Determination method and determination apparatus for under-navigation apical surgery path

A determination method of an under-navigation apical surgery fenestration path, comprising the following steps:

• at step S1, obtaining CT image data of affected teeth and jaw bone data of a patient, and calculating the CT image data of the affected teeth to obtain calculation parameters of a surgery path;
• at step S2, based on the calculation parameters of the surgery path and in combination with the data of the affected teeth and the jaw bone data, obtaining a start point and an ending point of the surgery path, and generating the surgery path based on the start point and the ending point;
• wherein the calculation parameters of the step S1 comprise a dental root tip point root_tip and a direction root_vec of a dental root long axis;
• the method of obtaining the calculation parameters comprises:
• at step S101, obtaining three-dimensional model data of the affected teeth based on the CT image of the affected teeth to obtain a three-dimensional model of the affected teeth, and by using computer graphics algorithm, obtaining a center root_center of polydata of a dental root in the three-dimensional model of the affected teeth, wherein polydata refers to three-dimensional model data of the dental root;
• at step S102, taking a center root_center of the dental root as origin and taking a direction of a dental long axis as normal direction, making a root-end resection plane plane_cut, wherein the direction of the dental long axis refers to pointing from a dental crown toward a dental root;
• at step S103, by using the root-end resection plane plane_cut, cutting the three-dimensional model of the affected teeth into a first part part1 and a second part part2, using the first part part1 to calculate a connected region to obtain n connected regions, and extracting root polydata of a single connected region, wherein root_polydata refers to root three-dimensional data of a single connected region;
• and calculating the dental root tip point root_tip based on the root three-dimensional data root_polydata of the single connected region;
• wherein the first part part1 is a positive direction part of the root-end resection plane plane_cut, and the second part part2 is a negative direction part of the root-end resection plane plane_cut;
• the dental root tip point root_tip is an angular point closest to a long axis origin in all angular points on the root polydata projected to the dental long axis;
• at step S104, calculating a length left_length of a line connecting an origin orgin_cut on the root-end resection plane plane_cut with the dental root tip point root_tip, and determining whether the length left_length of the connection line exceeds a threshold;
• when the length left_length of the connection line exceeds the threshold, step S105 is performed;
• when the length left_length does not exceed the threshold, step S106 is performed;
• at step S105, using a new origin obtained by translating the origin orgin_cut by a distance along the direction of the dental long axis and using the direction of the dental long axis as a normal direction, making the root-end resection plane plane_cut again, and repeating the steps S103 to S104 to perform multiple iterations on the single connected regions to extract the most connected regions until the length left_length is not beyond the threshold;
• at step S106, obtaining a second root-end resection plane by translating the root-end resection plane by a distance along the normal direction, and using the second root-end resection plane to cut the root_polydata into a first part part1′ and a second part part2′ again, wherein the first part part1′ is a positive direction part of the second root-end resection plane and the second part part2′ is a negative direction part of the second root-end resection plane;
• at step S107, using a center of the second part part2′ as a dental root top center root_top, using a line connecting the dental root tip point root_tip and the top center root_top as the direction root_vec of the dental root long axis, and using the dental root tip point root_tip and the direction root_vec of the dental root long axis as calculation parameters of the fenestration path;
• the method of performing the step S2 includes:
• at step S201, moving the dental root tip point root_tip along the direction root vec of the dental root long axis by an apicectomy distance to obtain a first calibration point Point1;
• at step S202, making a first line segment Line1 through the first calibration point Point1 along a negative direction of a dental buccolingual direction Vec_coronal, and dividing intersection points of the first line segment Line1 and the three-dimensional model data polydata of the dental root into penetration-in points and penetration-out points;
• wherein the penetration-in points and the penetration-out points are obtained by ranking the intersection points of the first line segment Line 1 and the three-dimensional model data polydata of the dental root, wherein the odd-numbered points are penetration-in points and the even-numbered points are penetration-out points;
• at step S203, finding the penetration-in point Point_tmp and the penetration-out point Point_end which are closest to the dental root tip point root_tip;
• at step S204, forming intersection points obtained by the first line segment Line1 and the jaw bone data;
• if the intersection points exist, taking a point among the intersection points, which is the closest point to a start point of the first line segment, as a start point Point_start of the path, and otherwise, taking the penetration-in point Point_tmp as the start point Point_start of the path.