Effect of thickness on the sealing ability of some root canal sealers

A Literature Review of the Effect of Heat on the Physical-Chemical Properties of Calcium Silicate-Based Sealers

INTRODUCTION

Recently, calcium silicate-based sealers (CSSs) have gained popularity in endodontic practice due to their biocompatibility and antimicrobial properties. They are considered viable alternatives to epoxy resin-based sealers. With the increased use of CSSs and warm vertical compaction techniques in root canal treatment, evaluating the impact of heat on CSSs properties is essential, therefore this review aimed to present a qualitative synthesis of available in vitro studies assessing the impact of heat on the physical-chemical properties of CSSs.

METHODS

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis 2020 guidelines, a systematic advanced electronic search was performed in Scopus, Embase, Medline (via PubMed), Web of Science, and Cochrane databases in November 2023 and updated in April 2024. In vitro studies that evaluated the physical-chemical properties of CSSs were eligible. PRILE 2021 guidelines were used for the assessment of the risk of bias-included studies.

RESULTS

The search identified a total of 6421 preliminary results and 10 studies were included for qualitative assessment. Eleven different physiochemical properties were assessed by the included studies. Setting time and flow were the most evaluated property among the studies. A qualitative synthesis of the evidence on each property is presented.

CONCLUSIONS

Based on the in vitro studies assessed in the present systematic review, results reveal that exposing CSSs to heat can accelerate their setting time, reduce their flow, and increase their film thickness. Concerns persist regarding solubility, viscosity, radiopacity, dimensional change, microhardness, porosity, and compressive strength, requiring further research. Certain CSSs, such as MTA Fillapex and Endosequence BC sealer HiFlow, show minimal changes under heat, making them potential candidates for warm filling techniques.

Heat-Induced Changes in the Physical Properties of a New Premixed Calcium Silicate-Containing Root Canal Sealer: An In Vitro Study

This study aimed to examine how heating affects the physical properties of a newly developed premixed calcium silicate-containing sealer (AH Plus Bioceramic Sealer; AHB), in comparison with EndoSequence BC Sealer (ES), AH Plus Jet (AH), and Pulp Canal Sealer. The setting time, flow, and film thickness were tested with or without heating at 100 °C for 30 or 60 s, in accordance with ISO6876:2012 standards. Ultrastructural and elemental analyses were performed with scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Data were analyzed using one-way analysis of variance (ANOVA) with a Tukey post hoc test (α = 0.05). All sealers exhibited significantly shorter setting time and flow after heating at 100 °C for 30 and 60 s (p < 0.05). After heating, AHB showed a significantly higher film thickness compared to that of the other materials (p < 0.05). None of the tested properties of heat-applied AHB and ES met ISO standards, except the setting time in ES. The SEM/EDS results for AHB and ES were not affected by heating. The detected changes in physical properties can negatively impact the performance of premixed calcium silicate-containing sealers, particularly AHB, when warm vertical compaction is employed.

Evaluation of the Impact of Calcium Silicate-Based Sealer Insertion Technique on Root Canal Obturation Quality: A Micro-Computed Tomography Study

BACKGROUND

Calcium silicate-based sealers have gained in popularity over time due to their physicochemical/biological properties and their possible use with single-cone obturation. The single cone technique is a sealer-based obturation and there is still a knowledge gap regarding the potential impact of the sealer insertion method on the root canal-filling quality. Therefore, the aim of this micro-CT study was to assess the impact of the calcium silicate-based sealer insertion technique on void occurrence and on the sealer extrusion following single-cone obturation.

METHODS

Thirty-six single-rooted mandibular premolars with one canal were shaped with Reciproc® R25 (VDW, Munich, Germany) then divided randomly into four groups of nine canals, each depending on the TotalFill® BC Sealer insertion technique used with single cone obturation: injection in the coronal two-thirds (group A); injection in the coronal two-thirds followed by direct sonic activation (group B); injection in the coronal two-thirds followed by indirect ultrasonic activation on tweezers (group C); sealer applied only on the master-cone (control group D). Samples were then scanned using micro-CT for voids and sealer extrusion calculation. Data were statistically analyzed using v.26 IBM; Results: No statistically significant differences were noted between the four groups in terms of voids; nevertheless, sonic activation (group B) followed by ultrasonic activation on the tweezers (group C) showed the best results (p = 0.066). Group D showed significantly less sealer extrusion when compared with group C (p = 0.044), with no statistically significant differences between groups D, A and B (p > 0.05).

CONCLUSIONS

Despite no significant differences observed between the different sealer placement techniques, the use of sonic and ultrasonic activation might be promising to reduce void occurrence. Further investigations are needed to demonstrate the potential benefit of calcium silicate-based sealer activation especially in wide and oval root canals in order to improve the quality of the single-cone obturation.

Calcium Silicate-Based Root Canal Sealers: A Narrative Review and Clinical Perspectives

Over the last two decades, calcium silicate-based materials have grown in popularity. As root canal sealers, these formulations have been extensively investigated and compared with conventional sealers, such as zinc oxide-eugenol and epoxy resin-based sealers, in in vitro studies that showed their promising properties, especially their biocompatibility, antimicrobial properties, and certain bioactivity. However, the consequence of their higher solubility is a matter of debate and still needs to be clarified, because it may affect their long-term sealing ability. Unlike conventional sealers, those sealers are hydraulic, and their setting is conditioned by the presence of humidity. Current evidence reveals that the properties of calcium silicate-based sealers vary depending on their formulation. To date, only a few short-term investigations addressed the clinical outcome of calcium silicate-based root canal sealers. Their use has been showed to be mainly based on practitioners' clinical habits rather than manufacturers' recommendations or available evidence. However, their particular behavior implies modifications of the clinical protocol used for conventional sealers. This narrative review aimed to discuss the properties of calcium silicate-based sealers and their clinical implications, and to propose rational indications for these sealers based on the current knowledge.

