Moon-Kyu Chung

The three-dimensional microstructure of the trabecular bone in the mandible.

This study investigated the three dimensional (3D) trabecular microstructure of the alveolar and basal bone in the mandible using micro-CT and compared the morphometric values of the different sites. Ten specimens were prepared and scanned using a micro-CT system. Both the alveolar and basal trabecular bone of the premolar region in the mandible were measured for the structural analysis. Cross-sectional 1024×1024 pixel images were created. From the two-dimensional (2D) images produced, 3D structural images were reconstructed. After scanning the specimen, the volumes of interest (VOI) of the alveolar and basal bone regions were selected from the 3D reconstruction images, and the structural parameters such as bone volume fraction, bone surface density, trabecular thickness, trabecular separation, trabecular number and structural model index were analyzed. The trabecular structure showed a marked variation within the sites of the specimen, especially in the basal trabecular bone inferior to the mandibular canal. In both the alveolar and basal bone regions, a mixture of both plate-like and rod-like structures was observed. The alveolar region showed a more compact, plate-type trabecular structure than the basal regions. In parametric comparison with the basal bone, the alveolar bone generally had a higher bone volume fraction, bone trabecular thickness and trabecular number, and lower bone surface density, trabecular separation and structural model index. The alveolar bone consisted of a compact bone structure with a large amount of thick plate-type trabecular bone, which was effectively resistant to the masticatory forces. As the measurements were made closer to the basal bone, a loose structure was observed with lower bone volume and fewer, thin, rod-like trabeculae.

Effect of alendronate on healing of extraction sockets and healing around implants.

OBJECTIVES The purpose of this study was to evaluate the effect of alendronates on healing of extraction sockets and healing around implants in the maxilla of rats. MATERIALS AND METHODS Twenty-four Sprague-Dawley rats were used. The rats in bisphosphonate group were subcutaneously injected with alendronate (5.0 mg kg(--1)) three times a week for 4 weeks. Both sides of the maxillary first molars were extracted, and customized titanium implants (Ø1.5 × 2.0 mm) were placed immediately into one side. Rats were killed at 3, 7, 14, or 28 days following surgery. RESULTS New bone formation in extraction sockets, bone area around the implant site, and bone-implant contact were not delayed in the bisphosphonate group. The tartrate-resistant acid phosphatase positive cell count did not differ between bisphosphonate and control groups; however, empty lacunae were observed significantly more in bisphosphonate group. The differences in empty lacunae were shown at different time points between the implant sites and extraction sites: at 7 days after extraction, and at 14 and 28 days after implantation. CONCLUSIONS Alendronates seemed to decrease bone resorption but not to decrease bone formation. Empty lacunae were observed significantly more at later time points in implant sites compared to extraction sockets.

The effect of several dentin desensitizers on shear bond strength of adhesive resin luting cement using self-etching primer

OBJECTIVES Dentin desensitizers can inhibit the bonding between dentin and resin cements. This study examined the effect of the previous application of desensitizers on the shear bond strength of one resin cement using self-etching primer to dentin. MATERIALS AND METHODS One hundred and twenty-five dentin exposed teeth were randomly assigned to four experimental groups and one control group of 25 teeth each. Four dentin desensitizers were applied to the four experimental groups, respectively. The dentin desensitizers used were SuperSeal (Phoenix Dental, Inc., USA), MS-Coat (Sun Medical Co. Ltd, Japan), Gluma (Heraeus Kulzer, Germany), and Copalite Varnish (Cooley & Cooley Ltd, USA). Panavia F (Kuraray Co. Ltd, Tokyo, Japan) was attached to the top of each experimental and control group teeth using an Ultradent testing jig (Ultradent Product, Inc., Utah, USA), and the shear bond strength was measured using a Universal testing machine (Model 6022, Instron Co., Canton, MA, USA). The tooth surface was examined by scanning electron microscopy (SEM, JSM-T2000, JEOL, Tokyo, Japan). RESULTS The control group showed the greatest shear bond strength (14.74 MPa) followed by SuperSeal (12.33 MPa), Gluma (5.28 MPa), MS-Coat (4.44 MPa) and Copalite Varnishtrade mark (3.14 MPa). There was no significant difference in shear bond strength between the control group and the experimental group treated with Superseal. The shear bond strength in the other experimental groups treated with Gluma, Varnish, and MS-Coat was similar to each other but significantly lower than control or Superseal. SEM showed revealed resin tags in most of the dentinal tubules in the experimental group treated with the Superseal. CONCLUSION Among the four dentin desensitizers, Superseal was the only one that did not interfere with the process of resin bonding. The other dentin desensitizers that contained a resin ingredient interfered with resin retention.

