Fracture of restored teeth is a problem in restorative dentistry since it has been estimated that 92 percent of fractured teeth have been previously restored. In a restored tooth, the stresses that occur at the tooth-restoration interface during loading could become large enough to fracture the tooth and/or restoration. The tooth preparation process for a dental restoration is therefore a classical optimization problem: tooth reduction must be minimized to preserve tooth tissue whilst stress levels must be kept low to avoid fracture of the restored tooth. The objective of the present study was to propose alternative optimized designs for a second upper premolar cavity preparation by means of structural shape optimization based on the finite element method and biological adaptive growth. Restored tooth models using the optimized cavity shapes exhibited significant reduction of stresses along the tooth-restoration interface. In the best case, the maximum stress value was reduced by more than 50 percent.