A comparison of leakage of filling materials in demineralized and non-demineralized resected root ends under vacuum and non-vacuum conditions

Present Status and Future Directions - Surgical Endodontics

Endodontic surgery encompasses several procedures for the treatment of teeth with a history of failed root canal treatment, such as root-end surgery, crown- and root resections, surgical perforation repair, and intentional replantation. Endodontic microsurgery is the evolution of the traditional apicoectomy techniques and incorporates high magnification, ultrasonic root-end preparation and root-end filling with biocompatible filling materials. Modern endodontic surgery uses the dental operating microscope, incorporates cone-beam computed tomography (CBCT) for preoperative diagnosis and treatment planning, and has adopted piezoelectric approaches to osteotomy and root manipulation. Crown- and root resection techniques have benefitted from the same technological advances. This review focuses on the current state of root-end surgery by comparing the techniques and materials applied during endodontic microsurgery to the most widely used earlier methods and materials. The most recent additions to the clinical protocol and technical improvements are discussed, and an outlook on future directions is given. While non-surgical retreatment remains the first choice to address most cases with a history of endodontic failure, modern endodontic microsurgery has become a predictable and minimally invasive alternative for the retention of natural teeth.

Evaluation of Coronal Leakage Following Different Obturation Techniques and in-vitro Evalution Using Methylene Blue Dye Preparation

INTRODUCTION

Coronal and apical leakage still remains one of the most important cause for endodontic failure in spite of the presence of advanced endodontic materials. The cause may attribute to different filling techniques, physical and chemical properties of sealers and presence or absence of smear layer assessment of coronal or apical leakage is used as a research method to compare the sealing ability of different techniques and endodontic materials.

AIM

To compare the coronal bacterial leakage using methylene blue in four different obturation techniques after protaper hand instrumentation.

MATERIALS AND METHODS

Ninety extracted single-rooted teeth were instrumented to an apical preparation size F3 Protaper hand files. Twenty teeth were randomly obturated with lateral compaction, 20 with vertical compaction, 20 with combination of vertical and lateral compaction and 20 with Thermafil. Ten teeth were used for positive and negative controls (five teeth in each group). Teeth were kept in 100% humidity for 90 days, and then subjected coronally to Proteus vulgaris for 21 days to assess bacterial leakage. After bacterial challenge, methylene blue was placed coronally for another 21 days, and then scoring was done according to depth of dye leakage. Chi-square test was done for statistical analysis.

RESULTS

Leakage as observed with combination of vertical and lateral compaction was significantly less than vertical compaction, lateral compaction and thermafil carriers during bacterial challenge. However, when dye was used it also showed statistically significant results with thermafil carriers showing the least leakage in comparison to vertical condensation, lateral condensation and combined groups.

CONCLUSION

The study concludes that two different methods i.e. bacterial and dye leakage revealed considerable variation on the same substrate Thus, due to the presence of variability among the results obtained by two different analytical methods used in the present study, the study emphasizes the need for standardization of methods as the lack of standardization hinders the comparison of different endodontic filling techniques.

Influence of reduced air pressure methods on dye penetration in standardized voids

OBJECTIVE

The objective of this study was to evaluate the influence of the moment when reduced pressure is applied on dye penetration patterns.

STUDY DESIGN

Nine hundred and sixty glass capillary tubes of different inner diameter (0.3 mm and 0.8 mm), divided into 48 groups, were submerged into dye in 3 different positions (horizontally, opening upwards, and opening downwards) under different vacuum conditions (passive, 5 kPa, 35 kPa, 70 kPa reduced pressure). When reduced pressure was applied half of the groups were submerged into dye before and half of the groups after the application of reduced pressure. Linear dye penetration was measured. Univariate analysis was performed with Mann-Whitney U test and Kruskal-Wallis test to select variables to be included in the regression model. A multiple logistic regression analysis with backward elimination was performed to assess the influence of different covariates on linear dye penetration.

