Three-dimensional clinical research method of deciduous tooth anchorage on maxilla hypoplasia under guidance of HPC (High Performance Concrete) line

Abstract

The invention discloses a three-dimensional clinical research method of deciduous tooth anchorage on maxilla hypoplasia under the guidance of an HPC line. According to the invention, the deciduous tooth anchorage technology guided by the HPC line breaks through the limitation of the traditional tooth support type and bone support type correction, and creates a third anchorage selection mode for osteomalocclusion. By accurately positioning the central axis of the deciduous tooth crown as a supporting point, the technology not only retains the effectiveness of the traditional method on the transverse expansion of the maxilla, but also remarkably reduces the side effects of mesial inclination, vertical lifting and the like of the permanent tooth, and realizes the dual purposes of bony reconstruction and dentition stabilization. The innovativeness is that the physiological characteristics of deciduous teeth are combined with the biomechanical principle, the technical scheme is provided for the first time in China, the blank of correction of complex malocclusion in mixed dentition is filled, and a safer and more efficient treatment path is provided for clinic.

Description

Technical Field

[0001] The present invention belongs to the technical field of dental research, and specifically relates to a three-dimensional clinical research method for the use of primary tooth anchorage guided by the HPC line for maxillary hypoplasia. Background Art

[0002] Skeletal Class III malocclusion is a common developmental malocclusion in children's oral cavity. Its clinical features are mainly maxillary hypoplasia and anterior crossbite, which have a serious impact on the aesthetics and function of the child's maxillofacial region. This malocclusion is mainly caused by the disharmonious growth and development of the jaws. The development of the maxilla lags behind that of the mandible, resulting in abnormal occlusion of the upper and lower teeth. Anterior crossbite means that the lower anterior teeth are located outside the upper anterior teeth, affecting chewing function, pronunciation clarity, and overall facial coordination. If not treated in time, skeletal Class III malocclusion may worsen with the growth and development of children, further affecting the physical and mental health and social activities of the children. Therefore, early detection and intervention are crucial for improving the prognosis. Usually, orthodontic treatment, orthognathic surgery, or a combination of both methods are required to correct the malocclusion and restore normal occlusion and facial aesthetics.

[0003] However, traditional tooth-supported orthodontics is prone to side effects such as mesial inclination and vertical extrusion of permanent teeth. The bone-supported technique relies on CBCT examinations with high radiation, increasing the health risks of children. In addition, the existing methods lack the systematic application of primary tooth anchorage in the intervention of complex malocclusions in the mixed dentition period. The three-dimensional evaluation methods are mostly limited to invasive or high-radiation imaging, making it difficult to accurately monitor the effect of bone remodeling, resulting in insufficient coordinated regulation in the transverse and sagittal directions of early diagnosis and treatment, and affecting the comprehensiveness and long-term stability of the treatment effect. Summary of the Invention

[0004] The purpose of the present invention is to provide a three-dimensional clinical research method for the use of primary tooth anchorage guided by the HPC line for maxillary hypoplasia in order to solve the above-mentioned problems.

[0005] The technical solution adopted by the present invention is as follows: A three-dimensional clinical research method for the use of primary tooth anchorage guided by the HPC line for maxillary hypoplasia, characterized in that the method comprises the following steps: S1: Screen children with maxillary hypoplasia and anterior crossbite in the mixed dentition period who meet the inclusion criteria, ensure that the first permanent molar and the second primary molar of the maxilla exist and are normal vital pulp teeth, and exclude those with a history of orthodontic treatment or systemic diseases.

[0006] S2: Use the random number method to divide the children into an experimental group and a control group. The experimental group uses the second primary molar as the anchorage, and the control group uses the first permanent molar as the anchorage to ensure that the baseline data of the two groups are consistent.

[0007] S3: Bond the HYRAX appliance with a front traction hook to the experimental group and the control group respectively, and perform semi-rapid palatal expansion at a standard of 0.2 mm per day until the target width is reached.

[0008] S4: After the palatal expansion is completed, initiate the front traction treatment. Regularly monitor the correction of anterior crossbite to I°-II° deep overbite. Take lateral cephalograms to measure the ANB angle and Wits value. Stop the front traction when the ANB angle increases by 2°-4° and the Wits value is greater than -2°.

[0009] S5: Maintain for 6 months after removing the appliance. During this period, record the occlusal stability of the children. Take impressions after 6 months and generate digital models through 3Shape or iTero scanning, and export STL format files.

