Relating developing root length to tooth eruption and mechanical sensing by soft tissues

This thesis uses finite-element analysis to understand the basis for tooth eruption, core to the development of future improvements in the management of unerupted teeth. In earlier work, it was found that the soft tissue dental follicle surrounding unerupted teeth undergoes compression in the direction of tooth eruption and tension in the opposing direction to drive bone remodelling. This new concept for tooth eruption adapts the traditional concept of 'Wolff's law'. A model of the mandible of an 8-year-old child was modified by 'copying in' the erupted second deciduous molar, into the position of the unerupted first molar tooth on both sides. Leaving the crowns of the newly placed and buried teeth in place, the roots were progressively shortened to simulate five stages of root formation, thus generating five separate 3-dimensional models of the jaw, where the only difference was the length of the unerupted tooth roots. Dental soft tissue follicles around these unerupted teeth were generated. Finite element analysis models were then created of these models, where normal bite forces were applied in three separate patterns. Results were counter to those expected in that consistent compression above, and tension below the teeth was not seen; however, the overall compression in the intercuspal clenching loading and overall tension in incisive loading was observed and a mix of compression and tension in right molar loading was recorded. Effects of increasing root length were nonetheless seen, although in a background of counterintuitively opposing results. A comparison of the new models with the original one revealed the only clear difference to be that the native unerupted teeth earlier modelled, all had soft tissue connections that penetrated the overlying bone. Such 'gubernacular canal' structures were not modelled in the current study, and this leads to a new hypothesis of the role of this structure in tooth eruption