RESULTS

The multivariate linear regression showed that the moment of vacuuming had the greatest positive effect on linear dye penetration value (beta = 10.6, P < .0001). Also the level of pressure reduction had a positive effect on the outcome variable (beta = 0.2, P < .0001) while the vertical positioning of the tubes has negatively affected the outcome variable both for the open end upside (beta = -1.01, P = .024) and the open end downside (beta = -1.05, P = .019). Diameter of the tubes (P = .442) and immersion time (P = .727) had no effect on the outcome of linear dye penetration.

CONCLUSIONS

Even minimum air pressure reduction applied before immersion of the specimens allowed the dye to extensively penetrate the voids.

Sealing Ability of New Adhesive Root Canal Filling Materials Measured by New Dye Penetration Method

The sealing ability of new adhesive root canal filling materials was evaluated using a new dye penetration method. Twenty-eight single-rooted mandibular premolars were randomly divided into four groups of seven teeth each and filled by lateral condensation using one of these combinations: Resilon point with Epiphany sealer (RE); gutta-percha point with Sealapex sealer (GS); gutta-percha point with dentin activator and Superbond sealer (GDS); or gutta-percha point with Accel primer, dentin activator, and Superbond sealer (GADS). Amount of 0.06% methylene blue dye solution (MB) that leaked from the coronal portion to the apical area was measured with a spectrophotometer at one, four, eight, 15, and 30 days in an accumulative manner. The total amount of leaked MB on day 30 was significantly higher for GDS than the other combinations (p < 0.05).

Effects of different root canal obturation techniques on bacterial penetration

OBJECTIVES

The aim of this study was to compare bacterial penetration following obturation with 5 different techniques.

STUDY DESIGN

This study was performed on 120 teeth including negative control (n = 10), positive control (n = 10), and experimental groups (n = 100). One hundred teeth were randomly divided into 5 groups of 20 teeth each and obturated with System B (Sb), Lateral Compaction (Lc), Thermafil (T), Single ProTaper Gutta-percha (P), and laterally compacted ProTaper Gutta-percha (PLc). Enterococcus faecalis was used for determination of the bacterial penetration. Evaluation was carried out for 60 days.

RESULTS

At 30 days, the chi2 test showed that the slowest penetration was observed in Group Sb and Group PLc, which were not significantly different from each other. The fastest penetration in the all experimental groups was observed in Group T and Group P, which were not significantly different from one another. Also, there was no statistically significance difference (P > .05) among all groups at 60 days.

CONCLUSION

It may be concluded that under the conditions of this study System B and laterally compacted ProTaper Gutta-percha prevent bacterial penetration of the root canal at 30 days. Furthermore, there was no difference among obturation techniques at 60 days.

Bacterial penetration after obturation with four different root canal sealers

The aim of this study was to compare bacterial penetration after obturation with lateral compaction technique using four different root canal sealers. This study was performed on 100 teeth including negative control (n = 10), positive control (n = 10), and experimental groups (n = 80). 80 teeth were randomly divided into five groups of 20 teeth each and obturated with AH 26 (A), AH Plus (AP), Sealapex (S), Ketac-Endo (K) root canal sealers. Evaluation was carried out for 60 days. After 30 days of comparing the bacterial penetration values, total penetration was observed in 85% of the Group AP, and group K, 80% of the group S, and 75% of the group A. According to the results of chi(2) test, there was no statistically significant difference observed between any groups (p > 0.05). After 60 days of comparing the bacterial penetration values, total penetration was observed in 100% of the group AP, group K, and group S and 95% of the group A. It may be concluded that under the conditions of this study, there was no difference in the bacterial penetration of the four root canal sealers tested at 30 and 60 days.

