Intermittent tongue, lip and cheek forces influence precise tooth position, so we here examine the possibility that tissue remodelling driven by functional
bite-force-induced jaw-strain accounts for tooth eruption. Notably, although a separate true 'eruptive force' is widely assumed, there is little direct evidence for such a force. We constructed a three dimensional finite
element model from axial computerized tomography of an 8 year old child mandible containing 12 erupted and 8
unerupted teeth. Tissues modelled included: cortical bone, cancellous bone, soft tissue dental follicle, periodontal ligament, enamel, dentine, pulp and articular cartilage. Strain and hydrostatic stress during incisive and unilateral molar
bite force were modelled, with force applied via medial and lateral pterygoid, temporalis, masseter and digastric muscles. Strain was maximal in the soft tissue follicle as opposed to surrounding bone, consistent with follicle as an effective mechanosensor. Initial numerical analysis of dental follicle soft tissue overlying
crowns and beneath the roots of
unerupted teeth was of volume and hydrostatic stress. To numerically evaluate
biological significance of differing hydrostatic stress levels normalized for variable finite
element volume, '
biological response units' in Nmm were defined and calculated by multiplication of hydrostatic stress and volume for each finite
element. Graphical representations revealed similar overall responses for individual teeth regardless if incisive or right molar
bite force was studied. There was general compression in the soft tissues over
crowns of most
unerupted teeth, and general tension in the soft tissues beneath roots. Not conforming to this pattern were the unerupted second molars, which do not erupt at this developmental stage. Data support a new hypothesis for tooth eruption, in which the follicular soft tissues detect
bite-force-induced bone-strain, and direct bone remodelling at the inner surface of the surrounding bony crypt, with the effect of enabling tooth eruption into the mouth.