Identification and Characterization of a Previously Undiscovered Anatomical Structure in Maxillary Second Molars: The Palato-Mesiobuccal Canal.

INTRODUCTION: This report aims to communicate the discovery of a novel anatomy in a 3-rooted maxillary second molar, named as palato-mesiobuccal canal. METHODS: The tooth selected for this report was found incidentally as a result of a study on extracted maxillary molars that was being conducted for an unrelated purpose and involved hundreds of teeth. This 3-rooted maxillary second molar was scanned using a micro-computed tomography device set at a pixel size of 13.68 µm. The images were reconstructed with previously tested parameters resulting in the acquisition of 1655 axial cross-sections. Three-dimensional (3D) models of the internal and external anatomies were generated in Standard Tessellation Language (STL) format and were texturized to simulate the pulp tissue. The inner structure of the tooth was analyzed through the axial cross sections and the 3D volume was qualitatively evaluated. RESULTS: The analysis of the 3D models revealed that the maxillary second molar under examination has 3 independent roots and 4 root canals. Each root (mesiobuccal, distobuccal, and palatal) contains 1 canal, while the fourth canal follows a unique path, originating in the coronal third of the palatal canal and proceeding in a buccal direction ultimately exiting through an independent foramen at the apex of the mesiobuccal root, near the mesiobuccal canal. CONCLUSIONS: This brief communication reports the discovery of a novel anatomy in a 3-rooted maxillary second molar, named as palato-mesiobuccal canal, and provides important insights into the complexity of the root canal system in this group of teeth.

Apically extruded debris of different file systems used with various kinematic movements during retreatment: An in vitro study.

This study aimed to examine the amount of apically extruded debris and time during retreatment with five current file systems, which exhibit various kinematic movements. One hundred upper central incisors were shaped with manual files and filled using the thermoplastic injection method. The root canal fillings in each group (n = 20) were removed using the Genius (GN), ProTaper Next (PTN), Reciproc (RCP) Blue, Tango-Endo (TE) and Twisted File Adaptive (TFA) file systems. The apically extruded debris was collected in preweighed Eppendorf tubes. Time to reach working length and total time were also recorded. The PTN, RCP Blue and TFA instruments caused significantly less apically extruded debris and shorter total retreatment time than the GN and TE file systems (p < 0.05). The time to reach the working length was the shortest in the PTN group compared to the other groups (p < 0.05). All file systems extruded debris while removing the root canal filling.

The effects of final irrigants on the push-out bond strength of two calcium silicate-based root canal sealers: an in vitro study.

PURPOSE: The purpose of the present study was to investigate the effect of the different irrigant combinations used in final irrigation on the push-out bond strength of root canal sealers that have different compositions. MATERIALS AND METHODS: In total 60 dentinal slices in 1 mm thickness were collected from 15 extracted mandibular premolar teeth; 4 slices from each tooth. 3 canal-like artificial cavities were opened on each dentinal slice. Samples were divided into 4 experimental groups, each of which consisted of 15 samples. In group 1, samples were immersed in 5.25% NaOCl and 17% EDTA solutions respectively; in group 2, immersed in 5.25% NaOCl and 2% CHX solutions respectively; in group 3, immersed in 5.25% NaOCl, 17% EDTA and 2% CHX solutions respectively; and in group 4 immersed in distilled water. After drying with absorbent papers, each cavity in dentinal slice sample was filled with different sealer (Endoseal MTA, Tech Biosealer Endo or AH Plus). Two days later, the push-out bond examination was performed. RESULTS: AH Plus showed higher push-out bond strength value in two combinations (group 2 and 3) in which final irrigants contained CHX (p<0.001). Dentinal push-out bond strengths of root canal sealers from Endoseal MTA and Tech BioSealer Endo were not affected by final irrigant (p=0.965). CONCLUSION: Using CHX after NaOCl in final irrigant increases push-out strength of epoxy resinbased sealer but, did not create any difference in dentinal push-out bond strength of calcium silicate-based sealers.

Efficacy of Erbium, Chromium-doped Yttrium, Scandium, Gallium and Garnet Laser-activated Irrigation Compared with Passive Ultrasonic Irrigation, Conventional Irrigation, and Photodynamic Therapy against Enterococcus faecalis.

