Coronal Barrier Research Articles

Coronal Discoloration Related to Bioceramic and Mineral Trioxide Aggregate Coronal Barrier in Non-vital Mature Teeth Undergoing Regenerative Endodontic Procedures

Coronal Discoloration Related to Bioceramic and Mineral Trioxide Aggregate Coronal Barrier in Non-vital Mature Teeth Undergoing Regenerative Endodontic Procedures

Effect of Different Irrigation Solutions on Coronal Microleakage in Endodontically Treated Teeth (An in vitro Study)

Background: The coronal microleakage in the endodontically treated teeth causes recurrent caries and can be associated with the restoration and the root canal treatment failures. Intra orifice barrier is an efficient alternative method to decrease coronal leakage in endodotically treated teeth and one of the best barriers is glass ionomer. The current study propose that using different irrigation solutions in root canals effect on coronal microleakage.
 Purpose: This study aimed to compare the coronal microleakage in glass ionomer obturated root canals in endodontically treated teeth using different irrigation solutions.
 Methods: Sixty extracted human single-rooted teeth with single canals were collected and disinfected with 0.5 choloro amin. After root canal therapy and evacuation of 2 mm coronal gutta percha, the teeth were divided into 3 groups of each 20, based on irrigation solutions. Glass ionomer was used as the coronal barrier and the teeth were stored in distilled water. The irrigation solutions used were: 17% EDTA, Alcohol and normal saline. Then all the specimen were submerged in 2% methylene blue dye for 24 hours at room temperature and sectioned sagittally and the dye penetration was assessed by stereomicroscope.
 Results: There were not penetration of dye only in 3.3% of teeth and all of the teeth that irrigated with saline showed dye penetration. The dye penetration was seen in 95%, 95% and 100% of the EDTA, alcohol and saline groups, respectively. Dye penetration was higher in Saline group than other two groups but coronal microleakage has not shown statistically significant differences in different groups.
 Conclusion: The results of current study indicated that using different irrigation solutions may be associated with decrease in coronal microleakage. Although, based on our findings there are not any significant differences among different irrigation solutions but more studies may be needed to confirm this results.

Release of Transforming Growth Factor Beta 1 from Human Tooth Dentin after Application of Either ProRoot MTA or Biodentine as a Coronal Barrier

IntroductionVarious factors may influence intracanal calcification in teeth treated with regenerative endodontic procedures. Bioactive materials, including ProRoot MTA (MTA; Dentsply Tulsa Dental Specialties, Memphis, TN) and Biodentine (BD; Septodont, Saint-Maur-des-Fossés, France), have been widely used as a coronal barrier in the final step of regenerative endodontic procedures. The purposes of this study were to evaluate the effect of either MTA or BD after application as a coronal barrier on transforming growth factor beta 1 (TGF-β1) release from root canal dentin and to observe the impact of these materials on human apical papilla cell (APC) mineralization. MethodsEither MTA or BD was applied in enlarged root canals of human root segments. After storing for 14 days in phosphate-buffered saline, TGF-β1 release was evaluated using an enzyme-linked immunosorbent assay. To investigate the effect of the materials on APC mineralization, APCs were grown in the presence of either the materials alone or material-filled root segments. Cell mineralization was quantified after 14 and 21 days using alizarin red S staining. Calcium deposits were quantitatively analyzed. Statistical analysis was performed using the Kruskal-Wallis and Mann-Whitney U tests with the significance level at .05. ResultsThe greatest amount of TGF-β1 release was observed in the root segments treated with BD. BD, used either alone or as a coronal barrier, promoted greater APC mineralization than did MTA on both days 14 and 21. Interestingly, when BD was applied as a coronal barrier, the mineralization effect was significantly reduced compared with the use of the materials alone (P < .05). ConclusionsWhen used as a coronal barrier, BD promoted the release of TGF-β1 from the root canal dentin. A higher mineralization effect was observed with BD than with MTA.

Do the intracanal medicaments affect the marginal adaptation of calcium silicate-based materials to dentin?

