The Effect of Smear Layer on Antimicrobial Efficacy of Three Root Canal Irrigants

Evaluation of Residual Debris and Smear layer After Root Canal Preparation by Three Different Methods: A Scanning Electron Microscopy Study

Introduction

This study investigated the amount of debris and smear layer remaining followed chemomechanical preparation using three systems: ProTaper Universal, reciprocating SafeSider, and hand K-Flexofiles with scanning electron microscope (SEM).

Materials and Methods

Sixty-five mandibular molars with mesiobuccal canal curvature (25 to 40^°) were extracted and divided into one control group (n=5), and three experimental groups (n=20) according to the preparation method; K-Flexofile, ProTaper Universal and SafeSider instruments. All canals were irrigated with 3 ml of 5.25% sodium hypochlorite solution and 3 mL of 17% EDTA. Subsequently, the canals were irrigated with 5 ml of normal saline. Then the teeth were examined under the scanning electron microscope (SEM). Kruskal-Wallis, Dunn-Q Bonferroni, and Friedman tests were used for statistical analysis of results.

Results

To assess the accumulation of debris, statistically significant differences were observed only in the coronal area among ProTaper Universal, SafeSider, K-Flexofile, and the control group. (P=0.029). To evaluate the residual smear layer amount, statistically significant differences were observed only in the coronal and middle areas, following the preparation of the canals using ProTaper Universal, SafeSider, and hand K-Flexofiles and control groups (P=0.019).

Conclusions

Based on the present in vitro study, we can declare that the canals were utterly cleaned of debris and smear layer in none of the groups. Manual Flexofile and ProTaper Universal groups result in cleaner canal walls than reciprocal SafeSider, in the coronal and middle thirds.

Irrigant Agitation Techniques versus Passive Ultrasonic Irrigation for Removing Debris from Curved Root Canals: An Environmental Scanning Electron Microscopic Study

Introduction

The aim of this study was to compare the efficacy of passive ultrasonic irrigation (PUI) versus mechanical agitation of the irrigant promoted by the EasyClean (EC) and XP-Endo Finisher (XP-F) systems in removing debris from root canal walls, using environmental scanning electron microscopy (ESEM).

Methods and Materials

Twelve curved mesiobuccal canals of mandibular molars were prepared with the ProTaper Next system up to file X2 (25/0.06). The specimens were embedded in flasks containing silicone putty, sectioned lengthwise, and a 4-mm long groove was made on the canal wall of the buccal half of the specimen, extending from 2 mm up to 6 mm short of the apex. Five cross-sectional markings were made along this groove to establish standardized locations for imaging. The same specimens were used to prepare a negative control group (without debris), a positive control group (completely covered by debris), and 3 experimental groups according to the final irrigation protocol employed: PUI, EC or XP-F. ESEM images were obtained and evaluated by 3 examiners. The amount of debris observed on the images was classified according to a 4-category scoring system. The kappa test was used to assess inter-examiner agreement, and the Kruskal-Wallis and Dunn tests were used to compare the scores (P<0.05).

Results

The scores attributed to the PUI, EC, and XP-F groups were statistically similar to those attributed to the negative control group (P>0.05).

Conclusion

Based on this in-vitro study, the mechanical agitation of the irrigant promoted by EC and XP-F was as effective as using PUI to remove debris from the root canal walls.

Quantitative Assessment of Dentinal Tubule Disinfection in Absence of Biofilm on Root Canal Walls: An in vitro Study

Introduction

This study aimed at assessing the quantitative effect of calcium hydroxide, 2% chlorhexidine gel, and 1.5% chlorhexidine linked to xanthan gel specifically against intratubular bacteria.

Methods and Materials

Fifty-two semi-cylindrical bovine dentin specimens were infected with Enterococcus (E.) faecalis by centrifugation with subsequent 7-days incubation. The surface of specimens was disinfected with 3% H₂O₂. Scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) and the count of bacterial colony-forming units (CFU/mg) were used to assess dentin infection. A total of 40 specimens were incubated for 2 weeks with one of the intracanal medication applied (10 samples for each group): 1) calcium hydroxide, 2) 2% chlorhexidine gel, 3) 1.5% chlorhexidine linked to xanthan gel and 4) sterile saline. Final passive ultrasonic irrigation with 3% sodium hypochlorite was performed in half of the total specimens. The effect of intracanal medications and irrigation against intratubular bacteria was assessed by bacterial culturing of dentin shavings. Two-Way ANOVA model was applied followed by post-hoc Tukey's test for multiple pair-wise comparisons of mean CFU/mg values.

Results

SEM, CLSM, and bacterial culturing confirmed the absence of the surface biofilm on the root canal wall and showed vital intratubular bacteria at the depth up to 700  m. Two-week application of 1.5% chlorhexidine with xanthan gel and 2% chlorhexidine gel significantly decreased intratubular bacterial counts compared with saline (P=0.0003 and P=0.0005, respectively). Subsequent passive ultrasonic irrigation with 3% sodium hypochlorite significantly reduced the number of intratubular bacteria in all groups except for the group with 1.5% chlorhexidine-xanthan gel (P=0.0054).

Conclusion

This modified ex vivo model study showed ultrasonically activated irrigation with sodium hypochlorite had greater effect on intratubular bacteria counts compared with 2-week application of intracanal medications.

Evaluation of Antimicrobial Effcacy of Calcium Hypochlorite as an Endodontic Irrigant on a Mixed-Culture Biofilm: An Ex vivo Study

Introduction

Calcium hypochlorite (CH) has been recently suggested as an endodontic irrigant. The aim of this investigation was to evaluate the antimicrobial efficacy of CH compared to sodium hypochlorite (NaOCl) and chlorhexidine (CHX) against multispecies biofilm in surface and deep dentinal tubules.

