The effects of wear on the morphology and puncture force of shark teeth

Sharks continuously replace their teeth throughout their lives, replacing an entire row of teeth every one to 5 weeks. It has been hypothesized that this is due to tooth wear, rather than tooth breakage. However, little is known about how quickly teeth wear and what affect this wear has on tooth puncture performance. Unworn teeth from five shark species, bull shark Carcharhinus leucas, blacktip shark C. limbatus, sandbar shark C. plumbeus, shortfin mako Isurus oxyrinchus and great hammerhead Sphyrna mokarran, were subjected to 400 puncture tests each on teleost prey. Wear and puncture forces were measured throughout the 400 trials. Puncture forces differ across species for both the first puncture and last puncture in the 400-puncture sequence. However, significant increases in puncture force occur after only 10 punctures. Similarly, significant tooth wear during puncture occurs quickly. Tooth sharpness significantly decreases after 20 punctures, and serrations on all mesial and distal regions of the tooth show significant wear after only 10 punctures. While increases in tooth wear and puncture force are correlated, the amount of tooth wear accrued during the experiment varies with both the region of the tooth and the species for serrated teeth. This study represents an initial step in exploring how tooth wear affects performance in shark teeth. There are several areas to explore in future studies, including mimicking lateral head-shaking behaviour, testing different prey items and testing different areas of the same prey item.