Biomedical subjects

Chong-Hyun Han

Publications and source records attributed to Chong-Hyun Han.

8 recordsLinked to original sources

PubMed2004

Development and evaluation of digital subtraction radiography computer program.

OBJECTIVE: We developed a new program for digital subtraction radiography (DSR) having useful functions to get the DSR image more accurately and efficiently. The purpose of this study was to evaluate the accuracy of the DSR image acquired using the new program as compared with the ready-made program. STUDY DESIGN: Four observers performed the DSR process using our program and the ready-made program for digital intraoral radiographs taken from incisor, premolar, and molar regions. The statistical difference was evaluated between the programs, between the observers, and between the regions. RESULTS: The DSR image using our program was superior to that with the ready-made program in all the observers and all the radiographed regions. Also, there was the statistical difference among the observers, especially in our program. CONCLUSION: The DSR image using the new program was very accurate compared with ready-made program, so the program was useful to get an accurate DSR image.

Humans↗

PubMed2002

Biological performance of calcium phosphate films formed on commercially pure Ti by electron-beam evaporation.

Thin and defect-free calcium phosphate films with a Ca/P ratio of 1.62 were formed by electron-beam evaporation. The as-deposited films had average bonding strengths to the metal implants of 64.8 MPa and the dissolution rates of 47.5 nm/h in isotonic saline solutions. The interface mechanical characteristics and histology of the as-machined, as-blasted, and calcium phosphate coating on the machined surfaces of commercially pure titanium were investigated. After a healing period of 12 weeks, the implants were unscrewed with a torque gauge instrument at the day of sacrifice. The coated sample showed a removal torque of 48.5 Ncm (SD 5.4) compared to 32.3 Ncm (SD 2.91) for the uncoated implant with the same surface roughness, and 47.3 Ncm (SD 5.8) for the grit blasted screw. The histomorphometric analyses of the calcium-phosphate-coated implants revealed a mean of 52.4% (SD 6.3) as the highest bone to implant contact.

Animals↗

PubMed2002

Fractal analysis of mandibular bony healing after orthognathic surgery.

OBJECTIVES: We evaluated the radiographic changes to the operational sites after orthognathic surgery by using fractal analysis. STUDY DESIGN: Panoramic radiographs from 35 patients who underwent orthognathic surgery on the mandible without any complications during the osseous healing process were selected. The radiographs taken before the operation (stage 0) and 1 or 2 days (stage 1), 1 month (stage 2), 6 months (stage 3), and 12 months (stage 4) after the operation were digitized at 600 dpi with 256 gray levels. The fractal dimension was calculated by means of a tile-counting method in the region of interest centered on the operational site and was statistically analyzed according to its stages. RESULTS: The fractal dimension was decreased immediately after the operation and increased gradually according to the time lapse (P <.05). The fractal dimension in the region of interest 12 months postoperatively was similar to that preoperatively. CONCLUSION: This result suggests that fractal dimension can be used to evaluate the bony healing process after orthognathic surgery.

Adult↗

PubMedDate not supplied

The effects of ion beam-assisted deposition of hydroxyapatite on the grit-blasted surface of endosseous implants in rabbit tibiae.

PURPOSE: This study was undertaken to evaluate ion beam-assisted deposition (IBAD) of hydroxyapatite (HA) on the grit-blasted surface of endosseous dental implants 6 weeks postplacement. MATERIALS AND METHODS: A total of 40 implants was placed in the tibiae of 10 New Zealand white rabbits. Twenty implants were grit-blasted only and the other 20 were grit-blasted and coated with HA by the IBAD method. After 6 weeks of healing, the rabbits were sacrificed and removal torque tests, histomorphometry, and morphometric analysis of microtomographic images were performed. RESULTS: The HA-coated group showed significantly higher removal torque, bone-to-implant contact, and bone volume than the other group. DISCUSSION AND CONCLUSION: In a previous study, the authors suggested that HA coating deposited on a machined surface by the IBAD method showed results comparable to or more favorable than the results obtained with a blasted surface. This study indicated that the HA coating produced by the IBAD method was also very effective on the aluminum oxide-blasted surface, as demonstrated by the early formation of osseointegration. Morphometric analysis by microtomography showed some promise in measuring the osseointegration rate. (More than 50 references.)

Animals↗

PubMedDate not supplied

Influence of implant abutment type on stress distribution in bone under various loading conditions using finite element analysis.

PURPOSE: The purpose of this study was to investigate the effect of 3 different abutment types on the stress distribution in bone with inclined loads using finite element analysis. MATERIALS AND METHODS: The 1-body, internal-hex, and external-hex implant systems were modeled to study the effect of abutment type on stress distribution in bone. The bone model used in this study comprised compact and spongious bone assumed to be homogeneous, isotropic, and linearly elastic. RESULTS: In the case of the 1-piece implant, the load was transferred evenly not only in the implant system but also in bone. However, the maximum Von Mises stress generated in bone with the 1-piece implant was always higher than that generated with the internal-hex implant, regardless of load angle inclination. In the case of the internal-hex implant, the contact condition with friction between abutment and implant in the tapered joints and at abutment neck reduced the effect of bending caused by horizontal component of inclined load. The maximum Von Mises stress in bone was the highest for the external-hex implant. DISCUSSION: It was found that the internal-hex implant system generated the lowest maximum Von Mises stresses for all loading conditions because of reduction of the bending effect by sliding in the tapered joints between the implant and abutment. CONCLUSIONS: It was concluded that abutment type has significant influence on the stress distribution in bone because of different load transfer mechanisms and the differences in size of the contact area between the abutment and implant.

