Conventional intraoral radiography continues to be the most widely used image modality for the diagnosis of dental caries. But, conventional intraoral radiography has several shortcomings, including the difficulty of exposing and processing intraoral film of consistently acceptable quality. In addition, radiographic retaking that was the result of processing errors, may result in increased discomfort and radiation dose to the patient.

Recently, various digital radiographies substitute for conventional intraoral radiography to overcome these disadvantages. The advantages of digital radiography are numerous. One of advantages is the elimination of processing errors. In addition, the radiation dose for digital system is approximately 20% to 25% of that required for conventional intraoral radiography. Another potential advantage of digital imaging is the ability to perform image quality enhancements such as contrast and density modulation, which may increase diagnostic accuracy.

The purpose of this study was to compare the diagnostic ability of artificial proximal defects to conventional intraoral radiography, direct digital image(CDX2000HQ®) and indirect digital image(Digora®).

Artificial defects were made in proximal surfaces of 60 extracted human molars using #1/2, #1, #2 round bur. Five dentists assessed proximal defects on conventional intraoral radiography, direct digital image(CDX2000HQ®) and indirect digital image(Digora®). ROC(Receiver Operating Characteristic) analysis and Two-way ANOVA test were used for the evaluation of detectability, and following results were acquired.

1. The mean ROC area of conventional intraoral radiography, direct digital image(CDX2000HQ®)and indirect digital image(Digora®) were 0.6766, 0.7538, 0.6791(Grade I), 0.7176, 0.7594, 0.7361(Grade II), and 0.7449, 0.7608, 0.7414(Grade III), respectively.

2. Diagnostic ability of direct digital image was higher than other image modalities. But, there was no statistically significant difference among other imaging modalities for Grade I, II, III lesion(p>0.05).

In conclusion, when direct and indirect digital system are comparable with conventional intraoral radiography, these systems may be considered an alternative of conventional intraoral radiography for the diagnosis of proximal surface caries.

Low-viscosity composite resins may produce better sealed margins than stiffer compositions (Kemp-Scholte and Davidson, 1988; Crim, 1989). Flowable composites have been recommended for use in Class V cavities but it is also controversial because of its high rates of shrinkage. On the other hand, in the study comparing elastic moduli and leakage, the microfill had the least leakage (Rundle et al. 1997). Furthermore, in the 1996 survey of the Reality Editorial Team, microfills were the clear choice for abfraction lesions.

The purpose of this study was to evaluate the microleakage of 6 compostite resins (2 hybrids, 2 microfills, and 2 flowable composites) with and without load cycling.

Notch-shaped Class V cavities were prepared on buccal surface of 180 extracted human upper premolars on cementum margin. The teeth were randomly divided into non-load cycling group (group 1) and load cycling group (group 2) of 90 teeth each. The experimental teeth of each group were randomly divided into 6 subgroups of 15 samples. All preparations were etched, and Single bond was applied. Preparations were restored with the following materials (n=15): hybrid composite resin [Z250(3M Dental Products Inc. St.Paul, USA), Denfil(Vericom, Ahnyang, Korea)], microfill [Heliomolar RO(Vivadent, Schaan, Liechtenstein), Micronew(Bisco Inc. Schaumburg, IL, USA)], and flowable composite [AeliteFlo(Bisco Inc. Schaumburg, IL, USA), Revolution(Kerr Corp. Orange, CA, USA)]. Teeth of group 2 were subjected to occlusal load (100N for 50,000 cycles) using chewing simulator(MTS 858 Mini Bionix II system, MTS Systems Corp., Minn. USA). All samples were coated with nail polish 1mm short of the restoration, placed in 2% methylene blue for 24 hours, and sectioned with a diamond wheel. Enamel and dentin/cementum margins were analyzed for microleakage on a sclale of 0 (no leakage) to 3 (3/3 of wall). Results were statistically analyzed by Kruscal-Wallis One way analysis, Mann-Whitney U-test, and Student-Newmann-Keuls method. (p=0.05)

One of the latest concepts in bonding are "total etch", in which both enamel and dentin are etched with an acid to remove the smear layers, and "wet dentin" in which the dentin is not dry but left moist before application of the bonding primer. Ideally, the application of a bonding agent to tooth structure should be insensitive to minor contamination from oral fluids. Clinically, contaminations such as saliva, gingival fluid, blood and handpiece lubricant are often encountered by dentists during cavity preparation.

The aim of this study was to evaluate the effect of contamination by hemostatic agents on shear bond strength of compomer restorations. One hundred and ten extracted human maxillary and mandibular molar teeth were collected. The teeth were removed soft tissue remnant and debris and stored in physiologic solution until they were used. Small flat area on dentin of the buccal surface were wet ground serially with 400, 800 and 1200 abrasive papers on automatic polishing machine. The teeth were randomly divided into 11 groups. Each group was conditioned as follows:

Group 1: Dentin surface was not etched and not contaminated by hemostatic agents.

Group 2: Dentin surface was not etched but was contaminated by Astringedent®(Ultradent product Inc., Utah, U.S.A.).

Group 3: Dentin surface was not etched but was contaminated by Bosmin®(Jeil Pharm, Korea.).

Group 4: Dentin surface was not etched but was contaminated by Epri-dent®(Epr Industries, NJ, U.S.A.).

Group 5: Dentin surface was etched and not contaminated by hemostatic agents.

Group 6: Dentin surface was etched and contaminated by Astringedent®.

Group 7: Dentin surface was etched and contaminated by Bosmin®.

