Acid and Microhardness of Mineral Trioxide Aggregate and Mineral Trioxide Aggregate–like Materials

The effect of acidity on the physicochemical properties of two hydraulic calcium silicate-based cements and two calcium phosphate silicate-based cements

BACKGROUND

Bioceramic cements have been widely used in endodontic treatment. This study aimed to compare the microhardness, elastic modulus, internal microstructure and chemical compositions of Biodentine, WMTA, ERRM Putty, iRoot FS and IRM after exposure to PBS, butyric acid, and butyric acid followed by PBS.

METHODS

Specimens of each material were prepared and randomly divided into 5 subgroups (n = 5): subgroup A: PBS (pH = 7.4) for 4 days, subgroup B: PBS (pH = 7.4) for 14 days, subgroup C: butyric acid (pH = 5.4) for 4 days, subgroup D: butyric acid (pH = 5.4) for 14 days, subgroup E: butyric acid for 4 days followed by 10 days in contact with PBS. The surface microhardness, elastic modulus, internal morphologic and chemical compositions of specimens were analyzed.

RESULTS

The microhardness and elastic modulus values of all materials were significantly higher in the presence of PBS compared to exposure to butyric acid, with the same setting time (P < 0.01). After 4-day exposure to butyric acid followed by 10-day exposure to PBS, the microhardness values returned to the same level as 4-day exposure to PBS (P > 0.05). Biodentine showed significantly higher microhardness and elastic modulus values than other materials, while IRM displayed the lowest (P < 0.01).

CONCLUSION

Biodentine seems the most suitable bioceramic cements when applied to an infected area with acidic pH. Further storage at neutral pH, e.g. PBS reverses the adverse effects on bioceramic cements caused by a low pH environment.

Compressive strength, surface roughness, and surface microhardness of principle tricalcium silicate-based endodontic cements after universal adhesive application

Aims and Background

It was aimed to evaluate compressive strength (CS), surface roughness, and microhardness of mineral trioxide aggregate (ProRoot MTA) and Biodentine (BD) after adhesive application.

Materials and Methods

Tests was carried out according to international ISO standard. ProRoot MTA and BD were prepared in Teflon molds according to manufacturer's instructions: n = 210 for CS; n = 210 for microhardness. Samples were incubated for 7 days at 37°C in 100% humidity. Surfaces were smoothed with up to 2000 grits of silicon-carbide sandpaper on abrasive device at 150 rpm, randomly divided into seven groups (n = 15). Clearfil Universal Bond, All Bond Universal, and Single Bond Universal (SBU) were applied in both total-etch and self-etch (SE) modes. Adhesives were applied according to manufacturers' recommendations (no adhesive used in control). CS was performed at speed of 1 mm/min, microhardness at 100 gr for 15 s. The surface roughness of the samples was analyzed with atomic force microscopy. Two-way analysis of variance and post hoc Tukey tests were used for the evaluation of the data.

Results

Man CS and microhardness values between ProRoot MTA and BD were as follows: 24.9 N, 72.6 HV; 59.8 N, 59.0 HV, respectively. In CS, BD was higher than ProRoot MTA (P < 0.05). In other comparisons except for SBU SE group (P < 0.05), BD and ProRoot MTA showed similar results (P > 0.05). However, ProRoot MTA was found higher than BD regarding microhardness (P < 0.05). As a result of the adhesive application in both BD and ProRoot MTA groups, a decrease in surface roughness was observed compared to the control group.

Conclusion

BD exhibited better results than ProRoot MTA regarding CS. However, ProRoot MTA was found to be more successful than BD in terms of microhardness. BD and ProRoot MTA showed similar physical properties in terms of surface roughness. To improve regenerative procedures, besides the selection of bioceramic cements, the interaction between cements and materials applied during coronal restoration should be considered.

Calcium hydroxide and niobium pentoxide treatment effects before MTA placement

The aim of this study was to evaluate the effect of calcium hydroxide (CH) and niobium pentoxide (NP) pretreatment on pH, dentin microhardness and sealing of Mineral Trioxide Aggregate (MTA; Angelus). The pH of CH, NP and CH-NP (3:1) was evaluated in neutral and acidic simulated tissue fluid over 28 days. The Vickers microhardness was measured in forty 4 mm coronal root slices filled with pretreatment materials stored in medium for 1, 7, 28 days. Forty 10 mm roots were packed with pretreatment materials, irrigated after 24 h, then a 3 mm MTA plug was placed. Sealing ability was evaluated after 7 days using fluid filtration method. Statistics was performed using ANOVA and post hoc Tukey HSD tests. Addition of NP to CH maintained the alkalinity of CH, increased the microhardness of root dentin and reduced the microleakage. CH-NP can be effectively used as a pretreatment medicament in root canals requiring placement of MTA under acidic conditions.

