WO2019076330A1 - 一种体外根管预备质量数字化评估方法及系统 - Google Patents

一种体外根管预备质量数字化评估方法及系统 Download PDF

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WO2019076330A1
WO2019076330A1 PCT/CN2018/110764 CN2018110764W WO2019076330A1 WO 2019076330 A1 WO2019076330 A1 WO 2019076330A1 CN 2018110764 W CN2018110764 W CN 2018110764W WO 2019076330 A1 WO2019076330 A1 WO 2019076330A1
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root canal
preparation
evaluation
cross
root
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PCT/CN2018/110764
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English (en)
French (fr)
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WO2019076330A9 (zh
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唐子圣
夏文君
王易维
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上海交通大学医学院附属第九人民医院
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Priority claimed from CN201810189798.7A external-priority patent/CN109674543A/zh
Application filed by 上海交通大学医学院附属第九人民医院 filed Critical 上海交通大学医学院附属第九人民医院
Publication of WO2019076330A1 publication Critical patent/WO2019076330A1/zh
Publication of WO2019076330A9 publication Critical patent/WO2019076330A9/zh

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
    • A61C5/00—Filling or capping teeth
    • A61C5/40—Implements for surgical treatment of the roots or nerves of the teeth; Nerve needles; Methods or instruments for medication of the roots

Definitions

  • the invention relates to the technical field of stomatology, in particular to a method and a system for digitally evaluating the quality of an external root canal preparation.
  • Root canal preparation refers to the mechanical and chemical methods to remove the infectious substances in the root canal system as much as possible to achieve the purpose of cleaning and shaping the root canal.
  • the quality of the root canal preparation is important for determining the long-term preservation of the affected teeth after root canal treatment. One of the factors.
  • the quality of root canal preparation is closely related to the level of doctor training, root canal preparation techniques and equipment use. Therefore, comprehensive assessment of root canal preparation quality can help improve the level of doctors' operation, root canal preparation methods and equipment evaluation and selection.
  • the degree of cleanliness of the root canal wall, root canal cleaning, shaping and rinsing can significantly reduce the number of bacteria that can be cultured.
  • the commonly used research methods for the cleanliness of root canal wall include bacterial culture method in root canal, measurement of isolated tooth section and micro-CT scan measurement of isolated teeth;
  • Formation of root canal steps is a common operation in root canal preparation process.
  • One of the sexual errors refers to the irregular shape formed artificially on the surface of the root canal wall, which causes the original path of the root canal to change. The instrument can be inserted into the tip of the original unobstructed root canal. If improperly handled, the root canal preparation will be insufficient. And the root canal is not fully filled.
  • the commonly used method for studying whether the root canal forms a step is to directly probe the root canal and compare the X-ray film after the root canal treatment. If the root canal filling position is shorter than the initial working length position by more than 1 mm or the root filling image deviates from the root canal.
  • the initial curved path is considered to form a step; 3, the apical foramen is enlarged, the apical foramen is enlarged, and the apical stenosis damage can increase the chance of flushing fluid, dentin debris, infectious material or filling material protruding into the periapical tissue. Augmentation of the canal may also increase the chance of microleakage of the root canal.
  • the enlargement of the apical foramen can be known through the exploration of the root canal preparation device; 4, the root canal deviation, the root canal deviation is one of the most common complications when preparing the curved root canal, and the greater the curvature of the root canal, the greater the The more severe the offset.
  • the root canal offset is also affected by the type of root canal preparation instrument, cross-section and tip design, the physical properties of the alloy, and the root canal preparation method.
  • a common method for root canal deviation is the measurement of the root canal center and the CBCT image before and after the preparation of the isolated tooth or resin block model. 5. The thickness of the residual dentin wall, the thickness of the remaining dentin wall and the strength of the root.
  • micro-CT scans are used to prepare the root canal before and after the study, although the data obtained are highly accurate and not destructive, the research is limited by the high cost of micro-CT, so most of them are small sample sizes, so that the results Credibility is affected.
  • the experimenter usually uses the excised teeth extracted from the clinical collection for root canal preparation.
  • the dentin of natural teeth is opaque, and the effect of root canal preparation cannot be directly observed, which is not conducive to the operator's feedback of its own operation effect, and is not conducive to the experimenter to evaluate the preliminary effect.
  • the previous assessment of the quality of root canal preparation relies only on visual observation and empirical judgment, and it is impossible to avoid the error caused by different evaluation criteria between different individuals, thus it is difficult to ensure the accuracy of the preliminary assessment of each operator's root canal. Sex and objectivity.
  • the technical problem to be solved by the present invention is to provide an external root canal preparation quality digital evaluation system for evaluating the evaluation of the root canal preparation effect of different operators through different instruments and methods, and digitizing
  • the evaluation method reflects the change of the shape of the root canal before and after preparation, which facilitates the accurate and objective evaluation of medical teaching, and provides new ideas for the exploration of instruments and methods for root canal preparation.
  • the present invention provides a digital evaluation method for external root canal preparation quality, which comprises the following steps: selecting an evaluation factor to establish a weighting formula of different weights according to an evaluation criterion, and performing an evaluation of root canal preparation quality, The sum of the weights of the evaluation factors in the scoring formula is 1.
  • the evaluation factor includes a device model of the root model prepared by the tooth model, a condition of the apical hole, a apical hole enlargement, a step formation, a root canal cleanness, a center deviation, and a remaining minimum root canal.
  • One or more of the wall thicknesses, and the evaluation factor in the scoring formula includes at least one of a central offset, a degree of root canal cleanliness, and a remaining minimum root canal wall thickness.
  • the method for evaluating the degree of root canal cleanliness, the center offset, and the remaining minimum root canal wall thickness includes performing a CBCT or micro CT scan, and using the scan results for the comparative evaluation.
  • the evaluation factor in the scoring formula is not less than two.
  • the dental model comprises a batch of 3D printed simulated resin tooth model based on the digitized image of the isolated tooth, wherein one resin tooth model is used as a standard tooth model, and the remaining resin tooth model is used as a root canal preparation tooth model.
  • the method for evaluating the degree of root canal cleanliness, the center offset, and the remaining minimum root canal wall thickness includes: the standard tooth model prepared for the root canal and the root canal preparation
  • the root canal preparation tooth model is respectively subjected to CBCT or micro CT scan, and the results of the two scans are compared to obtain the root canal cleanness degree, the central offset degree, and the remaining minimum root canal wall thickness.
  • the evaluation factor in the scoring formula includes the root canal cleanliness, the central offset, and the remaining minimum root canal wall thickness.
  • the resin tooth model is based on CBCT or micro-CT scanning of the root canal system of the real isolated tooth, and then processed by software to obtain a three-dimensional printed document, and is made of a resin material using a high-precision 3D printer.
  • the resin material is a Visijet M3 Crystal resin material.
  • the method for evaluating the degree of cleanliness of the root canal comprises: injecting a developer into the root canal of the standard dental model, and then performing a CBCT or micro-CT scan, and extracting a cross section of the root canal wall using image processing software ( A0); injecting the developer into the root canal of the prepared root canal preparation tooth model, performing CBCT or micro CT scan, and extracting the corresponding cross section of the root canal wall (A1) by using image processing software; A cross section (A0) of the root canal wall is compared with the corresponding cross section (A1) of the prepared root canal wall, and the coincidence degree of the front and rear edge lines of all corresponding cross sections is calculated in turn, and the degree of cleaning of the root canal of the resin can be obtained.
