Chemomechanical removal of pulpal and dentinal debris with sodium hypochlorite and hydrogen peroxide vs normal saline solution

Antibacterial effect of silver diamine fluoride and potassium iodide against E. faecalis, A. naeslundii and P. micra

Background

The aim of this study was to determine in vitro the bactericidal potential of 38% silver diamine fluoride (SDF) alone, potassium iodide (PI) alone, and the two in combination (SDF + PI) against three bacterial species commonly found in root canal samples (Enterococcus faecalis, Actinomyces naeslundii and Parvimonas micra).

Methods

The potential bactericidal rates for SDF, PI and SDF + PI against E. faecalis, A. naeslundii and P. micra were calculated as reduction of bacteria colony forming units.

Results

The bactericidal potential of SDF was at 99.97–100% against E. faecalis and 100% against A. naeslundii and P. micra. SDF + PI showed a 100% bactericidal effect against P. micra, 99.89–99.98% against E. faecalis and 99.98–100% against A. naeslundii. The bactericidal effect of PI was 99.51–99.98% against E. faecalis, 99.27–99.95% against A. naeslundii and 99.93–100% against P. micra. The differences between controls and bacteria exposed to the antibacterial agents were statistically significant (p < 0.05).

Conclusions

SDF had an effective bactericidal effect against the examined bacteria. However, the limitations of this in vitro study do not allow a recommendation of the employment of these solutions as root canal irrigants. Additional investigations are necessary to assess their endodontic clinical applicability.

Quantification of Bacterial Colonization in Dental Hard Tissues Using Optimized Molecular Biological Methods

Bacterial infections of root canals and the surrounding dental hard tissue are still a challenge due to biofilm formation as well as the complex root canal anatomy. However, current methods for analyzing biofilm formation, bacterial colonization of root canals and dental hard tissue [e.g., scanning electron microscopy, confocal laser scanning microscopy (CLSM) or determination of colony forming units (CFU)] are time-consuming and only offer a selective qualitative or semi-quantitative analysis. The aim of the present study is the establishment of optimized molecular biological methods for DNA-isolation and quantification of bacterial colonization via quantitative PCR (qPCR) from dental hard tissue. Root canals of human premolars were colonized with Enterococcus faecalis. For isolation of DNA, teeth were then grinded with a cryo mill. Since the hard tissues dentin and especially enamel belong to the hardest materials in the human organism, the isolation of bacterial DNA from root dentin is very challenging. Therefore, treatment steps for the isolation of DNA from grinded teeth were systematically analyzed to allow improved recovery of bacterial DNA from dental hard tissues. Starting with the disintegration of the peptidoglycan-layer of bacterial cells, different lysozyme solutions were tested for efficacy. Furthermore, incubation times and concentrations of chelating agents such as EDTA were optimized. These solutions are crucial for the disintegration of teeth and hence improve the accessibility of bacterial DNA. The final step was the determination of prior bacterial colonization of each root canal as determined by qPCR and comparing the results to alternative methods such as CFU. As a result of this study, optimized procedures for bacterial DNA-isolation from teeth were established, which result in an increased recovery rate of bacterial DNA. This method allows a non-selective and straightforward procedure to quantify bacterial colonization from dental hard tissue. It can be easily adapted for other study types such as microbiome studies and for comparable tissues like bones.

Evaluation of 2% Chlorhexidine and 2% Sodium Fluoride as Endodontic Irrigating Solutions on Root Dentine Microhardness: An In Vitro Study

Objectives  The aim of this study was to evaluate the effects of 2% chlorhexidine gluconate (CHG) and 2% sodium fluoride (NaF) as endodontic irrigants on microhardness of root dentin.

Materials and Methods  In this in vitro study, access cavity and root canal preparations were done on 24 freshly extracted anterior teeth. After sectioning into 24 dentin discs using hard tissue microtome in 2 mm thickness, all samples were immersed in solutions of 17% ethylenediamine tetra-acetic acid (EDTA) (2 minutes) followed by 2.5% of sodium hypochlorite (NaOCl) (10 minutes). Then samples were randomly divided into three groups based on the irrigant used: Group I: saline (control group); Group II: 2% NaF; Group III: 2% CHG for two minutes each. Dentin microhardness was measured before (pretreatment), during (after treatment with 17% EDTA and 2.5% NaOCl), and after the experimental period (after treatment with saline, 2% NaF, and 2% CHG) using a Vickers indenter. Statistical evaluation of the data was done using one-way analysis of variance (ANOVA) and the Student’s t -test, and the values are tabulated.

Results  Specimens rinsed in 2% CHG showed a significant increase in Vickers hardness number (VHN) values ( p < 0.05), as compared with EDTA and NaOCl groups, whereas saline and 2% NaF groups showed no significant difference.

Conclusions  NaF did not show any significant effect on microhardness of the root dentin. CHG as an irrigant was seen to have a strengthening effect on dentin microhardness in comparison to NaOCl and EDTA, which has decreased the strength of root dentin.

