Ahran Pae

Attachment and growth behaviour of human gingival fibroblasts on titanium and zirconia ceramic surfaces

The attachment, growth behaviour and the genetic effect of human gingival fibroblasts (HGF) cultured on titanium and different zirconia surfaces were investigated. HGF cells were cultured on (1) titanium discs with a machined surface, (2) yttrium-stabilized tetragonal zirconia polycrystals (Y-TZP) with a smooth surface and (3) Y-TZP with 100 microm grooves. The cell proliferation activity was evaluated through a MTT assay at 24 h and 48 h, and the cell morphology was examined by SEM. The mRNA expression of integrin-beta1, type I and III collagen, laminin and fibronectin in HGF were evaluated by RT-PCR after 24 h. From the MTT assay, the mean optical density values for the titanium and grooved zirconia surfaces after 48 h of HGF adhesion were greater than the values obtained for the smooth zirconia surfaces. SEM images showed that more cells were attached to the grooves, and the cells appeared to follow the direction of the grooves. The results of RT-PCR suggest that all groups showed comparable fibroblast-specific gene expression. A zirconia ceramic surface with grooves showed biological responses that were comparable to those obtained with HGF on a titanium surface.

Osteoblastic and osteoclastic differentiation on SLA and hydrophilic modified SLA titanium surfaces

PURPOSE We evaluated the activities of both osteoblastic and osteoclastic differentiation on sandblasted/acid etched (SLA), hydrophilic SLA surfaces (modSLA) and pretreatment titanium (PT). MATERIAL AND METHODS The osteoblastic differentiation was evaluated by alkaline phosphatase analysis and Alizarin Red S staining, and the expression of bone-related proteins, alkaline phosphatase (ALP), runt-related transcription factor 2 (Runx2), osteopontin (OPN), and osteocalcin (OCN), was investigated by reverse transcriptase-polymerase chain reaction (RT-PCR). Primary mice monocytes were expanded and differentiated in the presence of macrophage-colony stimulating factor (M-CSF), and osteoclastic differentiation was evaluated by actin ring formation assay and tartrate-resistant acid phosphatase (TRAP) activity assay. Real-time PCR tests were performed to investigate the expression of gene mRNA expression levels in osteoclast cells. RESULT Differentiation of osteoblasts in the Alizarin Red S test staining and ALP assay was significantly increased in the modSLA surface. The preceding results were supported by the result of RT-PCR for the expression of Runx2, OPN, and OCN. As for osteoclastic activity, differentiated osteoclasts rarely existed on the SLA and modSLA surface with actin ring. The results of real-time PCR and TRAP activity supported the preceding results. CONCLUSION It may be concluded that the modSLA surface promotes osteogenic effect and prevents osteoclastic differentiation. Promotion of osteoblastic proliferation after a short-term cell culture might be responsible for stimulated bone regeneration implying that early loading may be possible. Also, the anti-osteoclastic effect of the modSLA surface may contribute to maintenance of the marginal bone level of dental implants, implying long-term stability would be provided by this surface technology. The modSLA surface may not only make early loading possible but possibly reduce marginal bone loss during the maintenance phase.

The effect of surface treatment of fiber-reinforced posts on adhesion of a resin-based luting agent

STATEMENT OF PROBLEM Surface treatment of fiber-reinforced posts may not always increase adhesion, especially on the post/resin-based luting agent interface, which is a weaker interface than the dentin/adhesive interface. PURPOSE The purpose of this in vitro study was to evaluate the influence of different post surface treatments on the bond strength of a luting agent to a fiber post. MATERIAL AND METHODS Sixty-eight fiber-reinforced posts (D. T. Light-Post) were divided into 4 groups and treated with 1 of the following surface treatment procedures: no treatment (NS) (control), silanization (SA) (Monobond-S), airborne-particle abrasion (AB) (Airsonic Alu-Oxyd), or silanization subsequent to airborne-particle abrasion (AB plus SA). Specimens were bonded with dual-polymerizing resin-based luting material (Variolink II) and stored in water at 37 degrees C for 24 hours. Shear bond strength (MPa) was measured using a universal testing machine. Data were analyzed with 1-way ANOVA and the multiple comparisons Scheffé test with Bonferroni correction (alpha=.05). RESULTS Shear bond strength of the luting agent to the post was significantly affected by surface treatment (P<.05). Treating the surface of the post with airborne-particle abrasion resulted in a significantly higher bond strength compared with other treatments. There was no significant difference in bond strength between the silanization group and the no treatment group or the silanization plus airborne-particle abrasion group. CONCLUSIONS Airborne-particle abrasion provided a significant increase in bond strength between the post and the luting agent evaluated, without additional treatments.

