Jung-Suk Han

Publications of Jung-Suk Han

• Clinical use of alumina-toughened zirconia abutments for implant-supported restoration: prospective cohort study of survival analysis.

  Authors: Seung-Soo Kim, In-Sung Yeo, Shin-Jae Lee, Dae-Joon Kim, Brian Myeongwoo Jang, Soo-Hwan Kim, Jung-Suk Han

  Clinical oral implants research. 01/2012;

  OBJECTIVES: The aim of this prospective cohort study was to compute the long-term clinical survival and complication rates of alumina-toughened zirconia abutments used for implant-supportedOBJECTIVES: The aim of this prospective cohort study was to compute the long-term clinical survival and complication rates of alumina-toughened zirconia abutments used for implant-supported restorations and to evaluate the effects of several clinical variables on these rates. MATERIAL AND METHODS: From May 1998 to September 2010, 213 patients aged 18 years or older were recruited. The patients received 611 external hex implants and 328 implant-supported fixed restorations using alumina-toughened zirconia abutments. During the follow-up, each restoration was coded as a dental event, which included loosening or fracture of abutment screws, and abutment fracture. From the coded data, the effects of the investigated clinical variables-restored area (anterior/posterior), number of prosthodontic units (one/two units or over), prosthesis type (single-unit/multiunit without pontic/multiunit with pontic), implant system, and patient gender-on the survival of the abutments were evaluated. Survival analysis using Kaplan-Meier method and Cox proportional hazard model was applied. The 5-year survival and complication rates of the abutments were assessed. RESULTS: The number of prosthodontic units and the type of prosthesis had a significant association with complication rates (P < 0.05). Kaplan-Meier survival analysis estimated that the cumulative 5-year complication rate of the abutments used in single restorations was 19.7%. Multiunit-fixed dental prostheses without and with pontics had complication rates of 3.9% and 3.8%, respectively. The 5-year survival rate of the abutments was more than 95%, regardless of the type of prosthesis. CONCLUSIONS: Alumina-toughened zirconia abutments are likely to exhibit excellent long-term survival in clinical use for fixed restorations. Single tooth replacement with the abutment at the molar region may require special care and extra attention.

• The Effect of Internal Versus External Abutment Connection Modes on Crestal Bone Changes Around Dental Implants: A Radiographic Analysis.

  Authors: Eun-Jeong Lee, Ki-Tae Koo, Jae-Yoon Kim, Yang-Jo Seol, Jung-Suk Han, Tae-Il Kim, Yong Moo Lee, Young Ku, Ulf Me Wikesjö, In-Chul Rhyu

  Journal of periodontology. 12/2011;

  Background: The influence of external versus internal implant/abutment connections on crestal bone remodeling has not been reported. The aim of the present study was to investigate the influence ofBackground: The influence of external versus internal implant/abutment connections on crestal bone remodeling has not been reported. The aim of the present study was to investigate the influence of the abutment connection on peri-implant crestal bone levels using radiographic recordings. Methods: Radiographic recordings from 40 single-tooth implants (20 external/20 internal octagonal connection) in 40 patients, mean age 54.3 years (15 men/25 women; 1 implant/patient) were selected for this analyses. The radiographic evaluation included: (1) Linear bone change (LBC); (2) Dimensional change (DC); and (3) Angle between the implant and adjacent bone (AIB). Differences in LBC, DC, AIB between implant placement and 1 year post-loading for each system were evaluated using a paired t-test. Comparison of LBC, DC and AIB between systems at 1 year post-loading was done using analysis of covariance (ANCOVA). The significance level was set at p≤ 0.05. Results: Radiographic crestal bone levels (LBC) were reduced at 1 year post-loading compared with at implant placement to reach statistical significance for the external connection (P= 0.000) but not the internal connection (P= 0.939). Crestal bone level changes were significantly greater for the external compared with the internal connection (P= 0.000). Similarly, the DC for the external connection was significantly greater compared with that for the internal connection (P= 0.004). Conclusions: Within limitations of study, the implant/abutment connection technology appears to have a significant impact on peri-implant crestal bone levels, the external connection paralleled by a significant reduction of crestal bone levels.