  • the method for evaluating the degree of cleanliness of the root canal further comprises: taking a cross section (A0) of the pre-pre-root canal wall in cross section, and the minimum distance to the root canal wall after preparation is less than the measurement error distance.
  • a cross section (A0) of the root canal wall is a coincident portion, and the ratio of the length of the coincident portion of the cross section (A0) of the pre-pre-root canal wall to the total length can be calculated to obtain the coincidence degree of the root canal before and after preparation. The higher the value, the lower the cleanliness of the root canal.
  • the method for evaluating the central offset degree comprises: injecting a developer into a root canal of the standard tooth model, and then performing a CBCT or micro CT scan, and extracting a geometric center of each cross section of the root canal by using image processing software.
  • the geometric center point (B0) of each cross section of the pre-prepared root canal is compared with the geometric center point (B1) of each cross-section of the prepared root canal, and the distance between the geometric center points of the corresponding cross-sections is obtained, and the maximum value is taken.
  • the center deviation before and after the root canal preparation is obtained.
  • the method for evaluating the central offset degree further includes: the distance between the center point of the root canal before and after the cross section is prepared
  • the degree of offset is greater than the measurement error, that is, the root canal is considered to be offset.
  • the method for evaluating the remaining minimum root canal wall thickness comprises: injecting a developer into the root canal after root canal preparation, performing CBCT or micro CT scan, and using an image processing software to extract the root canal wall from the root tip by 4 mm.
  • the minimum distance from any point on the circumference of the cross section to the surface of the resin tooth, that is, the minimum wall thickness remaining after the root canal is prepared for this cross section, thereby reflecting the flexural strength of the root canal.
  • the method further comprises injecting a developer into the root canal of the resin tooth model without the root canal preparation and the root canal of the resin tooth after the root canal preparation to enhance the effect of scanning development.
  • the developer includes an iodized oil.
  • the method further comprises taking a plurality of cross sections of the root canal segment included in the evaluation according to a certain thickness, respectively measuring the coincidence degree of the root canal before and after preparation, the geometric center point deviation degree and the minimum root canal wall thickness of each cross section. .
  • the image processing software includes selecting Mimics and Geomagic software for three-dimensional reconstruction and overlapping comparison of images before and after root canal preparation.
  • the method further comprises: when the main tip of the instrument used for the root canal preparation operation is at least larger than the initial point, x 1 is recorded as 100, otherwise, x 1 is recorded as 0; when the root canal is not When the debris is broken, x 2 is recorded as 100, otherwise, x 2 is recorded as 0; when the apical foramen is enlarged, the main tip is beyond the apical hole, x 3 is recorded as 0, otherwise x 3 is recorded as 100; When the step is formed, that is, when the working length to the apex distance is less than or equal to 0.5 mm, x 4 is recorded as 100, and when the working length to the apex distance is greater than 0.5 mm and less than or equal to 1 mm, x 4 is recorded as 80, when the working length is When the apex distance is greater than 1 mm and less than or equal to 1.5 mm, x 4 is denoted as 60.
  • x 4 is denoted as 40, when the working length to the apex distance is greater than 2mm, x 4 is marked as 0; when the overall degree of coincidence before and after root canal preparation is k%, x 5 is recorded as 100-k; when the root canal preparation before and after the root canal center distance change is n mm, the measurement error is i mm, It is known that the average deviation of the instrument is j mm, when n ⁇ i, x 6 is recorded as 100, and when n > i, x 6 is recorded as (40n + 60i - 100j) / (ij), when there is a side wear condition , x 6 record 0; when the minimum remaining wall thickness greater than or equal to the root canal when 1mm, x 7 as 100, when the minimum remaining root canal wall thickness less than 1mm, x 7 referred to as Y / initial minimum thickness, wherein,
  • the system includes an evaluation unit of the evaluation method as described above.
  • system further includes: a dental mold making unit for fabricating a resin tooth model.
  • system further includes: a recording unit and a scanning comparison unit;
  • the recording unit is configured to record the type of the instrument used before and after the root canal preparation, the step, the apical hole enlargement and the root tube hole debris;
  • the scanning comparison unit is used for the resin prepared without the root canal.
  • the dental model and the resin tooth model after root canal preparation were respectively subjected to CBCT or micro-CT scan, and the results of the two scans were compared, and the cleaned degree, offset degree and remaining minimum root canal wall thickness of the prepared resin root canal were obtained. Sended to the recording unit, and recorded by the recording unit.
  • system further includes a processor and a memory storing a computer program, the processor running the computer program;
  • Step one the tooth model making unit creates a 3D printing simulation resin tooth model based on the digitized image of the isolated tooth;
  • Step two performing a root canal preparation operation on the resin tooth model, and recording the model of the instrument before and after the use of the root canal preparation operation, the step, the apical foramen enlargement and the external root canal debris;
  • Step 3 performing a CBCT scan or a micro-CT scan on the resin tooth model prepared without the root canal and the resin tooth model after the root canal preparation, and comparing the scan results of the two to obtain the pre-requisite resin tooth Root canal cleanliness, offset and remaining minimum root canal wall thickness;
  • Step 4 The evaluation unit establishes the scoring formula for evaluation.
  • the evaluation method and system of the present invention have the following beneficial effects: (1)
  • the research object of the present invention is a 3D printed model tooth having a shape of a real tooth and a root canal shape, and the appearance is transparent and reproducible. The operator's operation experience is good; (2) the invention is evaluated by CBCT scanning and software analysis, is not destructive, and has good repeatability; (3) the present invention uses CBCT scanning to prepare the root canal for evaluation before and after the cost. Low, time-consuming, can be used in clinical, convenient for large sample size research and clinical real-time evaluation; (4) The present invention weighs various factors and conducts comprehensive evaluation; (5) The present invention is evaluated by CBCT and software analysis, and has objective sexuality and accuracy, excluding the subjective factors of artificial eye score.
  • Fig. 2 is a view showing an example of cross-sectional alignment of the root canal wall before and after preparation.
  • the scoring formula is the type of the instrument prepared by the root canal of the tooth model, the condition of the root canal, the enlargement of the apical foramen, the step condition, the degree of root canal cleaning, and the center offset
  • One of the remaining minimum root canal wall thickness, in which the degree of root canal cleanliness, central offset, and residual minimum root canal wall thickness is assessed using CBCT or micro-CT scans, using scan results for comparative evaluation .
  • the scoring formula may also include the model of the instrument model prepared by the root canal of the tooth model, the condition of the root canal, the enlargement of the apical foramen, the step condition, the degree of root canal cleaning, and the center deviation. Two or more of the degree of displacement, the remaining minimum root canal wall thickness, and at least one of root canal cleanliness, central offset, and remaining minimum root canal wall thickness.
  • the sum of the weights of the evaluation factors is 1.
