Influence of Tooth Thickness on Degree of Conversion of Photo-Activated Resin Composite Irradi- ated Through the Tooth (original) (raw)
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Journal of International Dental and Medical Research, 2019
Polymerization of composite resins could be affected by iradiance levels of light curing units. Furthermore, imperfect polymerization of resin composite polymerization could cause low surface hardness and high cytotoxicity. This study examined the effect of the irradiance levels of the light curing units on the microhardness of cured resin composites and their cytotoxicity A pulse-lighting curing unit with irradiance levels of 800, 900 and 1,000 mW/cm2 in either 10 or 20 sec was employed for this study and a commercially available continuous-lighting curing unit of 900 mW/cm2 in 20 sec was used as comparison. Resin composite specimens were irradiated using the curing units, and the microhardness with Knoop system and cytotoxicity by the MTT were subsequently determined. The irradiance of 900±10 mW/m2 cm2 emitted from the pulse lighting is the closest value to that emitted by the continuous-lighting curing unit. The resin composites irradiated at higher irradiance levels exhibited si...
This paper evaluates the photopolymerization kinetics and degree of conversion of different com mercial dental composites when photoactivated by a LED curing unit using two different modes (standard and softstart mode). The investigation was performed on with RelyX ARC (dualcured), Filtek Z350 (Nanocomposite), Filtek Z250 (Hybrid), and Filtek Z350flow (Flowable) resin composites. The analysis used was attenuated total reflection with a Fourier transform infrared (ATRFTIR). The RelyX ARC resin demonstrated the highest degree of conversion with both LED photoactivation modes. For this resin a 28% decrease in maximum rate was observed and the time to reach its highest rate was almost 2.3 times higher than when the softstart photoactivation light curing was used. Z350flow resin recorder a higher maximum rate using the softstart mode rather than the standard mode. In contrast, the Z250 showed a higher value using the standard mode. Although Z250 and Z350 showed a higher total degree of conversion effectiveness using the softstart mode, RelyX and Z350flow achieved a higher value using the standard mode
Brazilian Oral Research, 2010
The aim of this study was to observe the influence of two light polymerization units (LED or halogen light) on the degree of conversion (DC) of three dental composites with lighter shades and a different photoinitiator system. The top (T) and bottom (B) surfaces of 60 discs of composite resin (Filtek Supreme, Filtek Z250, Tetric Ceram Bleach) cured either by LED or by halogen lamp (HL) were studied using an FT-Raman spectrometer. The degree of conversion (DC) was evaluated by following the changes in the intensity of the methacrylate C=C stretching mode at 1640 cm -1 . The calculated DC ranged from 54.2% (B) to 73.4% (T) and from 60.2% (B) to 76.6% (T) for the LED and HL, respectively. LED and halogen devices were able to produce an adequate DC for all the resins tested.
Materials
To study the influence of fast high-intensity (3-s) and conventional (20-s) light curing protocols on certain physical properties including light-transmission and surface wear of two nano-hybrid composite resins (Tetric PowerFill and Essentia U) specifically designed for both curing protocols. According to ISO standards, the following properties were investigated: flexural properties, fracture toughness and water sorption/solubility. FTIR-spectrometry was used to calculate the double bond conversion (DC%). A wear test using a chewing simulator was performed with 15,000 chewing cycles. A tensilometer was used to measure the shrinkage stress. Light transmission through various thicknesses (1, 2, 3 and 4 mm) of composite resins was quantified. The Vickers indenter was utilized for evaluating surface microhardness (VH) at the top and the bottom sides. Scanning electron microscopy was utilized to investigate the microstructure of each composite resin. The light curing protocol did not sh...
Comparative Effectiveness of Two Light Curing Units on the Properties of Dental Resin Composites
Pakistan Journal of Medicine and Dentistry, 2020
Background: Setting of conventional glass ionomers cement and dental resin composites as filling materials is predominantly through polymerization reaction, which is usually induced by light. The objective of this study was to assess the temperature changes, light intensities, sorption and solubility capability and comparative micro hardness in Dental Resin Composites (DRC) by using two different light curing units that is Quartz Tungsten Halogen (QTH) and Light Emitting Diodes (LED). Methods: This analytical, experimental, in-vitro study was spanned over one month, conducted in the laboratory of Dental Materials, Dr. Ishrat-ul-Ibad Khan Institute of Oral Health Sciences. Through non-probability, convenient sampling, 60 samples of DRCs was prepared as 10mm in diameter and 2mm in thickness in the steel moulds by a single trained operator. Effect of heat generation, light intensities, sorption and solubility and micro hardness during polymerization of DRCs were all measured. Statistica...
