Figure 8. Distribution of the occlusal forces. Left column: model-T, right column: model-I, “Natural dentition” indicates the results in model-N under the load during occlusal adjustment
Figure 7. Load-displacement curve of the left canine
Figure 6. FE model with natural dentition (model-N). Tooth root is displayed with permeability
Figure 5. Schematic diagram for each phase of the load-displacement curve after occlusal adjustment of implants. a: Before loading, only anterior natural teeth were in contact with opposing teeth. Occlusal forces were not yet exerted anywhere. b: When a slight load caused the displacement of the mandible upward by the distance corresponding to the gap, i.e., the quantity of occlusal adjust...
Figure 4. Occlusal adjustment was simulated by altering the load-displacement curves of the springs
Figure 3. Load-displacement curves of the springs
Figure 2. Boundary conditions to verify the displaceability of teeth (a) and analyze the distribution of occlusal forces (b). Arrows: loads, triangles: restricted nodes, zigzags: springs
Figure 1. Finite element models (model-I and model-T). The tooth roots and the implant bodies are displayed with permeability
Occlusal adjustment (model)
___
___
___
___
4
5
6
7
Adj40N (model-T)
25.0
26.0
13.0
12.0
Adj200N (model-T)
30.0
37.0
23.5
24.0
Adj40N (model-I)
39.4
41.0
42.8
43.5
Adj200N (model-I)
70.9
75.4
79.9
81.6
Materials
Modulus of elasticity (MPa)
Poisson ratio
Enamel
80,000
0.3
Dentin
17,600
0.25
Inplant (titanium)
117,000
0.32
Superstructure (gold alloy)
94,000
0.3
Cortical bone
14,000
0.3
Cancellous bone
7,900
0.3
Since it was far larger than that of the teeth and implants (Fig. 3), the TMJs and ramus of the mandible were displaced upward and the most posterior implants became fulcrums of the rotation of the mandible. On the other hand, posterior implants were considered to be separated from opposing teeth and implants when the load was less than that exerted during occlusal adjustment. However, becau...
Thus, the “occlusal adjustment” performed on the FE models in this study was not a clinical procedure itself but a procedure to set the models in the state of the ICP under various occlusal loads.
This problem can be clarified by the definition of the ICP itself. Although load and deformation of the bone, joints, periodontal ligaments, and teeth in the ICP depend on the amount of the oc...
Discussion
FE models
The FE models in this study were based on those reported by Kasai et al. The material properties of the soft tissues such as the PDL and the TMJ, which were mainly deformed in the analysis, were considered to be crucial, because the aim of this study was to investigate the distribution of occlusal forces on the teeth, implants, and TMJs. In Figs. 3 and ...
Under Load200N, 20.3 % of the occlusal force was distributed at the molar site implants and 14.0 % of the occlusal force was distributed at the premolar site implants. The POF in the TMJ was larger than that in model-N. Under Load800N, the POF at the molar site implants was 36.3 %. However, almost no occlusal force occurred at the premolar site implants and anterior teeth. The POF in the TMJ wa...
Results
Displaceability of teeth
The load-displacement curve of the left canine under vertical load indicated two-phase displacement as shown in Fig. 7.
Model-T
The results of model-T are shown in Fig. 8. Adj40N resulted in the concentration of approximately 25 % of the occlusal force at the most posteriorly located implant on each side. In other words, about half of the total occlusal force...
Loading conditions
The loading conditions assumed intercuspal clenching. On the assumption that occlusal force was generated by the contractile force of four bilateral masticatory muscles, the masseter, temporalis, mesial, and lateral pterygoid muscles, the loading points and the directions of the loads were determined based on the report by Korioth and Hannam and anatomical findi...
Boundary conditions of the model and simulation of occlusal adjustment
The boundary conditions used to verify the displaceability of teeth and analyze the distribution of occlusal forces are shown in Fig. 2a, b, respectively. In the former model, a vertical load was applied to the left canine with the restriction of nodes on the bottom of the mandible (Fig. 2a). FE analysis was pe...
Methods
Finite element model
Three-dimensional finite element (FE) models were based on those reported by Kasai et al. and consisted of a mandible, natural teeth with periodontal ligaments, and titanium implants with superstructures. All elements were homogenous and isotropic. In the models, eight implants replaced all of the premolars and molars (Fig. 1).
The mass/volume and ...
Background
Dental implants have been widely used to restore or maintain occlusion, function, and esthetics and are particularly effective for partially edentulous jaws. However, the difference of the displaceability of the implants and natural teeth with periodontal ligaments (PDLs) may cause a problem in an arch that includes both implants and teeth. There is controversy about ...
Effect of bite force in occlusal adjustment of dental implants on the distribution of occlusal pressure: comparison among three bite forces in occlusal adjustment
Abstract
Background
The purpose of this study was to investigate the influence of occlusal forces (the contractile force of masticatory muscles) exerted during occlusal adjustment on the distribution of the forces among teeth, i...