A three-dimensional finite element analysis of obturator prosthesis for edentulous maxilla / 대한치과보철학회지

PURPOSE: The purposes of this study were to evaluate the stress distributions and the displacements of obturator for edentulous maxillectomy patients and to compare them with those of complete denture using three-dimensional finite element analysis. MATERIALS AND METHODS: Based on the CT image of edentulous patient, three-dimensional finite element model of edentulous maxillae was constructed. Three-dimensional finite element model of edentulous maxillae with palatal defect was also fabricated. On each model, complete denture and obturator prosthesis were created. Vertical static force of 200 N was applied on the left maxillary premolar and molar region. The von Mises stress values and the displacements of models were analyzed using three-dimensional finite element analysis. RESULTS: Maximum von Mises stress values were recorded in the cortical bones of both models. The von Mises stress value in the complete denture model was 2.73 MPa and 2.69 MPa in the obturator model. High von Mises stress values were also observed on the tissue surface of prosthesis. The maximum value of the displacement in the obturator was higher than that of complete denture. CONCLUSION: The obturator showed a worse result in terms of stress distribution and displacement than complete denture. In the prosthodontic rehabilitation of edentulous maxillectomy patient accurate impression procedure based on patients' anatomy and application of prosthodontic principle should be considered.

One-Stage Posterior Debridement, Interbody Fusion and Instrumentation in the Treatment of Pyogenic Lumbar Spondylodiscitis

STUDY DESIGN: A retrospective study on the outcomes of surgical treatment for pyogenic lumbar spondylodiscitis. OBJECTIVES: To report the clinical outcomes of the surgical treatment of pyogenic lumbar spondylodiscitis using a one stage posterior approach. SUMMARY OF LITERATURE REVIEW: There are few reports on the treatment of pyogenic lumbar spondylodiscitis through a one stage posterior approach. MATERIALS AND METHODS: Between June 1999 and June 2005, this study examined the history of 12 patients with pyogenic lumbar spondylodiscitis treated by simultaneous posterior debridement, autogenous iliac bone graft and pedicle screw fixation. The clinical outcomes were evaluated in terms of the pain level, neurological status, hematological parameters and radiology findings. RESULTS: The clinical symptoms improved in all cases after surgery. There was no case of the infection recurring. The mean time for postoperative antibiotics and hospitalization was 6 weeks and 41.6 days, respectively. Radiological bony fusion was observed at 5.5 months on average. The mean preoperative, immediate postoperative and final follow-up sagittal angles were 4.6, 8.6 and 6.9degrees. CONCLUSION: One stage posterior interbody fusion and instrumentation for the treatment of pyogenic lumbar spondylodiscitis can provide radical debridement, bone graft and immediate stability without prohibiting the control of infection. Therefore, it can be used in selected cases.

Bone response of three different surface implants: histomorphometric and resonance frequency analysis in dogs / 대한치과보철학회지

STATEMENT OF PROBLEM: Reducing treatment time in implant dentistry is a matter of main concern. There are so many factors affecting the success rate of immediate or early loaded implant for the initial bone response. The especially microscopic properties of implant surfaces play a major role in the osseous healing of dental implant. PURPOSE: The aims of this study were to perform a histologic and histomorphometric comparison of the healing characteristics anodically roughened surface, HA coated surface and RBM surface implant, and to compare of ISQ values measured by Osstell(TM) for resonance frequency analysis in dogs mandible during 2 weeks. MATERIAL AND METHOD: Bone blocks from 2 dogs were caught after covered healing for 0 day(2h); Group I, 1 week; Group II and 2 weeks; Group III. One longitudinal section was obtained for each implant and stained with hematoxylin and eosin. Histomorphometric analysis was done with Kappa Imagebase system to calculate bone-to-implant contact and bone volumes inside the threads. ISQ values were measured in every time of surgery schedule. CONCLUSION: The experiment revealed that : 1. The percentages of bone-to-implant contact on the fixture in each group were not significantly different(P > 0.05). 2. The percentages of bone area inside the threads on the fixture in each group were not significantly different(P > 0.05). 3. The ISQ level showed clinical stability of each fixture during 2 weeks(all ISQ level >_71).

Scanning Electron Microscopic Study of the Effects of Citric Acid on the Change of Implant Surface According to Application Time / 대한치주과학회지

The present study was performed to evaluate the effect of citric acid on the change of implant surface microstructure according to application time. Implants with pure titanium machined surface, titanium plasmasprayed surface, and sand-blasted, large grit, acid etched surface were utilized. Implant surface was rubbed with pH 1 citric acid for 1/2 min., 1 min., 1 1/2 min., 2 min., and 3min. respectively in the test group and implant surface was not treated in the control group. Then, the specimens were processed for scanning electron microscopic observation. The following results were obtained. 1. Both test and control group showed a few shallow grooves and ridges in pure titanium machined surface implants. There were not significant differences between two groups. 2. In titanium plasma-sprayed surfaces, round or amorphous particles were deposited irregularly. The irregularity of titanium plasma-sprayed surfaces conditioned with pH 1 citric acid was lessened and the cracks were increased relative to the application time of pH 1 citric acid. 3. Sand-blasted, large grit, acid etched surfaces showed the macro/micro double roughness. The application of pH 1 citric acid didn't change the characteristics of the sand-blasted, large grit, acid etched surfaces. In conclusion, the application of pH 1 citric acid to titanium plasma-sprayed surface is improper. And pure titanium machined surface implants and sand-blasted, large grit, acid etched surface implants can be treated with pH 1 citric acid for peri-implantitis treatment if the detoxification of these surfaces could be evaluated.