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).     

Evaluation of alternatives to chloroform in endodontic practice

Chloroform is used in endodontics for plasticizing gutta-percha points and for facilitating removal of gutta-percha root canal fillings in need of re-treatment. Adverse health effects from exposure to chloroform have been reported, and to improve occupational health, it would be advantageous if a less hazardous solvent could replace chloroform. In this study, methylene chloride, methyl chloroform, tetrahydrofuran, xylol and eucalyptol were tested for their capacity to dissolve or soften gutta-percha points compared with chloroform. The effect of the test solvents was assessed by measuring the depth of penetration of a small indentor of fixed weight and shape into a gutta-percha disk covered with the test solution for various time periods. Chloroform showed the most pronounced effect, followed by methylene chloride, tetrahydrofuran, and methyl chloroform. When both occupational health and gutta-percha solvent capacity were considered, methyl chloroform seemed to be an interesting alternative to chloroform.     

Effectiveness of halothane used with ultrasonic or hand instrumentation to remove gutta-percha from the root canal

This study compared halothane and chloroform used with hand or ultrasonic instrumentation to remove gutta-percha and sealer from root canals. Apically extruded debris, residual debris, time for filling removal, and amount of solvent used were determined. The differences in extruded apical debris and radiographically visible residual debris were not significant (p greater than 0.05). Ultrasonic instrumentation required significantly less time to remove the root canal filling than did hand instrumentation (p = 0.02). The only significant difference in the amount of solvent used occurred when the ultrasonic-chloroform group was compared with the hand instrumentation-chloroform group (p = 0.05). Halothane was found to be an acceptable alternative to chloroform for removing gutta-percha and sealer from the obturated root canal.     

Evaluation of alternatives to chloroform in endodontic practice

Abstract Chloroform is used in endodontics for plasticizing gutta-percha points and for facilitating removal of gutta-percha root canal fillings in need of re-treatment. Adverse health effects from exposure to chloroform have been reported, and to improve occupational health, it would be advantageous if a less hazardous solvent could replace chloroform. In this study, methylene chloride, methyl chloroform, tetrahydrofuran, xylol and eucalyptol were tested for their capacity to dissolve or soften gutta-percha points compared with chloroform. The effect of the test solvents was assessed by measuring the depth of penetration of a small indentor of fixed weight and shape into a gutta-percha disk covered with the test solution for various time periods. Chloroform showed the most pronounced effect, followed by methylene chloride, tetrahydrofuran, and methyl chloroform. When both occupational health and gutta-percha solvent capacity were considered, methyl chloroform seemed to be an interesting alternative to chloroform.     

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.     

Does cold burnishing gutta-percha create a better apical seal?

This study investigated the seal created by cold burnishing the gutta-percha exposed after apical root resection of endodontically treated teeth. Sixty single-rooted extracted human teeth with a single straight canal were divided into four experimental groups of 15 teeth each. In two of the experimental groups the canals were instrumented and obturated well with laterally condensed gutta-percha and sealer. The remaining two groups were instrumented and poorly obturated with laterally condensed gutta-percha and sealer. The apical 2 mm of all the teeth were then resected and the effect of cold burnishing the exposed gutta-percha was investigated using a linear dye penetration technique. Under the condition of this study, cold burnishing gutta-percha after apical root resection of a well-obturated root canal resulted in a poorer apical seal than if no burnishing were performed. Cold burnishing the exposed gutta-percha after apical root resection of poorly obturated root canals improved the apical seal as compared with nonburnished poorly obturated canals.     

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.     

Evaluation of the Trifecta obturating technique

The aim of this project was to evaluate and compare the radiographic quality and sealability of root fillings in extracted human teeth using lateral condensation of gutta-percha or the Trifecta obturating system. One hundred freshly extracted human mature, single-rooted teeth were divided into four identical groups of 25 teeth on the basis of root canal shape. The root canals of two groups were prepared in such a way as to produce a relatively parallel canal shape with little or no flare towards the coronal orifice. The root canals of the other two groups were prepared in such a way as to produce a canal shape that was deliberately more flared to ensure that they were wider at the orifice than at the endpoint of the preparation. All root canals were flushed with 17% EDTA solution and 2.5% NaOCl to remove the dentinal smear layer. The canals of one flared and one parallel group were obturated using cold lateral condensation and the canals of the other two groups were obturated using the Trifecta system. The sealability of each technique was assessed by a dye penetration method. The radiographic quality of obturation was determined for each canal using a 4-point scale. Canals filled with thermoplasticised gutta-percha had significantly less apical dye penetration than those obturated by lateral condensation (P < 0.001). Lateral condensation achieved significantly better scores for radiographic quality than thermoplasticised gutta-percha from both the bucco-lingual (P < 0.001) and the mesio-distal views (P < 0.001). Root canals obturated using the Trifecta technique showed significantly more apical extrusion of sealer than those obturated by lateral condensation (P < 0.001). Under laboratory conditions the Trifecta technique had better sealability but poorer radiographic quality than lateral condensation.     

