Proteoglycan is highly hydrophilic and negatively charged which enable them attract the water. The objective of study was to investigate the effects of Proteoglycan on microtensile bond strength of dentin adhesives and on architecture of dentin collagen matrix of acid etched dentin by removing the chondroitin sulphate attached on Proteoglycan. A flat dentin surface in mid-coronal portion of tooth was prepared. After acid etching, half of the specimens were immersed in 0.1 U/mL chondroitinase ABC (C-ABC) for 48 h at 37℃, while the other half were stored in distilled water. Specimens were bonded with the dentin adhesive using three different bonding techniques (wet, dry and re-wet) followed by microtensile bond strength test. SEM examination was done with debonded specimen, resin-dentin interface and acid-etched dentin surface with/without C-ABC treatment.

For the subgroups using wet-bonding or dry-bonding technique, microtensile bond strength showed no significant difference after C-ABC treatment (p > 0.05). Nevertheless, the subgroup using rewetting technique after air dry in the Single Bond 2 group demonstrated a significant decrease of microtensile bond strength after C-ABC treatment. Collagen architecture is loosely packed and some fibrils are aggregated together and relatively collapsed compared with normal acid-etched wet dentin after C-ABC treatment. Further studies are necessary for the contribution to the collagen architecture of noncollagenous protein under the various clinical situations and several dentin conditioners and are also needed about long-term effect on bond strength of dentin adhesive.

The purpose of this study was to compare the root canal shaping ability of 4 rotary NiTi instruments in simulated root canals.

For the preparation of thirty two curved root canals, Mtwo instruments using "single length"technique, and Profile, ProTaper Universal, and K3 using crown-down technique (N = 8) were used. All canal samples were prepared by reaching an apical canal size of #30. Pre- and post-instrumentation digital images were recorded and an assessment of canal shape was determined using a computer image analysis program SigmaScan Pro (Systat Software Inc., San Jose, CA, USA). The changes of the dimension of inner walls of canals, (2) the changes of the dimension of outer walls of canals, and (3) the centering ratio were measured at 7 measuring points, and then data were statistically analyzed using one-way ANOVA and Duncan's test. The results were as below;

The root canal shaping ability of Profile was significantly faster than that of other rotary NiTi instruments (p < 0.05).

Results suggest that in the coronal part of canal preparation, active cutting files such as ProTaper Universal may efficiently flare the canal orifice and form a better taper, and in the apical part of the canal, files which have a better centering ability such as Profile may maintain the original canal curvature and reduce the shaping time.

The purpose of this study was to evaluate the effect of film thickness of various resin cements on bonding efficiency in indirect composite restoration by measurement of microtensile bond strength, polymerization shrinkage, flexural strength and modulus, fractographic FE-SEM analysis. Experimental groups were divided according to film thickness (< 50 µm-control, 50 µm-T50, 100 µm-T100, 150 µm-T150) using composite-based resin cements (Variolink II, Duo-Link) and adhesive-based resin cements (Panavia F, Rely X Unicem). The data was analyzed using ANOVA and Duncan's multiple comparison test (p < 0.05).

The results were as follows;

Variolink II showed higher microtensile bond strength than that of adhesive-based resin cements in all film thickness (p < 0.05) but Duo-Link did not show significant difference except control group (p < 0.05).

During the last two decades, there has been an increasing interest in the impact of oral health on atherosclerosis and subsequent cardiovascular disease (CVD). To date, some periodontal pathogens including Porphyromonas gingivalis (P. gingivalis) have been reported to be relevant to CVD. Porphyromonas endodontalis (P. endodontalis), which shares approximately 87% sequence homology with P. gingivalis, is mostly found within infected root canals. However, recent studies reveal that this pathogen also resides in the dental plaque or periodontal pocket in patients with periodontitis. It has been shown that P. endodontalis invades human coronary artery endothelial cells (HCAEC) and coronary artery smooth muscle cells (CASMC). To evaluate whether P. endodontalis can participate in the progression of atherosclerosis and CVD, we examined the changes in transcriptional gene expression profiles of HCAEC responding to invasion by P. endodontalis in this study.

