Evaluation of alternatives to chloroform in endodontic practice

Retreatment Strategies for Cases Containing Calcium Silicate-Based Root Canal Sealers: A Comprehensive Review

This review explores the field of retreatment strategies for cases filled with calcium silicate-based root canal sealers. Since the introduction of calcium silicate-based materials in dentistry, calcium silicate-based root canal sealers have become popular among dentists because of their biocompatibility, bioactivity, and sealing ability. Therefore, effective retreatment strategies are indispensable. This article aims to identify the challenges associated with the removal of calcium silicate-based sealers themselves and removal of gutta-percha with the sealers during retreatment, evaluate current techniques and materials, and provide future directions for research in this field. Regarding the strategies of removal of root canal sealers, calcium silicate-based sealers are still relatively new materials for clinicians compared with traditional sealers such as epoxy- or eugenol-based sealers. First, no clinically established solvents have been reported. Second, calcium silicate-based sealers are currently utilized by clinicians in either the cold sealer-based technique or the warm vertical condensation technique. Third, the setting process of calcium silicate-based sealers generates byproducts, primarily calcium hydroxide and secondarily hydroxyapatite, that could interact with dentine. Lastly, there is a lack of clinical studies evaluating the efficacy of retreatment protocols for teeth filled with calcium silicate-based sealers. Therefore, it is important to investigate the chemo-mechanical properties of calcium silicate-based sealers themselves and their reactions to solvents and/or mechanical instruments and identify the interfacial properties of calcium silicate-based sealers with respect to dentine and gutta-percha. In addition, researchers in the clinical field need to actively gather and report data on retreatments of teeth filled with calcium silicate-based sealers.

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.

An in vitro evaluation of effectiveness of Xylene, Thyme oil and Orange oil in dissolving three different endodontic sealers

Aims

The aim of the study is to compare the dissolution effectiveness of xylene, thyme oil, and orange oil on three different endodontic sealers.

Materials and Methods

Standardized stainless steel molds were used to prepare 210 samples (70 for each endodontic sealer). The samples were divided into three groups based on sealers. Three experimental groups with 20 samples each were immersed in organic solvents. One control group of 10 samples was immersed in distilled water. Each group was further subdivided into two subgroups based on immersion time (2 and 10 min). Inferential statistics included one-way ANOVA, post hoc Tukey, and paired t-test.

Results

Thyme showed significantly more dissolution capacity at 10 min compared to 2 min in dissolving AH Plus sealer whereas this difference was nonsignificant for Roekoseal and MTA Fillapex. Orange oil showed significantly more dissolution at 10 min compared to 2 min in dissolving AH Plus sealer and Roekoseal whereas this difference was nonsignificant concerning MTA Fillapex. Xylene showed significantly more dissolution capacity at 10 min compared to 2 min in dissolving AH Plus sealer, Roekoseal, and MTA Fillapex.

Conclusions

Among the three solvents, xylene showed the highest dissolution of all three sealers. Orange oil was superior to thyme oil in dissolving the sealers. All the sealers showed more dissolution in all the solvents at 10 min compared to 2 min.

Evaluation of the Antibacterial Effect of Xylene, Chloroform, Eucalyptol, and Orange Oil on Enterococcus faecalis in Nonsurgical Root Canal Retreatment: An Ex Vivo Study

Objectives

The present ex vivo study is aimed at evaluating the antibacterial efficacy of chloroform, eucalyptol, orange oil, and xylene against E. faecalis biofilm during nonsurgical root canal retreatment.

Materials and Methods

Eighty single-rooted teeth were instrumented. The samples were autoclaved, infected with E. faecalis for 4 weeks, and obturated with gutta-percha. Then the teeth were randomly assigned to 4 groups (n = 20): (1) chloroform, (2) eucalyptol, (3) orange oil, and (4) xylene. In all of the groups, gutta-percha removal was conducted according to the same protocol although the solvent used in each group was different. Bacterial samples were collected after gutta-percha removal and following additional apical enlargement. Intergroup and intragroup analyses were conducted using one-way ANOVA combined with the post hoc Tukey test and the paired-sample t-test, respectively. Statistical significance was set to 0.05.

Results

All of the groups showed more than 99% bacterial load reduction. The least bacterial load after gutta-percha removal was observed in the chloroform group (p < 0.001). The orange oil group showed a significantly lower bacterial load compared to the eucalyptol group (p = 0.001), while it was not different from the xylene group (p = 0.953). The xylene group also had a significantly lower bacterial load compared with the eucalyptol group (p = 0.017). After apical enlargement, the chloroform group had a significantly lower bacterial load compared to the other groups. The comparison of bacterial load values before and after apical enlargement in the chloroform and eucalyptol groups showed a statistically significant difference (p_choloroform = 0.011, p_eucalyptol = 0.001).

