An single component light-curable orthodontic adhesive includes a curable resin monomer component; a quaternary curing initiator system; and filler. The orthodontic adhesive has a long working time (W) and short curing time (C). The adhesives are suitable as light-curing and may include a colorant. Suitable colorants include reversible, thermochromic dyes. The adhesive may also include a resin toughening component.