Bioactivity of Calcium Silicate-Based Endodontic Materials: A Comparative in vitro Evaluation.

Background: Bioactivity refers to the ability of a material to interact with living organisms or biological systems in a way that elicits a specific response. In the context of materials science and medicine, bioactivity is particularly important because it can determine the suitability of material for various applications. Objective: To evaluate and compare different commercially available calcium silicate-based materials regarding: 1. Morphological and elemental analysis at the dentin/material interface. 2. Calcium and silicon release and uptake by adjacent root canal dentine by evaluating the calcium and silicon incorporation depth in adjacent root canal dentin. Materials and Methods: This study examined four calcium silicate-based cements: Biodentine, MTA Angelus, BioAggregate, and MTA Plus. One hundred extracted human teeth with intact apices and no cavities were selected. Root sections measuring 3 mm in length were created at the mid-root level using low-speed diamond discs. Bioactivity was evaluated at 1, 7, 30, and 90 days, respectively. Results: The principal composition of the interfacial dentine layer and incorporation of calcium and silicon into dentine was measured at 1, 7, 30, and 90 days. Statistical analysis was performed by multiple comparisons using post hoc Tukey HSD. Conclusion: All the materials have shown bioactivity, i.e. release of calcium, silicon, and their uptake in the adjacent dentin in the presence of phosphate-buffered saline.

Retarding Effect of Hemp Hurd Lixiviates on the Hydration of Hydraulic and CSA Cements.

Wood wool panels are widely used in the construction industry as sustainable cementitious composites, but there is a growing need to replace traditional Portland cement with a binder that has a lower embodied carbon footprint. In addition, the sustainability of these panels may face serious impediments if the required amount of wood for their production needs a harvest rate higher than the rate at which the tree sources reach maturity. One solution is to use the wooden part of fast-growing plants such as hemp. However, the compounds extracted from the mixture of plants and water are the main cause of the delay observed during the hydration process of hydraulic binders in these cementitious composites. The objective of this study is to evaluate the effect of bio-aggregate lixiviates (hemp hurd) on the hydration kinetics of calcium sulfoaluminate (CSA) cement as a low-embodied-carbon alternative to ordinary Portland cement (OPC). The isothermal calorimeter showed that the hemp hurd lixiviate caused a greater delay in GU's hydration process than CSA's. At a 5% concentration, the main hydration peak for GU cement emerged after 91 h, whereas for CSA cement, it appeared much earlier, at 2.5 h. XRD and TGA analysis showed that after 12 h of hydration, hydration products such as calcium silicate hydrates (C-S-H) and portlandite (CH) were not able to form on GU cement, indicating low hydration of silicate products. Moreover, at 5% concentration, the carbonation of ettringite was observed in CSA cement. The compressive strength values obtained from the mixes containing hemp hurd lixiviate consistently showed lower values compared to the reference samples prepared with distilled water. Furthermore, the CSA samples demonstrated superior compressive strength when compared to the GU samples. After 28 days of hydration, the compressive strength values for CSA cement were 36.7%, 63.5% and 71% higher than GU cement at a concentration of 0.5%, 2% and 5% hemp hurd lixiviate, respectively.

Roles of high/low nucleic acid bacteria in flocs and probing their dynamic migrations with respirogram.

