Biomechanical Finite Element Analysis of Short and Long Implants In Resorbed Maxillary Posterior Region

Biomechanical Finite Element Analysis of Short and Long Implants In Resorbed Maxillary Posterior Region | 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 Biomechanical Finite Element Analysis of Short and Long Implants In Resorbed Maxillary Posterior Region Nisa Nur Dinçer, Ammar Tarık Dinçer, Elif Öncü This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5943576/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Objectives This study aimed to analyze different implant treatment concepts in maxillary posterior region. The effects of using short or long implants, with or without bone graft, are investigated in terms of strength and integrity. Materials and Methods Three different 3D models were generated from a CBCT scan: SI (short implant), LISG (long implant after sinus lifting with graft) and LIS (long implant after sinus lifting without graft). After integrating necessary implant parts, models were analyzed by FEM. The resultant stress values in the cortical and cancellous bones are evaluated by applying vertical and oblique forces. Implant parts are also investigated in terms of integrity and stability. Treatment concepts are compared depending on the FEA results. Results FEA demonstrated that short implants resulted in higher stress concentrations within the peri-implant bone compared to long implants. The maximum principal stress values in cortical bone were 100 MPa (tensile) and 133 MPa (compressive), while cancellous bone exhibited 14 MPa (tensile) and 16 MPa (compressive), all within physiological limits. Long implants, with or without grafts, significantly reduced stress levels compared to short implants. There were significant reductions for both compression and tensile stresses in the long implant concepts. Stress distribution patterns indicated that oblique loading led to increased palatal stress concentration. Conclusions Although the stresses occurring in the short implant concept are higher under both masticatory loading conditions, the results obtained for both short and long implant concepts remain within physiological limits where the bone can maintain its continuity without deformation. Clinical Relevance Short implants are biomechanically viable alternatives when augmentation is not feasible, provided that stress thresholds remain within safe limits. Finite element analysis Dental implant Maxilla Sinus lift Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1. Introduction Dental implant is a commonly practiced treatment method for tooth loss. Although there is a general acceptance about dental implants, practicing techniques vary depending on the patient and application area. In the process following the tooth loss, vertical and horizontal resorption begins to appear in the alveolar ridge with the bone deterioration. As a result of this, both maxilla and mandible may present adverse conditions for implant applications due to insufficient bone height, low bone density and excessive occlusal forces [ 1 ]. A crucial parameter for determining characteristics of bone tissue of posterior maxilla is bone density. In this area, structure of bone tissue consists of cancellous tissue with a lamellar structure, and cortical tissue, which have a denser structure. Cancellous and cortical features in the bone structure define the density of the tissue [ 2 ]. In terms of structural features, the physiology of the bone tissue with which the molars in the posterior maxilla region interact and the sinus cavities located above it are of great importance. In case of tooth loss, remodeling process of bones begins in the edentulous area. Vertical bone loss rate in the edentulous maxilla or mandible varies from person to person, but has been reported to be 0.1 mm per year on average. In this process, the floor of the maxillary sinus is displaced in the opposite direction, that is, towards the alveolar crest. As a result, the thickness of the alveolar crest may decrease to less than 1 mm, and it is also reported that in such cases it might become impossible to place an implant without increasing the bone height and thickness [ 3 ]. Bone atrophy makes it difficult to place standard implants in the edentulous area, and in order to obtain sufficient bone volume, additional surgical procedures such as crest augmentation, block graft, distraction osteogenesis, sinus lift in the upper jaw, and nerve lateralization in the lower jaw are required. Such cases necessitate sinus lifting operation for the purpose of increasing thickness. In this surgical operation, a small window is cut into the side of the sinus, Schneiderian membrane is elevated and then graft material is placed into the related location to form an additional bone structure. An example surgical application by authors of this study is given in Fig. 1 stage by stage. Panoramic images of the relevant application before and after sinus membrane elevation and bone graft application are given in Fig. 2 . Increase in the bone thickness can be directly seen from panoramic images. Considering the additional time, cost and risk of complications as a result of these extra surgical procedures involved, short implants appear as a very advantageous option in the rehabilitation of resorbed edentulous areas. The advantages of short implants include the patient having a more comfortable post-operative period as it is a less invasive procedure, being less costly, and achieving the ideal implant position more easily. Among its disadvantages, it can be mentioned that the crown/root ratio increases, primary stabilization is more difficult and it is risky in Type 4 bone. [ 4 ]. The majority of studies conducted in recent years show that short implants can be used as an alternative to long implants [ 5 , 6 , 7 , 8 ]. These different methods used in implant treatment, might result in different stress values in bone tissue and the level of resultant stresses might affect the preferences for treatment. It is clear that stress analysis is necessary for structural evaluation, as well as other mentioned advantages and disadvantages of these treatments. In this study, long and short implant applications are compared biomechanically by utilizing FEA (finite element analysis). Considering the aforementioned differences in sinus lifting, long implant concept is modelled with and without graft use. Thus, 3 different FEM models were generated, analyzed and evaluated as, short implant (SI), long implant after sinus lifting with graft (LISG) and long implant after sinus lifting without graft (LIS). 2. Material and Method 2.1 Model establishment Ethics Committee of the Necmettin Erbakan University Faculty of Dentistry reviewed the study protocol and granted ethical approval with decision date of 10.05.2020 and Decision No. of 2020/04. Computer tomography (CT) image of an adult patient was used for the creation of the model used in the study. 