In vitro evaluation of apical sealing in root apex treated with demineralization agents and retrofiled with mineral trioxide aggregate through marginal dye leakage

The purpose of this study was to evaluate the apical seal in root apex treated with different demineralization agents and retrofilled with mineral trioxide aggregate (MTA) using marginal dye leakage. Fifty-six, human single-rooted teeth were instrumented, filled, resected and had retrofilling cavities prepared with ultrasonic tips. Demineralizing agents were applied before the apical cavities were retrofilled with Pro Root MTA. The specimens were assigned to 4 groups (n=14), as follows: group 1 (no demineralizing agent); group 2 (35% phosphoric acid, for 15 s); group 3 (17% EDTA solution, pH 7, for 3 min); and group 4 (24% EDTA gel, pH 7, for 4 min). The extension of dye (2% rhodamine B, at 37 degrees C, for 24 h) penetration was measured in millimeters using a stereomicroscope. Results were statistically analyzed by ANOVA and Tukey's test at 5% significance level. Among the experimental groups, the least extension of dye penetration was observed in group 1 (1.89 mm), followed by groups 2 (2.18 mm), 4 (2.54 mm) and 3 (2.64 mm). No statistically significant differences (p<0.05) were found in marginal microleakage among groups 1, 2 and 4 and groups 2, 3 and 4. Based on the results obtained in this study, it may be concluded that the application of demineralizing agents cannot be recommended when MTA is used in periradicular surgeries.

A Systematic Review of In Vitro Retrograde Obturation Materials

The purpose of this review was two-fold: (a) to determine which retrograde obturation material(s) best prevents dye/ink penetration in vitro; and (b) to determine whether in vitro results agree with in vivo results. A MEDLINE search was conducted to identify in vitro studies published between January 1966 and October, week 4, 2003, conducted on human teeth, and published in English, German, or French language, testing the resistance to retrograde penetration of retrograde filling materials. The MEDLINE search identified 278 published articles. Of those, 115 studies examined the resistance to penetration of various retrograde filling materials, in vitro. Thirty-four studies met all the inclusion and validity criteria. The results indicate that, beyond 10 days in vitro, the most effective retrofilling materials, when measured by dye/ink penetration are: composites>glass ionomer cement>amalgam>orthograde gutta-percha>EBA. The results of these in vitro studies are not congruent with in vivo study results, suggesting a need to re-evaluate the clinical validity and importance of in vitro studies.

Effect of root-end resection and root-end filling on apical leakage in the presence of core-carrier root canal obturation

AIM

To evaluate the apical seal of canals filled with a core-carrier obturator following root-end resection with and without a root-end filling.

METHODOLOGY

Thirty single-rooted human teeth with single canals were used. Root canal treatment was performed and canals filled with a core-carrier obturation technique. The teeth were then randomly assigned to three groups (n = 10). In the first group root canal filling only was performed. After orthograde filling, the teeth of the second group were resected apically, perpendicular to the major axis of the root. In the third group after apical resection, a root-end cavity was prepared using ultrasonic diamond retrotips and the cavities filled with Super-EBA cement. During a period of 3 h and with a headspace pressure of 0.12 atm, methylene-blue solution was forced through a tube that was connected to the apical end of each tooth specimen. The coronal end of the tooth was connected to a capillary tube containing an air bubble. Leakage was evaluated by observing the distal displacement of the air bubble. The roots were then sectioned along their long axis. Using a stereomicroscope, linear dye infiltration at the dentine-cement interface was determined. Kruskal-Wallis and Mann-Whitney tests were used to compare the three groups.

RESULTS

Linear dye infiltration was significantly greater in root canals filled with the core-carrier obturators and resected apically (0.9 +/- 0.9 mm) when compared with those that had root-end fillings (0.2 +/- 0.4 mm). Air bubble displacement was not observed.

CONCLUSION

Root-end filling improves the sealing of roots with core-carrier obturation following root-end resection.

Correlation between clinical success and apical dye penetration

AIM

This study was undertaken to examine whether a correlation exists between apical dye penetration and the clinical performance of root fillings.

METHODOLOGY

Apical dye penetration into 116 roots of human teeth that had been root-filled at least 6 months prior to extraction was tested in vitro using a vacuum technique and by measuring the length of dye penetration. Endodontic treatment was classified as clinically successful or unsuccessful and results for these groups were compared using analysis of variance and the Student's t-test. Positive and negative controls were used to test the experimental system.

RESULTS

All controls performed as expected. Dye penetrated significantly further in unsuccessful cases although the raw data suggested little difference. Overall, dye penetrated 99.5% of the specimens, indicating that the presence of dye in the canal is a poor indicator of whether the technique or material will succeed. However, the extent of dye penetration may be related to the clinical outcome.

