Catelan A1, de Araújo LS, da Silveira BC, Kawano Y, Ambrosano GM, Marchi GM, Aguiar FH.
1Department of Restorative Dentistry, Piracicaba Dental School, University of Campinas , Piracicaba, SP , Brazil.
This study evaluated the impact of the distance between the light guide tip of the curing unit and material surface on the degree of conversion and Knoop microhardness of a composite resin.
MATERIALS AND METHODS:
Circular samples were carried out of a methacrylate micro-hybrid resin-based composite and light cured at 0, 2 and 4 mm distance. Monomer conversion rate was measured using a Fourier-transform Raman spectrometer and Knoop hardness number was obtained using a microhardness tester on the top and bottom surfaces. Data were statistically analyzed by analysis of variance and Tukey’s test (α=0.05).
Overall, the increase of curing distance reduced the microhardness (p≤0.05), but did not influence the carbon double bond conversion rate (p>0.05) of the composite resin tested; and the top surface showed better properties compared to the bottom (p≤0.05).
The light curing at distance can reduce mechanical properties and could affect long-term durability of the composite restorations. Thus, the use of a curing device with high irradiance is recommended.
PMID: 25639534 [PubMed – indexed for MEDLINE] 1. Acta Odontol Scand. 2015 May;73(4):298-301. doi: 10.3109/00016357.2014.946965. Epub 2015 Feb 1.