The purpose of the study was to evaluate the cytotoxic effects of polycarboxylate cements and zinc phosphate cements in vitro. Human fibroblasts were cultured in ${\alpha}$-MEM, and each cement was manually mixed and filled in glass ring cylinder (8${\times}$8mm in diameter, in height.) Cement filled cylinders were placed in the center of the dish (35mm in diameter) containing 3ml of ${\alpha}$-MEM. Millipore filters to simulate dentinal barrier were also placed between the cylinder and the dish, then stored in 5% $CO_2$ containing chamber for 1 and 2 weeks at the temperature of $36.6^{\circ}C$. The results of the experiments were analyzed by counting the cells in the period of one week and two weeks respectively, and were assessed by calculating the cell multiplication rate and the relative growth rate. The experimental groups and the control group were compared. The results of the study were summarized as follows. 1. Durelone brand of the polycarboxylate cements showed marked cytotoxicity after one week, but after two weeks the toxicity decreased remarkably. Poly-F brand exhibited moderate cytotoxicity after one week, but after two weeks the toxicity slightly decreased. HY-BOND brand was weakly cytotoxic after one week, but after two weeks the toxicity became significant. 2. The cytotoxicity of the zinc phosphate cements was negligible after one week, but after two weeks Lee Smith brand revealed considerable cytotoxicity. 3. In general, the zinc phosphate cements were less cytotoxic than the polycarboxylate cements.

This study was conducted to evaluate the influence of 5 microfilled composite resin to fibroblast cultivated from human pulp (age 13). Each composite resin was manually mixed and filled in cylinder. Resin filled cylinders were placed in dishes (35mm in diameter) containing 3 ml of ${\alpha}$-MEM. Filters (pore size 0.22 ${\mu}m$) to simulate dentin were also placed between the bottom of cylinder and the dish floor. Then stored in 5% $CO_2$ containing incubator for 1 and 2 weeks at the temperature 36.6 C. The results analysed after 1 and 2 weeks were as follows: 1. Experimental group except group 2, 2 weeks incubation cases showed the cytotoxicity compared to the control group in cell count. 2. After 2 week-incubation of group 1 and group 4, cell count was more decreased than 1 week cases and cytotoxicity seemed to be constantly influenced to the cell multiplication. 3. The cell growth rate of 1 week incubation in group 3 and group 5 was similar to the control group and recognized the cytotoxicities of these groups were mild. 4. The cell multiplication rate of 2 week incubation cases in group 2 was greater than control group.