Physical, Chemical, Mechanical, and Biological Properties of Four Different Commercial Root-End Filling Materials: A Comparative Study

Commercial mineral trioxide aggregate (MTA) materials such as Endocem MTA (EC), Dia-Root Bio MTA (DR), RetroMTA (RM), and ProRoot MTA (PR) are increasingly used as root-end filling materials. The aim of this study was to assess and compare the physicochemical and mechanical properties and cytotoxicity of these MTAs. The film thicknesses of EC and DR were considerably less than that of PR; however, RM’s film thickness was greater than that of PR. In addition, the setting times of EC, DR, and RM were shorter than that of PR (p < 0.05). The solubility was not significantly different among all groups. The three relatively new MTA groups (EC, DR, and RM) exhibited a significant difference in pH variation and calcium ion release relative to the PR group (p < 0.05). The radiopacity of the three new MTAs was considerably less than that of PR. The mechanical strength of RM was not significantly different from that of PR (p > 0.05); however, the EC and DR groups were not as strong as PR (p < 0.05). All MTA groups revealed cytocompatibility. In conclusion, the results of this study confirmed that EC, RM, DR, and PR exhibit clinically acceptable physicochemical and mechanical properties and cell cytotoxicity.

Effects of heating on the physical properties of premixed calcium silicate-based root canal sealers

The purpose of this study was to examine the effect of heating on the physical properties of four types of premixed calcium silicate-based root canal sealers. Endoseal MTA, Well-Root ST, EndoSequence BC Sealer, EndoSequence BC Sealer HiFlow, and AH Plus (epoxy resin root canal sealer) were heated at 100°C for 1 min, and changes in setting time, flow, and film thickness were evaluated in accordance with ISO 6876:2012 standards. In addition, pH measurement and scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses of the set materials were performed. All root canal sealers heated at 100°C showed significant decreases in setting time and flow, particularly Endoseal MTA. In addition, the film thickness of Endoseal MTA increased significantly after heating at 100°C. The pH and SEM/EDS results were not affected by heating. Heating calcium silicate-based root canal sealers accelerated setting time, decreased flow, and increased film thickness. However, the degree of these changes varied among the products. The present findings indicate that heat-induced changes in the physical properties of calcium silicate-based root canal sealers could adversely affect the quality of warm vertical condensation technique.

A Comparative Evaluation of Efficacy of Different Obturation Techniques used in Root Canal Treatment of Anterior Teeth: An in vitro Study

Aim: This study was undertaken to evaluate the percentage of gutta-percha-filled area (PGFA) using microscopic analysis of the cross-sections in the apical third of root canals when filled either with Thermafil technique, Warm Vertical Condensation technique and Cold Lateral Condensation technique without using sealers.

Materials and methods: Sixty single rooted extracted per-manent teeth were collected. After crown amputation, the teeth were randomly divided into three experimental groups of 20 specimens each. Group I–Thermafil obturation technique, group II–warm vertical condensation obturation technique and group III–cold lateral condensation obturation technique. Obturation was performed by specific techniques without using sealers. After obturation, the teeth were cross-sectioned horizontally at 2 to 3 mm from apex with the help of double sided diamond disk. Sections were digitally photographed and measured under Stereomicroscope at magnification of 50×.

Using a KS 100 imaging system the area of canals and the gutta-percha was recorded, also the percentage of gutta-percha filled area (PGFA) was calculated. The observations thus ob-tained were subjected to statistical analysis using ANOVA and student ‘t’ test.

Results: Maximum group difference was observed between groups I and III (3.558 ± 0.138) while minimum difference was observed between groups I and II (1.223 ± 0.137). Thus, all the between group differences were statistically significant.

Conclusion: This study supports the belief that the Thermafil Obturation technique produces significantly higher percentage of gutta-percha filled area (PGFA) than the warm vertical condensation technique or cold lateral condensation technique.

How to cite this article: Samadi F, Jaiswal JN, Saha S, Garg N, Chowdhary S, Samadi F, Tripathi VP. A Comparative Evaluation of Efficacy of Different Obturation Techniques used in Root Canal Treatment of Anterior Teeth: An in vitro Study. Int J Clin Pediatr Dent 2014;7(1):1-5.

Evaluation of coronal leakage and pathway of dye leakage after obturation with various materials for open apical foramina

The aim of this study was to investigate coronal leakage after obturation with mineral trioxide aggregate (MTA), resin-based sealer, and silicon-based sealer for open apical foramina and to evaluate pathway of leakage. Twenty-eight maxillary premolars were used, and instrumented to ISO size #80. Teeth were randomly divided into four groups as follows: Group A filled with MTA, Group B with gutta-percha and resin-based sealer, Group C with polymer-based material and resin-based sealer, and Group D with gutta-percha and silicon-based sealer. All samples were evaluated for coronal leakage with methylene blue solution and spectrophotometry. After leakage testing, samples were cut, and sections were observed. Dye leakage of Group A was significantly lowest among all groups at 15 days and 30 days. Defects which induced coronal leakage in resin-based sealer were observed at 7 mm from the apex. Coronal leakage after obturation with MTA for open apical foramina was significantly lower than resin-based sealer and silicon-based sealer.

