Cytotoxic effects of gutta-percha solvents

Comparing the softening effect of three gutta-percha solvents on different types of gutta-percha with different application durations

Introduction

During non-surgical endodontic retreatment, gutta-percha (GP) solvents are indispensable in difficult cases when used with mechanical removal, however studies comparing their efficacy against different types of GP are limited. The purpose of this study was to investigate the softening effect of three solvents on the conventional (CGP), cross-linked carrier-based (CLGP), and thermoplasticized (TGP) and compare the effect of time on the softening effect of the solvents.

Methods

Tested GP were embedded in cuboidal blocks of stone with their upper surfaces exposed (1 mm diameter). Three commercial GP solvents based on D-Limonene (DL), Eucalyptol oil (EO), and orange oil (OO) were added to the exposed GP before an indenter (weight = 1Kg) was applied. Using a digital camera, the indentation depth was measured (mm) directly after applying the solvent and indenter (T = 0), and after 1, 2, and 3 min of application (T = 1,2,3). The means of indentation depth were calculated and compared using a two-way analysis of variance and Tukey's post-hoc test to assess the effect of the types of solvent, GP for each application duration, and Friedman's test to evaluate the effect of application duration on the softening effect of solvents.

Results

The type of GP (F = 261.43, p < 0.001), type of solvent (F = 3.57, p = 0.015), and application duration (F = 53.088, p < 0.001) were all found to significantly affect GP softening. DL exhibited the highest and only significant effect on CGP after 1 min (p < 0.05), while OO had the only significant effect against CLGP when applied for at least 2 min (p < 0.05). Both OO and EO had significant softening effects on TGP instantly or after 1 min of application, respectively.

Conclusions

The results of this study revealed that the softening effect of GP solvents varies depending on their type, their application duration, and the type of GP.

Are Endodontic Solvents Cytotoxic? An In Vitro Study on Human Periodontal Ligament Stem Cells

The aim of this study was to assess the influence of eucalyptol, chloroform, and Endosolv on the proliferative capability, cell viability, and migration rates of human periodontal ligament stem cells (hPDLSCs) in vitro. Solvent eluates were formulated following ISO 10993-5 guidelines, and 1%, 0.25%, and 0.1% dilutions were prepared. The HPDLSCs were isolated from the extracted third molars of healthy donors. The following parameters were assessed: cell viability via trypan blue and IC50 assays, cell migration via horizontal wound healing assay, cell morphology via cell cytoskeleton staining (phalloidin labeling), and cell oxidative stress via reactive oxygen species assay. The data were analyzed using one-way ANOVA and Tukey’s posthoc tests, and their significance was established at p < 0.05. Chloroform and eucalyptol exhibited significantly higher cytotoxicity on the hPDLSCs in vitro compared to the control group, as shown by the cell viability, migration, morphology, and reactive oxygen species release assays. Alternatively, Endosolv showed adequate cytotoxicity levels comparable to those of the control group. The cytotoxicity of the tested endodontic solvents increased in a dose-dependent manner. The results from the present study highlight the cytotoxicity of chloroform and eucalyptol. Thus, their limited and cautious use is recommended, avoiding solvent extrusion.

The Novel Role of Solvents in Non-Surgical Endodontic Retreatment

Non-surgical endodontic retreatment is a reliable conservative option for managing post-treatment apical periodontitis. However, effective microbial control, based on the maximization of filling removal and disinfection protocols, is not yet predictable. Traditional gutta-percha solvents, which are indistinctively used for both the core and sealer filling materials, became obsolete due to unprecedented advances in endodontic technology. Nonetheless, microtomography, scanning electronic microscopy findings, and histobacteriological analysis tend to confirm the persistence of filling materials and the lack of association between root canal enlargement and superior disinfection. There is a controversy regarding the most suitable clinical protocols surrounding the shaping procedures and the supplementary disinfection steps. Based on the literature and the previous work of the team, the authors aimed to summarize the current knowledge regarding specific solvent formulations that target filling materials. Additionally, the advantage of an additional irrigation step to optimize disinfection was highlighted. This adjunctive procedure serves a dual role in the dissolution of filling materials, and in conferring an antibiofilm effect. Further research is needed to understand the novel contribution of these strategies upon clinical practice outcomes.