CONCLUSIONS

Clinically placed root canal fillings do not provide an apical seal that prevents fluid penetration. The outcome of treatment cannot be predicted from the results of apical dye leakage studies.

Coronal leakage following three obturation techniques

AIM

To compare coronal bacterial and India ink leakage in three different obturation techniques with the smear layer having been removed.

METHODOLOGY

Seventy extracted single-rooted teeth were instrumented to an apical preparation size 7 Profile Series 29 (Tulsa Dental Products, Tulsa, OK, USA). The smear layer was removed and 20 teeth were randomly obturated with lateral compaction, 20 teeth with vertical compaction, and 20 teeth with Thermafil (Tulsa Dental Products, Tulsa OK, USA). Ten teeth were used for positive (five teeth) and negative (five teeth) controls. Teeth were stored for 90 days in 100% humidity, then subjected coronally to Proteus vulgaris for 21 days to assess bacterial leakage. Following bacterial challenge, India ink was placed coronally for a further 21 days, then scored according to depth of dye leakage.

RESULTS

Vertical compaction leaked significantly less than lateral compaction during bacterial challenge. However, when dye was used there were no significant differences.

CONCLUSIONS

Bacterial leakage and dye leakage demonstrated considerable variability. The use of a dye following bacterial testing may highlight the failure of experimental devices and vertical root fractures, thus avoiding false positive results found with bacterial testing alone.

Comparison of lateral condensation and thermomechanically compacted warm alpha-phase gutta-percha with a single cone for obturating curved root canals

OBJECTIVE

To evaluate and compare the sealability and radiographic quality of root fillings in extracted teeth by using lateral condensation of gutta-percha or alpha-phase gutta-percha in conjunction with a single gutta-percha cone.

STUDY DESIGN

A total of 108 single-rooted teeth were divided into 2 groups of 54 teeth based on canal shape. Canals were prepared to a minimum 0.055 taper and enlarged to a size 35 at the working distance. Irrigation was done with 17% EDTA and 2.5% sodium hypochlorite (NaOCl) to remove smear layer. One group was obturated by using cold lateral condensation of gutta-percha; the other group was obturated with thermomechanically compacted alpha-phase gutta-percha and a single cone of gutta-percha. Apical extrusion of sealer or gutta-percha was recorded. Sealability of each technique was assessed by dye penetration. The radiographic quality of obturation was also determined.

RESULTS

Root canals filled with alpha-phase gutta-percha and a single cone had significantly more extrusion of sealer than canals filled by lateral condensation. Lateral condensation achieved significantly better scores for radiographic quality. There was no significant difference between the 2 filling techniques in terms of apical or coronal leakage.

CONCLUSIONS

Thermomechanically condensed alpha-phase gutta-percha used in conjunction with a single gutta-percha cone had poorer radiographic quality than laterally condensed gutta-percha.

Apical microleakage after lateral condensation, hybrid gutta-percha condensation and Soft-Core obturation: an in vitro evaluation

The purpose of the present study was to evaluate the apical seal of root canals filled with a cold lateral condensation, a hybrid gutta-percha condensation technique and with Soft-Core obturators. Three groups of 35 maxillary anterior teeth and four control anterior teeth were treated with a crown-down/step-back technique. All roots were submerged in India ink for 1 week. The roots were cleared and the degree of linear dye penetration was measured. The mean apical leakage for the Soft-Core technique was at least twice as extensive as for the two other gutta-percha obturation techniques. No statistically significant differences were found between the two other condensation techniques.

Evaluation of the apical seal of root canal fillings with different methods

The purpose of the study was to compare dye penetration methods conducted passively, under negative pressure, or under high pressure conditions. Ninety human maxillary incisors were instrumented and obturated with either the lateral condensation or single cone technique. India ink was used as a dye for passive and negative pressure (60 Torr) penetration methods. For dye penetration under high pressure conditions (200 MPa), a colored epoxy resin was used. Apical leakage was linearly measured evaluating both the root surface that showed the highest degree of penetration and all four surfaces of each root. The results revealed no significant difference between passive and negative pressure penetration methods. The amount of apical leakage obtained using dye penetration under high pressure conditions was significantly lower. Lateral condensation and single cone techniques yielded similar sealing abilities. It is concluded that there is no need to use negative pressure for evaluating the sealing ability of root canal fillings in vitro.

