In many clinical cases there are decayed teeth and roots that we extract before the implantation. Although basal implants are anchored deeply in the cortical bone, this bone needs time to remodels after that. Therefore the construction has to be light (like metal - composite constructions).
During the period of 1 year the bone starts gradually to shrink (atrophy). This is a normal physio-anatomical process in which gums and bone reduces their volume. After that several sections of the constructions become unaesthetic.
Metal-composite constructions are light and cheaper and can be fixed in the mouth of the patient without sending to the dental laboratory.