Nature has provided 18 roots for 14 teeth in the lower jaw and 22 roots in the upper jaw (not counting the wisdom teeth). An implant is an artificial tooth root and every implantologist should try to replace every missing tooth with an implant. The consensus conference on implantology (Professional Association of Oral Surgeons (BDO), Federal Association of Implant Dentists in Europe (BDIZ EDI), German Society for Oral and Maxillofacial Surgery (DGMKG), German Society for Dental, Oral and Maxillofacial Implantology (DGI), German Society for Dental Implantology (DGZI) clearly recommends that every tooth should be fitted with an implant.
The minimum number is...
In the upper jaw for a fixed restoration: 8 abutments
In the upper jaw for a removable denture: 6 abutments
In the lower jaw for a fixed denture: 6 abutments
In the lower jaw for a removable denture: 4 abutments
However, in the case of a so-called locator restoration for removable dentures, practice has shown that half of these abutments can be sufficient.