Finite element analysis of the influence of perioral force on alveolar ridge healing in areas missing maxillary anterior teeth

Finite element analysis of the influence of perioral force on alveolar ridge healing in areas missing maxillary anterior teeth | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Finite element analysis of the influence of perioral force on alveolar ridge healing in areas missing maxillary anterior teeth An-Ke Li, Yan-Ting He, Xuan Li, Cheng-Yuan Han, Jian-Yong Dong, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4945548/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 04 Jan, 2025 Read the published version in BMC Oral Health → Version 1 posted 10 You are reading this latest preprint version Abstract Objective To study the biomechanical changes induced by differences in perioral force in patients with missing anterior maxillary teeth at rest via finite element analysis (FEA). Methods Using conical beam CT (CBCT) images of a healthy person, models of the complete maxillary anterior dental region (Model A) and maxillary anterior dental region with a missing left maxillary central incisor (Model B) were constructed. The labial and palatine alveolar bone and tooth surface of the bilateral incisor and cusp regions were selected as the application sites, the resting perioral force was applied perpendicular to the tissue surface, and the changes in maxillary stress and displacement after the perioral force was simulated were analyzed. Results Compared with those of Model A, the labial alveolar bone in the missing tooth area of Model B exhibited obvious stress concentration and displacement under the action of perioral force. Conclusion At rest, perioral force, especially the soft tissue pressure of the lip, has an adverse effect on alveolar ridge healing in areas with missing maxillary anterior teeth. Perioral force Upper lip pressure Maxillary anterior teeth Alveolar ridge healing Finite element analysis Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction Implants have long been used for the restoration of missing teeth in the aesthetic zone because of their association with good aesthetic and functional outcomes. However, it is still difficult for doctors to compensate for the effect of alveolar ridge absorption despite extensive experience in implant placement and the use of technology. Most patients whose maxillary anterior teeth are missing have different degrees of alveolar bone loss, which seriously affects patient prognosis and red–white aesthetics. In most cases, the decrease in alveolar ridge height occurs within 90 days after tooth extraction. Six months after extraction, the horizontal and vertical bone loss rates ranged from 29–63% and from 11–22%, respectively, and the width of the alveolar bone decreased by approximately 50% in the first year after tooth extraction[ 1 ]. The causes of alveolar bone resorption after tooth extraction include trauma, blood supply, bacteria, inflammation, age, adverse stress and systemic disease. The loss of bundle bone after tooth extraction is considered an unavoidable and important factor that leads to horizontal bone resorption. The loss of Sharpey fibers connecting the cementum and alveolar bone and the interruption of the blood supply to the periodontal ligament after tooth extraction lead to the resorption of bundle bone[ 2 ]. In addition, compared with thick-walled bone, thinner fascicular bone is associated with more severe bone plate resorption[ 3 , 4 ]. Jiang et al. [ 5 ] reported that a thin buccal bone plate entirely composed of fascicular bone does not disrupt resorption regardless of treatment method. Owing to the weak bony plate on the labial side of the anterior tooth root and the presence of several fasciculate bones, bone remodeling is more active, and bone resorption is more prominent than that on the palatal side. Compared with that before extraction, the position of the alveolar ridge of the anterior tooth after extraction is more palatine, resulting in a defect in the contour of the lip[ 6 – 8 ]. Farmer et al. [ 9 ] observed the range of bone resorption in the maxillary extraction socket. They reported that at 6–8 weeks after healing, the bone wall of the extraction socket was an "inverted V shape", and 42% of the patients lost at least 4 mm of buccal bone at the midpoint of the extraction socket. MacBeth et al. [ 10 ] reported that the equal area of alveolar bone on CBCT images decreased by 11% and that the rate of labial bone cracking was 85% at 4 months after anterior tooth extraction. As an incremental technology with definite clinical efficacy and long-term predictability, guided bone regeneration (GBR) has been widely accepted as a means to treat hard tissue defects[ 11 – 13 ] in the aesthetic zone. However, when used as an alveolar ridge preservation technology, GBR cannot completely prevent alveolar bone resorption, and the results at different sites receiving the same treatment differ[ 1 , 14 , 15 ]. There have been no reports of the obvious effect of soft tissue pressure on anterior alveolar healing. Jiang et al. [ 16 ] hypothesized that the collapse of labial soft tissue in areas with missing anterior teeth affects alveolar remodeling and demonstrated that the application of labial pressure-bearing devices results in better alveolar ridge preservation than does natural healing. They also reported that even the relatively rigid microtitanium scaffold became slightly deformed during the healing process and that the middle part of the scaffold shifted palatally. These findings suggest that pressure is exerted on the alveolar soft tissue during the healing process. Mir-Mari et al. [ 17 ] used GBR technology to study the volume stability of the enhanced area during mucosal flap suturing and reported that the suturing of the mucosal flap caused considerable pressure in the coronal part of the enhanced site, resulting in the displacement of granular graft materials and partial collapse of the collagen membrane. All the above studies suggest that long-term pressure on soft tissue may affect the healing process of the alveolar ridge. At present, there is still an insufficient theoretical basis on whether excessive stress is generated on the alveolar ridge in the missing tooth area. On the basis of the above background, the aim of this biomechanics study was to determine the influence of upper lip pressure on the distribution of stress in the area of missing maxillary anterior teeth via FEA to ultimately determine whether upper lip pressure affects the healing process of the alveolar ridge. Data and methods Establishment of a 3D finite element model of the maxillary anterior tooth region (Fig. 1 ) The research participant was a healthy adult male who provided informed consent and underwent CBCT of his head in accordance with ethical review by the Ethics Committee of Jinan Stomatology Hospital. The CBCT data were imported into Mimics 21.0 (Materialise, Belgium), a medical image modeling software, in DICOM format for 3D reconstruction. The maxillary anterior teeth (including the anterior maxilla and maxillary anterior teeth) were extracted, and the generated 3D model was output in stereolithography (STL) format. Geomagic Wrap 2021 (Geomagic, USA) was used to optimize the 3D model. According to previous studies[ 18 – 21 ], the maxillary bone was shifted 0.9 mm inward to obtain the cancellous bone model, and the bone cortex model was obtained via Boolean subtraction with the original maxillary model. The crown of the left maxillary central incisor was removed from the alveolar ridge plane and then used to obtain a more accurate STP-format model (Fig. 2 ). The solid model was combined via the engineering modeling software SOLIDWORKS 2021 (Dassault Systèmes, France) and then imported into the FEA software ANSYS 17.0 (ANSYS, USA) for solution. Material properties, mesh division, contact conditions and loading conditions With reference to previous studies[ 22 – 24 ], the model properties are set as homogeneous, continuous and isotropic linear elastomers (Table 1 ). The cancellous bone, cortical bone and tooth models are imported into finite element models A and B, respectively. The numbers of nodes and units are shown in Tables 2 and 3 . Binding contact between cancellous bone and cortical bone, between the tooth root and cancellous bone, and between the tooth root and cortical bone was set in the software, and the contact position did not change. When the geocentric gravitational constant was 10 N/kg, the resting upper lip pressure of normal people was 2 g/cm 2 [ 25 , 26 ]. For the convenience of the study, the perioral force on the anterior alveolar ridge and teeth was set as the ideal state of internal and external balance; that is, the palatal pressure was equal to the labial pressure. The pressure was applied to the alveolar bone and tooth surface of models A and B, and the stress areas were the labial surface of the anterior maxillary tooth and the alveolar bone and the palatal surface of the anterior maxillary tooth and the alveolar bone. The direction was perpendicular to the surface of the stressed tissue. Table 1 Material properties Materials Modulus of elasticity (MPa) Poisson's ratio Cancellous bone 7.9 * 10 3 0.3 Cortical bone 1.37 * 10 4 0.3 Teeth 2.0 * 10 4 0.3 Table 2 Number of material nodes and cells in Model A Materials Number of nodes Number of cells Cancellous bone 20380 10600 Cortical bone 28938 15686 Teeth 13883 7395 Table 3 Number of material nodes and cells in Model B Materials Number of nodes Number of cells Cancellous bone 20390 10608 Compact bone 28765 15512 Teeth 12287 6618 Mechanical analysis After the resting perioral force was loaded, the stress cloud map and displacement cloud map of the model were obtained, and the stress distribution and displacement changes in the maxillary bone and teeth were observed. The vertical color band on the left side of the cloud map indicates stress and displacement. The redder the color is, the larger the value, the more concentrated the stress and the greater the displacement. Observation indicators In this study, we selected the edges of the left maxillary central incisor alveolar ridge to observe the changes in the alveolar ridge von Mises stress and maximum displacement caused by perioral forces in the presence and absence of teeth, as well as the overall stress distribution and displacement of the model. The absolute values of the von Mises stress distribution and maximum displacement in each direction of models A and B were calculated. Results von Mises stress distribution results of the model after loading The von Mises stress distributions of the two models after loading are as follows (Fig. 3 A-D). In the labial view, the von Mises stress distribution of Model A was more uniform, and there was no obvious stress concentration area. Model B showed maximum von Mises stress at the crest of the labial alveolar ridge in the missing tooth area, with stress gradually decreasing from the crest of the alveolar ridge to the root area. The maximum von Mises stress at the crest of the labial alveolar ridge in the missing tooth area in Model B was approximately 16 times greater than the stress at the same observed site in Model A (Fig. 3 E). In the palatal view, neither Model A nor Model B had significant areas of stress concentration. Changes in displacement in each model after loading Figure 4 A-D shows the change in displacement in each model after loading. Model A showed maximum displacement in the incisors, a gradual decrease to the distal and root sides, and no obvious displacement of the alveolar ridge. The maximum displacement of Model B is distributed in the crest of the labial alveolar ridge in the missing tooth area and the incisors, and gradually decreases from the crest of the alveolar ridge to the root area. The displacement at the crest of the labial alveolar ridge in the missing tooth area was approximately twice that of the displacement at the same observation site in Model A. Discussion FEA is widely used in the field of oral biomechanics[ 23 , 27 ]. In this study, FEA was adopted to explore clinical problems, and force analysis was conducted with finite element software; thus, there was no need for an operation or long-term follow-up. Models can be used repeatedly, and their construction is simple and noninvasive. In the anterior maxillary region, the loss of alveolar ridge width after missing teeth is the main factor restricting implant restoration. This study is based on the theory that a lip shield can slow alveolar ridge absorption and that the inhibitory effect of perioral force on the growth and development of alveolar bone in the three-dimensional direction affects the practical demand for preservation of the alveolar ridge in the aesthetic zone. The aim of this study was to explore the biomechanical effects of perioral force on the alveolar ridge in the anterior maxillary region. Changes in von Mises stress and displacement in the maxillary anterior tooth area under perioral force Compared with Model A with complete dentition, Model B with missing teeth presented a stress concentration zone, and the stress was concentrated mainly at the crest of the labial alveolar ridge in the missing tooth area; that is, the soft tissue of the lips exerted adverse stress on the alveolar ridge in the missing tooth area of the maxillary anterior teeth. The gradual reduction in stress from the incisal end to the root is consistent with the "inverted V-shaped" absorption of the bone wall of the extraction socket observed by Farmer et al.