• Initial bacterial adhesion on resin, titanium and zirconia in vitro.

  Authors: Byung-Chul Lee, Gil-Yong Jung, Dae-Joon Kim, Jung-Suk Han

  The journal of advanced prosthodontics. 06/2011; 3(2):81-4.

  The aim of this in vitro study was to investigate the adhesion of initial colonizer, Streptococcus sanguis, on resin, titanium and zirconia under the same surface polishing condition. Specimens wereThe aim of this in vitro study was to investigate the adhesion of initial colonizer, Streptococcus sanguis, on resin, titanium and zirconia under the same surface polishing condition. Specimens were prepared from Z-250, cp-Ti and 3Y-TZP and polished with 1 µm diamond paste. After coating with saliva, each specimen was incubated with Streptococcus sanguis. Scanning electron microscope, crystal violet staining and measurement of fluorescence intensity resulting from resazurin reduction were performed for quantifying the bacterial adhesion. Surface of resin composite was significantly rougher than that of titanium and zirconia, although all tested specimens are classified as smooth. The resin specimens showed lower value of contact angle compared with titanium and zirconia specimens, and had hydrophilic surfaces. The result of scanning electron microscopy demonstrated that bound bacteria were more abundant on resin in comparison with titanium and zirconia. When total biofilm mass determined by crystal violet, absorbance value of resin was significantly higher than that of titanium or zirconia. The result of relative fluorescence intensities also demonstrated that the highest fluorescence intensity was found on the surface of resin. Absorbance value and fluorescence intensity on titanium was not significantly different from those on zirconia. Resin specimens showed the roughest surface and have a significantly higher susceptibility to adhere Streptococcus sanguis than titanium and zirconia when surfaces of each specimen were polished under same condition. There was no significant difference in bacteria adhesion between titanium and zirconia in vitro.

• Mediation of Rac1 activation by kindlin-2: an essential function in osteoblast adhesion, spreading, and proliferation.

  Authors: Gil-Yong Jung, Yoon-Jeong Park, Jung-Suk Han

  Journal of cellular biochemistry. 05/2011; 112(9):2541-8.

  Kindlins are focal adhesion proteins that regulate integrin signaling. Although integrin activation is critical for bone development, little is known about the expression and role of kindlins inKindlins are focal adhesion proteins that regulate integrin signaling. Although integrin activation is critical for bone development, little is known about the expression and role of kindlins in osteoblasts. We therefore investigated the function of kindlin-2 in osteoblast adhesion, spreading, and proliferation using small interfering RNA. In MC3T3-E1 cells, only kindlin-2 is highly expressed and localizes to focal adhesion. We found that kindlin-2 was involved in integrin activation in MC3T3-E1 cells and that kindlin-2 knockdown osteoblasts resulted in diminished cell adhesion, spreading, and proliferation. In this process, kindlin-2 knockdown impaired transient Rac1 activation, influencing Akt activation and AP-1 activity. In agreement with these data, pharmacological inhibition of Rac1 reduced MC3T3-E1 cell adhesion, spreading, and proliferation. Overall, these findings demonstrated that kindlin-2 governs Rac1 activation, which controls osteoblast function. Our findings provide the first insights concerning the function of kindlin-2 in osteoblast, and suggest that kindlin-2 is a critical mediator for osteoblast physiology.

• A study on the fracture strength of collarless metal-ceramic fixed partial dentures.

  Authors: Jong-Wook Yoon, Sung-Hun Kim, Jai-Bong Lee, Jung-Suk Han, Jae-Ho Yang

  The journal of advanced prosthodontics. 12/2010; 2(4):134-41.

