TY  - JOUR 
T1  - Radiopacity and microhardness changes and effect of X-ray operating voltage in resin-based materials before and after the expiration date
JO  - Materials Research
A1  - Tirapelli, Camila
A1  - Panzeri, Fernanda de Carvalho
A1  - Panzeri, Heitor
A1  - Pardini, Luiz Carlos
A1  - Zaniquelli, Osvaldo
SN  - 1516-1439
UL  - 10.1590/S1516-14392004000300006
VL  - 7 
Y1  - 2004
PB  - Brasil 
ER  -