The orchid symbiotic fungi were isolated from the roots of Korean native orchid (Cymbidium goeringii) collected and Chinese orchid (C. sinense) obtained from greenhouses. They were identified as a species of Rhizoctonia, based on the sequences of 18r rDNA, the microscopic observations of mycelia, and the symbiotic relationships with commercial orchids. The isolate collected from Chinese orchids was revealed to be a species of Ceratobasidium endophytica, and to be different from the other isolates at the thickness of the mycelia stained in the root cells of Korean native orchids. The other isolates collected from the Korean native orchids were considered to be a species of Tulsanella repens (anamorphic: Epulorhiza repens) or its related one. The physiologic or microscopic variations were oftenly observed among them, but the tendency of grouping these in the 18s rDNA sequences were observed to be consistent with those of the localities collected. The further taxonomical segregating for Korean symbiotic fungi was not made because the information concerned were limited in this moment, but was recognized as based on the sequences of 18s DNA.
Asian Continental Ancestry Group ; DNA ; DNA, Ribosomal ; Fungi* ; Humans ; Mycorrhizae ; Rhizoctonia ; Symbiosis

No abstract available.
Bone and Bones* ; Dental Implants*

All ceramic restorations have had a more limited life expectancy than metal ceramic crowns because of their lower strength. The relatively lower strength has limited the use of all-ceramic crowns to the areas where occlusal loads are lower. Therefore many researches have been done to increase the strength of all-ceramic crowns. IPS Empress 2 is a new type of lithium disilicate glass-ceramic with enhanced physical characteristics which has been in use clinically since 1998. Previous researches reported that the flexural strength of all-ceramic material was greater than 300MPa, and all-ceramic crowns can be used in staining or layering technique. The objective of this study was to investigate the influence of the thickness of IPS Empress 2 ceramic on fracture strength. Both staining technique and layering technique was investigated. Vita VMK was used as control. For all three groups, five specimens each of 0.8mm, 1.0mm, 1.4mm, 1.8mm, and 2.2mm thickness (a total of 75 specimens) were prepared. Control group: Vita VMK Porcelain specimens were prepared with dentine ceramic and liquid glazing was done. Group I: IPS Empress 2 were prepared with staining technique and stained twice and glazed once. Group II : IPS Empress 2 were prepared with layering technique and glazed after wash firing. The thickness and diameter of the specimen were measured and controlled after specimen preparation. Biaxial Flexure Test (ASTM Standard F394-78) was adopted as this test method produces results least affected by the edge condition of the specimens. Fracture strength was measured with Instron Universal Testing Machine. Conclusions are as follow : 1. The fracture strength was increase in order of control group, test group I, test group II. 2. Fracture strength of the group I(Empress 2 Staining) was 65.54 N in 0.8mm, 155.2 N in 1.0mm, 233.5 N in 1.44mm, 434.5 N in 1.8mm, and 600.1 N in 2.2mm. 3. Fracture strength of the group II (Empress 2 Layering) was 190.0 N in 0.8mm, 283.5 N in 1.0mm, 437.2 N in 1.4mm, 732.0 N in 1.8mm, and 1115.0 N in 2.2mm. 4. No statistical difference was found in flexural strengths according to thickness in a specified group(p>0.05).
Ceramics* ; Crowns ; Dental Porcelain ; Dentin ; Fires ; Life Expectancy ; Lithium

The ideal restorative material should mimic the properties of the tissues it replaces. Dental composite resins have been used widely as restorative materials due to its advantages such as excellent esthetics and ease of manipulation. But inadequate wear resistance has been a major factor limiting the use of composite restorative materials. Improved manufacturing techniques have allowed the development of hybrid composites, with a greater percentage volume filler loading, which have improved physical an mechanical properties. However they are lacking the study wear resistance. The purpose of this study was to evaluate the wear of human enamel against ceromer by the use of a pin-on-disk type wear testers. Discs of ceromer(Targis : Ivoclar, Vivadent, Amherst. NY) and discs of type III gold alloy as a control were used for test specimens. Intact cusp of premolar and molar were used for enamel specimens. The wear of enamel was determined by weighing the cusp before and after each test, and the weight converted to volumes by average density of enamel. Surface profilometer was used to quantify wear of the ceromer and gold specimens. Vicker's hardness tester was used to evaluate the surface hardness of test specimens. The SEM was used to evaluate the wear surfaces. The results were as follows; 1. Ceromer produced less enamel wear than gold(p<0.05). 2. The wear volume of ceromer was greater than that of gold(p<0.01). 3. The hardess of ceromer was lower than that of gold, but there was no correlation between the hardness and wear of the ceromer and gold. 4. SEM analysis revealed that there were many voids and microcracks in the wear tract of ceromer. in gold group, many minute V-shaped grooves were examined.
Alloys ; Bicuspid ; Composite Resins ; Dental Enamel* ; Esthetics ; Hardness ; Hardness Tests ; Humans* ; Molar

