One fifth dilution of formocresol is usually used for pulpotomy of the primary teeth and emergency pulpotomy of the permanent teeth. However, the use of formaldehyde has been subjected to criticism because it may be absorbed into the blood stream and become distributed systemically, it may also alter the pulp tissue rendering it immunologically active, and have carcinogenic potential. Recently Depulpin®(VoCo., Germany) gains popularity as a devitalizing agent during root canal therapy in spite of high concentration of 49% paraformaldehyde because it facilitate devitalization of pulp and make root canal therapy easier. But there have been not enough publications about the reaction of pulp and periapical tissue caused by Depulpin.

This study was performed to evaluate the histological changes in pulp and periapical tissue of rats after pulpotomy using formocresol and Depulpin and to elucidate the toxic effects of these agents. Thirty six Sprague-Dawley rats were anesthetized by intraperitoneal injection of ketamine. Maxillary first molar teeth were used for pulpotomy with formocresol and Depulpin. Rats were sacrificed after 2 days, 4 days, 1 week, 2 weeks, 3 weeks and 4 weeks respectively. Specimens were histologically observed by light microscope changes in pulp and periapical tissue. The obtained results were as follows.

1. Formocresol group

A zone of fixed tissue, in which odontoblasts could clearly be defined, was present directly underneath the pulpotomy dressing in almost all teeth of this group. This was followed by an area of necrotic tissue which resembled dried out fibrous tissue with no cellular detail except some pyknotic nuclei. In the specimens of after 2 days, 4 days, 1 week, 2 weeks in which vital tissue was present, it was separated from the fibrous area by a zone of inflammation. In the specimens of after 3 weeks and after 4 weeks, inflammatory infiltrate was in the periodontal ligament adjacent to the apical foramina of the teeth.

2. Depulpin® group

The area of necrotic tissue which had no cells and fibers, was present adjacent to the dressing. This was followed by dried out fibrous tissue with no cellular details except some pyknotic nuclei. A short stump of vital pulp with odontoblasts was present at the end of the canal after 2 days. Inflammatory infiltrate was in the periodontal ligament after 4 days and after 1week. Severe root resorption and necrosis of periapical tissue opposite the root resorption site were defined after 2 weeks and after 3 weeks. Periapical lesion which consist of necrotic tissue surrounded by a fibrous connective wall, was found after 4 weeks.

The results indicated that Depulpin can cause more adverse reaction to the dental pulp and periapical tissue than formocresol, and further studies are needed for its clinical use with safety.

This study was performed to evaluate the temperature rise on various position of the Buchanan plugger, the peak temperature of plugger's type and the temperature change by its touching time of heat control spring.

The heat carrier system 'System B'(Model 1005, Analytic Technologies, USA) and the Buchanan's pluggers of F, FM, M and ML sizes are used for this study. The temperature was set to 200℃ which Dr. Buchanan's "continuous wave of condensation" technique recommended on digital display and the power level on it was set to 10. In order to apply heat on the Buchanan's pluggers, the heat control spring was touched for 1, 2, 3, 4 and 5 seconds respectively. The temperature rise on the surface of the pluggers were measured at 0.5 mm intervals from tip to 20 mm length of shank using the infrared thermography (Radiation Thermometer-IR Temper, NEC San-ei Instruments, Ltd, Japan) and TH31-702 Data capture software program (NEC San-ei Instruments, Ltd, Japan). Data were analyzed using a one way ANOVA followed by Duncan's multiple range test and linear regression test.

The results as follows.

1. The position at which temperature peaked was approximately at 0.5 mm to 1.5 mm far from the tip of Buchanan's pluggers (p<0.001). The temperature was constantly decreased toward the shank from the tip of it (p<0.001).

2. When the pluggers were heated over 5 seconds, the peak temperature by time of measurement revealed from 253.3±10.5℃ to 192.1±3.3℃ in a touch for 1 sec, from 218.6±5.0℃ to 179.5±4.2℃ in a touch for 2 sec, from 197.5±3.0℃ to 167.6±3.7℃ in a touch for 3 sec, from 183.7±2.5℃ to 159.8±3.6℃ in a touch for 4 sec and from 164.9±2.0℃ to 158.4±1.8℃ in a touch for 5 sec. A touch for 1 sec showed the highest peak temperature, followed by, in descending order, 2 sec, 3 sec, 4 sec. A touch for 5 sec showed the lowest peak temperature (p<0.001).

