CN108472108B - System and method for acquiring intraoral digitized impressions - Google Patents
System and method for acquiring intraoral digitized impressions Download PDFInfo
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- CN108472108B CN108472108B CN201780004253.8A CN201780004253A CN108472108B CN 108472108 B CN108472108 B CN 108472108B CN 201780004253 A CN201780004253 A CN 201780004253A CN 108472108 B CN108472108 B CN 108472108B
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- A61C9/00—Impression cups, i.e. impression trays; Impression methods
- A61C9/004—Means or methods for taking digitized impressions
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- A—HUMAN NECESSITIES
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- A61C9/00—Impression cups, i.e. impression trays; Impression methods
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- A61C9/008—Mechanical means or methods, e.g. a contact probe moving over the teeth
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Abstract
An intraoral digital impression system, comprising: an intraoral impression scanner (5) and an intraoral scanning guide plate; the intraoral scanning guide plate comprises a fixing device (3) and a rigid guide plate (1), wherein the rigid guide plate (1) is provided with a scanning guide surface, and a guide mark is arranged on the scanning guide surface; the fixing device (3) has a connecting element for connecting the inner structure of the mouth for fixing the rigid guide plate (1) in the mouth. The method can acquire the data of the intraoral impression without accumulated measurement errors, meet the requirements of subsequent design and processing and improve the precision of the intraoral digital impression.
Description
Technical Field
The present invention relates to the field of oral hygiene, in particular dental restorative manufacture, and more particularly to a system and method for taking an intraoral digitized impression.
Background
At present, the technical route for obtaining a three-dimensional digital model (or called an intraoral digital impression) of the inside of the oral cavity by three-dimensional scanning mainly includes two types of extraoral scanning and intraoral scanning.
There are two main methods for extraoral scanning: scanning the copied plaster male mold and scanning the silica gel impression. The method of scanning the plaster male die requires a doctor to firstly obtain a silica gel impression (female die) of the dentition of a patient, then pour gypsum and other materials into the silica gel impression to obtain the plaster male die of the dentition, and finally scan the male die through a three-dimensional scanning device to obtain the digital impression of the dentition. The method for scanning the silica gel impression directly scans the silica gel impression of the dentition of a patient through a three-dimensional scanning device without copying a plaster male mold, thereby simplifying the operation process of a doctor. The advantages of extraoral scanning are: the plaster male mold or the silica gel impression model can be fixed on the base during scanning, the three-dimensional data obtained in the multiple scanning processes are ensured to be in the same coordinate system, and the digital model of dentition is convenient to fuse and reconstruct. The disadvantages of extraoral scanning are: the process of manufacturing the plaster male die is complex, and a doctor needs to spend a long time; although the procedure of scanning the silicone impression is simple, when a narrow portion deep in the impression is scanned, the data of the area is easily lost because the data cannot be observed by the device.
Intraoral scanning generally employs a handheld three-dimensional scanning device to directly scan the oral cavity of a patient to obtain a three-dimensional digital model of the dentition of the patient without obtaining a silicone impression of the dentition of the patient. Intraoral scanning techniques have been developed for nearly 30 years, during which time commercial digital impression systems have been introduced that employ intraoral scanning techniques, such as the CEREC system of the company Cenocord, the TRIOS system of the company 3Shape, and the Lava (TM) C.O.S., iTero, E4D, among others.
However, intraoral scanning is different from extraoral scanning, and during operation, the scanning device is in a motion state in the mouth of a patient, and a scanning coordinate system is constantly changed, which affects real-time synthesis of a dentition three-dimensional model, so that an ICP (Iterative Closest Point) algorithm is mostly adopted to synthesize the three-dimensional model. The ICP algorithm is realized by the following steps: determining all matching points in every two adjacent point cloud data; according to all the matching points, performing iterative calculation on the defined target function to obtain attitude transformation parameters between two adjacent frames of point cloud data; and accumulating the point cloud data according to the attitude transformation parameters to obtain target registration point cloud data. When every two adjacent point cloud data are registered, an unobvious registration error may occur, but for a point cloud sequence obtained by intraoral scanning, because the point cloud sequence contains a plurality of point cloud data, when the point cloud data are successively registered and fused by using an ICP (inductively coupled plasma) algorithm, the registration error is accumulated and amplified to form a so-called accumulated error, so that the registration result is inaccurate. Experiments show that when the scanning range exceeds four teeth, the accumulated errors can bring great influence; when the scan range reaches the full range of teeth, the accumulated error will make the scan accuracy less than the requirement for subsequent design and processing of certain dental preparations.
