Finite element analysis method for influence of maxillary anterior traction combined expansion in different directions on alveolar ridge fissure bone grafting

Abstract

The invention relates to the technical field of cleft lip and palate bone grafting, in particular to a finite element analysis method for influence of anterior maxillary traction combined arch expansion in different directions on alveolar ridge fissure bone grafting, which specifically comprises the following steps: establishing a three-dimensional finite element model after bone grafting of an alveolar ridge fissure cranial maxillary complex, and applying anterior traction combined arch expansion force in different directions on the three-dimensional finite element model; the total displacement of the skull maxillary complex after bone grafting under the orthodontic force effect and the biological stress of each bone seam under different working conditions are obtained. On the basis of establishing a unilateral alveolar crest fissure cranial maxillary complex model, full-fissure bone grafting is carried out on an alveolar crest defect area with the nose bottom side as the upper face and the oral cavity side as the lower face, and a 3D model after bone grafting of the unilateral alveolar crest fissure cranial maxillary complex is generated. And forward traction forces in different directions are applied to be combined with the expansion force, and the total displacement of the cranial maxillary complex under the orthodontic force after bone grafting and the biological stress of each bone seam are analyzed. And reference is provided for the forward traction force direction of the alveolar ridge fissure after bone grafting clinically.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cleft lip and palate bone grafting, in particular to a finite element analysis method for the influence of jaw forward traction in different directions combined with arch expansion on alveolar ridge cleft bone grafting. BACKGROUND

[0002] Cleft lip and palate is the most common congenital deformity of the head and neck, which is clinically manifested as cleft lip, cleft palate and alveolar ridge cleft. Among them, alveolar ridge cleft is a bone defect that occurs in the anterior arch of the maxilla, characterized by discontinuity of the maxillary alveolar ridge, tooth loss or impaction in the defect area, oral-nasal fistula, and maxillary dysplasia. In addition to the intrinsic genetic defect leading to congenital maxillary bone growth deficiency, multiple cleft lip and palate repair surgeries and postoperative scar contracture also have a significant inhibitory effect on maxillary bone growth. Alveolar ridge cleft is often accompanied by severe maxillary sagittal and transverse growth deficiency, which further leads to severe dental crowding, anterior and posterior teeth reverse, and midfacial depression.

[0003] In clinical practice, maxillary forward traction and maxillary expansion orthodontics are often used after alveolar ridge cleft bone grafting to correct maxillary bone growth deficiency. Currently, there is little research on the direction of forward traction after alveolar ridge cleft bone grafting. Some research has used three-dimensional finite element analysis to construct a three-dimensional model of the cranio-maxillary complex of cleft lip and palate, and simulated the biomechanics of the cranio-maxillary complex under different forward traction directions. Dan Zhang et al. established a three-dimensional finite element model of the craniofacial complex of unilateral cleft palate and alveolar ridge, simulated different directions of forward traction force and whether to combine with arch expansion force, and observed the biomechanical effects of the cranio-maxillary complex in three-dimensional directions under different loading conditions. However, the existing technology has the following shortcomings:

[0004] 1. Ignoring the influence of alveolar ridge cleft bone grafting on the craniofacial region of patients with alveolar ridge cleft and class III malocclusion, which may lead to (1) biomechanical imbalance: stress distribution is abnormal due to bone defect, which aggravates the deformity; (2) deterioration of function and aesthetics: impaired occlusion, breathing, and pronunciation function, and difficult to correct facial deformity; (3) treatment plan hindered: orthodontic, orthognathic, and prosthetic treatments are difficult to implement or ineffective due to bone defect;

[0005] 2. No stress analysis of the suture of the constructed three-dimensional finite element model of the cranio-maxillary complex, which may lead to incorrect prediction of the biomechanical behavior of the craniofacial region, affecting the rationality and safety of the treatment plan. SUMMARY

[0006] In view of the above shortcomings in the prior art, the present application aims to provide a finite element analysis method for the influence of jaw forward traction in different directions combined with arch expansion on alveolar ridge cleft bone grafting.

