The dental profession is currently experiencing a technology explosion. Processes are being replaced by modern, inexpensive, and precise techniques that can be used to solve complex restorative problems. Electrical discharge machining (DEM, known as spark erosion in Europe) is a nonconventional, industrial technique that has application in dentistry. EDM may be defined as a metal removal process using a series of sparks to erode material from a workpiece in a liquid medium under carefully controlled conditions. EDM is recently adopted in the dental laboratory to fabricate precision attachments, hybrid telescope crowns, Ti-ceramic crowns. EDM has also been used to achieve a passive precision metalto-metal fit between the substructure bar and the removable superstructure and to correct the fit of implant retained restorations. in this article, a brief history and explanation of EDM is discussed and a description of the use of this process for fabricating attachments and crowns or for correcting the fit of cast restorations is presented.
Crowns ; Cytochrome P-450 CYP1A1 ; Dentistry ; Explosions ; Laboratories, Dental ; Telescopes

Cortical support is an important factor, as the engagement of the fixture in strong compact bone offers an increased load-carrying capacity and initial stability. Because of the poor bone quality in the posterior mandible and other anatomic considerations, it has been suggested that implant fixtures be placed in these locations with apical engagement of the lingual cortical plate for so-called bicortication. The purpose of this investigation was to determine the effect of cortical engagements and in addtion polyoxymethylene (POM) intramobile connector(IMC) of IMZ implant on implant load transfer in edentulous posterior segment of mandible, using three-dimensional(3D) finite element analysis models composed of cortical and trabecular bone involving single implant. Variables such as (1) the crestal peri-implant defect, (2) the apical engagement of lingual cortical plate, (3) the occlusal contact position (a vertical load at central fossa or buccal cusp tip), and (4) POM IMC were investigated. Stress patterns were compared and interfacial stresses along the bone-implant interface were monitored specially. Within the scope of this study, the following observations were made. 1) Offset load and angulation of fixture led to increase the local interfacial stresses. 2) Stresses were concentrated toward the cortical bones, but the crestal peri-implant defect increased the interfacial stresses in trabecular bone. 3) For the model with bicortication, it was noticed that the crestal cortical bone provided more resistance to the bending moment and the lingual cortical plate provided more support for the vertical load. But Angulaton problem of the fixture from the lingual cortical engagement caused the local interfacial stress concentrations. 4) It was not clear that POM IMC had the effect on stress distribution under the present experimental conditions, expecially for the cases of crestal peri-implant defect.
Finite Element Analysis* ; Mandible*

Krukenberg tumor, which can account for 30-40% of metastatic cancers to the ovaries, arises in the ovarian stroma and is usually metastatic from the gastrointestinal tract, especially from the stomach. The pathognomonic feature is the presence of signet ring cells, which may be arranged in acini or appear as individual cells. We experienced a Krukenberg tumor which was bilateral and associated with left ovarian dermoid cyst. This patient was treated for a primary gastric carcinoma(Stage II) about 3 years ago. After bilateral salpingoophorectomy, she received adjuvant chemotherapy. But, she died about fow months after operation.
Chemotherapy, Adjuvant ; Dermoid Cyst* ; Female ; Gastrointestinal Tract ; Humans ; Krukenberg Tumor* ; Ovary ; Stomach

This study measured the relative displacements of the five-unit fixed partial dentures as cast with the same fixed partial dentures sectioned and assembled by investment-soldering, soldering stand-soldering, and cast-joining techniques. A total of fifteen specimens using a type IV gold alloy wee one-piece cast as control and then sectioned and assembled five test specimens for each method were prepared. A computerized three dimensional coordinate measuring machine and specially designed cylinder for this study were used. Displacement was defined by six displacement variables for the each of cylinders incorporated in each casting: three component displacements ( Lx, Ly, and Lz) and rotational displacements( thetax, thetay, thetaz). The global displacement was computed using the mathematical formula R= Global displacement ={{{{rm SQRT { (x'-x)^2 +(y'-y)^2 + (z'-z)^2} }} }} Under the conditions of this study, the following conclusions were drawn: 1. The investment-soldering group showed the largest mean value of final global displacements, followed by stand-soldering group, cast-joining group and one-piece cast group. However, between the mean values of final global displacement for the cast-joining group and one-piece cast group, there was no significant difference. 2. For investment-soldering and stand-soldering groups, the greater global displacements were recorded in soldering phase than in indexing or investing phase. 3. For one-piece cast group, the displacements occured mostly in the casting phase. And for castjoining group, there was no significant difference in global displacements among the fabrication procedures. 4. Intercentroidal distance decreased in framework-pattering, solder-indexing, solder-standing, and soldering phases, but increased in investment block-investing and casting phases. 5. Specially designed cylinder for touch-trigger type coordinate measuring machine was validated.
Abstracting and Indexing as Topic ; Alloys ; Denture, Partial, Fixed ; Investments ; Methods