Comparison of Five Different Irrigation Techniques on Smear Layer Removal in Apical Thirds of Root Canals of Mandibular First Premolar: A Scanning Electron Microscopic Study

Aim:

This study was conducted to compare smear layer removal by five different irrigation techniques—conventional needle irrigation (CI), manual dynamic activation (MDA), passive ultrasonic irrigation (PUI), sonic irrigation (SI), and negative apical pressure (NAP).

Materials and Methods:

Fifty freshly extracted mandibular first premolars were cleaned and shaped by One Curve rotary files and 3% sodium hypochlorite and 17% ethylenediaminetetraacetic acid. The samples were divided into five equal groups (n = 10), according to the final irrigation activation technique: Group I, CI; Group II, MDA; Group III, PUI; Group IV, SI; and Group V, NAP. The samples were prepared and observed under a scanning electron microscope. The photomicrographs were recorded and evaluated with a scoring system.

Results:

Group I and Group II had the highest scores, which showed a statistically significant difference between the other groups (P < 0.05). This was followed by PUI, NAP, and SI.

Conclusion:

Final irrigation activation with SI and NAP resulted in the better removal of smear layer when compared to that with other groups.

Knowledge, attitude, and practice regarding standardized treatment protocol for pulp therapy in deciduous dentition among general dental practitioners of Vadodara, Gujarat, India

INTRODUCTION

Dental caries is the most prevailing disease not only affecting permanent dentition, but also involving deciduous dentition. Deciduous teeth are considered a best space maintainer and preserve arch integrity for eruption of succedaneous permanent teeth. General dental practitioners (GDPs) seem to be less interventionist in their investigation and treatment planning and many times, the treatment done remains incomplete either due to the lack of knowledge of the dentist or due to noncooperation of the child and/or parents.

PURPOSE

The aim of this study was to assess the knowledge, attitude, and practice among GDPs of Vadodara city regarding standardized treatment protocol (STP) for pulp therapy in deciduous dentition.

MATERIALS AND METHODS

This questionnaire-based, cross-sectional study was conducted to assess the knowledge, attitude, and practice regarding standardized treatment options available for pulp therapy in deciduous dentition. The distribution of the self-made questionnaire pro forma was done in person to all the GDPs after obtaining their prior appointments. The GDPs were grouped on the basis of qualification and total clinical experience in years. The questionnaire consisted of 11 questions. The data were collected, and descriptive statistical analysis was performed. The Chi-square test was used to assess the knowledge, attitude, and practice among different groups of GDPs.

RESULTS

A statistically significant difference was observed in knowledge regarding STP for pulp therapy in deciduous dentition among both the groups, which is based on the qualification and on the year of clinical experience.

CONCLUSION

Qualification and years of clinical practice among GDPs affect the knowledge and treatment regarding pulp therapy in deciduous dentition. Most of the GDPs lack knowledge about the STP for pulp therapy in deciduous dentition.

Experimental Human Root Canal Irrigant NaOCl Against Enterococcus Faecalis and 3T3, and Determination of Cytotoxicity Effect

The main aim of endodontic treatment is disinfection of root canal and to prevent chances of reinfection. The most commonly isolated species due to oral infections is Enterococcus faecalis. For nonsurgical endodontic procedures Sodium hypochlorite (NaOCl) has been the irrigant of choice. The mechanism by which endodontic irrigants induce cytotoxicity is still unclear. However, many studies clearly indicated that rapid expression of the reactive oxygen species (ROS) leads to free radicals formation which results in cytotoxicity and cell death. Hence this study was done to determine the viability of cells and oxidative stress mediated by NaOCl, an endodontic irrigant. The irrigants were tested for their effect against fibroblast isolated from human primary buccal mucosa and against 3T3 Cell line. Antibacterial activity was performed against Enterococcus faecalis. Cytotoxicity was determined by MTT. To determine the oxidative stress, total intracellular glutathione, superoxide radical scavenging activity, and catalase assays were performed. The MIC (Minimal Inhibitory Concentration) for the irrigants against Enterococcus faecalis was found to be 10 µl. 10 µl of NaOCl plain 5.2% produced the same effect as that of 10 μl of NaOCl plain 3%. The higher concentration of the irrigants decreased viability of the cells during dye exclusion assay. Enzyme based study showed there is a decrease in enzyme dehydrogenase when treat with irrigants. Glutathione, SOD level was increased gradually on 3T3 cells. But CAT level was increased when the irrigants concentration less. The results of this study indicated that endodontic irrigants were potentially controlling the Enterococcus faecalis and non-toxic/reduced viability of 3T3 cells by MTT which could be due to the oxidative stress and loss of cellular integrity probably due to the liberation of ROS evidenced by the alteration of antioxidant enzymes Glutathione, SOD and CAT.

Is it really penetration? Part 2. Locomotion of Enterococcus faecalis cells within dentinal tubules of bovine teeth

OBJECTIVE

The aim of the present vitro study was to examine the question whether devitalized Enterococcus faecalis (E. faecalis) cells can migrate into dentinal tubules and if that process takes place in a time-dependent manner.

