Effect of abutment angulation on the strain on the bone around an implant in the anterior maxilla: A finite element study

Effect of angled abutments in the posterior maxillary region on tilted implants: a 3D finite element analysis

The aim of this study was to evaluate the bone tissue effects under dynamic loading using finite element analysis (FEA) for four angled abutments with different deviated palatal lateral tilt angles. A three-dimensional model of the posterior maxillary region and an implant crown model were reconstructed and assembled with a three-dimensional model of the implant, angled abutment, and central screw to create a total of 10 three-dimensional finite element models tilted at 15 ∘ , 20 ∘ , 25 ∘ , and 30 ∘ in three groups, and the dynamic loads simulating oral mastication were loaded on the implant crown to analyze the equivalent stresses and strains in the peri-implant bone tissues. Under the dynamic loading, the cortical bone on the buccal side of the implant neck showed different degrees of stress concentration, and the cortical bone stress was much higher than the cancellous bone, and the strain concentration area of each model was located in the bone tissue around the implant neck and base. For the use of angular abutment, under the premise that the cortical bone stresses and strains of the 10 models meet the requirements for use, the peak stresses of 2.907 MPa, 3.018 MPa, and 2.164 MPa were achieved by using the 20 ∘ angular abutment to achieve the tilt angles of 20 ∘ , 25 ∘ , and 30 ∘ implantation, which is more advantageous compared with other models.

A finite element analysis study on different angle correction designs for inclined implants in All-On-Four protocol

BACKGROUND

The aim of this study is to investigate, through finite element analysis (FEA), the biomechanical behavior of the built-in angle corrected dental implant versus implant with angled multiunit abutment used in All-On-Four treatment protocol.

METHODS

Two (3D) finite element models of a simplified edentulous mandible were constructed with two different posterior implant designs based on the All-On-Four protocol. Four implants were placed in each model, the two anterior implants were positioned vertically at the lateral incisor/canine sites. Depending on the implant fixture design in posterior area, there are two models created; Model I; the mandible was rehabilitated with four co-axis (4 mm in diameter × 15 mm in length) implants with distally built-in angle corrected implants (24-degree angle correction) .While Model II, the mandible was rehabilitated with four conventional (4 mm in diameter × 14 mm in length) implants with a distally inclined posterior implants (25 degree) and angled multiunit abutments. CAD software (Solidworks© 2017; Dassault Systems Solidworks Corp) was used to model the desired geometry. Axial and inclined Loads were applied on the two models. A Finite element analysis study was done using an efficient software ANSYS© with specified materials. The resultant equivalent Von-Misses stresses (VMS), maximum principal stresses and deformation analysis were calculated for each part (implants and prosthetic components).

RESULTS

When applying axial and non-axial forces, model II (angled multiunit model) showed higher deformation on the level of Ti mesh about 13.286 μm and higher VMS 246.68 MPa than model I (angle corrected implant). Model I exhibited higher maximum stresses 107.83 MPa than Model II 94.988 MPa but the difference was not statistically significant.

CONCLUSION

Within the limitation of the FEA study, although angle correcting implant design is showing higher values in maximum principle stresses compared with angled multiunit abutments, model deformation and resultant VMS increased with angled multiunit abutments. The angle correcting designs at implant level have more promising results in terms of deformation and VMS distribution than angle correction at abutment level.

Bioengineering Tools Applied to Dentistry: Validation Methods for In Vitro and In Silico Analysis

This study aimed to evaluate the use of bioengineering tools, finite element analysis, strain gauge analysis, photoelastic analysis, and digital image correlation, in computational studies with greater validity and reproducibility. A bibliographic search was performed in the main health databases PUBMED and Scholar Google, in which different studies, among them, laboratory studies, case reports, systematic reviews, and literature reviews, which were developed in living individuals, were included. Therefore, articles that did not deal with the use of finite element analysis, strain gauge analysis, photoelastic analysis, and digital image correlation were excluded, as well as their use in computational studies with greater validity and reproducibility. According to the methodological analysis, it is observed that the average publication of articles in the Pubmed database was 2.03 and with a standard deviation of 1.89. While in Google Scholar, the average was 0.78 and the standard deviation was 0.90. Thus, it is possible to verify that there was a significant variation in the number of articles in the two databases. Modern dentistry finds in finite element analysis, strain gauge, photoelastic and digital image correlation a way to analyze the biomechanical behavior in dental materials to obtain results that assist to obtain rehabilitations with favorable prognosis and patient satisfaction.

An In Vitro Study of the Reproducibility of the Drilling Access of Digitalized Surgical Guides Generated via Three Different Implant Planning Software Programs

Several implant planning software programs are widely use in implant treatments, but there has been no evidence of how different software programs affect the accuracy of static surgical guides used for implant placement. Thus, in this in vitro study, we aimed to compare the accuracy of static surgical guides that were prefabricated from three different software programs, including Implant Studio (Program A) (3Shape®, Copenhagen, Denmark), coDiagnostiX® (Program B) (Straumann®, Basal, Switzerland), and Blue Sky Plan (Program C) (Blue Sky Bio®, LLC, Libertyville, IL, USA). A total of 90 drillable polyurethane models were used as samples in this in vitro study; 30 study models were used to plan the same implant positions and design the surgical guides by each software program (n = 30) and then 90 implants were placed in the models using the surgical guides. The outcomes of the surgical guide accuracy were autonomically measured by the evaluation tool in the coDiagnostiX® (Straumann®, Basal, Switzerland) software program. The deviations between the planned and placed implants were automatically evaluated as three-dimensional and angular deviations. The mean three-dimensional implant position deviations from the implant platform of Program A, Program B, and Program C were 0.55 ± 0.25 mm, 0.52 ± 0.31 mm, and 0.56 ± 0.22 mm, respectively. The mean three-dimensional implant position deviations from the implant apex of Program A, Program B, and Program C were 0.72 ± 0.37 mm, 0.73 ± 0.4 mm, and 0.9 ± 0.46 mm, respectively. The mean depth deviations of Program A, Program B, and Program C were 0.19 ± 0.13 mm, 0.31 ± 0.32 mm, and 0.31 ± 0.22 mm, respectively. The mean angulation deviations of Program A, Program B, and Program C were 1.72 ± 0.88 degrees, 2.05 ± 1.24 degrees, and 2.74 ± 1.81 degrees, respectively. The results indicated that there were no significant differences among the three-dimensional positions at the implant platform, the three-dimensional positions at the implant apex, and the depth deviations between all three groups. However, it was found that there was a significant difference in the angular deviation of the implant position between the three groups (p = 0.02). The mean angular deviation of Program C was significantly greater than the Program A group (p = 0.001). In terms of the deviation directions of the implant platform and implant apex for the three groups, most of the deviations of a larger magnitude were toward the mesio-buccal direction. No matter which program was used to plan the implant position, deviations between the placed implant position and the planned position still occurred. Therefore, when planning implant positions with any implant planning software program, one must take into account an implant position deviation.

