Influence of Implant Length and Diameter, Bicortical Anchorage, and Sinus Augmentation on Bone Stress Distribution: Three-Dimensional Finite Element Analysis (original) (raw)
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Journal of Prosthodontic Research, 2010
Purpose: There is no clear evidence of the factors that could improve implant biomechanics in the posterior maxilla. Thus, a finite element analysis was performed to investigate the effect of maxillary cortical bone thickness, implant design and diameter on stress around implants. Methods: A total of 12 models of the posterior maxilla with implant were computer-simulated by varying the thickness of the alveolar cortical bone (1.5, 1.0, 0.5 or 0 mm) and implant characteristics (cylindrical implant of 4.1-mm diameter, screw-type implants of 4.1-mm or 4.8-mm outer diameters). On top of each implant, forces were separately applied axially (100 N) and buccolingually (50 N), and the von Mises stresses were calculated. Results: Regardless of load direction, implant design and diameter, cortical and cancellous bone stresses increased with the decrease of crestal cortical bone thickness. In the absence of crestal cortical bone, cancellous bone stresses were highest and, under axial load, were transferred to the sinus floor. Implant design and diameter influenced stress to a less extent, especially under buccolingual load and in the presence of crestal cortical bone. Conclusions: From a biomechanical viewpoint, to improve implant success odds in the posterior maxilla, rather than implant selection, careful preoperative evaluation of the cortical bone at the planned implant site is recommended. If this cortical bone is very thin or even lacking, implant treatment should be carried on with caution by progressive loading in the range of functional loads.
Oral & Implantology, 2017
Introduction. Although many previous studies have reported on the high success rate of short dental implants, prosthetic design still plays an important role in the long-term implant treatment results. This study aims to evaluate stress distribution characteristics involved with various prosthetic designs on standard implants or short implants in the posterior maxilla. Materials and methods. Six finite element models were simulated representing the missing first and second maxillary molars. A standard implant (PW+ implant: 5.0x10 mm) and a short implant (PW+ implant: 5.0x6.0 mm) were applied under the various prosthetic conditions. The peri-implant maximum bone stress (V on mises stress) was evaluated when 200 N 30° oblique load was applied. A type III bone was approximated and complete osseous integration was assumed. Results. Maximum Von mises stress was numerically located at the cortical bone around the implant neck in all models. In every standard implant model shows better stress distribution. Stress values and concentration area decreased in the cortical and cancellous bone when implants were splinted in both the standard and short implant models. With regard to the non-replacing second molar models found that the area of stress at the cortical bone around the first molar implant to be more intensive. Moreover, in the non-replacing second molar models, the stress also spread to the second pre-molar in both the standard and short implant models. Conclusions. The length of the implant and prosthetics designs both affect the stress value and distribution of stress to the cortical and cancellous bones around the implant.
The Journal of Prosthetic Dentistry, 2008
Numerical results suggest that implant diameter may be more effective than implant length as a design parameter to control the risk of bone overload. For a given implant in the molar region, the worst load transmission mechanisms arise with maxillary placement, and implant biomechanical behavior greatly improves if bone is efficiently preserved at the crest. Statement of problem. Load transfer mechanisms and possible failure of osseointegrated implants are affected by implant shape, geometrical and mechanical properties of the site of placement, as well as crestal bone resorption. Suitable estimation of such effects allows for correct design of implant features.
Purpose: The biomechanical effects of different strengths of grafted bone, bicortical anchorage, and dimensional alterations of a dental implant with maxillary sinus augmentation were investigated. Materials and Methods: Sixteen finite element (FE) models that included five implant lengths, two implant diameters, and grafted bone with two levels of stiffness were studied. A posterior maxillary model was constructed from computerized tomographic images of a human skull, and the implant models were created via computer-aided design software (SolidWorks 2006). All materials were assumed to be isotropic and linearly elastic. A 45-degree oblique force of 129 N was applied to the buccal cusp of the first molar. Results: The von Mises stress was highest in the 7-mm-long implant. Stresses in cortical and trabecular bone were reduced by at least 50% for all other implants (length ≥ 8.5 mm) with bicortical anchorage. Increasing the length of the bicortically anchored implant did not decrease the stress in native bone, but it decreased the stress in sinus grafts by at least 20%. The use of a wide implant decreased the stress by 24% to 42% in cortical bone and 17% to 36% in trabecular bone. Increasing the elastic modulus of grafted bone decreased the stress in native bone by approximately 10%. Conclusions: Bicortical fixation of implants and the presence of grafted bone with greater stiffness reduced the stresses in native bone. Increasing the length of the implant in grafted bone did not reduce the stress in native bone, but it did reduce the stress in grafted bone. The effects of implant diameters on reducing bone stress are primarily a result of the increased contact area between implant and bone. The results of the FE analysis imply that the success of a sinus-augmented dental implant is heavily dependent on the implant design and rigidity of the bone grafts. INT J ORAL MAXILLOFAC IMPLANTS 2009;24:455–462
Dental Materials, 2021
Objectives: The aim of this study was to evaluate the influence of three different dental implant neck geometries, under a combined compressive/shear load using finite element analysis (FEA). The implant neck was positioned in D2 quality bone at the crestal level or 2 mm below. Methods: One dental implant (4.2 x 9 mm) was digitized by reverse engineering techniques using micro CT and imported into Computer Aided Design (CAD) software. Non-uniform rational B-spline surfaces were reconstructed, generating a 3D volumetric model similar to the digitized implant. Three different models were generated with different implant neck configurations, namely 0°, 10° and 20°. D2 quality bone, composed of cortical and trabecular structure, was modeled using data from CT scans. The implants were included in the bone model using a Boolean operation. Two different fixture insertion depths were simulated for each implant: 2 mm below the crestal bone and exactly at the level of the crestal bone. The obtained models were imported to FEA software in STEP format. Von Mises equivalent strains were analyzed for the peri-implant D2 bone type, considering the magnitude and volume of the affected surrounding cortical and trabecular bone. The highest strain values in both cortical and trabecular tissue at the peri-implant bone interface were extracted and compared. Results: All implant models were able to distribute the load at the bone-implant contact (BIC) with a similar strain pattern between the models. At the cervical region, however, differences were observed: the models with 10° and 20° implant neck configurations (Model B and C), showed a lower strain magnitude when compared to the straight neck (Model A). These values were significantly lower when the implants were situated at crestal bone levels. In the apical area, no differences in strain values were observed. Significance: The implant neck configuration influenced the strain distribution and magnitude in the cortical bone and cancellous bone tissues. To reduce the strain values and improve the load dissipation in the bone tissue, implants with 10° and 20 neck configuration should be preferred instead of straight implant platforms.
