The effect of three additives on properties of mineral trioxide aggregate cements: a systematic review and meta-analysis of in vitro studies

BACKGROUND

Several efforts have been made to improve mechanical and biological properties of calcium silicate-based cements through changes in chemical composition of the materials. This study aimed to investigate the physical (including setting time and compressive strength) and chemical (including calcium ion release, pH level) properties as well as changes in cytotoxicity of mineral trioxide aggregate (MTA) after the addition of 3 substances including CaCl2, Na2HPO4, and propylene glycol (PG).

METHODS

The systematic review was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Electronic searches were performed on PubMed, Embase, and Scopus databases, spanning from 1993 to October 2023 in addition to manual searches. Relevant laboratory studies were included. The quality of the included studies was assessed using modified ARRIVE criteria. Meta-analyses were performed by RevMan statistical software.

RESULTS

From the total of 267 studies, 24 articles were included in this review. The results of the meta-analysis indicated that addition of PG increased final setting time and Ca2+ ion release. Addition of Na2HPO4 did not change pH and cytotoxicity but reduced the final setting time. Incorporation of 5% CaCl2 reduced the setting time but did not alter the cytotoxicity of the cement. However, addition of 10% CaCl2 reduced cell viability, setting time, and compressive strength.

CONCLUSION

Inclusion of 2.5% wt. Na2HPO4 and 5% CaCl2 in MTA can be advisable for enhancing the physical, chemical, and cytotoxic characteristics of the admixture. Conversely, caution is advised against incorporating elevated concentrations of PG due to its retarding effect.

TRIAL REGISTRATION

PROSPERO registration number: CRD42021253707.

Comparison of the Antibacterial Effect of AH26, Adseal and Beta RCS Root Canal Sealers against Enterococcus Faecalis, an in Vitro Study

Objectives: Antibacterial activity against endodontic pathogens is a desirable feature for root canal sealers. The objective of this study was to compare the antibacterial effect of three resin-based endodontic sealers (AH26, Adseal, and Beta RCS) against Enterococcus faecalis in vitro. Materials and Methods: The antibacterial properties of the sealers were assessed against E. faecalis using agar diffusion test (ADT) for fresh state (N=10) and direct contact test (DCT) for freshly-mixed and set states of the materials (N=10). In ADT, the diameter of the zones of inhibition was measured after 24h of contact. In DCT, the colony-forming units of the bacteria were counted after 30 minutes and 180 minutes of exposure. The results were analyzed with two-way ANOVA and independent sample t-test. P<0.05 was considered significant. Results: Regarding DCT results, all test materials indicated an antibacterial effect, both in freshly-mixed and set states. The highest antibacterial effect was related to Adseal, whereas the lowest was observed in Beta RCS. There was a significant difference between all study groups (different sealers, setting states, and contact times; P<0.001), except for freshly-mixed AH26 and Adseal at 180 minutes (P>0.05). According to ADT, AH26 and Adseal represented the widest and the smallest inhibition zones, respectively (P<0.001). Conclusion: Within the limitations of this in vitro study, AH26, Adseal, and Beta RCS showed antibacterial effects against E. faecalis in both freshly-mixed and set states. The antibacterial effect increased over time in all of the studied sealers.

Management of a supernumerary tooth fused to the labial surface of a permanent maxillary central incisor

Key Clinical Message

Management of supernumerary teeth fused to the labial surface of permanent maxillary central incisors would require a multidisciplinary approach comprising of endodontic treatment, periodontal recontouring, and cosmetic composite restoration.

Abstract

The reported cases of supernumerary teeth fused to the labial surface of maxillary central incisors are rare. Such cases need multidisciplinary approaches. Herein, management of a supernumerary tooth fused to the labial surface of a maxillary central incisor is reported. Due to the presence of a communication path between the root canal systems of the two fused teeth, root canal therapy was performed first for the maxillary left central incisor and the supernumerary tooth. The crown of the supernumerary tooth was then removed in a surgical setting while preserving the root to maintain the thin covering of alveolar bone and prevent future periodontal problems. Subsequently, an esthetic composite restoration was performed.

Comparative Biocompatibility and Odonto-/Osteogenesis Effects of Hydraulic Calcium Silicate-Based Cements in Simulated Direct and Indirect Approaches for Regenerative Endodontic Treatments: A Systematic Review

BACKGROUND

Regenerative dentistry is the operation of restoring dental, oral and maxillofacial tissues. Currently, there are no guidelines for the ideal cement/material in regenerative endodontic treatments (RET). Hydraulic calcium silicate-based cements (hCSCs) are currently the material of choice for RET.

OBJECTIVES

This systematic review was conducted to gather all of the different direct and indirect approaches of using hCSCs in RET in vitro and in vivo, and to ascertain if there are any superiorities to indirect approaches.

