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

Optimizing restorative procedure and material selection for pulpotomized primary molars: Mechanical characterization by 3D finite element analysis

Purpose

This study aimed to assess the stress distribution in pulpotomized primary molars with different types of restorative materials using 3D-finite element analysis (FEA), and provide valuable insights into the selection and application of restorative materials, with the ultimate goal of reducing the risk of pulpotomy failure and protecting residual dental tissue.

Methods

Four 3D models of pulpotomized primary molars with different restorative materials according to the material and its elastic modulus were analysed: resin composite, stainless steel crowns (SSCs), prefabricated zirconia crowns and endocrowns. The food layer was also designed before vertical and bucco-lingual forces were applied to simulate physiological masticatory conditions. The results were obtained by colorimetric graphs of the von Mises stresses (VMS) in the restoration and tooth remnant. The maximum shear stress on the bonding interfaces and pressure stress on the Mineral trioxide aggregate (MTA)-pulp interfaces were recorded.

Results

The results of the 3D-FEA showed that all restorative materials generated stresses and strains on the tooth structure after pulpotomy. In the resin composite group, the marginal enamel exhibited the highest stress peaks. In the zirconia crown and SSC groups, there was a concentration of stress at the dentin-restoration margin. The shear stress concentrations were mainly at the adhesive margins, with lower levels around endocrowns compared to other groups. MTA in the resin composite group experienced more VMS than in the other group. The resin composite group also generated relatively higher pressure stress values at the MTA-pulp interface compared to the other groups.

Significance

In the model of primary teeth following pulpotomy, the three types of restorations covering the occlusal surface can effectively reduce the stress on pulp capping materials under occlusal loads, thereby potentially decreasing the risk of pulpotomy failure. In addition, the group of endocrowns demonstrated reduced stress at the bonding interface and in the stress concentration zone near the dentist-restoration edge, making them more effective at protecting residual dental tissue.

Effect of nanosized bioactive glass addition on some physical properties of biodentine

The aim of this in vitro study was to investigate some physical properties of Biodentine (BD) (Septodont, France) that has been modified by adding nanosized bioactive glass (nBG) particles to it in different ratios. The cement was modified by adding 1% (7 mg) and 2% (14 mg) nBG powder to BD. BD was used as the control group in its commercial form. A total of 240 cement samples (n = 80) were prepared according to the standard measurements for each test. Subsequently, tests to determine compressive strength, microhardness, initial setting time, and solubility of the samples were performed. The obtained data were statistically analyzed using one-way ANOVA and Tukey's HDS tests, and the significance level was found to be 0.05. The compressive strength values of the samples modified with 1% and 2% nBG were higher than those of the unmodified BD; however, no statistically significant difference was found between them [BD + nBG (2 wt%) ⩾ BD+nBG (1 wt%) ⩾ control BD], (p > 0.05). The microhardness values of the samples modified with 1% and 2% nBG were found to be significantly higher than those of the control group [BD + nBG (2 wt%) > BD+nBG (1 wt%) > control BD], p < 0.05. Initial setting times were determined as 14 min for unmodified BD, 13 min for BD + nBG (1 wt%), and 12 min for BD + nBG (2 wt%). The addition of nBG to BD significantly reduced the initial setting time of BD (p < 0.05). A significant decrease was observed in the solubility of the BD modified with nBG samples compared to that of the control group [control BD > BD+nBG (1 wt%) >BD+nBG (2 wt%)], p < 0.05. Within the limitations of this study, it was found that the addition of certain amounts of nBG to BD positively affected some physical properties of the cement. Future in vitro and in vivo studies should be performed to prove the clinical applicability of the cements used in this study.

