Influence of the Method in Root Canal Filling Using Active Lateral Compaction Techniques

Ultrasonic activation of the endodontic sealer enhances its intratubular penetration and bond strength to irradiated root dentin

To evaluate the effect of ultrasonic activation of the endodontic sealer on its intratubular penetration and bond strength to irradiated root dentin. Forty human teeth were distributed into 4 groups (n = 10), according to the radiation therapy (RT) exposure-70 Gy-and ultrasonic activation (UA) of the endodontic sealer: RT/UA-irradiated teeth and sealer UA; RT/no-UA-irradiated teeth and no sealer UA; no-RT/UA-non-irradiated teeth and sealer UA and no-RT/no-UA-non-irradiated teeth and no sealer UA. Push-out bond strength test was performed in a Universal Testing Machine. Failure modes and adhesive interface were analyzed under Scanning Electron Microscopy. The data were statistically compared (two-way-ANOVA and posthoc Games-Howell test; Fisher's exact test - α = 5%). The different experimental conditions (radiation and UA) and the root third had a significant effect on push-out bond strength, and the interaction of these factors was significant (p < 0.05). UA of the sealer significantly increased its bond strength to both irradiated and non-irradiated dentin (p < 0.05). The irradiated groups mostly presented adhesive-type failure of the sealer (p < 0.01). Regardless of the irradiation, the ultrasonically activated groups showed a more homogeneous adhesive interface, with the presence of sealer tags in greater density and depth. Ultrasonic activation enhanced the intratubular penetration and the bond strength of the endodontic sealer to irradiated dentin. The impact of ultrasonic activation of the endodontic sealer on teeth undergoing radiotherapy is a gap in the scientific literature that needs to be bridged.

An automated method to analyze root filling voids and gaps using confocal microscopy images

This study evaluated the feasibility of an automated method to delimit the required area to quantitatively analyze root filling voids and gaps from cross-sectional confocal laser scanning microscopy (CLSM) images. Root canals of maxillary canines were prepared with rotary instruments and filled by lateral compaction technique using gutta-percha and AH Plus sealer. The roots were stored (100% humidity, 37 °C) for a period of 24 h and then transversally sectioned to obtain 2-mm-thick slices from the apical and middle thirds. The areas corresponding to filling materials, gaps, and voids were manually delimited or automatically demarked by ImageJ software after converting the images to the RGB color system. Based on manual and automatic delimitations, the percentages of voids and gaps were calculated. Data of voids and gaps between middle and apical thirds were individually compared by paired t-test. Pearson`s correlation test was used to assess the correlation of data between the methods. Irrespective of the method of area delimitation, no difference was observed between the root thirds for both voids and gaps, while the p-values calculated for each method were similar. Almost perfect correlations between the methods were observed for both outcomes. The proposed method to automatically delimit the areas corresponding to filling material, voids, and gaps appears to be a valid method to facilitate the quantitative analysis of defects in root canal fillings using topographic CSLM images.

Synthesis and characterization of calcium-releasing elastomeric resin-based endodontic sealers

OBJECTIVES

To evaluate the incorporation of halloysite nanotubes (HNTs) loaded with one of two calcium sources (i.e., calcium hydroxide/CaOH2 or beta-tricalcium phosphate/β-TCP) on the physicochemical and biological properties of an experimental resin-based dual-cured endodontic sealer.

MATERIALS AND METHODS

HNTs were encapsulated with CaOH2 or β-TCP at 10 wt.%. HNTs containing CaOH2 or β-TCP were added into the experimental sealers at 50 wt.%. The control sealers were the calcium-free HNT-modified resin-based experimental sealer and AH Plus™, a commercially available endodontic sealer. Degree of conversion, setting time, flow, film thickness, radiopacity, dimensional stability, and calcium ions release were determined. Antibiofilm properties and cytocompatibility of the formulated sealers and commercial control were also evaluated. One and two-way ANOVA analysis followed by Tukey's post hoc test was conducted to evaluate the effect of the independent variable on the evaluated properties.

RESULTS

FTIR confirmed the encapsulation of calcium sources into HNTs. Regarding flow and film thickness, the values obtained from these sealers were in accordance with the specifications provided by ISO 6876. For radiopacity, AH Plus™ achieved the highest radiopacity (p<0.05). Among the experimental formulations, all experimental HNT-containing compositions exhibited values below 3 mm Al. The experimental sealers showed greater dimensional changes when compared to the commercial (AH Plus™) control. The release of calcium ions was observed for the HNT_CaOH2 and HNT_β-TCP sealers without statistical differences. Experimental sealers containing HNT_CaOH2 and HNT_β-TCP significantly reduced the CFU/mL count and showed cell compatibility.

CONCLUSIONS

The findings of this study demonstrate that the incorporation of HNT_CaOH2 or HNT_β-TCP into resin-based experimental sealers promoted antimicrobial effects and gradual calcium release without impairing cytocompatibility or physicochemical properties of the sealers. Still, an adjustment to reach the minimal radiopacity established by ISO 6876 is needed.

