An implant is used to replace a missing tooth and this is more conservative with regards to tooth structure than a bridge as the adjacent teeth are left intact in the case of an implant.
If a gap remains at the back, some patients find it difficult to chew and sometimes the teeth on each side of the gap drift towards the space creating spaces for food packing and the opposing tooth will drift into the space making restoration of the gap difficult in the future by creating unfavourable stresses.
Implants have steadily evolved with continuous and subtle design changes over the last 30 years to become a very predictable way to replace a missing tooth.
Occasionally a conservative and economical type of bridge can be used to replace a missing tooth where retentive elements of a bridge can be buried in fillings in each side of the gap (“hybrid-bridge”).