Group 8: Dentin surface was etched and contaminated by Epri-dent®.

Group 9: Dentin surface was contaminated by Astringedent®. The contaminated surface was rinsed by water and dried by compressed air.

Group 10: Dentin surface was contaminated by Bosmin®. The contaminated surface was rinsed by water and dried by compressed air.

Group 11: Dentin surface was contaminated by Epri-dent®. The contaminated surface was rinsed by water and dried by compressed air.

After surface conditioning, F2000® was applicated on the conditoned dentin surface. The teeth were thermocycled in distilled water at 5℃ and 55℃ for 1,000 cycles. The samples were placed on the binder with the bonded compomer-dentin interface parallel to the knife-edge shearing rod of the Universal Testing Machine(Zwick Z020, Zwick Co., Germany) running at a cross head speed of 1.0 mm/min.

Group 2 showed significant decrease in shear bond strength compared with group 1 and group 6 showed significant decrease in shear bond strength compared with group 5.

There were no significant differences in shear bond strength between group 5 and group 9, 10 and 11.

The aim of this study was to investigate the effect of light irradiation modes on polymerization shrinkage, degree of cure and microleakage of a composite resin.

VIP™ (Bisco Dental Products, Schaumburg, IL, USA) and Optilux 501™ (Demetron/Kerr, Danbury, CT, USA) were used for curing Filtek™ Z-250 (3M Dental Products, St. Paul., MN, USA) composite resin using following irradiation modes: VIP™ (Bisco) 200mW/cm² (V2), 400mW/cm² (V4), 600mW/cm² (V6), Pulse-delay (200 mW/cm² 3 seconds, 5 minutes wait, 600mW/cm² 30seconds, VPD) and Optilux 501™ (Demetron/Kerr) C-mode (OC), R-mode (OR).

Linear polymerization shrinkage of the composite specimens were measured using Linometer (R&B, Daejeon, Korea) for 90 seconds for V2, V4, V6, OC, OR groups and for up to 363 seconds for VPD group (n=10, each).

Degree of conversion was measured using FTIR spectrometer (IFS 120 HR, Bruker Karlsruhe, Germany) at the bottom surface of 2 mm thick composite specimens. V2, V4, V6, OC groups were measured separately at five irradiation times (5, 10, 20, 40, 60 seconds) and OR, VPD groups were measured in the above mentioned irradiation modes (n=5, each).

Microhardness was measured using Digital microhardness tester (FM7, Future-Tech Co., Tokyo, Japan) at the top and bottom surfaces of 2mm thick composite specimens after exposure to the same irradiation modes as the test of degree of conversion(n=3, each).

For the microleakage test, class V cavities were prepared on the distal surface of the ninety extracted human third molars. The cavities were restored with one of the following irradiation modes: V2/60 seconds, V4/40 seconds, V6/30 seconds, VPD, OC and OR. Microleakage was assessed by dye penetration along enamel and dentin margins of cavities.

Mean polymerization shrinkage, mean degree of conversion and mean microhardness values for all groups at each time were analyzed using one-way ANOVA and Duncan's multiple range test, and using chi-square test for microleakage values.

The results were as follows:

·Polymerization shrinkage was increased with higher light intensity in groups using VIP™ (Bisco): the highest with 600mW/cm², followed by Pulse-delay, 400mW/cm² and 200mW/cm² groups. The degree of polymerization shrinkage was higher with Continuous mode than with Ramp mode in groups using Optilux 501™ (Demetron/Kerr).

·Degree of conversion and microhardness values were higher with higher light intensity. The final degree of conversion was in the range of 44.7 to 54.98% and the final microhardness value in the range of 34.10 to 56.30.

·Microleakage was greater in dentin margin than in enamel margin. Higher light intensity showed more microleakage in dentin margin in groups using VIP™ (Bisco). The micoleakage was the lowest with Continuous mode in enamel margin and with Ramp mode in dentin margin when Optilux 501™(Demetron/Kerr) was used.

Dental caries is a chronic disease that causes the destruction of tooth structure by the interaction of plaque bacteria, food debris, and saliva.

There has been attempts to induce remineralization by supersaturating the intra-oral environment around the surface enamel, where there is incipient caries.

In this study, supersaturated remineralized solution "R" was applied to specimens with incipient enamel caries, and the quantitative ananlysis of remineralization was evaluated using microradiography. Thirty subjects volunteered to participate in this study. Removable appliances were constructed for the subjects, and the enamel specimen with incipient caries were embedded in the appliances. The subjects wore the intra-oral appliance for 15 days except while eating and sleeping.

The removable appliance were soaked in supersaturated solution "R", saline, or Senstime® to expose the specimen to those solutions three times a day, 5 minutes each time. After 15 days, microradiography was retaken to compare and evaluate remineralization.

The results were as the following:

1. The ratio of remineralized area to demineralized area was significantly higher in the supersaturated solution "R" and Senstime® than in the saline. (p<0.05)

2. Remineralization in the supersaturated buffer solution "R" occurred in the significantly deeper parts of the tooth, compared to the Senstime® group containing high concentration of fluoride.(p<0.05)

As in the above results, the remineralization effect of remineralized buffer solution "R" on incipient enamel caries has been proven. For clinical utilization, further studies on soft tissue reaction and the effect on dentin and cementum are necessary.

In conclusion compared to commercially available fluoride solution, remineralization solution "R" showed better remineralization effect on early enamel caries lesion, so it is considered as effecient solution for clinical application.