Influence of composition on setting kinetics of new injectable and/or fast setting tricalcium silicate cements

ObjectivesNew commercial tricalcium silicate based cements were elaborated to improve handling properties and setting time. The goals of the present work were: (i) to determine the composition of the new injectable and/or fast setting calcium silicate based cements, and (ii) to investigate the impact of the differences in composition on their setting kinetics.MethodsThe materials considered were Angelus MTA™, Biodentine™, MM-MTA™, MTA-Caps™, and ProRoot MTA™ as control.Elemental composition of materials was studied by Inductively Coupled Plasma-Atomic Emission Spectroscopy and X-ray Energy Dispersive analysis, whereas phases in presence were analyzed by Micro-Raman spectroscopy and X-ray Diffraction analysis and cement surface by Scanning Electron Microscope. Setting kinetics was evaluated using rheometry.ResultsElemental analysis revealed, for all cements, the presence of three major components: calcium, silicon and oxygen. Chlorine was detected in MM-MTA, MTA-Caps and Biodentine. Different radio-opacifiers were identified: bismuth oxide in ProRoot MTA, Angelus MTA and MM-MTA, zirconium oxide in Biodentine and calcium tungstate (CaWO₄) in MTA-Caps. All cements were composed of di- and tri-calcium silicate, except Biodentine for which only the latter was detected. Major differences in setting kinetics were observed: a modulus of 8 × 10⁸ Pa is reached after 12 min for Biodentine, 150 min for MM-MTA, 230 min for Angelus MTA and 320 min for ProRoot MTA. The maximum modulus reached by MTA-Caps was 7 × 10⁸ Pa after 150 min.SignificanceEven if these cements possess some common compounds, major differences in their composition were observed between them, which directly influence their setting kinetics.     

Effect of Acid Etching Procedures on the Compressive Strength of 4 Calcium Silicate–based Endodontic Cements

Introduction

The purpose of this study was to evaluate the effect of acid etching on the compressive strength of 4 calcium silicate–based cements.

Methods

One gram of each corresponding powder of ProRoot MTA (Dentsply Tulsa Dental, Johnson City, TN), MTA Angelus (Angelus, Londrina, PR, Brazil), and CEM cement (BioniqueDent, Tehran, Iran) and a 0.33-g aliquot of liquid were placed in a plastic mixing capsule that was then mechanically mixed for 30 seconds at 4500 rpm in an amalgamator. For the preparation of Biodentine (Septodont, Saint Maur-des-Fossés, France), the liquid provided was added to the powder within the plastic capsule supplied by the manufacturer and then mechanically mixed for 30 seconds at 4500 rpm using the amalgamator. The resulting slurries were then placed incrementally into 40 cylindrical molds to give a total of 160 specimens that were incubated at 37°C for a week. Twenty specimens of each material were then subjected to the acid etch procedure. The compressive strength of the samples was then calculated in megapascals using a universal testing machine. The results were then subjected to 2-way analysis of variance analysis of variance followed by the Tukey post hoc test.

Results

The application of acid etch significantly reduced (P < .0001) the compressive strength of Angelus MTA and CEM cement; however, it did not reduce the compressive strength of ProRoot MTA or Biodentine. Regardless of the acid etch application, Biodentine showed significantly higher compressive strength values than the other materials (P < .0001), whereas CEM cement had the lowest compressive strength values. There was no significant difference between CEM cement and MTA Angelus. The compressive strength of ProRoot MTA was significantly lower (P < .0001) than Biodentine but significantly higher (P < .0001) than MTA Angelus and CEM cement in both the test and control groups.

Conclusions

When the application of acid etchants is required, Biodentine and ProRoot MTA seem to be better options than MTA Angelus or CEM cement.     

Bioactivity and fluoride release of strontium and fluoride modified Biodentine

Biodentine? is a novel tricalcium silicate based material used both as a coronal dentine replacement and in pulp therapy. Its multiple use in sealing perforations, pulp capping and as a temporary restoration arises from its ability to promote dentine formation and to confer an excellent marginal seal. However, there is still room for improvement of this cement as it lacks the anticariogenic effect typically conferred by fluoride ion release as seen in glass ionomer cement based dental materials. Therefore, this study was conducted to investigate the impact of bioactive glass addition to Biodentine?.

