Comparison of the Surface Hardness among 3 Materials Used in an Experimental Apexification Model under Moist and Dry Environments

Introduction

Procedures used in single-visit or multiple-visit approaches to apical barrier creation were used with an experimental apexification model to test the surface hardness of 3 materials. The purpose of this study was to examine the microhardness of the materials after setting in moist or dry conditions.

Methods

A simulated open apex and periapical environment model was created using polyethylene tubes placed into a porous block filled with phosphate-buffered saline. White ProRoot Mineral Trioxide Aggregate (MTA; Dentsply Tulsa Dental, Tulsa, OK), EndoSequence Root Repair Material (ESRRM; Brasseler USA, Savannah, GA), and Biodentine (BD; Septodont, Louisville, CO) were mixed and placed into the apical 4 mm of the tubes (N = 15). The moist group had a damp cotton pellet above the test materials (mineral trioxide aggregate or ESSRM) with Fuji II LC (GC America, Alsip, IL) sealing the coronal segment. The dry group had gutta-percha placed directly against the test materials with amalgam sealing the coronal segment. After 10 days of storage in 100% humidity at 37°C, samples were sectioned, and microhardness was independently measured at 2 mm and 4 mm from the apical end. Differences were assessed using analysis of variance and a Tukey post hoc test (α = .05).

Results

Analysis of variance analyses showed no significant effect of wet or dry conditions on resultant material hardness. A Tukey post hoc test showed that using ESRRM and BD would not result in a significant difference in hardness, but using MTA would result in statistically significant different hardness values when compared with ESRRM or BD.

Conclusions

Either a moist or dry environment could allow hardening of materials; thus, both methods could be acceptable for clinical treatment procedures.     

Comparison of Mineral Trioxide Aggregate and iRoot BP Plus Root Repair Material as Root-end Filling Materials in Endodontic Microsurgery: A Prospective Randomized Controlled Study

Introduction

This prospective randomized controlled study evaluated the clinical and radiographic outcome of endodontic microsurgery when using iRoot BP Plus Root Repair Material (BP-RRM; Innovative BioCeramix Inc, Vancouver, BC, Canada) or mineral trioxide aggregate (MTA) as the retrograde filling material and analyzed the relationship between some potential prognostic factors and the outcome of the surgery.

Influence of a bioceramic root end material and mineral trioxide aggregates on fibroblasts and osteoblasts

Objective

The biocompatibility of materials used in endodontic treatment is of high importance, because they can come in contact with periradicular tissues and there is a risk of possible systemic toxicity. The aim of the present study was to investigate the in vitro reaction to a bioceramic based root end material in comparison to mineral trioxide aggregates (MTA) as the established gold standard.

Design

The root end materials grey MTA Angelus (GMTA), white MTA Angelus (WMTA), ProRoot MTA, and EndoSequence Root Repair Material (ERRM) were incubated with human periodontal ligament fibroblasts and osteoblasts (10⁴ cells/ml) for up to 96 h. Cell proliferation (RFU) was determined by means of the Alamar Blue assay. In addition, fluorescence staining was carried out to visually monitor cell growth and morphology.

Results

For most of the observational time period of up to 96 h, there was no statistically significant difference between the proliferation rates of the control cells and those in contact with ERRM. In contrast, the mineral trioxide based materials caused from 24 to 96 h significantly lower proliferation rates in comparison to the controls (p < 0.001). For proliferation rates of cells in contact with MTAs and ERRM significant differences were observed throughout the whole observation time for the osteoblasts, but only up to 24 h for the human periodontal ligament fibroblasts.

Conclusion

Within the limits of this study the results suggest that the bioceramic root end material is biocompatible, but needs to be investigated in clinical studies before it can be recommended as retrograde sealer in endodontic practice.     

A new noninvasive model to study the effectiveness of dentin disinfection by using confocal laser scanning microscopy

Introduction

The present study was designed to develop a standardized model for quantification of the effectiveness of dentin disinfection by different antibacterial solutions including a new root canal irrigant, Qmix.