DESIGN

Sixty bovine root canals were incubated with devitalized and vital streptomycin-resistant E. faecalis strains after root canal enlargement (size 80, taper .02) with 3% NaOCl solution. Incubation times 7, 14, 21, 28, 35, and 42 days. Samples were processed for analysis by scanning electron microscopy (SEM) and DAPI (4',6-diamidino-2-phenylindole) staining. The penetration depth was calculated with the measurement tool of the Axio Vision program (Zeiss, Jena, Germany). Statistical analysis was performed by Kruskal-Wallis (α = 0.05) and Mann-Whitney U test (p < 0.05).

RESULTS

Devitalized E. faecalis strains were able to migrate into dentinal tubules. The total number and penetration depth of devitalized E. faecalis cells was lower compared to the vital suspension of E. faecalis. It was noted, that bacterial penetration was not common to all of the dentinal tubules in the vital E. faecalis control and especially in the devitalized control. The migration took place in a time-dependent migration characteristic.

CONCLUSIONS

Devitalized E. faecalis cells are still able to migrate into the dentinal tubules due to possible electrokinetic and osmotic processes. Thereby, increased exposure times lead to a time-dependent penetration characteristic.

CLINICAL RELEVANCE

Since devitalized bacteria can migrate as well into dentinal tubules, the presence of bacteria within dentinal tubules cannot be interpreted as a failure of tested preparation regimens.

How efficacious are Neem, Tulsi, Guduchi extracts and chlorhexidine as intracanal disinfectants? A comparative ex vivo study

Introduction:

In endodontics, despite careful instrumentation and antimicrobial irrigation, root canals still harbor cultivable microorganisms. Such cases require intra canal medicament that eliminates the microbial inhabitants from the canals. Recent trend advocates the use of herbal extracts due to easy availability, cost-effectiveness, low toxicity, and lack of microbial resistance. Hence, in the present study, Neem, Tulsi, and Guduchi extracts were used as intracanal medicaments.

Aim:

This study aimed to evaluate and compare the antibacterial efficacy of Neem, Tulsi, Guduchi extracts, and chlorhexidine against Enterococcus faecalis, when used as intracanal medicaments.

Materials and Methods:

One hundred and twenty-five extracted human teeth, inoculated with E. faecalis, were divided into four experimental groups and a control group (n = 25 in each group). The experimental groups were treated with chlorhexidine, Neem, Tulsi, and Guduchi extracts and their antibacterial property was evaluated by estimating microbial counting (CFU/ml).

Results:

The reduction in bacterial count for chlorhexidine, Neem, Tulsi, and Guduchi groups was 60.76%, 51.98%, 37.73%, and 34.93%, respectively. Statistically significant difference in reduction of bacterial count was observed in all the groups, when compared with the control group.

Conclusion:

Among all the herbal extracts, Neem was found to be the most potent medicament followed by Tulsi and Guduchi. However, chlorhexidine was found to be at epic.

Comparative evaluation of effect of different irrigation solutions against Enterococcus faecalis: A polymerase chain reaction-based study

Enterococcus faecalis is the most isolated or detected species from oral infections including marginal periodontitis, infected root canals, periradicular abscesses and also detected in cases of failed endodontic therapy. To prevent endodontic treatment failure irrigation is mandatory for the effective removal of smear layer, pulp tissue, and microorganisms. Cultivation and other traditional identification methods have been demonstrated to have several limitations when it comes to microbiological identification. Polymerase chain reaction was selected because it has an added advantage over traditional microbiological methods.

Effectiveness of different irrigation techniques on smear layer removal in apical thirds of mesial root canals of permanent mandibular first molar: A scanning electron microscopic study

Aim:

The aim of this study was to compare smear layer removal after final irrigant activation with sonic irrigation (SI), manual dynamic agitation (MDA), passive ultrasonic irrigation (PUI), and conventional syringe irrigation (CI).

Materials and Methods:

Forty mesial canals of mandibular first molars (mesial roots) were cleaned and shaped by using ProTaper system to size F1 and sodium hypochlorite 3% and 17% ethylenediaminetetraacetic acid. The specimens were divided into 4 equal groups (n = 10) according to the final irrigation activation technique: Group 1, PUI; group 2, manual dynamic activation (MDA); group 3, SI; and group 4, control group (simple irrigation). Samples were split longitudinally and examined under scanning electron microscope for smear layer presence.

Results:

Control groups had the highest smear scores, which showed the statistically significant highest mean score at P < 0.05. This was followed by ultrasonic, MDA, and finally sonic, with no significant differences between them.

Conclusions:

Final irrigant activation with sonic and MDA resulted in the better removal of the smear layer than with CI.