Bacterial migration is crucial for the stability of activated sludge but rarely reported. The static distribution was explored by changes in bacteria concentration with extracellular polymeric substances (EPS) extractions. Next, denitrification and aeration were conducted as normal running conditions for examining the bacterial migration between floc-attached and dispersed growth. Above observations were further explored by conducting copper ion (Cu2+) shock as an extreme running condition. After extracting EPS, low nucleic acid (LNA) bacteria migrated from the sludge to the supernatant primarily, and high nucleic acid (HNA) bacteria remained in the residual sludge, suggesting that HNA bacteria mainly distributed inside the sludge while LNA bacteria outside the sludge. During the denitrification process, LNA bacteria migrated out of flocs, which increased by 6.94 × 106 events/mL in the supernatant. During the feast phase of aeration, LNA bacteria grew attached to flocs, causing the increased flocs diameter from 45.60 to 47.40 µm. During the following aerobic famine phase, LNA bacteria grew dispersedly, but HNA bacteria remained unchanged. However, a further severe famine phase drove HNA bacteria to be dispersed, breaking flocs with the decreased diameter from 48.10 to 46.50 µm. When the Cu2+ shock was employed, LNA and HNA bacteria increased but the LNA/HNA ratio decreased in the supernatant, indicating more HNA bacteria migrating to the dispersed phase. From a structural perspective, HNA bacteria distributed inside the sludge and functioned as the backbone of flocs, undertaking the maintenance of flocs stability primarily; while LNA bacteria distributed outside the sludge and functioned as filling materials, having a secondary influence on flocs stability. These processes were also probed by respirogram exactly, correlating the system-scale measurement and microscale migrations and providing an early warning signal under abnormal circumstances. The processed HNA-backbone theory is promising for regulating the stability of activated sludge based on bacterial migrations.

Stresses in Teeth with External Cervical Resorption Defects Restored with Different Biomimetic Cements: A Finite Element Analysis.

INTRODUCTION: This study compared the stress distributions in teeth with simulated external cervical resorption defects restored with different restorative materials and identified areas of high stress concentration. METHODS: A maxillary central incisor created in a scanned model using HyperWorks software (Altair Engineering Inc, Troy, MI) served as the control. External cervical resorption defects based on Shanon Patel's classification were created (1Bd/2Bd/3Bd) in the scanned model. The defects were restored using mineral trioxide aggregate, Biodentine, glass ionomer cement, and Bioaggregate. On all the models, a force of 100 N was applied on the palatal aspect 2 mm incisal to the cingulum directed at 45° along the long axis of the tooth. RESULTS: The stresses generated in dentin and cementum are less, with a restorative material having a high Young's modulus. For the 1Bd defect, MTA and Bioaggregate showed least stresses in dentin and cementum, respectively, whereas Biodentine had consistently lower stresses in dentin and cementum. Larger defects like 2Bd and 3Bd restored with Bioaggregate exhibited minimum stresses in dentin and cementum. CONCLUSIONS: Bioaggregate and Biodentine replace dentin with maximum stress and maximum strain. Elastic moduli similar to or higher than dentin are preferred for restoring cervical third resorptive lesions of the tooth.

Rapid formation of bioaggregates and morphology transition to biofilm streamers induced by pore-throat flows.

Bioaggregates are condensed porous materials comprising microbes, organic and inorganic matters, and water. They are commonly found in natural and engineered porous media and often cause clogging. Despite their importance, the formation mechanism of bioaggregates in porous media systems is largely unknown. Through microfluidic experiments and direct numerical simulations of fluid flow, we show that the rapid bioaggregation is driven by the interplay of the viscoelastic nature of biomass and hydrodynamic conditions at pore throats. At an early stage, unique flow structures around a pore throat promote the biomass attachment at the throat. Then, the attached biomass fluidizes when the shear stress at the partially clogged pore throat reaches a critical value. After the fluidization, the biomass is displaced and accumulated in the expansion region of throats forming bioaggregates. We further find that such criticality in shear stress triggers morphological changes in bioaggregates from rounded- to streamer-like shapes. This knowledge was used to control the clogging of throats by tuning the flow conditions: When the shear stress at the throat exceeded the critical value, clogging was prevented. The bioaggregation process did not depend on the detailed pore-throat geometry, as we reproduced the same dynamics in various pore-throat geometries. This study demonstrates that pore-throat structures, which are ubiquitous in porous media systems, induce bioaggregation and can lead to abrupt disruptions in flow.

Bond Behavior of a Bio-Aggregate Embedded in Cement-Based Matrix.