Methods

Dentinal tubules from the root canal side in semicylindrical dentin specimens were infected with Enterococcus faecalis by centrifugation of the bacterial suspension into the tubules. Scanning electron microscopy (SEM) was used to verify the presence of bacteria in dentin. The outer side of dentin pieces was closed, and the specimens were subjected to 1-minute and 3-minute exposure to sterile water, 1%, 2%, 6% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX), and Qmix. Confocal laser scanning microscopy (CLSM) and viability staining were used to quantitatively analyze the proportions of dead and live bacteria inside dentin.

Results

A heavy invasion by E. faecalis was detected by both SEM and CLSM throughout the dentinal tubules. The amount of dead cells in dentin increased with increasing NaOCl concentration and time of exposure (P < .05). Qmix was equally effective in killing bacteria in dentin as 6% NaOCl; more than 40% and 60% of the bacteria were killed by both at 1 minute and 3 minutes, respectively. One percent and 2% NaOCl and 2% CHX killed 20%–30% and 30%–40% bacteria after 1 and 3 minutes of exposure, respectively, with no statistically significant differences among the 3 agents (P > .05). In the control group, which was treated with sterile water, only 4%–6% of the bacteria were dead.

Conclusions

Centrifugation helped to create a heavy, evenly distributed infection deep into the dentinal tubules. The new model made it possible to compare the effectiveness of several disinfecting solutions in killing bacteria inside dentin by a noninvasive CLSM method.     

Antifungal Activity of Endosequence Root Repair Material and Mineral Trioxide Aggregate

Introduction

The purpose of this study was to investigate the antifungal activity of Endosequence Root Repair Material (ERRM; Brasseler USA, Savannah, GA) as compared with mineral trioxide aggregate (MTA) using Candida albicans.

Methods

All materials were packed into sterilized intravenous tubing to obtain standardized samples and allowed to set for 3 or 24 hours and then exposed to a suspension of C. albicans for incubations of 24 or 48 hours. To analyze the mechanisms of the material's antifungal activity, additional samples of each test material were prepared in the same manner and allowed to set for 24 hours; these were then incubated in a culture medium for 24 hours. The pH of each conditioned media was measured before transferring to wells containing C. albicans. The development of biofilm was analyzed after 24 and 48 hours with 2,3-bis (2-methoxy-4-nitro-5-sulfophenyl)-5-([phenyl amino] carbonyl)-2H-tetrazolium hydroxide reduction assay.

Results

Materials in both experimental groups significantly limited biofilm formation at each interval (ie, 24 and 48 hours). After incubating for a 24-hour period in the presence of C. albicans, ERRM in both experimental groups showed a reduction in biofilm formation that was statistically significant in comparison with MTA. However, when set for 24 hours and incubated for 48 hours, gray MTA and white MTA showed a more substantial reduction in biofilm formation than comparable samples of ERRM. Cultured media conditioned with test materials showed statistically significant antifungal biofilm activity after 48 hours.

Conclusions

All materials tested have comparable antifungal biofilm activity. It appeared that changing the environment, such as the pH, contributed to this activity.     

Antibacterial and Anti-biofilm Activity of AH Plus with Chlorhexidine and Cetrimide

Introduction

The use of root canal filling materials with antibacterial activity can be considered beneficial to reduce the remaining microorganisms in the root canal system, where Enterococcus faecalis is often found, and prevent recurrent infection. The aim of this study was to evaluate the antimicrobial activity and capacity for inhibiting E. faecalis biofilm formation of AH Plus, alone and mixed with chlorhexidine (CHX), cetrimide (CTR), and combinations of the two.

Methods

AH Plus alone and mixed with 1% and 2% CHX, 0.1%–0.5% CTR, and combinations of both were tested to assess antimicrobial activity by a modified direct contact test and determine inhibition of E. faecalis biofilm formation at 24 hours. The results were expressed as log₁₀ viable counts. Eradication and inhibition of biofilm formation were understood as no bacterial growth or log₁₀ reduction = 5 with respect to the control (AH Plus alone).

