A micro-computed tomography evaluation of mineral trioxide aggregate root canal fillings

Effects of Access Cavity Design and Placement Techniques on Mineral Trioxide Aggregate Obturation Quality in Simulated Immature Teeth: A Micro-Computed Tomography Study

Background and Objectives: In teeth with open apices, performing single session apexification is a challenging treatment due to the difficulty in handling mineral trioxide aggregate (MTA). Minimally invasive approaches in dentistry have also influenced the cavity designs in endodontics. Until now, different techniques have not been investigated in addition to manual condensation during the process of placing MTA in traditional (TradACs) or conservative (ConsACs) endodontic access cavities. The aim of this in vitro study was to compare and evaluate the obturation quality of MTA apical plugs placed with different techniques in TradACs or ConsACs. Materials and Methods: Sixty upper central teeth were divided into two main groups based on cavity design, and then each main group was further divided into three subgroups according to MTA placement techniques (n = 10): TradAC-manual, TradAC-manual + indirect ultrasonic activation, TradAC-manual + XP-endo Shaper (XPS), ConsAC-manual, ConsAC-manual + indirect ultrasonic activation, and ConsAC-manual + XPS. Subsequently, the porosity percentages in the MTA apical plug were analyzed using micro-computed tomography. The statistical analysis was performed using the Kruskal-Wallis H test and Mann-Whitney U test. Statistical significance was set at p < 0.05. Results: There were differences in volume of porosity percentages (%) according to cavity designs and MTA application techniques (p < 0.05). Except for the XPS group, more porosity was observed in ConsACs compared to TradACs. In TradACs, the significantly lowest open and total porosity was observed in the manual, ultrasonic, and XPS techniques, respectively. In ConsACs, the significantly lowest porosity was observed in the manual, XPS, and ultrasonic techniques, respectively (p < 0.05). Conclusions: In MTA obturation, cavity designs and application techniques had an impact on the MTA porosity. Creating an apical plug in ConsACs may result in more porosity compared to TradACs, especially when manual or indirect ultrasonic activation is preferred. Opting for the manual technique alone may be considered sufficient for controlling porosity for both TradACs and ConsACs.

Root-end resection with or without retrograde obturation after orthograde filling with two techniques: A micro-CT study

To evaluate the filling ability of two orthograde obturation techniques followed by the apical resection with or without retrograde obturation through micro-computed tomography (CT). Thirty-two single-rooted permanent teeth were prepared and randomised into four groups (n = 8) according to the orthograde obturation technique (single cone technique [SCT] and mineral trioxide aggregate placement) combined or not with retrograde obturation. The volume of voids (VoV) within the entire endodontic space, the apical 3 mm, and 1 mm after root resection was calculated by micro-CT. Statistical analysis showed no significant difference among the groups regarding the total VoV in all root canals, as well as within the apical 1 mm after root resection. The SCT and apical resection without retrograde filling showed significantly better results in terms of VoV at the apical 3 mm after root resection. Within the study limitations, SCT associated with apical resection without retrograde preparation exhibited a similar or less amount of voids than the other groups.

Micro-CT comparative evaluation of porosity and dentin adaptation of root end filling materials applied with incremental, bulk, and ultrasonic activation techniques

The purpose of this study is to investigate the effect of different application methods on the adaptation to dentin and porosity properties of calcium silicate based materials. This study included 72 maxillary canine teeth that had been extracted for various reasons. Following the root canal treatment, root, end resections were performed on the specimens. After the apicectomy, 3 mm deep cavities were created. All materials were mixed according to the manufacturer's instructions. Retrograde cavities were filled with RetroMTA [Group 1a-1c], Biodentine [Group 2a-2c] and BioAggregate [Group 3a-3c]. Placement techniques were applied for each material by using incremental, bulk technique and ultrasonic activation, respectively. The samples were scanned with the SkyScan 1272 μCT system. Porosity values were higher in bulk fill and incremental placement techniques than ultrasonic technique when using MTA and BioAggregate (p < 0.05), but Biodentine showed no statistically significant difference (p > 0.05) on using different placement techniques. The ultrasonic activation technique is beneficial to improve the condensation quality of MTA and BioAggregate. Biodentine showed better results regardless of different application techniques.

Effect of root dentin conditioning using different chelating agents on pushout bond strength of MTA-fillapex and bioroot RCS: An in vitro study

Context:

The success of endodontic therapy depends on proper biomechanical preparation and obturation.

Aim:

To evaluate and compare the pushout bond strength (POBS) of MTA Fillapex (MF) and BioRoot RCS (BRCS) sealers in endodontically treated teeth with different irrigants-5.25% Sodium hypochlorite (NaOCl), 17% ethylenediaminetetraacetic acid (EDTA) and 0.2% Chitosan.

Materials and Methods:

60 premolars were divided into three groups. Each group was then subdivided into A and B. The three groups were Group 1A: 17% EDTA + 5.25% NaOCl with MF sealer (n = 10); Group 1B: 17% EDTA + 5.25% NaOCl with BRCS sealer (n = 10); Group 2A: 0.2% Chitosan + 5.25% NaOCl with MF sealer (n = 10); Group 2B: 0.2% Chitosan + 5.25%NaOCl with BRCS sealer (n = 10); Group 3A: 5.25% NaOCl + MF sealer (n = 10); and Group 3B: 5.25% NaOCl + BRCS sealer (n = 10). After obturation, they were sectioned horizontally (1.5 mm thick). The POBS was studied using a universal testing machine (Autograph AG-1). The sample size was calculated using the statistical package G * Power (3.1.5).

Results:

It was found that the POBS of BRCS was higher when the root canal was irrigated with 0.2% Chitosan + 5.25% NaOCl. Thus, Group 2B showed significantly higher POBS than Group 2A.

