Evaluation of the Effect of Intrinsic Material Properties and Ambient Conditions on the Dimensional Stability of White Mineral Trioxide Aggregate and Portland Cement

In vitro and in vivo evaluation of iRoot BP Plus as a coronal sealing material for regenerative endodontic procedures

OBJECTIVES

To investigate in vitro effects of a nanoparticle bioceramic material, iRoot BP Plus, on stem cells from apical papilla (SCAP) and in vivo capacity to induce pulp-dentin complex formation.

MATERIALS AND METHODS

The sealing ability of iRoot BP Plus was measured via scanning electron microscopy (SEM). SCAP were isolated and treated in vitro by iRoot BP Plus conditioned medium, with mineral trioxide aggregate (MTA) conditioned medium and regular medium used as controls, respectively. Cell proliferation was assessed by BrdU labeling and MTT assay and cell migration was evaluated with wound healing and transwell assays. Osteo/odontogenic potential was evaluated by Alizarin red S staining and qPCR. Pulp-dentin complex formation in vivo was assessed by a tooth slice subcutaneous implantation model.

RESULTS

iRoot BP Plus was more tightly bonded with the dentin. There was no difference in SCAP proliferation between iRoot BP Plus and control groups (P > 0.05). iRoot BP Plus had a greater capacity to elevated cell migration (P < 0.05) and osteo/odontogenic marker expression and mineralization nodule formation of SCAP compared with MTA groups (P < 0.05). Furthermore, the new continuous dentine layer and pulp-like tissue was observed in the iRoot BP Plus group in vivo.

CONCLUSIONS

iRoot BP Plus showed excellent sealing ability, promoted the migration and osteo/odontogenesis of SCAP and induced pulp-dentin complex formation without affecting the cell proliferation, which indicated iRoot BP Plus was a promising coronal sealing material in REPs.

CLINICAL RELEVANCE

The coronal sealing materials play crucial roles for the outcomes of REPs. This study showed that iRoot BP Plus has good coronal sealing and promote pulp-dentin complex formation compared with MTA, providing experimental evidences for the clinical application of iRoot BP Plus as a promising coronal seal material in REPs.

Portland Cement: An Overview as a Root Repair Material

Portland cement (PC) is used in challenging endodontic situations in which preserving the health and functionality of pulp tissue is of considerable importance. PC forms the main component of mineral trioxide aggregate (MTA) and demonstrates similar desirable properties as an orthograde or retrograde filling material. PC is able to protect pulp against bacterial infiltration, induce reparative dentinogenesis, and form dentin bridge during the pulp healing process. The biocompatibility, bioactivity, and physical properties of PC have been investigated in vitro and in animal models, as well as in some limited clinical trials. This paper reviews Portland cement's structure and its characteristics and reaction in various environments and eventually accentuates the present concerns with this material. This bioactive endodontic cement has shown promising success rates compared to MTA; however, considerable modifications are required in order to improve its characteristics and expand its application scope as a root repair material. Hence, the extensive chemical modifications incorporated into PC composition to facilitate preparation and handling procedures are discussed. It is still important to further address the applicability, reliability, and cost-effectiveness of PC before transferring into day-to-day clinical practice.

Hydration reaction analysis of calcium-silicate-based materials using Scanning Electron Microscopy and X-ray Diffraction method

Background/Aim: The components of calcium silicate-based materials can be identified through X-Ray Diffraction Analysis. This study aimed to determine the hydration reactions and particle size of MTA Angelus, Biodentine, and NeoMTA Plus as calcium-silicate-based materials. Material and Methods: The powder and set cement samples using divergence and scatter slits of 1 ○ and a receiver slit of 0.10 mm. The scanning range was set at 5 ○ to 70 ○ , and ongoing scans for the theta-2theta range was performed with a scan speed of 2 ○ /minute (-1). The patterns obtained were analyzed using search-match software. The three most substantial peaks were used to identify hydration reactions and major crystalline structures. Also, Scanning Electron Microscope (SEM) analysis was performed and the particle size of set materials were determined using an image analysis software. Results: According to X-Ray Diffraction Analysis, the main components were determined as tricalcium silicate and dicalcium silicate in the three calcium silicate-based materials. We determined that the main components of the materials were similar. We also identified the extensive presence of tricalcium aluminate in MTA Angelus, calcium carbonate in Biodentine, and calcium phosphate salts in NeoMTA Plus. Furthermore, the results of the present particle analysis show that the calcium-silicate-based materials' distribution of particle count and size varies. Biodentine has the widest, and MTA Angelus has the narrowest particle size distribution range. NeoMTA Plus has the largest number of fine, large-sized particles (p < 0.0001), while MTA Angelus and Biodentine have a more homogeneous and non-statistically significant particle distribution range (p > 0.05). Conclusions: The present findings provide insight into variations in performance between different calcium-silicate-based materials.

