Bohm Choi

Titanium oxide nanotube surface topography and microRNA-488 contribute to modulating osteogenesis

Understanding the biocomplexity of cell behavior in relation to the topographical characteristics of implants is essential for successful osseointegration with good longevity and minimum failure. Here, we investigated whether culture on titanium oxide (TiO2) nanotubes of various diameters could affect the behavior and differentiation of MC3T3-E1 cells. Among the tested nanotubes, those of 50 nm in diameter were found to trigger the expression of the osteoblast-specific transcription factors, sp7 and Dlx5, and upregulate the expression of alkaline phosphatase (ALP). Here, we report that miR-488 was significantly induced in osteoblasts cultured on 50 nm nanotubes and continued to increase with the progression of osteoblast differentiation. Furthermore, downregulation of miR-488 suppressed the expression levels of ALP and matrix metalloprotease-2 (MMP-2). This suppression of ALP transcription was overcome by treatment with the MMP-2 activator, bafilomycin A1. Collectively, these results suggest that 50 nm is the optimum TiO2 nanotube diameter for implants, and that modulation of miR-488 can change the differentiation activity of cells on TiO2 nanotubes. This emphasizes that we must fully understand the physicochemical properties of TiO2 nanotubes and the endogenous biomolecules that interact with such surfaces, in order to fully support their clinical application.

Novel application of the 2-piece orthodontic C-implant for temporary crown restoration after orthodontic treatment

INTRODUCTION This article reports the use of an orthodontic mini-implant for a temporary crown restoration in a small edentulous space after limited orthodontic treatment. METHODS Two clinical cases are presented: a 23-year-old woman and a 14-year-old boy. In the adult patient, a 2-piece orthodontic C-implant (Cimplant, Seoul, Korea) was placed in a 3-mm wide edentulous space to build up a temporary crown restoration after a short orthodontic treatment to regain space for a missing mandibular right permanent lateral incisor. In the boy, a C-implant was placed in the space resulting from an avulsed maxillary right permanent lateral incisor to prevent aggressive alveolar bone resorption after dental trauma. Both patients were followed for more than 4 years of retention to evaluate the stability of the temporary crown restoration built up on the orthodontic mini-implants. RESULTS Both patients had successful long-term results, confirmed by clinical and radiographic examinations. Both were pleased with the results and plan to retain the orthodontic mini-implant temporary crown restoration until they are ready for a permanent restoration later. CONCLUSIONS A 2-piece orthodontic C-implant system can be used to maintain edentulous space after active orthodontic treatment.

Tooth Movement in Demineralized Area by Etchant in Rabbits

Purpose: Among the facilitation of tooth movement in adult orthodontic treatment methods, surgical approaches are gaining popularity but complications following mechanical bone reduction are a problem. In this study, tooth movement was observed after alveolar bone was chemically demineralized to verify whether tooth movement had been facilitated. Materials and Methods: Twelve rabbits were used. In the experimental group, the alveolar bone of the left first molar area was exposed and demineralized. Thirty seven percents phosphoric acid was applied for 5 minutes for demineralization. The opposite first molar area was used as control. Two teeth were pulled with 200 g force and 4 rabbits each were sacrificed at 3, 7, and 14 days after the force was applied. Histologic examination was done with hematoxylin and eosin and tartrate-resistant acid phosphatase staining. Result: The histologic examination results revealed more bone resorption in the demineralized area. As time passed, the number of osteoclasts increased in the compressed area. The amount of tooth movement was larger in the experimental group compared to the control group but the difference was not statistically significant. Conclusion: The demineralization with etchant resulted in limited bone resorption, more tooth movement and less damage of the cementum after applied orthodontic force.

Osteoinductivity depends on the ratio of demineralized bone matrix to acellular dermal matrix in defects in rat skulls

Demineralized bone matrix (DBM) is the most commonly used allograft material. DBM has been applied in various fields because its healing effects are similar to those of autografts, with fewer side effects. Efforts to enhance its convenience have explored the use of human acellular dermal matrix (AM) as a carrier graft material for defective soft tissue, given the difficulty of using solid particles of DBM. The induction ability of AM combined with the osteoinduction ability of DBM is considered to have a synergistic effect. This study evaluated the outcomes of treatment with various ratios of a DBM/AM mixture in defects in rat skulls. Imaging measurements and histological analyses were performed 4 and 8 weeks after treatment to investigate the characteristics and formation of new bone in treated and untreated groups. Groups treated with 7:3 and 5:5 DBM: AM ratios showed no difference in osteogenetic ability compared with the group treated with DBM alone. This finding indicates that the use of a proper DBM: AM ratio maintains osteogenetic ability, providing a convenient and sufficient clinical application. This DBM/AM mixture is the first graft material developed in Korea.

TiO2 nanotube stimulate chondrogenic differentiation of limb mesenchymal cells by modulating focal activity

Vertically aligned, laterally spaced nanoscale titanium nanotubes were grown on a titanium surface by anodization, and the growth of chondroprogenitors on the resulting surfaces was investigated. Surfaces bearing nanotubes of 70 to 100 nm in diameter were found to trigger the morphological transition to a cortical actin pattern and rounded cell shape (both indicative of chondrocytic differentiation), as well as the up-regulation of type II collagen and integrin β4 protein expression through the down-regulation of Erk activity. Inhibition of Erk signaling reduced stress fiber formation and induced the transition to the cortical actin pattern in cells cultured on 30-nm-diameter nanotubes, which maintained their fibroblastoid morphologies in the absence of Erk inhibition. Collectively, these results indicate that a titanium-based nanotube surface can support chondrocytic functions among chondroprogenitors, and may therefore be useful for future cartilaginous applications.

Influence of Fixture Thread Exposure on Marginal Bone Level Around Different Implant Systems: A Preliminary Study in Dogs.

PURPOSE To evaluate the influence of implant neck structures on marginal bone loss around intentionally exposed implant fixtures by histomorphometric analysis. MATERIALS AND METHODS Twenty-four implants representing 3 implant systems were placed in three dogs; an implant system with SLA surface without microthreads (group A); one with SLA + calcium surface without microthreads (group B); and one with SLA surface with microthreads (group C). The histomorphometric analyses for vertical defect length (VDL), infrabony defect height (IDH), and defect depth (DD) were performed at the buccal and lingual sides of each fixture. RESULTS The VDL was lower in group A relative to groups B and C on the buccal and lingual sides. The IDH and DD were higher in group A than group C on the buccal and lingual sides; however, no statistically significant differences were noted between the groups in VDL, IDH, and DD on the buccal and lingual sides of the fixtures. CONCLUSIONS In this preliminary study, marginal bone resorption pattern in the canine mandible varied according to the neck design of each implant fixture. Further studies with larger sample size are needed to confirm the effect of microthreads and surface roughness on the marginal bone loss at the exposed implant fixture.