Biomaterials, 2003
To determine whether marginal adhesion is sensitive to different irradiation parameters, we investigated the in vitro adhesion values of four dental resins on metal surfaces. Four groups of eight specimens each of Z250, Filtek flow, Dyract AP and Dyract flow were placed in pre-treated stainless steel cavities and irradiated using different methods of exposure. The curing lights used were a Spectrum 800 halogen curing light at settings of 800 and 450 mW/cm(2) and an Optilux 501 ramping light. The maximum amount of push-out force required to displace the resin from the metal cavity was equated with adhesive value (shear bond strength). Comparisons (ANOVA, p<0.0001) were made within the same material and between the different materials when using different curing protocols. Significant lower bond strengths were recorded when curing was done by gradually increasing the intensity (ramping method) compared to curing with the fixed intensities (p>0.0001) Comparing the fixed intensities, significant lower bond strength values were obtained at 800 mW/cm(2) compared to 450 mW/cm(2) (p<0.0001). For all exposures, the two flowable materials demonstrated weaker values when compared to the higher filled materials. The advantage of initial slow polymerization (more elasticity and less tension) obtained by the so-called "soft start" method, was offset by a rise in total polymerization shrinkage, when final curing was completed at 1130 mW/cm(2). These tests demonstrated that using halogen units, exposure for 40s with an intensity of 450 mW/cm(2) appeared to be the most promising for light-curing dental resin composites.
Depth of cure of dental composites submitted to different light-curing modes
Journal of Applied Oral Science, 2006
OBJECTIVE: This study evaluated the depth of cure of five dental composites submitted to different light-curing modes. MATERIAL AND METHODS: Canal-shaped cavities with 5mm of length were prepared on the buccal surfaces of extracted third molars, and restored using P-60, A-110, Admira, Z-250 and Supreme resin composites. Materials were light-cured from the top, according to three modes (Group 1- Conventional (C): 500 mW/cm2 / 40 s; Group 2 Soft-Start (SS): 250 mW/cm2/ 20 s + 500 mW/cm2/ 20 s + 500 mW/cm2/ 10 s and Group 3 LED: 250 mW/cm2/ 40 s). After that, cavity longitudinal surfaces were polished and marked with a millimeter scale of 4mm of length. Depth of cure was evaluated by means of Knoop hardness number (KHN), so that five indentations were performed at each millimeter. Original data were submitted to three-way ANOVA and Fisher's LSD test (a = 0.01). RESULTS: All materials presented a significant reduction on KHN from first to third millimeter. Regarding depth of cure, the results obtained for Conventional and Soft-Start modes were similar, but statistically superiors to those found for group 3 (LED). CONCLUSION: This performance may be related to the differences among energy densities obtained with different light-curing modes.
Brazilian Dental Science
Objective: This study analyzed the effect of two light emitting diodes (LEDs) on the degree of conversion (DC) of a composite resin for bleached teeth under the influence of adhesives systems used as modeling liquid. Material and methods: A total of 60 samples of IPS Empress Direct resin (Ivoclar, Vivadent) in BL-L shade were made in a single increment and polymerized for 20 seconds. The treatments were: 1) Type of adhesive used as modeling liquid (Adper Single Bond 2; the bond component of Adper Scotchbond Multi-Purpose; or no adhesive systems used as modeling liquid were used in the control group); and 2) Type of LED (Bluephase, polywave; and Coltolux, monowave). The DC, percentage of monomers converted to polymer during polymerization, was were evaluated using Fourier Transform Infrared Spectroscopy (FTIR) with 10 scans and wavenumber related to 1/λ for observation of the peaks at 1608 and 1638 cm-1. Data were statistically analyzed by two-way analysis of variance (ANOVA) with…
BMC Oral Health
Background Reducing the necessary time to restore primary teeth improves the cooperation of paediatric patients. This study aimed to investigate the marginal integrity of restorations prepared with a bulk-fill resin-based composite (RBC) containing additional fragmentation chain transfer (AFCT) compared to a conventional RBC when light cured with a rapid high-irradiance (3 s) and a regular (10 s) curing mode. Methods Forty class-II cavities were prepared in 40 primary molars. The molars were randomly divided into four groups based on the applied light-curing modes (regular: 10 s @ 1200 mW/cm2 or high-irradiance: 3 s @ 3000 mW/cm2) and the used restorative material (AFCT-containing bulk-fill RBC “Power Fill” or AFCT-free conventional RBC “Prime”). After thermo-mechanical loading, the marginal integrity was analysed using scanning electron microscopy. A beta regression model and pairwise comparisons were used to statistically analyse the data. Results The mean marginal integrity (% ± ...