All-ceramic restorations have become an attractive alternative to porcelain-fused-to-metal crowns. In-Ceram, and more recently IPS Empress 2 were introduced as a new all-ceramic system for single crowns and 3-unit fixed partial dentures. But their strength and marginal fit are still an important issue. This study evaluated the fracture resistance and marginal fit of three systems of 3 unit all-ceramic bridge fabricated on prepared maxillary anterior resin teeth in vitro. The 3 all-ceramic bridge systems were: (1) a glass-infiltrated, sintered alumina system (In-Ceram) fabricated conventionally, (2) the same system with copy-milled alumina cores (copy-milled In-Ceram), (3) a heat pressed, lithium disilicate reinforced glass-ceramic system (IPS Empress 2). Ten bridges of each system with standardized design of framework were fabricated. All specimens of each system were compressed at 55degree at the palatal surface of pontic until catastrophic fracture occurred. Another seven bridges of each system were fabricated with standard method. All of the bridge-die complexes were embedded in epoxy resin and sectioned buccolingually and mesiodistally. The absolute marginal discrepancy was measured with stereomicroscope at x50 power. The following results were obtained: 1. There was no significant difference in the fracture strength among the 3 systems studied. 2. The Weibull modulus of copy-milled In-Ceram was higher than that of In-Ceram and IPS Empress 2 bridges. 3. Copy-milled In-Ceram (112micrometer) exhibited significantly greater marginal discrepancy than In-Ceram (97micrometer), and IPS Empress 2 (94micrometer at P=0.05. 4. The lingual surfaces of the ceramic crowns showed smaller marginal discrepancies than mesial and distal points. There was no significant difference between teeth (incisor, canine) at P=0.05. 5. All-ceramic bridges of three systems appeared to exhibit sufficient initial strength and acceptable marginal fit values to allow clinical application.
Aluminum Oxide ; Ceramics ; Crowns ; Denture, Partial, Fixed ; Hot Temperature ; Lithium ; Tooth

No abstract available.
Dental Implantation* ; Dental Implants* ; Osseointegration*

A 42-year old man was admitted for treatment of a fracture of the medial condyle of the left femur. After 10 days of cast immbilization of the above mentioned extremity, erythematous papulo-vesicular eruption was noted under the external splintage. We concluded that this was an unusual allergic contact dermatitis which is caused by CaSO4.1/2H20, and proved it by patch test in our clinic.
Calcium Sulfate ; Dermatitis, Allergic Contact ; Extremities ; Femur ; Patch Tests

STATEMENT OF PROBLEM: Recently, resin cements have become more widely used and have been accepted as prominent luting cements. Current resin cements exhibit less microleakage than conventional luting cements. However, the constant contact with water and exposure to occlusal forces increase microleakage even in resin cements inevitably. Most bonding resins have been modified to contain a hydrophilic resin such as 2-hydroxyethylmethacrylate (HEMA) to overcome some of the problems associated with the hydrophobic nature of bonding resins. By virtue of these modifications, bonding resins absorb a significant amount of water, and there may also be significant stresses at bonding interfaces, which may adversely affect the longevity of restorations. Therefore the reinforcement of water stability of resin cement is indispensable in future study. PURPOSE: This study was conducted to examine the influence of water retention on microleakage of two resin cements over the period of 6 months. MATERIALS AND METHODS: 32 ex acted human teeth were used to test the microleakage of a single full veneer crown. Two resin cements with different components and adhesive properties - Panavia F (Kuraray Co., Osaka, Japan) and Super-Bond C&B (Sun Medical Co., Kyoto, Japan)- were investigated. The storage medium was the physiological saline solution changed every week for 1 month, 3 months, and 6 months. One group was tested after storage for 1 day. At the end of the each storage period, all specimens were exposed to thermocycling from 5.C to 55.C of 500 cycles and chewing simulation of 50,000 cycles, and then stained with 50% silver nitrate solution. The linear penetration of microleakage was measured using a stereoscopic microscope at x 40 magnification and a digital traveling micrometer with an accuracy of +/-3 um. Values were analyzed using two-way ANOVA test, Duncan's multiple range tests (DMRT). RESULTS: Statistically significant difference of microleakage was shown in the 3-month group compared with the 1-day or 1-month group in bot systems (p<0.05) and there were statistically significant differences in microleakage between the 3-month group and the 6-month group in both systems (p<0.05). The two systems showed different tendency in the course of increased microleakage during 3 months. In Panavia F, microleakage increased slowly throughout the periods. In Super-Bond C&B, there was no significant increase of microleakage for 1 month, but there was statistically significant increase of microleakage for the next 2 months. For the mean microleakage for each period, in the 3-month group, microleakage of Super-Bond C&B was significantly greater than that of Panavia F. On the other hand, in the 6-month group, microleakage of Panavia F was significantly greater than that of Super-Bond C&B (p<0.05). CONCLUSION: Within the limitation of this study, water retention of two different bonding systems influence microleakage of resin cements. Further studies with the longer observation periods in viro are required in order to investigate water stabilty and the bonding durability of the resin cement.
Adhesives ; Bite Force ; Crowns ; Hand ; Humans ; Longevity ; Mastication ; Resin Cements* ; Silver Nitrate ; Sodium Chloride ; Tooth ; Virtues ; Water*