Immediate Maxillary Full-Arch Rehabilitation of Periodontal Patients with Terminal Dentition Using Tilted Implants and Bone Augmentation: A 5-Year Retrospective Cohort Study

Background: All-on-four protocols with tilted implants in the maxilla are used to rehabilitate the terminal dentition of the severe generalized periodontitis patients. Data on long-term biological complications are scarce. Methods: Eighty-four axial and forty-six tilted immediate implants have been placed in the extraction sockets of 23 patients according to a four–six implants protocol combined with ridge augmentation. Within 72 h, a provisional prosthesis was cemented to the implants; after 6 months, a cemented ceramic–metallic prosthesis was delivered. The patients were followed for up to 5 years. Results: The 5-year survival rate of the straight and tilted implants was 100% and 97.8, and the prosthetic one was 100%. Marginal bone loss (MBL) of the straight implants was 0.42 ± 0.67 and 0.59 ±1.01 mm on the mesial and distal sides; for the tilted, it was 0.37 ± 0.68 and 0.34 ±0.62 mm, and the differences were not statistically significant. Implant position, smoking, keratinized mucosal width, and cantilever did not affect MBL. Peri-implant mucositis involved 29.4% and 22.2% of the straight and tilted implants, respectively; peri-implantitis involved 5.8% and 4.4% of the straight and tilted implants, respectively, without statistical significance. Conclusions: This immediate loading protocol’s 5-year survival and success rates were high. No difference between the straight and tilted implants was found regarding survival, success rates, and MBL.

Evaluation of Stress Generated with Different Abutment Materials and Angulations under Axial and Oblique Loading in the Anterior Maxilla: Three-Dimensional Finite Element Analysis

Purpose

The aim of this study was to assess and correlate the stress distribution in an anterior maxillary implant-supported prosthesis with 0°(degree), 15°, and 25° angulated titanium and zirconia abutments using a three-dimensional (3D) finite element analysis (FEA).

Materials and Methods

Six FEA models consisting of a dentate anterior maxilla with a single bone-level implant of dimension 4.2 × 10 mm placed in the region of left maxillary central incisor and abutments of dimension 4.2 mm made of titanium and zirconia each with angulation 0° (IA and IB), 15° (IIA and IIB), and 25° (IIIA and IIIB) and ANSYS Workbench software were utilized to design a layered zirconia crown. Unilateral axial and oblique loads of 178 N were applied on the palatal aspect of the crown of left maxillary central incisor. Average von Mises stress values were evaluated in the implant and the peri-implant bone quantitatively and qualitatively.

Results

Stress was shown to increase with an increase in angulation in all the areas that were examined. Zirconia abutments showed lesser stress in the implant and surrounding bone than titanium abutments. When compared with the body and apex of the implant, the implant neck values were higher in all models. In between cortical and cancellous bone, the stress recorded was higher in the cortical bone.

Conclusion

Within the limitations of this study, straight abutments generated a more uniform and minimal stress in implant and peri-implant bone than angulated abutments. Titanium abutments generated higher stress levels than zirconia abutments. The stresses generated are directly proportional to an increase in abutment angulation, and therefore, straight abutments are most suitable for favourable stress transmission.

Investigation of the Type of Angled Abutment for Anterior Maxillary Implants: A Finite Element Analysis

PURPOSE

The optimal abutment material and design for an angled implant-abutment connection in the esthetic zone is unclear. The purpose of this finite element analysis (FEA) study was to compare different abutment models by evaluating the stress values in the implant components and strain values on the simulated bone around an anterior maxillary implant with different angled abutment models and loading conditions.

MATERIALS AND METHODS

One Ø3.5×12-mm implant was placed in 3D FEA models representing the anterior left lateral segment of the maxilla. Three different contemporary implant models were created with 17° or 25° angled abutments (Ti base abutment, zirconia abutment, and titanium abutment) and 3D-modeled. The implant abutment model was an angled Ti base abutment (TIB), an angled zirconia abutment (ZIR), or an angled titanium abutment (TIT). Vertical and oblique loads of 100 N for the central incisors were applied as boundary conditions to the cingulum area and incisal area in a nonlinear FEA.

RESULTS

The TIB model resulted in reduced stress conditions. According to the von Mises stresses occurring on the screw, abutment, crown, and implant, especially under oblique loads, the TIB model was exposed to less stress than the ZIR or TIT models. Strain values in simulated cortical and trabecular bones were obtained lower in the TIB model.

CONCLUSIONS

When a standard implant was placed in the esthetic zone at an increased angle, the implants, abutments, and screws had more unfavorable stress levels; therefore, using a Ti-base abutment may reduce stress. The amount of contact surface of the implant with the simulated cortical bone is also an important factor affecting stress and strain.

Impact of Bone Augmentation of Facial Bone Defect around Osseointegrated Implant: A Three Dimensional Finite Element Analysis

(1) Background: When dental implants are placed at the esthetic zone, facial bone fenestration might be expected. This study aimed to evaluate the biomechanical effect of bone augmentation around implants with facial bone fenestration defects using the finite element method. (2) Methods: An anterior maxillary region model with facial concavity was constructed with a threaded implant inserted following the root direction, resulting in apical threads exposure to represent the fenestration model. Several bone coverage levels were simulated by gradually shifting the deepest concavity point buccally, mimicking bone augmentation surgeries with different bone fill results. Oblique forces were applied, and analysis was performed. (3) Results: Peak compressive stress magnitude and distribution varied according to the level of exposure and facial concavity depth. The fenestration model demonstrated a slightly lower peak peri-implant bone stress, smaller implant displacement, and smaller bone volume with strain levels above 200 µ strain. A gradual increase in compressive stress, implant displacement, and bone volume exhibited strain level above 200 µ strain was observed with the increased bone fill level of the facial bone fenestration. (4) Conclusions: Exposure of implants apical threads at the maxillary anterior region does not significantly affect the peri-implant stress and strain results. However, increasing the buccolingual width and eliminating the buccal concavity might increase the peri-implant bone volume exhibited favorable loading levels.