3M Iluma CBCT (3M Imtec, OK, USA) device was used in 40-second shooting mode with 120 KvP 3.8mA values for CT imaging. The CT films were transferred to the 3D-DOCTOR software (Able Software Corp, Lexington, MA, USA), where the bone tissue was separated by looking at the Hounsfield values using the "Interactive Segmentation" method. After the segmentation process, a 3D model was generated with the "3D Complex Render" method, and the cortical bone tissue was modelled in this way. Cancellous bone was obtained from cortical bone tissue by the offsetting and load transfer was achieved by making the required adjustments. Operations accomplished to process CT images are represented in Fig. 3. Beside modelling the bones, the implant and prosthesis parts supplied in the study were scanned with the SmartOptics 3D scanner (SmartOptics, Bochum, Germany). Obtained models in .stl format were sent to Rhinoceros 4.0 software (Robert McNeel and Associates, Seattle, WA, USA). Harmonization was made between the upper and lower parts of the prosthesis, implant screws and bone tissues with the Boolean method in Rhino software. Through this, load transfer was achieved in the integrated part. Figure 3 Modification and adjustments on CT images. a) Raw CT image with section view, b) interactive segmentation, c) bone tissue defined In this way, mandibular cortical bone, cancellous bone, implants and prosthesis parts were included in the model to reflect the real morphology. The models were placed in the correct coordinates in 3D space in Rhinoceros software and the 3D modelling process was completed. 3D models of long implant parts are given in Fig. 4 . As it is mentioned before, there are 3 different models created for 3 different implant treatment concepts in this study. Outline of these concepts are given in Table 1 . Classification limit for defining ‘short’ and ‘long’ implants in literature varies between different studies. Consequently, reasonable values from similar studies are selected as 6 mm for short implant [ 9 , 10 ] and 12 mm for long implant length [ 11 , 12 ]. Frontal view of 3D models for SI, LISG and LIS concepts are shown in Fig. 5 . Table 1 Three different implant treatment concepts # Model Application 1 Short implant (SI) 6 mm implant application to 7 mm residual bone 2 Long implant after sinus lifting with graft (LISG) 12 mm implant application combined with sinus lift using graft 3 Long implant after sinus lifting without graft (LIS) 12 mm implant application with sinus lift procedure without the use of grafts After the final modifications, the models were submitted to the FEMPRO analysis program (Algor, Autodesk, CA, USA). During the meshing process, the models were constructed using hexahedral elements wherever possible. In strict regions of the models, tetrahedral elements were used due to their geometric flexibility and adaptivity. Using this modelling technique, it was aimed to facilitate computation by striving to create the highest quality mesh structure with the highest node-count elements possible. Steep and narrow regions within the mesh structure, which could complicate the analysis process, were modified to exclude linear elements. Thereby a more uniform configuration is achieved. 2.2 Material Properties Posterior maxilla is mostly consisting of Type 3 and Type 4 bone tissue. In this study, using the bone density classification of Lekholm and Zarb as a reference, a modeling consisting of cancellous bone with Type 3 bone characteristics and 1 mm cortical bone was made [ 13 , 14 ]. Reference implant model is standard screw-type dental implant system with 4.1 mm diameter by Institut Straumann AG (Straumann, Basel, Switzerland). This dental implant type is made of commercially pure (CP) titanium of Grade 4 (ISO 5832/II). For crown of the implant, porcelain material is defined. Required mechanical properties are obtained from literature and given in Table 2 [ 15 , 16 ]. All components were modelled as linear elastic and isotropic in FEMs. Table 2 Mechanical properties of used materials Young’s Modulus (GPa) Poisson Ratio Cancellous bone 1.37 0.3 Cortical bone 13.7 0.3 Feldspathic porcelain 82.8 0.35 Titanium 110 0.35 Graft 11 0.3 2.3 Loading and Boundary Conditions The models were subjected to rigid fixation ( \(\:\text{D}\text{o}\text{F}\:=\:0\) ) in the top and rear planar sections of the skull. The implants were assumed to be osseointegrated with the peri-implant bone. Masticatory forces vary among individuals. It varies depending on the age, sex, existing restorations in the mouth, parafunctional habits such as bruxism, and the mental state of the patient. Therefore, the value of molar occlusal forces occurring during chewing shows a wide range. According to Attia, adult occlusal forces are accepted as 400–800 N for the molar region, 300 N for the premolar region, and 200 N for the anterior region. In order to understand implant strength, it is necessary to specify the stress values created by the oblique forces acting on the implants in lateral movements in dynamic occlusion, in addition to the vertical force as oblique loads cause higher stress values in the bone [ 17 ]. Considering former studies, vertical load is determined as 450 N in this study [ 18 , 19 ]. Additionally, oblique load of 300 N with a 30° inclination is applied, in line with the former studies [ 20 , 21 ]. Applied loading and boundary conditions can be seen in Fig. 6 . 3. Result and Discussion In FEA, different stress values are evaluated. As it is known that the maximum principal stress is used as a criterion in brittle materials, both the cortical and cancellous bones are evaluated through it. To take compression into consideration, minimum principal stress values are also evaluated. Unlike the bones, Ti implant parts have comparatively ductile characteristics. Therefore, von Mises stress criterion is used for evaluation of Ti parts. Before bones, implant parts are evaluated through the resultant stress values on implant and abutment. Masticatory loads are transferred to bones through these parts. Therefore, these parts were needed to meet the occurring maximum stress values by their mechanical properties. Evaluating results, it has been seen that maximum von Mises stress ( \(\:{\sigma\:}_{v}\) ) on these parts are lower than the yield strength of grade 4 Ti (483 MPa) (ISO-5832-2, 2018). On occlusal surface of crown part, compression stresses of notable levels occur. However, maximum compressive stress among all cases is 302 MPa and it has been reported that the compressive strength for dental feldspathic porcelain is 340 MPa [ 22 ]. Resultant von Mises stress distributions are given in Fig. 7 . In each case, different stress distribution maps obtained but those with the maximum stress values are given here. It can be deduced from this that stress values occur within the safe range in all cases. Yield strength is used as limit in the evaluation of analysis results. Because materials exhibit plastic behavior and deforms irreversibly above the yield limit. Plastic deformation in the relevant region is not acceptable by the macroscopic biomechanical definition of osseointegration. From a macroscopic biomechanical perspective, the absence of movement between the implant and the surrounding bone tissue under functional loads, and the implant's ability to exhibit consistent deformation in response to specific intensities of stress throughout the patient's lifetime, indicate that the implant is osseointegrated. Both the cortical and cancellous bones are evaluated separately according to the occurring stress values. For SI, LISG and LIS models, vertical and oblique loads are applied respectively. In each analysis maximum principal stress ( \(\:{\sigma\:}_{1}\) ) and minimum principal stress ( \(\:{\sigma\:}_{3}\) ) values are generated to obtain highest tensile and compressive stress values. All 24 different resultant stress distributions (3 models X 2 