Results

AH Plus + CHX showed a low antimicrobial activity with respect to the control (at 2%, log₁₀ reduction = 1.30). None of the tested concentrations achieved eradication or inhibition of biofilm. AH Plus + CTR showed a direct relationship of concentration-antimicrobial effect, reaching a log₁₀ reduction of 2.92 at 0.5% and inhibition of biofilm formation at 0.2%. With the combination CHX + CTR, lower concentrations were needed for the same effect, and eradication and inhibition of biofilm were achieved.

Conclusions

The addition of CHX, CTR, or some combination of both to AH Plus confers it with bactericidal and anti-biofilm activity against E. faecalis.     

Antibiofilm Effects of Endodontic Sealers Containing Quaternary Ammonium Polyethylenimine Nanoparticles

Introduction

This study evaluated the antibiofilm effects of 2 endodontic sealers incorporated with quaternary ammonium polyethylenimine (QPEI) nanoparticles at a 2% concentration (w/w).

Methods

The materials tested were AH Plus and Pulp Canal Sealer EWT (PCS) in the commercial unmodified form or containing 2% QPEI. Antibiofilm assays were conducted by using direct-contact and membrane-restricted tests for evaluation of bacterial viability in biofilms grown onto membranes or paper disks and the crystal violet microtiter-plate assay to evaluate the effects of sealer extracts on the biofilm biomass. Two Enterococcus faecalis strains (ATCC and an endodontic isolate) were used.

Results

Direct contact and membrane-restricted antibiofilm tests revealed that PCS 2% was the only material to promote total killing of E. faecalis ATCC biofilms. All the materials significantly reduced bacterial counts in E. faecalis ATCC biofilms when compared with the positive control in both tests (P < .05). In the direct test against E. faecalis RW35, PCS 2% was significantly more effective than the other materials and was the only one that showed significantly lower counts than the positive control (P < .05). In the crystal violet assay, only AH Plus 2% presented optical density readings significantly lower than the positive control of the ATCC strain (P < .05). No other significant effects on the biofilm biomass of the 2 E. faecalis strains were observed for any of the sealers tested (P > .05).

Conclusions

Addition of QPEI nanoparticles improved the killing ability of PCS against biofilms of both E. faecalis strains and the effects of AH Plus on the biomass of biofilms from the ATCC strain.     

Time-dependent antibacterial effects of the self-adjusting file used with two sodium hypochlorite concentrations

Introduction

This in vitro study evaluated the time-dependent ability of the self-adjusting file (SAF) used with either of two NaOCl concentrations to reduce bacterial populations in long oval root canals.

Methods

Oval-shaped canals from extracted teeth were infected with Enterococcus faecalis for 30 days and subjected to preparation with the SAF system using continuous irrigation with either 2.5% NaOCl (n = 11) or 6% NaOCl (n = 11). Bacteriological samples were taken before preparation (baseline) and after 2, 4, and 6 minutes of SAF operation.

Results

Intragroup quantitative analyses revealed that the SAF operating for 2, 4, or 6 minutes yielded a highly significant bacterial reduction when compared with counts at baseline (P < .001) irrespective of the NaOCl concentration. No significant differences were found for intragroup analyses comparing the three time periods (P > .05). Likewise, intergroup quantitative analysis showed no significant difference for the SAF with 2.5% NaOCl or 6% NaOCl during 2, 4, or 6 minutes (P > .05). The incidence of positive cultures in the 2.5% NaOCl group was 6 of 11, 5 of 11, and 2 of 11 after 2, 4, and 6 minutes, respectively. Corresponding figures in the 6% NaOCl group were 4 of 11, 2 of 11, and 1 of 11. When all samples were gathered together, overall findings revealed that using the SAF for 6 minutes significantly reduced both the bacterial counts (P = .02) and the incidence of positive cultures (P = .04) when compared with 2 minutes.

