Evaluation of Stress in Tilted Implant Concept With Variable Diameters in the Atrophic Mandible: Three-Dimensional Finite Element Analysis
The beneficial mechanical properties provided by greater diameter or short implants increases their usage in the tilted implant concept. The aim of the present study is to compare the stress distribution of 4 different treatment models including variable implant numbers and diameters under a static loading protocol in the atrophic mandible using 3-dimensional finite element analysis. Three models included 2 tilted and 2 vertically positioned implants with different diameters, whereas 2 distally placed short implants were added to the fourth model. The von Mises stress as well as the maximum and minimum principal stress values were evaluated after applying 200 N bilateral oblique loads to the first molar teeth with the inclination of 45° to the longitudinal axis. Tilted implants were associated with higher stress values when compared with vertical implants in all models. The lowest stress values were obtained in the fourth model, including short implants. Although all stress values showed slight increases by descending implant diameters, the stress values of the model including implants with 3.3-mm diameter were within physiologic limits. All in all, an increasing number or diameter of implants may have a positive effect on implant survival. In addition, when narrow-diameter implants need to be inserted in the tilted implant concept, combination with short implants may be recommended for long-term success.
(a) Cobalt-chromium framework. (b) Feldspathic porcelain. (c) Simulation of hybrid prosthesis. (d) Modeling of atrophic mandible. (e) Tissue-level short implant. (f) Bone-level tapered, tilted implant, and abutment angled 30°. (g) Bone-level tapered implant. (h) All structures were adapted to the simulated jaw.
Illustrations of 4 models were generated. (a) Model 1 includes 4 implants with 3.3-mm diameter and 11-mm cantilever length. (b) Model 2 includes 4 implants with 4.1-mm diameter and 11-mm cantilever length. (c) Model 3 includes 4 implants with 4.8-mm diameter and 11-mm cantilever length. (d) Model 4 includes 6 implants. It was constituted by adding 2 short implants with 4.1-mm diameter and 4 mm in length to model 2. This model does not include cantilever extension. (I) Vertical implants were positioned into the second incisor region. (II) Tilted implants were positioned into the second premolar region. (III) Short implants were positioned into the first molar region.
Von Mises stress values and stress distribution of mandibular implants in oblique loading (MPa). (a) Implants of 3.3-mm diameter. (b) Implants of 4.1-mm diameter. (c) Implants of 4.8-mm diameter. (d) Model with 6 implants including short implants. X indicates the distal side; Y, buccal side; Z, occlusal side.
Minimum principal stress values and stress distribution of mandibular cortical bone in oblique loading (MPa). (a) Implants of 3.3-mm diameter. (b) Implants of 4.1-mm diameter. (c) Implants with 4.8-mm diameter. (d) Model with 6 implants including short implants. X indicates the distal side; Y, buccal side; Z, occlusal side.
Contributor Notes