[ 9 ]. The changes in von Mises stress and displacement were mainly reflected in the sagittal direction, suggesting that the stress on the alveolar ridge caused by perioral force was mainly exerted in the sagittal direction, which may have resulted in a reduction in the width of the alveolar ridge. This finding was also confirmed by a recent study. Pelegrine et al. [ 28 ] reported that the bone width in the anterior maxillary area was reduced by 31.35 ± 11.88% within 6 months after healing was completed without transplant surgery. Notably, the displacement of hard tissue shown in the cloud map often does not occur in real-world situations but is mostly reflected in the concessions of the soft tissue of the upper lip and the elastic soft tissue of the gum. The displacement cloud map shows that the more concentrated the displacement area is, the greater the possibility of the upper lip and gum compensating for collapse. The alveolar bone morphology of the maxillary anterior tooth region varies greatly across different regions and races. In the model built in this study, the buccal bone cortex of the maxillary anterior teeth was intact, but many patients had thin buccal bone walls or even different degrees of absence due to bone loss caused by congenital thin bone, tooth extraction trauma or original periodontal inflammation. Gakonyo et al.[ 29 ] reported that 26% of cheekbone walls were missing among 1104 teeth, meaning that approximately 1 in every 4 anterior maxillary teeth were missing buccal walls. The thinner the buccal bone wall is, the more likely the alveolar ridge and soft tissue are to undergo more prominent changes in size. Existing evidence suggests that this more prominent change in size is the result of a series of changes, such as osteoblast death and osteoclast activity[ 2 ], caused by interruption of the blood supply. Since the resting pressure of the upper lip can cause slight deformation of the alveolar ridge with normal bone thickness, when the buccal bone wall is missing or thin, the alveolar ridge in the missing tooth area will inevitably have difficulty maintaining spatial stability because of the persistent adverse stress of the upper lip, which ultimately affects the healing of the alveolar bone. In people with different occlusal relationships, the magnitude of perioral force varies greatly. Studies have shown[ 26 ] that the upper lip pressure of patients with Class II malocclusion is greater than that of Class I malocclusion patients. The upper lip pressure of patients with Class II malocclusion is the lowest. The position of the anterior teeth determines the upper lip pressure at rest. The lower upper lip pressure in patients with Class III malocclusion may be caused [ 30 ] by the spatial relationship of the jaws. The results of this study suggest that the abnormal sagittal spatial position of the anterior maxillary teeth can directly lead to changes in resting upper lip pressure and then lead to changes in the stress on the alveolar ridge in the missing tooth area. Patients with Class II malocclusion have a greater risk of insufficient regeneration space due to upper lip pressure on the alveolar ridge in the missing tooth area of the anterior maxillary teeth. Role of resistance to upper lip pressure in the preservation of the alveolar ridge in the anterior deficient area of maxillary teeth The PASS principle of GBR emphasizes the importance of space maintenance and blood clot stabilization. When GBR is performed with membrane materials, the soft tissue pressure from above the barrier membrane can collapse the barrier membrane, resulting in reduced areas of new bone[ 31 ]. The titanium mesh technique and the tent technique achieve better bone increment effects[ 32 – 34 ] than the barrier membrane alone by preserving the space for new bone formation and stabilizing the bone graft material, autogenous bone particles and blood clots below it. The results of this study suggest that some means to counteract adverse stress on the alveolar ridge in the missing tooth area are conducive to providing a stable physical environment for the healing of the alveolar socket, which has been confirmed in clinical studies. Jiang et al.[ 16 ] reported that both intra-alveolar transplantation and microtitanium scaffolds maintain space for new bone formation, which can be achieved by "supporting" the soft tissue of the lip externally or "occupying" the space internally with bone graft materials. Some studies also suggest that if the bone regeneration space can be maintained appropriately, ideal new bone formation [ 35 , 36 ] may be achieved without bone graft materials. These findings suggest that new bone formation space may be a key factor in alveolar bone regeneration or hard tissue preservation in the fossa at the site of tooth extraction. In addition, the deformation of rigid materials such as titanium mesh or microtitanium scaffolds also indicates[ 16 ] that stress on the alveolar ridge in the missing tooth area has adverse effects on the alveolar ridge. Prospects and limitations This study revealed the existence of undue stress on the alveolar ridge in the missing area of the maxillary anterior teeth, and additional studies on the treatment methods used to resist this undue stress will be conducted in the future. The concentration of stress in the alveolar bone in the missing tooth area was analyzed only from the perspective of biomechanics, without considering other influencing factors, and the extent of the influence of adverse stress on alveolar bone reconstruction was not clear. FEA requires ideal research conditions. In this study, the conditions related to missing teeth were discussed without categorically discussing factors such as different material properties of different bones, different thicknesses of the labial bone plate of the maxillary anterior teeth, the crown of the maxillary anterior teeth, the cushioning effect of gingival soft tissue on perioral force, and differences in the magnitude and direction of perioral force at different positions of the surface of action. Owing to the lack of data on the sucking and chewing habits of patients, we did not perform dynamic force analysis for the alveolar ridge. In future research, if one or several of the above factors can be discussed in depth, it will be highly beneficial for improving the research results. Conclusion In the resting state, the labial soft tissue exerts adverse stress on the alveolar ridge in the area of missing maxillary anterior teeth, which may affect the regeneration space and is not conducive to alveolar bone reconstruction. The measures taken to resist the pressure of the upper lip may have a positive effect on slowing alveolar ridge absorption in the anterior maxillary region. Declarations Funding This study was supported by the Projects of Jinan Medical and Health Technology Development Program (grant number 2021-2-116). Funding body did not have any role in the design of the study, collection, analysis and interpretation of the data or in the writing of the manuscript. Author Contribution Jian-Yong Dong, Kai-Qi Zhang and Jun Cui conceived the ideas and supervised this work; Xuan Li and Cheng-Yuan Han were responsible for data collection; An-Ke Li and Yan-Ting He conducted the experimental design, built the finite element models and wrote the manuscript. 