Biomechanical Behavior of All-on-4 and M-4 Configurations in an Atrophic Maxilla: A 3D Finite Element Method

BACKGROUND In edentulous patients, the concept of 4 implants with early loading has been widely used in clinical settings. In the case of bone atrophy in the anterior maxilla, using short implants or an angulated implant may be a good choice for treatment. The occlusal scheme remains a key aspect of All-on-4. The aim of this study was to use the 3-dimensional (3D) finite element method (FEM) to evaluate how different All-on-4 designs for canine-guided and group function occlusion affected the distribution of stress in the atrophic premaxilla. MATERIAL AND METHODS A 3D edentulous maxilla model was created and in 3D FEM, 3 different configurations - M4, All-on-4, and short implant - were modeled by changing the anterior implants and using 2 different occlusal schemes. For each model, the occlusal load was applied to simulate lateral movements. For cortical bone, the maximum and minimum principal stress values were generated, and for ductile materials, von Mises stress values were obtained. RESULTS No significant differences were detected among the models; generally, however, the highest stress values were observed in the M-4 model and the models with short implants. Slightly higher stress values were observed in the group function occlusion group than in the canine-guided occlusion group. CONCLUSIONS To promote better primary stabilization, M-4 or short implant configurations with canine-guided occlusion appear to be preferable for patients who have severe atrophy in the anterior maxilla.

Finite Element Analysis of Stress in Bone and Abutment-Implant Interface under Static and Cyclic Loadings

Objectives

The success of implant treatment depends on many factors affecting the bone-implant, implant-abutment, and abutment-prosthesis interfaces. Stress distribution in bone plays a major role in success/failure of dental implants. This study aimed to assess the pattern of stress distribution in bone and abutment-implant interface under static and cyclic loadings using finite element analysis (FEA).

Materials and Methods

In this study, ITI implants (4.1×12 mm) placed at the second premolar site with Synocta abutments and metal-ceramic crowns were simulated using SolidWorks 2007 and ABAQUS software. The bone-implant contact was assumed to be 100%. The abutments were tightened with 35 Ncm preload torque according to the manufacturer's instructions. Static and cyclic loads were applied in axial (116 Ncm), lingual (18 Ncm), and mesiodistal (24 Ncm) directions. The maximum von Mises stress and strain values were recorded.

Results

The maximum stress concentration was at the abutment neck during both static and cyclic loadings. Also, maximum stress concentration was observed in the cortical bone. The loading stress was higher in cyclic than static loading.

Conclusion

Within the limitations of this study, it can be concluded that the level of stress in single-unit implant restorations is within the tolerable range by bone.

Management of unfavorable implant positions and angulations in edentulous maxillae with different complete-arch fixed prosthetic designs: A case series and clinical guidelines

Implant-supported fixed prostheses in the edentulous maxilla can be difficult because of anatomic limitations and high esthetic demand. The choice between cement and screw retention depends on factors such as esthetics, occlusion, retrievability, and passivity. The choice is also often governed by the ability to manage technical or biologic complications. In the edentulous maxilla, because of the bone trajectory and resorption pattern, unfavorable implant angulations may be encountered. In such situations, a conventional screw-retained prosthesis is difficult to design. This article describes the restoration of edentulous maxillae for a series of patients with different complete-arch fixed prosthesis designs. The clinical guidelines, including indications, advantages, and limitations of each design, were discussed.

Analysis of stress distribution in ceramic and titanium implants in alveolar sockets of the anterior region of the maxilla

Background

In the routine of dentistry, knowing the biomechanical properties of implant systems and their inherent stress distribution under force loading is an essential step to predict structural damage and biological responses. This study aimed to investigate stress distribution in zirconia and titanium implants and their biomechanical response in alveolar sockets of the anterior region of the maxilla through tridimensional finite element analysis.

Material and Methods

From computed tomography scans of a reference patient, three models of the maxillary dental arch were designed with Rhinoceros 5.0 software (McNeel Europe™, Barcelona, Spain). In each model, a dental implant replaced the maxillary left central incisor. The implants consisted of M1) Zirconia Pure Ceramic Implant Monotype; M2) Zirconia Pure Ceramic ZLA; and M3) Titanium Bone Level - Roxolid SLA. Ceramic crowns were installed in all the implants. Implants and prostheses were loaded with 50N oblique and axial forces. Von-Mises and Mohr Coulomb criteria were used to assess stress distribution in the implant systems and perimplantar bone, respectively.

Results

Traction was detected in the cervical region of the palatal bone surface of all the models. Oppositely, compression was found in the cervical region of the vestibular bone surfaces.

Conclusions

Zirconia Pure Ceramic Implant Monotype had the best response under oblique force loading. Ceramic implants may be an alternative to replace titanium implants in fresh alveolar sockets in the anterior region of the maxilla. Key words:Finite elements, implants, stress, ceramic, titanium.

Effect of different implant configurations on biomechanical behavior of full-arch implant-supported mandibular monolithic zirconia fixed prostheses

Mechanical failure of zirconia-based full-arch implant-supported fixed dental prostheses (FAFDPs) remains a critical issue in prosthetic dentistry. The option of full-arch implant treatment and the biomechanical behaviour within a sophisticated screw-retained prosthetic structure have stimulated considerable interest in fundamental and clinical research. This study aimed to analyse the biomechanical responses of zirconia-based FAFDPs with different implant configurations (numbers and distributions), thereby predicting the possible failure sites and the optimum configuration from biomechanical aspect by using finite element method (FEM). Five 3D finite element (FE) models were constructed with patient-specific heterogeneous material properties of mandibular bone. The results were reported using volume-averaged von-Mises stresses (σ_VM^VA) to eliminate numerical singularities. It was found that wider placement of multi-unit copings was preferred as it reduces the cantilever effect on denture. Within the limited areas of implant insertion, the adoption of angled multi-unit abutments allowed the insertion of oblique implants in the bone and wider distribution of the multi-unit copings in the prosthesis, leading to lower stress concentration on both mandibular bone and prosthetic components. Increasing the number of supporting implants in a FAFDPs reduced loading on each implant, although it may not necessarily reduce the stress concentration in the most posterior locations significantly. Overall, the 6-implant configuration was a preferable configuration as it provided the most balanced mechanical performance in this patient-specific case.