A comparative study of the effects of gutta-percha solvents on human osteoblasts and murine fibroblasts

We aimed to investigate the in vitro physiologic effects of xylene, chloroform, orange oil and eucalyptus oil solvents for dissolving gutta-percha on L929 and HOB cell lines; 2.5 and 10 μL mL^-1 of these solvents were tested for 24, 48 and 72 h. Gutta-percha solvents inhibited the proliferation rate of fibroblasts in a dose- and time-dependent manner; however, no inhibition was detected in HOB (evaluated using MTT assay). None of the solvents induced apoptosis/necrosis in HOB cells at ≤2.5 μL mL^-1 concentration in contrast to L929 (determined using acridine orange/ethidium bromide dual staining). Each solvent tested reduced the migration rate of both L929 and HOB cell lines in a dose-dependent manner (evaluated using a scratch assay). Gutta-percha solvents can damage fibroblast-rich tissues. Osteoblasts seemed to be more resistant to the tested solvents, and excessive extrusion of solvents from the root canal may also damage the periradicular tissues and reduce the ability to repair.

Natural Polymer Eucommia Ulmoides Rubber: A Novel Material

As the second natural rubber resource, Eucommia ulmoides rubber (EUR) from Eucommia ulmoides Oliver is mainly composed of trans-1,4-polyisoprene, which is the isomer of natural rubber cis-1,4-polyisoprene from Hevea brasiliensis. In the past few years, the great potential application of EUR has received increasing attention, and there is a growing awareness that the natural polymer EUR could become an emerging research topic in field of the novel materials due to its unique and excellent duality of both rubber and plastic. To gain insight into its further development, in this review, the extraction, structure, physicochemical properties, and modification of EUR are discussed in detail. More emphasis on the potential applications in the fields of the environment, agriculture, engineering, and biomedical engineering is summarized. Finally, some insights into the challenges and perspectives of EUR are also suggested.

The efficacy of retreatment and new reciprocating systems in removing a gutta-percha-based filling material

Objectives

To investigate the efficacy of retreatment and reciprocating rotary systems in removing gutta-percha filling material from root-canal systems.

Methods

A total of 90 single-canal human teeth were instrumented using a F3 ProTaper file and obturated with gutta-percha and the Tubliseal sealer using the lateral-compaction technique. They were divided into five groups according to the rotary system used to remove the filling material: Reciproc, which used the Reciproc-R25 file; WaveOne, which used the WaveOne-Primary file; S1, which used the S1 (25/.06) file; ProTaper-R, which used the ProTaper-Retreatment system; and Mtwo-R, which used the Mtwo®-Retreatment system. The time required to remove the filling material (min) and the associated instrument separation, if any, were recorded. Teeth were cleaved longitudinally and photographed with a high-resolution camera. Images were imported to the AutoCAD application to measure the remaining filling material and the root-canal space. Data were analysed using the one-way analysis of variance and Chi-squared tests.

Results

The Mtwo-R group showed the highest mean remaining filling material (51%) (p < 0.001), with no significant differences among the other groups. The ProTaper group required the least time for filling-material removal (4.95 min), with significant differences compared to the other groups (p < 0.05), except the WaveOne group (5.83 min; p = 1.000). Overall, 13 instruments (15.9%) were used for filling-material removal, with a significantly greater proportion in the Mtwo-R group (33.3%) compared to the other groups (p = 0.009).

Conclusions

Within the limitations of this in vitro study, reciprocating rotary systems were as effective as retreatment rotary systems in removing root-canal filling material. The Mtwo-R system showed the poorest performance with respect to removal effectiveness and instrument separation.

Hazards of Improper Dispensary: Literature Review and Report of an Accidental Chloroform Injection

Several clear, transparent solutions are used in endodontics. Inappropriate dispensing methods can lead to accidental injection or accidental irrigation. These accidents can cause permanent tissue damage including damage to the bone, periodontium, nerves, and vasculature. This article reports on the consequences of an accidental chloroform injection. Nonsurgical retreatment of tooth #8 was planned as part of a restorative treatment plan in a 69-year-old woman. The dentist accidentally injected chloroform instead of local anesthesia because chloroform was loaded into the anesthetic syringe. The patient experienced severe pain and swelling and soft tissue necrosis and suffered permanent sensory and motor nerve damage. A review of the literature was performed on accidents caused by improper dispensary, namely accidental injections and accidental irrigations. The data were extracted and summarized. Sodium hypochlorite, chlorhexidine, formalin, formocresol, 1:1000 adrenaline, benzalkonium chloride, and lighter fuel were accidentally injected as an intraoral nerve block or as infiltration injections. Bone and soft tissue necrosis, tooth loss, and sensory nerve damage (anesthesia and paresthesia) were the most common consequences reported. Such disastrous events can be prevented by appropriate labeling and separate dispensing methods for each solution. There is a need for disseminating information on toxicity and biocompatibility of materials/solutions used in endodontics. The authors recommend training dental students and endodontic residents on immediate and long-term therapeutic management of patients when an accidental injection or accidental irrigation occurs.