In summary, when more than three dental bridges and/or dentitions and other complex restorations are manufactured, a high-precision intraoral scanning system and method are still needed.
Disclosure of Invention
In order to solve the above problems, the present invention provides an intraoral digital impression system, comprising: an intraoral impression scanner and an intraoral scanning guide plate; the intraoral scanning guide plate comprises a fixing device and a rigid guide plate, wherein the rigid guide plate is provided with a scanning guide surface, and a guide mark is arranged on the scanning guide surface; the fixture has a connector to an intraoral structure for securing the rigid guide within the intraoral cavity.
According to one aspect of the invention, an intraoral scanning guide plate is also provided.
According to one aspect of the invention, a method of obtaining an intraoral digitized impression is also provided.
According to one aspect of the invention, a method of acquiring dentition point cloud data is also provided.
According to an aspect of the invention, there is also provided a computer program for acquiring dentition point cloud data.
According to an aspect of the invention, a computing device for acquiring dentition point cloud data is also provided.
The system and the method of the invention have no accumulated error, effectively improve the precision of the intraoral digital impression and can meet the subsequent design and processing requirements on the dental prosthesis.
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FIG. 1 is a schematic view of a system for taking an intraoral digitized impression according to one aspect of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings. This description is made by way of example and not limitation to specific embodiments consistent with the principles of the invention, the description being in sufficient detail to enable those skilled in the art to practice the invention, other embodiments may be utilized and the structure of various elements may be changed and/or substituted without departing from the scope and spirit of the invention. The following detailed description is, therefore, not to be taken in a limiting sense.
In some embodiments of the invention:
the specific extraction method of the ISS key points refers to the prior art 1: zhong, y. (2009). Intrinsic shape signatures: a shape descriptor for 3D object recognition. in Proc. int. conf. on computer vision works (pp.1-8).
The specific calculation process of the SHOT characterization refers to prior art 2: tombari, f., salt, s, & Di Stefano, L. (2010), Unique signatures of histories for local surface description in proc, europ, conf.on computer vision (ECCV) (pp.356-369). Springer.
The initial transformation relation of local point cloud data to an auxiliary scanning device model is calculated by using a RANSAC algorithm, and the prior art 3 is referred to: fish sample consensus m.a. random sample consensus: a parallel for model fixing with applications to imaging and automated graphics, Commun. ACM 24, 6, 1981, 381-395).
The ICP algorithm is used to calculate the exact transformation relationship of the local point cloud data to the auxiliary scanning device model with reference to prior art 4: zhang. interactive point matching for registration of front curves and surfaces. int. j. compact. vision, 13, 2: 119-152, 1994.
The above prior art 1-4 is incorporated by reference in its entirety in the present invention.
According to a first aspect of the present invention, as shown in fig. 1, there is provided an intraoral digital impression system comprising an intraoral impression scanner (5) and an intraoral scanning guide. Intraoral impression scanners are typically implemented as hand-held three-dimensional scanning devices, but those skilled in the art will appreciate that any scanner capable of performing intraoral impression scanning can be considered an intraoral impression scanner of the present invention.
The intraoral scanning guide plate comprises a fixing device (3) and a rigid guide plate (1). The rigid guide plate has a scan guide surface with guide marks (not shown) provided thereon. The fixture has a connector to connect to the internal structure of the mouth for securing the rigid guide within the mouth. When the rigid guide plate is fixed in the oral cavity, at least the surface of the rigid guide plate which can be photographed by the intraoral impression scanner and is adjacent to the oral cavity area to be measured is used as a scanning guide surface, and the guide marks are distributed on at least the part of the scanning guide surface, which is close to the oral cavity area to be measured.
The meaning of the oral area to be measured in the present invention includes teeth and/or gums. Further, the meaning of "oral area to be measured", "teeth" and "gums" in the present invention is universal within the scope understood by those skilled in the art.
The guide plate is rigid, so that an accurate digital model related to the guide mark can be obtained in advance, and deformation is not generated in intraoral scanning.
The side of the rigid guide plate adjacent to the mouth area to be tested has a profile matching the mouth area to be tested so that the rigid guide plate fits the mouth area to be tested, for example, the rigid guide plate is bent along the lingual profile of the dentition and adjacent to the lingual profile of the dentition. Preferably, the side of the rigid guide plate adjacent the teeth is arch shaped so that the rigid guide plate fits as closely as possible to the teeth and/or gums, but it is not necessarily mandatory that the rigid guide plate fit closely to the teeth and/or gums. In addition, the side of the rigid guide plate away from the teeth has no requirement on shape. The rigid guide plate can be arranged on the outer side surface of the tooth, the tongue side surface or both sides.