Conclusion:

The irrigation regimen of Chitosan with NaOCl was found to have better debriding effect on the root canal. Of the two sealers, BRCS showed the higher bond strength values than MF.

The Effect of Ultrasonic Agitation on the Porosity Distribution in Apically Perforated Root Canals Filled with Different Bioceramic Materials and Techniques: A Micro-CT Assessment

The present study evaluated the effect of ultrasonic agitation on the porosity distribution of BioRoot RCS/single gutta-percha cone (BR/SC) and MTA Flow (MF) root canals fillings used as apical plugs in moderately curved and apically perforated roots. Eighty mesial root canals of mandibular first molars were enlarged up to ProTaper NEXT X5 rotary instrument 2 mm beyond the apical foramen, simulating apical perforations. Specimens were randomly divided into four experimental groups (20 canals per group) according to the material and technique used for root canal obturation: BR/SC, BR/SC with ultrasonic agitation (BR/SC-UA), MF and MF with ultrasonic agitation (MF-UA). The ultrasonic tip was passively inserted into the root canal after the injection of flowable cement and activated for 10 s. The specimens were scanned before and after obturation with a high-resolution micro-computed tomography scanner, and the porosity of the apical plugs was assessed. The differences between groups were analyzed using the Kruskal-Wallis and Mann-Whitney tests, with the significance level set at 5%. None of the obturation materials and techniques used in this study was able to provide a pore-free root canal filling in the apical 5 mm. Considerably higher percentages of open and closed pores were observed in the MF and MF-UA groups, with the highest porosity being in the MF-UA group (p < 0.05). No significant differences were observed between the BR/SC and BR/SC-UA groups, where the quantity of open and closed pores remained similar (p > 0.05).

Marginal gaps and voids of three root-end filling materials: A microcomputed tomographic study

A root-end filling material is required to fill the root-end cavity without gaps or voids, to prevent root canal reinfection and to provide periapical healing. Thus, this study evaluated the volume of marginal gaps and voids of three root-end filling materials using microcomputed tomography (micro-CT). Thirty maxillary incisors were prepared and filled with gutta-percha and endodontic sealer. The specimens were scanned using micro-CT and distributed into three groups (n = 10): White MTA, MTA Repair HP, and Bio-C Repair. The root tips were resected at 90° to the longitudinal axis and the cavity (3 mm depth) was prepared with an ultrasonic tip. The materials were handled, and the cavities were filled. The specimens were rescanned and the percentual volume of gaps and voids were analyzed. The data were analyzed using Kruskal-Wallis and Dunn tests (p < .05). No statistical difference was found in the percentage of gaps among the tested materials (p > .05). White MTA presented less voids than Bio-C and MTA Repair HP (p < .05). The materials presented a similar percentual volume of gaps and White MTA presented less voids than other tested materials.

Comparative Evaluation of Mineral Trioxide Aggregate Obturation Using Four Different Techniques-A Laboratory Study

This study aimed to compare the density of mineral trioxide aggregate (MTA) as a root canal filling material in the apical 5 mm of artificial root canals. Forty transparent acrylic blocks with 30-degree curved canals were instrumented and allocated into four compaction technique groups (n = 10): Lawaty (hand files); gutta-percha (GP) points; auger (nickel–titanium rotary files in reverse mode); and plugger technique. Filled canals were weighed after setting the MTA to calculate difference in mass. Two postoperative radiographs compared radiopacity by measuring luminance variations at 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, and 5 mm from the root apex. Obturation time was measured using a digital chronometer. The significance level was set to p < 0.05. The plugger group had a lower mass. Relative luminance was significantly higher for the Lawaty group than the plugger group at all examined apical levels. The relative luminance of the auger and GP groups were significantly higher than the plugger group at depths between 0.5 mm and 2 mm. Relative luminance was highest for the Lawaty technique at all depths between 0.5 mm and 4 mm. The Lawaty technique group was associated with increased obturation time compared with pluggers. Compacting MTA in curved canals with the Lawaty technique has the highest mass and radiopacity but requires more time.

Comparison of Obturation Quality after MTA Orthograde Filling with Various Obturation Techniques

This study aimed to quantify and compare the obturation quality after mineral trioxide aggregate (MTA) orthograde fillings with three different obturation techniques. Thirty-three extracted human maxillary molars were collected. Distobuccal and palatal canals were prepared to an apical size of #40/06 with a Profile Ni-Ti system. All 66 canals were divided into two groups according to the material (EZ-seal or OrthoMTA) and then obturated using three different techniques: manual compaction using S-kondenser (group H), compactor activation (group C), or reverse rotary motion of Ni-Ti file (group R). The obturated roots were scanned using micro-computed tomography (micro-CT). The percentage of voids located in the apical 5 mm was measured separately, that is, closed, open, and total porosity. There was no relation between the filling material and obturation technique (p > 0.05). The percentage volume of open and total porosity was higher in EZ-seal than in OrthoMTA (open: p = 0.002, total: p = 0.001). Group H showed higher open and total porosity than groups C and R. Micro-CT analysis showed that the void volume after orthograde MTA fillings significantly decreased when the additional activation was accompanied by hand condensation. Obturation with a Ni-Ti file using reverse motion could be recommended as an MTA orthograde filling technique.

Interface analysis after fatigue loading of adhesively luted bundled fiber posts to human root canal dentin

OBJECTIVES

The aim of this study was to assess the fatigue loading behavior and fracture resistance of endodontically treated teeth restored with adhesively luted bundled fiber posts in comparison to solid fiber posts. Image analysis (2D and 3D) was applied to evaluate modes of failure and to characterize susceptible parts of the post-and-core interface.

