Finite element analysis of the effect of cantilever and implant length on stress distribution in an implant-supported fixed prosthesis (original) (raw)
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Implant Dentistry, 2009
S everal studies have been conducted on the stresses around dental implants including bone quality and quantity, implant design, the use of cantilevers, the number and distribution of implants, and superstructure design. 1-8 The in vivo studies pose considerable technical problems and have largely been confined to the studies of occlusal force transmission and the effects of superstructure design. Modeling with either mechanical models or computer simulations enables isolation of selected factors, but usually requires assumptions about some of the variables. To date, these have excluded functional deformation of the mandible, although this may have considerable effects on the outcome. 1 The human mandible presents complex elastic biomechanical behavior under functional loading. This is a result of both its horseshoe-shaped anatomical conformation and its complex structure of the constituent bone, which is an elastic, anisotropic, and inhomogeneous tissue and can be deformed. 9,10 According to Misch, 11 mandibular flexure may be more than 10 to 20 times the movement of a healthy tooth; therefore, it is important in the patient evaluation as much as tooth-implant connections. According to one of the most common prosthetic protocols, in totally edentulous patients treated with full-arch implant-supported fixed partial dentures(FPDs), the implants are more often surgically positioned in the interforaminal region for anatomical and surgical reasons and the prosthetic superstructure designed with cantilever distal extensions. 12 Even though the applicability of implants placed in the molar region has increased by virtue of innovative materials and techniques including shorter implants, bone grafts, and lateralization of the alveolar nerve, 1-piece superstructure remain the first choice when designing implant-retained prostheses. 6-13 However, some authors 1,9,14,15 have suggested that an implantsupported fixed restoration in the mandible designed as a single, continuous, and rigid bar can generate dangerous stresses because of the mismatch in deformations between the mandible and the FPD and bone loss around implants, material fracture, or screw
Journal of Oral Rehabilitation, 2002
Although the destructive effect of cantilevered implant supported ®xed partial prosthesis is well known, in some cases usage of cantilever extension seems to be inevitable for many clinicians. The purpose of this study was to evaluate the effect of additional placement of a shorter implant in place of a cantilever extension on stress distribution compared with cantilevered ®xed prosthesis in mandibular posterior edentulism. A mandibular Kennedy II ®nite element model was constructed. Six different implant supported ®xed partial prosthesis were designed according to two main con®gurations; anterior and posterior cantilever extensions compared with the placement of additional shorter implant con®gurations. An oblique occlusal load of 400 N was applied. Tensile and compressive stress values in the cortical bone surrounding the cervical regions of implants and Von Misses stress values in the implants were evaluated. Signi®cant lower stress values were recorded at the shorter implant placement con®gurations compared with the cantilevered prosthesis. Posterior cantilever extension performed higher stress values than the anterior counterpart. In clinical applications where cantilevered ®xed partial prosthesis seems to be inevitable because of anatomical restrictions and/or complications such as loss of implant, an additional placement of a shorter implant should be considered.
A finite element analysis was used to compare the effect of different designs of implant-retained overdentures and fixed full-arch implant-supported prosthesis on stress distribution in edentulous mandible. Four models of an human mandible were constructed. In the OR (O'ring) group, the mandible was restored with an overdenture retained by four unsplinted implants with O'ring attachment; in the BC (bar-clip) -C and BC groups, the mandibles were restored with overdentures retained by four splinted implants with bar-clip anchor associated or not with two distally placed cantilevers, respectively; in the FD (fixed denture) group, the mandible was restored with a fixed full-arch fourimplant-supported prosthesis. Models were supported by the masticatory muscles and temporomandibular joints. A 100-N oblique load was applied on the left first molar. Von Mises (s vM ), maximum (s max ) and minimum (s min ) principal stresses (in MPa) analyses were obtained. BC-C group exhibited the highest stress values (s vM ¼ 398.8, s max ¼580.5 and s min ¼ À455.2) while FD group showed the lowest one (s vM ¼128.9, s max ¼185.9 and s min ¼ À172.1). Within overdenture groups, the use of unsplinted implants reduced the stress level in the implant/prosthetic components (59.4% for s vM , 66.2% for s max and 57.7% for s min versus BC-C group) and supporting tissues (maximum stress reduction of 72% and 79.5% for s max , and 15.7% and 85.7% for s min on the cortical and trabecular bones, respectively). Cortical bone exhibited greater stress concentration than the trabecular bone for all groups. The use of fixed implant dentures and removable dentures retained by unsplinted implants to rehabilitate edentulous mandible reduced the stresses in the periimplant bone tissue, mucosa and implant/prosthetic components.
