There were no statistically significant differences in bone level changes up to 1 year between short and longer implants in maxillae ( mean difference -0.28 mm , 95 % CI -0.56 to 0.01 , P = 0.051 ) and in mandibles ( mean difference -0.09 mm , 95 % CI -0.26 to 0.08 , P = 0.295 ) .