  The objective of this study was to evaluate fracture strength of collarless metal-ceramic FPDs according to their metal coping designs. Four different facial margin design groups were investigated.The objective of this study was to evaluate fracture strength of collarless metal-ceramic FPDs according to their metal coping designs. Four different facial margin design groups were investigated. Group A was a coping with a thin facial metal collar, group B was a collarless coping with its facial metal to the shoulder, group C was a collarless coping with its facial metal 1 mm short of the shoulder, and group D was a collarless coping with its facial metal 2 mm short of the shoulder. Fifteen 3-unit collarless metal-ceramic FPDs were fabricated in each group. Finished FPDs were cemented to PBT (Polybutylene terephthalate) dies with resin cement. The fracture strength test was carried out using universal testing machine (Instron 4465, Instron Co., Norwood MA, USA) at a cross head speed of 0.5 mm/min. Aluminum foil folded to about 1 mm of thickness was inserted between the plunger tip and the incisal edge of the pontic. Vertical load was applied until catastrophic porcelain fracture occurred. The greater the bulk of unsupported facial shoulder porcelain was, the lower the fracture strength became. However, there were no significant differences between experimental groups (P > .05). All groups of collarless metal-ceramic FPDs had higher fracture strength than maximum incisive biting force. Modified collarless metal-ceramic FPD can be an alternative to all-ceramic FPDs in clinical situations.

• Esthetic improvement in the patient with one missing maxillary central incisor restored with porcelain laminate veneers.

  Authors: Dong-Jin Park, Jae-Ho Yang, Jai-Bong Lee, Sung-Hun Kim, Jung-Suk Han

  The journal of advanced prosthodontics. 09/2010; 2(3):77-80.

  This article describes esthetic improvement in a patient with a missing maxillary left central incisor. Space analysis of the anterior dentition showed that minor tooth rearrangement was needed.This article describes esthetic improvement in a patient with a missing maxillary left central incisor. Space analysis of the anterior dentition showed that minor tooth rearrangement was needed. Optimal space distribution for restorations was attained by orthodontic treatment. Through transforming tooth shape with porcelain laminate veneers, the maxillary left lateral incisor was transformed into central incisor and the maxillary left canine into a lateral incisor. The maxillary right central incisor was also restored for esthetic improvement. In a case of changing a tooth shape with porcelain laminate veneers, pre-treatment evaluation, space analysis and diagnostic wax-up are important factors.

• Implants and all-ceramic restorations in a patient treated for aggressive periodontitis: a case report.

  Authors: Jin-Sun Hong, In-Sung Yeo, Sung-Hun Kim, Jai-Bong Lee, Jung-Suk Han, Jae-Ho Yang

  The journal of advanced prosthodontics. 09/2010; 2(3):97-101.

  A 23-year-old female with aggressive periodontitis was treated using dental implants and LAVA system. The severely compromised teeth were extracted irrespective of initial conservative periodontalA 23-year-old female with aggressive periodontitis was treated using dental implants and LAVA system. The severely compromised teeth were extracted irrespective of initial conservative periodontal treatment. An implant-supported overdenture with 4 implants was fabricated for the maxilla and all-ceramic restorations for the mandible. Esthetic and functional goals were achieved with team approach involving periodontists and prosthodontists. This case report describes a treatment procedure for a generalized aggressive periodontitis patient with severe bone resorption.

• Influence of porcelain veneering on the marginal fit of Digident and Lava CAD/CAM zirconia ceramic crowns.

  Authors: Hyun-Soon Pak, Jung-Suk Han, Jai-Bong Lee, Sung-Hun Kim, Jae-Ho Yang

  The journal of advanced prosthodontics. 06/2010; 2(2):33-8.

