Epoxy resin-based sealers are currently widely used, and several studies have considered AH Plus to be the gold-standard sealer. However, it still has limitations, including possible mutagenicity, cytotoxicity, inflammatory response, and hydrophobicity. Drawing upon the advantages of mineral trioxide aggregate, calcium silicate-based sealers were introduced with high levels of biocompatibility and hydrophilicity. Because of the hydrophilic environment in root canals, water resorption and solubility of root canal sealers are important factors contributing to their stability. Sealers displaying lower microleakage and stronger push-out bond strength are also needed to endure the dynamic tooth environment. Although the physical properties of calcium silicate-based sealers meet International Organization for Standardization recommendations, and they have consistently reported to be biocompatible, they have not overcome conventional resin-based sealers in actual practice. Therefore, further studies aiming to improve the physical properties of calcium silicate-based sealers are needed.

Bond strength depends on characteristics of bonding surface and restorative technique. The majority of studies dealing with dentin bond strength were carried out on flat bonding surface, therefore, difference of bond strength between axial wall and pulpal wall is not clear yet. This study evaluated bonding difference between cavity walls in class I composite resin restoration with different filling techniques.

Twenty extracted caries-free human third molars were used. Cavities were prepared in 6 × 4 × 3 mm box-type and divided into four groups according to filling technique and bonding surface: Group I; bulk filling - pulpal wall, Group II; bulk filling - axial wall, Group III; incremental filling - pulpal wall, Group IV; incremental filling - axial wall.

Cavities were filled with Filtek Z250®(3M/ESPE., USA) and Clearfill SE bond®(Kuraray, Japan). After 24 hour-storage in 37℃ water, the resin bonded teeth were sectioned bucco-lingualy at the center of cavity.

Specimens were vertically sectioned into 1.0 × 1.0 mm thick serial sticks perpendicular to the bond surface using a low-speed diamond saw (Accutom 50, Struers, Copenhagen, Denmark) under water cooling. The trimmed specimens were then attached to the testing device and in turn, was placed in a universal testing machine (EZ test, Shimadzu Co., Kyoto, Japan) for micro-tensile testing at a cross-head speed of 1 mm/min. The results obtained were statistically analyzed using 2-way ANOVA and t-test at a significance level of 95%.

The results were as follows:

1. There was no significant difference between bulk filling and incremental filling.

2. There was no significant difference between pulpal wall and axial wall, either.

Within the limit of this study, it was concluded that microtensile bond strength was not affected by the filling technique and the site of cavity walls.

This study was done to determine if there is any difference in microleakage between experimental composite resins, in which various proportions of three component photoinitiators (Camphoroquinone, OPPI, Amine) were included.

Four kinds of experimental composite resin were made by mixing 3.2% silanated barium glass (78 wt.%, average size; 1 µm) with each monomer system including variously proportioned photoinitiator systems used for photoinitiating BisGMA/BisEMA/TEGDMA monomer blend (37.5:37.5:25 wt.%). The weight percentage of each component were as follows (in sequence Camphoroquinone, OPPI, Amine): Group A - 0.5%, 0%, 1% / Group B - 2%, 0.2%, 2% / Group C - 0.2%, 1%, 0.2% / Group D - 1%, 1%, 2%.

Each composite resin was used as a filling material for round class V cavities (diameter: 2/3 of mesiodistal width; depth: 1.5 mm) made on extracted human premolars and they were polymerized using curing light unit (XL 2500, 3M ESPE) for 40 s with an intensity of 600 mW/cm². Teeth were thermocycled five-hundred times between 50℃ and 550℃ for 30s at each temperature.

Electrical conductivity (µA) was recorded two times (just after thermocycling and after three-month storage in saline solution) by electrochemical method.

Microleakage scores of each group according to evaluation time were as follows [Group: at first record / at second record; unit (µA)]: A: 3.80 (0.69) / 13.22 (4.48), B: 3.42 (1.33) / 18.84 (5.53), C: 4.18 (2.55) / 28.08 (7.75), D: 4.12 (1.86) / 7.41 (3.41).

Just after thermocycling, there was no difference in microleakage between groups, however, group C showed the largest score after three-month storage. Although there seems to be no difference in microleakage between groups just after thermocycling, composite resin with highly concentrated initiation system or classical design (Camphoroquinone and Amine system) would be more desirable for minimizing microleakage after three-month storage.