Conclusion

Chloroform was the most effective solvent in terms of antimicrobial activity against E. faecalis followed by orange oil and xylene, which were not significantly different though, and eucalyptol. All of the solvents showed more than 99% bacterial load reduction. Chloroform and xylene revealed to be associated with favorable antibiofilm activity among the examined solvents.

Management of iatrogenic chloroform mucosal burn in the palate: a case report

Chloroform is used widely in endodontic treatments for solving gutta-percha points, but it can have destructive effects if it comes in to contact with oral mucosa. This article presents a case of necrotic ulcer of palatal and buccal mucosa due to injudicious use of chloroform in endodontic treatment, which has caused severe destruction in maxilla. A conservative treatment method of repeated curettage and irrigation was used and although the lesion healed completely, it had major effects on the patient’s quality of life including loss of two teeth. It is important that dentist be aware of the devastating effects of imprudent application of various chemicals used in dentistry. The conservative treatment used for this case can be helpful option for similar cases.

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.

Influence of Passive Ultrasonic Irrigation on the Removal of Root Canal Filling Material in Straight Root Canals

Objective

This study evaluates the efficacy of passive ultrasonic irrigation (PUI) in removing root canal filling material from endodontically treated teeth after using one of two reciprocating systems, Reciproc (VDW, Munich, Germany) or WaveOne (Dentsply Maillefer, Ballaigues, Switzerland), or one nickel-titanium (NiTi) rotary system, ProTaper Universal Retreatment (Dentsply Maillefer).

Methods

One hundred and twenty straight root canals of extracted human maxillary incisors were instrumented and then obturated. The specimens were divided into six groups (n=20) as follows: Group R, Reciproc R25 instrument without PUI; Group W, WaveOne Primary instrument without PUI; Group PT, ProTaper Universal Retreatment system without PUI; Group R-PUI, Reciproc R25 with PUI; Group W-PUI, WaveOne Primary with PUI and Group PT-PUI, ProTaper Universal Retreatment system with PUI. After removing the filling material, the teeth were cleaved longitudinally and photographed. The total canal space and remaining material were quantified with the aid of an imaging software tool. The Kruskal-Wallis test was used to identify significant differences between the groups.

Results

No statistically significant differences (P>0.05) in residual filling material were observed between the groups.

Conclusion

The use of PUI did not improve the removal of filling material from the root canals, regardless of the previously used instrumentation system.

Effect of gutta-percha solvents on fiberglass post bond strength to root canal dentin

The purpose of this study was to investigate the influence of gutta-percha solvents on the bond strength of fiberglass post to root canal dentin. Forty bovine incisors were decoronated, prepared, filled, and randomly distributed into four groups (n = 10) according to the gutta-percha solvent used: control, xylene, eucalyptol and orange oil. After root canal treatment, the posts were cemented into the prepared root canals using a resin-based cement. A micro push-out test was executed, and the patterns of failure were assessed with microscopy. The data were analyzed using two-way ANOVA followed by Tukey's test. The control group exhibited greater bond strength compared to the eucalyptol group in the cervical and middle thirds of the root (P < 0.05); however, it did not differ significantly from the xylene and orange oil groups (P > 0.05). No difference was observed in the values of the xylene, orange oil, and eucalyptol groups (P > 0.05). The cervical third had higher values than the apical third for all tested solvents (P < 0.05). Adhesive failure between resin cement and dentin was the most frequent type of failure. The use of xylene and orange oil as gutta-percha solvents did not influence the bond strength of fiberglass posts to root canal dentin.

The effect of different organic solvents on the degradation of restorative materials

Objective:

To evaluate the solubility of three restorative materials exposed to the different endodontic solvents.

Materials and Methods:

The organic solvents eucalyptus oil, xylol, chloroform, and orange oil, with distilled water as the control group was utilized. The restorative materials light-cured resin (Filtek Z250/3M ESPE), light-cured-resin-reinforced glass ionomer (Riva Light Cure LC/Southern Dental Industries SDI]) and resin-modified glass ionomer (Vitremer/3M ESPE) were analyzed. A total of 50 disks containing specimens (2 mm × 8 mm Ø) were prepared for each of the three classes of restorative materials, which were divided into 10 groups (n = 5) for immersion in eucalyptus oil, xylol, chloroform, orange oil or distilled water for periods of either 2 min or 10 min. The means of restorative material disintegration in solvents were obtained by the difference between the original preimmersion weight and the postimmersion weight in a digital analytical scale. Data were statistically analyzed by two-way analysis of variance while the difference between the materials was analyzed by Student-Newman-Keuls test. The significance level set at 0.05.

Results:

Vitremer showed the highest solubility, followed by Riva LC, and these were statistically different from eucalyptus oil, xylol, chloroform, and distilled water (P < 0.05). Regarding the immersion time in solvents, there were no significant differences between the two tested periods (P > 0.05).

Conclusions:

The solvents minimally degraded the composite resin, although they did influence the degradation of both resin-modified glass ionomer resin and resin reinforced with glass ionomer.