Conclusions

Findings revealed that the SAF promoted a significant reduction in bacterial populations even after only 2 minutes regardless of the NaOCl concentration. The most impressive results were obtained after a 6-minute operation.     

Antibacterial Efficacy of Photosensitizer Functionalized Biopolymeric Nanoparticles in the Presence of Tissue Inhibitors in Root Canal

Introduction

Application of antibacterial nanoparticles to improve root canal disinfection has received strong interest recently. The current study aims to assess the antibacterial effect of a novel photosensitizer (rose bengal functionalized chitosan nanoparticles [CSRBnp]) to eliminate bacteria in the presence of various root canal constituents that are known to inhibit the antibacterial efficacy of root canal disinfectants.

Methods

The synthesized CSRBnp were evaluated for size, charge, and singlet oxygen release. The antibacterial effect of CSRBnp was tested on planktonic Enterococcus faecalis with or without pretreatment by using different inhibiting agents such as dentin, dentin-matrix, pulp tissue, bacterial lipopolysaccharides, and bovine serum albumin (BSA). Bacterial survival was assessed in a time-dependent manner. The antibacterial effects after photodynamic activation on CSRBnp, a cationic photosensitizer (methylene blue), and an anionic photosensitizer (rose bengal [RB]) in the presence of inhibitors were also evaluated.

Results

CSRBnp were 60 ± 20 nm in size and showed reduced rate of singlet oxygen release as compared with methylene blue and RB. Pulp and BSA inhibited the antibacterial effect of CSRBnp (without photoactivation) significantly (P < .05) even after 24 hours of interaction. In case of photodynamic therapy, the pulp and BSA significantly inhibited the antibacterial activity of all 3 photosensitizers. CSRBnp showed residual effect and completely eliminated the bacteria after 24 hours of interaction after photodynamic therapy.

Conclusions

The inherent antibacterial activity of polycationic chitosan nanoparticles and the singlet oxygen released after photoactivation of RB synergistically provided CSRBnp the potential to achieve significant antibacterial efficacy even in the presence of tissue inhibitors within root canals.     

Role of efflux pump inhibitors on the antibiofilm efficacy of calcium hydroxide, chitosan nanoparticles, and light-activated disinfection

Introduction

The purpose of this study was to evaluate the role of efflux pumps in altering the susceptibility of Enterococcus faecalis biofilms to calcium hydroxide (Ca(OH)₂), chitosan nanoparticles, and light-activated disinfection (LAD).

Methods

E. faecalis as 4-day-old biofilms and biofilm-derived cells were tested with aqueous Ca(OH)₂ in concentrations of 25%, 50%, and 100%; chitosan nanoparticles in concentrations of 10 and 20 mg/mL (3, 12, and 24 hours); and methylene blue (MB) mediated LAD at an energy dose range of 2–40 J/cm². An efflux pump inhibitor (EPI) was incorporated into all 3 modalities of treatment. The antimicrobial activity was assessed by determining the colony-forming units.

Results

E. faecalis biofilms, in contrast to the biofilm-derived cells, were found to persist even after 24-hour treatment with different concentrations of Ca(OH)₂ and chitosan nanoparticles. LAD at an energy dose of 40 J/cm² completely inactivated 4-day-old E. faecalis biofilms. The addition of EPI improved the antibiofilm efficacy of Ca(OH)₂ at lower concentrations (P < .001) and LAD (P < .001). EPI did not influence the antibiofilm effect of chitosan nanoparticles and Ca(OH)₂ at higher concentrations.

Conclusions

E. faecalis biofilms were more susceptible to killing by LAD, when compared with the tested concentrations of Ca(OH)₂ and chitosan nanoparticles. The effect of EPI was more significant with LAD, when compared with Ca(OH)₂ and chitosan nanoparticles. This study highlighted the role of biofilm matrix in providing resistance to antimicrobials.     

