Finite Element Analysis of Functionally Loaded Subperiosteal Implants Evaluated on a Realistic Model Reproducing Severe Atrophic Jaws

Abstract

Implant-supported prosthetic rehabilitation for patients with severely atrophic jaws is challenging due to complex anatomical considerations and the limitations of conventional augmentation techniques. This study explores the potential of subperiosteal (juxta-osseous) implants as an alternative solution, using finite element analysis (FEA) to evaluate mechanical performance. Realistic jaw models, developed from radiographic data, are utilized to simulate various implant configurations and load scenarios. Results indicate that different screw placements, implant designs, and structural modifications can significantly influence stress distribution and biomechanical behavior. Upper and lower jaw models were assessed under multiple load conditions to determine optimal configurations. Findings suggest that strategic adjustments, such as adding posterior screws or altering implant connections, can enhance load distribution and reduce stress concentration, particularly in critical areas. Tensile loads in critical bone areas near cortical fixing screws exceeded 50 MPa under anterior loading, while configurations with larger load distributions reduced stress on both implant and bone. The study provides evidence-based insights into optimizing subperiosteal implant design to improve stability, longevity, and patient outcomes.

Keywords: finite element analysis (FEA); juxta-osseous implants; severe jaw atrophy.

Figure 1

Different types of loads, indicated in yellow, were applied to the upper jaw. (a) Configuration 1: a uniform load is applied, distributed evenly across the entire jaw. (b) Configuration 2: a bilateral load is applied specifically in the molar region. (c) Configuration 3: an anterior unilateral load is applied to one side of the jaw. (d) Configuration 4: a unilateral load is applied in the premolar region. (e) Configuration 5: a unilateral load is applied in the molar region.

Figure 2

Different types of loads, indicated in yellow, were applied to the lower jaw. (a) Configuration 1: a uniform load is applied, distributed evenly across the entire jaw. (b) Configuration 2: a bilateral load is applied specifically in the molar region. (c) Configuration 3: an anterior unilateral load is applied to one side of the jaw. (d) Configuration 4: a unilateral load is applied in the premolar region. (e) Configuration 5: a unilateral load is applied in the molar region.

Figure 3

An image of the upper model, showing the “rigid” element in yellow and the central node with all six degrees of freedom locked (translations in x, y, z and rotations in x, y, z).

Figure 4

(a) An image of the lower model. The elastic pads were connected to a central node, which was constrained in all six degrees of freedom (translations in x, y, z and rotations in x, y, z). (b) The nodes corresponding to the condyles were constrained to two separate nodes (one for the right condyle and one for the left), which were further constrained only in translations (x, y, z). This setup represented a hinge corresponding to the mandibular joint.

Figure 5

(a) Design of the subperiosteal implant in upper jaw model V0. (b) Model V0 with the most critical anterior right side load configuration 3.

Figure 6

Model V0 with the least critical load configuration 1 distributed across the entire dentition.

Figure 7

Model V0 with the least critical load configuration 2 distributed across the posterior teeth.

Figure 8

Design of the subperiosteal implant in upper jaw model V1 with added posterior screws, reducing stress on anterior parts and achieving more balanced distribution.

Figure 9

(a) Design of the subperiosteal implant in upper jaw model V1. (b) Upper jaw model V1 with added posterior screws, reducing stress on anterior parts and achieving more balanced distribution.

Figure 10

Design of the upper jaw model V2 structure using screws placed posteriorly in the vestibular direction rather than the palatal direction.

Figure 11

(a) Design of the subperiosteal implant in upper jaw model V2. (b) Loading distribution across upper jaw model V2, similar in behavior to model V1.

Figure 12

Design of upper jaw model V3 using screws placed in the vestibular direction rather than the palatal direction.

Figure 13

(a) Design of the subperiosteal implant in upper jaw model V3. (b) Upper jaw model V3 with optimized front section with additional screws, the stress on the frontal screws remained unchanged.

Figure 14

Design of upper jaw model V4 with the added screws relocated towards the frontal process, aligning them vertically with the other screws and ensuring that both arms of the first and second abutments connect to this screw.

Figure 15

(a) Design of the subperiosteal implant in upper model V3. (b) Stress loading in upper model V4 exceeds 50 MPa in the vicinity of the screws. The crestal support shows stresses between 30 and 35 MPa.

Figure 16

Design of model V5 with the connection between the two hemi-implants, affecting the structure. A frontal connecting bar was added while the palatal bar was removed.

Figure 17

(a) Design of upper jaw model V5. (b) Stress loading in model V5 with the frontal connecting bar.

Figure 18

Design of model V6 divided into two hemi-arches without any connecting element.

Figure 19

(a) Design of upper jaw model V5. (b) Stress loading in model V6 on the bone and implant remains the same as in cases with the connection.

Figure 20

(a) Design of the subperiosteal implant in lower jaw model V0. (b) The most significant load on lower jaw model V0, corresponding to chewing in the anterior right sector.

Figure 21

Load configuration 1 distributed over a larger area of lower jaw model V0.

Figure 22

Load configuration 2 distributed over a larger area of lower jaw model V0.

Figure 23

Design of model V1 with two anterior appendages added in a crestal position.

Figure 24

(a) Design of the subperiosteal implant in lower jaw model V1. (b) Stress loading in model V1 and implant, with no improvement in the configuration observed.

Figure 25

Design of model V2 with extended anterior vestibular arms that connect to the first abutment.

Figure 26

(a) Design of the subperiosteal implant in lower jaw model V2. (b) The stresses near the holes in model V2 are similar to those observed in model V1.

Figure 27

Model V3 design with an additional screw, distributing the load of the anterior abutment across three screws instead of two.

Figure 28

(a) Design of the subperiosteal implant in lower jaw model V3. (b) Decreased stress loading on the material of model V3.

Figure 29

Model V4, design 3, adds a screw in the posterior sector, positioned in the vestibular direction to model V3.

Figure 30

(a) Design of the subperiosteal implant in lower jaw model V4. (b) The posterior alveolar area of model V4, particularly around the more posterior screws, remains notably stressed.

Figure 31

Model V5 design with the same geometry as version 4, with the addition of two connecting bars, one on the lingual side and one on the vestibular side.

Figure 32

(a) Design of the subperiosteal implant in lower jaw model V5. (b) Stress loading in model V5 on the two connecting bars exhibits stresses close to 0, indicating that no force is transmitted through them.