CHES Graduate Affiliate Fred Foster passed his doctoral dissertation defense on June 15, 2022. Fred’s dissertation, titled “Adaptations in the Structure, Composition, and Properties of Primate Tooth Enamel” applied tools from material science engineering to address problems in the dental ecology humans and primates with diets that include very hard and stiff foods. His projectinvolved extensive laboratory work in the Department of Material Science Engineering at Rutgers, using nanoindentation, scanning electron microscopy, electron microprobe analysis, among other advanced analytic tools to probe the nature of tooth enamel in a number of different species. His results helped to illustrate how our teeth, and the teeth of our closest primate relatives, work to break down the hard and tough foods that we eat without fracturing or wearing out during our lifetime. Fred’s research reframed and highlighted an important concept, that not all tooth enamel is created equal. Deep within our teeth the stiffness of enamel is relaxed to restrain the propagation of fractures that would otherwise limit our dental competence, while at the tooth surface enamel is at its hardest and stiffest to resist wear and chipping. Fred showed that these properties are ubiquitous across primate species, but with variation that reflects adaptations to different diets. Of special interest is Fred’s finding that the mechanical properties of teeth are related to the molecular structure of the hydroxyapatite mineral building blocks of teeth themselves. Within the enamel layer, where lower stiffness is desirable, the hydroxyapatite crystal lattice is spiked with magnesium and sodium that reduces stiffness. Towards the enamel surface, where high hardness is extremely beneficial, these impurities are greatly reduced while mineral density increases, providing teeth with the strength that they need to last.
Fred’s dissertation committee was chaired by Rob Scott (pictured with Fred, above), and included Erin Vogel and Susan Cachel from the Department of Anthropology, along with external committee members Adrian Mann from the Department of Material Science Engineering at Rutgers and Paul Constantino from the Department of Biology at St. Michael’s College. Below is a picture that shows the enamel microstructure in the molar tooth of a common marmoset, one of the many fantastic images that Fred managed to capture. Fred has just accepted a postdoctoral position in the lab of Joan Richtsmeier in the Department of Anthropology at Penn State University, where he will explore the genesis and dysgenesis of Meckel’s cartilage in the developing jaw using mice models. Good luck, Fred!
Michelle Night Pipe
Michelle Night Pipe successfully defended her dissertation, Reducing Anti-Native Bias in South Dakota: Indigenous Acts of Remembrance and Flexible Coalitional Psychology on November 8, 2022. Michelle's dissertation committee was chaired by Lee Cronk (pictured above with Michelle). Description and update to follow.