Evaluation of the antibacterial activity of three gutta-percha solvents against Enterococcus faecalis

PURPOSE

Enterococcus faecalis (E. faecalis) is implicated as the common etiological agent of root canal treatment failure. The study was aimed to compare the antibacterial efficacy and to assess the minimum inhibitory concentration (MIC) of 3 gutta-percha solvents-RC Solve, Endosolv-E, and xylene against E. faecalis.

METHODS

Agar well diffusion assay was performed to evaluate the antibacterial efficacy of the gutta-percha solvents against E. faecalis (ATCC 29212 and a clinical isolate). The standard drug vancomycin was used as the control. The MIC of the solvents was determined by broth microdilution assay. Two fold serial dilutions of the solvents were prepared and the lowest concentration of the solvent that inhibits visible bacterial growth was recorded as the MIC. Minimum bactericidal concentration (MBC) was determined by plating on Muller Hinton Agar plates and the lowest concentration of the solvent that resulted in 99% reduction of bacterial viability was scored as the MBC.

RESULTS

The antibacterial activity of RC Solve against E. faecalis was found to be comparable to that of the standard drug-vancomycin. Xylene did not exhibit antibacterial activity while the antibacterial activity of Endosolv-E was lesser than RC Solve. RC Solve recorded lower MIC values against both E. faecalis ATCC29212 and clinical isolate (1:2 and 1:4 dilution) than Endosolv-E (undiluted). RC Solve was found to possess antibacterial activity against E. faecalis even at half the concentration that is routinely being used.

CONCLUSIONS

Within the limitations of the study, we conclude that RC Solve can perform a dual role both as a gutta-percha solvent as well as a microbicide against E. faecalis.

The efficacy of two rotary NiTi instruments and H-files to remove gutta-percha from root canals

Objective: The aim of this study was to evaluate the efficacy of R-Endo® and K3® rotary nickel-titanium instruments compared with manual instrumentation with H-files, with use of a solvent, for removal of gutta-percha during retreatment. Study design: Forty five freshly extracted human single-rooted teeth, each with one root canal, were instrumented with K-files and filled using cold lateral compaction of gutta-percha and AH 26® sealer. The teeth were randomly divided into three groups of 15 specimens each. Removal of gutta-percha was performed with the following devices and techniques: Group 1 (H-files), Group 2 (R-Endo®), and Group 3 (K3®). The specimens were rendered transparent for the evaluation of the area of remaining gutta-percha/sealer in buccolingual and mesiodistal directions. Statistical analysis as performed by using one-way ANOVA and Kruskal-Wallis tests (p=0.05). Results: All retreatment techniques used in this study left some filling material inside the root canal. Images in buccolingual and mesiodistal directions showed no significant differences between the groups (p>0.05). Conclusions: Under the experimental conditions, the remaining filling material after retreatment was similar for each group.

Key words:Gutta-percha removal, K3®, NiTi, R-Endo®.

Influence of different organic solvents on degree of swelling of poly (dimethyl siloxane)-based sealer

The study evaluated the compatibility of chloroform, ether, and xylene with poly(dimethyl siloxane) (PDMS) based sealer. Freshly mixed sealer was placed in 90 glass molds with 5 mm diameter and 2 mm thickness. All samples were stored in 75% relative humidity at 37°C for 2 weeks. All the samples were divided into three groups: group A - chloroform; group B - ether, and group C - xylene and immersed in fresh solvent at room temperature. The specimens were weighed before and after immersion for each group at the end of 2, 5, and 10 min. The swelling ratio was calculated for all the groups. Intergroup comparison revealed no difference in the mean swelling ratio for 2, 5, and 10 min (P > 0.001; Tukey HSD Post Hoc). Intragroup comparison revealed significant difference in swelling ratio between 2 and 5 min for group B and group C (P < 0.001; Paired t test). Ether has the highest compatibility with PDMS-based sealer after 2 min followed by xylene after 5 min.

Dissolving efficacy of eucalyptus and orange oil, xylol and chloroform solvents on different root canal sealers

AIM

To evaluate the solubility of five root canal sealers in orange oil, eucalyptol, xylol and chloroform solvents.

METHODOLOGY

The solubility of RoekoSeal, Sealer 26, Epiphany, Endomethasone and EZ-Fill sealers was assessed in orange oil, eucalyptol, xylol, chloroform and distilled water. Seventy-five samples of root canal sealers were prepared and then divided into five groups for immersion in solvent for 2, 5 or 10 min. The means of loss weight were determined for each material in each solvent at all immersion periods, and the values were compared by factorial analysis of variance (anova) and SNK multiple comparisons.

RESULTS

In the orange and eucalyptus oil groups, there was no significant difference among RoekoSeal, Sealer26, Epiphany and EZ-Fill at the three immersion periods (P > 0.05). With xylol, no significant differences were found at 5 and 10 min (P > 0.05) for each root sealer. Orange and eucalyptus oil solvents were as effective as chloroform at 2 min in dissolving all the root sealers.