Cytotoxic Effects of Hydrogen Peroxide on Human Gingival Fibroblasts In Vitro

In-office bleaching is a popular treatment in modern esthetic dentistry. However, bleaching agents sometimes accidentally adhere to the gingiva and peripheral tissues, even when applied by well-trained dentists. This can lead to transient pain and whitish changes in the gingiva. Although these symptoms disappear within several hours, the effects of bleaching agents on gingiva have not been well described in the literature. The present study aimed to elucidate the cytotoxic effects of a bleaching agent on cultured human gingival fibroblasts (HGFs). We performed a comprehensive analysis of the toxic effects of in-office bleaching agents on gingiva using cultured HGFs and DNA microarray. Survival rates of HGFs decreased with increases in the concentration of hydrogen peroxide, which became significant at concentrations of 1.5 × 10(-3)% or higher at every time point. Concentrations lower than 1.5 × 10(-3)% did not affect survival rates of HGFs. Cytotoxicity of hydrogen peroxide was significantly weakened by the addition of vitamin E. Stimulation by in-office bleaching agents triggered the proinflammatory cytokine tumor necrosis factor (TNF)-α cascade in gingival fibroblasts. As the TNF-α cascade can be inhibited by vitamin E additives, treatment with vitamin E may protect gingival fibroblasts against the toxic effects of an in-office bleaching agent. The present results suggest that local administration of vitamin E to gingiva before in-office bleaching may be useful for preventing gingival irritation due to accidental adhesion of a bleaching agent.

A scanning electron microscopic study to evaluate the efficacy of NaviTip FX in removing the canal debris during root canal preparation: an in vitro study

OBJECTIVE

To evaluate the efficacy of NaviTip FX in removing the canal debris during root canal preparation using scanning electron microscopic study.

MATERIALS AND METHODS

Thirty single rooted teeth with completely formed apices were used in this study. Standard endodontic access cavity preparations were performed. Then the teeth were randomly divided into two groups: groups 1 and 2 of 15 teeth each group. For group 1, NaviTip FX (brush covered needle) was used to irrigate the canal with 5.25% sodium hypochlorite after each instrument use. For group 2, NaviTip (brushless needle) was used for irrigation following each instrument use. ProTaper rotary files were used for the canal preparation. The teeth were then cleaned and dried before splitting them into two halves. The half with most visible part of the apex was used for scanning electron microscopic evaluation. The results were statistically analyzed using the Mann-Whitney U-test at significance level p < 0.005.

RESULTS

The mean values for coronal and middle third of group 1 showed lower debris scores than group 2 and this difference was statistically significant at a p-value 0.01 and 0.05 respectively, but no significance difference between them at the apical third at a p-value of < 0.05.

CONCLUSION

The NaviTip FX (brush covered needle) showed effectively better canal wall debris removal than the NaviTip (brushless needle).

Root canal debridement efficacy of different final irrigation protocols

AIM

To compare the smear layer and debris removal effectiveness of four root canal irrigation protocols as well as their effectiveness in removing remaining soft tissues in curved root canals.

METHODOLOGY

The mesiobuccal and mesial root canals of 107 extracted human maxillary and mandibular molars were instrumented using Mtwo rotary NiTi instruments then randomly divided into four groups according to a final rinse protocol: Group 1 (n = 28) - manual agitation of 1% NaOCl and 15% EDTA; Group 2 (n = 26) - CanalBrush agitation of 1% NaOCl and 15% EDTA; Group 3 (n = 26) - 3% H(2) O(2) alternated with 1% NaOCl; Group 4 (n = 27) - passive ultrasonic agitation of 1% NaOCl and 15% EDTA. All irrigation protocols were performed in a closed system. Eleven roots per group were prepared and histologically stained (H&E) to assess percentage of remaining pulpal tissues in the apical thirds. The remaining specimens were split longitudinally and examined under scanning electron microscope at ×2000 magnification to assess smear layer and debris removal. Image Pro Plus 6.0 software was used to analyse smear layer and remaining pulp tissue. Debris presence was scored by two blinded investigators using a five-point scale. Data were analysed using Univariate analysis of variance (GenStat 13, α = 0.05).

RESULTS

CanalBrush and passive ultrasonic irrigation were equally effective with significantly less smear layer and debris than manual agitation and H(2) O(2) alternated with NaOCl (P < 0.05). The H(2) O(2) alternated with NaOCl protocol was significantly more effective in removing pulp tissue remnants in the apical level than manual agitation (P = 0.009) and passive ultrasonic irrigation (P = 0.01).

CONCLUSIONS

CanalBrush was as effective as passive ultrasonic irrigation in smear layer and debris removal. Alternating H(2) O(2) with NaOCl was effective in removing soft tissues from root canal complexities. Further studies are required to evaluate effectiveness of this regimen taking into account irrigant volume differences and effect of root canal system configuration.

A big role for the very small--understanding the endodontic microbial flora

Apical periodontitis, an inflammatory process around the apex of a tooth root, is primarily a sequel to microbial infection of the pulp space. The microbial flora is composed of a restricted group of the total oral flora, selected by environmental pressures of anaerobiosis, nutrition and competition with other species and inhabits the root canal as a biofilm of coaggregated communities in an extracellular matrix. The untreated infected canal is generally composed of a polymicrobial mix with approximately equal proportions of Gram-positive and Gram-negative species, dominated by obligate anaerobes. The type of microbial flora in the root-filled tooth with persistent apical periodontitis has very different characteristics. These infections are characterized by one or just a few species, predominantly Gram-positive micro-organisms with an equal distribution of facultative and obligate anaerobes. Enterococcus faecalis has been a conspicuous finding in most studies. Because the primary aetiological problem is infection, endodontic treatment is directed at control and elimination of the root canal flora by working in a sterile way. Based on current knowledge, the best available method for obtaining clean, microbe-free root canals is by instrumentation with antimicrobial irrigation reinforced by an intracanal dressing with calcium hydroxide.