The purpose of this study was to examine the effect of temperature dependence of the behavior on the physical properties of posterior composite resins. Three light cure posterior composite resins (Heliomolar, Litefil-P, and P-50) and one chemical cure posterior composite resin (Bisfil-II) were used as experimental materials. Composite resin was placed in a cylindrical brass mold (2.5 mm high and 6.5 mm inside diameter) that was rested on a glass plate. Another flat glass was placed on top of the mold, and the plate was tightly clamped together. After the mold had been filled with the light cure composite material, the top surface was cured for 30 seconds with a light source. Chemical cure resin specimens were made in the same manner as above. Three hundreds and twenty composite resin specimens were constructed from the four composite materials. One hundred and sixty specimens of them were placed in a heater at $50^{\circ}C$, $75^{\circ}C$, $100^{\circ}C$, $125^{\circ}C$, $150^{\circ}C$, $175^{\circ}C$ and $200^{\circ}C$ for 5 minutes or 10 minutes respectively before compressive strengths were measured. Another one hundred and sixty specimens were tested for the diametral tensile strengths in the same way as above. They were randomly divided into eight groups according to the mode of heating methods as follows and stored in distilled water at $37^{\circ}C$ for 24 hours. Group $37^{\circ}C$ - specimens were stored at $37^{\circ}C$ in distilled water for 24 hours. Group $50^{\circ}C$ - specimens were heated at $50^{\circ}C$ after curing. Group $75^{\circ}C$ - specimens were heated at $75^{\circ}C$ after curing. Group $100^{\circ}C$ - specimens were heated at $100^{\circ}C$ after curing. Group $125^{\circ}C$ - specimens were heated at $125^{\circ}C$ after curing. Group $150^{\circ}C$ - specimens were heated at $150^{\circ}C$ after curing. Group $175^{\circ}C$ - specimens were heated at $175^{\circ}C$ after curing. Group $200^{\circ}C$ - specimens were heated at $200^{\circ}C$ after curing. Twenty specimens of each of four composite resins were respectively made by insertion of materials into same mold for examining the dimensional changes between before and after heating. The final eighty specimens were stored in distilled water at $37^{\circ}C$ for 24 hours before testing the dimensional changes. Compressive and diametral tensile strengths were measured crosshead speed 1mm/minute and 500Kg in full scale with a mechanical testing machine (DLC 500 Type, Shimadzu Co., Japan). Dimensional changes were determined by measuring the diametral changes of eighty specimens with micrometer (Mitutoyo Co., Japan). Results were as follows: 1. Diametral tensile strengths of specimens in all groups were increased with time heated compared with control group except for that in group $50^{\circ}C$ and the maximum diametral tensile strength was appeared in the specimen of Litefil-P heated for 10 minutes at $100^{\circ}C$. In heliomolar and P-50, it could be seen in the specimen heated for 10 minutes at $150^{\circ}C$, but in Bisfil-II, it could be found in the specimen heated for 5 minutes at $150^{\circ}C$. 2. Compressive strengths of specimens in all groups was tended to be also increased with time heated but that in group $50^{\circ}C$ and the maximum compressive strengths were showed in the same specimens conditioned as the diametral tensile strengths of four composite materials tested. 3. In Heliomolar, Litefil-P, and Bisfil-II, it was decreased in diameters of resin specimens between before heating and increased in diameters of resin specimens after storing in distilled water, but it was not in P-50. 4. There is little difference in diametral tensile strengths, compressive strengths, and dimensional changes followed by heating the resin specimens for 5 minutes and 10 minutes, but there is no statistical significances.

The purpose of this study was to investigate the effect of salivary gland on the calcification of dentin in rats. 80 Sprague-Dawley male rats that weighed approximately 120gm were used in this study. 5 rats among them were shared as controls. 75 rats received sialoadenectomy were divided into submaxillary adenectomy group, parotidectomy group, and submaxillary-parotid gland combined removal group. In experimental groups, 25 rats in each of the 3 groups were sacrificed at the following intervals; 3 days, 1, 2, 3 and 4 weeks. All animals were sacrificed by vascular perfusion with 10% formalin. The maxillary incisors including periapical tissues were removed and defatted in 20% KOH solution at $0^{\circ}C$ for 24 hours, and dehydrated with acetone. Each tooth specimen was attached on the stab for scanning electron microscopic study. Gold was coated on the each specimen in the thickness of 300${\AA}$ at D.C. 1400V, 6mA for 6 minutes with coating machine (Eiko IB-3). Inner dentinal surfaces of the specimens were observed with SEM (Hitachi S-450). The results were as follows, 1. Parotidectomy groups were found to be inhibited the formation of dentinal calcification compared to submaxillary adenectomy groups in the eady stages. 2. Combined removal of submaxillary and parotid gland was appeared to cause more severe inhibition effect on the dentinal calcification than that of each salivary gland separately. 3. Inhibition of the calcification and mineralization of dentin caused by sialoadenectomy was more extreme from 3 day to 2 weeks after beginning of the experiments. However it was tended to be normalized after that. 4. Salivary gland was responsible for alterations in calcification and mineralization of dentinal growth.

