RPDfinal.txt

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  1. 1. What are some of the aspects of RPD’s that make them more challenging than Complete dentures? (Basically what consideration must be made in the construction of an RPD) - Due to presence of teeth and supported by teeth/mucosa:
    • a. Caries, tooth wear, changes in tooth position, VDO changes, Occlusal plane discrepancies, unstabile centric occlusal contacts, loss of posterior support, existing pathology, patient habits (i.e. bruxer)
    • b. All these factors have to be considered when constructing the RPD, and thus you don’t have the full control as you do in complete dentures
  2. Name 4 of the 7 RPD indications
    • 1. Long edentulous span
    • 2. lack of perio support
    • 3. compromised abutments
    • 4. Cross arch stabilization
    • 5. Distal extensions
    • 6. Restoration of hard and soft tissue contours
    • a. When Fixed Partial bridges are not a good choice
    • b. When need to restore occlusal plane without restoring every tooth
    • c. When need to restore contours of soft and hard tissues and not just teeth
    • i. i.e. anterior esthetics, lip support, bolus control, etc.
    • d. Hygiene potential – ease of plaque removal
    • e. When bone levels don’t support implants
    • f. Need for cross-arch stabilization
    • g. Age, health, attitude and desires of the patient
  3. What are the principles/objectives of RPD’s
    • a. Stabilize the individual arch and protect remaining structures
    • b. Gain control and organize interarch function
    • i. VDO, occlusal plane, centric, guidance and esthetics
    • c. Provide cross-arch support
    • d. Unite remaining teeth to better resist the forces of occlusion
    • e. Minimize negative forces on existing teeth an dsoft tissues/bones
    • f. Restore the function and control of direction of force on remaining teeth and structures
  4. What are the 3 RPD requirements and their definitions
    • a. Support – Resistance to occlusal or vertical seating forces – i.e. forces toward the teeth and mucosa
    • b. Stability – Resistance to lateral displacing forces
    • c. Retention – resistance against vertical displacing forces
  5. What are the components of Support, Stability and Retention
    • a. Support
    • i. Major connector
    • ii. Rests
    • iii. Denture bases
    • b. Retention
    • i. Retainers (active I bar)
    • ii. Proximal Plates
    • iii. Indirect retainer rests
    • c. Stability
    • i. Proximal plates/guide planes
    • ii. Retainers (reciprocation I bar)
    • iii. Lingual plate (mandibular arch)
    • iv. Rests (remember these are positive rests)
    • v. Denture bases
  6. What is the indications for making a record base and wax rim
    • a. When you don’t have adequate teeth in the arch to support the bite registration material to allow for a good mounting in CR
    • i. i.e. when you lack posterior teeth and don’t have a stable bite
    • b. Thus you construct one of these and make a wax rim
    • c. NOTE: The record base should be 2-3 mm short of the vestibule and there should be some space between the wax rim and the tooth (should not extend all the way to the remaining teeth)
    • i. Base should be 2-3 mm thick
    • ii. Space should be maintained between the two arches wax rims to allow room for the bitex registration material
  7. What are some properties of the record base and wax rim that allow for an accurate interocclusal record?
    a. It should be stable, rigid, comfortable and provide good support
  8. Why do you block-out when making a baseplate?
    • a. To obtain a stable and retentive record base and yet avoid damage on the cast