A Novel Accelerator for Improving the Handling Properties of Dental Filling Materials

IntroductionMineral trioxide aggregate (MTA) fulfills many of the ideal properties of a root end filling material and repair material for furcal perforation. However, its low cohesive property often makes it difficult to handle. To improve the handling properties of MTA root canal filling materials, MTA-like cement was made, and calcium lactate gluconate (CLG) aqueous solution was used to shorten the setting time and enhance the paste viscosity.MethodsCLG solution was prepared by mixing lactic acid, glucono delta lactone, and calcium oxide by wet process. The crystalline property of the CLG powder was characterized by x-ray diffraction. The MTA-like cements were prepared by mixing Portland cement/bismuth oxide/gypsum (75/20/5); ProRoot white MTA (Dentsply Tulsa Dental, Tulsa, OK) was used as a control group. The influence of various liquid phases on initial setting time, handling properties, and pH value were investigated by a Vicat needle, questionnaire of operational hand feel, and pH meter, respectively.ResultsBy using 23.1wt% CLG solutions as a liquid phase, the setting time of white MTA was significantly decreased from 155.5 ± 5.0 to 12.3 ± 2.5 minutes. The pH values for hydrated white MTA with deionized water and 23.1 wt% CLG solutions were 12.29 ± 0.02 and 11.81 ± 0.04 at 72 hours.ConclusionsThe results suggest that the addition of amorphous CLG-based liquid phase provides improvement in sealing ability as well as clinical manageability of dental filling materials.     

Mineral density changes in bovine carious dentin after treatment with bioactive dental cements: a comparative micro-CT study

Objectives

To evaluate the potential of conventional glass ionomer cement (GIC), Biodentine™, MTA, and Portland cement to induce mineral density changes in carious dentin compared to zinc oxide eugenol control cement (ZOE).

Materials and methods

Fifty blocks of bovine root dentin were prepared and a biofilm model using ATCC strains of S.mutans, S.sobrinus, and L.casei was used to promote artificial dentin lesions. After demineralization, the blocks were randomly divided into the five cement groups. Half of the surface of each specimen received the tested material and the other half was covered with wax (control). Samples were stored in phosphate buffered saline solution for 30 days and after that were scanned in a micro-CT with standardized parameters. Dentin mineral density changes were calculated using differences in plot profiles of the exposed and control carious dentin. Friedman’s test, followed by Wilcoxon signed-rank test was used with 5% significance.

Results

Mean ΔZ values for the cements were 48.63 ± 19.09 for the control (ZOE), 63.31 ± 32.59 for Biodentine™, 114.63 ± 72.92 for GIC, 109.56 ± 66.28 for MTA, and 106.88 ± 66.02 for Portland cement. All cements showed a statistically significant increase in ΔZ values compared to the control, but Biodentine™ values were statistically significantly lower compared to GIC and the other calcium silicate cements.

Conclusions

Tested materials present potential to induce mineral density changes in carious bovine dentin. MTA, Portland, and GIC showed higher bioactivity potential than Biodentine™.

Clinical relevance

Based on minimally invasive concept, materials with remineralization potential can be used to preserve diseased but still repairable dental tissue.

     

新型正畸粘接剂聚合特征和剪切粘接强度的研究

目的本研究测量一种新型丙烯酸类正畸粘接剂的聚合特征和剪切粘接强度,以评估其作为正畸粘接剂的可能性。方法将甲基丙烯酸甲酯、甲基丙烯酸羟乙酯、氟化钠和聚甲基丙烯酸甲酯按不同比例混合,构成3个实验组。分别测量样本的聚合特征、剪切粘接强度和粘接剂残留指数。聚合特征实验中的对照组为聚甲基丙烯酸甲酯,粘接强度实验中的对照组为光固化复合树脂（Transbond XT）。采用单因素或双因素方差分析和Kruskal-Wallis与Mann Whitney检验对数据进行统计分析。结果在同一温度下,实验组和对照组间的放热量无显著差异,实验组在23℃和37℃时的聚合时间均小于对照组。30min时实验组的粘接强度大于光固化复合树脂,1个月后光固化复合树脂的粘接强度大于实验组。1个月后实验组的粘接剂残留指数明显小于光固化复合树脂。结论这种新型粘接剂具有作为正畸粘接材料的潜力。     

