[Three dimensional shape measurement of teeth. (7) CAD of crown prosthesis by using the data measured]

A preliminary CAD system to design the inner and outer shape of crown prosthesis was developed using the data of 7 abutment and molar measured in the previous paper. The gingival and marginal line in the abutment tooth could be recognized more certainly by the "GIN-MAGN" program, and the three dimensional data of tooth crown above the gingival line could be output and saved. To prepare the data base of the occlusal surface of tooth crown, the data of tooth crown above the gingival line of 7 molar were also output by the "GIN-M" program. The data around the toothneck were excluded with an arbitrary height above the gingival line in order to connect smoothly with the margin line of the abutment tooth. The tooth crown data were set up on the abutment data by means of the program "AB-CR-E". In the present system, even though the occlusal condition with the antagonistic tooth could not be taken into account, the CAD procedure to set up a tooth crown with an arbitrary size on the arbitrary position of abutment tooth could be accomplished, and the toothneck data of crown were connected with the margin of abutment tooth.