    • b. To be able to get the base plate out without damaging cast
  9. What are the 3 parts to an RPD?
    • a. Metal framework
    • b. Acrylic
    • c. Denture teeth
  10. Name all the parts of the RPD, be specific.
    • a. Major connector (3)
    • b. Minor connector/proximal plate (2) - Prep
    • c. Rests (1) - Prep
    • d. Retainers (5) - Prep
    • e. Denture base connector (4)
    • f. Denture teeth
  11. What are the objectives of RPD (same question as above in lecture 1)
    • a. Stabilize interarch function
    • b. Organize interarch function by control of interarch contacts
    • c. Preserve remaining teeth and tissues
    • d. Esthetic recovery
    • e. Restore function and control
    • f. Minimize negative forces
  12. 4 objective of a mouth prep
    • 1. Postitive rests
    • 2. Parallel guiding surfaces
    • 3. Lower height of contour or remove excessive undercut
    • 4. Create desired undercut for retention
  13. Definition and principles of a Rest
    • a. Part of an RPD that provides primarily vertical support on the abutment teeth
    • b. Must direct the functional forces along the long axis of the tooth
    • i. NEVER PLACE A REST ON AN INCLINED PLANE
    • c. Placed as close of the tooth as possible
    • d. Rest must be positive to keep the prosthesis from sliding off the tooth
    • i.  must be deepest in its center than towards marginal ridge – i.e. spoon shaped (incisal is .75-1.25 and posterior 1.25-1.5, wider at marginal ridge and rounded
  14. Definition and principles of a Major Connector
    • a. Rigid part of the partial denture that unites the remaining structure of the arch to provide the greatest potential to destribute and share functional forces.
    • b. Rigidity is necessary!!!
    • c. Posterior part of the major connector on the maxilla should not extend beyond the vibrating line
    • d. Should be in intimate contact with the tissues since any space between them can accumulate debris and cause discomfort
  15. Name 4 types of major connectors
    • a. Double strap type (aka anterior-posterior connector) – the one we use
    • b. Single strap type – Distal extension
    • c. U shaped/horseshoe type – palatal tori
    • d. Complete coverage – only anteriors remain/perio compromised or when future anterior extension considered
  16. When do you use a lingual bar vs a lingual plate in the construction of a mandibular denture?
    • a. The 2 determining factors for which to use are:
    • i. Location of lingual frenum
    • ii. Periodontal status of remaining ANTERIOR teeth
    • LINGUAL BAR
    • Sufficient space between crest of gingival and floor of mouth (lingual frenum)
    • - (3mm space from gingival crest to margin of gingival to metal + 4 mm space for thickness of metal = 7-8 mm of space)
    • If placed too close to gingival crest tissue can cause hypertrophy of tissue and food impaction/tissue irritation between bar and tissue
    • Is the preferred design because it:
    • - reduces interference with mouth functions
    • - reduces food and plaque accumulation
    • - simplifies fabrication procedure
  17. LINGUAL PLATE
    • Not enough space from gingival crest tissue to bar
    • When have mobility of anterior teeth or recession of supporting teeth which may lead to loss of teeth
    • - lingual plate will allow for easier restorability of a loss of a tooth as it goes right up to the teeth, and thus if a tooth falls out you could just put a new denture tooth right there to replace it
  18. Definition and principles of minor connectors
    • a. Rigid parts of the RPD that connect other units, such as rests, with the major connector
    • b. Includes the proximal plates
    • c. The metal should extend onto the tissue for at least 2mm for the tooth-tissue junction
  19. 5 Functions of proximal plates
    • a. maintain arch integrity by anterior-posterior bracing action
    • b. act as retainers by frictional contact with guide planes on tooth
    • c. protect against food impaction and hypertrophy – b/c fill in IPX space
    • d. self cleansing affect and guides partial along path of insertion
    • e. provide reciprocation action to the partial denture retainer
  20. Definition and principles of denture base connectors
    • a. Form a structure of metal struts that engage and unite the metal casting with the denture base resin
    • b. Should allow for 1mm thickness of resin
    • c. There should be a 1mm space between the edge of the denture base connector and the edge of the metal framework of the major connector (see 5th slide on p.4 of 2nd lecture)
    • i. Should be a butt joint between the two as well
    • d. Should be placed on the crest and lingual side of the ridge
    • e. Avoid sharp line angles
  21. Definition and principles of Retainers
    • a. Flexible part of the framework that are deliberately designed to engage in the undercuts of abutment teeth to resist RPD dislodgement
    • b. Retention remains passive until activated by displacement or removal forces on the RPD
    • c. Originate in gingival area and cross tooth/tissue junction at 90 angle
    • d. .01 undercut around midline and 1mm above gingival margin
    • e. Must stay in the cervical 1/3 – if higher up it will cause damaging torsional forces
    • f. I-bar retainers cross the tooth-tissue junction at right angles and extend up the tooth along its long axis
