No abstract available.
Polymers*

No abstract available.
Polymers*

PURPOSE: Polymer infiltrated ceramic network (PICN) materials, also called hybrid ceramics, are new materials in dental market. The manufacturer of the PICN material VITA Enamic suggests 3 different finishing procedures for this new material. In the present study, surface roughness and color differences caused from different finishing procedures of VITA Enamic were investigated. MATERIALS AND METHODS: 120 specimens were prepared in dimensions 2 x 10 x 12 mm from VITA Enamic hybrid ceramic blocks with 'high translucency' and 'translucency 2M2' shades. The specimens were divided into 8 groups. For each group, different finishing procedures suggested by the manufacturer were performed. Surface roughness values were determined by a tactile portable profilometer. Color changes were evaluated using a clinical spectrophotometer. The data were analyzed using one-way ANOVA and Tukey's post-hoc comparison. The significance level was set at alpha=0.05. RESULTS: The roughest surfaces were observed in Glaze Groups. Their surface roughness values were similar to that of the control group. Clinical Kit and Technical Kit groups did not show a statistically significant difference regarding surface roughness (P>.05). The largest color difference regarding DeltaE00 was observed in Clinical Kit finishing groups. There were also statistically significant color changes between the groups (P<.05). However, all the groups showed clinically acceptable color change (DeltaE(00)<2.25) except Clinical Kit Groups (DeltaE(00)>2.25). CONCLUSION: Within the limitations of the present study, it may be suggested that finishing the VITA Enamic restorations by Technical Kit instead of Glaze and Clinical Kit gives better clinical performance in regard to surface roughness and shade matching.
Ceramics* ; Polymers*

The study was carried out on 48 workers producing polymer-composite material for over 2 years. The results showed that: although the exposure time is not so long, the polymer-composite material producing has influenced badly to workers' health such as: headache, fatigue... Workers have to be off more because of illness. There are functional changes of central nervous system such as: longer simple reaction time, impairment of short-term memory; decrease of concentration; decrease of electrical activeness of cerebral cortex and sleepy disorder.
Health ; Polymers

This study aimed to determine whether the curing times of Xtra Power and High Power modes of high-power light emitting diode (LED) curing light are sufficient for polymerization of resin sealants. The specimens were prepared and their microhardness values were measured and compared with those of specimens polymerized under conventional LED curing light.The filled sealant polymerized for 8 seconds in the High Power mode and for 3 seconds in the Xtra Power mode showed significantly lower microhardness than the control specimen (p = 0.000). The unfilled sealant polymerized for 8, 12 seconds in the High Power mode and for 6 seconds in the Xtra Power mode showed significantly lower microhardness than the control specimen (p = 0.000).The results of this study suggest that the short curing time with the Xtra Power and High Power modes of highpower LED curing light are not sufficient for adequate polymerization of sealants under specific conditions, taking into account the curing times and the type of sealant.
Polymerization ; Polymers

The purposes of this study were to estimate the material properties of the recently developed domestic composite resins for core filling material (Chemical, Dual A, Dual B; Vericom, Korea) and to compare them with other marketed foreign products (CorePaste, Den-Mat, USA; Ti-Core, Essential Dental Systems, USA; Support, SCI-Pharm, USA). Six assessments were made; working time, setting time, depth of polymerization, flexural strength, bonding strength, and marginal leakage. All items were compared to ISO standards. All domestic products satisfied the minimum requirements from ISO standards (working time: above 90 seconds, setting time: within 5 minutes), and showed significantly higher flexural strength than Core Paste. Dual A and B could, especially, reduce the setting time to 60 seconds when cured with 600 mW/cm2 light intensity. All experimental materials showed 6 mm depth of polymerization. Bond strengths of Ti-Core and Dual B materials were significantly higher than the other materials. Furthermore, three domestic products and Ti-Core could reduce the microleakage effectively.
Composite Resins* ; Polymerization ; Polymers