The following results were obtained.

Porphyromonas endodontalis was invasive of HCAEC.

Thus, these results show that P. endodontalis presents the potential to trigger and augment atherosclerosis leading to CVD.

The purpose of this study was to characterize functional distinction between human dental pulp cells(PC) and periodontal ligament cells(PDLC) using cDNA microarray assay and to confirm the results of the microarray assay using RT-PCR. 3 genes out of 51 genes which were found to be more expressed(>2 fold) in PC were selected, and 3 genes out of 19 genes which were found to be more expressed(>2 fold) in PDLC were selected for RT-PCR as well.

According to this study, the results were as follows:

1. From the microarray assay, 51 genes were more expressed (2 fold) from PC than PDLC.

2. RT-PCR confirmed that ITGA4 and TGF β2 were more expressed in PC than in PDLC.

3. From the microarray assay, 19 genes were more expressed (2 fold) from PDLC than PC.

4. RT-PCR confirmed that LUM, WISP1, and MMP1 were more expressed in PDLC than in PC.

From the present study, different expression of the genes between the PC and PDLC were characterized to show the genes which play an important role in dentinogenesis were more expressed from PC than PDLC, while the genes which were related with collagen synthesis were more expressed from PDLC than PC.

The aim of this study was to investigate the shapes and diameters of the physiological foramen and anatomy of the root canal at 3mm from apex in mandibular first molars.

Sixty mandibular first molars were randomly selected. The apical anatomy of 60 mandibular first molars was investigated by means of a stereomicroscope (60x magnification).

The results were as follows;

1. There was a high percentage of two physiological foramina in mesial (61.67%) and one foramen in distal(71.66%) roots of mandibular first molars.

2.There was a high frequency of accessory foramina in mesial roots with one foramen (26.07%).

3. The diameters of physiological foramen was as follows:

0.329mm in single mesial foramen

4. The most common physiological foramen shape was oval (69.93%).

5. The incidence of isthmus in mesial root at 3mm from apex was 55%. The 3mm-sections contained a complete isthmus 31.66% and a partial isthmus 23.34%.

6. 3mm from the apex, the most common canal shape was oval (50.64%).

Knowledge of the apical anatomy of mandibular first molar would be necessary for success of surgical and nonsurgical endodontic treatment.

The purpose of this study was to evaluate the bond strength of a new Single step system with different curing mode composites, and to evaluate the effect of the intermediate resins which have different hydrophilicity on bonding ability by means of the micro shear bond testing and TEM examination for the adhesive interface. The adhesive used in this study was an experimental single step system (Bisco Inc., Schaumburg, IL). Experimental groups were produced by using six kinds of intermediate resin having different hydrophilicity that was hydrophilic, hydrophobic and most hydrophobic resin and as filled or not after applying adhesive. Each experimental group was further divided into two subgroups whether the adhesive was light cured or not. Dual cured composite (Bis Core, Bisco Ltd., Schaumburg, IL) was placed on the adhesive layer as light cure or self cure mode. The results of bond strength were statistically analyzed using one way ANOVA and multiple comparisons are made using Tukey's test at α < 0.05 level.

The results of this study were as follows;

1. The application of intermediate resin did not increase the bond strength for light cured composite.

2. The bond strength of an experimental adhesive with self cured composite was significantly increased by the application of intermediate resin layer.

3. The bond strength of adhesive was irrespective of the cure or not of itself before intermediate resin layer applied.

4. As applied hydrophilic resin layer was, the initial bond strength was higher than both hydrophobic and most hydrophobic one used but there was no significance.