  22. What is the purpose of occlusal equilibration?
    • a. Bilateral balanced occlusion
    • b. Anterior guidance/canine guidance
    • c. Free of posterior interferences
  23. What is the design sequence in coming up with RPD design?
    • a. Occlusal rests
    • b. Minor connectors/proximal plates
    • c. Major connectors
    • d. Denture base connectors
    • e. Retainers
  24. What is a finish line?
    a. The junction between the acrylic and metal framework
  25. Objective of surveying
    To find MAP
  26. What is Surveying:
    Analysis/comparison of the prominences of the intraoral contours associated with the fabrication of the prosthesis
  27. Dental surveyor:
    instrument used to determine the relative parallelism of two or more surfaces of teeth/other parts of cast
  28. Good starting position for surveying:
    first make guiding surfaces as parallel as possible and then orient the occlusal plane as horizontal as possible
  29. Three factors to consider to dermine MAP:
    proximal surfaces, retention area and soft tissue undercut
  30. Managing lack of retention:
    • Check all surfaces, enamoplasty and crown
    • For excessive: lower height of contour
  31. Tripod to reproduce MAP:
    Metal post or three .01 undercuts at same vertical height
  32. What would happen if you didn’t have rests?
    • a. Ridge resorption
    • b. Mal-adaptation
    • c. Loss of vertical control
  33. Describe the Rest preparation
    • a. As center to the tooth as possible
    • b. Center is deeper (positive rest)
    • c. Depth > 1mm (~1.3mm) and width ~ 1/3 of the tooth
    • d. No sharp margins – Round in ALL aspects
    • e. No undercuts
    • f. Placed as low as possible (close to the gingival) to reduce leverage (on anteriors)
    • g. Should extend into central fossa (in posterior tooth-borne cases)
    • h. Should provide reciprocation and stabilization (in posterior cases)
    • i. Take advantage of existing anatomy
    • j. No interference with planned occlusion, should restore occlusion
    • k. WITHIN ENAMEL STRUCTURE
  34. Name 3 types of anterior rests. Which do we use when able to?
    • a. Cingulum rest  this is what we use if canine is available and has positive cingulum
    • b. Incisal rest  2nd choice
    • i. Should extend over incisal edge and onto the labial surface
    • ii. Use when esthetics is not a priority
    • iii. NEVER USE ON MAXILLARY ANTERIORS, only mand ant
    • iv. Concave mesiodistally
    • v. Convex buccolingually
    • c. Circular concave rest  rarely use!
    • i. Used when not sufficient bulk of abutment availabele and when esthetics is a concern
  35. Name 2 types of posterior rests. What are the indications?
    • a. Occlusal rest – most common, everyday rest
    • b. Continuous rest  splinting periodontally involved teeth
  36. Do rests serve as direct or indirect retainers?
    • a. INDIRECT!!!
    • i. Indirect retention is to resist dislodinging forces ALONG AXIS OF ROTATION!!!!
  37. What are 3 rest requirements?
    • a. Adequate thickness and width (>1mm and ~1/3 width of tooth)
    • b. Contoured to form half-circle
    • c. Harmonize with existing occlusion – no interference with occlusion
  38. Describe the sequelae of events that occurs if place anterior rest on an inclined surface.
    • a. Places lateral forces on the tooth which leads to:
