A tooth correction auxiliary method based on dental film processing

Abstract

The present application relates to the field of image processing, and particularly relates to a tooth correction auxiliary method based on dental film processing, collecting an oral tooth X-ray image, selecting a sliding window according to the surface area of each tooth, obtaining the demarcation point of gum and tooth enamel of each tooth according to the grayscale change in the sliding window, obtaining a fitting curve composed of the demarcation point, taking a straight line passing through the center point of each tooth and the demarcation point of gum and tooth enamel as the center line of each tooth, taking the normal line of the tangent line of the intersection point of the tooth center line and the fitting curve as the normal line of each tooth, obtaining the tooth inclination degree according to the included angle of the center line and the normal line of each tooth, taking the center point of each tooth as the center of a circle, taking the distance between the center and the intersection point of the center line and the fitting curve as the curvature radius to make a curvature circle, obtaining the position abnormality degree of each tooth according to the curvature circle and the inclination angle, and judging whether the tooth needs to be corrected according to the inclination angle and the position abnormality degree, which provides good assistance for tooth correction.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of image processing, in particular to a tooth correction auxiliary method based on dental film processing. BACKGROUND

[0002] Misaligned teeth can affect the appearance, function and health of teeth. Tooth correction is to align the teeth properly by using appliances, which can exert mechanical force to move the teeth to the normal position. In the process of tooth correction, a tooth correction appliance needs to be worn to correct the teeth. In the current tooth correction process, whether the teeth need to be corrected is determined, and the position of the bracket of the tooth correction appliance is mostly selected by the experience of the doctor, and the position of the bracket needs to be corrected regularly in the hospital.

[0003] The present application calculates the inclination degree and position abnormality degree of teeth by using image processing technology, and determines whether each tooth needs to be corrected according to the inclination angle and position abnormality degree of each tooth, thereby providing an auxiliary function for tooth correction. SUMMARY

[0004] The present application provides a tooth correction auxiliary method based on dental film processing, which solves the problem of inaccurate determination of whether the teeth need to be corrected, and adopts the following technical scheme:

[0005] Collecting an oral tooth X-ray image;

[0006] Detecting the edge profile of each tooth in the collected oral tooth X-ray image by using a Canny algorithm;

[0007] Taking the center of the minimum circumscribed rectangle of the edge profile of each tooth as the center point of the tooth, and taking the area of the minimum circumscribed rectangle as the surface area of the tooth;

[0008] Selecting a sliding window of different sizes according to the surface area of each tooth in the oral tooth X-ray image;

[0009] Sliding the sliding window from top to bottom for each tooth, and obtaining the boundary line between the gum and the enamel of each tooth according to the gray scale change of the pixel points in the sliding window, and taking the midpoint of the boundary line as the boundary point between the gum and the enamel of each tooth;

[0010] Obtaining a fitting curve of the boundary points between the gum and the enamel of all teeth;

[0011] Taking the straight line passing through the center point of each tooth and the boundary point between the gum and the enamel as the center line of each tooth;

[0012] Taking the intersection point of the center line of each tooth and the fitting curve as the tangent point to draw the tangent line of the fitting curve, and taking the normal line of the tangent line as the normal line of each tooth;

[0013] obtaining the tilt angle of each tooth according to the included angle between the center line and the normal line of each tooth;

[0014] drawing a curvature circle of the fitting curve with the center point of each tooth as the center and the distance between the center and the intersection of the center line and the fitting curve as the radius of curvature;

[0015] obtaining the position abnormality degree of each tooth according to the curvature circle and the tilt angle;

[0016] judging whether the tooth needs to be corrected according to the tilt angle and the position abnormality degree of each tooth.

[0017] The method for selecting the sliding window of different sizes is as follows:

[0018] calculating the mean value of the surface area of all teeth;

[0019] for the tooth with the surface area greater than or equal to the mean value of the surface area, the selected sliding window size is 5*5;

[0020] for the tooth with the surface area less than the mean value of the surface area, the selected sliding window size is 3*3.