[0010] S6: Use the GOM inspection kit software to perform three-dimensional overlay on the models before and after treatment. Take the palatal rugae as the overlapping area, and establish a three-dimensional coordinate system to measure the mesial movement amount, buccal tipping torque and axis inclination angle of the first permanent molar.

[0011] S7: Combine the lateral cephalogram data to analyze indicators such as SNA angle, SNB angle, ANS-Ptm length, soft tissue profile angle, etc., and evaluate the sagittal and vertical remodeling effects of the maxilla.

[0012] S8: Compare the treatment days, changes in the axis inclination angle of the molars and differences in palatal plane rotation between the experimental group and the control group to verify the advantages of primary tooth anchorage in reducing dental compensation and vertical side effects.

[0013] S9: Organize the data and write a paper, focusing on demonstrating the three-dimensional treatment effect and clinical promotion value of the primary tooth anchorage technology guided by the HPC line for skeletal class III malocclusion.

[0014] In a preferred embodiment, in the step S1, screening children with maxillary hypoplasia and anterior crossbite in the mixed dentition stage who meet the standards needs to meet the following conditions: the age range is 6 to 10 years old, in the mixed dentition stage, the first permanent molars and the second deciduous molars of the maxilla are complete and have normal vital pulp teeth, and the ANB angle measured by the lateral cephalogram is less than 0°, and the Wits value is less than 0, meeting the characteristics of skeletal class III malocclusion. The exclusion criteria include children with cleft lip and palate, history of orthodontic treatment, systemic diseases or mental disorders who are unable to cooperate with the treatment. All enrolled cases need to be signed by the parents for informed consent and reviewed by the ethics committee to ensure compliance with the ethical requirements of medical research.

[0015] In a preferred embodiment, in step S2, a computer-generated random number table is used to group the children, and the ratio of the number of children in the experimental group to that in the control group is 1:1. After grouping, the consistency of the baseline data of the two groups needs to be verified, including indicators such as age, gender, ANB angle, Wits value, and maxilla length, to ensure no statistical difference. In the experimental group, the second deciduous molar of the upper jaw is used as the anchorage point, and in the control group, the first permanent molar of the upper jaw is used as the anchorage point. After grouping, the initial occlusion model and lateral cephalogram data of the children are recorded as the baseline basis for subsequent efficacy comparison.

[0016] In a preferred embodiment, in step S3, HYRAX expansion appliances with anterior traction hooks are customized for the experimental group and the control group respectively. The bonding position of the appliance is strictly located according to the HPC line (the mid-axis of the tooth crown) to ensure that the anchorage point is at the center of the deciduous tooth crown. The expansion operation is completed by the same attending physician. The expansion appliance is rotated clockwise once a day using a screw key, and the single expansion amount is 0.2 mm, continuing until the palatal mid-suture is completely opened and the maxillary width reaches the target value. During the expansion period, the children are reviewed once a week to check the stability of the appliance and the adaptability of the children, to avoid data deviation caused by loosening or pain.

[0017] In a preferred embodiment, in step S4, after the expansion is completed, the anterior traction treatment is started. The anterior traction force is set to 400 to 500 g on each side, and the daily wearing time is not less than 14 hours. A lateral cephalogram is taken during the monthly review to measure the overjet of the anterior teeth. When the anterior crossbite is corrected to a deep overjet of I° to II°, a standard lateral cephalogram is immediately taken to measure the ANB angle and the Wits value. When the ANB angle increases to 2° to 4° and the Wits value is greater than -2°, the anterior traction is terminated, and the total treatment days and the removal time of the appliance are recorded. After the appliance is removed, a 6-month observation period is required. During this period, the occlusion stability is reviewed monthly and the data are recorded.

[0018] In a preferred embodiment, in step S5, after the observation period ends, a digital dental model of the child is obtained using a 3Shape Trios or iTero Element 5D intraoral scanner. The scanning accuracy is set to 20 μm, and the model data are exported in STL format and encrypted for storage. At the same time, standardized intraoral photos and lateral facial soft tissue photos are taken to record the occlusion relationship and soft tissue changes. All data need to be cross-checked by two independent physicians to ensure the integrity of the model and the accuracy of the measurement, and to avoid affecting subsequent analysis due to operation errors.