Using a single step adhesive with dual/self cured composite, the incompatibility between both of them should be solved by the application of intermediate hydrophobic resin to reduce the adhesive permeability. However, Single step adhesive can be used in the light cured composite restoration without any decrease of the initial bond strength.

The objective of this study is to evaluate the effect of an additional application of bonding resin on the bond strength of resin luting cements in both the light-cure (LC) and self-cure (SC) modes by means of the µTBS tests.

Three combinations of One-Step Plus with Choice, Single Bond with Rely X ARC, and One-Up Bond F with Bistite II were used. D/E resin and Pre-Bond resin were used for the additional application. Twelve experimental groups were made. Three mandibular 3^rd molars were used in each group. Indirect composite blocks were cemented on the tooth surface. 1 × 1 mm² dentin-composite beam for µTBS testing were made and tested.

When total-etching dentin adhesives were used, an additional application of the bonding resin increased the bond strength (P < 0.05). However, this additional application didn't influence the bond strength of self-etching dentin adhesives (P > 0.05).

In conclusion, the results suggest that an additional application of the bonding resin increases bond strength and enhances quality of bonding when using total-etching dentin adhesives.

The purpose of this study was to evaluate the effect of different etching times on microtensile bond strength (µTBS) to dentin both initial and after thermocycling with 3 different types of total-etching adhesives.

Fifty four teeth were divided into 18 groups by etching times (5, 15, 25 sec), adhesives types (Scotchbond Multipurpose (SM), Single Bond (SB), One-Step (OS)), and number of thermocycling (0, 2,000 cycles).

Flat dentin surfaces were prepared on mid-coronal dentin of extracted third molars. After exposed fresh dentin surfaces were polished with 600-grit SiC papers, each specimen was acid-etched with 35% phosphoric acid (5, 15, 25 sec) and bonded with 3 different types of total etching adhesives respectively. Then, hybrid composite Z-250 was built up. Half of them were not thermocycled (control group) and the others were subjected to 2,000 thermocycle (experimental group). They were sectioned occluso-gingivally into 1.0 × 1.0 mm² composite-dentin beams and tested with universal testing machine at a crosshead speed of 1.0 mm/min.

Within limited data of this study, the results were as follows

1. There was no statistically significant difference in µTBS between the thermocycled and non-thermocycled groups, except for both SM and SB etched for 25 sec.

2. In thermocycled SM and SB groups, bond strength decreased by extended etching time.

In total etching systems, adhesive durability for dentin could be affected by type of solvents in adhesive and etching time. Especially, extended etching time may cause deteriorate effects on bond strength when ethanol-based adhesive was used.

The purpose of this study was to evaluate the effects of cyanate methacylate on the shear bond strengths to bovine dentin surfaces as a dentin primers.

Seven experimental adhesives were made with different mass fraction of Isocyanatoetylmethacrylate (IEM), 40wt% HEMA (Wako Pure Chemical Industries Osaka, Japan), 0.6% camphoroquinone, 0.4% amine and ethanol as balance. dentin bonding agents (0, 2, 4, 6, 8, 10, 12%) were made and applied on the surface of bovine dentin specimens of 7 experimental groups.

Shear bond strengths were measured using a universal testing machine (Instro 4466).

To identify the ratio and modes of cohesive failures, microscopic examinationn was performed. The ultra-structure of resin tags were observed under scanning electron microscope.

The results were as follows ;

1) A higher shear bond strengths (33.62 _MPa) in group 8% of Cyanate methacrylate to dentin were found, but there were no statistically significancy between Groups (p > 0.05).

2) The higher ratio of cohesive failures mode in group 2, 6, an 10% could be seen than that in any other groups.

3) A shorter resin tags were observed in all experimental groups.

This could be resulted that the preventing from the cyanate methacrylate penetrate into dentin owing to reacting it with dentin collagen.

Therefore the resin tags were shorter in lengths.

Whether the higher bonding strengths of dentin bonding agents can be affected was not been assured with statistic results.