The effect of different sealer placement techniques on sealing Ability: An in vitro study

Aim:

The aim of this in vitro study was to evaluate the sealing ability of an endodontic sealer following different techniques of its placement.

Materials and Methods:

A total of 119 permanent human anterior teeth were prepared by using manual Protaper^® and randomly divided into three equal groups of 33 teeth each. The teeth were obturated with the cold lateral condensation technique and AH26 sealer which was placed by using the following: G1: rotary lentulo spiral; G2: manual lentulo spiral; and G3: master gutta-percha coating. The remaining 20 teeth served as positive and negative controls. The samples were immersed in the methylene blue solution for 3 days and longitudinally sectioned for dye penetration assessment and analyzed using a stereomicroscope.

Results:

There was no statistically significant difference (P = 0.305) among the three groups. However, the rotary lentulo spiral technique and the master gutta-percha coating technique showed the highest (4.5 mm) and the lowest (3.8 mm) microleakage values, respectively.

Conclusion:

Different techniques of sealer placement used in this study provided a comparable seal. However, the master gutta-percha coating technique might be preferable because of its ease of use.

Expansion of gutta-percha in contact with various concentrations of zinc oxide-eugenol sealer: a three-dimensional volumetric study

INTRODUCTION

Successful endodontic treatment depends on achievement of a fluid-tight seal that is not possible solely with gutta-percha and requires the use of a root canal sealer. Eugenol, which is a principal component in zinc oxide-eugenol (ZOE) based sealers, is reported to produce a volumetric expansion of gutta-percha. The aim of this study was to evaluate the three-dimensional expansion of gutta-percha at various powder/liquid ratios of ZOE-based sealer by using spiral computed tomography (SCT).

METHODS

Fifty freshly extracted premolars with single canal were decoronated and instrumented by using RaCe rotary instruments (35/06). The teeth were divided into 5 groups of 10 each, and volume of the canal was measured by using SCT. The teeth were then obturated with gutta-percha cones (35/04) in groups ZE 1:1 to ZE 1:4 with Pulp Canal Sealer EWT (ZOE-based) with powder/liquid ratio of 1:1, 1:2, 1:3, and 1:4, respectively, and gutta-percha alone in control group (no sealer group). The filled volume in each canal was measured by using SCT 1 day, 7 days, and 1 month after obturation, and percentages of obturated volume and of volume changes in groups over time were calculated. The data were statistically analyzed by using one-way analysis of variance and post hoc multiple comparison tests.

RESULTS

The groups ZE 1:2 and ZE 1:3 gave the highest mean volume values during a 1-month period and were significantly different in comparison with groups ZE 1:1 and ZE 1:4 (P < .05).

CONCLUSIONS

Increasing the ratio of eugenol in sealer resulted in volumetric increase of gutta-percha. However, further studies should be performed to confirm the expansion and sealing ability of gutta-percha of the size corresponding to the prepared canal, leading to the achievement of fluid impervious seal.

Biocompatibility of four root canal sealers: a histopathological evaluation in rat subcutaneous connective tissue

The aim of this study was to evaluate the subcutaneous biocompatibility of: Epiphany, AH Plus, Pulp Canal Sealer and Sealapex root canal sealers. Sixty rats were randomly assigned to 4 groups, according to the sealer. Polyethylene tubes containing the tested materials were inserted into the connective tissue. The implants were removed after 7, 15 and 30 days, and the tissue samples were processed, stained and examined by light microscopy. The descriptive analysis considered: thickness of the fibrous capsule, severity of the inflammatory reaction, and presence of giant cells. After 7 days, all sealers induced moderate to severe inflammatory reaction. After 15 days, Epiphany and AH Plus sealers showed a moderate inflammatory reaction, while Pulp Canal Sealer and Sealapex induced severe and mild inflammatory reactions, respectively. After 30 days, mild inflammatory reactions were observed for Epiphany, Sealapex and AH Plus. Sealapex induced the lowest inflammatory response at all evaluation periods, and only Pulp Canal Sealer did not show a decreased in the inflammatory reaction over time.

In vitro study assessing apical leakage of sealer-only backfills in root canals of primary teeth

AIM

To assess the sealing ability of zinc oxide-eugenol (ZOE), Apexit, and Sealapex used as sealer-only backfills in root canals of primary teeth using the high-pressure replica technique.

METHODOLOGY

Two hundred and seventy root canals of deciduous molars as well as primary anterior teeth were randomly assigned to three groups (n=90). Root canals were prepared to size 35 and filled with either zinc oxide-eugenol (ZOE), Apexit, or Sealapex using a lentulo filler. Twenty-four hours after setting of the materials the roots were nail-varnished (except for the apical tip), and half of the specimens (n=45) were penetrated by a coloured (rhodamine B) epoxy resin. The resin was infiltated into the pores and cavities of the teeth in a high-pressure vessel. The remaining groups (n=45) were stored in 100% humidity, and infiltration of the resin followed after 40d. Apical leakage was assessed by means of a grinding technique using eight steps of 0.5mm each.

