Young-Bum Park

Analysis of the anatomy of the maxillary sinus septum using 3-dimensional computed tomography.

PURPOSEnMaxillary posterior teeth exhibit a high incidence of periodontal bone and tooth loss. After tooth loss, the edentulous alveolar process of the posterior maxilla is often affected by resorption, which results in loss of vertical bone volume. Moreover, progressive sinus pneumatization leads to a decrease in the alveolar process from the cranial side. The sinus elevation and augmentation surgical technique opened a new way of anchoring endosseous implants despite discernible bone reduction. However, the surgical interventions require in-depth knowledge of maxillary sinus anatomy such as sinus septum and potential variations. The purpose of this study was to investigate the prevalence, location, height, morphology, and orientation of maxillary sinus septa by use of computed tomography (CT) and 3-dimensional imaging.nnnMATERIALS AND METHODSnTwo hundred patients undergoing implant treatment at the Yonsei University College of Dentistry, Seoul, South Korea, were randomly selected for analysis of maxillary sinus septa. CT and DentaScan (GE Medical Systems, Milwaukee, WI)-reformatted data from 400 sinuses were analyzed with the Preview program (Infinitt, Seoul, South Korea). Three-dimensional images were rendered for measurement by use of the Accurex program (CyberMed, Seoul, South Korea).nnnRESULTSnWe found 111 septa in 400 maxillary sinuses (27.7%). This corresponded to 37% of the patients. Among total septa, 25 sinus septa (22.5%) were located in the anterior, 51 (45.9%) in the middle, and 35 (31.5%) in the posterior regions. The directional orientation analyses showed that 106 septa were buccopalatal, 4 were sagittal, and 1 was transverse type. The mean septal heights were 7.78 ± 2.99 and 7.89 ± 3.09 mm in the right and left sinuses, respectively.nnnCONCLUSIONnThree-dimensional CT image analyses may provide useful information that can avoid unnecessary complications during sinus augmentation procedures by facilitating adequate, timely identification of the anatomic structures inherent to the maxillary sinus.

Molecular Mechanisms of Cell Death of Mycophenolic Acid-Treated Primary Isolated Rat Islets: Implication of Mitogen-Activated Protein Kinase Activation

Optimal immunosuppression after pancreas islet transplantation has not yet been established to achieve long-term graft survival. Mycophenolic acid (MPA) is widely used as an immunosuppressive drug after transplantation including among recipients of pancreas islet cells. Previously, we reported MPA-induced islet apoptosis in the HIT-T15 cell line. In this study, we confirmed the effects of MPA on cell death and its potential implications on the mitogen-activated protein kinase (MAPK) family expression levels in primary isolated rat islets. Lewis islets isolated by collagenase digestion were purified by the density gradient method. Cell death was analyzed by methylthiazoletetrazolium assay. Activation of MAPK kinase 4 (MKK4), c-jun N-terminal protein kinase (JNK), p38 MAPK, and caspase-3 cleavage was examined by Western blot analyses. MPA treatments (> 25 micromol/L) increased cell death significantly at 24 hours and in a dose-dependent manner activated MKK4, JNK, and p38 MAPK at 20 hours. Caspase-3 cleavage was also increased by MPA treatment. These results suggested that MPA induced significant cell death among primary isolated rat islets by activation of MKK4, JNK, and p38 MAPK, as well as caspase-3 cleavage.

Improvement of osteogenic potential of biphasic calcium phosphate bone substitute coated with two concentrations of expressed recombinant human bone morphogenetic protein 2.

Purpose The aim of this study was to determine whether biphasic calcium phosphate (BCP) bone substitute with two different concentrations of Escherichia coli-expressed recombinant human bone morphogenetic protein 2 (ErhBMP-2) enhances new bone formation in a standardized rabbit sinus model and to evaluate the concentration-dependent effect of ErhBMP-2. Methods Standardized, 6-mm diameter defects were made bilaterally on the maxillary sinus of 20 male New Zealand white rabbits. Following removal of the circular bony windows and reflection of the sinus membrane, BCP bone substitute without coating (control group) was applied into one defect and BCP bone substitute coated with ErhBMP-2 (experimental group) was applied into the other defect for each rabbit. The experimental group was divided into 2 subgroups according to the concentration of ErhBMP-2 (0.05 and 0.5 mg/mL). The animals were allowed to heal for either 4 or 8 weeks and sections of the augmented sinus and surrounding bone were analyzed by microcomputed tomography and histologically. Results Histologic analysis revealed signs of new bone formation in both the control and experimental groups with a statistically significant increase in bone formation in experimental group 1 (0.05 mg/mL ErhBMP-2 coating) after a 4-week healing period. However, no statistically significant difference was found between experimental group 1 and experimental group 2 (0.5 mg/mL ErhBMP-2 coating) in osteoinductive potential (P<0.05). Conclusions ErhBMP-2 administered using a BCP matrix significantly enhanced osteoinductive potential in a standardized rabbit sinus model. A concentration-dependent response was not found in the present study.