Effect of butyrate, a bacterial by-product, on the viability and ICAM-1 expression/production of human vascular endothelial cells: Role in infectious pulpal/periapical diseases

AIM

To investigate the effects of butyric acid (BA), a metabolic product generated by pulp and root canal pathogens, on the viability and intercellular adhesion molecule-1 (ICAM-1) production of endothelial cells, which are crucial to angiogenesis and pulpal/periapical wound healing.

METHODOLOGY

Endothelial cells were exposed to butyrate with/without inhibitors. Cell viability, apoptosis and reactive oxygen species (ROS) were evaluated using an MTT assay, PI/annexin V and DCF fluorescence flow cytometry respectively. RNA and protein expression was determined using a polymerase chain reaction assay and Western blotting or immunofluorescent staining. Soluble ICAM-1 (sICAM-1) was measured using an enzyme-linked immunosorbent assay. The quantitative results were expressed as mean ± standard error (SE) of the mean. The data were analysed using a paired Student's t-test where necessary. A p-value ≤0.05 was considered to indicate a statistically significant difference between groups.

RESULTS

Butyrate (>4 mM) inhibited cell viability and induced cellular apoptosis and necrosis. It inhibited cyclin B1 but stimulated p21 and p27 expression. Butyrate stimulated ROS production and hemeoxygenase-1 (HO-1) expression as well as activated the Ac-H3, p-ATM, p-ATR, p-Chk1, p-Chk2, p-p38 and p-Akt expression of endothelial cells. Butyrate stimulated ICAM-1 mRNA/protein expression and significant sICAM-1 production (p < .05). Superoxide dismutase, 5z-7oxozeaenol, SB203580 and compound C (p <  .05), but not ZnPP, CGK733, AZD7762 or LY294002, attenuated butyrate cytotoxicity to endothelial cells. Notably, little effect on butyrate-stimulated sICAM-1 secretion was found. Valproic acid, phenylbutyrate and trichostatin (three histone deacetylase inhibitors) significantly induced sICAM-1 production (p < .05).

CONCLUSION

Butyric acid inhibited proliferation, induced apoptosis, stimulated ROS and HO-1 production and increased ICAM-1 mRNA expression and protein synthesis in endothelial cells. Cell viability affected by BA was diminished by some inhibitors; however, the increased sICAM-1 secretion by BA was not affected by any of the tested inhibitors. These results facilitate understanding of the pathogenesis, prevention and treatment of pulpal/periapical diseases.

In vivo Biocompatibility and Bioactivity of Calcium Silicate-Based Bioceramics in Endodontics

Endodontic therapy aims to preserve or repair the activity and function of pulp and periapical tissues. Due to their excellent biological features, a substantial number of calcium silicate-based bioceramics have been introduced into endodontics and simultaneously increased the success rate of endodontic treatment. The present manuscript describes the in vivo biocompatibility and bioactivity of four types of calcium silicate-based bioceramics in endodontics.

Biocompatibility of a High-Plasticity, Calcium Silicate-Based, Ready-to-Use Material

The Bio-C Sealer is a recently developed high-plasticity, calcium-silicate-based, ready-to-use material. In the present study, chemical elements of the materials were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The biocompatibility of the Bio-C Sealer was investigated using cytotoxicity tests and histological responses in the roots of dogs’ teeth. XRD, SEM, and FTIR produced hydrated calcium silicate in the presence of water molecules. In addition, FTIR showed the formation of calcium hydroxide and polyethylene glycol, a dispersing agent. The 1:4 dilutions of Bio-C Sealer presented weaker cytotoxicity than the Calcipex II in an in vitro system using the V-79 cell line. After 90 d, the periradicular tissue response of beagle dog roots was histologically evaluated. Absence of periradicular inflammation was reported in 17 of the 18 roots assessed with the Bio-C Sealer, whereas mature vertical periodontal ligament fibers were observed in the apical root ends filled with the Bio-C Sealer. Based on these results and previous investigations, the Bio-C Sealer is recommended as an effective root-end filling material. These results are relevant for clinicians considering the use of Bio-C Sealer for treating their patients.

Calcium silicate cement interface with restorative materials through layering after different time intervals

The aim was to evaluate the interfacial characteristics of Biodentine, CEM Cement, and ProRoot MTA when restored with different final restorative materials after different time intervals. Biodentine, CEM Cement and ProRoot MTA were layered with amalgam, composite resin or light cure glass ionomer cement. Layering was done either immediately, 24 or 72 h after cement placement. The interface of cements with restorative materials was characterized using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) after separation. Vickers surface microhardness test was also performed on the interface. Statistical analysis included two-way Anova, Dunnett T3, and Tukey HSD. The significance level was set at P < 0.05. The highest microhardness values were seen when restorative materials were layered after 24 h in the case of Biodentine, and after 72 h in the case of CEM Cement and ProRoot MTA. In ProRoot MTA no significant difference was seen in the microhardness when layered with different restorative materials regardless of the time of layering. In immediate layering, Biodentine exhibited the highest microhardness values. Both immediate and delayed layering resulted in element transfer between calcium silicate cements (CSCs) and restorative materials. Deposition and depletion of element occurs subsequent to layering of restorative materials on CSCs. When immediate layering is necessary, Biodentine may be a better option compared to other CSCs evaluated.