The purposes of this study were to estimate the material properties of the recently developed domestic composite resins for core filling material (Chemical, Dual A, Dual B; Vericom, Korea) and to compare them with other marketed foreign products (CorePaste, Den-Mat, USA; Ti-Core, Essential Dental Systems, USA; Support, SCI-Pharm, USA). Six assessments were made; working time, setting time, depth of polymerization, flexural strength, bonding strength, and marginal leakage. All items were compared to ISO standards. All domestic products satisfied the minimum requirements from ISO standards (working time: above 90 seconds, setting time: within 5 minutes), and showed significantly higher flexural strength than Core Paste. Dual A and B could, especially, reduce the setting time to 60 seconds when cured with 600 mW/cm2 light intensity. All experimental materials showed 6 mm depth of polymerization. Bond strengths of Ti-Core and Dual B materials were significantly higher than the other materials. Furthermore, three domestic products and Ti-Core could reduce the microleakage effectively.
Composite Resins* ; Polymerization ; Polymers

In this study we measured the amount of light energy that was projected through the tooth material and analyzed the degree of polymerization by measuring the surface hardness of composites. For polymerization, Optilux 501 (Demetron, USA) with two types of light guide was used: a 12 mm diameter light guide with 840 mW/cm2 light intensity and a 7 mm diameter turbo light guide with 1100 mW/cm2. Specimens were divided into three groups according to thickness of penetrating tooth (1 mm, 2 mm, 0 mm). Each group was further divided into four subgroups according to type of light guide and curing time (20 seconds, 40 seconds). Vickers'hardness was measured by using a microhardness tester. In 0 mm and 1 mm penetrating tooth group, which were polymerized by a turbo light guide for 40 seconds, showed the highest hardness values. The specimens from 2 mm penetrating tooth group, which were polymerized for 20 seconds, demonstrated the lowest hardness regardless of the types of light guides (p < 0.05). The results of this study suggest that, when projecting tooth material over a specified thickness, the increase of polymerization will be limited even if light intensity or curing time is increased.
Hardness* ; Polymerization ; Polymers ; Tooth*

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

OBJECTIVES: This study evaluated the effect of camphorquinone (CQ)-amine ratio on the C=C double bond conversion of resins with binary and ternary photoinitiation systems. MATERIALS AND METHODS: Two monomer mixtures (37.5 Bis-GMA/37.5 Bis-EMA/25 TEGDMA) with binary systems (CQ/DMAEMA in weight ratio, group A [0.5/1.0] and B [1.0/0.5]) and four mixtures with ternary system (CQ/OPPI/DMAEMA, group C [0.1/1.0/0.1], D [0.1/1.0/0.2], E [0.2/1.0/0.1] and F [0.2/1.0/0.2]) were tested: 1 : 2 or 2 : 1 CQ-amine ratio in binary system, while 1 : 1 ratio was added in ternary system. The monomer mixture was cured for 5, 20, 40, and 300 sec with a Demetron 400 curing unit (Demetron). After each exposure time, degree of conversion (DC) was estimated using Fourier transform infrared (FTIR) spectrophotometer (Nicolet 520, Nicolet Instrument Corp.). The results were analyzed by ANOVA followed by Scheffe test, with p = 0.05 as the level of significance. RESULTS: DC (%) was expressed in the order of curing time (5, 20, 40, and 300 sec). Group A (14.63 +/- 10.42, 25.23 +/- 6.32, 51.62 +/- 2.69, 68.52 +/- 2.77); Group B (4.04 +/- 6.23, 16.56 +/- 3.38, 37.95 +/- 2.79, 64.48 +/- 1.21); Group C (16.87 +/- 5.72, 55.47 +/- 2.75, 60.83 +/- 2.07, 68.32 +/- 3.31); Group D (23.77 +/- 1.64, 61.05 +/- 1.82, 65.13 +/- 2.09, 71.87 +/- 1.17); Group E (28.66 +/- 2.92, 56.68 +/- 1.33, 60.66 +/- 1.17, 68.78 +/- 1.30); Group F (39.74 +/- 6.31, 61.07 +/- 2.58, 64.22 +/- 2.29, 69.94 +/- 2.15). CONCLUSION: All the monomers with ternary photoinitiation system showed higher DC than the ones with binary system, until 40 sec. Concerning about the effect of CQ-amine ratio on the DC, group A converted into polymer more than group B in binary system. However, there was no significant difference among groups with ternary system, except group C when cured for 5 sec only.
Camphor ; Fourier Analysis ; Polymers