Sung-Ok Hong

Simvastatin Promotes Odontoblastic Differentiation and Expression of Angiogenic Factors via Heme Oxygenase-1 in Primary Cultured Human Dental Pulp Cells

INTRODUCTION Although simvastatin has multiple demonstrable effects, its function in dentinogenesis remains unclear. In this study, we tested the hypothesis that the addition of simvastatin to human dental pulp cells (HDPCs) stimulates odontogenesis both by promoting odontoblastic differentiation and by favoring the release of angiogenic factors. In addition, the role of heme oxygenase-1 (HO-1) in these effects was investigated. METHODS The expression of markers for odontoblastic differentiation and angiogenesis was analyzed by means of alkaline phosphatase (ALP) activity, alizarin red staining, and Western blotting. RESULTS Simvastatin enhanced the differentiation of HDPCs by up-regulating mineralization nodules and odontogenic markers as well as angiogenic markers. These phenomena were then correlated with the induction of HO-1 protein levels. The inducing effect of simvastatin on odontoblastic differentiation and angiogenesis was nullified by an HO-1 inhibitor and a carbon monoxide (CO) scavenger. CONCLUSIONS These results suggested that simvastatin exerts its odontoblastic differentiation and angiogenesis-inducing effects in HDPCs through a mechanism that involves the action of HO-1 and its product CO.

Odontogenic Effect of a Fast-setting Pozzolan-based Pulp Capping Material

INTRODUCTION Mineral trioxide aggregate (MTA) is widely used as a pulp capping material. Recently, a MTA-derived fast-setting pozzolan cement (Endocem; Maruchi, Wonju, Korea) was introduced in the endodontic field. Our aim in this study was to investigate the odontogenic effects of this cement in vitro and in vivo. METHODS Human dental pulp cells (hDPCs) were cultured, and the effects of Endocem and a previously marketed MTA (ProRoot; Dentsply, Tulsa, OK) on biocompatibility were evaluated by assessing cell morphology and performing a cell viability test. Chemical composition of each material was analyzed by energy-dispersive X-ray spectroscopic analysis. Odontoblastic differentiation was analyzed by alkaline phosphatase activity and alizarin red S staining. The expression of odontogenic-related markers, namely dentin sialophosphoprotein, dentin matrix protein 1, and osteonectin, was evaluated by real-time polymerase chain reaction, Western blotting, and immunofluorescence analysis. Pinpoint pulp exposures were made on rat teeth and then capped with ProRoot or Endocem. After 4 weeks, reparative tertiary dentin formation and inflammatory responses were investigated histologically. RESULTS The biocompatibility of Endocem was similar to that of ProRoot. Energy-dispersive X-ray spectroscopic analysis showed that ProRoot and Endocem contained similar elemental constituents such as calcium, oxygen, and silicon. Alkaline phosphatase activity and mineralized nodule formation increased in ProRoot- and Endocem-treated cells compared with medium only-treated cells in the control group (P < .05). The expression of odontogenic-related markers was significantly higher in the ProRoot- and Endocem-treated groups than the control group (P < .05), but there was no significant difference in the expression of these markers between the 2 experimental groups (P > .05). Four weeks after the pulp capping procedure, continuous tertiary dentin had formed directly underneath the capping materials and the pulp exposure area in all samples in the 2 treated groups. Furthermore, most specimens either had no inflammation or minor pulpal inflammation. CONCLUSIONS Our results indicate that ProRoot and Endocem have similar biocompatibility and odontogenic effects. Therefore, Endocem is as effective a pulp capping material as ProRoot.

effect of a multi-layer infection control barrier on the micro-hardness of a composite resin

