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70 Cards in this Set
- Front
- Back
Reputation of RPDs
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Most dentists are not uber-comfortable designing RPDs
Has a bad rap due to poor planning and execution - 65% of RPDs in service had inadequate support |
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Deficient soft tissue and bone issues
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Difficult situation esthetically for fixed. Also a problem with food impaction and cleansability
More of a problem esthetically in the maxillary arch due to smile line and lip support |
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RPD Treatment planning considerations
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Support
Esthetics Health history Tolerance Dexterity Cost and insurance |
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Direct & Indirect retainers
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Direct:
Clasp assembly - Includes retentive and reciprocal clasp arms, rest, and proximal plate Intracoronal & Extracoronal attachments Indirect: Resists pull of sticky foods. Usually a rest |
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Proximal plate
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Considered a minor connector
- Contact guide planes and guide insertion and removal |
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Kennedy classification & Applegate's rules
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Class I - Bilateral edentulous areas posterior to natural teeth
Class II - Unilateral edentulous area posterior to natural teeth Class III - Unilateral edentulous space bound by teeth Class IV - Single edentulous space anterior to remaining teeth and crosses the midline 1) Most posterior edentulous area determines classification 2) Edentulous areas other than those determining classification are considered modifications. Can be more than one. 3) Missing second and 3rd molars that aren't replaced are not considered in the classification 4) Classification takes into account extractions |
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Determining path of insertion
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- Align majority of abutment teeth with the analyzing rod
- Occlusal plane no more than 20 degrees from the horizontal plane |
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Interferences
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Can only use POI with inteference if:
- It can be blocked out without leaving too much space under RPD - If it can be eliminated with mouth preparation - If not removed, it takes precedence over guide planes and retention in determining POI. Mandible - Most common for lingual bar is bony prominences and lingually inclined pre-molars Maxilla - Buccally inclined molars, bony prominences on buccal. |
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POI and anterior teeth
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Class 4 edentulous ridge or anterior modification space will often dictate the POI
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Minor connectors and POI
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Interferences can be blocked out of its not too much
Want the surfaces of the teeth crossed by minor connectors to act as guide planes as much as possible |
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Guide planes functions
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- To guide RPD without strain against teeth or tissue from forcing over undercuts
- Provide predictable clasp assembly function of retention and reciprocation - Prevent food impaction between RPD and abutment teeth - Enhance retention and stability |
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RPI guide plane measurements
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2-3mm in length with proximal plate contacting lower 1mm
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Guide plane characteristics and principles
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Should be flat. Some say they can be rounded following proximal curvature
- Parallel to the chosen POI - As parallel to the long axis of the abutment teeth as possible - Placed on any tooth adjacent to an edentulous space with the exception of pier abutment in a distal extension case or very weak abutment. - Should be 2/3 width between cusp tips and 2/3 length of tooth. Exception is 2-3mm for RPI - Avoid sharp line angles |
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Functions of a rest
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- Provides support against occlusal load
- Maintains occlusion by preventing settling - Distributes forces to abutment teeth - Can act as indirect retainer |
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Occlusal rests
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- Rouded triangular shape
- Equal width and length about 2-2.5mm - Marginal ridge of tooth reduced 1.5mm for sufficient bulk - Concave floor with deepest part toward center of tooth |
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Cingulum rest seat
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Chevron shaped started just incisally to the cingulum with the cingulum dictating the shape
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Incisal rest seats
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Saddle - Mesial of cuspids for RPI
Right angle - Usually as indirect retainers or auxillary rests. - Very unesthetic, but necessary if theres inadequate cingulum for rest seat |
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Circumferential Clasps
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Clasp arms originate occlusally
-Aker's: only 1/3 of retentive clasp engages far undercut -Ring: Engages near undercut - C clasp: Also engages near undercut. Tends to break circumferential and part bar. Wrought wire clasps |
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Bar clasps
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Clasp arm originates from the cervical direction. Atleast 3mm between top of approach arm and gingival margin
- I-bar: Retentive tip engages undercut. Can then exted up 2mm and even over height of contour for bracing. -T and L bar |
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Clasp principles
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Passive fit - except when placed or removed. Can damage PDL or cause movement
Encirclement - Greater than 180deg to prevent horizontal movement of clasp assembly from tooth and tooth movement. Reciprocation - Stabilizes horizontal movement Bilaterally-opposed retention - B/B or L/L retention clasps or no reciprocation. Clasp arm - As low as possible to prevent torquing and widening of occlusal table - Retention should be minimum necessary to retain RPD |
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RPI clasp assembly
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Move Rest seat fulcrum to mesial
Place I-bar on mid buccal or mesial to it so it disengages under occlusal load Shorten guide plane to 2mm with proximal plate contacting lower 1mm. Will disengage under occlusal load. |
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Bar clasp contraindications
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Too much tissue undercut. More than 2mm relief is excessive
Need 5mm vestibular depth from gingival margin. Or will get ulcers |
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Almost universally used for clasp
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Chrome cobalt. More gigid than gold.