It was reported that esthetic composite resin restoration reinforces the strength of remaining tooth structure with preserving the natural tooth structure. However, it is unknown how much the strength would be recovered. The purpose of this study was to compare the fracture resistance of three types of undermined cavity filled with composite resin with that of non-cavitated natural tooth.

Forty sound upper molars were allocated randomly into four groups of 10 teeth. After flattening occlusal enamel, undermined cavities were prepared in thirty teeth to make three types of specimens with various thickness of occlusal structure (Group 1 ~ 3). All the cavity have the 5 mm width mesiodistally and 7 mm depth bucco-lingually. Another natural 10 teeth (Group 4) were used as a control group. Teeth in group 1 have remaining occlusal structure about 1 mm thickness, which was composed of mainly enamel and small amount of dentin. In Group 2, remained thickness was about 1.5 mm, including 0.5 mm thickness dentin. In Group 3, thickness was about 2.0 mm, including 1 mm thickness dentin. Every effort was made to keep the remaining dentin thickness about 0.5 mm from the pulp space in cavitated groups. All the thickness was evaluated with radiographic Length Analyzer program.

After acid etching with 37% phosphoric acid, one-bottle adhesive (Single Bond™, 3M/ESPE, USA) was applied following the manufacturer's recommendation and cavities were incrementally filled with hybrid composite resin (Filtek Z-250™, 3M/ESPE, USA). Teeth were stored in distilled water for one day at room temperature, after then, they were finished and polished with Sof-Lex system.

All specimens were embedded in acrylic resin and static load was applied to the specimens with a 3 mm diameter stainless steel rod in an Universal testing machine and cross-head speed was 1 mm/min. Maximum load in case of fracture was recorded for each specimen.

The data were statistically analyzed using one-way analysis of variance (ANOVA) and a Tukey test at the 95% confidence level.

The results were as follows:

Fracture resistance of the undermined cavity filled with composite resin was about 75% of the natural tooth.

Within the limits of this study, it can be concluded the fracture resistance of the undermined cavity filled with composite resin was lower than that of natural teeth, however remaining tooth structure may be supported and saved by the reinforcement with adhesive restoration, even if that portion consists of mainly enamel and a little dentin structure.

Present tooth bonding system can be categorized into total etching bonding system (TE) and self-etching boding system (SE) based on their way of smear layer treatment. The purposes of this study were to compare the effectiveness between these two systems and to evaluate the effect of number of themocycling on microleakage of class V composite resin restorations.

Total forty class V cavities were prepared on the single-rooted bovine teeth and were randomly divided into four experimental groups: two kinds of bonding system and another two kinds of thermocycling groups. Half of the cavities were filled with Z250 follwing the use of TE system, Single Bond and another twenty cavities were filled with Metafil and AQ Bond, SE system. All composite restoratives were cured using light curing unit (XL2500, 3M ESPE, St. Paul, MN, USA) for 40 seconds with a light intensity of 600 mW/cm².

Teeth were stored in distilled water for one day at room temperature and were finished and polished with Sof-Lex system. Half of teeth were thermocycled 500 times and the other half were thermocycled 5,000 times between 5℃ and 55℃ for 30 second at each temperature.

Teeth were isolated with two layers of nail varnish except the restoration surface and 1 mm surrounding margins. Electrical conductivity (µA) was recorded in distilled water by electrochemical method. Microleakage scores were compared and analyzed using two-way ANOVA at 95% level.

From this study, following results were obtained: There was no interaction between variables of bonding system and number of thermocycling (p = 0.485). Microleakage was not affected by the number of thermocycling either (p = 0.814). However, Composite restoration of Metafil and AQ Bond, SE bond system showed less microleakage than composite restoration of Z250 and Single Bond, TE bond system (p = 0.005).

Competition will usually develop between the opposing walls as the restorative resin shrinks during polymerization. Magnitude of this phenomenon may be depended upon cavity configuration and volume.

The purpose of this sturdy was to evaluate the effect of cavity configuration and volume on microleakage of composite resin restoration that has margins on the enamel site only.

