Photopolymerization of dental resin as restorative material using an argon laser

A Comparative Study on the Microscale and Macroscale Mechanical Properties of Dental Resin Composites

Dental resin composites are universal restorative materials, and various kinds of fillers are used to reinforce their mechanical properties. However, a combined study on the microscale and macroscale mechanical properties of dental resin composites is missing, and the reinforcing mechanism of the composites is still not fully clarified. In this work, the effects of the nano-silica particle on the mechanical properties of dental resin composites were studied by combined dynamic nanoindentation tests and macroscale tensile tests. The reinforcing mechanism of the composites was explored by combining near-infrared spectroscopy, scanning electron microscope, and atomic force microscope characterizations. It was found that the tensile modulus increased from 2.47 GPa to 3.17 GPa, and the ultimate tensile strength increased from 36.22 MPa to 51.75 MPa, with the particle contents increasing from 0% to 10%. From the nanoindentation tests, the storage modulus and hardness of the composites increased by 36.27% and 40.90%, respectively. The storage modulus and hardness were also found to increase by 44.11% and 46.46% when the testing frequency increased from 1 Hz to 210 Hz. Moreover, based on a modulus mapping technique, we found a boundary layer in which the modulus gradually decreased from the edge of the nanoparticle to the resin matrix. Finite element modeling was adopted to illustrate the role of this gradient boundary layer in alleviating the shear stress concentration on the filler-matrix interface. The present study validates mechanical reinforcement and provides a potential new insight for understanding the reinforcing mechanism of dental resin composites.

New horizons for carbon dots: quantum nano-photoinitiating catalysts for cationic photopolymerization and three-dimensional (3D) printing under visible light

Citric acid-based carbon dots (CDs) as nano-photoinitiating catalysts for 3D printing.

Water-Soluble Photoinitiators in Biomedical Applications

Light-initiated polymerization processes are currently an important tool in various industrial fields. The advancement of technology has resulted in the use of photopolymerization in various biomedical applications, such as the production of 3D hydrogel structures, the encapsulation of cells, and in drug delivery systems. The use of photopolymerization processes requires an appropriate initiating system that, in biomedical applications, must meet additional criteria such as high water solubility, non-toxicity to cells, and compatibility with visible low-power light sources. This article is a literature review on those compounds that act as photoinitiators of photopolymerization processes in biomedical applications. The division of initiators according to the method of photoinitiation was described and the related mechanisms were discussed. Examples from each group of photoinitiators are presented, and their benefits, limitations, and applications are outlined.

Measurement of solubility and water sorption of dental nanocomposites light cured by argon laser

Different parameters used for photoactivation process and also composition provide changes in the properties of dental composites. In the present work the effect of different power density of argon laser and filler loading on solubility (SL) and water sorption (WS) of light-cure dental nanocomposites was studied. The resin of nanocomposites was prepared by mixing bisphenol A glycol dimethacrylate (Bis-GMA) and triethylene glycol dimethacrylate (TEGDMA) with a mass ratio of 65/35. 20 wt.% and 25 wt.% of nanosilica fillers with a primary particle size of 10 nm were added to the resin. Camphorquinone (CQ) and DMAEMA were added as photoinitiator system. The nanocomposites were cured by applying the laser beam at the wavelength of 472 nm and power densities of 260 and 340 mW/cm(2) for 40 sec. Solubility and water sorption were then measured according to ISO 4049, which in our case, the maximums were 2.2% and 4.3% at 260 mW/cm(2) and 20% filler, respectively. The minimum solubility (1.2%) and water sorption (3.8%) were achieved for the composite containing 25% filler cured at 340 mW/cm(2). The results confirmed that higher power density and filler loading decreased solubility of unreacted monomers and water sorption and improved physico-mechanical properties of nanocomposites.

The effect of curing light and chemical catalyst on the degree of conversion of two dual cured resin luting cements

The aim of this study was to evaluate the influence of different curing lights and chemical catalysts on the degree of conversion of resin luting cements. A total of 60 disk-shaped specimens of RelyX ARC or Panavia F of diameter 5 mm and thickness 0.5 mm were prepared and the respective chemical catalyst (Scotchbond Multi-Purpose Plus or ED Primer) was added. The specimens were light-cured using different curing units (an argon ion laser, an LED or a quartz-tungsten-halogen light) through shade A2 composite disks of diameter 10 mm and thickness 2 mm. After 24 h of dry storage at 37°C, the degree of conversion of the resin luting cements was measured by Fourier-transformed infrared spectroscopy. For statistical analysis, ANOVA and the Tukey test were used, with p ≤ 0.05. Panavia F when used without catalyst and cured using the LED or the argon ion laser showed degree of conversion values significantly lower than RelyX ARC, with and without catalyst, and cured with any of the light sources. Therefore, the degree of conversion of Panavia F with ED Primer cured with the quartz-tungsten-halogen light was significantly different from that of RelyX ARC regardless of the use of the chemical catalyst and light curing source. In conclusion, RelyX ARC can be cured satisfactorily with the argon ion laser, LED or quartz-tungsten-halogen light with or without a chemical catalyst. To obtain a satisfactory degree of conversion, Panavia F luting cement should be used with ED Primer and cured with halogen light.

Photopolymerization of a dental nanocomposite as restorative material using the argon laser

The aim of this study was to investigate the effect of power density and irradiation time of an argon laser on the physico-mechanical properties of light-cured dental nanocomposites. The composites were cured with 260 mW/cm(2) and 340 mW/cm(2) power densities at different irradiation times. The degree of conversion (DC), flexural strength, flexural modulus, water sorption, solubility and reaction temperature were measured. The maximum DC (50%), which was achieved after approximately 20 s irradiation, and the reaction temperature rise (20°C) were demonstrated by composite containing 20% filler cured at 340 mW/cm(2). The composite with 25% filler cured at 340 mW/cm(2) showed the highest flexural strength and modulus, which were 32.2 MPa and 1.89 GPa, respectively. The minimum water sorption (3.8%) and solubility (1.2%) were achieved with the composite containing 25% filler cured at 340 mW/cm(2). Finally, the composite with 25% filler cured at 340 mW/cm(2) showed higher physico-mechanical properties.