Method and system for finding tooth features on a virtual three-dimensional model

A method of finding ideal contact points on a virtual three-dimensional model of a tooth using a workstation, comprising the steps of:

• (a) intersecting surface of said virtual model of said tooth with an x-y plane based up on tooth axes system for said tooth;
• and
• (b) finding most mesial point and most distal point on said intersected surface of said virtual model of said tooth;
• whereby said most mesial point and said most distal point are two ideal contact points for said tooth.

A method of finding central groove for a virtual three-dimensional model of a tooth, wherein said tooth is a molar or a premolar, using a workstation, comprising the steps of:

• (a) determining most occlusal cusp tip on lingual side and most occlusal cusp tip on buccal side of said virtual three-dimensional model of said tooth;
• (b) rotating said tooth around x-axis of tooth axes system for said tooth using a rotation matrix in a manner so that said most occlusal cusp tip on lingual side and said most occlusal cusp tip on buccal side both have same z-coordinates;
• (c) finding a series of deepest points on occlusal contour of said tooth surface by:
• i. creating a plane parallel to y-z-plane of said tooth axes system;
• ii. cutting all edges of surface of said tooth by said plane parallel to y-z-plane of said tooth axes system thereby forming a slice of said tooth surface;
• iii. finding deepest point on occlusal contour of said slice of said tooth surface;
• iv. moving said plane parallel to y-z-plane of said tooth axes system until entire surface said tooth is covered;
• and repeating steps ii and iii for each new position of said plane parallel to y-z-plane of said tooth axes system;
• and
• (d) finding a line having minimal average distance from said series of deepest points;
• whereby said line is defined as said central groove for said tooth.

A method of finding buccal groove of a virtual three-dimensional model of a tooth, wherein said tooth is a molar, using a workstation, comprising the steps of:

• (a) determining mesial labial cusp tip and distal labial cusp tip of said virtual three-dimensional model of said tooth;
• (b) finding first vertex closest to said mesial labial cusp tip and second vertex closest to said distal labial cusp tip on surface of said virtual three-dimensional model of said tooth;
• (c) rotating said virtual three-dimensional model of said tooth around x-axis of said tooth based upon tooth axes system for said tooth lingually by 60°;
• (d) performing steps (i) to (iv);
• (i) rotating said virtual three-dimensional model of said tooth around an axis orthogonal to z-axis of said tooth based upon tooth axes system for said tooth and vector connecting said mesial labial cusp tip and said distal labial cusp tip in a manner such that said mesial labial cusp tip and said distal labial cusp tip have same z-coordinates;
• (ii) choosing one of said two cusp tips, which has been moved less up to now (or any, if they have been moved equally);
• (iii) moving said chosen cusp tip along said surface of said tooth until said cusp tip is on local maxima;
• (iv) repeating steps (i)-(iii) until said both cusp tips are at local maxima;
• and
• finding a saddle-point, wherein said saddle-point is lowest vertex along highest path from said mesial labial cusp tip to said distal labial cusp tip;
• whereby said saddle-point is defined as said buccal groove of said tooth.