A standardized leakage test with curved root canals in artificial dentine

Impact of root canal preparation size and taper on coronal-apical micro-leakage using glucose penetration method

OBJECTIVES

The purpose of this in vitro study was to assess the effect of root canal preparation size and taper on the amounts of glucose penetration.

MATERIAL AND METHODS

For conducting this experimental study, eighty mandibular premolars with single straight canals were divided randomly into 2 experimental groups of 30 samples each and 2 control groups. Using K-files and the balance force technique, canals in group 1 were prepared apically to size 25 and coronally to size 2 Peesoreamer. Group 2 were instrumented apically and coronally to size 40 and size 6 Peesoreamer, respectively. Rotary instrumentation was accomplished in group 1; using size 25 and .04 tapered and in group 2, size 35 and .06 tapered Flex Master files. Canals were then obturated by lateral compaction of cold gutta-percha. Glucose penetration through root canal fillings was measured at 1, 8, 15, 22 and 30 days. Data were recorded as mmol/L and statistically analyzed with Mann-Whitney U test (P value=. 05).

RESULTS

In comparison to group 1, group 2 showed significant glucose leakage during the experimental period (P value < .0001). Also, in each experimental group, the amount of micro-leakage was significantly increased at the end of the study.

CONCLUSIONS

Under the condition of this study, the amounts of micro-leakage through root canal fillings are directly related to the size and taper of root canal preparation and reducing the preparation size may lead to less micro-leakage. Key words:Dental leakage, root canal preparation, endodontics.

Restoflex--a revolutionary change in preclinical practice for restorative dentistry and endodontics

Preclinical exercises are very important for the dental students in order to master various dental techniques. The objective of this article is to introduce a new preclinical working model named Restoflex. It is especially designed for the students to carry out various restorative and endodontic procedures in an environment that closely simulate clinical situations. This will help them to provide a smooth transition from preclinical environment to the clinical one. It would also mean an increased confidence level and the efficiency with which the students would deal with their cases.

Evaluation of apical microleakage of teeth sealed with four different root canal sealers

Objectives:

to compare the apical sealing ability of four root canal sealers. Materials and methods: forty extracted human maxillary canines were instrumented 1 mm short of the anatomical apex and randomly assigned to four groups (n=10), according to the root canal sealer used for obturation: Endofill, AH Plus, EndoREZ and Epiphany. Root canals were obturated with guttapercha points, except for the Epiphany group, in which resin points (Resilon) were used. The teeth were immersed in India ink for seven days and clarified using methyl salicylate. The extent of apical dye penetration was measured with a measuroscope in all aspects of the canal.

Results:

AH Plus (0.02 mm ± 0.07), Epiphany (0.00 mm ± 0.00) and EndoREZ (0.32 mm ± 0.62) did not differ statistically to each other (p>0.01). EndoFill presented the highest dye penetration mean (0.83 mm ± 0.73) and was statistically different from the other sealers (p<0.01).

Conclusions:

the resin-based root canal sealers presented lesser apical microleakage than the zinc oxide and eugenol based sealer. No statistical differences were observed among resin based sealers.

A quantitative evaluation of apical leakage of four root-canal sealers

AIM

This in vitro study evaluated the microleakage of root fillings involving four root-canal sealers including AH Plus (De-Trey, Switzerland), RoekoSeal (Roeko, Germany). Ketac-Endo (ESPE, (Germany) and Sultan (Sultan Chemists, USA.

METHODOLOGY

Forty extracted human maxillary anterior teeth were used. The coronal part of each tooth was removed and the root canals were prepared using the step-back technique and apical enlargement to size 60 file. The specimens were randomly divided into four groups of 10 samples, filled with one of the test materials and gutta-percha cones by the cold lateral condensation technique. A fluid filtration method was used for quantitative evaluation of apical leakage. The leakage was measured by the movement of an air bubble in a capillary glass tube connected to the experimental root section. Measurements of fluid movement were made at 2-min intervals for 8 min. Water transport through existing voids in the obturated canals could be measured reproducibly in this way. The quality of the seal of each specimen was measured after 7,14 and 21 days.

RESULTS

Statistical analysis indicated that all the root fillings showed less leakage after 21 days (P < 0.05). Fillings incorporating Sultan showed significantly more leakage than all other sealers.

CONCLUSIONS

Root fillings with RoekoSeal in combination with cold lateral condensation technique showed better sealing than those with Ketac-Endo, AH Plus and Sultan sealers after 21 days. The fluid filtration test used in this study gave quantitative results and allowed nondestructive long-term evaluation of specimens.