  • the scoring formula includes two evaluation factors: the degree of root canal cleanliness and the remaining minimum root canal wall thickness. The two evaluation factors have a positive and negative relationship. When the root canal is cleaned, the remaining dentin wall thickness may be too small. In case, the bending strength of the root canal is too low, and the root longitudinal folding is easy to occur; therefore, the weights of the two can be set to different weight pairs such as 0.5 and 0.5 or 0.4 and 0.6 depending on the actual situation.
  • a 3D technique is used to make a dental model as a root canal preparation quality assessment.
  • a batch of simulated resin tooth model is prepared by using 3D printing based on the digitized image of the isolated tooth, wherein one resin tooth model is used as a standard tooth model, and the other resin tooth model is used as a root canal preparation tooth model.
  • the method of making the tooth model is to scan the root canal system of the real isolated tooth by CBCT or micro-CT, obtain the original DICOM data, obtain the macroscopic and microscopic bionic 3D printed STL file through the Mimics software three-dimensional processing, and reconstruct the STL file data. It is made of high-precision 3D printer and made of Visijet M3 Crystal resin material.
  • the resin tooth model prepared without the root canal and the resin tooth model after the root canal preparation are respectively subjected to CBCT scanning, and the scanning results of the two are compared to obtain the degree of cleaning and the degree of deviation of the resin root canal after preparation. And the remaining minimum root canal wall thickness.
  • the degree of cleanliness of the root canal is evaluated by injecting a developer into the root canal of the standard tooth model, then performing a CBCT or micro-CT scan, and extracting a cross section (A0) of the root canal wall using image processing software;
  • the prepared root canal is filled with the developer into the root canal of the tooth model, and subjected to CBCT or micro-CT scan, and the image processing software is used to extract the corresponding cross section of the root canal wall (A1); a cross section of the pre-root canal wall will be prepared (A0)
  • the central offset is evaluated by injecting the developer into the root canal of the standard tooth model, then performing a CBCT or micro-CT scan, and using image processing software to extract the geometric center points (B0) of the cross-sections of the root canal;
  • the developer is injected into the root canal of the dental model, and CBCT or micro-CT scan is performed, and the geometric center point (B1) of each cross section of the root canal is extracted by image processing software;
  • the geometric center point (B0) is compared with the geometric center point (B1) of each cross-section of the prepared root canal, and the distance between the geometric center points of the corresponding cross-sections is obtained, and the maximum value is obtained, and the center-offset of the root canal preparation is obtained. degree;
  • the remaining minimum root canal wall thickness is evaluated by injecting the developer into the root canal after root canal preparation, performing CBCT or micro-CT scan, and using image processing software to extract the cross-sectional perimeter of the root canal wall 4 mm from the apex.
  • the minimum distance from any point to the surface of the resin tooth, that is, the minimum wall thickness remaining after the root canal is prepared for this cross section, thereby reflecting the bending strength of the root canal.
  • the system comprises: a dental mold making unit for making a resin tooth model; and a recording unit for recording the type of the instrument, the step, and the apical foramen used before and after the root canal preparation And the external debris of the root canal;
  • the scanning contrast unit is used for performing a CBCT scan on the resin tooth model prepared without the root canal and the resin tooth model after the root canal preparation, and comparing the results of the two scans, and After preparation, the degree of cleaning of the root canal of the resin root, the degree of deviation and the remaining minimum root canal wall thickness are sent to the recording unit for recording by the recording unit;
  • the entire evaluation system further includes a processor and a memory storing a computer program, the processor running the computer program, as shown in FIG. 1, the specific steps are as follows:
  • Step (1) A batch of 3D printed simulated resin tooth model based on the digitized image of the isolated tooth is prepared, wherein one resin tooth model is used as the standard tooth model, and the remaining tooth model is used as the root canal preparation tooth model.
  • the resin tooth model in this step is based on CBCT or micro-CT scan of the root canal system of real isolated teeth, and the original DICOM data is obtained.
  • the three-dimensional printed STL file of macroscopic and microscopic bionics is obtained by Mimics software three-dimensional processing, and the STL file data is obtained.
  • the model was reconstructed using a high-precision 3D printer made of Visijet M3 Crystal resin.
  • Step (2) Perform a CBCT or micro-CT scan on the standard tooth model after injecting the developer into the root canal, and use image processing software to extract a cross section (A0) of the root canal wall and the geometric center point of each cross section of the root canal. (B0).
  • Step (3) Record the type of the instrument used before and after the root canal preparation of the remaining tooth model, the step, the apical foramen enlargement and the external debris of the root canal; inject the developer into the root canal for CBCT or micro CT scan, and The image processing software was used to extract the corresponding cross section of the root canal wall (A1), the geometric center point (B1) of each cross section of the root canal, and the minimum distance from the point of the cross section of the root canal wall to the root surface of the root tip to the surface of the resin tooth.
  • step (2) and step (3) it is also included to inject the iodized oil into the root canal of the resin tooth model without the root canal preparation and the root canal of the resin tooth model after the root canal preparation.
  • step of the agent which enhances the effect of scanning development.
  • a cross section (A0) of the pre-pre-root canal wall is compared with the corresponding cross-section (A1) of the post-warm root canal wall, and the cross-section of the cross-section of the cross-section before and after preparation is calculated to obtain a pre-requisite resin tooth.
  • Root canal cleanliness Specifically, the pre-pre-root canal wall (A0) is the pre-prepared root canal wall (A0), and the pre-pre-root canal wall (A0) with the minimum distance less than the measurement error distance is the coincident portion.
  • the ratio of the length of the overlapping portion of the wall (A0) to the full length can be obtained by the degree of coincidence of the root canal before and after preparation. The higher the value, the lower the degree of cleanliness of the root canal.
  • the geometric center point (B0) of each cross section of the pre-prepared root canal is compared with the geometric center point (B1) of each cross-section of the prepared root canal, and the distance between the geometric center points of the corresponding cross-sections is obtained, and the maximum value is obtained.
  • the center offset of the root canal before and after preparation In Fig. 2, the geometric center points of the two coincide, and the difference is marked in different positions in order to show the difference.
  • the distance between the center point of the root canal before and after the cross section is prepared
  • the root canal is considered to be offset
  • the distance between the center point of the root canal before and after preparation is calculated
  • the known mean offsets are compared and calculated, ie the degree of root canal offset before and after the evaluation is obtained.
  • the minimum distance (C1) from any point on the circumference of the cross-section of the root canal wall to the surface of the resin tooth at 4 mm from the root tip is the minimum wall thickness remaining after preparation of the root canal for this cross-section, thereby reflecting the flexural strength of the root canal.
  • the method further comprises the step (4): taking a plurality of cross sections of the root canal segment included in the evaluation according to a certain thickness, and measuring the coincidence degree of the root canal before and after preparation of each cross section. , geometric center point offset and minimum wall thickness. It is worth mentioning that step (4) can be completed at any time after the completion of the simulation resin tooth model.
  • x 1 is recorded as 100, otherwise, x 1 is recorded as 0; when there is no debris outside the root canal, x 2 Recorded as 100, otherwise, x 2 is marked as 0; when the apical hole enlargement exists, the main tip exceeds the apical hole, x 3 is recorded as 0, otherwise x 3 is recorded as 100; when no step is formed, the working length When the distance to the apex is less than or equal to 0.5mm, x 4 is recorded as 100.