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Cite Share Download PDF Status: Published Journal Publication published 04 Jan, 2025 Read the published version in BMC Oral Health → Version 1 posted Editorial decision: Revision requested 06 Nov, 2024 Reviews received at journal 01 Nov, 2024 Reviewers agreed at journal 22 Oct, 2024 Reviews received at journal 18 Sep, 2024 Reviewers agreed at journal 04 Sep, 2024 Reviewers invited by journal 03 Sep, 2024 Editor invited by journal 29 Aug, 2024 Editor assigned by journal 28 Aug, 2024 Submission checks completed at journal 28 Aug, 2024 First submitted to journal 20 Aug, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4945548","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":358353206,"identity":"93fa20a1-f755-4d22-94ae-27aadf476c10","order_by":0,"name":"An-Ke Li","email":"","orcid":"","institution":"Binzhou Medical University","correspondingAuthor":false,"prefix":"","firstName":"An-Ke","middleName":"","lastName":"Li","suffix":""},{"id":358353207,"identity":"8e9dc567-8d19-4817-8979-05800f52b2a9","order_by":1,"name":"Yan-Ting He","email":"","orcid":"","institution":"Jinan Stomatological 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Hospital","correspondingAuthor":true,"prefix":"","firstName":"Jun","middleName":"","lastName":"Cui","suffix":""}],"badges":[],"createdAt":"2024-08-20 13:56:56","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4945548/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4945548/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s12903-024-05317-z","type":"published","date":"2025-01-04T15:57:20+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":66887759,"identity":"defb3bab-fcda-47c5-be38-3e01e9091725","added_by":"auto","created_at":"2024-10-17 14:01:38","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":53329,"visible":true,"origin":"","legend":"\u003cp\u003eModel establishment process\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-4945548/v1/5cf99b187fa634c03b053037.png"},{"id":66887761,"identity":"d5eaaa6d-1f04-4bf8-a7a2-5410decf4437","added_by":"auto","created_at":"2024-10-17 14:01:38","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":171471,"visible":true,"origin":"","legend":"\u003cp\u003eSolid models of the maxillary anterior region in which the left maxillary central incisor is present/missing (Model A/B)\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-4945548/v1/6da10c57cfa3046589aa8b30.png"},{"id":66887760,"identity":"1ec72c15-6387-4bb2-b7e6-7cbf01b0198c","added_by":"auto","created_at":"2024-10-17 14:01:38","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":579116,"visible":true,"origin":"","legend":"\u003cp\u003eCloud map of the von Mises stress distributions for both models. \u003cstrong\u003eA\u003c/strong\u003e: Model A von Mises stress distribution (in the labial view) \u003cstrong\u003eB\u003c/strong\u003e: Model B von Mises stress distribution (in the labial view) \u003cstrong\u003eC\u003c/strong\u003e: Model A von Mises stress distribution (in the palatal view) \u003cstrong\u003eD\u003c/strong\u003e: Model B von Mises stress distribution (in the palatal view) \u003cstrong\u003eE\u003c/strong\u003e: Maximum von Mises stress at the alveolar crest of six anterior teeth (in the labial view)\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-4945548/v1/67dca2dff2f3c8092d145977.png"},{"id":66887762,"identity":"09a7de66-bc8f-47f5-9e76-00f84507b8fb","added_by":"auto","created_at":"2024-10-17 14:01:39","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":647196,"visible":true,"origin":"","legend":"\u003cp\u003eCloud map of displacement for both models. \u003cstrong\u003eA\u003c/strong\u003e: Changes in displacement in Model A (in the labial view) \u003cstrong\u003eB\u003c/strong\u003e: Changes in displacement in Model B (in the labial view) \u003cstrong\u003eC\u003c/strong\u003e: Changes in displacement in Model A (in the palatal view) \u003cstrong\u003eD\u003c/strong\u003e: Changes in displacement in Model B (in the palatal view) \u003cstrong\u003eE\u003c/strong\u003e: Maximum displacement at the alveolar crest of six anterior teeth (in the labial view)\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-4945548/v1/50358adc700f7f67a7ed7d4f.png"},{"id":73093466,"identity":"d85e900a-9f1d-4bd1-a9a7-a7a4cceba801","added_by":"auto","created_at":"2025-01-06 16:19:57","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1814549,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4945548/v1/f3105446-78ab-4372-b77d-652b3577afad.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Finite element analysis of the influence of perioral force on alveolar ridge healing in areas missing maxillary anterior teeth","fulltext":[{"header":"Introduction","content":"\u003cp\u003eImplants have long been used for the restoration of missing teeth in the aesthetic zone because of their association with good aesthetic and functional outcomes. However, it is still difficult for doctors to compensate for the effect of alveolar ridge absorption despite extensive experience in implant placement and the use of technology. Most patients whose maxillary anterior teeth are missing have different degrees of alveolar bone loss, which seriously affects patient prognosis and red\u0026ndash;white aesthetics. In most cases, the decrease in alveolar ridge height occurs within 90 days after tooth extraction. Six months after extraction, the horizontal and vertical bone loss rates ranged from 29\u0026ndash;63% and from 11\u0026ndash;22%, respectively, and the width of the alveolar bone decreased by approximately 50% in the first year after tooth extraction[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe causes of alveolar bone resorption after tooth extraction include trauma, blood supply, bacteria, inflammation, age, adverse stress and systemic disease. The loss of bundle bone after tooth extraction is considered an unavoidable and important factor that leads to horizontal bone resorption. The loss of Sharpey fibers connecting the cementum and alveolar bone and the interruption of the blood supply to the periodontal ligament after tooth extraction lead to the resorption of bundle bone[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. In addition, compared with thick-walled bone, thinner fascicular bone is associated with more severe bone plate resorption[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Jiang et al. [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e] reported that a thin buccal bone plate entirely composed of fascicular bone does not disrupt resorption regardless of treatment method. Owing to the weak bony plate on the labial side of the anterior tooth root and the presence of several fasciculate bones, bone remodeling is more active, and bone resorption is more prominent than that on the palatal side. Compared with that before extraction, the position of the alveolar ridge of the anterior tooth after extraction is more palatine, resulting in a defect in the contour of the lip[\u003cspan additionalcitationids=\"CR7\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Farmer et al. [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] observed the range of bone resorption in the maxillary extraction socket. They reported that at 6\u0026ndash;8 weeks after healing, the bone wall of the extraction socket was an \"inverted V shape\", and 42% of the patients lost at least 4 mm of buccal bone at the midpoint of the extraction socket. MacBeth et al. [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] reported that the equal area of alveolar bone on CBCT images decreased by 11% and that the rate of labial bone cracking was 85% at 4 months after anterior tooth extraction.