Study of diferent photoinitiators in experimental resin cements photoactivated by two light curing units / Estudo de diferentes fotoiniciadores em cimentos resinosos experimentais fotoativados com duas fontes de luz

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

The aim of this study was to evaluate the effect of different photoinitiators on the degree of conversion and microtensile bond strength of the photoactivated resin cement used to fix a ceramic veneer on the dental structure. Seven experimental resin cements was manipulated, as the organic matrix was standardized the only variable component was the photoinitiators. Different concentrations and combinations of Canphoroquinone (CQ) and Phenylpropanodione (PPD) were added in cements as following: C5=0.5% wt CQ; C8=0.8% wt CQ; P5=0.5% wt PPD; P8=0.8% wt PPD; C1P4=0.1% wt CQ and 0.4% wt PPD; C4P1=0.4% wt CQ and 0.1% wt PPD; and, C4P4=0.4% wt CQ and 0.4% wt PPD. The first study evaluated the influence of different combinations of photoinitiators in the degree of conversion on the resin cement photoactivated by LED and quartz- tungstenhalogen (QTH) through ceramic veneer. Forty two samples was prepared to Spectroscopy FTIR (n=3). The samples was made in round teflon mold and a feldspatic ceramic disc shade A3 (IPS e.max Ceram, Ivoclar /Vivadent) was placed over the mold and the photoactivation was carried through the ceramic with QTH (XL2500, 3M/ESPE) and LED (Ultralume Led5, Ultradent) for 100s. After 24 h at 37oC of dark storage, the samples were triturate, mixed with 100 mg of KBr powder salt and pressed to obtain a pellet to analyze Spectroscopy FTIR. The statistical analyze showed no significant difference between the light curing units (p>0,05), independent of the other factors. The P8 cement presented the major means of the degree of conversion. With QTH, P8 was major (60 % ± 1,6) and presented significant statistical different when was compared to C1P4 (50,7 % ± 1,8), C4P1 (50,4 % ± 1,2) and C5 (47,1 % ±1,2). With LED, P8 was major (58,8 % ± 4,3), but with significant statistical different only the C4P1 (50,9 % ± 3,3) and C5 (48,4 % ± 2,5) cements (p>0,05). The second work investigated the effect of different photoinitiators on the microtensile bond strength of photoactivated resin cement used to fix a ceramic to the bovine dentin. Silanized Ceramic discs were bonded to the bovine dentin with the experimental cement photoactivated by LED and QTH for 100s. After 24hs at 37oC and 100% relative wetting, the samples was submitted to the microtensile test in universal trail machine Instron (Mod. 4411, USA). The P5, C5 and C4P1 cements showed significant statistical different to the light curing units, however P5 e C5 was superiors with QTH and C4P1 was better with LED. Additionally, P5 obtain the major means of bond strength (19,6 MPa ± 3,51) with QTH, but no statistical difference was observed with C5 (16,8 MPa ± 1,62), C4P4 (16,2 MPa ±2,93) and P8 (15,4 MPa ± 2,34). With LED, C4P1 obtain the major means of bond strength (20,1 MPa ± 3,4) and presented significant statistical different to the other groups. Therefore, QTH and LED are effectives in the photoactivation of the resin cements through the ceramic with 1,4 mm height. More and then, PPD is viable alternative like photoinitiator in resin cements and it can be adequately photoactivated by LED light curing units.

ASSUNTO(S)

materiais dentarios dental materials

ACESSO AO ARTIGO

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