In vitro and in vivo studies demonstrated that telescopic crowns with an occlusal (0.3mm) and lateral clearance (0.03mm) between inner and outer part have potential as overdenture abutments specially in cases of severely mutilated dental arches. The aim of the study was to evaluate the influence of the plaque-accumulation (PI) at the margins of the copings for two different designs of telescopic crowns (CC, C0) and bases of the prostheses (LVC, LV0) on the plaque stream into the periodontal pocket (PP). Two identical models simulating a lower jaw with 3 prepared teeth served as in-vitro samples. The finishing lines of the cylindrical preparations were made with a chamfer at the gingival level (CC) on one model, in contrast to no chamfer (C0) on the second. Natural plaque cultivated on agar plates was applied on the copings to obtain a plaque-index (PI) of 2-3 (Silness & Löe, 1964). Central load of the dentures was provided by a pneumatic piston of a fatigue loading device (F=50N, interval=1Hz) via a metal plate. In the regions of the interrupted buccal flange of the denture (lingual vault complete (LVC)) the transparent PMMA model allowed an observation of the plaque-distribution inside the periodontal pocket. The number of chewing cycles necessary for the plaque to reach the bottom of the simulated periodontal pocket with a depth of 2,4 or 6mm was recorded. This experiment was repeated after the denture vault was removed at the lingual region of the abutments (LV0). Statistical evaluation of the data was conducted using StatView 5.0 (ANOVA: a= 0.001; post hoc-test after Bonferroni/Dunn). The results were: The numbers of cycles for the plaque to reach the bottom of PP correlated significantly. Keywords: Resilienzteleskop, in vitro, Plaque, Prothesenbasisextension