The purpose of this study was to compare and evaluate the shaping ability of the three different Ni-Ti file systems used by undergraduate students. Fifty undergraduate students prepared 150 simulated curved root canals in resin blocks with three Ni-Ti file systems - ProFile(R) (PF), Manual ProTaper(R) (MPT), Rotary ProTape(R) (RPT). Every student prepared 3 simulated root canals with each system respectively. After root canal preparation, the Ni-Ti files were evaluated for distortion or breakage. Assessments were made according to the presence of various types of canal aberrations. The pre- and post-instrumented canal images were attained and superimposed. The instrumented root canal width were measured and calculated for the net transportation (deviation) and the centering ratio. Under the condition of this study, both ProTaper(R) systems allowed significantly more removal of root canal wall than the ProFile(R) system. In the important other aspects such as the centering ratio, there was no significant differences between the systems. Novice dental students were able to prepare curved root canals with any kinds of Ni-Ti file systems with little aberration and great conservation of tooth structure. Students want to learn effective methods and at the same time simple rotary procedures. The rotary ProTaper(R) systems were one of the most compatible to these students from the point of view of cutting ability. The ProFile(R) system was also compatible in safe and gentle shaping.
Dental Pulp Cavity ; Humans ; Root Canal Preparation ; Students, Dental ; Tooth ; Transportation

The purpose of this study was to evaluate the effect of multiple application of all-in-one dentin adhesive system on microtensile bond strength using confocal laser scanning microscope and microtensile bond strength test. Flat occlusal dentin surfaces were prepared using low-speed diamond saw. In group I, Scotchbond Multipurpose (SM) was applied by manufacturer's recommendation. In group II, after Adper Prompt L-Pop was applied for 15s and light cured for 10s, the second coat was re-applied and light-cured. In group III, after light-curing the second layer, the third coat was re-applied and light-cured. Specimens bonded with a resin-composite were sectioned into resin-dentin stick for measuring the adhesive layer thickness by confocal laser scanning microscope and evaluating micro-tensile bond strength. The adhesive layers of three-step dentin adhesive system, 3 coats of Adper Prompt L-Pop had significantly thicker than SM, 2 coats of Adper Prompt L-Pop (p < 0.05). However, there was no significant differences in bond strengths between SM and 3 coats of Adper Prompt L-Pop (p > 0.05). And SM, 3 coats of Adper Prompt L-Pop had significantly higher than 2 coats of Adper Prompt L-Pop in bond strengths (p < 0.05).
Adhesives* ; Dentin* ; Diamond

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: 1. 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. 2. After restoration of the cavity, stresses were significantly reduced at the lesion apex, however cervical cavosurface margin, stresses were more increased than before restoration under both loading conditions. 3. When restoring the notch-shaped lesion, material with high elastic modulus worked well at the lesion apex and material with low elastic modulus worked well at the cervical cavosurface margin. 4. Cavity modification the rounding apex did not reduce compressive stress, but tensile stress was reduced.
Bicuspid ; Chimera ; Composite Resins ; Elastic Modulus ; Finite Element Analysis ; Tooth Cervix

The objectives of this study was to evaluate current visible light curing units regarding microhardness and microleakage. Fourty samples of composite resin(Z-250, 3M) were cured by different light curing units(Flipo, LOKKI; Credi II, 3M; XL 3000, 3M; Optilux 500,Demetron) in acrylic blocks. Microhardness was measured using a calibrated Vickers indenter on both top and bottom surfaces after 24 hours of storage in air at room temperature. Class V cavities were prepared on buccal and lingual surfaces of fourty extracted human molars. Each margin was on enamel and dentin/cementum. Composite resin(Z-250, 3M) was filled in cavities and cured by four different light curing units(Flipo, LOKKI; Credi II, 3M; XL 3000, 3M; Optilux 500, Demetron). The results of this syudy were as follows: Microhardness 1. Flipo showed low microhardness compared to Optilux 500, Credi II significantly in upper surface. Flipo didn't show a significant difference compared to XL 3000. 2. The microhardness resulting from curing with Flipo was lower than that of others on lower surfaces. Microleakage 1. Dentin margin showed significantly high dye penetration rate than enamel margin in all groups(p<0.05). 2. No significant differences were found on both enamel and dentin margin regarding curing units.
Dental Enamel ; Dentin ; Humans ; Light ; Molar

This study compared the shaping ability of nickel-titanium rotary files with different rake angle and radial land. The nickel-titanium files used in this study were Profile(Dentsply, Maillefer, Ballaigues, Switzerland), Hero 642(Micromega, Besancon, France), and K3(SybronEndo, Glendora, Ca, USA) file. Resin blocks substituted for root canals. 36 resin blocks were divided into 3 groups with 12 canals each. The time for canal preparation was recorded. The images of pre- and postoperative resin canal were scanned and those were superimposed. Amounts of canal deviation, total canal widths, inner canal widths, and outer canal widths were measured at apical 1, 2, 3, 4, 5, 6, and 7mm levels. The amount of canal deviation was the smallest in Profile group, and the time for canal preparation was the shortest in Hero 642 group. K3 group resulted in competent characteristics in both measurements. Positive rake angle seemed to result in fast shaping of root canal and radial land guide the instrument in center of the canals and around curvatures. Radial land also tended to reduce the sense of screwing into the root canal. The proper selection of the nickel-titanium file based on the knowledge about file design is needed for the safer, simpler and faster root canal therapy.
Dental Pulp Cavity ; Root Canal Therapy