The length of the rigid guide plate is at least approximately equal to the length of a dentition (2) formed by three or more continuous teeth at any position of the dental arch, so that the rigid guide plate is suitable for eliminating accumulated errors when manufacturing a dental bridge and/or dentition and other complex restorations comprising more than three teeth. Preferably, the rigid guide is an all-mouth guide, the length of which is approximately equal to the length of the dentition formed by all the teeth comprising the upper jaw or the lower jaw. Preferably, the rigid guide is a half-mouth guide, and the length of the half-mouth guide is approximately equal to the length of the dentition formed by the half teeth of the upper jaw or the lower jaw (e.g., the left half teeth, the right half teeth, the teeth extending to the left and right at the upper and lower incisors on the front side). It will be understood by those skilled in the art that a full or half mouth guide is not a limitation on the length of the guide in the sense of "centimeters" or "inches" because a child's full mouth guide may also be smaller in length than an adult's half mouth guide. Typically, a full-mouth guide is used for a full-mouth scan scenario and a half-mouth guide is used for a bridge/abutment scenario. It will be appreciated by those skilled in the art that the full mouth guide may also be used in a dental bridge/abutment scenario.
Preferably, the entire surface of the rigid guide plate is used as the scanning guide surface. More preferably, the guide marks are distributed over the scan guide surface. In some cases, the guide marks on the scan guide surface are substantially parallel to the proximate measured oral area.
The guide mark may be a continuous or discontinuous three-dimensional pattern, and the guide mark has the same or different patterns at different positions on the scan guide surface. The three-dimensional pattern may be a wave or any other suitable shape. Preferably, the guide mark is a continuous three-dimensional pattern, such that a portion of the guide mark can be scanned by the intraoral impression scanner at any time during the scanning process. Preferably, the guide marker has a different pattern at different positions of the scan guide surface, so that the intra-oral impression scanner obtains different local scan data of the guide marker in each scanning unit, thereby eliminating the need for a "decapsulation" operation.
The scan guide surface is generally at an obtuse angle of more than 90 degrees to the tooth surface. Preferably, the scan guide surface is substantially parallel to the surface of the oral area being measured (e.g., the dental surface) so that the intraoral impression scanner can more easily obtain scan data of the teeth (gums) and/or guide marks.
The fixing device is connected with the rigid guide plate. In one embodiment, the fixing device is integrally formed with the rigid guide plate to save manufacturing cost. In another embodiment, the fixture is removably attached to the rigid guide plate to ensure that the fixture can be installed over "good teeth" and avoid the fixture being positioned just over "bad teeth" when integrally formed.
Preferably, the securing means is adapted to secure the rigid guide plate to the upper and lower jaws, molars or incisors. For example, the fixation device is a clamp adapted for use in the mouth.
According to a second aspect of the present invention, there is provided a method of acquiring an intraoral digitized impression, preferably, a method of acquiring an intraoral digitized impression using an intraoral digitized impression system provided according to the first aspect of the present invention. The method comprises the following steps:
and S100, respectively obtaining point cloud data of the first dentition and the second dentition according to the first guide mark and the second guide mark. The first dentition is an intraoral maxillary dentition and the second dentition is an intraoral mandibular dentition, or the first dentition is a mandibular dentition and the second dentition is a maxillary dentition.
S200, point cloud data of occlusal surfaces of the first dentition and the second dentition are obtained.
S300, obtaining intraoral three-dimensional digital impression data according to the point cloud data of the first dentition, the point cloud data of the second dentition and the point cloud data of the occlusal surface.
The first guide flag and the second guide flag are the same guide flag or different guide flags.
Specifically, the method for obtaining the point cloud data of the dentition in step S100 includes the following steps:
and S110, installing a guide mark in the oral cavity.
S120, scanning dentition and a guide sign to obtain first point cloud data, wherein the first point cloud data is point cloud data comprising the dentition and the guide sign; the first point cloud data includes a plurality of point cloud data of dentition and guide signs, wherein each point cloud data of dentition and guide signs corresponds to a part of dentition and guide signs.
And S130, removing the guide mark from the oral cavity.
S140, scanning dentition, and obtaining second point cloud data according to the result of scanning the dentition and the first point cloud data, wherein the second point cloud data is the point cloud data of the dentition; the second point cloud data includes a plurality of point cloud data of dentition, wherein each point cloud data of dentition corresponds to a local portion of dentition.