[0021] The method for calculating the included angle between the center line and the normal line of each tooth is as follows:

[0022] obtaining the vector in the direction of the center line and the normal line of each tooth and

[0023] then the included angle between the center line and the normal line of each tooth is:

[0024] The method for obtaining the position abnormality degree of each tooth is as follows:

[0025]

[0026] wherein, Φ is the abnormality degree of each tooth, and K is the curvature of the curvature circle.

[0027] The method for judging whether the tooth needs to be corrected is as follows:

[0028] comparing the tilt angle and the position abnormality degree of the tooth with the tilt angle threshold and the position abnormality degree threshold respectively, if the tilt angle of the tooth is greater than the tilt angle threshold or the position abnormality degree of the tooth is greater than the position abnormality degree threshold, the tooth needs to be corrected.

[0029] The beneficial effect of the present application is that: based on image processing, the oral X-ray image of teeth is collected, the sliding window is selected according to the surface area of each tooth, the demarcation point of the gum and the enamel of each tooth is obtained according to the gray scale change in the sliding window, the fitting curve is obtained by acquiring the demarcation point, the straight line passing through the center point of each tooth and the demarcation point of the gum and the enamel intersects with the fitting curve at a point, the straight line passing through the center point and the intersection point is taken as the center line of each tooth, the normal line of the tangent of the fitting curve passing through the intersection point is taken as the normal line of each tooth, the tooth inclination degree is obtained according to the included angle of the center line and the normal line of each tooth, the curvature circle is made with the distance between the center point of each tooth and the intersection point of the center line and the fitting curve as the radius of curvature, and the position abnormality degree of each tooth is obtained according to the curvature circle and the inclination angle, so that whether the tooth needs to be corrected is judged according to the inclination angle and the position abnormality degree, and a good auxiliary effect is provided for tooth correction. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0031] Figure 1 It is a kind of based on dental film processing's tooth correction auxiliary method flow chart of the present application;

[0032] Figure 2 It is a kind of oral X-ray picture in the tooth correction auxiliary method based on dental film processing of the present application;

[0033] Figure 3 It is the midline, normal line of tooth in the tooth correction auxiliary method based on dental film processing of the present application;

[0034] Figure 4 It is the midline, normal line vector included angle coordinate system in the tooth correction auxiliary method based on dental film processing of the present application. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be described clearly and completely in the following with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0036] An embodiment of the tooth correction auxiliary method based on dental film processing of the present application is as follows: Figure 1As shown, including:

[0037] Step one: collect oral X-ray images of teeth;

[0038] The purpose of this step is to obtain X-ray images of oral teeth.

[0039] Wherein, the oral X-ray image of the teeth is very important for orthodontic treatment, which directly affects the judgment of orthodontic treatment. When collecting X-ray film of teeth, full mouth curved tomography film needs to be taken, the patient needs to stand, the upper and lower teeth are naturally separated, and the ball tube rotates 360 degrees around the patient to expose. When taking cephalometric film, the patient needs to take a squatting position, the upper and lower jaws are in rest jaw position, the ball tube is exposed to the front area of the tragus and the zygomatic part, and the oral X-ray image of the teeth is as shown in Figure 2 .

[0040] Step two: use the Canny algorithm to detect the edge profile of each tooth in the oral X-ray image of the teeth; the center of the smallest circumscribed rectangle of the edge profile of each tooth is taken as the center point of the tooth, and the area of the smallest circumscribed rectangle is taken as the surface area of the tooth; different sizes of sliding windows are selected according to the size of the surface area of each tooth in the oral X-ray image of the teeth; the sliding window is used to slide from top to bottom for each tooth, and the midpoint of the dividing line between the gum and the enamel of each tooth is obtained according to the gray scale change of the pixel points in the sliding window, and the midpoint of the dividing line is taken as the dividing point between the gum and the enamel of each tooth;

[0041] The purpose of this step is to accurately calculate the correction point and the best correction position of the teeth. Image processing needs to be performed on the taken X-ray film of the teeth, the gum and the enamel of the teeth are separated through image processing technology, the center position of the enamel is calculated, which is the best position for placing the corrector, and the correction effect of the teeth is good.