AIM: To compare the antimicrobial effects of two different irrigation solutions activated with erbium, chromium-doped yttrium, scandium, gallium and garnet (Er,Cr:YSGG) laser or an ultrasonic system and a photodynamic therapy (PDT) on Enterococcus faecalis (E. faecalis). MATERIALS AND METHODS: The root canals of 72 single-rooted human permanent incisors were prepared with ProTaper Universal rotary instruments and incubated with E. faecalis (ATCC 29212) for 4 weeks. Then the teeth were randomly divided into seven experimental groups with 10 specimens for canal disinfection procedures. Group I, standard needle irrigation (SNI) with 2.5% sodium hypochlorite (NaOCl); group II, SNI with 2% chlorhexidine gluconate (CHX); group III, laser-activated irrigation (LAI) by Er,Cr:YSGG of NaOCl; group IV, LAI of CHX; and group V, passive ultrasonic irrigation (PUI) of NaOCl; group VI, PUI of CHX; group VII, PDT. The remaining two teeth were used as the control group. After the disinfection procedures were completed, the root canals were filled with phosphate-buffered saline and bacterial samples were taken with sterile paper cones. The cultivation was performed on Mueller-Hinton agar (MHA) plates. The live bacteria were calculated by counting the colonies on these plaques. The statistical analysis was performed using Kruskal-Wallis H test and Miller's multiple comparison technique. RESULTS: Both LAI and PUI of NaOCl and PUI of CHX were more successful than the PDT on root canal disinfection (p < 0.05). CONCLUSION: Within the limitation of the present study, the activation of NaOCl solution by Er,Cr:YSGG laser or an ultrasonic system can be useful in the elimination of the E. faecalis from the canal. The PUI of CHX also has similar results. Photodynamic therapy showed a lower performance compared to these methods. CLINICAL SIGNIFICANCE: The activation of the sodium hypochlorite with Er,Cr:YSGG laser or PUI may be useful for removal of the E. faecalis biofilm layer in the root canal.

Neurotoxicity evaluation of three root canal sealers on cultured rat trigeminal ganglion neurons.

BACKGROUND: The aim of this study was to investigate the possible neurotoxic effects of 3 root canal sealers (RCSs) (AH Plus, GuttaFlow, iRoot SP) on cultured rat trigeminal ganglion (TG) neurons. MATERIAL AND METHODS: Primary cultures of TG neurons were obtained from 1 to 2-day old rats. Freshly mixed RCSs were incubated in sterile phosphate buffered saline and cells were incubated with supernatants of the RCSs for different time intervals (1-, 3-, 6- and 24-h; 1 or 1/10 diluted) and viability/cytotoxicity was tested by counting the number of live cells. Pair of dishes with cells from the same culture incubated with only culture medium was considered as negative controls. Cell images were captured and acquired at x200 magnification using a microscope equipped with a camera using special image program. The viable cells were manually counted assigned from the images for each dose and incubation duration. Data was analysed by using 1-way analysis of variance with Tukey post hoc tests. RESULTS: There was no significant change in cell viability after short duration of incubation (1- and 3-h) with the supernatant of any of RCSs, except for undiluted-AH Plus at 3-h. When AH Plus was compared with other RCSs, for diluted supernatants, there was only significant difference between iRoot SP and AH Plus at 24-h (P<0.05). Whereas undiluted-AH Plus was significantly more cytotoxic for 3-, 6- and 24-h periods as compared to respective incubation periods of undiluted other groups (P<0.05). GuttaFlow groups had similar neurotoxic effect on cells for all test periods. CONCLUSIONS: All tested RCSs exhibited a variable degree of neurotoxicity on these primary sensory neurons of orofacial tissues, depending on their chemical compositions. GuttaFlow and iRoot SP evoked a less toxic response to TG cells than AH Plus. Key words:Neurotoxicity, trigeminal ganglia, cell culture, root canal sealer, AH Plus, GuttaFlow, iRoot SP.

Neurotoxicity of various root canal sealers on rat sciatic nerve: an electrophysiologic and histopathologic study.