Objective The aim of this study was to evaluate the effect of multiple layers of an infection control barrier on the micro-hardness of a composite resin. Material and Methods One, two, four, and eight layers of an infection control barrier were used to cover the light guides of a high-power light emitting diode (LED) light curing unit (LCU) and a low-power halogen LCU. The composite specimens were photopolymerized with the LCUs and the barriers, and the micro-hardness of the upper and lower surfaces was measured (n=10). The hardness ratio was calculated by dividing the bottom surface hardness of the experimental groups by the irradiated surface hardness of the control groups. The data was analyzed by two-way ANOVA and Tukeys HSD test. Results The micro-hardness of the composite specimens photopolymerized with the LED LCU decreased significantly in the four- and eight-layer groups of the upper surface and in the two-, four-, and eight-layer groups of the lower surface. The hardness ratio of the composite specimens was <80% in the eight-layer group. The micro-hardness of the composite specimens photopolymerized with the halogen LCU decreased significantly in the eight-layer group of the upper surface and in the two-, four-, and eight-layer groups of the lower surface. However, the hardness ratios of all the composite specimens photopolymerized with barriers were <80%. Conclusions The two-layer infection control barrier could be used on high-power LCUs without decreasing the surface hardness of the composite resin. However, when using an infection control barrier on the low-power LCUs, attention should be paid so as not to sacrifice the polymerization efficiency.

Power density of light curing units through resin inlays fabricated with direct and indirect composites

Objectives: The purpose of this study was to measure the power density of light curing units transmitted through resin inlays fabricated with direct composite (Filtek Z350, Filtek Supreme XT) and indirect composite (Sinfony). Materials and Methods: A3 shade of Z350, A3B and A3E shades of Supreme XT, and A3, E3, and T1 shades of Sinfony were used to fabricate the resin inlays in 1.5 mm thickness. The power density of a halogen light curing unit (Optilux 360) and an LED light curing unit (Elipar S10) through the fabricated resin inlays was measured with a hand held dental radiometer (Cure Rite). To investigate the effect of each composite layer consisting the resin inlays on light transmission, resin specimens of each shade were fabricated in 0.5 mm thickness and power density was measured through the resin specimens. Results: The power density through the resin inlays was lowest with the Z350 A3, followed by Supreme XT A3B and A3E. The power density was highest with Sinfony A3, E3, and T1 (p

Power density of various light curing units through resin inlays with modified layer thickness

Objectives The purpose of this study was to enhance curing light penetration through resin inlays by modifying the thicknesses of the dentin, enamel, and translucent layers. Materials and Methods To investigate the layer dominantly affecting the power density of light curing units, resin wafers of each layer with 0.5 mm thickness were prepared and power density through resin wafers was measured with a dental radiometer (Cure Rite, Kerr). The dentin layer, which had the dominant effect on power density reduction, was decreased in thickness from 0.5 to 0.1 mm while thickness of the enamel layer was kept unchanged at 0.5 mm and thickness of the translucent layer was increased from 0.5 to 0.9 mm and vice versa, in order to maintain the total thickness of 1.5 mm of the resin inlay. Power density of various light curing units through resin inlays was measured. Results Power density measured through 0.5 mm resin wafers decreased more significantly with the dentin layer than with the enamel and translucent layers (p < 0.05). Power density through 1.5 mm resin inlays increased when the dentin layer thickness was reduced and the enamel or translucent layer thickness was increased. The highest power density was recorded with dentin layer thickness of 0.1 mm and increased translucent layer thickness in all light curing units. Conclusions To enhance the power density through resin inlays, reducing the dentin layer thickness and increasing the translucent layer thickness would be recommendable when fabricating resin inlays.

Effect of infection control barrier thickness on light curing units

Objectives: This study investigated the effect of infection control barrier thickness on power density, wavelength, and light diffusion of light curing units. Materials and Methods: Infection control barrier (Cleanwrap) in one-fold, two-fold, four-fold, and eightfold, and a halogen light curing unit (Optilux 360) and a light emitting diode (LED) light curing unit (Elipar FreeLight 2) were used in this study. Power density of light curing units with infection control barriers covering the fiberoptic bundle was measured with a hand held dental radiometer (Cure Rite). Wavelength of light curing units fixed on a custom made optical breadboard was measured with a portable spectroradiometer (CS-1000). Light diffusion of light curing units was photographed with DSLR (Nikon D70s) as above. Results: Power density decreased significantly as the layer thickness of the infection control barrier increased, except the one-fold and two-fold in halogen light curing unit. Especially, when the barrier was four-fold and more in the halogen light curing unit, the decrease of power density was more prominent. The wavelength of light curing units was not affected by the barriers and almost no change was detected in the peak wavelength. Light diffusion of LED light curing unit was not affected by barriers, however, halogen light curing unit showed decrease in light diffusion angle when the barrier was four-fold and statistically different decrease when the barrier was eight-fold ( p < 0.05). Conclusions: It could be assumed that the infection control barriers should be used as two-fold rather than one-fold to prevent tearing of the barriers and subsequent cross contamination between the patients. [J Kor

