Finite element analyses were performed to study effects on stress distribution generated in jaw bone for various shapes of dental implants: plateau type, plateau with small radius of curvature, triangular thread screw type in accordance with ISO regulations and square thread screw filleted with small radius partially. It was found that square thread screw filleted with small radius was more effective on stress distribution than other dental implants used in analyses. Additional analyses were performed on the implant with square thread screw filleted with small radius for verying design parameters, such as the width of thread end, the height of the thread of the implant and load direction, to determine the optimum dimensions of the implant. The highest stress concentration occurred at the region in jaw bone adjacent to the first thread of the implant. The maximum effective stress induced by a 15 degree oblique load of 100 N was twice as high as the maximum effective stress caused by an equal amount of vertical load. Stress distribution was more effective in the case when the width of thread end and the height of thread were p/2 and 0.46p, respectively, where p is the pitch of thread. At last, using tensile force calculated from the possible insert torque without breading bone thread, finite element analysis was performed on the implant to calculate pre-stress when the primary fixation of the implant was operated in jaw bone. The maximum effective stress was 136.8 MPa which proven to be safe.
Bread ; Dental Implants ; Finite Element Analysis ; Jaw ; Radius ; Social Control, Formal ; Torque

Balloon dacryocystoplasty has been reported to be a safe, easy and effective nonoperative treatment for nasolacrimal stenosis. The results were not encouraging, however, because of its high failure and recurrence rates. To evaluate the feasibility of using modified Gianturco expandable metallic stents for maintenance of the dilated nasolacrimal system(NLS), 20 stents of 3 mm in diameter and 10mm long were placed in 20 nasolacrimal ducts of 10 dogs for 1 month to 10 months. It was more difficult to introduce the stents into the proximal portion(A) of the NLS than into the distal portion(B) due to the narrow and bony canal of the A portion. Twenty stents showed no migration in follow-up studies of up to 10 months. One complete occlusion occurred in a stent placed in A portion. Autopsy studies showed stents were covered with epithelium within 2 months after placement. Our experience suggest that the placement of Gianturco self-expandable stents may be a useful method of dilating and maintaining the luminal diameter of the NLS, although care must be taken to select the proper stent size.
Animals ; Autopsy ; Constriction, Pathologic ; Dogs* ; Epithelium ; Follow-Up Studies ; Methods ; Nasolacrimal Duct ; Phenobarbital ; Recurrence ; Stents*

We have analyzed two (BclI and XbaI) intragenic restriction fragment length polymorphisms (RFLPs) and St14 (DXS52) variable number of tandem repeats (VNTR) by rapid PCR method in 97 unrelated normal subjects. The incidences for positive Bc1I and XbaI polymorphic sites in the Koreans were 81% and 72%, respectively, which were higher than other ethnic groups but similar to that reported in the Chinese or Japanese, giving the heterozygosity rate of 0.32 and 0.40, respectively. The amplified allele size was 880 bp with no other polymorphism in the analysis of St14 (DXS52) VNTR. This finding should be taken into account in the planning of a prenatal diagnosis program for ethnic Koreans
Base Sequence ; Gene Frequency ; Hemophilia A/epidemiology/*genetics ; *Heterozygote Detection/methods ; Human ; Korea/epidemiology ; Molecular Sequence Data ; Polymerase Chain Reaction ; Polymorphism, Restriction Fragment Length ; Prevalence

BACKGROUND AND OBJECTIVES: Vestibular schwannomas are intracranial neoplasms that compress adjacent structures as their volume grows. Although the clinically relevant parameter is most likely tumor volume, current clinical decisions are based on two-dimensional measurements of tumor diameter. This study was conducted to introduce a new software for accurate measurement of vestibular schwannoma volume and to determine the relationship between diameter and volume. Material and Method: Twenty-eight patients who had no previous treatment before MRI were included in this study. Diameter of the vestibular schwannoma was measured according to AAO guidelines and spherical volume was calculated from the diameter. For the accurate volume measurement of the vestibular schwannoma, we used a new software (Rapidia, 3D Med Co) developed in Korea. Paired t-test was used for the statistical analysis of correlation between the measured and calculated volumes. RESULTS: The difference between the measured and calculated volumes was statistically not significant (p=.120). However, as tumor size increased greater than 2 cm in diameter, our measured volume result was smaller than the calculated volume, although statistically not significant (p=.067). CONCLUSION: These results were due to tumor configuration, which was wider in the axial plane than in the longitudinal plane. From these results, we can realize that initial tumor growth was spherical, and as the size increased, it was distorted by the adjacent structures. These results suggest that special attention is needed in making clinical decisions on larger tumors, especially greater than 2 cm in diameter.
Brain Neoplasms ; Humans ; Korea ; Magnetic Resonance Imaging ; Neuroma, Acoustic* ; Tumor Burden