[1] Univ Groningen Hosp, Dept Oral & Maxillofacial Surg, NL-9700 RB Groningen, Netherlands
[2] Univ Groningen Hosp, Dept Ophthalmol, NL-9700 RB Groningen, Netherlands
[3] Univ Groningen Hosp, Dept Internal Med, NL-9700 RB Groningen, Netherlands
[4] Fac Dent, Div Oral Biochem, Dept Oral Biol, Amsterdam, Netherlands