TABLE 2.

Selected reviews that report the optimal number of supporting implants for maxillary overdentures

Systematic review	Number of implants	Survival rate of maxillary overdentures
Roccuzzo et al (2012) 81	Inconclusive	On the basis of available data, it is difficult to demonstrate that a particular number of implants offered a better outcome compared with another
Raghoebar et al (2014) 51	Inconclusive	Maxillary overdentures supported by splinted implants have a high implant and overdenture survival rate (both > 95% per year) ≤ 4 nonsplinted implants; the overdenture survival rate is 98.8% per year ≥ 6 implants and a splinted anchorage; the survival rate is 99.5% per year ≤ 4 implants and a splinted anchorage; the survival rate is 96.9% per year
Di Francesco et al (2018) 4	Not significantly influenced by the number of implants 94.7% to 100% for 6 or more implants with a splinted attachment 87.5% to 100% for 4 implants with a splinted attachment 95% to 100% for 4 implants without a splinted attachment 95% to 100% for fewer than 4 implants with or without splinted attachment