The purpose of this study was to evaluate the effect of tricalcium phosphate and Vitapex on the dogs' periapical tissues. Twenty mandibular premolars from 5 healthy dogs were used for this study. After the animals were anesthetized intramuscularly, pulp chambers were open and pulp tissue was extirpated with a barbed broach and H-file. Then the working length of the root canal was measured with H-file and pulp tissue was completely removed. Before the actual canal filling, the root canals of twenty teeth have been experimentally infected with opening the pulp chamber for 5 weeks. Periapical radiographs of the experimental teeth were taken to monitor the periapical pathological condition. Each root apex of 20 premolars was perforated with engine reamer and the root canals were enlarged with No. 30-60 H-files. They were divided into treated as follows. Control group: The root canal was filled with gutta-percha. Experimental group 1: The canal was dried with sterile paper points and mixture of tricalcium phosphate and physiological saline was overfilled beyond the root apex with a lentulo spiral. Then the root canal was filled gutta-percha and lateral condensation and the pulp chamber was filled with Caviton. Experimental group 2: The root canals were overfilled with Vitapex and were treated in the same manner as those in experimental group 1 At 1,2,3, and 8 weeks after experiment, the periapical tissues including the alveolar bone were fixed with 10% formalin solution for I week and decalcified with Plank-Rycho solution for 5 weeks. The specimens were embedded in paraffin and serial sections were cut into a thickness of 6 ${\mu}m$ at the plane of the root apex. Hematoxyline-eosin and Masson's trichrome stain were made for the histo-pathological examinations. The results were as follows: 1. Ingrowth of collagen fiber was observed from 1 week in control group and experimental groups. 2. The rate of bone formation of experimental group 1 was accelerated more than that of experimental group 2. 3. Resorption of cementum was seen in control group, but apposition of cementum was seen in experimental groups.

In the Infected root canals, the majority of the isolated bacteria are either strict anaerobes or microaerophilic organisms. Among thease, Black-pigmented Bacteroides species are the most important and have relation with clinical symptoms. The purpose of this study were to investigate on the 7 different types of bacteria which include Black-pigmented Bacteroides - Black--pigmented Bacteroides, Actinobacillus actinomycetemcomitans, Streptococcus, Capnocytophaga, Eiknella corrodens, Fusobacterium, Actinomyces - and the interrelationship between these 7 bacterical species, and to compare Black-pigmented Bacteroides with the clinical symptoms in infected root canals. The canal contents of 15 necrotized teeth with 8 clinical symptoms were sampled and cultured aerobically and anaerobically for growth in 7 selective agar plates for 7 bacterial species. Black-pigmented Bacteroides and Streptococcus subspecies were identified by biochemical tests. The results were as follows; 1. 70.51% of the bacteria isolated were anaerobes and 29.49% were aerobes. 2. B. loescheii, B. intermedius, B. denticola were isolated in 8 cases, Streptococcus was isolated in 8 cases, Fusobacterium was isolated in 6 cases, Actinomyces was isolated in 5 cases and Eiknella corrodens, Actinobacillus actinomycetemcomitans, Capnocytophaga were not isolated. 3. There were mutual inhibition of growth between Black-pigmented Bacteroides and Streptococcus. (P<0.01) But Actinomyces and Fusobacterium showed mutual aids for growth. (P<0.05) 4. Black-Pigmented Bacteroides was found to be related both to sinus tract formation and to apical sensitivity to palpation.(P < 0.05).

This study was conducted to evaluate and compare the apical leakage among the retrograde filling materials; retrograde filling with non-zinc amalgam, cavity varnish and non-zinc amalgam, z.o.e cement, Glass Ionomer cement, scotch bond and silux. Sixty single rooted teeth were divided into six groups and each tooth was individually prepared for its particular group. The specimens were incubated at $37^{\circ}C$ for 24 hrs and then were infiltrated by 2% methylene blue for 7 days. Apical leakage was evaluated by measuring the degree of dye penetration between the filling material and the canal wall. The results were as follows: 1. The scotch bond and silux group showed the least amount of apical leakage and the control group showed the greatest amount of apical leakage. 2. The groups retrofilled with cavity varnish and amalgam, glass-Ionomer cement, scotch bond and silux showed significantly good apical seal than control group. 3. The groups retrofilled with glass Ionomer cement, scotchbond and silux showed significantly good apical seal than the groups retrofilled with Amalgam and Zinc oxide eugenol cement.

