Exploring the Use of SEM-EDS Analysis to Measure the Distribution of Major, Minor, and Trace Elements in Bottlenose Dolphin (Tursiops truncatus) Teeth

Dolphin teeth contain enamel, dentin, and cementum. In dentin, growth layer groups (GLGs), deposited at incremental rates (e.g., annually), are used for aging. Major, minor, and trace elements are incorporated within teeth; their distribution within teeth varies, reflecting tooth function and temporal changes in an individual's exposure. This study used a scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) to determine the distribution of major (e.g., Ca, P), minor (e.g., Cl, Mg, Na), and trace elements (e.g., Cd, Hg, Pb, Zn) in teeth from 12 bottlenose dolphins (Tursiops truncatus). The objective was to compare elemental distributions between enamel and dentin and across GLGs. Across all dolphins and point analyses, the following elements were detected in descending weight percentage (wt %; mean +/- SE): O (40.8 +/- 0.236), Ca (24.3 +/- 0.182), C (14.3 +/- 0.409), P (14.0 +/- 0.095), Al (4.28 +/- 0.295), Mg (1.89 +/- 0.047), Na (0.666 +/- 0.008), Cl (0.083 +/- 0.003). Chlorine and Mg differed between enamel and dentin; Mg increased from the enamel towards the dentin while Cl decreased. The wt % of elements did not vary significantly across the approximate location of the GLGs. Except for Al, which may be due to backscatter from the SEM stub, we did not detect trace elements. Other trace elements, if present, are below the detection limit. Technologies with lower detection limits (e.g., laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS)) would be required to confirm the presence and distribution of trace elements in bottlenose dolphin teeth.

Automated summary

Dolphin teeth contain enamel, dentin, and cementum, with various major, minor, and trace elements distributed differently within teeth. Analyzing teeth from bottlenose dolphins, researchers found distinct differences in the distribution of magnesium and chlorine between enamel and dentin, suggesting the need for technologies with lower detection limits to confirm the presence and distribution of trace elements.