Shear Bond Comparison between 4 Bioceramic Materials and Dual-cure Composite Resin

IntroductionBioceramic materials have shown biologic and physical properties favorable for regenerative treatment. A key to treatment success is an adequate restoration to prevent microleakage; however, research is limited regarding the bond strength between restorative and bioceramic materials used in regenerative procedures. This study compared the bond strength between 4 bioceramic materials and a dual-cure composite resin.MethodsEighty wells in Teflon (ePlastics, San Diego, CA) blocks were filled with bioceramic materials representing 4 groups: White ProRoot mineral trioxide aggregate (MTA) (Dentsply Tulsa Dental, Tulsa, OK), Biodentine (Septodont, Saint Maur des Fosses, France), EndoSequence Root Repair Material Fast Set Putty (Brasseler USA, Savannah, GA), and NeoMTA (Avalon Biomed Inc, Houston, TX). After allowing samples to set according to the manufacturers’ instructions, exposed surfaces of the bioceramic materials were prepared using ClearFil SE Bond (Kuraray America, Inc., New York, NY) followed by restoration with ClearFil DC Core Plus (Kuraray America, Inc.). To test shear bond strength, each block was secured in a universal testing machine, and the crosshead was advanced at 0.5 mm/min until fracture. Newton peak force was recorded and megapascals calculated followed by data comparison.ResultsThe mean shear bond strengths between ClearFil DC Core Plus and the bioceramic materials were as follows: White ProRoot MTA, 7.96 MPa; Biodentine, 9.18 MPa; EndoSequence Root Repair Material Fast Set Putty, 4.47 MPa; and NeoMTA, 5.72 MPa. White ProRoot MTA and Biodentine were statistically similar, with a higher stress bond strength than NeoMTA, which had a statistically greater bond strength than EndoSequence Root Repair Material. All these values were lower than typical bond strengths shown for dentin–composite resin bonding.ConclusionsThe choice of which bioceramic material to use in regenerative procedures should be based on factors other than the bond between that material and the overlying coronal resin restoration.     

The effect of chlorhexidine and dimethyl sulfoxide on long-term sealing ability of two calcium silicate cements in root canal

ObjectivesTo evaluate the long-term effect of chlorhexidine (CHX) and dimethyl sulfoxide (DMSO) on the sealing ability and biomineralization of two different calcium silicate cements (CSC) in root canal.MethodsSixty human third molar root canals were obturated with ProRoot MTA or Biodentine. Before obturation the canals were irrigated with saline (control), 2% CHX or 5% DMSO. Microleakage was tested after three days and after six months. After additional six months (12 months after root filling) the roots were cut into 2 mm thick dentine discs. The discs were stored in artificial saliva for one year. The bond strength was measured with the push-out method, and the failure mode was evaluated with a stereomicroscope. The most apical disc of each tooth was used for Vickers hardness test.ResultsNo significant differences between the groups was found in initial microleakage. The leakage increased significantly during the 6-month storage in all groups except in Biodentine-CHX group and Biodentine-DMSO group. CHX and DMSO irrigation significantly increased the leakage with ProRoot MTA with time, but there was no statistically significant difference compared to the ProRoot MTA-control group at six months’ time point. CHX significantly reduced the push-out bond strength of ProRoot MTA. With Biodentine irrigation with CHX or DMSO resulted with significantly higher push-out strength compared to the Biodentine control group. Fracture analysis showed statistically significant difference in the distribution of the fractures between the groups, but neither CHX nor DMSO change the fracture pattern statistically significantly. With Vickers hardness test ProRoot MTA with and without DMSO as the final irrigant showed significantly higher dentin hardness than any Biodentine-group.SignificanceConsidering that aging increased the leakage in all groups except with Biodentine-DMSO and the differences in the push-out strength and surface microhardness data, it appears that the time-related biomineralizing effect of MTA and Biodentine does not improve sealing to dentin. CHX significantly reduced ProRoot MTA bond strength and increased pure adhesive failures with both cements.     

