In-Nam Hwang

Chemical composition, radiopacity, and biocompatibility of Portland cement with bismuth oxide

OBJECTIVE This study compared the chemical constitution, radiopacity, and biocompatibility of Portland cement containing bismuth oxide (experimental cement) with those of Portland cement and mineral trioxide aggregate (MTA). STUDY DESIGN The chemical constitution of materials was determined by scanning electron microscopy and energy-dispersive X-ray analysis. The radiopacity of the materials was determined using the ISO/6876 method. The biocompatibility of the materials was tested by MTT assay and tissue reaction. RESULTS The constitution of all materials was similar. However, the Portland cement and experimental cement were more irregular and had a larger particle size than MTA. The radiopacity of the experimental cement was similar to MTA. The MTT assay revealed MTA to have slightly higher cell viability than the other materials. However, there were no statistically significant differences between the materials, with the exception of MTA at 24 h. There was no significant difference in the tissue reaction between the experimental groups. CONCLUSIONS These results suggest that the experimental cement may be used as a substitute for MTA.

Polymerization Shrinkage and Depth of Cure of Bulk-Fill Resin Composites and Highly Filled Flowable Resin

The aim of this study was to evaluate the polymerization behavior and depth of cure (DOC) of recently introduced resin composites for posterior use: highly filled flowable composite and composites for bulk fill. A highly filled flowable (G-aenial Universal Flo [GUF]), two bulk-fill flowables (Surefil SDR Flow [SDR] and Venus Bulk fill [VBF]), and a bulk-fill nonflowable composite (Tetric N-Ceram Bulk fill [TBF]) were compared with two conventional composites (Tetric Flow [TF], Filtek Supreme Ultra [FS]). Linear polymerization shrinkage and polymerization shrinkage stress were each measured with custom-made devices. To evaluate DOC, the composite specimen was prepared using a mold with a hole of 4 mm depth and 4 mm internal diameter. The hole was bulk filled with each of the six composites and light cured for 20 seconds, followed by 24 hours of water storage. The surface hardness was measured on the top and the bottom using a Vickers microhardness (HV) indenter. The linear polymerization shrinkage of the composite specimens after photo-initiation decreased in the following order: TF and GUF > VBF > SDR > FS and TBF (p<0.05). The polymerization shrinkage stress of the six composite groups decreased in the following order: GUF > TF and VBF > SDR > FS and TBF (p<0.05). The mean bottom surface HV of SDR and VBF exceeded 80% of the top surface HV (HV-80%). However, the bottom of GUF and TBF failed to reach HV-80%. A highly filled flowable (GUF) revealed limitations in polymerization shrinkage and DOC. Bulk-fill flowables (SDR and VBF) were properly cured in 4-mm bulk, but they shrank more than the conventional nonflowable composite. A bulk-fill nonflowable (TBF) showed comparable shrinkage to the conventional nonflowable composite, but it was not sufficiently cured in the 4-mm bulk.

Improvement of the Properties of Mineral Trioxide Aggregate by Mixing with Hydration Accelerators

INTRODUCTION Mineral trioxide aggregate (MTA) is used widely in endodontic therapy. This study examined the setting time, compressive strength, and pH of MTA mixed with several hydration accelerators (calcium chloride, low-dose citric acid, calcium lactate gluconate solution). METHODS Group 1 (control) was obtained by mixing MTA with distilled water. In group 2, MTA containing 10% calcium chloride was mixed with distilled water. In group 3, MTA was mixed with 0.1% citric acid. In group 4, MTA was mixed with a calcium lactate gluconate solution. The setting time, compressive strength, and pH were examined. RESULTS The setting time of MTA mixed with hydration accelerators was significantly shorter than that of MTA mixed with water (P < .01). In particular, replacing distilled water with a calcium lactate gluconate solution provided a significant decrease in setting time. The compressive strengths of MTA mixed with hydration accelerators were significantly lower than that of MTA mixed with water (P < .01), but those values increased with time. The pH of MTA mixed with hydration accelerators was significantly lower than that of MTA mixed with water (P < .01) but stable at a high level (pH 11-12). CONCLUSIONS Hydration accelerators improved the setting time of MTA. Nevertheless, more study will be needed to improve MTA without impairing its preexisting advantages.