Background/purposeIn order to prevent reinfection of the pulp canal space and dressing for regenerative purpose, the coronal seal should have a perfect marginal adaptation. Mineral trioxide aggregate (MTA) and Biodentine are among the most popular sealing materials. These are commonly used in combination with antibiotic medicaments, to ensure disinfection. Aim of the present study was to evaluate the effect of 3 different medicaments on the marginal adaptation of MTA and Biodentine to the dentin. Materials and methodsTeeth were divided into 4 groups (n = 20) that were treated with the following medicaments; triple antibiotic paste (TAP), double antibiotic paste (DAP), a calcium hydroxide (CH) and a control group. The specimens were then assigned into two subgroups (n = 10), which received a coronal barrier of MTA or Biodentine. The specimens were scanned using an ex vivo micro-CT scanner. The data were statistically analysed using one-way ANOVA and the unpaired Student's t-test (P < 0.05). ResultsPercentage volume of external voids in the MTA group was as follows: DAP > TAP > Control > CH. In the Biodentine group, the percentage of voids was determined in the following order: TAP ≥ DAP > CH > Control. Significantly lower percentage of voids was observed in the CH-medicated specimens in the MTA group when compared to all test groups (P = 0.04). ConclusionThe application of CH as an intracanal medicament reduced the void occurrence between the ProRoot MTA and root dentin. However, TAP and or DAP decreased the marginal adaptation in both ProRoot MTA and Biodentine.

Effects of intracoronal bleaching agents on the surface properties of mineral trioxide aggregate.

Bleaching agents may affect surface properties of mineral trioxide aggregate (MTA) as a coronal barrier. The purpose of this study was to investigate surface properties of MTA after exposure to intracoronal bleaching agents. MTA was set in acrylic molds with a 4mm high central hole and a 6mm diameter. Specimens were divided into four groups (n = 10); three groups were exposed to bleaching agents three times on every fourth day (carbamide peroxide-CP, hydrogen peroxide-HP, sodium perborate-SP) and a control group-C. The surface roughness and Vickers surface microhardness were measured. Differences between groups were analyzed using a Kruskal-Wallis test and intergroup comparisons were assessed with a Mann-Whitney U test with a Bonferroni correction (p < 0.0001). The microstructure and elemental composition were observed using a scanning electron microscope (SEM) and an energy-dispersive X-ray microanalysis (EDX) system. In terms of microhardness, the decrease in the HP group was significantly greater than that of the CP and SP groups; CP group significantly greater than that of the SP group, however, there was no significant difference between the SP and C groups. Surface roughness values were compared between groups, and no significant differences were observed between the CP and HP groups, and they exhibited significantly higher roughness values than the SP and C groups. SEM/EDX showed that the bleaching agents affected the elemental distribution. Bleaching agents adversely affected the surface roughness, surface microhardness and elemental distribution of MTA, with exposure to SP causing fewer changes on the surface properties than CP or HP.

Coronal tooth discoloration induced by regenerative endodontic treatment using different scaffolds and intracanal coronal barriers: a 6-month ex vivo study.

ObjectiveThe aim of this study was to evaluate discoloration of teeth undergoing regenerative endodontic procedures (REPs) using blood clot or platelet-rich fibrin (PRF) as the scaffolds and different calcium silicate-based materials as the intracanal coronal barriers in an ex vivo model.Materials and MethodsForty-eight bovine incisors were prepared and disinfected using 1 mg/mL double antibiotic paste (DAP). The specimens were then randomly divided into 2 groups (n = 24) according to the scaffolds (blood or PRF). After placement of scaffolds each group was divided into 2 subgroups (n = 12) according to the intracanal coronal barriers (ProRoot MTA or Biodentine). The pulp chamber walls were sealed with dentin bonding agent before placement of DAP and before placement of scaffolds. The color changes (∆E) were measured at different steps. The data were analyzed using 2-way analysis of variance.ResultsCoronal discoloration induced by DAP was not clinically perceptible (ΔE ≤ 3.3). Regarding the type of the scaffold, coronal discoloration was significantly higher in blood groups compared with PRF groups at the end of REP and after 1 month (p < 0.05). However, no significant difference was found between PRF and blood clot after 6 months (p > 0.05). Considering the type of intracanal coronal barrier, no significant difference existed between ProRoot MTA and Biodentine (p > 0.05).ConclusionsWith sealing the dentinal tubules of pulp chamber with a dentin bonding agent and application of DAP as an intracanal medicament, coronal color change of the teeth following the use of PRF and blood sealed with either ProRoot MTA or Biodentine was not different at 6-month follow-up.