Methods and Materials

Minimal inhibitory concentration (MIC) of irrigant agents was assessed using a microdilution method. One hundred and twenty of human maxillary incisor teeth were prepared and infected with suspension of Entrococcus faecalis, Fusobacterium nucleatum and Prevotella intermedia in an anaerobic jar for 7 days. Depending on irrigation solutions, specimens were divided into 4 groups (n=30); group 1: 2% CHX, group 2: 5.25% sodium hypochlorite, group 3: 5% calcium hypochlorite, group 4: positive control (normal saline (NS)). Fifteen remained specimens were used as negative control. Surviving bacteria were sampled before (S1) and after irrigation from surface (S2) and deep (S3) dentin. The medium turbidity was visualized with spectrophotometry. Data were analyzed using analysis of variance followed by Tukey post hoc test (α=0.05).

Results

The MIC of CH against E. faecalis, F. nucleatum and P. intermedia was 25, 8 and 7.5 µg/mL respectively. There were no significant differences in S1 among the test groups. Moreover, 2% CHX and 5% CH had significantly lower medium turbidity at both S2 and S3, in comparison with 5.25% NaOCl (P=0.018 and 0.031, respectively). But there were no significant differences between 2% CHX and 5% CH at both S2 and S3 (P=0.862 and 0.978, respectively).

Conclusion

Under the conditions of this ex vivo study, 5% CH and 2% CHX are more effective than 5.25% NaOCl in the reduction of mixed-culture biofilm.

The Antifungal Effect of Propolis Endodontic Irrigant with Three Other Irrigation Solutions in Presence and Absence of Smear Layer: An In Vitro Study

INTRODUCTION

The aim of this in vitro study was to compare the antifungal effect of propolis as an endodontic irrigant agent with a mixture of doxycycline, citric acid, and a detergent mixture (MTAD), 2% chlorhexidine (CHX) and 3% sodium hypochlorite (NaOCl) against Candida albicans in presence and absence of smear layer.

METHODS AND MATERIALS

Extracted teeth with single canals (n=104) were prepared and randomly distributed into four experimental groups; 30% propolis, MTAD, 2% CHX and 3% NaOCl. Each group had two subgroups; with and without smear layer. The antifungal effectiveness was evaluated. The Kruskal-Wallis and Mann-Whitney tests were used to compare the overall effectiveness of different treatments at significance level of 0.05.

RESULTS

Propolis, CHX and NaOCl had similar levels of effectiveness to each other against C. albicans, and these levels were not affected by the presence or absence of the smear layer. Each irrigant was significantly more effective than MTAD or saline solution. MTAD was less effective in the presence of the smear layer than in its absence.

CONCLUSIONS

Propolis irrigation can produce root canals that are free of C. albicans, even in the presence of the smear layer.

Effects of Epigallocatechin-3-gallate (EGCG) on the bond strength of fiber posts to Sodium hypochlorite (NaOCl) treated intraradicular dentin

This study was to evaluate the effect of Epigallocatechin-3-gallate (EGCG) on the bond strength of two adhesive systems to the Sodium hypochlorite (NaOCl) treated intraradicular dentin. The roots were accepted regular root canal treatments and post space preparations, and further divided into eight groups according to the four post space pretreatments and two dentin adhesives [Single Bond 2 (SB2) and Clearfil SE Bond (CSB)] used. The push-out strength before and after thermocycling in different root region (coronal and apical), DC of the adhesive and morphologic patterns of treated post space were evaluated. NaOCl + EGCG groups showed the highest push-out strength regardless of the adhesive type, root region and time (P < 0.05). NaOCl pretreatment significantly decreased the push-out strengths and DC of CSB (P < 0.05). EGCG could improve the bonding properties of both SB2 and CSB to NaOCl treated intraradicular dentin. The effect of NaOCl on bonding of a fiber post depended on the type of the adhesive.

To Evaluate the Efficacy of an Innovative Irrigant on Smear Layer Removal - SEM Analysis

INTRODUCTION

The goal of endodontic therapy is to completely eliminate the microorganisms and the smear layer from the root canal in order to provide a good seal of the root filling materials.

AIM

The aim of this study was to find a viable alternative irrigant, which is easily available with less erosion and clinically acceptable smear layer removal by comparing the efficacy of EDTA and commercially available super-oxidized water, named Oxum, as a final rinse on smear layer removal and erosion in relation to coronal, middle and apical thirds of radicular dentin using Scanning Electron Microscope (SEM) analysis.

MATERIALS AND METHODS

Freshly extracted 30 human lower second premolar teeth with straight roots and type I canal anatomy were selected. The root canals were cleaned and shaped using Universal Protaper Rotary System. Irrigation was performed with 1 ml of 2.5% of NaOCl solution after each instrument change. The final irrigation (5 ml) sequence was as follows: Group I- 17% EDTA, Group II - OXUM, and Group III - 0.9% saline (control) for one minute. Then, the root canals were finally irrigated with 5ml of distilled water to remove any precipitate. The roots were then gently split into two halves using a chisel and subjected to SEM analysis.

RESULTS

The SEM photomicrographs were evaluated by two independent examiners and Mann Whitney results showed that there was no statistically significant difference between the two examiners. Non-parametric statistical analysis of all experimental groups showed significant difference between coronal, middle and apical third for smear layer removal with p-value<0.05. For erosion, in group II (oxum) showed statistically significant difference between coronal, middle and apical third and it showed significantly less dentine erosion when compared to EDTA.

CONCLUSION

Within the limitations of the present study, Oxum the commercially available super-oxidized water proved to be equally effective in smear layer removal with less erosion when compared to EDTA.