[0019] In a preferred embodiment, in step S6, the digital models before and after treatment are imported into the GOM Inspect Suite 2022 software, and the three-dimensional model superposition alignment is carried out with the palatal rugae as the reference area. A three-dimensional coordinate system is established: the lingual direction of the teeth is the X-axis, the mesiodistal direction is the Y-axis, and the occlusal vertical direction is the Z-axis. Measure the mesial movement amount, buccal tipping torque angle and axial inclination angle change of the maxillary first permanent molar, and control the accuracy within 0.1 mm and 0.1°. The software automatically generates a three-dimensional displacement cloud map and a data report to quantify the tooth movement trend and the bone remodeling effect.

[0020] In a preferred embodiment, in step S7, combined with the lateral cephalogram data, the Uceph 4.2.1 software is used to measure the SNA angle, SNB angle, ANS-Ptm length, Ptm-6 distance and soft tissue nasolabial angle. The sagittal elongation amount of the maxilla and the rotation angle of the palatal plane are analyzed by multi-planar reconstruction technology to evaluate the three-dimensional correction effect of skeletal class III malformations. The data needs to be independently analyzed by two orthodontic experts by the double-blind method. When the difference exceeds 5%, a third-party review is initiated to ensure the objectivity and credibility of the results.

[0021] In a preferred embodiment, in step S8, compare the total treatment days, the change value of the buccal tipping torque angle of the first permanent molar and the rotation angle of the palatal plane between the experimental group and the control group. The independent samples t-test is performed using SPSS 26.0 software, and the significance level is set at α = 0.05. Focus on analyzing the advantages of the experimental group in reducing the mesial inclination of the molars, vertical elevation and counterclockwise rotation of the palatal plane, and demonstrate the clinical value of primary tooth anchorage in reducing dental compensation and promoting bone remodeling in combination with the three-dimensional model data.

[0022] In a preferred embodiment, in step S9, summarize all clinical data and three-dimensional measurement results, and use GraphPad Prism 9 to draw statistical charts, including the line chart of the ANB angle change before and after treatment, the three-dimensional vector diagram of molar movement and the heat map of palatal plane rotation. The paper writing needs to follow the CONSORT guidelines, and focus on elaborating the innovation, treatment stability of the primary tooth anchorage technique under the guidance of the HPC line and its long-term impact on the jaw growth of children. The final results are published in an SCI journal after peer review, and provide evidence-based basis for formulating early intervention programs for skeletal class III malocclusions in clinical practice.

[0023] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are: 1. In the present invention, the deciduous teeth anchorage technology guided by HPC lines breaks through the limitations of traditional tooth-supported and bone-supported corrections, and creates a third anchorage selection mode for skeletal malocclusion. By accurately positioning the central axis of the deciduous tooth crown as the support point, this technology not only retains the effectiveness of traditional methods for lateral expansion of the maxillary bone, but also significantly reduces the side effects of mesial tilting and vertical elevation of permanent teeth, achieving the dual goals of bony reconstruction and dentition stability. Its innovation lies in combining the physiological characteristics of deciduous teeth with the principles of biomechanics. This is the first time that such a technical solution has been proposed in China, filling the gap in the correction of complex malocclusion in the mixed dentition period, and providing a safer and more efficient treatment path for clinical practice.

[0024] 2. In the present invention, the 3D digital model and lateral film multi-dimensional analysis technology introduced in the study abandoned the radiation dependence of traditional CBCT, and realized the dynamic evaluation of the transverse, sagittal and vertical development of the maxilla through high-precision scanning and three-dimensional reconstruction. This method not only greatly reduces the risk of radiation exposure for children, but also provides a reliable basis for the early diagnosis of maxillary underdevelopment by quantifying parameters such as tooth torque and axial inclination. Especially for children with skeletal Class III whose first permanent molars are obstructed from erupting, this technology can simultaneously promote the coordinated growth of the maxilla in three dimensions, lay the foundation for the clinical formulation of individualized intervention strategies, and promote the further improvement of the early screening and early treatment system for children's malocclusion. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the process principle of the present invention. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Example

[0027] Reference Figure 1 A three-dimensional clinical research method for maxillary bone underdevelopment using HPC lines as guidance for deciduous tooth anchorage, the method comprising the following steps: S1: Screen children with maxillary underdevelopment and anterior crossbite in the mixed dentition period who meet the inclusion criteria, ensure that the maxillary first permanent molars and second deciduous molars are present and have normal vital pulp, and exclude those with a history of orthodontic treatment or systemic diseases.

