Functional consequences of tooth design: effects of blade shape on energetics of cutting

Abstract

SUMMARYDental structures capture, retain and fragment food for ingestion. Gnathostome dentition should be viewed in the context of the preyʼs material properties. Animal muscle and skin are mechanically tough materials that resist fragmentation unless energy is continually supplied directly to the tip of the fracture by some device such as a blade edge. Despite the variety of bladed tooth morphologies in gnathostomes, few studies have experimentally examined the effects of different blade designs on cutting efficiency. We tested the effects of blades with and without contained notches and in a ʻfangʼ configuration on the force and energy required to fracture raw, unprocessed biological tissues (fish and shrimp) using a double guillotine device. Blade design strongly affects the work required to fragment biological tissues. A notched blade reduced the work to fracture of tissues tested by up to 600 J m -2 (50% reduction). The specific angle of the notch had a significant effect, with acute angles more effectively reducing work to fracture. A bladed triangle matched to a notch reduced work to fracture more than a notch-straight blade pair. Strain patterns seen while cutting photoelastic gelatin indicate that the reduction in work to fracture with triangular and notched blades arises from a combination of ʻtrapping abilityʼ and blade approach angle causing the material to fracture at lower overall strain levels. These results show that the notched blade designs found in a wide variety of vertebrate dentitions reduce the energy expenditure (and presumably handling time) when cutting tough prey materials like animal flesh.

Finite element modeling of occlusal variation in durophagous tooth systems

“…Cutting teeth, like shark teeth or the carnivore carnassials, are often notched. These notches reduce the work needed to process malleable prey (Anderson and LaBarbera, 2008;Anderson, 2009;Anderson and Rayfield, 2012) though they can also concentrate stresses in the tooth, thus making tooth failure more likely (Whitenack et al, 2011).…”

Virtual experiments, physical validation: dental morphology at the intersection of experiment and theory

“…The biological system we are focusing on is the processing of soft foods by teeth, as previously explored experimentally [14,15]. The evolution of food processing, the ability to physically break food down into ingestible pieces, is an important development in the history of vertebrate life, allowing animals to eat larger food items, including prey larger than their mouth opening.…”

“…Various qualitative descriptors (tearing, crushing and cutting) have often been used to denote different methods of food processing, but these descriptions do not lend themselves to precise comparative analyses. Recent experimental and theoretical work on fracture mechanics in foodstuffs has begun to quantify the relationship between the material properties of food items (such as brittleness and toughness) and the morphologies of the dental tools that are most efficient at processing the food [14,16,17].…”

“…Less focus has been given to the cutting of tough and/or extensible foods (animal tissues or fibrous plant materials) with bladed structures [14][15][16][20][21][22] (for a review, see [23]). There is a significant volume of literature concerning FE modelling of cutting in industry [24] including studies of the reaction of soft biological tissues to cutting dynamics [25,26] and measures of sharpness in scalpel blades [27,28].…”

“…Recent experimental work on the biomechanics of cutting biological tissues has used work to fracture, a measure of energy, as the metric to determine feeding efficiency [14,15]. Energy is the basic currency of biology; however, not all energy taken in during feeding is gained by the animal.…”