“…The predominant animal in the studies of our review was the rat [ 12 , 16 , 18 , 42 , 59 , 60 ], although Desai et al [ 44 ] experimented on rabbits and earlier studies have selected the monkey. The age of the animals is of importance because mandibular growth is related to general growth, and varies in relation to chronological age [ 6 , 70 , 71 ]. The age of the animals was clearly reported, but varied from 4 weeks [ 59 ], 5 weeks [ 12 ], 6 weeks in the papers by Hua et al [ 60 ] and Wang et al [ 42 ] up to 8 weeks [ 16 , 18 ], and even 9 months in rabbits [ 44 ].…”