Evaluation of the properties of Mineral Trioxide Aggregate mixed with Zinc Oxide exposed to different environmental conditions

Addition of zinc oxide (ZnO) to Mineral Trioxide Aggregate (MTA) has been shown to rectify tooth discoloration caused by Angelus MTA. This study evaluated the microhardness, compressive strength, calcium ion release and crystalline structures of MTA mixed with ZnO in different environmental conditions. Molds with a diameter of 4 mm and a height of 6 mm were used for compressive strength, calcium ion release and X-ray diffraction (XRD) evaluations. Molds with 6 mm diameter and 4 mm height were used for surface microhardness evaluations. Cements evaluated include Angelus MTA (Angelus, Brail), Angelus MTA + ZnO, ProRoot MTA (Dentsply Tulsa Dental, OK), and ProRoot MTA + ZnO. Each group was divided into 3 subgroups according to exposure conditions: normal saline (NS), phosphate buffered saline (PBS) or blood. After 7 days incubation, surface microhardness, compressive strength and XRD analysis was performed. Calcium ion release was evaluated after 3, 24 and 168h incubation using atomic absorption spectrophotometry. Data were analyzed by One Way Anova followed by the Tukey HSD Post hoc tests and T-Test. The significance level was set at 0.05. Addition of ZnO to Angelus and ProRoot MTA significantly decreased the compressive strength of these cements regardless of the environmental conditions (P < 0.001); however, it had no significant effect on their microhardness or calcium ion release. In conclusion, adding ZnO to Angelus and ProRoot MTA can adversely affect the compressive strength of Angelus and ProRoot MTA.

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Addition of ZnO can prevent tooth discoloration caused by MTA.

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Mixing 5% ZnO with ProRoot and Angelus MTA decreases the compressive strength of the cement.

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Calcium ion release also decreases with the addition of ZnO although this decrease is not statistically significant.

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It seems that mixing ZnO with MTA can initially impair the hydration of this cement.

Fracture Resistance of Immature Incisors Following Root Filling with Various Bioactive Endodontic Cements Using an Experimental Bovine Tooth Model

Objective The aim of this study was to compare the fracture resistance of immature bovine roots when using ProRoot MTA, CEM Cement, and Biodentine as root filling materials.

Materials and Methods An immature bovine tooth model was developed by removing the coronal and apical portions of 70 bovine incisors 8 mm above and 12 mm below the cementoenamel junction (CEJ). The specimens were then divided into five groups: ProRoot MTA, CEM Cement, Biodentine, gutta-percha/AH26 sealer, and control. All groups received a 5-mm apical plug with a temporary restorative material. Then, the remaining root canal space was filled with one of the afore-mentioned materials. After setting, the specimens were mounted in acrylic resin. Then, 3 mm coronal to the CEJ from the buccal side of the teeth and at a 135°angle to the long axis, the specimens were loaded until fracture.

Results The specimens in the Biodentine (2196 N) and ProRoot MTA (2103 N) groups had significantly greater fracture resistance in comparison to the control group ( p = 0.01). No significant difference was found between CEM Cement, gutta-percha and sealer AH26, and control groups. No significant differences occurred between the four experimental groups ( p = 0.45).

Conclusion Filling the root canal space with ProRoot MTA and Biodentine contributed to higher fracture resistance values.

Effects of intracoronal bleaching agents on the surface properties of mineral trioxide aggregate

Bleaching agents may affect surface properties of mineral trioxide aggregate (MTA) as a coronal barrier. The purpose of this study was to investigate surface properties of MTA after exposure to intracoronal bleaching agents. MTA was set in acrylic molds with a 4 mm high central hole and a 6 mm diameter. Specimens were divided into four groups (n = 10); three groups were exposed to bleaching agents three times on every fourth day (carbamide peroxide-CP, hydrogen peroxide-HP, sodium perborate-SP) and a control group-C. The surface roughness and Vickers surface microhardness were measured. Differences between groups were analyzed using a Kruskal-Wallis test and intergroup comparisons were assessed with a Mann-Whitney U test with a Bonferroni correction (p < 0.0001). The microstructure and elemental composition were observed using a scanning electron microscope (SEM) and an energy-dispersive X-ray microanalysis (EDX) system. In terms of microhardness, the decrease in the HP group was significantly greater than that of the CP and SP groups; CP group significantly greater than that of the SP group, however, there was no significant difference between the SP and C groups. Surface roughness values were compared between groups, and no significant differences were observed between the CP and HP groups, and they exhibited significantly higher roughness values than the SP and C groups. SEM/EDX showed that the bleaching agents affected the elemental distribution. Bleaching agents adversely affected the surface roughness, surface microhardness and elemental distribution of MTA, with exposure to SP causing fewer changes on the surface properties than CP or HP.