  • x 4 is recorded as 80, when the working length to the apex distance is greater than 1mm and When it is less than or equal to 1.5mm, x 4 is written as 60. When the working length to the apex distance is greater than 1.5mm and less than or equal to 2mm, x 4 is recorded as 40.
  • the composition of the scoring formula and the weight composition of each evaluation factor are given, and specific scoring is also exemplified.
  • Table 1 is based on the specific embodiment.
  • the measured root canal preparation evaluation form It can be seen from the table that the present invention digitally evaluates the external root canal preparation operation of the resin tooth by the scoring formula, and can provide specific data for the root canal preparation quality, so that the evaluation is accurate and objective, and the data can be compared with each other, and can be used for different operators.
  • the quality of the root canal preparation is compared, and the operator's operational shortcomings can be prompted according to the various scoring data to further improve the operation technique and improve the clinical skills, thereby being applicable to the teaching field.

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Abstract

一种体外根管预备质量数字化评估方法及系统，方法包括以下步骤：首先制作基于离体牙数字化影像的3D打印仿真树脂牙模型，再将根管预备前后的树脂牙模型进行CBCT或显微CT扫描，记录根管预备操作使用前后的器械型号、台阶、根尖孔扩大和根管孔外碎屑情况，并采用图像处理软件提取根管壁各横截面（A0，A1）形态、根管各横截面几何中心点（B0，B1）以及根管壁上各部位至牙体表面的最小距离，然后将预备前后对应图像进行重叠比对，得出预备后树脂牙根管清洁程度、偏移度和预备后剩余最小根管壁厚（C1）。通过对树脂牙体外根管预备操作进行数字化评估，能够提高根管预备效果评估的准确性和客观性。

Description

一种体外根管预备质量数字化评估方法及系统 技术领域
本发明涉及口腔医学技术领域，尤其涉及一种体外根管预备质量数字化评估方法及系统。
背景技术
根管预备是指采用机械和化学的方法尽可能地清除根管系统内的感染物质，达到清洁、成形根管的目的，根管预备的质量是决定根管治疗后患牙能否长期保存的重要因素之一。根管预备的质量与医生受训水平、根管预备技术及器械使用等环节紧密相关。因此，综合评估根管预备质量对医生操作水平的提升、根管预备方法和器械的评估和选择等均有帮助。
数十年来，对根管预备操作的体外评估主要包括以下几方面：
1、根管壁清洁程度，根管清理、成形和冲洗可显著减少可培养的细菌数目。根管壁清洁程度的常用研究方法有根管内细菌培养法、离体牙切片测量法及离体牙显微CT扫描测量法；2、根管台阶形成，是根管预备过程中常见的操作性失误之一，是指在根管壁表面人为形成的不规则形态，导致根管原有通路发生改变，可组织器械进入原通畅根管的尖部，如处理不当会导致根管预备不充分和根管充填不全。常用的研究根管是否形成台阶的方法有直接探查根管和比较根管治疗术中术后的X线片，若根管充填位置较初始工作长度位置短1mm以上或根充影像偏离了根管初始弯曲路径即认为形成台阶；3、根尖孔扩大，根尖孔扩大、根尖狭窄区破坏可增加冲洗液、牙本质碎屑、感染物或充填材料突入根尖周组织的机会，此外根尖孔扩大还可能增加根管微渗漏发生的几率。根尖孔的扩大通过根管预备器械探查即可获知；4、根管偏移，在预备弯曲根管时根管偏移是最常见的并发症之一，往往根管弯曲度越大，产生的偏移越严重。此外，根管偏移还受根管预备器械的类型、横断面及尖端设计、合金的物理性质、根管预备方法的影响。根管偏移的常见研究方法为离体牙或树脂块模型预备前后二维影像根管中心的测量和CBCT图像测量；5、剩余牙本质壁厚度，剩余牙本质壁厚度与牙根的强度之间存在直接关系，尽可能地保留健康的牙本质是至关重要的。过度切削根方牙本质可能造成带状穿孔和牙根纵折。剩余牙本质壁厚度的常用研究方法有离体牙截根测量、二维X线片测量和显微CT扫描测量；6、根尖孔外碎屑推出在根管治疗时，或多或少会有牙本质碎屑、牙髓组织、坏死组织、微生物及代谢产物以及冲洗液被推出根尖孔，造成根尖周炎症及术后疼痛肿胀。如何避免或尽量减少将碎屑推出根尖孔是根管治疗研究的重要课题之一。根尖孔外碎屑推出的常用研究方法是在离体牙 上行根管预备，收集预备过程中推出离体牙根尖孔的冲洗液和牙本质碎屑并称重。
综合现有研究来看，其局限性主要体现在两点：研究对象和研究方法。上述六项的研究对象主要均为离体牙，因此研究难免会受于离体牙的收集难度和变异度的影响。根管偏移可使用预成树脂块根管模型进行操作研究，但现有树脂块根管模型形态规则且与真实根管形态差异大，仅能简单反映根管弯曲度，在树脂块根管模型上的根管预备操作与实际根管预备操作存在明显差异。从研究方法的角度来看，部分研究因素如根管剩余牙本质壁厚需要对离体牙进行切片或截根等破坏性处理，操作繁杂且不具有可重复性。而若使用显微CT扫描预备前后根管的方法进行研究，尽管所得数据精度高而非破坏性，但研究受限于显微CT的高成本，故多为小样本量研究，使其结果的可信度受到影响。