This paper investigates the bond behavior between a bio-aggregate and a cement-based matrix. The experimental evaluation comprised physical, chemical, image, and mechanical characterization of the bio-aggregate. The image analyses about the bio-aggregate's outer structure provided first insights to understand the particularities of this newly proposed bio-aggregate for use in cementitious materials. A mineral aggregate (granitic rock), largely used as coarse aggregate in the Brazilian civil construction industry, was used as reference. The bond behavior of both aggregates was evaluated via pull-out tests. The results indicated that both aggregates presented a similar linear elastic branch up to each respective peak loads. The peak load magnitude of the mineral aggregate indicated a better chemical adhesion when compared to the bio-aggregate's. The post-peak behavior, however, indicated a smoother softening branch for the bio-aggregate, corroborated by the microscopy image analyses. Although further investigation is required, the macaúba crushed endocarp was found to be a thriving bio-material to be used as bio-aggregate.

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

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

Evaluation of a collagen-bioaggregate composite scaffold in the repair of sheep pulp tissue.

PURPOSE: This study aimed to compare the effects of the collagen-BioAggregate mixture (CBA-M) and collagen-BioAggregate composite (CBA-C) sponge as a scaffolding material on the reparative dentin formation. MATERIALS AND METHODS: CBA-C sponge (10:1 w/w) was obtained and characterized by Scanning Electron Microscopy (SEM) and Mercury Porosimetry. Cytotoxicity of the CBA-C sponge was tested by using the L929 mouse fibroblast cell line. Dental pulp stem cells (DPSCs) were isolated from the pulp tissue of sheep teeth and characterized by flow cytometry for the presence of mesenchymal stem cell marker, CD44. The osteogenic differentiation capability of isolated DPSCs was studied by Alizarin Red staining. The cells were then used to study for the compatibility of CBA-C sponge with cell proliferation and calcium phosphate deposition. The effect of CBA-C sponge and CBA-M on the induction of dentin regeneration was studied in the perforated teeth of sheep for the eight-week period. All the analyses were performed with appropriate statistical hypothesis tests. RESULTS: CBA-C sponge was found to be biocompatible for DPSCs. The DPSCs seeded on the CBA-C sponge were able to differentiate into the osteoblastic lineage and deposit calcium phosphate crystals in vitro. Reparative dentin formation was observed after the second week in the CBA-C sponge applied group. At the end of eight weeks, a complete reparative dentin structure was formed in the CBA-C sponge applied group, whereas necrotic tissue residues were observed in groups treated with the CBA-M. CONCLUSION: CBA-C sponge represents a better microenvironment for reparative dentin formation probably due to maintaining DPSCs and allowing their osteogenic differentiation and thus calcium phosphate deposition.

The effects of root canal perforation repair materials on the bond strength of fiber posts.

INTRODUCTION: This study aimed to evaluate the effect of calcium hydroxide and bioceramics used in perforation repair on the bonding strength of fiber posts via a push-out test. METHODOLOGY: This study used 106 extracted single-rooted human mandibular premolar teeth. Root canal preparations were performed with a rotary file system and perforations were created in the middle third of each tooth. The samples were randomized into two main experimental groups, one with calcium hydroxide and one without. Each group had four subgroups in which different bioceramic cements were applied (n = 11) and a control group (n = 9). The root canals perforations were repaired using MTA, Biodentine, Bioaggregate, and Endosequence BC root repair material. A fiber post was applied to each tooth and a push-out test was performed. The samples were examined at 40× magnification with a digital microscope in order to identify fracture type. RESULTS: Bonding strength was calculated in MPa. A statistical analysis showed that the calcium hydroxide had no effect on the bonding strength of the fiber posts. A comparison of the perforation repair materials revealed that Biodentine in the calcium hydroxide group and Bioaggregate in both groups decreased the bonding strength compared to the other materials (p < 0.05). The most common failure type was adhesive failure between the dentin and resin cement (38.16%). CONCLUSIONS: The use of different perforation repair materials can affect the bonding strength of fiber posts. Therefore, the choice of perforation repair material should be made on an individual basis.

Bio-active cements-Mineral Trioxide Aggregate based calcium silicate materials: a narrative review.