Comparison of intracanal EndoSequence Root Repair Material and ProRoot MTA to induce pH changes in simulated root resorption defects over 4 weeks in matched pairs of human teeth

Introduction

Intracanal mineral trioxide aggregate (MTA) may provide an alternative to calcium hydroxide in the treatment of external inflammatory root resorption. This in vitro study using human matched pairs of teeth compared white ProRoot MTA (WMTA; (Dentsply Tulsa Dental Specialties, Tulsa, OK) and an alternative material with purportedly improved handling properties, EndoSequence Root Repair Material (ES; Brasseler USA, Savannah, GA), by measuring pH in simulated root surface resorptive defects after intracanal placement. The null hypothesis tested was that there is no difference between WMTA and ES.

Methods

Bilaterally matched pairs (n = 24) of extracted, human, single-rooted teeth were instrumented to apical size 50/.06, and root surface cavities were prepared at 5 mm and 2 mm from the apex. Root canals of experimental matched pairs (n = 20) were filled with WMTA or ES; control pairs (n = 4) were filled with calcium hydroxide (positive control [POS]) or saline (negative control [NEG]). Teeth were sealed coronally and apically and immersed in saline. The pH in root surface cavities was measured at 20 minutes, 3 hours, 24 hours, 1 week, 2 weeks, 3 weeks, and 4 weeks.

Results

The pH at 5 mm when compared with the 2-mm level was significantly higher for the WMTA, ES, and POS groups (P < .05, paired t tests); therefore, each level was analyzed separately. At both the 2-mm and 5-mm levels, significant pH changes occurred over time in the WMTA, ES (both P < .0001, repeated-measures analysis of variance), and POS (P < .0001, Friedman test) groups and not in the NEG group (mean pH = 7.32 ± 0.04, P > .05). There were no differences between WMTA and ES at 20 minutes and 3 hours at both levels or at 24 hours at 5mm. The pH of WMTA was higher than ES by 24 hours at the 2-mm level (8.79 vs 8.56, P < .05, paired t test) and after 1 week at the 5-mm level (8.91 vs 8.05, P < .0001) and was thereafter always significantly higher in WMTA compared with ES (P < .0001). The null hypothesis was rejected.

Conclusions

In matched pairs of teeth, intracanal placement of WMTA compared with ES resulted in a higher pH in simulated root resorption defects that was time and root level dependent.     

Improvement of the properties of mineral trioxide aggregate by mixing with hydration accelerators

Introduction

Mineral trioxide aggregate (MTA) is used widely in endodontic therapy. This study examined the setting time, compressive strength, and pH of MTA mixed with several hydration accelerators (calcium chloride, low-dose citric acid, calcium lactate gluconate solution).

Methods

Group 1 (control) was obtained by mixing MTA with distilled water. In group 2, MTA containing 10% calcium chloride was mixed with distilled water. In group 3, MTA was mixed with 0.1% citric acid. In group 4, MTA was mixed with a calcium lactate gluconate solution. The setting time, compressive strength, and pH were examined.

Results

The setting time of MTA mixed with hydration accelerators was significantly shorter than that of MTA mixed with water (P < .01). In particular, replacing distilled water with a calcium lactate gluconate solution provided a significant decrease in setting time. The compressive strengths of MTA mixed with hydration accelerators were significantly lower than that of MTA mixed with water (P < .01), but those values increased with time. The pH of MTA mixed with hydration accelerators was significantly lower than that of MTA mixed with water (P < .01) but stable at a high level (pH 11–12).

Conclusions

Hydration accelerators improved the setting time of MTA. Nevertheless, more study will be needed to improve MTA without impairing its preexisting advantages.     

Comparison of the Biological Properties of ProRoot MTA,OrthoMTA, and Endocem MTA Cements

Introduction

OrthoMTA (BioMTA, Seoul, Korea) and Endocem MTA (Maruchi, Wonju-si, Korea) were recently developed to overcome the disadvantages of ProRoot MTA (Dentsply, Tulsa, OK). This study aimed to compare the biological properties of OrthoMTA and Endocem MTA with those of ProRoot MTA using the preosteoblastlike cell line MC3T3-E1.