Effect of Coronal Barrier Thickness on Fracture Strength of Immature Teeth

Objectives: Secondary trauma is one of the main causes of root fracture in regenerative endodontic cases. The aim of this study was to compare the influence of placing Biodentine as a barrier material at different thicknesses on the fracture strength of simulated immature teeth. Materials and Methods: The root canals of 65 human maxillary central incisors were instrumented using Peeso reamers to simulate immature teeth. Ten teeth were assigned to the negative control group and received no access cavity preparation. The access cavities of the remaining 55 teeth were prepared. Among them, the root canals of 10 teeth were filled with calcium hydroxide to serve as the positive control. Forty-five teeth were randomly distributed into 3 groups (n=15); Group 1: 2-3 mm thick coronal plug, Group 2: 5-6 mm thick coronal plug, Group 3: complete obturation. After the storage period, fracture testing was performed using a universal testing machine. One-way analysis of variance and Tukey tests were used to analyze the data. Results: No significant difference was found among the positive control, group 1 and group 2 (P &amp;gt; 0.05). The negative control and group 3 presented the highest fracture strength values (P &amp;lt; 0.05), while there was no significant difference between them (P &amp;gt; 0.05). All fractures occurred through the cervical region of the root horizontally or obliquely. Conclusions: No significant reinforcement effect was obtained when Biodentine was used as a coronal plug. The complete root canal obturation of simulated immature teeth using Biodentine provided the best reinforcement effect. The coronal plug thickness had no influence on the fracture strength of immature teeth.

Apical and Coronal Microleakage using Mineral Trioxide Aggregate (Comparative Study)

The purpose of this study was to evaluate the potential of using mineral trioxide aggregate (MTA) as a root canal filling material by comparing its apical sealing ability with that of laterally condensed gutta-percha with sealer in extracted one canal teeth. In addition, this study was evaluating the MTA and ZnPo4 cement as barriers to coronal microleakage.Forty single canal extracted teeth, were prepared in a standard manner using GT file, randomly divided into two groups of 20 teeth, and obturated with laterally condensed gutta-percha or MTA.In each group, 10 teeth received a 4-mm barrier of MTA or ZnPo4 cement. The sealing ability of each part was assessed by immersion in 1% methylene blue dye for 72 h. The leakage was recorded in apical and coronal part. Data were analyzed by One-Way ANOVA test, T-test, and LSD test.Canal filled with laterally condensed gutta-percha showed significantly less apical dye penetration than canals obturated with MTA. However, coronal barrier filled with MTA showed significantly less dye penetration than ZnPo4 cement barrier.

Effect of 3 Bioceramic Materials on Stem Cells of the Apical Papilla Proliferation and Differentiation Using a Dentin Disk Model

IntroductionThere is a complex interaction between biomaterials placed as a coronal barrier with stem cells and dentin in regenerative procedures. In this study, the effect of Biodentine (BD; Septodont, Saint-Maurdes-Fossés, France), Endosequence BC Root Repair Material-Putty (ES; Brasseler, Savannah, GA), Endosequence BC Root Repair Material-Putty Fast set (ES-fast, Brasseler), and ProRoot (Dentsply Tulsa Dental Specialties, Johnson City, TN) mineral trioxide aggregate (MTA) on the viability and differentiation of stem cells of the apical papilla (SCAP) was evaluated using an ex vivo dentin disk model. MethodsStandardized human dentin disks were treated using an established protocol. Disk lumens were filled with BD, ES, ES-fast, or MTA, and SCAP were cultured directly onto the samples. Cell viability was measured at 7 days, whereas differentiation into a mineralizing phenotype was evaluated by real-time reverse-transcription polymerase chain reaction and alizarin red staining at 21 days in culture. Results were analyzed using 1-way analysis of variance with the Bonferroni post hoc test or the Mann-Whitney U test (P ≤ .05). ResultsAll materials promoted SCAP viability and proliferation with a greater response in the BD and ES groups. Also, a greater expression of alkaline phosphatase messenger RNA and dentin sialophosphoprotein was noted in the BD and ES groups, whereas MTA promoted a greater expression of the osteoblastic marker IBSP. Interestingly, no difference in alizarin red staining was observed with MTA, BD, or ES, which were significantly greater than ES-fast. ConclusionsThese data suggest that BD and ES promoted greater survival and differentiation of SCAP and the increase of the odontoblastic marker DSPP, whereas MTA appeared to promote greater osteoblastic differentiation. Thus, BD and ES can be considered for regenerative and vital pulp therapies.