Comparison of the EndoVac System to Needle Irrigation of Root Canals

Past studies have shown that current irrigation methods are effective at cleaning root canals coronally but less effective apically. To be effective, endodontic irrigants should ideally be delivered near working length. The purpose of this study was to compare the efficacy of the EndoVac irrigation system and needle irrigation to debride root canals at 1 and 3 mm from working length. One tooth of each matched pair was instrumented and irrigated by using the EndoVac, which uses negative pressure to deliver irrigating solutions to working length. The other tooth of the matched pair was instrumented and irrigated with a 30-gauge ProRinse irrigating needle. All teeth were irrigated with sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (EDTA) for a predetermined amount of time, and total volume of irrigant used was recorded. After instrumentation and irrigation, the teeth were fixed, decalcified, and sectioned at 1 mm and 3 mm from working length. Serial sections were made and digitally photographed. The amount of remaining debris was determined as a percentage of the area of the canal lumen. Remaining debris and total irrigant were analyzed by using the Wilcoxon signed rank test at the 5% confidence level. At the 1-mm level, significantly less debris was found in the EndoVac group (p=0.0347). At the 3-mm level, there was no significant difference between groups. Significantly more irrigant was delivered with the EndoVac (p<0001). This study showed significantly better debridement at 1 mm from working length by using the EndoVac compared with needle irrigation.

Efficacy of irrigation with rotary instrumentation

The purpose of this study was to evaluate the efficacy of a handpiece-mounted irrigation device and compare it to irrigation with a syringe and needle in the apical 5 mm of the root canal system. Twenty matched pairs of extracted teeth were used. The only variable within each matched pair was the method of irrigation. A syringe and needle were used in group A and the handpiece-mounted system in group B. Sections 1, 3, and 5 mm from the working length were examined microscopically, and images of the slides were digitized. The percentage of canal space occupied by pulpal and dentinal debris was calculated to be 6% +/- 12.7% in group A, versus 3.8% +/- 7% in group B (p = 0.264). The percentages at each level were as follows: 1 mm from the working length, 14.1% +/- 19% for group A and 5% +/- 7.5% for group B; 3 mm from working length, 1.8% +/- 5.4% for group A and 3.9% +/- 6.9% for group B; and 5 mm from working length, 3.1% +/- 7.7% for group A and 2.6% +/- 7.3% for group B. In group A, there was significantly more debris in the 1-mm section than in the 3- or 5-mm sections. In group B, the differences between levels were not significant. There was no significant difference in the amount of debris remaining in the apical 5 mm of canals when comparing the handpiece-mounted irrigation device to irrigation with a syringe and needle. The average times for instrumentation in group A (needle irrigation) and group B (Quantec-E irrigation system) were 8.7 +/- 2.7 min and 6.5 +/- 1.9 min, respectively. Group B was associated with statistically significant shorter instrumentation time (p < 0.0005). An average of 12.5 +/- 4.9 ml of irrigant was used in group A and 17.3 +/- 4.8 ml in group B. The difference was statistically significant (p < 0.0005).

A preliminary study of the percentage of gutta-percha-filled area in the apical canal filled with vertically compacted warm gutta-percha

AIM

The aim of this study was to determine the influence of the width of apical root canals and the depth of heat application during warm vertical compaction on the percentage of gutta-percha-filled area (PGFA) in the apical root canal.

METHODOLOGY

Two groups of extracted human canines (total 60) were instrumented and filled with vertically compacted warm gutta-percha up to the apical foramen (AF). Using the Touch 'n Heat device heat was applied 4 mm from the AP in one group and 2 mm in the other. The number of teeth with gutta-percha extrusion was recorded. A horizontal section was cut 1.5 mm from the AF of each tooth. The cross-sectional area of the canal and the gutta-percha was measured using an image-analysis programme. The PGFA was then calculated. Multiple linear regression was performed to investigate the association between the experimental variables and the PGFA, and the occurrence of gutta-percha extrusion.

RESULTS

A significant association was seen between the depth of heat application and the PGFA (P= 0.000), and between the canal area and the PGFA (P= 0.038). The average PGFA reached 96.1% when heated to 2 mm, as compared with 87.0% when heated to 4 mm. PGFAs were lower in wide apical canals than in small canals. Gutta-percha extruded in seven teeth (12%) and was independent of experimental variables.

CONCLUSIONS

After warm vertical compaction, the quality of adaptation of gutta-percha to the wall of the apical root canal varies; the influencing factors in this study were the depth of heat application and the width of the apical root canal.