OBJECTIVES: The aim of this study was to compare the neurotoxicity of various root canal sealers on rat sciatic nerve by electrophysiologic and histopathologic analyses. MATERIALS AND METHODS: A total of 40 male rats were randomly divided into five groups: Control, AH Plus, GuttaFlow, Sealapex and Smartpastebio. Sciatic nerves of the rats were uncovered using the surgical procedures, and the prepared sealers were then applied on nerves with a polyethylene tube vehicle for 15 days. Nerve potentials were recorded at initial exposure, 5, 30 and 120 min (early phase), and 15 days (late phase) by an electrophysiologic analysis system for all groups. The obtained measurements were then used to calculate the nerve conduction velocities (NCV). Subsequently, all rats were sacrificed, and their sciatic nerves were removed for histopathologic analysis. Statistical analysis was performed using the Kruskal-Wallis and Mann-Whitney U tests for intergroup variables and the Friedman and Wilcoxon test for intragroup variables. Statistical significance was set at P < 0.05. RESULTS: There was no significant difference between early and late phase results in the control group. This group showed little or no lasting damage to nerve tissue. All sealers decreased the NCV in the early phase time periods, but this decrease was only statistically significant in the AH Plus group at 120-min time period (P < 0.0125). During the late phase, the AH Plus and GuttaFlow groups almost reached initial NCV values, and it was lower than the initial values in the Sealapex and Smartpastebio groups. However, this decrease was not statistically significant. When intergroup comparisons were performed, statistically significant differences occurred at 30 min in the Sealapex group and 120 min in the AH Plus group compared with the control group (P < 0.0125). All sealers induced neurotoxicity as a result of degenerative and inflammatory responses of nerve tissue in histologic analysis. Histologic analysis revealed Sealapex and GuttaFlow to be the most and least neurotoxic, respectively. CONCLUSIONS: All tested root canal sealers exhibited a variable degree of neurotoxicity depending on their chemical compositions. CLINICAL RELEVANCE: Apical extrusion of endodontic filling materials may cause undesired consequences, such as inflammation and severe neurotoxic damage; therefore, extrusion factor plays an important role during the root canal treatment.

Conservative treatment and follow-up of type III dens invaginatus using cone beam computed tomography.

Dens invaginatus is a well-recognized phenomenon, and its endodontic treatment poses a challenge, especially for peri-invagination lesions with vital pulp. Here we describe the outcome of conservative treatment and follow-up in a case of type III dens invaginatus. Cone-beam computed tomography was used for diagnosis and follow-up. Pulp vitality was preserved with endodontic treatment of only an invaginated canal. At the 24-month follow-up examination, the tooth was asymptomatic and repair of the lesion was evident radiographically. This case was managed successfully with endodontic treatment of the invagination. (J Oral Sci 56, 307-310, 2014).

Bond strength of calcium silicate-based sealers to dentine dried with different techniques.

OBJECTIVE: To assess the influence of various canal-drying techniques on the push-out bond strength between radicular dentine and both MTA Fillapex and iRoot SP sealers. MATERIALS AND METHODS: Eighty extracted single-root teeth were instrumented with ProTaper Universal rotary instruments to a size F4. The teeth were randomly assigned to 1 of 4 groups as follows: group 1, excess fluid in the canals was removed using a Luer vacuum adapter; group 2, the canals were dried with a single paper point; group 3, the canals were dried with 3-5 paper points, and group 4, the canals were rinsed with 95% ethanol and then dried with 3-5 paper points. In each group, the specimens were subgrouped according to root canal sealer into either subgroup A (MTA Fillapex) or subgroup B (iRoot SP sealer). Horizontal sections (thickness 1 ± 0.1 mm) were obtained from each specimen and a push-out test was performed using a universal testing machine at a crosshead speed of 1 mm/min on root slices. Statistical analysis was done using the Kruskal-Wallis test and Dunn's test for pair-wise comparisons. p < 0.05 was considered statistically significant. RESULTS: Canals dried with only 1 paper point and obturated with the iRoot SP sealer (subgroup 2B) showed significantly higher bond strengths to the root canal wall compared to all other subgroups (p < 0.05), except for subgroup 1B (p > 0.05). CONCLUSIONS: The canal-drying technique influenced the adhesive bond strength between calcium silicate-based root canal sealers and the root canal wall.

Electrophysiological evidence on epileptiform activity enhanced by electrical stimulation of teeth in rats.