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Depth of undercuts engaged
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RPI - 0.25mm
Circumferential - 0.5mm T or L 0.25-0.5mm Wrought wire - 0.5-0.75mm |
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Clap retention depends on
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Flexibility of clasp
Depth of undercut Presence of tripping action Angle of convergence - Greater the angle, greater the convergence |
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Possible areas of major connector impingement
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Floor of mouth
Lingual frenum Soft palate |
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Types of maxillary major connectors
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Palatal plate
Palatal strap Ant-post palatal strap Palatal bar Ant-post palatal bar U shaped or horseshoe palatal connector |
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Palatal strap indications and characteristics
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Use for unilateral or bilateral tooth supported posterior teeth.
8mm minumum width and thicker in middle 1.5mm for rigidity |
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Anterior-posterior palatal strap indications and characteristics
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Indications:
When there is mid-palatal torus When more rigidity is needed than a single strap Characteristics - Posterior strap flat and atleast 8mm width. - Both straps as posterior as possible. - not as much support as palatal plate and decreased patient acceptance due to multiple borders |
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Palatal plate characteristics and types
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Any thin maxillary major connector that connects half or more of the palate
- Aids in retention via interfacial surface tension between metal and tissue - May interfere with taste, temp and tactile Modified palatal plate - varying widths connecting two or more edentulous areas. Greater patient acceptance. If last tooth on either side is cuspid or 1st bicuspid, complete palatal coverage is recommended. Complete palatal plate - Extends to junction of hard and soft palates Complete palatal plate with acrylic. PPS done in anticipation of transition to CD. |
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U shaped palatal connector characteristics and indications
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aka horseshow or anterior palatal strap
- Can be flexible unless wide enough or in two planes to increase rigidity. Esp for distal extention cases. Indications: - Large palatal torus, and can't use ant/post strap - If replacing just a few anterior teeth |
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Palatal bar
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Less than 8mm wide
- WIdely used but undesirable - Either not enough bulk for rigidity or thick and annoying |
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When to place relief for maxillary major connectors and beading
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If midline is not very displaceable or palatal torus
Margins are beaded to depth of 0.5mm fading near gingival tissues or thin tissues - Increase retention, prevention of food catch, more comfortable for tongue, provides visible finishing line to tech |
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Maxillary major connectors general characteristics
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-Uniformly thin
-Atleast 6mm away and parallel to gingival margin - Anterior border should lie between crest of rugae, and end at posterior border of rugae. - If must cross rugae, cross at a right angle. - Framework should extend to hamular notch - Framwork should end where horizontal and vertical parts of palate meet. Exception is horseshoe |
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Mandibular major connectors
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Lingual bar
Lingual plate Swing-Lock Cingulum bar Labial bar Sublingual bar Know lingual bar and lingual plate details. Know what rest look like |
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Lingual bar characteristics and requirements
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Half-pear shaped with fat part on bottom
- Bottom rounded out after casting to eliminate sharp edge - Must be 4mm in height, 4mm below gingiva, and 2mm in thickness. Need atleast 8mm between gingival margin and floor of mouth in function. |
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Lingual plate indications and characteristics
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-Not enough room for lingual bar