A laboratory study to test the responses of human dental pulp stem cells to extracts from three dental pulp capping biomaterials

AIM

This laboratory study aimed to investigate the effects of three endodontic biomaterials; MTA-HP, iRoot-BP-Plus and ACTIVA on the proliferation, adhesion and osteogenic differentiation of human Dental Pulp Stem Cells (hDPSCs).

METHODOLOGY

The hDPSCs were isolated from the dental pulps of 21 patients scheduled for surgical extraction of their impacted third molars. The MTT assay was used for assessing cellular proliferation. Ninety-six-well plates were used and the experiment was repeated four times under the same condition and the assay was done in triplicate. Four groups were assigned in which the hDPSCs were cultured in complete media only and considered as negative control. Whilst in the 2^nd , 3^rd and 4^th groups, the cells were treated with CM supplemented with 1.5 μl MTA-HP (CM-MTA, iRoot-BP-Plus (CM-BP), and ACTIVA(CM-AC) extracts, respectively. Attachment adhesion and growth morphology of hDPSCs were observed using SEM and the osteogenic differentiation assay was evaluated by Alizarin red stain test (ARS). The data of proliferation and osteogenic differentiation were analysed using two-way ANOVA followed by Tukey's post hoc multiple comparison test. A p-value < 0.05 was considered significant to analyse the differences amongst the means of groups.

RESULTS

Both CM-MTA and CM-BP groups were associated with a significant increase in hDPSC proliferation in comparison with CM-AC and CM groups (p = 0.001). hDPSCs exhibited a greater cellular attachment to iRoot-BP-Plus surfaces followed by MTA-HP, whilst less attachment was observed in the ACTIVA group. Moreover, at day 7 there was a significant difference in formation of mineralizing nodules; CM-BP, CM-MTA and CM-AC groups respectively (p = 0.001). Whilst there was no significance of difference between CM-AC and CM groups (p > 0.05).

CONCLUSIONS

In a laboratory setting, ACTIVA, MTA-HP and iRoot-BP-Plus promoted hDPSCs proliferation, mineralization and attachment, which may explain their in-situ success as endodontic biomaterials.

Tannic acid speeds up the setting of mineral trioxide aggregate cements and improves its surface and bulk properties

HYPOTHESIS

The setting time and mechanical properties of cements are a major technical concern for a long time in civil engineering. More recently those practical problems became a major concern for biomedical applications -in bone surgery and in dentistry- in particular concerning the setting time which should be minimized. The possibility to add organic additives to interact with the different constituting ions in cements constitutes a way to modify the setting kinetics. We made the assumption that a hydrolysable polyphenol like tannic acid could modify the setting time and the physical properties of Mineral Trioxide Aggregate (MTA).

EXPERIMENTS

Tannic acid is added in variable proportions to the water used to set MTA. The formation of the hybrid organic-mineral cements is investigated using a combination of structural, chemical and mechanical methods. X-ray tomography was also used to investigate the changes in porosity and pore size distribution upon incorporation of tannic acid in MTA based cements. The hydrophilicity of the cements was evaluated by measuring the permeation kinetics of small water droplets.

FINDINGS

We found that tannic acid allowed to reduce markedly the setting time of MTA based cements. The obtained cements have an increased hydrophilicity and display excellent resistance to compression. The number of pores but not the average pore size is also affected. The possible roles of tannic acid in modifying the cement properties are discussed.

Physicochemical Properties of a Bioceramic Repair Material - BioMTA

This study aimed to assess the physicochemical properties of a repair material in the Brazilian market, BioMTA, in comparison to other two materials currently in use (Biodentine and MTA Angelus). The initial setting time was evaluated using Gillmore needle. The pH was measured with a pH-meter after 24 h, 3, 7, 14 and 21 days. The radiopacity was determined using the equivalence in millimeters of aluminum (mm Al) from digitized occlusal radiographs. Solubility was determined after immersion in water for 7 days. The data were analyzed by one-way ANOVA and Tukey tests (a=0.05). The BioMTA initial setting time (5.2 min) was lower than the other materials (p<0.05). All materials showed an alkaline pH at 21 days. At 24 h, BioMTA was the most alkaline material (p<0.05); and at 3, 7, 14 and 21 days there was no difference between BioMTA and Biodentine (p>0.05), both being more alkaline than MTA Angelus (p<0.05). The radiopacity of BioMTA (4.2 mm Al) was significantly higher compared to Biodentine (p<0.05) and lower than MTA Angelus (p<0.05). The solubility of the materials was -4.2%, -1.6% and 4.1% for BioMTA, MTA Angelus and Biodentine, respectively, with a significant difference between them (p<0.05). Therefore, it can be concluded that BioMTA displayed a shorter setting time, an alkaline pH, a higher radiopacity, and a gain in mass.