Retrospective study on traumatic dental injuries in preschool children at Kyung Hee Dental Hospital, Seoul, South Korea

The purpose of this study was to analyse the traumatic dental injuries (TDI) of Korean preschoolers by investigating the occurrence, type, area, cause, injured region, seasonal variation and the interval between injury and treatment. In this study, data from 1856 preschoolers aged 4 months to 6 years and 11 months (mean age : 3.6 +/- 1.6) were used, out of a total of 2761 patients who attended the Department of Pediatric Dentistry, Kyung Hee Dental Hospital for TDI between January 1998 and December 2007. All the data were statistically analysed using the anova and chi-square statics. Most of the patients were 1-2, 2-3 years old (24.5%, 25.4%) and boys were 1.67 times more likely to have TDI. The most common cause, location and seasonal variation of the trauma, were respectively falling (50.8%), at home (48.8%) and late spring. The treatment intervals usually occurred within a day. Most of the injuries involved single (47%) or double (38%) tooth/teeth. However, car accidents or sports trauma often involved multiple teeth. In both primary and permanent dentition, the most common teeth injured were maxillary central incisors (72.6%), and periodontal injury was caused by subluxation or concussion. Among the various types of hard tissue injuries, enamel fracture in the primary dentition (35.0%) and enamel-dentin fracture in the permanent dentition (45.8%) were the most common types.

The effects of enamel matrix derivative on the proliferation and differentiation of human mesenchymal stem cells

PURPOSE This study was designed to investigate the effect of enamel derivative matrix (EMD) on the proliferation, mineralization, and differentiation of human mesenchymal stem cells (hMSCs). MATERIAL AND METHODS For the proliferation assay, water-soluble tetrazolium salt-8 tests were carried out after culturing for 24 and 48 h. For the evaluation of mineralization, Alizarin red S (ARS) tests were performed after 21 days of culturing in an osteogenic medium. In order to investigate some of the bone-related proteins, namely type I collagen (Col I A2), bone sialoprotein (BSP), and bone gamma-carboxyglutamate (Gla) protein (BGLAP, osteocalcin), real-time polymerase chain reaction (RT-PCR) tests were carried out after 2, 3, and 4 weeks of culturing, respectively. RESULTS The activity of proliferation and mineralization increased significantly depending on the concentration of EMD (P<0.05). In the control group, the expression of Col I A2 decreased, but EMD enhanced its expression over time and was correlated to the concentration. The amount of expression of BSP in this group increased over time, but EMD strikingly suppressed its expression in the fourth week. As well, the amount of expression of BGLAP increased as the culture duration lengthened in the control group. However, the expression of BGLAP was suppressed in the experimental group with EMD. CONCLUSION Within the limits of this study, EMD enhanced the proliferation of hMSCs. After evaluation with ARS staining, EMD seemed to enhance mineralization, and the RT-PCR test revealed that EMD promoted early-stage osteoblast differentiation by enhancing Col I A2 expression, but exerted an inhibitory effect on the mineralization by lowering the gene expression of BSP and BGLAP. Mineralized nodules formed with EMD may be composed of substances other than normal bone. Because most of the organic matrix of bone is type I collagen, which acts as the mineralization site, bone or bone-like mineralized mass might have been formed in spite of the different components of the non-collagenous proteins.

Immediate loading of two implants supporting a magnet attachment-retained overdenture: one-year clinical study.

Purpose:The aim of this 1-year evaluation was to assess the stability of implants and the responses of the supporting tissues to magnet-retained mandibular implant overdentures. Methods:Six patients with completely edentulism were enrolled in this study. Each patient received 2 implants with sandblasted with large-grit and acid-etched surfaces in the interforaminal region. The implants were loaded immediately with magnet attachment-retained overdentures. The stability of the implants and periimplant tissues was examined by performing clinical examinations, resonance frequency analysis, and radiographic examinations at 1, 2, 6, 12, and 24 weeks and 1 year after surgery. Results:Two implants in 2 patients failed. The surviving implants were clinically and radiographically stable. The mean Implant Stability Quotient values were relatively stable, showing no significant differences (P > 0.05). The crestal bone changes were −1.18 ± 0.68 mm, −1.35 ± 0.69 mm, −1.47 ± 0.68 mm, and −1.51 ± 0.74 mm at the follow-up check performed at 6, 12, and 24 weeks and 1 year, respectively. The bleeding on probing index was not significant. Conclusions:The immediate loading of 2 implants using magnet attachment-retained mandibular overdentures may be a viable treatment option in cases of complete arch edentulism. This clinical approach offers increased stability to conventional dentures.

Accurate transfer of soft tissue morphology with interim prosthesis to definitive cast

With conventional fixed dental prostheses, the interim restoration is a valuable diagnostic tool in the evaluation of esthetics and function. To achieve predictable definitive esthetic results, information about the subgingival and the supragingival contour of a properly designed restoration should be communicated to the dental laboratory technician. The technique described enables the accurate transfer of the soft tissue morphology developed with an interim prosthesis to the definitive cast. This modified definitive cast allows the dental laboratory technician to fabricate a restoration with an emergence profile identical to that of the interim prosthesis.