RESULTS

ZOE and Apexit failed to seal the root canals in both subgroups. This was significantly different from the root canals filled with Sealapex where in both subgroups some 30% of the specimens revealed a tight seal up to a distance of 2.9mm of the apex.

CONCLUSIONS

Under the conditions of this study it can be concluded that Sealapex shows less leakage than ZOE and Apexit. With regard to the three materials tested, Sealapex should be a viable alternative for sealer-only obturation of pulpectomized primary teeth. The high-pressure replica technique seems to be suitable for assessing leakage of root canal filling materials.

Sealer area associated with cold lateral condensation of gutta-percha and warm coated carrier filling systems in canals prepared with various rotary NiTi systems

AIM

To compare the area of sealer surrounding root fillings completed by two coated carrier systems (Thermafil Obturator and System GT Obturator) and the cold lateral compaction technique, following root canal preparation with two different NiTi rotary systems (Profile ISO and System GT).

METHODOLOGY

Sixty extracted human mandibular premolars were instrumented with ProFile ISO 0.06 taper and System GT instruments (n = 30 each). The teeth were divided into four subgroups (n = 15) for filling as following: group 1: ProFile + Thermafil Obturator, group 2: ProFile + Cold Lateral Compaction, group 3: System GT + GT Obturator, and group 4: System GT + Cold Lateral Compaction. In all groups the canals were prepared to a final size of 40, 0.06 taper in accordance with the manufacturer's instructions and Topseal was used as a sealer. Horizontal sections were obtained every 1 mm up to 12 mm from the apical foramen. Sections were digitally photographed under a stereomicroscope and the images were transferred to an IBM-compatible PC for image analysis. The cross-sectional area of the root canal and the area filled by sealer were calculated for each section and compared statistically both at all levels and by grouping the data as apical, middle and coronal segments; using the Kruskal-Wallis test with Bonferroni correction and chi-square tests (P = 0.05).

RESULTS

In the apical third (1-4 mm), the GT Obturator (group 3) had significantly less area of sealer (P < 0.05), while the difference between groups 1 and 2 was not significant (P > 0.05). For the middle and coronal thirds, both coated-carrier systems had significantly less area of sealer compared with their laterally compacted counterparts (P < 0.05).

CONCLUSIONS

With the combined use of ProFile + Thermafil Obturator and System GT + GT Obturator, significantly less area of sealer occurred than that achieved with both NiTi preparation systems followed by cold lateral compaction.

Degradation of trans-polyisoprene over time following the analysis of root fillings removed during conventional retreatment

AIM

To evaluate in vivo degradation of root filling materials over time.

METHODOLOGY

Thirty-six root filled teeth with or without periapical lesions were selected. Teeth with poor coronal restoration were not included. The teeth had been root filled 3-30 years previous and were scheduled for conventional retreatment. The association of root canal treatment, age, periapical lesion and root filling degradation was investigated. The filling material was removed from the root canal using files and no solvent. Trans-1,4-polyisoprene was isolated through solubilization of root filling remnants in chloroform followed by filtration and centrifugation. Gel permeation chromatography (GPC) and infrared spectroscopy (FT-IR) were utilized to study the occurrence and degree of degradation. The GPC and FT-IR data were collected for each sample and analysed statistically using the Kruskal-Wallis test.

RESULTS

Degradation of trans-1,4-polyisoprene was a slow process. The process was identified as an oxidation reaction through the production of carboxyl and hydroxyl groups. Compared with the control group, significant molar mass decrease was noted after 15 years (P = 0.0146) in teeth with no periapical lesions. However, in teeth associated with periapical lesions the number of years for significant degradation was reduced to 5 (P = 0.0009).

CONCLUSION

Polyisoprene degrades inside root canals as an oxidative process. The presence of periapical lesions was associated with a more rapid onset of degradation.

Clinical relevance of trans 1,4-polyisoprene aging degradation on the longevity of root canal treatment

This in vivo study investigated the time of degradation of root filling material (trans 1,4-polyisoprene) retrieved from endodontically treated teeth and correlated the occurrence of degradation with the longevity of endodontics. Thirty-six root-filled teeth with different filling times (2 to 30 years) and with and without periapical lesions were selected. All teeth presented clinical indication for root canal retreatment. The association among filling time, presence of periapical lesion and root filling material degradation was investigated. Root filling samples were retrieved from the root canals using a Hedströ m file without solvent. The trans 1,4-polyisoprene was isolated by root filling solubilization in chloroform followed by filtration and centrifugation. GPC and FT-IR were the analytical techniques utilized. Degradation of trans 1,4-polyisoprene occurred with time, as a slow process. It is an oxidative process, and production of carboxyl and hydroxyl groups in the residual polymer were observed. Statistically significant decrease of molar mass was observed after 5 (p=0.0001) and 15 (p=0.01) years in teeth with and without periapical lesion, respectively. Bacteria participated in polymer degradation. Gutta-percha aging was proven an important factor for the long-term success of endodontic treatment. The findings of the present study showed that, after 15 years, polymer weight loss may decrease the capacity of the filling mass to seal the root canal space and prevent re-infection, thus compromising significantly the longevity of root canal therapy.