Further, the method for obtaining the point cloud data of the first dentition and the second dentition in steps S110-S140 is mainly implemented according to the third aspect of the present invention.
According to a third aspect of the present invention, there is provided a method of acquiring dentition point cloud data using an intraoral digital impression system, preferably an intraoral digital impression system provided according to the first aspect of the present invention, the method comprising the steps of:
and S1000, obtaining first point cloud data according to the pre-stored point cloud data and the first scanning data. The pre-stored point cloud data is point cloud data of a guide mark, the first scanning data is point cloud data obtained by scanning dentition and the guide mark, and the first point cloud data is point cloud data comprising the dentition and the guide mark. Preferably, the pre-stored point cloud data is point cloud data obtained in advance from a model of the guide mark, for example, point cloud data obtained from a CAD (computer aided design) model of the guide mark, and further, for example, point cloud data obtained by scanning a model of the guide mark prepared in advance. Preferably, the first scan data is point cloud data obtained by real-time scanning of the dentition and the guide mark mounted on the intraoral scan guide by the intraoral impression scanner. Since the intraoral impression scanner can scan only a limited part of the mouth at a time and can obtain only the point cloud data of the limited part (i.e. equivalent to only a part of the first scan data corresponding to the limited part at a time and the complete first scan data can be obtained after a plurality of scans), the first point cloud data includes a plurality of point cloud data of the dentition and the guidance sign, wherein each point cloud data of the dentition and the guidance sign (i.e. equivalent to the point cloud data obtained from the pre-stored point cloud data and the aforementioned part of the first scan data) corresponds to one part of the dentition and the guidance sign.
S1100, second point cloud data are obtained according to the first point cloud data and the second scanning data. The second point cloud data is dentition point cloud data, and the second scanning data is point cloud data obtained by scanning dentition. Preferably, the intraoral scan guide has been removed from the mouth when the second scan data is acquired. Since the intraoral impression scanner can only scan a limited part of the mouth at a time and can only obtain point cloud data of the limited part (that is, only partial second scan data corresponding to the limited part can be obtained at a time, and complete second scan data can be obtained after a plurality of scans), the second point cloud data also includes a plurality of point cloud data of the dentition, wherein each point cloud data of the dentition (that is, point cloud data obtained according to the first point cloud data and the partial second scan data) corresponds to one part of the dentition.
Each point cloud data of the dentition and the guide mark obtained in the step S1000 includes:
s1005, obtaining the local point cloud data of the dentition and the guide sign, and extracting a first characteristic key point, wherein the first characteristic key point is the characteristic key point of the local point cloud data of the dentition and the guide sign.
And S1010, obtaining an initial coordinate transformation relation between the local point cloud data and the pre-stored point cloud data according to the feature key points and the first feature key points of the pre-stored point cloud data.
And S1020, performing coordinate transformation on the local point cloud data according to the initial coordinate transformation relation to complete initial registration of the local point cloud data.
And S1030, calculating the accurate transformation relation from the initially registered local point cloud data to the pre-stored point cloud.
And S1040, performing coordinate transformation on the initially registered local point cloud data according to the accurate coordinate transformation relation, completing registration of the local point cloud data, and obtaining point cloud data corresponding to local dentition and guide marks.
Obviously, by performing the initial registration of step S1020 and the registration of step S1040 on the "local point cloud data of dentition and guide mark" (i.e., corresponding to part of the first scan data) obtained in step S1005, point cloud data (i.e., corresponding to part of the first point cloud data) corresponding to the local dentition and guide mark can be obtained. By performing two registrations of steps S1020 and S1040 on each partial first scan data obtained by intraoral impression scanner scanning, complete first point cloud data can be obtained.
Preferably, the feature key points and the first feature key points of the pre-stored point cloud data are ISS key points. Preferably, the accurate transformation relation from the initially registered local point cloud data to the pre-stored point cloud is obtained by calculation according to an ICP algorithm.
The step S1010 of obtaining an initial coordinate transformation relationship between the local point cloud data and the pre-stored point cloud data further includes:
s1012, obtaining a first SHOT feature descriptor, where the first SHOT feature descriptor is a SHOT feature descriptor corresponding to the first ISS key point.
S1014, obtaining the best matching based on the SHOT feature descriptor in the ISS key points and the first ISS key points of the pre-stored point cloud data based on the first SHOT feature descriptor and the SHOT feature descriptor of the pre-stored point cloud data, and forming the matching point pairs of the pre-stored point cloud data and the local point cloud data of dentition and guide marks; and the SHOT feature descriptor of the pre-stored point cloud data is obtained by calculation according to ISS key points of the pre-stored point cloud data.