Alveolar Process↗

PubMedDate not supplied

Displacement of implant components from impressions to definitive casts.

PURPOSE: Four possible displacements of implant components from a patient model to a definitive cast were assessed to suggest a standard method of comparing the accuracies of implant impression techniques. MATERIALS AND METHODS: Two techniques for impression making were assessed: a nonsplinted open-tray technique and a light-curing resin splinted open-tray technique. A mandibular model with 5 parallel implants was fabricated. Five definitive casts were fabricated per technique. Using a computerized coordinate measuring machine, 5 part coordinate systems were established, and 7 sets of data were obtained for each sample. From the data, the amount of displacement while connecting components and the linear and angular displacement of components during impression making and cast fabrication were calculated. The Mann-Whitney test was used to determine significant differences between the impression techniques (P < .05). RESULTS: The average displacements while connecting impression copings and abutment replicas were 31.3 and 30.4 microm, respectively. Less displacement occurred in the nonsplinted group compared to the splinted group during impression making (P = .001) but greater displacement occurred in that group during definitive cast fabrication (P = .015). DISCUSSION: In contrast to previous studies, the current study excluded displacement resulting from component connection, because displacement from that source has no relation to impression technique and cannot be controlled. CONCLUSIONS: Connecting a component produced as great a displacement as that resulting solely from a impression or cast fabrication. The nonsplinted group was more accurate during impression making but less accurate during cast fabrication.

Acrylic Resins↗

PubMedDate not supplied

Radiographic evaluation of marginal bone level around implants with different neck designs after 1 year.

PURPOSE: To evaluate the influence of macro- and microstructure of the implant surface at the marginal bone level after functional loading. MATERIALS AND METHODS: Sixty-eight patients were randomly assigned to 1 of 3 groups. The first group received 35 implants with a machined neck (Ankylos); the second group, 34 implants with a rough-surfaced neck (Stage 1); and the third, 38 implants with a rough-surfaced neck with microthreads (Oneplant). Clinical and radiographic examinations were conducted at baseline (implant loading) and 3, 6, and 12 months postloading. Two-way repeated analysis of variance (ANOVA) was used to test the significance of marginal bone change of each tested group at baseline, 3, 6, and 12 month follow-ups and 1-way ANOVA was also used to compare the bone loss of each time interval within the same implant group (P < .05). RESULTS: At 12 months, significant differences were noted in the amount of alveolar bone loss recorded for the 3 groups (P < .05). The group with the rough-surfaced microthreaded neck had a mean crestal bone loss of 0.18 +/- 0.16 mm; the group with the rough-surfaced neck, 0.76 +/- 0.21 mm; and the group with the machined neck, 1.32 +/- 0.27 mm. In the rough-surfaced group and the rough-surfaced microthreaded group, no statistically significant changes were observed after 3 months, whereas the machined-surface group showed significant bone loss for every interval (P < .05). DISCUSSION: To minimize marginal bone loss, in addition to the use of a rough surface at the marginal bone level, a macroscopic modification such as the addition of microthreads could be recommended. A rough surface and microthreads at the implant neck not only reduce crestal bone loss but also help with early biomechanical adaptation against loading in comparison to the machined neck design. CONCLUSION: A rough surface with microthreads at the implant neck was the most effective design to maintain the marginal bone level against functional loading.

Adult↗

PubMedDate not supplied

Osseointegration of anodized titanium implants coated with fibroblast growth factor-fibronectin (FGF-FN) fusion protein.

PURPOSE: The synergistic effect of fibroblast growth factor (FGF) and human fibronectin fragment (hFNIII9-10) on osteoblast cell adhesion has been demonstrated in vitro. The purpose of this study was to evaluate the bone response around anodized titanium implants treated with FGF-FN fusion protein using the histomorphometric analysis and the removal torque test. MATERIALS AND METHODS: Threaded implants were manufactured by machining a commercially pure titanium (grade 4). Two different groups of samples were prepared: Group 1 samples were anodized under a constant voltage of 300 V, and group 2 samples were anodized under a constant voltage of 300 V and then soaked in a solution containing fusion protein (65 microg/mL) for 24 hours. Ten implants from each group were placed in rabbit tibiae (1 implant per group per rabbit; each rabbit served as its own control). After a 3-month healing period, the animals were sacrificed. Removal torque testing and histomorphometric analysis was then carried out. RESULTS: The mean removal torque value of group 2 (44.8 Ncm) was greater than that of group 1 (37.6 Ncm). The percentages of bone-implant contact of the best 3 consecutive threads were 76.37% for group 1 and 88.02% for group 2. The percentage of bone-implant contact for the total length of the implant was higher for group 2 (36.91%) than for group 1 (29.47%). However, the percentage of the area inside the threads that consisted of bone did not differ significantly for the 2 groups. DISCUSSION AND CONCLUSION: This study demonstrated that the FGF-FN fusion protein coating on anodized implants may enhance osseointegration. However, the influence of fibronectin- and FGF-treated rough surfaces on long-term prognosis and the propagation of inflammation are subjects for further study.

Animals↗