Efficacy of Different Irrigation Protocols for Removing Gutta-Percha and Sealer Remnants in Artificial Un-instrumented Areas

Objective:

The purpose of this study was to determine the efficacy of different irrigants and irrigation protocols in the removal of gutta-percha and sealer from simulated un-instrumented areas.

Methods:

Eighty-four uniradicular teeth were used. After standardizing working length (WL) and preparing the glide path, coronal flaring was performed. The instrumentation phase was completed with ProFile rotary instruments up to size #35 LightSpeed LSX. Roots were split into halves: in one of them, a groove was prepared in the apical 6 mm. In the opposite one, 5 depressions were made (at 2, 4, 6, 8 and 10 mm). Irregularities were filled with AH Plus sealer and flowable gutta-percha. The Efficacy of sodium hypochlorite (NaOCl) and chloroform in removal of material and the effect of positive pressure (PP), passive ultrasonic irrigation (PUI) (one or three cycles) and paper points were analysed with the chi-square test.

Results:

Delivery by PP did not eliminate the obturator material from any artificial depression. Chloroform, when activated, demonstrated a significant linear trend in the amount of gutta-percha removed at all tested levels (P<0.01). The use of paper points after passive delivery of chloroform increased significantly the removal of gutta-percha in the groove and at 4 and 10 mm (P<0.05). Three cycles of PUI and chloroform showed significantly fewer remnants of gutta-percha (P<0.01).

Conclusion:

Positive pressure was not effective in the removal of obturator materials with any of the tested irrigants. Chloroform delivered by PP in combination with paper points obtained a better cleaning efficacy, although its activation using PUI for three cycles of 20 s showed the best cleanliness.

The effectiveness of eucalyptus oil, orange oil, and xylene in dissolving different endodontic sealers

Objective:

The objective of this study was to evaluate the dissolution effectiveness of eucalyptus oil, orange oil, xylene, and distilled water on three different endodontic sealers.

Materials and Methods:

About 240 samples of root canal sealers (eighty for each sealer) were prepared and divided into four groups of 20 each for immersion in different organic solvents. Each group was further subdivided into two subgroups (n = 10) for 2 and 10 min of immersion time. The mean percentage of weight loss was determined for each sealer in each solvent at both time periods. Data were statistically analyzed by two factor analysis of variance and significance of mean difference was obtained by Tukey's post hoc test (P < 0.05).

Results:

The lowest level of solubility was observed for Adseal followed by Apexit Plus and Endomethasone N at both time periods in all solvents. Apexit Plus showed no significant (P > 0.05) difference in its dissolution in all the organic solvents except distilled water at both the time periods. The solubility profile of Endomethasone N and Adseal did not differ significantly among eucalyptus oil, orange oil, and xylene at 2 min and between eucalyptus oil and orange oil at 10 min. However, at 10 min, Endomethasone N and Adseal showed a more pronounced solubility in xylene as compared to both eucalyptus oil and orange oil.

Conclusions:

In general, xylene was the most effective in dissolving root canal sealers than other organic solvents. Essential oils (eucalyptus oil and orange oil) were found similar in their ability to dissolve Apexit Plus and Endomethasone N.

Do the Sealer Solvents Used Affect Apically Extruded Debris in Retreatment?

INTRODUCTION

We evaluated apically extruded debris in the retreatment of root canals filled with different root canal sealers and gutta-percha using different solvents.

METHODS

Ninety human mandibular central and lateral teeth were prepared using the Reciproc #25 .08 nickel-titanium system (VDW GmbH, Munich, Germany) and were divided randomly into 6 groups. In groups 1, 2, and 3, root canals were filled with epoxy resin-based sealer and gutta-percha, and in groups 4, 5, and 6, root canals were filled with zinc oxide-eugenol-based sealer and gutta-percha. Each tooth was placed in a glass vial experimental apparatus. All root canal fillings were removed with the ProTaper Retreatment nickel-titanium system (Dentsply Maillefer, Ballaigues, Switzerland). During the retreatment procedure, in group 1, Resosolv (Pierre Rolland, Merignac, France) was used; in group 4, Endosolv E (Septodont, Paris, France) was used; and in groups 2 and 5, Guttasolv (Septodont) was used as the solvent. In the control groups (groups 3 and 6), no solvent was used. Reciproc #40 .06 was used for the final preparation. The times required for retreatments were recorded.