And S1016, calculating an initial transformation relation from the local point cloud data of the dentition and the guide mark to pre-stored point cloud data by using a RANSAC algorithm according to the matching point pairs.
In step S1100, each point cloud data of dentition is obtained, which further includes:
s1110, obtaining local point cloud data of dentition, and extracting second characteristic key points, wherein the second characteristic key points are characteristic key points of the dentition local point cloud data.
And S1120, obtaining an initial coordinate transformation relation between the dentition local point cloud data and the first point cloud data according to the feature key points and the second feature key points of the first point cloud data, and performing coordinate transformation on the dentition local point cloud data to complete initial registration of the dentition local point cloud data.
S1130, calculating an accurate transformation relation from the dentition local point cloud data after initial registration to the first point cloud data.
And S1140, performing coordinate transformation on the dentition local point cloud data after initial registration according to the accurate coordinate transformation relation, and finishing registration of the dentition local point cloud data to obtain point cloud data corresponding to local dentition.
Obviously, by performing the initial registration of step S1120 and the registration of step S1140 on the "local point cloud data of dentition" (i.e., corresponding to part of the second scan data) obtained in step S1110, point cloud data corresponding to local dentition (i.e., corresponding to part of the second point cloud data) can be obtained. The complete second point cloud data can be obtained by performing two registrations of steps S1020 and S1040 on each partial second scan data obtained by the intraoral impression scanner scan.
Preferably, the feature key points and the second feature key points of the first point cloud data are ISS key points. Preferably, the accurate transformation relation from the initially registered dentition local point cloud data to the first point cloud data is obtained by calculation according to an ICP algorithm.
The obtaining of the initial coordinate transformation relationship between the dentition local point cloud data and the first point cloud data in step S1120 further includes:
and S1122, obtaining a second SHOT feature descriptor, wherein the second SHOT feature descriptor is a SHOT feature descriptor corresponding to the second ISS key point.
S1124, obtaining the best matching based on the SHOT feature descriptor in the ISS key points and the second ISS key points of the first point cloud data based on the second SHOT feature descriptor and the SHOT feature descriptor of the first point cloud data, and forming matching point pairs of the first point cloud data and the dentition local point cloud data; and the SHOT feature descriptor of the first point cloud data is obtained by calculation according to the ISS key points of the first point cloud data.
S1126, calculating an initial transformation relation from local point cloud data of the dentition to first point cloud data by using a RANSAC algorithm according to the matching point pairs.
In the present invention, the ISS keypoint, the SHOT feature descriptor, the RANSAC algorithm, and the ICP algorithm are the preferred technical solutions used in the present invention, and those skilled in the art may also use other keypoints, feature descriptors, and algorithms already existing in the prior art to implement corresponding functions, and those skilled in the art may also use various improvements or modifications of the ISS keypoint, the SHOT feature descriptor, the RANSAC algorithm, and the ICP algorithm already existing in the prior art to implement corresponding functions. Obviously, the technical solutions formed by such variations still fall within the scope of the present invention.
According to a fourth aspect of the present invention, there is provided a computer program for implementing the above-described acquisition of dentition point cloud data using an intraoral digital impression system. According to a fifth aspect of the present invention, there is provided a computer readable storage medium having stored thereon a computer program for implementing the above-described acquisition of dentition point cloud data using an intraoral digital impression system. According to a sixth aspect of the invention, there is provided a computing device comprising a processor capable of executing the above-described computer program for acquiring dentition point cloud data. Preferably, the computing device further comprises the computer-readable storage medium described above, in which is stored a computer program for implementing the above-described acquisition of dentition point cloud data using an intraoral digital impression system.
According to a seventh aspect of the present invention, there is provided a system for taking an intraoral digitized impression, comprising: intraoral scanning guide plates, intraoral impression scanners, computing devices. Wherein the intraoral impression scanner and the computing device are electrically connected. Preferably, the electrical connection is a wired connection or a wireless connection.
Wherein the intraoral impression scanner obtains first scan data over a first time and transmits the first scan data to the computing device. The intraoral impression scanner obtains second scan data at a second time and transmits the second scan data to the computing device. The first scanning data is point cloud data obtained by scanning dentition and a guide mark; the second scanning data is point cloud data obtained by scanning dentition.
