Figure 1.
Simplified two dimensional representation of a tooth-PDL-bone complex illustrating three hypotheses for strain-based bone remodelling during orthodontic tooth movement.
(a) “pressure-tension hypothesis” showing tooth displacement leading to compression and tension in the surrounding bone; (b) “alveolar bending hypothesis” showing tooth movement causing bending of the alveolar bone; (c) “stretched fibre hypothesis” showing stretching and compression of PDL fibres leading to low and high strain areas in the surrounding bone. The red arrows indicate the direction of the applied orthodontic force.
Figure 2.
Single tooth FE model including dimensions in millimetres.
(a) the whole 3D single tooth model; (b) section through tooth, PDL and alveolar bone showing the location of the link elements which span the PDL layer connecting the tooth and alveolar bone; (c) section through the centre of the model showing the tooth, PDL and alveolar bone including an expanded view of the apex region.
Table 1.
Mechanical properties assigned to each material in the fibrous PDL model.
Figure 3.
Tooth model showing loading and boundary conditions applied, where triangles represent constraints and red arrows represent applied forces.
(a) vertical occlusal load; (b) buccolingual orthodontic load; (c) mesiodistal orthodontic load; (d) section through centre of tooth model showing a typical plane from which strain results were taken.
Figure 4.
Contour plots showing nodal solutions for the principal microstrains on the outside surface of the alveolar bone for the solid PDL and fibrous PDL models due to the 500 N occlusal load.
(a) maximum principal microstrain; (b) minimum principal microstrain. Directions are represented by M for mesial and D for distal.
Figure 5.
Maximum and minimum principal strains on the buccal and lingual sides of the tooth model from the 500 N occlusal load, along three regions within the model.
The graphs relate strain to the vertical distance away from the top of the tooth socket.
Figure 6.
Maximum and minimum principal strains on the mesial and distal sides of the tooth model from the 1 N orthodontic load in the mesiodistal direction, along three regions within the model.
The graphs relate strain to the vertical distance away from the top of the tooth socket.
Figure 7.
Maximum and minimum principal strains on the buccal and lingual sides of the tooth model from the 1 N orthodontic load in the buccolingual direction, along three regions within the model.
The graphs relate strain to the vertical distance away from the top of the tooth socket.