Effect of root canal preparation techniques on chlorhexidine substantivity on human dentin: a chemical analysis

Antimicrobial action, cytotoxicity and erosive potential of hypochlorous acid obtained from an electrolytic device compared with sodium hypochlorite

OBJECTIVES

This study aimed to compare the antimicrobial action, cytotoxicity, cleaning ability, and erosion of dentine of hypochlorous acid (HClO) obtained from an electrolytic device at two different concentrations (Dentaqua) and three concentrations of sodium hypochlorite (NaOCl).

METHODS

Microbiological test-The root canals of sixty single-rooted extracted human teeth were inoculated with Enterococcus faecalis and divided into 6 groups (n = 10), according to decontamination protocol: DW (control); 1% NaOCl; 2.5% NaOCl; 5.25% NaOCl; 250 ppm HClO and 500 ppm HClO. The colony-forming units were counted to evaluate the decontamination potential of each group, calculating the reduction in bacterial percentage. Cytotoxicity test-Cytotoxicity was evaluated after inoculation of the same tested protocols in fibroblastic cells for 3 min, calculating the cell viability percentages. Specifical statistical analysis was performed (α = 5%). Cleaning ability and erosion-Fifty-six single-rooted bovine lower incisors were divided into seven groups of 8 roots each, being the test groups 1% NaOCl; 2.5% NaOCl; 5,25% NaOCl; 250 ppm HClO and 500 ppm HClO, and a negative and positive control. Negative control was not contaminated, and the other groups were inoculated with Enterococcus faecalis. SEM images were ranked as from the cleanest to the least clean. Erosion was also assessed, being ranked from the least to the most eroded dentine.

RESULTS

The highest bacterial reduction was observed in experimental groups, with no statistical differences between them (p > 0.05). The highest number of viable cells was observed in control group, followed by 250 ppm HClO and 500 ppm HClO groups, with statistical differences between them (p < 0.05). 1% NaOCl; 2.5% NaOCl; 5.25% NaOCl and 500 ppm HClO displayed the cleanest areas. All sodium hypochlorite groups displayed erosion with higher ranks with greater concentration, while hypochlorous acid did not display any erosion regardless the concentration.

CONCLUSIONS

It is possible to conclude that HClO obtained from an electrolytic device presented high antimicrobial activity and low cytotoxicity in both tested concentrations. 500 ppm HClO did not display erosion and showed great cleaning ability.

CLINICAL RELEVANCE

The use of 500 ppm hypochlorous acid may reduce unfavorable behavior of sodium hypochlorite whilst maintaining its antimicrobial action.

Effect of different root canal irrigants on push-out bond strength of two novel root-end filling materials

BACKGROUND

The aim of this in vitro study was to evaluate push-out bond strength of different root-end filling materials using various irrigant solutions.

METHODS

A push-out bond strength test was performed to evaluate the bond strength of two experimental root-end filling materials: namely, nano-hybrid mineral trioxide aggregate (MTA) and polymethyl methacrylate (PMMA) cement filled with 20% weight nano hydroxyapatite (nHA) fillers compared to conventional MTA. The irrigant solutions employed were sodium hypochlorite (NaOCl) in concentrations 1%, 2.5% and 5.25% and 2% chlorhexidine gluconate (CHX) followed by application of 17% ethylene diamine tetra-acetic acid (EDTA). A freshly extracted sixty single-rooted human maxillary central incisors were used. The crowns were removed, the canal apex was widened to simulate immature teeth. Each type of irrigation protocols was performed. After application and setting of the root-end filling materials, a slice of one mm thickness was cut transversely from the apical end of each root. Specimens were stored for 1 month in artificial saliva and were subjected to a push-out test to evaluate the shear bond strength. Data were analyzed using two-way ANOVA and Tukey test.

RESULTS

The experimental nano-hybrid MTA showed the highest significant push-out bond strength values when irrigated by NaOCl at several concentrations (1%, 2.5% and 5.25%) (P< 0.05). Meanwhile, irrigation with 2% CHX resulted in highest bond strength values in nano-hybrid white MTA (18 MPa) and PMMA filled with 20% weight nHA (17.4 MPa) with nonsignificant difference between them (p = 0.25). In each root-end filling material, irrigation with 2% CHX led to the highest significant bond strength, followed by NaOCl 1%, while the least significant bond strength was produced after irrigation with NaOCl 2.5% and 5.25% (P< 0.05).