Cureus
This study's objective was to assess and analyze, using 3D Finite Element Analysis, the impact of four mandibular complete arch superstructures on the distribution of stress in the crestal bone during mandibular flexure. Materials and methods Four Finite element models of the mandible with different implant-retained framework designs have been developed. Three of these models had six axial implants placed at intervals of 11.8 mm, 18.8 mm and 25.8 mm from the midline, respectively. One model had two tilted implants and four axial implants splinted with a single piece of framework at intervals of 8.4 mm, 13.4 mm and 18.4 mm from the midline. For analyzing the stress distribution, the finished product was transferred to ANSYS R 18.1 software (Sirsa, Haryana, India) for finite element simulation, the models were constructed, the ends were restrained, and bilateral vertical loads of 50N, 100N and 150N were applied to the distal part of the framework. Results Bilateral loads were applied to each of the four 3D FEM and after assessment of Von Mises Stress and Total Deformation, a finding was made that the model with six axial implants supported by a single piece of framework underwent the highest total deformation and the model with four axial implants and two implants with distal tilts displayed most significant Von Mises stress. Clinical significance When it comes to edentulous jaws, reducing stress in implant-supported restorative systems at varying degrees of the bone and implant interfaces and superstructures of prosthetics is one of the fundamental goals of implant treatment. A framework with proper design and a low modulus of elasticity reduces mechanical risk. Additionally, a larger number of implants helps to prevent cantilevers and spacing between the implants.
Clinical Oral Implants Research, 2009
Objectives: The purpose of this in vitro study was to analyze the stress distribution on components of a mandibular-cantilevered implant-supported prosthesis with frameworks cast in cobalt-chromium (Co-Cr) or palladium-silver (Pd-Ag) alloys, according to the cantilever length. Material and methods: Frameworks were fabricated on (Co-Cr) and (Pd-Ag) alloys and screwed into standard abutments positioned on a master-cast containing five implant replicas. Two linear strain gauges were fixed on the mesial and distal aspects of each abutment to capture deformation. A vertical static load of 100 N was applied to the cantilever arm at the distances of 10, 15, and 20 mm from the center of the distal abutment and the absolute values of specific deformation were recorded. Results: Different patterns of abutment deformation were observed according to the framework alloy. The Co-Cr alloy framework resulted in higher levels of abutment deformation than the silver-palladium alloy framework. Abutment deformation was higher with longer cantilever extensions. Conclusion: Physical properties of the alloys used for framework interfere with abutment deformations patterns. Excessively long cantilever extensions must be avoided.
Archives of Oral Biology, 1993
The design of dental superstructures influences the loading on dental implants and the deformation of the anterior interforarninal bone in an edentulous mandible. This deformation causes stress in the bone around the implants and may lead to bone resorption and loss of the implant. The stress distribution around dental implants in an edentulous mandible was calculated by means of a threedimensional, finite-element model of an entire lower jaw. This model was built from data obtained from slices of a single human mandible and was provided with two endosseous implants in the interforaminal region. The implants were either connected with a bar or remained solitary, and were loaded with a horizontal bite force of 10 N, a vertical bite force of 35 N, or an oblique bite force of 70 N. The most extreme principal stresses in the bone were always located around the neck of the implant. Stress around the implant was, therefore, not only caused by the local deformation of the bone due to movement of the implant and interface relative to the surrounding bone but also by the bending of the mandible. The most extreme principal stress was found with oblique bite forces. The highest maximum and lowest minimum principal stresses were 7.4 and-16.2 MPa in the model without the bar and 6.5 and-16.5 MPa in the model with the bar. When differences in the amount of bite force were eliminated, the vertical bite force resulted in the lowest stress. Differences in the stress concentration between the model with and without a bar were small and the direction of the bite force had much more influence than the connection of the implant abutments.
The International journal of oral & maxillofacial implants
The aim of this study was to compare the bone stress generated by rehabilitation using regular and short-length Morse taper implants (11 and 5 mm, respectively) in the same context and allied with splinted (SP) and nonsplinted (NSP) prostheses in the posterior area of the mandible using finite element analysis. Three-dimensional geometric models using regular implants (Ø4 × 11 mm) and short implants (Ø4 × 5 mm) were simulated with a left posterior mandible that had the first premolar tooth and all teeth posterior to that premolar removed. The four experimental groups were as follows: Group 1 NSP (two regular implants and one short implant rehabilitated with nonsplinted prostheses), Group 1 SP (two regular implants and one short implant rehabilitated with splinted prostheses), Group 2 NSP (one regular implant and two short implants rehabilitated with nonsplinted prostheses), and Group 2 SP (one regular implant and two short implants rehabilitated with splinted prostheses). Oblique fo...