Direct and Indirect Retainers

Direct and Indirect RetainersDEPARTMENT OF PROSTHODONTICS& IMPLANTOLOGY, SRM KDC & H Direct Retainers Structure of clasp assembly Requirements of clasp assembly Cast circumferential clasp Infrabulge clasp Indirect retainersRetainers:any type of device used for thestabilization or retention of a prosthesis.(GPT 8) Direct retainer:that component of apartial removable dental prosthesis usedto retain and prevent dislodgment,consisting of a clasp assembly or of Direct retainersIntracoronalExtracoronalClasps According to construction Cast Wrought wire Combination According to design Circumferential Bar typeIntracoronal Direct Retainers Introduced by Herman Chayes in 1906 Consists of two components-Matrix (slot)-Patrix (flange)Intracoronal Direct retainersAdvantages Elimination of visibleretention and supportsystem Better vertical support Better stimulation of underlying soft tissuesDisadvantages Require prepared abutment and castings Complicated clinical and lab procedures Eventually wear Difficult to repair and replace Least effective on short tooth Extracoronal Direct retainersRetentive clasp assembliesMechanics of retainer can be understood with two concepts path of insertion and removal, and height of contour Prothero s cone theory Share common base referred to as greatest diameter

• Direct retainers 1. Intracoronal retainers 2. Extracoronal retainers – Structure of clasp assembly – Requirements of clasp assembly – Cast circumferential clasp

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