load type X 2 stress type X 2 bone type) are given as a diagram in Fig. 8 . Here, location and general distribution of stress can be seen. Beside distribution, Fig. 9 represents maximum stress values for each case. Before comparing the models, it can be stated as a general evaluation, the maximum stress values obtained for the cortical bone among all results are 100 MPa (tensile) and 133 MPa (compression) stress. This obtained results are below the ultimate tensile ( \(\:{\sigma\:}_{u,\:cor}=\:135\:\) MPa) and compression stress ( \(\:{\sigma\:}_{c,\:cor}=\:205\) MPa) of cortical bone [ 23 ]. Maximum stress values obtained at cancellous bone are 14 MPa (tensile) and 16 MPa (compression). In similar, these results are below the ultimate tensile ( \(\:{\sigma\:}_{u,\:can}=16\) MPa) and compression stress ( \(\:{\sigma\:}_{c,\:can}=\:\) 22–28 MPa) of cancellous bone [ 24 , 25 ]. However, it should be noted that strength of maxilla and mandible depends on many parameters (such as age, sex and living conditions) [ 26 ]. As a result, all stress values are in the safe zone. General stress distribution through the load path represents that the stress occurring in cortical bone is considerably higher than that occurring in cancellous bone. This finding supports the studies and evaluations in the literature [ 27 , 28 ]. Comparing results of different models, it can be seen that the resultant stress values strongly depend on implant concept and loading type. When short and long implants are compared by averaging load types and bones, lower than half of the average maximum stress occurred when long implants are used. Additionally, graft use in LI models are compared and results showed that stress values occurred in LISG and LIS models are almost equal, so graft use has a neglectable effect in this case in terms of structural strength. Stress values (both tensile and compression) at the cortical bone can be compared as; \(\:{\sigma\:}_{SI}>{\sigma\:}_{LISG}\approx\:{\sigma\:}_{LIS}\) under vertical loading and \(\:{\sigma\:}_{SI}>{\sigma\:}_{LISG}\approx\:{\sigma\:}_{LIS}\) under oblique loading. Similarly, stress values at the cancellous bone can be compared as; \(\:{\sigma\:}_{SI}>{\sigma\:}_{LISG}>{\sigma\:}_{LIS}\) under vertical loading and \(\:{\sigma\:}_{SI}>{\sigma\:}_{LISG}\approx\:{\sigma\:}_{LIS}\) under oblique loading. Table 3 Maximum stress concentration regions and tooth number for each case Vertical Load Oblique Load Tension Compression Tension Compression SI Cortical 26 / Palatal 26 / Buccal 26 / Palatal 26 / Palatal Cancellous 27 / Buccal 26 / Buccal 26 / Palatal 26 / Mesial LISG Cortical 26 / Buccal 27 / Buccal 26 / Buccal 26 / Palatal Cancellous 26 / Buccal 26 / Buccal 26 / Mesial 27 / Palatal LIS Cortical 26 / Buccal 27 / Buccal 26 / Buccal 27 / Palatal Cancellous 27 / Buccal 26 / Buccal 26 / Mesial 26 / Buccal Although an exceptional tensile stress state was found in the cortical bone of the SI model, vertical loads are resulting in highest load concentration in buccal region in general. This characteristic is depending on the morphology of maxilla. Besides, it can be seen that stress concentration center is approaching towards the palatal and mesio-palatal regions with the oblique loading angle. Stress concentration regions for each case are given in Table 3 . When compared, higher values of both tensile and compressive stresses have been observed in short implants. However, when considering the mechanical properties ( \(\:{\sigma\:}_{u}\) , \(\:{\sigma\:}_{c}\) ) of both cortical and cancellous bone, it is seen that the stresses emerging in both concepts remain within the elastic region, and excessive stresses do not occur. This finding has been interpreted as an indication that short implant treatment can provide healthy results as an alternative to conventional long implant treatment. This determination made as a result of calculations is also consistent with clinical findings in the literature. In a randomized controlled study conducted by Gulje F. et al, the follow-up of implants with diameters of 4 mm and lengths of 6 mm and 11 mm applied to the posterior region for 1 year was performed [ 29 ]. At the end of 1-year, similar survival rates were found, and there was no significant difference between bone losses, and it was reported that it could be used as an alternative to bone augmentation procedures. In addition to implant length, the use of hard tissue grafts in models has also been considered as a parameter. When the results are examined, it is seen that the use of hard tissue grafts in long implant models does not cause a significant change in terms of the stresses formed. This is a finding that indicates that the application of long implants with direct sinus elevation without the use of hard tissue grafts is appropriate. This evaluation made as a result of FEA is consistent with a large number of past studies on the subject. In a study covering 47 patients with a minimum residual bone height of 5 mm, a total of 75 implants were placed by performing a sinus lift procedure without the use of hard tissue grafts, and it was reported that the bone height increased from 3 to 9 mm at the end of a two-year follow-up, no complications were observed, and the survival rate was 100% [ 30 ]. In another study, in a bilateral randomized controlled study with 15 patients, while simultaneous dental implants were placed in one quadrant of the patients with autogenous bone grafts along with sinus lift application, simultaneous dental implants were placed in the other quadrant without using grafts with sinus lift procedure. In all patients followed up for 6 months, it was reported that new bone formation was radiographically observed in the area where the sinus membrane was elevated, and there was no significant difference between the groups in radiographic measurements [ 31 ]. 4. Conclusions In summary, the study examined the stresses and the areas where they occur in different implant treatment concepts under the relevant loads. The stresses in the posterior maxilla were compared with the implant and abutment parts modeled in accordance with the real treatment. As a result, the following evaluations were made: In all FEMs, the highest stress was transmitted to the cortical bone under both vertical and oblique forces. Although the stress transferred to the bone in short implants is greater for both vertical and oblique forces compared to long implants, the load transmitted to the bone in both long and short implants is within the physiological limit where the bone can maintain its continuity without deformation. Considering these results, it can be predicted that short implants may be an alternative to long implants that require augmentation procedures. The stress values transferred to the bone were found to be quite close in implants placed with and without the use of hard tissue grafts during sinus lift procedures. This result suggests that augmentation without using hard tissue graft following maxillary sinus membrane elevation is an alternative treatment option. Declarations Funding This study was funded and supported by Necmettin Erbakan University within the scope of Scientific Research Project (BAP) with project no 201924009. Ethics Declarations Conflict of interest The authors declare that they have no conflict of interest. Ethics approval and consent to participate The scientific ethical compliance of this study has been approved by the Necmettin Erbakan University Faculty of Dentistry Ethics Committee with the decision dated 10.05.2020 and numbered 2020/04. All procedures involving human subjects were conducted with informed consent according to the Helsinki Declaration. 