RESULTS

The weight of the extruded debris and the time required for retreatment were decreased significantly in the groups in which a solvent that was intended specifically for the root canal sealer was used (groups 1 and 4). In the Guttasolv groups (groups 2 and 5), the amount of apically extruded debris and the time required decreased for both root canal sealers.

CONCLUSIONS

The amount of apically extruded debris and the duration of retreatment were reduced by the use of a solvent specific to the sealer compared with a gutta-percha solvent or no solvent.

Effect of chloroform, orange solvent and eucalyptol on the accuracy of four electronic apex locators

The aim of this study was to evaluate the effect of three retreatment solutions on the accuracy of four electronic apex locators, the Root ZX mini, the Mini Apex Locator, the Root ZX and the Elements Diagnostic Unit and Apex Locator. Forty extracted single-rooted human teeth were used in this study. The four electronic apex locators were operated according to the manufacturer's instructions to locate the 'apical constriction' in the presence of chloroform, orange solvent or eucalyptol in the canal. The accuracy of each apex locator was not affected by the type of retreatment solution present in the root canal. In addition, the accuracy of the four apex locators was similar in the presence of each of the tested solutions.

Efficacy of different solvents in removing gutta-percha from curved root canals: a micro-computed tomography study

The aim of this study was to compare the root filling material that remained after retreatment of curved root canals with chloroform and Endosolv R as solvents. The evaluation employed micro-computed tomography (CT) imaging. Thirty-six extracted molar teeth with curved roots were selected. After preparation with ProTaper rotary instruments, the canals were filled with gutta-percha and AH26 sealer. The teeth were randomly divided into three groups according to solvent used (n = 12) as follows: group 1: chloroform; group 2: Endosolv R; group 3: no solvent (negative control). ProTaper Universal Retreatment files were used to remove each root canal filling and then the self-adjusting file was applied for two minutes. Preoperative and postoperative micro-CT images were used to assess the percentage of residual filling material. The mean percentage of residual filling material was quantified. There were no statistically significant differences between the groups in terms of percentage volume of residual root canal filling.

Efficacy of grapefruit, tangerine, lime, and lemon oils as solvents for softening gutta-percha in root canal retreatment procedures

AIM

In the present study, we evaluate the efficiency of four kinds of oil as solvents for softening gutta-percha in root canal retreatment procedures. The performance of grapefruit, tangerine, lime, and lemon oils specifically were evaluated and compared to chloroform.

METHODS

Eighty-four cylinder-shaped glass tubes (5 × 30 mm) were filled with gutta-percha. A total of 0.1 mL solvent was added to the upper part of the glass tubes. After 5 min, the spreader attached to the universal testing machine was moved downward through gutta-percha with header speed of 5 mm/min into a depth of 5 mm. An initial depth of spreader penetration without force produced was recorded in millimeters. The load used to penetrate the spreader into the 5-mm depth was recorded in Newton.

RESULTS

The results of the surface-dissolving depth and maximum force used to penetrate the spreader to 5 mm revealed that chloroform was significantly the best solvent in softening gutta-percha (P < 0.05), followed by grapefruit oil and tangerine oil, while the least effective solvents were lime oil and lemon oil.

CONCLUSIONS

Under the conditions of the present study, grapefruit oil and tangerine oil performed best as gutta-perch solvents among four natural oils.

Properties and applications of calcium hydroxide in endodontics and dental traumatology

Calcium hydroxide has been included within several materials and antimicrobial formulations that are used in a number of treatment modalities in endodontics. These include, inter-appointment intracanal medicaments, pulp-capping agents and root canal sealers. Calcium hydroxide formulations are also used during treatment of root perforations, root fractures and root resorption and have a role in dental traumatology, for example, following tooth avulsion and luxation injuries. The purpose of this paper is to review the properties and clinical applications of calcium hydroxide in endodontics and dental traumatology including its antibacterial activity, antifungal activity, effect on bacterial biofilms, the synergism between calcium hydroxide and other agents, its effects on the properties of dentine, the diffusion of hydroxyl ions through dentine and its toxicity. Pure calcium hydroxide paste has a high pH (approximately 12.5-12.8) and is classified chemically as a strong base. Its main actions are achieved through the ionic dissociation of Ca(2+) and OH(-) ions and their effect on vital tissues, the induction of hard-tissue deposition and the antibacterial properties. The lethal effects of calcium hydroxide on bacterial cells are probably due to protein denaturation and damage to DNA and cytoplasmic membranes. It has a wide range of antimicrobial activity against common endodontic pathogens but is less effective against Enterococcus faecalis and Candida albicans. Calcium hydroxide is also an effective anti-endotoxin agent. However, its effect on microbial biofilms is controversial.

