How come Chinese people have such awful teeth?
Chinese people in China have awful teeth quite simply because dentistry in China is non existent in many areas of China still. Even people with fairly good jobs even in places like HK and Taipei can't afford to go to the dentist because it is very very expensive. (these places have semi socialised health care) TCG's ex GF needed some serious dental work when TCG first met her and she had to fly to HK to get it done as Taipei dentists were and are extortionate.
When you do go to a dentist they (or in my experience) do not perform any preventative care, they will merely check your teeth and only wait for something to go wrong. While my UK dentist will tell me to do this and that and even give me freebies like micro between the teeth brushes to clean my teeth.
While in mainland China with many poor people they simply don't go to dentists nor brush their teeth. EVEN city slickers only 10% clean their teeth regularly and properly as cited here.
There is also an issue of traditional, in China you get die hards who believe well its worked for the last 5000 years why change? In regards to Chinese medicine or chopsticks (chopsticks increase the chance of bone problems I forget which one). In China the traditional method in which to clean your teeth practiced by none other than Mao was this. You drink some green tea with lots of leaves in it. You then chew the leaves a bit spit out the green leaves and wipe with a towel.... Or use twigs (I'm not sure what the twig method happens to be btw). And hey twigs and green tea are virtually free so why do I need to buy a tooth brush? etc etc thinking
Thus in a nut shell it is about cost (dentists are expensive in the UK even with socialised health care), availability and thus people don't go to the dentist.