Recent advances in the field of endodontics have greatly improved the outcome and success rate of dental materials. For last three decades, there has been great interest in the development of bioactive dental material with the ability to interact and induce surrounding dental tissues to promote regeneration of pulpal and periradicular tissues. As these bioactive materials are mainly based on calcium silicates, they are also referred to as Calcium Silicate materials. The first material introduced was Mineral Tri-oxide Aggregate, which, due to its favourable biological properties, gained importance initially. However, later, due to its drawbacks, liked is colouration, long setting time and difficult manipulation, several modifications were done and newer bioactive materials, such as Biodentine, BioAggregate, Endosequence, Calcium-Enriched Mixture etc., were developed. The main applications of these materials are for pulp capping (direc t/indirec t), pulpotomy, perforation repair, resorption defects, apexogenesis and as retrograde filling materials, apexification and endodontic sealers. This review discusses the various types of bioactive materials, their composition, setting mechanism, and literature evidence for current applications.

Finite element analysis of immature teeth filled with MTA, Biodentine and Bioaggregate.

BACKGROUND AND OBJECTIVE: Finite element based simulation has emerged as a powerful tool to analyse the tooth strength and its fracture characteristics. The aim of this study is to compare and evaluate the fracture resistance of immature teeth reinforcement with MTA, Biodentine and Bioaggregate as an apical plug and backfill material using Finite Element Method. METHODS: A 3D finite element analysis model was generated using a simulated immature maxillary central incisor. Seven different models were developed representing (Model 1): control group having an immature tooth model without any reinforcement material; (Model 2): Mineral trioxide aggregate (MTA) as apical plug 4 mm; (Model 3): Biodentine as apical plug 4 mm; (Model 4): Bioaggregate as apical plug 4 mm; (Model 5): MTA filled in the entire root canal 8.5 mm; (Model 6): Biodentine filled in the entire root canal 8.5 mm; (Model 7): Bioaggregate filled in the entire root canal 8.5 mm. A force of 100 N was applied at an angle of 130° to the palatal surface of the tooth. Stress distribution at cemento­enamel junction was measured using the Von Mises stress criteria. RESULTS: It was found that the 4 mm apical plug using MTA showed higher fracture resistance when compared to 8.5 mm backfill using MTA. When MTA was replaced as backfill material by Biodentine and Bioaggregate, the von mises stress increased by 64% and 94% respectively. CONCLUSIONS: It is not desirable to restore the entire root canal of an immature teeth using same material due to higher stress concentration at the cervical region. Considering the shorter setting time and improved handling characteristics, Biodentine can be preferred over the time­tested MTA as an apical plug.

Are Bioceramics the Dernier Cri in the Management of Stage 4 Developed Root? A Finite Element Analysis.

AIM: To compare the stress distribution of four modalities of reinforcing the radicular space of a pulpless central incisor exhibiting stage 4 root development. MATERIALS AND METHODS: The model of a pulpless immature central incisor with a stage 4 of root development supporting periodontium was generated based on the properties. The longitudinal growth of the root was completed. Four such models were developed. Then, the radicular space was rehabilitated as follows: Model 1: Ceramicrete; Model 2: Biomimetic Mineralization; Model 3: Biodentine; Model 4: Bioaggregate. They were subjected to three different loading conditions. One was to mimic the mastication by applying a load of 70 N applied at 45° angle. Second loading condition was a vertical load of 100 N to mimic bruxism. The third loading condition was to mirror the impact of a frontal trauma. A load of 100 N was applied labially. RESULTS: It was observed that during mastication, Model 2 has exhibited the lowest concentration of von Mises stresses, followed by Model 3 and then Model 4 followed by Model 1; this could be because the modulus of elasticity of Model 2 is comparable to that of Dentin. During bruxism and horizontal impact, the maximal stress concentration was found in Model 4, Model 3, Model 2, followed by Model 1. CONCLUSION: The closer the elasticity of modulus of the primary endodontic replacement monoblock was to that of dentin, the lower were the stresses generated. However, as the increase in stress values was minimal between groups, these obturating materials can be viable reinforcement materials for the rehabilitation of cases of stage 4 developing root. Biomimetic mineralization strategies can be a viable treatment option for managing cases of the open apex. CLINICAL RELEVANCE: Biomimetic mineralization strategies and bioceramics can be used for obturation of root canals with open apex, instead of utilizing these bioceramics as apical plugs.