This study was to investigate the influence of combining composite resins with different elastic modulus, and occlusal loading condition on the stress distribution of restored notch-shaped non-carious cervical lesion using 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 was modeled and filled with hybrid, flowable resin or a combination of both. 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. Results showed that combining method such that apex was restored by material with high elastic modulus and the occlusal and cervical cavosurface margin by small amount of material with low elastic modulus was the most profitable method in the view of tensile stress that was considered as the dominant factor jeopardizing the restoration durability and promoting the lesion progression.
Bicuspid ; Chimera ; Composite Resins ; Elastic Modulus ; Finite Element Analysis

The purpose of this study was to evaluate the rewetting effect of water-based primer on the air-dried dentin. In this in vitro study, freshly extracted non-caries human molars and three-step adhesive system(SBMP) were used. Freshly extracted non-caries human molars and three-step adhesive system(SBMP) were used. Flat occlusal dentin surface were prepared using low-speed diamond saw. Prepared teeth were randomly divided into three groups. Group 1.(W); etched(35% phosphoric acid for 15s) and blot-dried, Group 2.(5D); 5s air-dried, Group 3.(30D); 30s air-dried. To obtain color contrast in CLSM observation, primer was mixed with rhodamine B and bonding resin was mixed with fluorescein. Microscopic sample of each group were obtained after longitudinal section. Morphological investigation of resin-dentin interface and thickness of hybrid layer measurement using CLSM were done. Microtensile bond strength for each specimen was measured. Specimen were observed under microscope to examine the failure patterns of interface between resin and dentin. The results of this study were as follows: 1. The results(mean) of Thickness of hybrid layer were W;19.67, 5D;20.9, 30D;10microm. Only 30D had statistically significant differences to W and 5D(P<0.05). 2. The results(mean) of Microtensile bond strength were W;16.02, 5D;14.69, 30D;11.14MPa. Only 30D had statistically significant differences to W and 5D(P<0.05). 3. There were positive correlation between Thickness of hybrid layer and microtensile bond strength(P<0.05).
Adhesives ; Dentin* ; Diamond ; Fluorescein ; Humans ; Molar ; Rhodamines ; Tooth

The purpose of this study was to evaluate the correlation between hybrid layer thickness and bond strength using confocal laser scanning microscope and microtensile bond strength test of two adhesive systems. The dentin surface of human molars, sectioned to remove the enamel from the occlusal surface. Either Scotchbond Multi-Purpose(3M Dental Product, St. Paul, MN, U.S.A) or Clearfil SE Bond(Kuraray, Osaka, Japan) was bonded to the surface, and covered with resin-composite. The resin-bonded teeth were serially sliced perpendicular to the adhesive interface to measure the hybrid layer thickness by confocal laser scanning microscope. The specimen were trimmed to give a bonded cross-sectional surface area of 1mm2, then the micro-tensile bone test was performed at a crosshead speed of 1.0 mm/min. All fractured surfaces were also observed by stereomicroscope. There was no significant differences in bond strengths the materials(p>0.05). However, the hybrid layers of three-step dentin adhesive system, SM, had significantly thicker than self-etching adhesive system, CS(p<0.05). Pearson's correlation coefficient showed no correlation between hybrid layer thickness and bond strengths(p>0.05). Bond strengths of dentin adhesive systems were not dependent on the thickness of hybrid layer.
Adhesives* ; Dental Enamel ; Dentin* ; Humans ; Molar ; Tooth

The purpose of this study was to evaluate the efficiency of the preparation of oval canals using hand and engine-driven instruments with SEM observation. Thirty single-rooted teeth with oval canal were used in this study. The teeth were divided into 3 groups. In group A, the teeth were instrumented up to a size 35 K-file using RC-prep and irrigated with 5% NaOCl between each file size. In group B, the teeth were instrumented with Profile according to the manufacture's instructions using RC-Prep and irrigated with 5% NaOCl between each file size. In group C, the teeth were instrumented with GT file according to the manufacture's instructions using RC-prep and irrigated with 5% NaOCl between each file size. Then, in all teeth, a final flush of 5ml of distilled water delivered for 30s. Canals were dried with sterile standardized paper points. After preparing the canals, the teeth were sectioned along their mesial and diatal surfaces by using low-speed diamond disc, chisel and mallet. Each root section was then dehydrated in graded concentration of alcohol (70, 80, 90, 100%), mounted on an aluminum stub, sputter-coated with gold-palladium and observed with scanning electron microscope (HITACHI S-4200) in middle and apical area. The results of this study were as follows: 1. In the middle area, group B and group C showed less smear layer than group A, and it was statistically significant (p < 0.05). 2. In the middle area, group B showed greater smear layer than group C, but it was not statistically significant (p > 0.05). 3. In the apical area, group C showed less smear layer than group A, and it was statistically significant (p < 0.05). 4. In the apical area, group A showed greater smear layer than group B, but it was not statistically significant (p > 0.05). 5. In the apical area, group B showed greater smear layer than group C, but it was not statistically significant (p > 0.05). 6. In all groups, the middle area was less smear layer than the apical area, and it was statistically significant (p < 0.05).
Aluminum ; Diamond ; Hand* ; Smear Layer ; Tooth ; Water

The purpose of the present study were to evaluate microleakage of a fourth generation dentin-bonding agent following a walking bleaching treatment, to determine the effect of temporary postbleaching dressing with calcium hydroxide on microleakage and to investigate the effect of delayed intracoronal restoration on microleakage. The results of this study were as follows: 1. Bleached groups showed more microleakage than unbleached group. 2. Immediately restored group following bleaching procedure showed the highest microleakage score. 3. One-week delayed restorations showed less microleakage but there were no statistically significant difference between group II and III. 4. Provisional dressing with calcium hydroxide had no influence on microleakage. It is necessary to know the time that has elapsed from the bleaching treatment to the restoration procedure to achieve optimal seal, as well as to reduce the risk of microleakage in adhesive restoration.
Adhesives ; Bandages ; Calcium Hydroxide ; Walking