Residue of gutta-percha and a glass ionomer cement sealer following root canal retreatment

A previous report indicates that root canals obturated with a new glass ionomer cement endodontic sealer (Ketac-Endo, Espe, Germany) and laterally condensed gutta-percha can be retreated by ultrasonic instrumentation. To address the possibility of Ketac-Endo being used without condensation of gutta-percha, the purpose of this study was to evaluate the efficacy of ultrasonic retreatment in canals obturated with single-cone gutta-percha and Ketac-Endo. Thirty root canals were prepared in a standardized way to ISO size 40 and obturated with gutta-percha and Ketac-Endo. Either a size 40 gutta-percha cone was used with and without lateral condensation, or a size 25 single cone, without condensation. After 14 days, the canals were retreated using chloroform and ultrasonic instrumentation. The roots were split vertically, and the amount of residual debris on the canal walls was assessed by three examiners using a dissecting microscope. Debris was recorded in the apical, middle and coronal canal levels according to a preset evaluation scale. The mean scores for each group were compared by ANOVA and Mann-Whitney U-test, with a 5% level of significance. In the roots obturated with lateral condensation the amount of residual debris in the coronal and middle canal levels was lower than in the other two groups, whereas in the apical level it was higher. Statistically, only the differences in the apical level were significant (P < 0.03). It was concluded that ultrasonic retreatment may be performed effectively in root canals obturated with single-cone gutta-percha and Ketac-Endo.     

Comparison of laterally condensed and low-temperature thermoplasticized gutta-percha root fillings

The aim of this study was to evaluate and compare the radiographic quality and sealability of root fillings in extracted human teeth using lateral condensation of gutta-percha or low-temperature thermoplasticized gutta-percha (Ultrafil). One hundred freshly extracted human, mature single-rooted teeth were divided into four identical groups of 25 teeth on the basis of root canal shape. The root canals of two groups were prepared in such a way to produce a relatively parallel shape with little or no flare toward the coronal orifice. The root canals of the other two groups were prepared in such a way as to produce a canal shape that was deliberately more flared to ensure that they were wider at the orifice than at the end point of the preparation. All root canals were flushed with 17% EDTA solution and 2.5% NaOCl to remove the dentinal smear layer. The canals of one flared group and one parallel group were obturated using cold lateral condensation, and the canals of the other two groups were obturated using low-temperature thermoplasticized gutta-percha. The sealability of each technique was assessed by a dye penetration method. The radiographic quality of obturation was determined for each canal using a 4-point scale. Canals filled with thermoplasticized gutta-percha had significantly less apical dye penetration than those obturated by lateral condensation (p < 0.001). Lateral condensation achieved significantly better scores for radiographic quality than thermoplasticized gutta-percha from both the buccolingual (p < 0.005) and mesiodistal views (p < 0.001). Low-temperature thermoplasticized gutta-percha root fillings were associated with significantly more apical extrusion of sealer (p < 0.001) and gutta-percha (p < 0.005). Under laboratory conditions the low-temperature thermoplasticized gutta-percha had better sealability but poorer radiographic quality than lateral condensation.     

Cleanliness of dentinal tubules following gutta-percha removal with and without solvents: a scanning electron microscopic study

Aim  To determine the influence of solvents on gutta-percha and sealer remaining on root canal walls and in dentinal tubules.
Methodology  The root canals of 70 teeth were prepared chemomechanically to apical size 40. In group 1 ( n  = 10; control group), the canals remained unfilled. In groups 2–4 ( n  = 20 each), the canals were filled using lateral compaction with gutta-percha and sealer. Removal of root fillings was undertaken after 2 weeks using Gates Glidden burs and hand files without solvent (group 2), with eucalyptol (60 μL; group 3) and with chloroform (60 μL; group 4) to size 50. After further irrigation using sodium hypochlorite and ethylenediaminetetraacetic acid, the roots were split, photographed and scanning electron microscopy (SEM) was performed. The number of filled dentinal tubules (SEM) and the surface covered by root filling remnants (photographs) were evaluated for the coronal, middle and apical third of each root half. Statistical analysis was performed via mixed model for clustered data followed by Tukey's test.
Results  After pooling the results of all thirds of the canal, open tubules were more prevalent in the control group, followed by the nonsolvent group, the eucalyptol group and the chloroform group ( P  < 0.05 between all groups). Less surface was covered by root filling remnants in the nonsolvent group than in the eucalyptol group and the chloroform group ( P  < 0.05); again, fewer remnants were found in the control group than in all other groups ( P  < 0.05).
Conclusions  Solvents led to more gutta-percha and sealer remnants on root canal walls and inside dentinal tubules.     