Investigation of Biodentine as dentine replacement material

Objective

Biodentine was compared to glass ionomer and resin modified cements in an “open sandwich” restoration.

Methods

Fuji IX, Vitrebond and Biodentine were characterised using various techniques. The effect of etching with 35% phosphoric acid was investigated by assessment of surface topography, Fourier transform infrared (FT-IR) spectroscopy, surface micro-hardness and micro-leakage using tagged carboxylated-modified fluorescent microspheres and tracing the presence of these particles with a confocal microscope.

Results

Acid etching resulted in erosion of the material surface with exposure of the glass particles in the glass ionomer-based materials. Biodentine exhibited a reduction in the chlorine peak and the calcium–silicon ratio. There was no difference in the micro-hardness in etched and un-etched materials. The FT-IR plots did not show any chemical changes caused by etching for all the materials investigated. Both Vitrebond and Fuji IX exhibited no leakage at the dentine to material interface while Biodentine exhibited leakage both when it was etched and also when the surface was left unprepared. The sandwich technique was effective and prevented micro-leakage with glass ionomer-based materials but micro-leakage occurred with Biodentine.

Conclusions

Biodentine demonstrated both structural and chemical changes when etched with 37% phosphoric acid. Biodentine exhibited a lower calcium to silicon ratio and a reduction in the chloride peak height when etched. When used as a dentine replacement material in the sandwich technique overlayed with composite, significant leakage occurred at the dentine to material interface. On the other hand materials based on glass ionomer cement were etched successfully and no chemical and physical changes or micro-leakage were detected when the materials were used as bases under composite restorations. The micro-hardness of all the materials was unaffected by etching.     

Hydration characteristics of Biodentine and Theracal used as pulp capping materials

Objectives

Investigation of the hydration and characterization of Theracal and Biodentine used for pulp capping.

Methods

The setting mechanism and characterization of set Biodentine and Theracal after immersion in Hank's balanced salt solution (HBSS) for 28 days was investigated by scanning electron microscopy (SEM) of polished specimens and X-ray diffraction (XRD) analysis. The bioactivity and surface microstructure of cements immersed in HBSS or water was also assessed by similar techniques together with leaching in solution investigated by ion chromatography (IC).

Results

Biodentine hydration resulted in the formation of calcium hydroxide which was present in the material matrix and also on the material surface. Theracal was composed of large cement particles which showed some evidence of reaction rims on hydration. The material matrix included a barium zirconate phase as radiopacifier and also a glass phase composed of strontium, silicon and aluminum. This phase could not be detected in XRD analysis. Formation of a calcium phosphate phase was demonstrated on Theracal immersed in HBSS. Both materials leached calcium ions in solution.

Conclusions

The presence of a resin matrix modifies the setting mechanism and calcium ion leaching of Theracal. The clinical implications of these findings need to be investigated.     

Influence of the powder/liquid ratio on the properties of zinc oxide–eugenol-based root canal sealers

OBJECTIVE: The purpose of this study was to investigate the effects of modifications of the powder/liquid ratio by endodontists on the physical properties recommended by ISO standards as well as on other clinically relevant properties of zinc oxide-eugenol-based root canal sealers. METHODS: The powder/liquid ratio of two zinc oxide-eugenol-based root canal sealers (Cortisomol and Pulp Canal Sealer EWT) was recorded by 10 endodontists. The materials, prepared according to the different consistencies, were tested according to ISO standards to evaluate their physical properties. Their sealing efficiency and the release of eugenol were also evaluated on 20 single rooted teeth. RESULTS: Some results varied according to the material. Nevertheless, for both cements, an increased powder/liquid ratio led to a decreased flow, an increased radiopacity and a decreased amount of eugenol released. The variations in the powder/liquid ratio did not influence the dimensional changes and the apical leakage of both cements. SIGNIFICANCE: Variations in the powder/liquid ratio of zinc oxide-eugenol-based root canal sealers have a limited influence on the properties of the sealers. The endodontists can prepare the zinc oxide-eugenol-based root canal sealers at their chosen consistency according to the filling technique they use.     

Determination of the properties of an experimental glass polyalkenoate cement prepared from niobium silicate powder containing fluoride.