Biocompatibility of Mineral Trioxide Aggregate Mixed with Hydration Accelerators

INTRODUCTION The aim of this study was to evaluate the biocompatibility of mineral trioxide aggregate mixed with selective hydration accelerators such as calcium chloride (CaCl2), citric acid (CA), and calcium lactate gluconate solution (CLG). METHODS Inductively coupled plasma-atomic emission spectrometry analysis was used to measure calcium ions in the extracts of test materials. The 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium hydroxide assay was performed using MG-63 cells to examine the cytotoxicity of the test materials. The surface of each sample and the growth pattern of the attached cells were observed using scanning electron microscopy (SEM). RESULTS MTA mixed with 10 wt% CaCl2 and MTA mixed with 43.4 wt% CLG released a higher amount of calcium ions than the other groups. The 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium hydroxide assay revealed that the cell viability of MTA mixed with 0.1 wt% CA was significantly higher than pure MTA on 7-day extract (P < .05). MTA mixed with 43.4 wt% CLG showed significantly higher cell viability than the other groups on 1-day extract (P < .05). MTA mixed with 10 wt% CaCl2 in all groups showed the lowest cell viability at all time points (P < .05). Under SEM, elongated and confluent cells were observed in all samples except in samples of MTA mixed with 10 wt% CaCl2. CONCLUSIONS MTA mixed with 0.1 wt% CA showed good biocompatibility. MTA mixed with 43.4 wt% CLG showed favorable biocompatibility on 1 day. MTA mixed with 10 wt% CaCl2 in all groups showed the lowest cell viability at every time point and poor cell attachment under SEM.

Chemical constitution, physical properties, and biocompatibility of experimentally manufactured Portland cement.

INTRODUCTION An experimental Portland cement was manufactured with pure raw materials under controlled laboratory conditions. The aim of this study was to compare the chemical constitution, physical properties, and biocompatibility of experimentally manufactured Portland cement with those of mineral trioxide aggregate (MTA) and Portland cement. METHODS The composition of the cements was determined by scanning electron microscopy (SEM) and energy-dispersive x-ray analysis (EDAX). The setting time and compressive strength were tested. The biocompatibility was evaluated by using SEM and XTT assay. RESULTS SEM and EDAX revealed the experimental Portland cement to have a similar composition to Portland cement. The setting time of the experimental Portland cement was significantly shorter than that of MTA and Portland cement. The compressive strength of the experimental Portland cement was lower than that of MTA and Portland cement. The experimental Portland cement showed a similar biocompatibility to MTA. CONCLUSIONS The experimental Portland cement might be considered as a possible substitute for MTA in clinical usage after further testing.

Cytotoxicity of newly developed ortho MTA root-end filling materials.

INTRODUCTION Various materials have been advocated for use as root-end filling materials. The purpose of the present in vitro study was to compare the cytotoxicity of 4 root-end filling materials: glass ionomer cement (GIC; Fuji II, GC Corp, Tokyo, Japan), reinforced zinc oxide-eugenol cement (IRM; Dentsply Tulsa Dental, Tulsa, OK), and 2 types of mineral trioxide aggregate. METHODS This study used MG-63 cells derived from a human osteosarcoma. To quantitatively evaluate the cytotoxicity of test materials, the 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) assay was used. The cells were exposed to the extracts and incubated. Cell viability was recorded by measuring the optical density of each test well in reference to controls. Each specimen was examined by scanning electron microscopy for the observation of cell morphology. RESULTS The XTT assay showed that the cell viability of ProRoot MTA (Dentsply Tulsa Dental) was higher than that of GIC and Ortho MTA (BioMTA, Seoul, Republic of Korea) at all time points. IRM showed significantly lower cell viability than the other groups. The scanning electron microscopic analysis revealed that elongated, dense, and almost confluent cells were observed in the cultures of GIC, Ortho MTA, and ProRoot MTA specimens. In contrast, cells on the surface of IRM were rounded in shape, and the numbers and the density of the cells were smaller than that in the other groups. CONCLUSIONS ProRoot MTA and GIC showed good biocompatibility in this study. However, Ortho MTA showed lower biocompatibility compared with ProRoot MTA and GIC.

Glycol Chitin–based Thermoresponsive Hydrogel Scaffold Supplemented with Enamel Matrix Derivative Promotes Odontogenic Differentiation of Human Dental Pulp Cells

INTRODUCTION Hydrogels have been widely studied as tissue engineering scaffolds over the past 2 decades because of their favorable biological properties. Recently, a new biodegradable glycol chitin-based thermoresponsive hydrogel scaffold (GC-TRS) was developed that can be easily applied as a mild viscous solution at room temperature but quickly transforms into a durable hydrogel under physiological conditions. The aim of this study was to investigate the effects of GC-TRS on the proliferation and odontogenic differentiation of colony-forming human dental pulp cells (hDPCs) in the presence of enamel matrix derivative. METHODS Glycol chitin was synthesized by N-acetylation of glycol chitosan. The morphology of the thermoresponsive hydrogel scaffold was observed by using scanning electron microscopy. The sol gel phase transition of the aqueous solution of glycol chitin was investigated by using the tilting method and rheometer studies. hDPCs were isolated based on their ability to generate clonogenic adherent cell clusters. The effect of GC-TRS and collagen on cell viability was examined by performing 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Expression of markers for odontogenic/osteogenic differentiation (ie, dentin sialophosphoprotein, dentin matrix protein-1, osteonectin, and osteopontin) was analyzed by performing real-time polymerase chain reaction. RESULTS GC-TRS exhibited a highly macroporous and well-interconnected porous structure. The polymer solution existed in a mildly viscous sol state, but it transitioned to a gel state and did not flow above approximately 37°C. Rheometer studies showed that the glycol chitin solution exhibited a fast sol gel transition approximately at body temperature. GC-TRS and collagen did not inhibit cell viability until 7 days. Dentin sialophosphoprotein and dentin matrix protein-1 were expressed by cells cultured in GC-TRS at a higher level than that in cells cultured in collagen (P < .05). In both the scaffold groups, dentin sialophosphoprotein, dentin matrix protein-1, and osteopontin messenger RNA was up-regulated significantly in EMD-treated hDPCs when compared with the nontreated cells (P < .05). CONCLUSIONS GC-TRS allowed the proliferation and odontogenic differentiation of hDPCs. Furthermore, the differentiation was facilitated by EMD. These results suggest that GC-TRS has the potential to be used in tissue engineering techniques for dentin regeneration.

