Orthodontic articles and polymerizable resin compositions are described. The orthodontic article comprises a cured composition comprising the reaction product of free-radically polymerizable resin comprising 30 to 70 wt. %, inclusive, of at least one urethane component, and 25 to 70 wt. %, inclusive, of reactive diluent(s) comprising at least one monofunctional (meth)acrylate monomer. The polymerizable resin comprises no greater than 35 wt. % of reactive diluent(s) having a high affinity for water. Reactive diluent(s) such as monofunctional (meth)acrylate monomers having a high affinity for water have low log P values. In one embodiment, the polymerizable resin comprises at least one acidic monomer.