Efficacy of instrumentation techniques and irrigation regimens in reducing the bacterial population within root canals

The purpose of this study was to compare the in vitro intracanal bacterial reduction produced by using two instrumentation techniques and different irrigation methods. Root canals inoculated with Enterococcus faecalis were prepared by using the following techniques and irrigants: alternated rotary motions (ARM) technique, hand nickel-titanium files and 2.5% sodium hypochlorite (NaOCl) as irrigant; ARM technique and combined irrigation with 2.5% NaOCl and citric acid; ARM technique and combined irrigation with 2.5% NaOCl and 2% chlorhexidine gluconate; and Greater Taper rotary files, using 2.5% NaOCl as irrigant. Controls were instrumented by using the ARM technique and irrigated with sterile saline. Canals were sampled before and after preparation. After serial dilution, samples were plated onto Mitis-Salivarius agar, and the colony forming units that were grown were counted. All test techniques and solutions significantly reduced the number of bacterial cells within the root canal (p < 0.05). There was no significant difference between the experimental groups (p > 0.05). Nonetheless, all of them were significantly more effective than the control group (p < 0.05). These findings support the importance of using antimicrobial irrigants during the chemomechanical preparation, regardless of the solutions or instrumentation techniques used.

Endotoxin activity measured by limulus assay

The binding activity of endotoxin (Escherichia coli 0111) to dentin powder pre-treated with 10% sodium hypochlorite and with 3% hydrogen peroxide was investigated. This was carried out for periods of 30, 10 and 1 min. The endotoxin was diluted into 100 ng/ml solutions. Dentin powder suspended in a 34 micrograms/ml protein concentration was used in the study. The limulus amoebocyte lysate test was used to determine the amount of endotoxin binding, which was measured by the microtiter plate reader. The binding activity level of that concentration of endotoxin was significantly lower in dentin powder treated with 10% sodium hypochlorite than in that treated with 3% hydrogen peroxide at 1 and 10 min. Endotoxin binding activity measured the lowest in the 30 min test period.

A comparative study of the removal of smear layer by three endodontic irrigants and two types of laser

AIM

The effects of three endodontic irrigants and two types of laser on a smear layer created by hand instrumentation were evaluated in vitro in the middle and apical thirds of root canals.

METHODOLOGY

Sixty human mature extracted mandibular premolar teeth with a single root canal and a closed apex were distributed randomly into five groups of 12 teeth each. Whilst cleaning and shaping up to a size 60 master apical file with a step-back technique, the root canals were irrigated with 3 mL of 5.25% NaOCL and 3% H2O2, alternately, between each file size. Group 1 (G1) were control specimens that were irrigated with a final flush of 17% EDTA. The teeth in group 2 (G2) were irrigated with a final flush of 6% phosphoric acid, and group 3 (G3) with 6% citric acid. In the specimens of group 4 (G4) the root canals were irradiated with a carbon dioxide (CO2) laser, and specimens of group 5 (G5) were irradiated using an Er:YAG laser. The teeth were split longitudinally and prepared for examination by scanning electron microscopy.

RESULTS

Control specimens (G1) showed clean root-canal walls with open dentinal tubules in the middle one-third, but in some specimens thick smear layer was observed in the apical one-third. Specimens irrigated with a final flush of 6% phosphoric acid (G2) or 6% citric acid (G3) were cleaner than with 17% EDTA, showing very clean root canal surfaces in the middle one-third but in the apical one-third the smear layer was not completely removed, especially at the openings of the dentinal tubules. The specimens irradiated with the CO2 laser (G4) showed clean root-canal walls with the smear layer absent, charred, melted, recrystallized and glazed in both middle and apical thirds. The root-canal walls of the specimens irradiated with the Er:YAG laser (G5) revealed an absent smear layer with open dentinal tubules in the middle and apical thirds. Statistical analysis showed no significant difference in the cleanliness of root-canal wall between G1 and G2, and G1 and G3. However, there were statistically significant differences (P < 0.01) between G1 and G4, and G1 and G5 in the cleanliness of the middle and apical one-thirds of the root canals.

CONCLUSIONS

Irrigation with 17% EDTA, 6% phosphoric acid and 6% citric acid did not remove all the smear layer from the root-canal system. In addition, these acidic solutions demineralized the interbular dentine around tabular openings, which became enlarged. The CO2 laser was useful in removing and melting the smear layer on the instrumented root-canal walls and the Er:YAG laser was the most effective in removing the smear layer from the root-canal wall.

Effect of Er:YAG laser treatment on the root canal walls of human teeth: an SEM study

The purposes of the study were to observe the morphological changes on root canal walls after instrumentation and irrigation, and assess the efficacy of conventional cleansing procedures and the effectiveness of Er:YAG laser in removing debris and smear layer from the root canal walls. Thirty-six endodontically treated human mandibular incisor teeth with single root canals were bisected longitudinally and divided into three groups of 12 teeth. Group 1 (G1) was left unlased as a control. The teeth of group 2 (G2 and group 3 (G3) were irradiated by Er:YAG laser (laser parameters were set at 1 W, 100 mJ/pulse and 10 Hz) for 3 s and 5 s. The teeth were prepared for scanning electron microscope study. Control specimens showed debris and heavy smear layer obscuring the dentinal tubules at all levels in the canals. The root canal walls irradiated by Er:YAG laser were free of debris, with an evaporated smear layer and open dentinal tubules. These results suggested that Er:YAG laser irradiation had an efficient cleaning effect on the prepared root canal walls.

