ABSTRACT
The purpose of this study comparatively analyzed the machinability of various dental hybrid blocks manufactured by using the CAD/CAM system. Three hybrid composite blocks (Vita enamic, Lava Ultimate, GC Cerasmart) were used for experimental groups and one conventional ceramic block (Vita Mark II) was used for control. The digital impression of the master model and abutment was taken by using a scanner, and then the CAD software program was used to design restorations. The four-axis milling machine (inLab MCXL; Sirona Dental Systems GmbH, Bensheim, Germany) was used four materials. The digitized data was superimposed with 3D inspection software to quantitatively obtain the machinability of a ceramic crown, and visual differences were confirmed with a color map. The root mean square (RMS) values of ceramic crown group were statistically analyzed with one-way ANOVA (α=0.05). While there was a significant difference in the machinability of the internal surface, among four groups, there was statistically significant difference between conventional (VM group) and hybrid ceramic (VE, LU, GC groups) (p<0.05). Consequently, the machinability of VM is lower than that of other hybrid ceramics, and the machinability of VE is better than that of LU and GC. For ceramics as final restorations, manufacturing of dental restorations using hybrid composite ceramic is recommended.
Subject(s)
Ceramics , CrownsABSTRACT
PURPOSE: To measure the cement mantle thickness that developed from a rotation of the femoral stem in virtual space made by the broach. MATERIALS AND METHODS: The C stem and Versys stem of the subjects enrolled in this study were examined. A C250/400VZ(Steinbichler Co. Germany) and S/W: Geomagic & CATIA V5 was used to examine the three-dimensional configurations. The axial images were acquired after neutral placement of the femoral stem, horizontal rotation, coronal tilting, and a combination of both. The thickness was measured from the distance between the outer surface of the femoral stem and the closest vertex in the outer contour of the broach in cross-sectional images. RESULTS: The distance was <1 mm at the horizontal rotation of 3 degrees in the C stem, and at 5 degrees in the Versys stem. The distance was <1 mm at varus of 0.25 degrees in the C stem, and touched at 0.8 degrees. In the case of the Versys stem, the femoral stem touched at a varus of 1 degree. A combination of both horizontal and pivot rotation made the distance <1 mm at rotation of all angles. CONCLUSION: It might be necessary to develop a new instrument for the accurate insertion of the femoral stem along the broached space or to modify the stem design to stand against the change in the femoral stem position in the broached space.
Subject(s)
Statistics as TopicABSTRACT
Diagnosis of dentofacial deformity needs three dimensional comprehensive understanding of craniofacial skeleton. Eventhough three dimensional computerized tomogram has been developed, the quantified measurement analysis is merely depend on cephalomeric analysis. In our pilot study using the ordinary cephalometric radiogram which is commonly used in clinical basis, we tried to reconstruct three dimensional coordinates from frontal and lateral cephalogram taken from five dry skulls attached with small metal ball. To evaluate the reproducibility of the cephalogram, intra-examiner error was measured and compared with the three dimensional coordinates. Fourteen linear measurement of dry skull and three dimensional value has been compared. The results were as follows: 1. The intra-examiner error of the two dimensional cephalogram showed a similar variation below 1 mm in frontal and lateral cephalogram. The error ranged from 0.11-0.13mm in the case of frontal cephalometrics and 0.12-0.57mm for lateral cephalometrics Three dimensional coordinates showed relatively high reproducibility except 7 coordinates out of 90 (7.8%). The average error of the single measurement of x,y,z point shown to be 0.04+/-0.21mm, 0.01+/-0.01mm. 0.08+/-0.08mm. 2. Compare the 14 linear measurement of dry skull and three dimensional measurement, the mean difference was 0.13+/-1.54mm, ranging from 2.59+/-3.00mm (L-Co, R-Co) to 0.01+/-0.38 (ANS, L-Or). From the result by taking real value percentage rate by 3 dimensional measuring value, the mean value was 100.74+/-3.92% and the measurement which showed the most shortening compared with the real value was the distance between R-Or and ANS (97.75+/-3.11%) and the most enlarged measurement was the distance between L-VMC, L-VIC (106.59+/-20.33%). 3. However, compare the real value and two dimensional cephalometric radiograph, difference between the two is significant degree which hinder the use of two dimensional measurement in clinical situation. This potential pitfall of the cephalogram might be overcome by using our three dimensional coordinate system. If the reproducibility of the frontal and lateral cephalogram is achieved, major concern related to the accuracy of three dimensional measurement is correct detection of anatomical landmark. Further investigation of anatomical investigation of facial skeleton will make this system more accurate and popular in clinical field.