Removable Test 3 Flashcards
How many impressions are required to make a tooth-supported RPD (e.g Kennedy C III)?
One, as long as it records the teeth and soft tissue in anatomic form
Does the edentulous ridge offer support for the RPD?
No, abutment teeth absorb the forces
Can a tooth-tissue supported RPD (Kennedy C I or Kennedy C II) be made from one impression?
No, must be made using corrected cast
What does a corrected cast do?
Captures teeth in their anatomic position and the residual ridge tissue in functional form
What are 3 requirements for a corrected cast?
- Record and relate tissues under uniform loading
- Distribute load over as large an area as possible
- Accurately delineate peripheral extension of denturebase
What type of bone displays an irregular surface that can irritate overlying soft tissue when stress is applied?
Cancellous
What are 5 factors influencing support of the distal extension base?
- Quality of soft tissue covering edentulous ridge
- Type of bone in denture bearing area
- Design of prosthesis
- Amount of tissue coverage of denture base
- Anatomy of denture bearing arch
Will the ridge give the denture base more or less support if its overlying soft tissue is thick and displaceable?
Less support
What soft tissue covering of the edentulous ridge offers the greatest support for the RPD?
Firm, tightly attached mucosa of moderate thickness (2-3 mm)
What are 2 improvements removal of redundant tissue, especially over the maxillary tuberosities, offers the RPD?
- Minimize vertical displacement
2. Improve resistance to lateral displacement
Cancellous or cortical bone: which is less able to resist vertical forces?
Cancellous because its irregular surface irritatesoverlying tissue
Where should a practitioner direct forces when considering underlying bone of the denture-bearing area?
To dense cortical regions, e.g. the buccal shelf
What is the most efficient method of controlling rotational movement of a distal extension?
The use of one or more indirect retainers anterior to the fulcrum line
If the RPD is a bilateral distal extension (Kennedy Class I), how many and where are the indirect retainers placed?
One indirect retainer on each side of the arch
How many and where are the indirect retainers placed in a unilateral distal extension?
One, anterior to the fulcrum line and on opposite sides of the arch from the distal extension
If the distal extension RPD denture base is overextended and impinges on movable tissues, orthodontic movement of teeth will occur where?
Anterior to the fulcrum line
What is the maxillary arch primary stress bearing area?
Crest of the ridge
Why can the maxillary arch vertical slope be used as a stress bearing area?
Not oriented perpendicular to vertical forces
The maxillary buccal slope resists what forces?
Lateral
What other part of the maxilla provides some resistance to displacement from vertical forces, but is prone to ulceration as its mucosa is thin?
Hard palate
What must be done is the maxillary crestal mucosa is not firm and dense?
Surgical correction
Can the mandibular crestal ridge be used as a primary stress-bearing area and why?
No, it is covered by cancellous bone
What is the mandibular primary stress-bearing area for distal extension?
Buccal shelf
What provides vertical force resistance in the mandible?
Buccal shelf, almost perpendicular to vertical forces
What provides resistance to horizontal forces on the mandibular distal extension?
Buccal and lingual slopes of ridge
If an acrylic resin covered distal extension framework is placed in the mouth and pressed down, and the indirect retainers or lingual plates lift away from the teeth, what must be done?
New framework created using dual impression technique
For which arch and why is a dual impression technique most often indicated?
Mandibular because only limited ridge area is stress-bearing
Why is it difficult to get the peripheral extension of the mandibular denture base recorded?
The floor of the mouth is distensible
Of the two arches, which one normally requires only a single impression?
Maxillary
What other RPD type requires a dual impression technique?
Long span anterior edentulous (at least 6 anterior teeth) (Kennedy C IV)
What is the impression technique that records the ridge portion of the cast in its functional form by placing an occlusal load on the impression tray during the impression procedure?
Physiological impression
What is the impression technique intended to equalize the support between the abutments and the soft tissues and to direct forces to the portions of the ridge that are most capable of withstanding such forces (done by relieving the tray in some areas and allowing ht tray to contact the ridge in other areas)?