\u003c/p\u003e \u003cp\u003eAs an incremental technology with definite clinical efficacy and long-term predictability, guided bone regeneration (GBR) has been widely accepted as a means to treat hard tissue defects[\u003cspan additionalcitationids=\"CR12\" citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] in the aesthetic zone. However, when used as an alveolar ridge preservation technology, GBR cannot completely prevent alveolar bone resorption, and the results at different sites receiving the same treatment differ[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThere have been no reports of the obvious effect of soft tissue pressure on anterior alveolar healing. Jiang et al. [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] hypothesized that the collapse of labial soft tissue in areas with missing anterior teeth affects alveolar remodeling and demonstrated that the application of labial pressure-bearing devices results in better alveolar ridge preservation than does natural healing. They also reported that even the relatively rigid microtitanium scaffold became slightly deformed during the healing process and that the middle part of the scaffold shifted palatally. These findings suggest that pressure is exerted on the alveolar soft tissue during the healing process. Mir-Mari et al. [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] used GBR technology to study the volume stability of the enhanced area during mucosal flap suturing and reported that the suturing of the mucosal flap caused considerable pressure in the coronal part of the enhanced site, resulting in the displacement of granular graft materials and partial collapse of the collagen membrane. All the above studies suggest that long-term pressure on soft tissue may affect the healing process of the alveolar ridge.\u003c/p\u003e \u003cp\u003eAt present, there is still an insufficient theoretical basis on whether excessive stress is generated on the alveolar ridge in the missing tooth area. On the basis of the above background, the aim of this biomechanics study was to determine the influence of upper lip pressure on the distribution of stress in the area of missing maxillary anterior teeth via FEA to ultimately determine whether upper lip pressure affects the healing process of the alveolar ridge.\u003c/p\u003e"},{"header":"Data and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eEstablishment of a 3D finite element model of the maxillary anterior tooth region (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e)\u003c/h2\u003e \u003cp\u003eThe research participant was a healthy adult male who provided informed consent and underwent CBCT of his head in accordance with ethical review by the Ethics Committee of Jinan Stomatology Hospital. The CBCT data were imported into Mimics 21.0 (Materialise, Belgium), a medical image modeling software, in DICOM format for 3D reconstruction. The maxillary anterior teeth (including the anterior maxilla and maxillary anterior teeth) were extracted, and the generated 3D model was output in stereolithography (STL) format. Geomagic Wrap 2021 (Geomagic, USA) was used to optimize the 3D model. According to previous studies[\u003cspan additionalcitationids=\"CR19 CR20\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e], the maxillary bone was shifted 0.9 mm inward to obtain the cancellous bone model, and the bone cortex model was obtained via Boolean subtraction with the original maxillary model. The crown of the left maxillary central incisor was removed from the alveolar ridge plane and then used to obtain a more accurate STP-format model (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The solid model was combined via the engineering modeling software SOLIDWORKS 2021 (Dassault Syst\u0026egrave;mes, France) and then imported into the FEA software ANSYS 17.0 (ANSYS, USA) for solution.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eMaterial properties, mesh division, contact conditions and loading conditions\u003c/h2\u003e \u003cp\u003eWith reference to previous studies[\u003cspan additionalcitationids=\"CR23\" citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e], the model properties are set as homogeneous, continuous and isotropic linear elastomers (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The cancellous bone, cortical bone and tooth models are imported into finite element models A and B, respectively. The numbers of nodes and units are shown in Tables\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and \u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. Binding contact between cancellous bone and cortical bone, between the tooth root and cancellous bone, and between the tooth root and cortical bone was set in the software, and the contact position did not change. When the geocentric gravitational constant was 10 N/kg, the resting upper lip pressure of normal people was 2 g/cm\u003csup\u003e2\u003c/sup\u003e[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. For the convenience of the study, the perioral force on the anterior alveolar ridge and teeth was set as the ideal state of internal and external balance; that is, the palatal pressure was equal to the labial pressure. The pressure was applied to the alveolar bone and tooth surface of models A and B, and the stress areas were the labial surface of the anterior maxillary tooth and the alveolar bone and the palatal surface of the anterior maxillary tooth and the alveolar bone. The direction was perpendicular to the surface of the stressed tissue.