The aim of this study was to evaluate the possible effects of electrical stimulation (ES) of tooth on penicillin-induced epileptiform activity in rats. Experiment was realized on 24 adult male Sprague Dawley rats. Rats were assigned three groups [stimulation group (SG), penicillin group (PG), and penicillin+stimulation group (PSG)]. In SG, ES was only applied. Ten pulses of electrical current were delivered to the teeth for a duration of 2 milliseconds at 1-second intervals from a stimulator. Currents were applied in the range of 40-240 µA with 40 µA steps. Electrocorticography (ECoG) recordings were taken before and after ES. In PG, ECoG recordings were taken before and during the injection of penicillin. In PSG, after epileptiform activity was induced, ES was applied and ECoG recordings were taken as in SG. All the data were analyzed with Student's t test. Applied currents did not cause any epileptiform activity in SG. When the PSG was compared with the PG it was seen that the spike frequency of epileptiform activity increased in a statistically significant way after application of 240 µA (P < 0·05). On the other hand current application caused an increase in the spike amplitude of the PSG compared with the amplitude of the PG, but it was not statistically significant. We concluded that ES of tooth with high current can trigger epileptiform activity in rats. For this reason, further research is required to evaluate the effects of ES of tooth for pulp testing on epileptic human subjects and antiepileptic drug users.

In vitro bonding effectiveness of new self-adhering flowable composite to calcium silicate-based material.

The purpose of this study was to compare in vitro bonding effectiveness of Vertise Flow (VF), a new self-adhering flowable composite (FC), and Ultimate Flow (UF), a conventional FC, to BioAggregate (BA), and to investigate whether the use of self-etch or etch-andrinse adhesive improved the bond strength of VF to BA. Shear bond strengths of FC to BA were measured for this reason. Data were analyzed using Wilcoxon and Mann-Whitney U-tests (p=0.05). There were significant differences of bond strengths after 24- and 72-h (p<0.05, p<0.001). After 72-h, self-adhering FC may be used successfully with BA and no other adhesive, as an alternative to the combined use of conventional FC and self-etch adhesives. The use of etch-and-rinse adhesives with self-adhering FC may improve adhesion to BA.

Push-out bond strength of three calcium silicate cements to root canal dentine after two different irrigation regimes.

OBJECTIVES: The aim of this study was to compare the push-out bond strength of three calcium silicate cements to dentine after two different irrigation regimes. MATERIALS AND METHODS: One hundred eighty 2-mm-thick root sections were prepared. The sections were divided into three main groups (n = 60). In group A, the sections were immersed in 1 % NaOCl for 3 min. In group B, the sections were immersed in 17 % EDTA for 3 min followed by 1 % NaOCl for the same period of time. In group C (control group), no irrigation was applied to the sections. The samples from each group were divided into four subgroups (n = 15). In subgroups A1, B1 and C1, DiaRoot BioAggregate; in subgroups A2, B2 and C2, MTA-Angelus and in subgroups A3, B3 and C3, MM-MTA were mixed with hand-mixing. In subgroups A4, B4 and C4, MM-MTA was mixed with auto-mixing. The mixed cements were then placed into cavities with a carrier. The samples were submitted to the push-out test and were loaded. All the data were analysed with one-way analysis of variance and the Tukey HSD multiple comparisons (p < 0.05). RESULTS: There were no statistically significant differences between the irrigation regimes regardless of the used materials. The resistance to displacement in subgroup B4 was significantly greater than that presented by subgroups A3, B3 and C3 (p < 0.05) while not different than all other groups. CONCLUSIONS: Irrigation regimes had not affected the push-out bond strength of the calcium silicate cements. Also, strength of auto-mixed MM-MTA was similar to the other cements. CLINICAL RELEVANCE: The novel calcium silicate cements would be a potentially useful material in endodontic procedures with favourable properties.

Comparative study of 6 rotary nickel-titanium systems and hand instrumentation for root canal preparation in severely curved root canals of extracted teeth.