[0007] To achieve the above-mentioned purpose of the application, the technical solution adopted by the present application is as follows:

[0008] A finite element analysis method for the influence of maxillary protraction combined with expansion in different directions on bone grafting in alveolar cleft is provided, which comprises the following steps:

[0009] A three-dimensional finite element model of the cranio-maxillofacial complex after bone grafting in alveolar cleft is established, and different direction protraction force combined with expansion force is applied thereon to obtain the overall displacement of the cranio-maxillofacial complex under the action of orthodontic force in different working conditions and the biological stress of each suture, and the effect of different direction protraction force combined with expansion force on the cranio-maxillofacial complex is analyzed.

[0010] Further, the method for establishing a three-dimensional finite element model of the cranio-maxillofacial complex after bone grafting in alveolar cleft comprises the following steps:

[0011] The scanning data of the cranio-maxillofacial complex in alveolar cleft is obtained; the scanning data is imported into a three-dimensional reconstruction software, the skull, maxilla and mandible are preliminarily extracted from the image by threshold segmentation, the full cleft bone is implanted in the alveolar cleft defect area with the nasal bottom side as the upper surface and the oral side as the lower surface, a 3D model of the cranio-maxillofacial complex after bone grafting is generated, a solid model is fitted, material properties are assigned to the model, boundary and load settings are made, and finally a three-dimensional finite element model of the cranio-maxillofacial complex after bone grafting in alveolar cleft is obtained.

[0012] Further, the method for applying different direction protraction force combined with expansion force based on the three-dimensional finite element model of the cranio-maxillofacial complex after bone grafting in alveolar cleft comprises the following steps:

[0013] A protraction force is applied to the bilateral maxillary canine buccal alveolar ridge top area, and the direction is forward and forms different angles with the occlusal plane; the occlusal plane is formed by the mesial contact point of the maxillary central incisor and the bilateral maxillary first molar mesial buccal tooth tip; when the angle is positive, the protraction force is forward and upward relative to the occlusal plane, and when the angle is negative, the protraction force is forward and downward relative to the occlusal plane; at the same time, an expansion force is applied to the bilateral maxillary first premolar and first molar palatal alveolar ridge top area, and the direction is horizontal to both sides.

[0014] Further, a protraction force of 5N is applied to the bilateral maxillary canine buccal alveolar ridge top area, and the direction is forward and forms angles of -30°, -20°, -10°, 0°, 10°, 20° and 30° with the occlusal plane, a total of seven working conditions.

[0015] Further, the overall displacement of the cranio-maxillofacial complex is analyzed by observing the displacement of the landmark points in the sagittal, vertical and horizontal directions of the maxilla.

[0016] Further, the displacement of the landmark points in the sagittal, vertical and horizontal directions of the maxilla is as follows:

[0017] Sagittal displacement landmark points: the upper alveolar seat point, the upper central incisor point, the left first molar palatal apex point and the right first molar palatal apex point represent the displacement characteristics of the dentition and alveolar bone; the nasal root point, the most concave part of the nasal bone, the lower part of the nasal bone and the anterior nasal spine point represent the skeletal displacement characteristics of the cranio-maxillofacial complex;

[0018] Vertical displacement landmark points: two landmark points are selected in the vertical direction, which are the anterior nasal spine point and the posterior nasal spine point, representing the vertical displacement of the cranio-maxillofacial complex;

[0019] Horizontal displacement landmark points: the horizontal direction selects the distance between the cusps of the bilateral canines as the anterior arch width, the distance between the central fossae of the bilateral first premolars as the middle arch width, and the distance between the central fossae of the bilateral first molars as the posterior arch width, and the average value of the horizontal displacement of the three arches represents the horizontal displacement of the cranio-maxillofacial complex.

[0020] Further, the suture biological stress indicators include: the equivalent stress of the bilateral nasofrontal suture, the frontomaxillary suture, the zygomaticomaxillary suture, the pterygopalatine suture and the zygomaticotemporal suture.