METHODS AND MATERIALS

This systematic review was conducted according to the 2020 PRISMA guidelines. The study question according to the PICO format was as follows: Comparison of the biological behavior (O) of stem cells (P) exposed to hCSCs through direct and indirect methods (I) with untreated stem cells (C). An electronic search was executed in Scopus, Google Scholar, and PubMed.

RESULTS

A total of 78 studies were included. Studies were published between 2010 and 2022. Twenty-eight commercially available and eighteen modified hCSCs were used. Seven exposure methods (four direct and three indirect contacts) were assessed. ProRoot MTA and Biodentine were the most used hCSCs and had the most desirable results. hCSCs were either freshly mixed or set before application. Most studies allowed hCSCs to set in incubation for 24 h before application, which resulted in the most desirable biological outcomes. Freshly mixed hCSCs had the worst outcomes. Indirect methods had significantly better viability/proliferation and odonto-/osteogenesis outcomes.

CONCLUSION

Biodentine and ProRoot MTA used in indirect exposure methods result in desirable biological outcomes.

Endodontic Management of a Maxillary Lateral Incisor with Dens Invagination and Periapical Lesion: A Case Report and Mini Review of the Literature

Dens invagination (DI) is a dental anomaly that can cause pulpal and periapical pathoses of the affected tooth. We describe the treatment of a healthy 18-year-old female with a chief complaint of recurrent facial swelling pertaining to a peg-shaped maxillary lateral incisor with DI. Examinations showed necrosis of the involved tooth with symptomatic apical periodontitis. Cone-beam computed tomography corresponded to Oehlers type II DI. Orthograde endodontic treatment was performed. To completely debride the canal and resolve the persistent purulent discharge, various methods and medicaments were used in separate sessions including passive ultrasonic activation of 5.25% sodium hypochlorite solution, calcium hydroxide mixed with 2% chlorhexidine, and double antibiotic paste as intracanal medicament. After resolution of the symptoms, the root canal and the invaginated space were filled by a mineral trioxide aggregate plug and backfilled with thermoplasticized gutta-percha. At the one-year follow-up, complete bone healing was noted in the affected periradicular area.

Antibacterial effectiveness of diluted preparations of intracanal medicaments used in regenerative endodontic treatment on dentin infected by bacterial biofilm: An ex vivo investigation

BACKGROUND

Conventional drug mixtures used in regenerative endodontic procedures have a toxic effect and no consensus has been reached about their best composition and concentration. Therefore, the aim of this study was to determine minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and minimum biofilm inhibitory concentration (MBIC) of the antimicrobial preparations and to compare their antimicrobial efficacy on bovine dentin infected by Enterococcus faecalis.

MATERIALS AND METHODS

For this original ex vivo investigation, prepared concentrations (MIC, MBC, and MBIC) of triple antibiotic paste (TAP), double antibiotic paste (DAP), modified triple antibiotic paste (MTAP)-1, MTAP2, co-amoxiclav, and calcium hydroxide (CH) were added to the prepared bovine dentin blocks (which incubated in E. faecalis suspension previously) and incubated for 3 days. The samples were subsequently prepared for culture and CFU counts. Statistical analysis of data was carried out using one-way analysis of variance and post hoc tests. The statistical power was set at P < 0.05.

RESULTS

All medicament groups significantly showed an antimicrobial efficacy compared with negative control (without antibiotic) (P < 0.001). TAP, DAP, co-amoxiclav, and CH (at its MBC value) were significantly capable of eliminating E. faecalis biofilm and showed no significant difference in comparison with positive control (complete biofilm removal) (P < 0.05).

CONCLUSION

TAP, DAP, co-amoxiclav, and CH (at its MBC value) could effectively eliminate biofilm bacteria on the dentin surface. Antimicrobial efficacy of other medicaments containing cefaclor or clindamycin was limited.

Modulation of virulence in Enterococcus faecalis cells surviving antimicrobial photodynamic inactivation with reduced graphene oxide-curcumin: An ex vivo biofilm model

BACKGROUND

Enterococcus faecalis, as a major microorganism in persistent/secondary infections of endodontically treated teeth, is less likely to be eliminated during endodontic therapy. In this study, the effect of root canal disinfection and anti-virulence activities of photodynamic inactivation (PDI) of E. faecalis utilizing reduced graphene oxide-curcumin (rGO-Cur) as a photosensitizing agent following irradiation with light-emitting diode (LED), as well as intracellular ROS production were evaluated on ex vivo biofilms of E. faecalis in comparison with sodium hypochlorite (NaOCl) as the traditional endodontic irrigation solution.