Comparative SEM evaluation of three solvents used in endodontic retreatment: an ex vivo study

This study compared, by scanning electron microscopy (SEM), the efficacy of three solvents on the removal of filling materials from dentinal tubules during endodontic retreatment. Forty human maxillary canines with straight canals were prepared according to a crown-down technique and enlarged to a#30 apical file size, before obturation with gutta-percha and a zinc-oxide-eugenol based sealer. The samples were stored for 3 months before being randomly assigned to four groups: chloroform (n=10), orange oil (n=10), eucalyptol (n=10) and control (n=10). Solvents were applied to a reservoir created on the coronal root third using Gates Glidden drills. The total time for retreatment using the solvents was 5 minutes per tooth. Following retreatment the roots were split longitudinally for SEM evaluation. SEM images were digitized, analyzed using Image ProPlus 4.5 software, and the number of dentinal tubules free of filling material from the middle and apical thirds was recorded. No significant difference was found among the solvent groups regarding the number of dentinal tubules free of root filling remnants in the middle and apical root thirds (p>0.05). However, the control group had fewer dentinal tubules free of filling material (p<0.05). Under the tested conditions, it may be concluded that there was no significant difference among the solvents used to obtain dentinal tubules free of filling material remnants.

Retreatment efficacy of the Epiphany soft resin obturation system

AIM

To assess the efficacy of retreatment of canals filled with the Epiphany System with and without solvent, with particular reference to the extent of canal enlargement during retreatment.

METHODOLOGY

Sixty roots with canals prepared to apical size 45 were embedded in resin blocks and sectioned vertically. Digital micrographs of canal walls were captured. Roots were re-assembled and filled with Epiphany/Resilon (experimental) or gutta-percha/AH Plus (control). After 8 weeks, canals were retreated to size 45 with or without chloroform, and the time recorded. Roots were split, imaged, re-assembled, retreated to size 55, split and imaged. Root-filling residue, traced at three canal levels, was expressed as percentage of canal surface.

RESULTS

Residue percentage was greater (t-test, P < 0.01) in the experimental group than in the control. Most residue in all specimens was in the apical third (ANOVA, P < 0.01). Chloroform and enlargement to size 55 decreased residue in both groups (t-test, P < 0.01). Retreatment time was longer in the experimental group (P < 0.05), and reduced by chloroform in both groups (P < 0.05).

CONCLUSIONS

The Epiphany System was retreatable with and without chloroform, with lesser efficacy than gutta-percha and AH Plus sealer.

Efficacy of Two Rotary NiTi Instruments in the Removal of Gutta-Percha During Root Canal Retreatment

The aim of this study was to evaluate the efficacy of ProTaper and K3 in the removal of gutta-percha during root canal retreatment in comparison with hand Hedstrom files. Time of gutta-percha removal and amount of apically extruded debris were also evaluated. Sixty extracted single-rooted anterior teeth and premolars were instrumented and obturated with laterally condensed gutta-percha technique. The teeth were cleared and randomly divided into three groups of 20 teeth each. The roots were split longitudinally, digital images were created using a scanner, and the areas of remaining filling material were traced using Ulead Photoimpact7 then calculated using SigmaScan software. The results indicated that the two rotary nickel-titanium instruments left significantly less remaining filling material than hand instruments (p < 0.001). The ProTaper and K3 required significantly less time for filling material removal than hand instruments (p < 0.001). There was no statistically significant difference among the three techniques regarding the amount of apically extruded debris (p = 0.159). In conclusion, ProTaper and K3 were found to be effective and faster in removing gutta-percha.

Efficacy of automated versus hand instrumentation during root canal retreatment: an ex vivo study

AIM

To compare automated and manual instrumentation techniques for removing filling material from root canal walls during root canal retreatment.

METHODOLOGY

One hundred extracted human single-rooted teeth were root filled and stored. Specimens were divided into two groups: group A, Endofill plus gutta-percha; group B, Sealer 26 plus gutta-percha. The filling material was removed using the following techniques: group I - Gates-Glidden and K-type files; group II - ProFile; group III - ProTaper; group IV - K3; group V- Micro Mega Hero 642. The remaining filling debris on the root canal walls were assessed radiographically, images were digitized and analysed using Image ProPlus software. The roots were split for evaluation in a stereomicroscope by epiluminescence and photomicrographs were taken for further analysis. The area covered with filling debris was analysed by means of Student's t-test to compare the evaluation methods. The student's t-test was also used to compare the removal of filling materials. An anova test was applied to compare the different techniques (P < 0.05).