Cytotoxicity and physical properties of tricalcium silicate-based endodontic materials

Objectives The aim of this study was to evaluate the cytotoxicity, setting time and compressive strength of MTA and two novel tricalcium silicate-based endodontic materials, Bioaggregate (BA) and Biodentine (BD). Materials and Methods Cytotoxicity was evaluated by using a 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-((phenylamino)carbonyl)-2H-tetrazolium hydroxide (XTT) assay. Measurements of 9 heavy metals (arsenic, cadmium, chromium, copper, iron, lead, manganese, nickel, and zinc) were performed by inductively coupled plasma-mass spectrometry (ICP-MS) of leachates obtained by soaking the materials in distilled water. Setting time and compressive strength tests were performed following ISO requirements. Results BA had comparable cell viability to MTA, whereas the cell viability of BD was significantly lower than that of MTA. The ICP-MS analysis revealed that BD released significantly higher amount of 5 heavy metals (arsenic, copper, iron, manganese, and zinc) than MTA and BA. The setting time of BD was significantly shorter than that of MTA and BA, and the compressive strength of BA was significantly lower than that of MTA and BD. Conclusions BA and BD were biocompatible, and they did not show any cytotoxic effects on human periodontal ligament fibroblasts. BA showed comparable cytotoxicity to MTA but inferior physical properties. BD had somewhat higher cytotoxicity but superior physical properties than MTA.

A review of the regenerative endodontic treatment procedure

Traditionally, apexification has been used to treat immature permanent teeth that have lost pulp vitality. This technique promotes the formation of an apical barrier to close the open apex so that the filling materials can be confined to the root canal. Because tissue regeneration cannot be achieved with apexification, a new technique called regenerative endodontic treatment was presented recently to treat immature permanent teeth. Regenerative endodontic treatment is a treatment procedure designed to replace damaged pulp tissue with viable tissue which restores the normal function of the pulp-dentin structure. After regenerative endodontic treatment, continued root development and hard tissue deposition on the dentinal wall can occur under ideal circumstances. However, it is difficult to predict the result of regenerative endodontic treatment. Therefore, the purpose of this study was to summarize multiple factors effects on the result of regenerative endodontic treatment in order to achieve more predictable results. In this study, we investigated the features of regenerative endodontic treatment in comparison with those of other pulp treatment procedures and analyzed the factors that have an effect on regenerative endodontic treatment.

Pulp response of mineral trioxide aggregate, calcium sulfate or calcium hydroxide

This study was performed to verify the possibility of MTA and calcium sulfate as a pulp capping agent through comparing the dental pulp response in dogs after capping with MTA, calcium sulfate, and calcium hydroxide. 24 teeth of 2 dogs, 8 month old, were used in this study. Under general anesthesia, cervical cavities were prepared and pulp was exposed with sterilized #2 round bur in a high speed handpiece. MTA calcium hydroxide, and calcium sulfate were applied on the exposed pulp. Then the coronal openin,fs were sealed with IRM and light-cured composite. Two months after treatment, the animals were sacrificed. The extracted teeth were fixed in 10% neutral-buffered formalin solution and were decalcified in formic acid-sodium citrate. They were prepared for histological examination in the usual manner. The sections were stained with haematoxylin and eosin. In MTA group, a hard tissue bridges formation and newly formed odontoblasts layer was observed. There was no sign of pulp inflammatory reaction in pulp tissue. In calcium hydroxide group, there was no odontoblast layer below the dentin bridge. In pulpal tissue, chronic inflammatory reaction with variable intensity and extension occurred in all samples. In calcium sulfate group, newly formed odontoblast layer was observed below the bridge. Mild chronic inflammation with a few neutrophil infiltrations was observed on pulp tissue. These results suggest that MTA is more biocompatible on pulp tissue than calcium hydroxide or calcium sulfate.