Comparative Biology: Using Micro-CT to Examine Shark Teeth
In honor of SharkWeek, we used the power of micro-CT to compare and contrast a modern day shark tooth and a fossilized megalodon tooth. Teeth are important in both modern and fossil studies of sharks and other fish, providing information such as feeding habits, estimations of age, and phylogenetic relationships. Micro-CT is a non-invasive, nondestructive technique that provides 3D studies of mineralized tissues and data on their physical properties. Similarly, micro-CT also has found use in paleontology for the examination of fossils, and has facilitated important developments in paleoanthropology. 1
For this month’s demonstration, we chose to utilize our Bruker SkyScan 1173 system because of its high X-ray energy, allowing better transmission through dense samples such as the fossilized megalodon tooth examined in this study. Megalodon, meaning “big tooth,” are prehistoric ancestors of today’s sharks and went extinct about 2.5 million years ago. These giant fish grew to an estimated length of over 50 feet and hunted large prey such as whales for sustenance.2
Figure 1: Cross-sectional planar views of a shark tooth (top) and fossilized megalodon tooth halve (bottom)Micro-CT Scan of Shark Teeth
After reconstructing the X-ray attenuation data for the teeth, we were able to isolate our view on specific regions of interest. When examining the teeth in two dimensions, we are able to easily visually note some similarities in construction and shape between the two samples (Figure 1). Both the samples show a clear delineation between the thin enamel layer on the cutting edge of each tooth and the dentin, which comprises the remainder of the teeth for these samples. The soft pulp is not readily apparent due to the fossilization process but it is possible that some of the voids observed in the dentin may indicate the location of areas where pulp would have been observed.
Taking a look from a side view in a three dimensional rendering, we can inspect the interior of each sample for the different components, such as the enamel and dentin (Figure 2). Differences in mineral content in these tooth components allow us to visualize the location of each component within
Taking a look from a side view in a three dimensional rendering, we can inspect the interior of each sample for the different components, such as the enamel and dentin (Figure 2). Differences in mineral content in these tooth components allow us to visualize the location of each component within the samples. The enamel shows up as the brighter white area at the top edge of both teeth. It’s fascinating that even after the fossilization process and many million years we can see that the megalodon tooth shares so many similar characteristics with the modern day shark tooth.
Conclusion
Micro-CT excels as a tool to nondestructively examine fossils and dental samples through the generation of a detailed 3D model that can be reoriented in any direction for examination. We hope you found this image of the month interesting. If you have an image of the month sample that you would like us to scan, please contact us by calling Seth Hogg at 610-366-7103 or e-mailing seth.hogg@microphotonics.com.
Scan Specifications
| Sample | Shark Tooth | Megalodan Tooth |
| Voltage (kV) | 100 | 130 |
| Current (µA) | 80 | 61 |
| Filter | 1.0 mm Aluminum | 0.25 mm Brass |
| Pixel Size (µm) | 17 | 50 |
| Rotation Step | 0.2 | 0.4 |
| Scan Time (HH:MM:SS) | 02:01:40 | 01:49:45 |
All scans completed on our large capacity SkyScan 1173 micro-CT system at the Micro Photonics Imaging Laboratory in Allentown, PA. Reconstructions were completed using NRecon and visualization of 2D and 3D results were completed using DataViewer and CTVox.
Works Cited
