Table 1.

Terminology clarification

Edentulous	No functional teeth in place
Functional tooth	A tooth was considered functional if it could make contact with an opposing (prosthetic) tooth. Roots or impacted teeth are considered as nonfunctional
Functional unit	Functional tooth, bridge pontic, or crown (on implants), which could make contact with an opposing (prosthetic) tooth, is considered a functional unit
Occlusal unit [22]	A measure to represent the chewing surface of the postcanine functional unit. One pair of occluding premolars is equal to one occlusal unit. One pair of occluding molars is considered as two occlusal units. Third molars are excluded
Eichner index [23, 24]	A validated measure describing the existing posterior functional units in support zones. It is divided into 3 main classes
Eichner index A	Functional units exist in all 4 posterior support zones
Eichner index B	Functional units are present in one to three posterior support zones or within the anterior area only
Eichner index C	No functional units left