Removable Test 2 (Midterm) Flashcards
Surfaces on proximal or lingual surfaces of teeth that are parallel to each other and to the path of insertion and removal of the RPD are called what?
Guiding planes
What are the dimensions of guide planes adjacent to a tooth supported segment RPD?
2-4 mm occlusogingival height following natural curve of the tooth
What are the dimensions of guide planes adjacent to a distal extension?
1.5-2.0 mm high
What is the major reason for placing a guiding plane on a lingual surface of abutment tooth?
Reciprocation
When should reciprocation be in play to avoid periodontal support destruction?
When in contact with tooth as lateral forces are generated
What should also be used when a clasp arm is the reciprocal element?
Lingual guide plane
What are 3 reasons for lingual guide plane?
- Enhance reciprocation
- Minimize number of pathways for insertion
- Maximize resistance to lateral forces
What are the dimensions of lingual guide planes?
2-4 mm occlucogingival height in middle 1/3 clinical crown
Why create guide planes on anterior teeth?
- Reestablish normal width of edentulous space
- Minimize effects of tipping
- Improve esthetics
Why is the height of contour changed on teeth when an RPD is being designed and fabricated?
To provide more favorable positions for clasp arms or lingual plating
What is the ideal placement for a retentive clasp arm?
No further occlusally/incisally than the junction of gingival and middle thirds
Maxillary posterior teeth often tip which direction versus mandibular posterior teeth?
Maxillary posterior tip facial
Mandibular posterior tip lingual
What limits the amount of correction accomplished by enameloplasty?
Enamel thickness
If a tooth has favorable anatomy to place a retentive undercut (ie. The facial and lingual surfaces are nearly vertical), what are the dimensions of the undercut placed?
4mm MD length
3mm occlusogingival height
0.010 inch undercut
If restorations are required for the RPD abutments, should those restorations be completed before or after the recontouring procedures are done?
After recontouring has been completed
Ceramic materials are _____ in compression but ____ in tension
Strong in compression, weak in tension
Stewart’s authors prefer what fixed restoration
material for RPD support if indicated?
Metal-ceramic restorations
Stewart’s recommends rest seats for metal-ceramic restorations be placed entirely in what material?
Metal
How far should the borders of metal extend beyond the rest seat in a PFM abutment crown?
1 mm beyond borders of proposed rest
What component of an RPD has the following:
Directs forces of mastication along long axis of abutment tooth
Prevents gingival displacement of RPD
Maintains relationship between clasp assembly and the associated tooth
Can be an indirect retainer
Can close small spaces between teeth to restore arch continuity and prevent food impaction
Can establish a more acceptable occlusal plane to prevent extrusion
Rest
What is the form of an occlusal rest prep?
Triangle with base at the marginal ridge and rounded apex
Is a rest prep preferred in an existing amalgam?
No, but can be if in a small amalgam with good remaining tooth structure
What is a prep that crosses the occlusal embrasure of 2 approximating posterior teeth from the mesial fossa of one tooth to the distal fossa of the adjacent tooth?
Embrasure rest seat
What is preferred and why: posterior occlusal rest seat or anterior cingulum or incisal rest seat?
Occlusal. Cingulum/incisal rests give incline that may direct forces off long axis
When an anterior tooth must have a rest prep, which tooth is preferred: canine, lateral, or central?
Canine
If anterior rest seat must be prepared, which type is preferred: cingulum or incisal?
Cingulum
Of the canines, which are favorable to cingulum rests?
Maxillary
What are alternatives for placing cingulum rests on mandibular canines without prepping the tooth?
Make a cingulum rest with a conservative casting or a composite (bond them to the tooth)
Can a mandibular canine have a cingulum rest put in it?
Yes, with alternative cingulum rest in the middle to apical 1/3 of clinical crown as a crescent shaped depression
What is the major drawback of incisal rests?
Located far away from rotational center of tooth
Incisal rests are commonly used on what anterior
teeth?
Mandibular canines
If a cast restoration is planned for an anterior tooth, should an incisal rest or a cingulum rest be planned in it, if applicable?
Only cingulum rests
If an incisal rest is placed, to what is it closely placed?
Near a proximal surface (normally distal)
What is the depth of an incisal rest prep?
1.5-2.0mm
What is the depth of a maxillary canine cingulum rest?
0.5-0.7mm
What is the thickness of an occlusal rest?
1mm at its thickest
What is the width of embrasure rest seats facially and lingually?
3.0-3.5mm
What is the depth of an embrasure rest seat?
1.5-2.0mm
Do you “make” or “take” an impression?
Make
Does Dr. Betzhold make or take love?
Both, for his appetites are many
What is the primary drawback of alginate impression material?
Inability to store for a long time
Alginate impressions should be poured within how many minutes of removal from mouth?
12 min
Where is a common problem area in stock tray alginate impression that leads to slumping which eventually leads to poor adaptation of major connectors?
Palatal region maxillary arch
In the 12 minutes before you pour up your alginate, how should it be stored: resting on a bench top or suspended by the tray handle?
Suspended by the tray handle
What land area should be maintained around the cast when trimming it?
5mm
Do dental laboratories have to be certified?