    • i. Tooth displacement and bone resorption
    • ii. Allows the prosthesis to move out of position and displace tissue
    • iii. Disrupts and disorganize occlusion
  39. 5 Functions of proximal plates
    • a. maintain arch integrity by anterior-posterior bracing action
    • b. act as retainers by frictional contact with guide planes on tooth
    • c. protect against food impaction – b/c fill in IPX space
    • d. maintain soft tissue health at IPX tooth tissue junctions
    • e. provide reciprocation action to the partial denture retainer
  40. What happens if no proximal plate?
    • a. Impaction of food
    • b. Hypertrophy of tissues
    • c. Reduced bracing effects between the remaining teeth
    • d. ’d periodontal involvement
  41. What is the material of choice for proximal plate?
    • a. Metal
    • b. It can be precisely cast to fit the tooth contour and is not readily abraded or distorted during fabrication or function
    • c. Covers soft tissue AT LEAST 2mm BEYOND TOOTH-MUCOSA junction
    • d. Termination of the metal should be shaped into a right angle so that the acrylic and metal can make a butt-joint with sufficient thickness of acrylic (finish line is a butt-joint)
  42. What are 2 types of retainers?
    • a. Infrabulge retainers – I-bar
    • b. Suprabulge retainers – C-clasp
  43. Does the I-bar cross the survey line of the tooth? List 6 advantages of the I-bar.
    • a. NO. The I-bar approaches the crown of the tooth from an apical direction and doen not cross the survey line of the tooth.
    • b. Advantages:
    • i. Minimal tooth contact
    • ii. Exact placement of retention contact
    • iii. Minimal interference with natural tooth contour
    • iv. Maximum natural cleansing action
    • v. Passive functional movement on abutment
    • vi. Reduced display of metal, for better esthetics
  44. Discuss the design of the I-bar
    • a. Cross tooth-tissue junction at 90 degrees along long axis of tooth
    • b. Extend in a straight line to the UNATTACHED tissues to minimize debris, maximize esthetics and create sufficient flexibiltity
    • c. Contact the tooth in a circular or oval shape
    • d. Engage a .01 or .25mm undercut in the cervical 1/3 of the tooth
  45. Name a contraindication to the use of an I-bar
    • a. Severe soft tissue undercuts are an absolute contraindication of an I-bar!!!
    • b. Severely tilted tooth and shallow buccal/labial vestibules
  46. Where are proximal plates placed?
    a. Are placed for EVERY abutment next to an edentulous area
  47. Does the C-clasp cross the survey line of the tooth? Name 3 disadvabtages.
    • a. YES. It is a DIRECT retainer that begins at the occlusal ortion and extends onto the tooth, crossing the survey line and extending into the tooth undercut
    • b. Disadvantages:
    • i. It has a greater area of tooth contact and interferes with food flow
    • ii. Poor esthetics and hygiene
    • iii. Potential to torque abutment tooth in extension situation
  48. What is the definition of a dental surveyor?
    a. An instrument used to determine the relative parallelism of 2 or more surfaces of the cast
  49. What is the diagnostic rod used for?
    a. To check the parallelism of guide planes and evaluate the height of contours of the teeth and soft tissues
  50. What is the purpose of tripoding?
    a. To be able to reproduce the MAP on the cast at a later date
  51. What do you use the carbon rod for?
    a. To mark the heights of contours of teeth and soft tissues
  52. When shaving the proximal surfaces to make parallel guiding planes, what rule must you follow?
    a. Must make the contour curvilinear – i.e. follow shape of tooth
  53. What are the 3 main parts of an RPD?
    • a. Metal framework
    • b. Acrylic
    • c. Denture teeth
  54. 6 specific parts of an RPD
    • a. Rests
    • b. Major connectors
    • c. Minor connectors/proximal plate
    • d. Retainers
    • e. Teeth
    • f. Denture base connectors
  55. Major connector double strap type – dimensions of strap?
    • a. Anterior strip is made as thin as possible to allow for proper speech control