CONCLUSIONS

Xylol was the most effective solvent followed by the chloroform and the essential oils (eucalyptol and orange oil). Orange oil behaved in a similar way to eucalyptus oil.

Dissolving efficacy of some organic solvents on gutta-percha

The aim of this study was to evaluate the solubility of gutta-percha in four organic solvents used in endodontics. The solubility of gutta-percha (Dentsply) was assessed in xylol, orange oil, eucalyptol, chloroform and distilled water. A hundred and fifty samples of gutta-percha were prepared using a standardized stainless steel mould and divided into five groups for immersion in the different solvents tested and in distilled water (control group) for 2, 5 and 10 minutes. The means of gutta-percha dissolution in the solvents were obtained by the difference between the pre-immersion original weight and the post-immersion weight in a digital analytical scale (Gehaka - AG2000). Data were statistically analyzed by Analysis of Variance (ANOVA) and multiple comparisons with Scheffe’s test (p < 0.05). The best solvency capacity was obtained with xylol. Chloroform, orange oil and eucalyptol presented similar results, and distilled water did not promote alterations in the gutta-percha.

Biocompatibility of gutta-percha solvents using in vitro mammalian test-system

OBJECTIVES

Taking into consideration that DNA damage and cellular death play important roles during carcinogenesis, the purpose of the present study was to evaluate in vitro genotoxic or cytotoxic effects of chloroform and eucalyptol by single cell gel (comet) assay and trypan blue exclusion test, respectively.

STUDY DESIGN

Chloroform and eucalyptol were exposed to Chinese hamster ovary cells in culture directly for 3 hours at 37 degrees C at final concentrations ranging from 1.25 to 10 microL/mL. The negative control group was treated with vehicle control (phosphate-buffered solution), and the positive control group was treated with methyl metasulfonate (MMS, at 1 microg/mL concentration). All data were analyzed by the Kruskal-Wallis nonparametric test followed by the Dunn test.

RESULTS

The results showed that both gutta-percha solvents were cytotoxic at concentrations of 2.5, 5, and 10 microL/mL (P < .05). On the other hand, both solvents did not induce DNA breakage at 1.25 microL/mL concentration.

CONCLUSIONS

These results suggest that both chloroform or eucalyptol are strong cytotoxicants, but they may not be a factor that increases the level of DNA lesions in mammalian cells.

Retreatment efficacy of hand versus automated instrumentation in oval-shaped root canals: an ex vivo study

AIM

To compare the efficacy of hand versus automated instrumentation when retreating oval-shaped root canals.

METHODOLOGY

Sixty human premolars with single oval canals were instrumented and filled with gutta-percha and sealer and divided into three groups (n = 20)--group 1: ProFile .04 taper rotary instruments; group 2: Anatomic Endodontic Technology (AET), and group 3: manual instrumentation with Hedström files. The teeth were split longitudinally and gutta-percha/sealer remnants in the coronal, middle and apical thirds were assessed with light microscopy. The mean percentage of gutta-percha/sealer remnants for each group was calculated and statistically analysed for significance using an ANOVA repeated measures (P < 0.001) and Tukey's multiple comparison test. The time required for retreatment was analysed using a one-way ANOVA and Tukey's test (P < 0.001).

RESULTS

Overall, 10-18% of the canal walls were covered with gutta-percha/sealer remnants after preparation using any technique. Statistical analysis demonstrated that the mean values for remnants of filling material in the ProFile group were significantly higher than for the other groups (P < 0.001), except in the apical third where no significant difference occurred. In all groups, the mean values in the middle third were higher than the coronal and apical thirds. The retreatment time for ProFile and AET was significantly shorter compared to manual instrumentation with Hedström files (P < 0.001).

CONCLUSIONS

Under the experimental conditions, AET instruments and manual instrumentation with Hedström files resulted in cleaner canals. However, completely clean root canal walls were not produced with any of the techniques investigated.

Comparison Between Gutta-Percha and Resilon Removal Using Two Different Techniques in Endodontic Retreatment

This study compared the remaining filling material and working time when removing gutta-percha/AH 26 and Resilon/Epiphany from root filled extracted teeth. The root fillings were removed using chloroform and two different rotary systems (K3 and Liberator files). The amount of residual filling material on the canal walls was imaged and measured using image analyzer software. The group filled with Resilon/Epiphany and retreated with K3 files demonstrated the least residual filling material on the walls (p < 0.05). There was no statistically significant difference between the gutta-percha/AH26 and Resilon/Epiphany groups when the Liberator files were used (p > 0.05). In the groups filled with Resilon/Epiphany, the filling was removed faster than groups filled with gutta-percha/AH 26 (p < 0.05). K3 rotary system was faster than Liberator to remove both gutta-percha and Resilon (p < 0.05). Resilon/Epiphany was effectively removed with K3 or Liberator rotary files.