MATERIALS AND METHODS

After formulation and confirmation of synthesized rGO-Cur using scanning electron microscopy (SEM), Fourier transformation infrared (FT-IR), UV-Vis spectra, dynamic light scattering (DLS), and Zeta potential, the minimum biofilm inhibitory concentrations (MBICs) and in vitro anti-biofilm activity of rGO-Cur, light-emitting diode (LED) at the wavelength of 435 ± 20 nm, and rGO-Cur-PDI were determined against 4-week-old pre-formed biofilms of E. faecalis. After preparation of ex vivo biofilm model in root canals, the ex-vivo anti-biofilm potential of rGO-Cur, LED, and rGO-Cur-PDI against E. faecalis were analyzed using the XTT assay and scanning electron microscopy (SEM) in comparison with NaOCl. The effects of sub-MBIC of rGO-Cur and NaOCl, sub-lethal dose of LED, and sub-significant inhibitory (SSI) potential of rGO-Cur-PDI for E. faecalis biofilms on virulence genes (efa, esp, gel, and fsr) expression of E. faecalis were analyzed using real-time polymerase chain reaction (qRT-PCR) assay. Intracellular reactive oxygen species (ROS) level was measured in rGO-Cur-PDI-treated bacterial cells compared to control cells with 2',7'-dichlorfluorescein-diacetate (DCFH-DA) fluorescent probe.

RESULTS

The FTIR, DLS, Zeta potential, SEM, and UV-Vis spectra analysis indicated the successful synthesis of rGO-Cur. The MBIC of rGO-Cur was 250 μg/ml, which inhibited the growth ofE. faecalis. LED showed insignificant anti-biofilm activity against E. faecalis even after treating for a long irradiation time (300 s). According to checkerboard assay, the MBIC value of rGO-Cur-PDI was reduced noticeably compared to the individual MBIC values of rGO-Cur and LED for E. faecalis. The expression levels of efa, esp, gel, and fsr genes in pre-formed E. faecalis biofilms were markedly reduced after rGO-Cur, rGO-Cur-PDI, and NaOCl treatment in comparison with the control group. Conversely, LED revealed no significant change in the expression of the virulence genes. The intracellular ROS assay showed a significant increase (8.3-fold) in rGO-Cur-PDI when compared to the control.

CONCLUSION

Our data support that rGO-Cur-PDI showed dual inhibitory effects on biofilm formation ability and virulence activity of E. faecalis with potential clinical applications for infection control in endodontics.

Comparison of Tooth Color Change After Bleaching With Conventional and Different Light-Activated Methods

Introduction: The demand for esthetic dental treatments is increasing in recent years mainly due to improved oral hygiene and better maintenance of oral health and teeth in older individuals. Bleaching of discolored anterior teeth is the most popular among esthetic dental treatments. Even individuals with sound teeth and adequate esthetics seek to have whiter teeth in the anterior region. The aim of this study was to evaluate tooth color changes following conventional in-office bleaching techniques compared to light-activated methods using different light sources. Methods: Seventy sound anterior teeth (devoided of caries and/or fracture), extracted for periodontal and orthodontic reasons were selected and allocated to 7 groups: (A) control, (B) conventional bleaching (C) LED-activated bleaching, (D) KTP laser-activated bleaching, (E) diode laser-activated bleaching, (F) Nd:YAG laser-activated bleaching and (G) CO2 laser-activated bleaching. Colorimetric evaluation was carried out before and after treatment using a spectrophotoradiometer. Data were analyzed by one- and two-way analysis of variance (ANOVA) as well as multiple comparison methods. Results: The results showed that all bleaching procedures were effective in reducing the yellowness index. However, the KTP laser-activated bleaching was significantly more effective than the other techniques in 95% confidence level. It was also seen that CO2 laser activated method has outperformed groups E, F and G and the conventional bleaching without light activation was not effective at all and represented similar results with the control group. Furthermore, the groups E and G had almost the same results in decreasing the yellowness index. Conclusion: The results showed that all bleaching techniques were effective however, the KTP laser-activated bleaching was significantly more efficient, closely followed by the CO2 laser-activated bleaching technique.

Comparison of laser and power bleaching techniques in tooth color change

Background

Laser-assisted bleaching uses laser beam to accelerate release of free radicals within the bleaching gel to decrease time of whitening procedure. The aim of this study was to compare the efficacy of power bleaching using Opalescence Xtra Boost® and laser bleaching technique using LaserSmile gel and diode laser as an activator in their tooth whitening capacity.

Material and Methods

Student t test showed that the laser bleaching group significantly outperformed the power bleaching group in changing ∆E (p=0.977).

