The 89th Annual Meeting of the American Association of Physical Anthropologists (2020)

How many tooth hops does it take to accurately measure saw blade teeth-per-inch in bone?


Anthropology Department, University of Pittsburgh

April 16, 2020 , Platinum Ballroom Add to calendar

Forensic anthropological research has demonstrated that tooth hop (TH) is a valuable measurement from saw-cut bones as it can be used to indicate the number of teeth-per-inch (TPI) of a saw. But how many hops in a chain do you need? It is hypothesized that more hops in a chain would increase accuracy when estimating blade TPI; however, the amount of bone impacts the presence of long chains. This study used one unused hand saw to cut seven pig humeri. Individual hops were measured and sorted into groups based on number of hops in their respective chains, single (n = 196), double (n = 141), or three-plus (n = 57). Random measurements were also collected between adjacent saw teeth for comparison (n = 49). ANOVA, comparing the effect of chain size on TH mean, shows no significant differences among groups measured from bone (p>0.05). However, when blade measurements were included, means were significantly different (p<0.05). Pairwise ANOVA results show that blade mean is significantly different from single and double groups but is not significantly different from the three-plus group. Thus, three or more hops in a chain did more accurately reflect blade TPI. However, when comparing standard deviations between blade and bone measurements, the analyst would have to report a confidence interval much wider than that of the actual blade to account for all variation introduced when cutting bone tissue. Ultimately, one-hop or two-hop chains should not be discarded as chains with three or more are rarer to find.

Slides/Poster (pdf)