  Marginal fit is a very important factor considering the restoration's long-term success. However, adding porcelain to copings can cause distortion and lead to an inadequate fit which exposes moreMarginal fit is a very important factor considering the restoration's long-term success. However, adding porcelain to copings can cause distortion and lead to an inadequate fit which exposes more luting material to the oral environment and causes secondary caries. The purpose of this study was to compare the marginal fit of 2 different all-ceramic crown systems before and after porcelain veneering. This study was also intended to verify the marginal fit of crowns originated from green machining of partially sintered blocks of zirconia (Lava CAD/CAM system) and that of crowns obtained through machining of fully sintered blocks of zirconia (Digident CAD/CAM system). 20 crowns were made per each system and the marginal fit was evaluated through a light microscope with image processing (Accura 2000) at 50 points that were randomly selected. Each crown was measured twice: the first measurement was done after obtaining a 0.5 mm coping and the second measurement was done after porcelain veneering. The means and standard deviations were calculated and statistical inferences among the 2 groups were made using independent t-test and within the same group through paired t-test. The means and standard deviations of the marginal fit were 61.52 ± 2.88 µm for the Digident CAD/CAM zirconia ceramic crowns before porcelain veneering and 83.15 ± 3.51 µm after porcelain veneering. Lava CAD/CAM zirconia ceramic crowns showed means and standard deviations of 62.22 ± 1.78 µm before porcelain veneering and 82.03 ± 1.85 µm after porcelain veneering. Both groups showed significant differences when analyzing the marginal gaps before and after porcelain veneering within each group. However, no significant differences were found when comparing the marginal gaps of each group before porcelain veneering and after porcelain veneering as well. The 2 all-ceramic crown systems showed marginal gaps that were within a reported clinically acceptable range of marginal discrepancy.

• Esthetic restorations of maxillary anterior teeth with orthodontic treatment and porcelain laminate veneers: a case report.

  Authors: Ji-Eun Moon, Sung-Hun Kim, Jung-Suk Han, Jae-Ho Yang, Jai-Bong Lee

  The journal of advanced prosthodontics. 06/2010; 2(2):61-3.

  If orthodontists and restorative dentists establish the interdisciplinary approach to esthetic dentistry, the esthetic and functional outcome of their combined efforts will be greatly enhanced. ThisIf orthodontists and restorative dentists establish the interdisciplinary approach to esthetic dentistry, the esthetic and functional outcome of their combined efforts will be greatly enhanced. This article describes satisfying esthetic results obtained by the distribution of space for restoration by orthodontic treatment and porcelain laminate veneers in uneven space between maxillary anterior teeth. It is proposed that the use of orthodontic treatment for re-distribution of the space and the use of porcelain laminate veneers to alter crown anatomy provide maximum esthetic and functional correction for patients with irregular interdental spacing.

• Trend analysis of prosthodontic treatment modality between 2005 and 2008 in Seoul National University Dental Hospital.

  Authors: Hongbo Li, Jai-Bong Lee, Hongchen Liu, Jung-Suk Han, Jae-Ho Yang, Jai-Young Koak, Seong-Joo Heo

  The journal of advanced prosthodontics. 03/2010; 2(1):4-6.

  The aim of this article is to analyze the preference for treatment modality of dentists. Data of 20,038 patients was involved. Data analysis were done by distribution according to the various kindsThe aim of this article is to analyze the preference for treatment modality of dentists. Data of 20,038 patients was involved. Data analysis were done by distribution according to the various kinds of prosthesis, including complete denture, removable partial denture, fixed partial denture, implant-supported dental prosthesis as well as distribution according to the professional titles of the dentists finishing the treatment, including resident and professors. The number of cases of dental prosthesis increased year by year. 61.06% of the patients accepted fixed partial denture restoration. The number of patients who accepted implant supported restoration is also increasing year by year. The number of complete denture, implant-supported dental prosthesis finished by professors was larger than that done by residents, while it was contrary for removable partial denture, fixed partial denture, and the difference was statistically significant (P<.05). Professors and residents have some difference in the categorization of prosthesis finished. Fixed partial denture and implant-supported dental prosthesis are preferred.

• Comparison of polymer-based temporary crown and fixed partial denture materials by diametral tensile strength.

  Authors: Seung-Ryong Ha, Jae-Ho Yang, Jai-Bong Lee, Jung-Suk Han, Sung-Hun Kim

  The journal of advanced prosthodontics. 03/2010; 2(1):14-7.