Dental discoloration caused by Grey-MTAFlow cement: analysis of its physicochemical, biological and antimicrobial properties

Tricalcium silicate-based cement are materials used in reparative and regenerative procedures in endodontics. A recently proposed formulation aimed to enhance handling during clinical use with a versatile material applicable by syringe. Although, the use of bismuth oxide as radiopacifier and grey raw powder are drawbacks considering aesthetics.

The effect of three different pulp capping cements on mineralization of dental pulp stem cells

This study evaluated the osteogenic differentiation of human dental pulp stem cells in response to substances released by the pulp capping agents, Biodentine (BD), mineral trioxide aggregate (MTA) and two-paste calcium hydroxide cement (CHC), along with their physicochemical characteristics. The dimensional stability test showed that of the materials studied, only BD met the standards recommended by the International Organization for Standardization (ISO) for pulp capping materials and thus can be used safely. In the chemical tests, BD was the most stable material. In the Alizarin red S test, BD formed the higher amount of mineralized nodules in the mineralizing medium and also formed mineralized nodules in a non-mineralizing medium. BD releases substances that can significantly induce formation of the human dental pulp stem cell-mineralized extracellular matrix, with physicochemical characteristics that are more conducive to pulp repair than those of MTA and CHC.

Antimicrobial and anti-inflammatory drug-delivery systems at endodontic reparative material: Synthesis and characterization

OBJECTIVE

The aim of this study was to synthesize and characterize an experimental endodontic paste.

METHODS

An experimental endodontic paste (EX) was characterized by its particle size, zeta potential, drug content and morphology. The powder of EX is composed of amoxicillin microspheres, calcium tungstate and α-tricalcium phosphate, mixed with an indomethacin nanocapsules suspension. Ultracal^® (Ultradent), an iodoform-based paste (GP) and the EX were evaluated by its physical properties (flow, film thickness and radiopacity). The cytocompatibility was performed by MTT and SRB-colorimetric assays; the cell-migration was tested with scratch assay and cell-ability to remineralization with ALP and Alizarin Red S, with fibroblastic cell line. The antibacterial activity was assessed by the formation of inhibition zones and against planktonic bacteria.

RESULTS

The EX and UL flow achieved ISO6876 standard, and GP was lower than 17mm. All pastes achieved the film thickness required. Radiopacity was equivalent to 1.81±0.25mmAl for EX, which did not differ from GP group 1.39±0.33mmAl (p>0.05). The UL presented 3.04±0.33mmAl. The values for SRB showed better citocompatibility in comparison with MTT for all materials. The ALP activity and formation of mineralized nodules demonstrated the remineralization potential for UL and EX. Cell migration showed continuous wound closure until complete cell healing, however, the EX accelerated the process (p<0.05). The EX showed the greatest inhibition zone (p<0.05) and was the only group with antibacterial activity against planktonic bacteria.

SIGNIFICANCE

The synthesized endodontic paste demonstrated reliable physical and biological properties and could be a promising material for periapical tissue repair.

Solubility, porosity and fluid uptake of calcium silicate-based cements

Objective:

To evaluate the absorption/fluid uptake, solubility and porosity of White mineral trioxide aggregate (MTA) Angelus, Biodentine (BIO), and zinc oxide-eugenol (ZOE).

Material and Methods:

Solubility was evaluated after immersion in distilled water for 7 and 30 days. Porosity was evaluated using digital inverted microscope, scanning electron microscope (SEM) and micro-computed tomography (micro-CT). For the fluid uptake test, specimens were immersed in Hank's balanced salt solution (HBSS) for 1, 7, 14 and 28 days. Fluid absorption, solubility and porosity of the materials were measured after each period. Statistical evaluation was performed using one-way analysis of variance (ANOVA) and Tukey tests, with a significance level at 5%.

