By both Art. 9(1) AVG and the Personal Data Authority, a biometric personal data is described as a unique body characteristic. Those unique body characteristics could be used by companies or organizations to identify and authenticate individuals. This is prohibited. In addition, the AVG defines biometric personal data as "data resulting from a specific technical processing involving the physical, physiological or behavioral characteristics of a natural person on the basis of which unambiguous identification of that natural person is possible or confirmed, such as facial images or fingerprint data."
Now teeth are 1) a physical characteristic of a natural person, 2) from the dental impression a person can be identified, and 3) the impression is a piece of data that came as a result of a specific technical processing.
A tooth is a physical feature, it is a material feature of your body.
People can be identified from a dental impression, the more dental data (think x-rays and possibly a plaster cast of the teeth and information about any surgeries), the easier it is.
Taking a dental impression is specific technical processing.
In answer to the question, I would argue that a dental impression certainly qualifies as biometric personal data.
