The purpose of this study was to evaluate the effect of a new resin monomer, filler size and polishing technique on the surface roughness of composite resin restorations using confocal laser scanning microscopy. By adding new methoxylated Bis-GMA (Bis-M-GMA, 2,2-bis[4-(2-methoxy-3-methacryloyloxy propoxy) phenyl] propane) having low viscosity, the content of TEGDMA might be decreased. Three experimental composite resins were made: EX1 (Bis-M-GMA/TEGDMA = 95/5 wt%, 40 mm nanofillers); EX2 (Bis-M-GMA/TEGDMA = 95/5 wt%, 20 mm nanofillers); EX3 (Bis-GMA/TEGDMA = 70/30 wt%, 40 mm nanofillers). Filtek Z250 was used as a reference.

Nine specimens (6 mm in diameter and 2 mm in thickness) for each experimental composite resin and Filtek Z250 were fabricated in a teflon mold and assigned to three groups. In Mylar strip group, specimens were left undisturbed. In Sof-lex group, specimens were ground with #1000 SiC paper and polished with Sof-lex discs. In DiaPolisher group, specimens were ground with #1000 SiC paper and polished with DiaPolisher polishing points. The Ra (Average roughness), Rq (Root mean square roughness), Rv (Valley roughness), Rp (Peak roughness), Rc (2D roughness) and Sc (3D roughness) values were determined using confocal laser scanning microscopy. The data were statistically analyzed by Two-way ANOVA and Tukey multiple comparisons test (p = 0.05).

The type of composite resin and polishing technique significantly affected the surface roughness of the composite resin restorations (p < 0.001). EX3 showed the smoothest surface compared to the other composite resins (p < 0.05). Mylar strip resulted in smoother surface than other polishing techniques (p < 0.05).

Bis-M-GMA, a new resin monomer having low viscosity, might reduce the amount of diluent, but showed adverse effect on the surface roughness of composite resin restorations.

The purpose of this study was: (1) to compare nanoleakage patterns of a conventional 3-step etch and rinse adhesive system and two experimental hydrophobic adhesive systems and (2) to investigate the change of the nanoleakage patterns after load cycling. Two kinds of hydrophobic experimental adhesives, ethanol containing adhesive (EA) and methanol containing adhesive (MA), were prepared. Thirty extracted human molars were embedded in resin blocks and occlusal thirds of the crowns were removed. The polished dentin surfaces were etched with a 35% phosphoric acid etching gel and rinsed with water. Scotchbond Multi-Purpose (MP), EA and MA were used for bonding procedure. Z-250 composite resin was built-up on the adhesive-treated surfaces. Five teeth of each dentin adhesive group were subjected to mechanical load cycling. The teeth were sectioned into 2 mm thick slabs and then stained with 50% ammoniacal silver nitrate. Ten specimens for each group were examined under scanning electron microscope in backscattering electron mode. All photographs were analyzed using image analysis software. Three regions of each specimen were used for evaluation of the silver uptake within the hybrid layer. The area of silver deposition was calculated and expressed in gray value. Data were statistically analyzed by two-way ANOVA and post-hoc testing of multiple comparisons was done with the Scheffe's test. Silver particles were observed in all the groups. However, silver particles were more sparsely distributed in the EA group and the MA group than in the MP group (p < .0001). There were no changes in nanoleakage patterns after load cycling.

The purpose of this study was to evaluate the consistency of two electronic apex locators in vitro model.

Materials consisted of fifty two extracted premolars and two electronic apex locators; Root ZX (J. Morita, Osaka, Japan) and E-Magic Finder Deluxe (S-Denti, Cheonan, Korea). After access preparation, the teeth were embedded in a saline-mixed alginate model. Canal lengths of each tooth were measured at "0.5" and "Apex" mark of the apex locators, respectively so that each tooth had two measurements from 0.5 and Apex points. The file was fixed at final measurement using a glass ionomer cement. The apical 4 mm from the apex was exposed to measure the distance from the file tip to the major apical foramen of each tooth. Average distances and standard deviations were used to evaluate the consistency.

Results showed that all measurements of both Root ZX and E-Magic Finder located the major foramen the range of ± 0.5 mm level. Both apex locators showed better consistency at Apex mark than at 0.5 mark. The average distance of file tip-major foramen was - 0.18 mm at 0.5 mark and - 0.07 mm at Apex mark in Root ZX, - 0.25 mm at 0.5 mark and - 0.02 mm at Apex mark in E-Magic Finder. Standard deviation was 0.21 at 0.5 mark and 0.12 at Apex mark in Root ZX, 0.12 at 0.5 mark and 0.09 at Apex mark in E-Magic Finder.

This study was to investigate the influence of composite resins with different elastic modulus, cavity modification and occlusal loading condition on the stress distribution of restored notch-shaped noncarious cervical lesion using 3-dimensional (3D) finite element (FE) analysis.