Polymicrobial Leakage of Four Root Canal Sealers at Two Different Thicknesses

The present study investigated the sealing ability of four root canal sealers at two different thicknesses. There were 82 maxillary incisors roots prepared with Gates Glidden drills up to size 6 and divided into four groups: Pulp Canal Sealer, EndoREZ, Sealapex, and AH Plus. Each group was divided in two subgroups and gutta-percha cylinders 1.5 or 1 mm wide were used, respectively. The roots were mounted in a bacterial leakage model and the system was checked daily during the following 12 wk. Data were analyzed by Log-Rank test and Student t-test. In the thin layer samples, the sealers demonstrated similar results while, in the thick layer samples, AH Plus revealed the best performance. Generally, greater sealer thickness influenced negatively the sealing ability of the root canal filling, except in AH Plus samples.

Assessment of the Sealing Ability of a New Root Canal Obturation Material

This study was designed to compare the leakage allowed by different obturation materials, using a fluid-transport method. Sixty-six single-rooted human anterior teeth were fully instrumented by using the "step-back" technique and irrigated with 5.25% sodium hypochlorite. The smear layer was removed by washing in 10 ml of 17% EDTA. The specimens were randomly divided into three experimental groups of 18 teeth each, plus two groups of 6 teeth each for positive and negative controls. The specimens were obturated by the lateral condensation technique, with gutta-percha and AH 26 or AH plus sealers, or Epiphany sealer and Resilon core material. The fluid transport method used in this study gave quantitative results and allowed nondestructive evaluation of the specimens. The teeth filled with gutta-percha and AH 26 exhibited the most leakage. The least leakage was seen with Epiphany sealer and Resilon core material. The differences in leakage among the groups were statistically significant (p < 0.05). It was concluded that of the materials tested under the conditions of this study, Epiphany allowed the least leakage.

A laboratory analysis of gutta-percha-filled area obtained using Thermafil, System B and lateral condensation

AIM

To determine the percentage of gutta-percha-filled area (PGFA) in the apical third of root canals when filled with either Thermafil, System B or lateral condensation.

METHODOLOGY

Sixty extracted human maxillary central incisor teeth were root filled as following: G1: lateral condensation (n = 20), G2: System B (n = 20) and G3: Thermafil system (n = 20). A horizontal section was cut 2 and 4 mm from the apical foramen of each tooth. The samples were prepared for microscopic analysis and photomicrographs of each apical surface were taken at a magnification of 50x. Through digital image analysis, the cross-sectional area of the canal and the gutta-percha was measured. The PGFA was calculated. The PGFA data obtained in the three groups were analysed using a nonparametric Friedman and Wilcoxon signed-rank tests.

RESULTS

Significant differences in PGFA were found between the Thermafil System (G3) and both System B (G2) and lateral condensation (G1) (P < 0.01). The greatest PGFA occurred in the Thermafil group. No significant statistical difference was found between System B and lateral condensation (P > 0.05).

CONCLUSIONS

The coated carrier gutta-percha system Thermafil produced significantly higher PGFAs than lateral condensation and System B techniques.

The influence of root canal shape on the sealing ability of two root canal sealers

AIM

To evaluate the influence of root canal form on the sealing ability of two root canal sealers.

METHODOLOGY

Twenty radiographically confirmed straight and 20 curved root canals were prepared with a stepback hand filing technique. Root canal aberrations created during preparation were determined by the use of double exposure radiographic technique. The prepared canals were filled with lateral condensation of gutta-percha and one or other of two root canal sealers (Pulp Canal Sealer and Sealapex). Leakage along the apical 10 mm of roots was measured with a fluid transport model at 1, 3, 6, 9 and 12-month intervals.

RESULTS

There were no statistically significant differences between straight and curved root canals (P > 0.05) for prevalence of root canal transportation. The prevalence of apical transportation was 80% in the straight and 85% in the curved root canals. A complete seal was more frequently observed in straight canals compared with curved canals. Utilizing the pi* index, analysis showed the filling with Sealapex allowed more leakage than Pulp Canal Sealer at 1 year.

CONCLUSION

Under the conditions of the study, root canal form influenced short-term sealing ability. In the long-term the seal was affected by the sealer rather than root canal form.

Presence of pores and vacuoles in set endodontic sealers

AIM

To assess qualitatively the presence of pores and vacuoles in the structure of various endodontic sealers when set.

METHODOLOGY

Eight specimens were prepared in keeping with Instituto Argentino de Racionalización de Materiales (IRAM) and ISO regulations for each of the 10 sealers assessed. Four specimens per sealer were examined to identify the presence of structural defects, termed pores, on the external surface. The remaining four specimens were used to examine the presence of defects on the surface exposed by cross-sectional fracture; these were termed vacuoles. The largest and smallest diameters of the pores and vacuoles were measured by scanning electron microscope on both surfaces. The structural defects were classified according to their frequency as abundant, frequent, scarce or exceptional.

RESULTS

Pores and vacuoles were consistently found in every specimen of each sealer. However, their frequency and dimensions were greater in zinc-eugenol-based sealers than in epoxy-resins and glass-ionomer sealers; they increased if the sealer contained calcium hydroxide. The diameter of the pores ranged from 5 to 320 microm and the diameter of the vacuoles ranged from 80 to 500 microm. The diameter of the vacuoles always exceeded that of the pores.

CONCLUSIONS

Pores and vacuoles were a consistent finding in set sealers. Their frequency and size depended on the density of the sealer and increased when the sealers contained calcium hydroxide.