[0042] It should be noted that the taken X-ray photo of the teeth is a gray scale image, and the gum and the enamel of the teeth can be separated by the gray scale change of the image. Because there is a gray scale change between the images of the gum and the enamel, the gray scale value of the enamel and the gum is smaller and easier to identify, while the gray scale value of the dividing line part is large, so the sliding window technology is used for detection, the enamel and the gum are separated according to the gray scale change, and the appropriate correction position is selected.

[0043] The different sizes of the sliding window are selected for finding the gray scale change area of the gum and the tooth enamel, and the sliding window is searched based on the category of the single pixel point according to the application, but the size of the change area is uncertain, so the size of the corresponding sliding window is also uncertain. In order to find the window size that can find the distribution area of the gum and the tooth enamel boundary, the application first uses a small window to slide, measures whether the window size can find the distribution area of the gum and the tooth enamel boundary, if not, the window size is increased, and the measurement is re-measured until the optimal window size is found.

[0044] In order to measure the difference of the gray scale value in the window area, the area is set to be composed of m 2 windows in the form of m*m, the difference of the gray scale value between the windows in the area is measured to determine the boundary between the gum and the tooth enamel in the area, in order to adapt to the different sizes of the teeth, the size of the appropriate sliding window is selected, the surface area of each tooth is calculated according to the X-ray photo of the tooth, and the appropriate window is selected according to the size of the surface area.

[0045] The different sizes of the window are selected according to the surface area of the tooth as follows:

[0046] (1) The edge of each tooth is separated by using the DNN neural network, and the edge contour of the tooth is detected by using the canny algorithm;

[0047] (2) The minimum circumscribed rectangle area of the edge contour of each tooth is taken as the surface area of each tooth: since the surface area of each tooth is calculated, the surface area of the tooth X-ray photo is an irregular figure, and it is difficult to calculate the surface area, so the surface area of the minimum circumscribed rectangle of the tooth is calculated to measure the surface area of the tooth, so that the size of the sliding window is determined according to the area of the minimum circumscribed rectangle of the tooth, and the minimum circumscribed rectangle of the contour of each tooth is drawn in the embodiment, and the two straight edges of the rectangle are taken as the x-axis and y-axis of the coordinate system. Assuming that the coordinates of the rectangle point not on the coordinate axis are (a, b), the area S of the rectangle is:

[0048] S=a*b

[0049] The area of the rectangle is used to represent the surface area of the tooth, and the size of the sliding window is selected according to the surface area of the tooth. The larger the area is, the larger the size of the corresponding sliding window is. According to the X-ray film of the tooth, the area of the slot tooth is the largest, and the areas of other teeth are similar.

[0050] (3) The average of the surface areas of all teeth is calculated

[0051]

[0052] In the formula, n is the total number of n teeth, and the area of each tooth is S1, S2, …, Sn.n .

[0053] (4) According to The size of the sliding window is divided into two types:

[0054] When the tooth surface area (the area of the minimum circumscribed rectangle) is greater than , the size of the sliding window is 5*5 sliding window for detection;

[0055] When the tooth surface area (the area of the minimum circumscribed rectangle) is less than , the size of the sliding window is 3*3 sliding window for detection, that is:

[0056]

[0057] In the formula, δ is the size of the sliding window, and S is the tooth surface area.

[0058] The method for obtaining the junction point of the gum and the enamel of each tooth is as follows:

[0059] According to the sliding window principle, a window with a size of δ is used to start from the lower teeth and slide through each tooth for detection in a top-to-bottom direction. According to the pixel change of the window, the junction line of the gum and the enamel of each tooth is obtained, and the midpoint of the junction line is taken as the junction point of the gum and the enamel.