Selected pressure impression
In the selected pressure impression technique, areas where the tray is not relieved will have greater or less soft tissue displacement?
Greater displacement
For the corrected cast impression, what is attached to the impression tray?
The RPD framework
Soft tissues are ____________ if insertion and wear to the prosthesis produces no adverse soft tissue response?
Minimally displaced
Soft tissues have been ______________ when they have an inflammatory response and accompanying bone resorption
Excessively displaced
What is an impression technique in which you use a custom tray for the edentulous area, make an impression with it, put that custom tray into an impression tray with hydrocolloid and take a full arch impression (think of the custom tray as a substitute for a framework)?
McLean physiologic impression
What is the drawback of the McLean physiologic impression?
Related ridge and teeth in anatomic position as if masticating, so the base could cause compromised blood flow if retainers hold it down, or it could have premature occlusal contact if the retainers do not hold it in the anatomic position
What is a method that adds a new surface to the intaglio of the denture base?
Functional reline method
When doing a reline, what is placed on the cast to allow for new material to be added?
Thing layer of metal (Ash’s no 7 metal)
In the mouth, what is used as the final impression material for the functional reline?
Zinc Oxide Eugenol paste or light bodied polysulfide paste
For the reline, when will occlusal discrepancies be corrected?
After processing of base
When making an impression tray for the corrected cast procedure, what is used to make the new tray?
Framework on the master cast and resin placed over the framework, then tried in the mouth
When trying in the resin covered framework tray, the edge of the tray should be how far from the depth of the buccal vestibule in the patient’s mouth?
2-3mm
When trying in the resin covered framework tray, how far should the posterior portion of the tray reach?
2/3 the height of the retromolar pad
How is the distolingual fit of the framework tray assessed?
The patient places tongue to upper lip, if operator feels the tray lift, the distolingual extension should be shortened
An overextended tray will cause what on abutment teeth?
Constant force on abutment teeth as border tissues attempt to unseat denture
What are 2 bolder moldings that must be done on the distal extension framework tray?
- Anterior to posterior of buccal flange
2. Lingual and distolingual flanges
Proper border molding results in what?
Tongue and other tissues move without dislodging tray
What are 3 objectives of the fluid wax impression?
- Obtain maximum extension of peripheral borders without interfering with movable tissues
- Record stress bearing areas of ridge in functional form
- Record non-pressue bearing areas in their non-
functional form
What type of waxes are firm at room temperature and have the ability to flow at mouth temperatures (Iowa wax, Korrecta Wax No. 4)?
Fluid wax
Will a thin layer or a thick layer of fluid wax flow less readily?
Thin layer flows less readily
What is the temperature range for a fluid wax water bath?
51°C to 54°C
Fluid wax will not support itself beyond how many millimeters?
2mm
After 5 minutes in the mouth, the fluid wax will look dull or glossy in areas of tissue contact?
Glossy
What mouth position is required to do the buccal and distobuccal extensions of the fluid wax impression?
Wide open mouth to activate buccinators and pterygomandibular raphe
How long must the fluid wax impression be left in the mouth once the borders are verified and total tissue contact (all internal surface are glossy) is achieved?
12 min
What is an impression technique that seeks to direct forces to
those portions of the ridge able to absorb stress and to protect areas of the ridge least able to absorb stress (to do so, the intaglio surface of the tray is selectively relieved)?
Selected pressure
Which area is relieved on a mandibular distal extension tray?
Posterior crest of ridge. Relieved down to metal, allowing for minimal tissue displacement during impression
Does a more-viscous or less-viscous impression material result in greater tissue displacement?
Less viscous
What is the impression material of choice if residual ridge is
free of gross undercuts, or when soft, flabby tissue is involved?
Zinc oxide eugenol
What impression material is appropriate for ridges with
moderate to severe undercuts of the ridge (must use a tray adhesive and drill holes to prevent excess tissue
displacement)?
Polysulfide rubber base
What would be an indicator that the framework was not fully seated during the impression process?
Impression material under the rests
What is done with the original master cast to make the final corrected cast?