The computing device includes a processor and a display for displaying the second point cloud data. The processor can execute computer program modules implementing the above-described acquisition of dentition point cloud data using an intraoral digital impression system, comprising:
and the first program module is used for obtaining first point cloud data according to the pre-stored point cloud data and the first scanning data.
And the second program module is used for obtaining second point cloud data according to the first point cloud data and the second scanning data, and the second point cloud data is dentition point cloud data.
In other embodiments, an intraoral digitized impression can be obtained using the system shown in fig. 1 by:
s200, standard three-dimensional data of a guide mark (6) arranged on an intraoral scanning guide plate (1) in the intraoral digital impression system is acquired. Because the three-dimensional model data of the auxiliary scanning device is known, a certain number of ISS key points can be extracted from the three-dimensional data in advance, and corresponding three-dimensional local SHOT feature descriptors are calculated for each key point, wherein the specific extraction method of the ISS key points refers to Zhong, y. (2009). a shape descriptor for 3D object registration. in proc. int. conf. on computer vision works (pp.1-8), and the specific calculation process of the SHOT feature description refers to tombai, f., sali, s., & Di stem ino, L. (2010), Unique signatures of histories for registration. in proc. euro. conf.on computer vision (ECCV) (pp.356-369), Berlin: spring section 3.1 of the article gives an extraction method of ISS key points, and in short, representative significant feature points are extracted from three-dimensional data according to a certain rule. The rule is as follows: and calculating a diffusion matrix and a characteristic value of each point of the three-dimensional data by combining with the neighborhood points of the three-dimensional data, and extracting the characteristic points according to the sizes of the three characteristic values. Since the three-dimensional model of the auxiliary device is known in advance, the extraction of the key points can be performed in advance.
In section 4 of this document, a method for calculating a local SHOT descriptor based on section 3 is introduced, which essentially defines a histogram for a certain point in combination with neighborhood data, except that the text is calculated for part of random sampling points of an input model (see a section of text below fig.7 of section 5 of this document), and the invention is calculated for ISS key points.
The calculation method of the SHOT descriptor comprises the following steps: a local reference system is established for each ISS key point by combining three-dimensional data, a plurality of three-dimensional grids are subdivided for neighborhood data under the local reference system, an angle histogram is calculated for each grid, and then the histograms are overlapped to form a total histogram, namely feature description. Somewhat similar to SIFT feature description in two-dimensional images.
S300, fixing the intraoral scanning guide plate (1) near a detected oral cavity area inside an oral cavity through a fixing device (3), wherein the intraoral scanning guide plate is a dentition (2) in this example, so that a guide mark (6) is adjacent to the dentition (2) and the position relation is fixed;
s400, scanning at least part of the dentition (2) and at least part of the guide mark (6) in the oral cavity by using an intraoral impression scanner (5) to acquire an image, and obtaining three-dimensional data (or three-dimensional point cloud data, or point cloud data or point cloud for short) of the image; then, the dentition provided with the auxiliary scanning device is scanned by an intraoral digital scanning device, local three-dimensional point cloud data of the dentition is obtained, and ISS key points and corresponding SHOT feature descriptors are extracted for the dentition.
S500, searching and identifying three-dimensional data of at least part of the guide mark (6) from the three-dimensional data of the image according to the standard three-dimensional data of the guide mark (6), wherein at least part of the guide mark (6) comprises at least three non-collinear feature mark points (namely ISS key points), and determining the three-dimensional data of at least part of dentition (2) in the rest part of the three-dimensional data of the image;
s600, determining a coordinate conversion relation between the three-dimensional data of at least part of the guide mark (6) and a corresponding part of the standard three-dimensional data by using at least three non-collinear feature mark points; at this time, each ISS key point of the local three-dimensional point cloud data searches for an optimal matching based on the SHOT feature descriptor in the ISS key points of the auxiliary scanning device model to form a matching point pair, and calculates an initial transformation relationship from the local point cloud data to the auxiliary scanning device model by using a RANSAC algorithm (refer to the references fischeler m.a. random sample consensus: a space for model matching with applications to the images and automatic card mapping. com. acm 24, 6, 1981, 381 and 395), that is, completes the initial registration.
And S700, applying the conversion relation of the S600 to the three-dimensional data of at least part of the dentition (2) to obtain the converted three-dimensional data of at least part of the dentition (2) as a digital impression of at least part of the dentition (2).
In some embodiments, the method of obtaining an intraoral digital impression further comprises obtaining a digital impression of the entire dentition (2) by repeating steps S400 to S700, wherein repeating S400 results in overall three-dimensional data of the dentition (2), and each scan obtains three-dimensional data comprising at least part of the dentition (2) and at least part of the guide mark (6).