[0028] S2: The children were divided into an experimental group and a control group using the random number method. The experimental group used the second deciduous molars as anchorage, and the control group used the first permanent molars as anchorage to ensure that the baseline data of the two groups were consistent.

[0029] S3: Bond the HYRAX appliance with a front traction hook to the experimental group and the control group respectively, and perform semi-rapid palatal expansion at a standard of 0.2 mm per day until the target width is reached.

[0030] S4: After the palatal expansion is completed, start the anterior traction treatment. Regularly monitor the correction of anterior crossbite to I°-II° deep overbite, take lateral cephalograms to measure the ANB angle and Wits value, and stop the anterior traction when the ANB angle increases by 2°-4° and the Wits value is greater than -2°.

[0031] S5: Maintain for 6 months after removing the appliance. During this period, record the occlusal stability of the children. Take impressions after 6 months and generate digital models through 3Shape or iTero scanning, and export STL format files.

[0032] S6: Use the GOM inspection kit software to perform three-dimensional superposition on the models before and after treatment. Take the palatal rugae as the overlapping area, and establish a three-dimensional coordinate system to measure the mesial movement amount, buccal inclination torque and axial inclination angle of the first permanent molar.

[0033] S7: Combine the lateral cephalogram data to analyze indicators such as SNA angle, SNB angle, ANS-Ptm length, soft tissue profile angle, etc., and evaluate the sagittal and vertical remodeling effects of the maxilla.

[0034] S8: Compare the treatment days, changes in the axial inclination angle of the molars and differences in palatal plane rotation between the experimental group and the control group to verify the advantages of primary tooth anchorage in reducing dental compensation and vertical side effects.

[0035] S9: Organize the data and write a paper, focusing on demonstrating the three-dimensional orthodontic effect and clinical promotion value of the primary tooth anchorage technology guided by the HPC line for skeletal class III malocclusion.

[0036] In step S1, select children with maxillary hypoplasia and anterior crossbite in the mixed dentition stage who meet the criteria. The following conditions need to be met: the age range is 6 to 10 years old, in the mixed dentition stage, the first permanent molar and the second deciduous molar of the maxilla are complete and have normal vital pulp teeth. The ANB angle measured by the lateral cephalogram is less than 0°, and the Wits value is less than 0, which conforms to the characteristics of skeletal class III malocclusion. The exclusion criteria include children with cleft lip and palate, orthodontic treatment history, systemic diseases or mental disorders who are unable to cooperate with the treatment. All enrolled cases need to be signed by the parents for informed consent and reviewed by the ethics committee to ensure compliance with the ethical requirements of medical research.

[0037] In step S2, the children are grouped using a computer-generated random number table, and the ratio of the number of children in the experimental group to the control group is 1:1. After grouping, the consistency of the baseline data of the two groups needs to be verified, including indicators such as age, gender, ANB angle, Wits value, and maxillary bone length, to ensure no statistical differences. The second deciduous molar in the upper jaw is used as the anchorage point in the experimental group, and the first permanent molar in the upper jaw is used as the anchorage point in the control group. After grouping, the initial occlusal model and lateral cephalogram data of the children are recorded as the baseline basis for subsequent efficacy comparison.

[0038] In step S3, HYRAX expansion appliances with anterior traction hooks are customized for the experimental group and the control group respectively. The bonding position of the appliance is strictly located according to the HPC line (the mid-axis of the tooth crown) to ensure that the anchorage point is at the center of the deciduous tooth crown. The expansion operation is completed by the same attending physician. The expansion appliance is rotated clockwise once a day using a screw key, and the single expansion amount is 0.2 mm, continuing until the median palatal suture is completely opened and the maxillary width reaches the target value. During the expansion period, the children are reviewed once a week to check the stability of the appliance and the adaptability of the children, avoiding data deviation caused by loosening or pain.

[0039] In step S4, after the expansion is completed, the anterior traction treatment is initiated. The anterior traction force is set to 400 to 500 g on each side, and the daily wearing time is not less than 14 hours. Lateral cephalograms are taken during the monthly review to measure the overjet of the anterior teeth. When the anterior crossbite is corrected to a deep overjet of I° to II°, a standard lateral cephalogram is immediately taken to measure the ANB angle and the Wits value. When the ANB angle increases to 2° to 4° and the Wits value is greater than -2°, the anterior traction is terminated, and the total treatment days and the removal time of the appliance are recorded. After the appliance is removed, a 6-month observation period is required. During this period, the occlusal stability is reviewed monthly and the data are recorded.