A new method for the quantitative analysis of endodontic microleakage

The aim of this in vitro study was to evaluate the apical seal obtained with three commonly used root canal sealing cements: Sealapex, AH Plus or Topseal, and Sealite, using a new method based on the quantitative analysis of 125I-radiolabeled lysozyme penetration. One hundred thirteen teeth with straight single root canals were instrumented to master apical point #25/30. These were divided into three groups: (i) negative control (4 roots) covered with two layers of nail polish, (ii) test group (105 roots) obturated by laterally condensed guttapercha with the three cements; and (iii) positive control (4 roots) obturated without cement. The groups were then immersed in 125I lysozyme solution for a period of 1, 7, 14, or 28 days. After removal, six sections of 0.8 mm length each were made of each root with a fine diamond wire. Each section was analyzed for activity by a gamma counter, corrected for decay, and used to quantify protein penetration. Leakage was high in the positive control and almost negligible in the negative control. AH Plus (Topseal) and Sealapex showed similar leakage behavior over time, with AH Plus (Topseal) performing better. Sealite showed acceptable leakage up until day 14, after which a large increase occurred, presumably due to three-dimensional instability.

Development of an anaerobic bacterial leakage model

The majority of bacteria associated with infections of endodontic origin are strict anaerobes. The purpose of this study was to develop an endodontic microleakage model using strict anaerobic bacteria in a two-chamber system. Nine species of anaerobic bacteria were tested for viability and detection by either turbidity or color change of the broth. A survey of pH chromogenic substrates revealed that bromcresol purple (pH 5.2 = yellow, pH 6.8 = purple) could be used as a chromogenic indicator to detect the growth of anaerobic bacteria. Peptone-yeast extract-glucose broth (PYG) and brain heart infusion broth (BHI) were each used alone and with bromcresol purple (bpPYG, bpBHI) in this study. Fusobacterium nucleatum and F. necrophorum were viable in all four media for > 2 wk and produced both turbidity and a color change after only 1 day of incubation. Veillonella parvula in either bpBHI or BHI and Peptostreptococcus anaerobius in either bpPYG or BHI were viable for > 2 wk and showed a color change or turbidity after 1 or 2 days. The results indicate that leakage of strict anaerobes may be evaluated in a two-chamber system.

Apical sealing using two thermoplasticized gutta-percha techniques compared with lateral condensation

This study was conducted to compare the apical sealing capacity of three filling techniques, a multiphase gutta-percha obturation technique, JS Quickfill, and lateral gutta-percha condensation. A four-stage stepback preparation was executed with circumferential filing in a total of 70 recently extracted permanent maxillary incisors and canines. Three experimental groups (20 teeth in each group) and two control groups (5 teeth in each group) were formed at random. Each experimental group was obturated with a different technique. The positive control group was not obturated. In the negative control group, the whole root was covered with two full nail varnish layers. Teeth were immersed in India ink for 48 h, demineralized, cleared with methyl salicylate, and examined with a stereomicroscope. None of the specimens obturated with the multiphase gutta-percha obturation system showed any penetration of India ink beyond the end of the preparation. In the groups of teeth obturated by JS Quickfill or lateral gutta-percha condensation, leakage was detected in one specimen from each group. No statistically significant differences were seen among groups. We conclude that the newer thermoplasticized filling techniques can be used successfully to obturate root canals in large, straight roots.

A model for the teaching of clinical techniques in root canal treatment

A practical model to aid the understanding and practice of endodontic techniques is described. The model uses extracted teeth mounted in light-cured acrylic resin and set in a preformed model tray. Before mounting, the root surfaces of teeth are dipped in wax to simulate the periodontal ligament space. This model allows endodontic techniques to be practised in the operative technique classroom in a way that simulates the clinical situation and enables radiographs of good diagnostic quality to be taken during treatment. Subsequently, teeth can be reset to allow restoration of the root-filled tooth.

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.

Sealing ability of potential retrograde root filling materials

The sealing ability of two potential retrograde root filling materials, a light-cured glass ionomer cement (Vitrebond) and a reinforced zinc oxide-eugenol cement (Kalzinol) was compared with that of amalgam using three methods of assessment: bacterial leakage, confocal microscopy and Indian ink leakage. the root canals of 80 extracted human single-rooted teeth were prepared. All the teeth were apicected, retrograde cavities were prepared and then divided into four equal groups of 20 teeth. The teeth were sterilised by autoclaving and the retrograde cavities filled with the test materials. In the control group, retrograde cavities in 10 teeth were left unfilled while cavities in another 10 teeth were sealed with cyanoacrylate cement. The teeth were first subjected to a bacterial leakage test using Enterococcus faecalis as a leakage marker. After which, the adaptation of the retrograde root fillings was assessed using a confocal optical microscope. Finally, the teeth were processed for the Indian ink leakage test. Bacterial leakage occurred in more teeth filled with amalgam compared with both Vitrebond and Kalzinol (P<0.001), between which there were no differences. With confocal microscopy, the size of the marginal gap was largest with amalgam and smallest with Vitrebond; all differences were statistically significant (<0.001). Finally, there was more Indian ink penetration with amalgam compared with both Vitrebond and Kalzinol (P<0.001) but there were no differences between Vitrebond and Kalzinol. Although there were individual differences within samples, overall, the three methods of assessment produced similar results. The sealing ability of Vitrebond and Kalzinol was similar and both materials were better than amalgam.

