New book chapter: challenges of studying dental cementum in deciduous teeth

A new book is out from Cambridge University Press, Dental Cementum in Anthropology, edited by Stephan Naji, William Rendu, and Lionel Gourichon. Although human teeth are not my area of expertise, I ended up coauthoring the twelfth chapter of the book, “Tooth cementum annulations method for determining age at death using modern deciduous human teeth: challenges and lessons learned”. Of all of my publications, this one is the hardest to write about. In part that’s because our original project failed, for various reasons that we document in the chapter, and the final publication is mostly a catalog of things not to do. But more importantly, it’s because Vicki Wedel, the lead author and my spouse of nearly 25 years, passed away unexpectedly last May.

I haven’t written here about Vicki’s passing because I’ve never been sure what to say. Other than two memorial ceremonies last year and a handful of Facebook posts in the month or so after, I haven’t talked about it in public at all. I hoped that I’d know what to say by the time that the book chapter was published, but here we are, and words still feel like grotesquely inadequate tools with which to sketch the horrifying suddenness and totality of the loss. I thought that time would dull the edge of grief, but it doesn’t hurt any less 10 months after, it just hurts less often. I haven’t become numb to any of the obvious triggers, I’ve just gotten good at side-stepping them. All that means is that it’s a cruel surprise when, at unpredictable and frequent intervals, grief sidles up and slips a dagger between my ribs.

Vicki and I met in high school, when we were both 16. We dated for five years, and got married when we were 21. Professionally, she was always ahead of me: she earned her bachelor’s degree first, and her master’s, and her doctorate; presented at a conference before I did, and traveled internationally, and published a journal article, and a book; got a tenure-track job first, and mentored a graduate student first. Far from being resentful, I was emboldened by her successes in every one of those arenas, and grateful for her example and her encouragement. She passed on May 15, 2021, three weeks short of our 25th wedding anniversary, and five months before our 30th anniversary as a couple. 

As a forensic anthropologist, Vicki was frequently asked how she wanted to die. Her standard answer was that she wanted to go quietly in her sleep, at home, in clean clothes; to be found almost immediately by family; and to be conveyed rapidly to a funeral home. The timing was nothing that any of us had imagined or hoped for, but in the actual event she got everything she had wanted, and that is no small comfort. She went out at the apex of her personal and professional development, with no decline and no suffering, which is something that most of us will not get.

Vicki and I daydreamed of coauthoring papers together, and we always figured we’d get around to it eventually, although we both expected that any joint publications would be on dinosaur bone histology (she was the hard-tissue histologist, I would have supplied the dinosaurs). In the actual event, she was working on a project to determine age at death of human adolescents by counting cementum bands in deciduous teeth (‘baby teeth’), and she hit a wall transmuting the results into a discussion. I volunteered to help with that, and pretty soon I’d gotten sucked into being genuinely interested in the problem that she was up against.

The development and loss of deciduous teeth restrict cementochronology to the interval in which the root apex is complete. (Wedel et al. 2022: fig. 12.1)

I’ve written here before about the method of counting dental cementum bands, which are laid down annually, to determine age and season at death (this post). Vicki wanted to know if that method, which she’d used successfully on permanent teeth, would work on deciduous teeth. That turns out to be a surprisingly tricky problem, for several reasons. One of the foremost reasons is sampling. Human deciduous teeth have three fates:

1. Most deciduous teeth complete development normally, which means that the roots are resorbed and the teeth fall out. The resorption of the root destroys the cementum bands, so there’s nothing to study. 
2. Some deciduous teeth are retained in the jaw instead of being resorbed, and usually these retained teeth are pulled by dentists when it becomes clear that they are not going to fall out on their own. Practically by definition, these retained teeth do not represent the typical course of development — not great when you’re trying to validate a method on ‘normal’ samples.
3. Tragically, some deciduous teeth stop developing because they belong to people who die as children or adolescents. For reasons of privacy and respect for grieving loved ones these teeth are rarely used in research, and they don’t represent a controlled sample anyway. The remains of children from archaeological sites have the additional problem that there’s often no good independent line of evidence for age at death, which makes them useless for a validation study.

As we put it in the chapter, “normal, healthy deciduous teeth are unlikely to be extracted, and extracted deciduous teeth are therefore unlikely to be normal”.

We did have some deciduous teeth, culled from a sample of more than 1000 teeth collected by dentists at Creighton University in Omaha, Nebraska, and sent to Vicki by her collaborator, Ken Hermsen, who coauthored the chapter with us. Unfortunately, the methods that had worked so well for Vicki on adult teeth broke down when applied to deciduous teeth, in multiple ways that left us scratching our heads and chasing phantoms. I won’t go through the whole litany of failures here — it’s too depressing, and I already coauthored a whole chapter about it. Suffice it to say that peer review worked in this case, when an anonymous reviewer caught and called attention to our errors. We were ready to shelve the chapter, but lead editor Stephan Naji encouraged us to not let all our effort go to waste. About all we could do in the remaining time was catalog the stuff we’d done wrong, so…that’s the paper. It’s very much an ‘eating our vegetables’ affair, but hopefully it will steer future researchers away from the reefs that our original study foundered on. I’m grateful to Stephan for the opportunity to publish — not least because it would be my last chance to collaborate with my partner — and for the lovely words about Vicki that he wrote in the dedication of the book.

It is supremely bittersweet that Vicki and I finally got to coauthor something, only for it to come out when she’s no longer around to see it. It also hit me with unexpected force that with the publication of this book, Vicki’s scientific legacy is almost complete (there is one more collaboration, with folks other than me, that will hopefully still get published). Like many things related to her passing, those thoughts don’t point anywhere. There’s no neat resolution, no bow to tie things up with. Sometimes things just stop, awkwardly and before their time, and there’s nothing to do but go on.

Reference

Wedel†, V., Hermsen, K., & Wedel, M. 2022. Tooth cementum annulations method for determining age at death using modern deciduous human teeth: challenges and lessons learned. pp. 215-225 in Naji, S., Rendu, W., and Gourichon, L. (eds.), Dental Cementum in Anthropology. Cambridge University Press, Cambridge, UK. doi:10.1017/9781108569507.014