[0040] In step S5, after the observation period ends, a 3Shape Trios or iTero Element 5D intraoral scanner is used to obtain the digital dental models of the children. The scanning accuracy is set to 20 μm, and the model data are exported and encrypted in STL format. At the same time, standardized intraoral photos and lateral soft tissue photos of the face are taken to record the occlusal relationship and soft tissue changes. All data need to be cross-checked by two independent physicians to ensure the integrity of the model and the accuracy of the measurement, avoiding influencing subsequent analysis due to operation errors.

[0041] In step S6, the digital models before and after treatment are imported into the GOM Inspect Suite 2022 software, and the three-dimensional model is superimposed and aligned with the median palatal rugae as the reference area. A three-dimensional coordinate system is established: the lingual direction of the teeth is the X-axis, the mesiodistal direction is the Y-axis, and the occlusal vertical direction is the Z-axis. The mesial movement amount, buccal tipping torque angle, and axial inclination angle changes of the first permanent molar in the upper jaw are measured, and the accuracy is controlled within 0.1 mm and 0.1°. The software automatically generates a three-dimensional displacement cloud map and a data report to quantify the tooth movement trend and the bone remodeling effect.

[0042] In step S7, in combination with the lateral radiograph data, the SNA angle, SNB angle, ANS-Ptm length, Ptm-6 distance, and soft tissue nasolabial angle were measured using Uceph 4.2.1 software. The sagittal elongation of the maxilla and the rotation angle of the palatal plane were analyzed through multi-planar reconstruction technology to evaluate the three-dimensional correction effect of skeletal class III malformations. The data needed to be independently analyzed by two orthodontic experts through a double-blind method. When the difference exceeded 5%, a third-party review was initiated to ensure the objectivity and credibility of the results.

[0043] In step S8, the total treatment days, the change value of the buccal tipping torque angle of the first permanent molar, and the rotation angle of the palatal plane were compared between the experimental group and the control group. Independent sample t-tests were performed using SPSS 26.0 software, and the significance level was set at α = 0.05. The advantages of the experimental group in reducing the mesial inclination of molars, vertical elevation, and counterclockwise rotation of the palatal plane were analyzed, and the clinical value of primary tooth anchorage in reducing dental compensation and promoting bone remodeling was demonstrated in combination with the three-dimensional model data.

[0044] In step S9, all clinical data and three-dimensional measurement results were summarized, and statistical charts were drawn using GraphPad Prism 9, including the line graph of the change in ANB angle before and after treatment, the three-dimensional vector graph of molar movement, and the heat map of palatal plane rotation. The paper writing needed to follow the CONSORT guidelines, focusing on the innovation, treatment stability, and long-term impact on the jaw growth of children of the primary tooth anchorage technique guided by the HPC line. The final results were published in an SCI journal after peer review, providing evidence-based basis for formulating early intervention programs for skeletal class III malocclusions in clinical practice.

[0045] It can be seen from the above that: In the present invention, the primary tooth anchorage technique guided by the HPC line breaks through the limitations of traditional tooth-supported and bone-supported orthodontics, creating a third anchorage selection mode for skeletal malocclusions. By accurately positioning the central axis of the primary tooth crown as the support point, this technique not only retains the effectiveness of the traditional method in transverse expansion of the maxilla but also significantly reduces side effects such as mesial inclination and vertical elevation of permanent teeth, achieving the dual goals of bone remodeling and dental arch stability. Its innovation lies in combining the physiological characteristics of primary teeth with biomechanical principles, which is the first time such a technical solution has been proposed in China, filling the gap in the treatment of complex malocclusions in the mixed dentition period and providing a safer and more efficient treatment path for clinical practice.

[0046] In the present invention, the 3D digital model and multi-dimensional analysis technology introduced in the research discard the radiation dependence of traditional CBCT. Through high-precision scanning and three-dimensional reconstruction, the dynamic evaluation of the transverse, sagittal and vertical development of the maxilla is realized. This method not only greatly reduces the risk of radiation exposure for children, but also provides a reliable basis for the early diagnosis of maxillary hypoplasia by quantifying parameters such as tooth torque and axis inclination angle. Especially for skeletal Class III children with impacted first permanent molars, this technology can simultaneously promote the coordinated three-dimensional growth of the maxilla, laying a foundation for formulating individualized intervention strategies in clinical practice and promoting the further improvement of the early screening and treatment system for children's malocclusions.