In vitro cytotoxic and non-genotoxic effects of gutta-percha solvents on mouse lymphoma cells by single cell gel (comet) assay

Chloroform and eucalyptol are widely used in clinical dentistry as gutta-percha solvents. However, these compounds may represent a hazard to human health, especially by causing injury to genetic apparatus and/or inducing cellular death. In this study, the genotoxic and cytotoxic potentials associated with exposure to chloroform and eucalyptol were assessed on mouse lymphoma cells in vitro by the single cell gel (comet) assay and trypan blue exclusion test, respectively. Both gutta-percha solvents proved to be cytotoxic at the same levels in concentrations of 2.5, 5 and 10 muL/mL (p<0.05). On the other hand, neither of the solvents induced DNA breakage. Taken together, these results suggest that although both tested compounds (chloroform and eucalyptol) are strong cytotoxicants, it seems that they are not likely to increase the level of DNA damage on mammalian cells.

Dissolving efficacy of organic solvents on root canal sealers

The aim of this study was to evaluate the solubility of three types of root canal sealers in three organic solvents used in endodontics. The solubility of calcium-hydroxide-based (Sealer 26), silicon-polydimethylsiloxane-based (RoekoSeal), and zinc-oxide-eugenol based (Endofill and Intrafill) sealers was assessed in eucalyptol, xylol, orange oil, and distilled water. Eighty samples of each filling material were prepared according to the manufacturers' instructions and then divided into four groups for immersion in solvent for 2 or 10 min. The means of sealer dissolution in solvents were obtained by the difference between the original preimmersion weight and the postimmersion weight in a digital analytical scale. Data were statistically analyzed with the Student's t test, and multiple comparisons were performed with Student-Newman-Keuls. Xylol and orange oil showed similar effects, with significant solubilization (P<0.05) of the tested cements. Endofill and Sealer 26 did not show any significant difference in solubilization at the two immersion times, whereas RoekoSeal and Intrafill showed a more pronounced solubility at 10 min. The lowest levels of solubilization occurred in RoekoSeal, Sealer 26, Endofill, and Intrafill. It is concluded that xylol and orange oil presented similar solvent effects with a significant solubility of the tested cements.

The Effect of Endodontic Solutions on Resorcinol-Formalin Paste in Teeth

This study determined if any of six endodontic solutions would have a softening effect on resorcinol-formalin paste in extracted teeth, and if there were any differences in the solvent action between these solutions. Forty-nine single-rooted extracted teeth were decoronated 2 mm coronal to the CEJ, and the roots sectioned apically to a standard length of 15 mm. Canals were prepared to a 12 mm WL and a uniform size with a #7 Parapost drill. Teeth were then mounted in a cylinder ring with acrylic. The resorcinol-formalin mixture was placed into the canals and was allowed to set for 60 days in a humidor. The solutions tested were 0.9% sodium chloride, 5.25% sodium hypochlorite, chloroform, Endosolv R (Endosolv R), 3% hydrogen peroxide, and 70% isopropyl alcohol. Seven samples per solution were tested and seven samples using water served as controls. One drop of the solution was placed over the set mixture in the canal, and the depth of penetration of a 1.5-mm probe was measured at 2, 5, 10, and 20 min using a dial micrometer gauge. A repeated-measures ANOVA showed a difference in penetration between the solutions at 10 min (p = 0.04) and at 20 min (p = 0.0004). At 20 min, Endosolv R, had significantly greater penetration than 5.25% sodium hypochlorite (p = 0.0033) and chloroform (p = 0.0018); however, it was not significantly better than the control (p = 0.0812). Although Endosolv R, had statistically superior probe penetration at 20 min, the softening effect could not be detected clinically at this time.

Removal of Two Types of Root Canal Filling Material Using Pulsed Nd:YAG Laser Irradiation

OBJECTIVE

The aim of this study was to examine the usefulness of a pulsed Nd:YAG laser in removing two types of endodontic obturation material from the root canal in vitro.

BACKGROUND DATA

Recently, a fine flexible glass fiber made of quartz has been developed to transmit the laser beam more effectively and permit its concentration in a specific area. This has increased the potential usefulness of the Nd:YAG laser in root canal treatment.

METHODS

The time required for removing the root canal obturation material (Gutta-percha cones and, Sealapex or AH26) by means of either Nd:YAG laser irradiation or a conventional method (Gates Glidden drills and K files) was measured. Contact microradiography was used to assess the radiopacity of the root canals before and after the removal of obturation material. The surfaces of the root canal after removal of the obturation materials were also observed by scanning electron microscopy.

RESULTS

Although none of the methods used in this study resulted in complete removal of debris from the root canal wall, the time required for the removal of any of the root canal obturation materials using laser ablation was significantly shorter than that required using the conventional method (p < 0.05). It appeared that some orifices of the dentinal tubules were blocked with melted dentin following laser irradiation.

CONCLUSIONS

Nd:YAG laser irradiation is an effective tool for the removal of root canal obturation materials, and may offer advantages over the conventional method.

