Adhesive interface and bond strength of endodontic sealers to root canal dentine after immersion in phosphate-buffered saline

Ultrasonic activation of adhesive systems increases bond strength and intratubular penetration of resin cement in root dentin subjected to radiation therapy

OBJECTIVE

This study aimed to evaluate the effect of ultrasonic activation of etch-and-rinse and self-etch adhesive systems on the bond strength of resin cement to irradiated root dentin.

MATERIALS AND METHODS

Eighty human maxillary anterior teeth were distributed into 8 groups (n = 10), according to the type of adhesive system used (etch-and-rinse and self-etch), the ultrasonic activation of the adhesive systems, and the dentin condition (irradiated or non-irradiated - 70 Gy). Endodontic treatment was performed followed by fiberglass post-space preparation. After fiberglass posts' luting, the roots were transversely sectioned on dentin discs and submitted to the push-out bond strength test (0.5 mm/min). The fractured specimens were analyzed under a stereomicroscope and Scanning Electron Microscope (SEM) for failure mode classification. One of the dentin discs was analyzed under SEM to evaluate the characteristics of the adhesive interface.

RESULTS

Irradiated specimens had lower bond strength than non-irradiated specimens (P < 0.0001). Ultrasonic activation of both adhesive systems increased the bond strength of the resin cement to irradiated dentin (P < 0.0001). Radiotherapy significantly affected the failure mode in the middle (P = 0.024) and apical thirds (P = 0.032) (adhesive failure).

CONCLUSION

Non-irradiated specimens had a more homogeneous adhesive interface. When ultrasonically activated, both adhesive systems showed a greater number of resinous tags, regardless of the dentin condition.

CLINICAL RELEVANCE

Ultrasonic activation of adhesive systems is a feasible strategy to enhance fiberglass posts retention in oncological patients.

Comparative Analysis of AH Plus Bond Strength to Root Canal Dentin and Adhesive Interface Quality after Calcium Hydroxide Removal using Different Irrigation Protocols

INTRODUCTION

To evaluate the push-out bond strength (POBS) of AH Plus sealer to root dentin and the adhesive interface quality after calcium hydroxide (Ca(OH)2) intracanal dressing removal with different final irrigation protocols.

METHOD

After root canal instrumentation and irrigation, 40 root canals were filled with Ca(OH)2 and sealed. After 14 days, the specimens were randomly distributed according to the irrigation protocols for Ca(OH)2 removal (n = 10): GH2O (control) - distilled water; GNaOCl - 1% NaOCl; GEDTA - 17% EDTA; GEDTA + NaOCl - 17% EDTA + 1% NaOCl. The root canals were filled with AH Plus sealer and gutta-percha. After 7 days, the roots were sectioned into dentin slices and submitted to POBS test and analysis of the adhesive interface under scanning electron microscope. The POBS data were statistically evaluated (analysis of variance and Tukey test). The Kruskal-Wallis and Mann-Whitney tests were used to analyze the adhesive interface (α = 0.05).

RESULTS

GH2O, GNaOCl, and GEDTA + NaOCl had similar POBS values, with higher values on the apical third, in comparison with other thirds (P < .05). A homogeneous and free-of-gaps adhesive interface was observed for GH2O, GNaOCl, and GEDTA + NaOCl, with difference between GH2O and GEDTA (P < .05). GH2O and GEDTA + NaOCl presented higher sealer tags formation (P < .05).

CONCLUSION

The final rinse with EDTA for Ca(OH)2 dressing removal had a negative effect on the POBS of the filling material to root dentin. The use of EDTA followed by NaOCl had results similar to the distilled water, providing uniform and free-of-gaps adhesive interface, and a higher number of sealer tags.

An In Vitro Comparative Study of the Push-out Bond Strengths of Various Endodontic Sealers to Radicular Dentin

BACKGROUND

The bond strength of an endodontic sealer to the root dentin is an important factor in maintaining the integrity of the root canal seal. The present study aimed to assess the push-out bond strength of three endodontic sealers used with the single-cone obturation technique.

MATERIALS AND METHODS

The root canals of 40 central maxillary incisors were instrumented using ProTaper Universal NiTi rotary files. The roots were divided into 4 groups (N = 10) according to the type of root canal sealers: Group 1 (control group): AH Plus/Gutta-percha lateral condensation technique (LC); Group 2: AH Plus/Gutta-percha single-cone technique (SC); Group 3: GuttaFlow 2/SC; Group 4: Realseal SE/SC. After obturation, each tooth was prepared for push-out assessment. The total and sectional push-out bond strengths were measured and statistically analysed. Furthermore, failure modes were identified microscopically.

RESULTS

The results indicated that samples in the first group showed the highest total and sectional bond strengths. Samples from other groups showed statistically similar total bond strengths. The highest sectional bond strength was found mainly in the apical root sections. Cohesive failure was predominant for the first group, whereas adhesive failure was predominant in the other groups.