Results:

After 7 and 30 days, BIO showed the highest solubility (p<0.05). All methods demonstrated that MTA had total porosity higher than BIO and ZOE (p<0.05). Micro-CT analysis showed that MTA had the highest porosity at the initial period, after its setting time (p<0.05). After 7 and 30 days, ZOE had porosity lower than MTA and BIO (p<0.05). Absorption was similar among the materials (p>0.05), and higher fluid uptake and solubility were observed for MTA in the fluid uptake test (p<0.05).

Conclusions:

BIO had the highest solubility in the conventional test and MTA had higher porosity and fluid uptake. ZOE had lower values of solubility, porosity and fluid uptake. Solubility, porosity and fluid uptake are related, and the tests used provided complementary data.

Novel Calcium Zirconate Silicate Cement Biomineralize and Seal Root Canals

This study evaluated the sealing ability of gutta-percha (GP) with a calcium silicate-based sealer and a novel calcium zirconate containing calcium silicate cement (ZC). The root canals of the extracted premolars were prepared, which were then randomly allocated to three experimental groups (12 root canals per group) for obturation by continuous wave of condensation with the GP and AH 26 sealer (CW); obturation using a single GP with a calcium silicate-based EndoSequence BC sealer (SC); or obturation with ZC. The roots were inserted into sterile Eppendorf tubes, which were inoculated coronally with Porphyromonas gingivalis. The amount of endotoxin leakage into the apical reservoirs were measured using the Limulus Amebocyte Lysate (LAL) assay over 21 days, with comparisons made using one-way ANOVA and Scheffe’s tests (α = 0.05). After 21 days, 75% of the canals that had been obturated by SC, 50% of those obturated by CW and 42% of those obturated by ZC showed endotoxin leakage. The amount of leakage was higher in the SC canals than in the CW (p = 0.031) or ZC (p = 0.03) canals, although there was no significant difference in the amount of leakage for CW and ZC (p > 0.05). X-ray diffraction revealed the presence of tricalcium silicate (Ca₃SiO₅) and calcium zirconate (CaZrO₃) in the synthesized ZC. Scanning electron microscopy revealed mineralized precipitates on the dentin of canals obturated by ZC. The novel calcium zirconate silicate cement appears to promote biomineralization and seal root canals at least as effectively as the conventional sealer.

Systemic bone marker expression induced by grey and white mineral trioxide aggregate in normal and diabetic conditions

AIM

To investigate the relationship between diabetes mellitus and local/systemic effects of both grey and white mineral trioxide aggregate (MTA) Angelus on bone marker expression.

METHODOLOGY

Wistar rats were divided into two groups: healthy and diabetic (Alloxan induced), which were further divided into three subgroups (control, GMTA Angelus and WMTA Angelus). Polyethylene tubes filled with MTA materials or empty tubes were implanted in dorsal connective tissue. On days 7 and 30, blood samples were collected for calcium, phosphorus and ALP measurement. The animals were euthanized; implanted tubes were removed and processed for immunohistochemical analysis of osteocalcin (OCN) and osteopontin (OPN). Kruskal-Wallis followed by Dunn's multiple comparison test was performed for nonparametric data, and anova followed by Tukey's test for parametric data.

RESULTS

No difference in systemic serum calcium levels between both groups was observed. On day 7, serum phosphorus levels within the WMTA healthy group were higher than that of the diabetic group. On day 30, healthy rats exhibited lower phosphorus levels than diabetic ones. At both time points, the diabetic group was associated with more ALP activity than the healthy group. Immunohistochemical analyses of the healthy group revealed OCN- and OPN-positive cells in the presence of both MTA materials. However, under diabetic conditions, both OCN and OPN were absent.

CONCLUSION

Both MTA materials were associated with an increase in serum calcium, phosphorus and ALP, suggesting a potential systemic effect, along with triggered differentiation of OCN- and OPN-positive cells. Moreover, in diabetic conditions, an inhibitory effect on MTA-induced differentiation of OCN- and OPN-positive cells was detected.

Calcium chloride-enriched calcium aluminate cement promotes in vitro osteogenesis

AIM

To evaluate the effects of 2.8% or 10% calcium chloride (CaCl₂ ) in calcium aluminate cement (CAC) with either bismuth oxide (Bi₂ O₃ ) or zinc oxide (ZnO) as radiopacifiers on the progression of osteogenic cell cultures.