Evaluation of the marginal and internal discrepancies of CAD-CAM endocrowns with different cavity depths: An in vitro study

Statement of problem. The marginal and internal discrepancies of computer‐aided design and computer‐aided manufacturing (CAD‐CAM) endocrowns are unknown. Purpose. The purpose of this in vitro study was to evaluate the marginal and internal discrepancies of endocrowns with different cavity depths by measuring them with microcomputed tomography (&mgr;CT). Material and methods. Endocrowns (n=48) of 2 different cavity depths (2 mm and 4 mm) were fabricated in 2 different chairside CAD‐CAM systems (CEREC AC and E4D). A &mgr;CT scan was made before and after cementation. For analysis of the marginal and internal discrepancies, reference points were selected in 2‐dimensional views of 3 buccolingual cross‐sections and 3 mesiodistal cross‐sections. To calculate the total discrepancy volume, the &mgr;CT sections were reconstructed 3‐dimensional views, and changes in volume and surface area were examined. Statistical analysis was performed using 2‐way ANOVA with Bonferroni correction (&agr;=.05). Results. An endocrown with a 4‐mm cavity showed a larger marginal and internal volume than one with a 2‐mm cavity. Cementation did not show significant differences in total discrepancy thickness. Discrepancies on the pulpal floor were largest in other sites. Both chairside CAD‐CAM systems showed similar discrepancy in the endocrowns. Conclusions. Based on the present study, marginal and internal discrepancies increased depending on cavity depth. Cementation did not increase the dimension of the discrepancy between the restoration and the cavity wall. The discrepancy on the pulpal floor appeared to affect these results.

Osseointegration of implants surface-treated with various diameters of TiO 2 nanotubes in rabbit

The aim of this study was to evaluate the osseointegration of implants which were surface-treated with various diameters of TiO2 nanotubes (30 nm, 70 nm, and 100 nm) in rabbit. Resorbable blast media (RBM) surfaced implants (Osstem, Busan, Korea) 3.5 mm in diameter and 8.5 mm in length were designated as the control group and the implants surface-treated with various diameters of nanotubes (30 nm, 70 nm, and 100 nm) with the same shapes were designated as the experimental groups. The implants were maintained unloaded for 4 and 12 weeks. After this period, the animals were sacrificed and micro-CT analysis, histomorphometric analysis (bone to implant contact (BIC), bone volume (BV)), and removal torque test were performed. Micro-CT analysis, histomorphometric analysis, and removal torque test results all showed the similar pattern, showing that 70 nm experimental group had the highest value at 4 weeks while 30 nm experimental group had the highest value at 12 weeks. Therefore, on the basis of the results above, it can be concluded that 30 nm and 70 nm TiO2 nanotubes may have positive effects on osteogenesis and osseointegration depending on the healing time.

Comparative study of decalcification versus nondecalcification for histological evaluation of one-wall periodontal intrabony defects in dogs.

Biological reactions between biomaterials and surrounding tissues, analyzed by histology, may be important predictors of clinical healing pattern and selection of slide preparation techniques requires a careful consideration regarding sample properties. In this study, we compared histology of bone specimens prepared with or without decalcification and performed histological and histomorphometrical assessments. For the histological evaluation, one‐wall intrabony defects were created around the mandibular molars of six adult dogs, filled with biphasic calcium phosphate, synthetic bone graft material/recombinant human bone morphogenic protein‐2, and healing pattern was histologically evaluated at 4 and 12 weeks. New bone formation in 5u2009×u20094u2009×u20094 mm defects and the length of new cementum, connective tissue attachments around the teeth and number of osteoclasts were measured by histomorphometric analysis. After decalcification, new cementum was easily observed and was significantly increased at week 4. In nondecalcified samples, significantly increased connective tissue attachments were seen at week 12. After 12 weeks, the number of countable multinucleated osteoclasts was significantly increased by 62% in nondecalcified versus calcified tissue sections (Pu2009=u20090.030). Histomorphometric results may be significantly affected by histological preparation method and therefore, selecting the most appropriate histological preparation method is essential for reliable diagnosis and evaluation of bony samples in studies analyzing tissue regeneration. Microsc. Res. Tech. 78:94–104, 2015.