Demineralization of resected root-ends with methylene blue dye

OBJECTIVES

This study evaluated the ability of methylene blue solutions of different concentration, pH, and time exposure to remove the smear layer from resected root-ends.

STUDY DESIGN

Resected root-ends were treated with either 2% methylene blue dye for intervals of 5 to 11 minutes or 1% methylene blue for 7 to 9 minutes and examined with a scanning electron microscope for smear layer removal. Two minute applications of saline solution and 50% citric acid served as controls.

RESULTS

All methylene blue solutions were found to be ineffective in removing the smear layer at all time intervals tested. An experimental solution of 1% methylene blue in 50% citric acid was found to predictably remove the smear layer during a 2 minute application and retained all the favorable staining characteristics of the dye. Fifty percent citric acid solutions applied for 3 minutes appeared to overdemineralize the root-end and gave poorer results than 2 minute applications.

CONCLUSIONS

Smear layer removal was pH dependent. Methylene blue solutions are clinically unsuitable for smear layer removal.

Root end filling materials: a review

When non-surgical attempts prove unsuccessful or are contraindicated, surgical endodontic therapy is needed to save the tooth. The procedure usually consists of exposure of the involved area, root end resection, root end preparation and insertion of a root end filling material. Numerous materials have been suggested as root end filling materials. This article is a review of the literature on the suitability of various root end filling materials based on their leakage assessment, marginal adaptation, cytotoxicity, and usage test in experimental animals and humans.

The effect of smear layer on microbial coronal leakage of gutta-percha root fillings

The aim of this in vitro study was to determine the effect of removal of the smear layer on canal obturation as measured by penetration of bacteria from a coronal direction. One hundred and twenty extracted human teeth with straight, single root canals were decoronated. The canals were prepared using the modified double-flared technique with balanced force under copious irrigation. The apical matrix was prepared to size 40 and apical patency subsequently confirmed with a size 15 file. The teeth were divided randomly into experimental groups (80 teeth) and control groups (40 teeth). The root canals of 40 experimental and 20 control teeth were rinsed with 40% citric acid and 2% NaOCl to remove the smear layer before obturation. In experimental groups, 20 teeth with smear layer intact and 20 teeth with smear layer removed were obturated with lateral condensation of cold gutta-percha and Apexit sealer. A further 20 teeth with smear layer intact and 20 teeth with smear layer removed were obturated with the Trifecta technique with the same sealer. In control groups, 10 teeth with smear layer intact and 10 teeth with smear layer removed were obturated with lateral condensation of cold gutta-percha and Apexit sealer. These teeth were completely sealed both coronally and apically to serve as negative controls. The remaining 20 teeth with either smear layer intact or smear layer removed were not obturated and served as the positive controls. The root surface of each tooth was sealed with nail varnish. The cut end of a polypropylene tube was sealed around the coronal part of each root canal so that bacteria placed therein could move only through the obturated canal space. Each root was placed in a glass bottle containing sterile Todd-Hewitt Broth (THB) and aliquots of 0.5 ml of THB were injected into the polypropylene tube. The model system was centrifuged at 168 g. An innoculum of Streptococcus sanguis in THB was placed in each coronal chamber at 5-day intervals and daily observations were made for bacterial growth in the apical reservoir for 90 days. All positive control teeth showed bacterial penetration within 24 h, while the negative control teeth remained uncontaminated throughout the test period. Leakage through the experimental teeth was variable ranging from 7 to 86 days. There was no statistical significant difference (P > 0.05) in leakage between the obturated canal when the smear layer was either removed or intact.