RESULTS

A significant difference occurred between radiographic and photomicrographic evaluation methods (P < 0.05). No significant difference was observed between the filling materials on terms of their removal (P > 0.05). Manual instrumentation left more filling debris on the root canal walls when compared to K3 (P < 0.05) and ProTaper (P < 0.01).

CONCLUSIONS

A photomicrographic method by epiluminescence was more effective than the radiographic method to evaluate filling debris. There was no significant difference between the filling materials in terms of their removal. K3 and ProTaper were more efficient than manual instrumentation.

Halothane affects focal adhesion proteins in the A 549 cells

Halothane is a volatile anaesthetic, which is known to induce alterations in cellular plasma membranes, modulating the physical state of the membrane lipids and/or interacting directly with membrane-bound proteins, such as integrin receptors. Integrin-mediated cell adhesion is a general property of eukaryotic cells, which is closely related to cell viability. Our previous investigations showed that halothane is toxic for A 549 lung carcinoma cells when applied at physiologically relevant concentrations and causes inhibition of adhesion to collagen IV. The present study is focused on the mechanisms underlying halothane toxicity. Our results imply that physiologically relevant concentrations of halothane disrupt focal adhesion contacts in A 549 cells, which is accompanied with suppression of focal adhesion kinase activity and paxillin phosphorylation, and not with proteolytic changes or inhibition of vinculin and paxillin expression.We suggest that at least one of the toxic effects of halothane is due to a decreased phosphorylation of the focal contact proteins.

In vitro evaluation of macrophage viability after incubation in orange oil, eucalyptol, and chloroform

OBJECTIVE

The aim of this study was to evaluate the cytotoxicity of orange oil, eucalyptol, and chloroform in a cell culture assay by using peritoneal macrophages from Swiss mice.

STUDY DESIGN

Control (Dulbecco's modified Eagle's medium [DMEM] plus 1.25% ethyl alcohol) and experimental (orange oil, eucalyptol, and chloroform) groups were studied. Solvents used were tested at 0.025% and 0.050% concentrations in DMEM plus 1.25% ethyl alcohol.

RESULTS

Orange oil, eucalyptol, and chloroform were all cytotoxic in comparison to the control group (P < .001). Orange oil showed the least cytotoxicity (P < .001). No significant differences were observed regarding cell viability when comparing the eucalyptol and chloroform groups (P < .05). There were significant differences in the cytotoxicity of eucalyptol and chloroform with an increase in concentration (P < .0001). Nevertheless, this difference was not significant in the orange oil group (P < .05).

CONCLUSION

Orange oil was less cytotoxic than eucalyptol and chloroform.

Effectiveness of rotary and hand files in gutta-percha and sealer removal using chloroform or chlorhexidine gel

The purpose of this study was to assess in vitro the efficacy of nickel-titanium K³ rotary files and hand files for removal of gutta-percha and sealer from obturated root canals using either chloroform or chlorhexidine as solvents. Sixty extracted single-rooted bovine teeth with straight, large canals were prepared, obtured and randomly assigned to 3 groups (n=20). The teeth were stored at 37ºC for 1 month and then the gutta-percha and sealer were removed using different techniques, as follows. Group I: size 3 Gates-Glidden drills plus size 30 hand K-files and Hedström files and chloroform; Group II: K³ NiTi rotary files and chloroform; and Group III: K³ NiTi rotary files and 2% chlorhexidine gel. Radiographs were taken and scanned and the images were digitized. The total area of the canal and the area with remaining obturation material were measured in millimeters using a computed image analysis system (ImageLab). Data were analyzed statistically by one-way ANOVA and Tukey test at 5% significance level. The groups differed statistically (p<0.05) with respect to the average percentage of remaining gutta-percha and sealer, presenting the following sequence of effectiveness (from most to least effective): Group I (15.48%), Group II (28.42%) and Group III (35.96%). The findings of this study showed that, despite the technique used for removal of filling material, none of the retreated canals were completely free of gutta-percha and sealer remnants. The use of stainless steel hand files resulted in a lesser amount of filling debris than the use of nickel-titanium rotary instruments.

