SEM Survey of Human, Shark, and Rodent Teeth

James Yuzawa
University of Rochester, Department of Computer Science
Rochester, NY 14627 -

Human Teeth


These samples came from the author's wisdom tooth extraction in May 2013. Samples were air-dried after the extraction and have been placed in an airtight bag since that time. The wisdom teeth were not impacted or damaged during the extraction, but contained cavities and tooth decay.

Enamel

Figure 1: SE2 detector. The stratified layers of the enamel are visible in this view of the edge of the polished cross section and the surface of the enamel. These are the same layers as visible in Figures 3 and 4. This section of enamel surface is closer to the gum line and not near the crown. The crown is to the right. Less wear has occurred, as the layers are visible from the surface. Using the scale in ImageJ, the layers are between 8 to 15 μm thick.
Figure 2: BSE detector. Tooth decay at bottom surface valley visible in cross section. Crown of tooth is towards the right. Tooth decay has eaten away at a weak spot in the enamel. The BSE detector provides good contrast between the high atomic number of the calcium mineral in the enamel (bright) and the low atomic number of the biological debris accumulated in the cavity (dark). Using the scale in ImageJ, the cavity before it starts to narrow is about 150 μm wide.

Figure 3: False-color image of tool mark damage to enamel surface incurred during extraction process. This damage was half way between the gum line and the top of the crown. The undamaged surface of the enamel is generally smooth and somewhat worn. The damaged area has visible layers of enamel. Red background image from SE2 detector. Blue highlights from the InLens detector.
Figure 4: SE2 detector. Inset of layers from Figure 3. Crystal microstructure is aligned perpendicular to the stratification.

Dentin

Figure 5: BSE Detector. A cross sectional view of the dentin tubules.
Figure 6: Image analysis done in ImageJ on part of Figure 5.

The ImageJ data found 87 dentin tubules. The average area of a hole was 1.773 μm2 with a standard deviation of 0.580. The average Feret diameter of a hole was 2.438 μm with a standard deviation of 0.524.

Composition

Figure 7: The EDS results for human tooth. Calcium, phosphorus, carbon, and oxygen are all present as expected. There is a small peak identified as magnesium. This may be possible, or it could be a misidentified peak.