METHOD

Crowns of 72 human similar-sized central upper incisors were removed and roots received a conventional root canal filling prior to establishing 4 groups of core build-up: No Post group (nP) received a 4 mm deep filling made of composite inside the canal with no dental post, fiber post group (FP) received a conventional solid post, and two experimental groups received bundles of 6 (FB6) or 12 (FB12) 0.3 mm thin fiber posts, respectively. Posts were placed adhesively inside the root canal using a dual-curing build-up composite in combination with a self-etch adhesive, the latter was also used for nP group. Upon completion of core build-ups, all teeth received full-ceramic crowns that recreated the original tooth form. Samples were subjected in a 135° angle to thermo-mechanical loading (TML) for 1.2 Mill. chewing cycles followed by static load tests (fracture resistance). Fracture modes as well as intracanal failure modes with respect to failed interfaces were analyzed using optical and electron microscopy (SEM). Microcomputer tomography (μCT) was used to exemplary compare pre and post TML geometries.

RESULTS

Static load test was significantly different between groups (p < 0.0005; Kruskal-Wallistest). Pairwise comparison showed that the nP group (221 ± 103N) failed at significantly lower forces compared to the FP (454 ± 184N), FB6 (477 ± 250N) and FB12 (478 ± 260N) groups (p ≤ 0,001; Mann-Whitney-U-test). Fracture modes were significantly affected by the presence or absence of a post (p ≤ 0,016; Chi-square test) revealing increased incidence of restorable fractures at the cervical region for nP group. Microscopic analysis revealed more intracanal failures at interfaces between post surfaces and composite for solid posts, whereas fiber bundled posts mostly failed at the interfaces between composite and dentin. Micro-CT analysis showed no alterations of the root-post-and-core structure after TML except slight deformations of occasionally entrapped voids.

CONCLUSION

Fracture resistance and fracture modes were significantly affected by the presence or absence of a post, whereas the investigated post groups did not differ from each other. However intracanal failure revealed differences in adhesive failures between solid fiber posts and bundled fiber posts. Deformations of entrapped voids, revealed by micro-Ct analyses after TML, lead to the assumption that applied forces result in alterations in the regions of voids.

Effects of Ultrasonic Activation on Root Canal Filling Quality of Single-Cone Obturation with Calcium Silicate-Based Sealer

Background: We evaluated the effects of ultrasonic activation on root canal filling quality of the single-cone (SC) obturation technique with calcium silicate sealers and gutta percha cones. Methods: Thirty-six human single-rooted premolars were obturated with gutta percha and sealer. For the continuous wave (CW) group (n = 12), AH Plus with a continuous wave technique was used. The SC group (n = 12) received EndoSequence BC sealer with a single-cone technique. The SCU (SC with the addition of ultrasonic activation) group (n = 12) received the same treatment. Micro-computed tomography was used to scan the teeth, and the void volume within the root canal was evaluated at the apical, middle, and coronal levels. Then cross-sections were observed under a light microscope and scanning electron microscope (SEM). Results: Void volume was significantly lower in the SCU group than in the CW and SC groups. There were no statistically significant differences between the CW and SC groups. The SCU group had fewer voids than the CW and SC groups in the coronal and middle third areas. Specimens showed no apparent gaps or voids in any group. SEM images revealed both gap-free and gap-containing regions at different levels in all groups. Conclusions: Single-cone obturation with calcium silicate-based sealers might obtain enhanced filling quality when used with ultrasonic activation.

Micro-computed tomography high resolution evaluation of dimensional and morphological changes of 3 root-end filling materials in simulated physiological conditions

The aim of this study was to evaluate volumetric and morphological stability of 3 root-end filling materials in addition to porosity and interface voids, using micro-computed tomography (µCT) in high resolution and a highly accurate approach for image analysis. Following root-end resection and apical preparation, two-rooted maxillary premolars were divided into three groups, according to the filling materials: White MTA Angelus, Biodentine, and IRM. Samples were scanned by µCT at 5 µm after the setting time and at time intervals of 7 and 30 days after immersion in phosphate-buffered saline (PBS). Volumetric and morphological changes besides material porosity and interface voids were evaluated by comparing initial values and those obtained after immersion. Data were analyzed statistically, using ANOVA and t-tests (α = 0.05). All materials showed volumetric stability. Regarding the morphological changes, Biodentine had a significant thickness reduction after storage in PBS when compared with MTA. Biodentine also showed an increase in porosity, as well as in percentage and thickness of voids after 30 days of immersion. In conclusion, µCT in high resolution and an accurate image analysis approach may be used to evaluate morphological changes of endodontic materials. Although Biodentine showed suitable adaptability and lower values of porosity than MTA, after PBS immersion there was a dimensional reduction of this material, besides an increase in porosity and interface voids.

A micro-computed tomography evaluation of voids using calcium silicate-based materials in teeth with simulated internal root resorption

Objectives

The obturation quality of MTA, Biodentine, Total Fill BC root canal sealer (RCS), and warm gutta-percha (WGP) in teeth with simulated internal root resorption (IRR) was evaluated by using micro-computed tomography.

Materials and Methods

Standardized IRR cavities were created using 40 extracted maxillary central incisor teeth and randomly assigned into 4 groups (n = 10). IRR cavities were filled with MTA, Biodentine, Total Fill BC RCS (bulk-fill form) and WGP + Total Fill BC RCS. Percentage of voids between resorptive cavity walls and obturation material (external void), and inside the filling materials (internal voids) were measured.

Results

Total Fill BC sealer in the bulk-fill form presented significantly highest values of external and internal void percentages (p < 0.05). Biodentine showed a significantly lowest external void percentage (p < 0.05). WGP + Total Fill BC RCS presented significantly lower values of internal void percentages than all groups (p < 0.05), except Biodentine (p > 0.05).