    • b. Posterior should be thicker, but narrower
  56. What do you do in the 1st clinical appointment?
    • a. Preliminary impressions
    • b. Pour up study casts
    • c. Design RPD
    • d. Survey and determine MAP
  57. What are the 3 parts of the RPD framework that need adjustment in the mouth?
    • a. Rests
    • b. Proximal plates/Minor connectors
    • c. Retainers
    • d. NOT THE MAJOR CONNECTOR OR DENTURE BASE CONNECTORS
  58. What do you do if an abutment tooth doesn’t have a retentive area (undercut)?
    • a. Create a dimple retention area by enameloplasty
    • b. Crown the tooth if it is an extremely important part of the PD
  59. What is the definition of a dental surveyor?
    a. An instrument used to determine the relative parallelism of 2 or more surfaces of the cast
  60. What is the definition of surveying?
    a. An analysis and comparison of the heights of contours associated with the fabrication of a prosthesis in order to establish the Most Advantageous Position (MAP)
  61. What is the primary purpose of surveying?
    a. To identify the modifications of oral structures that are necessary to fabricate an RPD with a successful prognosis
  62. Name 4 purposes of dental surveyor.
    • a. Surveying the diagnostic casts
    • b. Contouring wax patterns
    • c. Surveying and machining restorations before cementation
    • d. Surveying the master casts
  63. When surveying, which directions affect retention vs parallelism?
    • a. If move cast anterior-posterior it affects parallel guiding surfaces
    • b. If move cast left-right it affects retention areas
  64. What is the survey line?
    a. A line on a cast by the surveyor, marking the greatest prominence of the contour on the RPD abutment teeth and associated soft tissue in relation to the planned path of placement of a prosthesis
  65. What are the steps in surveying and tripoding
    • a. Cast orientation
    • i. Put it in the most parallel position by eyeballing the cast
    • b. Surveying
    • i. Determine MAP
    • ii. Mark the survey line on all RPD abutments and soft tissues
    • iii. Mark the areas of alteration with a BLUE pencil
    • c. Tripod
  66. What are the uses of passive retainers vs active retainers?
    • a. Active retainers – provide retention
    • b. Passive retainers – provide reciprocation
    • 58. What do you do if there is excessive retention? What about inadequate retention?
    • a. Excessive – tooth alteration to lower height of contour
    • b. Inadequate retention
    • i. create a dimple retention via enameloplasty
    • ii. crown the tooth if it is an extremely important part of the RPD
  67. What does RPI stand for?
    • a. Rest
    • b. Proximal Plate
    • c. I-bar
  68. What does a rest control?
    • a. Position of the prosthesis in relation to the teeth
    • b. Position of the prosthesis in relation to the periodontium and mucosa
    • c. Magnitude and direction of forces on abutment teeth (movement)
    • i. Load distribution to the abutment tooth
  69. Where do you want to position the rest with respect to the extension base?
    • a. On opposite side
    • b. If distal extension, want mesial extension
    • i. Allows for better load distribution to the abutment tooth
  70. What happens if you didn’t follow the above rule?
    a. The base will adversely load the abutment tooth leading to the distal movement of that tooth (get diastema) and bone loss
  71. What determines the axis of rotation?
    a. The rest positions on the abutment teeth adjacent to the edentulous regions and the farthest rest on the opposite side in a distal extension RPD
  72. Where do you want to extend the proximal plate preparations to?
    a. Down to the gingival margin and buccal-lingually to the line angles
  73. Defintion of retainers
    • a. Any portion of the prosthesis that contacts the tooth and helps prevent removal of the prosthesis
    • NOTE: active retainers should become inactive with occlusal forces and passive retainers become active
  74. An active I-bar must be reciprocated by what?
    • a. At least one of the following:
    • i. Opposing reciprocation clasp
    • ii. Combination of rest, minor connector and guide plane
    • iii. Lingual or palatal plate
  75. Define Axis of Rotation
    • a. A fulcrum line that is determined by the position of the rests.
    • b. Only exists in distal extension RPD’s
    • c. The line connecting the rest closes to the edentulous region and the rest furthest away or most posterior across the arch
    • d. It allows for stress relief
  76. Where are active retainers placed?
    • a. On the abutment teeth on the axis of rotation
    • A. Reciprocation:
    • The mechanism by which lateral forces generated by a retentive clasp passing over a
    • height of contour are counterbalanced by a reciprocal clasp passing (achieved by retainers, lingual plates and rests/proximal plates
