Orthodontic articles comprising polymerized composition comprising at least two free-radical initiators

An orthodontic article is described comprising the reaction product of a free-radically polymerizable resin; a first free-radical photoinitiator having sufficient absorbance at a first wavelength range; and a second free-radical initiator selected from a second photoinitiator having sufficient absorbance at a second wavelength range, wherein the second wavelength range is different than the first wavelength range, or a thermal free-radical initiator. In some embodiments, the first free-radical photoinitiator exhibits a maximum absorbance at a wavelength of the range of 370-380 nm or 320-330 nm and/or comprises photoinitiator groups selected from acyl phosphine oxide or alkyl amine acetophenone. Also described are photopolymerizable compositions and methods.