The extracted maxillary second premolar was scanned serially with Micro-CT. The 3D images were processed by 3D-DOCTOR. ANSYS was used to mesh and analyze 3D FE model. A notch-shaped cavity and a modified cavity with a rounded apex were modeled. Unmodified and modified cavities were filled with hybrid or flowable resin. After restoration, a static load of 500N was applied in a point-load condition at buccal cusp and palatal cusp. The stress data were analyzed using analysis of principal stress.

The results were as follows:

In the unrestored cavity, the stresses were highly concentrated at mesial CEJ and lesion apex and the peak stress was observed at the mesial point angle under both loading conditions.

The treatment of esthetic areas with single-tooth implants represents a new challenge for the clinician. In 1993, a modification of the forced eruption technique, called "orthodontic extrusive remodelling," was proposed as a way to augment both soft- and hard-tissue profiles at potential implant sites. This case report describes augmentation of the coronal soft and hard tissues around a fractured maxillary lateral incisor associated with alveolar bone loss, which was achieved by forced orthodontic extrusion before implant placement. Through these procedures we could reconstruct esthetics and function in a hopeless tooth diagnosed with subgingival root fracture by trauma.

The purpose of this study was to determine the effects on the elastic moduli of the adhesive and the hybrid layer from thermocycling. Twenty one human molars were used to create flat dentin surfaces. Each specimen was bonded with a light-cured composite using one of three commercial adhesives (OptiBond FL [OP], Clearfil SE Bond [CL], and Xeno III [XE]). These were sectioned into two halves and subsequently cut to yield 2-mm thickness specimens; one specimen for immediate bonding test without thermocycling and the other subjected to 10,000 times of thermocycling. Nanoindentation test was performed to measure the modulus of elasticity of the adhesive and the hybrid layer, respectively, using an atomic force microscope. After thermocycling, XE showed a significant decrease of the modulus in the adhesive layer (p < 0.05). Adhesives containing hydrophilic monomers are prone to hydrolytic degradation. It may result in the reduced modulus of elasticity, which leads to the mechanically weakened bonding interface.

The purpose of this study was to determine the effect of sodium hypochlorite and steam autoclaving on the cyclic fatigue of nickel-titanium endodontic files.

Two types of files with a .06 taper and #30 were used, K3^® (SybronEndo, Glendora, California, USA) and Hero642^®(Micro-Mega, Besançon, France).

The files were divided into 6 experimental groups containing 10 files each group depending the soaking time in 6% sodium hypochlorite solution and number of cycles of steam autoclave. After sterilization, a cyclic fatigue test was performed on each file, and the fracture time was recorded in seconds. The control group underwent the cyclic fatigue test only. After the test, the surface characteristics of the files were observed using scanning electron microscopy (SEM).

All groups containing the Hero 642^® files showed a similar cyclic fatigue fracture time. However, the cyclic fatigue fracture time with the K3^® files was significantly shorter in groups which were treated with sodium hypochlorite than in the control group (P < 0.05). SEM revealed both Hero642^® and K3^® files to have significant corrosion on the file surface in groups treated with sodium hypochlorite, compared with the sharp and regular blades of the control group. K3^® files showed more corrosion than the Hero642^® files. Bluntness of the blades of the K3^® file was observed in groups treated with steam autoclave. Although there was no obvious destruction on the surface of steam autoclaved Hero642^® files, slight bluntness was observed.

Sterilizing with a steam autoclave is much less destructive to K3^® files than sodium hypochlorite. The longer time exposed to sodium hypochlorite, the more destructive pattern was shown on the blades of the files. Therefore, when using sodium hypochlorite solution, the exposure time should be as short as possible in order to prevent corrosion and increase the cyclic fatigue fracture time.

This study examined the influence of the apical sizes on the sealing ability of a root canal filling.

Thirty-six single rooted teeth with a single canal were divided into 3 groups (n = 12) and instrumented with either the Profile® or LightSpeed® system to achieve three different apical sizes (master apical file [MAF] of #25, #40, or #60). The teeth were filled with gutta percha using a modified continuous wave technique. The level of microleakage was determined by immersing ten teeth from each group into India ink for 1 week followed by clearing with nitric acid, ethyl-alcohol, and methylsalicylate. The microleakage was measured using vernier calipers. The data was analyzed statistically using Kruskal-Wallis one-way ANOVA and a Student-Newman-Keuls Method. Two teeth from each group were sectioned horizontally at 1, 2, 3 and 4 mm from the apex in order to observe a cross section.

The apical size was significantly (p < .05) influenced the level of microleakage. In the Student-Newman-Deuls Method, MAF sizes of #25 and #40; and MAF sizes of #25 and #60, respectively showed a statistically significant difference. There was no significant difference between #40 and #60. In most cross sections, oval-shaped canals were observed, and the irregularity of the internal surface increased with decreasing apical size. There was also an increase in the area of recess, which is the area where the canal space is not filled with either gutta-percha or sealer.

When the root canals are filled using a modified continuous wave technique, canal filling with more consistent and predictable outcome may be expected as the apical preparation size is increased.