Conclusion

None of the filling materials were created void-free obturation in resorption cavities. Biodentine may favor its application in teeth with IRR over Angelus MTA and bulk-fill form of Total Fill BC.

Volume of Voids in Retrograde Filling: Comparison between Calcium Silicate Cement Alone and Combined with a Calcium Silicate-based Sealer

INTRODUCTION

The aim of this study was to compare the volume of voids between retrograde filling using calcium silicate cement alone and retrograde filling using a combination of calcium silicate cement with a calcium silicate-based sealer.

METHODS

Twenty single-rooted, extracted human teeth were instrumented with nickel-titanium files and obturated with gutta-percha. We resected the roots at a point 3 mm from the apex, prepared the root ends, and filled the root-end cavities with Endocem Zr (Maruchi, Wonju, Korea) or Endoseal MTA (Maruchi) plus Endocem Zr. Then, we scanned the prepared samples using micro-computed tomographic imaging and performed 3-dimensional reconstruction. The percentage volume of the gap between the canal wall and root-end filling was calculated along with the percentage volume of voids in the filling materials. All data were analyzed using the Mann-Whitney U test. Selected specimens were further observed using scanning electron microscopy.

RESULTS

There were no significant differences in the percentage volumes of the gaps and internal voids between the 2 groups. Both calcium silicate and the calcium silicate-based sealer exhibited good adaptation to the cavity wall.

CONCLUSIONS

The findings of our micro-computed tomographic and scanning electron microscopic analyses suggested that the volume of voids in retrograde filling using a combination of calcium silicate cement and calcium silicate-based sealer was comparable with that in retrograde filling using calcium silicate cement only. Calcium silicate-based sealers could be used in retrograde filling for clinical convenience without harmful effects on the quality of filling.

Porosity Distribution in Apically Perforated Curved Root Canals Filled with Two Different Calcium Silicate Based Materials and Techniques: A Micro-Computed Tomography Study

The present study evaluated the porosity distribution of BioRoot RCS/single gutta-percha point (BR/SC) and MTA flow (MF) fillings, which were used as plugs for the apical perforation repair in curved canals of extracted mandibular molars using micro-computed tomography (μCT). Forty mesial root canals of mandibular first molars were shaped with ProTaper NEXT X1-X5 files 2 mm beyond the apex to simulate apical perforations that were randomly divided into two groups (n = 20) according to the material and technique used for the apical plug: BR/SC or MF. The specimens were scanned before and after canal filling at an isotropic resolution of 9.9 μm. The volumetric analysis of voids in the apical 5 mm of the fillings was performed. Data were analyzed using one-way ANOVA with Bonferroni correction (p < 0.05). Micro-computed tomography (µCT) evaluation revealed significant differences between the groups in terms of porosity: the total volume and percentage volume of voids was lower in the BR/SC group in comparison with the MF group (p < 0.05), with the predominance of open pores in both groups. Neither of the materials and/or application techniques were able to produce void-free root fillings in the apical region of artificially perforated curved roots of mandibular molars.

Do the intracanal medicaments affect the marginal adaptation of calcium silicate-based materials to dentin?

Background/purpose

In order to prevent reinfection of the pulp canal space and dressing for regenerative purpose, the coronal seal should have a perfect marginal adaptation. Mineral trioxide aggregate (MTA) and Biodentine are among the most popular sealing materials. These are commonly used in combination with antibiotic medicaments, to ensure disinfection. Aim of the present study was to evaluate the effect of 3 different medicaments on the marginal adaptation of MTA and Biodentine to the dentin.

Materials and methods

Teeth were divided into 4 groups (n = 20) that were treated with the following medicaments; triple antibiotic paste (TAP), double antibiotic paste (DAP), a calcium hydroxide (CH) and a control group. The specimens were then assigned into two subgroups (n = 10), which received a coronal barrier of MTA or Biodentine. The specimens were scanned using an ex vivo micro-CT scanner. The data were statistically analysed using one-way ANOVA and the unpaired Student's t-test (P < 0.05).

Results

Percentage volume of external voids in the MTA group was as follows: DAP > TAP > Control > CH. In the Biodentine group, the percentage of voids was determined in the following order: TAP ≥ DAP > CH > Control. Significantly lower percentage of voids was observed in the CH-medicated specimens in the MTA group when compared to all test groups (P = 0.04).

Conclusion

The application of CH as an intracanal medicament reduced the void occurrence between the ProRoot MTA and root dentin. However, TAP and or DAP decreased the marginal adaptation in both ProRoot MTA and Biodentine.

Obturation quality of calcium silicate-based cements placed with different techniques in teeth with perforating internal root resorption: a micro-computed tomographic study

OBJECTIVES

To evaluate and compare the obturation quality of mineral trioxide aggregate (MTA) and Biodentine placed with hand condensation or indirect ultrasonic activation technique in teeth models simulating perforating internal root resorption (IRR) using micro-computed tomographic (micro-CT) imaging.

MATERIALS AND METHODS

Standardized models with perforating IRR cavities were created using 40 extracted single-rooted human teeth and randomly divided into four groups (n = 10). The specimens were obturated with either MTA or Biodentine and the placement technique applied was either hand condensation or indirect ultrasonic activation. Micro-CT scans were performed for the volumetric analysis of voids and filling materials in the resorption cavities and apical portion of the specimens. Data were analyzed using one-way analysis of variance and paired t test.

RESULTS

No significant difference was observed between the groups in terms of the percentage volume of filling materials (p > 0.05). The apical portion of the specimens significantly presented less percentage volume of filling materials than the resorption cavities in each group (p < 0.05).

CONCLUSIONS

No placement technique produced void-free fillings in teeth with perforating IRR. There was no significant difference between the obturation quality of Biodentine and MTA. The obturation quality in the apical portion of the root canals was inferior than that in the resorption cavities.