Discoloration Improvement by Mechanically-Milled Binary Oxides as Radiopacifier for Mineral Trioxide Aggregates

Mineral trioxide aggregates (MTA) have been widely used in endodontic treatments, but after some time, patients suffer tooth discoloration due to the use of bismuth oxide (Bi2O3) as a radiopacifier. Replacement of Bi2O3 with high energy ball-milled single (zirconia ZrO2; hafnia, HfO2; or tantalum pentoxide, Ta2O5) or binary oxide powder was attempted, and corresponding discoloration improvement was investigated in the present study. Bi2O3-free MTA is expected to exhibit superior discoloration. The radiopacity, diametral tensile strength, and discoloration of MTA-like cements prepared from the as-milled powder were investigated. Experimental results showed that MTA-like cements prepared using Ta2O5 exhibited a slightly higher radiopacity than that of HfO2 but had a much higher radiopacity than ZrO2. Milling treatment (30 min to 3 h) did not affect the radiopacities significantly. These MTA-like cements exhibited superior color stability (all measured ΔE00 < 1.0) without any perceptible differences after UV irradiation. MTA-like cements prepared using ZrO2 exhibited the best color stability but the lowest radiopacity, which can be improved by introducing binary oxide. Among the investigated samples, MTA-like cement using (ZrO2)50(Ta2O5)50 exhibited excellent color stability and the best overall performance with a radiopacity of 3.25 mmAl and a diametral tensile strength of 4.39 MPa.

Push-out bond strength of the calcium silicate-based endodontic cements in the presence of blood: A systematic review and meta-analysis of in vitro studies

OBJECTIVES

The push-out bond strength (POBS) of calcium silicate-based cements (CSCs) to the dentinal wall is considered one of the essential physical properties for clinical success. The presence of blood in the treatment area affects the POBS of these types of cement. This study aimed to evaluate the impact of blood contamination on the bond strength of CSCs and dentinal walls.

MATERIAL AND METHODS

This systematic review was performed by searching electronic databases (MEDLINE-PubMed, Scopus, and EMBASE) to include relevant in vitro studies published between 1992 and April 2020. Two reviewers independently evaluated the selected studies and extracted data on the type of studied CSCs, evaluated area of the teeth, sample size, the dimension of a prepared area, slice thickness, storage duration, the setting of the universal testing machine (UTM), effects of blood contamination on POBS of CSCs and their failure modes. The bond strength of evaluated CSCs in studies was used for network meta-analysis.

RESULTS

Initial searches identified 292 articles, while only 13 articles met the inclusion criteria. Full texts of these articles were evaluated, and data extraction was performed. The effect of blood contamination on bond strength to the dentinal wall was assessed in various CSCs such as PMTA, Biodentine, and AMTA. The network meta-analysis results showed that the bond strength of Biodentine was significantly higher than other types of cement in blood presence (p < .05).

CONCLUSIONS

Based on the current systematic review, despite controversies among the result of the different articles and the lack of data for some CSCs like bioaggregate, it could be concluded that the bond strength of Biodentine to the dentinal wall is better than other evaluated CSCs in the presence of blood.

A 3D finite element analysis of stress distribution on different thicknesses of mineral trioxide aggregate applied on various sizes of pulp perforation

OBJECTIVES

The aim of this study was to evaluate the stress distribution on different thicknesses of mineral trioxide aggregate (MTA) placed on various widths of pulp perforations during the condensation of the composite resin material.

MATERIALS AND METHODS

The mandibular molar tooth was modeled by COSMOSWorks program (SolidWorks, Waltham, MA). Three finite elemental analysis models representing 3 different dimensions of pulp perforations, 1, 2, and 3 mm in diameter, were created. The perforation area was assumed as filled with MTA with different thicknesses, 1, 2, and 3 mm for each pulp perforation width, creating a total of 9 different models. Then, a composite resin material was layered on MTA for each model. A 66.7 N load was applied and an engineering simulation program (ANSYS, Canonsburg, US) was used for the analysis. Results were presented considering von Mises stress criteria.

RESULTS

As MTA thickness increased, the stress values recorded within the area between pulp and MTA decreased. Strain was decreased when the thickness of MTA increased.

CONCLUSIONS

Stresses at MTA-pulp interface and strain on MTA decreased with the increase in MTA thickness.

CLINICAL RELEVANCE

In clinical practice, when MTA is required for pulp capping, using a thick layer of the material seems to be a better option in order to reduce the stress under forces of hand condensation of overlying restorative materials.

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.