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMaterial properties\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMaterials\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eModulus of elasticity (MPa)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePoisson's ratio\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCancellous bone\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e7.9 * 10\u003csup\u003e3\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCortical bone\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.37 * 10\u003csup\u003e4\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTeeth\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.0 * 10\u003csup\u003e4\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eNumber of material nodes and cells in Model A\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMaterials\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNumber of nodes\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNumber of cells\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCancellous bone\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e20380\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e10600\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCortical bone\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e28938\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e15686\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTeeth\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e13883\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e7395\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eNumber of material nodes and cells in Model B\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMaterials\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNumber of nodes\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNumber of cells\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCancellous bone\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e20390\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e10608\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCompact bone\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e28765\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e15512\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTeeth\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e12287\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e6618\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eMechanical analysis\u003c/h2\u003e \u003cp\u003eAfter the resting perioral force was loaded, the stress cloud map and displacement cloud map of the model were obtained, and the stress distribution and displacement changes in the maxillary bone and teeth were observed. The vertical color band on the left side of the cloud map indicates stress and displacement. The redder the color is, the larger the value, the more concentrated the stress and the greater the displacement.\u003c/p\u003e \u003cdiv id=\"Sec6\" class=\"Section3\"\u003e \u003ch2\u003eObservation indicators\u003c/h2\u003e \u003cp\u003eIn this study, we selected the edges of the left maxillary central incisor alveolar ridge to observe the changes in the alveolar ridge von Mises stress and maximum displacement caused by perioral forces in the presence and absence of teeth, as well as the overall stress distribution and displacement of the model. The absolute values of the von Mises stress distribution and maximum displacement in each direction of models A and B were calculated.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003evon Mises stress distribution results of the model after loading\u003c/h2\u003e \u003cp\u003eThe von Mises stress distributions of the two models after loading are as follows (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA-D). In the labial view, the von Mises stress distribution of Model A was more uniform, and there was no obvious stress concentration area. Model B showed maximum von Mises stress at the crest of the labial alveolar ridge in the missing tooth area, with stress gradually decreasing from the crest of the alveolar ridge to the root area. The maximum von Mises stress at the crest of the labial alveolar ridge in the missing tooth area in Model B was approximately 16 times greater than the stress at the same observed site in Model A (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eE). In the palatal view, neither Model A nor Model B had significant areas of stress concentration.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eChanges in displacement in each model after loading\u003c/h3\u003e\n\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eA-D shows the change in displacement in each model after loading. Model A showed maximum displacement in the incisors, a gradual decrease to the distal and root sides, and no obvious displacement of the alveolar ridge. The maximum displacement of Model B is distributed in the crest of the labial alveolar ridge in the missing tooth area and the incisors, and gradually decreases from the crest of the alveolar ridge to the root area. The displacement at the crest of the labial alveolar ridge in the missing tooth area was approximately twice that of the displacement at the same observation site in Model A.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eFEA is widely used in the field of oral biomechanics[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. In this study, FEA was adopted to explore clinical problems, and force analysis was conducted with finite element software; thus, there was no need for an operation or long-term follow-up. Models can be used repeatedly, and their construction is simple and noninvasive. In the anterior maxillary region, the loss of alveolar ridge width after missing teeth is the main factor restricting implant restoration. This study is based on the theory that a lip shield can slow alveolar ridge absorption and that the inhibitory effect of perioral force on the growth and development of alveolar bone in the three-dimensional direction affects the practical demand for preservation of the alveolar ridge in the aesthetic zone. The aim of this study was to explore the biomechanical effects of perioral force on the alveolar ridge in the anterior maxillary region.\u003c/p\u003e \u003cp\u003e \u003cb\u003eChanges in von Mises stress and displacement in the maxillary anterior tooth area under perioral force\u003c/b\u003e \u003c/p\u003e \u003cp\u003eCompared with Model A with complete dentition, Model B with missing teeth presented a stress concentration zone, and the stress was concentrated mainly at the crest of the labial alveolar ridge in the missing tooth area; that is, the soft tissue of the lips exerted adverse stress on the alveolar ridge in the missing tooth area of the maxillary anterior teeth. The gradual reduction in stress from the incisal end to the root is consistent with the \"inverted V-shaped\" absorption of the bone wall of the extraction socket observed by Farmer et al.[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. The changes in von Mises stress and displacement were mainly reflected in the sagittal direction, suggesting that the stress on the alveolar ridge caused by perioral force was mainly exerted in the sagittal direction, which may have resulted in a reduction in the width of the alveolar ridge. This finding was also confirmed by a recent study. Pelegrine et al. [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e] reported that the bone width in the anterior maxillary area was reduced by 31.35\u0026thinsp;\u0026plusmn;\u0026thinsp;11.88% within 6 months after healing was completed without transplant surgery.