(a)
(b)
Figure 1: The total group of 3902 included patients was arranged into two subgroups with regard to time at surgery ((a) 1986 to 1996; (b) 1997 to 2014). Distribution of number of treated implant patients according to age is presented for the two subgroups (subgroup #1, <60 years at implant surgery; subgroup #2, 60 to 79 years; subgroup #3, >79 years).