CONCLUSION

Considering the limitations of this study, it may be concluded that the application of 2% CXH and 17% EDTA provides superior push-out bond strength to root canal dentin compared with irrigation with NaOCl irrigants and 17% EDTA, experimental nano-hybrid MTA root-end filling material provides enhanced shear bond strength than conventional micron-sized MTA root-end filling material.

The dentine-sealer interface: modulation of antimicrobial effects by irrigation

AIM

Assess whether sodium hypochlorite (NaOCl) or chlorhexidine (CHX) and two irrigation protocols may alter the antibacterial properties of dentine and three endodontic sealers using a novel ex vivo tooth model.

METHODOLOGY

Prior to antibacterial testing, the tooth model was validated by means of scanning electron microscopy (SEM) to evaluate the separation between dentine and sealer surfaces. Root blocks prepared from extracted human roots were pretreated with 17% EDTA + 0.9% saline and subsequently treated with 1% NaOCl (G1), 2% CHX (G2) or no irrigant (G3). Two irrigation protocols were further investigated, "1% NaOCl + 17% EDTA" (P1) and "1% NaOCl + 17% EDTA + 2% CHX" (P2). Following irrigation, the root blocks were either filled with AH Plus, BioRoot RCS and Pulp Canal Sealer (PCS), or left empty. All groups were incubated for 1, 7 and 28 days. Direct contact tests for planktonic E. faecalis and 48 hours E. faecalis biofilms were performed at the level of dentine and sealer surfaces. Statistical analysis was performed on the bacterial survival between irrigants (G1, G2 and G3) and between irrigation protocols (P1 and P2) (p<0.05).

RESULTS

The model was considered reproducible as SEM examination of dentine samples indicated consistent separation between dentine and sealer surfaces. Irrigation with CHX (G2) and irrigation protocol (P2) enhanced the antibacterial properties of dentine without sealer application as well as dentine in contact with all three sealers tested, especially against planktonic E. faecalis. G2 and P2 also improved the antibacterial effect of AH Plus surfaces for all three incubation times. No irrigation groups (G1, G2) or irrigation protocols (P1, P2) altered the antibacterial properties of BioRoot RCS surfaces against planktonic bacteria or biofilms. Only BioRoot RCS surfaces eliminated the planktonic E. faecalis in all irrigation groups (G1, G2, G3) and protocols (P1, P2) investigated while PCS surfaces eliminated E. faecalis in biofilms in all groups up to 7 days.

CONCLUSIONS

The tooth model was reproducible. CHX improved the antibacterial activity upon both sealer and dentine surfaces. Among sealers, BioRoot RCS was less affected by NaOCl and CHX, and exhibited high antibacterial properties regardless the irrigation applied.

Influence of the apical limit of instrumentation and photodynamic therapy on the postoperative pain of lower molars with asymptomatic apical periodontitis

INTRODUCTION

The aim of present study was to evaluate the influence of apical limit of instrumentation and PDT on the postoperative pain of lower molars with asymptomatic apical periodontitis.

METHODS

Forty patients were included in the present study and were divided into 4 groups (n=10), according to apical limit of instrumentation and use of PDT: instrumentation at 0.0 measurement; instrumentation at 0.0 measurement+PDT; instrumentation 1mm beyond 0.0 measurement; instrumentation 1mm beyond 0.0 measurement+PDT. In the PDT, the root canals were filled with 0.01% methylene blue, remaining for 5 min. The low-intensity laser was used with 100 mW, 660-690 nm wavelength), using intra-canal fibre. Root canals were irradiated for 90 s, delivering total dose of 9 J and energy density of 320 J/cm2. After root canal preparation and PDT protocols, root canals were filled with gutta-percha and AH Plus endodontic sealer, being sealed with composite resin.The evaluation of postoperative pain was performed by visual analog scale after 24, 48, 72 hours and 7 days. Data were analysed by specific statistical tests, at level of 5%.