The results indicated that the relation between tensile strengths of the dentin adhesives to bovine dentin and resin tags formed into the dentin could not affected.

The main reason of increasing the shear bond strength to bovine dentin in experimental groups could not be assured.

The fracture toughness test is believed as a clinically relevant method for assessing the fracture resistance of the dentinal restoratives. The objectives of this study were to measure the fracture toughness (K_1C) and microtensile bond strength of dentin-resin composite interface and compare their relationship for their use in evaluation of the integrity of the dentin-resin bond.

A minimum of six short-rod specimens for fracture toughness test and fifteen specimens for microtensile bond strength test was fabricated for each group of materials used. After all specimens storing for 24 hours in distilled water at 37℃, they were tensile-loaded with an EZ tester universal testing machin. Statistical analysis was performed using ANOVA and Tukey's test at the 95% confidence level, Pearson's coefficient was used to verify the correlation between the mean of fracture toughness and microtensile bond strength. FE-SEM was employed on fractured surface to describe the crack propagation.

Fracture toughness value of Clearfil SE Bond (SE) was the highest, followed by Adper Single Bond 2 (SB), OptiBond Solo (OB), ONE-STEP PLUS (OS), ScotchBond Multi-purpose (SM) and there was significant difference between SE and other 4 groups (p < 0.05). There were, however, no significant difference among SB, OB, OS, SM (p > 0.05). Microtensile bond strength of SE was the highest, followed by SB, OB, SM, OS and OS only showed significant lower value (p < 0.05). There was no correlation between fracture toughness and microtensile bond strength values. FE-SEM examination revealed that dentin bonding agent showed different film thickness and different failure pattern according to the film thickness.

From the limited results of this study, it was noted that there was statistically no correlation between K1C and µTBS. We can conclude that for obtaining the reliability of bond strength test of dentin bonding agent, we must pay more attention to the test procedure and its profound scrutiny.

The purpose of this study was to investigate the effect of calcium hydroxide on dentin bonding strength of various dentin bonding systems as a function of time in composite resin restoration.

Dentin adhesives used in this study were Scotchbond Multipurpose, Single Bond, SE Bond and Prompt L-Pop. Flat dentin surfaces adjacent to pulp chamber were created, then Ca(OH)₂ and saline were mixed and applied on dentin surface of experimental group, then IRM was used to cover the mixture on dentin surface and the specimens were stored at 36.5℃ for experiment period (7 days, 30 days). After removing IRM and Ca(OH)₂, each dentin adhesives were treated on dentin surfaces.

Composite resin (Z-250, 3M) was placed with 5 mm height and was light-cured for 20 seconds. After stored in distilled water for 24 hours, each dentin-composite bonded spicemen was embedded in epoxy resin and sectioned into 1.0 × 1.0 mm² cross section composite-dentin beams. Specimen was mounted on zig of Universal testing machine and µTBS test was performed. SEM analysis was performed to examine the fractured surfaces.

The results suggested that applying calcium hydroxide did not show significant difference in dentin bonding strength.

This study was to verify that the combined application of NaOCl and EDTA was more effective in removal of smear layer than the application of NaOCl alone. Furthermore it was aimed to find out the optimal time for the application of EDTA.

Thirty five single rooted teeth were cleaned and shaped. NaOCl solution was used as an irrigant during instrumentation. After instrumentation, root canals of the control group were irrigated with 5 ml of NaOCl for 2 minutes. 30 sec, 1 min, and 2 min group were irrigated with 5 ml of 17% EDTA for 30 sec, 1 min, and 2 min respectively. Then the roots were examined with scanning electron microscopy for evaluating removal of smear layer and erosion of dentinal tubule.

The results were as follows;

The control group:

The smear layer was not removed at all.

The results suggest that 2 min application of 17% EDTA should be adequate to remove smear layer on both apical⅓ and middle⅓.