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Dinçer","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA4klEQVRIiWNgGAWjYPACZh4w9cEATBkQr4VxhoEBVEsCYS0wjURo4Z92OvFzBYO1jDn74WOfbQr+JDawN2+TYPxxD6cWidu5myXPMKTzWPakJc/OMTBIbOA5VibBkFCM25rbuRskGxgO8xjc4DFmBmuRyDEDasHtMnmgLT8hWvg/M1uAtMi/wa/F4HbuNpgtzMwMYFt48GsxBGqxbDBI5zE4k2bM2GNgbNzGk1ZskZCGW4sc0GE3Gyqs7Q2OH37M8OOPnGw/++GNNz7Y4NYCdR4Smw1EENIwCkbBKBgFowA/AAAmNEmQt0o1DQAAAABJRU5ErkJggg==","orcid":"","institution":"Istanbul Technical University","correspondingAuthor":true,"prefix":"","firstName":"Ammar","middleName":"Tarık","lastName":"Dinçer","suffix":""},{"id":411339717,"identity":"ae7f493d-7878-438f-886b-f3cddc1860c4","order_by":2,"name":"Elif Öncü","email":"","orcid":"","institution":"Necmettin Erbakan University","correspondingAuthor":false,"prefix":"","firstName":"Elif","middleName":"","lastName":"Öncü","suffix":""}],"badges":[],"createdAt":"2025-02-01 21:38:15","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5943576/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5943576/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":75706985,"identity":"73059491-5ff7-477a-b4a7-a00315ba38ee","added_by":"auto","created_at":"2025-02-07 10:27:35","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":859115,"visible":true,"origin":"","legend":"\u003cp\u003eExemplary sinus lift operation. a) Window borders prepared on the buccal bone, b) Released sinus membrane after osteotomy, c) Grafting procedure following the elevation of the Schneiderian membrane, d) Application of the membrane fixed with the help of pins\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-5943576/v1/3f8e9512bcdfa5fbbb63848a.png"},{"id":75708781,"identity":"b60a725d-3be5-4607-80f4-e85ce022ef05","added_by":"auto","created_at":"2025-02-07 10:43:35","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":339198,"visible":true,"origin":"","legend":"\u003cp\u003ePanoramic image a) before, and b) after membrane elevation\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-5943576/v1/4e34947962d01a16516e894e.png"},{"id":75707297,"identity":"d0edd4a4-2f5a-4557-a0b7-17abbf55bd3f","added_by":"auto","created_at":"2025-02-07 10:35:35","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":381826,"visible":true,"origin":"","legend":"\u003cp\u003eModification and adjustments on CT images. a) Raw CT image with section view, b) interactive segmentation, c) bone tissue defined\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5943576/v1/a9a91dab52ebe9cdb0dabfae.png"},{"id":75706993,"identity":"36fc8172-0b8e-4a5d-ae14-8b379d8a4ef8","added_by":"auto","created_at":"2025-02-07 10:27:36","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":237674,"visible":true,"origin":"","legend":"\u003cp\u003eLong implant supported prosthesis 3D design render\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-5943576/v1/c6f229719d77e04c8c453ad9.png"},{"id":75706992,"identity":"889b07d1-222f-469a-9ae2-6981916aedb3","added_by":"auto","created_at":"2025-02-07 10:27:35","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":334077,"visible":true,"origin":"","legend":"\u003cp\u003ea) Frontal view of SI model, b) view of graft material in LISG, c) frontal view of LISG and LIS\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-5943576/v1/23f6c761402e5ef6bc29f8bb.png"},{"id":75709486,"identity":"aef93140-8c97-4c12-8d97-cfa6765b3aa9","added_by":"auto","created_at":"2025-02-07 10:51:35","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":559772,"visible":true,"origin":"","legend":"\u003cp\u003eBoundary conditions and applied loads in FEM\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-5943576/v1/7ce71838c76a187e3fd03a53.png"},{"id":75708783,"identity":"35b0fb94-8e6f-4ef4-9bc6-92f040890ecd","added_by":"auto","created_at":"2025-02-07 10:43:36","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":998373,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-5943576/v1/3ef2a90fa7f5772cbc6f4566.png"},{"id":75707300,"identity":"4d0badc1-8648-40f6-8332-04fa0f73f6ee","added_by":"auto","created_at":"2025-02-07 10:35:36","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":3221747,"visible":true,"origin":"","legend":"\u003cp\u003eMaximum and minimum principal stress diagram of three models for vertical and oblique loading cases. (T: tensile, maximum principal stress distribution; C: compression, minimum principal stress distribution)\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-5943576/v1/2670966decb76545d46fdf4a.png"},{"id":75707018,"identity":"0115fda4-f7f2-48ef-b94c-f38bdc756591","added_by":"auto","created_at":"2025-02-07 10:27:37","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":295756,"visible":true,"origin":"","legend":"\u003cp\u003eMaximum (tensile) and minimum (compression) principal stress values occurred on either cortical or cancellous bone for all loading direction and implant concepts. a) SI model, b) LISG model and c) LIS model. Compression stress values are shown in their absolute values\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-5943576/v1/b9d362bd894eb02d80d67ea1.png"},{"id":76401486,"identity":"8f0b13c2-f3e2-47d2-84ac-6a64536e05f1","added_by":"auto","created_at":"2025-02-16 16:16:43","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":10405046,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5943576/v1/c3532dd5-6dba-49c6-ba34-2be362bf23c3.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Biomechanical Finite Element Analysis of Short and Long Implants In Resorbed Maxillary Posterior Region","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eDental implant is a commonly practiced treatment method for tooth loss. Although there is a general acceptance about dental implants, practicing techniques vary depending on the patient and application area. In the process following the tooth loss, vertical and horizontal resorption begins to appear in the alveolar ridge with the bone deterioration. As a result of this, both maxilla and mandible may present adverse conditions for implant applications due to insufficient bone height, low bone density and excessive occlusal forces [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eA crucial parameter for determining characteristics of bone tissue of posterior maxilla is bone density. In this area, structure of bone tissue consists of cancellous tissue with a lamellar structure, and cortical tissue, which have a denser structure. Cancellous and cortical features in the bone structure define the density of the tissue [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn terms of structural features, the physiology of the bone tissue with which the molars in the posterior maxilla region interact and the sinus cavities located above it are of great importance. In case of tooth loss, remodeling process of bones begins in the edentulous area. Vertical bone loss rate in the edentulous maxilla or mandible varies from person to person, but has been reported to be 0.1 mm per year on average. In this process, the floor of the maxillary sinus is displaced in the opposite direction, that is, towards the alveolar crest. As a result, the thickness of the alveolar crest may decrease to less than 1 mm, and it is also reported that in such cases it might become impossible to place an implant without increasing the bone height and thickness [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Bone atrophy makes it difficult to place standard implants in the edentulous area, and in order to obtain sufficient bone volume, additional surgical procedures such as crest augmentation, block graft, distraction osteogenesis, sinus lift in the upper jaw, and nerve lateralization in the lower jaw are required.