Load-carrying capacity of short implants in edentulous posterior maxilla: A finite element study

Dental implant dimensions, and bone quality and quantity play a key role in early osseointegration and long-term prognosis in posterior edentulous maxilla. Treatment with short implants, preferably in a bicortical manner, is an accepted modality; however, short implants have limitations leading to increased stress concentrations in alveolar bone, potential overload and implant failure. Implant models of 3.3, 4.1, 4.8 and 5.4 mm diameter and 4.5, 5.5, 6.5, 7.5 and 8.5 mm length were placed in posterior maxilla 3-D models with corresponding residual bone heights. Bone-implant assemblies were analyzed in finite element software ANSYS 15. All materials were assumed to be linearly elastic and isotropic. 118.2 N oblique loading was applied to investigate stress distributions in bone tissues. The concept of ultimate functional load (UFL) was selected as a criterion to compare load-carrying capacity of implants and to evaluate the influence of available bone height and implant dimensions on load-carrying capacity. For all implants, UFL was calculated by limiting von Mises stresses in cortical or cancellous bone with bone strength (100 MPa for cortical and 2 MPa for cancellous bone). Implant load-carrying capacity depends on diameter and available bone height. Wide implants have higher load-carrying capacity than narrow implants. Short implants with proper diameter and length avoid bone overstress, even in Type IV bone.

Biomechanical effect of inclined implants in fixed prosthesis: strain and stress analysis

Abstract Introduction Implant inclinations can be corrected using mini abutments at different angulations. Objective To analyze the influence of external hexagon implants in different inclinations (3 levels) on the microstrain distribution generated around three implants. Method A geometric bone model was created through Rhinoceros CAD software (version 5.0 SR8, Mcneel North America, Seattle, WA, USA). Three implants (4.1 × 13 mm) were modeled and inserted inside the substrate at three different inclinations: 0º, 17º and 30º. Next, all groups received mini conical abutments, fixation screws and a simplified prosthesis. The final geometry was exported in STEP format to analysis software and all materials were considered homogeneous, isotropic and linearly elastic. An axial load (300N) was applied on the center of the prosthesis. An in vitro study was conducted with same conditions and groups for validating the tridimentional model. Result Stress was concentrated on the external area of the implants, in contact with the cortical bone and external hexagon. For the bone simulator, the strain increased in the peri-implant region according to the increase in the implant’s inclination. The difference between groups was significant (p = 0.000). The 30º group presented higher stress and strain concentration. Conclusion The microstrain and stress increase around implants directly proportional to the increase of the installation angle.

Premaxilla Stress Distribution and Bone Resorption Induced by Implant Overdenture and Conventional Denture

PURPOSE

To relate the principal stress, strain, and total deformation in the premaxilla region beneath a complete denture to the pattern of premaxilla bone resorption when opposed by a conventional complete denture (CD) or by a two-implant-retained overdenture (IOD) using finite element analysis (FEA).

MATERIALS AND METHODS

Three-dimensional solid models of the maxilla, mucosa, and denture of a selected edentulous patient were created using Mimics and CATIA software. The FEA model was created and duplicated in ANSYS 16.0 to perform two simulations for the IOD and the CD models. The values of maximum stress and strain and total deformation were obtained and compared to the outcomes of premaxilla resorption from a parallel clinical study.

RESULTS

The maximum principal stress in the premaxilla in the IOD model ranged from 0.019 to 0.336 MPa, while it ranged from 0.011 to 0.193 MPa in the CD model. The maximum principal strain in the IOD model was 1.75 times greater than that in the CD model. Total deformation was 1.8 times higher in the IOD model. Greater bone resorption was observed in regions of higher stress, which were on the occlusal and buccal sides of the premaxilla residual ridge.

CONCLUSION

Stress, strain, and total deformation values present in the premaxilla area beneath a CD were approximately two times greater in a comparison between an opposing mandibular two-IOD and an opposing mandibular CD. The results were consistent with a parallel clinical study in which the rate of premaxilla bone resorption was almost three times greater in the IOD group.

Abutment screw loosening in angulation-correcting implants: An in vitro study

STATEMENT OF PROBLEM

Techniques that allow angulation correction for screw-retained implant-supported restorations are now available. However, whether angulation correction built into the head of the implant affects abutment screw loosening is unclear.

PURPOSE

The purpose of this in vitro study was to assess abutment screw loosening in angulation-correcting implants and straight implants subjected to simulated nonaxial occlusal loading.

MATERIAL AND METHODS

Seven external connection 12-degree angulation-correcting implants and 7 straight implants were embedded in an acrylic resin housing, and titanium abutments were secured with titanium screws tightened to 32 Ncm. Each specimen was secured in a tooth wear machine and subjected to 1 000 000 cycles of 50-N nonaxial load to simulate 1 year of clinical service. The mean abutment screw removal torque values were calculated, and the association between number of cycles and the abutment screw removal torque was analyzed using a linear mixed-effects model and statistical software (α=.05) RESULTS: The mean abutment screw torque loss was 59.8% for the angulation-correcting implant group and 68.7% for the straight implant group. A statistically significantly greater mean abutment screw removal torque was recorded in the angulation-correcting implant group compared with the straight implant group after 1 000 000 cycles (P=.019).

CONCLUSIONS

A significant loss of abutment screw torque was found in both implant groups with increased cycles of occlusal loading. The angulation-correcting implants resisted screw loosening significantly more than the straight implants because of the reduced angle of abutment screw loading.

Fatigue lifetime prediction of a reduced-diameter dental implant system: Numerical and experimental study

OBJECTIVE

To validate the fatigue lifetime of a reduced-diameter dental implant system predicted by three-dimensional finite element analysis (FEA) by testing physical implant specimens using an accelerated lifetime testing (ALT) strategy with the apparatus specified by ISO 14801.

METHODS

A commercially-available reduced-diameter titanium dental implant system (Straumann Standard Plus NN) was digitized using a micro-CT scanner. Axial slices were processed using an interactive medical image processing software (Mimics) to create 3D models. FEA analysis was performed in ABAQUS, and fatigue lifetime was predicted using fe-safe^® software. The same implant specimens (n=15) were tested at a frequency of 2Hz on load frames using apparatus specified by ISO 14801 and ALT. Multiple step-stress load profiles with various aggressiveness were used to improve testing efficiency. Fatigue lifetime statistics of physical specimens were estimated in a reliability analysis software (ALTA PRO). Fractured specimens were examined using SEM with fractographic technique to determine the failure mode.

