Simulation of Human Periodontal Ligament (PDL)

(more detailed image)		What is the Periodontal Ligament (PDL)? The PDL, see Fig. 1 for the anatomy, is a thin fibrous connective tissue of about 0.15 to 0.35 mm thickness present at the interface between teeth and the mandibular corpus. Structural behaviour of the periodontal ligament is responsible for bone remodelling and orthodontic tooth movement. Fig. 1: Micro-CT slice of a human premolar in vitro Resolution 160 µm x 160 µm x 320 µm
Procedure Segmentation (Amira 3.1.1) of dental anatomy including PDL, tooth, lamina dura, cancellous and cortical bone (see Fig. 2) Mesh generation (ScanFE) of dental anatomy including PDL, tooth, lamina dura, cancellous and cortical bone (see Fig. 3) Finite Element simulation (ABAQUS) of orthodontic load cases (see Fig. 4)
Fig. 2: Segmentation (more detailed image)		Fig. 3: FE mesh		Fig. 4: FE Simulation - stress distribution

Segmentation in Amira

A cropped region of interest of a clinical CT-data set (originally 0.6 mm z-distance, 0.3 mm² pixel size) comprising a premolar and surrounding bone tissue was resampled by a factor of 5 in x- and y-direction and by a factor of 10 in z-direction. The resulting data were semi-automatically segmented into the following structures:

• Tooth,
• PDL,
• Cortical bone with lamina dura, and
• Cancellous bone.

Mesh generation in ScanFE

For the PDL, a hybrid mesh comprising 432372 elements was generated whereas tooth and bone were modelled as stiff shell.

Finite Element Simulation in Abaqus

The load case was realized by means of two forces of 0.25 N each, applied on the labial and lingual side of the crown simulating a total intrusive force of 0.5 N, see the yellow arrows in Fig. 4. By fixation of the interface bone/PDL, displacement of bone was prevented. See Fig. 4 for maximum principal stress distribution in the periodontal ligament for the applied intrusive force.