3. A each type of pluggers showed different peak temperatures. The peak temperature was the highest in F type and followed by, in descending order, M type, ML type. FM type revealed the lowest peak temperature (p<0.001).

The results of this study indicated that pluggers are designed to concentrate heat at around its tip, its actual temperature does not correlate well with the temperature which Buchanan's "continuous wave of condensation" technique recommend, and finally a quick touch of heat control spring for 1sec reveals the highest temperature rise.

Compomer is composed of matrix and filler; matrix is made of the combination of resins and polycarboxylic molecules that are light-cured, and a filler is a glass component which is capable of ion-release. The resin content of compomers produces polymerization shrinkage which can adversely affect marginal adaptation. Pretreatment is a fundamental step which is treated with conditioner or primer in the use of these materials.

Microleakage of restorative materials has been investigated mostly by dye penetration method. Dye penetration method was not quantitative and not measured repeatedly. Fluid filtration method, introduced and developed by Pashley's group, has been extensively used for 20 years for research purpose to understand the physiology of dentin, as well as the effects of various restorative treatments on dentin permeability. It permits quantitative, nondestructive measurment of microleakage in a longitudinal manner. The purpose of this study was to evaluate the change of dentin permeability according to the process of compomer restoration.

In this study, ClV cavities were prepared on buccal surface of thirty extracted human molars. The prepared cavities were etched by 37% phosphoric acid. The experimental teeth were randomly divided into three groups. Each group was treated with following materials; Group 1 : Prime & Bond NT/Dyract AP, Group2 : Single Bond/F2000 compomer, Group 3 : Syntac Single Component/Compoglass. The bonding agent and compomer were applied for each group following manufacturers information. Dentin permeability of each group was measured at each process by fluid filtration method; Step 1 : preparation(smear layer), Step 2 : etching(smear layer removal), Step 3 : applying the bonding agent, Step 4 : filling the compomer. Dentin permeability was expressed by hydraulic conductance(µl min^-1cmH₂O^-1).

The data were analysed statistically using One-way ANOVA and Sheffe's method.

The results were as follows :

1. Dentin permeability differences between each process were significant except between step 1 and step 2(p<0.01).

2. Dentin permeability after removal of smear layer was highly increased(p<0.01).

3. In most case, decrease of dentin permeability was obtained by applying bonding agent(p<0.01).

4. Dentin permeability differences among the experimental groups were not significant(p>0.05).

5. None of compomers used in this study showed perfect seal at the interface.

The marginal integrity of the crown can be broken during endodontic access cavity preparation due to the vibration of burs. Therefore, the purpose of this study was to evaluate the effect of endodontic access cavity preparation on the marginal leakage of full veneer gold crowns. 24 intact molars were mounted in acrylic resin blocks and prepared for crowns by a restorative dentist and crowns were cast with gold alloy. 20 Crowns were cemented with glass ionomer cement and 2 crowns were not cemented for positive control. 200 thermo-cycles from 5℃ to 50℃ with a travel time of 20s were completed. Then samples were randomly divided into 2 experimental groups of 9 each. Endodontic access preparation and zinc-oxide eugenol temporary fillings were done in Group 1. Teeth in Group 2 were not treated. Samples were coated with 2 layers of nail varnish and were immersed in 1% methylene blue dye for 20 hrs. Endodontic access was prepared in 2 samples, which were coated with nail varnish on all surfaces for negative control. After washing in running water, gold crowns were cut with a #330 bur. Four buccolingual sections, 2 mm apart, were cut from the central section of each tooth and were examined and scored under the microscope for dye leakage. Score 1: leakage to the cervical 1/3 of the axial wall, Score 2: leakage to the middle 1/3 of the axial wall, Score 3: leakage to the coronal 1/3 of the axial wall, Score 4: leakage to the occlusal surface. The median value for Group 1 is 4 and for Group 2 is 2. The result of this study showed that samples in Group 1 leaked more than those in Group 2. This finding was significant(P<0.001).

Several ways of curing are being tried to improve material’s properties and reduce marginal gap. However, all are considering about the pattern of light intensity. It was noted from the preliminary study the change of light wavelength from filter changing may give an impact on material’s property and microleakage.