Results

Similarly, while comparing the groups in changing ∆L, the laser bleaching group indicated significantly superior results (p=0.953). Statistical data from student t test while comparing the groups in changing the parameter of yellowness indicated that samples in laser bleaching group underwent a more significant reduction than power-bleached samples (p=0.85). Correspondingly, changes in whiteness were statistically tested through student t test, showing that laser bleaching technique increased whiteness of the samples significantly more than those treated by power bleaching (p=0.965). The digital color evaluation data was in accordance with spectrophotometry and showed that laser bleaching outperformed power bleaching technique. Both techniques were able to increase whiteness and decrease yellowness ratio of the samples. ΔE decrease for laser bleaching and power bleaching groups were 3.05 and 1.67, respectively. Tooth color change in laser bleaching group was 1.88 times more than that of power bleaching group (p<0.001).

Conclusions

It could be concluded that under the conditions of this study, both laser-assisted and power bleaching techniques were capable of altering tooth color change, but laser bleaching was deemed a more efficient technique in this regard.

Key words:Laser, power bleaching, tooth color introduction.

Accuracy of CBCT, Digital Radiography and Cross-Sectioning for the Evaluation of Mandibular Incisor Root Canals

Introduction:

The aim of this study was to compare the accuracy of cone-beam computed tomography (CBCT), digital radiography and tooth sectioning in evaluating root canal morphology of mandibular incisors in an in vitro setting.

Methods and Materials:

A total of 76 samples were imaged using CBCT, and digital radiography in straight and angled views. The samples were then sectioned at different distances from the apex for further visualization under stereomicroscope. The agreement between the observers was statistically analyzed by kappa correlation coefficient and the chi-square test.

Results:

The results showed that the majority of the samples had a single canal (Vertucci’s Type I). CBCT analysis reported more frequent multi-canal roots in comparison with the other techniques. In pairwise comparisons, the highest agreement was found between digital radiographic imaging and microscopic cross-sectioning both in terms of canal configuration and the number of root canals.

Conclusion:

None of the used imaging techniques per se could adequately show the exact internal anatomical configuration in accordance with the gold standard.

Effect of Bacterial Lipopolysaccharide Contamination on Gutta Percha- versus Resilon-Induced Human Monocyte Cell Line Toxicity

OBJECTIVES

Cytotoxic effects of obturation materials were tested in presence and absence of endotoxin on human monocytes in vitro.

MATERIALS AND METHODS

Human monocytes from THP-1 cell line were cultured. Three millimeters from the tip of each Resilon and gutta percha points were cut and directly placed at the bottom of the culture wells. Cultured cells were exposed to gutta percha (groups G1 and G2) and Resilon (R1 and R2). Ten μg/ml bacterial lipopolysaccharide (LPS) was added to the culture wells in groups G1 and R1. Positive control included the bacterial LPS without the root canal filling material and the negative control contained the cells in culture medium only. Viability of cells was tested in all groups after 24, 48, and 72 hours using the methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay for at least 3 times to obtain reproducible results. Optical density values were read and the data were analyzed using three-way ANOVA and post hoc statistical test.

RESULTS

The results showed that cells in G2 had the lowest rate of viability at 24 hours, but the lowest rate of viable cells was recorded in G1 at 48 and 72 hours. The effect of LPS treatment was not statistically significant. Resilon groups showed cell viability values higher than those of gutta percha groups, although statistically non-significant (P=0.105). Cell viability values were lower in gutta percha than Resilon groups when LPS-treated and LPS-untreated groups were compared independently at each time point.

CONCLUSION

It could be concluded that none of the tested root canal filling materials had toxic effects on cultured human monocyte cells whether in presence or absence of LPS contamination.

Co-existence of two dens invaginations with one dens evagination in a maxillary lateral incisor: a case report

A case with two simultaneous dens invaginations (DIs) and one dens evagination (DE) in a permanent maxillary lateral incisor is reported for the first time in a 21-year-old girl. DE known as talon cusp of the anterior teeth is a rare entity and its co-existence with DI has been reported scarcely in the literature. Simultaneous occurrence of two DIs with one DE has not been reported elsewhere. Undoubtedly, familiarity with the internal anatomy of such a rare condition can help prevent pulpal disease while performing restorative procedures.

Cone-beam Computed Tomographic Assessment of Canal Centering Ability and Transportation after Preparation with Twisted File and Bio RaCe Instrumentation

OBJECTIVE

Use of rotary Nickel-Titanium (NiTi) instruments for endodontic preparation has introduced a new era in endodontic practice, but this issue has undergone dramatic modifications in order to achieve improved shaping abilities. Cone-beam computed tomography (CBCT) has made it possible to accurately evaluate geometrical changes following canal preparation. This study was carried out to compare canal centering ability and transportation of Twisted File and BioRaCe rotary systems by means of cone-beam computed tomography.