CLINICAL RELEVANCE

The obturation of the apical region of teeth with perforating IRR is challenging irrespective of the material type and placement technique.

Effect of Root Dentin Conditioning on the Pushout Bond Strength of Biodentine

INTRODUCTION

Sodium hypochlorite (NaOCl) is the main irrigant to clean root canals. Decalcifying agents are advocated as additional means to condition the root dentin. The aim of this study was to evaluate the effect of alternating (EDTA) or continuous 1-hydroxyethane 1,1-diphosphonic (HEDP) chelation in conjunction with NaOCl irrigation on the pushout bond strength of Biodentine (Septodont, Saint Maur des Fosses, France).

METHODS

Single root canals of 50 extracted, mature human teeth were divided into 5 groups (n = 10) and enlarged using rotary instruments. Canals were irrigated with 5 mL irrigant after each instrument and then with 5 mL after mechanical preparation as follows: 2.5% NaOCl during and then 2.5% NaOCl, 17% EDTA, or 17% EDTA followed by 2.5% NaOCl after preparation. Continuous chelation with 2.5% NaOCl/9% Dual Rinse HEDP (Medcem GmbH, Weinfelden, Switzerland) during and after preparation. The control group was irrigated with water during and after preparation. Canals were then filled with Biodentine. A horizontal section of 1.5-mm thickness was taken from the middle root third, and a pushout bond test was performed. Data were statistically analyzed using 1-way analysis of variance/Tukey honest significant different test.

RESULTS

The pushout bond strength of Biodentine was significantly higher when the root canal was irrigated with 2.5% NaOCl/9% Dual Rinse HEDP (19.6 ± 2.3 MPa) than with NaOCl alone (15.5 ± 1.5 MPa) or the NaOCl/EDTA sequences (15.7 ± 2.2 MPa and 16.9 ± 2.9 MPa) (P < .05), which did not differ among each other (P > .05). The lowest pushout bond strength values were found with water irrigation (11.5 ± 0.5 MPa) (P < .05 to all other groups).

CONCLUSIONS

Irrigation with 2.5% NaOCl/9% Dual Rinse HEDP significantly improved the pushout bond strength of Biodentine to the root canal dentin.

Analysis of the porosity of endodontic sealers through micro-computed tomography: A systematic review

Endodontic treatments have as their objective the appropriate sealing of the space caused by the root canal, providing a complete seal of the canal in all dimensions, creating an airtight seal against fluids. Thus, endodontic cements must possess physical properties such as solubility and long-term dimensional stability. An electronic search in the main endodontic magazines using appropriate keywords to identify studies that investigated the porosity of endodontic materials using micro-computed tomography. Of the 125 studies researched, 16 fulfilled the criteria for inclusion. Four studies analyzed the porosity of endodontic cements specifically. Twelve studies investigated and compared different techniques of root canal obturation and the repercussions from the lowering of porosity in the interior of the endodontic cement. The presence of porosity inside the endodontic cement is a constant in the treatments of root canals, even now when there is a great variety of endodontic cements.

Micro-CT analysis of filling ability and porosity of root-end filling materials

Abstract Introduction Filling ability of retrograde cavity and porosity are important properties for root-end filling materials and may be evaluated by using microcomputed tomography (micro-CT). Objective To evaluate filling ability and porosity of root-end filling materials using microcomputed tomography (micro-CT). Material and method Cavities with 1 mm internal diameter and 3 mm depth were prepared in bovine dentin sections by using ultrasonic tips (CVD No. 6.1107-6), and filled by Mineral Trioxide Aggregate (MTA); Sealer 26 (S26) and zinc oxide and eugenol cement (ZOE). Before and after filling, cavities were scanned by using micro-CT (SkyScan 1176). Filling and porosity were analyzed by using CTAn software. Filling ability was calculated based on volumetric percentage of the filled cavity. The number and percentage of closed pores were measured throughout entire extension of the filled cavity (total) and in each third (cervical, middle and apical), by using bi and tridimensional analyses. The filling data were submitted to ANOVA and Tukey statistical tests, and porosity data to Kruskall-Wallis and Dunn tests, at a 5% significance level. Result S26 and ZOE presented higher filling ability than MTA (p<0.05). S26 showed the highest total porosity (number and percentage) (p<0.05). In all thirds after 2D and 3D analyses, porosity was higher for S26 in comparison to MTA and ZOE (p<0.05). Conclusion Although Sealer 26 presented more porosity, the material was associated with a great filling ability. Micro-CT analysis showed no correlation between filling ability and porosity.

3D Micro-CT Analysis of Void and Gap Formation in Curved Root Canals

Objective:

This study used microcomputed tomography (micro-CT) to compare the volumes of voids and gaps in curved root canals instrumented and filled using various techniques.

Methods:

Twenty extracted mandibular first molars with two curved mesial root canals were used. Root canals were instrumented using a self-adjusting file (SAF) or Revo-S file system. For standardization, mesiobuccal canals were instrumented with SAF and mesiolingual canals were instrumented with Revo-S in each root. The canals were divided into four experimental groups (n=10 in each). The canals were then filled via cold lateral compaction (CLC) or a thermoplasticized injectable technique (TT) using gutta-percha and AH Plus root canal sealer. The roots were scanned with a micro-CT, and the volumes of the voids and gaps were calculated using three-dimensional (3D) micro-CT images. Data were analyzed using unpaired t- and Kruskal-Wallis tests. A value of P<0.05 was considered significant.

Results:

None of the tested techniques provided void- or gap-free fillings. Nevertheless, the SAF showed more gap formation than the Revo-S, and TT showed higher gap formation in all experimental groups. These differences, however, were not statistically significant (P>0.05).