\u003c/p\u003e \u003cp\u003eSuch cases necessitate sinus lifting operation for the purpose of increasing thickness. In this surgical operation, a small window is cut into the side of the sinus, Schneiderian membrane is elevated and then graft material is placed into the related location to form an additional bone structure. An example surgical application by authors of this study is given in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e stage by stage. Panoramic images of the relevant application before and after sinus membrane elevation and bone graft application are given in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. Increase in the bone thickness can be directly seen from panoramic images.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eConsidering the additional time, cost and risk of complications as a result of these extra surgical procedures involved, short implants appear as a very advantageous option in the rehabilitation of resorbed edentulous areas. The advantages of short implants include the patient having a more comfortable post-operative period as it is a less invasive procedure, being less costly, and achieving the ideal implant position more easily. Among its disadvantages, it can be mentioned that the crown/root ratio increases, primary stabilization is more difficult and it is risky in Type 4 bone. [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. The majority of studies conducted in recent years show that short implants can be used as an alternative to long implants [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThese different methods used in implant treatment, might result in different stress values in bone tissue and the level of resultant stresses might affect the preferences for treatment. It is clear that stress analysis is necessary for structural evaluation, as well as other mentioned advantages and disadvantages of these treatments.\u003c/p\u003e \u003cp\u003eIn this study, long and short implant applications are compared biomechanically by utilizing FEA (finite element analysis). Considering the aforementioned differences in sinus lifting, long implant concept is modelled with and without graft use. Thus, 3 different FEM models were generated, analyzed and evaluated as, short implant (SI), long implant after sinus lifting with graft (LISG) and long implant after sinus lifting without graft (LIS).\u003c/p\u003e"},{"header":"2. Material and Method","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003e2.1 Model establishment\u003c/h2\u003e\n \u003cp\u003eEthics Committee of the Necmettin Erbakan University Faculty of Dentistry reviewed the study protocol and granted ethical approval with decision date of 10.05.2020 and Decision No. of 2020/04. Computer tomography (CT) image of an adult patient was used for the creation of the model used in the study. 3M Iluma CBCT (3M Imtec, OK, USA) device was used in 40-second shooting mode with 120 KvP 3.8mA values for CT imaging. The CT films were transferred to the 3D-DOCTOR software (Able Software Corp, Lexington, MA, USA), where the bone tissue was separated by looking at the Hounsfield values using the \u0026quot;Interactive Segmentation\u0026quot; method. After the segmentation process, a 3D model was generated with the \u0026quot;3D Complex Render\u0026quot; method, and the cortical bone tissue was modelled in this way. Cancellous bone was obtained from cortical bone tissue by the offsetting and load transfer was achieved by making the required adjustments. Operations accomplished to process CT images are represented in Fig.\u0026nbsp;3.\u003c/p\u003e\n \u003cp\u003eBeside modelling the bones, the implant and prosthesis parts supplied in the study were scanned with the SmartOptics 3D scanner (SmartOptics, Bochum, Germany). Obtained models in .stl format were sent to Rhinoceros 4.0 software (Robert McNeel and Associates, Seattle, WA, USA). Harmonization was made between the upper and lower parts of the prosthesis, implant screws and bone tissues with the Boolean method in Rhino software. Through this, load transfer was achieved in the integrated part.\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eFigure\u0026nbsp;3\u003c/strong\u003e Modification and adjustments on CT images. a) Raw CT image with section view, b) interactive segmentation, c) bone tissue defined\u003c/p\u003e\n \u003cp\u003eIn this way, mandibular cortical bone, cancellous bone, implants and prosthesis parts were included in the model to reflect the real morphology. The models were placed in the correct coordinates in 3D space in Rhinoceros software and the 3D modelling process was completed. 3D models of long implant parts are given in Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e. As it is mentioned before, there are 3 different models created for 3 different implant treatment concepts in this study. Outline of these concepts are given in Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. Classification limit for defining \u0026lsquo;short\u0026rsquo; and \u0026lsquo;long\u0026rsquo; implants in literature varies between different studies. Consequently, reasonable values from similar studies are selected as 6 mm for short implant [\u003cspan class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e] and 12 mm for long implant length [\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e]. Frontal view of 3D models for SI, LISG and LIS concepts are shown in Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e.\u0026nbsp;\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eThree different implant treatment concepts\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e#\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eModel\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eApplication\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eShort implant (SI)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6 mm implant application to 7 mm residual bone\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLong implant after sinus\u003c/p\u003e\n \u003cp\u003elifting with graft (LISG)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e12 mm implant application combined with sinus lift using graft\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLong implant after sinus\u003c/p\u003e\n \u003cp\u003elifting without graft (LIS)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e12 mm implant application with sinus lift procedure without the use of grafts\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003eAfter the final modifications, the models were submitted to the FEMPRO analysis program (Algor, Autodesk, CA, USA). During the meshing process, the models were constructed using hexahedral elements wherever possible. In strict regions of the models, tetrahedral elements were used due to their geometric flexibility and adaptivity. Using this modelling technique, it was aimed to facilitate computation by striving to create the highest quality mesh structure with the highest node-count elements possible. Steep and narrow regions within the mesh structure, which could complicate the analysis process, were modified to exclude linear elements. Thereby a more uniform configuration is achieved.