Evaluation of the effectiveness of sodium hypochlorite used with three irrigation methods in the elimination of Enterococcus faecalis from the root canal, in vitro

The effectiveness of 4.0% sodium hypochlorite (NaOCl) used with three irrigation methods in the elimination of Enterococcus faecalis from the root canal was tested in vitro. Root canals contaminated with E. faecalis were treated as follows: (i) irrigation with 2 mL of NaOCl solution and agitation with hand files; (ii) irrigation with 2 mL of NaOCl solution and ultrasonic agitation; (iii) irrigation with NaOCl alternated with hydrogen peroxide. Contaminated canals irrigated with sterile saline solution served as the control. Paper points used to sample bacteria from the root canals were transferred to tubes containing 5 mL of brain heart infusion (BHI) broth. Tubes were incubated and the appearance of broth turbidity was indicative of bacteria remaining in the root canal. There were no statistically significant differences between the experimental groups. However, NaOCl applied by the three methods tested, was significantly more effective than the saline solution (control group) in disinfecting the root canal.

Canal debridement: effectiveness of sodium hypochlorite and calcium hydroxide as medicaments

The action of chemicals such as calcium hydroxide (Ca(OH)2) and sodium hypochlorite (NaOCl) that are used as tissue solvents may be enhanced by prolonged contact. The objective of this study was to determine if sealing Ca(OH)2 and NaOCl into the canal space would improve debridement of both the main canal and areas inaccessible to files. Mesial root canals of 75 freshly extracted mandibular molars were step-back hand-instrumented. Another six molars were controls. Either Ca(OH)2, NaOCl, or no medication was sealed in the canals for 1 or 7 days. Canals were finally irrigated with H2O and prepared for histological evaluation. The cleanliness of main canals and inaccessible areas (isthmi and fins) at the apical, middle, and coronal thirds was examined, scored, and compared by nonparametric statistical analysis. Results showed no significant differences among different groups in either the 1-day or 7-day time intervals in either the main canal or inaccessible areas. Instrumentation combined with NaOCl irrigation alone accounted for the removal of tissue in the main canal. In conclusion, in this system, prolonged contact with Ca(OH)2 and NaOCl was similarly ineffective; neither contributed significantly to canal debridement.

Biological properties of peroxide-containing tooth whiteners

Peroxides have been used in tooth whitening for more than 100 years. Current peroxide-containing whiteners can be classified into three categories: (1) those containing high concentrations of peroxides for professional use only; (2) materials dispensed by dentists and used by patients at home; and (3) over-the-counter products available directly to consumers for home use. Hydrogen peroxide (H2O2) and carbamide peroxide are the most commonly used active ingredients in these whiteners. Both peroxides have long been used safely in oral health products and are accepted by the US Food and Drug Administration. However, questions have been raised regarding the safety of at-home whiteners because the peroxides appear to constitute a new use. Substantial differences exist in the manner of application between at-home whiteners and oral health products. In addition, tooth whiteners are a mixture of various ingredients; possible interactions may occur because of the active nature of peroxides. Therefore, the safety evidence for peroxide-containing whiteners is considered inadequate. This paper will review the history of using peroxides for tooth whitening, the toxicology of H2O2 and carbamide peroxide, and available information on the safety of whiteners. The rationale and approaches for evaluating biological properties of peroxide containing whiteners are also discussed.

Efficacy of three techniques in cleaning the apical portion of curved root canals

Various techniques for root canal instrumentation may have different effects in cleaning curved root canals, especially their apical portions. One hundred thirty-five mesiobuccal canals with an average curvature of 25 degrees from human mandibular molars were treated with step-back, crown-down pressureless, or balanced-force techniques with 2% sodium hypochlorite used as an irrigant. The cleaning efficacy of these techniques was evaluated by counting the remaining surface debris under a stereomicroscope with a calibrated eyepiece micrometer. The results indicated that the apical portion of the canal was less clean than the middle and coronal portions regardless of the technique performed and that the balanced-force technique produced a cleaner apical portion of the canal than did the other techniques studied.

Smear layer removal by root canal irrigants. A comparative scanning electron microscopic study

The effect of six endodontic irrigants on smear layers created by hand instrumentation was evaluated in vitro in the middle and apical sections of 53 root canals. The irrigants evaluated were: 1% and 5% sodium hypochlorite, a combination of 24% phosphoric acid and 10% citric acid, 0.2%, 17%, and 3% ethylenediaminetetraacetic acid. After instrumentation and treatment with the respective irrigants, the root canal specimens were examined by scanning electron microscopy to determine the presence or absence of smear layer. The two sodium hypochlorite solutions did not remove the smear layer, even when 5% sodium hypochlorite was scrubbed on the dentinal walls. The 0.2% ethylenediaminetetraacetic acid solution was more effective than sodium hypochlorite, but it did not completely remove the smear layer, especially at the orifices of the dentinal tubules. The other three solutions effectively removed the smear layer, but no significant difference was found between them (p > 0.05). The solution of 3% ethylenediaminetetraacetic acid was as effective as phosphoric-citric acid and 17% ethylenediaminetetraacetic acid. Ethylenediaminetetraacetic acid, however, did not show the marked demineralizing effect on the dentinal walls and tubules as the acidic solution.

