The aim of this study was to compare the vertical fracture resistance of roots obturated with different root canal filling materials and sealers. Crowns of 55 extracted mandibular premolar teeth were removed to provide root lengths of 13 mm. Five roots were saved as negative control group (canals unprepared and unfilled). Fifty root canals were instrumented and then five roots were saved as positive control group (canals prepared but unfilled). The remaining 45 roots were randomly divided into three experimental groups (n = 15 root/group) and obturated with the following procedures: in group 1, glass ionomer-based sealer and cone (ActiV GP obturation system); in group 2, bioceramic sealer and cone (EndoSequence BC obturation system); and in group 3, roots were filled with bioceramic sealer and cone (Smartpaste bio obturation system). All specimens were tested in a universal testing machine for measuring fracture resistance. For each root, the force at the time of fracture was recorded in Newtons. The statistical analysis was performed by using Kruskal-Wallis and post hoc test. There were no significant differences between the three experimental groups. The fracture values of three experimental and negative control groups were significantly higher than the positive control group. Within the limitations of this study, all materials increased the fracture resistance of instrumented roots.

Antibiofilm activity, pH and solubility of endodontic sealers

To evaluate antibiofilm activity against Enterococcus faecalis, pH and solubility of AH Plus, Sealer 26, Epiphany SE, Sealapex, Activ GP, MTA Fillapex (MTA-F) and an experimental MTA-based Sealer (MTA-S). Sealer samples were manipulated and stored for 2 or 7days. Prepared sealers were evaluated by a modified direct contact test (DCT) for 5h, 10h or 15h with biofilm previously induced on bovine dentine for 14days. In the control group, the biofilm was not exposed to the sealers. The number of colony-forming units (CFU mL(-1) ) in the remaining biofilm was determined. Sealer solubility was assessed by the percentage of mass loss after 15h of immersion in distilled water. Sealer pH was measured at 5h, 10h and 15h. Statistical analysis was performed using Kruskal-Wallis and Dunn or anova and Tamhane's T2 tests, at 5% significance. At 2days post-manipulation, the DCT showed that Sealapex and MTA-F were associated with a reduction in the number of bacteria in all 3 contact periods evaluated, compared with the control group (P<0.05). At 7days, Sealapex had the greatest antibiofilm action at 10h and 15h. Sealapex had the highest pH values 2 and 7days post-manipulation. Regarding the solubility, at 2days the highest values were observed for MTA-F, MTA-S, Sealapex and Activ GP (P<0.05). At 7days, MTA-S and MTA-F had greater solubility than the other materials (P<0.05). AH Plus had the lowest solubility for both post-manipulation periods (P<0.05). Sealapex and MTA-F were associated with a reduction in the number of bacteria in biofilms and had greater solubility. The high solubility and pH may be related to the antibacterial activity of these materials.

Push-out bond strength of different root canal obturation materials

The aim of this study was to evaluate the push-out bond strength of four different obturation materials to intraradicular dentin and to determine the failure mode. Materials and method: forty straight palatal roots of the maxillary first molars teeth were used in this study, the roots were instrumented using crown down technique and rotary EndoSequence system, the roots were randomly divided into four groups according to the materials used for obturation (n=10).Group (1): AH Plus sealer and gutta-percha. Group (2): Activ GP glass ionomer sealer and Activ GP gutta-percha (Activ GP system). Group (3): Bioceramic sealer and Bioceramic gutta-percha. Group (4): GuttaFlow2 sealer and gutta-percha. For all groups single cone obturation technique was used. After incubation period of one week, the roots were embedded in clear acrylic resin and each root sectioned into three levels apical, middle and cervical. The bond strength was measured using computerized universal testing machine, each section fixed in the machine so that the load applied from apical to coronal direction at 0.5mm/min speed and the computer drew curve to show the higher bond force before dislodgment of the filling material. After de-bonding each sample was examined under Stereomicroscopic and the type of failure mode was recorded. Results: showed a non significant difference between AH plus group and Bioceramic group. AH Plus group showed a very highly significant difference with Activ GP group and a highly significant difference with GuttaFlow2 group. There were significant differences between coronal level and both apical and middle levels with no significant differences between apical and middle levels within each group.