The purpose of this study was to investigate the bio-stimulating effect of low power density laser radiation on the mechanically exposed pulp. Class V cavities on dog's teeth were prepared and the pulps were mechanically exposed with a round bur. In control group, the exposed pulps were capped with $Ca(OH)_2$ powder and the cavities were sealed with Z.O.E.. In experimental group A, the pulps were irradiated with GaA1As laser for 5 minutes and then they were treated the same as control group. In experimental group B, the exposed pulps were covered by aluminum foil and sealed with Z.O.E. after they were irradiated with the laser as the experimental group A. In the all groups, the pulps were histopathologically observed at the time intervals of 1, 2 and 3 week after experiment and the results were statistically evaluated. The results were as follows: 1) In control and experimental groups, mild vascular congestion and bleeding was found in most of the specimens and for the new formation of dentin bridge, experimental group A had the most cases. The dentin bridge had discontinuous osteodentin like appearance without any dentinal tubules. Inflammatory cell infiltration consisted of acute and chronic inflammatory cell, and the formation of microabscess was also observed. 2) The degree of inflammatory cell infiltration was not significantly different among control group and experimental groups at 1 week, 2 week and 3 week. 3) The formation of new dentin bridge was not significantly different between control group and experimental group A at 1 week, but at 2 week and 3 week, experimental group A showed significantly more cases of new dentin formation than control groups. (P < 0.05). 4) Between control group and experimental group B, there was no significant difference in formation of the new dentin bridge at 1, 2 and 3 week. (P> 0.05). 5) There was no significant difference in formation of the new dentin bridge at 1 and 2 week between experimental group A and experimental group B, but at 3 week, the former significantly had more cases of new dentin bridge formation than the latter.(P < 0.05).

In order to compare the accessory canal filling effects of the three root canal filling methods with gutta-percha, the author fabricated artificial root canal mold with the first and second accessory canals of chrome-cobalt alloy. After the artificial root canal was filled with gutta-percha by lateral condensation, vertical condensation and low-temperature thermoplasticized gutta-percha injection-molded method, twenty five times respectively, the gutta-percha forced into the first and second accessory canals were measured with caliper for length. The results were as follows: 1. The filling in both accessory canals was most effective in low-temperature thermoplasticized gutta-percha injection-melded method followed in such order as: vertical condensation method and lateral condensation method (p < 0.01). 2. The filling effect of the second accessory canal was more or less higher than that of the first one (p < 0.05). 3. Low-temperature thermoplasticized gutta-percha injection-molded method was fastest in time needed for root canal filling followed by lateral condensation method and vertical condensation method.

The purpose of this study was to evaluate the periodic effect of desensitizing drug such as potassium oxalate(D.D.S. # I&II), strontium chloride (ZAROSEN)$^{(R)}$, and placebo group. The 193 teeth of 93 patients who had been complained dental hypersensitivity, and were divided into three groups by application agent and desensitizing treatment was completed. The interval of observation and treatment period were immediately, 1 week, 2 week, 3 week, 4 week, before and after treatment. The data was statistically analized and the results were as followed. 1. Group I showed best desensitizing effect to the stimuli, followed by Group II, Group III. 2. There was a significant difference (p < 0.005) in desensitizing effect among the Group I, Group III and Group II, Group III but there was no significant difference (p < 0.005) in Group I, Group II. 3. The cold stimuli was most effective in desensitization and there was a significant difference (p < 0.005) in cold, air-blast, but there was no significant difference (p < 0.005) in other stimuli. 4. There was no significant difference (p < 0.005) in effect of the desensitization of the cause of exposed dentine. 5. Anterior teeth was more effective than posterior teeth in desensitization and there was a significant difference (p < 0.005) between anterior teeth and posterior teeth. 6. In analysis of stimuli on the potassium oxalate, there was a significant difference (p < 0.005) in cold, air-blast but there was no significant difference (p < 0.005) in other stimuli.

