Biomedical Engineering Reference
In-Depth Information
Another difficulty in FEM simulation is related to the biomechanical boundary
conditions applied to the mandible and how important they are in replicating
physiological loading and kinematics.
Modeling the mandible using the finite element technique is described in Sect.
3
.
2
Characterization of the Temporomandibular Joint
Three localized dissections, carried out on recently deceased patients, provided
the qualitative and quantitative information needed for the geometrical analysis of
the articulation. The protocol required information on morphological anatomy, the
articular surfaces and the main masticatory muscles.
Three dissection planes (superficial, medial and deep) were observed to describe
the articular surfaces and to determine the directions of the muscle actions.
A geometric scale was used to for the subsequent exploitation of photographic data.
2.1
Geometry and Contacts of the Articular Surfaces
The parts of the temporal and mandibular surfaces involved and also their contacts
evolve according to the interincisal opening. The contact model is not continuous
and as a result, several loading configurations or examples must be considered.
2.1.1
Centric Occlusion and OcclusionfromtheRestPosition
Centric or maximum intercuspation occlusion, with a null opening and dental
contact (occlusal faces of the dental crowns), corresponds to the swallowing position
or also to those moments when mastication begins and ends. The mandibular
condyle is situated at the base of the temporal glenoid. The contact, or more exactly
the glenoid-condyle relationship, is established via the meniscus which does not
support much weight.
The rest position (comfort occlusion), with lips closed, and with a slight dental
opening (no dental contact), corresponds to reduced muscle tone, strong enough
only to overcome gravity. The mandibular condyle is placed in the upper area of the
temporal condyle without exerting any significant pressure on the disc. The space
between the first two antagonistic premolars is then about 1-2 mm.
The obstacle of the incisor influences the positioning of the mandible. To
overcome this obstacle, all propulsion movement starts by an opening movement
needed to pass from the centric position to a null interincisor distance.
