PROSTHODONTICS Part 1 Flashcards
fixed dental prostheses with ___ of bone support and loss of ___ have a poor prognosis
half or less of bone support and loss of attachment
what is the prognosis of a single retainer cantilever FPD?
poor
in prosthodontics, splinting teeth is generally done to ___
- distribute occlusal forces
- this is recommended where the periodontal surface of the abutment tooth does not provide the needed support for an FPD or RPD
T or F:
multiple splinted abutment teeth does not compromise long-term prognosis
false
T or F:
intermediate abutments compromise long-term prognosis
true
do rigid or nonrigid connectors have a better prognosis?
rigid
when replacing the maxillary or mandibular canine with an FDP, why is it necessary to splint the central and lateral?
to prevent lateral drifting of the FDP
can compromised endodontically treated teeth be used as retainers?
no, they should not be
teeth with a short crown/root ratio (what ratio?) and with what root shape are not good choices for abutments?
<2:1 with conical roots
why are complete dentures contraindicated when only mandibular anterior teeth are present?
because severe damage to the opposing premaxilla occurs (combination syndrome)
___ is considered a terminal hinge position and is defined as “the maxillomandibular relationship in which the condyles articulate with the thinnest avascular portion of their respective discs with the condyle-disc complex in the anterior-superior position against the shapes of the articular eminences”
centric relation
___ is the complete intercuspation of the opposing teeth independent of condylar position
maximal intercuspal position, maximum intercuspation (MI), or centric occlusion
in ___% of people, CR and MI do not coincide
90%
accurate CR interocclusal records require precise manipulation of the mandible by the dentist. which technique is recommended?
the bimanual manipulation technique
casts produced with ___ are more accurately mounted with wax records, and casts obtained with ___ materials are more accurately mounted with elastomeric registration materials or zinc oxide eugenol paste
- irreversible hydrocolloid (alginate)
- elastomeric materials
what is the composition of irreversible hydrocolloid impression material?
- aka alginate
- mainly sodium or potassium salts of alginic acid
- the salts react chemically with calcium sulfate to produce insoluble calcium alginate
- diatomaceous earth is added for strength, and trisodium phosphate and other compounds are added to control the setting rate
how long after mixing the alginate material (“gelation”) should the tray be removed from the mouth?
2-3 minutes
after removing an alginate impression from the patients mouth, how should it be disinfected?
rinse with water and disinfect with glutaraldehyde or iodophor
after taking an alginate impression, what type stone is recommended for pouring the cast? how long does the stone take to set?
type IV or V, and usually takes 30-60 minutes to set
what are the two types of semiadjustable articulators?
arcon and nonarcon
describe arcon semiadjustable articulators
- condyles are attached to the lower member of the articulator, and fossae are attached to the upper member
- more accurate for fabricating fixed restorations
describe nonarcon semiadjustable articulators
- upper and lower members are rigidly attached
- useful for setting teeth for complete and partial dentures
what is an arbitrary facebow?
- orients the cast in the anterior-posterior and mediolateral position in the articulator to anatomic average values
- external auditory meatus is used to stabilize the bow
how do kinematic facebows differ from arbitrary facebows?
they allow more accuracy when mounting casts
what are the 3 major groups of dental implants? what is the most common used today?
- subperiosteal
- transosteal
- endosteal (most common)
what are the contraindications for dental implants?
- acute illness
- terminal illness
- pregnancy
- uncontrolled metabolic disease
- unrealistic patient expectation
- improper patient motivation
- lack of operator experience
- inability to restore with prosthesis
when placing several implants, they should be at least ___mm apart from each other, and ___mm away from the adjacent tooth
- 3mm
- 1mm
what is the recommended number of implants for placement in the elderly edentulous patient?
- two in the mandible
- four in the maxilla
describe the difference between one stage and two stage restoration with implants
- one stage involves the implant body that projects through the soft tissue with a cover screw after surgical placement
- two stage restoration involves covering the cover screw with soft tissue at the time of placement, which is then uncovered in a second operation
after placing a dental implant, how much time should you give to allow for adequate healing before taking final impressions?
2 weeks in a noncritical esthetic area, and 3-5 weeks in esthetic areas
T or F:
attaching implants to natural teeth is not recommended
true
when is it possible for two implants to support a 3-unit FDP?
- when the crown/implant ratio is favorable
- if implants are short and crowns are long, one implant to replace each missing tooth is highly recommended
what are the advantages of cement-retained implant crowns?
- more economical (in some systems)
- allows minor angle corrections to compensate for discrepancies between the implant inclination and the facial crown contour
- easier to use in small teeth than screw-retained implant crowns
what is the disadvantages of cement-retained implant crowns?
requires more chair time and has the same propensity to loosen as screw-retained implants
what are the advantages of screw-retained implant crowns?