INTRODUCTION: Some improvements have been developed with new generations of nickel-titanium (NiTi) rotary instruments that led to their successful and extensive application in clinical practice. The purpose of this in vitro study was to compare the root canal preparations performed by using GT Series X and Twisted File systems produced by innovative manufacturing process with Revo-S, RaCe, Mtwo, and ProTaper Universal systems manufactured directly from conventional nitinol and with stainless steel K-Flexofile instruments. METHODS: The mesiobuccal root canals of 140 maxillary first permanent molars that had between 30°-40° curvature angle and 4- to 9-mm curvature radius of the root canal were used. After root canal preparations made by using GT Series X, Twisted File, Revo-S, RaCe, Mtwo, and ProTaper Universal NiTi rotary systems and stainless steel K-Flexofile instruments, transportation occurred in the root canal, and alteration of working length (WL) was assessed by using a modified double-digital radiographic technique. The data were compared by the post hoc Tukey honestly significant difference test. RESULTS: NiTi rotary systems caused less canal transportation and alteration of WL than K-Flexofile instruments (P < .05). There was no significant difference between NiTi rotary system groups at any levels (P > .05) except 2.5 mm from the WL. At this level ProTaper Universal system caused significant canal transportation (P < .05). CONCLUSIONS: GT Series X and Twisted File rotary systems produced with innovative process were concluded to shape the curved canals to result in minimal canal transportation, similar to Revo-S, RaCe, Mtwo, and ProTaper Universal rotary systems manufactured by traditional methods.

Comparison of influence of different manufacturing methods on the cleaning efficiency of rotary nickel-titanium files.

The purpose of this study was to evaluate and compare cleaning effectiveness of TwistedFile, GT series X, Revo-S, RaCe, Mtwo, and ProTaper Universal rotary files in curved canals. Seventy mesiobuccal canals of extracted human first maxillary molars were divided into seven groups of 10 samples each. Canals were prepared with six nickel-titanium (NiTi) rotary systems and manual K-Flexofile. Irrigation was performed with 2 mL 2.5% NaOCl solution after each file, and 5 mL 2.5% NaOCl was used for the final flush. After the roots were split longitudinally, the presence of debris and smear layer was visualized using scanning electron microscopic photomicrographs taken at coronal, middle, and apical third. Mean scores for debris and the smear layer were calculated and statistically analyzed for significance between groups using the Kruskal-Wallis nonparametric analysis of variance (P < 0.05) and Mann-Whitney U test (P < 0.001). There was no significant difference among the groups in terms of debris and smear layer scores (P > 0.05). Without considering the preparation method used, while no statistically significant difference was found between the coronal third and the middle third (P > 0.05), higher amount of debris and smear layer were found in apical third (P = 0.001). The new generation of NiTi rotary files including the Twisted File and GT Series X presented similar cleaning effectiveness compared with traditionally ground NiTi rotary files.

Fracture resistance of retreated roots using different retreatment systems.

OBJECTIVES: This study was designed to evaluate the fracture resistance of retreated roots using different rotary retreatment systems. METHODS: Forty eight freshly extracted human canine teeth with single straight root canals were instrumented sequentially increasing from size 30 to a size 55 using K-files whit a stepback technique. The teeth were randomly divided into three experimental and one control groups of 12 specimens each. The root canals were filled using cold lateral compaction of gutta-percha and AH Plus (Dentsply Detrey, Konstanz, Germany) sealer in experimental groups. Removal of gutta-percha was performed with the following devices and techniques: ProTaper Universal (Dentsply Maillefer, Ballaigues, Switzerland), R-Endo (Micro-Mega, Besançon, France), and Mtwo (Sweden & Martina, Padova, Italy) rotary retreatment systems. Control group specimens were only instrumented, not filled or retreated. The specimens were then mounted in copper rings, were filled with a self-curing polymethylmethacrylate resin, and the force required to cause vertical root fracture was measured using a universal testing device. The force of fracture of the roots was recorded and the results in the various groups were compared. Statistical analysis was accomplished by one-way ANOVA and a post hoc Tukey tests. RESULTS: There were statistically significant differences between the control and experimental groups (P<.05). However, there were no significant differences among the experimental groups. CONCLUSIONS: Based on the results, all rotary retreatment techniques used in this in vitro study produced similar root weakness.

Intentional replantation of periodontally hopeless teeth using a combination of enamel matrix derivative and demineralized freeze-dried bone allograft.

