Hyunjung Ko

Cytotoxicity of mineral trioxide aggregate (MTA) and bone morphogenetic protein 2 (BMP-2) and response of rat pulp to MTA and BMP-2.

OBJECTIVE The aim of this study was to assess the cytotoxicity of mineral trioxide aggregate (MTA) and bone morphogenetic protein 2 (BMP-2) and the response of rat pulp tissue to MTA and BMP-2. STUDY DESIGN For cytotoxicity studies, 1 g MTA was mixed with or without 1 microg of BMP-2 and allowed to set for 1, 24, 48, or 72 hours before addition of samples to 2-mL aliquots of culture medium. The viability of MG-63 cells was determined using the dimethyl-thiazol-diphenyltetrazolium bromide (MTT) assay. For animal studies, upper first molars from 32 Sprague-Dawley rats were used, the molars were exposed, and 1 g MTA cement was placed in the first molars. In left molars, 1 microg BMP-2 was additionally placed on exposed pulps with MTA. After 2 weeks and 7 weeks, rats were killed and histologic sections assessed by light microscopy. RESULTS In MTT assay, the viability was higher in the MTA with BMP-2 group than in the MTA-only group up to 24 hours, but was not significantly different thereafter. In animal study, inflammation was higher in the MTA-only group than in the MTA with BMP group, although this difference did not attain statistical significance. CONCLUSIONS The addition of BMP-2 had a beneficial effect in vitro, reducing the initial cytotoxicity of freshly mixed MTA. However, the pulp reaction to a combination of MTA and BMP-2 was not significantly better than use of MTA alone.

Evaluation of physical and biologic properties of the mixture of mineral trioxide aggregate and 4-META/MMA-TBB resin.

OBJECTIVE This study examined whether 4-methacryloxyethyl trimellitate anhydride/methylmethacrylate-tri-n-butyl borane (4-META/MMA-TBB) resin can be used with mineral trioxide aggregate (MTA) to overcome MTAs shortcomings. The biologic reactions of the mixture of MTA powder and 4-META/MMA-TBB resin (MTA/4-META) and its potential in clinical applications were also investigated. STUDY DESIGN MTA powder was mixed with 4-META/MMA-TBB resin instead of water at the appropriate proportions determined by a series of studies prior to this experiment. MTA powder mixed with sterile water was used as control. The setting time, compressive strength, pH, and dye leakage of MTA/4-META and MTA were assessed by Gilmore apparatus, universal mechanical testing machine, pH meter, and methylene blue penetration method, respectively. Cytotoxicity also was evaluated by MTT assay with MC3T3-E1 cells. RESULTS The setting time of MTA/4-META was significantly lower than that of MTA: 11.2 ± 0.8 minutes versus 318 ± 56.0 minutes, respectively (P < .05). The mean compressive strength of MTA/4-META after 24 hours was significantly higher than that of MTA: 57.4 ± 11.6 MPa versus 18.7 ± 3.0 MPa, respectively (P < .05). MTA/4-META showed significantly less leakage than MTA (P < .05). The initial pHs for MTA and MTA/4-META at 2 hours were 10.73 ± 0.95 and 10.08 ± 0.13, respectively, and reached plateaus of 10.92 ± 0.31 and 10.54 ± 0.39 at 24 hours, respectively. The pH of MTA was higher than that of MTA/4-META in the entire period, but the differences were only significant up to 48 hours (P < .05). MTA and MTA/4-META both showed no cytotoxicity. CONCLUSIONS 4-META/MMA-TBB resin as a mixing vehicle of MTA powder can improve the setting and handling properties of MTA and may maintain or improve its other biophysical properties.

The effects of bone morphogenetic protein-2 and enamel matrix derivative on the bioactivity of mineral trioxide aggregate in MC3T3-E1cells