OBJECTIVES: The purpose of this paper is to modify the conventional calcium fluoro-alumino-silicate glass, which is used in the formation of glass ionomer cements (CIGs) by the niobium addition and to study the properties of GICs obtained. MATERIALS AND METHODS: Sol-gel process was used to prepare the powder at lower temperature than fusion method. Glass-ceramic powder obtained in this way was used to prepare the GICs. The properties such as working and setting times, microhardness and diametral tensile strength were evaluated for the experimental GICs and a commercial luting cement. RESULTS: The ideal powder:liquid (P:L) ratio determined to prepare the experimental GICs was equal to 1:1. The cements prepared using this ratio showed working and setting times similar to the commercial GICs. In mechanical tests it was observed that microhardness and diametral tensile strength of the experimental GICs decreased significantly with the reduction of P:L ratio. On the other hand, the results obtained in microhardness tests indicated that the presence of niobium was a positive factor. SIGNIFICANCE: The chemical process allows the development of glass-ceramic powder at 600 degrees C which is the goal of the present paper. It was concluded that GICs containing niobium might be used in dental applications and these results encourage further researches on other compositions.     

Nanomodification of mineral trioxide aggregate for enhanced physiochemical properties

Saghiri MA, Asgar K, Lotfi M, Garcia-Godoy F. Nanomodification of mineral trioxide aggregate for enhanced physiochemical properties. International Endodontic Journal.,?45, 979-988, 2012. ABSTRACT: Aim To analyse the physicochemical properties of a Nano white mineral trioxide aggregate (NWMTA) and compare it with white mineral trioxide aggregate (WMTA). Methodology White mineral trioxide aggregate and NWMTA were prepared and mixed according to the manufacturer's instructions. Surface area of powder before hydration, setting time, X-ray diffraction and microhardness at pH values of 4.4 and 7.4 were evaluated by Brunauer-Emmett-Teller, ISO Specification no.6876, Vickers microhardness, and energy-dispersive X-ray spectroscopy equipped with X-ray colour (dot) map for both cements. anova and Mann-Whitney were used for statistical analysis at a significance level of 0.5. Results The mean?±?SD of surface area and setting time were 1.8 ± 0.2 m(2) g(-1) and 43?±?2?min for WMTA and 7.8?±?1.2?m(2) g(-1) and 6?±?1?min for NWMTA, respectively. Mean?±?SD of Microhardness were 16?± 2, 51 ±?1, 69?±?1 and 81?±?2 for WMTA at pH values of 4.4 and 7.4 and for NWMTA correspondingly. Numbers of open porosity over the surface were 88?± 24 and 44?±?13 for WMTA and NWMTA, respectively. Statistical tests revealed significant differences between the groups (P?相似文献   

The influence of using vacuum-dried poly(alkenoic) acids upon the physical properties of a glass polyalkenoate (ionomer) cement

Some of the physical characteristics of two glass polyalkenoate cements have been measured. The two cements differ in terms of the presentation of the poly(alkenoic) acid used to form the cement and in the method of mixing of the materials. The 'conventional' cement uses an aqueous solution of poly(acid) and is an encapsulated mechanically mixed material. The alternative material contains a vacuum-dried poly(acid) powder with the ion-leachable glass, and is mixed by hand with a 15 per cent aqueous solution of tartaric acid. There were some minor differences between the two products, including a delay in the onset of the setting reaction for the material containing the vacuum-dried poly(acid) powder. These differences would probably have little significant effect upon the clinical performance of the materials.     

Characterization of glass-ionomer cements: 2. Effect of the powder: liquid ratio on the physical properties

An investigation has been made of the relationship between the powder:liquid ratio and the properties of glass-ionomer cements. Four types of this cement were studied. An increase in the powder:liquid ratio led to increases in stiffness of mix, setting rate, compressive strength, superficial hardness and resistance to aqueous attack. It is concluded that the highest powder:liquid ratio compatible with convenient mixing and adequate working should be used.     

