- Dental Drill (preferred) or Dremel™ tool with low speed (5000 rpm). If using the Dremel™ tool, it is necessary to get parts for the chuck so that it can hold dental burrs, which have a much smaller diameter than typical Dremel bits. These adaptors are available as a kit from Dremel.
- Carbide dental burrs of various sizes and shapes that will fit in the drill you’re using. These are usually the ‘HP’ style. I have on hand: HP 2 (round), HP ½ (small round), HP 35 (inverted cone), HP 702 (cylinder), HP 699 (small cylinder).
- Weigh paper and 1.5–1.7mL microcentrifuge vials to collect the samples
- A binocular microscope can be helpful.
- A Sharpie pen, for labeling vials
- A notebook, that includes a sketch of the tooth I’m about to sample, so that I can label the sketch as I sample with the sample numbers. Alternatively, one can photograph the tooth and put the photo in the notebook.
PREPARING THE TOOTH:
It is essential that tooth enamel specimens be free of any cementum on the outside and/or dentine on the inside, as these have their own unique isotopic signatures. Additionally, any sediment stuck to the tooth must be removed. I usually use older, duller burrs for this. Alternatively, I use the various larger burrs that came with the Dremel tool.
Each analysis requires about 2mg of powdered tooth enamel. The goal is to collect 2 or 3 times that much, so that we can get replicate analyses.
Shown above is one of the regular sample vials we use. The blue line drawn at the bottom shows the ideal level to which to fill the vial to insure adequate material for analysis. In practice, this is seldom possible. To fill the vial halfway to that line is excellent.
Bulk analysis provides an average isotopic value for the entire tooth, which is presumed to represent the average delta values of food and water consumed by the animal. Such a sample is collected by drilling a line of powder off of the tooth along its length, from root to crown, perpendicular to any obvious perikymata (growth lines), if possible. Better, yet, if the growth rate of the tooth is already known, drill only the length of the tooth that represents one year. Use caution to not drill into the dentine.
Serial analysis allows us to create a time-series of isotopic change during the life of the animal during the time that its tooth was mineralizing. These samples are collected by drilling at regular intervals along the length (growth-axis) of the tooth (so perpendicular to the bulk analysis line). Typically, I sample every 2.5 to 3 mm. If perikymata are visible, sample lines should trace them.
In the rhino tooth pictured above, the bulk sample line is nearly vertical, whereas the sample sites for serial analysis are approximately perpendicular to it. Note that the serial samples are not parallel to each other. This is because I was tracing visible perikymata.
The next photo shows a close-up of sampling of a Trachytherus tooth. Again, see how the serial lines parallel perikymata and the bulk sample line is perpendicular.
Though it is not necessary to collect a bulk sample from each tooth, I typically do 1) for reference as a baseline, and 2) as a test sample to detect diagenetic alteration or low carbonate in the sample.
SEND US YOUR SAMPLES:
The analysis of bioapatites from tooth enamel is a specialty at SIREAL. Send us your samples and we will provide the results that you want.
THE END RESULT:
The goal is to be able to create images such as this to better understand the behavior in live of these long-extinct organisms.