CLINICAL RELEVANCE

The experimental resin-based sealers seemed to be an alternative for endodontics. The incorporation of calcium sources exerts promising antimicrobial effects while displaying low cell toxicity.

Physicochemical properties of a novel bioceramic silicone-based root canal sealer

Background/purpose

With introduction into endodontics, bioceramic-based sealers have gained considerable popularity for excellent properties. The aim of this study was to investigate the physicochemical properties of a novel bioceramic silicone-based sealer, GuttaFlow Bioseal, and measure heat flow of setting reactions.

Materials and methods

Film thickness, flow, working and setting time of Bioseal were compared with other 4 kinds of sealers: iRoot SP, AH Plus, RoekoSeal and GuttaFlow2. Differential scanning calorimetry test was performed to measure heat flow.

Results

Bioseal demonstrated the highest film thickness of 44 μm, double to triple that of the other 4 sealers (P < 0.05). The highest flow was detected in iRoot SP and RoekoSeal, with values of 27.35 and 27.20 mm, while GuttaFlow2 and Bioseal had the lowest of 22.31 and 21.43 mm (P < 0.05). For each sealer, working time at 37 °C was shorter than that at 23 °C (P < 0.05). At 37 °C, Bioseal had the shortest working and setting time of 4.5 and 16.3 min, while iRoot SP showed the longest of 105.0 and 571.7 min (P < 0.05). Differential scanning calorimetry test revealed that setting process of all the tested sealers was exothermic. Bioseal reached an exothermic peak at 14 min, with almost 1.5 times peak intensity of GuttaFlow2 and RoekoSeal. Whereas iRoot SP and AH Plus reached an exothermic peak 5 h after mixing, with intensity 1/2 to 2/3 that of Bioseal.

Conclusion

The novel bioceramic silicone-based sealer Bioseal showed intense and fast exothermic reactions with characteristic physicochemical properties.

Filling Ability and Flow of Root Canal Sealers: A Micro-Computed Tomographic Study

This study evaluated by micro-computed tomography (μCT) the filling ability in curved root canals, besides the flow of AH Plus (AHP) and Neo MTA Plus (NMTAP) sealers using different methodologies. Mandibular molars mesial roots with two root canals and degree of curvature between 20° and 40° were selected. The specimens were prepared with the ProDesign R system up to size 35.05 and were filled with the sealers by a continuous wave of condensation technique, Thermo Pack II (n=12). The teeth were scanned using μCT after root canal preparation and obturation. The volumetric percentage of filling material and voids were calculated. Flow was evaluated based on ISO 6876/2012 (n=10). Flow and filling were also evaluated in μCT using a glass plate with a central cavity and four grooves from the central cavity (n=6). Flow was linearly calculated into the grooves. The central cavity filling (CCF) and lateral cavity filling (LCF) were calculated in mm³. Data were submitted to non-paired t test with a significance threshold at 5%. The percentage of filling and voids between the root canals filled with AHP or NMTAP was similar (p>0.05). NMTAP presented the lowest flow in conventional test (p<0.05). Using μCT, sealers had similar CCF, LCF and linear flow (p>0.05). In conclusion, NMTAP and AHP had similar filling ability in curved mesial root canals of mandibular molars without presence of isthmus. Although AHP presented better flow than NMTAP using ISO methodology, there was no difference between these materials regarding volumetric filling when evaluated by μCT.

Filling Effectiveness and Dentinal Penetration of Endodontic Sealers: A Stereo and Confocal Laser Scanning Microscopy Study

Abstract: The aim of this study was to evaluate the filling effectiveness and dentinal penetration of the sealers AH Plus, Pulp Canal Sealer EWT, Sealapex and MTA Fillapex applied according to the vertical condensation technique using thermoplastic gutta-percha. Forty single-rooted teeth were selected. After chemical-mechanical preparation and root-canal filling, sections of the root (2, 4 and 6 mm from the apex) were obtained and analyzed by stereo microscopy and confocal laser scanning microscopy. Data were tabulated and statistically analyzed. With regard to the assessment of void spaces in the filling material at 2 mm from the apex, the sealers showed similar results, but at 4 and 6 mm from the apex, MTA Fillapex had inferior performance compared to AH Plus (at 4 mm), Pulp Canal Sealer EWT (at 4 and 6 mm) and Sealapex (at 6 mm) (p<0.05). With regard to the penetration into dentinal tubules at 2 mm from the apex, the sealers also showed similar results, but at 4 and 6 mm Pulp Canal Sealer EWT had an inferior performance compared to MTA Fillapex and AH Plus, respectively (p<0.05). All four sealers were found to be similar regarding adaptation of the filling material to the root canal walls, except the MTA Fillapex, which showed failures at 4 and 6 mm from the root apex. With regard to the ability to penetrate into the dentinal tubules, the sealers were found to be equivalent, except for the Pulp Canal Sealer EWT as it had poorer results at 4 and 6 mm compared to MTA Fillapex and AH Plus, respectively.