OBJECTIVE: The purpose of this study was to investigate the viscoelastic properties related to handling characteristics of composite resins. METHODS: A custom designed vertical oscillation rheometer (VOR) was used for rheological measurements of composites. The VOR consists of three parts: (1) a measuring unit, (2) a deformation induction unit and (3) a force detecting unit. Two medium viscous composites, Z100 and Z250 and two packable composites, P60 and SureFil were tested. The viscoelastic material function, including complex modulus E* and phase angle delta, were measured. A dynamic oscillatory test was used to evaluate the storage modulus (E'), loss modulus (E") and loss tangent (tandelta) of the composites as a function of frequency (omega) from 0.1 to 20 Hz at 23degrees C. RESULTS: The E' and E" increased with increasing frequency and showed differences in magnitude between brands. The E*s of composites at omega = 2 Hz, normalized to that of Z100, were 2.16 (Z250), 4.80 (P60) and 25.21 (SureFil). The magnitudes and patterns of the change of tandelta of composites with increasing frequency were significantly different between brands. The relationships between the complex modulus E*, the phase angle delta and the frequency omega were represented by frequency domain phasor form, E* (omega) = E*e(idelta) = E* 45 degree angle delta. CONCLUSIONS: The viscoelasticity of composites that influences handling characteristics is significant different between brands. The VOR is a relatively simple device for dynamic, mechanical analysis of high viscous dental composites. The locus of frequency domain phasor plots in a complex plane is a valuable method of representing the viscoelastic properties of composites.
Composite Resins

No abstract available.
Composite Resins* ; Dental Porcelain*

136 anterior-teeth of 46 patients have been sealed for restoration and monitored. After 24 months, the results are 69.11% good at sealing surface, 67.64% at color, 72.06% at surgery and 58.08% at the integrity of the sea
Incisor ; Composite Resins

Composite resin has been used commonly in dentistry. Bonding the teeth with composite resin was based on two mechanisms: 1) The adhesion between composite and enamel, and 2) the adhesion between composite and dentine. The bond strength of these two mechanisms was compared in 1225 teeth after 2 years of bonding. The results showed that the first mechanism provided stronger bond than the second did.
Composite Resins ; Tooth

112 patients with 1089 teeth were covered directly. The results were evaluated after 6, 12, 18, 24 months of the treatment and have shown that the surface of the composite was good in 70.33% of patients, the fine color of the composite was 68.22%. The rate of anatomical success was 59.68% and the completion of the rear of composite was 67.30%.
Tooth ; Composite Resins ; therapeutics

No abstract available.
Composite Resins ; Dentin

OBJECTIVES: The aim of this study was to evaluate the surface color of indirect resin restoration according to the layering placement of different shade of incisal composite. MATERIALS AND METHODS: In this study, CIE L*a*b* value of 16 Body composite of Tescera ATL (Bisco, Schaumburg IL,USA) was measured by spectrophotometer (NF999, Nippon Denshuku, Japan), and compared to CIE L*a*b* value of Vitapan shade guide. Nine shade Incisal composite of Tescera ATL were build-up to 1 mm thickness on Body composites inlay block, and CIE L*a*b* value was measured. Incisal composite was ground to 0.5 mm thickness and CIE L*a*b* value was re-measured. Color difference between Body composite and Incisal composites layered on Body composite was calculated as a function of thickness. RESULTS: Color difference between corresponding shade of Tescera Body composite and Vitapan shade guide was from 6.88 to 12.80. L* and b*value was decreased as layering thickness of Incisal composite on Body composite was increased. But, a* value did not show specific change tendency. CONCLUSIONS: Surface color difference between Body composites and Incisal composites layered on Body composite was increased as the layering thickness of Incisal composite increased (p < 0.05).
Composite Resins ; Inlays