The influence of root-end resection and root-end cavity preparation on microleakage of root filled teethin vitro

AIM

To investigate in vitro the influence of root-end resection and root-end cavity preparation on leakage of root filled teeth.

METHODOLOGY

The root canals of 48 roots, 16 mandibular premolars (G1), 16 mandibular incisors (G2) and 16 maxillary incisors (G3), 12 mm in length, were enlarged using a modified 'balanced force' technique and filled with gutta-percha and sealer using lateral compaction. After setting, leakage along the canal was measured using a fluid transport model. Root-end resection and root-end cavity preparation were then performed, leaving roots 10 mm in length with root fillings of 7 mm (groups R1, R2 and R3, respectively). Fluid transport was measured again along the remaining root fillings of all groups using the same experimental conditions. Results of leakage before and after root-end resection were analysed statistically using the Kruskal-Wallis and Wilcoxon tests.

RESULTS

A total of 31% of the roots leaked before and 54% after root-end preparation; the difference was significantly different (P < 0.001). No significant differences were found either among groups G1, G2, G3 (P = 0.565) or among groups R1, R2, R3 (P =0.2628). Significant differences, however, were shown between groups G1-R1 (P = 0.0053), G2-R2 (P =0.0089) and G3-R3 (P = 0.0461).

CONCLUSIONS

Root-end resection and root-end cavity preparation compromised the seal of 7 mm root fillings in all tooth groups. Increased leakage was recorded in the following order: mandibular incisors > mandibular premolars > maxillary incisors.

The use of glass ionomer cements in both conventional and surgical endodontics

The capacity to bond to dental tissues, especially to dentine, their long-term fluoride release and their biocompatibility make glass ionomer cements (GICs) advantageous for use in endodontics, as well as in restorative dentistry. This review provides information on the basic properties of GICs, such as adhesion, antimicrobial effects and biocompatibility, particularly as they relate to use in endodontics. Indications for the use of GICs in endodontics are orthograde root canal sealing, root-end filling, repair of perforations and root resorption defects, treatment of vertical fractures and maintenance of the coronal seal. The paper includes a review on each of these indications. It is concluded that in spite of the critical handling characteristics and the inconclusive findings regarding sealing ability and antimicrobial activity, there is substantial evidence to confirm their satisfactory clinical performance. Both soft tissue and bone compatibility make them suitable for use during endodontic surgery.

A comparative study of selected physical properties of five root-canal sealers

AIM

To investigate selected physical properties of five root-canal sealers.

METHODOLOGY

The solubility, film thickness, flow, working and setting times of Roth 801, Tubli-Seal EWT, AH Plus, Apexit and Endion were evaluated. Solubility was measured by weight change of standard specimens in water over a 3-month period. Film thickness was measured as the distance between weighted glass slides containing a standard quantity of sealer. Flow was assessed by rate of sealer extrusion through a standard bore diameter, after unit time. Working time was taken as the point at which flow rate was reduced by 10%. The indentation test using a modified Gilmore needle was employed to investigate the setting times.

RESULTS

AH Plus was the least soluble, whilst Apexit was the most unstable in water. The solubility values in increasing order were: AH Plus<Tubli-Seal EWT<Endion<Apexit. Also, AH Plus had the highest film thickness. All sealers showed comparable flow rates. The working time varied from 50 min for Endion to over 2 h for AH Plus and Tubli-Seal EWT. The range of setting times recorded was from 70 min for Tubli-Seal EWT to 8 days for Roth 801.

CONCLUSIONS

1. AH Plus showed the greatest stability in solution and Tubli-Seal EWT performed well, but Apexit and Endion had higher solubility values. 2. The film thickness values in increasing order were: Tubli-Seal EWT<Apexit<Endion=Roth 801<AH Plus. 3. The flow rates for all sealers were similar. 4. The working times for all sealers were greater than 50 min. 5. Roth 801 did not set when incubated in volumes sufficient to fill the test matrices.

Rheological properties and biocompatibility of endodontic sealers

AIM

To determine the flow characteristics and subcutaneous tissue reactions to five endodontic sealers.

METHODOLOGY

The materials used were Procosol, AH26, Endomethasone, Sealapex and Endion. The sealers were prepared following the manufacturers' instructions, and 0.075 mL of each material was placed on a glass surface, which was then rotated 90 degrees. The samples were stored at 37 degrees C and 95% humidity. The displacement of the sealer was recorded by measuring the difference between its original position and the position recorded at 15 and 60 min. Three samples of each material were used. Two pockets were created in the back of Wistar rats, and one silicone tube, 1 mm in diameter and 1 cm in length, was implanted in each. One was filled with one of the materials under study, and the other empty tube was implanted as a control. Fourteen days after implantation, the animals were sacrificed, and samples of the skin containing the tubes were histologically processed. Histological and histomorphometric evaluations of the tissues adjacent to the open end of the tube were carried out the volume of tissue reaction was measured histomorphometrically according to standard stereological principles. Results were statistically analysed using analysis of variance and Duncan's test.

RESULTS

The highest flow values were obtained with Sealapex and AH26. Time significantly affected the flow and the material (P < (1001). Procosol and Endion produced the most severe histological reactions: these were outlined by fibrous tissue; AH26. Endomethasone and Sealapex produced reactions of smaller size and with more moderately defined limits.