\u003c/p\u003e \u003cp\u003eNotably, the displacement of hard tissue shown in the cloud map often does not occur in real-world situations but is mostly reflected in the concessions of the soft tissue of the upper lip and the elastic soft tissue of the gum. The displacement cloud map shows that the more concentrated the displacement area is, the greater the possibility of the upper lip and gum compensating for collapse.\u003c/p\u003e \u003cp\u003eThe alveolar bone morphology of the maxillary anterior tooth region varies greatly across different regions and races. In the model built in this study, the buccal bone cortex of the maxillary anterior teeth was intact, but many patients had thin buccal bone walls or even different degrees of absence due to bone loss caused by congenital thin bone, tooth extraction trauma or original periodontal inflammation. Gakonyo et al.[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e] reported that 26% of cheekbone walls were missing among 1104 teeth, meaning that approximately 1 in every 4 anterior maxillary teeth were missing buccal walls. The thinner the buccal bone wall is, the more likely the alveolar ridge and soft tissue are to undergo more prominent changes in size. Existing evidence suggests that this more prominent change in size is the result of a series of changes, such as osteoblast death and osteoclast activity[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e], caused by interruption of the blood supply. Since the resting pressure of the upper lip can cause slight deformation of the alveolar ridge with normal bone thickness, when the buccal bone wall is missing or thin, the alveolar ridge in the missing tooth area will inevitably have difficulty maintaining spatial stability because of the persistent adverse stress of the upper lip, which ultimately affects the healing of the alveolar bone.\u003c/p\u003e \u003cp\u003eIn people with different occlusal relationships, the magnitude of perioral force varies greatly. Studies have shown[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e] that the upper lip pressure of patients with Class II malocclusion is greater than that of Class I malocclusion patients. The upper lip pressure of patients with Class II malocclusion is the lowest. The position of the anterior teeth determines the upper lip pressure at rest. The lower upper lip pressure in patients with Class III malocclusion may be caused [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e] by the spatial relationship of the jaws. The results of this study suggest that the abnormal sagittal spatial position of the anterior maxillary teeth can directly lead to changes in resting upper lip pressure and then lead to changes in the stress on the alveolar ridge in the missing tooth area. Patients with Class II malocclusion have a greater risk of insufficient regeneration space due to upper lip pressure on the alveolar ridge in the missing tooth area of the anterior maxillary teeth.\u003c/p\u003e \u003cp\u003e \u003cb\u003eRole of resistance to upper lip pressure in the preservation of the alveolar ridge in the anterior deficient area of maxillary teeth\u003c/b\u003e \u003c/p\u003e \u003cp\u003eThe PASS principle of GBR emphasizes the importance of space maintenance and blood clot stabilization. When GBR is performed with membrane materials, the soft tissue pressure from above the barrier membrane can collapse the barrier membrane, resulting in reduced areas of new bone[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. The titanium mesh technique and the tent technique achieve better bone increment effects[\u003cspan additionalcitationids=\"CR33\" citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e] than the barrier membrane alone by preserving the space for new bone formation and stabilizing the bone graft material, autogenous bone particles and blood clots below it. The results of this study suggest that some means to counteract adverse stress on the alveolar ridge in the missing tooth area are conducive to providing a stable physical environment for the healing of the alveolar socket, which has been confirmed in clinical studies. Jiang et al.[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] reported that both intra-alveolar transplantation and microtitanium scaffolds maintain space for new bone formation, which can be achieved by \"supporting\" the soft tissue of the lip externally or \"occupying\" the space internally with bone graft materials. Some studies also suggest that if the bone regeneration space can be maintained appropriately, ideal new bone formation [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e] may be achieved without bone graft materials. These findings suggest that new bone formation space may be a key factor in alveolar bone regeneration or hard tissue preservation in the fossa at the site of tooth extraction. In addition, the deformation of rigid materials such as titanium mesh or microtitanium scaffolds also indicates[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] that stress on the alveolar ridge in the missing tooth area has adverse effects on the alveolar ridge.\u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eProspects and limitations\u003c/h2\u003e \u003cp\u003eThis study revealed the existence of undue stress on the alveolar ridge in the missing area of the maxillary anterior teeth, and additional studies on the treatment methods used to resist this undue stress will be conducted in the future. The concentration of stress in the alveolar bone in the missing tooth area was analyzed only from the perspective of biomechanics, without considering other influencing factors, and the extent of the influence of adverse stress on alveolar bone reconstruction was not clear. FEA requires ideal research conditions. In this study, the conditions related to missing teeth were discussed without categorically discussing factors such as different material properties of different bones, different thicknesses of the labial bone plate of the maxillary anterior teeth, the crown of the maxillary anterior teeth, the cushioning effect of gingival soft tissue on perioral force, and differences in the magnitude and direction of perioral force at different positions of the surface of action. Owing to the lack of data on the sucking and chewing habits of patients, we did not perform dynamic force analysis for the alveolar ridge. In future research, if one or several of the above factors can be discussed in depth, it will be highly beneficial for improving the research results.