Methods

The setting times of calcium silicate–based cements (CSCs) and their effects on the pH of distilled water during storage were determined according to ISO standards. MC3T3-E1 cells were cultured with ProRoot MTA, OrthoMTA, and Endocem MTA. The viability of the cells was assessed using the Cell Counting Kit-8 assay (Dojindo Laboratory, Kumamoto, Japan) on the supernatants of CSCs, and the cells' osteopontin production was determined by an enzyme-linked immunosorbent assay on a culture with the materials on days 3 and 7 of incubation.

Results

Endocem MTA exhibited a significantly shorter setting time (15.3 ± 0.5 minutes) than did ProRoot MTA and OrthoMTA (318.0 ± 56.0 and 324.3 ± 2.1 minutes, P < .05). Additionally, all CSCs caused their storage water to become highly alkaline after 7 days. OrthoMTA was significantly more cytotoxic than ProRoot and Endocem MTA (P < .05). ProRoot MTA induced significantly more OPN production than OrthoMTA and Endocem MTA on both days 3 and 7 (P < .05).

Conclusions

ProRoot MTA appeared to be superior to OrthoMTA and Endocem MTA in terms of biological properties although Endocem MTA exhibited the shortest setting time and presented lower cytotoxicity with osteoblastlike cells.     

Nanomechanical properties of endodontically treated teeth

Introduction

Although it is apparent that teeth become more susceptible to fracture after root canal treatment, the contributing factors for this are not completely established. The purpose of this study was to determine whether there are changes in nanomechanical properties of dentin in root canal–treated teeth compared with non–root canal–treated control teeth.

Methods

Atomic force microscopy–based nanoindentation testing was performed on root canal–treated teeth and age- and type-matched control teeth. Radicular intertubular dentin was indented in 6 locations, and triplicate measurements were averaged. Paired t tests were used to compare root canal–treated teeth with control teeth.

Results

The moduli of elasticity were 17.8 ± 2.9 GPa and 18.9 ± 2.9 GPa for root canal–treated teeth and controls, respectively; the hardness values for the 2 groups were 0.84 ± 0.25 GPa and 0.84 ± 0.18 GPa, respectively. Neither the modulus of elasticity nor the hardness differed between groups (P > .05).

Conclusions

It appears that root canal treatment does not result in nanomechanical changes to radicular intertubular dentin.     

Evaluation of the Antibacterial Efficacy of Silver Nanoparticles against Enterococcus faecalis Biofilm

Introduction

The purpose of this study was to evaluate the antibacterial efficacy of silver nanoparticles (AgNPs) as an irrigant or medicament against Enterococcus faecalis biofilms formed on root dentin.

Methods

Dentin sections were inoculated with E. faecalis for 4 weeks to establish a standard monospecies biofilm model. These biofilms were tested in 2 stages. In stage 1, the biofilms were irrigated with 0.1% AgNP solution, 2% sodium hypochlorite, and sterile saline for 2 minutes, respectively. In stage 2, the biofilms were treated with AgNP gel (0.02% and 0.01%) and calcium hydroxide for 7 days. The ultrastructure of one half of the specimens from each group was evaluated by using scanning electron microscopy, whereas the structure and distribution of viable bacteria of the other half of the specimens were assessed with confocal laser scanning microscopy combined with viability staining.

Results

Syringe irrigation with 0.1% AgNP solution did not disrupt the biofilm structure, and the proportion of viable bacteria in the biofilm structures was not different from that of the saline group (P > .05) but was less than that of the control group (P < .05). The biofilms treated with 0.02% AgNP gel as medicament significantly disrupted the structural integrity of the biofilm and resulted in the least number of post-treatment residual viable E. faecalis cells compared with 0.01% AgNP gel and calcium hydroxide groups (P < .05).