A comparison of apical seal: chloroform versus halothane-dipped gutta-percha cones.

A dye penetration study was done to compare apical leakage among three groups of extracted teeth obturated with a lateral condensation technique. In one group the master gutta-percha cones were customized in the apical portion of the canals after being dipped in chloroform. A second group used halothane as the customizing agent. No dip was used in the third group, and all three were then laterally condensed. The teeth were cleared and dye penetration was measured. Statistical analysis using a Kruskal-Wallis one-way analysis of variance of the data showed no significant difference among the groups at the p < 0.05 level.     

A comparison of apical seal: chloroform versus eucalyptol-dipped gutta-percha obturation

Three groups of extracted teeth were obturated using gutta-percha and lateral condensation. In one group the gutta-percha was dipped in chloroform before condensation. In a second a eucalyptol dip was used. No dip was used in the third group. A dye penetration study was done to compare leakage among the three groups. The teeth were cleared for viewing and measurements of dye penetration were made using a stereomicroscope. Statistical analysis using Kruskal-Wallis one-way analysis of variance of the results showed no significant difference among test groups at the 0.05 level.     

Effect of apical resections and reverse fillings on Thermafil root canal obturations

This in vitro dye leakage study examined the influence of apical root resection and reverse amalgam fillings on the apical seal of root canals obturated with Thermafil. Fifty human canine teeth were instrumented and obturated with either laterally condensed gutta-percha or Thermafil using Roth's zinc oxide-eugenol Type I regular sealer. After 24 h, one of the following additional procedures was performed on 30 of the teeth: 2-mm apical resection, 4-mm apical resection, and 2-mm apical resection plus reverse amalgam filling 2 mm in depth and diameter. The external root surfaces were coated with enamel paint and the teeth were exposed to 1% methylene blue dye at 37 degrees C for 2 wk. The roots were split longitudinally and the depth of linear dye penetration was measured through a stereozoom microscope. Statistical analysis showed no significant differences in the linear dye penetration among the various groups of teeth.     

In vitro evaluation of three techniques to obturate 0.06 taper canal preparations

The aim of this study was to evaluate the ability of three obturation methods to seal root canals prepared using 0.06 taper rotary instruments. Forty-five extracted human single-rooted teeth were instrumented with 0.06 taper Profile nickel-titanium rotary files and randomly divided into three experimental groups containing 15 teeth each. The first group was obturated using the System B technique with 0.06 taper standardised gutta-percha points, the second group was obturated using the System B technique with non-standardised MF gutta-percha points, the third group was obturated by cold lateral condensation technique using standardised 0.02 taper master gutta-percha points. Apical leakage of the roots was evaluated by dye penetration using a stereomicroscope after sectioning the roots. The group obturated using System B and 0.06 taper gutta-percha points showed the least dye penetration. However, the difference in the linear extent of dye penetration was not statistically significant.     

Evaluation of the apical leakage of isobutyl cyanoacrylate when used as a root canal sealant

The sealing properties of isobutyl cyanoacrylate were evaluated in extracted single-rooted human teeth. In the experimental group, instrumented root canals were obturated with isobutyl cyanoacrylate and gutta-percha by using the lateral condensation technique. In the control group instrumented root canals were obturated with gutta-percha only. The penetration of radioactive 131I was evaluated by an autoradiographic technique. No leakage was observed in the experimental group. This study shows that isobutyl cyanoacrylate is a good apical sealant.     

Comparison of the obturation of lateral canals by six techniques.

The following obturation techniques were compared on their ability to obturate lateral canals in vitro, lateral condensation (LC), continuous wave of condensation (CW), warm vertical condensation (WV), carrier-based thermoplasticized gutta-percha (CB), warm lateral condensation (WL), and vertically condensed high-temperature gutta-percha (HT). A root canal system with lateral canals in the coronal, middle, and apical thirds was prepared in resin blocks. Each block was obturated using each technique (n = 30, 15 each, with and without sealer). The length of gutta-percha and sealer in each of the lateral canals was measured with a measuring microscope and statistically compared. All techniques obturated all three levels of lateral canals with sealer. WV, CB, and CW were able to fill the lateral canals with gutta-percha significantly better when root canal sealer was used. WV, CB, CW, and HT filled the coronal and middle lateral canals significantly better with gutta-percha than LC or WL condensation. CB and CW filled the apical lateral canal significantly better with gutta-percha than HT, WV, WL, or LC.     