The labial enamel of forty bovine teeth was ground using a model trimmer to expose a flat enamel surface. Four groups with cylindrical cavities were defined, according to volume and configuration factor (Depth × Diameter / C-factor) - Group I: 1.5 mm × 2.0 mm / 4.0, Group II: 1.5 mm × 6.0 mm / 2.0, Group III: 2.0 mm × 1.72 mm / 5.62, Group IV: 2.0 mm × 5.23 mm / 2.54.

After treating with fifth-generation one-bottle adhesive - BC Plus™ (Vericom, AnYang, Korea), cavities were bulk filled with microhybrid composite resin - Denfill™ (Vericom). Teeth were stored in distilled water for one day at room temperature and were finished and polished with Sof-Lex system. Specimens were thermocycled 500 times between 5℃ and 55℃ for 30 second at each temperature.

Teeth were isolated with two layers of nail varnish except the restoration surface and 1 mm surrounding margins. Electrical conductivity (µA) was recorded in distilled water by electrochemical method. Microleakage scores were compared and analyzed using two-way ANOVA at 95% level.

The results were as follows:

1. Small cavity volume showed lower microleakage score than large one, however, there was no statistically significant difference.

2. There was no relationship between cavity configuration and microleakage.

Factors of cavity configuration and volume did not affect on microleakage of resin restorations with enamel margins only.

The purpose of this study was to estimate the relation between techniques used for microleakage from dye penetration and for marginal adaptation from SEM evaluation of the restoration.

Using high speed #330 bur, class V cavities (4 × 3 × 1.5 mm around CEJ) were prepared on the buccal surface of 20 extracted human molars. Six dimples as reference points for SEM and dye penetration evaluation were made with 1/2 round bur. Cavity was bulk filled with microhybrid composite resin (Esthet X) and all-in-one adhesive (Xeno III). Teeth were stored in saline solution for one day, after then, they were finished and polished using Sof-Lex system.

Fifty percent silver nitrate dye solution was used for the evaluation of microleakage and resin replica was used for marginal adaptation. All of these were done after 1000 times thermocycling between 5 and 55℃.

Vertical sections were made through three dimples of restoration to obtain samples for the evaluation of dye penetration and inner marginal adaptation. Outer adaptational estimation was done with an intact restoration before sectioning. Dye penetration was determined in three degrees and percentage of outer and inner leaky margin was estimated from SEM image.

The data were analysed statistically: Spearman's rho test were used to check relationships between two methods.

The result were as follows:

There were significant relationships between degree of dye penetration and inner and outer marginal adaptations each (p < 0.01).

Within the results of this study, relationship between the percentage of marginal adaptation and microleakage shows significant relationship. However, inner and outer marginal adaptation did not show any significant relationship mutually.

This study was done to evaluate whether there were any differences in microleakage of class V composite restorations according to restoration site and cavity size.

Total sixty-four restorations were made in molar teeth using Esthet-X. Small (2 × 2 × 1.5 mm) and large (4 × 2 × 1.5 mm) restorations were made at the buccal/lingual surface and the proximal surface each. After 1,000 times of thermocycling (5℃ - 55℃), resin replica was made and the percentage of marginal gap to the whole periphery of the restoration was estimated from SEM evaluation.

Thermocycled tooth was dye penetrated with 50% silver nitrate solution. After imbedding in an auto-curing resin, it was serially ground with a thickness of 0.25 mm. Volumetric microleakage was estimated after reconstructing three dimensionally.

Two-way ANOVA and independent T-test for dye volume, Mann-Whitney U test for the percentage of marginal gap, Spearman's rho test for the relationship between two techniques were used.

The results were as follows:

1. The site and size of the restoration affected on the microleakage of restoration. Namely, much more leakage was seen in the proximal and the large restorations rather than the buccal/lingual and the small restorations.

2. Close relationship was found between two techniques (Correlation coefficient = 0.614 / P = 0.000).

Within the limits of this study, it was noted that proximal and the large restorations leaked more than buccal/lingual and the small restorations. Therefore, it should be strictly recommended large exposure of margins should be avoided by reducing unnecessary tooth reduction.

Established microleakage tests have their own disadvantages. In this study, 3D reconstruction method was tried to overcome these disadvantages.

Four types of microleakage tests were used and relationships among them were estimated: penetrated dye volume; marginal adaptability; degree of dye penetration and relative penetrated length to cavity wall.