International Journal of Innovation and Applied Studies, 2014
Objective: To investigative the influence of immediate loading on the stress distribution around dental implants with reductions in buccal cortical bone thickness. Materials and Methods: Three bone level dental implants (3.8mm, 4.5mm and 5.0mm diameters and a standard length of 10mm) were modeled and each placed in three mandibular bone segments having variations in buccal cortical bone thickness (2.0mm, 1.5mm and 1.0mm). A total of 9 such models were created and discretized with tetrahedral elements of parabolic displacement function. Implant-bone interface was simulated with non-linear contacts zone with friction. Implants were assumed to be placed at an insertion torque of 40Ncm and the fixation force was mathematically calculated for each of the three implants. A uniformly distributed vertical static load of a 150N was applied to the horizontal surfaces of the abutments. The overall stress distribution of von Mises criteria and micro-strain were recorded along the contact areas of implant and surrounding bone and statistically analyzed. Results: At an insertion torque of 40Ncm the pre-load calculations indicate a reduction in the compressive stresses as the diameters of the implants increase with fixation forces of 93.14N, 83.49N and 75.49N for the 3.8mm, 4.5mm and 5.0mm diameter implants. The maximum stresses were seen in the upper one third of the buccal cortical bony plates which tends to reduce as the diameter of the implant increases. The peak von Mises stresses were 173MPa, 126MPa and 98MPa for the 3.8mm, 4.5mm and 5.0mm implants. The total maximum mesh displacement seen for the 3.8mm, 4.5mm and 5.0mm models was 55µm, 32µm and 12µm respectively. Conclusions: Implants placed at the same level of insertion torque seem to be at different levels of stability as a consequence of implant thread variations. Stresses reduce with an increase in diameter of the implants. With reductions in thickness of the buccal bone there is an increase in stress transmission and micro-movements. The magnitude of stress transmission however does not vary significantly with reductions in thickness of the buccal bone for the larger diameter implants.
2021
The aim of this study was to compare the stress values on the implant caused by the change in the implant diameter, length, and the angle of the implant placement. Thus, our goal was to determine the correct implant preference with regard to the appropriate diameter, length, and insertion angle. In our study, a total of 6 different types of implants with 2 different diameters (3.7 mm and 4.7 mm) and 3 different lengths (5 mm, 10mm, and 13mm) belonging to these diameters were selected. These 6 different sized dental implants were applied to the maxilla and mandible, vertically and angled, and a total of 24 models were obtained. The maximum and minimum principal stress values in cortical and cancellous bone were determined as a result of the applied forces. The maximum and minimum von misses stress values and the places where they occurred were determined as a result of the application of the vertical and oblique (30 °) forces, with a total of 300 N from the 3 different occlusal point...
International Journal of Oral & Maxillofacial Implants, 2022
To examine the stress distribution in the maxillary All-on-4 treatment concept supported by implants of different diameters under two different loading forces using finite element analysis. Materials and Methods: Two distinct All-on-4 designs were prepared in a fully edentulous maxilla, supported by 3.3-and 4.1-mm-diameter implants. Posterior implants were tilted distally, approximately 30 degrees to the occlusal plane, and anterior implants were placed axially. Bone, implant, and prosthetic components were modeled separately and were tightly connected to each other. Under two distinct loading conditions representing the occlusal forces of healthy and bruxist individuals, the stresses on peri-implant bone, implant, and prosthetic components were evaluated using finite element analysis. Results: There were higher stresses on cortical bone than on trabecular bone. The stresses on bone and implant components were concentrated around the posterior implants, whereas stresses on the prosthesis were concentrated anteriorly. With increasing implant diameter, the stresses on trabecular bone, abutments, and crowns increased, whereas the stresses on cortical bone, implants, and frameworks decreased. Compressive stresses in the cortical bone and von Mises stresses in the frameworks exceeded the overload limit in both models under bruxist loading. Conclusion: The stresses on the cortical bone, implants, and frameworks were slightly higher in the model with 3.3-mm-diameter implants, whereas the stresses on the trabecular bone, abutments, and crowns were slightly higher in the model with 4.1-mm-diameter implants.