RESULTS

FEA predicted lifetime was within the 95% confidence interval of lifetime estimated by experimental results, which suggested that FEA prediction was accurate for this implant system. The highest probability of failure was located at the root of the implant body screw thread adjacent to the simulated bone level, which also agreed with the failure origin in physical specimens.

SIGNIFICANCE

Fatigue lifetime predictions based on finite element modeling could yield similar results in lieu of physical testing, allowing the use of virtual testing in the early stages of future research projects on implant fatigue.

A REVIEW OF FINITE ELEMENT APPLICATIONS IN ORAL AND MAXILLOFACIAL BIOMECHANICS

Finite element method (FEM) is preferred to carry out mechanical analyses for many complex biomechanical structures. For most of the biomechanical models such as oral and maxillofacial structures or patient-specific dental instruments, including nonlinearities, complicated geometries, complex material properties, or loading/boundary conditions, it is not possible to accomplish an analytical solution. The FEM is the most widely used numerical approach for such cases and found a wide range of application fields for investigating the biomechanical characteristics of oral and maxillofacial structures that are exposed to external forces or torques. The numerical results such as stress or strain distributions obtained from finite element analysis (FEA) enable dental researchers to evaluate the bone tissues subjected to the implant or prosthesis fixation from the viewpoint of (i) mechanical strength, (ii) material properties, (iii) geometry and dimensions, (iv) structural properties, (v) loading or boundary conditions, and (vi) quantity of implants or prostheses. This review paper evaluates the process of the FEA of the oral and maxillofacial structures step by step as followings: (i) a general perspective on the techniques for creating oral and maxillofacial models, (ii) definitions of material properties assigned to oral and maxillofacial tissues and related dental materials, (iii) definitions of contact types between tissue and dental instruments, (iv) details on loading and boundary conditions, and (v) meshing process.

Stress Distribution in an Implant-Supported Mandibular Complete Denture Using Different Cantilever Lengths and Occlusal Coating Materials

PURPOSE

The aim of this study was to assess stress distribution in the bone-implant interface of a mandibular implant-supported prosthesis with different cantilever lengths, aesthetic coating materials, and implant abutments.

MATERIALS AND METHODS

A photoelastic model of an edentulous mandible, containing 5 external hexagon implants, was constructed. Experimental models were divided into 6 groups: group 1-UCLA component and metal bar; group 2-UCLA component and acrylic resin coating; group 3-UCLA component and porcelain coating; group 4-abutment and metal bar; group 5-abutment and acrylic resin coating; and group 6-abutment and porcelain coating. Forces were applied to the most anterior implant, the most posterior implant, and different cantilever lengths.

RESULTS

The results showed a higher number of high-stress fringes as the cantilever length increased. Fringes were better distributed in groups with prostheses composed of acrylic resin and in groups that contained an abutment.

CONCLUSION

The stress distribution in the bone-implant interface is improved when the cantilever is eliminated and when abutments in an acrylic resin prosthesis are used.

Combined implant-residual tooth supported prosthesis after tooth hemisection: A finite element analysis

Tooth hemisection preserves partial tooth structure and reduces the resorption of alveolar bone. The aim of this study was to analyze the feasibility of preserving a molar after hemisection and inserting a dental implant with different prosthetic superstructures by means of finite element analysis. First, the distance between the root of the mandibular second premolar and the distal root of the first molar were measured in 80 cone beam computed tomography (CBCT) data sets. Based on these data, the lower right posterior jaw segment was reconstructed and the geometries of the appropriate implant were imported. Four models were created: (1) Hemi-1: An implant (3.7×9mm) replaced the mesial root of the molar, and a single crown was placed on the implant and residual tooth. (2) Hemi-2: Two separate crowns were generated for the implant and the residual tooth. (3) Single: An implant (5.5×9mm) with crown replaced the whole molar. (4) FPD: A 3-unit fixed partial denture combined the distal residual part of the molar and premolar. The results indicated that stresses in the cortical bone and strains in the majority region of the spongious bone were below the physiological upper limits. There were higher stresses in implant with the Hemi-1 and Single models, which had the same maximum values of 45.0MPa. The FPD models represented the higher values of stresses in the teeth and strains in PDL compared to other models. From a biomechanical point of view, it can be concluded that a combination of an implant and residual molar after tooth hemisection is an acceptable treatment option.

Magnet and Semi Precision Attachment in an Implant Retained Partial Denture for the Rehabilitation of an Irradiated Marginal Mandibulectomy Patient: A Case Report

Surgical treatment of malignancies in the oral cavity (mandible, tongue, floor of the mouth, alveolus, buccal sulcus) often results in an unfavourable anatomic condition for prosthodontic rehabilitation. Hence, maxillofacial prosthetic rehabilitation becomes a mightier task when resection is accompanied by radiation therapy. In selected cases, implant therapy comes to rescue. The following report throws light on the case of prosthetic rehabilitation of a patient who underwent right marginal mandibulectomy and right partial glossectomy, with the aid of a single implant, semi precision attachment and magnet supported partial denture.

The effect of implant angulation and splinting on stress distribution in implant body and supporting bone: A finite element analysis

Objective:

The aim of this study was to investigate the influence of implant crown splinting and the use of angulated abutment on stress distribution in implant body and surrounding bone by three-dimensional finite element analysis.

Materials and Methods:

For this study, three models with two implants at the site of mandibular right second premolar and first molar were designed (1): Both implants, parallel to adjacent teeth, with straight abutments (2): Anterior implant with 15 mesial angulations and posterior implant were placed parallel to adjacent tooth, (3): Both implants with 15 mesial angulations and parallel to each other with 15° angulated abutments. Restorations were modeled in two shapes (splinted and nonsplinted). Loading in tripod manner as each point 50 N and totally 300 N was applied. Stress distribution in relation to splinting or nonsplinting restorations and angulations was done with ABAQUS6.13.

Results:

Splinting the restorations in all situations, led to lower stresses in all implant bodies, cortical bone and spongy bone except for the spongy bone around angulated first molar. Angulated implant in nonsplinted restoration cause lower stresses in implant body and bone but in splinted models more stresses were seen in implant body in comparison with straight abutment (model 2). Stresses in nonsplinted and splinted restorations in cortical bone of angulated molar region were more than what was observed in straight molar implant (model 3).