Evaluation of Mineral Trioxide Aggregate, Resin-modified Glass Ionomer Cements, and Composite as a Coronal Barrier: An in vitro Microbiological Study

The purpose of the study is to evaluate the bacterial micro-leakage of three different materials, mineral trioxide aggregate (MTA), resin-modified glass ionomer cement (RMGIC), and flowable composite, as a coronal barrier against Enterococcus faecalis. A total of 100 human extracted single-rooted teeth were selected. Access opening done, working length determined, and canals were cleaned and shaped with ProTaper F3 and obturated with AH26 and gutta-percha (GP) using lateral condensation technique. Samples were divided into three experimental and two control groups. Approximately 3 mm GP was removed from the coronal orifice and restored with one of the test materials. Teeth were suspended in glass tubes containing brain heart infusion (BHI) broth and equipped with microcaps, which were used to check bacterial leakage. A 24-hour broth of E. faecalis was placed in the pulp chamber. Tubes were incubated and checked for turbidity for 90 days. Data were analyzed using chi-squared test between the test and control groups and Fisher test between the test groups. Significantly lesser number of samples turned turbid in the RMGIC group followed by MTA group and the maximum number of samples turned turbid in the flowable composite group. The RMGIC is a better coronal sealer, followed by MTA and flowable composite. Coronal sealing ability of RMGIC is more promising in comparison with the other agents.

Regenerative Endodontic Procedures among Endodontists: A Web-based Survey

IntroductionThe protocols that endodontists implement for regenerative endodontic procedures (REPs) are unknown. The aim of this study was to examine current REP protocols among practicing endodontists in the United States. MethodsA Web-based survey was sent to 4060 active members of the American Association of Endodontists (AAE). A total of 850 participants completed the survey, representing a 20.9% response rate. ResultsResponses indicated 60% reported having performed REPs; most performed 1 to 3 per year. The most commonly selected source (60.8%) for the clinical protocol was the “AAE Clinical Considerations for a Regenerative Procedure.” Time constraints were the most common reason why 92.4% of respondents did not report their REP cases to the AAE.org database; additionally, 15.5% were unaware of it. Almost half (49.8%) of the participants reported they would attempt an REP on a patient of any age. The most commonly used irrigants were >3% sodium hypochlorite at the first appointment and EDTA at the scaffold formation appointment. As the intracanal medicament, 52.2% used calcium hydroxide, whereas 23.5% used triple antibiotic paste. At the scaffold formation appointment, 77.1% used a local anesthetic without a vasoconstrictor, and 94.3% used a blood clot as the scaffold. Mineral trioxide aggregate was the coronal barrier most often selected. Considering factors most likely to encourage the use of REPs in the future, 79.8% reported the availability of good candidates followed by 40.1% who desired better evidence. ConclusionsBased on the results of this survey, REP protocols appear to be heterogeneous and do not strictly conform to the “AAE Clinical Considerations for a Regenerative Procedure.”

