The purpose of this study was to compare the retention and fitness of crown treated with various desensitizing agents on natural teeth. Varnish, dentin primer, bonding agent and potassium oxalate treated groups and control group with no treatment were used. The retention test was executed with the Instron test machine(Instron Co.,U.S.A.) on 24 hours after cementation with zinc phosphate cement. After retention test, the teeth and crowns were washed and recemented. The cemented crowns were embedded in clear resin and sectioned with a diamond saw. The occlusal and marginal fitnesses, were measured indirectly with a stereomicroscopic photographs. The result of this study were obtained as follows : 1. The retention of control group was higher than any other desensitizing agent treated group. 2. The differences of retention among varnish, dentin primer, bonding agent and potassium oxalate treated groups were not statistically significant. 3. There were no statistically significant difference in fitness at occlusal surface and margin among control, varnish, dentin primer, bonding agent and potassium oxalate treated groups. According to these results, desensitizing agents used to protect the pulp from irritation of luting agents may adversely affect the retention of castings. Therefore, desensitizing agents should be used in limited areas carefully.

The purpose of this study was to evaluate the fracture resistance of the four kinds of dental porcelains for the all-ceramic crown(Vita In-Ceram, Vita Hi-Ceram, IPS-Empress, Vitadur-N) and one kind for the metal-ceramic non(Vita VMK 68) was used as the control group. In order to determine the fracture resistance, the hi-axial flexure strength was measured at a crosshead speed of 0.5mm/min, and the Vickers hadrness was measured at an indentation load of 1kg for 20 seconds. The results obtained were summarized as follows ; 1. The maximum Weibull modulus of 24.61 for Vitadur-N and the minimum one of 852 for IPS-Empress were observed ; the maximum characteristic strength of 353.26MPa for Vita In-Ceram and the minimum that of 63.20MPa for Vitadur-N were also observed. 2. The maximum mean bi-axial flexure strength of 339.12MPa for Vita In-Ceram and thd minimum one of 61.99MPa for Vitadur-N were calculated. Results of the Scheffe test indicated that the statistically significant difference(P<0.05) existed between Vita In-Ceram or Vita Hi-Ceram and the others ; also between IPS-Empress and Vitadur-N. 3. The maximum mean hardness of $980.55kg/mm^2$ for Vita VMK 68 appeared. Results of the Scheffe test indicated that statistically significant difference(P<0.05) existed between Vita In-Ceram or Vita Hi-Ceram and the others ; also between IPS-Empress and Vita VMK 68.

The purpose of this study was to evaluate and compare film thickness of five kinds of resin luting cements [Comspan, Panavia Ex, Maryland bridge adhesive, All-bond C & B cementation kit, and Super-bond C & B]. Zinc-phosphate cement and glass-ionomer cement were used as the control group. In order to measure the film thickness the methods used were in broad compliance with ADA Specification No. 8, a tapered-die system that simulates clinical conditions more closely, and the connected tapered-die system that simulates bridge conditions. The inorganic filler size of resin cements was also examined with scanning electron micrographs. The results were obtained as follows ; 1. The film thickness of resin cements was increased in the order of Comspan, Panavia Ex, Super-bond C & B, Maryland bridge adhesive, and All-bond C & B cementation kit. Maryland bridge adhesive and All-bond C & B cementation kit showed significantly higher film thickness than the control group(p<0.01). 2. For all resin cements, there was a significant difference of film thickness between the ADA method and the tapered-die system. Generally, the tapered-die system demonstrated lower film thickness than the ADA method(p<0.01). 3. There was no significant difference in film thickness between the tapered-die system and the tapered-die bridge system in all resin cements(p<0.01). 4. The scanning electron microscope showed that the cement with larger filler had a tendency to be higher in film thickness.

The restorations of the severely damaged teeth by post core have been increased with the developement of endodontic procedures. But high failure rates of these procedures being reported, various restorative modifications were induced for successful treatments. Cast post-core and prefabricated post with core buildups are choice of treatment. The main causes of failure of the restorations are the fracture of post and core, root fracture, and recurrent caries due to microleakage. Recently, the acid etching technique and the use of dentin bonding agent at tooth surface to reduce the possible microleakage at the tooth-restoration interfaces were introduced. The object of this study was to measure and compare the microleakage by the types and cementation methods of post-core. For this study, forty extracted human anterior teeth were selected for specimen. After cleansing and routine endodontic procedures, anatomic crowns of each specimen were removed at the level of 2mm above the cementoenamel junction. Canals were preparated for post insertion and specimens were divided into four groups randomly. Post-cores were fabricated according to method for each group. Microleakage was measured by length of dye penetration at the tooth-restoration interfaces with measuring microscope at 50 magnification. Oneway ANOVA and t-test were performed for statistical analysis of resulting data. The following results were obtained from this study. 1. There wert significant statistical differences in degree of microleakage between each group (p<0.01). 2. Cast post-core cemented with ZPC (Group I) showed the most severe microleakage pattern$(1.5547{\pm}0.0872mm)$, and cast post-core cemented with adhesive resin cement after tooth surface treatment with dentin bonding agent (Group II) showed the least microleakage $(0.1497{\pm}0.0872mm)$. 3. Group IV revealed less dye penetrations than group III, but no statistical significance was seen between two groups.

