Predicting failure in mammalian enamel

Lawn, Brian R.; Lee, James Jin-Wu; Constantino, Paul J.; Lucas, Peter W.

doi:10.1016/j.jmbbm.2008.05.007

Cited by 64 publications

(56 citation statements)

References 52 publications

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“…However, the fracture and removal of small rsif.royalsocietypublishing.org J R Soc Interface 10: 20120923 enamel chips were clear in our experiments (figures 1f and 2c inset). In this respect, enamel may resemble modern 'tough' ceramics that permit micro-cracking in a confined region under an indenter because, somewhat ironically, this inhibits the possibility of any catastrophic fracture [39]. Cone cracks, typical of scratching damage on homogeneous fine-grained ceramics [40], have been suggested as explanations for such fractures in enamel [41].…”

Section: Discussionmentioning

confidence: 99%

Mechanisms and causes of wear in tooth enamel: implications for hominin diets

Lucas

Omar

Al‐Fadhalah

et al. 2013

J. R. Soc. Interface.

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243

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The wear of teeth is a major factor limiting mammalian lifespans in the wild. One method of describing worn surfaces, dental microwear texture analysis, has proved powerful for reconstructing the diets of extinct vertebrates, but has yielded unexpected results in early hominins. In particular, although australopiths exhibit derived craniodental features interpreted as adaptations for eating hard foods, most do not exhibit microwear signals indicative of this diet. However, no experiments have yet demonstrated the fundamental mechanisms and causes of this wear. Here, we report nanowear experiments where individual dust particles, phytoliths and enamel chips were slid across a flat enamel surface. Microwear features produced were influenced strongly by interacting mechanical properties and particle geometry. Quartz dust was a rigid abrasive, capable of fracturing and removing enamel pieces. By contrast, phytoliths and enamel chips deformed during sliding, forming U-shaped grooves or flat troughs in enamel, without tissue loss. Other plant tissues seem too soft to mark enamel, acting as particle transporters. We conclude that dust has overwhelming importance as a wear agent and that dietary signals preserved in dental microwear are indirect. Nanowear studies should resolve controversies over adaptive trends in mammals like enamel thickening or hypsodonty that delay functional dental loss.

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Section: Discussionmentioning

confidence: 99%

Mechanisms and causes of wear in tooth enamel: implications for hominin diets

Lucas

Omar

Al‐Fadhalah

et al. 2013

J. R. Soc. Interface.

Self Cite

243

303

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“…Such an understanding is vital to paleontologists and paleoanthropologists because teeth constitute a large portion of the fossil record (13). Arguments have been made asserting that such critical elements as enamel thickness, and to some extent tooth size, act as optimal organizations to frustrate tooth failure in relation to diet (8,13,17,22,(37)(38)(39). However, it would seem that enamel microstructure, and especially tufts, are also important factors.…”

Section: Discussionmentioning

confidence: 99%

“…Recent studies are revealing how the enamel of bunodont teeth fractures under simulated biting and are providing explicit relations for predicting critical forces for each fracture mode in terms of material properties and tooth/food contact geometry (8,17). Enamel thickness and cusp size emerge as key dimensions in these models.…”

mentioning

confidence: 99%

Remarkable resilience of teeth

Chai

Lee

Constantino

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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218

146

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Tooth enamel is inherently weak, with fracture toughness comparable with glass, yet it is remarkably resilient, surviving millions of functional contacts over a lifetime. We propose a microstructural mechanism of damage resistance, based on observations from ex situ loading of human and sea otter molars (teeth with strikingly similar structural features). Section views of the enamel implicate tufts, hypomineralized crack-like defects at the enamel-dentin junction, as primary fracture sources. We report a stabilization in the evolution of these defects, by ''stress shielding'' from neighbors, by inhibition of ensuing crack extension from prism interweaving (decussation), and by self-healing. These factors, coupled with the capacity of the tooth configuration to limit the generation of tensile stresses in largely compressive biting, explain how teeth may absorb considerable damage over time without catastrophic failure, an outcome with strong implications concerning the adaptation of animal species to diet. dental enamel ͉ evolutionary biology ͉ fracture ͉ microstructure ͉ tufts

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“…Studies have been devoted to the validation of FE models using both experimental and sensitivity analyses [8 -10]. A few recent FEA studies have begun to eschew the use of complex models based on scan data altogether in favour of basic 'hypothetical' models, which represent specific aspects of morphology [11][12][13]. These 'hypothetical' models allow precise shifts in morphological structure to be tested for functional consequences, while holding other morphological variables that are not of interest constant.…”

Section: Introductionmentioning

confidence: 99%

“…The majority of experimental work and almost all theoretical work performed on dental shape and food processing has focused on the cracking of hard or brittle foods such as nuts or seeds with blunt tools (see [11,12,18]; for a review, see [19]). 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]).…”

Section: Introductionmentioning

confidence: 99%

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

Anderson

Rayfield

2012

J. R. Soc. Interface.

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Computational models such as finite-element analysis offer biologists a means of exploring the structural mechanics of biological systems that cannot be directly observed. Validated against experimental data, a model can be manipulated to perform virtual experiments, testing variables that are hard to control in physical experiments. The relationship between tooth form and the ability to break down prey is key to understanding the evolution of dentition. Recent experimental work has quantified how tooth shape promotes fracture in biological materials. We present a validated finite-element model derived from physical compression experiments. The model shows close agreement with strain patterns observed in photoelastic test materials and reaction forces measured during these experiments. We use the model to measure strain energy within the test material when different tooth shapes are used. Results show that notched blades deform materials for less strain energy cost than straight blades, giving insights into the energetic relationship between tooth form and prey materials. We identify a hypothetical 'optimal' blade angle that minimizes strain energy costs and test alternative prey materials via virtual experiments. Using experimental data and computational models offers an integrative approach to understand the mechanics of tooth morphology.

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Predicting failure in mammalian enamel

Cited by 64 publications

References 52 publications

Mechanisms and causes of wear in tooth enamel: implications for hominin diets

Mechanisms and causes of wear in tooth enamel: implications for hominin diets

Remarkable resilience of teeth

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

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