4 Components of RPD Flashcards
Components of an RPD (6)
- Major connector
- Denture base
- Direct retainers
- Indirect retainers
- Guide planes
- Minor connector
The six components of an RPD provide what six features?
- Support
- Stability
- Retention
- Resistance
- Reciprocation
- Passivity
Major Connector - Features (3)
- Connect parts of prosthesis from one side of dental arch to the other
- All other parts are directly/indirectly attached
- Provides “cross-arch stability” and resists displacement from functional stresses
Major Connectors - Single Palatal Bar - Bar is less than __ mm in width (half oval __ gauge thickness)
8 mm
Half oval 6 gauge thickness
Major Connectors - Palatal strap - Strap is __ mm or greater in width and can be thinner (__ gauge)
8 mm
24 gauge
Major Connectors - AP strap
- AP strap is minimum __ to __ wide and Lateral strap are __ to __ wide
AP strap: 8-10 mm
Lateral strap: 7-9 mm
Major Connectors - at least __ mm away from free gingival margins
6 mm away
Major Connectors - Palatal plate
- Recommended in Class __ RPD’s when canine or premolar is the most M/D? abutment
- Maximizes support and __
- Class I RPD’s
2. Support and rigidity
What major connector should be used as a last support?
- Why?
- What situations warrant its use?
- Horseshoe / U shaped
- Lacks rigidity and support
- Great when inoperable torus or Kennedy Class III/IV
Mand. Major Connectors: Lingual bar
- What shape is the bar and how tall?
- How far away from free gingival margin?
- 1/2 pear shaped and 4 mm tall
2. 3-4 mm away from free gingival margin
Sublingual bar
- What shape is the bar?
- Used when you have too much or too little distance to floor of mouth? How much?
- 1/2 pear shape
2. Too little (less than 7-8 mm, because you need 4 mm from FGM)
Lingual plate
- Used when you have too much or too little distance to FOM?
- What shape is the bar?
- You must have what design feature at the end of the plates?
- Too little (less than 7-8 mm)
- 1/2 pear shape
- Rest seats at terminal ends of plate
Cingulum bar (located on cingula of anterior teeth) - Indicated when? (3)
- Indicated if too much blockout for lingual bar or if open embrasures of plate visible from anterior
- Also indicated to avoid large inoperable lingual tori
What mandibular major connector is used as a last resort?
Labial bar
Requirements of a clasp assembly (6)
- Support
- Stability
- Retention
- Resistance
- Reciprocation
- Passivity
Rest Seat Purpose (3)
- Provides __
- Maintains __ in their planned positions
- Maintains occlusal relationships by preventing __
- Provide support
- Maintains components in their planned positions
- Maintains establish occlusal relations by preventing settling of the denture?
Rest seats
- Outline is what shape?
- Width?
- Depth?
- Angle formed by occlusal rest and vertical minor connector should be greater/less than 90 degrees to direct forces where?
- Rounded triangle
- 2.5 mm width
- 1.5 mm depth
- Less than 90 degrees to direct along long axis
Embrasure rests
- M-D dimension should be __ mm or big enough to hold two __ gauge wires
a. 2.54 mm
b. two 18 gauge wires
Cingulum rests
- Incisors or Canines preferred?
- Keep far away or close to gingiva?
- Max or Mand canines have thin enamel?
- Canines preferred
- Keep close to gingiva
- Mand canines have thin enamel
Cingulum rests
- M-D dimension
- F-L dimension with __ depth
a. M-D: 2.5 to 3 mm
b. F-L: 2 mm with 1.5 mm depth
Circumferential clasp - Adv (3) and Disadvantage (4)
- Retentive, stable, simple
- Covers more tooth than bar type, more metal display, adds bulky contour to tooth, and in 1/2 round profile, adjustments are difficult
Ring clasp
- Infra or supra bulge
- Adv (1) and Disadvantages (3)
- Supra
- Flexibility due to greater length, must incorporate bracing strut to reduce flexibility, covers too much tooth structure
Embrasure clasp
- Infra or supra bulge?
- Advantage (1)
- Disadvantages (4)
- Depth of prep
- Supra
- Allows cross-arch clasping when no mod. space
- High failure rate, significant tooth reduction, opposing teeth frequently interfere, and requires rests on both teeth
- 2.54 mm to fit two 18 gauge wires
What clasps are great when the only available undercut lies close to the proximal plate?
- Disadvantages (4)
Reverse action clasp
- Covers a lot of tooth structure
- Food trap
- Generally widens occlusal table
- Unesthetic
Bar clasp - Adv/disadv (2)
Adv: Less tooth coverage and more esthetic
Disadv: Tissue undercuts may require a lot of blockout causing food trap
- Length of clasp arm may be too flexible
Utilization of an RPI changes the Class I lever to a Class __?
Class 2 lever
RPI Designs - Kratovil
- Guide plane
Long guide plane, engaging as much tooth structure as possible
RPI designs - Krol
- Guide plane
Guide plane contacts plate 1 mm of the gingival portion (approximately the junction of the occlusal and middle thirds of the crown)
RPI designs - Demer
- Guide plane
Minimal guide plate prep and contacts 1 mm at height of contour (as occlusal as possible)
RPA clasp (Eliason)
- M/D rest?
- What kind of clasp?
- Used for Kennedy class?
- Proximal 2/3rd of clasp arm MUST do what?
- M rest
- Aker’s clasp
- Kennedy Class I/II
- 2/3rd of arm must be on height of contour
Twin flex clasp
- CC or WW?
- Used in distal extension and/or tooth borne?
- Kennedy class?
- Disadvantage?
- WW in 0.010””
- Tooth borne
- Class IV, sometimes III
- Difficult to adjust
Features of ideal denture base material (9)
- Tissue adaptation accuracy
- Dense, non-irritating surface
- Thermal conductivity
- Low specific gravity
- Sufficient strength
- Easily kept clean
- Esthetic acceptability
- Future reline potential
- Low initial cost
Acrylic denture base (ANSI/ADA Spec #12)
- Adv (2)
- Disadv (4)
- Able to reline and flanges can be contoured better
2. No thermal conductivity, less wear/abrasion resistance, requires bulk for strength, porosity
Metal denture base (ANSI/ADA Spec #14)
- Adv (4)
- Disadv (
- Accurate, naturally cleaner, better thermal conductivity, less weight/bulk, acrylic retentive features
- Poor esthetics, cannot reline
