The purpose of this study was to estimate the morphology and the size of permanent mandibular molar in Korean Adult. The 100 dental college students with a normal dentition and without any dental prosthesis and severe caries were selected for this study. The subjects were taken impression to make study model. On the study model, the 5 dentists measured those sizes and estimated morphological structures with a calipers, a Boley gauge and a protractor. The results were as follows : 1. The clinical crown height, width, thickness and the other anatomical structures had symmetrical relationship between the left and right mandibular molar. 2. In the clinical crown heights aspect, the buccal crown heights always were higher than the lingual crown height. The heights of the each surface, the buccal or lingual surface, were gradually decreased from the 1st molar to the 2nd molar and the difference on the buccal surface was higher than that on the lingual surface. 3. In the clinical crown width aspect, the mesiodistal measurement of the mandibular 1st molar was higher than that of the mandibular 2st molar. 4. In the clinical crown thickness aspect, the mesial buccolingual measurement was highest on the mandibular 1st molar and the distal buccolingual distance was lowest on the mandibular 2nd molar. This distal thickness of the mandibular molar always was higher than that of the mesial half. 5. The well-developed mesiobuccal groove of the 1st mola was observed more often than that of the 2nd molar. The buccal pit was also observed more frequently at the 1st molar, but the frequency(35%) was not high. 6. The occlusal type according to the number of cusp was almost 5-cusp(98%) in the 1st molar and was also 5-cusp(63%) in the 2nd molar. The frequency of the 6th cusp was 31% in the 1st molar and was 22% in the 2nd molar. The frequency of the 7th cusp was below 2% in the both teeth. 7. In the buccolingual intercuspal distance aspect of the mesial and distal half, the intercuspal distance of distal half was higher than that of the mesial half on the 1st and 2nd molar, but the difference on the 1st molar was higher than that on the 2nd molar. 8. The difference between the widths of the buccal and lingual half was 1.5mm in the 1st molar and 0.8mm in the 2nd molar. Therefore the lingual convergency of the occlusal surface was more higher in the 1st molar. 9. On the mandibular 1st and 2nd molar, the distobuccal external angle was more acute than the mesiobuccal external angle. But the mesiobuccal internal angle was more acute than the distobuccal internal angle. 10. When the mandibular molar was a 5-cusp type, the development of the distal cusp on the 1st molar was better than that on the 2nd molar. The difference between the cusps was around 0.4mm.
Adult* ; Crowns* ; Dental Prosthesis ; Dentists ; Dentition ; Humans ; Molar* ; Tooth

The purpose of this study was to investigate the causes of food impaction and to explore solutions as well. For this study, 39 patients with food impaction wee selected. 77 contact areas in these patients were investigated mobility, tightness of contact area, gingival index, plaque index, attachment loss, alveolar bone loss, proximal caries, marginal ridge distance and occlusal relationships. The results were as follows ; 1. Teeth without distal support were found to be the most frequent site of food impaction (41.6%). Food impaction was found to be more frequent in the upper teeth (66.2%) than the lower teeth (33.8%). 2. Food impaction was found in tight contact cases (71.4%). Alveolar bone loss was not found in the early stage of food impaction (83.1%) 3. The distance between the marginal ridges of food impaction sites (mean=0.48mm) was shorter than that of the control group. (mean=0.77mm) (p<0.001) 4. In 18.2% of t he cases, proximal carries were found at the food impaction site. 5. Food impaction affected patient's occlusion with the following frequencies ; cusp to marginal ridge relationship (72.7%), cusp to fossa relationship (3.9%) and stepped relationship (23.4%).
Alveolar Bone Loss ; Humans ; Periodontal Index ; Tooth

This investigation was designed to estimate the biaxial flexure strength and fracture toughness of lithium disilicate glass-ceramics of IPS Empress 2 system pressed with as-received ingots and their sprue buttons. Two groups of the lithium disilicate glass-ceramics were prepared as follows: group 1 is ingot-pressed group; group 2 is sprue button-pressed group. A ball-on-three-ball test was used to determine biaxial flexure strength (BFS) of disks in wet environment. Scanning electron microscopy(SEM) analysis was conducted to observe the microstructure of the ceramics. Unpaired t-test showed that there were no differences in the mean biaxial flexure strength (BFS) and KIC values between group 1 and 2 (p>0.05). Two groups showed similar values in the KIC and the strength at 5% failure probability. The SEM micrographs of the IPS Empress 2 glass-ceramic showed a closely packed, multi-directionally interlocking pattern of numerous lithium disilicate crystals protruding from the glass matrix. The lithium orthophosphate crystals could not be observed on the fracture surface etched. There was no a marked difference of the microstructure between group 1 and 2. Although there were no tests including color stability, casting accuracy, etc., the results of this study implied that we could reuse the sprue button of the pressed lithium disilicate glass-ceramic of IPS Empress 2 system.
Celiac Disease ; Ceramics ; Glass ; Lithium* ; Phosphates