[0021] The beneficial effects of the present application are:

[0022] The present application is based on the establishment of a unilateral cleft alveolar ridge cranio-maxillofacial complex model, and the full split bone is implanted in the alveolar ridge defect area with the nasal bottom side as the upper surface and the oral cavity side as the lower surface to generate a 3D model of the unilateral cleft alveolar ridge cranio-maxillofacial complex after bone implantation. Different direction forward traction force combined with expansion force is applied, and the overall displacement of the cranio-maxillofacial complex under the action of orthodontic force and the biological stress of each suture after bone implantation are analyzed. The direction of the forward traction force for the cleft alveolar ridge after bone implantation in the clinic is provided. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The coronal plane grid model of the cranio-maxillofacial complex after simulated bone implantation in the example;

[0024] Figure 2 The horizontal plane grid model of the cranio-maxillofacial complex after simulated bone implantation in the example;

[0025] Figure 3 The schematic diagram of the coordinate axis setting of the cranio-maxillofacial complex in the example;

[0026] Figure 4 The schematic diagram of the boundary condition setting of the cranio-maxillofacial complex in the example. DETAILED DESCRIPTION

[0027] The specific embodiments of the present application are described below to facilitate the understanding of the present application for those skilled in the art, but it should be clear that the present application is not limited to the scope of the specific embodiments, and for those skilled in the art, it is obvious that various changes are within the spirit and scope of the present application defined and determined by the appended claims, and all the inventions utilizing the concept of the present application are within the scope of protection.

[0028] Embodiment

[0029] A finite element analysis method for the influence of maxillary protraction combined with arch expansion in different directions on alveolar cleft bone grafting is provided, which specifically comprises the following steps:

[0030] 1. Obtain CBCT scan data of the cranio-maxillofacom complex of alveolar cleft, import the CBCT scan data into Mimics three-dimensional reconstruction software, preliminarily extract the skull, maxilla and mandible from the image by threshold segmentation, perform full fracture bone grafting in the alveolar cleft defect area with the nasal bottom side as the upper surface and the oral side as the lower surface, generate a 3D model of the cranio-maxillofacom complex after bone grafting, output the model in STL format, import it into Geomagic reverse engineering processing software, fit a CAD solid model of the cranio-maxillofacom complex after bone grafting, output the model in STEP format, and assign material properties, set boundaries and loads, and finally obtain a three-dimensional finite element model of the unilateral cleft lip and palate cranio-maxillofacom complex after bone grafting.

[0031] 2. Import the established three-dimensional finite element model of the cranio-maxillofacom complex after bone grafting into ANSYS software, and apply a forward traction force of 5N on the bilateral maxillary canine buccal alveolar ridge top area, with a direction of forward and an angle of -30°, -20°, -10°, 0°, 10°, 20°, 30° with the occlusal plane, a total of seven working conditions; the occlusal plane is formed by the mesial contact point of the upper central incisor and the bilateral upper first molar mesial buccal alveolar ridge; when the angle of traction is positive, the forward traction force is forward and upward relative to the occlusal plane, and when the angle of traction is negative, the forward traction force is forward and downward relative to the occlusal plane. At the same time, apply an arch expansion force of 5N horizontally to both sides on the palatal alveolar ridge top area of the bilateral upper first premolar and first molar.

[0032] 3. Observe the displacement of the marker points in the sagittal, vertical and horizontal directions of the maxilla to analyze the overall displacement of the cranio-maxillofacom complex.

[0033] To facilitate the analysis of the overall displacement of the maxillofacom complex, representative nodes are selected from the sagittal, vertical and horizontal directions to determine their displacement.

[0034] 3.1 Sagittal displacement landmarks: The upper alveolar point (A), upper central incisor point (U1), left first molar palatal point (ML1), and right first molar palatal point (MR1) represent the displacement characteristics of the dentition and alveolar bone. The nasal root point (N), the most concave part of the nasal bone (Cn), the lower part of the nasal bone (In), and the anterior nasal spine point (ANS) represent the skeletal displacement characteristics of the cranio-maxillofacial complex.

