NaOCl effects on primary and permanent pulp chamber dentin

OBJECTIVES: The dentin quality of primary and permanent pulp chamber was inspected by Fourier-transformed Raman spectroscopy (FT-Raman) and scanning electron microscopy (SEM). Fragments of pulp chamber dentin were obtained from 20 human molar crowns (primary and permanent). METHODS: The fragments were assigned to 8 groups (n=5)-Primary teeth: G1, pulp chamber dentin; G2, pulp chamber dentin irrigated with NaOCl 1% (30min); G3, pulp chamber dentin irrigated with NaOCl 1% (30min) and etched by 35% phosphoric acid; G4, pulp chamber dentin etched by 35% phosphoric acid. Permanent teeth: G5, pulp chamber dentin; G6, pulp chamber dentin irrigated with NaOCl 1% (30min); G7, pulp chamber dentin irrigated with NaOCl 1% (30min) and etched by 35% phosphoric acid; G8, pulp chamber dentin etched by 35% phosphoric acid. The spectra were subjected to the Cluster analysis. The SEM images were scored. RESULTS: Inorganic content: There was a difference between primary and permanent dentin. The groups treated with NaOCl were statistically similar between them, but differed from the groups not treated. Organic content: There was no difference between primary and permanent dentin. The groups became similar after NaOCl and phosphoric acid treatments. The microscopic images showed the presence of calcospherites on permanent dentin and their absence on primary dentin. CONCLUSIONS: The NaOCl changed the inorganic content in both dentitions; regardless of the following phosphoric acid etching. However, the chemical changes caused by NaOCl were not detected by SEM when it was followed by etching.     

A scanning electron microscopic study of dentinal erosion by final irrigation with EDTA and NaOCl solutions

AIM: The purpose of this in vitro study was to examine dentinal erosion caused by final irrigation with EDTA and NaOCl. METHODOLOGY: Twenty-five single-rooted human teeth were instrumented with rotary nickel-titanium Series 29 Profile Instruments. The teeth were divided into five groups and subjected to final irrigation as follows: group A, irrigated with 6% NaOCl (3 mL) for 2 min; group B, 15% EDTA (3 mL) for 1 min; group C, 15% EDTA (3 mL) for 1 min, followed by 6% NaOCl (3 mL) for 2 min; group D, 15% EDTA (3 mL) for 3 min and group E, 15% EDTA (3 mL) for 3 min, followed by 6% NaOCl (3 mL) for 2 min. Photomicrographs of dentinal walls were produced using a scanning electron microscope (3000 x) at 1, 3 and 6 mm from the apex. The amount of debris and dentinal tubule diameter were evaluated, and values were statistically analysed using one-way ANOVA and Fisher's PLSD test. RESULTS: When the root canal was irrigated with 15% EDTA alone, the dentine had a smooth and plane appearance, and dentinal tubule orifices were regular and separated. When the root canal was irrigated with EDTA followed by NaOCL the dentine was eroded and the dentinal tubule orifices were irregular and rough. Dentinal tubule diameter increased to 3.43 +/- 0.23 microm in group C and to 3.93 +/- 0.44 microm in group E. Significant differences were observed between groups B and C, and between groups D and E (P < 0.05). However, more debris was removed by irrigation with EDTA followed by NaOCl than with EDTA alone (P < 0.05). CONCLUSIONS: Final irrigation with 6% NaOCl accelerates dentinal erosion following treatment with 15% EDTA.     

Evaluation of the effect of MTAD in comparison with EDTA when employed as the final rinse on the shear bond strength of three endodontic sealers to dentine

The purpose of the study was to evaluate the effect of MTAD in comparison with EDTA as a final rinse on the shear bond strength of Kerr, Apexit and AH plus. Dentine surfaces of 135 extracted human non-carious maxillary premolars were divided into three groups (n = 45). Groups I and II were conditioned with 1.3% NaOCl for 20 min, followed by a final rinse of 17% EDTA for 1 min and MTAD for 5 min respectively. Group III was treated with distilled water. Each group was further divided into three subgroups (n = 15). Subgroup 1: Kerr, Subgroup 2: Apexit and Subgroup 3: AH plus. Three-millimetre-long sections of polyethylene tubes were filled with freshly mixed sealer and placed on the dentine surfaces. The bonding between the sealer and dentine surface was evaluated using shear bond testing. The values were statistically evaluated using one way anova followed by Tukey's test. Significant difference was found among the bond strength of the sealers and irrigating regimes. AH plus showed superior bond strength among the tested sealers, when EDTA was employed as the final rinse (P < 0.05). MTAD as a final rinse affected the bond strength of AH plus and Apexit, which were significantly lower than the control group.     

