FEM Analysis Applied to OT Bridge Abutment with Seeger Retention System

Immediate full-arch fixed rehabilitation of a narrow mandible with newly conceived connection system implants: A case report

Rehabilitating thin jaws without reconstructive surgery entails using narrow implants. The proposed treatment adopted an innovative implant system, allowing the mini-screws to be parallel and immediately loaded. A mandible, wearing an overdenture, was functionalized contextually to the residual dental extraction and the placement of six 2.4-mm thick one-piece implants. Low-profile intermediate abutments, the LEMs, able to rotate over the spherical heads of the fixtures, were connected after suturing, oriented, and blocked in a mutual parallel position. The copings, engaging with a tapered juncture of the LEMs, resulted in their alignment to be intraorally wedged together. The provisional superstructure enclosed the copings and was immediately connected to the implants, and the definitive prosthesis was delivered after three months. No clinical signs of peri-implantitis or radiographically evident bone loss were recorded after a two-year follow-up without any prosthetic complication. No cases have been published regarding mini-implants bearing fixed prosthesis rehabilitation.

Evaluation of Tension and Deformation in a Mandibular Toronto Bridge Anchored on Three Fixtures Using Different Framework Materials, Abutment Systems, and Loading Conditions: A FEM Analysis

OBJECTIVE

 The aim of this study was to investigate by finite element method analysis the behaviour of a three-implant mandible Toronto framework made by three different materials, with two abutment systems and two loading conditions.

MATERIALS AND METHODS

 Three implants were virtually inserted in a mandible model in positions 3.6, 4.1, and 4.6. Three prosthetic framework bars with the same design and dimension (4.8 × 5.5 mm) were projected. The variables introduced in the computer model were the framework materials (glass fiber reinforced resin, Co-Cr, TiAl6V4), the abutment systems (Multi-Unit-Abutment [MUA]/OT-Bridge), and the loading conditions (500 N vertical load on all the framework area and 400 N on a 7-mm distal cantilever). The computer was programmed with physical properties of the materials as derived from the literature. Maximum tension and deformation values for each variable were registered at framework, screws, and abutment level and then compared.

RESULTS

 Metal frameworks Cr-Co and TiAl6V4 resulted in lower deformation than glass fiber-reinforced resin frameworks while presenting higher tension values. The OT-Bridge exhibited lower maximum tension and deformation values than the MUA system. The first loading condition reached higher tension and deformation values than the second and it resulted in more uniformly distributed load on all the framework area, especially with the OT-Bridge system.

CONCLUSION

 More rigid materials and OT-Bridge system decrease the deformation on the prosthetic components. Tension stresses are more uniformly distributed with glass fiber-reinforced resin, in the OT-Bridge system and avoiding cantilever loading.

Evaluation of Load Distribution in a Mandibular Model with Four Implants Depending on the Number of Prosthetic Screws Used for OT-Bridge System: A Finite Element Analysis (FEA)

In full-arch implant rehabilitations, when the anterior screw abutment channel compromises the aesthetic of the patient, the OT-Bridge system used with its Seeger rings may provide the necessary retention of the prosthesis. However, no studies have evaluated the forces generated at the Seeger level during loading. This Finite Element Analysis aims to investigate the mechanical behavior of Seeger rings in a mandibular model with four implants and an OT-Bridge system, used without one or two anterior prosthetic screws. A 400 N unilateral load was virtually applied on a 7 mm distal cantilever. Two different variables were considered: the constraint conditions using two or three screws instead of four and the three different framework materials (fiberglass reinforced resin, cobalt-chrome, TiAl6V4). The FEA analysis exhibited tensile and compressive forces on the Seeger closest to the loading point. With the resin framework, a tension force on abutment 3.3 generates a displacement from 5 to 10 times greater than that respectively expressed in metal framework materials. In a full-arch rehabilitation with four implants, the case with three prosthetic screws seems to be a safer and more predictable configuration instead of two. Considering the stress value exhibited and the mechanical properties of the Seeger, the presence of only two prosthetic screws could lead to permanent deformation of the Seeger in the screwless abutment closest to the loading point.