  77. What constitutes a combination case?
    • a. Pt requires fixed restoration on teeth that will serve as abutment for removable prosthesis
    • b. Do fixed first, then removable
    • A. How to work up treament plan – Pre ATP (mount casts, tentative treatment plan and RPD design) Post ATP (finalize plan/design with instructor by survey, MAP, determine required prep areas)
    • B. Sequence: guide planes and rests then fixed and then prosthesis
    • C. Importance: to provide quality dentistry
    • D. Importance of diagnostic wax up – to 3 dimensionally map out treatment plan endpoint to develop and visualize occlusal plane, VDO, esthetics. To help guide dentist and facilitate communication between dentist and lab, and present to patient
  78. What determines adequate occlusal reduction?
    a. Rest clearance + adequate amalgam thickness
  79. What determines adequate axial reduction?
    a. Reduction to gain parallel guiding surface + adequate amalgam thickness
  80. What do you need to make sure your final fixed impression has?
    • a. Good margin
    • b. Critical anatomical landmarks
    • i. Tuberosity
    • ii. Retromolar pad
    • iii. Edentulous ridge
  81. How many casts do you need to have for a combination case? What are their names and what are each used for?
    • a. Need 2 casts
    • b. Pindex cast
    • i. Pindex cast for wax-up and final margination
    • ii. Do the preps and RPD design
    • c. Soft Tissue cast - to retain peri abutment soft tissue contour
    • i. Check:
    • 1. wax pattern
    • 2. Parallel guiding surface
    • 3. Rest seat & minor connector
    • 4. Retention and reciprocation
    • 5. Soft tissue contour – same level or lateral to crown contour
    • ii. DO NOT ALTER THIS CAST
  82. What kind of occlusion is desired when have opposing denture teeth?
    a. Bilateral Balanced Occlusion is required anytime opposing denture teeth are opposing in order to minimize destructive forces
  83. PFM prep considerations
    • a. 2mm reduction on fxnl cusp
    • b. 1.5mm reduction on non-functional cusps
    • c. Occlusal reduction at rest area =
    • i. PFM occlusal rdxn + RPD rest thickness
    • d. Shoulder is planed with 1.0mm wide chisel
    • i. Shoulder margin is placed from mid-mesial to mid-buccal (end it before the furca on posterior teeth)
    • e. Chamfer margin in the rest of the prep
    • f. Lingual – 1mm supragingival finishing line
    • g. Buccal – Crestal finishing line
    • NOTE: If I-bar retainer is planned, the soft tissue should be lateral to the abutment tooth at the end of the axial recution (look at 1st slide on p. 10 of lecture 6)
  84. List the Kennedy-Appelgate classification scheme
    • a. Class I – bilateral edentulous areas located to posterior remaining natural teeth
    • b. Class II – Unilateral Edentulous areas located posterior to remaining natural teeth
    • c. Class III – Unilateral edentulous areas with natural teeth both anterior and posterior
    • d. Class IV – Single, but bilateral (crossing midline) edentulous area located anterior to the remaining natural teeth
  85. Describe the UCLA functional design classification
    • a. Tooth Borne
    • i. Abutment teeth border all edentulous areas
    • ii. Functional forces are transmitted through abutment teeth to bone
    • iii. NO AXIS OF ROTATION IN THESE
    • b. Extension Base
    • i. Distal and Anterior Extension RPD’s
    • ii. Functional forces are transmitted through abutment teeth AND MUCOSA to bone
    • A. Three impact of rests: On abutment, I bar movement and direction of force on edentulous area
    • B. Design for destal extension: I bar with .01 retention on mid buccal or mesial half, mesial rest
  86. Describe difference between the displacement between PDL & mucosa
    • a. PDL – has 0.25mm of give
    • b. Mucosa – has 2.0mm of give
    • c. Need to control the uneven functional movement of extension base partial denture to achieve favorable biomechanical outcome
    • d. Do it by taking into consideration the type of retainer, location of retainer and rest positions
    • i. Also by physiologically adjusting it in the mouth
  87. Describe how position of the rests affect the I-bar movement in distal extension base RPD’s under functional loads
    • a. With a distal rest, I bar anterior to the axis will move up and into the undercut, thereby creating adverse loading
    • b. With a mesial rest, I bar will move down, forward and out of the undercut, therefore not creating adverse loading