  The purpose of this study was to investigate the diametral tensile strength of polymer-based temporary crown and fixed partial denture (FPD) materials, and the change of the diametral tensileThe purpose of this study was to investigate the diametral tensile strength of polymer-based temporary crown and fixed partial denture (FPD) materials, and the change of the diametral tensile strength with time. One monomethacrylate-based temporary crown and FPD material (Trim) and three dimethacrylate-based ones (Protemp 3 Garant, Temphase, Luxtemp) were investigated. 20 specimens (ø 4 mm × 6 mm) were fabricated and randomly divided into two groups (Group I: Immediately, Group II: 1 hour) according to the measurement time after completion of mixing. Universal Testing Machine was used to load the specimens at a cross-head speed of 0.5 mm/min. The data were analyzed using one-way ANOVA, the multiple comparison Scheffe test and independent sample t test (α = 0.05). Trim showed severe permanent deformation without an obvious fracture during loading at both times. There were statistically significant differences among the dimethacrylate-based materials. The dimethacrylate-based materials presented an increase in strength from 5 minutes to 1 hour and were as follows: Protemp 3 Garant (23.16 - 37.6 MPa), Temphase (22.27 - 28.08 MPa), Luxatemp (14.46 - 20.59 MPa). Protemp 3 Garant showed the highest value. The dimethacrylate-based temporary materials tested were stronger in diametral tensile strength than the monomethacrylate-based one. The diametral tensile strength of the materials investigated increased with time.

• Effects of HA released calcium ion on osteoblast differentiation.

  Authors: Gil-Yong Jung, Yoon-Jeong Park, Jung-Suk Han

  Journal of materials science. Materials in medicine. 02/2010; 21(5):1649-54.

  Hydroxyapatite (HA) is a widely used calcium phosphate implant substitute and has dissolution property. Although HA has been shown a beneficial effect on osteoblast differentiation, the exactHydroxyapatite (HA) is a widely used calcium phosphate implant substitute and has dissolution property. Although HA has been shown a beneficial effect on osteoblast differentiation, the exact mechanism is still unclear. In the present study, we proposed that Ca(2+) released from HA activated the expression bone associated proteins, OPN and BSP, mediated by L-type calcium channel and calcium/calmodulin-dependent protein kinase (CaMK) 2 which resulted into improved osteoblast differentiation. Results showed that HA elevated ALP expression as well as OPN and BSP expression in MC3T3-E1 cells. The result from western blot of CaMK2alpha indicated that HA released Ca(2+) activated CaMK2 through L-type calcium channel. Furthermore, upregulation of OPN and BSP mRNA expression was significantly inhibited when blocking both the L-type calcium channel and CaMK2. These findings suggested that HA accelerated the osteoblast differentiation by releasing Ca(2+).

• The effect of low temperature aging on the mechanical property & phase stability of Y-TZP ceramics.

  Authors: Hyung-Tae Kim, Jung-Suk Han, Jae-Ho Yang, Jai-Bong Lee, Sung-Hun Kim

  The journal of advanced prosthodontics. 11/2009; 1(3):113-7.

  Recently Yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) has been introduced due to superior flexural strength and fracture toughness compared to other dental ceramic systems. AlthoughRecently Yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) has been introduced due to superior flexural strength and fracture toughness compared to other dental ceramic systems. Although zirconia has outstanding mechanical properties, the phenomenon of decrease in the life-time of zirconia resulted from degradation in flexural strength after low temperature aging has been reported. The objective of this study was to investigate degradation of flexural strength of Y-TZP ceramics after various low temperature aging treatments and to evaluate the phase stability and micro-structural change after aging by using X-ray diffraction analysis and a scanning electron microscope (SEM). Y-TZP blocks of Vita In-Ceram YZ (Vita Zahnfabrik, Bad Säckingen, Germany) were prepared in 40 mm (length) × 4 mm (width) × 3 mm (height) samples. Specimens were artificially aged in distilled water by heat-treatment at a temperature of 75, 100, 125, 150, 175, 200, and 225℃ for 10 hours, in order to induce the phase transformation at the surface. To measure the mechanical property, the specimens were subjected to a four-point bending test using a universal testing machine (Instron model 3365; Instron, Canton, Mass, USA). In addition, X-ray diffraction analysis (DMAX 2500; Rigaku, Tokyo, Japan) and SEM (Hitachi s4700; Jeol Ltd, Tokyo, Japan) were performed to estimate the phase transformation. The statistical analysis was done using SAS 9.1.3 (SAS institute, USA). The flexural strength data of the experimental groups were analyzed by one-way analysis of variance and to detect statistically significant differences (α= .05). The mean flexural strength of sintered Vita In-Ceram YZ without autoclaving was 798 MPa. When applied aging temperature at below 125℃ for 10 hours, the flexural strength of Vita In-Ceram YZ increased up to 1,161 MPa. However, at above 150℃, the flexural strength started to decrease. Although low temperature aging caused the tetragonal-to-monoclinic phase transformation related to temperature, the minimum flexural strength was above 700 MPa. The monoclinic phase started to appear after aging treatment above 100℃. With the higher aging temperature, the fraction of monoclinic phase increased. The ratio of monoclinic/tetragonal + monoclinic phase reached a plateau value, circa 75% above 175℃. The point of monoclinic concentration at which the flexural strength begins to decrease was between 12% and 54%.