This study evaluated the clinical and radiographic results of the intentional replantation of periodontally hopeless teeth with combined enamel matrix derivative and demineralized freeze-dried bone allograft therapy. Eleven patients (five female, six male; age range, 13 to 53 years) with 12 periodontally hopeless teeth resulting from extensive alveolar bone loss and vertical defects extending to the apexes were studied. At the 12-month clinical and radiologic follow-up, significant improvement was observed for all clinical and radiographic parameters except gingival recession (P < .05). These preliminary findings show that intentional replantation combined with regenerative techniques is a successful alternative to tooth extraction.

Antibacterial activity and physical properties of conventional glass-ionomer cements containing chlorhexidine diacetate/cetrimide mixtures.

STATEMENT OF THE PROBLEM: Hand excavation instruments are not as efficient as that with rotary burs in atraumatic restorative treatment (ART). PURPOSE: To evaluate the antibacterial activity (ABA), microhardness numbers (VHN), and cumulative fluoride releasing (CFR) patterns of conventional GICs (Fuji IX (FX) and Ketac Molar (KM)) containing chlorhexidine diacetate/cetrimide mixtures (2.5%/2.5%) (AB). MATERIALS AND METHODS: The powders of ABs were added to powders of FX and KM selected as experimental groups (EXPs). FX and KM were assigned as controls (CNTs). ABA against S.mutans (MS) and L.casei (LB) were examined between 1-90 days. VHN were calculated after 24 hours and CFR patterns measured between 1-30 days. Analysis of variance was used for comparison (p<0.05) RESULTS: Differences were found between EXPs regarding MS levels at days 1, 7 and 60 as well as for LB at all time periods (p<0.05). VHN decreased in EXPs compared to CNTs (p<0.05), and no differences were found between EXPs (p>0.05). CFR patterns tended to decrease in EXPs compared to the CNTs, but no differences were found between EXPs (p>0.05) CLINICAL SIGNIFICANCE These mixtures could be recommended for ART procedures to provide beneficial antibacterial effects without seriously deteriorating the physical properties of selected GICs.

Effect of unintentionally extruded mineral trioxide aggregate in treatment of tooth with periradicular lesion: a case report.

INTRODUCTION: This case report describes the effect of unintentionally extruded mineral trioxide aggregate (MTA) into periradicular lesions and tissues on the prognosis of periradicular healing in maxillary left central incisor with periradicular lesion. METHODS: A 17-year-old girl with a large periradicular lesion from the apices of her maxillary left central to lateral incisors was referred. Tooth #9 had an open apex, but tooth #10 was normal. Conservative root canal treatment was performed to tooth #10. The apical third of the canal of tooth #9 was filled with MTA as an apical plug because of open apex. During this procedure, a radiograph was taken, and it showed an excessive extrusion of MTA into the periradicular lesion. The remaining canal space was filled with gutta-percha and AH Plus sealer by using a lateral condensation technique. RESULTS: At follow-up examinations, the tooth was asymptomatic and radiographically showed repair of the lesion. Healing was achieved without any need for further endodontic surgical intervention. CONCLUSIONS: The results of this case showed that complete periapical healing is possible despite the extrusion of the MTA. This might be due to biologic properties of the MTA. Even so, extrusion of the filling material is not advocated.

Effect of smear layer and root-end cavity thickness on apical sealing ability of MTA as a root-end filling material: a bacterial leakage study.

OBJECTIVE: The aim of this study was to investigate the effect of the cavity thickness and smear layer on apical sealing ability of mineral trioxide aggregate (MTA) as a root-end filling material. STUDY DESIGN: Seventy single-rooted maxillary central teeth were used in this study. All teeth were instrumented to size 50 using a step-back technique. The selected teeth were randomly divided into 4 groups, each containing 15 experimental samples and 5 positive and 5 negative control samples. In the first and second groups (smear+), the teeth were irrigated with only 5.25% NaOCl. In the third and fourth groups (smear-), the teeth were irrigated with 17% EDTA and 5.25% NaOCl to remove the smear layer. Also, in the first and third groups, cavities were prepared as 3 mm. In the second and fourth groups, cavities were prepared as 5 mm. All the root-end cavities were then filled with MTA. Nail varnish was applied to all external root surfaces to the level of the resected root-ends to prevent lateral microleakage. Samples were sterilized in an ethylene oxide sterilizer for 12 hours. The apical 3-4 mm of the roots were immersed in brain heart infusion culture medium with phenol red indicator within culture chambers. The coronal access of each specimen was inoculated every 48 hours with a suspension of Enterococcus faecalis. Bacterial leakage was monitored every 24 hours for 4 weeks. The data obtained were analyzed using a chi-squared test, with alpha = .05 as the level for statistical significance. RESULTS: There were no statistically significant differences in rate of bacterial leakage among the experimental groups at 1-4 weeks (P > .05). Also, there was no difference between the groups when the 2 thickness groups were combined (P > .05). However, there was statistically significant differences when the 2 smear groups were combined for 4-week observation periods (P < .05). Removal of the smear layer caused significantly more apical microleakage than when the smear layer was left intact for 4 weeks. CONCLUSION: The thickness of root-end cavity (3 or 5 mm) had no influence in the bacterial leakage of the root end filled with MTA. Removing the smear layer may not be necessary in root-end cavities filled with MTA.

