PURPOSE: Clinicians commonly encounter cases in which it is difficult to determine whether adjacent radiopacities are normal or pathologic. The ideal radiopacity of composite resin is equal to or higher than that of the same thickness of aluminum. We aimed to investigate the possible effects of different curing times on the post-24-hour radiopacity of composite resins on digital radiographs. MATERIALS AND METHODS: One mm thick samples of Filtek P60 and Clearfil resin composites were prepared and cured with three regimens of continuous 400 mW/cm2 irradiance for 10, 20 and 30 seconds. Along with a 12-step aluminum step wedge, digital radiographs were captured and the radiopacities were transformed to the equivalent aluminum thicknesses. Data were compared by a general linear model and repeated-measures of ANOVA. RESULTS: Overall, the calculated equivalent aluminum thicknesses of composite resins were increased significantly by doubling and tripling the curing times (F(2,8)=8.94, p=0.002). Notably, Bonferroni post-hoc tests confirmed that the radiopacity of the cured Filtek P60 was significantly higher at 30 seconds compared with 10 seconds (p=0.04). Although the higher radiopacity was observed by increasing the time, other comparisons showed no statistical significance (p>0.05). CONCLUSION: These results supported the hypothesis that the radiopacity of resin composites might be related to the duration of light curing. In addition to the current standards for radiopacity of digital images, defining a standard protocol for curing of dental materials should be considered, and it is suggested that they should be added to the current requirements for dental material.
Aluminum ; Composite Resins ; Dental Materials ; Light ; Light-Curing of Dental Adhesives ; Linear Models ; Radiography, Dental, Digital

OBJECTIVE: To investigate clinical effect of individual light-curing resin tray as edge plastic material in complete denture modulo.
 METHODS: A total of 30 patients with poor condition for alveolar ridge of mandible were chosen individual tray with individual light-curing resin tray for material edge shaping or traditional individual impression tray for edge shaping cream to produce complete denture. The operability, questionnaire about denture retention, comfort, mucosal cases and chewing function in the process of shaping the edge were investigated three months later after wearing dentures.
 RESULTS: There was no significant difference in retention, comfort, mucosa and the chewing function between the two mandibular denture impression methods. However, the patients with individual light-curing resin tray as edge shaping material felt better in the process than that in the patients with die-cream as the edge shaping material (P<0.05). Furthermore, the manipulation with individual light-curing resin tray as edge shaping material is easy for doctor.
 CONCLUSION Although the clinical effect of Individual light-curing resin tray material as the edge shaping material is equal to that of impression cream, it saves time and human resource. Moreover, it is more acceptable for the patients and thus it can be spread in clinics.
Acrylic Resins ; Dental Impression Materials ; Dental Impression Technique ; Denture, Complete ; Humans ; Light-Curing of Dental Adhesives ; instrumentation

OBJECTIVETo evaluate the effect of thermal cycling on surface microstructure of different light-curing composite resins.

METHODSA nanofilled composite (Z350) and 4 microhybrid composites (P60, Z250, Spectrum, and AP-X) were fabricated from lateral to center to form cubic specimens. The lateral surfaces were abrased and polished before water storage and 40 000 thermal cycles (5/55 degrees celsius;). The mean surface roughness (Ra) were measured and compared before and after thermal cycling, and the changes of microstructure were observed under scanning electron microscope (SEM).

RESULTSSignificant decreases of Ra were observed in the composites, especially in Spectrum (from 0.164±0.024 µm to 0.140±0.017 µm, P<0.001) and Z250 (from 0.169±0.035 µm to 0.144±0.033 µm, P<0.001), whose Ra approximated that of P60 (0.121±0.028 µm) with smoothly polished surface. SEM revealed scratches and shallower pits on the surface of all the 5 resins, and fissures occurred on Z350 following the thermal cycling.

CONCLUSIONWater storage and thermal cycling may produce polishing effect on composite resins and cause fissures on nanofilled composite resins.