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003e2.2 Material Properties\u003c/h2\u003e\n \u003cp\u003ePosterior maxilla is mostly consisting of Type 3 and Type 4 bone tissue. In this study, using the bone density classification of Lekholm and Zarb as a reference, a modeling consisting of cancellous bone with Type 3 bone characteristics and 1 mm cortical bone was made [\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e\n \u003cp\u003eReference implant model is standard screw-type dental implant system with 4.1 mm diameter by Institut Straumann AG (Straumann, Basel, Switzerland). This dental implant type is made of commercially pure (CP) titanium of Grade 4 (ISO 5832/II). For crown of the implant, porcelain material is defined. Required mechanical properties are obtained from literature and given in Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e [\u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e16\u003c/span\u003e]. All components were modelled as linear elastic and isotropic in FEMs.\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eMechanical properties of used materials\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eYoung\u0026rsquo;s Modulus (GPa)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ePoisson Ratio\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCancellous bone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCortical bone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFeldspathic porcelain\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e82.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.35\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eTitanium\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e110\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.35\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eGraft\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n \u003ch2\u003e2.3 Loading and Boundary Conditions\u003c/h2\u003e\n \u003cp\u003eThe models were subjected to rigid fixation (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\text{D}\\text{o}\\text{F}\\:=\\:0\\)\u003c/span\u003e\u003c/span\u003e) in the top and rear planar sections of the skull. The implants were assumed to be osseointegrated with the peri-implant bone. Masticatory forces vary among individuals. It varies depending on the age, sex, existing restorations in the mouth, parafunctional habits such as bruxism, and the mental state of the patient. Therefore, the value of molar occlusal forces occurring during chewing shows a wide range. According to Attia, adult occlusal forces are accepted as 400\u0026ndash;800 N for the molar region, 300 N for the premolar region, and 200 N for the anterior region. In order to understand implant strength, it is necessary to specify the stress values created by the oblique forces acting on the implants in lateral movements in dynamic occlusion, in addition to the vertical force as oblique loads cause higher stress values in the bone [\u003cspan class=\"CitationRef\"\u003e17\u003c/span\u003e]. Considering former studies, vertical load is determined as 450 N in this study [\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e19\u003c/span\u003e]. Additionally, oblique load of 300 N with a 30\u0026deg; inclination is applied, in line with the former studies [\u003cspan class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e21\u003c/span\u003e]. Applied loading and boundary conditions can be seen in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e.\u003c/p\u003e\n\n\u003c/div\u003e"},{"header":"3. Result and Discussion","content":"\u003cp\u003eIn FEA, different stress values are evaluated. As it is known that the maximum principal stress is used as a criterion in brittle materials, both the cortical and cancellous bones are evaluated through it. To take compression into consideration, minimum principal stress values are also evaluated. Unlike the bones, Ti implant parts have comparatively ductile characteristics. Therefore, von Mises stress criterion is used for evaluation of Ti parts.\u003c/p\u003e \u003cp\u003eBefore bones, implant parts are evaluated through the resultant stress values on implant and abutment. Masticatory loads are transferred to bones through these parts. Therefore, these parts were needed to meet the occurring maximum stress values by their mechanical properties. Evaluating results, it has been seen that maximum von Mises stress (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\sigma\\:}_{v}\\)\u003c/span\u003e\u003c/span\u003e) on these parts are lower than the yield strength of grade 4 Ti (483 MPa) (ISO-5832-2, 2018). On occlusal surface of crown part, compression stresses of notable levels occur. However, maximum compressive stress among all cases is 302 MPa and it has been reported that the compressive strength for dental feldspathic porcelain is 340 MPa [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Resultant von Mises stress distributions are given in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003e. In each case, different stress distribution maps obtained but those with the maximum stress values are given here. It can be deduced from this that stress values occur within the safe range in all cases.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eYield strength is used as limit in the evaluation of analysis results. Because materials exhibit plastic behavior and deforms irreversibly above the yield limit. Plastic deformation in the relevant region is not acceptable by the macroscopic biomechanical definition of osseointegration. From a macroscopic biomechanical perspective, the absence of movement between the implant and the surrounding bone tissue under functional loads, and the implant's ability to exhibit consistent deformation in response to specific intensities of stress throughout the patient's lifetime, indicate that the implant is osseointegrated.\u003c/p\u003e \u003cp\u003eBoth the cortical and cancellous bones are evaluated separately according to the occurring stress values. For SI, LISG and LIS models, vertical and oblique loads are applied respectively. In each analysis maximum principal stress (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\sigma\\:}_{1}\\)\u003c/span\u003e\u003c/span\u003e) and minimum principal stress (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\sigma\\:}_{3}\\)\u003c/span\u003e\u003c/span\u003e) values are generated to obtain highest tensile and compressive stress values. All 24 different resultant stress distributions (3 models X 2 load type X 2 stress type X 2 bone type) are given as a diagram in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e8\u003c/span\u003e. Here, location and general distribution of stress can be seen. Beside distribution, Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e9\u003c/span\u003e represents maximum stress values for each case.