Apical sealing ability of a new glass ionomer root canal sealer

This study compared the sealing ability of Ketac Endo with and without smear layer and Tubli Seal. Thirty upper central incisors and canines with straight canals were instrumented and randomly divided into three equal groups of 10. All teeth were obturated with laterally condensed gutta-percha. An additional group of five teeth with unobturated++ root canals served as positive controls. The sealers were Tubli Seal (group A), Ketac Endo (group B), and Ketac Endo preceded by the removal of the smear layer (group C). The teeth were immersed in India ink for 7 days, centrifuged for 5 min at 3000 rpm, cleared, and then examined under a light microscope at X 50 magnification. The mean value of ink penetration for group A was 0.14 mm, for group B 0.24 mm, and for group C 0.48 mm. No statistically significant differences were observed among groups (p > 0.05).

A comparison of the apical seals achieved using retrograde amalgam fillings and the Nd:YAG laser

The purpose of this in vitro study was to compare the apical seals achieved using retrograde amalgam fillings or the Nd:YAG laser. Freshly extracted teeth were randomly separated into groups that would have their apices treated either with a Nd:YAG laser or retrograde amalgam. After instrumentation and obturation, bacterial reservoirs were prepared in the coronal portion of canals. Teeth to receive retrofillings had their apices prepared and amalgams placed. Teeth to be lasered had no apical preparations. Teeth and culture media were then sterilized by irradiation. Streptococcus salivarius was deposited in the opened bacterial reservoirs. At intervals, culture media with an indicator in culture chambers was observed for color change. Specimens that demonstrated color change were cultured for S. salivarius. Under the conditions of this in vitro study, no statistically significant difference was found in bacterial leakage between the laser-treated group and the retrograde amalgam group.

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.

Influence of age on the extent of voids in root canals sealed using a cold lateral condensation technique

The aim of this study was to examine whether it is more difficult to achieve complete obturation of the root canal in teeth from different age groups, using the measurement of voids within the obturated canal to determine the quality of endodontic therapy. One-hundred and fifty-two single-rooted premolar teeth extracted from patients of known age were collected. Following cleaning and storage the teeth were decoronated and radiographed. Forty selected teeth were allocated to one of four age-groups, (under 20, 20-35, 36-50, over 50 years) each consisting of 10 teeth. The working length was determined radiographically and preparation was carried out using the step-back technique. Each canal was obturated using cold lateral condensation with Tubliseal cement. The roots were then sectioned longitudinally and photographed. Sections and transparencies were subjected to image analysis to determine the total areas of root canal, sealer and voids respectively and statistical analysis of the differences between the various age groups was undertaken. There was a trend towards a reduction in the areas of sealer and sealer plus void with respect to increasing age group, although no significant differences existed. A significant relationship (P < 0.05) was found between the area of voids found in the youngest group when compared with all other groups, the greatest cumulative area of voids being found in the youngest teeth.

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.

Apical dye penetration with four root canal sealers and gutta-percha using longitudinal sectioning

The purpose of this study was to compare the level of apical dye penetration when different sealers were used with lateral condensation of gutta-percha. Fifty teeth with single root canals were biomechanically prepared using the step-back technique and irrigation with 15% ethylenediaminetetraacetic acid with cetrimide and 1% NaOCl solutions. The teeth were divided into five groups of 10 teeth each. The control group root canals were filled with laterally condensed gutta-percha without sealer and the other four groups were filled with laterally condensed gutta-percha and either Apexit, Sealapex, Tubli-Seal, or AH-26 sealer. After storage in 100% humidity at 37 degrees C for 48 h, the root surfaces were coated with nail varnish (except at the apex), placed in 2% methylene blue dye solution, and centrifuged at 30 x g for 3 min. The roots were sectioned longitudinally to determine the following mean levels of dye penetration: AH-26, 0.48 mm; Apexit, 1.33 mm; Sealapex, 4.59 mm; Tubli-Seal, 5.58 mm; and gutta-percha alone, 7.99 mm. This study demonstrated that a root canal sealer should be used in conjunction with laterally condensed gutta-percha and that AH-26 sealer had significantly less dye penetration than the other three sealers while Apexit had significantly less dye penetration than Sealapex and Tubli-Seal. There was no significant difference between Sealapex and Tubli-Seal.