The old ridge is cut out
The framework impression is placed on the remaining teeth and fixed there with modeling plastic
Bead and box to give a 2-3 mm land area
What is the quality control for dental laboratories?
Competition
What is the minimum information required on an RPD work authorization?
- Signature and license number of dentist
- Date signed
- Description of service or material ordered
- Perhaps patient’s name and address
Work authorization is equal to what?
Prescription
Legal document
How long is a lab required to keep a work authorization?
2 yrs
What should always accompany a master cast to the lab?
Properly designed diagnostic cast
What should be clearly identified on the work authorization?
- Major connector to be used
- Teeth to be clasped
- Type of clasp to use
- Amount undercut each assembly engages
What are 3 things the dentist must provide the lab for a good RPD?
- Written work authorization describing RPD
- Properly surveyed diagnostic cast w/ RPD design
- Properly articulated master cast
What is the term for placing three easily identifiable marks on the the same horizontal plane, widely separated, and on anatomic portions of the diagnostic cast allowing for rapid orientation and reorientation of the diagnostic cast?
Tripodization
What is the term for the act of scraping the outline of the major connector into the master cast to a depth of 0.5 mm, producing a raised edge on the final framework to ensure positive contact of the major connector with palatal tissues?
Beading
Are bead lines used on mandibular major connectors?
No. Tissue will be irritated.
What is the overall shape of the blockout for tooth-tissue supported RPD (KennedyClass I and II)?
Parallel or tapered
What is the term for wax intended to make the framework stand away from the master cast, usually to allow 1 mm of space between the framework and the surface of the master cast to allow for resin to encompass the lattice work?
Relief (1 thickness of baseplate wax)
How far is a finish line to be placed from an abutment?
1.5 mm to ensure resin will not contact marginal ginigiva
What determines the ultimate fit of the framework as far as processing is concerned?
Refractory cast expansion
Refractory materials are also called what?
Investments
Gypsum-bonded refractory materials are called what type of investments? These are used to cast what materials?
- Low heat investments
2. Type IV partial denture gold and Ticonium
What is the temperature for low-heat investments?
704°C (1300°F)
Refractory materials used for Vitalium, Nobillium,
Jelenko’s LF, other chrome-cobalt alloys, titanium, and
titanium alloys are called what? What is their heating temp?
- High heat investments
2. 1037°C (1900°F)
A cast made from what material is the foundation for waxing and casting procedures?
Refractory material
How long must a refractory cast dry before trimming?
30-60 min at 93°C (200°F)
Why is the refractory cast trimmed within 6mm of the proposed design?
To ensure gas escapes during casting
What is the refractory cast dipped in to ensure smooth, dense surface and to eliminate need for soaking the cast prior to investment?
Hot beeswax (138°C-149°C [280°F-300°F]) for 15 sec
What is the most critical part of the design transfer to the refractory cast?
Individual clasp position
If a clasp is short, must it be thick or thin to ensure adequate flexibility?
Thin
What is the method of choice for RPD casting?
Induction casting
What is the term for casting based on the electric currents in a metal core induced from a magnetic field?
Induction casting
What is the term for rough finishing where atoms of metal from rough projections on the framework go into solution before those on smooth areas do giving a satin-like finish?
Electropolishing
Preliminary adjustment of occlusion of the RPD should be done where?
The lab
Wrought wire being round allows flexion in how many different directions?
All directions
What is the gauge of the most popular wrought wire?
18 and 19 gauge nickel-chromium-cobalt metals
In what situations is wrought wire used?
Interim RPD, transitional prosthesis, or repair of fractured or distorted clasps
What are 4 ways to attach wire clasps?
- Embed wire into denture resin
- Incorporate wire into wax pattern and cast metal to the wire
- Solder wire onto the framework
- Laser welding
What is the method of attaching wrought wire in a repair situation?
Embed the wire in resin
What is the most dependable method to attach wrought wire to RPD?
Solder the wire to the framework after the framework is complete
What is the disadvantage of incorporating the wire into the wax up and casting metal to it?