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eBefore comparing the models, it can be stated as a general evaluation, the maximum stress values obtained for the cortical bone among all results are 100 MPa (tensile) and 133 MPa (compression) stress. This obtained results are below the ultimate tensile (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\sigma\\:}_{u,\\:cor}=\\:135\\:\\)\u003c/span\u003e\u003c/span\u003eMPa) and compression stress (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\sigma\\:}_{c,\\:cor}=\\:205\\)\u003c/span\u003e\u003c/span\u003e MPa) of cortical bone [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Maximum stress values obtained at cancellous bone are 14 MPa (tensile) and 16 MPa (compression). In similar, these results are below the ultimate tensile (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\sigma\\:}_{u,\\:can}=16\\)\u003c/span\u003e\u003c/span\u003e MPa) and compression stress (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\sigma\\:}_{c,\\:can}=\\:\\)\u003c/span\u003e\u003c/span\u003e22\u0026ndash;28 MPa) of cancellous bone [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. However, it should be noted that strength of maxilla and mandible depends on many parameters (such as age, sex and living conditions) [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. As a result, all stress values are in the safe zone.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eGeneral stress distribution through the load path represents that the stress occurring in cortical bone is considerably higher than that occurring in cancellous bone. This finding supports the studies and evaluations in the literature [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eComparing results of different models, it can be seen that the resultant stress values strongly depend on implant concept and loading type. When short and long implants are compared by averaging load types and bones, lower than half of the average maximum stress occurred when long implants are used. Additionally, graft use in LI models are compared and results showed that stress values occurred in LISG and LIS models are almost equal, so graft use has a neglectable effect in this case in terms of structural strength. Stress values (both tensile and compression) at the cortical bone can be compared as; \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\sigma\\:}_{SI}\u0026gt;{\\sigma\\:}_{LISG}\\approx\\:{\\sigma\\:}_{LIS}\\)\u003c/span\u003e\u003c/span\u003e under vertical loading and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\sigma\\:}_{SI}\u0026gt;{\\sigma\\:}_{LISG}\\approx\\:{\\sigma\\:}_{LIS}\\)\u003c/span\u003e\u003c/span\u003e under oblique loading. Similarly, stress values at the cancellous bone can be compared as; \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\sigma\\:}_{SI}\u0026gt;{\\sigma\\:}_{LISG}\u0026gt;{\\sigma\\:}_{LIS}\\)\u003c/span\u003e\u003c/span\u003e under vertical loading and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\sigma\\:}_{SI}\u0026gt;{\\sigma\\:}_{LISG}\\approx\\:{\\sigma\\:}_{LIS}\\)\u003c/span\u003e\u003c/span\u003e under oblique loading.\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\u003eMaximum stress concentration regions and tooth number for each case\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003eVertical Load\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003eOblique Load\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eTension\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCompression\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eTension\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eCompression\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eSI\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCortical\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e26 / Palatal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e26 / Buccal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e26 / Palatal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e26 / Palatal\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCancellous\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e27 / Buccal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e26 / Buccal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e26 / Palatal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e26 / Mesial\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eLISG\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCortical\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e26 / Buccal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e27 / Buccal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e26 / Buccal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e26 / Palatal\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCancellous\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e26 / Buccal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e26 / Buccal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e26 / Mesial\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e27 / Palatal\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eLIS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCortical\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e26 / Buccal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e27 / Buccal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e26 / Buccal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e27 / Palatal\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCancellous\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e27 / Buccal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e26 / Buccal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e26 / Mesial\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e26 / Buccal\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\u003eAlthough an exceptional tensile stress state was found in the cortical bone of the SI model, vertical loads are resulting in highest load concentration in buccal region in general. This characteristic is depending on the morphology of maxilla. Besides, it can be seen that stress concentration center is approaching towards the palatal and mesio-palatal regions with the oblique loading angle. Stress concentration regions for each case are given in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e \u003cp\u003eWhen compared, higher values of both tensile and compressive stresses have been observed in short implants. However, when considering the mechanical properties (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\sigma\\:}_{u}\\)\u003c/span\u003e\u003c/span\u003e, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\sigma\\:}_{c}\\)\u003c/span\u003e\u003c/span\u003e) of both cortical and cancellous bone, it is seen that the stresses emerging in both concepts remain within the elastic region, and excessive stresses do not occur. This finding has been interpreted as an indication that short implant treatment can provide healthy results as an alternative to conventional long implant treatment. This determination made as a result of calculations is also consistent with clinical findings in the literature. In a randomized controlled study conducted by Gulje F. et al, the follow-up of implants with diameters of 4 mm and lengths of 6 mm and 11 mm applied to the posterior region for 1 year was performed [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. At the end of 1-year, similar survival rates were found, and there was no significant difference between bone losses, and it was reported that it could be used as an alternative to bone augmentation procedures.