[0035] 3.2 Vertical displacement landmarks: Two landmarks were selected in the vertical direction: the anterior nasal spine point (ANS) and the posterior nasal spine point (PNS) represent the vertical displacement of the cranio-maxillofacial complex.

[0036] 3.3 Horizontal displacement landmarks: The horizontal direction selects the distance between the cusps of the bilateral canines as the anterior arch width, the distance between the central fossae of the bilateral first premolars as the middle arch width, and the distance between the central fossae of the bilateral first molars as the posterior arch width. The average value of the horizontal displacement of the three segments of the arch represents the horizontal displacement of the cranio-maxillofacial complex.

[0037] By integrating the displacement of the maxilla in three different directions, the overall displacement of the cranio-maxillofacial complex can be inferred. This provides a theoretical basis for the implementation of pre-traction combined with expansion in the post-osteotomized cleft lip and palate.

[0038] 4. Analysis of the overall biomechanical effect of the cranio-maxillofacial complex: Suture stress observation indicators: Observe the equivalent stress (EQV) of the nasofrontal suture, frontomaxillary suture, zygomaticomaxillary suture, pterygopalatine suture, and zygomaticotemporal suture on both healthy and affected sides under different loading conditions. EQV is the Von Mises stress, also known as Von Mises stress. When an object is subjected to external load, internal forces are generated to counteract it. According to Hooke's Law and the principles of elastic mechanics, the internal forces drive the object to return to its initial undeformed position along the elastic recovery path, maintaining structural integrity and mechanical balance. The internal force per unit area on a cross-sectional point is the stress. EQV stress is widely used in biomechanics research and is one of the gold standards for evaluating bone stress distribution, so EQV stress is used as an indicator for analyzing the biomechanical changes of the maxillofacial bones.

[0039] After three-dimensional finite element solution, the displacement vector of each node of the output model is output, showing the overall movement direction and amplitude of the bone under the action of the treatment force. It can predict the expansion amount of the palatine suture under the action of the maxillary expander in clinical practice, or the displacement direction of the maxilla in orthodontic traction. The maximum displacement, displacement distribution uniformity, symmetry, and abnormal displacement may indicate treatment risks; suture stress can judge suture adaptability, and high stress areas may indicate active areas of suture remodeling, guiding the optimization of the force system. In clinical practice, it can assist in judging whether the growth potential of the maxilla is activated or inhibited.

[0040] In conclusion, the application predicts the effect of the cranio-maxillofacial complex under the combined action of the different angle anterior traction force and the expansion force by obtaining the suture stress of the healthy and diseased sides of the cranio-maxillofacial complex under different loading conditions, and optimizes the scheme.

[0041] It will be obvious to a person skilled in the art that the application is not limited to the details of the foregoing exemplary embodiments, and that the application can be implemented in other concrete forms without departing from the spirit or essential characteristics of the application. Therefore, the embodiments should be considered as exemplary and not limiting in any way, and the scope of the application is defined by the appended claims and not by the foregoing description, and all changes falling within the meaning and range of equivalence of the essential features of the claims are intended to be embraced therein.

[0042] Furthermore, it should be understood that although the present specification describes exemplary embodiments, not every exemplary embodiment includes only one independent technical solution, and the present specification is described in this way only for the sake of clarity, and a person skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by a person skilled in the art.

Claims

1. The finite element analysis method of the effect of maxillary protraction combined with arch expansion in different directions on alveolar ridge cleft bone grafting is characterized by: The following steps are involved: A three-dimensional finite element model of the craniomaxillary complex in alveolar cleft after bone grafting was established, and anterior traction combined with expansion force in different directions was applied to it. The overall displacement of the craniomaxillary complex under orthodontic force and the biological stress of each suture after bone grafting under different working conditions were obtained, and the effect of anterior traction combined with expansion force in different directions on the craniomaxillary complex was analyzed.