Conclusion:

Implant restorations splinting lead to a better distribution of stresses in implant bodies and bone in comparison with nonsplinted restorations, especially when the load is applied off center to implant body. Angulations of implant can reduce stresses when the application of the load is in the same direction as the implant angulation.

Influence of a micro-thread at cervical position and a cylindrical intermediate zone on the mechanical behaviour of dental implants: A three-dimensional finite element analysis

The purpose of this work is to analyse the influence on the biomechanical behaviour of dental implants of a micro-thread at their cervical part as well as of a cylindrical geometry at an intermediate zone. Stresses and strains in the elements involved, that is, bone, implant, screw and abutment, have to be considered in detail. Three different three-dimensional finite element models are generated to analyse the behaviour of the various components under the so-called tightening and operating conditions. For the modelling, material specifications for the cancellous bone and cortical bone, on one hand, and titanium properties for the implant, screw and abutment, on the other, are implemented. The tightening condition was fixed according to the stresses in the screw. The operating conditions were simulated by applying a force of 150 N, taking into account ISO 14801:2007 standard. The maximum stress under tightening conditions occurs always in the screw, while under operating conditions it is produced at the screw or the abutment, although considerable stress values are also present in the implant. In all the models, the maximum stress at the junction between the implant and the bone occurs within the cortical bone. Implants provided with micro-thread at the cervical position are advantageous over homogeneously threaded implants since lower stresses in both the implant and the adjacent bone are produced. A cylindrical intermediate portion on the implant surface does not present special advantage over the implants with continuous external thread under tightening and operating conditions.

Biomaterial aspects: A key factor in the longevity of implant overdenture attachment systems

Background:

New attachment systems are released for mandibular two-implant overdentures often without evidence-based support. Biomaterial aspects are now the parameters considered when choosing the appropriate attachment. Studies regarding their properties remain scarce.

Purpose:

The purpose of this review was to help the clinician in selrcting the most adapted stud attachments according evidence-based dentistry.

Materials and Methods:

An electronic search was conducted using specific databases (PubMed, Medline, and Elsevier libraries). Peer-reviewed articles published in English up to July 2014 were identified. Emphasis was given on the biomaterial aspects and technical complications. No hand search was added.

Results:

The electronic search generated 115 full-text papers, of which 84 papers were included in the review. The majority were clinical and in vitro studies. Some review articles were also considered. Papers reported survival and failures of overdenture connection systems. Emphasis was laid on attachment deformation.

Conclusion:

Implant overdentures long-term follow-up studies may provide useful guidelines for the clinician in selecting the type of attachment system and overdenture design. Locator attachments are more and more used, with lesser complications reported.

A SIMPLE AND EFFICIENT METHODOLOGY TO IMPROVE DESIGN PROPOSALS OF DENTAL IMPLANTS — A DESIGN CASE STUDY

Objective: To propose a methodology based on virtual simulation to assist in the design proposals of dental implants. Methods: The finite element method (FEM) was used to analyze the biomechanical dental implant system behavior, determining von Mises stress distribution induced by functional loads, varying parameter as load direction and geometric characteristic of the implant (taper, length, abutment angulation, thread pitch and width pitch). A final design was obtained by considering the parameters that showed improved performance. The estimated lifetime of the final design was calculated by reproducing in a virtual way the experimental fatigue test required by the ISO:14801 standards. Results: For all the studied cases, the maximum stresses were obtained in the connecting screw under oblique loads (OLs). The estimated lifetime for this critical part is at least 5 × 106 cycles, which meets the requirement of the ISO:14801. In bone tissue, the largest stresses were concentrated in cortical bone, in the zone surrounding the implant, in good agreement with previous reports. Conclusions: A dental implant design was obtained and validated through a simple and efficient methodology based on the application of numerical methods and computer simulations.

Replacement of a Congenitally Missing Maxillary Incisor by Implant Supported Prosthesis

Maxillary central incisors have the least incidence of congenital absence. When it does happen, the patient may present with over retained deciduous centrals or the contralateral central may have drifted into the available space presenting as generalised anterior spacing with loss of midline. In such cases a multi-disciplinary approach may be required with orthodontic treatment to re-organise the space available in order to rehabilitate the patient with a fixed prosthesis. This case report presents the treatment of a patient with congenitally missing maxillary left central incisor using dental implant with angulated abutment after orthodontic correction and stabilization of the remaining maxillary anteriors.

The Use of Tilted Implant for Posterior Atrophic Maxilla

PURPOSE

To retrospectively analyze the influence of implant inclination on marginal bone loss at freestanding implant-supported fixed partial prostheses (FPPs) over a medium-term period of functional loading.

MATERIALS AND METHODS

Twenty-nine partially edentulous patients with freestanding FPDs supported by two implants placed in a two-stage procedure comprised the study group. The anterior implant was placed axially, and the posterior tilted distally. Mesial or distal inclination of each implant was measured in relation to the vertical axis perpendicular to the occlusal plane. Average bone loss was compared between straight and tilted implants, smokers, and nonsmokers.

RESULTS

Mean angulation of the anterior axial-positioned implant was 3.45 degrees distally (range 0-8) and of the distal implants was 32.83 degrees distally (range 20-50 degrees). Average bone loss after 1, 3, and 5 years was 0.89 (SD = 0.73), 1.18 (SD = 0.74), and 1.50 (SD = 0.81), respectively, for axial implants, and 0.98 (SD = 0.69), 1.10 (SD = 0.60) and 1.50 (SD = 0.67) for tilted implants, with no significant correlation between implant angulation and bone loss. A significant correlation between implant angulation and annual bone loss was obtained for tilted implants only (r = 0.52, p = .004).Using Albrektsson criteria, the success rate was 89.6% (26 out of 29 implants) for straight and 93.1% (27 out of 29) for tilted implants.

CONCLUSION

The study demonstrates no effect of implant angulation on peri-implant bone loss in the posterior maxilla.

A further finite element stress analysis of angled abutments for an implant placed in the anterior maxilla

To systematically measure and compare the stress distribution on the bone around an implant in the anterior maxilla using angled abutments by means of finite element analysis, three-dimensional finite element simplified patient-specific models and simplified models were created and analyzed. Systematically varied angled abutments were simulated, with angulation ranging from 0° to 60°. The materials in the current study were assumed to be homogenous, linearly elastic, and isotropic. Force of 100 N was applied to the central node on the top surface of the abutments to simulate the occlusal force. To simulate axial and oblique loading, the angle of loading was 0°, 15°, and 20° to the long axis of implant, respectively. There was the strong resemblance between the response curves for simplified patient-specific models and simplified models. Response curves under oblique loading were similar in both models. With abutments angulation increased, maximum von Mises stress firstly decreased to minimum point and then gradually increased to higher level. From a biomechanical point of view, favorable peri-implant stress levels could be induced by angled abutments under oblique loading if suitable angulation of abutments was selected.