\u003c/p\u003e \u003cp\u003eIn addition to implant length, the use of hard tissue grafts in models has also been considered as a parameter. When the results are examined, it is seen that the use of hard tissue grafts in long implant models does not cause a significant change in terms of the stresses formed. This is a finding that indicates that the application of long implants with direct sinus elevation without the use of hard tissue grafts is appropriate. This evaluation made as a result of FEA is consistent with a large number of past studies on the subject. In a study covering 47 patients with a minimum residual bone height of 5 mm, a total of 75 implants were placed by performing a sinus lift procedure without the use of hard tissue grafts, and it was reported that the bone height increased from 3 to 9 mm at the end of a two-year follow-up, no complications were observed, and the survival rate was 100% [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. In another study, in a bilateral randomized controlled study with 15 patients, while simultaneous dental implants were placed in one quadrant of the patients with autogenous bone grafts along with sinus lift application, simultaneous dental implants were placed in the other quadrant without using grafts with sinus lift procedure. In all patients followed up for 6 months, it was reported that new bone formation was radiographically observed in the area where the sinus membrane was elevated, and there was no significant difference between the groups in radiographic measurements [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e].\u003c/p\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eIn summary, the study examined the stresses and the areas where they occur in different implant treatment concepts under the relevant loads. The stresses in the posterior maxilla were compared with the implant and abutment parts modeled in accordance with the real treatment. As a result, the following evaluations were made:\u003c/p\u003e \u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eIn all FEMs, the highest stress was transmitted to the cortical bone under both vertical and oblique forces.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eAlthough the stress transferred to the bone in short implants is greater for both vertical and oblique forces compared to long implants, the load transmitted to the bone in both long and short implants is within the physiological limit where the bone can maintain its continuity without deformation. Considering these results, it can be predicted that short implants may be an alternative to long implants that require augmentation procedures.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe stress values transferred to the bone were found to be quite close in implants placed with and without the use of hard tissue grafts during sinus lift procedures. This result suggests that augmentation without using hard tissue graft following maxillary sinus membrane elevation is an alternative treatment option.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was funded and supported by Necmettin Erbakan University within the scope of Scientific Research Project (BAP) with project no 201924009.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics Declarations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe scientific ethical compliance of this study has been approved by the Necmettin Erbakan University Faculty of Dentistry Ethics Committee with the decision dated 10.05.2020 and numbered 2020/04. All procedures involving human subjects were conducted with informed consent according to the Helsinki Declaration.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors read and approved the final manuscript and consented to publication.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eChiapasco M, Zaniboni M, Boisco M (2006) Augmentation procedures for the rehabilitation of deficient edentulous ridges with oral implants. \u003cem\u003eClin Oral Implants Res\u003c/em\u003e. https://doi.org/10.1111/j.1600-0501.2006.01357.x\u003c/li\u003e\n\u003cli\u003eFernandez-Tresguerres Hernandez-Gil I, Alobera Gracia MA, Del Canto Pingarr\u0026oacute;n M, Blanco Jerez L (2006) Physiological bases of bone regeneration I. 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(2011) Simultaneous Sinus Membrane Elevation and Dental Implant Placement Without Bone Graft: A 6‐Month Follow‐Up Study. \u003cem\u003eJ Periodontol\u003c/em\u003e. https://doi.org/10.1902/jop.2010.100343\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Finite element analysis, Dental implant, Maxilla, Sinus lift","lastPublishedDoi":"10.21203/rs.3.rs-5943576/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5943576/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eObjectives\u003c/h2\u003e \u003cp\u003eThis study aimed to analyze different implant treatment concepts in maxillary posterior region. The effects of using short or long implants, with or without bone graft, are investigated in terms of strength and integrity.\u003c/p\u003e\u003ch2\u003eMaterials and Methods\u003c/h2\u003e \u003cp\u003eThree different 3D models were generated from a CBCT scan: SI (short implant), LISG (long implant after sinus lifting with graft) and LIS (long implant after sinus lifting without graft). After integrating necessary implant parts, models were analyzed by FEM. The resultant stress values in the cortical and cancellous bones are evaluated by applying vertical and oblique forces. Implant parts are also investigated in terms of integrity and stability. Treatment concepts are compared depending on the FEA results.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eFEA demonstrated that short implants resulted in higher stress concentrations within the peri-implant bone compared to long implants. The maximum principal stress values in cortical bone were 100 MPa (tensile) and 133 MPa (compressive), while cancellous bone exhibited 14 MPa (tensile) and 16 MPa (compressive), all within physiological limits. Long implants, with or without grafts, significantly reduced stress levels compared to short implants. There were significant reductions for both compression and tensile stresses in the long implant concepts. Stress distribution patterns indicated that oblique loading led to increased palatal stress concentration.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eAlthough the stresses occurring in the short implant concept are higher under both masticatory loading conditions, the results obtained for both short and long implant concepts remain within physiological limits where the bone can maintain its continuity without deformation.\u003c/p\u003e\u003ch2\u003eClinical Relevance\u003c/h2\u003e \u003cp\u003eShort implants are biomechanically viable alternatives when augmentation is not feasible, provided that stress thresholds remain within safe limits.\u003c/p\u003e","manuscriptTitle":"Biomechanical Finite Element Analysis of Short and Long Implants In Resorbed Maxillary Posterior Region","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-02-07 10:27:31","doi":"10.21203/rs.3.rs-5943576/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"9187e7c7-90c8-4f9d-9a98-ba8eac45329c","owner":[],"postedDate":"February 7th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-02-16T16:08:32+00:00","versionOfRecord":[],"versionCreatedAt":"2025-02-07 10:27:31","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5943576","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5943576","identity":"rs-5943576","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}