Finite element analysis on stress distribution of maxillary implant-retained overdentures depending on the Bar attachment design and palatal coverage

PURPOSE The purpose of this study was to determine the effect of anchorage systems and palatal coverage of denture base on load transfer in maxillary implant-retained overdenture. MATERIALS AND METHODS Maxillary implant-retained overdentures with 4 implants placed in the anterior region of edentulous maxilla were converted into a 3-D numerical model, and stress distribution patterns in implant supporting bone in the case of unilateral vertical loading on maxillary right first molar were compared with each other depending on various types of anchorage system and palatal coverage extent of denture base using three-dimensional finite element analysis. RESULTS In all experimental models, the highest stress was concentrated on the most distal implant and implant supporting bone on loaded side. The stress at the most distal implant-supporting bone was concentrated on the cortical bone. In all anchorage system without palatal coverage of denture base, higher stresses were concentrated on the most distal implant and implant supporting bone on loaded side. CONCLUSION It could be suggested that when making maxillary implant retained overdenture, using Hader bar instead of milled bar and full palatal coverage rather than partial palatal coverage are more beneficial in distributing the stress that is applied on implant supporting bone.

The effect of saliva decontamination procedures on dentin bond strength after universal adhesive curing.

Objectives The purpose of this study was to investigate the effectiveness of multiple decontamination procedures for salivary contamination after curing of a universal adhesive on dentin bond strength according to its etch modes. Materials and Methods Forty-two extracted bovine incisors were trimmed by exposing the labial dentin surfaces and embedded in cylindrical molds. A universal adhesive (All-Bond Universal, Bisco) was used. The teeth were randomly divided into groups according to etch mode and decontamination procedure. The adhesive was applied according to the manufacturers instructions for a given etch mode. With the exception of the control groups, the cured adhesive was contaminated with saliva for 20 sec. In the self-etch group, the teeth were divided into three groups: control, decontamination with rinsing and drying, and decontamination with rinsing, drying, and adhesive. In the etch-and-rinse group, the teeth were divided into four groups: control, decontamination with rinsing and drying, decontamination with rinsing, drying, and adhesive, and decontamination with rinsing, drying, re-etching, and reapplication of adhesive. A composite resin (Filtek Z350XT, 3M ESPE) was used for filling and was cured on the treated surfaces. Shear bond strength was measured, and failure modes were evaluated. The data were subjected to one-way analysis of variation and Tukeys HSD test. Results The etch-and-rinse subgroup that was decontaminated by rinse, drying, re-etching, and reapplication of adhesive showed a significantly higher bond strength. Conclusions When salivary contamination occurs after curing of the universal adhesive, additional etching improves the bond strength to dentin.

Healing outcomes of root canal treatment for C-shaped mandibular second molars: a retrospective analysis.

Objectives This study aimed to evaluate the healing rate of non-surgical endodontic treatment between C-shaped and non-C-shaped mandibular second molars. Materials and Methods Clinical records and radiological images of patients who had undergone endodontic treatment on mandibular second molars between 2007 and 2014 were screened. The periapical index scoring system was applied to compare healing outcomes. Information about preoperative and postoperative factors as well as the demographic data of the patients was acquired and evaluated using chi-square and multinomial logistic regression tests. Results The total healing rate was 68.4%. Healing rates for the mandibular second molar were 70.9% in C-shaped canals (n = 79) and 66.6% in non-C-shaped ones (n = 117). The difference was not statistically significant. Conclusions The presence of a C-shaped canal in the mandibular second molar did not have a significantly negative effect on healing after treatment. Instead, proper pulpal diagnosis and final restoration were indicated as having significantly greater influence on the healing outcomes of C-shaped and non-C-shaped canals, respectively.

Endodontic management of mandibular first premolar with C-shaped canals by using cone-beam computed tomography and dental operating microscope

Aberrant anatomy of mandibular premolars is very rare in Korean, but aberration can contribute the endodontic failure as it makes difficult to remove the irritants during cleaning and shaping procedure. This case report describes the successful root canal treatment of a rare mandibular first premolar with C-shaped root canal as using a cone-beam computed tomography to understand the internal shape of root canal system and a dental operating microscope to improve the magnification and illumination.