[1] Carl von Ossietzky Univ Oldenburg, Dept Hlth Serv Res, D-26129 Oldenburg, Germany
[2] Univ Bremen, Dept Hlth Long Term Care & Pens, SOCIUM Res Ctr Inequal & Social Policy, D-28359 Bremen, Germany
[3] Univ Bremen, High Profile Area Hlth Sci, D-28359 Bremen, Germany
[4] Univ Bremen, Competence Ctr Clin Trials, D-28359 Bremen, Germany
[5] Univ Med Ctr, Clin Prosthet Dent & Dent Mat Sci, Div Gerodontol, D-04103 Leipzig, Germany
[6] Univ Zurich, Clin Gen Special Care & Geriatr Dent, Ctr Dent Med, CH-8032 Zurich, Switzerland
[7] Stadt Klinikum Harlaching Munchen, Special Care & Geriatr Dent, D-81545 Munich, Germany