Connection device (3; 37) and mounting tool (5; 59), wherein said connection device (3; 37) is adapted for connecting a prosthesis structure with an implant structure or a capped tooth, said connection device (3; 37) comprises a holding shell (2; 27) and a retention insert (1; 17; 18; 19), wherein said retention insert (1; 17; 18; 19) has an end side (12; 127; 128; 129) and a substantially ring-shaped retention rim (11; 117; 118; 119) projecting therefrom, said holding shell (2; 27) has an end side (22; 227) and a substantially ring-shaped holding rim (21; 217) projecting therefrom, said holding rim (21; 217) and said end side (22; 227) of said holding shell (2; 27) form a retainer in which said retention insert (1; 17; 18; 19) can be arranged such that an outer surface (114; 1147; 1148; 1149) of said retention rim (11; 117; 118; 119) of said retention insert (1; 17; 18; 19) is adjacent to an inner surface (212; 2127) of said holding rim (21; 217) of said holding shell (2; 27), and said outer surface (114; 1147; 1148; 1149) of said retention rim (11; 117; 118; 119) of said retention insert (1; 17; 18; 19) is at least partly spaced from and adjacent to said inner surface (212; 2127) of said holding rim (21; 217) of said holding shell (2; 27) when said retention insert (1; 17; 18; 19) is arranged in the retainer of said holding shell (2; 27) and when essentially no radial forces are acting on said holding rim (21; 217) of said holding shell (2; 27) and on said retention rim (11; 117; 118; 119) of said retention insert (1; 17; 18; 19), and said mounting tool (5; 59) comprises a sleeve-shaped demounting head (52; 529) which is arrangeable between said outer surface (114; 1147; 1148; 1149) of said retention rim (11; 117; 118; 119) of said retention insert (1; 17; 18; 19) and said inner surface (212; 2127) of said holding rim (21; 217) of said holding shell (2; 27) when said retention insert (1; 17; 18; 19) is arranged in said retainer of said holding shell (2; 27). said retention insert (1; 17; 18; 19) has an end side (12; 127; 128; 129) and a substantially ring-shaped retention rim (11; 117; 118; 119) projecting therefrom, said holding shell (2; 27) has an end side (22; 227) and a substantially ring-shaped holding rim (21; 217) projecting therefrom, said holding rim (21; 217) and said end side (22; 227) of said holding shell (2; 27) form a retainer in which said retention insert (1; 17; 18; 19) can be arranged such that an outer surface (114; 1147; 1148; 1149) of said retention rim (11; 117; 118; 119) of said retention insert (1; 17; 18; 19) is adjacent to an inner surface (212; 2127) of said holding rim (21; 217) of said holding shell (2; 27), and said outer surface (114; 1147; 1148; 1149) of said retention rim (11; 117; 118; 119) of said retention insert (1; 17; 18; 19) is at least partly spaced from and adjacent to said inner surface (212; 2127) of said holding rim (21; 217) of said holding shell (2; 27) when said retention insert (1; 17; 18; 19) is arranged in the retainer of said holding shell (2; 27) and when essentially no radial forces are acting on said holding rim (21; 217) of said holding shell (2; 27) and on said retention rim (11; 117; 118; 119) of said retention insert (1; 17; 18; 19), and