CONCLUSIONS

It could be concluded that the dentin bond strengths of the tested sealers used with the single-cone technique were nearly similar but lower than those of AH Plus/LC. The highest sectional bond strength was observed in the apical thirds. The failure mode was mostly cohesive for AH Plus/LC and adhesive for sealers used with the single-cone obturation technique.

Calcium Silicate-Based Sealer Dentinal Tubule Penetration-A Systematic Review of In Vitro Studies

The aim of this systematic review was to perform a qualitative synthesis of in vitro studies which evaluate and compare the penetration of calcium silicate-based sealers into dentinal tubules. A systematic advanced search was performed in Scopus, Embase, Medline (via PubMed), Web of Science, and Cochrane databases on the 1 December 2022. In vitro studies that compared the tubular penetration of at least two calcium silicate-based sealers in extracted human teeth were eligible. PRILE 2021 guidelines were used for the assessment of the risk of bias included studies. The search identified a total of 680 preliminary records, among which 12 studies were eligible for review. The most used methodology to evaluate sealer penetration was the use of a fluorochrome together with the tested sealers and the analysis of their penetration under confocal laser microscopy. Regarding the results of the included studies, calcium silicate-based sealers exhibit a favorable dentinal tubule penetration. Tubular penetration, however, can be affected by factors such as the irrigation protocol, sealer activation, the filling method used, and root canal morphology. EndoSequence BC Sealer showed the highest sealer penetration among the tested sealers. The influence of different fluorochromes on the results of dentinal tubule penetration studies should also be further explored. The in vitro nature of the included studies limits the applicability of the results into the clinical setting. Prospero registration: CRD42022383896.

Comparison of Dentinal Tubule Penetration between a Calcium Silicate-Based Sealer with Ultrasonic Activation and an Epoxy Resin-Based Sealer: A Study Using Confocal Laser Scanning Microscopy

OBJECTIVE

 The aim of this study was to compare the degree of dentinal penetration between an epoxy resin-based sealer applied by using two different filling methods and an ultrasonically activated calcium silicate-based sealer via confocal laser scanning microscopy (CLSM).

MATERIALS AND METHODS

 Forty-five extracted permanent maxillary premolars with type II canals (Vertucci's classification) were subjected to the experiment. The root canals were instrumented and distributed randomly into the following three groups: AH Plus + continuous wave technique (AHC group); AH Plus + single cone technique (AHS group); and Endoseal MTA + single cone technique with ultrasonic activation (EMS) group. Each sealer was labeled with rhodamine B dye to allow visualization under CLSM. The sealer penetration depth in each sample was observed at 2 mm and 5 mm from the apex by using CLSM. The data were statistically analyzed by using analysis of variance or Kruskal-Wallis H test according to normality of variable (α = 0.05).

RESULTS

 In all groups, the maximum sealer penetration depth, mean fluorescence intensity, and sum fluorescence intensity values were higher at the 5-mm level than at the 2-mm level. At the 5-mm level, the EMS group showed the lowest value (p = 0.02). At the 2-mm level, there were no statistically significant differences among any of the groups. The AHC group showed higher values than the other groups, but there was no statistically significant difference in the apical area where access of instruments was difficult.

CONCLUSION

 The AHC group showed the highest dentinal tubule penetration, but had questionable filing efficacy in the apical area, which is of particular importance for the success of root canal treatment. Therefore, in areas such as the apical 2 mm of premolars with type II canals, which are difficult to access by using instruments such as heat carriers, other appropriate approaches may be required accordingly.

Correlation between Bond Strength to Dentin and Sealers Penetration by Push-Out Test and CLSM Analysis

This study correlated the bond strength (BS) and dentin penetration of different sealers by push-out test and Confocal Laser Scanning Microscopy (CLSM) analysis. Forty-five root canals were prepared according to the crown-down technique and filled with gutta-percha associated to the following sealers (n=15): Endofill, AH Plus and MTA Fillapex. Five canals of each group were filled with the sealers added with 0.1% Rhodamine B dye. Next, the specimens were transversely sectioned and submitted to the push-out test (n=10) and CLSM analysis (n=5). The BS data showed the following means (MPa) and standard deviation: AH Plus (4.17±1.86); MTA Fillapex (3.13±1.96) and Endofill (2.10±1.03). Statistical analysis (two-way ANOVA, α=0.05) showed significant difference among sealers (p<0.001) and root canal thirds (p<0.001). The BS results of Endofill and MTA Fillapex were statistically similar (p>0.05), however, they were statistically different from AH Plus (p<0.001). The regional analysis of BS showed similarity between middle and apical thirds (p>0.05), and both were different from coronal portion (p<0.001). CLSM analysis verified tags formation in all groups and higher penetration of the specimens filled with AH Plus (p<0.05). The Kendall test (correlation between BS to dentin and sealer penetration into dentinal tubules) and the Pearson test (between failures pattern and sealer penetration into dentinal tubules) did not show correlation between the variables evaluated for all the tested sealers (p>0.05). AH Plus group had higher BS to dentin, and deeper tags formation than the other sealers. There was no significant correlation between BS and intratubular penetration of the tested sealers.