The purpose of this clinical study is to assess whether calcium hydroxide as an intracanal medication affects post-treatment pain in teeth especially odontogenic pain which comes from inflammation of the pulp and periradicular tissues when compared with no intracanal medication.

From 213 patients who has been treated 237 root canals due to significant pain (moderate-to-severe), we recorded their age, sex, treated tooth, degree of pain, pre-operative states of the tooth. We classified patients into 2 test group; Group 1 (not gain intracanal Ca(OH)₂), Group 2 (gain intracanal Ca(OH)₂). Through the survey from the patients, we let them write down the occurrence and degree of post-treatment pain in 4hours, 2days, 7days after treatment as none, mild, moderate or severe. The followings were evaluated; the overall incidence of flare-ups, the overall incidence of post-treatment pain in each group at each time period, the incidence of post-treatment pain in each group at each time period as related to pre-operative states of the teeth. These were compared statistically with Chi-square analysis (p < 0.05).

Under the condition of this investigation, no difference was observed in the incidence of post-treatment pain between the two groups. Therefore, Ca(OH)₂ as intracanal medication had no effect on preventing or decreasing the post-treatment pain.

The purpose of this study was to compare the sealing ability of root canal obturation with or without the treatment of smear layer. Eighty extracted human teeth with one canal were selected. Instrumentation was performed with crown-down technique. After instrumentation, root canals of the NaOCl group and NaOCl-6 group were irrigated with 3% NaOCl. EDTA group and EDTA-6 group were irrigated with 17% EDTA. Then all teeth were obturated using continuous wave obturation technique.

NaOCl group and EDTA group were immersed in methylene blue solution for 84hours. NaOCl-6 group and EDTA-6 group were immersed in methylene blue solution for 6months. The teeth were sectioned at 1.5 mm (Level 1), 3.0 mm (Level 2) and 4.5 mm (Level 3) from the root apex. The length of dye-penetrated interface and the circumferential length of canal at each level were measured using Sigma-Scan Pro 5.0.

The mean leakage ratio was decreased cervically.

The induction of the IL-8 and MCP-1 by the stimulation of Substance P and TNF-α (IL-8 agonist) and the specificity for SP using Spantide (SP antagonist) in the dental pulp tissues was measured quantitatively. In addition, the secretion of the IL-8 in the human dental pulp tissue 36 hrs after the stimulation of SP was observed after the stimulation of SP qualitatively.

According to this study, the results were as follows:

1. There was the significant IL-8 induction at 36 h after SP (10^-4M) stimulation of the pulp tissue comparing with the unstimulated dental pulp tissues (p < 0.05). IL-8 immunostaining was weakly detected along the periphery of the pulp tissue after Mock stimulation and IL-8 immunostaining was detected around the fibroblast in the pulp tissue 36h After SP (10^-4M) stimulation,

2. The secretion of MCP-1 from the dental pulp tissues comparing with Mock stimulation was induced at 36 hrs after TNF-α (40 ng/ml) stimulation, but no induction with SP(10^-4M). TNF-α (40 ng/ml) did not induce the IL-8 secretion from the pulp tissue, weak IL-8 immunostaining was detected along the periphery of the pulp tissue.

3. Spantide (10^-5M) inhibited IL-8 induction from the pulp tissues 36 h after SP (10^-4M) stimulation.

These results suggest that SP significantly induces IL-8 recruiting neutrophils in localized human dental pulp tissue. MCP-1 appears to be less involved in the early establishment of pulpal inflammation in response to irritation such as mechanical insult of dentin. SP may have positive relation with the inflammation of the human dental pulp tissues.

The purpose of this study was to assess the incidence of flare-ups among patients who received endodontic treatment and to examine the correlation with pre-operative and operative variables.

Analysis was in two aspects (a) overall incidence of flare-ups as expressed by a percentage of all patients visits and (b) percentage of flare-ups that occurred as related to various factors such as patient demographics, diagnosis, and treatment procedures.