METHODOLOGY

Rat calvaria-derived cells were grown on Thermanox^® coverslips for 24 h and exposed to samples of (i) CACb: with 2.8% CaCl₂ and 25% Bi₂ O₃ ; (ii) CACb+: with 10% CaCl₂ and 25% Bi₂ O₃ ; (iii) CACz: with 2.8% CaCl₂ and 25% ZnO; or (iv) CACz+: with 10% CaCl₂ and 25% ZnO, placed on inserts. Nonexposed cultures served as the control. Calcium and phosphorus contents in culture media were quantified. The effects of the cements on cell apoptosis, cell viability and acquisition of the osteogenic cell phenotype were evaluated. Data were compared by Kruskal-Wallis test (α = 5%).

RESULTS

CACb+ promoted the highest levels of calcium in the culture media; CACz+, the lowest levels of phosphorus (P < 0.05). CACz+ and CACb increased cell apoptosis (P < 0.05). CACb reduced cell viability (P < 0.05) and the expression of the osteoblastic phenotype. CACz+ and CACb+ promoted greater cell differentiation and matrix mineralization compared to CACz and CACb (P < 0.05).

CONCLUSION

For CAC with the lower CaCl₂ content, the use of Bi₂ O₃ was detrimental for osteoblastic cell survival and differentiation compared to ZnO, while CAC with the higher CaCl₂ content supported the acquisition of the osteogenic cell phenotype in vitro regardless of the radiopacifier used. Thus, CAC with 10% CaCl₂ would potentially promote bone repair in the context of endodontic therapies.

Mineral Trioxide Aggregate-A Review of Properties and Testing Methodologies

Mineral trioxide aggregate (MTA) restoratives and MTA sealers are commonly used in endodontics. Commonly referenced standards for testing of MTA are ISO 6876, 9917-1 and 10993. A PubMed search was performed relating to the relevant tests within each ISO and "mineral trioxide aggregate". MTA restoratives are typically tested with a mixture of tests from multiple standards. As the setting of MTA is dependent upon hydration, the results of various MTA restoratives and sealers are dependent upon the curing methodology. This includes physical properties after mixing, physical properties after setting and biocompatibility. The tests of flow, film thickness, working time and setting time can be superseded by rheology as it details how MTA hydrates. Physical property tests should replicate physiological conditions, i.e. 37 °C and submerged in physiological solution. Biocompatibility tests should involve immediate placement of samples immediately after mixing rather than being cured prior to placement as this does not replicate clinical usage. Biocompatibility tests should seek to replicate physiological conditions with MTA tested immediately after mixing.

Evaluation of physicochemical properties of root-end filling materials using conventional and Micro-CT tests

Objective

To evaluate solubility, dimensional stability, filling ability and volumetric change of root-end filling materials using conventional tests and new Micro-CT-based methods.

Material and Methods

7.

Results

The results suggested correlated or complementary data between the proposed tests. At 7 days, BIO showed higher solubility and at 30 days, showed higher volumetric change in comparison with MTA (p<0.05). With regard to volumetric change, the tested materials were similar (p>0.05) at 7 days. At 30 days, they presented similar solubility. BIO and MTA showed higher dimensional stability than ZOE (p<0.05). ZOE and BIO showed higher filling ability (p<0.05).

Conclusions

ZOE presented a higher dimensional change, and BIO had greater solubility after 7 days. BIO presented filling ability and dimensional stability, but greater volumetric change than MTA after 30 days. Micro-CT can provide important data on the physicochemical properties of materials complementing conventional tests.

Solubility and bacterial sealing ability of MTA and root-end filling materials

Objective

To evaluate solubility and sealing ability of Mineral Trioxide Aggregate (MTA) and root-end filling materials.

Material and Methods

The materials evaluated were: MTA, Calcium Silicate Cement with zirconium oxide (CSC/ZrO₂), and zinc oxide/eugenol (ZOE). Solubility test was performed according to ANSI/ADA. The difference between initial and final mass of the materials was analyzed after immersion in distilled water for 7 and 30 days. Retrograde cavities in human teeth with single straight root canal were performed by using ultrasonic tip CVD 9.5107-8. The cavities were filled with the evaluated materials to evaluate sealing ability using the bacterial leakage test with Enterococcus faecalis. Bacterial leakage was evaluated every 24 hours for six weeks observing the turbidity of Brain Heart infusion (BHI) medium in contact with root apex. Data were submitted to ANOVA followed by Tukey tests (solubility), and Kruskal-Wallis and Dunn tests (sealing ability) at a 5% significance level.

Results

For the 7-day period, ZOE presented highest solubility when compared with the other groups (p<0.05). For the 30-day period, no difference was observed among the materials. Lower bacterial leakage was observed for MTA and CSC/ZrO₂, and both presented better results than ZOE (p<0.05).