Retention of BioAggregate and MTA as coronal plugs after intracanal medication for regenerative endodontic procedures: an ex vivo study

Objectives

This study compared the retention of BioAggregate (BA; Innovative BioCeramix) and mineral trioxide aggregate (MTA; Angelus) as coronal plugs after applying different intracanal medications (ICMs) used in regenerative endodontics.

Materials and Methods

One-hundred human maxillary central incisors were used. The canals were enlarged to a diameter of 1.7 mm. Specimens were divided into 5 groups (n = 20) according to the ICM used: calcium hydroxide (CH), 2% chlorhexidine (CHX), triple-antibiotic paste (TAP), double-antibiotic paste (DAP), and no ICM (control; CON). After 3 weeks of application, ICMs were removed and BA or MTA were placed as the plug material (n = 10). The push-out bond strength and the mode of failure were assessed. The data were analyzed using 2-way analysis of variance, the Tukey's test, and the χ² test; p values < 0.05 indicated statistical significance.

Results

The type of ICM and the type of plug material significantly affected bond strength (p < 0.01). Regardless of the type of ICM, BA showed a lower bond strength than MTA (p < 0.05). For MTA, CH showed a higher bond strength than CON, TAP and DAP; CHX showed a higher bond strength than DAP (p < 0.01). For BA, CH showed a higher bond strength than DAP (p < 0.05). The mode of failure was predominantly cohesive for BA (p < 0.05).

Conclusions

MTA may show better retention than BA. The mode of bond failure with BA can be predominantly cohesive. BA retention may be less affected by ICM type than MTA retention.

In Vitro Mechanical Properties of Mineral Trioxide Aggregate in Moist and Dry Intracanal Environments

Introduction:

The purpose of this study was to examine the microhardness and modulus of elasticity (MOE) of White ProRoot MTA (Dentsply Tulsa Dental, Tulsa, OK) after setting in moist or dry intracanal conditions.

Methods and Materials:

To simulate root canal system, 14 polyethylen molds with internal diameter of 1 mm and height of 12 mm were used. These molds were filled with 9-mm thick layers of White ProRoot Mineral Trioxide Aggregate (MTA; Dentsply Tulsa Dental, Tulsa, OK). The experimental group (n=7) had a damp cotton pellet with 1.5 mm height and a 1.5 mm layer of resin composite placed on it. In control group (n=7) the whole 3 mm above MTA were filled with resin composite. The specimens were kept in 37^°C and relative humidity of 80% for 4 days in order to simulate physiological conditions. Specimens were longitudinally sectioned and nanoindentation tests were carried out using Berkovich indenter at loading rate of 2 mN/s at 4×5 matrices of indents which were located in the coronal, middle and apical thirds of the specimen’s cross section, to evaluate the microhardness and modulus of elasticity of the specimen to appraise the progression of the setting process. Differences were assessed using nonparametric generalized Friedman rank sum and Wilcoxon Rank-Sum tests.

Results:

Statistical analysis showed that there was a significant difference in microhardness and MOE between control and experimental groups at coronal (P<0.001), middle (P<0.001) and apical (P<0.001) thirds of the simulated rod from simulated apical foramen. Kruskal-Wallis test showed no significant effect of depth on microhardness of material in experimental or control groups.

Conclusion:

Within limitations of this in vitro study, it seems that moist intracanal environment improves setting of MTA in various depths.

Microstructure and chemical analysis of four calcium silicate-based cements in different environmental conditions

OBJECTIVE

The objective of this study was to analyze the microstructure and crystalline structures of ProRoot MTA, Biodentine, CEM Cement, and Retro MTA when exposed to phosphate-buffered saline, butyric acid, and blood.

METHODS AND MATERIALS

Mixed samples of ProRoot MTA, Biodentine, CEM Cement, and Retro MTA were exposed to either phosphate-buffered saline, butyric acid, or blood. Scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopic (EDX) evaluations were conducted of specimens. X-ray diffraction (XRD) analysis was also performed for both hydrated and powder forms of evaluated calcium silicate cements.

RESULTS

The peak of tricalcium silicate and dicalcium silicate detected in all hydrated cements was smaller than that seen in their unhydrated powders. The peak of calcium hydroxide (Ca(OH)₂) in blood- and acid-exposed ProRoot MTA, CEM Cement, and Retro MTA specimens were smaller than that of specimens exposed to PBS. The peak of Ca(OH)₂ seen in Biodentine™ specimens exposed to blood was similar to that of PBS-exposed specimens. On the other hand, those exposed to acid exhibited smaller peaks of Ca(OH)₂.