A novel noninstrumented technique for cleansing the root canal system

The aim of this study was to develop a machine to clean root canals without conventional instruments. This goal was achieved with a device which was able to develop controlled cavitation in the root canal. Under reduced pressure, alternating pressure fields generated microscopic and macroscopic cavitation bubbles. Subsequently, these vapor-filled cavitation bubbles collapsed, creating hydrodynamic turbulence. These two phenomena allowed the irrigant to penetrate the canal system and then be exchanged with new irrigant. To test the cleaning ability of the device 79 freshly extracted vital molars with 222 root canals were collected. The control group (27 molars, 73 canals) was prepared with the step-back technique using NaOCl (3%) as an irrigant. The three test groups (52 molars, 149 canals) were prepared with the new machine using NaOCl (1, 2, or 3%). The treatment time ranged from 16 to 32 min in the hand group and from 10 to 15 min in the machine groups. The teeth were then prepared histologically and examined by light microscopy. Overall, the treatment with NaOCl (2 and 3%) resulted in similar or better cleanliness in all three root sections when comparing machine and hand instrumentation. In curved canals, however, the apical one third was also significantly cleaner when using the machine and 3% NaOCl than with hand instrumentation. This in vitro study shows that it is possible to clean a root canal system by a noninstrumented technique as well as by conventional hand instrumentation.

Histologic evaluation of three endodontic instrument/preparation techniques

33 curved canals were prepared to quantify both the increase in canal area and predentin removal in the apical region. Compared were three different file designs/instrumentation techniques, that is "stepback" with K-flex file, "balanced force" with Flex-R file, and the Canal Master system. Following canal preparation and histological processing, cross-sections at 1 and 3 mm levels were examined using the Bioquant image analysis system. Results showed that, at the 3 mm leve, the mean increase in canal area and predentin removal showed no statistically significant difference (p > 0.05) between the techniques. At 1 mm, the step-back technique (with K-flex files) resulted in a significant increase in canal area and greater predentin removal than did the "balanced forces" (with Flex-R files) or the Canal Master system. However, although there were statistical differences, the actual differences were small; these may not translate to clinically significant differences in the 3 techniques.

Effectiveness of a brush in removing postinstrumentation canal debris

The purpose of this study was to evaluate the effectiveness of a brush in removing debris in the root canal after endodontic instrumentation. Seventeen extracted human maxillary first molars with mesiobuccal canal curvatures of 25 to 35 degrees were divided into two groups. After endodontic access and determination of working length, one group was hand instrumented to a #45 file and the other group to a #35 file at the working length. After the teeth were sectioned at the working length and at 2, 4, and 6 mm from the working length, they were evaluated for debris remaining in the canal space. The specimens were reassembled, brushed with an Endobrush, and reevaluated. The scores for instrumentation alone (controls) and instrumentation plus brushing were compared with paired t tests. Instrumentation with brushing was significantly better than instrumentation alone in debriding the root canal.

Response of the human eye to accidental exposure to sodium hypochlorite

Sodium hypochlorite is used in endodontic therapy as an intracanal irrigant during hand, mechanical, and ultrasonic instrumentation of the root canal space. Regardless of the technique utilized, particular attention must be given to the appropriate and safe use of this chemical solution. A case is presented in which a 5.25% sodium hypochlorite solution was accidentally splashed in a patient's eyes during endodontic therapy. Ocular irrigation was performed immediately and continued for 10 min. The patient was promptly taken to an ophthalmologist for further treatment and follow-up. When chemical trauma of the eye by sodium hypochlorite solution is sustained, the entire surface of the affected eye(s) and the fornices must be thoroughly irrigated. This is best accomplished with a continuous stream of normal saline from a 1-I bag which is attached to an intravenous line with a 16-gauge Teflon catheter placement sleeve affixed to the distal end of the line. Arrangements must then be made for immediate evaluation, treatment, and consultation by an ophthalmologist.

Hydrogen peroxide inhibits glucose metabolism and collagen synthesis in bone

Effects of H2O2 on bone were evaluated in an organ culture system. Tibiae from chick embryos were incubated for up to 3 days in culture medium containing 0.07 to 20 mM H2O2. Glucose metabolism was monitored by measuring lactate production and oxygen consumption, and collagen synthesis was determined by hydroxylation of proline. In addition to markedly inhibiting these parameters, H2O2 also decreased bone weight and alkaline phosphatase activity. Multiple exposures to H2O2 were somewhat more effective than a single exposure. Since H2O2 inhibits bone at low concentrations in vitro, the results suggest that the potential for harmful effects of H2O2 in the oral cavity should be investigated.

The hardness of bovine dentine after glutaraldehyde treatment

Bovine dentine specimens were treated with glutaraldehyde 2% for periods of 10, 20 min. and 48 h. The differences in Knoop hardness were measured and evaluated. It can be concluded that treatment of bovine dentine with glutaraldehyde gives first a remarkable softening (+/- 15%); afterward the treated dentine is +/- 15% harder than untreated dentine.