Corrosion and cytotoxicity evaluation of thermafil endodontic obturator carriers

Biocorrosive behavior of sulphate-reducing bacteria in kerr endodontic files: Determination of the corrosion

Aims:

This study determined the corrosion rate by mass loss caused by oral strains of sulphate-reducing bacteria (SRB) in Kerr endodontic files (KF), aiming the development of a biopharmaceutical that facilitates the removal of endodontic limb fragments from root canals.

Materials and Methods:

Nine new KF were analyzed after immersion in the modified Postgate E culture medium inoculated with Desulfovibrio desulfuricans oral (84 days), Desulfovibrio fairfieldensis in the consortium (84 days) and environmental D. desulfuricans (119 days).

Results:

Optical microscopy revealed corrosion suggestive areas in all files submitted to immersion in SRB cultures, presenting a statistical difference (P < 0.05) between the samples environmental D. desulfuricans and KF control and between oral D. desulfuricans and KF control. Epifluorescence microscopy revealed an active SRB biofilm over the entire metal surface of the KF, as evidenced by the SYTO^® 9 fluorophore.

Conclusion:

SRB were capable of promoting biocorrosion in Kerr type endodontic files, but with low rate.

A Prospective Randomized Comparative Study of Cold Lateral Condensation Versus Core/Gutta-percha in Teeth with Periapical Lesions

INTRODUCTION

The aim of this study was to compare the outcome of root canal treatment using either Thermafil (TF; Dentsply Maillefer, Ballaigues, Switzerland) or the cold lateral condensation (CLC) obturation technique in teeth with periapical lesions and to investigate the influence on postoperative pain and treatment outcomes.

METHODS

After standardized root canal preparation technique, 112 teeth were obturated with either the TF or the CLC technique during 2 sessions by single operator. Postoperative pain, obturation length, and treatment outcomes were recorded. The teeth were reviewed clinically and radiographically for 2 years.

RESULTS

Although there were no significant differences between the techniques in the incidence of postoperative pain at 24 hours (P > .05), the incidence of pain was significantly higher in the TF group than in the CLC group at 48 hours (P < .05). During the 2-year follow-up period, there was no statistically significant difference in the success rate of the teeth treated with TF (96.4%) in comparison with those treated with CLC (98.2%) (P > .05).

CONCLUSIONS

In this study, the outcome of the root canal treatment of teeth using the TF and CLC techniques revealed that these techniques are useful for root canal obturation.

Accuracy of an electronic apex locator in the retreatment of teeth obturated with plastic or cross-linked gutta-percha carrier-based materials: an ex vivo study

INTRODUCTION

This ex vivo study evaluated the accuracy of the Root ZX electronic apex locator (EAL) (J Morita Corp, Kyoto, Japan) in determining the working length during retreatment of canals sealed with 2 different carrier-based obturating materials (ProTaper Obturator [Dentsply Maillefer, Ballaigues, Switzerland] and GuttaCore [Dentsply Maillefer]) and also evaluated whether they influenced its accuracy differently.

METHODS

Fifty extracted single-rooted human teeth with sound apices were selected for the study. We measured canals with the direct visual technique using a #10 K-file and shaped them with ProTaper Universal instruments (Dentsply Maillefer) up to this predetermined length. After instrumentation, we determined the canal length again using the visual technique (direct length [DL]). This value was considered the "reference point." Specimens were then placed in a tooth holder (Pro-Train; Simit Dental, Mantova, Italy), and the canal length was electronically measured (electronic length 1 [EL1]). Specimens were then obturated with ProTaper Obturators (group 1, n = 25) and GuttaCore (group 2, n = 25). Seven days later, a new electronic length was determined (electronic length 2 [EL2]) during retreatment procedures in the presence of the obturating material. EL1 and EL2 values were compared with DL using the Bland and Altman method. The different influences of the tested materials on the accuracy of the EAL were calculated with repeated measures analysis of variance.