MATERIALS AND METHODS

Thirty root canals from freshly extracted mandibular and maxillary teeth were selected. Teeth were mounted and scanned before and after preparation by CBCT at different apical levels. Specimens were divided into 2 groups of 15. In the first group Twisted File and in the second, BioRaCe was used for canal preparation. Canal transportation and centering ability after preparation were assessed by NNT Viewer and Photoshop CS4 software. Statistical analysis was performed using t-test and two-way ANOVA.

RESULTS

All samples showed deviations from the original axes of the canals. No significant differences were detected between the two rotary NiTi instruments for canal centering ability in all sections. Regarding canal transportation however, a significant difference was seen in the BioRaCe group at 7.5mm from the apex.

CONCLUSION

Under the conditions of this in vitro study, Twisted File and BioRaCe rotary NiTi files retained original canal geometry.

Residual Antimicrobial Activity of MTAD(®) in Human Dentin After Obturation with Gutta-Percha/AH26 and Resilon/RealSeal SE at Different Time Intervals; An Ex Vivo Study

OBJECTIVES

To eliminate microorganisms that are responsible for pulpal and periapical infections and to prevent reinfection of the root canal system an effective chemomechanical preparation by irrigants with sustained antimicrobial activity is beneficial. Hereby, we evaluated the residual antibacterial activity of MTAD after canal obturation at different time intervals.

MATERIALS AND METHODS

A total of 120 human single-canalled anterior teeth were selected. The root canals were instrumented to a standardized apical size. Among all, 90 teeth received final irrigation with MTAD and were divided into three groups according to their obturation materials; i.e. gutta-percha/AH26, Resilon/RealSeal SE and positive controls. All these groups were divided into three 1-, 3- and 6-week time interval subgroups. Thirty teeth as negative control had no final irrigation with MTAD, but were obturated with gutta-percha/AH26 or Resilon/RealSealSE. Dentin powder was prepared after 1, 3 and 6 weeks. Dentin powder was exposed to Enterococcus faecalis for 24h and then cultured. Colony Forming Unit (CFU) was counted.

RESULTS

Residual antimicrobial activity of MTAD in the teeth obturated with guttapercha/AH26 was significantly higher than the teeth obturated with Resilon/RealSeal SE (p<0.001). It also showed a time dependent decrease in MTAD antimicrobial activity for all groups. The highest antimicrobial activity of MTAD was found in the 1-week positive control and 1-week gutta-percha/AH26 specimens. The lowest antimicrobial activity of MTAD was found in 6-week Resilon/RealSeal SE samples and then the negative controls.

CONCLUSION

MTAD had antimicrobial activity even at the sixth week, although it had a time-dependent decrease. Resilon/Epiphany SE significantly decreased antimicrobial activity of MTAD at all time points.

Push-out bond strength of two root-end filling materials in root-end cavities prepared by Er,Cr:YSGG laser or ultrasonic technique

This study compared the push-out bond strength of mineral trioxide aggregate (MTA) and a new endodontic cement (NEC) as root-end filling materials in root-end cavities prepared by ultrasonic technique (US) or Er,Cr:YSGG laser (L). Eighty single-rooted extracted human teeth were endodontically treated, apicectomised and randomly divided into four following groups (n = 20): US/MTA, US/NEC, L/MTA and L/NEC. In US/MTA and US/NEC groups, root-end cavities were prepared with ultrasonic retrotip and filled with MTA and NEC, respectively. In L/MTA and L/NEC groups, root-end cavities were prepared using Er,Cr:YSGG laser and filled with MTA and NEC, respectively. Each root was cut apically to create a 2 mm-thick root slice for measurement of bond strength using a universal testing machine. Then, all slices were examined to determine the mode of bond failure. Data were analysed using two-way anova. Root-end filling materials showed significantly higher bond strength in root-end cavities prepared using ultrasonic technique (US/MTA and US/NEC) (P < 0.001). The bond strengths of MTA and NEC did not differ significantly. The failure modes were mainly adhesive for MTA, but cohesive for NEC. In conclusion, bond strengths of MTA and NEC to root-end cavities were comparable and higher in ultrasonically prepared cavities.