[0060] Step three: Obtain the fitting curve of the junction points of the gum and the enamel of all teeth; take the straight line passing through the center point of each tooth and the junction point of the gum and the enamel as the center line of each tooth; take the intersection point of the center line of each tooth and the fitting curve as the tangent point to draw the tangent line of the fitting curve, and take the normal line of the tangent line as the normal line of each tooth.

[0061] The purpose of this step is to obtain the center line and the normal line of each tooth.

[0062] It should be noted that this embodiment is based on the position of the detected junction point of each tooth to find the fitting curve of all points by using the Bezier curve principle.

[0063] The method for obtaining the center line of each tooth is as follows: take the straight line passing through the center point of each tooth and the junction point of the gum and the enamel as the center line of each tooth.

[0064] The method for obtaining the normal line of each tooth is as follows: extend the intersection of the center line of each tooth and the fitting curve, draw the tangent line of the fitting curve with the intersection point as the tangent point, draw the normal line of the tangent line through the intersection point, and take it as the normal line of each tooth.

[0065] As Figure 3The outer rectangle, the outer circle (curvature circle), the center point, the demarcation point (gingival and enamel), the Bezier curve (fitting curve), the center line, the normal line, and the tangent line of the tooth are shown.

[0066] Step four: obtaining the inclination angle of each tooth according to the included angle of the center line and the normal line of each tooth;

[0067] The purpose of this step is to obtain the included angle of the center line and the normal line of each tooth, and take the angle as the inclination angle of each tooth.

[0068] The method for obtaining the included angle of the center line and the normal line of each tooth is as follows:

[0069] The included angle θ of the normal line and the center line is obtained, the center point of the tooth is taken as the origin, the center line is taken as the y-axis direction, the normal line is shifted to the position of the origin, and the included angle can be calculated according to two vectors, as shown in the following formula: Figure 4 The included angle θ of the normal line and the center line can be calculated according to two vectors, as shown in the following formula:

[0070]

[0071] In the formula, and are the vectors in the direction of the tooth normal line and the center line, respectively.

[0072] Step five: taking the center point of each tooth as the center, taking the distance between the center and the intersection point of the center line and the fitting curve as the radius of curvature, and making the curvature circle of the fitting curve; obtaining the position abnormality degree of each tooth according to the curvature circle and the inclination angle;

[0073] The purpose of this step is to determine whether the tooth position is abnormal according to the curvature circle and the inclination angle of the tooth. The greater the radius of the curvature circle, the farther the tooth position is from the fitting curve, and the greater the abnormality degree.

[0074] It should be noted that the tooth may not only have inclination abnormalities but also have position abnormalities, such as left-right and up-down shifts.

[0075] The method for obtaining the position abnormality degree is as follows:

[0076] The abnormality degree of the tooth is calculated according to the curvature of the curvature circle of the fitting curve of the demarcation point of the tooth gingiva and enamel, and the specific method is as follows:

[0077] (1) Taking the center point of each tooth as the center, taking the distance between the center point and the intersection point of the center line and the fitting curve as the radius of curvature, and making the curvature circle of the fitting curve, as shown in the following formula: Figure 3 The outer circle is the curvature circle of the fitting curve;

[0078] (2) According to the curvature of the curvature circle, the curvature radius R is inversely proportional to the curvature K:

[0079]

[0080] If the curvature is greater, the curvature radius of the circle is smaller, the distance between the points on the fitting curve and the center point of the tooth is closer, the tooth is in the normal curve range, and the tooth does not need to be corrected. On the contrary, if the curvature is smaller, the curvature radius of the circle is larger, the distance between the points on the fitting curve and the center point of the tooth is farther, the tooth is not in the normal curve range, and the tooth needs to be corrected.