Comparison of cold lateral condensation and a warm multiphase gutta-percha technique for obturating curved root canals

AIM: The aim of this project was to evaluate and compare the radiographic quality and sealability of root fillings in extracted human teeth using lateral condensation of gutta-percha or multiphase gutta-percha obturation (Alphaseal). METHODOLOGY: A total of 108 freshly extracted human, mature single-rooted teeth were divided into two identical groups of 54 teeth on the basis of root canal shape. The canals were prepared to a minimum 0.055 taper and enlarged to size 35 at the apex. All root canals were flushed with 17% EDTA solution and 2.5% NaOCl to remove the dentinal smear layer. The canals of one group were obturated using cold lateral condensation of gutta-percha and the canals of the other group were filled using a warm multiphase gutta-percha obturation technique. The extrusion of sealer and/or gutta-percha through the apex of the teeth was recorded using a simple yes/no scheme. The sealability of each technique was assessed by a dye penetration method. The radiographic quality of obturation was determined for each canal using a four-point scale. RESULTS: Root canals filled by multiphase obturation had significantly more extrusion of sealer (P < 0.001) and gutta-percha (P < 0.001) than canals filled by lateral condensation. Canals filled by multiphase gutta-percha obturation had significantly less apical dye leakage than those obturated by lateral condensation (P < 0.05). Lateral condensation achieved significantly better scores for radiographic quality than multiphase obturation from the bucco-lingual view (P < 0.01). CONCLUSIONS: Under laboratory conditions multiphase gutta-percha had better sealability but poorer radiographic quality than lateral condensation.     

Evaluation of the apical seal in root canals prepared with a new rotary system and obturated with a methacrylate based endodontic sealer: an in vitro study

The purpose of this study was to evaluate in vitro the apical seal of root canals prepared with a new rotary system, Anatomic Endodontic Technology (AET) and filled with a methacrylate based endodontic sealer and a single gutta-percha cone and a lateral condensation technique, using the methacrylate based endodontic sealer/filler or Grossman's cement. The root canals of 45 freshly extracted human maxillary anterior teeth were prepared and then randomly assigned to three groups of 15 teeth each. After cleaning and shaping the teeth were obturated as follows: in group 1 the canals were filled with a methacrylate based sealer and a single gutta-percha cone; in group 2 the canals were filled using a lateral condensation technique with gutta-percha and the methacrylate based sealer; and in group 3, the canals were filled by means of lateral condensation of gutta-percha and Grossman's cement (control group). The specimens were stored in 100% relative humidity at 37 degrees C for 72 h, after which the coronal portion and the root surface of each tooth was covered with three layers of nail varnish and a final layer of sticky wax. After immersion in 2% methylene blue dye for 7 days, the specimens were imbedded in clear orthodontic resin and sectioned. Dye penetration was evaluated by an independent investigator using a stereo microscope. The results demonstrated that more pronounced leakage occurred in root canals obturated with the lateral condensation technique and Grossman's cement (p < 0.05). The least amount of dye leakage was observed for group 1 and 2 in which the methacrylate based sealer was used, either with a single gutta-percha cone or with lateral condensation of gutta-percha.     

Effectiveness of different obturation techniques in the filling of simulated lateral canals

The purpose of this in vitro study was to evaluate the ability of lateral compaction of gutta-percha and of five thermoplasticized gutta-percha filling techniques to obturate simulated lateral canals. Sixty extracted single-rooted human teeth were instrumented at the working length to a #35 file before creating three simulated lateral canals on the mesial and distal surfaces of the root, one in each third, using a #15 engine reamer. After enlarging root canals to a #45 file, the teeth were randomly divided into six equal groups of 10 and obturated according to the following techniques: lateral compaction of gutta-percha (group A), hybrid technique (group B), Ultrafil (group C), Obtura II (group D), System B + Obtura II (group E), and Thermafil (group F). AH26 was used as the sealer. A greater number of simulated lateral canals were obturated when Ultrafil, Thermafil, and System B + Obtura II were used, in comparison with canals obturated with the hybrid technique, Obtura II, or lateral compaction of gutta-percha. This difference was statistically significant (p < 0.05). No statistically significant differences were found between results obtained in the obturation of simulated lateral canals in the different thirds of the root (p > 0.05).