New discoveries have found exceptions to Mendel's basic laws, but none of Mendel's things have been proven to be flat-out wrong. Hail to the Father of Genetics ! The name is ma-ma-ma-ma-ma-Mendel.
Dental crowns should last on average from 10 to 20 years. Crowns are still subject to fracture and cavities, so it is important to take extra care in brushing and flossing around crowned teeth to prevent them from needing replacement too often.
The middle teeth are usually the first to go (at 6 to 7 years), followed by the ones on either side (at 7 to 8 years). The molars can be lost any time after that but will likely be gone between 9 and 12 years. 12 years: Your child has a set of 28 permanent, adult teeth. (Her four wisdom teeth will come in when she's 17 to 21 years old.)