The effects of mouthguards on the athletic ability of professional golfers

The purpose of this study was to determine the effect of stabilization splints and mouthguards on the athletic ability of professional golfers. For this study, eight professional golfers with a mean age of 20.5 were selected. These participants performed four trials of 10 driver swings and 10 putts with or without a stabilization splint (control group) or mouthguard. For the 4th trial, the splints were adjusted using a simple blind test so that the participants were unaware of the unilateral molar contact. The drive distance, club head speed, initial ball speed, and putting accuracy were compared and analyzed before and after the application of equal bilateral molar occlusion. When the bilateral molar occlusion was applied using a mouthguard or stabilization splint, the club head speed and driving distance in the presence of the oral appliances were significantly increased compared with those without the presence of either appliance (P < 0.05). Alternatively, the initial ball speed and putting accuracy in the presence of these appliances were increased compared with those without the presence of an appliance; however, this effect was not statistically significant. When the mouthguards or stabilization splints were adjusted to result in unilateral molar occlusion, the club head speed and driving distance in the presence of the appliances were significantly decreased compared with those that were obtained without these appliances (P < 0.05). The initial ball speed and the putting accuracy were not affected by the use of the appliances. No difference was observed in the effectiveness of the stabilization splint and mouthguard when bilateral molar occlusion was performed. The occlusion stability that results from stabilization splints and mouthguards is thought to increase the club head speed and driving distance in professional golf players.

Wettability of denture relining materials under water storage over time

STATEMENT OF PROBLEM Poor wettability of denture relining materials may lead to retention problems and patient discomfort. PURPOSE Purpose of this study is to compare and evaluate wettability of nine denture relining materials using contact angle measurements under air and water storage over time. MATERIAL AND METHODS Nine denture relining materials were investigated in this study. Two heat-curing polymethyl-methacrylate (PMMA) denture base materials: Vertex RS, Lang, one self-curing polyethyl-methacrylate (PEMA) chairside reline resin: Rebase II, six silicone relining materials: Mucopren soft, Mucosoft, Mollosil® plus, Sofreliner Touch, GC Reline™ Ultrasoft, Silagum automix comfort were used in this experiment. Contact angles were measured using high-resolution drop shape analysis system (DSA 10-MK2, KRUESS, Germany) under three conditions (in air after setting, 1 hour water storage, and 24 hours water storage). Nine materials were classified into three groups according to material composition (Group 1: PMMA, Group 2: PEMA, Group 3: Silicone). Mean values of contact angles were compared using independent samples t-test and one-way ANOVA, followed by a Scheffes post hoc analysis (α= 0.01). RESULTS Contact angles of materials tested after air and water storage increased in the following order: Group 1 (PMMA), Group 2 (PEMA), Group 3 (Silicone). Heat-cured acrylic denture base resins had more wettability than silicone relining materials. Lang had the highest wettability after 24 hours of water storage. Silicone relining materials had lower wettability due to their hydrophobicity. Wettability of all denture relining materials, except Rebase II and Mollosil® plus, increased after 24 hours of water storage. CONCLUSIONS Conventional heat-cured resin showed the highest wettability, therefore, it can be suggested that heat-cured acrylic resin is material of choice for denture relining materials.

Cellular viability and genetic expression of human gingival fibroblasts to zirconia with enamel matrix derivative (Emdogain

PURPOSE The objective of this study was to investigate the biologic effects of enamel matrix derivative (EMD) with different concentrations on cell viability and the genetic expression of human gingival fibroblasts (HGF) to zirconia surfaces. MATERIALS AND METHODS Immortalized human gingival fibroblasts (HGF) were cultured (1) without EMD, (2) with EMD 25 µg/mL, and (3) with EMD 100 µg/mL on zirconia discs. MTT assay was performed to evaluate the cell proliferation activity and SEM was carried out to examine the cellular morphology and attachment. The mRNA expression of collagen type I, osteopontin, fibronectin, and TGF-β1 was evaluated with the real-time polymerase chain reaction (RT-PCR). RESULTS From MTT assay, HGF showed more proliferation in EMD 25 µg/mL group than control and EMD 100 µg/mL group (P<.05). HGFs showed more flattened cellular morphology on the experimental groups than on the control group after 4h culture and more cellular attachments were observed on EMD 25 µg/mL group and EMD 100 µg/mL group after 24h culture. After 48h of culture, cellular attachment was similar in all groups. The mRNA expression of type I collagen increased in a concentration dependent manner. The genetic expression of osteopontin, fibronectin, and TGF-β1 was increased at EMD 100 µg/mL. However, the mRNA expression of proteins associated with cellular attachment was decreased at EMD 25 µg/mL. CONCLUSION Through this short term culture of HGF on zirconium discs, we conclude that EMD affects the proliferation, attachment, and cell morphology of HGF cells. Also, EMD stimulates production of extracellular matrix collagen, osteopontin, and TGF-β1 in high concentration levels. CLINICAL RELEVANCE With the use of EMD, protective barrier between attached gingiva and transmucosal zirconia abutment may be enhanced leading to final esthetic results with implants.