Are there any good sources of information about the effect coffee has on the health of teeth? These could be scientific sources and material for readers who are not medical experts.
Since this site is about coffee, not dentistry, I will answer from a Coffee perspective. I can think of three issues with coffee that can affect one's teeth:
Acidity. Brewed coffee has a pH around 5. That means it is an acidic beverage, but not as acidic Coca Cola which has a pH as low as 2.6 or many fruits which have pH levels ranging from 2.3 to 4.2. It's about the same as black tea which has pH levels ranging from 4.9 to 5.5. Coffee acidity may affect dental health because acidic foods can erode the teeth. Coffee is a bit on the border with sources saying tooth demineralization may start at a pH of 5.5 (and lower pH means increased acidity).
Tannins. Coffee contains tannins, which are a class of chemical compounds. According to healthline.com:
Tannins cause color compounds to stick to your teeth. When these compounds stick, they can leave an unwanted yellow hue behind. It only takes one cup of coffee a day to cause stained teeth.
Sugar. Of course not all coffee contains a lot of sugar, but sugar is commonly added to coffee. Sugar affects dental hygiene because bacteria in the mouth feed on the sugars (and in turn they produce acids that may damage the teeth). As the WHO writes:
The majority of dental caries occurs in adults because the disease is cumulative. There is a clear dose-response relationship between sugars consumption and dental caries.
I found this from a dentist
Essentially reinforcing what @JJJ has said in their answer (Acidity, Tannins and sugars), along with a commentary about how coffee dry's the mouth, reduces saliva, along with sulphur compounds, can cause bad breath (halitosis)