The purpose of this study was to compare the effect of exponential curing method with conventional curing and soft start curing method on polymerization shrinkage of composite resins. Three brands of composite resins (Synergy Duo Shade, Z250, Filtek Supreme) and three brands of light curing units (Spectrum 800, Elipar Highlight, Elipar Trilight) were used. 40 seconds curing time was given. The shrinkage was measured using linometer for 90 seconds. The effect of time on polymerization shrinkage was analysed by one-way ANOVA and the effect of curing modes and materials on polymerization shrinkage at the time of 90s were analysed by two-way ANOVA. The shrinkage ratios at the time of 20s to 90s were taken and analysed the same way. The results were as follows: 1. All the groups except Supreme shrank almost within 20s. Supreme cured by soft start and exponential curing had no further shrinkage after 30s (p < 0.05). 2. Statistical analysis revealed that polymerization shrinkage varied among materials (p = 0.000) and curing modes (p = 0.003). There was no significant interaction between material and curing mode. 3. The groups cured by exponential curing showed the statistically lower polymerization shrinkage at 90s than the groups cured by conventional curing and soft start curing (p < 0.05). 4. The initial shrinkage ratios of soft start and exponential curing were statistically lower than conventional curing (p < 0.05). From this study, the use of low initial light intensities may reduce the polymerization rate and, as a result, reduce the stress of polymerization shrinkage.
Composite Resins* ; Polymerization* ; Polymers*

The objectives of this study were to evaluate the effect of surface roughness on the surface color and translucency of the composite resins. Two composite resins (Esthet-X, Dentsply, Milford, USA and Charisma, Kulzer, Domagen, Germany) were used to investigate the surface color. Charisma was used to investigate the translucency. 40 disc samples (diameter: 8 mm, thickness: 5 mm) were made by each product to measure the surface color. Polymerized each sample's one side was treated by Sof-Lex finishing and polishing system (Group C, M, F, SF). 40 disc samples (diameter: 6 mm, thickness: 1 mm) were prepared to measure the opacity. 1 mm samples were ground one side with #600, #1000, #1500 and #2000 sandpapers. CIE L*a*b* values of each 5 mm thickness samples, and XYZ values of 1 mm thickness samples on the white and black background were measured with spectrophotometer (Spectrolino, GretagMacbeth, Regensdorf, Switzerland). Mean surface roughness (Ra) of all samples before and after surface treatment was measured using the Surface Roughness Tester SJ-301 (Mytutoyo, Tokyo, Japan). Regardless of type and shade of the composite resin, L* values measured in group C were higher than others (p < 0.05), and L* value decreased as the Ra value decreased except B3 shade of Esthet-X. But there were no significant difference in a* values among groups. In control group and SF, highest b* values were measured (p < 0.05), except B1 shade of Esthet-X. Contrast ratio decreased as the Ra value decreased (p < 0.05). With the above results, difference of surface roughness has influence on surface color and translucency of dental composite resins.
Composite Resins* ; Polymers

"Residual stress" can be developed during polymerization of the dental composite and it can be remained after this process was completed. The total amount of the force which applied to the composite restoration can be calculated by the sum of external and internal force. For the complete understanding of the restoration failure behavior, these two factors should be considered. In this experiment, I compared the residual stress of the recently developed nanofilled dental composite by ring slitting methods. The composites used in this study can be categorized in two groups, one is microhybrid type-Z250, as control group, and nanofilled type-Grandio, Filtek Supreme, Ceram-X, as experimental ones. Composite ring was made and marked two reference points on the surface. Then measure the change of the distance between these two points before and after ring slitting. From the distance change, average circumferential residual stress (sigmatheta) was calculated. In 10 minutes and 1 hour measurement groups, Filtek Supreme showed higher residual stress than Z250 and Ceram-X. In 24 hour group, Filtek showed higher stress than the other groups. Following the result of this experiment, nanofilled composite showed similar or higher residual stress than Z250, and when comparing the Z250 and Filtek Supreme, which have quite similar matrix components, Filtek Supreme groups showed higher residual stress.
Composite Resins ; Polymerization ; Polymers