Bleaching of a Discolored Tooth with Retrieval of Remnants after Successful Regenerative Endodontics

IntroductionThis report presents the retrieval of remnants from a discolored mandibular right second premolar (tooth #29) of a 17-year-old female after a successful regenerative endodontic procedure (REP). MethodsThe REP was performed in October 2011. Coronal discoloration became of great concern to the patient at a review visit in 2016. A cone-beam computed tomographic scan was taken to investigate the formation of hard tissues within the root canal as well as a region of no calcified tissue formation. During internal bleaching of tooth #29, a black material with particulate inclusions was retrieved and examined histopathologically. ResultsFive years after the REP, there was complete periapical healing, hard tissue formation within the root canal, and complete maturation of the root apex. A hard tissue bridge was noted at the cementoenamel junction when the pulp chamber of #29 was reaccessed. The remnants retrieved from the pulp chamber were confirmed to be partly mineral trioxide aggregate (MTA). A normal tooth color was achieved after 3 weeks of internal bleaching. ConclusionsMTA remnants within the pulp chamber contributed to the tooth discoloration and appear to have obstructed hard tissue formation. A matrix of oxidized regenerated cellulose seems not to hinder tissue regeneration and is resorbed by these tissues. Other materials with color stability should be selected as coronal barriers for REPs to avoid a potential adverse effect of the MTA on the REP outcome and discoloration.

A Review of Tooth Discoloration after Regenerative Endodontic Therapy

IntroductionThe American Association of Endodontists clinical considerations for regenerative therapy (April 2015) advise of the risk of the possible adverse effect of staining of teeth. It is widely acknowledged that before these guidelines were developed there was no standardized protocol for regenerative therapy, and different approaches using different materials have been reported. The purpose of this review was to undertake a systematic review of published cases to determine the incidence of reported discoloration and examine whether there was any particular association with any material. MethodsA PubMed search was performed using key words for regenerative endodontic therapy consistent with prior published systematic reviews. ResultsThere were 80 studies identified with 379 teeth treated. Many of the studies did not report on the presence or absence of discoloration. It was noted that there was a strong association of discoloration with the use of triple antibiotic paste containing minocycline; however, discoloration was also noted when other materials were used. Unfortunately, bleaching of stained teeth was not predictably achieved in some studies. ConclusionsThe use of triple antibiotic paste with minocycline as the intracanal medicament should be reconsidered. Either calcium hydroxide or the double antibiotic paste of metronidazole and ciprofloxacin may limit discoloration. Mineral trioxide aggregate was also associated with discoloration. However, there is little evidence of an alternative superior material as a coronal barrier. Because discoloration is a patient-orientated outcome, further research should document and identify the incidence of discoloration in regenerative endodontic treatment.

The Decision for Regenerative Endodontic Therapy

Regenerative endodontics is described as biologically based procedures designed to replace damaged structures, including dentin and root structures, as well as cells of the pulp-dentin complex, and is considered as an optimal approach for treating the immature permanent tooth with a necrotic pulp. Since the establishment of the foundations of regenerative endodontic therapy in 1960’s a plethora of relevant clinical cases and studies have been published. However, until now the case selection as well as the clinical protocol applied during regenerative endodontic therapy have not been totally determined and supported by clinical studies with high level of evidence. This review summarizes the current literature regarding the prognostic factors and clinical outcomes of regenerative endodontic therapy and the various applied clinical protocols in terms of administration of mechanical instrumentation, irrigation, intracanal medicaments, intracanal bleeding and intracanal coronal barrier. The aim of this review is to clarify and determine all the factors that willcontribute to the decision making for the application of regenerative endodontic therapy.

Evaluation of Different Dentin Bonding Agents Accompanied with Composite Coronal Barrier

Introduction: The purpose of this study was to evaluate the sealing ability of dentin bonding agents in root canals obturated with gutta-percha and MTA. Methods: Forty-five single rooted human premolar teeth were decoronated so that remaining root portions were 12 mm in length. The samples were divided randomly into three experimental (n=13) and two control groups (n=3). All teeth were instrumented up to #40 K-file using step-back technique. The roots were obturated with gutta-percha/AH26 and MTA for 5 and 3 mm, respectively. Excite, Clearfil SE Bond, and iBond were applied for experimental groups and then 2mm was filled with composite Filtek Z250. The roots in the controls were merely instrumented and obturated. Two coats of nail varnish were applied on the surface of the teeth in the experimental and positive groups, except 2 mm around the apical foramen and coronal surfaces. In the negative control, the surfaces were completely covered by two layers of nail varnish. After thermocycling, the roots mounted in plastic caps of tubes containing BHI medium and inoculated coronally with Enterococcus faecalis. The data were statistically analyzed using Fisher's exact and Kaplan-Meier survival Analysis. Results: There were no statistically significant differences between three experimental groups regarding the leakage rate (P=0.738). Conclusion: Within the limitations of this study, it was observed that the adhesive systems in alliance with gutta-percha and MTA obturation could not entirely