Conclusions

The findings from this study suggested that the antibiofilm efficacy of AgNPs depends on the mode of application. AgNPs as a medicament and not as an irrigant showed potential to eliminate residual bacterial biofilms during root canal disinfection.     

Antimicrobial activity of nanoemulsion on cariogenic Streptococcus mutans

Objective

To assess antimicrobial activities of nanoemulsion (NE) to control the adhesion and biofilm formation by Streptococcus mutans by in vitro.

Design

In vitro antimicrobial susceptibility of nanoemulsion was determined as per National Committee for Clinical Laboratory Standards guidelines and agar diffusion, serial dilution technique for the determination of minimum inhibitory concentration and minimum bactericidal concentration (MIC/MBC). Efficacy was tested by kinetics of killing, biofilm assay and scanning electron microscopy.

Results

: NE concentrations ranging from 1:100 to 1:10,000 dilutions were effective against S. mutans as shown through MIC/MBC assays. NE showed antimicrobial activity against planktonic cells at high dilutions, confirmed by time kill studies. 4-day-old S. mutans biofilms were treated with NE; subsequent reductions of bacterial cell counts were noticed with decreasing dilutions. Staining of NE-treated biofilms with LIVE/DEAD BacLight resulted in dead cell areas of up to 48% in 1 min, 84% at 1 h and significant (<0.05) increases in dead cell counts at all time points. Damage to cell membranes and cell walls of S. mutans by NE was demonstrated using scanning electron microscopy (SEM).

Conclusion

These results suggest that nanoemulsion has effective antibacterial activity against S. mutans and may be a useful medication in the prevention of dental caries.     

Reinforcement of simulated immature roots restored with composite resin, mineral trioxide aggregate, gutta-percha, or a fiber post after thermocycling

Introduction

The purpose of this study was to evaluate the fracture resistance after thermocycling of simulated immature teeth restored with composite, a fiber post, mineral trioxide aggregate (MTA), or gutta-percha.

Methods

Eighty-four primary bovine mandibular incisors were divided into 7 groups (n = 12). Negative controls received no treatment. Teeth in all other groups were prepared to an internal diameter of 1.75 mm. After placement of 4-mm apical barrier of MTA, the canals were filled with their respective test materials to the facial cementoenamel junction. For the fiber post group, a fiber post was fitted to extend from the MTA barrier to 2 mm below the incisal edge and was cemented with Build-It FR. The positive controls were left unfilled. The access openings were filled with BisFil II composite. All teeth were then thermocycled for 500 cycles at 5°C and 55°C with a 30-second dwell time and 5-second transfer time. Each root was horizontally fractured through the test material by using an Instron Universal Testing Machine, and the peak load to fracture was recorded. The data were analyzed with analysis of variance and Tukey post hoc tests (P < .05).

Results and Conclusions

Thermocycled composite was not significantly stronger than gutta-percha and MTA. The only material that significantly strengthened the simulated immature teeth was the fiber-reinforced composite with a fiber post.     

Effects of a chewing gum containing phosphoryl oligosaccharides of calcium (POs-Ca) and fluoride on remineralization and crystallization of enamel subsurface lesions in situ

Objectives

Manufacturers are adding fluoride (F) to calcium-containing chewing gums to further promote enamel remineralization. The aim of this study was to assess the effect of a chewing gum containing phosphoryl oligosaccharides of calcium (POs-Ca) and fluoride on remineralization of enamel subsurface lesions, in a double-blind, randomized controlled in situ trial.

Methods

Thirty-six volunteer subjects wore removable buccal appliances with three different insets of bovine enamel with subsurface demineralized lesions. For 14 days the subjects chewed one of the three chewing gums (placebo, POs-Ca, POs-Ca + F), three times a day. After each treatment period, the insets were removed from the appliance, embedded, sectioned, polished and then subjected to laboratory tests; mineral level was determined by transverse microradiography (TMR; n = 36), and hydroxyapatite (HAp) crystallites were assessed by synchrotron radiation wide-angle X-ray diffraction (WAXRD; n = 13). Data were analysed by t-test or Wilcoxon rank-sum test with Bonferroni corrections at 0.05 significance level.