  88. Why do we need to do physiologic adjustment for extension base RPD?
    • a. To establish a safety factor for abutment teeth to minimize the torquing or binding force from future excessive movement of the RPD due to bone resorption or poor edentulous area support
    • b. Due to difference in compliance in mucosa and PDL
    • c. Coat with chloroform and rouge and put in mouth. Stimulate rocking forces and look at it
  89. When should we stop the physiologic adjustment?
    a. Until the casting moves easily with the rest at the axis of rotation, rolling smoothly in its rest seat w/o lifting and the abutment tooth is not torquing
  90. Ideal rests/minor connector:
    • - smooth contour
    • - adequate size
    • - no sharp angles
  91. Ideal retainer:
    • - smooth
    • - tapering (continuous)
    • - no sharp angles
  92. Polyacytal
    produces high stress on distal lateral roots leading to resorption of alveolar ridge
  93. Advantages of Co-Cr
    • Corrosion resistance
    • High strength
    • High modulus of elasticity (stiff)
    • Low cost
    • Low density
  94. Advantages of titanium alloy:
    • Low weight to volume (low density)
    • High strength to weight
    • Fatigue/corrosion resistance
    • Biocompatible
  95. What is the difference between Type I and Type II alloys?
    • a. Melting temperatures
    • i. Type I  high fusing (> 1300oC)
    • ii. Type II  low fusing (< 1300oC)
  96. What is the main type of RPD alloy that we use?
    a. Chromium-Cobalt
  97. RPD alloy must have what property?
    a. Corrosion resitance
  98. (T/F) Type IV gold alloy is 2 x’s as dense as Co-Cr and Ni-Cr!
    True
  99. What type of resin do we use?
    a. PolyMethyl MethAcrylate (PMMA)
  100. What are 4 essential properties of denture resins
    • a. Sufficient stiffness and low creep
    • b. Sufficient strength and resilience
    • c. Biologically inert
    • d. Resist oral environment
  101. What is the purpose of the dyes and dyed organic fibers in the powder portion of the acrylic?
    • a. They are for esthetics
    • b. They give the appearance of blood vessels in tissues
  102. Chemical Cure initiation
    • a. An organic amine reacts with organic peroxide
    • b. Free radicals are formed
    • c. Free radicals attack double bonds
    • d. Addition polymerization occurs
    • i. NO BY-PRODUCTS FORMED!!!
  103. What is the purpose of plasticizers?
    • a. Used to reduce the brittleness of cross-linked polymers
    • b. Generally don’t enter the reaction, they serve as interference for the cross-linking, or lubricant between the chains
  104. What are thermal characteristics of synthetics resins?
    • a. HIGH coefficient of expansion
    • b. VERY LOW conductivity
  105. Know that heat and cold cure have more polymerization shrinkage than light cure (6% vs 3%, respectively)
    • a. Also cold cure has most residual MMA monomer leakage and thus potential tissue irritation
    • b. Light cure has NO MMA monomer leakage
  106. Plastic vs Porcelain Teeth
    • Plastic: tough, not abrasion resistant, good bond, silent sound, easy to finish
    • Porcelain: brittle, hard(abrasive resistant, mechanically retained, clicking sound, finishing removes glaze
  107. What is the purpose of the soft liner?
    • a. To improve fit and comfort of the denture
    • b. Should be elastic and resilient
    • c. Attached to the tissue bearing surface of the denture base
  108. Types of soft liners (MC type question)
    • a. Ethyl methyl methacrylate
    • b. Polydimethylysiloxanes
    • c. Polyphosphazines
  109. Difference between Type I and Type II impression compounds
    • a. Type I – impression taking
    • b. Type II – tray preparation (border molding)
    • 97. Characteristic of impression compounds
    • a. Thermoplastic
    • b. Low thermal conductivity
    • c. Stiff and brittle in room temp
  110. Clasp configuration
    a. Should be smooth, tapering/continuous and have no sharp angles
  111. How can you minimize the potential fracture of the minor connector to the rest
    • a. Smooth contour
    • b. Adequate size
    • c. No sharp angles
  112. Principles of RPD design (yet again)
    • a. Major connectors must be rigid
    • b. Occlusal rest must direct force along long axis of teeth
    • c. Guide planes and proximal plates enhance stability and braixing
    • d. Retention must be within physiologic tolerance of PDL and manual dexterity of pt
    • e. Maximum support is gained from adjacent soft tissue denture bearing surfaces
    • f. Designs must consider the needfs of cleansibility
  113. List the basic principles of partial denture design.
    • Major connectors must be rigid.