2. The finite element analysis method for the effect of maxillary protraction combined with arch expansion in different directions on alveolar ridge cleft bone grafting according to claim 1, characterized in that: The method for establishing a three-dimensional finite element model of the alveolar ridge cleft craniomaxillary complex after bone grafting specifically comprises the following steps: Scanning data of the craniomaxillary complex with alveolar ridge cleft were obtained; the scan data were imported into 3D reconstruction software, and the skull, maxilla, and mandible were preliminarily extracted from the image through threshold segmentation. Full-cleft bone grafting was performed in the alveolar ridge defect area with the nasal floor side as the upper side and the oral side as the lower side. A 3D model of the craniomaxillary complex after bone grafting was generated, and a solid model was fitted. Material properties were assigned to the model, and boundaries and loads were set. Finally, a 3D finite element model of the craniomaxillary complex with alveolar ridge cleft after bone grafting was obtained.

3. The finite element analysis method for the effect of maxillary protraction combined with arch expansion in different directions on alveolar ridge cleft bone grafting according to claim 1, characterized in that: The method of applying anterior traction forces in different directions combined with arch expansion forces based on a three-dimensional finite element model of the alveolar ridge cleft craniomaxillary complex after bone grafting specifically includes the following steps: Anterior traction force is applied to the buccal alveolar ridge top area of ​​the maxillary canines on both sides, in the forward direction and at different angles to the occlusal plane; the occlusal plane is formed by the mesial contact point of the maxillary central incisor and the mesial buccal cusps of the maxillary first molars on both sides; when the traction force angle is positive, the anterior traction force is forward and upward relative to the occlusal plane, and when the traction force angle is negative, the anterior traction force is forward and downward relative to the occlusal plane; at the same time, a horizontal expansion force is applied to the palatal alveolar ridge top area of ​​the maxillary first premolars and first molars on both sides.

4. The finite element analysis method for the effect of maxillary protraction combined with arch expansion in different directions on alveolar ridge cleft bone grafting according to claim 3, characterized in that: A forward traction force of 5 N was applied to the buccal alveolar ridge top area of ​​the maxillary canines on both sides, with the angles of -30°, -20°, -10°, 0°, 10°, 20°, and 30° to the occlusal plane, respectively, for a total of seven working conditions.

5. The finite element analysis method for the effect of maxillary protraction combined with arch expansion in different directions on alveolar ridge cleft bone grafting according to claim 1, characterized in that: The overall displacement of the craniomandibular complex was analyzed by observing the displacement of maxillary landmarks in the sagittal, vertical, and horizontal directions.

6. The finite element analysis method for the effect of maxillary protraction combined with arch expansion in different directions on alveolar ridge cleft bone grafting according to claim 5, characterized in that: The displacement of the maxillary landmarks in the sagittal, vertical, and horizontal directions is as follows: Sagittal displacement landmarks: the upper alveolar seat point, upper central incisor point, left first molar palatal cusp point, and right first molar palatal cusp point represent the displacement characteristics of the dentition and alveolar bone; The nasion, the most concave part of the nasal bone, the inferior part of the nasal bone, and the anterior nasal spine represent the skeletal displacement features of the craniomaxillary complex; Vertical displacement landmarks: Two landmarks were selected vertically: the anterior nasal spine and the posterior nasal spine to represent the vertical displacement of the craniomandibular complex. Horizontal displacement landmarks: The distance between the cusps of the bilateral canines was selected as the width of the anterior dental arch, the distance between the central fossae of the bilateral first premolars was selected as the width of the middle dental arch, and the distance between the central fossae of the bilateral first molars was selected as the distance between the posterior dental arches. The average value of the horizontal displacement of the three dental arches was taken to represent the horizontal displacement of the craniomaxillary complex.

7. The finite element analysis method for the effect of maxillary protraction combined with arch expansion in different directions on alveolar ridge cleft bone grafting according to claim 1, characterized in that: The biological stress indicators of sutures include the equivalent stress of the bilateral nasofrontal suture, frontomaxillary suture, zygomaticomaxillary suture, pterygopalatine suture, and zygomaticotemporal suture.

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