No
What are the minimum requirements for a work authorization?
- Signature and license number of dentist
- Name/address patient
- Description of service/material ordered
What is the term for a written request for dental laboratory services that is equivalent to a prescription?
Work authorization
Dentist and lab must keep work authorizations for how many years?
2 years
What always accompanies the master cast and work authorization to the lab?
Properly designed diagnostic casts
What are the minimum descriptions on the work authorization?
- Clearly identified major connector
- List of teeth to be clasped and clasp type to be used
- Amount undercut engaged by each clasp
If a lab tech screws up the RPD construction, who is responsible for the overall patient treatment?
Dentist
What are 3 requirements dentist must provide to lab for a successful RPD construction?
- Written work authorization describing prosthesis
- Surveyed diagnostic cast with RPD design on it
- Articulated master cast showing hard and soft tissue contours
What are 3 identifiable marks on a cast on the same horizontal plane positioned on anatomic portions of the diagnostic cast to allow rapid orientation and reorientation of diagnostic cast?
Tripodization
What is the act of scraping the outline of the major connector into the master cast. It is a line approximately 0.5mm deep and becomes less distinct as it approaches the gingival margins?
Beading
What is the purpose of the bead line?
Produces raised edge at border of major connector to ensure positive contact of major connector with palatal tissue to minimize food impaction
Are bead lines used in conjunction with mandibular major connectors?
No, gingival tissue too thin to tolerate
All tooth-supported RPD should be blocked out how: parallel to path of insertion or tapered?
Parallel to path of insertion
Tooth-tissue supported RPD should be blocked out how: parallel to path of insertion or tapered?
Either parallel or tapered
What is the addition of wax intended to make the framework stand away from the master cast?
Relief
Relief is most commonly used in conjunction with what?
Denture bases
How much space should be placed between the relief struts and the surface of the master cast to allow the denture base resin to encompass the lattice work?
1mm
The finish line of an RPD (where resin meets metal) should be how far from neighboring abutment or abutments to ensure that the porous resin will not contact the marginal gingivae?
1.5mm
What determines the ultimate fit of the framework?
Refractory cast expansion in the duplication process
Can duplicating colloids be used repeatedly?
Yes
What is a synonym for refractory materials?
Investment
Gypsum-bonded investments are heated up to 704°C are called what?
Low-heat investment
Refractory materials used for Vitallium, chrome- cobalt alloys, titanium, and titanium alloys can be heated to approximately 1,037°C are called what?
High heat investment
What is the purpose of a cast made from refractory materials?
It is a foundation for waxing and casting procedures
Following removal from the refractory mold, the refractory cast is placed in a drying oven at what temperature for how long?
93°C for 30-60min
Refractory cast is trimmed to what dimensions in order to allow for escape of gases during casting procedure?
6mm
Refractory cast is dipped in what to ensure a smooth, dense surface and to eliminate the need for soaking the cast prior to investment process?
Hot beeswax at 130°C to 149°C for 15 sec
What is the most critical step in transferring the diagnostic cast design onto the refractory cast?
Position of individual clasp tips
When a clasp is shorter, must it be thinner or thicker than a longer clasp to ensure adequate flexibility?
Thinner
What is the casting method of choice for RPD?
Induction casting
What is the term for when electric currents in a metal core induced from a magnetic field making eddy currents of electrons in the crucible and the alloy to melt the alloy and is then spun onto the mold?
Induction casting
What is the first step in polishing the framework where atoms of metal from rough projections go into solution before those in smooth areas giving a consistent, satin-like finish?
Electropolishing
Where should preliminary adjustments to the
occlusion of a RPD be accomplished?
In the lab
What is the character of wrought wire?
Round, therefore can flex in all directions
In how many planes does a half-round clasp flex?
One
Which clasp type is thought to apply less force?
Round wrought wire
What are the dimensions and material of the currently popular wrought wire?
18-19 gauge nickel-chromium-cobalt wire
To bend wire, the best results occur when the wire is held and bent how?
Wire held with pliers and bent with fingers
What are 4 ways wire clasps can be attached to and RPD frame?
- Embed wire in denture base
- Solder wire clasp to framework
- Incorporate wire into wax pattern and cast metal to the pattern
- Laser weld the clasp
When is embedding the wire into the resin of the denture base commonly used?
Repair situations
What is a disadvantage of attaching clasp to RPD by incorporating it into the wax pattern?
Adversely affects clasp longevity
Which clasp attachment method offers the most dependable results?
Solder clasp to framework
What is the best method for soldering the wire clasp to the framework?
Solder on the lattice framework well away from area where it will be required to flex
Wrought wire clasp technique that provides a flexible clasp that is less noticeable to the patient?
Twin-flex clasp
What wire material is used for the twin-flex clasp method?
19-gauge Ticonium wrought wire
How is the 19-gauge Ticonium wrought wire placed for the twin-flex clasp?
Adapted into a measured undercut area on a proximal surface of abutment on master cast
What does putting the wrought wire on the master cast do in the long run?
Creates a channel on the tissue surface of the major connector which the wrought wire can be soldered into
What is the outcome in the twin-flex clasp?
Flexible hidden clasp that engages an interproximal undercut