[0047] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent in such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of additional identical elements in the process, method, article or device including the element.

[0048] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A three-dimensional clinical research method for the use of deciduous teeth anchorage guided by the HPC line for maxillary hypoplasia, characterized in that: The method includes the following steps: S1: Screen children with maxillary hypoplasia and anterior crossbite in the mixed dentition stage who meet the inclusion criteria, ensuring that the first permanent molar and the second deciduous molar of the maxilla are present and have vital pulp, and excluding those with a history of orthodontic treatment or systemic diseases; S2: Use the random number method to divide the children into an experimental group and a control group. The experimental group uses the second deciduous molar as the anchorage, and the control group uses the first permanent molar as the anchorage, ensuring that the baseline data of the two groups are consistent; S3: Bond HYRAX appliances with anterior traction hooks to the experimental group and the control group respectively, and perform semi-rapid maxillary expansion at a standard of 0.2 mm per day until the target width is reached; S4: After the maxillary expansion is completed, initiate anterior traction treatment, regularly monitor the correction of anterior crossbite to I°-II° deep overbite, take lateral cephalograms to measure the ANB angle and Wits value, and stop anterior traction when the ANB angle increases by 2°-4° and the Wits value is greater than -2°; S5: Maintain for 6 months after removing the appliance. During this period, record the occlusal stability of the children. After 6 months, take impressions and generate digital models through 3Shape or iTero scanning, and export STL format files; S6: Use GOM inspection kit software to perform three-dimensional superposition on the models before and after treatment. Take the palatal rugae as the overlapping area, and establish a three-dimensional coordinate system to measure the mesial movement amount, buccal inclination torque and axial inclination angle of the first permanent molar; S7: Combine the lateral cephalogram data, analyze the SNA angle, SNB angle, ANS-Ptm length, soft tissue profile angle indicators, and evaluate the sagittal and vertical remodeling effects of the maxilla; S8: Compare the treatment days, changes in the axial inclination angle of the molars and differences in palatal plane rotation between the experimental group and the control group, and verify the advantages of deciduous tooth anchorage in reducing dental compensation and vertical side effects; S9: Organize the data and write a paper, focusing on demonstrating the three-dimensional orthodontic effect and clinical promotion value of the deciduous tooth anchorage technique guided by the HPC line for skeletal class III malocclusion; 2. A three-dimensional clinical research method for the orthopedic effect of primary teeth anchorage guided by HPC line on maxillary hypoplasia according to claim 1, characterized in that: In the step S1, to screen children with maxillary hypoplasia and anterior crossbite in the mixed dentition stage who meet the standards, the following conditions need to be met: the age range is 6 to 10 years old, in the mixed dentition stage, the first permanent molar and the second deciduous molar of the maxilla are complete and have vital pulp, the ANB angle measured by lateral cephalogram is less than 0°, the Wits value is less than 0, meeting the characteristics of skeletal class III malocclusion; the exclusion criteria include children with cleft lip and palate, a history of orthodontic treatment, systemic diseases or mental disorders who are unable to cooperate with the treatment; all enrolled cases need to be signed by the parents for informed consent and reviewed by the ethics committee to ensure compliance with the ethical requirements of medical research.

3. A three-dimensional clinical research method for using deciduous teeth anchorage guided by the HPC line to treat maxillary hypoplasia as described in claim 1, characterized in that: In the step S2, use a computer-generated random number table to group the children. The ratio of the number of people in the experimental group to the control group is 1:1; after grouping, it is necessary to verify the consistency of the baseline data of the two groups, including age, gender, ANB angle, Wits value and maxilla length index, to ensure no statistical difference; the experimental group uses the second deciduous molar of the maxilla as the anchorage point, and the control group uses the first permanent molar of the maxilla as the anchorage point. After grouping, record the initial occlusal model and lateral cephalogram data of the children as the baseline basis for subsequent efficacy comparison.