The use of MTA/blood mixture to induce hard tissue healing in a root fractured maxillary central incisor. Case report and treatment considerations

To report the use of MTA/blood mixture for the induction of hard tissue healing of multiple horizontal root fractures in a maxillary incisor. An 18-year-old male patient was referred after suffering trauma to the anterior maxilla. Radiographic evaluation revealed multiple horizontal fractures in the middle and cervical third of his maxillary right central incisor. Clinical evaluation revealed third grade mobility of the coronal segment. The patient's accompanying radiographs revealed that root canal treatment of all segments had been previously initiated and both segments had been rendered pulpless. The coronal segment was repositioned and stabilized. A bi-antibiotic mixture, containing equal parts of ciprofloxacin and metronidazole, was used for the disinfection of the root canal segments. A blood clot was induced from the periapical area and MTA powder was mixed with the blood creating a bioceramic mixture covering all the fractures. Thick MTA was placed as a coronal barrier and the tooth was restored. Recall examination after 24months revealed healing of the horizontal fractures. The MTA mixed with the blood lost its radio-opacity over time. Tooth mobility returned to normal limits. A low range of 5-25% of all horizontally root fractured cases develop pulp necrosis, confined in the coronal segment, leaving the apical segment with vital tissue. In the unfortunate situation that the pulp of both segments becomes necrotic or the entire pulp tissue is removed, the use of MTA/blood mixture may be beneficial for the induction of hard tissue healing. MTA when mixed with blood seems to lose its radio-opacity over time.

Sealing Ability of Various Restorative Materials as Coronal Barriers between Endodontic Appointments

To evaluate and compare the microleakage of various restorative materials used as coronal barriers between endodontic appointments. Eighty extracted human permanent posterior teeth were prepared for standardized access cavities with dimensions of 4 × 4 × 4 mm. The teeth were then randomly divided into four groups; Kalzinol, Caviton, GC Fuji IX and GC Fuji II LC. After incubation, the samples were immersed in 2% methylene blue for 7 days. The depth of penetration was measured using a digital macroscope after longitudinal sectioning of each tooth. Kruskal-Wallis (p < 0.05) and multiple Mann-Whitney test with Bonferroni correction (p < 0.008) were used for data analysis. The degree of microleakage varied at the material/ tooth interface among the test materials, and the difference was statistically significant (p < 0.05). GC Fuji II LC group showed the least median microleakage value (0.8105 ± 0.305), followed by Caviton (1.1885 ± 0.396), GC Fuji IX (3.3985 ± 0.305) and Kalzinol (4.161 ± 0.853). Within the limitations of this study, GC Fuji II LC exhibited the best marginal seal, and has the potential to be used as a suitable coronal barrier between endodontic appointments. Given the prime importance that dental practitioners should thoroughly restore any tooth with a suitable coronal barrier between endodontic appointments, this study shows that Fuji II LC has the ability to maintain a hermetic seal for 7 days.

An in vitro comparison of coronal microleakage of three orifice barriers filling materials.

