I once read a short story where the narrator (I believe) is an alien, or is at least someone who has no idea of any cultural norms or meaning behind anything related to our world. They are observing humans go to the dentist and describe the process of it, going twice a year, waiting in boxed rooms, people wearing weird clothes and describing all the procedures but not described with terminology such that the audience automatically knows that you are at the dentist. You can't really tell what experience they are describing until the end. It talks about how people basically volunteer to be poked and prodded and act as if it's normal and speak in strange languages (when tools are in mouth), things like that.
This sounds like "Body Ritual Among the Nacirema" by Horace Mitchell Miner. Originally published in American Anthropologist (June, 1956), it has been anthologized in A Stress Analysis of a Strapless Evening Gown (Robert A. Baker, ed.) and in Apeman, Spaceman (Leon E. Stover and Harry Harrison, eds.); there is a pdf here. (The same story is probably also the subject of this old question.)
Here is the Wikipedia summary:
In the paper, Miner describes the Nacirema, a little-known tribe living in North America. The way in which he writes about the curious practices that this group performs distances readers from the fact that the North American group described actually corresponds to modern-day Americans of the mid-1950s. The article sometimes serves as a demonstration of a gestalt shift with relation to sociology.
Miner presents the Nacirema as a group living in the territory between the Canadian Cree, the Yaqui and Tarahumare of Mexico, and the Carib and Arawak of the Antilles. The paper describes the typical Western ideal for oral cleanliness, as well as providing an outside view on hospital care and on psychiatry. The Nacirema are described as having a highly developed market economy that has evolved within a rich natural habit.
Miner's article became a popular work, reprinted in many introductory anthropology and sociology textbooks. It is also given as an example of process analysis in The Bedford Reader, a literature textbook. The article itself received the most reprint permission requests of any article in American Anthropologist, but has become part of the public domain.
Some of the popular aspects of Nacirema culture include: Medicine men and women (doctors, psychiatrists, and pharmacists), a charm-box (medicine cabinet), the mouth-rite ritual (brushing teeth), and a cultural hero known as Notgnihsaw (Washington spelled backwards). These ritual practices are prescribed as how man should comport himself in the presence of sacred things. These sacred aspects are the rituals that the Nacirema part take in throughout their lives.
Here is the passage from "Body Ritual Among the Nacirema" about going to the dentist:
In addition to the private mouth-rite, the people seek out a holy-mouth-man once or twice a year. These practitioners have an impressive set of paraphernalia, consisting of a variety of augers, awls, probes, and prods. The use of these objects in the exorcism of the evils of the mouth involves almost unbelievable ritual torture of the client. The holy-mouth-man opens the client's mouth and using the above-mentioned tools, enlarges any holes which decay may have created in the teeth. Magical materials are put into these holes. If there are no naturally occurring holes in the teeth, large sections of one or more teeth are gouged out so that the supernatural substance can be applied. In the client's view, the purpose of these ministrations is to arrest decay and to draw friends. The extremely sacred and traditional character of the rite is evident in the fact that the natives return to the holy-mouth-men year after year, despite the fact that their teeth continue to decay.