此外，尽管对根管预备效果的各项评估已分别有大量研究，但尚未有对上述因素进行综合考量的数字化评价方法。在实际根管预备操作中，上述因素间是存在正反变关系的。如对于根管壁薄弱处而言，当根管清洁程度越高，剩余牙本质壁厚度越可能存在过小的情况，使根管抗折强度过低、易发生牙根纵折。在类似此种情况下，权衡各项因素并进行综合评估有明显重要性。
目前在临床根管预备的效果研究中，实验者通常采用从临床收集拔除的离体牙进行根管预备的练习。然而，天然牙齿的牙本质为不透明物质，根管预备的效果无法直接观察到，不利于操作者反馈自身的操作效果，也不利于实验者评估预备效果。同时值得注意的是，以往对根管预备质量的评估仅靠肉眼观察及经验判断，无法避免不同个体之间不同评判标准而造成的误差，从而难以保证对每一个操作者根管预备评估的准确性和客观性。
因此，本领域的技术人员致力于开发一种体外根管预备质量数字化评估方法及系统，能够对根管预备的效果进行综合评估考量，提高根管预备评估的准确性和客观性。
发明内容
有鉴于现有技术的上述缺陷，本发明所要解决的技术问题是提供一种体外根管预备质量数字化评估系统，用于评价不同操作者通过不同器械及方法根管预备效果的评估，以数字化的评估方式反映根管预备前后形态的变化，便于医学教学准确且客观的进行评估，同时为根管预备的器械与方法的探索提供新思路。
为实现上述目的，本发明提供了一种体外根管预备质量数字化评估方法，其特征在于，包括如下步骤：根据评估标准，选择评估因子建立不同权重的评分算式，进行根管预备质量的评估，所述评分算式中的各评估因子的权重之和为1。
进一步地，所述评估因子包括牙模型根管预备的器械型号情况、根尖孔外碎屑情况、根尖孔扩大情况、台阶形成情况、根管清洁程度、中心偏移度、剩余最小根管壁厚中的一种或多种，且所述评分算式中的评估因子至少包括中心偏移度、根管清 洁程度以及剩余最小根管壁厚中的一种。
进一步地，所述根管清洁程度、所述中心偏移度和所述剩余最小根管壁厚中的评估方法包括：进行CBCT或显微CT扫描，使用扫描结果进行比对评估。
进一步地，所述评分算式中的评估因子不少于两种。
进一步地，所述牙模型包括一批基于离体牙数字化影像的3D打印仿真树脂牙模型，其中一颗树脂牙模型作为标准牙模型，其余树脂牙模型作为根管预备用牙模型。
进一步地，所述根管清洁程度、所述中心偏移度和所述剩余最小根管壁厚中的评估方法包括：对未经根管预备的所述标准牙模型和经根管预备后的所述根管预备用牙模型分别进行CBCT或显微CT扫描，比较两者扫描结果，得出所述根管清洁程度、所述中心偏移度和所述剩余最小根管壁厚。
进一步地，所述评分算式中的评估因子同时包含所述根管清洁程度、所述中心偏移度和所述剩余最小根管壁厚。
进一步地，所述树脂牙模型是基于CBCT或显微CT扫描真实离体牙的根管系统，然后通过软件处理得到三维打印文件，并采用高精度3D打印机，使用树脂材料制作。
进一步地，所述树脂材料为Visijet M3 Crystal树脂材料。
进一步地，所述根管清洁程度的评估方法包括：在所述标准牙模型的根管内注入显影剂，然后进行CBCT或显微CT扫描，并采用图像处理软件提取根管壁某横截面(A0)；在预备后的所述根管预备用牙模型的根管内注入显影剂，进行CBCT或显微CT扫描，并采用图像处理软件提取根管壁对应横截面(A1)；将预备前根管壁某横截面(A0)与预备后根管壁对应横截面(A1)进行比对，依次计算所有相对应横截面预备前后边缘线重合度，得出预备后树脂牙根管清洁程度。
进一步地，所述根管清洁程度的评估方法还包括：以横截面上所述预备前根管壁某横截面(A0)为准，至预备后根管壁的最小距离小于测量误差距离的所述预备前根管壁某横截面(A0)即为重合部分，计算所述预备前根管壁某横截面(A0)的重合部分长度与全长的比值即可得预备前后根管的重合度，该数值越高，表示根管清洁程度越低。
进一步地，所述中心偏移度的评估方法包括：在所述标准牙模型的根管内注入显影剂，然后进行CBCT或显微CT扫描，并采用图像处理软件提取根管各横截面几何中心点(B0)；在预备后的所述根管预备用牙模型的根管内注入显影剂，进行CBCT或显微CT扫描，并采用图像处理软件提取根管各横截面几何中心点(B1)；将预备前根管各横截面几何中心点(B0)与预备后根管各横截面几何中心点(B1)进行比对，得出各对应横截面几何中心点的距离，取其最大值，得出根管预备前后中心偏移度。
进一步地，所述中心偏移度的评估方法还包括：横截面上预备前后根管中心点的距离|B0-B1|大于测量误差时即认为根管发生偏移，即得到评估预备前后根管偏移程度。
进一步地，所述剩余最小根管壁厚的评估方法包括：在根管预备后的根管内注入显影剂，进行CBCT或显微CT扫描，并采用图像处理软件提取根管壁距根尖4mm处横截面周长上任一点至树脂牙体表面的最小距离，即为此横截面上根管预备后剩余最小壁厚，从而反映根管抗折强度。
进一步地，所述方法还包括在未经根管预备的树脂牙模型根管内和根管预备后的树脂牙模型根管内注入显影剂以增强扫描显影的效果。
进一步地，所述显影剂包括碘化油。
进一步地，所述方法还包括将计入评估的根管段按一定厚度截取若干横截面，分别测量各横截面上预备前后根管的重合度、几何中心点偏移度及最小根管壁厚。
进一步地，所述图像处理软件包括选择Mimics和Geomagic软件进行三维重建和根管预备前后图像的重叠比对。
进一步地，评分算式为y＝ax 1+bx 2+cx 3+dx 4+ex 5+fx 6+gx 7，其中，x 1为根管预备操作使用的器械型号情况、x 2为根管孔外碎屑情况、x 3为根尖孔扩大情况、x 4为台阶情况、x 5为根管清洁程度、x 6为中心偏移度、x 7为剩余最小根管壁厚、a、b、c、d、e、f、g为权重且a+b+c+d+e+f+g＝1。
进一步地，所述方法还包括当根管预备操作使用的器械的主尖锉至少比初尖锉大三号时，x 1记为100，否则，x 1记为0；当根管孔外无碎屑时，x 2记为100，否则，x 2记为0；当根尖孔扩大情况存在时即主尖锉超出根尖孔，x 3记为0，否则x 3记为100；当无台阶形成时即工作长度至根尖距离小于或等于0.5mm时，x 4记为100，当工作长度至根尖距离大于0.5mm且小于或等于1mm时，x 4记为80，当工作长度至根尖距离大于1mm且小于或等于1.5mm时，x 4记为60，当工作长度至根尖距离大于1.5mm且小于或等于2mm时，x 4记为40，当工作长度至根尖距离大于2mm，x 4记为0；当根管预备前后整体重合度为k％时，x 5记为100-k；当根管预备前后根管中心距离改变量为n mm，测量误差为i mm，已知器械平均偏移为j mm，当n≤i时，x 6记为100，当n＞i时，x 6记为(40n+60i-100j)/(i-j)，当存在侧穿情况时，x 6记为0；当剩余最小根管壁厚大于或等于1mm时，x 7记为100，当剩余最小根管壁厚小于1mm时，x 7记为Y/初始最小厚度，其中，Y为剩余最小根管壁厚；a＝b＝c＝d＝0.05，e＝0.4，f＝g＝0.2。