1. From the 840 teeth which were examined in this study, the total number of flare-ups was 13.

2. As to gender of patients, there was no significant difference in flare-ups.

3. As to tooth groups, there was no significant difference in flare-ups.

4. In the teeth with pre-operative symptom, there was a statistically significant higher incidence of flare-ups than the teeth without it.

5. In the teeth with apical periodontitis, there was a statistically significant higher incidence of flare-ups.

6. As to pulp and periapical status, non-vital teeth had a higher incidence as compared with vital teeth, irreversible pulpitis.

7. Multi-visit treatment resulted in the higher incidence of flare-ups than one visit treatment.

8. Re-treatment procedures had a statistically significant higher incidence of flare-ups than root canal treatment.

In this study, overall percentages of flare-ups was 1.55%. It showed a statistically significant higher incidence related to pre-operative symptom, apical periodontitis, and re-treatment. There was no significant difference in flare-ups related to gender, tooth groups, and fistula.

The purpose of this study was to compare the sealing ability of root canal obturation with or without the use of dentin adhesive system. Forty extracted human teeth with one canal were selected and decoronated. The teeth were divided into two Groups. The obturation procedure of Group 1 was the same as that of Group 2 with the exception of dentin adhesive system. Group 2 were obturated with dentin adhesive system, AH-26, and gutta-percha.

After obturation, the teeth were immersed in methylene blue solution for 84 hours. The teeth were sectioned horizontally at 1.5 mm (Level 1), 2.0 mm (Level 2), 2.5 mm (Level 3) from the root apex using a low speed microtome. Distance of dye-penetrated surface and total dentinal surface were measured using SigmaScan Pro 5.0, and the ratio of dye-penetrated distance to the total dentinal distance was analyzed statistically by Mann-Whitney U-test.

In both groups, the mean leakage ratio was decreased cervically.

The purpose of this study is to evaluate the sealing effect of several root-end filling materials using spectrophotometric analysis. 180 single root teeth with one canal were instrumented and canal filled. Root resected and root end preparation was made. Teeth were randomly classified to 5 experimental group(MTA, EBA, IRM, TCP, ZOE) and 1 control group according to root-end filling material MTA group used PRO ROOT MTA, EBA group used Super EBA, TCP group used NEW APATITE LINER TYPE II main component of which is α-tricalcium phosphate(TCP). According to manufacture's instruction experimental material was mixed and retrfilled. After 2% methylene blue solution penetration absorbance for each test sample was measured with spectrophotometer (JASCO UV-530, Japan).

The mean absorbance of control and experimental group was as follows;

MTA : 0.092, IRM : 0.226, Super EBA : 0.255, ZOE : 0.374, Control : 0.425, TCP : 0.501 and the result analyzed by Turkey test at P=0.05 level.

Conclusions of this study are as follows;

The absorbance increase in follwing sequence MTA, IRM, Super EBA, ZOE, Control, TCP.

This study was performed to observe the antibacterial effect of polyphosphate (polyP) with various chain lengths (P3~P75) on virulent, invasive strains of P. gingivalis A7A1-28 and W50, and multidrug resistant E. faecalis ATCC29212. P. gingivalis strains were grown in brain-heart infusion broth (BHI) containing hemin and vitamin K with or without polyP. PolyP was added at the very beginning of the culture or during the exponential growth phase of the culture. Inhibition of the growth of P. gingivalis was determined by measuring the absorbancy at 540nm of the grown cells. Viable cell counts of the culture and release of intracellular nucleotide from P. gingivalis were measured. E. faecalis was grown in plain BHI with antibiotics alone or in combination with polyP(calgon; 0.1~1.0%) and the bacterial absorbancy was measured.