Comparative Evaluation of Retreatability of Endodontically Treated Teeth using AH 26, Fluoride Varnish and Mineral Trioxide Aggregate-based Endodontic Sealers

Background and Objectives:

Endodontic sealers are used to fill the gap between the root filling material and canal walls. Retrievability is an important requirement for sealers and root filling materials in non-surgical endodontic retreatment. This study sought to assess the retreatability of fluoride varnish, AH 26 and Mineral Trioxide Aggregate (MTA)-based sealers using Cone-Beam Computed Tomography (CBCT).

Materials and Methods:

This in vitro, experimental study evaluated 45 extracted single-rooted, single-canal human mandibular premolars. Teeth with cracks or fracture were excluded. The root canals were prepared using ProTaper Universal rotary system up to size F4 according to the manufacturer’s instructions. The teeth were then randomly divided into three groups of 5% fluoride varnish, AH 26 and MTA Fillapex. CBCT scans were obtained of the teeth with 200 μm voxel size. MATLAB R2012 software was used to quantify the amount of sealer remaining in the canal. Two observers evaluated the images. Data were analyzed using SPSS via the Kruskal-Wallis and Mann Whitney tests.

Results:

The amount of sealer remaining in the root canals was significantly different among the three groups (P<0.05). The amount of AH 26 sealer remaining in the root canals (1.91±1.46) was significantly greater than MTA Fillapex (0.62±0.26) and fluoride varnish, but the latter two were not significantly different in this respect (P>0.05).

Conclusion:

Considering the adequate adhesion of fluoride varnish to dentin, its cariostatic effect and low cost, it seems to be a suitable alternative to the commonly used endodontic sealers.

Influence of environment on testing of hydraulic sealers

In vitro material testing is undertaken by conducting a series of tests following procedures outlined in international standards. All material properties are measured in water; however biological behavior is undertaken in alternative media such as Dulbecco’s modified eagle medium (DMEM) or simulated body fluid. The aim of this study was to characterize four dental root canal sealers and study their properties in different media. Four dental root canal sealers were assessed. They were characterized by a combination of techniques and the sealer properties were tested as specified by ISO 6876 (2012) and also in alternative media. The sealer biocompatibility was measured by cell function and proliferation assays of elutions. All sealers complied with ISO specifications. The material properties were effected by the type of soaking medium used and the surface micromorphology and elemental composition were dependent on the soaking solution type. Both BioRoot and MTA Fillapex showed cytotoxicity which reduced at higher dilutions. The material chemistry, presentation, environmental conditions and testing methodology used affected the sealer properties. Standards specific to sealer type are thus indicated. Furthermore the methodology used in the standard testing should be more relevant to clinical situations.

Wear profile of canal wall surfaces and bond strength of endodontic sealers after in situ acid challenge

AIM

To evaluate the wear of root wall surfaces, the bond strength of sealers to dentine and the demineralization around root filling materials after canals were exposed to acid challenge in situ.

METHODOLOGY

Eighty-seven roots of mandibular incisors were selected. Thirty-two were used in the laboratory bond strength study (n = 8), and 55 in the in situ study (n = 11). Root canals were prepared biomechanically and then filled with gutta-percha and AH Plus, MTA Fillapex, Sealapex or Endofill. For 14 days, 11 participants used intra-oral devices with five sterilized roots (four experimental and one control - only canal prepared). Drops of sucrose were dripped onto roots allowing the accumulation of biofilm on canal surfaces. Roots were removed, sectioned and analysed for the following: bond strength of filling material using a push-out test and also wear profile and dentine demineralization using confocal microscopy. Bond strength (MPa) was evaluated by two-way anova and Tukey test (α = 0.05), and wear profile was assessed by Kruskal-Wallis and t-tests (α = 0.05).

RESULTS

AH Plus had the highest bond strength values. Intermediate results were found in roots with MTA Fillapex and Endofill, whilst Sealapex had inferior results (P < 0.05). No significant differences were found amongst root thirds (P > 0.05). For wear profile, samples were associated with degradation of the filling materials after exposure to the oral environment (P < 0.05). Roots had signs of demineralization around the filling material when Sealapex and Endofill were used.

CONCLUSIONS

Sealers were not able to prevent degradation of the adhesive interface and dentine. AH Plus and MTA Fillapex had superior bond strength to dentine and less intense demineralization around the root filling.