Correlation between abutment angulation and off-axial stresses on biomechanical behavior of titanium and zirconium implants in the anterior maxilla: A three-dimensional finite element analysis study

Load, unload and repeat: Understanding the mechanical characteristics of zirconia in dentistry

OBJECTIVES

Zirconia-based dental restorations and implants are gaining attention due to their bioactivity, corrosion resistance and mechanical stability. Further, surface modification of zirconia implants has been performed at the macro-, micro- and nanoscale to augment bioactivity. While zirconia's physical and chemical characteristics have been documented, its relation to mechanical performance still needs to be explored. This extensive review aims to address this knowledge gap.

METHODS

This review critically compares and contrasts the findings from articles published in the domain of 'mechanical stability of zirconia\ in dentistry' based on a literature survey (Web of Science, Medline/PubMed and Scopus databases) and a review of the relevant publications in international peer-reviewed journals. Reviewing the published data, the mechanical properties of zirconia, such as fracture resistance, stress/tension, flexural strength, fatigue, and wear are detailed and discussed to understand the biomechanical compatibility of zirconia with the mechanical performance of modified zirconia in dentistry also explored.

RESULTS

A comprehensive insight into dental zirconia's critical fundamental mechanical characteristics and performance is presented. Further, research challenges and future directions in this domain are recommended.

SIGNIFICANCE

This review extends existing knowledge of zirconia's biomechanical performance and it they can be modulated to design the next generation of zirconia dental restorations and implants to withstand long-term constant loading.

Simultaneous Le Fort I osteotomy and zygomatic implant placement

The aim of this retrospective study was to evaluate the outcomes of simultaneous LeFort I osteotomy and zygomatic/dental implant placement for oral rehabilitation of patients with extremely atrophic/dysmorphic edentulous maxilla. Simultaneous LeFort I osteotomy and zygomatic/dental implant placement was performed with patient-specific anatomical models and surgical guides produced through three-dimensional virtual planning methods. All patients received their final prosthesis, with immediate loading, on the day after surgery. The primary outcome variables were the implant survival rate, and the incidence of intra/postoperative complications. In total, 15 zygomatic implants and 33 conventional dental implants were inserted in eight patients. The mean follow-up of the patients was 38.5 months. The implant survival rate was 93.3% for zygomatic implants and 100% for dental implants. No intra/postoperative complications were observed. Simultaneous LeFort I osteotomy associated with zygomatic/dental implant surgery can be considered as a valuable treatment option for rehabilitation of patients with extremely atrophic edentulous maxilla and esthetic issues of the face.

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.

A finite element analysis to study the stress distribution on distal implants in an all-on-four situation in atrophic maxilla as affected by the tilt of the implants and varying cantilever lengths

Aim:

The aim of this work was to evaluate stress distribution on implants in All-on-Four situation with varying distal implant angulations (30°,40°,45°) and varying cantilever lengths (4 mm, 8 mm, 12 mm, 16 mm) in atrophic maxilla using finite element analysis.

Setting and Design:

A in vitro study, finite element analysis.

Materials and Methodology:

Three-dimensional finite element model of an edentulous maxilla restored with a prosthesis supported by four implants was reconstructed to carry out the analysis. Three different configurations, corresponding to 3 tilt degrees of the distal implants (30°, 40°, and 45°) were subjected to 4 loading simulations.

Statistical Analysis Used:

The results of the simulations obtained were evaluated in terms of Von Mises equivalent stress levels at the bone-implant interface.

Result:

From a stress-level viewpoint, the 45° model was revealed to be the most critical for peri-implant bone. In all the loading simulations, the maximum stress values were always found at the neck of the distal implants. With increasing distal implant tilt, cantilever length reduces depending on the quality of bone. At 30° angulation of distal implant a maximum cantilever length of 16 mm may be given if the quality of bone is D3 but only 8 mm cantilever may be recommended if bone quality is D4. At 40° angulation, 16 mm in D3 bone and 0 mm in D4 bone whereas at 45° angulation, it reduces to 12 mm in D3 bone and no cantilever is recommended with D4 bone.

Conclusion:

The 45° tilt induced higher stress values at the bone-implant interface, especially in the distal aspect, than the other 2 tilts analyzed. Stress values increased with increased cantilever length which was further influenced by the distal implant tilt and the quality of the bone.