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.

Portland cement induces human periodontal ligament cells to differentiate by upregulating miR-146a.

BACKGROUND/PURPOSE: Bioaggregates such as Portland cement (PC) can be an economical alternative for mineral trioxide aggregate (MTA) with additional benefit of less discoloration. MTA has been known to induce differentiations of several dental cells. MicroRNAs are important regulators of biological processes, including differentiation, physiologic homeostasis, and disease progression. This study is to explore how PC enhances the differentiation of periodontal ligament (PDL) cells in microRNAs level. METHODS: PDL cells were cultured in a regular PC- or MTA-conditioned medium or an osteoinduction medium (OIM). Alizarin red staining was used to evaluate the extent of mineralization. Transfection of microRNA mimics induced exogenous miR-31 and miR-146a expression. The expression of microRNAs and differentiation markers was assayed using reverse-transcriptase polymerase chain reaction. RESULTS: PC enhanced the mineralization of PDL cells in a dose-dependent manner in the OIM. Exogenous miR-31 and miR-146a expression upregulated alkaline phosphatase (ALP), bone morphogenic protein (BMP), and dentin matrix protein 1 (DMP1) expression. However, miR-31 and miR-146a modulates cementum protein 1 (CEMP1) expression in different ways. PC also enhanced ALP and BMP but attenuated CEMP1 in the OIM. Although the OIM or PC treatment upregulated miR-21, miR-29b, and miR-146a, only miR-146a was able to be induced by PC in combination with OIM. CONCLUSION: This study demonstrated that PC enhances the differentiation of PDL cells, especially osteogenic through miR-146a upregulation. In order to control the ankylosis after regenerative endodontics with the usage of bioaggregates, further investigations to explore these differentiation mechanisms in the miRNA level may be needed.

Comparison of Flexural Strength of Mineral Trioxide Aggregate, Calcium-enriched Mixture and BioAggregate.

Introduction: The aim of this study was to compare the flexural strength of mineral trioxide aggregate (MTA), calcium-enriched mixture (CEM), and BioAggregate (BA). Methods and Materials: In this study, the flexural strength of materials was measured using a 3-point bend test. After being prepared, MTA, CEM, and BA were inserted into the intra-putty molds using amalgam plugger. The specimens were covered with a sponge wetted with synthetic tissue fluid (STF) and incubated for 96 h. They were then subjected to a 3-point bend test using Universal Testing Machine. The Kruskal-Wallis and Mann-Whitney U tests were used to compare flexural strength in groups. In this study, P<0.05 was considered as the significant level. Results: There were significant differences between the three groups in terms of the flexural strength (P<0.001). The mean flexural strength in the BA, CEM, and MTA groups were 27.32±2, 9.09±1.16, and 10.25±1.6, respectively. Pairwise comparison showed significant differences between the three groups. Conclusion: This in vitro study showed that BA has the highest and CEM has the lowest flexural strength.

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.

The influence of the casting process on the internal structure and physical properties of hemp-lime.

Bio-aggregate composites such as hemp-lime offer a more sustainable alternative to traditional walling infill material. Hemp-lime, whether in situ or prefabricated, is generally either cast or sprayed, which results in a directionally dependent, typically layered, physical structure. This paper considers the impact of compaction and layering on the directional thermal conductivity, compressive strength and internal structure of the material through use of a novel image analysis method. The results presented indicate that production variables have a significant, and crucially, directionally dependent impact on the thermal and mechanical properties of cast hemp-lime.

Comparison of the Potential Discoloration Effect of Bioaggregate, Biodentine, and White Mineral Trioxide Aggregate on Bovine Teeth: In Vitro Research.