Conclusion:

The SAF and Revo-S rotary file systems yielded comparable results. No statistically significant difference was found between the results of the various instrumentation and filling techniques.

Effect of irrigation technique for removal of triple antibiotic paste on bond strength of MTA to root dentin

This study evaluated the bond strength of mineral trioxide aggregate (MTA) to root canal dentin after the performance of various irrigation procedures to remove triple antibiotic paste (TAP). A total of 56 single-rooted human mandibular premolars were instrumented using a rotary system to size 40 and divided randomly into a control group (no intracanal dressing) and three experimental groups (TAP application for 28 days). TAP was then removed by rinsing with 10 mL 2.5% NaOCl using three irrigation systems (Vibringe sonic irrigation, CanalBrush, and syringe irrigation). The coronal and middle parts of root canals were then obturated with MTA. After storage for 1 week, each specimen was embedded in an acrylic block and sectioned horizontally (2-mm-thick slices) at two levels (coronal and middle). Bond strength of MTA to root canal dentin was assessed in 28 samples per group via push-out test using a universal testing machine. Data from the four groups were compared using one-way analysis of variance. Tukey's test was used for multiple comparisons. Push-out bond strength values were significantly higher in the control and Vibringe groups than in the CanalBrush and syringe irrigation groups (p < 0.001). TAP removal from root canals with the Vibringe irrigation system may increase the push-out bond strength of MTA compared with the use of the CanalBrush or syringe irrigation.

Experimental polyethylene-hydroxyapatite carrier-based endodontic system: an in vitro study on dynamic thermomechanical properties, sealing ability, and measurements of micro-computed tomography voids

The dynamic thermomechanical properties, sealing ability, and voids formation of an experimental obturation hydroxyapatite-reinforced polyethylene (HA/PE) composite/carrier system were investigated and compared with those of a commercial system [GuttaCore (GC)]. The HA/PE system was specifically designed using a melt-extrusion process. The viscoelastic properties of HA/PE were determined using a dynamic thermomechanical analyser. Human single-rooted teeth were endodontically instrumented and obturated using HA/PE or GC systems, and then sealing ability was assessed using a fluid filtration system. In addition, micro-computed tomography (μCT) was used to quantify apparent voids within the root-canal space. The data were statistically analysed using one-way anova and post hoc tests. The HA/PE composite exhibited important modulus and damping changes with an increase of temperature. The HA/PE system was more flexible than GC as the modulus of GC appeared to be significantly higher than that of HA/PE as a result of the high positive glass transition temperature (Tg ). However, HA/PE and GC presented similar sealing abilities. In conclusion, because sealing ability and voids formation were comparable between the tested materials, the experimental HA/PE system may be considered a suitable alternative material for root-canal obturation. Moreover, HA/PE possesses specific viscoelastic behaviour and lower melting points, which may facilitate root-canal retreatments.

Comparison of Mechanical and Indirect Ultrasonic Placement Technique on Mineral Trioxide Aggregate Retrofill Density in Simulated Root-end Surgery

INTRODUCTION

The objective of this study was to evaluate the density of mineral trioxide aggregate (MTA) root-end filling placed by either manual condensation or manual condensation with indirect ultrasonic activation under simulated root-end surgery conditions in vitro.

METHODS

Extracted human molar teeth were obtained and sectioned to provide single-rooted samples (n = 50). Roots were instrumented to a size of 40 with a .04 taper and obturated with a warm vertical technique. The coronal end of each root was embedded in resin. A root-end resection and root-end preparation were completed on each root. Samples were randomly assigned to receive root-end fillings with ProRoot MTA (Dentsply, Tulsa, OK) by 1 of 2 techniques: manual condensation alone (group M, n = 25) or manual condensation with indirect ultrasonic activation (group U, n = 25). MTA was placed incrementally to the level of the root end using the enumerated technique. Samples were weighed immediately before and after filling placement. MTA was removed from all samples so as not to change the root-end preparation, rinsed, and dried. Each sample then underwent MTA placement by the opposite technique, and weight was again measured immediately before and after MTA placement. MTA filling weights for each technique were analyzed statistically using a technique for repeated measures analysis. Statistical analysis was conducted to account for any carryover or order effects.

RESULTS

After adjustment for carryover effects, it was found that regardless of the order of placement, the mean fill weight of MTA produced by the indirect ultrasonic method was on average 4.42 mg heavier than that produced by manual condensation alone. This result was statistically significant (P < .0003).

CONCLUSIONS

Under simulated root-end surgery conditions, indirect ultrasonic condensation of MTA root-end fillings was shown to produce a filling that was significantly denser than MTA placed by manual condensation alone.

Evaluation of three obturation techniques in the apical third of mandibular first molar mesial root canals using micro-computed tomography

Background/purpose

Recent studies have demonstrated a high incidence of isthmuses in mandibular first molar mesial roots, and intratubular mineralization following mineral trioxide aggregate obturation. This study assessed the filling quality of three obturation techniques in the apical 5 mm of mandibular first molar mesial root canals.

Materials and methods

Sixty extracted human mandibular first molar mesial roots with two separate canals that had interconnecting isthmuses, were prepared to an apical size of 40/0.06. They were allocated to three groups of 20 roots for obturation by either cold lateral compaction (CLC) or the continuous wave of condensation (CW) that used gutta-percha and AH Plus sealer, or by an orthograde canal obturation using OrthoMTA. The obturated roots were scanned by micro-computed tomography and assessed for the volumetric ratio (%) of gutta-percha, sealer, and OrthoMTA within the main canals or isthmuses in the apical 5 mm area. Measurements were analyzed statistically for differences among three obturation techniques.

Results

In the main canals, filled volume ratios were not significantly different among groups. Within isthmuses, the filled volume ratio for CLC was lower than in CW (P = 0.025) or OrthoMTA (P = 0.002). In isthmuses, the gutta-percha volume ratio in CLC was lower than in CW (P = 0.005), although the sealer volume ratio was higher than in CW (P = 0.049).

