An orthodontic appliance (100, 200, 300, 400, 500, 600, 700, 800, 900) comprising: a base (102, 202, 302, 402, 502, 602, 802); a body (104, 204, 304, 404, 504, 604, 704, 804) extending outwardly from the base (102, 202, 302, 402, 502, 602, 802); an archwire slot (108, 208, 408, 508, 608, 808, 908) extending across the body (104, 204, 304, 404, 504, 604, 704, 804) in a generally mesial-distal direction; a recess (122, 222, 322, 422, 522, 622, 722, 822) located on the body (104, 204, 304, 404, 504, 604, 704, 804) adjacent the archwire slot (108, 208, 408, 508, 608, 808, 908), the recess having a bottom wall and opposing first and second side walls; a retention member (120, 220, 320, 420, 520, 620, 720, 820, 920) received in the recess (122, 222, 322, 422, 522, 622, 722, 822), the retention member (120, 220, 320, 420, 520, 620, 720, 820, 920) dividing the recess (122, 222, 322, 422, 522, 622, 722, 822) into at least first (138, 238, 338, 440) and second regions (140, 240, 340, 441); and a door (110, 210, 410, 510, 610, 710, 810, 910) slidably engaged with the body (104, 204, 304, 404, 504, 604, 704, 804) and having a first protrusion (136, 236a, 336, 436, 536, 636, 736a) extending into the recess (122, 222, 322, 422, 522, 622, 722, 822), wherein the first protrusion (136, 236a, 336, 436, 536, 636, 736a) comprises a generally trapezoidal profile as viewed from the mesial or distal direction, the first protrusion (136, 236a, 336, 436, 536, 636, 736a) having a gingival-facing edge forming a first sidewall angle β 1 and an occlusal-facing edge forming a second side-wall angle β 2. the first protrusion (136, 236a, 336, 436, 536, 636, 736a) extending into the first region (138, 238, 338, 440) when the door (110, 210, 410, 510, 610, 710, 810, 910) is open to allow access to the archwire slot (108, 208, 408, 508, 608, 808, 908) and extending into the second region (140, 240, 340, 441) when the door (110, 210, 410, 510, 610, 710, 810, 910) is closed to prevent access to the archwire slot (108, 208, 408, 508, 608, 808, 908). a base (102, 202, 302, 402, 502, 602, 802); a body (104, 204, 304, 404, 504, 604, 704, 804) extending outwardly from the base (102, 202, 302, 402, 502, 602, 802); an archwire slot (108, 208, 408, 508, 608, 808, 908) extending across the body (104, 204, 304, 404, 504, 604, 704, 804) in a generally mesial-distal direction; a recess (122, 222, 322, 422, 522, 622, 722, 822) located on the body (104, 204, 304, 404, 504, 604, 704, 804) adjacent the archwire slot (108, 208, 408, 508, 608, 808, 908), the recess having a bottom wall and opposing first and second side walls; a retention member (120, 220, 320, 420, 520, 620, 720, 820, 920) received in the recess (122, 222, 322, 422, 522, 622, 722, 822), the retention member (120, 220, 320, 420, 520, 620, 720, 820, 920) dividing the recess (122, 222, 322, 422, 522, 622, 722, 822) into at least first (138, 238, 338, 440) and second regions (140, 240, 340, 441); and a door (110, 210, 410, 510, 610, 710, 810, 910) slidably engaged with the body (104, 204, 304, 404, 504, 604, 704, 804) and having a first protrusion (136, 236a, 336, 436, 536, 636, 736a) extending into the recess (122, 222, 322, 422, 522, 622, 722, 822), wherein the first protrusion (136, 236a, 336, 436, 536, 636, 736a) comprises a generally trapezoidal profile as viewed from the mesial or distal direction, the first protrusion (136, 236a, 336, 436, 536, 636, 736a) having a gingival-facing edge forming a first sidewall angle β 1 and an occlusal-facing edge forming a second side-wall angle β 2. the first protrusion (136, 236a, 336, 436, 536, 636, 736a) extending into the first region (138, 238, 338, 440) when the door (110, 210, 410, 510, 610, 710, 810, 910) is open to allow access to the archwire slot (108, 208, 408, 508, 608, 808, 908) and extending into the second region (140, 240, 340, 441) when the door (110, 210, 410, 510, 610, 710, 810, 910) is closed to prevent access to the archwire slot (108, 208, 408, 508, 608, 808, 908).