Response of stem cells from human exfoliated deciduous teeth (SHED) to three bioinductive materials – An in vitro experimental study

IntroductionStem cells have unmatched capacity and potential for regeneration and when used alone or in combination with scaffolds to replace or repair damaged cells, can differentiate into any mature cell.AimTo evaluate the functional differentiation potential of EMD (Enamel Matrix Derivative), MTA (Mineral Trioxide Aggregate) and Biodentine on Stem Cells from Human Exfoliated Deciduous teeth (SHED).ObjectiveTo determine functional differentiation potential (osteogenic/odontogenic) of various biomaterials on SHED.Material and methodSHED derived from 5^th linear passage after sub-culturing were treated with EMD, MTA and Biodentine individually and their effect on cell viability was compared and evaluated by MTT (3-4,5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide) assay for 7 days. Alizarin red S staining was used to assess mineralization potential of these materials by the staining calcium deposits for 14 days. The results were analyzed using One-way ANOVA, Post hoc Tukey’s test for multiple comparisons.ResultsIt was observed that EMD imparted the highest cell viability at the end of 7 days (p < 0.001) followed by Biodentine and MTA. Likewise EMD showed highest potential to enhanced mineralization and expression of dentine sialoprotein (p < 0.001) followed by Biodentine and MTA at the end of 14 days (p<0.001).ConclusionIt can be concluded that all the tested materials are bioinductive to SHED. EMD can be used for various vital pulp therapies as that of Biodentine and MTA with predictable as well as enhanced success rate.     

Effect of variations from the recommended powder/liquid ratio on some properties of resin-modified cements

OBJECTIVES: The powder and liquid contents of cements are mixed in accordance with the recommended mixing ratio, but discrepancies occur despite the use of proportioning scoops. Little is known about powder/liquid ratio variations on certain properties of resin-modified cements. METHODS: Two resin-modified glass ionomer cements (RMGIC) were mixed using various powder/liquid ratios: (a) Recommended ratio: Fuji Plus: powder/liquid 2:1; ProTecCEM p/l 2.25:1. (b) Maximal variation arising using proportioning aids (17% liquid surplus): Fuji Plus 1.66:1, ProTecCEM 1.875:1. Limits of mixing and specimen construction: either (c) both groups with more liquid (1.5:1) or (d) more powder (3:1). Flexural strength was determined using a 3-point bending test (after 24 h) and wear using a 3-body abrasion device. The extent of cure reaction was characterized using differential thermal analysis (DTA). RESULTS: While higher powder content did not significantly affect the flexural strength of Fuji Plus and ProTecCEM, it considerably reduced wear of Fuji Plus. Increasing liquid content reduced flexural strength. A substantial increase in wear for Fuji Plus 1.5:1, and ProTecCEM 1.875:1 and 1.5:1 mixtures was observed. DTA demonstrated that a higher liquid content resulted in incomplete setting reactions, which could be detected even after 24 h of cure. CONCLUSIONS: If RMGICs are mixed with powder/liquid variations, given the inaccuracy of proportioning aids the properties of RMGIC will change slightly and may be disregarded. If set with higher powder/liquid variations, a surplus of powder has less influence on the properties than a surplus of liquid.     

Antimicrobial effect of bioceramic cements on multispecies microcosm biofilm: a confocal laser microscopy study

Objectives

To assess the viability of multispecies microcosm biofilm after contact with NeoMTA Plus, Biodentine, and MTA Angelus.

Materials and methods

Fifty-four human dentin blocks (4 × 5 × 4 mm) were allocated to Hawley retainers, worn by six volunteers for 72 h. The blocks were then individually incubated in BHI broth for 21 days at 37 °C. At the end of experimental time for biofilm growth, the samples were randomly divided into four groups (n = 12): NeoMTA Plus, Biodentine, MTA Angelus, and negative control. The materials were placed in contact with the blocks. All samples were placed in cell-culture plate wells and incubated in BHI broth for 7 days at 37 °C. One sample from each volunteer (n = 6) was analyzed by SEM to describe the biofilm morphology. CLSM was performed to determine the percentage of viable biofilm biovolume. The data were statistically analyzed by one-way ANOVA and Tukey’s multiple comparison test (α = 5%).

Results

SEM showed biofilm formed by spherical and rod-shaped bacteria surrounded by an extracellular matrix. No material was able to kill all biofilm cells, and all groups had more than 50% of viable bacteria. NeoMTA Plus was significantly different from the negative control group (P < .05).