BACKGROUND: Recent evidences suggest that anesthetic action within the spinal cord is important in suppressing somatic responses to painful stimuli. Intrathecal endothelin-1 (ET-1) is known to have antinociceptive effect. The purpose of this experiment was to determine whether intrathecal ET-1 may influence the minimum alveolar concentration (MAC) of isoflurane in rats and access the role of the spinal cord as the sites of anesthetic action in blocking somatic responsiveness. METHODS: In Sprague-Dawley rats fitted with an indwelling intrathecal catheter, we determined the MAC of isoflurane using a tail-clamp technique as a painful stimulus, combined with end-tidal anesthetic sampling. In experiment 1, the control MAC was determined and changes of control MAC were observed after intrathecal ET-1 (4x10-2 nmol, 4x10-3 nmol) administration. In experiment 2, we observed the effects of L or N type Ca++ channel blocker such as verapamil (50 g) or W-conotoxin (0.5 g) on the MAC after measurement of the control MAC. In experiment 3, after measurement of the control MAC, ET-1 (10-2 nmol) was administered intrathecally and the MAC was determined again. Next, intrathecal verapamil (50 g) or W-conotoxin (0.5 g) was injected. After that, the MAC was determined again. RESULTS: In experiment 1, ET-1 decreased the MAC of isoflurane and its effect was sustained over 2 hours. In experiment 2, the MAC, determined following administration of verapamil or W-conotoxin, was not different from that of the control. In experiment 3, the MAC was decreased after ET-1 administration and then increased following injection of verapamil or W-conotoxin. CONCLUSIONS: These results suggested that ET-1, in relation to calcium, might play an important role in determining the MAC of isoflurane in the spinal cord.
Animals ; Calcium ; Catheters ; Endothelin-1* ; Isoflurane* ; Rats* ; Rats, Sprague-Dawley ; Spinal Cord ; Verapamil

The purpose of this study was to evaluate the effect of wattage and curing time on surface hardness, three-point bending strength and internal porosity of microwave curing denture base resin. Two sizes of resin spicimens were made of Acron MC ; 3.5x10x60mm for surface hardness and three-point bending strength measurement and 5x12x60mm for internal porosity measurement. They were cured by microwave energy at varing wattages(500W, 700W) and curing times(2min., 3min., 4min.) to determine if a certain wattage/curing time combination would improve physical properties. Surface hardness was measured with Vikers hardness tester, three-point bend-ing strength with universal testing machine and internal porosity was calculated by measuring the weight in air and in water. The results obtained were as follows : 1. There was no significant difference in percent porosity among experimental groups(p>0.05). 2. 500W/3min, group showed the higher surface hardness than 700W/2, 3, 4min. groups(p<0.05), and 700W/4 min. group showed the lower surface hardness than 500W/2, 3, 4min. groups(p<0.05), but there was no significant difference among others(p>0.05). 3. 500W/3min. group yielded the higher value of bending strength than 500W/2min., 700W/3, 4min. groups(p<0.05), but there was no significant difference among others(p>0.05).
Denture Bases* ; Dentures* ; Hardness ; Hardness Tests ; Microwaves* ; Polymethyl Methacrylate ; Porosity ; Water

The purpose of this study is to evaluate the color differences that can exist between differnet brands of dentin porcelain having identical shade designations. The instrumental colorimetric technique was used to determine these differences. The three brands of dentin porcelain used were Vita VMK-68, Shofu Vintage, and Ceramco II. The three shades selected were the Vita Lumin shades A2, B2, and C2. The color difference values were compared with each other using L*, a*, b*, three variables of the CIELAB color system, and E. The results of this study were as follows: 1. Corresponding shades of different brands of dentin porcelain produced different L*, a*, b* values. 2. The greatest E value in corresponding shade was found to exist between Ceramco II and Shofu Vintage, followed by between Vita VMK-68 and Ceramco II, and then between Vita VMK-68 and Shofu Vintage. 3. The E values in shade C2 were mainly influenced by L* value ; however none of L*, a*, b* values had greater influence on E values than the others in shade A2, B2. 4. Shofu Vintage had the highest b* value, followed by Vita VMK-68, and then Ceramco II.
Dental Porcelain* ; Dentin*