Er,Cr:YSGG laser influence on microleakage of class V composite resin restorations

One of the most challenging issues following restoration is microleakage. The aim of this study was to investigate the effects of Er,Cr:YSGG laser with and without acid etching on microleakage of class V composite restorations. A total of 68 human intact premolars were selected, disinfected, and randomly allocated to four experimental groups (n = 16) as well as positive and negative controls (n = 2 each). Dimensionally, similar class V cavities were prepared on buccal surface of each tooth under the following conditions: group 1, bur cavity preparation and chemical etching (BE); group 2, bur cavity preparation and Er,Cr:YSGG laser conditioning (BLc); group 3, Er,Cr:YSGG laser cavity preparation and chemical etching (LE); and group 4, Er,Cr:YSGG laser cavity preparation and Er,Cr:YSGG laser conditioning (LLc). All samples were restored with composite. The teeth were sealed and immersed in 1 % methylene blue for 48 h before being sectioned. The microleakage evaluation was done under a stereomicroscope (×20). The leakage scores were recorded and Kruskal-Wallis and Mann-Whitney tests were used for statistical evaluations. The highest microleakage score was seen in gingival margins of group 4 (LLc) and the lowest in occlusal margins of group 3 (LE). The overall difference in leakage scores among the groups was statistically significant (p < 0.001) with gingival margins showing a significantly higher score than its occlusal counterparts (p < 0.001). It was noted that less microleakage could be achieved when cavities were prepared by laser compared to bur. In addition, less microleakage was seen in acid-etched cavities than laser-conditioned counterparts.

Effect of phosphate-buffered saline on push-out bond strength of a new bioceramic sealer to root canal dentin

BACKGROUND

The aim of this study was to compare push-out bond strength of a new bioceramic endodontic sealer, EndoSequence BC sealer (Brasseler USA, Savannah, GA), used with gutta-percha in the presence or absence of phosphate-buffered saline solution (PBS) within the root canals.

MATERIALS AND METHODS

Forty single-rooted human teeth were prepared and randomly divided into four groups. Samples in groups 1 and 2 were dried, but those in groups 3 and 4 were moistened with PBS before obturation. All root canals were obturated with gutta-percha/EndoSequence BC sealer. The specimens were stored in PBS for 7 days in groups 1 and 3 and for 2 months in groups 2 and 4. Push-out bond strength values and failure modes were evaluated. The data on push-out bond strength were analyzed using two-way ANOVA.

RESULTS

The mean value for the bond strength of the obturation material in moistened canals was significantly higher than that in dried ones at 1 week (P = 0.00). Contrarily, there was no significant difference between dried and moistened root canals at 2 months (P = 0.61). In dried canals, bond strength increased significantly with time but in moistened ones, the difference was not significant. Inspection of the specimens revealed the bond failure to be mainly cohesive for all groups.

CONCLUSION

The presence of PBS within the root canals increased the bond strength of EndoSequence BC sealer/gutta-percha at 1 week. However, no difference was found between the bond strength of EndoSequence BC sealer/gutta-percha in the presence or absence of PBS in the root canals at 2 months.

Coronal microleakage in root canals obturated with lateral compaction, warm vertical compaction and guttaflow system

INTRODUCTION

Root canal obturation seals the root canal system to prevent re-entry and/or growth of microorganisms. The provision of an appropriate restoration to coronally seal the access cavity affects the success of endodontic treatment. The purpose of this study was to evaluate the coronal microbial leakage in root canals that were either filled by lateral compaction, GuttaFlow or warm vertical compaction.

MATERIALS AND METHODS

In this ex vivo study, 80 single-rooted human extracted teeth were randomly divided into three experimental groups (n=20) and two positive and negative control groups (n=10). The teeth in experimental groups were obturated with cold lateral compaction, GuttaFlow system or warm vertical compaction techniques. After sterilization of the whole system with gamma-ray, saliva leakage was tested using a split-chamber model. Specimens were monitored every 24 hours for 30 days. The data were analyzed using log-rank and Kaplan-Meier survival analysis tests.

RESULTS

There were no significant differences in impeding saliva leakage between the three experimental groups (P>0.05).

CONCLUSION

Under the conditions of this ex vivo study, it can be concluded that the sealing ability of cold lateral compaction, warm vertical compaction and GuttaFlow system was comparable.

Endodontic treatment of two-canalled maxillary central and lateral incisors: a case report

Familiarity with the intricacies and variations of root canal morphology is essential for successful endodontic treatment. Maxillary central and lateral incisors are known to be single-rooted with one canal, however, this case report describes endodontic treatment of maxillary central and lateral incisors with two buccopalatal root canals.

In vitro comparison of the effectiveness of chlorhexidine and two calcium hydroxide formulations on enterococcus faecalis

INTRODUCTION

The aim of this in vitro study was to compare the effectiveness of three intracanal medicaments in disinfecting the root canal and dentin of experimentally infected human teeth with Enterococcus faecalis (EF).

MATERIALS AND METHODS

One hundred extracted human single-rooted teeth were used. After root canal preparation, teeth were mounted in epoxy resin. Following sterilization, the teeth were infected for 28 days with EF. Then root canals were filled with one of three different disinfectants: viscous 2% Chlorhexidine (CHX), calcium hydroxide paste (CH) or a mixture of CH and CHX (n=30 in each group). Antimicrobial assessments were performed at 1, 3 and 7 days (n=10 in each time period). Microbial samples were obtained from root canals before and after the experiment. Also dentin samples were examined. The data was analyzed using Two- Way ANOVA test.