Effect of Solvents on Bonding to Root Canal Dentin

The long-term success of resin cementation of post/cores is likely increased with improvement in resin-root canal dentin bonding. The adverse effect of some irrigation constituents (NaOCl, H2O2) or medications (eugenol) on the bond strengths of resins to dentin have been reported. The purpose of this in vitro study was to evaluate the effect of two gutta-percha solvents (chloroform versus halothane) on microtensile bond strength to root canal dentin. Thirty, extracted, human, single-rooted teeth were instrumented to a #70 file and randomly divided into 3 groups of 10 each. The root canals were treated with water, chloroform, or halothane for 60 s. All root canals were obturated using C&B Metabond. After 24 h of storage in distilled water, serial 1-mm-thick cross-sections were cut and trimmed. Microtensile bond strength to apical, middle, and coronal root canal dentin were measured using an Instron machine. Using pooled data, the results indicated that water-treated roots had significantly higher resin-dentin bond strengths compared with chloroform or halothane treatment groups (control: 23.9 MPa; chloroform: 18.3 MPa; halothane: 17 MPa; p < 0.05). Gutta-percha solvents have an adverse effect on bond strengths of adhesive cements to root canal dentin.

Efficacy, cleaning ability and safety of different rotary NiTi instruments in root canal retreatment

AIM

To evaluate the efficacy, cleaning ability and safety of three different rotary nickel-titanium instruments with and without a solvent (eucalyptol) versus hand files in the removal of gutta-percha root fillings.

METHODOLOGY

Eighty extracted single-rooted anterior teeth were enlarged to size 35 and obturated with laterally condensed gutta-percha using AHPlus as the sealer. Removal of gutta-percha was performed with the following devices and techniques: FlexMaster, GT Rotary, ProTaper and Hedström files. All techniques were used with and without the solvent eucalyptol. The following data were recorded: time taken to reach the calculated working length and time required for the removal of gutta-percha. The teeth were split longitudinally and photographed. Cleanliness of the root canal walls was scored using the projected slides with a total magnification of approximately 70x. Statistical analysis was performed using the two-way anova (P < 0.001) for the analysis of working time.

RESULTS

The technique that reached the working length most rapidly was that using ProTaper instruments and eucalyptol (+E), followed by FlexMaster + E, ProTaper, FlexMaster, Hedström files + E, GT Rotary + E, Hedström files, and GT Rotary. No significant differences were found for retreatment with or without a solvent in all groups. ProTaper and FlexMaster worked significantly more rapidly than Hedström files and GT Rotary (anova, P < 0.001). Time for complete removal of gutta-percha was again shortest with ProTaper + E, followed by FlexMaster + E, ProTaper, FlexMaster, GT Rotary + E, Hedström files + E, Hedström files, and GT Rotary. ProTaper and FlexMaster again worked significantly faster than the other techniques (anova, P < 0.001). There was no visible filling material extruded apically. Root canal cleanliness proved best following the use of FlexMaster + E, and Hedström files + E, followed by ProTaper + E, and GT Rotary + E.

CONCLUSION

Under the experimental conditions, FlexMaster and ProTaper NiTi instruments proved to be efficient and time-saving devices for the removal of gutta-percha. The use of eucalyptol as a solvent shortened the time to reach the working length and to remove the gutta-percha, but this was not significant.

In vitro study of effect of solvent on root canal retreatment

The aim of this study was to assess the effectiveness of five different solvents: xylol, eucalyptol, halothane, chloroform and orange oil on softening gutta-percha in simulated root canals. One drop of solvent was placed into a reservoir made in a simulated canal whose channel was previously instrumented and filled with gutta-percha and N-Rickert sealer. After 5 min, softening was evaluated for each solvent by the penetration of a spreader while applying force with a 442 Instron apparatus to reach a depth of 5 mm. The results were analyzed statistically by the Kruskal-Wallis test. Xylol and orange oil were better in softening gutta-percha than the other solvents. There was no significant difference between xylol and orange oil, but these were statistically different from eucalyptol, halothane and chloroform (p < 0.01).

The effect of endodontic solutions on resorcinol-formalin paste

This study determined if any of four endodontic solutions would have a softening effect on resorcinol-formalin paste and if there were any differences in the solvent action between these solutions. Resorcinol, formalin, and zinc oxide were mixed and allowed to set for 30 days. The solutions tested were 0.9% sodium chloride, 5.25% sodium hypochlorite, chloroform, and Endosolv R. Seven samples per solution were tested and an additional seven samples served as controls. Each sample was saturated with one of the solutions and the depth of penetration was tested at 1, 2, 5, 10, and 20 min using a dial strain gauge. At 2 min, sodium hypochlorite and sodium chloride had significantly greater penetration than the other groups (p < 0.0010). Sodium hypochlorite was superior to all other groups after 5 min. This study showed that both sodium chloride and sodium hypochlorite exhibited a significant softening effect within 2 min.

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.

