Short implants showed less bone loss when compared to long implants and the differences up to 1 year were statistically significant both in maxillae ( mean difference = 0.48 mm , 95 % CI 0.22 to 0.73 , P = 0.0011 ) and in mandibles ( mean difference = 0.44 mm , 95 % CI 0.21 to 0.66 , P = 0.0009 ) .