Investigating the cause of dental disease in the domesticated rabbit using computational biomechanics

Background

Variation in diet due to factors such as climate change, changes of habitat or competition over food sources can impact on animal health and development. For example, switching from a diet of hard to soft foods has been shown to reduce alveolar bone density[1], which can lead to subsequent tooth loss and instigates a cycle of further alveolar resorption[2]. Computational biomechanics has the capability to predict the effects of such ecological factors upon aspects of animal health and potentially morphological diversity. The integration of multi-body dynamics (MDA) and finite element analysis (FEA) provides a non-invasive method to predict the musculoskeletal loading (muscle, joint and bite forces) when consuming a range of foods types, and then compute the associated strains in the bone and tooth movement[3].

This PhD project aims to demonstrate the potential of computational biomechanics in predicting how apparently modest changes in food resources can affect animal health and development. This will be undertaken through an investigation of causes of dental disease in the domesticated rabbit. This is an ideal species for this case study as it has varied feeding habits and domestication is thought to contribute to development of dental disease. One theory proposes that the change in diet of the domesticated rabbit to predominately soft foods (e.g. pellets) leads to a reduction in natural dental wear, elongated tooth roots and subsequent malocclusion[4]. Another theory suggests that reduced exposure to sunlight, and the subsequent lowered intake of vitamin D, causes metabolic bone disease and reduction of alveolar bone density[5]. Alternatively, it could be a combination of the two[6].

Another advantage of studying this species is the wealth of data currently available for the rabbit, and the supervisor’s role in a current BBSRC funded study (Universities of Hull, Leeds and Liverpool) which is developing a novel framework for such in silico biomechanical models and 3Rs in musculoskeletal research. As part of that project, the investigators are collecting a unique dataset of physiological muscle properties in the rabbit skull, muscle activations and jaw movement during mastication of various foods, to create the most complex and fully-validated MDA and FEA model of a skull. The long-term goal of this work is to reduce and eventually replace the number of highly invasive in vivo rabbit studies, which are still used to assess new biomaterials. This proposed PhD project aims to use these models to investigate potential causes of dental disease in domesticated rabbits by simulating the effects of elongated tooth roots and reduction in bone density on tooth movement, and thus analyse potential mechanisms of tooth loss.

Objectives

This PhD study will adapt an existing MDA-FEA model of a rabbit skull to test and evaluate the current theories describing the cause of dental disease in the domesticated rabbit. In particular, this will entail the creation of further detailed FEA models of the rabbit skull to simulate:

  1. a reduction in alveolar bone density and its effect on tooth movement;
  2. the reduction in dental wear through modelling elongated roots and the effect this has on malocclusion and tooth movement;
  3. the effect of tooth loss on bone density throughout the alveolar ridge, and further potential tooth loss.

This outcome of this modelling will help to identify the most likely cause of dental disease in domesticated rabbits and assist veterinary science in formulating treatments and making future recommendations on their care. For example, the potential modification of a pellet-based diet to alternative tougher foods which lower the risk of dental disease. This will successfully demonstrate the potential of conventional engineering computational methods (MDA and FEA) in behavioural and conservation ecology. In addition, successful application of the biomechanical computational modelling in this manner has use in palaeobiology to study fossil organisms for which the development of FEA models is obviously extremely challenging.

References

[1] Fujita Y et al. 2016 Arch Oral Biol. 72, 200-210

[2] Hansson S & Halldin A. 2012 J Dent Biomech. 3:1758736012456543

[3] Blanke A et al. 2017 Proc R Soc B Biol Sci. 284(1848)

[4] Crossley DA. 1995 J. Vet. Dent. 12, 137– 140.

[5] Harcourt-Brown F. 2009 In Pract. 31, 370– 379.

[6] Jekl V & Redrobe S. J. Small Anim. Pract. 54, 481– 490