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Dental biomechanics of root-analog implants in different bone types
João Paulo M Tribst1, Amanda Maria de O Dal Piva2, Erik J Blom3
1Assistant Professor, Department of Oral Regenerative Medicine, Academic Centre for Dentistry Amsterdam (ACTA), Universiteit van Amsterdam and Vrije Universiteit, Amsterdam, the Netherlands.
Statement Of Problem:
When implants are applied to restore oral function, the masticatory load on the crown will lead to stress development in all parts of the crown-abutment-implant-bone system. An optimal design of the whole system will be important for sustained function.
Purpose:
The purpose of this 3-dimensional (3D) finite element analysis (FEA) study was to evaluate the influence of the root-analog implant (RAI) design in molar rehabilitation and bone type.
Material And Methods:
Twelve 3D models of single posterior implant-supported restorations were created according to the zirconia implant design (monotype, 2-piece, or RAI) and bone type (D1, D2, D3, and D4, according to the Misch classification). The models were composed of cortical bone, cancellous bone, implant, cement layers, and a monolithic ceramic crown. For the 2-piece zirconia implant model, the titanium base, prosthetic screw, and framework were also designed. All materials were assumed to behave elastically throughout the entire analysis. The bone was fixed, and an axial loading of 600 N was applied to the contacts on the occlusal surface of the crowns. Results for the crown and implant were obtained in maximum principal stress, as well as the von Mises stress for the model and bone microstrain.
Results:
High stress concentration was observed at the intaglio surface of the crowns near the loading region. Regardless of the design, the stress trend in the implant was similar, increasing proportionally to the bone type (D1>D2>D3>D4). RAI showed a homogeneous stress field near the values calculated for the conventional designs, but with lower magnitudes. The 2-piece zirconia model showed the highest stress magnitude regardless of the bone type and, therefore, the highest failure risk. All models showed a higher strain in the cortical bone than in the cancellous bone, located predominantly in the cervical region. A strain analysis showed that both conventional implant models presented similar behavior for D1 and D2 bone types, with an increasing difference for D3 and D4. RAI showed the lowest strain regardless of the bone type.
Conclusions:
Root-analog zirconia implants present a promising biomechanical behavior for dissipating the masticatory load in comparison with conventional screw-shaped implants.