[0081] (3) According to the change of the inclination angle and the curvature radius of the tooth, the abnormal degree of the tooth is obtained:

[0082]

[0083] In the formula, Φ is the abnormal degree of each tooth, and K is the curvature of the curvature circle.

[0084] Step six: judging whether the tooth needs to be corrected according to the inclination angle and the position abnormal degree of each tooth.

[0085] The purpose of this step is to judge whether the tooth needs to be corrected.

[0086] The method for judging whether the tooth needs to be corrected is:

[0087] The inclination angle and the position abnormal degree of the tooth are compared with the inclination angle threshold and the position abnormal degree threshold respectively, if the inclination angle of the tooth is greater than the inclination angle threshold or the position abnormal degree is greater than the position abnormal degree threshold, the tooth needs to be corrected.

[0088] In this embodiment, the inclination angle threshold is 10 degrees, and the position abnormal degree threshold is 0.03.

[0089] Further, for the tooth that needs to be corrected, the position of the appropriate correction point is selected, and the bracket is fixed at the appropriate correction point position to change the stress point of the tooth, thereby assisting the tooth correction.

[0090] The above only describes the preferred embodiments of the present application and is not used to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A tooth correction auxiliary method based on dental film processing, characterized in that: include: Collect oral dental X-ray images; Use the Canny algorithm to detect the edge contour of each tooth in the oral dental X-ray image; The center of the minimum circumscribed rectangle of the edge contour of each tooth is taken as the center point of the tooth, and the area of ​​the minimum circumscribed rectangle is taken as the surface area of ​​the tooth; Select sliding windows of different sizes according to the surface area of ​​each tooth in the oral dental X-ray image; Use a sliding window to slide each tooth from top to bottom, and obtain the boundary line between the gum and enamel of each tooth based on the grayscale change of the pixel points in the sliding window. The midpoint of the boundary line is used as the boundary point between the gum and enamel of each tooth; Obtain fitting curves of the gingiva-enamel boundary points for all teeth; The straight line passing through the center point of each tooth and the dividing point between the gum and the enamel is taken as the center line of each tooth; The intersection point of each tooth centerline and the fitting curve is used as the tangent point to draw the tangent line of the fitting curve, and the normal line of the tangent line is used as the normal line of each tooth; The inclination angle of each tooth is obtained according to the angle between the center line of each tooth and the normal line; With the center point of each tooth as the center of the circle and the distance from the center of the circle to the intersection of the center line and the fitting curve as the curvature radius, a curvature circle of the fitting curve is drawn; The degree of positional abnormality of each tooth is obtained based on the curvature circle and inclination angle; The method for obtaining the degree of positional abnormality of each tooth is as follows: Where Φ is the degree of abnormality of each tooth, K is the curvature of the curvature circle, and θ is the angle between the center line and the normal line of each tooth; The degree of abnormality in the inclination angle and position of each tooth is used to determine whether the tooth needs correction.

2. The tooth correction auxiliary method based on dental film processing according to claim 1, characterized in that: The method for selecting sliding windows of different sizes is: Calculate the mean surface area of ​​all teeth; For teeth with a surface area greater than or equal to the mean surface area, the sliding window size was selected as 5 × 5; For teeth with a surface area smaller than the mean surface area, the sliding window size was selected as 3 × 3.

3. The tooth correction auxiliary method based on dental film processing according to claim 1, characterized in that: The method for calculating the angle between the center line and the normal line of each tooth is: Get the vectors in the centerline and normal directions of each tooth and Then the angle between the center line and the normal line of each tooth is:

4. The tooth correction auxiliary method based on dental film processing according to claim 1, characterized in that: The method for determining whether teeth need correction is: The inclination angle and position abnormality of the tooth are compared with the inclination angle threshold and the position abnormality threshold respectively. If the inclination angle of the tooth is greater than the inclination angle threshold or the position abnormality of the tooth is greater than the position abnormality threshold, the tooth needs to be corrected.

Images