-Anticipating extractions -Where theres lingual tori - Class 1 case with severe ridge resorption and need additional stability against horizontal rotation - Thin as possible - Follow contours of teeth and remains in contact to prevent food impaction - Ends at middle third of ant teeth and above height of contour for post teeth. Otherwise can become inclined plane - Rests on teeth behind the plate or cuspids under the plate to direct forces vertically |
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2 ways to record height of floor of mouth
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In the impression:
- Anterior lingual border is molded while pt licks lips Measure clinically and record on cast - From lingual gingival margin to floor of mouth while pt touches upper vermillion border |
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Mandibular major connector general guidelines
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-Atleast 4mm from gingival margin on lingual and 3mm on labial
- Can't interfere with floor of mouth - Relieve lingual bar with 32 gauge relief wax - Relief placed over tori |
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Minor connector general requirements
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- Rigidity
- Unobstructive to the tongue by locating in the interdental embrasure and not pass over convex surface - If pass convex surface, use plate - Cross gingival tissue at right angle to minimize gingival coverage - Minimum of 5mm between vertical components - Slight relief under minor connectors where they cross gingival tissues |
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Requirements of proximal plate minor connectors
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Should be broad buccolingually but thin mesiodistally
Wider lingually to lessen interference with tooth set-up |
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Denture base minor connectors fabrication
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- Relief is placed over ridge for space of the resin to wrap around the connector
- Cast stop is created at distal end of minor connector. Contacts cast so connector doesn't bend or move - Joint of resin and metal needs to be smooth to tongue. Thus must have a finish line - Internal finish line 90deg, external finish line less than 90 to aid in acrylic retention. |
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Denture base minor connectors characteristics and types
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Maxillary: Should extend as far back as practical in DE cases.
Mand: Should extend 2/3 length of ridge, and extend acrylic to cover retromolar pad Open construction - Strongest attachment of acrylic to framework. - No longitudinal bar at crest of ridge, and transverse struts between necks of where teeth are to be placed Mesh construction: - Junction of mesh and major connector should be parallel to ridge - Finish line 2mm from where lingual surfaces of teeth will be |
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Minor connectors as approach arms for bar clasps
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Only minor connectors not required to be rigid
Should not cross deep tissue undercut |
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Indirect retainer characteristics
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Part of RPD that resists lever action from opposite side of fulcrum line in distal extensions.
Required in most Kennedy class I, II, and extensive class 4 cases. Esp on mandibular Mesial of bicuspids or lingual of cuspids |
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Effectiveness of indirect retainers
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Determined by:
- Retentive ability of clasp - Distance from fulcrum - Rigidity of minor connector - Geometry of rest seat. Must be positive or can act as inclined plane - Str of supporting tooth |
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Indirect Retainer Functions
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- Resist unseating forces
- Prevent major connector from impinging on tissue - Adds support and stability - Reduce torque on abutment teeth, particularly on lone-standing abutment. - Can indicate when reline of base is necessary if it unseats when base is depressed |
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3 axis of rotation for distal extension RPD
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- Horizontal axis formed by fulcrum line passing through most posterior abutments
- Saggital axis through crest of ridge - Vertical axis through center of arch |
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Residual ridge and basal seat
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RR - Soft tissue and bone it overlies
Basal seat - Area covered by denture base |
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3 types of denture bases
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Acrylic - Same as CD. Easy to reline, adjust, acrylic teeth adhere well.
