R. M. K. Emera and G. Y. Altonbary, “Retention force of zirconia bar retained implant overdenture: Clinical comparative study between PEEK and plastic clips”, Int Dent Res, vol. 9, no. 3, pp. 92–98, Dec. 2019, doi: 10.5577/intdentres.2019.vol9.no3.1.