background and aims. today light cured composites are widely used. physical and mechanical properties of composites are related to the degree of conversion. light curing unit (lcu) is an important factor for composite polymerization. aim of this study is evaluation of composite resins hardness using halogen and led light curing units. materials and methods. in this study, 30 samples of filtek z...

1. In the retina, central areas whose diameter is less than 2 degrees possess only cones, while larger areas have rods and cones. In conformity with this, the relation of critical fusion frequency to intensity is a single function for centrally fixated areas below 2 degrees , and a double function for similarly fixated, larger areas. The two sections of such data are easily identified with rod ...

OBJECTIVE This study was designed to evaluate the effect of argon laser irradiation on development and progress of enamel demineralization around orthodontic brackets. MATERIALS AND METHODS Fifty caries-free, intact human premolars were randomly assigned to one of the following five equal groups: Groups 1 (control) and 2: The brackets were bonded using conventional halogen light for 40s and a...

The aqueous photoreactions of three halide ions (chloride, bromide and iodide) were studied using a diode array spectrophotometer to drive and detect the process at the same time. The concentration and pH dependences of the halogen formation rates were studied in detail. The experimental data were interpreted by improving earlier models where the cage complex of a halogen atom and an electron h...

The objectives of this study were to compare the polymerization shrinkage of three orthodontic adhesives. In addition we wanted to determine the effectiveness of the high-intensity quartz tungsten halogen (HQTH) in curing orthodontic adhesives on polymerization shrinkage with that of the quartz tungsten halogen (QTH). A total of 120 glass ring molds were prepared using a low-speed saw. The inte...