• Shear bond strength of veneering porcelain to zirconia and metal cores.

  Authors: Bu-Kyung Choi, Jung-Suk Han, Jae-Ho Yang, Jai-Bong Lee, Sung-Hun Kim

  The journal of advanced prosthodontics. 11/2009; 1(3):129-35.

  Zirconia-based restorations have the common technical complication of delamination, or porcelain chipping, from the zirconia core. Thus the shear bond strength between the zirconia core and theZirconia-based restorations have the common technical complication of delamination, or porcelain chipping, from the zirconia core. Thus the shear bond strength between the zirconia core and the veneering porcelain requires investigation in order to facilitate the material's clinical use. The purpose of this study was to evaluate the bonding strength of the porcelain veneer to the zirconia core and to other various metal alloys (high noble metal alloy and base metal alloy). 15 rectangular (4×4×9mm) specimens each of zirconia (Cercon), base metal alloy (Tillite), high noble metal alloy (Degudent H) were fabricated for the shear bond strength test. The veneering porcelain recommended by the manufacturer for each type of material was fired to the core in thickness of 3mm. After firing, the specimens were embedded in the PTFE mold, placed on a mounting jig, and subjected to shear force in a universal testing machine. Load was applied at a crosshead speed of 0.5mm/min until fracture. The average shear strength (MPa) was analyzed with the one-way ANOVA and the Tukey's test (α= .05). The fractured specimens were examined using SEM and EDX to determine the failure pattern. The mean shear strength (± SD) in MPa was 25.43 (± 3.12) in the zirconia group, 35.87 (± 4.23) in the base metal group, 38.00 (± 5.23) in the high noble metal group. The ANOVA showed a significant difference among groups, and the Tukey's test presented a significant difference between the zirconia group and the metal group. Microscopic examination showed that the failure primarily occurred near the interface with the residual veneering porcelain remaining on the core. There was a significant difference between the metal ceramic and zirconia ceramic group in shear bond strength. There was no significant difference between the base metal alloy and the high noble metal alloy.

• Biomechanical evaluation of dental implants with different surfaces: Removal torque and resonance frequency analysis in rabbits.

  Authors: Jung-Woo Koh, Jae-Ho Yang, Jung-Suk Han, Jai-Bong Lee, Sung-Hun Kim

  The journal of advanced prosthodontics. 07/2009; 1(2):107-12.