Effect of halothane on lung carcinoma cells A 549

The halogenated hydrocarbons, such as halothane, are widely used as anesthetics in clinical practice; however their application is often accompanied with metabolic, cardiovascular and respiratory complications. One of the possible factors for this negative outcome might be the severe toxicity of these agents. In this paper, we investigate in vitro effects of halothane on human lung carcinoma A 549 cells, namely on their cytotoxicity, adhesive properties and metabolic activity. The cytotoxicity response of lung carcinoma A 549 cells to halothane was determined by lactate dehydrogenase (LDH) assay (for cytotoxicity), by detachment assay after adhesion to type IV collagen (for cell adhesive properties) and by surface tension measurements of culture medium (for cell metabolic activity). Regarding the cytotoxicity, the determined maximal non-toxic concentration of halothane on A 549 cells, given here as volume percentages (vol.%) was 0.7 vol.% expressed as aqueous concentration in the culture medium. Direct measurement of the actual halothane concentration in the culture medium showed that 0.7 vol.% corresponds to 1.05 mM and 5.25 aqueous-phase minimum alveolar concentration (MAC). Concentrations equal or higher than 1.4 vol.% (2.1 mM; 10.5 MAC) of halothane provoked complete detachment (cell death), or reduction of initial adhesion to collagen IV in half of the cell population. Surfactant production of A 549 cells, registered up to 48 h after halothane treatment, was inhibited by halothane concentrations as low as 0.6 vol.% (0.9 mM; 4.5 MAC). Our results demonstrate that sub toxic halothane concentrations of 0.6 vol.% inhibits surfactant production; concentrations in the range 0.8-1.4 vol.% induce membrane damages and concentrations equal and higher than 1.4 vol.%--cell death of approximately 50% of the cells.

Biocompatibility of dental materials used in contemporary endodontic therapy: a review. Part 2. Root-canal-filling materials

Root-canal-filling materials are either placed directly onto vital periapical tissues or may leach through dentine. The tissue response to these materials therefore becomes important and may influence the outcome of endodontic treatment. This paper is a review of the biocompatibility of contemporary orthograde and retrograde root-canal-filling materials.

Biocompatibility of dental materials used in contemporary endodontic therapy: a review. Part 1. Intracanal drugs and substances

Irrigation solutions and intracanal medicaments are used within the root canal to clean and aid in disinfecting the dentinal walls. Although these materials are intended to be contained within the root canal, they invariably contact the periapical tissues, either through inadvertent extrusion through the apex or leaching. This paper is a review on the methodology involved in biocompatibility testing followed by a discussion on biocompatibility of contemporary intracanal drugs and substances used in endodontics.

A comparison of the effectiveness of chloroform and eucalyptus oil in dissolving root canal sealers

OBJECTIVE

The solubility of 8 different root canal sealers in chloroform and in eucalyptus oil was compared.

STUDY DESIGN

For standardized samples (n=12), ring molds were filled with mixed sealers based on epoxy resin, silicone, calcium hydroxide, zinc oxide-eugenol, glass ionomer, and polyketone. These samples were immersed in chloroform or eucalyptus oil for 30 seconds, 1 minute, 2 minutes, 5 minutes, 10 minutes, and 20 minutes. Then, the mean weight loss was determined and statistically analyzed.

RESULTS

With the exception of the silicone, all the sealers showed significantly higher solubilities (P <.05) in chloroform than in eucalyptus oil. Epoxy resin was the most soluble sealer in chloroform. In eucalyptus oil, calcium hydroxide, and zinc oxide-eugenol showed the highest solubility.

CONCLUSION

Under the conditions of this study, chloroform was a far more effective solvent of root canal sealers than eucalyptus oil. Because of the potential hazards of chloroform, further studies on the dissolution of root canal sealers in different solvents seem to be necessary.

Cytotoxicity of halothane on human gingival fibroblast cultures in vitro

Recently halothane has been reported to be the most suitable alternative to chloroform in dissolving gutta-percha. Periapical tissue toxicity of halothane is not completely known. In this study gutta-percha dissolved by halothane was evaluated with the almar blue dye assay using human gingival fibroblast cultures. The cytotoxic effects of halothane on human gingival fibroblasts depended on the exposure dose, frequency, and duration. A reduced concentration and smaller amount of gutta-percha solvents may minimize the cytotoxic effects on host tissues.