No abstract available.
Denture, Partial, Fixed*

PURPOSE: This study was performed to measure the accuracy of adjustable dental impression trays by a scanning laser three-dimensional digitizer. MATERIALS AND METHODS: The metal stock, individual, and adjustable stock trays were used for 60 stone casts(10 casts each) duplicated a resin master model of mandible and maxilla. The type IV dental stone was poured in a vinyl polysiloxane impressions and allowed to set for one hour. The master model and the duplicated casts were digitized using an optical digitizer. The distance between the reference points were measured and analyzed on the graphic image of 3-D graphic software(CATIA version 5.0). The statistical significance of the differences between the groups was determined by a two-way ANOVA. RESULTS: There were no significant differences between the accuracies of the adjustable stock tray and the master model except only anterior arch width on the upper arch and the diagonal arch length and arch length on one side of the lower arch. CONCLUSION: The adjustable stock trays showed clinically acceptable accuracies of the study cast produced by them.
Mandible ; Maxilla ; Siloxanes

The purpose of this study was to compare the wear characteristics of Type III Gold Alloy (Degular C; Degussa AG), VMK 95 (Vita Zahnfabrik), Vitadur Alpha (Vita Zahnfabrik), IPS Empress (Ivoclar-Vivadent) and Targis (Ivoclar-Vivadent). Ten samples of each material were abraded against enamel of extracted incisors for 160,000 cycles on the wear machine. The depth of wear scars on enamel was analized with profilometer (Alpha-step 200; Tencor). And the wear of material specimen was determined with micrometer (PB-1B; Mitutoyo Co. Japan). The results obtained were as follows : 1. Type III gold alloy (2.47micrometer) and Targis (5.89micrometer) caused less wear of enamel specimens compared to VMK 95 (75.59micrometer), IPS Empress (78.60micrometer) and Vitadur Alpha (78.89micrometer) (p<0.05). 2. The wear of material specimen when opposing enamel was the lowest in type III gold alloy (3.0micrometer), followed by Targis (69.8micrometer), IPS Empress (148.4micrometer). VMK 95 (298.0micrometer) and Vitadur Alpha (300.8micrometer) exhibited the most severe wear against enamel (p<0.05).
Alloys ; Cicatrix ; Dental Enamel ; Incisor

BACKGROUND: Fine Needle Aspiration Cytology (FNAC) is widely accepted as the most accurate procedure to differentiate malignant from benign thyroid nodules. It is a simple, safe, and inexpensive procedure, and the accuracy of FNAC is relatively high; however, its success usually depends upon the skill in using the aspiration technique and the experience and skill of the cytologist. The authors confirmed the diagnostic value of preoperative FNAC in differential diagnosis of thyroid nodules treated by the surgical resection. METHODS: Three hundred fifty specimens were taken in the Department of Surgery, Inje University College of Medicine, from July 1990 to June 1996. Fifty-one males and 299 females with ages ranging from 11 to 73 years were enrolled. The cytology of FNAC was compared to the final histologic diagnosis. RESULTS: The number of inadequate smears (or sampling error) was 15.7%. Preoperative cytologic diagnoses was consisted of 198 cases of benign disease (92 cases of nodular goiters, 96 cases of follicular lesion types III, and 10 cases of thyroiditis), 12 cases of highly suspicious malignant lesions (follicular lesions type II), and 85 cases of malignant disease (71 cases of papillary carcinomas and 14 cases of follicular lesions type I). Histologic diagnoses consisted of nodular goiters in 116 cases, adenomas in 66 cases, thyroiditis in 9 cases, papillary carcinomas in 84 cases, and follicular carcinomas in 20 cases. These results has an 84.6% sensitivity, a 95.2% specificity, a 15.3% false negative rate, and a 4.7% false positive rate. In the fifty-five cases of inadequate sampling, 13 cases (23.6%) were malignant lesions histologically. In the 16 cases proven as false negative, nine cases were papillary carcinomas, and 7 cases were follicular carcinomas histologically. Thirteen cases (16.1% of 27 cases of cystic lesions) of cystic nodules revealed malignant neoplasms histologically. CONCLUSION: FNAC is a single, useful diagnostic procedure for the initial screening for malignancy in thyroid nodules. Performing repeated aspiration in cystic nodules and clinically suspicious cases could reduce inadeguate sampling and the false negative rate.
Adenoma ; Biopsy, Fine-Needle* ; Carcinoma, Papillary ; Diagnosis ; Diagnosis, Differential* ; Female ; Goiter, Nodular ; Humans ; Male ; Mass Screening ; Sensitivity and Specificity ; Thyroid Gland* ; Thyroid Nodule* ; Thyroiditis