Variation in the microleakage produced by four different techniques in root fillings in a simulated root canal model

An in-vitro investigation was performed to assess the extent of apical microleakage in simulated canals in clear resin blocks. Four different methods of producing dye penetration were employed: passive dye penetration alone, centrifugation alone, vacuum plus passive dye penetration, and increased pressure plus passive dye penetration. Forty simulated root canals were prepared and obturated. The specimens were randomly allocated into four groups and each group was subjected to a different leakage technique using methylene blue dye as the detector. The maximum apical dye penetration observed through each of the four faces of the blocks was recorded. There were large variations in the leakage recorded in each individual specimen and between the specimens within each group. There were statistically significant differences between passive dye penetration and each of the other three techniques. There was no significant differences between the centrifugation, vacuum and pressure techniques.

An in-vitro study of smear layer removal and microbial leakage along root-canal fillings

The objective of this study was to determine the effect of removal of the smear layer on canal obturation as measured by penetration of bacteria from a coronal direction. Fifty-four extracted human teeth were decoronated and instrumented in a uniform manner. Following instrumentation the root canals of 20 teeth were rinsed with 17% EDTA and 5.25% NaOCl to remove the smear layer before obturation. A second group of 20 teeth were flushed with NaOCl alone. The teeth of both groups were obturated with Thermafil plastic carriers and Roth's sealer. The root canals of another 10 teeth, five rinsed with EDTA and five without, were obturated with Thermafil without sealer. Two teeth serving as positive controls were instrumented but not obturated, while another set of two were sealed coronally and apically to serve as negative controls. The root surface of each tooth was sealed with nail varnish. A small chamber was thoroughly sealed around the coronal aspect of each tooth so that bacteria placed therein could move only through the obturated canal space. Each tooth was placed in a test tube containing sterile trypticase soy broth (TSB). An inoculum of Proteus vulgaris in TSB was placed in each coronal chamber at five day intervals and daily observations were made for bacterial growth in the apical reservoir for 21 days. Both positive control teeth showed bacterial penetration after 24 h. Neither of the two negative control teeth demonstrated penetration for the duration of the study. The frequency of bacterial penetration through teeth obturated with intact smear layer (70%) was-significantly greater than that of teeth from which the smear layer had been removed (30%) P < 0.05. All but one tooth obturated without sealer exhibited bacterial penetration, irrespective of the presence or absence of smear layer. Removal of the smear layer enhanced sealability as evidenced by increased resistance to bacterial penetration.

Effect of reduced air pressure on dye penetration in standardized voids

OBJECTIVE

This study determined the correlation between the degree of dye penetration in standardized voids to various reduced pressures.

STUDY DESIGN

Standardized voids of 0.50 and 0.22 mm in diameter were created in 60 human roots; specimens were divided into five groups. Four groups were subjected to a 2% filtered aqueous methylene blue dye solution under different conditions of atmospheric pressure for 7 days and reduced pressures of a 10 torr, a 260 torr, and a 510 torr for 30 minutes. The conditions for the fifth group were similar to the last group except that ethyl alcohol was substituted for water in the dye.

RESULTS

All positive control specimens showed complete dye penetration. The least linear dye penetration was observed in passively immersed specimens. The results were significantly different from those when reduced pressure had been used (p < 0.001). There were no significant differences among the groups with reduced pressure. No significant difference was found at any pressure level between the means of dye diffusion in the 0.50 and the 0.22 mm voids. The smallest standard deviations were observed for the most reduced air pressure of 10 torr, followed by the group of the least reduced pressure of 510 torr, with the use of the tincture dye solution.

CONCLUSIONS

A 10-torr reduced pressure and an application of the tincture dye solution would provide an improved method for microleakage studies.