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn the resting state, the labial soft tissue exerts adverse stress on the alveolar ridge in the area of missing maxillary anterior teeth, which may affect the regeneration space and is not conducive to alveolar bone reconstruction. The measures taken to resist the pressure of the upper lip may have a positive effect on slowing alveolar ridge absorption in the anterior maxillary region.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eThis study was supported by the Projects of Jinan Medical and Health Technology Development Program (grant number 2021-2-116). Funding body did not have any role in the design of the study, collection, analysis and interpretation of the data or in the writing of the manuscript.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eJian-Yong Dong, Kai-Qi Zhang and Jun Cui conceived the ideas and supervised this work; Xuan Li and Cheng-Yuan Han were responsible for data collection; An-Ke Li and Yan-Ting He conducted the experimental design, built the finite element models and wrote the manuscript. All authors read and approved the final version of the manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAvila-Ortiz G, Elangovan S, Kramer KW, Blanchette D, Dawson DV. Effect of alveolar ridge preservation after tooth extraction: a systematic review and meta-analysis. J Dent Res. 2014;93(10):950\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMonje A, Roccuzzo A, Buser D, Wang HL. 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J Biomed Mater Res B Appl Biomater. 2006;78(1):35\u0026ndash;46.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eC\u0026eacute;sar Neto JB, Cavalcanti MC, Sapata VM, Pannuti CM, H\u0026auml;mmerle CHF, Naenni N, Thoma DS, Romito GA. The positive effect of tenting screws for primary horizontal guided bone regeneration: A retrospective study based on cone-beam computed tomography data. Clin Oral Implants Res. 2020;31(9):846\u0026ndash;55.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKonstantinidis I, Kumar T, Kher U, Stanitsas PD, Hinrichs JE, Kotsakis GA. Clinical results of implant placement in resorbed ridges using simultaneous guided bone regeneration: a multicenter case series. Clin Oral Investig. 2015;19(2):553\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRoccuzzo M, Ramieri G, Bunino M, Berrone S. Autogenous bone graft alone or associated with titanium mesh for vertical alveolar ridge augmentation: a controlled clinical trial. Clin Oral Implants Res. 2007;18(3):286\u0026ndash;94.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLekovic V, Kenney EB, Weinlaender M, Han T, Klokkevold P, Nedic M, Orsini M. A bone regenerative approach to alveolar ridge maintenance following tooth extraction. Report of 10 cases. J Periodontol. 1997;68(6):563\u0026ndash;70.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePinho MN, Roriz VL, Novaes AB Jr., Taba M Jr., Grisi MF, de Souza SL, Palioto DB. Titanium membranes in prevention of alveolar collapse after tooth extraction. Implant Dent. 2006;15(1):53\u0026ndash;61.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-oral-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ohea","sideBox":"Learn more about [BMC Oral Health](http://bmcoralhealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ohea/default.aspx","title":"BMC Oral Health","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Perioral force, Upper lip pressure, Maxillary anterior teeth, Alveolar ridge healing, Finite element analysis","lastPublishedDoi":"10.21203/rs.3.rs-4945548/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4945548/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eObjective\u003c/h2\u003e \u003cp\u003eTo study the biomechanical changes induced by differences in perioral force in patients with missing anterior maxillary teeth at rest via finite element analysis (FEA).\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eUsing conical beam CT (CBCT) images of a healthy person, models of the complete maxillary anterior dental region (Model A) and maxillary anterior dental region with a missing left maxillary central incisor (Model B) were constructed. The labial and palatine alveolar bone and tooth surface of the bilateral incisor and cusp regions were selected as the application sites, the resting perioral force was applied perpendicular to the tissue surface, and the changes in maxillary stress and displacement after the perioral force was simulated were analyzed.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eCompared with those of Model A, the labial alveolar bone in the missing tooth area of Model B exhibited obvious stress concentration and displacement under the action of perioral force.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eAt rest, perioral force, especially the soft tissue pressure of the lip, has an adverse effect on alveolar ridge healing in areas with missing maxillary anterior teeth.\u003c/p\u003e","manuscriptTitle":"Finite element analysis of the influence of perioral force on alveolar ridge healing in areas missing maxillary anterior teeth","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-10-17 14:01:34","doi":"10.21203/rs.3.rs-4945548/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-11-06T09:34:25+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-11-01T04:44:15+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"316296735578432540739406780443749675781","date":"2024-10-23T03:49:20+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-09-18T12:28:11+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"127810753923184762777286766848798313858","date":"2024-09-04T11:09:52+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-09-03T08:45:09+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2024-08-29T10:15:08+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-08-28T13:45:09+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-08-28T13:41:51+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Oral Health","date":"2024-08-20T13:55:26+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-oral-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ohea","sideBox":"Learn more about [BMC Oral Health](http://bmcoralhealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ohea/default.aspx","title":"BMC Oral Health","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"c559fca2-1400-4ed0-9826-a4ab3cba600f","owner":[],"postedDate":"October 17th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-01-06T16:04:53+00:00","versionOfRecord":{"articleIdentity":"rs-4945548","link":"https://doi.org/10.1186/s12903-024-05317-z","journal":{"identity":"bmc-oral-health","isVorOnly":false,"title":"BMC Oral Health"},"publishedOn":"2025-01-04 15:57:20","publishedOnDateReadable":"January 4th, 2025"},"versionCreatedAt":"2024-10-17 14:01:34","video":"","vorDoi":"10.1186/s12903-024-05317-z","vorDoiUrl":"https://doi.org/10.1186/s12903-024-05317-z","workflowStages":[]},"version":"v1","identity":"rs-4945548","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4945548","identity":"rs-4945548","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}