Effect of alendronate on bone remodeling around implant in the rat

PURPOSE The purpose of this study was to evaluate the effect of alendronates on bone remodeling around titanium implant in the maxilla of rats. MATERIALS AND METHODS The maxillary first molars were extracted and customized-titanium implants were placed immediately in thirty male Sprague-Dawley rats. The rats were divided into experimental (bisphosphonate) group and control group. At 4 weeks after implantation, the rats in the bisphosphonate group were subcutaneously injected with alendronate three times a week for 6 weeks where as the rats in control group were injected with saline. The rats were sacrificed at 1, 2, 3, 4, or 6 weeks after starting of injection and maxillary bones were collected subsequently. Alveolar bone remodeling around the implants were evaluated by radiographic and histologic analysis. Microarray analysis and immunohistomorphologic analysis were also performed on one rat, sacrificed at 6 weeks after starting of injection, from each group. Statistical analysis was performed using repeated measures analysis of variance and independent t test at a significance level of 5%. RESULTS There was no statistically significant difference in the bone area (%) around implant between the bisphosphonate group and the control group. However, the amount of empty lacuna was significantly increased in the bisphosphonate group, especially in the rats sacrificed at 4 weeks after starting of injection compared to that of the corresponding control group. The bisphosphonate group showed the same level of TRAP positive cell count, osteocalcin and angiopoietin 1 as the control group. CONCLUSION Alendronate may not decrease the amount of osteoclast. However, the significantly increased amount of empty lacuna in the bisphosphonate group may explain the suppression of bone remodeling in the bisphosphonate group.

Improvement of osteogenic potential of biphasic calcium phosphate bone substitute coated with synthetic cell binding peptide sequences

Purpose The aim of this study was to evaluate the improvement of osteogenic potential of biphasic calcium phosphate (BCP) bone substitute coated with synthetic cell-binding peptide sequences in a standardized rabbit sinus model. Methods Standardized 6-mm diameter defects were created bilaterally on the maxillary sinus of ten male New Zealand white rabbits, receiving BCP bone substitute coated with synthetic cell binding peptide sequences on one side (experimental group) and BCP bone substitute without coating (control group) on the other side. Histologic and histomorphometric analysis of bone formation was carried out after a healing period of 4 or 8 weeks. Results Histological analysis revealed signs of new bone formation in both experimental groups (4- and 8-week healing groups) with a statistically significant increase in bone formation in the 4-week healing group compared to the control group. However, no statistically significant difference in bone formation was found between the 8-week healing group and the control group. Conclusions This study found that BCP bone substitute coated with synthetic cell-binding peptide sequences enhanced osteoinductive potential in a standardized rabbit sinus model and its effectiveness was greater in the 4-week healing group than in the 8-week healing group.

Effect of Serial Use of Bone Morphogenetic Protein 2 and Fibroblast Growth Factor 2 on Periodontal Tissue Regeneration

Purpose: This study evaluates the synergistic effect of serial application of bone morphogenetic protein 2 (BMP2) and fibroblast growth factor 2 (FGF2) on both new bone formation and periodontal tissue regeneration using 1-wall intrabony defect in mongrel dogs. Materials and Methods: One-wall defects were created at the mesial aspect of the mandibular first molars of 6 male mongrel dogs. Each mandibular defect received 1 of the 2 experimental treatments randomly (BMP2 or BMP2 + FGF2), and it was allowed to heal for either 4 or 8 weeks postoperatively. Histologic and histomorphometric analyses were performed for the evaluation of the overall healing patterns of new bone formation and periodontal tissue regeneration. Results: The results showed that after 8 weeks, serial application of BMP2 and FGF2 significantly improved the periodontal tissue regeneration, whereas application of BMP2 only showed greater new bone formation after 4 weeks. Conclusions: The serial application of BMP2 and FGF2 may have synergistic effects on periodontal tissue regeneration over time.

Near-infrared laser-mediated drug release and antibacterial activity of gold nanorod–sputtered titania nanotubes:

The infection control of implants is one of the hot issues in the field of medicine and dentistry. In this study, we prepared gold nanorod–sputtered titania nanotubes on titanium surface, which is the main component of implant material, and aimed to estimate the remote-controlled tetracycline release and resulting antibacterial effects of gold nanorod–sputtered titania nanotubes using near-infrared laser irradiation. Gold nanorods prepared by ion plasma sputtering (aspect ratiou2009=u20091:3) showed optical properties like those of chemically synthesized gold nanorods, exhibiting photothermal effects in the near-infrared region, as demonstrated using field-emission scanning electron microscopy, transmission electron microscopy, and diffuse ultraviolet–visible–near-infrared spectrophotometry. In addition, a 2u2009wt% tetracycline/polycaprolactone mixture was found to be the most suitable experimental group to demonstrate the biological compatibilities and antibacterial activities. The results of antibacterial agar diffusion tests and near-infrared-mediated tetracycline release tests in vivo confirmed that remote-controlled tetracycline elution using near-infrared laser irradiation was highly effective. Therefore, gold nanorod–sputtered titania nanotubes would be expected to enable the continued use of the photothermal therapy of gold nanorods and extend the limited use of titania showing photocatalytic activity only within the ultraviolet-to-near-infrared region.