Presentation on theme: "Rpd Design considerations"— Presentation transcript:
1Rpd Design considerations Dr Balendra Pratap SinghBDS, MDS, MAMS, FISDR, FPFA, FAAMP, ICMR-IFAssistant ProfessorDeptt. of Prosthodontics
2Differentiation between tooth and tooth-tissue supported denture Manner in which each is supportedMethod of impression registration and jaw recordNeed for indirect retentionUse of denture base material
3Essentials of partial denture design How the partial denture is supportedConnection of tooth and tissue support units- major and minor connectorHow the RPD is to be retained- claspsConnection of retention units to the support units- direct and indirect retainer to connectorsOutline and join the edentulous area to the already established design components
4Components of RPD design All RPD must be supported by oral structureMust be retained against reasonable dislodging forces
6CLASS I - DESIGNPremolar abutmentsmandiblemaxilla
7INDIRECT RETENTIONThe component of an RPD that assists the direct retainers (clasps) in preventing displacement of a distal extension base by functioning through lever action on the opposite side of the fulcrum line when the denture base rotates away from the tissues around the fulcrum line.
8Class I – Premolar abutments - Mandible IndirectRetainer restsPrimaryrestswrought wire claspsPrimaryrestsClasparmPrimary fulcrumlineMajor connectorLingual bar with reliefIndirect retainer rests
9Class I – Premolar abutments - Maxilla Primary restsIndirect retainer restsClasp armT bar cast claspPrimary restsIndirect retainersPrimary fulcrum lineAnterior border of palatal plate ending in valley of rugaeMajor connector
10Class I – Canine, lateral and premolar abutments – maxilla and mandible ½ round cast claspI barModified T clasp
13Class II - MandibularFull gold crown with DO rest, lingual guideplane and MB undercutIndirect retainerClasps as appropriate for the abutmentPrimary fulcrum lineMO and DO rests, lingual guide plane, mid-buccal undercutMO rest for indirect retainer
14Class II - Maxillary ML cingulum ball rest as part of RPI system Indirect retainerMajor connector – anteroposterior palaltal strapIndirect Retainer½ round cast claspT-bar cast claspClasp arms as appropriatePrimary fulcrum line
16Metal bases; re-line not likely to be necessary Class 3-P – Mandibular (bilateral)Mesial and distal rest seats on lone-standing molars preferred to mesial rest aloneMolars: gold crowns, MO & DO rests, buccal guide planes, and ML retention#20 - DO rest, lingual guide plane, & MB retention#27 - raised cingulum composite rest, lingual guide plane, & MB retentionMetal bases; re-line not likely to be necessary
17An additional rest seat on the distal of the molar is desirable. Class 3-A - MandibularAn additional rest seat on the distal of the molar is desirable.
18Class 3 - MaxillaryFor patient comfort, a full palatal plate major connector, as shown in the diagram on the right, along with a secondary rest on the premolar, is more desirable than the design shown below.
19Class 3-A-P - MaxillaryAnterior Palatal Strap or Open Horseshoe major connector to circumvent the palatal torus
20An adaptation of a modified T-bar clasp Class 3-P-2A - MaxillaryAn adaptation of a modified T-bar clasp
22Ledge type cingulum rest seats on #22 & 27 to support anterior base. Class 4 - MandibularRest seat location - try to place a rest seat on the two teeth adjacent to the edentulous area and also the most posterior teeth remaining on each side; preferably molars and on the distal surface as shown on right image- Embrasure clasps on #20,21 & #28,29Lingual plate major connectorMolars tipped too far lingually to use as direct retainers.Ledge type cingulum rest seats on #22 & 27 to support anterior base.
23Class 4 – Mandibularlingual inclination of all molars preculdes using a conventional major connectorLingual plate imparts rigidity and bracing (reciprocation) for I-bar clasps on the premolarsLabial bar#21,28: I-bar cast claspsLabial bar major connector#18,32: i/2 rd. cast clasps to ML retentionBracing/reciprocation: #18: horizontal arm,#32: buccal plate
24I-bar clasps on the premolars Class 4 - MaxillaRest seat location - try to place a rest seat on the two teeth adjacent to the edentulous area and also the most posterior teeth remaining on each side; preferably molars and on the distal surface as shown on the image at right.major connector choices are full palate (preferred), closed horseshoe (as shown) or open horseshoe#2 & #15: DO rests #12: gold inlayMajor connector at least 6mm from fgm.T-bar cast clasps on both molar abutments have retention on both “wings” of the “T”I-bar clasps on the premolars
25Class 4 - MaxillaTwo more examples of Class 4 RPD’s – on the right with a full palate major connector, and below with a closed horseshoe (ant/post palatal strap)Note the red, irritated palatal tissue associated with the RPD base and major connector caused by occlusal trauma and plaque on the tissue surface of the rpd