Immediate loading: from biology to biomechanics. Report of the Committee on Research in fixed Prosthodontics of the American Academy of fixed Prosthodontics

One of the key issues of modern implant rehabilitation is the overall shortening of treatment time. High survival rates for immediately loaded implants have been reported in many but not all treatment modalities. In recent years, considerable evidence for the successful immediate loading outcome has been documented in both animal and human studies. The mechanical force generated by immediate loading may explain the favorable biologic response of bone and surrounding tissue when the design is biomechanically sound. However, in certain treatment modalities, including but not limited to immediately placed maxillary anterior single implants, immediately placed single molar implants, unsplinted implants in overdentures, and implants in maxillary anterior partial fixed dental prostheses, loading dental implants indiscriminately and immediately is not safe because of potentially unfavorable stress distribution and a negative cellular response under such high stress during early healing.

Correction of Malpositioned Implants through Periodontal Surgery and Prosthetic Rehabilitation Using Angled Abutment

When dental implants are malpositioned in relation to the adjacent teeth and alveolar bone or in an excessive buccal or lingual position, the final prosthesis rehabilitation impairs the peri-implant health of the gingival tissues and the aesthetics of the patient. Thus, the purpose of this case was to report and discuss a multidisciplinary protocol for the treatment of a compromised maxillary tooth in a patient with an abscess in his right central incisor due to an excessive buccal implant position. The patient presented with an implant-supported provisional restoration on his right maxillary central incisor and a traumatic injury in his left central incisor. The treatment protocol consisted in (i) abutment substitution to compensate the incorrect angulation of the implant, (ii) clinical crown lengthening, (iii) atraumatic extraction of the left central incisor, and (iv) immediate implant placement. Finally, (v) a custom abutment was fabricated to obtain a harmonious gingival contour around the prosthetic crown. In conclusion, when implants are incorrectly positioned in relation to the adjacent teeth, associated with soft-tissue defects, the challenge to create a harmonious mucogingival contours may be achieved with an interdisciplinary approach and with the placement of an appropriate custom abutment.

A three-dimensional finite element study on the stress distribution pattern of two prosthetic abutments for external hexagon implants

Objective:

The purpose of this study was to evaluate the mechanical behavior of two different straight prosthetic abutments (one- and two-piece) for external hex butt-joint connection implants using three-dimensional finite element analysis (3D-FEA).

Materials and Methods:

Two 3D-FEA models were designed, one for the two-piece prosthetic abutment (2 mm in height, two-piece mini-conical abutment, Neodent) and another one for the one-piece abutment (2 mm in height, Slim Fit one-piece mini-conical abutment, Neodent), with their corresponding screws and implants (Titamax Ti, 3.75 diameter by 13 mm in length, Neodent). The model simulated the single restoration of a lower premolar using data from a computerized tomography of a mandible. The preload (20 N) after torque application for installation of the abutment and an occlusal loading were simulated. The occlusal load was simulated using average physiological bite force and direction (114.6 N in the axial direction, 17.1 N in the lingual direction and 23.4 N toward the mesial at an angle of 75° to the occlusal plan).

Results:

The regions with the highest von Mises stress results were at the bottom of the initial two threads of both prosthetic abutments that were tested. The one-piece prosthetic abutment presented a more homogeneous behavior of stress distribution when compared with the two-piece abutment.

Conclusions:

Under the simulated chewing loads, the von Mises stresses for both tested prosthetic-abutments were within the tensile strength values of the materials analyzed which thus supports the clinical use of both prosthetic abutments.

Finite element analysis of three zygomatic implant techniques for the severely atrophic edentulous maxilla

STATEMENT OF PROBLEM

A variety of zygomatic implantation techniques currently exist; however, a consensus regarding the most suitable method has not yet been reached.

PURPOSE

The purpose of this study was to evaluate and compare 3 zygomatic implantation techniques and to clarify the optimal number and position of zygomatic and dental implants for the reconstruction of the severely atrophied edentulous maxilla.

MATERIAL AND METHODS

A 3-dimensional finite element analysis craniofacial model was constructed from the computed tomography data of a selected patient with a severely atrophic edentulous maxilla. Modeled zygomatic implants were inserted into the craniofacial model with 3 surgical techniques (classic Brånemark, exteriorized, and extramaxillary), and with 3 model variations that involved the number and position of zygomatic and dental implants. The zygomatic implants were loaded with a vertical force of 150 N and a lateral force of 50 N. The stresses on and deformations of the bones and implants were then observed and compared.

RESULTS

No obvious differences in the amount and distribution of stress on the external craniofacial bones were detected in the models. The lowest stresses on the zygomatic implants were observed in the exteriorized technique group. The lowest deformations of the bone that surrounds zygomatic implants and dental implants were observed in the exteriorized technique and classic Brånemark technique groups. For the exteriorized technique group, the model with 1 dental implant in the site of the maxillary lateral incisor exhibited the lowest stress on the zygomatic implants and the least deformation of the bone surrounding the zygomatic and dental implants.

CONCLUSIONS

All 3 zygomatic implant techniques resulted in more or less homogeneous transference of force and thus could reconstruct the edentulous maxilla; however, the exteriorized technique with 1 dental implant in the lateral incisor appeared to be the most appropriate reconstruction method for the severely atrophied edentulous maxilla.