Adversely affect clasp longevity
What is the best method to attach wrought wire to the completed framework and why?
Solder onto lattice work well away from area where it will flex. Soldering limited to an area covered by denture base and heat will not affect the working part of the wrought wire
What is the laser used for laser-welding of the clasp to the framework?
Neodymium:yttrium aluminum-garnet (Nd:YAG)
Twin-flex clasp method provides what and how?
It provides a flexible clasp that is less noticeable to the patient by placing it in a measured undercut on a proximal surface of an abutment
What does placing the wrought wire on the cast then investing do on the RPD tissue surface?
Creates a channel into which the wire can be soldered
What percentage of RPDs do not fit on the day of insertion?
75%
Each completed RPD must be (pick one:) completely passive OR completely active in the mouth?
Passive
The tip of each retentive clasp is designed to (pick one:) lie passively OR lie actively in a measured undercut?
Lie passively
If the tip of the retentive clasp does not reach the undercut will it be passive or active?
Active
The tissue surface of the framework should be finished to what texture?
Fine matte
What are 2 requirements of internal and external finish lines on the framework?
- Sharply defined
2. Undercut to provide mechanical retention
What is the first and most important requirement of a major connector?
Rigidity
The framework is adjusted in what order: opposing occlusion first, then to the supporting arch or vice versa?
Fit to teeth and tissues of supporting arch first, then occlusion is adjusted second
Is spray type disclosing media indicated for intraoral framework fitting?
No
What is the greatest advantage of disclosing wax over other disclosing agents for framework fitting?
The three dimensional nature of the wax
Should a framework be forced into position if significant resistance is met?
No
When checking a distal extension framework, should any pressure be placed over the distal extension area?
No, it would cause the framework to rock and give inaccurate disclosing wax readings
Areas of show-through in disclosing wax indicate what?
Interferences
What is the most common area of interferences?
- The shoulders of circumferential clasps
2. Interproximal extensions of lingual plate
What is the difference between an interference and a guiding surface on the disclosing wax?
Guiding surfaces thin the wax
How will disclosing wax appear when evenly displaced on alloy frameworks?
Grayish
What must occur when the framework is tried in with respect to occlusion?
Natural tooth occlusion should remain the same as when framework is absent
Are maxillary and mandibular frameworks placed and adjusted at the same time?
No, done individually. Once each arch is good, they are placed simultaneously and occlusion is checked
What should be used to ensure that undue thinning of the framework does not occur during try-in?
Use a metal thickness gauge (Iwanson gauge)
After the framework try-in, what would be required if the patient does not have enough teeth or distribution of teeth to permit accurate hand articulation?
Jaw relations record
What will be required after the framework try-in if the patient will have a mandibular distal extension RPD, a long-span maxillary distal extension RPD, or a long-span anterior RPD?
Corrected cast impression procedure
What will be required after framework try-in for a patient having anterior teeth replaced with denture teeth on a denture base?
Esthetic try-in
What is required when the opposing casts cannot be accurately hand articulated or when the RPD will be constructed at a position other than MIP?
Jaw relations record
When is a jaw relations record normally taken?
After corrected cast procedure for a Kennedy CI or C II RPD
What is the desired occlusal scheme for a complete denture?
Bilaterally balanced
What is the desired occlusal scheme for a fixed partial dentures?
Disclude posterior teeth
What is the goal for an RPD occlusal scheme?
Establish and maintain harmonious relationship b/w oral structures and provide effective, esthetic mastication
What are 2 general arbitrary points for vertical dimension measurement?
- Top of the patient’s nose
2. Patient’s chin
What are 2 important vertical dimensions?
- Physiologic rest
2. Occlusal vertical dimension
What is the term for the vertical dimension when the patient is upright, completely at rest, and the maxillary and mandibular teeth are slightly separated?
Physiologic rest
What determines the mandibular position in physiologic rest position?
Muscle balance between muscles of mastication,
postcervical muscle group, infrahyoid muscles, suprahydoid muscles
What is the term for the measure of the vertical dimension when the patient’s teeth are in MIP?
Occlusal vertical dimension