Received: 4 February 2019
Accepted: 31 May 2019
First Online: 17 June 2019
Ethics approval and consent to participate
: The study was approved by the Regional Ethical Review Board in Stockholm, Sweden (no. 2014/874–31). According to Swedish Law there was no need for individual consent to participate.
: FL is an employee and AC, RL and MA are former employees of the National Board of Health and Welfare, the holder of the Dental Health Register. R.L. is employed at the Swedish Medical Products Agency, SE-751 03 Uppsala, Sweden. The views expressed in this paper do not necessarily represent the views of the Government agencies.