Effect of Implant Height Differences on Different Attachment Types and Peri-Implant Bone in Mandibular Two-Implant Overdentures: 3D Finite Element Study

Implant-supported overdentures with self-aligning attachment systems are preferred to improve the stability and retention of complete dentures. The positioning of the implant attachments is a very important aspect of two-implant overdentures in obtaining better stress distribution. Therefore, the objective of this study was to compare two different attachment systems in a two-implant overdenture by evaluating the stress distributions in peri-implant bone and stresses on the attachments with positioning at different height levels using the 3D FEA method. Six models with ball attachments and 6 models with locator attachments-totaling 12 models (including 2 controls)-with the left implant positioned unilaterally at different height levels were subjected to 3 loading conditions (anterior, right posterior, and left posterior). Data for Von Misses stresses were produced numerically, color coded, and compared among the models for attachments and peri-implant cortical bone. The configurations in which implants presented 3 mm height differences in the bone level showed the most successful results in the peri-implant bone. When stresses on the attachments were compared, greater stress values were obtained from the ball attachments. As a conclusion, the configurations with a considerable (3 mm) height difference between quadrants of the mandible in the anterior segment showed the most successful results in the peri-implant bone. On the contrary, peak stress values around the implant observed from the models with less (1 mm) bone height difference may require leveling of the bone during surgery. However, these findings should be corroborated with clinical studies.

In Situ Tooth Replica Custom Implant: A 3-Dimensional Finite Element Stress and Strain Analysis

This study is a phase of a biomechanical study, a part of a research program concerned with the new concept of in situ tooth replication. The purpose of the study was to evaluate tooth replica under each of two possible circumstances: (1) attachment via periodontal ligament and (2) osseointegration. Replicas were made of Cortoss, a bioactive glass, bone substitute. Three-dimensional finite element analysis was used to assess the stresses and strains resulting from each of 2 types of loads: off-vertical pressure and vertical point force acting on natural mandibular second premolar and corresponding replicas. Natural tooth tolerated 19 MPa pressure or 85 N vertical force, periodontally attached replica tolerated 15 MPa pressure or 80 N force, and osseointegrated replica tolerated 23 MPa pressure or 217 N force.

Immediate implant-supported provisional restoration with a root-form pontic for the replacement of two adjacent anterior maxillary teeth: A clinical report

In implant therapy, the replacement of 2 adjacent maxillary anterior teeth presents several unique challenges: mesiodistal space constraints, the need to maintain or create natural gingival esthetics, the need for esthetic provisional restorations, and the management of nonaxial forces. The treatment presented addresses these challenges through the use of an immediately placed single implant at the central incisor position with a central to lateral incisor cantilever prosthesis in both the immediate provisional and definitive restorations. The provisional restoration was designed to minimize pressure on the surgical site, optimize space for the gingival tissues, and control occlusal loading of the implant during the initial stages of osseointegration. The pontic was modified to replicate the subgingival root anatomy and enhance the gingival esthetic outcome.

Finite Element Analysis of the Influence of Implant Inclination on Stress Distribution in Mandibular Overdentures

The purpose of this finite element study was to evaluate the influence of implant inclination on the stress pattern in the bone surrounding the implants that support mandibular overdentures. The models used in this study were 3-implant-supported mandibular overdentures with a bar-and-clip attachment system. Each model was modified according to the distal implant inclination (0 and 20°). A unilateral vertical load was applied unilaterally to the first molar and first premolar of the overdenture, and the stress distribution in the bone was analyzed. Implant inclination decreased the stress distribution pattern in bone surrounding the implants when the load was applied on the molar site, but when applied at the premolar site, similar stress value changes were not found. Within the limitation of this study, it seems that the inclination of splinted implants in mandibular overdentures does not have any adverse effect on stress distribution pattern values around the implant.

Stud attachments for the mandibular implant-retained overdentures: Prosthetic complications. A literature review

A plethora of attachment systems for mandibular two-implant overdentures is currently available often without evidence-based support. Technical aspects are now parameters considered when choosing the appropriate attachment. Despite the increasing use of the Locator attachments, studies regarding their properties remain scarce. Peer reviewed articles published in English up to 2011, were identified through a MEDLINE search (Pubmed and Elsevier) and a hand search of relevant textbooks and annual publications. Emphasis was made on the technical complications as well as the loss of retention related to the attachments in implant-retained overdentures, primarily the Locator attachment. The evaluation of the long-term outcome of implant overdentures and complications associated with different attachment systems may provide useful guidelines for the clinician in selecting the type of attachment system and overdenture design.

Three dimensional finite element analysis of stress distribution around implant with straight and angled abutments in different bone qualities

The aim of the study was to compare the stress distribution around implant in different bone qualities of D1, D2, D3, and D4 with straight and angled abutments using three dimensional finite element analysis. A three dimensional finite element model of the premaxilla region, and two solid 4.3 × 10 mm implant, one with a straight abutment and the other with an angled abutment was done. Four distinctly different bone qualities of D1, D2, D3, and D4 were made. A static load of 178 N was applied at the centre of incisal edge along the long axis of each abutment. The maximum equivalent von Misses stress values around the implants were recorded. The distribution of stresses changed considerably with abutment angulation. As angulation increased from 0° to 15° the concentration of Von Misses stresses shifted to the cortical layer of bone on the facial side of the fixture. Although Von Misses stress increased in straight abutment as the bone quality changed from D1 to D4, it was more noticeable under the loading side of the angulated abutments. The high stresses induced through angled abutments at the cervical zone of the implant due to forces and moments could be a dominant factor that may aggravate the peri-implant bone loss or changes the existing peri-implantitis direction.

Influence of platform and abutment angulation on peri-implant bone. A three-dimensional finite element stress analysis

The aim of this study was to evaluate stress distribution on the peri-implant bone, simulating the influence of Nobel Select implants with straight or angulated abutments on regular and switching platform in the anterior maxilla, by means of 3-dimensional finite element analysis. Four mathematical models of a central incisor supported by external hexagon implant (13 mm × 5 mm) were created varying the platform (R, regular or S, switching) and the abutments (S, straight or A, angulated 15°). The models were created by using Mimics 13 and Solid Works 2010 software programs. The numerical analysis was performed using ANSYS Workbench 10.0. Oblique forces (100 N) were applied to the palatine surface of the central incisor. The bone/implant interface was considered perfectly integrated. Maximum (σmax) and minimum (σmin) principal stress values were obtained. For the cortical bone the highest stress values (σmax) were observed in the RA (regular platform and angulated abutment, 51 MPa), followed by SA (platform switching and angulated abutment, 44.8 MPa), RS (regular platform and straight abutment, 38.6 MPa) and SS (platform switching and straight abutment, 36.5 MPa). For the trabecular bone, the highest stress values (σmax) were observed in the RA (6.55 MPa), followed by RS (5.88 MPa), SA (5.60 MPa), and SS (4.82 MPa). The regular platform generated higher stress in the cervical periimplant region on the cortical and trabecular bone than the platform switching, irrespective of the abutment used (straight or angulated).