Conclusion

MTA and CSC/ZrO₂ presented better bacterial sealing capacity, which may be related to lower initial solubility observed for these materials in relation to ZOE.

Effect of different mixing methods on the physical properties of Portland cement

Background

The Portland cement is hydrophilic cement; as a result, the powder-to-liquid ratio affects the properties of the final mix. In addition, the mixing technique affects hydration. The aim of this study was to evaluate the effect of different mixing techniques (conventional, amalgamator and ultrasonic) on some selective physical properties of Portland cement.

Material and Methods

The physical properties to be evaluated were determined using the ISO 6786:2001 specification. One hundred sixty two samples of Portland cement were prepared for three mixing techniques for each physical property (each 6 samples). Data were analyzed using descriptive statistics, one-way ANOVA and post hoc Tukey tests. Statistical significance was set at P<0.05.

Results

The mixing technique had no significant effect on the compressive strength, film thickness and flow of Portland cement (P>0.05). Dimensional changes (shrinkage), solubility and pH increased significantly by amalgamator and ultrasonic mixing techniques (P<0.05). The ultrasonic technique significantly decreased working time, and the amalgamator and ultrasonic techniques significantly decreased the setting time (P<0.05).

Conclusions

The mixing technique exerted no significant effect on the flow, film thickness and compressive strength of Portland cement samples.

Key words:Physical properties, Portland cement, mixing methods.

Physical properties and hydration behavior of a fast-setting bioceramic endodontic material

Background

To investigate the physical properties and the hydration behaviour of the fast-setting bioceramic iRoot FS Fast Set Root Repair Material (iRoot FS) and three other endodontic cements.

Methods

iRoot FS, Endosequence Root Repair Material Putty (ERRM Putty), gray and white mineral trioxide aggregate (G-MTA & W-MTA), and intermediate restorative material (IRM) were evaluated. The setting time was measured using ANSI/ADA standards. Microhardness was evaluated using the Vickers indentation test. Compressive strength and porosity were investigated at 7 and 28 days. Differential scanning calorimetry (DSC) was employed for the hydration test.

Results

iRoot FS had the shortest setting time of the four bioceramic cements (p < .001). The microhardness values of iRoot FS, ERRM Putty and MTA increased at different rates over the 28 days period. At day one, ERRM Putty had the lowest microhardness of the bioceramic cements (p < .001), but reached the same level as MTA at 4, 7 and 28 days. The microhardness of iRoot FS was lower than that of W-MTA at 7 and 28 days (p < .05). The porosity of the materials did not change after 7 days (p < .05). The compressive strength values at 28 days were significantly greater for all bioceramic groups compared to those at 7 days (p < .01). ERRM Putty had the highest compressive strength and the lowest porosity of the evaluated bioceramic cements (p < .05), followed by iRoot FS, W-MTA, and G-MTA, respectively. DSC showed that iRoot FS hydrated fastest, inducing an intense exothermic reaction. The ERRM Putty did not demonstrate a clear exothermic peak during the isothermal calorimetry test.

Conclusions

iRoot FS had a faster setting time and hydrating process than the other bioceramic cements tested. The mechanical properties of iRoot FS, G-MTA and W-MTA were relatively similar.

Effects of Chlorhexidine and Sodium Hypochlorite on the Setting Time of Calcium-Enriched Mixture Cement

Introduction:

The aim of the present study was to evaluate whether adding 2% chlorhexidine (CHX) and 2.6% sodium hypochlorite (NaOCl) to calcium-enriched mixture (CEM) cement would affect its setting time (ST), or not.

Methods and Materials:

In this study, the setting time of CEM cement was evaluated in three groups (n=9) as follows: group 1; CEM cement, group 2; CEM cement+2% CHX and group 3; CEM cement+2.6% NaOCl. Then the mean values of ST were calculated and the Kolmogorov-Smirnov test was used to evaluate the normal distribution of data. The Kruskal-Wallis and Mann-Whitney U tests were used for statistical analysis. Statistical significance was set at 0.05.

Results:

The mean ST for groups 1, 2 and 3 were 105, 120 and 220 min, respectively. There was a significant increase in the duration of ST in group 3 (NaOCl) in comparison with the two other groups (P<0.05).

Conclusion:

NaOCl significantly increased the ST of CEM cement, whereas chlorhexidine did not alter the ST.