The overall results suggest that polyP has a strong antibacterial effect on the growth of the virulent strains of P. gingivalis and the antibacterial activity of polyP seems largely bactericidal, accompanying bacteriolysis in which chelation phenomenon is not involved. Although polyP does not exert antibacterial activity against E. faecalis, it appears to increase antibacterial effect of erythromycin and tetracycline on the bacterium. Therefore, polyP alone or in combination with antibiotics may be developed as a candidate for the agent controlling oral infections including endodontic infection.

It has been documented that periodontopathic bacteria are also implicated in endodontic infections. 16S rDNA gene-directed PCR was to examine the prevalence of periodontopathic bacteria including Actinobacillus actinomycetemcomitans (Aa), Prevotella intermedia (Pi), Prevotella nigrescens (Pn), Porphyromonas gingivalis (Pg), Porphyromonas endodontalis (Pe), and Treponema denticola (Td) in the root canals of 36 endodontically infected teeth having apical lesions with or without clinical symptoms like pain, swelling, and fistula.

In 36 infected root canals, most frequently detected bacterial species was Pg (61.1%), followed by Td (52.8%) and Pe (38.9%).

High prevalence of BPB in the symptomatic teeth but low in the asymptomatic teeth suggests that BPB may play an important role in the pathogenesis of periapical lesions.

This study is to investigate the canal system in the mesiobuccal root of the maxillry first molar.

61 maxillary first molars were randomly selected. Serial transverse sections were made perpendicular to the long axis of the mesiobuccal root. Each section was placed in 3% sodium hypochlorite for 24 hours and rinsed in water and dried. The resected surface was stained with 2% methylene blue dye and examined with stereomicroscope.

Canal configuration analysis showed that 36.1% of the specimen classified as type I, 16.4% as type II, 37.7% as type III and 9.8% as type IV.

63.9% of the mesiobuccal root of maxillary first molar had two canaland 76.5% of sections with two canals in 5 MM had an isthmus. Because of this complexity the clinician should always search for extra canal carefullyand root canal system, including an isthmus, should be cleaned and shaped completelyand obturated three dimensionally for successful endodontic treatment.

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 purpose of this study is to evaluate the effectiveness of customized master cone on apical sealing in various apical size of prepared root canals, that is MAF(Master Apical File) and to know at which apical size the apical leakage is to be significantly reduced using customized master cone.

120 extracted single rooted premolars were divided into four groups according to their apical size(MAF), #30, 40, 50 and 60. And then, each group was subdivided into three in accordance with three obturation methods, lateral condensation with standardized master cone, lateral condensation with chloroform-dipped customized master cone, and continuous wave of obturation technique.

Resorcinol-formaldehyde resin was used for the microleakage test of this study. Teeth were sectioned horizontally at 1.5mm(Level 1), 2.5mm(Level 2), and 3.5mm(Level 3) from the anatomical root apex using low speed microtome. All sections were examined under ×40 magnification with a stereomicroscope, photographed, and then scanned. With the scanned images, resin-infiltrated area presenting the microleakage was calculated using SigmaScan/Image, and the ratio of leakage to the total root canal area of each group was analyzed statistically(one way ANOVA).

The results were as follows;

1. In groups of MAF #30, there was no significant difference of mean leakage ratio among three obturation methods at all three levels.

2. In groups of MAF #40, the group using lateral condensation with customized master cone had the lowest mean leakage ratio at all three levels, but there was no significant difference among three obturation techniques.

3. In groups of MAF #50, the mean leakage ratio of the group using lateral condensation with standard master cone was the highest among those of three obturation techniques at level 1, and this difference was statistically significant(p<0.05).

4. In groups of MAF #60, the groups using lateral condensation with standard master cone had also the highest mean leakage ratio at all levels, but there was no significant difference at level 1 and 2. At level 3, the leakage of the group using lateral condensation with standard master cone was significantly higher than that of the group using continuous wave of obturation(p<0.05).

The results of this study suggested that the obturation method using customized master cone or the continuous wave of obturation is more effective for apical sealing than that using standardized master cone when MAF is larger than #50.