The object of this study was to verify the effect of filters with various wavelength width on the microhardness and microleakage of composite resin; hybrid type of DenFil and submicron hybrid type of Esthet X. Composite resins were cured using 3 kinds of filter; narrow-banded(465-475 nm), mid-banded(430-470 nm), wide-banded(400-500 nm). After the estimation of microhardness, degree of dye penetration and the maximum gap from SEM evaluation were done between 4 groups that showed no difference in microhardness value of the lower surface.

The results were as follows:

Adequate microhardness could not be gained with a narrow-banded filter irrespective of curing time. At the upper surface, DenFil should be polymerized with middle or wide-banded filter for 20 seconds at least, while Esthet X be cured with middle or wide-banded filter for 30 seconds at least to get similar hardness value to control group.

From these results, it could be concluded that curing with wide-width filter would be better than the other techniques, even though the curing technique using mid-width filter seems to have its own unique advantage.

The aim of this study is to compare the adaptability of thermoplasticized injectable gutta-percha technique to the canal walls in ribbon-shaped canals.

Thirty resin models simulated ribbon-shape canals were instrumented to #40 using .06 taper Profile systems. Three groups of each 10 resin models were obturated by the lateral condensation technique(LC) and the two thermoplasticized injectable gutta-percha technique; Ultrafil Endoset+Obtura II(EO) and Ultrafil Firmset(UF), respectively.

After resin model were kept at room temperature for 4 days, they were resected horizontally with microtome at 1, 2, 3, 4 and 5mm levels from apex. At each levels, image of resected surface were taken using CCD camera under a stereomicroscope at ×40 magnification and stored. Ratio of the area of gutta-percha was obtained by calculating area of gutta-percha cone to the total area of canal using digitized image-analyzing program. The data were collected then analyzed statistically using One-way ANOVA.

The results were as follows.

1. At 1mm levels, there was no statistically significant difference in the mean ratio of gutta-percha among the groups.

2. At 2mm level, EO showed the highest mean ratio of gutta-percha (p<0.05) and there was no significant difference between LC and UF.

3. At 3, 4, 5mm levels, EO and UF had significantly greater mean ratio of gutta-percha than LC(p<0.05) and there was no significant difference between EO and UF.

In conclusion, the thermoplasticized injectable gutta-percha techniques demonstrated relatively favorable adaptability to canal walls than lateral condensation technique in ribbon-shaped canals except for 1mm level.

C-shaped canal configuration is very difficult to treat because that clues about preoperative canal anatomy cannot be ascertained from clinical crown morphology and limited information can be derived from radiographic examination.

This study was done to get more informations about the root and canal configuration of C-shape root by 3-dimensionally reconstructing for the purpose of enhancing success rate of endodontic treatment.

30 mandibular molars with C-shaped root were selected. Six photo images from occlusal, apical, mesial, distal, buccal, lingual directions and radiographic view were taken as preoperative ones to compare them with 3-D image. After crown reduction to the level of 1-2mm over pulpal floor was performed, teeth were stored in 5.25% sodium hypochlorite solution for the removal of pulp tissue and debris. They were cleaned under running water, allowed to bench dry and embedded in a self-curing resin. This resin block was serially ground with a microtome (Accutom-50, Struers, Denmark) and the image of each level was recorded by digital camera (FinePix S1-pro, Fuji Co., Japan). The thickness of each section was 0.25mm. Photographs of serial sections through all root canal were digitized using Adobe Photoshop 5.0 and then minimum thickness of open and closed sites were measured (open site is the surface containing occluso-apical groove : closed site is oppsite). After dizitization using 3-D Doctor (Able software Corp, USA), 3D reconstruction of the outer surface of tooth and the inner surface of pulp space was made. Canal classsification of C-shaped roots was performed from this 3-D reconstructed image.

The results were as follows:

1. Most C-shape rooted teeth showed lingual groove (28/30).

2. According to Vertuccis'calssification, type I, II, III, IV, VII were observed, but also new canal types such as 2-3-2, 1-2-3-2, 2-3-2-1, 2-3-2-3 were shown.

3. There was little difference in minimum thickness on coronal and apical portions, but open site were thinner than closed site on mid portion.

Conclusively, 3D reconstruction method could make the exact configurations of C-shape root possible to be visualized and analyzed from multi-directions. Data from minimum thickness recommend cleaning and shaping be more carefully done on dangerous mid portion.