Nylon (Valplast) - Not stable and subject to settling and damaging ridges. Need to set adjacent teeth before sending to lab. Can't reline or repair. Metal - Rarely used. Main indication is little occlusal clearance. |
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Denture base general characteristics
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- Some bulk below teeth on buccal of lower to help control food flow
- Concavity below gingival prominance on labial of mandibular posterior - Concavity lingual surface to give room for tongue to help retain denture |
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RPD teeth
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Acrylic or composite resin (IPN)
Porcelain Denture teeth processed to metal backing in framework Acrylic processed to metal backing in framework Metal occlusals or entire tooth in metal |
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Acrylic or composite resin teeth advantages and disadvantages
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-Easy to set and adjust
-Don't wear opposing teeth -Bond to acrylic denture base -Tend to wear over time leading to supraeruption -Composite resin (IPN) wears less quickly than acrylic resin |
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Porcelain denture teeth
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Requires gross mechanical retention - Diatoric holes, undercuts, pins
Or micro mechanical retention - Bur roughening, sandblasting - Will wear natural teeth. So porcelain has to be match with porcelain teeth. Acrylic or metal work well against acrylic, metal or natural teeth. |
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Metal backing indications
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- Deep overbite, not enough space to fit adequate thickness for acrylic
- Occasionally for replacement of single anterior tooth. Acrylic base and denture tooth can be prone to fracturing off. |
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Metal occlusals indications
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-Opposing gold restorations
-Want to develop precise occlusion - Not enough occlusal clearance - Not enough mesial distal space for acrylic base and teeth - Need to restore vertical dimension |
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Selecting teeth
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Anterior - Use remaining teeth as guide. Otherwise use same criteria as for CDs.
Posterior - Use opposing teeth as guide for size and cusp height - Otherwise measure from mesial of canine to incline of ramus on mandible or mesial or tuberosity. 28-32mm - Use teeth that are narrower buccal lingually to decrease force on ridge |
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RPD occlusion important point
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Cannot open vertical dimension with just RPD. Natural teeth have to occlude
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Goals of RPD occlusion
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- All cases:Simultaneous bilateral contact of posterior teeth in CO.
- Tooth born: Anterior guided or group function. - CD/RPD or C1/C1: Acheive balance like CD - Mand C1/Natural teeth: Group function if possible or ant guided - Max C1: Balanced if possible or atleast group function - Unilateral DE: Group function - Class4: Anterior contact in CO to prevent extrusion. Avoid ant contact in excursions |
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Planning phase
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History
Exam Radiographs Mounted study casts Take impression of existing RPD if there is Survey and design RPD |
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Sample RPD design
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Please fabricate RPD framework in Vitallium
Major connector: Horsewhoe #2 M prox plate, M rest, C clasp in MB undercut Retentive mesh in all edentulous areas - Do not put minor connectors - Rest seats in red, rest of framework in blue |
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Mouth preparation
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- Extractions, perio etc
- Tooth modifications - Survey crowns: Completed and cemented in place before the impression. Additional reduction in rest seat area - Guide planes before rest seats - Attachment crown: Picked up in impression for RPD framework. In lab on master cast for framework fabrication |
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Attachment crown fabrication
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Machined with handpiece attached to surveyor (Semi-precision attachment)
Soldered into the crown using surveyor to parallel it to other attachments and POI. (Precision attachment) |
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Preliminary impression
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- May be able to use study cast as preliminary
- Use alginate and add Periphery wax for DE. - Capture borders, esp retromolar pad and hamular notches - Survey it if its different from preliminary cast |
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Locating retromolar pad and hamular notch
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Retromolar pard - Dry tissue. Junction of shiny/dull tissue is where lower RPD should end
Max - Run mirror along tuberosity till it drops into hamular notch. Usually distal to where u think it us. |
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Final impression
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Use PVS for almost all RPD final impressions
- May use alginate for tooth born cases with faculty approval. Must be disinfected for 10min and poured immediately - Cut tray off model first before removing to prevent teeth breaking |
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Framework try in visit
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Try in framework. If doesn't seat:
- Use Occlude or indicating liquid, and check rests, rigid clasp arms, minor connectors. Check master cast for abrasions or fractures. - May need to tighten or loosen clasps. Risky - Check occlusion esp at rests. |
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Registration in CR vs CO
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Use CR
- any RPD opposing a new CD - Any double class1 - Any case that can't be hand articulated CI - Tooth-born cases - Any case that can be hand articulated, and the existing occlusion is acceptable |
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Insertion
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- Finished RPD can be adjusted in edentulous areas like CD
- If acrylic next to abutment teeth prevents seating, use PIP paste to check. |
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Recall
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- Check occlusion and have patient come back within a week to check for sore spots.
- Recall every 3-6 months for prophy - Check RPD yearly for reline. Hold on rests and push down on DE area to see if theres much movement. |