Twenty-four Class V cavities were bulk filled with composite (Esthet X) following surface treatments: N group (no treatment); E group (etching only); T group (etching + Prime & Bond NT). 50% silver nitrate was used as a dye solution after thermocycling (5℃ & 55℃, 1,000 times). Teeth were serially ground with a thickness of 0.2 mm. Volume of dye penetration was estimated from a three-dimensionally reconstructed image with a software (3D-DOCTOR). Percentage of margin without gap was estimated from SEM and degree of dye penetration and the relative length of dye penetration to overall cavity wall were also estimated.

ANOVA and Scheffe test for dye volume, Kruskal-Wallis and Mann-Whitney test for marginal quality, Spearman's rho test for checking of relationships among methods were used.

The results were as follows:

1. Dye penetration could be seen from several directions, furthermore, its volumetric estimation was possible.

2. Reverse relationship was found between dye volume and marginal quality (r = -0.881 / p = 0.004).

3. Very low relationship was seen between dye volume and two-dimensional tests (degree of dye penetration and relative length). However, 2D evaluation methods showed high relationship (p = 0.002-0.054) each other.

4. Three times vertical section could be recommended as a 2D test.

The purposes of this study were to estimate the material properties of the recently developed domestic composite resins for core filling material (Chemical, Dual A, Dual B; Vericom, Korea) and to compare them with other marketed foreign products (CorePaste, Den-Mat, USA; Ti-Core, Essential Dental Systems, USA; Support, SCI-Pharm, USA). Six assessments were made; working time, setting time, depth of polymerization, flexural strength, bonding strength, and marginal leakage. All items were compared to ISO standards.

All domestic products satisfied the minimum requirements from ISO standards (working time: above 90 seconds, setting time: within 5 minutes), and showed significantly higher flexural strength than Core Paste. Dual A and B could, especially, reduce the setting time to 60 seconds when cured with 600 mW/cm² light intensity. All experimental materials showed 6 mm depth of polymerization.

Bond strengths of Ti-Core and Dual B materials were significantly higher than the other materials. Furthermore, three domestic products and Ti-Core could reduce the microleakage effectively.

All-in-one adhesives were recently developed for reducing the techique sensitivity and chair time, but lots of concerns were made on bondability, longevity, and microleakage.

The object of this study was to evaluate microleakage and marginal quality of all-in-one adhesives using electrochemical method and SEM analysis quantitatively.

After making Class V cavities, they were bulk filled with Heliomolar(#A1) after surface treatment with three adhesives: Adper Prompt (Group A), One up bond F (Group O), Xeno III (Group X). Electrical conductivity (microamphere, µA) was checked two times: before and after cavity filling.

Percentage of leaky margin was estimated from SEM image (×1,000).

The data were statistically analysed: ANOVA and Paired T test for electrical conductivity, Kruskal-Wallis and Mann-Whitney test for marginal quality, Spearman's rho test for checking of relationships between 2 methods.

The result were as follows:

1. There was no difference in microleakage between adhesive systems and every specimen showed some of microleakage after filling.

2. Microleakage was reduced about 70% with composite resin filling.

3. Marginal quality was the best in group A, decreasing among groups in the following order: group O, followed by group X. There were significant differences between group A and group X (p=0.015), and between group O and group X (p=0.019).

4. There was no relationship between the microleakage measured by electrochemical method and marginal quality measured by SEM analysis.

Within the results of this study, there was no difference in microleakage among groups by electrical conductivity. However, significant difference in marginal quality was seen among groups. It was believed that these dissimilar results might be induced because of their own characteristics. Analysis of microleakage needs various methods for accuracy.

Complete understanding of the exterior and interior structure of the tooth would be prerequisite to the successful clinical results, especially in the restorative and endodontic treatment.

Although three-dimensional reconstruction method using x-ray microtomography could not be used in clinical cases, it may be the best way to reconstruct the morphologic characteristics of the tooth structure in detail without destructing the tooth itself. This study was done to three dimensionally reconstruct every teeth in the arch in order to increase the understanding about the endodontic treatment and to promote the effective restorative treatment by upgrading the knowledge of the tooth morphology.

After placing tooth between the microfocus x-ray tube and the image intensifier to obtain two-dimensional images of each level, scanning was done under the condition of 80 keV, 100 µA, 16.8 magnification with the spot size of 8 µm. Cross-section pixel size of 16.28 µm and 48.83 cross-section to cross-section distance were also used.