The efficacy of ProTaper Universal rotary retreatment instrumentation to remove single gutta‐percha cones cemented with several endodontic sealers

To evaluate residual root filling material following removal of three newly developed root canal sealers used with a matched-taper single-cone root filling technique and to compare the efficacy of ProTaper Universal rotary retreatment instruments with that of a conventional manual technique. The canals of 120 palatal roots in maxillary molar teeth were instrumented with EndoWave nickel-titanium rotary instruments and filled using Hybrid Root SEAL, EndoSequence BC Sealer, Activ GP system or AH Plus with matched-taper single gutta-percha cones. The root fillings were then removed with ProTaper Universal retreatment rotary instruments or a manual technique. Buccolingual and proximal digital radiographs of the roots were exposed to determine the area of remaining filling material in the coronal, middle and apical thirds. The area percentages of remaining filling material in each third and total canal area were calculated. Data were analysed statistically with Kruskal-Wallis and Mann-Whitney U-tests. The level of significance was set at P<0.05. Irrespective of the sealer type and retreatment technique, filling material could not be removed completely from the root canals. Significantly, more remaining filling material was observed in the apical third (P<0.05). When comparing the sealers, the only significant difference was detected between AH Plus/manual and Activ GP/manual groups with respect to residual material in the total canal area (P<0.05). There were no significant differences between manual and ProTaper groups. When using gross radiographic criteria, the Activ GP was more effectively removed from root canals than AH Plus with hand instrumentation. Hybrid Root SEAL, EndoSequence BC Sealer and AH Plus were removed to a similar extent. ProTaper Universal retreatment instruments were as safe and effective as hand instruments in reaching the working length.

Relationship between sealing ability of Activ GP and Gutta Flow and methods of calcium hydroxide removal

Aim:To evaluate the effect of method of calcium hydroxide intracanal dressing removal, on sealing ability of Gutta Flow and Activ GP.Materials and Methods:Seventy extracted mandibular premolars were sectioned at CEJ and canals were prepared with profile 4% rotary file till #40. Canals were filled with calcium hydroxide, coronally sealed with Cavit G and stored at 37°C. After 7 days, samples were divided on the basis of calcium hydroxide removal method (Master apical file, Navi Tip FX, and F File) and obturating material (Activ GP and Gutta Flow). Three coats of nail polish were applied except 2 mm around apical foramen and samples were immersed in India ink dye, sectioned, and observed under stereomicroscope for microleakage.Results:The results were statistically analyzed with one way ANOVA-F with Tukey HSD test with the null hypothesis set as 5%.Conclusions:The seal of the canal system was adversely impacted by residual calcium hydroxide when Activ GP and Gutta Flow were used as obturating material and the sealing ability of Activ GP and Gutta Flow was better when MAF was used for removal of calcium hydroxide than F file or Navi tip FX.

Cytotoxicity of 5 endodontic sealers on L929 cell line and human dental pulp cells

To investigate the cytotoxicity of five root canal sealers on L929 mouse fibroblasts and primary human dental pulp cells. Cylindrical specimens of AH Plus (Dentsply De Trey GmbH, Konstanz, Germany), RoekoSeal (Coltène Whaledent, Langenau, Germany), EndoREZ (Ultradent Products Inc., South Jordan, UT, USA), Epiphany (Pentron Clinical Technologies, LLCC, Wallingford, CT, USA) and Activ GP (Brasseller Inc., USA, Savannah, GA, USA) were kept at 37 °C in a humidified atmosphere of 5% CO(2) for thrice the length of the setting time given by the manufacturer. Extraction of specimens was performed after setting in cell growth medium for 1, 4 and 7 days. Undiluted, 50% and 25% diluted eluates were incubated with cultured cells for 24 and 72 h. Cytotoxicity was assessed using MTS colorimetric bioassay. Kruskal-Wallis test and post hoc Dunn's multiple comparison test were used to compare the sealers and diluted/undiluted eluates in terms of cell viability (% of control). Friedman test and post hoc Dunn's multiple comparison test were performed to compare extraction periods. Wilcoxon test was utilized in comparing 24- and 72-h readings. Undiluted 1-day eluate of Activ GP was significantly more cytotoxic than all other sealers (P < 0.0001). Undiluted 4- and 7-day eluates of Epiphany and Activ GP were significantly more cytotoxic than the other three sealers (P < 0.0001). Diluted eluates of Activ GP and Epiphany were generally less toxic than the undiluted ones. The cytotoxicity of Epiphany significantly increased as the extraction period increased (P < 0.0001). Epiphany became more toxic with time of exposure to cells. No or minimal cytotoxicity was observed with RoekoSeal, AH Plus and EndoREZ. The sealers exhibited varying degrees of cytotoxicity dependent on their chemical composition.

