Yoon-Goo Kang

Compressive stress induced the up-regulation of M-CSF, RANKL, TNF-α expression and the down-regulation of OPG expression in PDL cells via the integrin-FAK pathway

OBJECTIVES This study was performed to elucidate the involvement of integrin-FAK (focal adhesion kinase) pathway in compressive stress-induced mRNA expression of macrophage colony stimulating factor (M-CSF), tumour necrosis factor (TNF)-α, receptor activator of nuclear factor κB (RANKL) and osteoprotegerin (OPG) and to further confirm the role of the integrin-FAK complex as a mechanoreceptor in PDL cells. DESIGN Periodontal ligament (PDL) cells were obtained from patients having healthy first premolars extracted for orthodontic purposes. Cultured PDL cells were divided into three groups: the control group in which compressive stress was administered; the negative control group in which mechanical stress was administered after transfection of negative control siRNA; and FAK knockdown group in which mechanical stress was administered after FAK siRNA treatment. Compressive stress (2g/cm(2)) was for various time durations (0.5, 2, 6, 24, 48h). Total RNA was collected after the experiment and real-time PCR analysis was performed to determine the mRNA expression levels of M-CSF, TNF-α, RANKL and OPG. Also the supernatant was analysed with ELISA to detect the corresponding cytokine concentrations. RESULTS The cells of the control group and the negative control group expressed higher mRNA levels of M-CSF, TNF-α, and RANKL but a lower mRNA level of OPG compared to those of baseline. FAK knockdown cells showed lower mRNA expression levels of M-CSF, TNF-α, and RANKL but a higher mRNA expression level of OPG than that in the control. The OPG mRNA expression level in FAK knockdown cells was even higher than that of baseline. ELISA results showed similar pattern of cytokine concentration changes. CONCLUSIONS Results of this study indicate that the integrin-FAK pathway regulates compressive stress-induced expression of M-CSF, TNF-α, RANKL and OPG and suggests that the integrin-FAK complex acts as a mechanoreceptor in PDL cells.

Stability of Mini-Screws Invading the Dental Roots and Their Impact on the Paradental Tissues in Beagles

OBJECTIVE To examine the stability of mini-screws that invade a dental root by measuring the retention period/failure rate, and to illustrate their effects on paradental tissues. MATERIALS AND METHODS Three adult male beagle dogs received 48 orthodontic mini-screws. Half of the mini-screws were implanted to invade the roots, and the rest were placed in the middle of the alveolar bone. Half of the mini-screws were loaded immediately. The retention period of the mini-screws was documented. The dogs were euthanized after 8 weeks, and tissue samples were examined histologically. RESULTS The failure rate of the mini-screws that invaded the roots was 79.2%, and that of the mini-screws in the middle of the alveolar bone was 8.3%. The application of force had little effect on the failed mini-screws. Moderately injured roots were repaired with osteoid and/or cementoid tissues with normal periodontal ligaments, followed by recovery of the original configuration. CONCLUSION Orthodontic mini-screws had a higher failure rate when placed to invade the dental roots. However, minimally damaged dental roots do not adversely affect the healing process.

Orthodontic miniplate with tube as an efficient tool for borderline cases

An orthodontic miniplate tube device, the C-tube, was designed for use in patients for whom a conventional miniscrew is not suitable, such as those with narrow interradicular spaces, extended maxillary sinuses, dilacerated roots, or severe alveolar bone loss. After local anesthesia, 2 parallel horizontal incisions are made in the area of placement, and the periosteum is elevated. The C-tube is slipped under the mucosal flap and fixed with self-drilling miniscrews (diameter, 1.5 mm; length, 4 mm). Because the screws are short, there is adequate retention in the alveolar plate, and the clinician can avoid the increased morbidity of anchoring to the zygomatic buttress. This makes placement possible with superficial anesthesia. A small rolled tube at the head part can act as an orthodontic tube and accommodate archwires or as a hook to attach orthodontic elastics. However, in some patients with pneumatization or systemic diseases, such as diabetes mellitus, or in heavy smokers, cross-type C-tubes with longer miniscrews are recommend for better stability. This new type of orthodontic miniplate can be an effective alternative to conventional 1-component screws or miniplates in complex situations.