CONCLUSION

Exposure to blood or acidic pH decreased Ca(OH)₂ crystalline formation in ProRoot MTA, CEM Cement and Retro MTA. However, a decrease in Ca(OH)₂ was only seen when Biodentine™ exposed to acid.

CLINICAL RELEVANCE

The formation of Ca(OH)₂ which influences the biological properties of calcium silicate cements was impaired by blood and acid exposures in ProRoot MTA, CEM Cement, and Retro MTA; however, in the case of Biodentine, only exposure to acid had this detrimental effect.

Evaluation of the bioactivity of fluoride-enriched mineral trioxide aggregate on osteoblasts

AIM

To investigate whether a combination of mineral trioxide aggregate (MTA) and fluoride compounds affects bone cells.

METHODOLOGY

Mineral trioxide aggregate (MTA) discs (ProRoot^® , Dentsply Sirona, Ballaigues, Switzerland) with and without the addition of 0.1%, 0.25% and 0.5% sodium fluoride were characterized for their surface roughness by laser scanning microscopy and for the adhesion of human alveolar osteoblasts by scanning electron microscopy. Using eluates from fluoride-enriched MTA discs, the cell proliferation was measured by monitoring the DNA incorporation of 5-bromo-2'-deoxyuridine. Further, gene expression was evaluated by qPCR arrays, extracellular matrix mineralization was quantified by absorption measurement of Alizarin red stains, and effects were calculated with repeated measures analysis and post hoc P-value adjustment.

RESULTS

Irrespective of fluoride addition, cell adhesion was similar on MTA discs, of which the surface roughness was comparable. Control osteoblasts had a curvilinear proliferation pattern peaking at d5, which was levelled out by incubation with MTA. The addition of fluoride partly restored the MTA-related reduction in the cellular proliferation rate in a dose-dependent manner. At the mRNA level, both fluoride and MTA modulated a number of genes involved in osteogenesis, bone mineral metabolism and extracellular matrix formation. Although MTA significantly impaired extracellular matrix mineralization, the addition of fluoride supported the formation of mineralized nodules in a dose-dependent manner.

CONCLUSION

The addition of fluoride modulated the biocompatibility of MTA in terms of supporting bone cell proliferation and hard tissue formation. Hence, fluoride enrichment is a trend-setting advancement for MTA-based endodontic therapies.

Effect of acidic pH on microhardness and microstructure of theraCal LC, endosequence, mineral trioxide aggregate, and biodentine when used as root repair material

Introduction:

The aim of this study was to investigate the microhardness and microstructural features of newer tricalcium silicate materials: TheraCal LC, mineral trioxide aggregate (MTA), biodentine (BD), and Endosequence Root Repair Material (ERRM) putty, after exposure to acidic environments in comparison with distilled water.

Materials and Methods:

A total of 80 extracted single-rooted premolars were collected. All the selected specimens were sectioned vertically, and cavities were prepared on the root surface. Specimens were divided into four groups of 20 each, i.e., Group 1: (n = 15) MTA (ProRoot, Dentsply Tulsa Dental, Tulsa, OK, USA), Group 2: (n = 15) BD (Septodont, France), Group 3: (n = 15) ERRM putty (Brasseler, USA), and Group 4: (n = 15) TheraCal LC (Bisco Inc Schaumburg). Materials were placed into prepared cavities. About 10 specimens per each group were exposed to butyric acid buffered at a pH level of 5.5 for 7 days at 37c, and 10 specimens from each group were exposed to distilled water serving as a control group. The surface microhardness was measured after exposure to either acid or distilled water. Scanning electron microscope was used to observe the internal microstructure morphology. Two-way analysis of variance was applied to evaluate the Knoop microhardness value (KHN).

Results:

Results showed that the microhardness values of the materials were significantly higher in the neutral environment of butyric acid at pH 7.4 when compared to those in the acidic condition of pH 5.4 for all groups (P < 0.001). TheraCal LC had higher microhardness values than BD, MTA, ERRM putty at 5.5 pH levels (P < 0.001).

Conclusion:

The microhardness values of TheraCal LC, BD, ERRM Putty, and MTA were reduced in an acidic environment, which resulted in these materials having more porous and less crystalline microstructures. TheraCal LC seems the most suitable material for application to an area of inflammation where a low pH value may exist.

Different Setting Conditions Affect Surface Characteristics and Microhardness of Calcium Silicate-Based Sealers

OBJECTIVE

To investigate the effect of different setting conditions on surface microhardness and setting properties of calcium silicate-based sealers.