The purpose of this study is to identificate root canal system including ideal access placement, root curvature, canal configuration, incidence of isthmus in mandibular incisors for success of endodontic treatment.

200 mandibular incisors were selected. The ideal access placement was determimed as follows. The teeth were radiographed from mesiodistal and buccolingual views using intraoral dental film. The image was divided into coronal, middle and apical third using the proximal film. Straight line access was determined by measuring the faciolingual canal width and placing points at midway point between the buccal and lingual wall at the junction of the middle and apical third and at the juntion of coronal and middle third of the root canal. A line was drawn connecting these two points extending through the crown of the tooth. The point at which the line crossed the external crown surface was recorded as facial, incisal, lingual. Degree of root curvature was determined by Schneider Protractor Method. Both section method and clearing method were used in this study. By section method, 100 mandibular incisors were embedded in clear resin and transeverse serial sectioned at 0.5, 1.0, 2.0, 3.0, 4.0, 5.0mm level from root apex. The resected surfaces were stained by methylene blue and examined under ×40 magnification with a stereomicroscope. By clearing method, 100 mandibular incisors were cleared in methysalicylate after decalcification with 10% nitric acid and evaluated under ×18 magnification with a stereomicroscope.

The results were as follows ;

1. 29% had the center of the plotted straight-line access facial to incisal edge, whereas 71% had straight-line access at the incisal edge. When incisal wear classified as extensive, the straight-line access was plotted on the incisal edge 95.5%. When incisal wear classified as slight/none, the straight-line access was plotted on the facial 65.9%.

2. Degree of curvature of main canal was straight or almost straight, and only 10% in buccolingual direction had a degree of curvature greater than 20 degrees and 5.5% in mesiodistal direction had.

3. In section method, canal configuration analysis showed that 51% of the specimen classified as type I, 27% as type II, 12% as type III, 10% as type IV. For thoses setions with two canals, the incidence of an isthmus was 26.7%, 64.3%, 79.2%, 96.3%, 97.4%, 97.6% at each level and highest in 3~5mm sections.

4. In clearing method, canal configuration analysis showed that 74% of the specimen classified as type I, 11% as type II, 6% as type III, 9% as type IV.

These results suggested that traditional access from lingual should be moved as far toward the incisal as possible to locate and debride the lingual canal and root canal system should be cleaned, shaped completely and obturated three dimensionally for successful endodontic treatment.

The bleaching of discolored nonvital teeth is conservative treatment that satisfy the cosmetic desire. The most common method for this treatment, walking bleaching, is using 30% hydrogen peroxide and sodium perborate.

Many alternatives are suggested for preventing the external cervical root resorption that is the common complication of the nonvital teeth bleaching with 30% hydrogen peroxide.

The same extent of oxidation reactions as that resulted by the bleaching with the application of 30% hydrogen peroxide and sodium perborate can also be acquired more safely by materials that contain 10% carbamide peroxide, used primarily for the bleaching of vital teeth. Therefore, this study was performed to evaluate the efficacy of 10% and 15% carbamide peroxide bleaching gel in nonvatal teeth bleaching.

The internal bleaching of intentionally discolored teeth was performed in vitro with 10% carbamide peroxide (Group 1), 15% carbamide peroxide (Group 2), mixture of distilled water and sodium perborate (Group 3), and mixture of 30% hydrogen peroxide and sodium perborate (Group 4). The bleaching materials were refreshed following 3, 6, 9 and 12 days. To evaluate the bleaching effect, the color change of the crowns was measured at 1, 2, 3, 4, 7 and 15 days of bleaching using the colorimeter.

The results were as follows :

1. L* and ΔE* values were increased with time in all bleaching agents(p<0.01).

2. There was no significant difference in L* and ΔE* value among bleaching agents.

3. ΔE* value higher than 3 was shown after 3 days of bleaching with 10% carbamide peroxide gel, 1 day with 15% carbamide peroxide gel, 4 days with mixture sodium perborate and distilled water and 4 days with mixture sodium perborate and 30% hydrogen peroxide, respectively.

These results revealed that the use of 10% and 15% carbamide peroxide bleaching gel in non-vital teeth bleaching is as effective as mixture of distilled water and sodium perborate and mixture of 30% hydrogen peroxide and sodium perborate. Accordingly, carbamide peroxide could be used clinically to bleach discolored non-vital teeth.