This study was performed to evaluate the effect of aging and thermal cycling on the biaxial flexure strength of four commercially available veneering resin composites for crown(Dentacolor : DC, Artglass : AG, Esternia : ET and Targis : TG). Disc specimens were fabricated in a teflon mold giving 12mm in diameter and 1mm in thickness. All samples were divided into 4groups. Group 1 was dried in a dessicator at 25degrees C for 30 days. Group 2 was immersed in distilled water at 37degrees C for 30 days. Group 3 was immersed in distilled water at 65degrees C for 30 days. Group 4 was subjected to 10,000 thermal cycles between 5degrees C and 55degrees C, and the immersion time in each bath was 15 seconds per cycle. Biaxial flexure test was conducted using the ball-on-three-ball method at the cross head speed of 0.5mm/min and fracture surfaces were observed with scanning electoron microscope. The results obtained were summarized as follows ; 1. Weibull modulus values, except for the AG group, decreased after thermal cycling treatment. 2. Biaxial flexure strength values of aging group at 37degrees C were th lowest in all sample groups. Except for the DC group, strength values were significntly decreased for the drying group. 3. After thermal cycling test, the highest value of biaxial flexure strength of 188.8 MPa was observed in the ET group and the lowest value of 73.2 MPa was observed in the DC group. The strength values showed the significant differences in each group (p<0.05). 4. Observation of surfaces after thermal cycling test revealed the ditching in the part f surrounding large fillers.
Aging* ; Baths ; Crowns* ; Fungi ; Head ; Immersion ; Polytetrafluoroethylene ; Water

No abstract available.

STATEMENT of PROBLEM: There were several studies on the effects of irradiation to periimplant bone tissue. However, no clear biological effect of irradiation on peri-implant bone tissue was reported yet. PURPOSE: This study compared the effect of irradiation on the surrounding tissue of a HA-coated implant fixture with controls. MATERIAL AND METHODS: 6 Steri-Oss implants were implanted into the femur of 6 mongrels. The implanted dogs were divided into three groups and received irradiation. After 1 month, 2months and 4 months healing period, the histologic examination and mobility test and digital radiographic imaging analyses were performed to compare the control and experimental group respectively. RESULTS: The irradiated group showed slower healing than control group in light microscopic observations. The mobility test demonstrated significant less number (Periotest) in control group than that of irradiated groups. The digital radiographic imaging analysis showed that the bone density of irradiated group was higher than control group. CONCLUSION: Generally, control group showed favorable bilogical response and less mobility than irradiated group. The conflict result of bone density value were measured by the dig-.
Animals ; Bone and Bones ; Bone Density ; Dogs ; Femur ; Radiation Effects*

No abstract available.
Dental Enamel* ; Lasers, Solid-State*

No abstract available.

STATEMENT OF PROBLEM: HA has been used as a coating material on Ti implants to improve osteoconductivity. However, it is difficult to form uniform HA coatings on implants with complex surface geometries using a plasma spraying technique. PURPOSE: To determine if Ti6Al4V sintered porous-surfaced implants coated with HA solgel coated and hydrothermal treated would accelerate osseointegration. MATERIALS AND METHODS: Porous implants which were made by electric discharge were used in this study. Implants were anodized and hydrothermal treatment or HA sol-gel coating was performed. Hydrothermal treatment was conducted by high pressure steam at 300 degrees C for 2 hours using a autoclave. To make a HA sol, triethyl phosphite and calcium nitrate were diluted and dissolved in anhydrous ethanol and mixed. Then anodized implant were spin-coated with the prepared HA sols and heat treated. Samples were soaked in the Hanks' solution with pH 7.4 at 37 degrees C for 6 weeks. The microstructure of the specimens was observed with a scanning electron microscope (SEM), and the composition of the surface layer was analyzed with an energy dispersive spectroscope (EDS). RESULTS: The scanning electron micrographs of HA sol-gel coated and hydrothermal treated surface did not show any significant change in the size or shape of the pores. After immersion in Hanks' solution, the precipitated HA crystals covered macro- and micro-pores. The precipitated Ca and P increased in Hanks' solution that surface treatment caused increased activity. CONCLUSION: This study shows that sol-gel coated HA and hydrothermal treatment significantly enhance the rate of HA formation due to the altered surface chemistry.
Calcium ; Chemistry ; Dental Implants* ; Ethanol ; Hot Temperature ; Hydrogen-Ion Concentration ; Immersion ; Osseointegration ; Plasma ; Steam

STATEMENT OF PROBLEM: Ti-6Al-7Nb alloy is used instead of Ti-6Al-4V alloy that was known to have toxicity. PURPOSE: This study was performed to investigate the effect of electrolyte concentration on the surface characteristics of anodized and hydrothermally-treated Ti-6Al-7Nb alloy. MATERIALS AND METHODS: Discs of Ti-6Al-7Nb alloy of 20 mm in diameter and 2 mm in thickness were polished sequentially from 300 to 1,000 SiC paper, ultrasonically washed with acetone and distilled water for 5 min, and dried in an oven at 50 degrees C for 24 hours. Anodizing was performed at current density 30 mA/cm2 up to 300 V in electrolyte solutions containing beta-glycerophosphate disodium salt hydrate (beta-GP) and calcium acetate (CA). Hydrothermal treatment was conducted by high pressure steam at 300 degrees C for 2 hours using a autoclave. All samples were soaked in the Hanks' solution with pH 7.4 at 36.5 degrees C for 30 days. RESULTS AND CONCLUSION: The results obtained were summarized as follows; 1. After hydrothermal treatment, the precipitated HA crystals showed the dense fine needle shape. However, with increasing the concentration of electrolyte they showed the shape of thick and short rod. 2. When the dense fine needle shape crystals was appeared after hydrothermal treatment, the precipitation of HA crystals in Hanks' solution was highly accelerated. 3. The crystal structures of TiO2 in anodic oxide film were composed of strong anatase peak and weak rutile peak as analyzed with thin-film X-ray diffractometery. 4. The Ca/P ratio of the precipitated HA layer was equivalent to that of HA crystal in Hanks' solution.
Acetone ; Alloys* ; Calcium ; Hydrogen-Ion Concentration ; Needles ; Steam ; Water