Calcium Silicate-Based Cements Associated with Micro- and Nanoparticle Radiopacifiers: Physicochemical Properties and Bioactivity

Objective. The aim of this study was to evaluate the physicochemical properties and bioactivity of two formulations of calcium silicate-based cements containing additives (CSCM) or resin (CSCR), associated with radiopacifying agents zirconium oxide (ZrO2) and niobium oxide (Nb2O5) as micro- and nanoparticles; calcium tungstate (CaWO4); and bismuth oxide (Bi2O3). MTA Angelus was used as control. Methods. Surface features and bioactivity were evaluated by scanning electron microscopy and the chemical composition by energy dispersive X-ray spectrometry (EDS-X). Results. CSCM and CSCR presented larger particle sizes than MTA. Hydroxyapatite deposits were found on the surface of some materials, especially when associated with the radiopacifier with ZrO2 nanoparticles. All the cements presented calcium, silicon, and aluminum in their composition. Conclusion. Both calcium silicate-based cements presented composition and bioactivity similar to MTA when associated with the radiopacifiers evaluated.

Influence of radiopacifying agents on the solubility, pH and antimicrobial activity of portland cement

The aim of this study was to evaluate the interference of the radiopacifiers bismuth oxide (BO), bismuth carbonate (BC), bismuth subnitrate (BS), and zirconiun oxide (ZO) on the solubility, alkalinity and antimicrobial properties of white Portland cement (WPC). The substances were incorporated to PC, at a ratio of 1:4 (v/v) and subjected to a solubility test. To evaluate the pH, the cements were inserted into retrograde cavities prepared in simulated acrylic teeth and immediately immersed in deionized water. The pH of the solution was measured at 3, 24, 72 and 168 h. The antimicrobial activity was evaluated by a radial diffusion method against the microorganisms S. aureus (ATCC 25923), P. aeruginosa (ATCC 27853), E. faecalis (ATCC 29212) and C. albicans (ATCC 10231). The zone of microbial growth inhibition was measured after 24 h. The addition of BS and BC increased the solubility of the cement. The pH values demonstrated that all materials produced alkaline levels. At 3 h, BS showed lower pH than WPC (p<0.05). At 168 h, all materials showed similar pHs (p>0.05). The materials did not present antimicrobial activity for S. aureus, P. aeruginosas and E. faecalis (p>0.05). With regards to C. albicans, all materials formed an inhibition zone, mainly the mixture of WPC with ZO (p<0.05). The type of radiopacifier incorporated into WPC interfered with its physical and antimicrobial properties. ZO was found to be a viable radiopacifier that can be used with WPC.

Influence of light and oxygen on the color stability of five calcium silicate-based materials

INTRODUCTION

Difficult handling, long setting time, and potential discoloration are important drawbacks of white mineral trioxide aggregate (WMTA). The development of Biodentine, a recently developed calcium silicate-based material (CSM), has overcome some of these shortcomings; however, there are no available data on its color stability. A previous study showed that WMTA discolors under light irradiation in an oxygen-free environment. The present study evaluated the influence of light irradiation and oxygen on the color stability of 5 CSMs.

METHODS

Fifteen samples of 5 CSMs (ProRoot WMTA, Angelus WMTA, White Portland Cement [PC], PC with bismuth oxide, and Biodentine) were divided into 5 groups. Each group was exposed to different oxygen and light conditions. A spectrophotometer was used to determine the color of each specimen at 0, 120 seconds, and 5 days. Data were analyzed by using analysis of variance and Tukey honestly significant difference test.

RESULTS

The materials PC with bismuth oxide, Angelus WMTA, and ProRoot WMTA showed dark discoloration after light irradiation in an oxygen-free environment, which was statistically significantly different from Biodentine and PC. In groups that were exposed to no light irradiation or to an oxygen atmosphere, all materials showed color stability over time, and no significant differences were observed among them. PC and Biodentine maintained color stability in all conditions over time and showed no significant differences.

CONCLUSIONS

The combination of light and anaerobic conditions (similar to those in clinical situations) results in differences in color of the tested CSMs during a period of 5 days, of which Biodentine and PC demonstrated color stability.

The shear bond strength of resin-based composite to white mineral trioxide aggregate

BACKGROUND

It is unknown if resin-based composite can be placed on top of mineral trioxide aggregate (MTA) immediately after placement of the MTA. The authors aimed to measure the bond strength of a resin-based composite to white MTA (WMTA) with different bonding strategies at different intervals.

METHODS

The authors bonded resin-based composite to MTA with three bonding protocols (n = 45 per group) (group 1, total-etching adhesive; group 2, two-step self-etching adhesive; or group 3, one-step self-etching adhesive), immediately (subgroup A), 45 minutes (subgroup B) or 24 hours (subgroup C) after placement of the MTA. The authors measured shear bond strength by means of a universal testing machine and performed statistical analysis of the data by means of two-way and one-way analysis of variance (P < .05).