In some embodiments, the method of obtaining an intraoral digitized impression further comprises the steps of:
s-1, executing the steps S400 to S700, wherein P1 is scanned in S400 to obtain three-dimensional data P1D 1; in S500, the standard three-dimensional data of the guide mark (6) is set as G0, at least part of the three-dimensional data G1 corresponding to G0 is searched and identified in P1D1, G1 comprises at least three non-collinear feature mark points, and the three-dimensional data A1D1 of at least part of dentition (2) A1 is determined in the rest of P1D 1; determining a conversion relationship between corresponding ones of G1 and G0 using at least three non-collinear feature landmark points in S600; in S700, the conversion relation of S600 is applied to A1D1, and three-dimensional data Z1 is obtained through conversion and serves as a digital stamp of A1;
s-2, repeatedly executing the steps S400 to 700, wherein in S400, P2 is scanned, and three-dimensional data P2D1 are obtained; in S500, when at least part G0 is not found from P2D1, instead searching from P2D1 and identifying at least part of the three-dimensional data a1 ', a 1' corresponding to Z1, including at least three non-collinear landmark points, and determining in the remainder of P2D1 the three-dimensional data A2D1 of at least part of dentition (2) A2; determining a conversion relationship between corresponding parts in a 1' and Z1 using at least three non-collinear feature landmark points in S600; in S700, the transformation relation of S600 is applied to A2D1, and three-dimensional data Z2 is obtained as a digitized stamp of A2.
In some cases, according to the method of obtaining an intraoral digitized impression, further comprising:
s-1, executing steps S400 to S700, wherein in S400, P1 is scanned, and three-dimensional data P1D1 is obtained; in S500, let the standard three-dimensional data of the guide mark be G0, search and identify in P1D1 the three-dimensional data G1 corresponding to at least part of G0, G1 including at least three non-collinear feature mark points, and determine in the rest of P1D1 the three-dimensional data A1D1 of at least part of dentition (2) A1; determining a conversion relationship between corresponding ones of G1 and G0 using at least three non-collinear feature landmark points in S600; in S700, the conversion relation of S600 is applied to A1D1, and three-dimensional data Z1 is obtained through conversion and serves as a digital stamp of A1;
s800, after S-1, taking the intraoral scanning guide plate out of the oral cavity, so as to expose the dentition (2) B1 originally shielded by the intraoral scanning guide plate;
s-4, after S800, repeatedly executing the steps S400 to 700, wherein B1 is scanned in S400 to obtain three-dimensional data B1D 1; searching and identifying three-dimensional data a1 "corresponding to at least part of Z1 from B1D1, a 1" comprising at least three non-collinear landmark points, and determining three-dimensional data A3D1 of at least part of dentition (2) A3 in the rest of B1D1 in S500; determining a conversion relationship between corresponding parts in A1' and Z1 using at least three non-collinear feature landmark points in S600; in S700, the transformation relation of S600 is applied to B1D1, and three-dimensional data Z3 is obtained as a digitized stamp of B1.
In the above embodiment, after obtaining a digitized impression of all the portions of the dentition (2), post-processing such as fusion, smoothing, etc., may be performed on the portions that overlap each other.
The system and the method of the invention have no accumulated multiple scanning measurement errors, effectively improve the precision of the intraoral digital impression and can meet the subsequent design and processing requirements on the dental restoration.
