Effects of Light Curing Method and Exposure Time on Mechanical Properties of Resin Based Dental Materials

Abstract

Objectives The aim of this study was to investigate microhardness and compressive strength of composite resin (Tetric-Ceram, Ivoclar Vivadent), compomer (Compoglass, Ivoclar, Vivadent), and resin modified glass ionomer cement (Fuji II LC, GC Corp) polymerized using halogen light (Optilux 501, Demetron, Kerr) and LED (Bluephase C5, Ivoclar Vivadent) for different curing times. Methods Samples were placed in disc shaped plastic molds with uniform size of 5 mm diameter and 2 mm in thickness for surface microhardness test and placed in a diameter of 4 mm and a length of 2 mm teflon cylinders for compressive strength test. For each subgroup, 20 samples for microhardness (n=180) and 5 samples for compressive strength were prepared (n=45). In group 1, samples were polymerized using halogen light source for 40 seconds; in group 2 and 3 samples were polymerized using LED light source for 20 seconds and 40 seconds respectively. All data were analyzed by two way analysis of ANOVA and Tukey’s post-hoc tests. Results Same exposure time of 40 seconds with a low intensity LED was found similar or more efficient than a high intensity halogen light unit (P>.05), however application of LED for 20 seconds was found less efficient than 40 seconds curing time (P=.03). Conclusions It is important to increase the light curing time and use appropriate light curing devices to polymerize resin composite in deep cavities to maximize the hardness and compressive strength of restorative materials.

In Vitro Evaluation of Cell Compatibility of Dental Cements Used with Titanium Implant Components

“…Additionally, self-curing mechanisms were employed for the five cement compositions to subject the investigative materials to the same experimental conditions, but RMGIC cements are typically light-cured in the clinic, a process which significantly expedites the cement setting time. 49 Lastly, the inherent variability in the specified specimen preparation protocol for ZOE and ZP cement compositions, both of which are powder-liquid formulations, can lead to undesired alterations in material properties. For example, the manufacturer's instructions for ZOE and ZP cement permit the user to incorporate additional liquid monomer to achieve a desired consistency, but the increased liquid concentration (e.g., eugenol) will lead to increased monomer leaching and subsequent cytotoxicity.…”

Comparison of the Degree of Conversion of Resin Based Endodontic Sealers Using the DSC Technique

“…23 Two other phenomena connected with the polymerization of the resins are volumetric shrinkage and heating. 24 The adequacy of the polymerization is influenced by many factors such as the distance of the light source from the resin; the type of resin (shade, translucency and thickness, viscosity); 25 the temperature; the curing and post-irradiation time; 24,26 the reactivity of the monomer; the types and amounts of inhibitors, the light; the oxygen permeability 27 and also the type and amount of photo initiator/co-initiator systems. 13,28 It has also been shown that dynamic heating of the resin samples increases the rate of polymerization resulting in higher conversion.…”

“…Adequate polymerization of dental resins depends also on the intensity of the light source (power density measured in mW/cm²), correct Cotti, Scungio, Dettori, Ennas wavelength of the light and duration of the exposure. 25,26 If these parameters are not adequate an incomplete polymerization will occur, together with the exhibition of poor physical properties of the material, higher solubility and consequently an early failure. 31 In our experiment we used Ul-traLume LED 5 and Mini LED.…”

The Effects of Mouth Rinses on the Color Stability of Resin‐Based Restorative Materials

“…The material was covered with another celluloid strip, and the glass slide weighed of 200 g for 1 minute until the slide touched the mold completely, thus allowing excess composite to flow prior to curing. [18][19][20] Next, the excess restorative material was removed. The tested restorative material was light cured for 20 seconds on each side using a light-curing unit QHL75 (505 mW/cm 2 ) (Dentsply, York, PA, USA).…”