Conclusions

All tested materials were not effective against multispecies microcosm biofilm.

Clinical relevance

NeoMTA Plus, Biodentine, and MTA Angelus were not effective against multispecies microcosm biofilm. It is essential to understand that these bioceramic cements are indicated for infected clinical situations. Thus, complementary disinfection procedures should be conducted prior to filling with these materials.

     

The effect of radiotherapy delivery time and obturation materials on the fracture resistance of mandibular premolars

Objectives

This ex vivo study was performed to investigate the effect of radiotherapy (RT) delivery time on fracture resistance of mandibular premolars filled with Biodentine or gutta-percha/sealer (GPS).

Materials and methods

Seventy-two mandibular premolars were used in this study. Randomly selected 24 teeth were kept intact for the control groups (with and without irradiation). Then, the remaining 48 teeth were randomly assigned into 4 groups (n = 12) according to RT delivery time (irradiated before or after root canal treatment) and obturation materials as follows: Group RT + GPS, Group: GPS + RT, Group RT + Biodentine and Group Biodentine + RT. The samples were either initially endodontically treated and then irradiated or initially irradiated and then endodontically treated with one of the abovementioned materials. The samples were irradiated at 2 Gy per fraction, 5 times a week for a total dose of 60 Gy in 30 fractions over 6 weeks. The roots were embedded in self-polymerizing acrylic resin. The fracture resistance was evaluated in a universal testing machine. Data was analyzed by one-way ANOVA and Games-Howell post hoc test at p < 0.05.

Results

Radiation therapy significantly reduced fracture resistance of intact teeth (p < 0.05). The highest fracture resistance was observed in intact/non-irradiated teeth and the lowest fracture resistance in Biodentine + RT group (p < 0.05). The effect of RT delivery time was insignificant when GPS was preferred as the root canal filling material (p > 0.05); it was significant when preferring Biodentine (p < 0.05). When RT was applied to the teeth after Biodentine obturation, the fracture resistance decreased significantly compared to the teeth that were obturated with GPS after or before RT application (p < 0.05).

Conclusion

Both RT time and obturation materials (Biodentine or gutta-percha/sealer) affect the fracture resistance of the endodontically treated teeth.

Clinical relevance

Endodontic treatment could be completed with both materials after RT; however, when the endodontic treatment was initially completed and the teeth were subsequently exposed to RT, it was shown that the reinforcement effect of Biodentine decreased.

     

Spectrophotometric Analysis of Coronal Tooth Discoloration Induced by Tricalcium Silicate Cements in the Presence of Blood

IntroductionNew tricalcium silicate cements have been shown to induce less coronal discoloration. The purpose of this in vitro study was to evaluate the degree of color change induced by various silicate materials in the presence and absence of blood.MethodsOne hundred human extracted anterior single-canal teeth were sectioned to standardized root lengths, accessed, and instrumented. Eight random experimental groups and 2 control groups were created wherein specimens were filled with experimental materials below the buccal cementoenamel junction as follows: EndoSequence RRM putty (Brasseler USA, Savannah, GA), EndoSequence RRM fast set putty (Brasseler USA), Biodentine (Septodont, Saint-Maur-des-Fossés, France), and white mineral trioxide aggregate (Dentsply Sirona, York, PA) either with the presence or absence of blood. Blood-only and saline-only samples were used for the positive and negative controls. After incubation in 100% humidity at 37°C, color changes were evaluated with a spectrophotometer (Ocean Optics, Dunedin, FL) on days 0, 30, 60, and 180 after material placement. Data were transformed into Commission International de I'Eclairage's L1a1b color values, and corresponding ΔE values were calculated. The 1-way analysis of variance test was performed for statistical analysis.ResultsDiscoloration was observed in all specimens in the presence of blood. There was no statistical significance when comparing different materials in contact with blood. Intragroup observation at various time points, Biodentine, and EndoSequence RRM fast set putty showed significant difference between the presence and absence of blood at 180 days (P < .05).ConclusionsContamination with blood of tricalcium silicate materials has the potential to cause coronal tooth discoloration.