Purpose: The effect of accelerated aging on color stability of various dual-cured self-adhesive resin cements were evaluated in this study. Materials and Methods: Color stability was examined using three different brands of dual-cured self-adhesive resin cements: G-CEM LinkAce (GC America), MaxCem Elite (Kerr), and PermaCem 2.0 (DMG) with the equivalent color shade. Each resin cement was filled with Teflon mold which has 6 mm diameter and 2 mm thickness. Each specimen was light cured for 20 seconds using light emitting diode (LED) light curing unit. In order to evaluate the effect of accelerated aging on color stability, color parameters (Commission Internationale de l'Eclairage, CIE $L^*$, $a^*$, $b^*$) and color differences (${\Delta}E^*$) were measured at three times: immediately, after 24 hours, and after thermocycling. The $L^*$, $a^*$, $b^*$ values were analyzed using Friedman test and ${\Delta}E^*$ values on the effect of 24 hours and accelerated aging were analyzed using t-test. These values were compared with the limit value of color difference (${\Delta}E^*=3.7$) for dental restoration. One-way ANOVA and Scheff's test (P<0.05) were performed to analyze each ${\Delta}E^*$ values between cements at each test period. Result: There was statistically significant difference in comparison of color specification ($L^*$, $a^*$, $b^*$) values after accelerated aging except $L^*$ value of G-CEM LinkAce (P<0.05). After 24 hours, color difference (${\Delta}E^*$) values were ranged from 2.47 to 3.48 and $L^*$ values decreased and $b^*$ values increased in all types of cement and MaxCem Elite had high color stability (P<0.05). After thermocycling, color change's tendency of cement was varied and color difference (${\Delta}E^*$) values were ranged from 0.82 to 2.87 and G-CEM LinkAce had high color stability (P<0.05). Conclusion: Color stability of dual-cured self-adhesive resin cements after accelerated aging was evaluated and statistically significant color changes occurred within clinically acceptable range.

Purpose: This study was conducted to determine cell viability and differentiation capability of human periodontal ligament (PDL) cells and to elucidate the effects of cryopreservation on the activity of human third molar PDL cells by comparing PDL cells with and without cryopreservation. Materials and Methods: Human PDL fibroblasts obtained from immature third molars were cultured and divided into two groups. The experimental group was cryopreserved with a slow freezing rate of $0.5^{\circ}C/min$ from $4^{\circ}C$ to $-35^{\circ}C$ followed by plunging in liquid nitrogen at $-196^{\circ}C$ and cultured after fast thawing. The control group was cultured without cryopreservation. Cell viability, growth capacity and morphology were evaluated in both groups. Bivariate statistics were used to compare 2 groups and linear mixed model analysis was used to investigate the growth trends difference over time. Result: Cell viability and growth capacity were not significantly different between the 2 groups (P>0.05). Cultured cell of both groups showed fibroblast-like in appearance, and there were no significant differences in morphology between 2 groups. The mixed model analysis revealed no significant difference of growth capacity between 2 groups over time (${\beta}=-0.0009$; P=0.138). Conclusion: This study demonstrates that cryopreservation under control does not affect the biological properties of PDL cells, supporting the feasibility of autotransplantation of cryopreserved impacted third molars.

Purpose: Parathyroid hormone (PTH) therapy has drawn attention, as an alternative to anti-resorptive drugs since PTH accelerates bone density by anabolic action. The purpose of this study was to identify the effect of intermittent PTH administration on jaw bones of rat undergone bilateral ovariectomy. Materials and Methods: Nine female Sprague-Dawley rats were divided into three groups. PTH group was ovariectomized (OVX) to induce osteoporosis and PTH $30{\mu}g/kg$ was administered 1 week after the surgery. In OVX group, ovariectomy was performed and only vehicle was administered by subcutaneous injection 3 times per week. Control group was subjected to sham surgery. The animals were sacrificed 8 weeks after the surgery and specimens were obtained from ilium and upper and lower jaw bones. Histological investigation was carried out by using an optical microscope and micro-computed tomography was taken to examine structural property changes in each bone sample. Result: In the ilium, the bone volume ratio (bone volume/total volume, BV/TV) of PTH, OVX and control groups was $53.75%{\pm}7.57%$, $50.61%{\pm}12.89%$, $76.20%{\pm}5.92%$ (P=0.061) and bone mineral density (BMD) was $1.12{\pm}0.09$, $0.88{\pm}0.48$, $1.38{\pm}0.07g/cm^3$ (P=0.061). In the mandible, BV/TV of PTH, OVX and control groups was $64.60%{\pm}12.17%$, $58.26%{\pm}9.63%$, $67.54%{\pm}14.74%$(P=0.670) and BMD was $1.21{\pm}0.17$, $1.19{\pm}0.13$, $1.27{\pm}0.18g/cm^3$ (P=0.587). In the maxilla, BV/TV of PTH, OVX and control groups was $61.19%{\pm}8.92%$, $52.50%{\pm}11.22%$, $64.60%{\pm}12.17%$ (P=0.430) and BMD was $1.20{\pm}0.11$, $1.11{\pm}0.16$, $1.21{\pm}0.17g/cm^3$ (P=0.561). No statistically significant difference was found in any variables in all groups. Histological observation revealed that the ilium in OVX group demonstrated sparsely formed trabecular bones compared with other groups. However, upper and lower trabecular bones did not present significant differences. Conclusion: Intermittent administration of PTH appears to affect the microstructure of rat jaw bones, but statistical significance was not found. However, the measurements in this study partly implicated the possible anabolic effect of PTH in vivo.