A coronal barrier in root-filled teeth is one of the most effective methods for prevention of coronal microleakage. The aim of this study was to compare coronal microleakage of three materials [light-cured glass-ionomer (GI), mineral trioxide aggregate (MTA), and composite resin] as coronal barriers. A total of 188 intact maxillary incisors were used. After instrumentation, all the canals were obturated with gutta-percha and lateral condensation technique using AH26 sealer. Then, the teeth were sectioned just apical to the cemento-enamel junction. The roots were randomly assigned to three experimental groups (n=56) and two negative and positive control groups (n=20). After placing the orifice barrier, the samples were immersed in 2% methylene blue solution for 2 weeks at 37°C. Then the teeth were longitudinally sectioned mesiodistally and dye penetration was measured under a stereomicroscope at ×10 magnification. Data were analyzed with one-way ANOVA and a post-hoc Tukey test. The positive control group leaked significantly more than all the experimental groups (P=0.001). MTA exhibited less leakage than composite and GI (P=0.002) but no significant differences were found between GI and composite groups. Immediate placement of a suitable intra-orifice barrier like MTA, before final restoration, may help minimize recontamination of the remaining apical gutta-percha.

Microleakage comparison of glass-ionomer and white mineral trioxide aggregate used as a coronal barrier in nonvital bleaching

There is some evidence that the pH at the root surface is reduced by intracoronal placement of bleaching pastes, which is known to enhance osteoclastic activity. Therefore, it is recommended that a protective barrier be used over the canal filling to prevent leakage of bleaching agents. Glass-ionomer (GI) is commonly used as a coronal barrier before nonvital bleaching. Because mineral trioxide aggregate (MTA) creates high alkalinity after mixing with water, using MTA as a protective barrier over the canal filling may not only prevent leakage of bleaching agents and microorganisms, but may prevent cervical resorption. The aim of this study was to evaluate sealing ability of white mineral trioxide aggregate (WMTA) as a coronal barrier before nonvital bleaching. Root canals of one hundred thirty human maxillary incisors were instrumented and filled with gutta-percha without sealer. Gutta-percha was removed up to 3 mm below the cementoenamel junction (CEJ). The teeth were randomly divided into six experimental groups of 20 teeth each and two control groups of 5. In three experimental groups, WMTA was packed into the canal to the level of CEJ. In the remaining experimental groups, glass-ionomer (GI) was used as a coronal barrier. After a 24-hour incubation period, one of the following three bleaching agents was placed in the access cavity of each of the WMTA or GI groups. These three bleaching agents were 30% hydrogen peroxide, sodium perborate mixed with 30% hydrogen peroxide, and sodium perborate mixed with distilled water. The bleaching agents were replaced every 3 days for three times. In the positive controls, no coronal barrier was used. In the negative controls, all the tooth surfaces were covered by two layers of nail varnish. Microleakage was evaluated using protein leakage test. Statistical analyses were performed with the Kruskal-Wallis and Mann-Whitney tests. The experimental groups showed minimum leakage which was not significantly more than tha in the negative controls. There was no statistically significant difference in leakage between the experimental groups (p<0.05). This study indicated that different bleaching agents have no effect on sealing ability of WMTA.

Coronal Microleakage of Four Restorative Materials Used in Endodontically Treated Teeth as A Coronal Barrier - An In Vitro Study

The present in vitro study was undertaken to evaluate sealing ability of access restoration using, four different dentin adhesives under composite with conventional glass ionomer cement and resin modified glass ionomer cement as intracoronal barrier 65 extracted human maxillary premolars were randomly divided into 15 teeth each in 4 experimental groups and 5 intact teeth each in control group. Following the biomechanical preparation,all teeth were obturated using Protaper gutta percha points and AH plus sealer. Once the sealer set, about 3mm of gutta-percha was removed from canal orifice in all the teeth. The base was placed till canal orifice extending 1mm coronally. All the specimens were thermocycled for 500 cycles at 5° – 55° c for 30 sec, and then placed in Rhodomine 6G fluorescent dye for 24 hrs. The coronal leakage was measured under a fluorescent microscope. Data obtained from the study were subjected to statistical analysis using one way Anova Test and Tukey’s HSD test. RESULTS - It showed statistically significant difference in coronal leakage among all the groups, but with no statistically significant difference seen between high strength glass ionomer cement (Group I and Group II) and Ketac N 100 (group III and Group IV when placed as intraorifice barrier. CONCLUSION - Under the limitations of the present study the following conclusions were made that, Composite restoration with Xeno III adhesive and Ketac N 100 as intraorifice barrier showed better coronal sealing ability in access cavities.