CONCLUSIONS

The flow did not correlate with the degree of inflammatory response. Procosol and Endion produced the most severe tissue reactions, whereas Endomethasone, Sealapex and AH26 produced only minimum reactions.

Influence of a microbrush on bonding fiber post into root canals under clinical conditions

OBJECTIVE

The objective of this clinical report was to evaluate the effectiveness of a microbrush as a carrier of priming-adhesive solution in formation of resin tags, adhesive lateral branches, and resin-dentin interdiffusion zone (RDIZ) when the brush was used to bond fiber posts under clinical conditions.

STUDY DESIGN

Twenty endodontically treated teeth, already scheduled for extraction for endodontic or periodontal reasons, were selected for this study. The patients were informed, and their written consent was obtained. The samples were randomly divided into 2 groups of 10 samples each. In group 1, One-Step (Bisco, Schaumburg, Ill) was applied with a brush with Duo-Link resin cement (Bisco). In group 2, One-Step was applied with a microbrush with Duo-Link resin cement (Bisco). Use of the adhesive systems and resin cements was strictly according to manufacturers' instructions. The priming-adhesive solution was light-cured before the dual resin cement and the post were placed. Twenty Aestheti-Plus posts (white quartz fiber posts; RTD, St. Egreve, France) were used. A week after application, the root samples were extracted and processed for SEM observations.

RESULTS

Both adhesive systems showed RDIZ and resin tag and adhesive lateral branch formation. In Group 2 samples, RDIZ morphology was easily detectable and uniform along root canals. Also, resin tag formation was well represented in all thirds. In group 1 samples, resin tag formation at the apical third and RDIZ formation was less evident. Statistically significant differences were found among the two groups at the apical third.

CONCLUSION

The microbrush permitted a more uniform RDIZ and resin tag formation along the entire length of the canal than did the standard brush. The microbrush can be routinely used for bonding fiber posts into root canal preparations.

Apical leakage of five root canal sealers after one year of storage

A fluid transport model study was used to compare the sealing ability of five root canal sealers (AH26, AH Plus, Apexit, Diaket, and Ketac-Endo) on 60 single-rooted teeth after 1 yr of storage. The root canals were prepared with Gates Glidden drills by using a step-back technique before lateral condensation of gutta-percha with the tested sealers. The specimens were stored in saline solution for 1 yr at 37 degrees C. The leakage was measured by the movement of an air bubble in a capillary glass tube connected to the experimental root section. Apexit (0.490 microl) leaked significantly more than AH Plus (0.378 microl) and Ketac-Endo (0.357 microl), whereas AH26 (0.390 microl) and Diaket (0.429 microl) showed no significant difference from either Apexit or from AH Plus and Keto-Endo.

Quality of cold and warm gutta-percha fillings in oval canals in mandibular premolars

AIM

The aim of this study was to determine the quality of cold and warm gutta-percha fillings in oval canals.

METHODOLOGY

Two groups of mandibular premolars with oval canals were selected after bucco-lingual and mesio-distal radiographs indicated an internal long: short diameter of > or =1.6 at a level 5 mm from the apex. After instrumentation they were obturated, respectively, by cold lateral compaction of gutta-percha cones (cold GP) and vertical compaction of warm gutta-percha (warm GP). Leakage along apical root fillings was measured using a fluid transport model. After the leakage test, horizontal sections were cut 2 and 4 mm from the apex. The area of the canal and gutta-percha in cross-sections was measured using an image analysis program. The quality of root fillings was evaluated by calculating the percentage of gutta-percha-filled canal area (PGP).

RESULTS

No significant difference in leakage was found between the two groups (P = 0.570). The warm GP group produced significantly higher PGPs than the cold GP group 4 mm from the apex only (P = 0.522 at 2 mm: P = 0.000 at 4 mm).

CONCLUSIONS

The percentage of gutta-percha-filled canal area using warm GP was greater than that of the cold GP in oval canals.

Dye penetration in dry and water-filled gaps along root fillings

AIM

The aim of this study was to investigate the influence of hydration in voids along root fillings on methylene blue penetration.

METHODOLOGY

A total of 80 human root canals were prepared using a step-back technique and filled with a zinc oxide based sealer and gutta-percha. Leakage along the fillings was measured by a transport fluid model and classified into three categories: gross leakage (GL), slight leakage (SL) and no leakage (NL). Specimens with NL and SL were immersed into methylene blue (MB) 2% for 24 h (group I). Specimens with GL which had wide gaps filled with water were randomly divided into two groups (II, III). Transport air was applied to remove water from gaps only in specimens of group III. All tested specimens from groups II and III were also immersed into MB 2% for 24 h. Each specimen was then split longitudinally and linear measurements of dye penetration were recorded.

RESULTS

Group III (with dry gaps) showed significantly more dye penetration than group II. No significant difference was found between group I and group II.

CONCLUSIONS

Methylene blue penetrates along root fillings more easily in dry gaps than in water-filled gaps.