Gutta-percha softening: "Hemo-De" as a xylene substitute

The putative hazardous nature of chloroform and xylene implies that safer substitutes should be considered. Standard cylindrical gutta-percha samples were immersed in Hemo-De, a xylene substitute, for 60 s at 37 degrees C. Weight loss of a sample, after drying, was used as a measure of its solubility. Master and accessory cone gutta-percha of three brands were compared. The highest solubility of all kinds of gutta-percha was in chloroform, which served as a positive control. The average solubility of all samples in xylene and Hemo-De was 61% and 52% of that in chloroform, respectively. DMS gutta-percha was more soluble than of Hygienic and DeTrey. Master cone gutta-percha of all brands was more soluble than that of their accessory cones. These results indicate that (a) large differences exist in the solubility of gutta-percha and (b) Hemo-De dissolved gutta-percha in a range similar to that of xylene and may be considered as a potential substitute for this organic solvent.

Effect of chloroform, xylene, and halothane on enamel and dentin microhardness of human teeth

OBJECTIVE

The purpose of this study was to assess in vitro the effect of commonly used gutta-percha solvents on the microhardness of human enamel and dentin.

STUDY DESIGN

Crowns of human teeth were cut and treated with chloroform, xylene, and halothane. Treatment consisted of exposing the specimens for 5 or 15 minutes to the test solvents. Acid-treated and saline-treated specimens served as controls. After each treatment period, the specimens were rinsed, dried, and prepared for Vicker's microhardness analysis. Vicker's microhardness values for each specimen were recorded before and after treatment, and the differences were statistically compared.

RESULTS

A statistically significant decrease in enamel and dentin microhardness was found in most solvent-treated groups; the amount of the decrease was directly related to the exposure time.

CONCLUSIONS

Chloroform, xylene, and halothane may cause a significant softening effect on both enamel and dentin. This softening is already apparent after 5 minutes of treatment.

Cytotoxicity of four root canal sealers in permanent 3T3 cells and primary human periodontal ligament fibroblast cultures

OBJECTIVES

The purposes of this study were to determine the cytocompatibility of four endodontic sealers and gutta-percha using various extracts and to compare the cellular injuries resulting from these materials in permanent 3T3 monolayers and primary human periodontal ligament fibroblasts.

STUDY DESIGN

Set specimens from four sealers (AH26, Apexit, Sealapex, N2) as well as gutta-percha were eluted with cell culture medium for 24 hours, 5 days, 5 days, and 24 hours, respectively. Cytotoxic effects due to these extracts were evaluated by determining proliferation of permanent 3T3 cells and primary human periodontal ligament fibroblasts by means of the fluorochrome propidiumiodide.

RESULTS

No statistically significant cellular alterations were induced by gutta-percha and Apexit, whereas various extracts of AH26 and Sealapex caused significant moderate or severe growth inhibition. Severe cellular damage was documented for all extracts of N2, which was statistically significantly different from the other materials in both cell lines (p < 0.05).

CONCLUSIONS

Our results confirm that various root canal sealers constantly segregate substances after being exposed to an aqueous environment for extended periods, possibly causing moderate or severe cytotoxic reactions and possibly contributing to failure.

Risk assessment of the toxicity of solvents of gutta-percha used in endodontic retreatment

Three randomly assigned groups of single-canaled extracted teeth obturated with gutta-percha were retreated using controlled application of one of three organic solvents: chloroform, xylene, or halothane. Two additional groups of teeth served as positive and negative controls. Residual volume of solvent expressed through the apical foramen during retreatment was determined by the difference of pretreatment and posttreatment weights of hermetically sealed receptacles attached to the root surface of the teeth. Results indicate that the amount of solvent that has been determined to have leached out through the apical foramen is several orders of magnitude below the permissible toxic dose. Thus, it is proposed that the use of any of the aforementioned solvents used in the retreatment of root canals would pose negligible risk to the patient.

Effect of gutta-percha solvents on calcium and phosphorus levels of cut human dentin

Fresh intact human teeth were cut and treated with 3 commonly used gutta-percha solvents: chloroform, xylene, and Endosolv-E. Treatment consisted of embedding the specimens of each group for 15 or 30 min in the test solution. After each time interval, the specimens were rinsed, dried, and prepared for surface energy dispersive spectrometric analysis. The calcium and phosphorus levels in each specimen were recorded and the differences between the test groups were statistically analyzed. The changes in the calcium and phosphorus levels following treatment with the gutta-percha solvents were minimal and statistically nonsignificant.

Clinical uses of rectified turpentine oil

Rectified turpentine oil can be used to soften or dissolve gutta-percha in the root canal space to facilitate endodontic retreatment or preparation of space for a post. For endodontic retreatment, the turpentine oil can be heated to 71 degrees C which significantly increases its ability to dissolve gutta-percha. For removing only a portion of the gutta-percha while leaving the rest intact, as for the preparation of space for a post, the turpentine oil is delivered to the canal at body temperature (37 degrees C).