Claims (7)
1. A method for taking an intraoral digitized impression, comprising:
s100, respectively obtaining point cloud data of a first dentition and a second dentition according to a guide mark of the intraoral scanning guide plate; further comprising:
s110, installing an intraoral scanning guide plate in the oral cavity; wherein the intraoral scan guide comprises: the device comprises a fixing device and a rigid guide plate, wherein the rigid guide plate is provided with a scanning guide surface, and a guide mark is arranged on the scanning guide surface; the fixing device is provided with a connecting piece connected with the inner structure of the oral cavity, and the connecting piece is used for fixing the rigid guide plate in the oral cavity;
s120, scanning dentition and a guide mark to obtain first scanning data; obtaining first point cloud data according to pre-stored point cloud data and first scanning data, wherein the first point cloud data comprises dentition and a guide mark; the first point cloud data comprises a plurality of point cloud data of dentition and guide marks, wherein each point cloud data of the dentition and the guide marks corresponds to one part of the dentition and the guide marks; the pre-stored point cloud data is point cloud data of a guide mark;
s130, removing the intraoral scanning guide plate from the oral cavity;
s140, scanning dentition, and obtaining second point cloud data according to the result of scanning the dentition and the first point cloud data, wherein the second point cloud data is the point cloud data of the dentition; the second point cloud data comprises a plurality of point cloud data of dentition, wherein each point cloud data of dentition corresponds to a local part of dentition;
s200, point cloud data of occlusal surfaces of the first dentition and the second dentition are obtained;
s300, acquiring intraoral three-dimensional digital impression data according to the point cloud data of the first dentition, the point cloud data of the second dentition and the point cloud data of the occlusal surface;
the fixing device is a clamp;
when the rigid guide plate is fixed in the oral cavity, at least the surface of the rigid guide plate which can be shot by an intraoral impression scanner and is adjacent to the oral cavity area to be detected is used as a scanning guide surface, and the guide marks are distributed on at least the part, close to the oral cavity area to be detected, of the scanning guide surface;
the side of the rigid guide plate close to the oral cavity area to be detected is provided with a profile matched with the oral cavity area to be detected, so that the rigid guide plate is matched with the oral cavity area to be detected, and the length of the rigid guide plate is approximately equal to the length of a dentition formed by three or more continuous teeth at any position of the dental arch.
2. A method according to claim 1, wherein the entire surface of the rigid guide plate is taken as a scan guide surface and the guide marks are distributed throughout the scan guide surface.
3. The method according to claim 1, wherein the guide mark is a continuous or discontinuous three-dimensional pattern, and the guide mark has the same or different pattern at different positions on the scan guide surface.
4. The method of claim 1, wherein the guide markings on the scanning guide surface are substantially parallel to the proximate oral area being measured.
5. The method of claim 1, wherein the rigid guide plate is an all-mouth guide plate having a length approximately equal to a length of a dentition formed by all teeth comprising the upper or lower jaw; or the rigid guide plate is a half-mouth guide plate, and the length of the half-mouth guide plate is approximately equal to the length of the dentition formed by the left or right half part of the teeth of the upper jaw or the lower jaw.
6. Method according to claim 1, characterized in that the rigid guide plate is mounted on the lateral flank and/or the lingual flank.
7. The method of claim 1, wherein the securing device is attached to the rigid guide plate and is removable or the securing device is integrally formed with the rigid guide plate.
Priority Applications (3)
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| CN201810684582.8A CN108992191B (en) | 2016-07-29 | 2017-07-27 | System and method for acquiring intraoral digitized impressions |
| CN201810684583.2A CN108904084B (en) | 2016-07-29 | 2017-07-27 | System and method for acquiring intraoral digitized impressions |
| CN201810684483.XA CN108852540B (en) | 2016-07-29 | 2017-07-27 | System and method for acquiring intraoral digitized impressions |
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| PCT/CN2017/094748 WO2018019274A1 (en) | 2016-07-29 | 2017-07-27 | System and method for acquiring digital intraoral impression |
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| CN201810684483.XA Division CN108852540B (en) | 2016-07-29 | 2017-07-27 | System and method for acquiring intraoral digitized impressions |
| CN201810684582.8A Division CN108992191B (en) | 2016-07-29 | 2017-07-27 | System and method for acquiring intraoral digitized impressions |
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| CN110063806B (en) * | 2019-04-30 | 2021-03-23 | 北京大学口腔医学院 | Auxiliary device for improving three-dimensional scanning precision in multi-tooth-position mouth and using method |
| CN110276758B (en) * | 2019-06-28 | 2021-05-04 | 电子科技大学 | Tooth occlusion analysis system based on point cloud space characteristics |
| CN110942520B (en) * | 2019-11-27 | 2022-06-28 | 中南大学 | Auxiliary positioning method, device and system for operation equipment and storage medium |
| IT202100027989A1 (en) * | 2021-11-03 | 2023-05-03 | Diego Crovato | APPARATUS AND METHOD FOR ACQUIRING A DENTAL IMPRESSION BY MEANS OF INTRAORAL DIGITAL SCAN |
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Also Published As
| Publication number | Publication date |
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| CN108904084B (en) | 2020-12-29 |
| CN108472108A (en) | 2018-08-31 |
| CN108852540A (en) | 2018-11-23 |
| CN108852540B (en) | 2020-12-29 |
| WO2018019274A1 (en) | 2018-02-01 |
| CN108992191A (en) | 2018-12-14 |
| CN108904084A (en) | 2018-11-30 |
| CN108992191B (en) | 2020-12-29 |
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