进一步地，所述系统包括如上述所述评估方法的评估单元。
进一步地，所述系统还包括：牙模制作单元，所述牙模型制作单元用于制作树脂牙模型。
进一步地，所述系统还包括：记录单元和扫描比对单元；
其中，所述记录单元，用于记录根管预备前后使用的器械型号、台阶、根尖孔扩大和根管孔外碎屑情况；所述扫描对比单元，用于对未经根管预备的树脂牙模型和根管预备后的树脂牙模型分别进行CBCT或显微CT扫描，比较两者扫描结果，并将得 出的预备后树脂牙根管清洁程度、偏移度和剩余最小根管壁厚发送给所述记录单元，由所述记录单元进行记录。
进一步地，所述系统还包括处理器和存储有计算机程序的存储器，所述处理器运行所述计算机程序；
所述计算机程序的步骤如下：
步骤一，所述牙模型制作单元制作基于离体牙数字化影像的3D打印仿真树脂牙模型；
步骤二，在所述树脂牙模型上进行根管预备操作，记录所述根管预备操作使用前后的器械型号、台阶、根尖孔扩大和根管孔外碎屑情况；
步骤三：对所述未经根管预备的树脂牙模型和所述根管预备后的树脂牙模型分别进行CBCT扫描或显微CT扫描，比较两者扫描结果，得出所述预备后树脂牙根管清洁程度、偏移度和剩余最小根管壁厚；
步骤四：所述评估单元建立所述评分算式进行评估。
本发明的评估方法及系统具有如下有益效果：(1)本发明的研究对象为3D打印模型牙，具有真实牙齿的外形以及根管形态，外观透明，具有可重复性。操作者的操作体验佳；(2)本发明通过CBCT扫描及软件分析进行评价，不具有破坏性，具有较好的可重复性；(3)本发明使用CBCT扫描预备前后根管进行评价，成本低、耗时短、可运用于临床，方便大样本量研究以及临床即时评测；(4)本发明权衡各项因素并进行综合评估；(5)本发明通过CBCT及软件分析进行评价，具有客观性及准确性，排除人工肉眼评分的主观因素。
以下将结合附图对本发明的构思、具体结构及产生的技术效果作进一步说明，以充分地了解本发明的目的、特征和效果。
附图说明
图1是本发明的一个较佳实施例的方法流程图；
图2是预备前后根管壁横截面比对示例图。
具体实施方式
以下参考说明书附图介绍本发明的多个优选实施例，使其技术内容更加清楚和便于理解。本发明可以通过许多不同形式的实施例来得以体现，本发明的保护范围并非仅限于文中提到的实施例。
在本发明的一个具体较佳实施例中，评分算式为牙模型根管预备的器械型号情况、根管孔外碎屑情况、根尖孔扩大情况、台阶情况、根管清洁程度、中心偏移度、剩余最小根管壁厚中的一种，其中根管清洁程度、中心偏移度和剩余最小根管壁厚中的评估方法为使用CBCT或显微CT扫描，使用扫描结果进行比对评估。
在本发明的其他较佳实施例中，评分算式也可以包括牙模型根管预备的器械型号情况、根管孔外碎屑情况、根尖孔扩大情况、台阶情况、根管清洁程度、中心偏移度、剩余最小根管壁厚中的两种及以上，且包含根管清洁程度、中心偏移度和剩余最小根管壁厚中的至少一种。在评分算式中，各项评估因子的权重之和为1。如评分算式包含根管清洁程度和剩余最小根管壁厚两种评估因子，这两种评估因子存在正反变关系，当根管清洁程度越高，剩余牙本质壁厚度越可能存在过小的情况，使根管抗折强度过低、易发生牙根纵折；因此可以根据实际情况的不同，将两者的权重设置为0.5和0.5或者0.4和0.6等不同的权重对。
在本发明的另一个具体较佳实施例中，采用了3D技术制作牙模型作为根管预备质量评估。具体为使用基于离体牙数字化影像的3D打印制作一批仿真树脂牙模型，其中一颗树脂牙模型作为标准牙模型，其余树脂牙模型作为根管预备用牙模型。制作牙模型的方法为CBCT或显微CT扫描真实离体牙的根管系统，得到原始DICOM数据，通过Mimics软件三维处理得到宏观及微观仿生的三维打印STL文件，并将STL文件数据进行模型重建，采用高精度3D打印机，使用Visijet M3 Crystal树脂材料制作。
在本实施例中，对未经根管预备的树脂牙模型和根管预备后的树脂牙模型分别进行CBCT扫描，比较两者扫描结果，得出预备后树脂牙根管清洁程度、偏移度和剩余最小根管壁厚。
具体地，根管清洁程度的评估方法为：在标准牙模型的根管内注入显影剂，然后进行CBCT或显微CT扫描，并采用图像处理软件提取根管壁某横截面(A0)；在预备后的根管预备用牙模型的根管内注入显影剂，进行CBCT或显微CT扫描，并采用图像处理软件提取根管壁对应横截面(A1)；将预备前根管壁某横截面(A0)与预备后根管壁对应横截面(A1)进行比对，计算预备前后横截面边缘线重合度，得出预备后树脂牙根管清洁程度；
中心偏移度的评估方法为：在标准牙模型的根管内注入显影剂，然后进行CBCT或显微CT扫描，并采用图像处理软件提取根管各横截面几何中心点(B0)；在预备后的根管预备用牙模型的根管内注入显影剂，进行CBCT或显微CT扫描，并采用图像处理软件提取根管各横截面几何中心点(B1)；将预备前根管各横截面几何中心点(B0)与预备后根管各横截面几何中心点(B1)进行比对，得出各对应横截面几何中心点的距离，取其最大值，得出根管预备前后中心偏移度；
剩余最小根管壁厚的评估方法为：在根管预备后的根管内注入显影剂，进行CBCT或显微CT扫描，并采用图像处理软件提取根管壁距根尖4mm处横截面周长上任一点至树脂牙体表面的最小距离，即为此横截面上根管预备后剩余最小壁厚，从而反映根管抗折强度。
在本发明评估系统的一个具体较佳实施例中，系统包括：牙模制作单元，用于制 作树脂牙模型；记录单元，用于记录根管预备前后使用的器械型号、台阶、根尖孔扩大和根管孔外碎屑情况；扫描对比单元，用于对未经根管预备的树脂牙模型和根管预备后的树脂牙模型分别进行CBCT扫描，比较两者扫描结果，并将得出的预备后树脂牙根管清洁程度、偏移度和剩余最小根管壁厚发送给记录单元，由记录单元进行记录；评估单元，用于根据各项评分标准建立不同权重的评分算式进行评估，其中，评分算式为y＝ax 1+bx 2+cx 3+dx 4+ex 5+fx 6+gx 7，其中，x 1为根管预备操作使用的器械型号情况、x 2为根管孔外碎屑情况、x 3为根尖孔扩大情况、x 4为台阶情况、x 5为根管清洁程度、x 6为偏移度、x 7为剩余最小根管壁厚、a、b、c、d、e、f、g为权重且a+b+c+d+e+f+g＝1。
整个评估系统还包括处理器和存储有计算机程序的存储器，所述处理器运行所述计算机程序，如图1所示，具体步骤如下：
步骤(1)：制作一批基于离体牙数字化影像的3D打印仿真树脂牙模型，其中，一颗树脂牙模型作为标准牙模型，其余牙模型作为根管预备用牙模型。该步骤中的树脂牙模型是基于CBCT或显微CT扫描真实离体牙的根管系统，得到原始DICOM数据，通过Mimics软件三维处理得到宏观及微观仿生的三维打印STL文件，并将STL文件数据进行模型重建，采用高精度3D打印机，使用Visijet M3 Crystal树脂材料制作。
