Tooth Eruption Results from Bone Remodelling Driven by Bite Forces Sensed by Soft Tissue Dental Follicles: A Finite Element Analysis

Abstract

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.

Impacted Third Molars and Its Propensity to stimulate External Root Resorption in Second Molars: Comparison of Orthopantomogram and Cone Beam Computed Tomography

“…45 However, according to our study, Position B is more prone for ERR. The study published by Sarrafpour et al 46 stated that eruptive tooth movements do not cease with completion of root formation and closure of the apex, which implies that a retained tooth continues to exert pressure on the adjacent tooth, stimulating and progressing root resorption. In cases of resorption, third molars should be advised for surgical removal.…”

Tooth eruption disorders associated with systemic and genetic diseases: clinical guide

“…Recently, Sarrafpour et al have proposed a new theory of eruption, in which DF is central to the initiation of the phenomenon 36 . Their theory is that the mastication forces between the bone and the soft tissues surrounding the erupting tooth lead to tissue remodeling, which results in tooth eruption.…”

Effect of orthotropic material on finite element modeling of completely dentate mandible

“…In both cases, tooth enamel, dentin, and articular cartilage were considered to be isotropic, homogenous, and linearly elastic [11][12][13][14]: E = 84.1 GPa and ν = 0.33 for tooth enamel, E = 18.6 GPa and ν = 0.31 for dentin, Fig. 1.…”

“…The value of each masticatory force in Newtons was calculated from the product of the cross-sectional area of the muscle, a constant for skeletal muscles, and the scaled value of each muscle contraction relative to its maximum response to the biting task [11,14]. The mandible model was then used to simulate the biting task in the intercuspal position.…”

“…For occlusal tasks involving posterior teeth, the model was restrained from movement at the buccal and central thirds of the occlusal surfaces; for those involving the anterior teeth, restraints were placed on the entire incisal surface of each tooth involved [11,14]. These restraints acted perpendicularly to the occlusal plane (z-direction), allowing freedom of displacement in the horizontal plane [11,14]. Additionally, to model the temporomandibular joint, contact pairs were generated in the disk-fossa cartilage interface and disk-condylar cartilage interface, as well as a group of capsular ligaments.…”