One year after implant placement , mean marginal bone level was 0.93 0.26 mm ( 95 % CI 0.81 to 1.05 ) in RP group and 0.84 0.23 mm ( 95 % CI 0.73 to 0.95 ) in the PS group and no statistically significant differences between the two groups were observed ( P = 0.18 ) .