Effect of immediate and delayed post space preparation on the apical seal of root canals obturated with different sealers and techniques.

UNLABELLED: During mechanical preparation of the post space, the root canal filling may be twisted or vibrated, depending on several factors associated with the preparation technique and quality of filling. OBJECTIVE: The purpose of this study was to investigate the effect of immediate and delayed post space preparation on the integrity of the apical seal. MATERIAL AND METHODS: Sixty-four extracted human incisors were biomechanically prepared using the step-back technique. Sixty roots were randomly assigned to 6 experimental groups of 10 teeth each and the remaining 4 roots served as positive and negative controls (n=2). The root canals in the different groups were obturated with cold lateral and warm vertical condensation of gutta-percha and one of two sealers (Sealapex and Diaket). Post space was prepared either individually or simultaneously. An insulated copper wire was cut into 10-cm-long pieces. In each canal, one piece was inserted to maintain contact with gutta-percha and extended to the outside as one of two working electrodes. A stainless steel wire with the same dimensions of those of the copper wire, used as the other working electrode, was immersed into the background electrolyte from the center of the bottle. The electrical current between standard and experimental electrodes in canals was measured over a period of 10 days applying a conductivity meter. The Kruskal-Wallis test (p=0.05) determined whether there was a significant difference in microleakage among the groups and the Mann-Whitney U test (p=0.01) was used for multiple comparison grouping variables. RESULTS: The results suggest that only the differences between the root canal filling techniques were statistically significant (p<0.01). There were no statistically significant difference in the sealers and the times of filling removal for post space preparation (p>0.01). CONCLUSION: The quality of the root canal filling is important for the integrity of the apical seal.

Effect of immediate and delayed post space preparation on the apical seal of root canals obturated with different sealers and techniques

During mechanical preparation of the post space, the root canal filling may be twisted or vibrated, depending on several factors associated with the preparation technique and quality of filling. OBJECTIVE: The purpose of this study was to investigate the effect of immediate and delayed post space preparation on the integrity of the apical seal. MATERIAL AND METHODS: Sixty-four extracted human incisors were biomechanically prepared using the step-back technique. Sixty roots were randomly assigned to 6 experimental groups of 10 teeth each and the remaining 4 roots served as positive and negative controls (n=2). The root canals in the different groups were obturated with cold lateral and warm vertical condensation of gutta-percha and one of two sealers (Sealapex and Diaket). Post space was prepared either individually or simultaneously. An insulated copper wire was cut into 10-cm-long pieces. In each canal, one piece was inserted to maintain contact with gutta-percha and extended to the outside as one of two working electrodes. A stainless steel wire with the same dimensions of those of the copper wire, used as the other working electrode, was immersed into the background electrolyte from the center of the bottle. The electrical current between standard and experimental electrodes in canals was measured over a period of 10 days applying a conductivity meter. The Kruskal-Wallis test (p=0.05) determined whether there was a significant difference in microleakage among the groups and the Mann-Whitney U test (p=0.01) was used for multiple comparison grouping variables. RESULTS: The results suggest that only the differences between the root canal filling techniques were statistically significant (p<0.01). There were no statistically significant difference in the sealers and the times of filling removal for post space preparation (p>0.01). CONCLUSION: The quality of the root canal filling is important for the integrity of the apical seal.