  Macroscopic and especially microscopic properties of implant surfaces play a major role in the osseous healing of dental implants. Dental implants with modified surfaces have shown strongerMacroscopic and especially microscopic properties of implant surfaces play a major role in the osseous healing of dental implants. Dental implants with modified surfaces have shown stronger osseointegration than implants which are only turned (machined). Advanced surface modification techniques such as anodic oxidation and Ca-P application have been developed to achieve faster and stronger bonding between the host bone and the implant. The purpose of this study was to investigate the effect of surface treatment of titanium dental implant on implant stability after insertion using the rabbit tibia model. THREE TEST GROUPS WERE PREPARED: sandblasted, large-grit and acid-etched (SLA) implants, anodic oxidized implants, and anodized implants with Ca-P immersion. The turned implants served as control. Twenty rabbits received 80 implants in the tibia. Resonance frequencies were measured at the time of implant insertion, 2 weeks and 4 weeks of healing. Removal torque values (RTV) were measured 2 and 4 weeks after insertion. The implant stability quotient (ISQ) values of implants for resonance frequency analysis (RFA) increased significantly (P < .05) during 2 weeks of healing period although there were no significant differences among the test and control groups (P > .05). The test and control implants also showed significantly higher ISQ values during 4 weeks of healing period (P < .05). No significant differences, however, were found among all the groups. All the groups showed no significant differences in ISQ values between 2 and 4 weeks after implant insertion (P > .05). The SLA, anodized and Ca-P immersed implants showed higher RTVs at 2 and 4 weeks of healing than the machined one (P < .05). However, there was no significant difference among the experimental groups. The surface-modified implants appear to provide superior implant stability to the turned one. Under the limitation of this study, however, we suggest that neither anodic oxidation nor Ca-P immersion techniques have any advantage over the conventional SLA technique with respect to implant stability.

• Biomechanical and histological behavior of zirconia implants: an experiment in the rat.

  Authors: Ralf J Kohal, Martin Wolkewitz, Marc Hinze, Jung-Suk Han, Maria Bächle, Frank Butz

  Clinical oral implants research. 05/2009; 20(4):333-9.

  OBJECTIVE: This study aimed at evaluating the integration of zirconia implants in a rat femur model. MATERIAL AND METHODS: Zirconia implants with two distinct surface topographies were compared withOBJECTIVE: This study aimed at evaluating the integration of zirconia implants in a rat femur model. MATERIAL AND METHODS: Zirconia implants with two distinct surface topographies were compared with titanium implants with similar topographies. Titanium and zirconia implants were placed into the femurs of 42 male Sprague-Dawley rats. Four groups of implants were utilized: machined zirconia implants, zirconia implants with a rough surface, machined titanium implants, and titanium implants with an electrochemically roughened surface. After a healing period of 28 days, the load-bearing capacity between the bone and the implant surface was evaluated by a push-in test. Additionally, after a healing period of 14 and 28 days, respectively, bone tissue specimens containing the implants were processed and histologically analyzed. RESULTS: The mean mineralized bone-to-implant contact showed the highest values after 14 and 28 days for the rough surfaces (titanium: 36%/45%; zirconia: 45%/59%). Also, the push-in test showed higher values for the textured implant surfaces, with no statistical significance between titanium (34 N) and zirconia (45.8 N). CONCLUSIONS: Within the limits of the animal investigation presented, it was concluded that all tested zirconia and titanium implant surfaces were biocompatible and osseoconductive. The presented surface modification of zirconia implants showed no difference regarding the histological and biomechanical results compared with an established electrochemically modified titanium implant surface.

• Double-layered Mobile P2P Systems Using Energy-Efficient Routing Schemes

  Authors: Jung-Suk Han, Jin-Woo Song, Taek-Hun Kim, Song-Bong Yang

  Telecommunication Networks and Applications Conference, 2008. ATNAC 2008. Australasian; 01/2009

  As the mobile technology advances, various mobile peer-to-peer (P2P) systems have been developed. Since mobile devices have limited energy capacity, efficient use of the energy is indispensable forAs the mobile technology advances, various mobile peer-to-peer (P2P) systems have been developed. Since mobile devices have limited energy capacity, efficient use of the energy is indispensable for mobile P2P systems. In this paper, we propose an energy-efficient P2P system that is a type of the double-layered P2P systems in which files are searched mainly through the peers in the upper level, called super peers. The proposed system selects greedily the peers with more energy as super peers. The peers in the proposed system can identify themselves as super peers or sub-peers autonomously in a decentralized manner. We also propose three energy-efficient routing schemes, each of which is incorporated with the proposed system individually. The first routing scheme tries to utilize the energy of the peers on the routes more evenly, the second scheme chooses a route with the `strongest' peer among the peers each of which is the `weakest' peer on a route, and the last scheme selects a route with the second scheme among the routes with the smallest number of hops. Note that a routing scheme is applied each time when a route between a pair of super peers is chosen during the message transmission. Functionality and performances were evaluated through various experiments, and the results showed that the proposed P2P system with the third routing scheme improved the average network lifetimes by 368% and 22% over the double-layered and the proposed systems without applying any proposed scheme, respectively.