RESULTS

Both EL1 and EL2 values provided a statistically significant overestimation of the actual canal length (DL [P < .05]), with the EL2 values higher from DL. The 2 different materials did not influence the accuracy of the EAL differently (P = .486).

CONCLUSIONS

The measurements obtained with the EAL tested during orthograde retreatments can lead clinicians to overinstrumentation and consequent overfilling of the endodontic space.

In vitro Evaluation of the Cytotoxicity of Different Root Canal Filling Materials

OBJECTIVE

Aim of the present study was to evaluate the cytotoxicity of Real Seal 1 compared to other commercially available endodontic filling materials: Real Seal (SybronEndo, Orange, CA, USA) and Thermafil (Tulsa Dental, Tulsa, OK, USA).

MATERIAL AND METHODS

Periodontal ligament cells from healthy patients were cultured. The eluate of Real Seal 1(TM) (RS1), Real Seal (RS) and Thermafil (TF) samples was used for the cells viability tests, both diluted (50%) or undiluted (100%). Incubation of the specimens was performed in culture medium for 24 h, 48 h and 72 h at 37 °C under sterile conditions. The cellular mortality was evaluated by MTT test. Results were statistically analysed and the statistical significance was set at p< 0.05.

RESULTS

None of the studied materials showed toxic effects during the period of observation (0 -72 h) when compared to the control group. Only RS induced a very modest increase in cell mortality (about 3% at both concentrations used, during the first 24 hours), when increasing the incubation time, however, only the lower concentration continued to show modest toxicity.

CONCLUSIONS

Results of the present study showed that all tested materials did not exhibit cytotoxic effects when compared to the control group.

In vitro infrared thermographic assessment of root surface temperature rises during thermafil retreatment using system B

The purpose of this in vitro study was to measure the temperature rise on the outer root surface during retreatment of Thermafil using the System B HeatSource. Twenty extracted human maxillary premolars were filled with Thermafil with plastic carriers and divided into two groups of 10 teeth each. In group 1, Thermafil obturators were retrieved using System B HeatSource fitted with a medium plugger at a temperature of 225 degrees C. The plugger was placed first on the buccal, then on the lingual of the plastic carrier for 5 s each. This melted the gutta-percha and softened the plastic carrier. In group 2, Thermafil obturators were retrieved in the same manner except that the heated plugger was placed for 8 s. The temperature changes on the outer root surfaces were recorded using a thermal imaging camera. Thermafil retreatment in vitro using a System B HeatSource causes temperature rises ranging from 26.7 degrees C to 46.0 degrees C. This finding could possibly have implications for creating injury of the periodontal tissues.

Corrosion rates of stainless-steel files in different irrigating solutions

AIM

The present study was designed to evaluate and compare the corrosion rates of the stainless-steel endodontic files when immersed in 0.2% chlorhexidine gluconate, 5.25% NaOCl, chlorinated soda with KOH, and 17% EDTA irrigating solutions.

METHODOLOGY

Corrosion rates of stainless-steel K-files in irrigating solutions were determined electrochemically by the Tafel extrapolation method. The cutting flutes of files were immersed in solutions and used as an electrode. A saturated calomel electrode (SCE) was used as a reference, and a platinum plate was used as a counter electrode. In order to determine corrosion rates, the linear part of anodic currents obtained from electrochemical current-potential curves, was extrapolated to corrosion potentials.

RESULTS

The corrosion rates of stainless-steel files in the tested solutions from the highest to the lowest were: 0.2% chlorhexidine gluconate>5.25% NaOCl>chlorinated soda with KOH>17% EDTA. The differences between the corrosion rates of files were not found to be statistically different for chlorinated soda with KOH and EDTA (P >0.05), but statistically significant differences were found amongst other groups.

CONCLUSIONS

The results of the present study indicated that 0.2% chlorhexidine gluconate, 5.25% NaOCl and chlorinated soda with KOH cause severe corrosion on the surface of selected stainless-steel files.