The purpose of this study was to evaluate the penetration pattern of dentin adhesives according to the orientation of dentinal tubules with confocal laser scanning microscopy. Specimens having perpendicular, parallel and oblique surface to dentinal tubules were fabricated. The primer of dentin adhesives (ALL BOND® 2, CLEARFIL™ SE BOND and PQ1) was mixed with fluorescent material, rhodamine B isothiocyanate (Aldrich Chem. CO., Milw., USA). It was applied to the specimens according to the instructions of manufactures. The specimens were covered with composite resin (Estelite, shade A2) and then cut to a thickness of 500 µm with low speed saw (Isomet™, Buehler, USA). The adhesive pattern of dentin adhesives were observed by fluorescence image using confocal laser scanning microscopy.

The results were as follows.

For the groups with tubules perpendicular to bonded surface, funnel shape of resin tag was observed in all specimen. However, resin tags were more prominent in phosphoric acid etching system (ALL BOND® 2 and PQ1) than self etching system (CLEARFIL™ SE BOND).

This study was done to present a criterion in selection of the most proper light sources and materials by measuring metamerism index(MI) of the light curing composite resins with spectrocolorimeter. Metamerism is defined when two objects appear to be the same color in one illuminant but different in another. This is due to the fact that they have different spectral curves that fail to match under the second illuminant.

In this study, A1 & A3 shade of five light curing composite resins (Esthet-X, Filteck Z250, Filteck A110, Charisma, Vitalescence) were chosen based on Vita shade. Five samples were made for shade of each product with Teflon mold (diameter: 15mm, thickness: 2mm).

Metamerism index of each samples on a Barium sulfate plate (L*=96.54, a*=0.19, b*=0.01) prepared for sample fixation were measured with spectrocolorimeter(Miniscan XE plus, Model 4000s, Hunter Lab, USA) by applying standard light source D₆₅, C, Fcw, TL84 and A. Standardization was done with reference standard (X=80.8, Y=85.7, Z=90.8) and light trap. The results were as follows.

Different resins with same Vita shade showed recognizable color difference(ΔE*>2).

This study was performed to evaluate the actual temperature rise on the surface of Buchanan plugger using thermocouple. The heat carrier system 'System B Heatsource' (Model 1005, Analytic Technologies, Redmond, WA, USA) and the Buchanan pluggers of F, FM, M and ML sizes are used for this study. The temperature was set to 200℃ on digital display and the power level on it was set to 10. Five thermocouples were placed in direct contact with the surface of each size of Buchanan's pluggers at 1 mm increments from the tip to the 4 mm length of shank. The heat control spring was touched for 5 seconds, and the temperature rise on the surface of the pluggers were measured at 1 sec intervals for more than 5 seconds with an accuracy of 0.01 using Data Logger. The data were statistically analyzed by one-way ANOVA.

The results were as follows.

The position at which the temperature peaked was approximately at 1~2 mm far from the tip of Buchanan plugger (p<0.01).

This results suggest that the actual temperature on the surface of the pluggers does not correlate well with the temperature set on digital display. Heat concentrates around the tip. The larger plugger reveals lower temperature rise relatively.

This study was conducted to evaluate the temperature rise on the root surface while the root canal is being obturated using continuous wave of condensation technique. Maxillary central incisor was prepared for repeated canal obturation. Ten thermocouples (Omega Engineering Inc., Stanford, USA) were placed at 1 mm increment from the anatomical root apex. The real temperature of Buchanan plugger was recorded before insertion into the root canal. The root canal was obturated with continuous wave of condensation technique as described by Buchanan and the root surface temperature was recorded during obturation at 150℃, 200℃, 250℃ and 300℃ temperature settings of System B HeatSource (Model 1005, Analytic technologies, Redmond, WA, USA). After completion of the temperature recording, the dentinal-cementum thickness at each sites was measured. The data were analyzed using one-way ANOVA followed by Scheffe' s test and linear regression test.

The results were as follows.

When the temperature was set at 150℃, 200℃, 250℃ and 300℃ on the digital display of System B HeatSource, the real temperature of the plugger at the 1mm point from the tip revealed 130.82±2.96℃, 158.00±5.26℃, 215.92±6.91℃ and 249.88±3.65℃ respectively.

These results suggest that it be relatively kind to the supporting tissues of the root that the root canal is obturated using continuous wave of condensation technique at 150℃, 200℃, 250℃ and 300℃ temperature settings on digital temperature display of System B HeatSource.

This study was performed to evaluate the interfacial shear bond strength of base (direct and indirect) and repair composites with aging and surface treatment methods.

Direct composite resin specimens (Charisma®, Heraeus Kulzer, Germany) were aged for 5 min, 1 hour, 24 hours, and 1 week in 37℃ distilled water before surface treatment, and then divided into five groups: Group 1, grinding; Group 2, grinding and application of bonding agent; Group 3, grinding, etching with 37% phosphoric acid for 30sec, and application of bonding agent; Group 4, grinding, etching with 37% phosphoric acid for 30sec, silane treatment, and application of bonding agent; Group 5, grinding, etching with 4% hydrofluoric acid for 30sec, silane treatment, and application of bonding agent.

Indirect composite resin specimens (Artglass®, Heraeus Kulzer, Germany) were aged for 1 week in 37℃ distilled water and divided into seven groups: Group 1 - Group 5, equal to Charisma specimens; Group 6, grinding, etching with 37% phosphoric acid for 60sec, silane treatment, and application of bonding agent; Group7, grinding, etching with 4% hydrofluoric acid for 60 sec, silane treatment, and application of bonding agent.

The repair material(Charisma®) was then added on the center of the surface (5 mm in diameter, 5 mm in height). The shear bond strength was tested and the data was analyzed using one-way ANOVA and the Student-Newman-Keuls test.

The following conclusions were drawn.

1. The shear bond strength of Charisma® specimens aged for 1 hour was significantly higher in Group 2 and Group 5 than in Group 1 (p<0.05), and that of Charisma® specimens aged for 1 week was significantly higher in Group 3 and Group 5 than in Group 1 (p<0.05). No significant difference was found in the bond strength of specimens aged for 5 min and 24 hours.

2. In Group 2 of the Charisma® specimens, there was significant difference between the bond strength of 24 hours and that of 1 week (p<0.05).

3. In Group 4 of the Charisma® specimens, the shear bond strength of specimens aged for 24 hours was significantly higher than the others(p<0.05).

4. There was no significant difference between the shear bond strength of the Artglass® specimens.

5. Most of the Charisma® specimens showed cohesive fractures. Artglass® specimens that were etched with acid (phosphoric or hydrofluoric) for 30 sec showed more cohesive fractures.

Purpose of this research is estimating polymerization depth of different source of light. XL 3000 for halogen light, Apollo 95E for plasma arc light and Easy cure for LED light source were used in this study. Different shade (B1 & A3) resin composites (Esthet-X, Dentsply, U.S.A.) were used to measure depth of cure. 1, 2, and 3 mm thick samples were light cured for three seconds, six seconds or 10 seconds with Apollo 95E and they were light cured with XL-3000 and Easy cure for 10 seconds, 20 seconds, or 40 seconds. Vicker's hardness test carried out after store samples for 24 hours in distilled water.

Results were as following.

Curing time increases from all source of lights, curing depth increased(p<0.05).

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.

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.