The purpose of this study was to assess the effects of wavelength and intensity of light curing units on the curing of composite resin. The wavelength and intensity of nine units were evaluated with Optical Multichannel Analyzer and Radiometer. Two-part split stainless steel mold with a cylindrical hole-3.0mm in diameter, 6.0mm in hgieht-was prepared. After placing a Mylar strip between two parts, 100 specimens were made by inserting each of four composite resins into the mold and irradiating for 20 seconds with five light units alternatively. The curing depths were measured by scraping method and evaluated by two-way ANOVA. And Vicker's hardness measurements were made on the longitudinally sectioned surface at 0.5mm interval. The results were as follows: 1. Visilux 2 showed a narrow spectral band within the effective wavelength in initiating polymerization and the highest intensity. Translux showed the diffuse spectrum of wavelength and the lower light intensity. 2. Visilux 2 showed the highest curing effect in any composite resin and then followed by Optilux, Efos 35, Heliomat and Translux. (p < 0.01) 3. Durafill showed the deepest curing depth in any light unit and then followed by Bisfil M, Silux and Heliosit. (p < 0.01). 4. Maximum hardness values showed 0.1mm and 0.5mm under top surface and then gradually decreased with depth.

The purpose of this study was to evaluate and compare the sealing ability of ZOE, FR and Sealapex, as a root canal sealer. Ninety six extracted anterior or premolar human teeth with single root were instrumented by using conventional method. After instrumentation, the teeth were divided into three groups and thirty two teeth in each group were filled as follows: ZOE group: ZOE cement as a root canal sealer in combination with guttapercha cone FR group: FR root canal sealer in combination with guttapercha cone Sealapex group: Sealapex root canal sealer in combination with guttapercha cone $^{45}Ca$ in the form of calcium chloride, was employed as the tracer in this study and produce the auto-radiograph. The depth of isotope penetration into the root canal was evaluated by method by Yates and Hembree at the intervals of 1 day, 7 days, 14 days and 30 days. The following conclusions were derived from the results obtained; 1. After 1 day, ZOE group exhibited the greatest penetration degree of radioisotope (p < 0.05). 2. After 14 days, there was some difference of the radioisotope penetration between each group, but its difference was not significant statistically. 3. After 30 days Sealapex group exhibited the least penetration degree of radioisotope (p < 0.025). 4. In ZOE and Sealapex groups, there was no change of the degree of radioisotope penetration with time.

As widely known major cause of tooth discoloration is red blood cell in dentinal tubules after tooth trauma and extirpation. Hemoglobin in the red cells easily conbine with hydrogen sulfide and change natural tooth color into dark brown. To confirm and compare the effect of bleaching agents test material was made as fellows: No. 40 paper points were soaked in blood and put into the oven for 24 hours to dry. Dried paper points were again soaked in diluted yolk by distilled water for a minute and kept the points for a week to get fully sulfide. Hydrogen peroxide (25%), Sodium hypochlorite (2%), Sodium hyposulfate (2%), Sodium perborate and mixture of Hydrogen peroxide (25%) and Sodium perborate were employed as bleaching agents. About 0.2ml of each medicaments were put into the small test tubes and blood soaked paper points were gently placed vertically with the apex downward and kept 24 hours in the oven ($37^{\circ}C$). Every 24 hours the medicaments were renewed at 24 and 48 hours. Following are the results of the study: 1. Significant bleaching effect was found on the case of hydrogen peroxide (25%) after 24 hours. The area above 2mm from apex also fully bleached after 48 hours. 2. A mixture of hydrogen peroxide and sodium perborate treated case showed moderate effect at 24 hours and significant effect at 48 hours. High portion of the point (above 2mm) was bleached satisfactory at 72 hours. 3. The effect of sodium perborate at 48 hours showed moderate and significant at 72 hours. 4. Sodium hypochlorite and sodium hyposulfate were weak agent in bleaching. At 72 hours case revealed moderate effect and influenced on high portion of the point very weak effect.