From the results of this study, precise three dimensional reconstructed images of every teeth could be obtained. Furthermore, it was possible to see image that showed interested area only, for example, enamel portion only, pulp and dentin area without enamel structure, pulp only, combination image of enamel and pulp, etc.

It was also possible to see transparent image without some part of tooth structure. This image might be used as a guide when restoring and preparing the full and partial crown by showing the positional and morphological relationship between the pulp and the outer tooth structure.

Another profit may be related with the fact that it would promote the understanding of the interior structure by making observation of the auto-rotating image of .AVI file from the various direction possible.

The aim of this study was to evaluate the effect of two polishing methods and chemical conditioning on the surface of hybrid composites.

Ninety cylindrical specimens (diameter: 8 mm, depth: 2 mm) were made with three hybrid composites - Filtek Z250, Tetric Ceram, DenFil. Specimens for each composite were randomly divided into three treatment subgroups - ① Mylar strip (no treatment), ② Sof-Lex XT system, ③ PoGo system. Average surface roughness(Ra) was taken using a surface profilometer at the time of setting and after immersion into 0.02N lactic acid for 1 week and 1 month. Representative specimens were examined by scanning electron microscopy. The data were analyzed using ANOVA and Scheffe's tests at 0.05% significance level.

The results were as follows:

Mylar strip resulted in smoother surface than PoGo and Sof-Lex system(p<0.001). Sof-Lex system gave the worst results.

The PoGo system gave a superior polish than Sof-Lex system for the three composites. However, the correlation to clinical practice may be limited, since there are several processes, such as abrasive, fatigue, and corrosive mechanisms. Thus, further studies are needed for polishing technique under in vivo conditions.

Mechanical properties and microleakage of two composites [conventional hybrid type DenFil (VERICOM Co., Anyang, Korea) / micro matrix hybrid type Esthet X (Dentsply Caulk, Milford, DE, U.S.A.)] were evaluated to assess whether variable light intensity curing is better than conventional curing technique.

Curing was done for 40 seconds in two ways of 2 step soft-start technique and 5 step ramping technique. Three kinds of light intensities of 50, 100, 200 mW/cm² were initially used for 10, 20, 30 seconds each and the maximum intensity of 600 mW/cm² was used for the rest of curing time in a soft-start curing technique. In a ramping technique, curing was done with the same initial intensities and the light intensity was increased 5 times with the same rate to the maximum intensity of 600 mW/cm².

After determining conditions that showed no different mechanical properties with conventional technique, Esthet X composite was filled in a class V cavity, which dimension was 4×3×1.5 mm and cured under those conditions.

Microleakage was evaluated in two ways of dye penetration and maximum gap estimation through SEM observation. ANOVA and Spearman's rho test were used to confirm any statistical significance among groups.

The results were as follows:

Several curing conditions of variable light intensities resulted in the similar mechanical properties with a conventional continuous curing technique, except conditions that start curing with an initial light intensity of 50 mW/cm²,

From the results of this study, it was revealed that ramping technique would be better than conventional technique in mechanical properties, however, soft-start technique might be better than conventional one in microleakage.

It was concluded that much endeavor should be made to find out the curing conditions, which have advantages of both aspects or to solve these kinds of problems through a novel idea of polymerization.

The object of this study was to compare the microleakage between various composite resin systems of multistep, one-bottle, and self-etching systems using electrical conductivity.

After making class V cavities (4×3×1.5 mm around CEJ), they were bulk filled with three kinds of resins of A3. Teeth were storaged in a saline solution for one day, after then, they were finished and polished using Sof-Lex system. Another stress of thermocycling was made for 500 times from 5° to 55℃ with each dwelling time of 10 seconds. Electrical conductivity (microamphere, µA) was checked four times: before and after cavity preparation, after filling, after thermocycling.

One-way ANOVA and 95% Scheffe Post Hoc test was used for checking any statistical difference among groups. Another 95% Paired Samples T-test was also used for estimating any significant difference within group after cavity filling or thermocycling.

The results were as follows:

Every specimen showed various range of microleakage after filling.

There was, however, no difference between composite resin systems.

Within the limits of this study, it was concluded that much more consideration should be needed when using thermally unstable one-bottle and self-etching systems that have multi-advantages from simplified step. More studies will be needed to solve these kinds of problems.

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.

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.