Conclusion

CLC demonstrated lower filling densities in isthmuses in the apical region than either CW or OrthoMTA. Orthograde MTA obturation showed comparable filling quality to gutta-percha with sealer.

Dynamic intratubular biomineralization following root canal obturation with pozzolan-based mineral trioxide aggregate sealer cement

The application of mineral trioxide aggregates (MTA) cement during the root canal obturation is gaining concern due to its bioactive characteristic to form an apatite in dentinal tubules. In this regard, this study was to assess the biomineralization of dentinal tubules following root canal obturation by using pozzolan-based (Pz-) MTA sealer cement (EndoSeal MTA, Maruchi). Sixty curved roots (mesiobuccal, distobuccal) from human maxillary molars were instrumented and prepared for root canal obturation. The canals were obturated with gutta-percha (GP) and Pz-MTA sealer by using continuous wave of condensation technique. Canals obturated solely with ProRoot MTA (Dentsply Tulsa Dental) or Pz-MTA sealer were used for comparison. In order to evaluate the biomineralization ability under different conditions, the PBS pretreatment before the root canal obturation was performed in each additional samples. At dentin-material interfaces, the extension of intratubular biomineralization was analyzed using scanning electron microscopy (SEM) and energy dispersive spectroscopy. When the root canal was obturated with GP and Pz-MTA sealer, enhanced biomineralization of the dentinal tubules beyond the penetrated sealer tag was confirmed under the SEM observation (p < 0.05). Mineralized apatite structures (calcium/phosphorous ratio, 1.45-1.89) connecting its way through the dentinal tubules were detected at 350-400 μm from the tubule orifice, and the pre-crystallization seeds were also observed along the intra- and/or inter-tubular collagen fiber. Intratubular biomineralization depth was significantly enhanced in all PBS pretreated canals (p < 0.05). Pz-MTA cement can be used as a promising bioactive root canal sealer to enhance biomineralization of dentinal tubules under controlled environment.

Porosity and sealing ability of root fillings with gutta-percha and BioRoot RCS or AH Plus sealers. Evaluation by three ex vivo methods

AIM

To investigate the ability of BioRoot RCS, a tricalcium silicate-based root canal sealer and AH Plus to effectively fill the root canals of contralateral teeth using three evaluation methods, and to investigate also the correlation between the methods.

METHODOLOGY

The prepared root canals of ten pairs of contralateral mandibular premolar teeth were filled with gutta-percha and sealer using lateral compaction. The percentage of voids within the root canal was assessed by micro-computed tomography, whilst sealing ability was investigated by fluid transport and leakage of fluorescent microspheres. The interaction of sealer with dentine, and sealer penetration were assessed by confocal microscopy. The void volume, fluid flow, microsphere leakage and sealer interaction with dentine for both materials were compared. Nonparametric (Mann-Whitney) tests were used to compare the % void and fluid transport of the two sealers. Spearman correlation was used to assess the pairwise relationships between the techniques. The level of significance was set to 0.05.

RESULTS

BioRoot RCS exhibited significantly more percentage of voids than AH Plus. There was no difference in fluid flow and microsphere penetration. BioRoot RCS exhibited a different pattern of sealer penetration and interaction with the dentine walls compared to AH Plus. For both materials, the pairwise correlations between the three techniques were close to zero, indicating weak relationships.

CONCLUSIONS

MicroCT analysis revealed a higher void volume for BioRoot RCS. The other techniques did not show a difference between the sealing ability of the sealers. The correlation between the three ex vivo methods of assessment was weak demonstrating their complementarity rather than their concordance.

Quality of obturation achieved by a non-gutta-percha-based root filling system in single-rooted canals

INTRODUCTION

The present study examined the quality of obturation in root canals filled by an experimental non-gutta-percha-based (NGP) root filling system using warm vertical or cold lateral compaction. The quality of obturation was evaluated by comparing the volumetric percentage of gaps and voids identified from similar canals obturated with gutta-percha and an epoxy resin-based sealer using the same obturation techniques.

METHODS

Forty single-rooted premolars with oval-shaped canals were cleaned, shaped, and obturated with 1 of the 4 material/obturation technique combinations (n = 10). Filled canals were scanned with micro-computed tomographic imaging. Reconstructed images were analyzed for the volumetric percentage of gaps and voids at 3 canal levels (0-4, 4-8, and 8-12 mm from the working length). Roots were sectioned at the 4-mm, 8-mm, and 12-mm levels. Scanning electron microscopic images of negative replicas of root sections were examined to quantify the circumferential percentage of interfacial gaps and the area percentage of intracanal voids. Data were analyzed with parametric or nonparametric statistical methods.

RESULTS

A statistically significant difference was found for the volumetric percentage distribution of gaps and voids for "obturation technique" but not for "material." Significantly higher percentages of gaps and voids were identified in canals obturated with the NGP system using cold lateral compaction. Examination of negative replicas ascribed this difference to a higher area percentage of interfacial gaps rather than more intracanal voids.

CONCLUSIONS

Using warm vertical compaction, the NGP system fulfils the objective of 3-dimensional obturation of the canal space in a manner comparable with the results achieved with gutta-percha and a root canal sealer.