RESULTS

The findings showed that there was no difference between experimental groups at different time periods. The mixture of CH/CHX in 7 days was able to eliminate EF completely from root canal system. The most elimination of EF was from dentinal tubules.

CONCLUSION

According to the results of this in vitro study, viscous 2% CHX, mixture of CH with distilled water and 2% CHX are all effective disinfectants.

Cytotoxicity Evaluation of Proroot MTA, Root MTA and Portland Cement on Human Gingival Fibroblasts

INTRODUCTION

The aim of this study was to compare the cytotoxicity of ProRoot MTA (PMTA), Root MTA (RMTA) and Portland cement (PC) on human gingival fibroblasts (HGFs).

MATERIALS AND METHODS

The extracts of the test materials were placed close to human gingival fibroblasts (HGFs) within 96-well plates. Cellular viability was assessed using MTT assay in different intervals (freshly mixed, 4, 24, and 168 hours after mixing). The data were analyzed using the One-way ANOVA and Tukey's test at 95% significance level.

RESULTS

It was indicated that there was not a significant difference in cytotoxicity of test materials (p>0.05). In addition, there was not a statistically significant difference between different time intervals within each group (p>0.05).

CONCLUSION

PMTA, RMTA and PC showed comparative biocompatibility while evaluated in-vitro.

Serotoninergic denervation suppresses the sympathetic outflow induced by thyrotropin-releasing hormone in conscious rats

Intrathecal administration of thyrotropin-releasing hormone (TRH) resulted in an increase in plasma epinephrine (E) and glucose levels in conscious rats. To elucidate the mechanisms by which TRH stimulates the release of E, the animals were pretreated with 5,7-dihydroxytryptamine, parachlorophenylalanine, methysergide or ketanserin. Serotoninergic denervation suppressed the TRH-induced increase in plasma E and glucose levels, whereas inhibition of serotonin (5-HT) synthesis or blockade of 5-HT receptors did not suppress the responses. These findings suggest that the serotoninergic neurons, but not 5-HT itself, are involved in stimulating the sympathetic outflow by TRH at the spinal level.

[Clinical application of a sensitive immunoradiometric assay for human growth hormone]

A sensitive immunoradiometric assay (IRMA) for human growth hormone (GH) using monoclonal antibodies was evaluated for clinical application. The detection limit of GH in serum was 0.05 ng/ml using 0.1 ml of serum. The specificity and assay precision were satisfactory. GH levels in serum determined by the IRMA were well correlated to those determined by the sensitive enzyme immunoassay or the commercial radioimmunoassay. Most of the basal GH levels in serum from normal adult subjects were detectable; mean values in male and female were 0.21 and 0.65 ng/ml, respectively. Serum GH levels decreased to less than 1 (0.5) ng/ml after oral glucose loading in normal subjects. Postoperative acromegalic patients were classified into two groups according to their GH responses to glucose. In group 1, GH levels were suppressed less than 1 ng/ml, suggesting normal GH dynamics. On the other hand, in group 2, GH levels remained elevated above 1 ng/ml, and postinhibitory rebound rise in serum GH after dopamine infusion was observed, suggesting the presence of residual adenoma tissues. Determination by sensitive IRMA of GH responses during oral glucose loading is useful for evaluating the activity of postoperative acromegaly.

Secretion of alpha and TSH-beta subunits in patients with acromegaly: an in vivo study

Plasma alpha and TSH-beta subunit responses to iv administration of GHRH were examined in 19 patients with active acromegaly. In 4 patients (21%), plasma alpha subunit levels were increased over 50% of basal levels after administration of GHRH, whereas plasma TSH-beta subunit levels were increased in response to GHRH in another 5 patients (26%). No patient showed simultaneous increases of alpha and beta subunits. After successful surgery, alpha and TSH-beta subunits did not respond to GHRH. These findings support the idea that some pituitary adenomas in acromegaly cosecrete GH and either alpha subunit or TSH-beta subunit.