步骤(2)：对在根管内注入显影剂后的标准牙模型进行CBCT或显微CT扫描，并采用图像处理软件提取根管壁某横截面(A0)、根管各横截面几何中心点(B0)。
步骤(3)：记录其余牙模型根管预备前后使用的器械型号、台阶、根尖孔扩大和根管孔外碎屑情况；在根管内注入显影剂，进行CBCT或显微CT扫描，并采用图像处理软件提取根管壁对应横截面(A1)、根管各横截面几何中心点(B1)以及根管壁距根尖4mm处横截面周长上任一点至树脂牙体表面的最小距离。
值得一提的是，在步骤(2)和步骤(3)之前还包括在未经根管预备的树脂牙模型根管内和根管预备后的树脂牙模型根管内注入碘化油等显影剂的步骤，如此可增强扫描显影的效果。
如图2所示，将预备前根管壁某横截面(A0)与预备后根管壁对应横截面(A1)进行比对，计算预备前后横截面边缘线重合度，得出预备后树脂牙根管清洁程度。具体为：以横截面上预备前根管壁(A0)为准，至预备后根管壁的最小距离小于测量误差距离的预备前根管壁(A0)即为重合部分，计算预备前根管壁(A0)的重合部分长度与全长的比值即可得预备前后根管的重合度，该数值越高，表示根管清洁程度越低。
将预备前根管各横截面几何中心点(B0)与预备后根管各横截面几何中心点(B1)进行比对，得出各对应横截面几何中心点的距离，取其最大值，得出根管预备前后中心偏移度。图2中两者的几何中心点重合，为了显出区别特别标在不同位置。具体为：横截面上预备前后根管中心点的距离|B0-B1|大于测量误差时即认为根管发生偏移，计 算预备前后根管中心点的距离|B0-B1|并与所使用器械的已知平均偏移进行比较和计算，即得到评估预备前后根管偏移程度。
预备后根管壁距根尖4mm处横截面周长上任一点至树脂牙体表面的最小距离(C1)即为此横截面上根管预备后剩余最小壁厚，从而反映根管抗折强度。
在本发明系统的另一具体较佳实施例中，还包括步骤(4)：将计入评估的根管段按一定厚度截取若干横截面，分别测量各横截面上预备前后根管的重合度、几何中心点偏移度及最小壁厚。值得一提的是，步骤(4)可以在制作仿真树脂牙模型完成后任意时刻完成。
步骤(5)：根据各项评分标准，建立不同权重的评分算式进行评估，评分算式为y＝ax 1+bx 2+cx 3+dx 4+ex 5+fx 6+gx 7，其中，x 1为根管预备操作使用的器械型号情况、x 2为根管孔外碎屑情况、x 3为根尖孔扩大情况、x 4为台阶情况、x 5为根管清洁程度、x 6为偏移度、x 7为剩余最小根管壁厚、a、b、c、d、e、f、g为权重且a+b+c+d+e+f+g＝1。其中，当根管预备操作使用的器械的主尖锉至少比初尖锉大三号时，x 1记为100，否则，x 1记为0；当根管孔外无碎屑时，x 2记为100，否则，x 2记为0；当根尖孔扩大情况存在时即主尖锉超出根尖孔，x 3记为0，否则x 3记为100；当无台阶形成时即工作长度至根尖距离小于或等于0.5mm时，x 4记为100，当工作长度至根尖距离大于0.5mm且小于或等于1mm时，x 4记为80，当工作长度至根尖距离大于1mm且小于或等于1.5mm时，x 4记为60，当工作长度至根尖距离大于1.5mm且小于或等于2mm时，x 4记为40，当工作长度至根尖距离大于2mm，x 4记为0；当根管预备前后整体重合度为k％时，x 5记为100-k；当根管预备前后根管中心距离改变量为n mm，测量误差为i mm，已知器械平均偏移为j mm，当n≤i时，x 6记为100，当n＞i时，x 6记为(40n+60i-100j)/(i-j)，当存在侧穿情况时，x 6记为0；当剩余最小根管壁厚大于或等于1mm时，x 7记为100，当剩余最小根管壁厚小于1mm时，x 7记为Y/初始最小厚度，其中，Y为剩余最小根管壁厚；a＝b＝c＝d＝0.05，e＝0.4，f＝g＝0.2。
在本发明的评估方法和系统的另一较佳具体实施例中，给出了评分算式的组成以及各个评估因子的权重构成，还对具体计分进行了示例，表1是根据本具体实施方式测得的根管预备评估表。通过该表可见，本发明通过评分算式对树脂牙体外根管预备操作进行数字化评估，能够对根管预备质量给出具体数据，使评估准确客观，数据可以进行相互比较，可以对不同操作者之间进行根管预备质量的比较，并且可以根据各项评分数据，提示操作者的操作缺点，以进一步改进操作技术，提高临床技能，从而适用于教学领域。
表1
Figure PCTCN2018110764-appb-000001
以上详细描述了本发明的较佳具体实施例。应当理解，本领域的普通技术无需创造性劳动就可以根据本发明的构思作出诸多修改和变化。因此，凡本技术领域中技术人员依本发明的构思在现有技术的基础上通过逻辑分析、推理或者有限的实验可以得到的技术方案，皆应在由权利要求书所确定的保护范围内。

Claims (24)

  1. 一种体外根管预备质量数字化评估方法，其特征在于，包括如下步骤：根据评估标准，选择评估因子建立不同权重的评分算式，进行根管预备质量的评估，所述评分算式中的各评估因子的权重之和为1。
  2. 如权利要求1所述的一种体外根管预备质量数字化评估方法，其特征在于，所述评估因子包括牙模型根管预备的器械型号情况、根尖孔外碎屑情况、根尖孔扩大情况、台阶形成情况、根管清洁程度、中心偏移度、剩余最小根管壁厚中的一种或多种，且所述评分算式中的评估因子至少包括中心偏移度、根管清洁程度以及剩余最小根管壁厚中的一种。
  3. 如权利要求2所述的一种体外根管预备质量数字化评估方法，其特征在于，所述根管清洁程度、所述中心偏移度和所述剩余最小根管壁厚中的评估方法包括：进行CBCT或显微CT扫描，使用扫描结果进行比对评估。
  4. 如权利要求2或3所述的一种体外根管预备质量数字化评估方法，其特征在于，所述评分算式中的评估因子不少于两种。
  5. 如权利要求3所述的一种体外根管预备质量数字化评估方法，其特征在于，所述牙模型包括一批基于离体牙数字化影像的3D打印仿真树脂牙模型，其中一颗树脂牙模型作为标准牙模型，其余树脂牙模型作为根管预备用牙模型。
  6. 如权利要求5所述的一种体外根管预备质量数字化评估方法，其特征在于，所述根管清洁程度、所述中心偏移度和所述剩余最小根管壁厚中的评估方法包括：对未经根管预备的所述标准牙模型和经根管预备后的所述根管预备用牙模型分别进行CBCT或显微CT扫描，比较两者扫描结果，得出所述根管清洁程度、所述中心偏移度和所述剩余最小根管壁厚。
  7. 如权利要求6所述的一种体外根管预备质量数字化评估方法，其特征在于，所述评分算式中的评估因子同时包含所述根管清洁程度、所述中心偏移度和所述剩余最小根管壁厚。
  8. 如权利要求5所述的一种体外根管预备质量数字化评估方法，其特征在于，所述树脂牙模型是基于CBCT或显微CT扫描真实离体牙的根管系统，然后通过软件处理得到三维打印文件，并采用高精度3D打印机，使用树脂材料制作。