INTRODUCTION: Tricalcium silicate cements can be used for pulp capping, pulpotomies, apical barrier formation in teeth with open apices, repair of root perforations, regenerative endodontics, and root canal filling. The aim of this study was to evaluate and compare the discoloration potential of 3 different tricalcium cements using a bovine tooth model. METHODS: Forty bovine anterior teeth have been used for the study. Crowns separated from the roots were randomly divided into 4 groups: the BioAggregate (IBC, Vancouver, Canada) group, the Biodentine (Septodont, Saint Maur des Fosses, France) group, the mineral trioxide aggregate Angelus (Angelus, Londrina, PR, Brazil) group, and the only blood group. Materials have been placed to the standardized cavities on the lingual surfaces of the crowns, and their contact with blood has been provided. The color values of the samples were measured with a digital tooth shade determinator (VITA Easyshade; VITA Zahnfabrik, Bad Sackingen, Germany) before the placement of the materials, after the placement of the materials, in the 24th hour, in the first week, in the first month, in the third month, and in the first year. The mean value of all groups was compared using the Tukey multiple comparison test (α = 0.05). RESULTS: All groups displayed increasing discoloration during a period of the first year. The "only blood group" showed the highest color change values, and it was followed as BioAggregate, mineral trioxide aggregate Angelus, and Biodentine, respectively. Statistically significant differences were found for Biodentine when compared with the only blood and BioAggregate groups (P < .05). CONCLUSIONS: Considering the results of the study, Biodentine is found to have the least discoloration potential among the tested materials.

Effect of carbon sources on the aggregation of photo fermentative bacteria induced by L-cysteine for enhancing hydrogen production.

Poor flocculation of photo fermentative bacteria resulting in continuous biomass washout from photobioreactor is a critical challenge to achieve rapid and stable hydrogen production. In this work, the aggregation of Rhodopseudomonas faecalis RLD-53 was successfully developed in a photobioreactor and the effects of different carbon sources on hydrogen production and aggregation ability were investigated. Extracellular polymeric substances (EPS) production by R. faecalis RLD-53 cultivated using different carbon sources were stimulated by addition of L-cysteine. The absolute ζ potentials of R. faecalis RLD-53 were considerably decreased with addition of L-cysteine, and aggregation barriers based on DLVO dropped to 15-43 % of that in control groups. Thus, R. faecalis RLD-53 flocculated effectively, and aggregation abilities of strain RLD-53 cultivated with acetate, propionate, lactate and malate reached 29.35, 32.34, 26.07 and 24.86 %, respectively. In the continuous test, hydrogen-producing activity was also promoted and reached 2.45 mol H2/mol lactate, 3.87 mol H2/mol propionate and 5.10 mol H2/mol malate, respectively. Therefore, the aggregation of R. faecalis RLD-53 induced by L-cysteine is independent on the substrate types, which ensures the wide application of this technology to enhance hydrogen recovery from wastewater dominated by different organic substrates.

Evaluation of reparative dentin formation of ProRoot MTA, Biodentine and BioAggregate using micro-CT and immunohistochemistry.

OBJECTIVES: The purpose of this study was to assess the ability of two new calcium silicate-based pulp-capping materials (Biodentine and BioAggregate) to induce healing in a rat pulp injury model and to compare them with mineral trioxide aggregate (MTA). MATERIALS AND METHODS: Eighteen rats were anesthetized, cavities were prepared and the pulp was capped with either of ProRoot MTA, Biodentine, or BioAggregate. The specimens were scanned using a high-resolution micro-computed tomography (micro-CT) system and were prepared and evaluated histologically and immunohistochemically using dentin sialoprotein (DSP). RESULTS: On micro-CT analysis, the ProRoot MTA and Biodentine groups showed significantly thicker hard tissue formation (p < 0.05). On H&E staining, ProRoot MTA showed complete dentin bridge formation with normal pulpal histology. In the Biodentine and BioAggregate groups, a thick, homogeneous hard tissue barrier was observed. The ProRoot MTA specimens showed strong immunopositive reaction for DSP. CONCLUSIONS: Our results suggest that calcium silicate-based pulp-capping materials induce favorable effects on reparative processes during vital pulp therapy and that both Biodentine and BioAggregate could be considered as alternatives to ProRoot MTA.