A New Approach for the Tribological and Mechanical Characterization of a Hip Prosthesis Trough a Numerical Model Based on Artificial Intelligence Algorithms and Humanoid Multibody Model

In recent years, thanks to the development of additive manufacturing techniques, pros-thetic surgery has reached increasingly cutting-edge levels, revolutionizing the clinical course of patients suffering from joint arthritis, rheumatoid arthritis, post-traumatic arthrosis, etc. This work aims to evaluate the best materials for prosthetic surgery in hip implants from a tribological and mechanical point of view by using a machine-learning algorithm coupling with multi-body modeling and Finite Element Method (FEM) simulations. The innovative aspect is represented by the use of machine learning for the creation of a humanoid model in a multibody software environment that aimed to evaluate the load and rotation condition at the hip joint. After the boundary conditions have been defined, a Finite Element (FE) model of the hip implant has been created. The material properties and the information on the tribological behavior of the material couplings under investigation have been obtained from literature studies. The wear process has been investigated through the implementation of the Archard’s wear law in the FE model. The results of the FE simulation show that the best wear behavior has been obtained by CoCr alloy/UHMWPE coupling with a volume loss due to a wear of 0.004 μm3 at the end of the simulation of ten sitting cycles. After the best pairs in terms of wear has been established, a topology optimization of the whole hip implant structure has been performed. The results show that, after the optimization process, it was possible to reduce implant mass making the implant 28.12% more lightweight with respect to the original one.

Full Digital Workflow for Prosthetic Full-Arch Immediate Loading Rehabilitation Using OT-Bridge System: A Case Report

Nowadays, digital technologies have brought very important advancements in clinical prosthetic dentistry. However, a full digital workflow is still considered to be challenging in the management of full-arch implant cases with immediate prosthetic loading. The aim of this case report is to show a full-digital workflow for the fabrication of an implant-prosthetic fixed provisional prosthesis for immediate loading on seven implants in the upper maxilla. The static guided implant surgery and the OT Bridge prosthetic system were used to rehabilitate the patient. In this way, the combination of a well-known surgical technique with a peculiar prosthetic system that allows for a certain degree of tolerance resulted in it being useful for full-arch immediate loading. Future research and studies are necessary to prove the reliability of this full-digital protocol.

Assessment of Preload Loss after Cyclic Loading in the OT Bridge System in an “All-on-Four” Rehabilitation Model in the Absence of One and Two Prosthesis Screws

The aim of this study was to evaluate the stability of prosthetic screws after applying cyclic loadings in an “all-on-four” rehabilitation model with the OT Bridge system. The model was tested both with and without anterior screws. Four implant analogues following the “all-on-four” concept were inserted in an edentulous mandibular resin model. An OT Bridge system with a Cr–Co prosthetic framework was fabricated. Depending on the presence or absence of one or two anterior screws on the implant analogues, three groups were created, i.e., Gr.1: three tightening screws, Gr.2: two tightening screws, Control Group: four tightening screws. Each single group underwent subsequent 400,000 cyclic loads, simulating approximately a year of chewing by using a dynamometer machine. This cycle was repeated five times for each group, and preload loss values were evaluated on each prosthetic screw after each cycle. All the data obtained were analyzed by one-way ANOVA and Student’s t-test. No statistically significant differences after intragroup analysis were found. A statistically significant difference within the Gr.1 between the screws in positions 33 and 36, equal to 15.2% (p-value = 0.0176), was found. The OT Bridge seems a useful system to maintain the retention of a prosthesis during mechanical stress conditions even in the absence of one screw in an “all-on-four” rehabilitation. This could represent a good solution to solve the esthetic problem of the screw buccal access hole for fixed solutions.

Influence of the Inclination of the Incisal Edge of Planas Direct Tracks on Deciduous Dentition with Anterior Crossbite: Finite-Elements Study

Objective  This study aimed to evaluate the influence of three different inclinations of the incisal edge of Planas direct tracks (PDTs) on the upper deciduous incisors (15, 30, and 45 degrees) through simulations using the finite-elements method.

Materials and Methods  A three-dimensional virtual model of tooth 51 was elaborated by using the Rhinoceros computer-aided design (CAD) software. A mesh was constructed by using the Patran software, and the evaluations were processed by using the ANSYS 15.0 software. The geometry of the elements used consisted of a triangular-base tetrahedron composed of 2,167,386 elements and 3,012,995 nodal points.