  9. 如权利要求8所述的一种体外根管预备质量数字化评估方法，其特征在于，所述树脂材料为Visijet M3 Crystal树脂材料。
  10. 如权利要求5所述的一种体外根管预备质量数字化评估方法，其特征在于，所述根管清洁程度的评估方法包括：在所述标准牙模型的根管内注入显影剂，然后进行CBCT或显微CT扫描，并采用图像处理软件提取根管壁某横截面(A0)；在预备 后的所述根管预备用牙模型的根管内注入显影剂，进行CBCT或显微CT扫描，并采用图像处理软件提取根管壁对应横截面(A1)；将预备前根管壁某横截面(A0)与预备后根管壁对应横截面(A1)进行比对，依次计算所有相对应横截面预备前后边缘线重合度，得出预备后树脂牙根管清洁程度。
  11. 如权利要求10所述的一种体外根管预备质量数字化评估方法，其特征在于，所述根管清洁程度的评估方法还包括：以横截面上所述预备前根管壁某横截面(A0)为准，至预备后根管壁的最小距离小于测量误差距离的所述预备前根管壁某横截面(A0)即为重合部分，计算所述预备前根管壁某横截面(A0)的重合部分长度与全长的比值即可得预备前后根管的重合度，该数值越高，表示根管清洁程度越低。
  12. 如权利要求5所述的一种体外根管预备质量数字化评估方法，其特征在于，所述中心偏移度的评估方法包括：在所述标准牙模型的根管内注入显影剂，然后进行CBCT或显微CT扫描，并采用图像处理软件提取根管各横截面几何中心点(B0)；在预备后的所述根管预备用牙模型的根管内注入显影剂，进行CBCT或显微CT扫描，并采用图像处理软件提取根管各横截面几何中心点(B1)；将预备前根管各横截面几何中心点(B0)与预备后根管各横截面几何中心点(B1)进行比对，得出各对应横截面几何中心点的距离，取其最大值，得出根管预备前后中心偏移度。
  13. 如权利要求12所述的一种体外根管预备质量数字化评估方法，其特征在于，所述中心偏移度的评估方法还包括：横截面上预备前后根管中心点的距离|B0-B1|大于测量误差时即认为根管发生偏移，即得到评估预备前后根管偏移程度。
  14. 如权利要求5所述的一种体外根管预备质量数字化评估方法，其特征在于，所述剩余最小根管壁厚的评估方法包括：在根管预备后的根管内注入显影剂，进行CBCT或显微CT扫描，并采用图像处理软件提取根管壁距根尖4mm处横截面周长上任一点至树脂牙体表面的最小距离，即为此横截面上根管预备后剩余最小壁厚，从而反映根管抗折强度。
  15. 如权利要求10-14任一权利要求所述的一种体外根管预备质量数字化评估方法，其特征在于，所述方法还包括在未经根管预备的树脂牙模型根管内和根管预备后的树脂牙模型根管内注入显影剂以增强扫描显影的效果。
  16. 如权利要求15所述的一种体外根管预备质量数字化评估方法，其特征在于，所述显影剂包括碘化油。
  17. 如权利要求10-14任一权利要求所述的一种体外根管预备质量数字化评估方法，其特征在于，所述方法还包括将计入评估的根管段按一定厚度截取若干横截面，分别测量各横截面上预备前后根管的重合度、几何中心点偏移度及最小根管壁厚。
  18. 如权利要求10-14任一权利要求所述的一种体外根管预备质量数字化评估方法，其特征在于，所述图像处理软件包括选择Mimics和Geomagic软件进行三维重建和根管预备前后图像的重叠比对。
  19. 如权利要求18所述的一种体外根管预备质量数字化评估方法，其特征在于，评分算式为y＝ax 1+bx 2+cx 3+dx 4+ex 5+fx 6+gx 7，其中，x 1为根管预备操作使用的器械型号情况、x 2为根管孔外碎屑情况、x 3为根尖孔扩大情况、x 4为台阶情况、x 5为根管清洁程度、x 6为中心偏移度、x 7为剩余最小根管壁厚、a、b、c、d、e、f、g为权重且a+b+c+d+e+f+g＝1。
  20. 如权利要求19所述的一种体外根管预备质量数字化评估方法，其特征在于，所述方法还包括当根管预备操作使用的器械的主尖锉至少比初尖锉大三号时，x 1记为100，否则，x 1记为0；当根管孔外无碎屑时，x 2记为100，否则，x 2记为0；当根尖孔扩大情况存在时即主尖锉超出根尖孔，x 3记为0，否则x 3记为100；当无台阶形成时即工作长度至根尖距离小于或等于0.5mm时，x 4记为100，当工作长度至根尖距离大于0.5mm且小于或等于1mm时，x 4记为80，当工作长度至根尖距离大于1mm且小于或等于1.5mm时，x 4记为60，当工作长度至根尖距离大于1.5mm且小于或等于2mm时，x 4记为40，当工作长度至根尖距离大于2mm，x 4记为0；当根管预备前后整体重合度为k％时，x 5记为100-k；当根管预备前后根管中心距离改变量为n mm，测量误差为i mm，已知器械平均偏移为j mm，当n＜i时，x 6记为100，当n＞i时，x 6记为(40n+60i-100j)/(i-j)，当存在侧穿情况时，x 6记为0；当剩余最小根管壁厚大于或等于1mm时，x 7记为100，当剩余最小根管壁厚小于1mm时，x 7记为Y/初始最小厚度，其中，Y为剩余最小根管壁厚；a＝b＝c＝d＝0.05，e＝0.4，f＝g＝0.2。
  21. 一种体外根管预备质量数字化评估系统，其特征在于，所述系统包括如权利要求1所述评估方法的评估单元。
  22. 如权利要求21所述的一种体外根管预备质量数字化评估系统，其特征在于，所述系统还包括：牙模制作单元，所述牙模型制作单元用于制作树脂牙模型。
  23. 如权利要求22所述的一种体外根管预备质量数字化评估系统，其特征在于，所述系统还包括：记录单元和扫描比对单元；
    其中，所述记录单元，用于记录根管预备前后使用的器械型号、台阶、根尖孔扩大和根管孔外碎屑情况；所述扫描对比单元，用于对未经根管预备的树脂牙模型和根管预备后的树脂牙模型分别进行CBCT或显微CT扫描，比较两者扫描结果，并将得出的预备后树脂牙根管清洁程度、偏移度和剩余最小根管壁厚发送给所述记录单元，由所述记录单元进行记录。
  24. 如权利要求23所述的一种体外根管预备质量数字化评估系统，其特征在于，所述系统还包括处理器和存储有计算机程序的存储器，所述处理器运行所述计算机程序；
    所述计算机程序的步骤如下：
    步骤一，所述牙模型制作单元制作基于离体牙数字化影像的3D打印仿真树脂牙 模型；
    步骤二，在所述树脂牙模型上进行根管预备操作，记录所述根管预备操作使用前后的器械型号、台阶、根尖孔扩大和根管孔外碎屑情况；
    步骤三：对所述未经根管预备的树脂牙模型和所述根管预备后的树脂牙模型分别进行CBCT扫描或显微CT扫描，比较两者扫描结果，得出所述预备后树脂牙根管清洁程度、偏移度和剩余最小根管壁厚；
    步骤四：所述评估单元建立所述评分算式进行评估。
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