STATEMENT OF PROBLEM: Die materials require abrasion resistance, dimensional stability with time, and high surface wettability for adequate material properties. Wear of gypsum materials is a significant problem in the fabrication of accurately fitting cast prosthetic devices. So It has been recommended that the use of die hardener before carving or burnishing ofthe wax pattern. PURPOSE: The purpose of this study was to compare the abrasion resistance and surface microhardness(Knoop) with 3 commonly used gypsum die materials(MG Crystal Rock, Super plumstone, GC FUJIROCK(R) EP) with and without the application of 2 die hardeners. MATERIAL AND METHODS: Three die materials were evaluated for abrasion resistance and surface microhardness after application of 2 die hardeners(Die hardener and Stone die & plaster hardener). Thirty specimens of each gypsum material were fabricated using an impression of resin die(Pattern resin; GC Corporation, Japan) with 1-mm high ridges, sloped 90 degrees. Gypsum materials were mixed according to manufacturer's recommendations and allowed to set 24 hours before coating. Specimens were arbitrary assigned to 1 of 3 treatment subgroups (n=10/subgroup): no treatment(control), coated with Die hardener, and coated with Stone die & plaster hardener. Abrasion resistance(measured by weight loss) was evaluated using device in 50g mass perpendicular to the ridges. Knoop hardness was determined by loading each specimen face 5 times for 15 seconds with a force of 50g. A scanning electron microscope was used to evaluate the surface of specimens in each treatment subgroup. Conclusions: The obtained results were as follows: 1. 3 types of die stone evaluated in this study did not show significant differences in surface hardness and abrasive resistance(P<.05). 2. In the abrasive resistance test, there were no significant differences between GC FUJIROCK(R) EP and MG Crystal Rock with or without 2 die hardener(P<.05). 3. Super plumstone treated with Stone die & plaster hardener showed increased wear loss(P<.05). 4. Die hardener coatings used in this study decreased the surface hardness of the gypsum material(P<.05).
Calcium Sulfate* ; Hardness ; Wettability

PURPOSE: The purpose of this study was to compare the accuracy of the implant master cast according to the type (pick-up, transfer) and the length (long, short) of the impression copings. MATERIALS AND METHODS: The metal master cast was fabricated with three internal connection type implant analogs (Osstem GS III analog), embedded parallel and with 10degrees of mesial angulation to the center analog. Four types of impression coping were prepared with different combinations of types (transfer, pick-up) and lengths (long, short) of the coping. The impressions were made using vinyl polysiloxane (one step, heavy + light body) with an individual tray, and 10 impressions were made for each group. Eventually, 40 experimental casts were produced. Then, the difference in the distance between the master cast and the experimental cast were measured, and the error rate was determined. The analysis of variance was performed using the SPSS (v 12.0) program (alpha = .05), and the statistical significance was set at P < .05. RESULTS: The ANOVA showed that the pick-up type impression coping exhibited a significantly lower error rate than the transfer type. However, no significant difference was observed with respect to the length of the impression coping. Additionally, no significant difference was observed between the parallel and mesial angulated groups. CONCLUSION: Within the limitations of this study, the pick-up type impression coping exhibited a more accurate implant master cast than the transfer type in parallel group. The accuracy of the implant master cast did not differ for different lengths of impression coping of at least 11 mm. Additionally, the accuracy of the implant cast was not different for the parallel and 10degrees mesial angulated groups.
Light ; Polyvinyls ; Siloxanes

This study was performed to evaluate the dynamic fatigue characteristics of the dental ceramics for all-ceramic crown. A feldspathic porcelain of VMK68, glass ceramic of IPS-Empress, and glass infiltrated alumina ceramic of In-Ceram were used. Disc specimens were prepared to the final dimensions of 12 mm in diameter and 1 mm in thickness. The biaxial flexure test was conducted using a ball-on-three-ball method. 240 specimens were tested in 37degrees C water by testing 20 samples at each of four loading rates:0.05, 0.2, 1, and 5mm/min. 60 specimens were tested in a moisture-free environment by testing 20 samples at 5mm/min. The inert strength of VMK68 was 80.25MPa, and the fatigue parameters were n=29.1, sfo=52.90MPa. The inert strength of IPS-Empress was 104.76MPa, and the fatigue parameters were n=32.46, sfo=67.52MPa. The inert strength of In-Ceram was 429.33MPa, and the fatigue parameters were n=31.46, sfo=258.36MPa. 10-year failure stresses of VMK68, IPS-Empress, and In-Ceram were 20.3MPa, 24.8MPa, and 93.6MPa, respectively. failure strength and fatigue life showed the highest value in In-Ceram, and then, IPS-Empress and VMK68.
Aluminum Oxide ; Ceramics* ; Crowns* ; Dental Porcelain ; Fatigue* ; Glass ; Water