4. A three-dimensional clinical research method for the use of deciduous teeth anchorage guided by HPC line for maxillary hypoplasia, characterized in that: In the said step S3, HYRAX expansion appliances with anterior traction hooks are customized for the experimental group and the control group respectively. The bonding positions of the appliances are strictly located according to the HPC line to ensure that the anchorage points are at the centers of the crowns of deciduous teeth. The expansion operation is completed by the same attending physician. The expansion appliance is rotated clockwise once a day using a screw key, and the single expansion amount is 0.2 mm, continuing until the palatal suture is completely opened and the maxillary width reaches the target value. During the expansion period, a follow-up visit is made once a week to check the stability of the appliance and the adaptability of the child, so as to avoid data deviation caused by loosening or pain.

5. A three-dimensional clinical research method for the orthodontic anchorage of primary teeth to correct maxillary hypoplasia guided by the HPC line, characterized in that: In the said step S4, after the expansion is completed, the anterior traction treatment is initiated. The anterior traction force is set at 400 to 500 g on each side, and the daily wearing time is not less than 14 hours. A lateral cephalogram is taken during the monthly follow-up visit to measure the overjet of the anterior teeth. When the anterior crossbite is corrected to a deep overjet of I° to II°, a standard lateral cephalogram is immediately taken to measure the ANB angle and the Wits value. When the ANB angle increases to 2° to 4° and the Wits value is greater than -2°, the anterior traction is terminated, and the total number of treatment days and the appliance removal time are recorded. A 6-month observation period needs to be maintained after the appliance is removed, and the occlusal stability is rechecked monthly during this period and the data is recorded.

6. A three-dimensional clinical research method for using deciduous teeth anchorage guided by HPC line to treat maxillary hypoplasia as described in claim 1, characterized in that: In the said step S5, after the observation period ends, a digital dental model of the child is obtained using a 3Shape Trios or iTero Element 5D intraoral scanner. The scanning accuracy is set at 20 μm, and the model data is exported in STL format and encrypted for storage. At the same time, standardized intraoral photos and lateral soft tissue profile photos of the face are taken to record the occlusal relationship and soft tissue changes. All data needs to be cross-checked by two independent physicians to ensure the integrity of the model and the accuracy of the measurement, so as to avoid affecting the subsequent analysis due to operation errors.

7. A three-dimensional clinical research method for using deciduous teeth anchorage guided by the HPC line to treat maxillary hypoplasia as described in claim 1, characterized in that: In the said step S6, the digital models before and after treatment are imported into the GOM Inspect Suite software, and the three-dimensional model is superimposed and aligned with the palatal rugae as the reference area. A three-dimensional coordinate system is established: the lingual direction of the teeth is the X-axis, the mesiodistal direction is the Y-axis, and the occlusal vertical direction is the Z-axis. The mesial movement amount, buccal inclination torque angle, and axis inclination angle changes of the maxillary first permanent molars are measured, and the accuracy is controlled within 0.1 mm and 0.1°. The software automatically generates a three-dimensional displacement cloud map and a data report to quantify the tooth movement trend and the bone remodeling effect.

8. A three-dimensional clinical research method for using deciduous teeth anchorage guided by the HPC line to treat maxillary hypoplasia as described in claim 1, characterized in that: In the said step S7, combined with the lateral cephalogram data, the sagittal elongation amount of the maxilla and the rotation angle of the palatal plane are analyzed through multi-planar reconstruction technology to evaluate the three-dimensional correction effect of skeletal class III malformations.

9. A three-dimensional clinical research method for using deciduous teeth anchorage guided by the HPC line to treat maxillary hypoplasia as claimed in claim 1, characterized in that: In the said step S8, the total number of treatment days, the change value of the buccal inclination torque angle of the first permanent molars, and the rotation angle of the palatal plane of the experimental group and the control group are compared. The independent samples t-test is performed using SPSS 26.0 software, and the significance level is set at α = 0.

05. The advantages of the experimental group in reducing the mesial inclination of the molars, vertical elevation, and counterclockwise rotation of the palatal plane are mainly analyzed, and the clinical value of deciduous tooth anchorage in reducing dental compensation and promoting bone remodeling is demonstrated in combination with the three-dimensional model data.

10. A three-dimensional clinical research method for using primary teeth anchorage guided by HPC line to treat maxillary hypoplasia as described in claim 1, characterized in that: In the step S9, all clinical data and three-dimensional measurement results are summarized, and statistical charts are drawn using GraphPad Prism 9, including the line graph of the ANB angle change before and after treatment, the three-dimensional vector graph of molar movement, and the heat map of palatal plane rotation.

Images