The purpose of this study was to compare the fracture strength of the IPS Empress ceramic crown according to the occlusal depth (1.5mm, 2.0mm, 2.5mm) and axial inclination (4degree, 8degree, 12degree) of the upper first premolar. After 10 metal dies were made for each group, the IPS Empress ceramic crowns were fabricated and each crown was cemented on each metal die with resin cement. The cemented crowns mounted on the testing jig were inclined 30 degrees and a universal testing machine was used to measure the fracture strength. The results were : 1. The fracture strength of the ceramic crown with 2.5mm depth and 12degreeinclination was the highest (630N). Crowns of 1.5mm depth and 4degreeinclination had the lowest strength(378N). There were no significant differences of the fracture strength by axial inclination in same occlusal depth group. 2. The fracture mode of the crowns was similar. Most of fracture lines began at the loading area and extended through proximal surface perpendicular to the margin, irrespective of occlusal depth.
Bicuspid* ; Ceramics ; Crowns* ; Resin Cements

This study was undertaken to clarify the microstructure of the different IPS Empress ingots by etching and to observe the change of leucite crystal structure according to subsequent heat treatment and the crystal distribution according to sprue types(0 2.8mm, single sprue; 0 1.8mm, double sprue) by scanning electron microscopy. IPS Empress T1, O1 ingots used for staining technique, and Dentin(A2) ingots used for layering technique were selected for this study. To observe the microstructures of these ingots before pressing, the specimens were prepared in splinters(3x3x3mm) taken from the original ingots. And to estimate crystal distribution and microstructural change by sprue type and subsequent heat treatment, the specimens(3x3x3mm) were heat-pressed through the two types of sprues with different diameters and numbers, and all specimens were fired according to the recommended firing schedule. The observed surface was ground with waterproof papers(#800~#1800) on the grind polisher and was cleaned ultrasonically. All specimen were etched with 0.5% hydrofluoric acid. After etching, the surface was treated by ion sputter coating for SEM observation at an accelerating voltage of 20kV. In all specimens, the central area of ground surface was observed because there was less difference in microstructure between the peripheral area and the central area. The results were as follows ; 1. In the microstructure according to the ingot type, there was a wide difference between the staining (T1,O1) and layering(Dentin A2) ingots, but there was not a considerable difference between the T1 ingot and the O1 ingot for staining technique. 2. In all specimens, the crystal dispersion of IPS Empress ceramic using double sprue was significantly more scattered than that of IPS Empress ceramic using single sprue. The degree of scattering was strongest in the Dentin(A2) specimen and weakest in the O1 ingot. 3. In the microstructural change according to the subsequent heat treatment, all of ingots had some microcracks in the inside of the leucite crystal and the glass matrix after pressing. The inner splinters of the leucite crystal became smaller, and more microcracks occurred in the glass matrix due to increasing heat treatment times. 4. The size of leucite crystals varied from 1micrometerto 5micrometer. The mean size of mature crystals was about 5micrometer. The form of the crystal was similar to a circle when it was smaller and similar to an ellipse when it was larger.
Appointments and Schedules ; Celiac Disease* ; Ceramics* ; Fires ; Glass ; Hot Temperature* ; Hydrofluoric Acid ; Microscopy, Electron, Scanning

The purpose of this study was to compare the microleakage of the IPS Empress ceramic crown according to 1) margin types such as rounded shoulder and bevel, 2) margin locations such as enamel and dentine, 3) resin cement types such as Variolink and Bistite. For this study, 80 extracted premolar teeth were used. After 10 experimental dies were prepared for each group, the IPS Empress ceramic crowns were fabricated on the dies and cemented with one of two types of resin cement. After 1,000 cycles of thermal changes were given with the thermocycling unit, each specimen was sectioned with a low speed diamond saw in both the buccolingual and the mesiodistal direction. The microleakage was then measured with a stereo microscope. The obtained results were as follows : 1. Every experimental group showed microleakage. The microleakage of the crowns which had a rounded shoulder on enamel cemented with Variolink was the lowest of all. The resulting rank of the mean microleakage was rounded shoulder on enamel using Variolink(0.601mm), rounded shoulder on enamel using Bistite (0.794mm), bevel on enamel using Variolink (0.826mm), rounded shoulder on dentine using Variolink(1.054mm), bevel on enamel using Bistite(1.087mm), rounded shoulder on dentine using Bistite(1.176mm), bevel on dentine using Variolink(1.258mm), and bevel on dentine using Bistite(1.467mm). 2. The statistically significant differences in the microleakage were found in 4 cases: rounded shoulder on enamel using Variolink and bevel on dentine using Variolink, rounded shoulder on enamel using Variolink and bevel on dentine using Bistite, rounded shoulder on enamel using Bistite and bevel on dentine using Bistite, bevel on enamel using Variolink and bevel on dentine using Bistite. 3. The microleakage of rounded shoulder finish line was lower than that of bevel finish line. The statistically significant differences were found with respect to the type of finish lines. 4. The microleakage of the finish line on enamel was lower than that of finish line on dentine. The statistically significant differences were found with respect to the location of the finish lines. 5. The microleakage of the Variolink cement was lower than that of the Bistite cement. The statistically significant differences were found with respect to the resin cements.
Bicuspid ; Ceramics* ; Crowns* ; Dental Enamel ; Dentin ; Diamond ; Resin Cements* ; Shoulder ; Tooth