There were many studies that distribute the partial edentulous states and examine the removable partial denture designs in the planning of removable partial denture treatment. This study was performed in the point of removable partial denture prescription to evaluate partial edentulism and its removable partial denture designs. The data was collected from the dental laboratory of each three dental colleges in Seoul and from two dental laboratories only for removable partial dentures as a prescription form. A total of 1411 cases with prescription form collected from dental laboratories were distributed for this study, then 788 cases were selected for this study. The case selection was done according to the contents of prescription form. The selected cases were divided into maxillary arch and mandibular and classified in terms of types of major connector and direct retainer, unbroken anterior teeth, Kennedy classification, the number of remaining teeth, and distribution of age and sex. The analyzed results were as follows : 1. The Kennedy classification I showed highest frequency both in maxilla and mandible. 2. The arch distribution of removable partial denture was 50.08% for maxilla and 49.92% for mandible. 3. The highest frequency in the distribution of direct retainer was the RPA clasp design. 4. The frequency of unbroken anterior 6 was 73.36% for maxilla and 82.30% for mandible. 5. The design of broad palatal strap and lingual bar revealed the highest prevalence in the major connector construction. 6. The mean number of remaining teeth per arch was 8.25 for maxilla and 8.37 for mandible. 7. The mean age of the patients supplied with removable partial denture was 52.25 years for men, 51.68 years for women, 52.11 years for maxilla, and 51.76 years for mandible and women showed more prevalence.

The purpose of this study was to compare the fatigue, physical properties, flexibility and surface roughness of titanium used in removable partial dentures with those of a type IV and alloy and a cobalt- chromium alloy. Fatigue testing subjected the test specimen to rapid cycling at a given stress until failure occurred by using a small-sized, electrodynamic type bending fatigue testing machine. The S-N curves for the framework materials were generated. For tensile testing, a tensile bar as described in the ADA Specification No.14 was subjected to tensile loading until failure occurred. Load-displacement curves were generated for 18 gauge round specimen and tapered half round specimen. Then the flexibilities were calculated. The surface roughnesses were compared by analyzer. Through analyses of the data, the following conclusions were obtained. 1. The fatigue property of titanium was higher than that of a type IV gold alloy$(p\leq0.05)$, but there was no significant difference between titanium and a cobalt-chromium alloy $(p\geq0.05)$. 2. The yield strength, the ultimate tensile strength and Victors hardness of titanium were higher than those of a type IV gold alloy but lower than those of a coalt-chromium alloy$(p\leq0.05)$. 3. The percentage of elongation and reduction of area of titanium were the highest $(p\leq0.05)$. 4. The surface roughness of titanium was the greatest$(p\leq0.05)$. 5. The flexibility of titanium was lower than that of a type IV gold alloy but higher than that of a cobalt-chromium alloy$(p\leq0.05)$.

Tissue conditioners have been used for treatment of denture stomatitis caused by wearing of dentures. Early studies pointed out Candide albicans (C. albicans) as main etiologic factor, and antifugal agents were added for control of the species. But there is a little information about broad comparison on the effect of tissue conditioners and antifungal agents added. The purpose of the present study was to compare the inhibiting effect of four tissue conditioners and one temporary soft liner on the growth of C. albicans for treatment of denture stomatitis using gel diffusion method by measuring diameter of the zone of growth inhibition. Three antifungal agents were added to each material for evaluation of the effect of added agents. Finally, observation was made to evaluate the effect of the loss of antifungal elements by aging of the specimen. The results of this study were obtained as follows : 1. Tempo had remarkable antifungal effect showing the zone of growth inhibition as 2.35 mm at 1st day, and was most effective on End: 4th and 7th day from incubation (p<0.05). But Coecomfort, Dura conditioner, Visco-gel, Coe-soft had little antifungal effect from the 1st day of incubation. 2. Nystatin was most effective showing 9.60-12.04 mm of zone of inhibition at the 1st day from incubation. The antifungal properties were reduced to amphotericin B, chlorhexidine and materials without agent (p<0.05), and the effect was diminished by time. 3. As pretreatment with amphotericin B, nystatin, chlorhexidine, Tempo was very effective at the 1st day from incubation showing zone of inhibition as 3.65, 12.04, 4.78 mm with addition of each agent. Dura conditioner had strongest antifungal effect at the next day as 2.86, 5.33, 1.29 mm of zone of inhibition, and yielding results of Coe-comfort, Tempo, Coe-soft was shown at 4th and 7th day from incubation (p<0.05). Taken all together, tissue conditioners have little antifungal effect except Tempo. Formation of the zone of growth inhibition was due to agents amphotericin B, nystatin, chlorhexidine and nystatin was most effective. Conclusively, it is advisable to select material which is effective on the growth of C. albican and consider addition of antifungal agents for treatment of denture stomatitis.