Mechanical stress-activated immune response genes via Sirtuin 1 expression in human periodontal ligament cells

Recently, Sirtuin 1 (SIRT1) has been implicated in the molecular control of ageing and immune response. Although the remodelling of periodontal ligament (PDL) in response to mechanical stress (MS) is mediated by several host factors, including cytokines and chemokines, the transmission of mechanical stimuli into specific cellular activity is still not understood fully. This study aimed to investigate the effects of MS, particularly cyclic strain, on immune response genes, as well as SIRT1 and its signal transduction pathways, in human PDL cells. MS up‐regulated the expression of SIRT1 and immune response genes encoding cytokines [tumour necrosis factor (TNF)‐α, interleukin (IL)‐1β], chemokines [IL‐8, monocyte cheoattractant protein (CCL)‐20], defensins [human β‐defensin (hBD)‐2, hBD‐3] and Toll‐like receptors (TLR‐2 and TLR‐4) in a force‐ and time‐dependent manner. The SIRT1 inducers resveratrol and isonicotinamide attenuated MS‐induced cytokine and chemokine expression, but enhanced the expression of defensins and TLRs. Blockade of SIRT1 activity by the SIRT1 inhibitors sirtinol and nicotinamide and down‐regulation of SIRT1 expression by SIRT1 siRNA reduced the stimulatory effects of MS on defensins and TLRs, but increased its effects on cytokines and chemokines. MS induced activation of protein kinase B (Akt), protein kinase C (PKC), nuclear factor (NF)‐κB and p38 mitogen‐activated protein kinase (MAPK), c‐Jun N‐terminal kinase (JNK) and extracellular signal‐regulated kinase (ERK). Treatment with the anti‐oxidants N‐acetylcysteine and glutathione inhibited MS‐induced reactive oxygen species production and expression of cytokines, chemokines, defensins and TLRs. These results suggest that MS activates human PDL cells to express immune/defence genes encoding cytokines, chemokines, defensins and TLRs via a SIRT1 pathway.

Control of maxillary dentition with 2 midpalatal orthodontic miniscrews.

The midpalatal area has no critical anatomic structures and has thick cortical bone. These conditions are favorable for miniscrew implantation. Also, there is no concern that damaging a dental root in this area would cause failure of the miniscrew. Although these advantages can decrease the failure rate of miniscrews, midpalatal miniscrews have not been as popular as interdental miniscrews. Because the midpalatal area is far from the teeth, the utility of midpalatal miniscrews has been considered to be limited. This article describes a new method for controlling the maxillary dentition with 2 midpalatal miniscrews.

Use of rhythmic wire system with miniscrews to correct occlusal-plane canting

Occlusal-plane canting is a challenging problem for orthodontists because it cannot be solved easily without surgical intervention. Normally, a LeFort I osteotomy and concomitant mandibular surgery is used to correct the problem, even in patients with mild facial asymmetry but with noticeable occlusal-plane canting. Skeletal anchorage can be used in patients with occlusal canting to reduce the need for orthognathic surgery. The purpose of this article was to introduce a biomechanical system-rhythmic wire- to correct occlusal-plane canting. The records of 2 patients treated with this system are shown.