RESULTS

No statistical significant difference was observed among experimental groups in all evaluation periods, as well as in the intragroup analysis over time, regarding postoperative pain and analgesic medication consumption (p>0.05).

CONCLUSIONS

Apical limit of instrumentation and PDT have no influence on the postoperative pain of lower molars with asymptomatic apical periodontitis.

Smear Layer Removal from Root Canal Dentin and Antimicrobial Effect of Citric Acid-modified Chlorhexidine

Objective:

To study the effectiveness of various concentrations of citric acid (CA) added to 2% chlorhexidine (CHX) on smear layer removal from the root canal wall and antimicrobial efficacy against Enterococcus faecalis (E. faecalis) and Candida albicans (C. albicans).

Methods:

Fifty-three single-rooted mandibular premolars were decoronate and the root canals underwent mechanical instrumentation using MTwo rotary files to size 40/0.06. The samples were then randomly divided into 5 groups according to the root canal irrigants to be used: 17% ethylenediaminetetraacetic acid (EDTA), 2% CHX, 1%, 6%, and 10% citric acid-modified 2% chlorhexidine (CAmCHX). Three teeth irrigated with phosphate-buffered saline (PBS) were used as a negative control. The smear layer removal effectiveness was evaluated under scanning electron microscopy (SEM). Images were randomly taken at the apical, middle, and coronal third level. Statistical analysis was performed using Kruskal-Wallis and Mann-Whitney U tests. Disc diffusion and direct exposure tests were performed along with three additional control groups consisting of 1%, 6%, and 10% CA groups to assess and compare the antimicrobial efficacy of irrigants against E. faecalis and C. albicans. Statistical analysis was conducted using one-way ANOVA and Dunnett’s T3 tests.

Results:

Smear layer removal effectiveness in 17% EDTA group and 6% and 10% CAmCHX groups were not significantly different in the coronal and apical third of the root canal (P>0.05), however at the middle third of the root canal, the 10% CAmCHX group had significantly less remaining smear layer than all of the other experimental groups (P<0.05). There was significantly more smear layer remnant in the CHX group (P<0.01). For antimicrobial efficacy, the largest growth inhibition zone against E. faecalis was recorded in the 10% CAmCHX group (P<0.05). For planktonic E. faecalis, 1%, 6%, and 10% CAmCHX demonstrated an insignificant difference in antimicrobial efficacy compared to CHX (P>0.05). CA demonstrated no antifungal effect against C. albicans. Whereas, 6% and 10% CAmCHX resulted in the largest growth inhibition zone. Also, adding CA to CHX resulted in an insignificant difference in antifungal effect against planktonic C. albicans compared to CHX (P>0.05).

Conclusion:

When CA was added into CHX, the mixed irrigant demonstrated smear layer removal ability. Additionally, its antimicrobial effect remained the same.

Antibacterial Efficacy of the Grape Seed Extract as an Irrigant for Root Canal Preparation

Objective:

The purpose of this research was to compare relative effectiveness of sodium hypochlorite 5.25% (NaOCl), 2% chlorhexidine gel (CHX) and 6.5 % grape seed extract (GSE) against Enterococcus faecalis using instrument Reciproc R25 in root canal preparation.

Methods:

Forty-five mesiobuccal root canals from extracted human maxillary molars were collected and infected with Enterococcus faecalis. The samples were divided into five groups according to the different types of irrigants: saline (positive control) (n=5); in the other groups were used 10 root canals for each group: NaOCl+EDTA; CHX gel+EDTA; GSE solution+EDTA; GSE gel+EDTA. All the groups were prepared with reciprocating instruments Reciproc R25. Bacterial reduction was measured by two-way ANOVA (P<0.001) followed by Tukey HSD post-hoc tests, from the counting of colony forming units (CFUs) from samples collected before instrumentation and after. The significance level established at 5% (P<0.05).

Results:

The group prepared with the NaOCl resulted in highest antimicrobial capacity among of all (P>0.05), followed by CHX and GSE gel (P<0.05). Control and GSE solution showed similar results (P<0.05) and resulted in the lowest percentage of the reduction of the microorganism into the root canals.

Conclusion:

NaOCl had the higher elimination capacity of Enterococcus faecalis than GSE and CHX.