Ultrasonic preparation and obturation of root-end cavities

This study evaluated the preparation of root-end cavities using an ultrasonically activated file, and the obturation of such cavities. In the first part, the root canals of 40 extracted teeth were prepared to size 40 and irrigated with NaOCl and EDTA. The root ends were resected and the teeth inoculated with Enterococcus faecalis, incubated for 10 days and divided into four groups: control; saline; irrigation; hand instrumentation performed via a retrograde approach up to size 50 using saline irrigant; ultrasonic instrumentation with prebent size 40 K-flex file inserted into a Piezon Master using saline irrigant. The teeth were fixed, sectioned longitudinally and viewed under scanning electron microscopy. Bacterial and smear layer scores were obtained at 1, 3, and 5 mm from the resected end. The bacterial scores for control and saline groups were similar; the scores for each instrumentation group were significantly lower than the control group (P<0.001). In addition, there were significantly fewer bacteria in the ultrasonic group compared with the hand instrument group (P<0.001). The smear layer scores for control and saline groups were similar, and significantly lower than in either instrumentation group (P<0.001). In the second part, root-end cavities were ultrasonically prepared in 20 extracted teeth. Ten cavities were filled with amalgam, and 10 with thermoplasticized gutta-percha and Grossman's sealer. After 24-h storage, the root ends were immersed in dye for 48 h. Cross-sectional slices of the obturated part of the root were evaluated using both light and confocal microscopy for dye leakage along the interface of filling material and dentine. There were no statistical differences between the leakage of amalgam and gutta-percha root-end fillings, nor between the two methods of microscopy.

Effects of vacuuming on dye penetration patterns in root canals and glass tubes

This study compared the dye leakage pattern of prepared root canals with that of glass tubes, with and without vacuuming. The apical 12 mm of 40 calcified root canals were prepared to tubes with a diameter of 0.5 mm. The coronal end of these canals and 40 glass tubes with similar diameters (12 mm x 0.5 mm) were closed with 2 mm of Cavit. Twenty samples from each group were left empty, and the rest (20) were filled with gutta-percha without sealer. Half of the samples of filled (10) and unfilled (10) specimens were then placed horizontally in 2% methylene blue dye. The other half (10) of the samples from each group were placed in a vacuum (25 mm Hg) and submerged in the dye. Leakage was then measured in millimeters and statistically analyzed using analysis of variance. The 20 empty glass tubes with or without vacuum leaked 17% or less of their lengths. The 20 glass tubes filled with gutta-percha averaged 70.5% leakage. Of those, the 10 glass tubes that were vacuumed had 100% leakage. Empty root canals exhibited mean leakage of 74% without vacuum and 91% of their length with vacuum. Canals filled with gutta-percha leaked a mean of 95.5% of their entire lengths without vacuum and 100% with vacuum (no significant difference). The results showed that filled and unfilled, prepared root canals leaked significantly more than their glass tube counterparts (p < 0.001), and vacuuming may not be necessary for dye leakage studies in filled root canals.

Reliability of reduced air pressure methods used to assess the apical seal

The reliability of two commonly used methods of sealability testing, dye leakage under normal atmospheric pressure and dye leakage in a partial vacuum, was tested using a repeated studies design. Forty extracted teeth were instrumented and obturated using lateral condensation of gutta-percha and Sealapex sealer. One-half of the teeth were placed in India ink under normal atmospheric pressure and the other half underwent air evacuation before immersion in the ink. After 24 h the teeth were removed from the ink and rendered transparent for linear leakage analysis. A second study, repeated within the exact parameters of the first, was performed approximately 1 month later. Mann-Whitney U tests indicated that there was no significant difference (P>0.05) between the air and vacuum groups or within each group (air or vacuum) between trials, indicating that the methodology is repeatable and that application of reduced air pressure did not enhance reliability. A large majority of the teeth placed under partial vacuum showed evidence of vacuum-induced artefacts that may negate the value of vacuum as a research tool.

Testing of sealing ability of endodontic filling materials

Incomplete obturation of the root canal system is the major cause of endodontic failure. Endodontic filling materials with ability to seal the root canal are, therefore, essential for successful endodontic therapy. However, assessment of sealing ability is not included in the requirements specified in the current international standard covering root canal sealers. A number of different in vitro methods have been used to evaluate the sealing quality of endodontic filling materials. The tests have usually been leakage tests, i.e. based on assessment of penetration of a tracer along the obturated root canal. Leakage tests have poor reproducibility and are, therefore, not suited for standardized test programs. By selecting the properties necessary for sealing ability and testing them separately, it might be possible to find a number of tests, which individually are suitable for a standardized test program, and which combined will give information on the sealing ability of the test material.