Composite Resins ; Dental Polishing ; Light-Curing of Dental Adhesives ; Materials Testing ; Surface Properties ; Temperature

OBJECTIVETo evaluated the effect of curing modes and light-cure times on knoop hardness (KH) and microtensile bond strength (µTBS) of dentin adhesives in vitro.

METHODSTwenty molars were made into 80 dentin slices (about 1 mm thick). The dentin slices were prepared with an etch&rinse adhesive A (ONE-STEP PLUS) and a self-etch adhesive B (Clearfil SE Bond), and light-cured respectively under fast mode, i.e.1250 mW/cm(2) light intensity for 10 s, 15 s, 20 s, and ramp mode (soft start curing mode), i.e.initial 0 mW/cm(2) gradually increasing to 1250 mW/cm(2) in first 10 s, then steady for the next 10 s. The prepared dentin slices were kept in dark dry room for 24 h at 37°C, and KH were tested. The other 40 molars were flattened to expose coronal dentin, prepared with adhesives as above. Then the prepared teeth were restored with resin composites incrementally and cured under fast mode. The restored teeth were stored in water for 24 h at 37°C, and slowly sectioned to obtain multiple bonded beams. After 7 d water-storage, the samples received microtensile bond test, and the failure models of beams were observed under a stereomicroscope. Data were analyzed by ANOVA and LSD test (α = 0.05).

RESULTSNo statistical difference in KH [(28.20 ± 5.36), (29.13 ± 5.60), (28.13 ± 4.40), (27.06 ± 3.77) MPa] and µTBS [(22.30 ± 5.07), (22.73 ± 6.59), (26.32 ± 6.17), (25.67 ± 4.31) MPa] of adhesive A were found between four curing conditions (fast mode for 10 s, 15 s, 20 s and ramp mode for 20 s) (P > 0.05). In adhesive B, KH of Fast 20 s [(28.23 ± 3.67) MPa] were significantly higher than those of Fast 10 s [(14.15 ± 2.24) MPa] and Fast 15 s [(17.63 ± 2.17) MPa] (P < 0.05). The µTBS of Fast 20 s [(42.52 ± 3.59) MPa] were significantly higher than those of Fast 10 s [(24.21 ± 3.60) MPa], Fast 15 s [(22.25 ± 4.16) MPa] and Ramp 20 s [(31.12 ± 5.40) MPa] (P < 0.05). In Fast 20 s and Ramp 20 s modes, there were no statistical difference in KH of adhesive A and B, while µTBS of adhesive B were higher than that of adhesive A(P < 0.05).

CONCLUSIONSAs for different type dentin adhesives, the appropriate curing time in fast mode is different, and ramp mode (soft start curing mode) has no advantage over fast mode.

Dentin-Bonding Agents ; Hardness ; Humans ; In Vitro Techniques ; Light-Curing of Dental Adhesives ; methods ; Tensile Strength

OBJECTIVE: To explore the effect of Radii barrier sleeves on the cure depth of composite resin. METHODS: Cylinder mold was prepared, and the resin was filled strictly into the mold. The surface was flattened and then cured with plastic engraver's knife.The depth of composite resin which was cured by QHL75TM with or without Radii barrier sleeves was compared. RESULTS: The cure depth of composite resin which were cured by QHL75TM with or without Radii barrier sleeves of photo-curing machine was 4.38 mm and 4.27 mm respectively,with no statistical difference. CONCLUSION The cure depth of composite resin is not influenced by Radii barrier sleeves under the same light condition.
Composite Resins ; chemistry ; Cross Infection ; prevention & control ; Curing Lights, Dental ; Dental Equipment ; Disposable Equipment ; Equipment Contamination ; prevention & control ; Humans ; Light-Curing of Dental Adhesives ; instrumentation ; methods ; Technology, Dental ; instrumentation