Bacterial entombment by intratubular mineralization following orthograde mineral trioxide aggregate obturation: a scanning electron microscopy study

The time domain entombment of bacteria by intratubular mineralization following orthograde canal obturation with mineral trioxide aggregate (MTA) was studied by scanning electron microscopy (SEM). Single-rooted human premolars (n=60) were instrumented to an apical size #50/0.06 using ProFile and treated as follows: Group 1 (n=10) was filled with phosphate buffered saline (PBS); Group 2 (n=10) was incubated with Enterococcus faecalis for 3 weeks, and then filled with PBS; Group 3 (n=20) was obturated orthograde with a paste of OrthoMTA (BioMTA, Seoul, Korea) and PBS; and Group 4 (n=20) was incubated with E. faecalis for 3 weeks and then obturated with OrthoMTA–PBS paste. Following their treatments, the coronal openings were sealed with PBS-soaked cotton and intermediate restorative material (IRM), and the roots were then stored in PBS for 1, 2, 4, 8 or 16 weeks. After each incubation period, the roots were split and their dentin/MTA interfaces examined in both longitudinal and horizontal directions by SEM. There appeared to be an increase in intratubular mineralization over time in the OrthoMTA-filled roots (Groups 3 and 4). Furthermore, there was a gradual entombment of bacteria within the dentinal tubules in the E. faecalis inoculated MTA-filled roots (Group 4). Therefore, the orthograde obturation of root canals with OrthoMTA mixed with PBS may create a favorable environment for bacterial entombment by intratubular mineralization.

Quality of obturation achieved by an endodontic core-carrier system with crosslinked gutta-percha carrier in single-rooted canals

OBJECTIVES

The present study examined the quality of obturation in root canals obturated by GuttaCore, a gutta-percha-based core-carrier system with a cross-linked thermoset gutta-percha carrier, by comparing the incidence of gaps and voids identified from similar canals obturated by cold lateral compaction or warm vertical compaction.

METHODS

Thirty single-rooted premolars with oval-shaped canals were shaped and cleaned, and obturated with one of the three obturation techniques (N=10): GuttaCore, warm vertical compaction or cold lateral compaction. Filled canals were scanned with micro-computed tomography (micro-CT); reconstructed images were analysed for the volumetric percentage of gaps and voids at three canal levels (0-4mm, 4-8mm and 8-12mm from working length). The roots were subsequently sectioned at the 4-mm, 8-mm and 12-mm levels for analyses of the percentage of interfacial gaps, and area percentage of interfacial and intracanal voids, using scanning electron microscopy (SEM) to examine negative replicas of root sections. Data were analysed with parametric or non-parametric statistical methods at α=0.05.

RESULTS

Both micro-CT and SEM data indicated that canals obturated with GuttaCore core-carriers had the lowest incidence of interfacial gaps and voids, although the results were not significantly different from canals obturated by warm vertical compaction. Both the GuttaCore and the warm vertical compaction groups, in turn, had significantly lower incidences of gaps and voids than the cold lateral compaction group.

CONCLUSIONS

Because of the similarity in obturation quality between GuttaCore and warm vertical compaction, practitioners may find the GuttaCore core-carrier technique a valuable alternative for obturation of oval-shaped canals.

CLINICAL SIGNIFICANCE

The quality of obturation achieved by GuttaCore in single-rooted canals is not significantly different from that achieved by warm vertical compaction.

Effect of ultrasonication on physical properties of mineral trioxide aggregate

Aim. To evaluate the effect on physical properties of Mineral Trioxide Aggregate (MTA) of using direct hand compaction during placement and when using hand compaction with indirect ultrasonic activation with different application times. Methods. One hundred acrylic canals were obturated in 3 increments with MTA in sample sizes of 10. One group was obturated by hand with an endodontic plugger and the remainder obturated with indirect ultrasonic application, with times ranging from 2 seconds to 18 seconds per increment. Microhardness values, dye penetration depths, and radiographs of the samples were evaluated. Results. As ultrasonic application time per increment increased, microhardness values fell significantly (P < 0.001) while dye penetration values increased (P < 0.001). Microhardness of MTA ultrasonicated for 2 seconds was significantly higher than hand compaction (P = 0.03). Most radiographic voids were visible in the hand-compacted group (P < 0.001), which also had higher dye penetration depths than the 2-second ultrasonicated samples. Ultrasonication of MTA for 10–18 seconds resulted in significantly more voids than 2–8 seconds of ultrasonication (P = 0.02). Conclusion. The use of ultrasonics with MTA improved the compaction and flow of MTA, but excessive ultrasonication adversely affected MTA properties. A time of 2 seconds of ultrasonication per increment presented the best compromise between microhardness values, dye penetration depths, and lack of radiographic voids.

Micro-CT evaluation of root filling quality in oval-shaped canals

AIM

To assess the percentage volumes of filling materials and voids in oval-shaped canals filled with either cold lateral compaction or warm compaction techniques, using micro-computed tomography (micro-CT).

METHODOLOGY

Twenty-four single-rooted maxillary premolar teeth with oval-shaped canals were selected and the root canals prepared and assigned to two groups (n = 12), according to the filling technique: cold lateral compaction (CLC) or warm vertical compaction (WVC). Each specimen was scanned using a micro-CT device at an isotropic resolution of 12.5 μm. Percentage volumes of root filling materials and voids were calculated, and data were statistically analysed using Student's t-test and Friedman's test, with a significance level of 5%.

RESULTS

Overall, mean percentage volumes of gutta-percha, sealer and voids were 82.33 ± 3.14, 13.42 ± 2.91 and 4.26 ± 0.74 in the CLC group and 91.73 ± 4.48, 7.70 ± 4.44 and 0.57 ± 0.44 in the WVC group, respectively, with a statistically significant difference between groups (P < 0.05). At the apical level, differences in the percentage volumes of filling materials and voids between groups were not significant (P > 0.05).

CONCLUSIONS

No root fillings were void free. Warm vertical compaction produced a significantly greater volume of gutta-percha and a significantly lower percentage of voids than those achieved with cold lateral compaction. Distribution of sealer and voids within the root canal space after root filling was unpredictable, irrespective of the technique used.