Induction of S100A4 in periodontal ligament cells enhances osteoclast formation

BACKGROUND An increase in the expression of S100A4 has been reported in various inflammatory diseases. However, little is known about the association between periodontal inflammation and S100A4 expression. The aims of this study were to investigate changes in S100A4 expression in human periodontal ligament (hPDL) cells in response to inflammatory stimuli and to describe a possible mechanism underlying the change. METHOD Human PDL cells were treated with lipopolysaccharide (LPS) and the level of S100A4 was analyzed by real-time RT-PCR and Western blotting. LPS was added to co-cultures of hPDL and osteoclast progenitor cells under osteoclastogenic condition and the formation of osteoclasts was assessed. Alternatively, progenitor cells were directly treated with recombinant S100A4 for evaluation of osteoclastogenesis. The activity of nuclear factor kappaB (NFκB) was examined by Western blotting for phosphorylated forms of inhibitor kappaB (IκB) and p65. An NFκB inhibitor was added to the culture of hPDL cells with LPS and the level of S100A4 was measured by real-time RT-PCR. RESULTS We found that LPS stimulation resulted in a significant increase of S100A4 expression in hPDL cells. S100A4 protein secretion from hPDL cells was also increased. The enhanced expression of S100A4 in hPDL cells under inflammatory conditions led to stimulation of the generation of osteoclasts. In addition, direct S100A4 treatment stimulated osteoclastogenesis. The underlying mechanism for the increased S100A4 expression in hPDL cells was activation of the NFκB signaling pathway. CONCLUSION Our results suggest that bone destruction in periodontitis might be associated with increased S100A4 expression in hPDL cells.

Promotion of osteoblastic differentiation and osteogenic transcription factor expression on a microgroove titanium surface with immobilized fibronectin or bone sialoprotein II

We demonstrate that a composite surface of microgroove titanium (Ti) with immobilized fibronectin (FN) or bone sialoprotein II (BSP2) promotes osteoblastic differentiation and osteogenic transcription factor expression in human bone marrow-derived mesenchymal stem cells (MSCs). Comparisons made between smooth microgrooves, microgrooves with silanization and microgrooves with matrix protein (FN or BSP2)-immobilization Ti surfaces revealed a significant promotion of in vitro osteogenic activity and osteoblastic differentiation at various timelines of culture. An even more significant increase was verified on microgrooves with a matrix protein-immobilization Ti surface in 28 d time-dependent gene expression of the main osteogenic transcription factors, such as ARF4, FRA1, RUNX2, and OSX. As a result, a synergestic effect regarding the promotion of osteogenic transcription factor expression and osteoblastic differentiation in the matrix protein-microgroove Ti composite surface was confirmed. From a multiple regression analysis using various timelines of osteogenic culture as independent variables, day 13 was verified as the most prominent influential timeline for the promotion of osteoblastic differentiation induced by the matrix protein-microgroove Ti composite surface. The FN- or BSP2-microgroove Ti composite surface resulting from silanization can strongly induce the promotion of osteoblastic differentiation in human MSCs. The proposed surface is expected to be useful in the development of a variety of osteogenic biomaterial surfaces.

Asymmetric transverse control of maxillary dentition with two midpalatal orthodontic miniscrews.

There have been several orthodontic modalities for maxillary transverse control with most addressing symmetric control. The asymmetric transverse control of maxillary dentition is challenging to orthodontists due to the lack of certain modalities and possible dental side effects. Skeletal anchorages provide biomechanics without orthodontic side effects, but reports of their utilization for transverse control of maxillary dentition are scarce. The purpose of this article is to introduce a novel method utilizing two midpalatal orthodontic miniscrews and a connecting wire system for the asymmetric transverse control of maxillary dentition. Records of two patients consecutively treated with this system are reported, and the related biomechanical considerations are presented.

Uprighting mesially impacted mandibular molars with 2 miniscrews

Mesially tilted or impacted mandibular molars cause occlusal disharmony and periodontal problems. For proper restoration of the occlusion and to prevent further periodontal damage, uprighting of tilted molars is the recommended treatment option. Although several orthodontic methods including miniscrews have been proposed, most of them have innate limitations and problems such as the possibility of unwanted tooth movement. In this case series, we introduce a new system that uses 2 miniscrews with slots that can accommodate rectangular orthodontic wires to 3 dimensionally control the tilted molar in 3 patients. We also discuss the advantages and possible disadvantages of this new system.