A visit to the dentist offers a reminder of good engineering
Recently, while visiting a new dental office to have my teeth cleaned, I was reminded of how much overlap there is in the technical interests of dentists and engineers, especially structural engineers.
When the dentist asked me what my occupation was, I told him that I taught engineering. His response was that dentistry was a kind of oral engineering. He also offered that his son almost studied engineering in college but in the end decided he wanted to be a dentist. One of my former students, who did a term paper on Charleston bridges and eventually wrote a book on the subject, went to dental school after practicing engineering for several years. Unfortunately, I do not know any dentists who left their practice to study engineering.
Regardless of their professional roots, dentists and engineers alike have to know a good deal about mechanics, materials, and maintenance. They have to understand the forces at play on a bridge, whether it be between two soft riverbanks or between two sound teeth. They have to understand the holding strength of concrete and alloys or of amalgams and epoxies. And they have to understand the importance of limiting deterioration, whether it be in the form of painting steel to prevent rust or of prophylactic procedures to control dental caries.
Perhaps it is with regard to inspection that dentistry has the most to offer engineering, in the sense that it can make evident even to the nontechnical layperson how important regular and thorough dental examinations are to ensure the health of our oral infrastructure. Everyone knows, perhaps by having learned the hard way, that neglecting one’s teeth can surely lead to their deteriorating beyond repair.
Teeth are subject to repeated thermal stresses induced by hot and cold liquids and to repeated impacts due to the nature of eating and chewing food, forces sometimes supplemented by the grinding that takes place while some of us sleep. Such actions can cause hairline cracks to start and grow over time, thus weakening a tooth and setting it up for breaking when it chomps down unexpectedly upon a small piece of bone in a hamburger or an especially hard nut in a candy bar. This is the process of fatigue-crack growth and fracture, something engineers have to take into account when designing a bridge over which traffic runs that in time chews up the pavement and eats up the structure.
In a routine dental checkup, the structures in our mouth are gone over with picks and probes to detect the small irregularities that can be harbingers of worse to come, to find the cracks that can lead to spontaneous fractures, to locate and fill cavities that, left unchecked, can threaten an entire tooth. Every year or so, x-rays are taken, and suspicious areas are compared with benchmark images from an earlier visit.
Given that we all have—or at least once had—teeth, we know the importance of regular dental examinations and prophylactic care. It is the same with the concrete and steel bridges that carry our highways over rivers and other obstacles. If they are not given an analogously regular and careful inspection and appropriate repairs, then we risk their failing under a heavy truck during evening rush hour, just as we risk a cracked tooth breaking on a too-hard filbert in a box of holiday chocolates.
Going to the dentist can get us thinking about a lot more than our teeth. The experience can remind us of knowledge and lessons about good engineering practice that are forgotten at our peril.
Henry Petroski is the Aleksandar S. Vesic Professor of Civil Engineering and a professor of history at Duke University. His latest book is The Toothpick: Technology and Culture.