Objectives The effects of bone morphogenetic protein-2 (BMP-2) and enamel matrix derivative (EMD) respectively with mineral trioxide aggregate (MTA) on hard tissue regeneration have been investigated in previous studies. This study aimed to compare the osteogenic effects of MTA/BMP-2 and MTA/EMD treatment in MC3T3-E1 cells. Materials and Methods MC3T3-E1 cells were treated with MTA (ProRoot, Dentsply), BMP-2 (R&D Systems), EMD (Emdogain, Straumann) separately and MTA/BMP-2 or MTA/EMD combination. Mineralization was evaluated by staining the calcium deposits with alkaline phosphatase (ALP, Sigma-Aldrich) and Alizarin red (Sigma-Aldrich). The effects on the osteoblast differentiation were evaluated by the expressions of osteogenic markers, including ALP, bone sialoprotein (BSP), osteocalcin (OCN), osteopontin (OPN) and osteonectin (OSN), as determined by reverse-transcription polymerase chain reaction analysis (RT-PCR, AccuPower PCR, Bioneer). Results Mineralization increased in the BMP-2 and MTA/BMP-2 groups and increased to a lesser extent in the MTA/EMD group but appeared to decrease in the MTA-only group based on Alizarin red staining. ALP expression largely decreased in the EMD and MTA/EMD groups based on ALP staining. In the MTA/BMP-2 group, mRNA expression of OPN on day 3 and BSP and OCN on day 7 significantly increased. In the MTA/EMD group, OSN and OCN gene expression significantly increased on day 7, whereas ALP expression decreased on days 3 and 7 (p < 0.05). Conclusions These results suggest the MTA/BMP-2 combination promoted more rapid differentiation in MC3T3-E1 cells than did MTA/EMD during the early mineralization period.

An interesting healing outcome of a replanted immature permanent tooth: a case report.

A case of an avulsed upper left central incisor that was replanted after 3 h in a 7-year-old girl is presented. The tooth showed signs of an acute periapical abscess at 2 weeks after replantation. Apexification with mineral trioxide aggregate (MTA) following application of calcium hydroxide was attempted. At 3-year and 6-month follow-up, the tooth was asymptomatic with adequate clinical function. The radiograph showed resolution of the periapical lesion and apparent radiopaque tissue under MTA plug resembling root end morphology.

A new resin-bonded retrograde filling material.

OBJECTIVE This study determined the physical properties and cytotoxicity of a novel root-end filling material (NRC). STUDY DESIGN NRC is a powder and liquid system. The liquid is composed of hydroxyethylmethacrylate, benzoyl peroxide, toluidine, and toluenesulfinate. And the powder is made of calcium oxide, calcium silicate, and triphenylbismuth carbonate. The setting time, compressive strength, and pH change of NRC and gray and white mineral trioxide aggregate (MTA) were determined according to ISO standardization. MC3T3-E1 cells were cultured on NRC and white MTA for determining MTT scores. The absorbance of formazan was measured at 570 nm with a spectrophotometer. The MTT assay was performed in triplicate and repeated in 2 cultures. One-way analysis of variance was used to determine statistical differences in physical properties and MTT assay (P < .05). RESULTS Mean setting time of materials tested were: NRC 12.5 +/- 0.3 minutes, gray MTA 345.5 +/- 96.2 minutes, and white MTA 318.0 +/- 56.0 minutes. After 24 hours, the mean compressive strengths were: NRC, 21.6 +/- 5.5 MPa, gray MTA: 7.7 +/- 3.3 MPa, and white MTA, 18.9 +/- 3.2 MPa. The pH of the test materials were: NRC 12.0, gray MTA 12.2, and white MTA 11.9. There were no statistically significant differences in compressive strength and pH between white MTA and NRC. The compressive strength of gray MTA was significantly lower than white MTA and NRC (P < .05). The setting time of NRC was significantly lower than white and gray MTA. In MTT assay, both NRC and white MTA were not cytotoxic to MC3T3-E1 cells. CONCLUSIONS It was concluded that the setting time, compressive strength, pH, and initial biocompatibility results of NRC are favorable for a root-end filling material.

Accuracy of Root ZX in teeth with simulated root perforation in the presence of gel or liquid type endodontic irrigant

Objectives To evaluate the accuracy of the Root ZX in teeth with simulated root perforation in the presence of gel or liquid type endodontic irrigants, such as saline, 5.25% sodium hypochlorite (NaOCl), 2% chlorhexidine liquid, 2% chlorhexidine gel, and RC-Prep, and also to determine the electrical conductivities of these endodontic irrigants. Materials and Methods A root perforation was simulated on twenty freshly extracted teeth by means of a small perforation made on the proximal surface of the root at 4 mm from the anatomic apex. Root ZX was used to locate root perforation and measure the electronic working lengths. The results obtained were compared with the actual working length (AWL) and the actual location of perforations (AP), allowing tolerances of 0.5 or 1.0 mm. Measurements within these limits were considered as acceptable. Chi-square test or the Fishers exact test was used to evaluate significance. Electrical conductivities of each irrigant were also measured with an electrical conductivity tester. Results The accuracies of the Root ZX in perforated teeth were significantly different between liquid types (saline, NaOCl) and gel types (chlorhexidine gel, RC-Prep). The accuracies of electronic working lengths in perforated teeth were higher in gel types than in liquid types. The accuracy in locating root perforation was higher in liquid types than gel types. 5.25% NaOCl had the highest electrical conductivity, whereas 2% chlorhexidine gel and RC-Prep gel had the lowest electrical conductivities among the five irrigants. Conclusions Different canal irrigants with different electrical conductivities may affect the accuracy of the Root ZX in perforated teeth.