Results  Progressive alterations of proportional intensity and distribution were seen in the areas of tension on the dentoalveolar structures, with increasing inclination of the edge of the PDT. The tractive contact tensions were seen to be concentrated in the vestibular apical thirds and palatine cervical thirds, while the compressive contact tensions were in the palatine apical thirds and vestibular cervical thirds.

Conclusion  It was concluded that a 30-degree inclination for the PDT was most appropriate for the cases of anterior crossbite in the deciduous dentition. Nevertheless, because this was a laboratory evaluation, clinical criteria and complementary examinations for each case need to be taken into consideration in making therapeutic decisions.

Mechanical Response of PEKK and PEEK As Frameworks for Implant-Supported Full-Arch Fixed Dental Prosthesis: 3D Finite Element Analysis

Objective  Polymeric framework represent an innovative approach for implant-supported dental prostheses. However, the mechanical response of ultra-high performance polymers as frameworks for full-arch prostheses under the “all-on-four concept” remains unclear. The present study applied finite element analysis to examine the behavior of polyetherketoneketone (PEKK) and polyetheretherketone (PEEK) prosthetic frameworks.

Materials and Methods  A three-dimensional maxillary model received four axially positioned morse-taper implants, over which a polymeric bar was simulated. The full-arch prosthesis was created from a previously reported database model, and the imported geometries were divided into a mesh composed of nodes and tetrahedral elements in the analysis software. The materials were assumed as isotropic, elastic, and homogeneous, and all contacts were considered bonded. A normal load (500 N magnitude) was applied at the occlusal surface of the first left molar after the model was fixed at the base of the cortical bone. The microstrain and von-Mises stress were selected as criteria for analysis.

Results  Similarities in the mechanical response were observed in both framework for the peri-implant tissue, as well as for stress generated in the implants (263–264 MPa) and abutments (274–273 MPa). The prosthetic screw and prosthetic base concentrated more stress with PEEK (211 and 58 MPa, respectively) than with PEKK (192 and 49 MPa), while the prosthetic framework showed the opposite behavior (59 MPa for PEEK and 67 MPa for PEKK).

Conclusion  The main differences related to the mechanical behavior of PEKK and PEEK frameworks for full-arch prostheses under the “all-on-four concept” were reflected in the prosthetic screw and the acrylic base. The superior shock absorbance of PEKK resulted in a lower stress concentration on the prosthetic screw and prosthetic base. This would clinically represent a lower fracture risk on the acrylic base and screw loosening. Conversely, lower stress concentration was observed on PEEK frameworks.

A One-Year, Multicenter, Retrospective Evaluation of Narrow and Low-Profile Abutments Used to Rehabilitate Complete Edentulous Lower Arches: The OT Bridge Concept

Purpose: To evaluate preliminary data on survival and success rates of immediately loaded, screw-retained, restorations delivered on lower arches using narrow and low-profile OT Equator abutments. Methods: This retrospective study analyzed data of patients rehabilitated with OT Bridge (fixed prosthetic system built on OT Equator) prosthetic concept from November 2017 to February 2019 in five different centers. Outcome measures were implant and prosthetic survival rates, biological and technical complications, marginal bone loss (MBL), oral health impact profile (OHIP), bleeding on probing, and plaque index. Results: A total of 60 implants were inserted in 12 patients. Patients were followed for a mean period of 15.8 months (range 12–24). All the patients received OT Equator as intermediate abutments. Four out of 60 implants were connected to the prosthetic framework using only the Seeger system, without a screw. One year after loading, three implants failed (implant survival rate of 95.0%) in two patients. No prosthesis failed and no major biological and technical complications were experienced. One year after initial loading, the marginal bone level was 0.32 ± 0.2 mm. The OHIP before treatment was 87.7 ± 6.0. One year after treatment, OHIP was 23.6 ± 1.2. The difference was statistically significant (64.1 ± 7.2; p = 0.0000). One year after loading, 8.9% of the examined implant sites present positive bleeding on probing, while 5.8% of the implant sites presented plaque. Conclusions: The OT Equator abutments showed successful results when used to support mandible fixed dental prosthesis delivered on 4–6 implants. Whole prosthetic survival and success rates, high patient satisfaction, and good biological parameters were experienced one year after function. Further prospective studies are needed to confirm these preliminary results.