치환물의 안정성이 부분적으로 결여되어 있는 경우를 2 형, 신전 기능은 손상이 없으나 치환물이 불안정한 경우를 3 형으로 분류하였다.
The case where the stability of the substitute was partially lacked was classified as type 2, and the case where the extended function was not impaired but the substitute was unstable was classified as type 3.