Trabecular bone ratio of mandible using micro-computed tomography in Korean.

Cortical bone and trabecular portion play important roles in maintaining the general structure of bone. It has been reported that a decrease in bone mineral density is related with increasing age, sex, and teeth loss. However, most of the studies were done with conventional radiographic analysis. In addition, data from Korean population are rare. The aim of this study was to analyze trabecular pattern of the mandible using micro-computed tomography. Thirty-nine specimens of the mandible were prepared. Specimens were scanned with micro-computed tomography and reconstructed three-dimensionally. Sections were made parallel to the axis of each tooth. Trabecular bone ratio (TBR) was measured. Data were statistically analyzed with 1-way analysis of variance (&agr; = 0.05). There was a statistically significant difference of TBR between dentate and edentulous mandibles in the molar region. Trabecular bone ratio of edentulous mandible in males was greater than that in females. Trabecular bone ratio of dentate mandibles reduced regularly with increasing age, whereas that of edentulous mandibles did not. It could be concluded that there were statistically significant differences in TBR according to presence of tooth, sex, and increasing age on specific areas.

The role of rhFGF-2 soaked polymer membrane for enhancement of guided bone regeneration

Abstract The purposes of this study are to confirm the role of Fibroblast Growth Factor-2 (FGF-2) in bone regeneration by adding various concentrations of FGF-2 to the collagen membrane and applying it to the Biphasic Calcium Phosphate (BCP) bone graft site for guided bone regeneration, to explore the potential of collagen membrane as FGF-2 carrier, and to determine the optimum FGF concentration for enhancement of bone regeneration. Four bone defects of 8 mm in diameter were created in 18 New Zealand rabbit calvaria. After BCP bone graft, graft material was covered with collagen membranes adding various concentration of FGF-2. The concentration of FGF-2 was set at 1.0, 0.5, 0.1 mg/ml, and same amount of saline was used in the control group. To confirm the bone regeneration over time, six New Zealand rabbits were sacrificed each at 2, 4, and 12 weeks, and the amounts of new bone and residual bone graft material were analyzed by histologic and histomorphometric analysis. Qualitative analyses are also conducted through immunohistochemistry, Tetrate-resistant acid phosphatase (TRAP) stain and Russell-Movat pentachrome stain. As the healing period increased, the formation of new bone increased and the amount of residual graft material decreased in all experimental groups. Immunohistochemistry, TRAP staining and pentachrome staining further showed that the addition of FGF-2 promoted bone regeneration in all experimental groups. It was also confirmed that polymer collagen membrane can be used as a useful carrier of FGF-2 when enhanced early stage of new bone formation is required.

Comparative study of recombinant human bone morphogenetic protein-2 carriers in rat subcutaneous tissues: Pilot study

The purpose of this study was to evaluate and compare the potential of using various biomaterials as a carrier of rhBMP-2 in the subcutaneous layer of rats. 5 subcutaneous defects were made in each of the dorsal surfaces of 10 rats. Then, the rats were divided into the following groups: Control group: sham-surgery control, Experimental group 1: rhBMP-2/Bio-Oss®, Experimental group 2: rhBMP-2/Collatape®, Experimental group 3: rhBMP-2/nCS. Histological and histometrical analysis were performed after the rats were sacrificed at 2 and 4 weeks. Regardless of the type of carrier, the groups treated with rhBMP-2 showed significantly greater bone formation when compared to the control group. The amount of new bone formation was greater at 4 week than 2 week. Total bone formation (%) at 4 week was the greatest in rhBMP/Bio-Oss® (26.76±10.13) group, followed by rhBMP/Collatape® (20.38±5.27) and rhBMP/nCS (4.34±2.58). Within the limitation of this study, the results showed that Bio-Oss®, Collatape®, nanocalcium sulfate all showed new bone formation when used as a carrier of rhBMP-2 in the subcutaneous layer of rats, indicating potential use as carriers for rhBMP-2.