It is very important for the ideal restorations of anterior openbite patients to record the mandibular movement and to harmonize mandibular movement with other organs in stomatognathic systems. This study was designed to compare the mandibular movement of anterior openbite patients with that of normal bite(Angle Class I) patients, to ascertain which components of mandibular movement have differences between two groups, and to use for occlusal treatment of mandibular movement. Saphon Visi-trainer Model 3(Tokyo Shizaisha Co. Japan) and Denar Pantronic(Denar Corp.,U.S.A.) were used to record mandibular movement. Pantronic survey was peformed by using an arbitrary hinge axis according to manufacturer's direction. Twenty-eight adult who have physiologically normal occlusion(Angle Class I) and are free of TM dysfunction were selected as a control group(Group 1). Fifteen adult who are anterior openbite patient and have not anterior guidance function and have posterior interference at protrusion were selected as a experimental group(Group 2). The results are as follows : 1. There was no statistically significant difference between the average immediate and progressive side shift of anterior openbite patients(0.54mm, $7.57^{\circ}$) and those of normal group(0.49mm, $5.96^{\circ}$). 2. The average protrusive and orbiting condylar inclination of anterior openbite patient$(30.87^{\circ},\;32.27^{\circ})$ were significantly lower than those of normal group$(36.11^{\circ},\;39.04^{\circ})$ (P<0.05). 3. In the results of Visi-trainer recordings, the mean for the maximum protrusion, the maximum laterotrusion, the angle of laterotrusion and the angle of protrusion in the horizontal trajectory between group 1 and 2 did not differ significantly. 4. The mean for the angle of protrusion, the maximum opening in the frontal trajectory, the ICP-RCP(A-P) distance and the angle of protrusion in the sagittal trajectory differ significantly(P<0.05). 5. The significant correlation was found between orbiting condylar inclination and protrusive condylar inclination.

The purpose of this study was to evaluate the mechanical effects when one implant fixture was connected to the natural teeth with reduced alveolar bone height. This study also examined the effects of increasing the number of abutment teeth and the effects of the intramobile connector and the titanium connector as they were inserted between the implant superstructure and the fixture. The distribution and concentration load was applied to the fixed partial denture(FPD) supported by implant and the natural teeth with reduced alveolar bone height. The stress and displacement of each element was observed and compared by the two-dimensional finite element method. The following results were obtained : 1. The greater the loss of alveolar bone in natural teeth area, the greater the displacement of FPD and the stress concentration in alveolar bone around implant, especially at the stress concentration in the mesial alveolar bone crest around implant fixture. 2. The displacement of FPD was increased more and that of implants fixture was decreased more when intramobile connector was used than titanium connector was used. Also the stress concentration in alveolar bone around implant fixture was greater when intramobile connector than titanium connector. One implication of this finding was that the difference in stiffness of implant and the natural teeth with reduced alveolar bone height could be partially compensated in case of the POM intramobile connector. 3. The amount and direction of displacement and the stress distribution of the 4-unit FPD was better than those of the 3-unit FPD. It implied that the difference of stiffness of implant and natural teeth with reduced alveolar bone height could be partially compensated in case of the 4 unit FPD.

This study was performed to evaluate the effects of number and alignment of implant fixture and various bar designs on the retention of denture and the stress distribution. Six kinds of photoelastic mandibular models and nine kinds of overdenture specimens were designed. A unilateral vertical load was gradually applied on the right first molar to calculate the maximal dislodgement load of each specimen. A unilateral vertical load of 17 Kgf was applied on the right first molar and a vertical load of 10 Kgf was applied on the interincisal edge region. The stress pattern which developed in each photoelastic model was analyzed by the reflection polariscope. The results obtained were as follows: 1. The maximal dislodgement load reversely increased with the distance from the loading point to the implant fixture, while it linearly increased with that from the most posterior implant fixture to the mesial clip. The maximal dislodgement load also increased with the use of a cantilever bar. 2. Under the posterior vertical load, the stress to the supporting tissue of the denture base increased with the distance from the loading point to the implant future. The stress concentration on the apical area of the implant future reversely increased with the distance from the loading point to the implant future. 3. In the overdentures supported by two implant fixtures under the posterior vertical load. the specimen implanted on lateral incisor areas with a cantilever bar exhibited more favorable stress distribution than that without a cantilever bar. The specimen implanted on the canine areas without a cantilever bar, however, exhibited more favorable stress distribution. 4. In the overdentures supported by three implant fixtures. the specimen implanted ell the midline and canine areas exhibited more favorable stress distribution than that implanted oil the midline and the first premolar areas. 5. In the overdentures supported by four implant fixtures. the specimen implanted with two adjacent implant fixtures exhibited more favorable stress distribution than that implanted at equal distance under the posterior vertical load. 6. Under the anterior vertical load, the overdentures supported by three implant fixtures exhibited stress concentration on the supporting structure of the middle implant future. In overdentures supported by two or four implant futures, no significant difference was noted in stress distribution between the types of bars. These results indicate that the greater the number of implant fixtures, the better the stress distribution is. A favorable stress distribution may be obtained in the overdentures supported by two or three implant fixtures, if the location and the design of the bar are appropriate.