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).

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.

The purpose of this in vitro study was to compare the effects of root canal debridement following rotary Ni-Ti instruments with positive versus negative rake angle. Seventy sound, extracted human anterior teeth & premolars were randomly divided into four groups. The used rotary instruments were Ni-Ti HERO 642(Micro-Mega in France, 20 specimen), Ni-Ti ProFile(Maillefer, Ballaigues, Switzerland, 20 specimen), stainless steel engine reamer(Mani, Matsutani Seisakusho Co.,Japan, 20 specimen) and negative control group(10 specimen) was only extirpated with barbed broach(Mani, Matsutani Seisakusho Co.,Japan)

Group 1 & 2 teeth were prepared to a #40 at the apex followed by 1 mm using crown-down technique. Group 3 teeth were instrumented from a #15 to a #40 in sequential order. After preparation and final irrigation, the roots split longitudinally into a bucco-lingual direction. Root halves were cross-sectioned in apical third portion again. all root specimens were prepared for SEM investigation & photographed. Separate evaluations were undertaken for smear layer on prepared walls with a five score-index for each using reference photograph in root halves. the penetration depth of smear layer into dentinal tubules was also estimated in the other halves. the following results were obtained :

1. Smear layer was observed on all the prepared walls with three experimental groups except negative control group

2. Smear layer characteristics

1) HERO 642 groups showed snowy & dusty appearance & were observed only few some dentinal tubuli open on the prepared walls, and the penetration depth of it into dentinal tubules may be 1-2 µm thick.

2) ProFile groups showed shiny & burnished appearance & complete root canal wall covered by a homogenous smear layer with no open dentinal tubuli and penetration depth of it into dentinal tubules may be 1-2 µm thick.

3) Engine reamer groups showed obviously file's passed tracks on the prepared walls & were observed complete root canal wall covered by a homogenous smear layer with no open dentinal tubuli.

The results revealed that a completely clean root canal could not be achieved regardless of positive & negative rake angle, which is in accordance with the majority of studies on root canal cleanliness.

In conclusion, throughout irrigation with antibacterial solutions or chelating agents is recommended to remove the smear layer on prepared canal walls.

Extracellular single unit recordings were made from the ventral posteromedial thalamic (VPM) nociceptive neurons to determine mechanoreceptive field (RF) and response properties. A total of 44 VPM thalamic nociceptive neurons were isolated from rats anesthetized with urethane-chloralose.

Based on responses to various mechanical stimuli including touch, pressure and pinch applied to the RF, 32 of 44 neurons were classified as nociceptive specific (NS) neuron. The other 12 neurons, classified as wide dynamic range (WDR), showed a graded response to increasingly intense stimuli, with a maximum discharge to noxious pinch.

The VPM nociceptive neurons showed various spontaneous activity ranged from 0-6 Hz. They were located throughout the VPM, and had an contralateral RF including mainly intraoral (and perioral) regions. The RF size was relatively small, and very few neurons had a receptive field involving 3 trigeminal divisions. The NS neurons activated only by pressure and pinch stimuli had high mechanical thresholds compared to WDR neurons activated also by touch stimuli. The VPM nociceptive neurons were tested with suprathershold graded mechanical stimuli. Most of 21 NS and 8 WDR neurons showed a progressive increase in number of spikes as mechanical stimulus intensity was increased. In some neurons, the responses reached a peak before the highest intensity was given. Application of 5 mM CoCl₂ (10 µl) solution to the trigeminal subnucleus caudalis did not produce any significant changes in the spontaneous activity, RF size, mechanical threshold, and response to suprathresold mechanical stimuli of 9 VPM nociceptive neurons tested.

17 of 33 VPM nociceptive neurons responded to noxious heat as well as noxious mechanical stimuli applied to their RF. Application of the mustard oil, a small-fiber excitant and inflammatory irritant, to the right maxillary first molar tooth pulp induced an immediate but short-lasting neuronal discharges upto approximately 4 min in 16 of 42 VPM nociceptive neurons.

These results suggest that VPM thalamic nucleus may contribute to the sensory discriminative aspect of orofacial nociception.