The efficacy of gutta-percha removal using ProFiles

AIM

The purpose of this study was to compare the efficacy in vitro of gutta-percha removal from obturated root canals using ProFiles.

METHODOLOGY

Forty-eight human root canals with curvatures ranging between 25 and 45 degrees were instrumented by a standardized method to an apical ISO size 30 and 0.04 taper. They were obturated with vertically condensed gutta-percha. Retreatment was performed with the following techniques: K-Flexofiles with chloroform; Hedstrom files with chloroform; ProFiles 0.04 taper with chloroform; ProFiles 0.04 taper alone. The time for each method was measured. A microfocal macroradiographic technique was used to evaluate the amount of debris remaining within the root canals after the retreatment procedure. Roots were divided into apical, middle and coronal parts and scored on a scale of 0 (no debris) to 3 (> 50% of walls covered with debris) by trained observers on two separate occasions.

RESULTS

The scores for debris remaining within root canals for K-Flexofiles with chloroform and ProFiles with chloroform were the lowest and not significantly different at all three levels of the roots examined (P > 0.05), and Hedstrom files with chloroform and ProFiles with chloroform were not significantly different in the apical part. In general, coronal parts were cleaner than apical parts. The difference in scores at the three levels between ProFiles with chloroform and ProFiles alone were each significant (P < 0.01). Instrumentation using ProFiles with chloroform (mean 6.42 min) was significantly faster than using hand files (mean 11.67 min) (P < 0.01).

CONCLUSION

The results indicated that ProFiles or hand files with chloroform produced similarly clean canals, but that ProFiles were faster.

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.

Effectiveness of ProFile .04 taper rotary instruments in endodontic retreatment

This study investigated the retreatment effectiveness of .04 Taper nickel-titanium rotary ProFiles. Thirty extracted single-rooted anterior teeth were instrumented and obturated with gutta-percha/Roth's Sealer using lateral condensation. They were distributed into three groups of 10 each. Retreatment for group A was done using Profile alone, group B using Profile and chloroform, and group C using hand files with chloroform. The teeth were then split longitudinally into halves. The remaining gutta-percha/sealer on the root canal wall in the cervical, middle, apical thirds, and the whole canals were visually scored with the aid of light microscopes. The results showed that the mean scores in groups A and B were generally lower (better) than group C. Mean scores of the apical thirds tended to be higher (worse) than the middle and the cervical thirds, except in group A. ProFile with or without chloroform seemed to be a viable alternative retreatment method.

Dissolution of root canal sealer cements in volatile solvents

AIM

There are few published data on the solubility profiles of endodontic sealers in solvents commonly employed in root canal retreatment. This study tested the hypothesis that root canal sealer cements are insoluble in the volatile solvents chloroform and halothane.

METHODOLOGY

Standardized samples (n = 5) of glass ionomer (Ketac Endo), zinc oxide-eugenol (Tubli-Seal EWT), calcium hydroxide (Apexit) and epoxy resin (AH Plus) based sealers were immersed in chloroform or halothane for 30 s, 1 min, 5 min and 10 min. Mean loss of weight was plotted against time of exposure, and differences in behaviour assessed by multiple paired t-tests (P < 0.01).

RESULTS

Clear differences were shown in the solubility profiles of major classes of root canal sealer cements in two common volatile solvents. In comparison with other classes of material, Ketac Endo was the least soluble in chloroform and halothane (P < 0.01), with less than 1% weight loss after 10 min exposure to either solvent. Apexit had low solubility with 11.6% and 14.19% weight loss after 10 min exposure to chloroform and halothane, respectively. The difference between solvents was not significant (P > 0.01). Tubli-Seal EWT was significantly less soluble in halothane than chloroform (5.19% and 62.5% weight loss after 10 min exposure, respectively (P < 0.01)). Its solubility in halothane was not significantly different from that of Apexit. AH Plus was significantly more soluble than all other materials in both chloroform and halothane (96% and 68% weight loss after 10 min exposure, respectively (P < 0.01)).

CONCLUSIONS

There are significant differences in the solubility profiles of major classes of root canal sealer in common organic solvents. Efforts should continue to find a more universally effective solvent for use in root canal treatment.

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.

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.

Efficacy, cleaning ability and safety of different devices for gutta-percha removal in root canal retreatment