Dye leakage and SEM study of roots obturated with Thermafill and dentin bonding agent

The apical seal of roots obturated with a dentin bonding agent and Thermafill with and without the use of sodium hypochlorite as an irrigating solution was compared by a dye leakage test. Roots obturated with Thermafill and a zinc oxide eugenol sealer were used as controls. Thirty-eight roots were prepared chemomechanically and divided into three experimental groups. The teeth of group 1 were filled with Thermafill and the dentin bonding agent using sodium hypochlorite as the irrigant. The teeth of group 2 were filled in the same way, but saline solution was used as the irrigant. Before the root canal was filled the smear layer was removed from the root canal walls of both groups by rinsing the root canal with a 17% EDTA solution. The teeth of group 3 were filled with Thermafill and a zinc oxide eugenol sealer. The teeth were immersed in 2% methylene blue solution. The root fillings of groups 1 and 2 leaked significantly more than those of group 3. The resin-dentin-guttapercha interface of group 1 was observed by scanning electron microscopy and showed a typical hybrid layer. An intimate contact between resin and dentin was present in group 2, but a resin-dentin interdiffusion zone was only occasionally observed. The use of dental adhesives and the hybrid layer formation did not improve the seal of Thermafill root canal fillings.

Effect of calcium hydroxide dressing on seal of permanent root filling

Low apical leakage along root fillings following an application of calcium hydroxide was reported in a few methylene blue dye penetration studies. It has been found recently that methylene blue is decolored by calcium hydroxide, indicating that the short penetration of methylene blue may not be due to a tight seal only. Of the 80 roots of human maxillary central incisors used in this study, 40 roots (group 1) received calcium hydroxide root canal dressing whereas another 40 roots (group 2) did not. All the roots were then obturated with gutta-percha and Tubli-Seal sealer. Leakage along 20 filled roots in each group was measured using a modified fluid transport model at 48 h, 2, 4, 8 and 16 weeks after obturation; whereas leakage of another 20 filled roots in each group was measured using dye penetration with 1% methylene blue. Using the fluid transport model, no significant difference was found between the two groups at any time interval (P = 0.4847, 0.3875, 0.9490, 0.4786, 0.9148 respectively after 48 h, 2, 4, 8 and 16 weeks); using the methylene blue penetration method, leakage in group 1 (with root canal dressing) was significantly less than that in group 2 (without root canal dressing) (P = 0.0374). The contradiction in results from the different models indicated that problems existed with the models.

Effect of sealer thickness on long-term sealing ability: a 2-year follow-up study

Long-term sealing ability of root-canal sealer is of clinical importance. We compared the performance of five sealers and a dentine bonding agent, at thicknesses of 0.05 mm (thin layer) and 0.3 mm (thick layer), in 212 standard human root specimens, before and after storage in water for 2 years. Thick layers of Roth and Pulp Canal Sealer EWT (PCS-EWT) allowed more leakage than did thin layers (P = 0.0000, 0.0358 for Roth and PCS-EWT, respectively) whereas no significant difference was found between the thin and thick layers for AH26, Ketac-Endo, Sealapex and J&J Bonding Agent. The pooled results of the thin and thick layers, which have clinical relevance, showed that after storing the specimens in water for 2 years, AH26, Sealapex, Ketac-Endo and PCS-EWT leaked more than before storage in water (P = 0.0008, 0.0000, 0.0035, 0.0257 for AH26, Sealapex, Ketac-Endo and PCS-EWT respectively), and that J&J Bonding Agent allowed less leakage and PCS-EWT more leakage than the other four sealers (P = 0.0000).

Dental materials: 1995 literature review

This critical review of the published literature on dental materials for the year 1995 has been compiled by the Dental Materials Panel of the United Kingdom. It continues the series of annual reviews started in 1973 and published in the Journal of Dentistry. Emphasis has been placed upon publications which report upon the materials science or clinical performance of the materials. The review has been divided by accepted materials classifications (fissure sealants, glass polyalkenoate cements, resin composites, dentine bonding, dental amalgam, endodontic materials, casting alloys, investment materials, resin-bonded bridges and ceramo-metallic restorations, all ceramic restorations, denture base and soft lining materials, impression materials, dental implants, orthodontic materials and biomechanics). Three hundred and thirty articles published in 68 titles have been reviewed.

Leakage of AH26 and Ketac-Endo used with injected warm gutta-percha

Condensing warm gutta-percha (GP) can greatly reduce the distance between the GP and the root canal walls (RCW). Different sealers with different film thicknesses may seal such close fits differently. With the use of a fluid transport model, leakage of AH26 and Ketac-Endo used with injected warm GP to fill root canals was measured. The distance between the condensed GP and RCW and the film thickness of the two sealers was determined as well. After condensation, the distance between GP and RCW was mostly less than 25 microns. AH26, with a film thickness of 39 microns, leaked more than Ketac-Endo (p < 0.05) of which the film thickness was 22 microns. It seems that film thickness of sealer is an influencing factor on the sealing ability of a root canal filling when condensation of thermoplasticized GP is performed.

An in-vitro evaluation of sealer placement methods

Successful root canal therapy is dependent upon obturating the root canal system. A critical component of the filling procedure is sealer placement. This in vitro study investigated the efficacy of six methods of sealer placement using clear plastic blocks with simulated curved canals instrumented to the apex using a step-back technique. After sealer placement and setting, the blocks were cross-sectioned at 2 mm intervals from mid-canal to apex. The sections were evaluated with a stereo operating microscope at x6 magnification for placement of an evenly distributed layer of sealer around the prepared canal walls. The lentulo spiral and the Max-i-Probe Delivery System were the most effective means of sealer placement, followed by ultrasonic and sonic files. The least effective methods were the paper point and the K file.