METHODS

Three sealers, EndoSequence Bioceramic (BC; Brasseler USA, Savannah, GA, USA), Endoseal MTA (ES; Maruchi, Wonju, Korea), and Well-Root ST (WR; Vericom, Chuncheon, Korea), were compared. Specimens were exposed to either butyric acid (pH 5.4) or phosphate-buffered saline (PBS [pH 7.4]) for 48 h and stored at 100% humidity for 12 days. The control specimens were stored at 100% humidity for 14 days. Surface microhardness was measured, topographic changes were observed, and phase analysis was performed using X-ray diffraction. Microhardness according to storage conditions was compared using one-way analysis of variance and Tukey's multiple comparison tests (P < .05).

RESULTS

The BC and ES sealers exhibited decreased microhardness when stored in acid or PBS compared with control (P < .05). In the WR group, acid exposure lowered microhardness of the specimens compared with control (P < .05). Scanning electron microscopy revealed different topographies in specimens from all tested sealers exposed to acid or PBS.

CONCLUSION

The surface microhardness of calcium silicate-based sealers was reduced by exposure to either acid or PBS. Acid solutions, however, had a more detrimental effect than PBS.

Effect of blood contamination on the compressive strength of three calcium silicate-based cements

The aim of this study was to investigate the effect of human blood exposure on the compressive strength of various calcium silicate-based cements. Two hundred and eighty-eight customised cylindrical moulds were randomly divided into three groups according to material used: ProRoot MTA, Biodentine or CEM cement (n = 96). Each group was divided into two subgroups according to exposure conditions: PBS or blood. Then, the compressive strength of the specimens was measured after 6 h, 24 h, 72 h and 7 days. The compressive strength of CEM cement could not be measured after 6 and 24‏ h regardless of the exposure conditions nor could the compressive strength of 6 h blood-exposed ProRoot MTA. The compressive strength of blood-exposed ProRoot MTA was only significantly lower after 6 h, but no difference was seen at other time intervals. Blood exposed did adversely affected the compressive strength of Biodentine. The compressive strength of all groups significantly increased over time (P < 0.005).

Effects of smear layer removal agents on the physical properties and microstructure of mineral trioxide aggregate cement

OBJECTIVE

To compare the effect of QMix (Dentsply Sirona), 7% maleic acid (MA), and 17% ethylenediaminetetraacetic acid (EDTA) on the microhardness, flexural strength and microstructure of mineral trioxide aggregate (MTA; ProRoot MTA, Dentsply Sirona).

METHODS

Forty MTA specimens were divided into four groups: [I] QMix [II] 7% MA [III] 17% EDTA and [IV] distilled water (control). After treatment with 5mL of the respective solution for 1min, the specimens were tested for microhardness using a Knoop hardness tester. Forty additional specimens were similarly treated and evaluated for the flexural strength using a universal testing machine. For microstructure evaluation, MTA specimens were treated in a similar manner and examined by X-ray diffractometry and scanning electron microscopy (SEM).

RESULTS

For microhardness, there were no differences between distilled water, QMix and EDTA groups. However, MTA exposed to distilled water had higher microhardness than MA. When compared with QMix and EDTA, MA had lower microhardness; there was no difference between EDTA and QMix. For flexural strength, distilled water group had higher flexural strength than the other agents. There were no differences between EDTA vs MA and EDTA vs QMix. Specimens treated with QMix had higher flexural strength than MA. X-ray diffraction indicated that EDTA inhibited hydration of MTA. For SEM, all the tested agents altered the microstructure of MTA when compared to distilled water.

CONCLUSION

MA had more detrimental effect on the physical properties of MTA and EDTA was more detrimental to the hydration of MTA.

CLINICAL SIGNIFICANCE

The present study highlights the effect of newer chelating agents on the physical properties and microstructure of MTA. Preventing the deterioration of MTA is important for its long term success in endodontic procedures.

Push-Out Bond Strength and Surface Microhardness of Calcium Silicate-Based Biomaterials: An in vitro Study

OBJECTIVE

This was an in vitro evaluation of push-out bond strength and surface microhardness of calcium silicate-based biomaterials in coronal and apical root dentin.

MATERIALS AND METHODS

Ninety sections (2 mm thick) of coronal and apical root dentin were obtained from roots of 60 extracted teeth; the canals were enlarged to a standardized cavity diameter of 1.3 mm. Sections were randomly divided into 6 groups (n = 15 per group), and cavities were filled with Biodentine™, BioAggregate, or ProRoot mineral trioxide aggregate (MTA), according to the manufacturers' instructions. Push-out bond strength values were measured using a universal testing machine under a compressive load at a speed of 1 mm/min. Samples were analyzed under a light microscope to determine the nature of bond failure. Ten samples (2 mm thick) were prepared for all the materials, and Vickers microhardness was determined using a digital hardness tester. Data were analyzed using one-way analysis of variance and Tukey-Kramer multiple comparison tests at a significance level of p < 0.05.

