Table 1 Patient characteristics of total group and of patients with two, three, or four implants

Gender (men/women)

158/137

78/46

41/45

39/46

Mean age in years at implant placement (sd, min–max)

64 (10, 32–88)

62 (11, 32–88)

64 (9, 42–83)

67 (9, 46–86)

Mean edentulous period (years) of mandible before implant placement (sd, min–max)

21 (16, 1–60)

16 (15, 1–60)

21 (16, 1–56)

28 (14, 1–53)

Mean height of mandible in millimeters (sd, min–max)

16 (3.9, 10–25)

17 (3.7, 10–25)

16 (3.7, 10–25)

14 (3.2, 10–25)

Classification according to Cawood and Howell [18] in the symphysis region

Class III, 17%

Class IV, 30%

Class V, 32%

Class VI, 17%

Class VII, 4%

Class III, 24%

Class IV, 36%

Class V, 24%

Class VI, 16%

Class VII, 0%

Class III, 12%

Class IV, 35%

Class V, 29%

Class VI, 17%

Class VII, 7%

Class III, 12%

Class IV, 18%

Class V, 46%

Class VI, 18%

Class VII, 6%