Table 3.

Excluded studies and reasons for the exclusion

Excluded studies	Reason for exclusion
Arvidson et al.[21]	Number of implants (more than four implants)
Arvidson et al.[24]	Number of implants
Astrand et al.[25]	Overdentures
Agliardi et al.[28]	Number of implants
Ata-Ali et al.[29]	Literature review
Bedrossian[30]	Zygoma implants
Bedrossian[31]	Zygoma implants
Butura et al.[32]	Case reports
Cannizzaro et al.[33]	Study design
Degidi et al.[34]	Number of implants
Del Fabbro et al.[35]	Literature review
Di et al.[36]	Language
Ekelund et al.[37]	Number of implants
Eccellente et al.[38]	Removable prosthesis
Friberg and Jemt[39]	Implants not tilted
Ferreira et al.[40]	Case report
Graves et al.[41]	Zygoma implants
Graves et al.[42]	Zygoma implants
Heschl et al.[43]	Removable prosthesis
Jensen et al.[44]	Case report
Jensen et al.[45]	Case report
Jensen et al.[46]	Case report
Jensen et al.[47]	Case report
Jensen and Adams[48]	Case report
Krekmanov et al.[49]	Number of implants
Khatami and smith[50]	Case report
Li et al.[51]	Number of implants
Menini et al.[52]	Literature review
Orentlicher and Abboud[53]	Letter
Oyama et al.[54]	Study design
Penarrocha et al.[55]	Overdentures
Peñarrocha et al.[56]	Zygoma implants
Pomares[57]	Number of implants
Penarrocha-Oltra et al.[58]	Literature review
Pomares[59]	Number of implants
Parel and Philips[60]	Number of implants
Osen and Gynther[61]	Number of implants
Romanos et al.[62]	Removable prosthesis
Wu et al.[63]	Study design
Christopher et al.[64]	Study design
Babbush et al.[65]	Case report
Maló et al.[66]	Study design
Molina et al.[67]	Case report
Niedermaier et al.[68]	Study design
Sannino et al.[69]	Study design