PURPOSE: We evaluated the correlation between the carcinogenesis of gallbladder and the expression of lysozyme, p53, c-erbB2 and CEA in gallbladder lesions. MATERIALS AND METHODS: Thirty cases of gallbladder lesions (containing 17 cases of GB carcinoma) were examined. We analyzed the clinicopathologic findings of the early (stage I & II) and advanced carcinoma (stage III, IV & V) and those of carcinoma with or without metaplasia in the tumor. We performed p53, c-erbB2 and CEA immunohistochemical staining and compared their findings with those of normal mucosa and preneoplastic lesions. We also performed lysozyme immunohistochemical staining and compared its finding with metaplastic and non-metaplastic lesions. RESULTS: There are two distinct genetic pathways in gallbladder cacinogenesis and metaplastic carcinoma was more frequent than non-metaplastic carcinoma. Metaplasia of gallbladder did not reveal any difference of the clinicopathologic findings and depth of invasion (Nevin stage). Lysozyme expression was found in all metaplastic lesions but non-expression did not indicate non-metaplastic lesions. p53 mutations and c-erbB2 alterations may have a role in the carcinogenesis of gallbladder carcinomas, especially, in a late event, and in an early and late events, respectively. The correlation of p53 and c-erbB2 expressions was found but which did not indicate that the co-expression was needed in the carcinogenesis. CEA immunohistochemical staining may be helpful in the differential diagnosis of benign lesions and precancerous and cancerous lesions of the gallbladder. CONCLUSION: These results suggest that p53 mutations and c-erbB2 alterations may have a role in the carcinogenesis of gallbladder carcinomas, especially, in a late event, and in an early and late events, respectively.
Carcinogenesis ; Diagnosis, Differential ; Gallbladder* ; Metaplasia* ; Mucous Membrane ; Muramidase

The purpose of this study was to investigate the effect that three resin indexing materials had on the distortion of split cast in the procedures of solder indexing and block fabrication. The specimen had two cylinders and connecting bar. Two cylinders were a reference cylinder and a test cylinder that were machined precisely and placed on metal base. The total of specimens wee 30 and they were divided into 3 groups according to the resin indexing materials : Acrylic solder , G-C Pattern resin , Z-100 . The relative coordinates (X, Y, Z) of centroids of both cylinders were measured by using 3-D coor dinates measuring machine. The value of indexing distortion was obtained after application of indexing material, and the value of the block distortion was obtained after fabrication of soldering block, and the value of total distortion was a value sum of indexing distortion and block distortion. Intercentroidal linear distortion({{{{ SQRT {X'^2 + Y'^2 +Z'^2 }- SQRT {X^2 + Y^2 +Z^2} }} }}) and global distortion {{{{rm SQRT {(X'-X)^2 +(Y'-Y^)2 +(Z'-Z^)2} }} }} were calculated from data of coordinates of centroids at each mea s u r ing stages. The results of this study were as belows ; 1. The intercentroidal distance between the split casts was reduced by indexing distortion and increased by block distortion. 2. The indexing global distortion between the split casts was smaller than block global distortion. 3. The intercentoidal linear distortion and the global distortion were no significant difference between indexing materials.
Abstracting and Indexing as Topic

This study evaluated the effect of dagassing on the ceramic bond strength of two Ni-Cr alloys under varying holding time at the upper limit temperature and atmospheric conditions. Metal specimens were divided into 5 groups for each alloy according to degassing conditions prior to porcelain application : no degassing, degassing under vacuum without hold, degassing under vacuum with hold for 5min. and 10 min. respectively at the upper limit temperature and degassing in air. Total number of metal ceramic specimens was eighty and each group had eight specimens : The ceramic bond strength was measured by four-point flexural test using Instron and the fractured surface was examined under SEM. The results obtained were as follows. 1. Degassing in air improved the ceramic bond strength of Ni-Cr alloys. 2. in degassing under vacuum, hold at the upper limit temperature was advantageous to the ceramic bonding of Ni-Cr alloys. 3. After ceramic metal bond test, metal surfaces were partially covered with the thin porcelain layer, and the cohesive failures in porcelain were predominant in groups showing higher ceramic bond strength.
Alloys* ; Ceramics* ; Dental Porcelain ; Vacuum