    • Occlusal rest must direct occlusal forces along the long axis of the teeth.
    • Guide planes are employed to enhance stability and bracing.
    • Retention must be within the limits of physiologic tolerance of the periodontal ligament.
    • Maximum support is gained from the adjacent soft tissue denture bearing surfaces.
    • Designs must consider the needs of cleansibility.
    • The RPD must achieve retention, stability and support via the following.
    • The rests must be positive and direct functional forces in the long axis of the tooth and as close to the center of the tooth as possible.
    • The Major connectors must be rigid in order to achieve cross arch stabilization and must be in intimate contact to soft tissues in order to promote cleansibility.
    • Parallel guiding surfaces allow for passive insertion and bracing utilizing proximal plates.
    • Reciprocation is achieved utilizing minor connectors, proximal plates and retainers.
    • Undue stress to PDL should be minimized w/ rest design and the RPD must not actively engage the dentition in function.
    • Soft tissue support in adjacent edentulous areas maximizes support.
  114. List the 6 requirements of a clasp
    • 1. Retention
    • 2. Bracing
    • 3. Support
    • 4. Reciprocation
    • 5. Encirclement of the tooth over 180 degrees
    • 6. Passivisity
    • 1. Minimal tooth contact
    • 2. Exact placement of retention contact
    • 3. Minimal interference with natural tooth contour
    • 4. Maximum natural cleansing action
    • 5. Passive functional movement of an extension prosthesis
    • 6. Reduced display of metal, for better esthetics
  115. Crowns are necessary as RPD abutments to:
    • 1. establish the proper guide plane if abutment has previous crown
    • 2. reposition the clinical crown
    • 3. restore a badly broken down clinical crown
    • 4. also, a proper rest could be incorporated into the crown which is not normally present on the tooth, such as a cingulum rest on a mandibular canine
  116. Name the three types of “positive” rests that can be used on anterior abutments.
    • 3 types of positive anterior rests:
    • 1. incisal
    • 2. circular concave
    • 3. cingulum
    • (1)Cingulum rest –
    • a. Crescent-shaped
    • b. As center as possible when viewed from all directions
    • c.The center is deeper buccal-lingually (positive rest)
    • (2)Insisal rest- concave mesiodistally and convex buccolabially.
    • (3)Circular concave
    • a) circular concave rest
    • i. #2 or #4 round bur
    • b) incisal rest
    • i. two planes preparation with flame shaped bur
    • 1. incisal plane
    • 2. labial plane
    • ii. concave mesiodistally, convex buccolingually
    • iii. 1/3 of mesiodistal incisal width
    • c) cingulum rest
    • i. flamed shape and inverted cone shape burs
    • 1. use flamed shape bur at 45 to create an outline form
    • 2. use inverted cone shape bur to create positive rest seat
  117. What type of suprabulge retainer do we recommend at UCLA? Why? When do we recommend that such a retainer be used?
    • Recommendation: Circumferential Clasp (aka: Akers Clasp) because
    • i. With flexible retentive arm that crosses the height of contour into the undercut and a rigid reciprocating arm that stays above the height of contour
    • ii. Fulfills the requirements of clasp
    • 1. Retention
    • 2. Bracing
    • 3. Support
    • 4. Reciprocation
    • 5. Encirclement
    • 6. Passivity
    • Indications for use of a circumferential clasp
    • b. Bulbous gingival contours
    • c. Lack of access for an I-bar clasp due to a shallow vestibule, a frenum attachment, or a severe gingival undercut
    • d. Short teeth with poor or no guide planes
    • e. Tilted teeth
    • f. Significant recession and/or abfraction

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