Unconventional implant placement part III: implant placement encroaching upon residual roots - a report of six cases - Szmukler-Moncler, S; Davarpanah, M; Davarpanah, K; Capelle-Ouadah, N; Demurashvili, G; Rajzbaum, P (Clin Implant Dent Relat Res, 2015)