RESULTS

Biodentine (42.02; 39.35 MPa) and ProRoot MTA (21.86; 34.13 MPa) showed significantly higher bond strengths than BioAggregate (6.63; 10.09 MPa) in coronal and apical root dentin, respectively (p < 0.05). Biodentine also differed significantly from ProRoot MTA in coronal dentin. Bond failure was predominantly adhesive in Biodentine and ProRoot MTA, while BioAggregate showed predominantly mixed failure. ProRoot MTA (158.52 HV) showed significantly higher microhardness and BioAggregate (68.79 HV) showed the lowest hardness.

CONCLUSION

Biodentine and ProRoot MTA showed higher bond strength and microhardness compared to BioAggregate.

Ion Release, Microstructural, and Biological Properties of iRoot BP Plus and ProRoot MTA Exposed to an Acidic Environment

INTRODUCTION

This study evaluated how exposing the novel calcium silicate nanoparticulate bioceramic iRoot BP Plus (Innovative Bioceramix, Vancouver, Canada) to an acidic environment affects ion release from this material and alters MC3T3-E1 preosteoblast viability on and attachment to this material. These factors were compared against those of ProRoot MTA under similar conditions.

METHODS

Each material was exposed to phosphate-buffered saline (pH = 7.4) or butyric acid (pH = 5.4) for 5 days. Trace metal elements within the 2 materials and released ions were identified using inductively coupled plasma optical emission spectroscopy. The microstructures and elemental compositions of MTA and iRoot BP Plus after treatment with butyric acid were determined using scanning electron microscopy with an energy-dispersive X-ray spectrometer. Furthermore, the viability of MC3T3-E1 cells on and their levels of attachment to the materials after the butyric acid treatment were compared.

RESULTS

iRoot BP Plus contained fewer toxic metal elements than MTA. Under acidic conditions, both materials displayed similar ion release abilities, with increased release of Si and Ca ions. Substantial changes in microstructure, including reduced apatite formation, were observed for both materials after exposure to acidic pH. Furthermore, exposing iRoot BP Plus and MTA to an acidic environment increased and decreased MC3T3-E1 cell viability on these materials, respectively. MC3T3-E1 cell attachment to both materials was not significantly affected by acidic pH.

CONCLUSIONS

iRoot BP Plus seems more biologically appropriate for application in an inflamed acidic environment than ProRoot MTA.

Conservative Management of Unset Mineral Trioxide Aggregate Root-End Filling: A Case Report

This case report presents conservative management of unset mineral trioxide aggregate (MTA) after being placed as a root-end filling material following periapical surgery. Periapical surgery was indicated for a maxillary lateral incisor of a 15-year-old male due to persistent exudate and a large periapical lesion. During surgery Angelus MTA was placed as root-end filling. The next session it was noticed that MTA had failed to completely set. In an orthograde approach, calcium-enriched mixture (CEM) cement was used to obturate the root canal space. The patient was followed up for 27 months and did not exhibit any clinical signs and symptoms. Radiographic images showed complete healing of the lesion.

In Vitro Evaluation of Different Solvents for Retrieval of Mineral Trioxide Aggregate and Calcium-Enriched Mixture

Introduction:

The purpose of this study was to evaluate the effect of different solvents; carbonic acid (H₂CO₃), hydrochloric acid (HCl), chlorhexidine (CHX) and sodium hypochlorite (NaOCl) on the surface hardness of mineral trioxide aggregate (MTA) and calcium-enriched mixture (CEM) cement.

Methods and Materials:

Plexiglass molds were prepared and filled with Angelus MTA or CEM cement and then exposed to 2% carbonic acid, 37% hydrochloric acid, 2% chlorhexidine, 5.25% sodium hypochlorite and normal saline at intervals of 1 and 21 days, respectively (n=4). Surface microhardness of all specimens was analyzed by a universal testing machine and an electron microscope for some selected samples. Data were analyzed using the three-way ANOVA. Subgroup analysis was performed by Student’s t-test, One-way ANOVA and Tukey’s tests. The level of significance was set at 0.05.

Results:

On the first day, all solvents and on 21^st day HCl, and H₂CO₃ were more effective in reducing the microhardness of MTA compared to CEM cement (P<0.05).

Conclusion:

The two experimental cements were differently affected by the solvents at specific time intervals. The solvents were more effective on MTA.

X-ray Diffraction Analysis of ProRoot Mineral Trioxide Aggregate Hydrated at Different pH Values

INTRODUCTION

The aim of this study was to compare the chemical compounds of white ProRoot mineral trioxide aggregate (WMTA) hydrated at different pH environments.

METHODS AND MATERIALS

Mixed samples of WMTA were kept in acidic (pH=5.4), neutral (pH=7.4) and alkaline (pH=9.4) environments for 48 h. Then, X-ray diffraction (XRD) analysis was performed for both hydrated and powder forms of WMTA. Portlandite crystalline structures of environments were compared from three aspects: intensity (height of the peak, corresponding to the concentration), crystallinity (peak area/total area) and crystal size (full-width at half-maximum of the peak).