Fluid transport and dye penetration along root canal fillings

Dye penetration along root canal fillings may be hindered by the presence of entrapped air. In this study, the sensitivity of a dye penetration method was compared with that of a fluid transport model. Sixty root sections from human maxillary central incisors were prepared and obturated by a modified technique to ensure a slight amount of leakage, and divided into three equal groups. Twenty root sections were first mounted in a fluid transport device and assessed for fluid transport under 10 kPa (0.1 atm.) pressure. Another 20 root sections were mounted in the same device before being subjected to air transport under the same pressure. The remaining 20 root sections were not exposed to fluid or air transport. Then, all the 60 root sections were assessed for penetration of a 2% methylene blue solution. The results showed that fluid transport was a much more sensitive method of detecting voids along root canal fillings than dye penetration. After fluid transport for 3 h under low pressure, to eliminate entrapped air, dye penetrated significantly deeper than without previous fluid transport, which suggested that entrapped air in voids along the root canal filling prevented dye penetration.

Comparison of apical leakage in root canals obturated with various gutta percha techniques using a dye vacuum tracing method

In this study, residual apical microlumina remaining after obturation with five different gutta-percha obturation methods were traced with an efficient vacuum method. Seventy-nine human maxillary anterior teeth were instrumented and divided into five groups. The groups were obturated with single-cone techniques, lateral condensation, vertical condensation, Thermafil, and Ultrafil techniques. All specimens were immersed in a vacuum flask containing 2% methylene blue dye solution. The air was evacuated with a vacuum pump to an absolute pressure of 75 torr for 30 min. The roots were sectioned longitudinally and the linear extent of dye penetration was measured. Group mean linear dye penetration values were: single-cone technique, 1.55 +/- 0.95 mm; lateral condensation, 2.25 +/- 1.46 mm; vertical condensation, 2.61 +/- 2.61 mm; Thermafil 1.41 +/- 1.16 mm; and Ultrafil 3.51 +/- 4.70 mm. There were no statistically significant differences between the gutta-percha obturation methods. The clinical implications of these findings are discussed.

Fluid transport and bacterial penetration along root canal fillings

Convective transport of water from the coronal to the apical end of obturated root canals was determined by the movement of an air bubble in a capillary glass tube connected to the apex of the experimental root section using a headspace pressure of 120 kPa (1.2 atm). Water transport through existing voids in the obturated canals could be measured reproducibly in this way. The root canals of 60 human maxillary canines were filled with gutta-percha and sealer by the cold lateral condensation technique. Thirty of these were first exposed to a small motile bacterium, Pseudomonas aeruginosa, growing in a reservoir at the coronal end of each root. After 50 days, two specimens allowed penetration of bacteria to a reservoir at the apical end. All the roots were then assessed quantitatively for convective transport of water. The results were divided into three defined categories: 39 obturated canals were in the 'bacteria tight' category, 14 canals in the 'slight leakage' and 7 canals in the 'gross leakage' category. The two specimens that showed bacterial penetration fell into the slight and gross leakage categories. The previous test for bacterial passage did not statistically influence the fluid transport pattern of these roots which was measured subsequently. These findings indicate that fluids transport through obturated root canals, most of which do not allow the passage of bacteria.

Endodontic leakage studies reconsidered. Part I. Methodology, application and relevance

An increasing number of endodontic leakage studies have been published. In the 1990 volumes of Journal of Endodontics and International Endodontic Journal, there was one leakage study to every 4.3 scientific articles. The most popular method was linear measurement of tracer (dye or radioisotope) penetration along a root filling. Comparing some data on linear measurement of dye penetration following the cold lateral condensation of gutta-percha that were published between 1980 and 1990, a high level of variation has been found, although the experimental methods used in these studies were quite similar. In almost all studies evaluating various techniques, the cold lateral condensation technique has been used as a standard control for comparison. The reliability of these results is questionable. The problems with such studies are discussed. It seems that more research should be done on leakage study methodology, instead of continuing to evaluate the sealing ability of different materials and techniques by methods that may give little relevant information.