Dental restorative materials must have the physical properties to withstand wear and corrosion. Base metal alloys possess better mechanical properties and lower price than the gold alloys. For these reason such alloys have largely replaced the precious metal alloys. One aspect to consider is the release of metal substances to oral environment. The release of elements from dental alloys is a continuing concern because the elements may have the potentially harmful biological effects on local tissue. The purpose of this study was to minimize metal release on the nonprecious metal surfaces by ion bea assisted deposition(IBAD) of titanium nitride (TiN). Ni-Cr-Be alloys with and without TiN coatings were secured in an wear test machine opposing ruby ball to determine their relative resistance to wear with 100m, 200m, 300m and 400m sliding distance. And the corrosion behavior of the Ni-Cr-Be alloys with and without TiN coating and 3 dental noble alloys have been studied. Potentiodynamic curves were used to analyse the corrosion characteristics of the alloys. The measurement of the released Ni and Ci ions was conducted by analysis of the electrolyte solution with atomic absorption spectroscopy. The results were as follows : 1. The critical sliding distance that wore down TiN coating of 2.5micrometer thickness in this study condition was 300m. 2. Ion beam assisted deposition of TiN showed a good surface modification with respect to the properties of wear and corrosion resistance. 3. X-ray diffraction showed that the strongest peak of TiN(111) in the coatings. 4. The release of Ni and Cr ions from alloys measured by means of atomic absorption spectroscopy was reduced by ion beam assisted deposition of TiN.
Absorption ; Alloys* ; Corrosion ; Dental Alloys ; Gold Alloys ; Ions ; Spectrum Analysis ; Tin* ; Titanium ; X-Ray Diffraction

The success of porcelain laminate veneer depends on the bond strength between tooth structure and ceramic restoration and the design of tooth preparation. In particular, incisal coverage and incisal finish line are the two most important factors in long-term fracture resistance. Although the majority of clinicians are practicing incisal coverage and there are various opinions on the geometrical ratio between the clinical crown length of the remaining tooth structure and the length of incisal extension in porcelain laminate veneer and the optimal incisal finish lines, scientific evidence still leaves much to be desired. The purpose of this study was to determine the effects of the amounts of incisal coverage and the types of incisal finish line on th stress distribution in maxillary anterior porcelain laminate veneers under two different loading conditions. Three-dimensional finite element models of a maxillary anterior porcelain veneer with different amounts of incisal coverage ; 0, 1, 2, and 3mm and different incisal finish lines ; feathered edge, incisal bevel, reverse bevel and lingual chamfer with various amounts of lingual extension were developed. 300N force was applied at the point 0.5mm cervical of the linguoincisal edge in two loading conditions ; A) 125 degrees, B) 132 degrees. tensile and compressive stress in ceramic and shear stress in the resin cement layer wee analyzed using three-dimensional finite element method. The results were as follows : 1. The types of incisal finish line had more influence on the stress distribution in porcelain laminate veneer than the amounts of incisal coverage. 2. In case of no incisal coverage, incisal beveled laminate exhibited more evenly distributed tensile stress than feathered edged laminate. And in case of incisal coverage, reverse beveled laminate and lingual chamfered laminate with 1mm lingual extension exhibited more evenly distributed tensile stress than lingual chamfered laminates with 2 mm and 3mm lingual extension. 3. As long as the lingual chamfer goes, less tensile stress was found at the incisal edge, while much more tensile stress was found at the lingual margin area in proportion to length of lingual extension. 4. Under 125 degree load, tensile stress in porcelain laminate veneer had increased compared with that under 132 degree load and the difference exhibited by the change of the amount of tooth support was larger. 5. The types of incisal finish line and the distance from the incisal finish line to the loading point had more influence on the shear stress distribution in the resin cement layer than the amount of incisal coverage. In contrast loading condition had little influence.
Animals ; Ceramics ; Crowns ; Dental Porcelain* ; Feathers ; Finite Element Analysis* ; Resin Cements ; Tooth ; Tooth Preparation