The purpose of this study was to evaluate the efficacy, cleaning ability and safety of five different devices and techniques to remove gutta-percha root canal fillings. One hundred and twenty extracted single-rooted anterior and premolar teeth were enlarged to ISO size 35 and obturated with laterally condensed gutta-percha using AH 26 as the sealer. Removal of gutta-percha was performed with the following devices and techniques: (a) Gates-Glidden and Hedstrom files, (b) only Hedstrom files, (c) Hedstrom files and chloroform, (d) the Endotec and Hedstrom files, and (e) the XGP drill and Hedstrom files. The following data were recorded: time taken to reach the desired working length, time required for the removal of the gutta-percha, and the amount of material extruded apically. The teeth were split longitudinally and photographed. Cleanliness of the root canal walls was scored using the projected slides with a total magnification of approximately 70x. The fastest technique to reach the working length was using the XGP drill (e), followed by the Gates-Glidden drills (a), Hedstrom files and chloroform (c), and the Endotec device (d). The use of Hedstrom files (b) without any additional support proved to be most time-consuming. Differences were statistically significant (U-test, P > 0.05) between the rotary devices and the manual techniques. Time for complete removal of gutta-percha was again shortest with the XGP drills (e), followed by the Gates-Glidden burs (a), the Endotec device (d), Hedstrom files with chloroform (c), and Hedstrom files alone (b). The XGP burs and the Gates-Glidden drills worked significantly faster than the other techniques. The amount of debris and filling material extruded apically in most cases did not exceed 0.1 mg. No significant differences could be detected between the groups (U-test, P > 0.05). Root canal cleanliness proved best following the use of Hedstrom files without additional support (b) and the Gates-Glidden drills (a), followed by Hedstrom files in combination with chloroform (c), the XGP-gutta-percha remover (e), and the Endotec device (d). When using the XGP two instrument fractures occurred in the apical parts of the root canals preventing further instrumentation to the apical foramen. When using the Gates-Glidden burs four instrument fractures occurred, but all fragments could be removed with forceps immediately. The results suggest that the XGP gutta-percha remover and the Gates-Glidden drills are efficient and time saving devices to remove gutta-percha but include a certain risk of instrument breakage and may leave some filling material inside the root canal. The best root canal cleanliness was achieved with Hedstrom files alone which, on the other hand, were shown to be the most time-consuming.

Chloroform uptake by gutta-percha and assessment of its concentration in air during the chloroform-dip technique

The use of chloroform as an adjunct to the practice of endodontics has been a matter of debate. In the present study the chloroform uptake of gutta-percha cones was determined by a gravimetric assay for different times of chloroform dip. In conjunction with an assessment of the amount of gutta-percha dissolved during dip, this provided an estimate of the amount of chloroform that patients are exposed to in clinical conditions. An assay was also performed of the chloroform concentration in the air in a dental office. Chloroform uptake was shown to increase with an increasing dipping time. There also seems to be a difference in this uptake between pure chloroform and a chloroform preparation with colophonium. The concentration levels of chloroform evaporated during the practice of chloroform dip within a dental office do not exceed the safety limits.

Using a 1-ml syringe for the chloroform dip root canal filling technique

This article describes using a 1-ml syringe as an alternative to a dappen dish to hold chloroform during the chloroform dip root canal filling technique. The syringe effectively holds chloroform while limiting its exposure to the endodontic operatory air.

The relationship between the root canal filling and post space preparation

The restoration of root treated teeth often requires the use of posts. Their use may affect the quality of the seal of the root canal filling. The various aspects of the relationship between root canal filling and post space preparation are discussed in this review. It is recommended that the use of posts should be avoided whenever possible. Where the preparation of post space is required, immediate removal of gutta-percha using heated instruments and small Gates Glidden drills is the method of choice.

Exposure of dental personnel to chloroform in root-filling procedures

The exposure of dental personnel to chloroform in root-filling procedures was evaluated. Four different root filling procedures were studied. In all the procedures studied, guttapercha was used as the root-filling material and chloroform or sealers containing chloroform were used. Ten teeth in each group were root-filled. In the first group, chloroform and 5% rosin in chloroform were administered in medical cups, in the second group chloroform and Kloroperka NO was administered in medical cups. In Group three a specially designed glass tube (S-endodip) was used for administration and in the fourth group specially selected plastic tubes were used. In the last two groups the sealers were chloroform and 5% rosin in chloroform. When medical cups were used the exposure reached levels close to the accepted limit values in Sweden, indicating that only one root filling per day can be performed without the dental team being unacceptably exposed. Using either the glass tube or the specially designed plastic tube, the exposure was significantly reduced for the dentist (p < 0.005) and for the nurse (p < 0.005). The mean exposure was 19.1 mg/m3 for the dentist and 11.6 mg/m3 for the nurse in the first experimental group. The mean values in the second group were 15.4 mg/m3 and 16.6 mg/m3 respectively. In the third group, the dentist was exposed to a mean of 4.4 mg/m3 and the nurse to 6.3 mg/m3. In the fourth group, the mean exposure was 2.2 mg/m3 and 3.4 mg/m3 respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Endodontic retreatment--case selection and technique. 3. Retreatment techniques

The necessity to remove filling materials from the root canals is one of the major differences between primary endodontic therapy and retreatment. The obturating material has to be removed from the root canals before routine endodontic therapy can be performed. The removal of the material should not result in a change in the canal morphology, so that the objectives of endodontic therapy can be maintained. Numerous techniques may be used for removing filling materials and other obstructions from root canals. This article reviews the techniques that were suggested in the literature for this purpose and discusses their advantages and disadvantages.