RESULTS

After matching the peaks of each sample with those of the International Center for Diffraction Data (ICDD) database, the main constituent of all set cements and powder form was found to be bismuth oxide. Acidic environment exhibited lower intensity and crystallinity of portlandite in comparison with neutral environment.

CONCLUSION

The highest concentration and crystallinity of portlandite were observed in WMTA samples hydrated at neutral pH and the highest crystal size was detected after hydration in alkaline pH.

Effect of calcium chloride on physical properties of calcium-enriched mixture cement

The aim of this study was to evaluate the effect of adding 10% calcium chloride (CaCl2) on the setting time, solubility and the pH of calcium-enriched mixture (CEM) cement. Setting time was assessed in accordance with American Dental Association specification N°57. Solubility was measured at 24 and 72 h, 7 and 14 days in hydrated and dehydrated conditions by calculating weight change. The pH of MiliQ water in which the CEM cement samples were immersed was measured immediately after each time interval with and without the addition of CaCl2. The data were analysed using the Mann-Whitney U-test and the Student's t-test. The initial setting time was significantly decreased after the addition of 10% CaCl2. The pH of water increased immediately when in contact with the cements in both groups. The weight loss of hydrated and dehydrated specimens was more than 3% and was significantly reduced by the addition of 10% CaCl2.

Comparison of pH changes induced by calcium enriched mixture and those of calcium hydroxide in simulated root resorption defects

INTRODUCTION

External resorption usually occurs after dental trauma and the loss of root cementum. Because it has the ability to induce alkaline pH, calcium hydroxide is used in treatment of external resorption, which is reportedly not free from disadvantages. Driven by such understanding, the aim of this in vitro study was to compare the pH changes induced by calcium enriched mixture (CEM) and those of calcium hydroxide in simulated root resorption defects.

METHODS

Twenty-one paired extracted human premolars were cut to the length of 14 mm. Root canal preparation was performed by using ProTaper rotary system. Cavities of 0.7-mm depth and 1.4-mm diameter were prepared on the external root surface, 5 mm from the apex. Half of the teeth were filled with CEM and the other half with calcium hydroxide. Five premolars were also assigned as the negative control group and filled with normal saline. To be assured of the filling quality, a radiograph was obtained from each tooth. Subsequently, pH of the cavity was measured with a microelectrode at 20-minute, 3-hour, and 1-, 7-, 14-, 21-, and 28-day intervals after filling.

RESULTS

Mean pH in the CEM and in the calcium hydroxide groups were significantly varied during the study period, with pH of the calcium hydroxide group significantly higher than that of CEM in all of the measurements. However, no significant difference was observed between the pH of the calcium hydroxide group and that of the control group at the 7-day and 14-day measurements and between those of the CEM group and the control group at days 7, 21, and 28.

CONCLUSIONS

In comparison with calcium hydroxide, CEM hardly maintained alkaline pH during the first month of use, and so CEM may be an inappropriate material in treatment of external root resorption.

Effect of BioAggregate on osteoclast differentiation and inflammatory bone resorption in vivo

AIM

To investigate the effect of BioAggregate (Innovative Bioceramix, Vancouver, BC, Canada) on lipopolysaccharide (LPS)-induced bone destruction in vivo and to compare its performance with that of mineral trioxide aggregate (MTA; Dentsply Tulsa Dental, Tulsa, OK, USA).

METHODOLOGY

Mouse bone marrow macrophages (BMMs) were primary cultured and treated with several concentrations of BioAggregate and MTA extracts. Cell viability was measured with a Cell Counting Kit-8 assay, whilst in vitro osteoclast differentiation was evaluated with tartrate-resistant acid phosphatase (TRAP) staining. LPS-induced mouse calvarial bone destruction model was established to assess the effect of BioAggregate and MTA extracts in vivo. Mice were killed on day 7, and calvarial bones were prepared for microcomputed tomography scanning, histologic analysis and double-immunofluorescence staining. Statistical tests used were one-way anova followed by Student-Newman-Keuls test.

RESULTS

BioAggregate extracts displayed no obvious cytotoxicity to BMMs and significantly inhibited (P < 0.01) the differentiation of RANKL-stimulated BMMs. Comparable effects were induced by MTA. BioAggregate and MTA extracts markedly reduced (P < 0.01) osteoclast numbers and attenuated (P < 0.05) bone resorption in LPS-challenged mouse calvaria. The expression levels of osteoclastogenic cathepsin K and its upstream regulator nuclear factor of activated T-cell cytoplasmic 1 and c-Fos were also decreased by BioAggregate and MTA extracts.

CONCLUSIONS

BioAggregate and MTA showed comparable inhibitory effect on osteoclast differentiation and inflammatory bone resorption in vivo.