The purpose of this study was to measure Micro vicker's hardness of 4 kinds of anterior Composite resins (Pyrofil light bond anterior, Lite-fil anterior, Photo clear fil anterior, Silux) and 6 kinds of posterior Composite resin (Pyrofil light bond posterior. Lite-fil posterior, Photo clear fil posterior, Occlusin posterior, Palfique light posterior, P-30, posterior) according to deference of depth and distance of light tip from surface of composite resin. Each composite resin was filled into Teflon tube of 5mm in diameter and 5mm in depth, celluloid matrix was covered and the light in accordance with each composite resin was irradiated in distance of zero millimeter and 1 cm from light tip to surface of composite resin for 30 seconds. Specimens were sectioned longitudinally with cutting device. Microvicker's hardness measurements ware made at the depth of surface, 1mm, 2mm, 3mm, 4mm and 5mm from the surface to deep portion. Vicker's hardness numbers were taken on each depth under 200gm load for 30 seconds with MVK-E. The following results were: 1. The highest hardness value was measured at 1 mm depth. Then the deeper the depth, the lesser the hardness was observed. 2. The hardness value of anterior composite resins is lower than one of posterior composite resins. 3. Hardness number of composite resin irradiated in distance of zero millimeter from surface of composite resin was higher than one of 1 cm from surface of composite resin. 4. The pattern of hardness change at varying depth was similar to all the experimental material with no relation to distance of light from specimen.

The purpose of this study was to observe the resulting canal shape after using hand, sonic and ultrasonic instrumentation. Thirty canals from extracted human upper or lower 1st and 2nd molars were divided into 3 groups: hand, sonic and ultrasonic instrumentation group. 10 canals of each group were individually prepared with one of three instrumentation methods. After instrumentation and histological processing, apical, middle and coronal third cross sections were examined on the roundness of the canal by microscope. The result were as follows. 1. All experimented groups showed no significant difference in canal roundness regardless of size and level of the canal. 2. Sonic air instrumentation groups revealed Significantly better canal roundness than ultrasonic groups at the middle third of the fine canal. 3. In ultrasonic instrumentation groups, the roundness of the large canal was significantly better than that of fine canal.

The purpose of this study was to observe the anodic polarization curve from 4 kinds of low copper amalgam (Fine cut alloy, Spheralloy, Aristalloy and Amalcap) and 4 kinds of high copper amalgam (Dispersalloy, Sybraloy Orosphere and Tytin) obtained by using the potentiostat. The specimen made as the direction of manufacturer was stored at room temperature for about 7 days. The standard surface preparation was routinely carried out. The 0.9% saline solution was used as electrolyte in pH 6.8-7.0 at $37^{\circ}C$. The open circuit potential was determined after 30 minutes' immersion of specimen. The scan rate was 1mV/sec and the surface area of amalgam exposed to the solution was 0.785$cm^2$ for each specimen. All potentials reported are with respect to Ag/AgCl eelctrode. The following results were obtained. 1. The corrosion potential of high copper amalgams was higher than one of low copper amalgams, and the current density of high copper amalgam was lower than one of low copper amalgams. 2. The low copper amalgams had the similar pattern of polarization curve, but the high copper amalgams had the different pattern one another. 3. The polarization curve of Orosphere amalgam which is the admixed type was similar to one of low copper amalgam.

The purpose of this study was to observe the minim pins of Link plus (which has buttress thread and shoulder stop design) inserted into dentin and the dentin surrounding pin. The gingival walls of class II cavity were prepared with high speed handpiece in molar teeth not elapsed time after teeth were extracted, and pinhole of 2mm in depth was positioned about 1 mm to the dentinoenamel junction and minim pin was inserted with wrench. After initial examination of the specimens, the specimens were sectioned longitudinally and horizontally to the pins with carborundum disc and low speed diamond saw (Isomet Buehler Ltd) All specimens were coated Au of 250-300${\AA}$ in thickness with Ion Sputter JFC 100 and observed under Scanning Electron Microscope (JSM-35) The following results were obtained. 1. The shoulder stop was seated on the enterance of pinhole in gingival wall, and there were the irregular space between the pin and dentin at the enterance to the pin hole and flakes of dentin lifting from the dentin floor. 2. In case of section to pin horizontally or longitudinally, the dentin debris were observed in gap between pin and dentin, and small cracks were often seen in the dentin surrounding minim pins.