Evaluation of physicochemical properties of four root canal sealers

To assess the physicochemical properties and the surface morphology of AH Plus, GuttaFlow, RoekoSeal and Activ GP root canal sealers. Five samples of each material were evaluated for setting time, dimensional alteration, solubility and radiopacity tests, according to ANSI/ADA Specification 57. A total of 50 mL of deionized distilled water from the solubility tests were used to measure the metal solubility by atomic absorption spectrometry. The morphologies of the external surface and the cross-section of the samples were analysed by means of a scanning electron microscope (SEM). Statistical analysis was performed by using one-way anova and post hoc Tukey-Kramer tests with the null hypothesis set as 5%. AH Plus had the longest setting time (580.6 ± 3.05 min) (P<0.05). Activ GP did not have a mean value on the radiopacity and solubility tests (1.31 ± 0.35 mm and 11.8 ± 0.43%, respectively) in accordance with ANSI/ADA, being significantly different from the other materials (P<0.05), which had mean values for these tests in accordance with the ADA's requirements. GuttaFlow was the only sealer that conformed to the Specification 57 concerning the dimensional alteration test (0.44 ± 0.16%) (P<0.05). The spectrometry test revealed significant Ca(2+), K(+), Zn(2+) ion release from Activ GP sealer (32.57 ± 5.0, 1.57 ± 0.22 and 8.20 ± 1.74 μg mL(-1), respectively). In SEM analysis, the loss of matrix was evident and the filler particles were more distinguishable in all groups. The setting time of all sealers was in accordance with ANSI/ADA's requirements. Activ GP did not fulfill ANSI/ADA's protocols regarding radiopacity, dimensional alteration and solubility. GuttaFlow was the only sealer that conformed to the Specification 57 in all tests. SEM analysis revealed that the surfaces of all sealers had micromorphological changes after the solubility test.

Microleakage of various root filling systems by glucose filtration analysis

The aim of this study was to evaluate the microleakage of Resilon + Epiphany, EndoRez, Activ GP, and conventional AH Plus + gutta-percha technique using the glucose filtration model. One hundred twenty maxillary incisors were divided into 5 experimental and 2 control groups. After root canal shaping, the experimental groups were filled with AH Plus + gutta-percha (lateral compaction), Resilon + Epiphany (lateral compaction), AH Plus + Protaper's proprietory cone, EndoRez + sealer, or Activ GP + sealer). The specimens were mounted on a glucose model and samples were taken for 3 weeks for leakage measurement. No statistically significant difference was observed between the leakage of all groups at the 3 testing periods (P > .05). The filling materials with the monoblock concept do not seem to be superior to the conventional AH Plus + gutta-percha system regarding microleakage.

Micro‐CT evaluation of residual material in canals filled with Activ GP or GuttaFlow following removal with NiTi instruments

To assess the efficacy of removing Activ GP or GuttaFlow from canals using NiTi instruments. Root canals in 55 extracted pre-molars were prepared to apical size 40, 0.04 taper. The teeth were imaged with micro-CT, and 30 teeth selected that had consistent apical size and taper of the shaped canals. They were randomly assigned to root filling with either the glass-ionomer-based ActivGP system (n = 15) or the polyvinylsiloxane-based GuttaFlow system (n = 15). After 2 weeks, canals were retreated stepwise with size 40-50 EndoSequence 0.04 taper instruments. Micro-CT scans (8 mum) were taken after use of each instrument to detect root filling residue in the coronal, middle and apical segment, and the retreatment time recorded. Residue, expressed as percentage of canal surface area, was compared between groups with t-tests, and within groups with repeated measures anova and Bonferroni-adjusted pairwise comparisons. Retreatment time was analysed with one-way anova. The percentage of sealer residue-coated canal surface was consistently highest (P < 0.001) in the apical third of canals, and it did not differ significantly between the two root filling groups. Stepwise enlargement from size 40 to 50 significantly decreased the amount of sealer residue in both groups (P < 0.001). Retreatment time did not differ significantly between groups. Both root fillings with ActivGP and GuttaFlow were removed with nickel-titanium rotary instruments. Enlargement of canals up to two sizes beyond the pre-retreatment size was necessary to minimize the amount of sealer remaining.

Fracture resistance of roots using different canal filling systems

To evaluate the fracture resistance of teeth filled with various canal filling materials. The crowns of 100 single-rooted teeth were removed leaving 12 mm of the roots. The canals were shaped using Endo-Sequence files. Following instrumentation, 80 teeth were divided into four groups. The remaining 20 teeth were divided into two groups. The teeth in each group were filled as follows: Group 1: AH-Plus + Gutta-percha (Cold lateral compaction), Group 2: Resilon + Epiphany (Cold lateral compaction), Group 3: ActiV GP cone + ActiV GP sealer, Group 4: ActiV GP sealer + Gutta-percha (Cold lateral compaction), Group 5: No instrumentation or filling, Group 6: Instrumentation but no filling. After the sealers had set, the roots were embedded in acrylic moulds and subjected to a compressive loading at a rate of 1 mm min(-1). The load at which fracture occurred was recorded and statistically analysed using Kruskal-Wallis one-way analysis of variance and Z-tests. The fracture values of the experimental teeth were significantly higher than those of the instrumented but unfilled group (P < 0.05). Teeth in the AH-Plus + lateral compaction group had higher fracture resistance compared with the ActiV GP sealer + Gutta-percha group (P < 0.05). Systems aiming to obtain a monoblock system were not superior to the conventional AH-Plus + Gutta-percha technique in terms of fracture resistance. The fracture resistance of roots using ActiV GP + lateral compaction Gutta-percha was significantly reduced compared with the AH-Plus + Gutta-percha group.