RESULTS

In all three groups, subgroup A demonstrated greater bond strengths than the other subgroups. Group/subgroup 3/A demonstrated the highest bond strength (mean [standard deviation] 49.2 [2.1] megapascals), which was significantly higher than that in all other groups (P < .05). This was followed by group/subgroup 1/A (40.2 [2.5] MPa), 2/A (38.4 [1.3] MPa) and 1/B (38.5 [1.91] MPa). The lowest bond strength was shown by group/subgroup 2/C (14.7 [1.90] MPa). There was a significant difference between the two-step and one-step self-etching adhesives at all three intervals (P < .05).

CONCLUSIONS

Within the limitations of this study, the representative one-step self-etching adhesive demonstrated the strongest bond to WMTA immediately after fabrication of MTA samples.

CLINICAL IMPLICATIONS

One-step self-etching adhesive may be used to bond resin-based composite to WMTA immediately after placement, thereby offsetting the need for a second appointment for permanent restoration.

Effects of calcium silicate-based materials on the flexural properties of dentin

INTRODUCTION

Prolonged exposure of root dentin to calcium hydroxide alters the fracture resistance of dentin. Calcium silicate-based materials (CSMs) used in endodontics release calcium hydroxide on setting. This study examined whether prolonged contact of dentin with CSMs adversely affects its mechanical properties.

METHODS

Dentin beams prepared from extracted human molars (7 × 3 × 0.3 mm) were divided into 3 groups on the basis of the material to which dentin was exposed (Biodentine, MTA Plus, and untreated control beams). Three-point flexure to failure was performed for each beam at designated exposure times (24 hours, 1, 2, and 3 months; n = 10). Data were analyzed with 2-factor repeated-measures analyses of variance to determine the effects of material and aging time on flexural modulus, flexural strength, and modulus of toughness (α = 0.05).

RESULTS

For flexural modulus, there was no significant difference for material (P = .947) or aging time (P = .064) when compared with baseline control. For flexural strength, significant differences were associated with aging time (P < .001) but not with material (P = .349). Flexural strength of dentin exposed to Biodentine decreased significantly after 2 and 3 months, whereas that exposed to MTA Plus decreased significantly after 3 months of aging (P < .05). For modulus of toughness, significant declines were observed for both material (P < .004) and aging time (P < .001).

CONCLUSIONS

Both CSMs alter material toughness more than the strength and stiffness of dentin after aging in 100% relative humidity. Because dentin toughness is attributed to its collagen matrix, the amount of collagen extracted from mineralized dentin and changes in collagen ultrastructure should be further examined after exposure of dentin to CSMs.

The effect of curing conditions on the physical properties of tricalcium silicate cement for use as a dental biomaterial

AIM

To investigate the physical properties of tricalcium silicate (TCS) with and without the addition of a radiopacifier and compare them with that of Portland cement (PC) and radiopaque PC in an mineral trioxide aggregate-like system.

METHODOLOGY

Tricalcium silicate, PC and radiopacified variants containing 20% bismuth oxide were tested for radiopacity, compressive strength, setting time and dimensional stability. All the testing was performed at 37 °C and under different environmental conditions namely at 100% humidity or immersed in either water or Hank's balanced salt solution (HBSS). Testing was performed after both 1 and 28 days.

RESULTS

The cements exhibited radiopacity values equivalent to <3 mm. Addition of 20% bismuth oxide resulted in adequate radiopacity. The strength of TCS was independent of the curing conditions. The cements without radiopacifier had improved strength characteristics when immersed in HBSS, whilst the radiopacified cements exhibited higher strengths when soaked in water. Tricalcium silicate demonstrated the shortest setting time. Addition of bismuth oxide increased the setting time of the cements while HBSS inhibited the setting of bismuth oxide-replaced cements. The PC-based materials exhibited a net contraction higher than that recorded for TCS-based cements in all curing conditions. The dimensional change exhibited by the specimens was generally greater in the first few hours of setting, but then stabilized with time.

CONCLUSIONS

Tricalcium silicate cement required the addition of a radiopacifying agent to make it suitable for use as a dental material. Tricalcium silicate exhibited adequate physical properties and thus was shown to be a suitable replacement for the PC component in MTA. Bismuth oxide drastically increased the setting time of the test cements in phosphate-containing solutions. Alternative radiopacifiers that do not retard the setting time need to be investigated.