Presentation on theme: "Rpd Design considerations"— Presentation transcript:
1 Rpd Design considerations Dr Balendra Pratap SinghBDS, MDS, MAMS, FISDR, FPFA, FAAMP, ICMR-IFAssistant ProfessorDeptt. of Prosthodontics
2 Differentiation 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
3 Essentials 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
4 Components of RPD design All RPD must be supported by oral structureMust be retained against reasonable dislodging forces
6 CLASS I - DESIGNPremolar abutmentsmandiblemaxilla
7 INDIRECT 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.
8 Class I – Premolar abutments - Mandible IndirectRetainer restsPrimaryrestswrought wire claspsPrimaryrestsClasparmPrimary fulcrumlineMajor connectorLingual bar with reliefIndirect retainer rests
9 Class 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
10 Class I – Canine, lateral and premolar abutments – maxilla and mandible ½ round cast claspI barModified T clasp
13 Class 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
14 Class 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
16 Metal 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
17 An 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.
18 Class 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.
19 Class 3-A-P - MaxillaryAnterior Palatal Strap or Open Horseshoe major connector to circumvent the palatal torus
20 An adaptation of a modified T-bar clasp Class 3-P-2A - MaxillaryAn adaptation of a modified T-bar clasp
22 Ledge 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.
23 Class 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
24 I-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
25 Class 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