Cytotoxicity and biocompatibility of Zirconia (Y-TZP) posts with various dental cements

Objectives Endodontically treated teeth with insufficient tooth structure are often restored with esthetic restorations. This study evaluated the cytotoxicity and biological effects of yttria partially stabilized zirconia (Y-TZP) blocks in combination with several dental cements. Materials and Methods Pairs of zirconia cylinders with medium alone or cemented with three types of dental cement including RelyX U200 (3M ESPE), FujiCEM 2 (GC), and Panavia F 2.0 (Kuraray) were incubated in medium for 14 days. The cytotoxicity of each supernatant was determined using 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays on L929 fibroblasts and MC3T3-E1 osteoblasts. The levels of interleukin-6 (IL-6) mRNA were evaluated by reverse transcription polymerase chain reaction (RT-PCR), and IL-6 protein was evaluated by enzyme-linked immunosorbent assays (ELISA). The data were analyzed using one-way ANOVA and Tukey post-hoc tests. A p < 0.05 was considered statistically significant. Results The MTT assays showed that MC3T3-E1 osteoblasts were more susceptible to dental cements than L929 fibroblasts. The resin based dental cements increased IL-6 expression in L929 cells, but reduced IL-6 expression in MC3T3-E1 cells. Conclusions Zirconia alone or blocks cemented with dental cement showed acceptable biocompatibilities. The results showed resin-modified glass-ionomer based cement less produced inflammatory cytokines than other self-adhesive resin-based cements. Furthermore, osteoblasts were more susceptible than fibroblasts to the biological effects of dental cement.

Tissue response of Pro-Root® MTA with rhBMP-2 in pulpotomized rat teeth

The purpose of this study was to investigate whether rhBMP-2 (BMP2) could induce synergistic effect with Pro-RootMTA (MTA) in pulpotomized teeth in the rats. Healthy upper first molars from thirty-two, 10 weeks old, Sprague-Dawley rats were used for this investigation. The molars were exposed with round bur, and light pressure was applied with sterilized cotton to control hemorrhage. 1.2 grams of MTA cement was placed in right first molars as a control group. In left first molars, 1 ㎍ of BMP2 was additionally placed on exposed pulps with MTA. All cavities were back-filled with light-cured glass-ionomer cements. The rats were sacrificed after 2 weeks and 7 weeks, respectively. Then histologic sections were made and assessed by light microscopy. Data were statistically ana- lyzed via student t-test with SPSSWIN 12.0 program (p < 0.05). Inflammation observed in 2 weeks groups were severe compared to the 7 weeks groups. But the differences were not statistically significant. BMP2-addition groups had less inflammation than MTA groups in both periods, though these differences were also not statistically significant. In conclusion, the combination of BMP2 and MTA showed no differences with MTA only for pulpotomy of rat teeth. ABSTRACT

Cytotoxicities and genotoxicities of cements based on calcium silicate and of dental formocresol

Increasing interest is being paid to the toxicities of dental materials. The purpose of this study was to determine the cytotoxicities and genotoxicities of endodontic compounds to Chinese hamster ovary (CHO-K1) reproductive cells. Cultured CHO-K1 cells were treated with dental formocresol, two types of calcium hydroxide paste, and two types of mineral trioxide aggregate cement for 24h. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay was performed on each culture, and the micronucleus frequency was determined by performing a micronucleus assay. Alkaline comet assay and γ-H2AX immunofluorescence assay were used to detect DNA damage. Out of the five materials tested, only dental formocresol significantly increased DNA damage. The mineral trioxide aggregate cements based on calcium silicate were not found to be potentially genotoxic. The data suggest that dental formocresol should not be recommended for use in vital pulp therapy on young teeth.