The purpose of this study was to compare the corrosion characteristics between implant fixture and two types of abutment screw; gold screw, titanium screw. The anodic polarization behavior, the galvanic corrosion behavior, and the crevice corrosion behavior of prepared samples were investigated using potentiostat and scanning electron microscope. The results were as follows : 1. Anodic polarization behavior of samples: The primary passivation potential of implant fixture was -420mV, implant abutment was -560mV, titanium screw was -370mV and gold screw was -230mV. All samples were shown to have a high corrosion potential and good formation of passive film. The critical passive current density of gold screw was higher than of other samples and the sample of gold screw showed a unstable passive film formation at passive region. 2. Galvanic corrosion behavior of samples: Contact current density between implant fixture and titanium screw showed 8.023x 10-5C/cm2. Contact current density between implant fixture and gold screw showed 5.142x 10-5C/cm2. 3. Crevice corrosion behavior of samples : The crevice corrosion resistance of sample using titanium screw was higher than that of sample using gold screw, and a severe corrosion morphologies were observed at the fixture-screw interface by the scanning electron microscope.
Corrosion* ; Titanium

This study helps to clarify conflicting reports by comparing the physical properties and accuracy of complete denture processed by the pack and press technique, continuous-pressure injection technique(SR-Ivocap system) and Mark press technique. The 6 different specimens have been evaluated using the SEM, Impact test, DSC (Differential Scanning Calorimetry) and DMTA(Dynamic Mechanical Thermal Analysis). Each sample was made of SR-Ivocap resin and QC-20 resin by different processing methods. The results were as follows ; 1. As the result of the observation on the fracture surface of resin by use of SEM, sample SR-Ivocap resin cured by continuous pressure injection method showed the most homogeneous structure. This is why molecules in SR-Ivocap resin have no orientation. 2. As the result of the Impact test in order to measure the deformity, fracture energy and impact resistance of resin, the samples with QC-20 acrylic resin and SR-Ivocap resin cured by continuous pressure injection method were exellent. 3. In consequence of measuring alpha-glass transition temperature by use of DSC on the basis of temperature change, the glass transition temperatures of sample QC-20 resin cured by pack and press method and sample SR-Ivocap resin cured by continuous pressure injection method were very similar. Thus volumetric stability could not be evaluated only by glass transition temperature. 4. In comparing volumetric stability data by DMTA, the glass transition temperature(Tg) showed 137.88degrees C at sample QC-20 resin cured by pack and press method and 139.78degrees C at sample SR-Ivocap resin cured by continuous pressure injection method. Therefore sample SR-Ivocap resin cured by continuous pressure injection method seems to be superior to sample QC-20 resin cured by pack and press method in the dimensional stability at high temperature. 5. In comparing storage modulus data by DMTA, the storage modulus of sample SR-Ivocap resin cured by continuous pressure injection method was higher than that of sample QC-20 resin cured by pack and press method. So, sample SR-Ivocap resin cured by continuous pressure injection method seems to be superior to sample QC-20 resin cured by pack and press method in impact strength.
Congenital Abnormalities ; Denture, Complete ; Glass ; Transition Temperature

This investigation evaluated patients who received Steri-Oss implants from the Dental Hospital of Chosun University during the period from March 1989 to August 1997. 346 fixtures of 127 patients were included in this study . The results were as follows ; 1.The follow-up period was defined as the period between the surgical placement of the implants and the last follow-up examination. The mean follow-up period was 2.17+/-1.21 years. 2.The period between fixture installation and second surgery was 0.71+/-0.44 years in the maxilla and 0.46+/-0.21 years in the mandible. 3.The number of fixtures which were installed in the upper jaw(112) was less than that in the lower jaw(234) and in the posterior region(260) was more than in the anterior region(86). 4.The length of fixture which was most frequently used was 12 mm and least was 8mm. Screw implants were installed more than cylindrical implants. 3.8mm implant was the most common implans, followed by 4.5mm and 3.25mm. 5.The number of augmentation cases was more than that of non-augmentation cases and the rate of augmentation cases in the maxilla was more than that in the mandible. 6.Implant restorations for partial edentulos patients(94cases) were more than single-tooth implant restorations(33cases) or implant restorations for complete edentulos patients(10cases). 7.Free-standing prostheses for partially edentulous patients were more commom than any other type of connection between implants and natural teeth. 8.Plaque Index(0.95+/-0.74) and Gingival Index(0.31+/-0.52) were very similar around the natural teeth and reflected an acceptable level of plaque and gingivitis control. Mean value for keratinized mucosa index(1.93+/-1.20) remained fairly constant around level 2(1-2 mm keratinized epithelium). 9.Patients were generally satisfied with implant in terms of comfort, function, speech and esthetics. 10.There was not a statistically significant differences in overall survial rate between implants placed in the maxilla (91.5%) and those placed in the mandible (93.8%). Fourteen implants lost before the prosthetic rehabilitation and eleven implants lost following variable periods in function after the prosthetic phase of the treatment. 11.Cause of implant failures was exfoliation or removal of fixture due to non-osseointegration before the prosthetic rehabilitation or due to fracture of fixture, masticatory pain after the prosthetic rehabilitation. 12.The survival rate of Steri-Oss implants using the Kaplan-Meier statistical analysis was 93.8% at 2 year and 86.6% at 5 year. In all cases, implant losses occured predominantly in the healing period. There was a steep decline in the rate of implant loss after the first year. 13.The survival rate of Steri-Oss implants in the anterior region was 94.8% at 2 year and 94.8% at 5 year and that in the posterior region was 92.8% at 2 year and 75.9% at 5 year. In conclusion, this study revealed a number of parameters and guidelines for achieving an optimal success rate in osseointegration.
Dental Implants, Single-Tooth ; Esthetics ; Follow-Up Studies ; Gingivitis ; Humans ; Mandible ; Maxilla ; Mucous Membrane ; Osseointegration ; Prostheses and Implants ; Rehabilitation ; Survival Rate ; Tooth