The purpose of this study was to compare the histomorphological change of curved root canal preparation using GT rotary File, Profile .04 taper and stainless steel K-file. 45 mesial canals(over 20 degree) of extracted human mandibular first molars were mounted in resin using a modified Bramante muffle system and divided into three groups. The roots were cross-sectioned at 2.5mm, 5mm and 8mm levels from apical foramen. Tracings of the canals were made from preinstrumentation pictures of the cross section. The canals were prepared using a step-back technique with stainless steel K file(group 1), Profile .04 taper rotary file(group 2) and GT rotary file(group 3). Tracings of the prepared canals were made from postinstrumentation picture. Canal centring ratio, amount of transportation, area of dentin removed and shape of canal were measured and statistically were evaluated with Student-Newman-Keuls test using Sigma Stat(Jandel Scientific Software, USA).

The results were as followings:

1. Amount of transportation of group 2 was the lowest at apical part, but there was no statistical difference. The direction of transportation was the outside of curvature at apical part.

2. Centering ratio at the apical part of group 1 was the highest, and there was statistical differences between apical and middle part, apical and coronal part(p<0.05). Centering ratio at the middle part of group 3 was the lowest, and there was statistical difference between apical and middle part(p<0.05). Centring ratio of group 2 was the lowest at apical part, but there was no statistical difference.

3. Amount of dentin removed of group 1 was the highest at coronal, middle and apical part among three groups, and there was statistical difference(p<0.05).

4. The majority of the cross-sectioned canal shape after instrumentation were irregular at coronal, middle and apical part. But there are more number of round shaped canals at group 3 than other group.

To understand the recent characteristics of the papers published in the Journal of Korean Academy of Conservative Dentistry(JKACD), All the papers in the JKACD of 1992 to 2001 were analyzed. A total of 513 papers were classified according to its type, field and subject of the study, school and the number of authors, references, and written language.

The results were as follows;

According to the type of the paper, 506(98.6%) were original articles, 3(0.6%) were review articles, and 4(0.8%) were case reports.

The purpose of this study was two-fold. First was to evaluate whether the molecular sieving model was appropriate for ionic dissociation experiment. Second was to compare the dissociation of calcium and hydroxyl ions from five types of calcium hydroxide pastes (Pure calcium hydroxide paste, DT temporary dressing®, Metapaste®, Chidopex®, Metapex®) in three vehicles (aqueous, viscous and oily) and the antibacterial effect.

Each calcium hydroxide pastes was placed into 0.65ml tube with cap and then 15% polyacrylamide gel was placed onto calcium hydroxide pastes. After the gel was hardened, the tubes were filled with tridistilled water (pH 7.14) and closed with cap. The tubes were stored in 37℃, 100% incubator. The pH reading and the concentration of calcium ions were taken at 1, 4, 7, 10, and 14 days. The brain heart infusion agar plates with S. mutans and A. actinomycetemcomitans were used for antibacterial activity test. Middle of agar plate was filled with the calcium hydroxide pastes. The plates were incubated at 37℃ and observations were made to detect the zones of inhibition. These data were evaluated statistically by use of the analysis of variance and duncan test.

The results were as follows.

1. In fresh mixing state, the pH of five types of calcium hydroxide pastes were measured between 12.5 and 12.8.

2. The pH was increased in all five types of calcium hydroxide pastes compared with control group. In 14 days, Pure calcium hydroxide paste (11.45) and DT temporary dressing® (11.33) showed highest pH, followed by Metapaste® (9.49), Chidopex® (8.37) and Metapex® (7.59).

3. Calcium was higher in all five types of calcium hydroxide pastes compared with control group. In 14 days, Pure calcium hydroxide paste (137.29 mg%) and DT temporary dressing® (124.6 mg%) showed highest value, followed by Metapaste® (116.74 mg%), Chidopex® (111.84 mg%) and Metapex® (60.22 mg%).

4. The zones of bacterial inhibition were seen around all five types of calcium hydroxide pastes. Chidopex® and Metapex® groups which include iodoform were observed significantly larger zone of inhibition in A. actinomycetemcomitans compared with the other calcium hydroxide groups (p<0.05). However, Metapex® showed the least antibacterial effect on S. mutans compared with other groups (p<0.05).

The molecular sieving model was found to be acceptable in dissociation experiment of hydroxyl and calcium ions when compared with the previous tooth model study. But this model was not appropriate for the antibacterial test.