• Reliability Schemes for P2P Systems in Dynamic Mobile Environments

  Authors: Ji-Hoon Kim, Jin-Woo Song, Taek-Hun Kim, Ju-Hee Lee, Kwang-Jo Lee, Jung-Suk Han, Sung-Bong Yang

  Computer Science and its Applications, 2008. CSA '08. International Symposium on; 11/2008

  In the double-layered mobile peer-to-peer (P2P) systems, peers are classified into two types, super peers and sub-peers; a super peer manages its sub-peers. The communications are done mostly amongIn the double-layered mobile peer-to-peer (P2P) systems, peers are classified into two types, super peers and sub-peers; a super peer manages its sub-peers. The communications are done mostly among super peers to reduce the network traffic in searching files. In mobile networks, reliability that guarantees communications among peers is one of the crucial factors. However, most of the previous P2P systems were evaluated under the 'static' mobile P2P environment where the number of peers was fixed and there were no dynamic joins and leaves. In this paper, we propose two schemes, the avoidance scheme and the role changing scheme, to improve the reliability of a system in the dynamic mobile P2P environment. The experimental results show that the proposed schemes improve the communication failure rates by 3% and 5% over the system without them, respectively.

• The biologic stability of alumina-zirconia implant abutments after 1 year of clinical service: a digital subtraction radiographic evaluation.

  Authors: Kyu-Hyun Bae, Jung-Suk Han, Yang-Jo Seol, Frank Butz, Jack Caton, In-Chul Rhyu

  The International journal of periodontics & restorative dentistry. 05/2008; 28(2):137-43.

  The purpose of the present clinical study was to evaluate the biologic stability of alumina-zirconia implant abutments by histologic and radiographic examination. Nineteen partially edentulousThe purpose of the present clinical study was to evaluate the biologic stability of alumina-zirconia implant abutments by histologic and radiographic examination. Nineteen partially edentulous patients were treated with 37 external-hexagon implants. After a healing period of 3 to 6 months, alumina-zirconia abutments were connected and restored with cemented single crowns or short-span fixed partial dentures. Periapical radiographs were taken at the time of prosthesis delivery and after 3, 6, and 12 months of follow-up. Crestal alveolar bone level changes were assessed by digital subtraction of consecutive images, and 1-way analysis of variance was used for statistical analysis. No implant, abutment, or restoration failed during the observation period. Bone level changes were statistically insignificant and histologic examination revealed no signs of inflammation. Stable and healthy soft and hard tissue conditions may be expected around alumina-zirconia abutments after 1 year of clinical service. However, long-term data are needed to confirm the present results.

• Biomechanical and histomorphometric study of dental implants with different surface characteristics.

  Authors: In-Sung Yeo, Jung-Suk Han, Jae-Ho Yang

  Journal of biomedical materials research. Part B, Applied biomaterials. 05/2008;

  The aim of this study was to investigate the early bone response to the titanium dental implants with different surface characteristics using the rabbit tibia model. Calcium metaphosphate coated,The aim of this study was to investigate the early bone response to the titanium dental implants with different surface characteristics using the rabbit tibia model. Calcium metaphosphate coated, anodic oxidized, hydroxyapatite particle-blasted, and turned (control) surfaces were compared. Surface topography was evaluated by field emission scanning electron microscope and optical interferometer. Eighteen rabbits received 72 implants in the tibia. Resonance frequency was analyzed every week for 6 weeks. Removal torque values were measured 2 and 6 weeks after placement. The implant-bone interfaces were directly observed by light microscope and bone-to-implant contact ratios were measured 2 and 6 weeks after insertion. All the surface-modified implants showed superior initial bone responses to the control. No significant differences were found among the surface-modified groups. Data suggest that various surface modification methods can provide favorable bone responses for early functioning and healing of dental implants. (c) 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008.