Purpose: In osteoclast differentiation, actin-rich membrane protrusions play a crucial role in cell adhesion. Odontogenic ameloblast-associated protein (Odam) contributes to cell adhesion by inducing actin rearrangement. Odam-mediated RhoA activity may play a significant role in multinucleation of osteoclasts. However, the precise function of Odam in osteoclast cell adhesion and differentiation remains largely unknown. Here, we identify a critical role for Odam in inducing osteoclast adhesion and differentiation. Materials and Methods: The expression of Odam in osteoclasts was evaluated by immunohistochemistry. Primary mouse bone marrow and RAW264.7 cells were used to test the cell adhesion and actin ring formation induced by Odam. Result: Odam was expressed in osteoclasts around alveolar bone. Odam transfection induced actin filament rearrangement and cell adhesion compared with the control or collagen groups. Overexpression of Odam promoted actin stress fiber remodeling and cell adhesion, resulting in increased osteoclast fusion. Conclusion: These results suggest that Odam expression in primary mouse osteoclasts and RAW264.7 cells promotes their adhesion, resulting in the induction of osteoclast differentiation.

Purpose: To evaluate the effect of light-curing on the immediate and delayed micro-shear bond strength (${\mu}SBS$) between yttria-tetragonal zirconia polycrystal (Y-TZP) ceramics and RelyX Ultimate when using Single Bond Universal (SBU). Materials and Methods: Y-TZP ceramic specimens were ground with #600-grit SiC paper. SBU was applied and RelyX Ultimate was mixed and placed on the Y-TZP surface. The specimens were divided into three groups depending on whether light curing was done after adhesive (SBU) and resin cement application: uncured after adhesive and uncured after resin cement application (UU); uncured after adhesive, but light cured after resin cement (UC); and light cured after adhesive and light cured resin cement (CC). The three groups were further divided depending on the timing of ${\mu}SBS$ testing: immediate at 24 hours (UUI, UCI, CCI) and delayed at 4 weeks (UUD, UCD, CCD). ${\mu}SBS$ was statistically analyzed using one-way ANOVA and Student-Newman-Keuls multiple comparison test (P<0.05). The surface of the fractured Y-TZP specimens was analyzed under a scanning electron microscope (SEM). Result: At 24 hours, ${\mu}SBS$ of UUI group ($8.60{\pm}2.06MPa$) was significantly lower than UCI group ($25.71{\pm}4.48MPa$) and CCI group ($29.54{\pm}3.62MPa$) (P<0.05). There was not any significant difference between UCI and CCI group (P>0.05). At 4 weeks, ${\mu}SBS$ of UUD group ($24.43{\pm}2.88MPa$) had significantly increased over time compared to UUI group (P<0.05). The SEM results showed mixed failure in UCI and CCI group, while UUI group showed adhesive failure. Conclusion: Light-curing of universal adhesive before or after application of RelyX Ultimate resin cement significantly improved the immediate ${\mu}SBS$ of resin cement to air-abrasion treated Y-TZP surface. After 4 weeks, the delayed ${\mu}SBS$ of the non-light curing group significantly improved to the level of light-cured groups.

As popularity of dental implantation is increasing, the number of cases associated with complications also increase. Evaluation on diabetes mellitus is often neglected due to the disease's irrelevance to implantability. However, patients with diabetes mellitus are susceptible to infection due to impaired bactericidal ability of neutrophils, cellular immunity and activity of complements. Due to this established connection between diabetes mellitus and infection, a couple of cases were selected to present patients with diabetes mellitus with glycemic incontrollability, suffering from post-implantation dentigerous inter-fascial space abscess.