Galanin interacts with serotonin in stimulating prolactin secretion in the rat

Abstract The interaction of galanin (GAL) with serotonin (5-HT) in the regulation of prolactin (PAL) secretion was investigated in urethaneanesthetized male rats. Intracerebroventricular administration of 5-HT (1 and 10 mu g) and GAL (1 mu g) caused an increase in plasma PRL levels, but co-administration of GAL did not show any additive effect on 5-HT-induced PRL secretion. Pretreatment with methysergide (0.25 mg/kg), a nonselective 5-HT1 and 5-HT2 receptor antagonist, partially inhibited the PRL increase induced by GAL. On the other hand, neither ketanserin (0.25 mg/kg), a selective 5-HT2 receptor antagonist, nor ICS 205-930 (0.25 mg/kg), a selective 5-HT3 receptor blocker, had any effect on GAL-induced increase in PRL secretion. Parachlorophenylalanine (300 mg/kg), a 5-HT synthesis inhibitor, however, caused a marked enhancement of PRL release induced by GAL, which was partially inhibited by a 5-HT neurotoxin, 5, 6-dihydroxytryptamine. Parachlorophenylalanine also caused a potentiation of 5-HT-induced PRL release, possibly by sensitizing 5-HT receptors. These findings suggest that 5-HT receptors are, at least partly, involved in GAL-induced PRL release in the rat.

Growth hormone responses to oral glucose loading measured by highly sensitive enzyme immunoassay in normal subjects and patients with glucose intolerance and acromegaly

Plasma GH levels were determined during a 75-g oral glucose tolerance test using a highly sensitive enzyme immunoassay. Most normal subjects and patients with varying degrees of impaired glucose tolerance showed a decrease in plasma GH levels during the first 60 min. A GH rise within 60 min was observed in 3 of 37 normal subjects. The incidence of the GH rise (8%) was significantly lower than that (40%) in control experiments after water loading. The median minimum GH levels were 0.15 and 0.14 micrograms/L after glucose and water loading, respectively. Plasma GH responses to glucose ingestion were not different between normal subjects and patients with glucose intolerance. After surgery, 12 of 16 patients with acromegaly showed low basal GH levels (less than 5.0 micrograms/L). Six of the 12 patients showed normal GH responses to glucose loading (median minimum GH level, 0.21 micrograms/L) and normal plasma insulin-like growth factor-I levels. Plasma GH levels were not suppressed below 1.0 micrograms/L in the remaining 6 acromegalic patients. Determination of plasma GH levels after glucose loading by the highly sensitive enzyme immunoassay is useful for evaluating the effect of surgical treatment of acromegaly.

Galanin-induced prolactin release in rats: pharmacological evidence for the involvement of alpha-adrenergic and opioidergic mechanisms

The mechanism by which galanin (GAL) stimulates prolactin (PRL) secretion was investigated in urethane-anesthetized male rats. The PRL release induced by intracerebroventricular (i.c.v.) injection of porcine GAL (pGAL) was similar to that induced by rat GAL. The PRL release induced by pGAL was partially blocked by alpha-adrenergic antagonists, phentolamine (1 microgram/rat, i.c.v.; 29.1 +/- 4.5 ng/ml vs control 66.9 +/- 10.2 ng/ml, P less than 0.01) and tolazoline (1 microgram/rat, i.c.v.; 25.9 +/- 4.4 ng/ml vs control 59.6 +/- 10.9 ng/ml, P less than 0.05). Neither propranolol (1 microgram/rat, i.c.v.), a beta-adrenergic antagonist, nor prazosin (1 microgram/rat, i.c.v.), an alpha 1-adrenergic antagonist, inhibited pGAL-induced PRL release. Naloxone (125 micrograms/100 g body wt., i.v. 30 min before), an opiate antagonist, also inhibited pGAL-induced PRL release (25.9 +/- 4.0 ng/ml vs 59.1 +/- 7.2 ng/ml, P less than 0.01). Combined treatment with naloxone and phentolamine caused greater inhibition of pGAL-induced PRL release than did phentolamine alone (10.3 +/- 1.5 ng/ml vs 23.2 +/- 4.7 ng/ml, P less than 0.05), but the inhibition was similar to that induced by naloxone alone. These findings suggest that alpha 2-adrenergic and opioidergic mechanisms are involved in PRL release induced by GAL.

Urinary excretion of human growth hormone: daily variation and relationship with albumin and alpha 1-microglobulin in urine

Urinary excretion of growth hormone during night-time was measured by a highly sensitive enzyme immunoassay in 6 normal men for 18-24 days. Urinary GH excretion distributed widely from 0.12 to 4.7 pg/mumol creatinine and the coefficient of variation in each subject ranged from 37 to 57% (mean 49%). Urinary excretion of albumin and alpha 1-microglobulin also showed moderate day-to-day variations (mean coefficients of variation: 37 and 42%, respectively). No correlation was found among urinary excretion of GH, albumin and alpha 1-microglobulin. Plasma and urinary GH levels were determined every 5 min and 2 h, respectively, from 09.00 h to 17.00 h in 4 normal men. Urinary GH excretion every 2 h during daytime closely reflected the change of plasma GH levels in each subject, suggesting that physiological GH secretory dynamics are reflected on the urinary GH excretion. Repeated measurements of urinary GH excretion are required to evaluate GH secretory capacity.