The apical seal of root canal sealing cements using a radionuclide detection technique

The aim of this study was to evaluate the apical seal obtained with various root canal sealing cements using a new method based on the use of a radionuclide and an external detection technique. A total of 150 maxillary incisors and canines, which had been kept in saline solution, were used. The root canals were instrumented with a stepback technique and circumferential filing. Six experimental groups and two control groups were randomly formed. Each experimental group was obturated by a lateral condensation technique with gutta-percha points and a different sealing cement (two based on zinc oxide-eugenol cement, two based on resins and two on calcium hydroxide); the positive control used gutta-percha without sealing cement, while in the negative control the apex was covered with nail varnish, leaving the root canal empty. The apical leakage was measured using an external detection technique after submerging the root apices in a solution containing the radioisotope metastable 99Tc. No leakage was observed in the negative control group. There was a large difference between the leakage observed in the positive control group and the experimental groups. The best seal was obtained using Sealapex cement, which differed significantly from AH26, Tubli-Seal and Diaket; there was no significant difference between the latter. The poorest results were obtained with Endomethasone and CRCS; there was a significant difference between these and the previous three sealing cements.

A comparative study of the apical leakage of four root canal sealers and laterally condensed gutta-percha

Previous studies have shown that lateral condensation of gutta-percha and sealer can provide an adequate apical seal. The purpose of this study was to compare the level of apical dye penetration when different sealers were used. One-hundred twenty-five teeth with single root canals were biomechanically prepared using the step-back technique and irrigation with EDTAC and 1% NaOCl solutions. The teeth were divided into five groups of 25 teeth each. The control group root canals were filled with laterally condensed gutta-percha and no sealer and the other four groups were filled with laterally condensed gutta-percha and either Apexit, Sealapex, Tubli-Seal, or AH26 sealer. After storage in 100% humidity at 37 degrees C for 48 h, the root surfaces were coated with nail varnish (except at the apex) and placed in 2% methylene blue dye solution and centrifuged at 3 x g for 3 min. The roots were sectioned transversely at 1-mm intervals to determine the following mean levels of dye penetrations: Apexit, 1.67 mm; Sealapex, 2.28 mm; Tubli-Seal, 1.95 mm; AH26, 0.82 mm; and gutta-percha alone, 8.37 mm. This study demonstrated that a root canal sealer should be used in conjunction with laterally condensed gutta-percha and that AH26 sealer provides a significantly better apical seal than the other sealers.

Quantitative microleakage study on a new retrograde filling technique

An in vitro endodontic leakage model was used to compare the sealing ability of conventional retrograde amalgam fillings with a new retrograde filling technique by measuring dye leakage quantitatively. The new technique consisted of retrograde preparation of the root canal using the Endocursor, an endodontic handpiece. The canal was then filled with sealer and injection-moulded gutta-percha, using either the Hygenic Ultrafil system or the Unitek Obtura method. In both cases the gutta-percha was vertically condensed and subsequently cold-burnished. The two experimental groups and the amalgam group each consisted of 20 extracted human canine teeth and lower premolars. The results were analysed statistically by ANOVA and a Student-Newman-Keuls multiple comparison test. After 1 week at 37 degrees C, very little leakage was observed in the amalgam and gutta-percha groups. After a second week, during which leakage was enhanced by gas pressure, leakage in the amalgam group was significantly greater than that in the gutta-percha groups (P less than 0.01). There were no significant differences between the two experimental gutta-percha groups. It is concluded that the new retrograde filling technique causes less leakage than the conventional amalgam retrograde filling technique in an in vitro model.

Particles and molecules in endodontic leakage

It is assumed that above a critical level, microleakage causes periapical disease and jeopardizes periapical tissue repair. The purpose of this investigation was first to find out to what degree obturation prevents leakage of bacteria-sized particles or large protein molecules, and second if leakage of the commonly used dye methylene blue is comparable with that of a small bacterial metabolic product of similar molecular size. Sections, 9 mm long, obtained from 46 extracted human incisor roots had their root canals prepared in a standardized manner and obturated in four experimental ways using gutta-percha. The root sections were mounted in the middle of tubes that were closed at both ends with rubber membrane stoppers, which permitted sampling from the apical reservoir. The coronal reservoir was filled with a solution of 1 mg/ml latex beads, 4 micrograms/ml endotoxin, 0.5 per cent butyric acid, 0.1 per cent valeric acid and 0.1 per cent methylene blue water. After 1 and 2 weeks, samples were taken from the apical reservoir and tested for the presence of latex beads by phase-contrast microscopy, for endotoxin with a limulus lysate test, for butyric acid with gas-chromatography and for methylene blue with spectrophotometric analysis. Leakage of bacteria-sized particles and large-sized protein molecules could be prevented only when both sealer and pressure were used in obturating root canals with gutta-percha. Leakage of butyric acid proved to be comparable with leakage of methylene blue; microleakage of these small molecules could not be prevented in this study whatever method of filling was used.