Results

Chewing POs-Ca and POs-Ca + F gums resulted in 21.9 ± 10.6 and 26.3 ± 9.4 (mean ± SD) percentage mineral recovery, which was significantly higher than that of placebo gum (15.0 ± 11.4) (p < 0.05). Chewing POs-Ca + F gum resulted in 24.9 ± 5.4 (mean ± SD) percentage HAp crystallites recovery, which was significantly higher compared to POs-Ca (16.0 ± 4.1%) or placebo (11.1 ± 4.8%) gums (p < 0.05).

Conclusions

Addition of POs-Ca to the chewing gum resulted in significant remineralization of enamel subsurface lesions. Although POs-Ca + F gum was not superior in TMR recovery rate when compared with POs-Ca gum, WAXRD results highlighted the importance of fluoride ion bioavailability in the formation of HAp crystallites in enamel subsurface lesions in situ (NCT01377493).     

In Vitro Evaluation of the Antibacterial Activities of MTAD in Combination with Nisin against Enterococcus faecalis

Introduction

MTAD is a common intracanal irrigant. Although MTAD inhibits Enterococcus faecalis in root canals, its bactericidal effect against E. faecalis remains to be improved. Nisin, an antibacterial peptide, possesses a strong bactericidal effect. The study evaluated the synergetic action between MTAD and nisin against E. faecalis.

Methods

The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were used to measure the antibacterial activities of MTAD, MTAN (substitution of doxycycline with nisin), and MTADN (nisin in combination with doxycycline), respectively. The synergetic effect between nisin and doxycycline was evaluated by fractional inhibitory concentration (FIC) and time-killing curves. Furthermore, morphologic changes in E. faecalis were observed by scanning electron microscopy after E. faecalis was treated with MTAD, MTAN, or MTADN for 24 hours.

Results

The MBC of MTADN against E. faecalis was lower than that of MTAD and MTAN. The combination of nisin and doxycycline had a significantly synergetic antibacterial effect on E. faecalis. Among the 3 antimicrobial treatments, MTADN caused the most severe damage to E. faecalis.

Conclusions

The combination of nisin and doxycycline has a synergetic antibacterial effect on E. faecalis, and MTAD in conjunction with nisin inhibits E. faecalis better than MTAD alone.     

Retrospective Analysis of Root-end Microsurgery Outcomes in a Postgraduate Program in Endodontics Using Calcium Silicate–based Cements as Root-end Filling Materials

IntroductionThe purpose of this retrospective study was to determine the clinical and radiographic outcomes of root-end microsurgery in a postgraduate program in endodontics using modern techniques and calcium silicate–based root-end filling materials (ProRoot MTA; Dentsply International, Johnson City, TN, and EndoSequence Root Repair Material [ERRM]; Brasseler USA, Savannah, GA) and to identify any potential prognostic factors that may have affected healing outcomes.MethodsClinical records and periapical radiographs were collected from patients who had undergone endodontic microsurgery between 2007 and 2018 in a postgraduate endodontic clinic with a minimum follow-up interval of 6 months. Either ProRoot MTA or ERRM was used as the root-end filling material. Outcomes were categorized into healed, healing, and nonhealing based on clinical and radiographic findings. Healed and healing cases were pooled and considered as successes, whereas nonhealing cases were considered as failures.ResultsA total of 129 patients with 142 teeth were included in the final analysis. Seventy-six cases were root-end filled with ProRoot MTA and 66 root-end filled with ERRM. The ProRoot MTA group had a success rate of 92.1%, and the ERRM group had a success rate of 92.4% with no significant difference between the groups (P > .05). Vertical root fracture was found to be the predominant cause of failure. No patient- or treatment-related factor was identified to have any significant impact on healing.ConclusionsHigh overall success can be achieved in a postgraduate endodontic program when either ProRoot MTA or ERRM is used as the root-end filling material.