Effect of Irrigants on the Survival of Human Stem Cells of the Apical Papilla in a Platelet-rich Plasma Scaffold in Human Root Tips

Introduction

Intracanal disinfection is a crucial step in regenerative endodontic procedures. However, this novel endodontic treatment lacks standardization, and numerous treatment protocols have been reported without knowledge of the effect of disinfection protocols on the survival of stem cells. The aim of this study was to test the hypothesis that different root canal irrigation protocols alter survival of stem cells from the apical papilla (SCAP).

Methods

SCAP were isolated from immature human third molars, and a subpopulation of STRO-1 expressing cells was selected and expanded in vitro. Standardized human root segments (n = 5/group) were irrigated with 1 of 4 protocols: (1) 17% ethylenediaminetetraacetic acid (EDTA), (2) 6% NaOCl/17% EDTA/6% NaOCl, (3) 17% EDTA/2% chlorhexidine (CHX), or (4) 6% NaOCl/17% EDTA/6% NaOCl/isopropyl alcohol/2% CHX. Subsequently, STRO-1-enriched SCAP were mixed with platelet-rich-plasma, seeded into the root tips, and cultured for 21 days. Roots were then decalcified, processed for immunohistochemistry, and stained for vimentin and TO-PRO-3. The proportion of viable (vimentin-positive) cells was calculated on the basis of the total cell counts (TO-PRO-3) for each group.

Results

Irrigation with 17% EDTA best supported cell survival (89% viability; P < .001 versus all other groups), followed by irrigation with 6% NaOCl/17% EDTA/6% NaOCl (74%; P < .001 versus the 2 groups containing 2% CHX). Conversely, protocols that included 2% CHX lacked any viable cells.

Conclusions

Collectively, the results suggest that irrigants alone greatly affect the survivability of STRO-1-enriched SCAP within the root canal environment and that inclusion of EDTA in irrigation protocols might be beneficial in regenerative procedures.     

Evaluation of photodynamic therapy using a light-emitting diode lamp against Enterococcus faecalis in extracted human teeth

Introduction

Photodynamic therapy (PDT) with high-power lasers as the light source has been proven to be effective in disinfecting root canals. The aim of this study was to evaluate the antimicrobial effect of PDT using toluidine blue O (TBO) and a low-energy light-emitting diode (LED) lamp after the conventional disinfection protocol of 6% NaOCl.

Methods

Single-rooted extracted teeth were cleaned, shaped, and sealed at the apex before incubation with Enterococcus faecalis for 2 weeks. Roots were randomly assigned to five experimental groups and three control groups. Dentin shavings were collected from the root canals of all groups with a #50/.06 rotary file, colony-forming units were determined, and the bacterial survival rate was calculated for each treatment.

Results

The bacterial survival rate of the NaOCl/TBO/light group (0.1%) was significantly lower (P < .005) than the NaOCl (0.66%) and TBO/light groups (2.9%).

Conclusions

PDT using TBO and a LED lamp has the potential to be used as an adjunctive antimicrobial procedure in conventional endodontic therapy.     

A New Method to Assess Available Chlorine in Small Volumes of Liquid

Introduction

There is no robust and simple way to quantify available chlorine from small volumes such as human root canals. Therefore, a new method was developed and assessed.

Methods

Standardized size-40 paper points were soaked in a 15% (w/v) potassium iodide solution for 1 minute. Subsequently, the paper points were placed in an incubator and dried at 110°C for 4 hours. The paper points (n = 5 per measurement) were then dipped in different concentrations of NaOCl and photographed under standardized conditions in RAW format. The pictures were imported to image processing software and adjusted to the standardized background. The red, green, and blue levels of the paper points were assessed at a predefined area. Inverse regression was used to determine NaOCl concentration from red, green, and blue values, with both explanatory and outcome variables log-transformed to base 10.

Results

The red value measurements were chosen for further analysis based on a comparison of the coefficient of determination (R²) and a residual analysis. The method was applied to concentrations of NaOCl between 0.0001% and 1% (R² = 0.92). In this range, NaOCI concentrations could be assessed with an error not larger than 3-fold the determined concentration.

Conclusions

The present method proved to be robust to determine the order of magnitude of available chlorine that is present in a small volume. This should be useful for endodontic research.