- retrievability allows for crown removal, facilitating maintenance (soft tissue evaluation, calculus removal)
- future modification capability
- access hole is through the occlusal table of posterior teeth or lingual of anterior
what is the main disadvantage of screw-retained implant crowns?
the screw may loosen during function because of excessive lateral forces, excessive cantilever force, or improperly screwed crowns
are lateral forces in the posterior or anterior more destructive?
posterior (forces are greater and more destructive)
in dental implants, when unable to eliminate lateral forces, what should you do?
balance the occlusion so that the stress is distributed over as many teeth as possible
in treatment planning for dentures, what is the general rule for residual root tips?
- root tips with no radiolucency and cortical margin of bone intact may remain; inform the patient of their presence and risk and of the need to have them removed in the future
- they should be removed if the cortical plate is perforated or the periodontal ligament or radiolucent area is enlarging
frenectomy surgery is sometimes indicated when treatment planning for complete dentures. what are the most common areas for frenectomy?
in order of most to least common: labial > buccal > lingual
what is a hypermobile ridge and how should it be treated when planning for complete dentures?
- excessive moveable tissue due to fibrous tissue deposition
- should be treated with tissue conditioner
- if tissue conditioner is ineffective, electrosurgery or laser surgery can eliminate tissue
- this procedure might also eliminate the vestibule and risk making it even more difficult to attain a seal
- immediately after surgery, a soft liner must be placed to prevent epulis fissurata from forming
___ is a hyperplastic tissue reaction caused by an ill-fitting or overextended flange in a denture
epulis fissurata
fibrous maxillary tuberosity is common when ___
large maxillary tuberosities contact mandibular retromolar pads
___ is believed to be a specific pattern of bone resorption in the anterior portion of edentulous maxillae, caused by wearing a complete denture opposing anterior teeth
combination syndrome
___ is defined as multiple papillary projections of the epithelium caused by local irritation, poor fitting denture, poor oral hygiene, and leaving dentures in all day and night
- papillary hyperplasia
- candidiasis is the primary cause
- found in the palatal vault
what is the treatment for papillary hyperplasia?
- soak dentures for 30 minutes in a 1% solution of sodium hypochlorite and rinse thoroughly
- use tissue conditioner
___ is characterized by pinpoint hemorrhage or white patches or both, and requires a cytologic smear to confirm infection
candidiasis (candida albicans)
what is the treatment for candidiasis?
- nystatin or clotrimazole pastilles (both contain sugar and should be avoided in diabetic patients)
- clotrimazole or nystatin powder in oral suspension
what are treatment planning modifications for complete denture patients or RPD patients with pagets disease of bone?
denture or RPD may have to be remade periodically because of bone expansion
what are examples of hard tissue surgery that may need to be completed when planning for complete dentures?
- alveoloplasty,
- pendulous tuberosities (limits interarch space)
- sharp, spiny, or extremely irregular ridges
___ is a surgery that increases the relative height of the alveolar process
vestibuloplasty (soft tissue surgery)
T or F:
in the event that a complete denture is impinging on a neurovascular bundle, repositioning of the neurovascular bundle is never indicated
false
what are examples of augmentation surgeries for complete dentures?
- bone grafts
- hydroxyapatite
- freeze-dried bone
- connective tissue
in bone graft procedures, ___% of the bone graft is often lost due to resorption
75%
the ___ record of an edentulous patient provides the ability to increase or decrease the vertical dimension of occlusion more accurately
centric relation
a ___ record registers the anterior-inferior condyle path at one particular point in the translatory movement of the condyles
protrusive
___ phenomenon refers to the distal space created between the maxillary and mandibular occlusal surfaces of the occlusion rims of dentures when the mandible is protruded
christensen’s phenomenon
___ is the position of the mandible when the elevator and depressor muscles are in a state of equilibrium or balance
vertical dimension of rest or physiologic rest position of the mandible
the vertical dimension of rest position commonly results in a separation of the maxillary and mandibular teeth of about ___mm at the premolar region. this separation is called the ___ space
- 3mm
- interocclusal space
what are common effects of excessive vertical dimension of occlusion in complete denture cases?
- excessive display of mandibular teeth
- complaint of fatigue of muscles of mastication
- clicking of the posterior teeth when speaking
- strained appearance of the lips
- patient unable to wear dentures
- discomfort
- excessive trauma to the supporting tissues
- gagging
what are the common effects of insufficient vertical dimension of occlusion in complete denture cases?
- aging appearance on the lower third of the face because of thin lips, wrinkles, chin too near to the nose, and overlapping corners of the mouth
- diminished occlusal force
- angular cheilitis (occurs in conjunction with candidiasis)
___ is an imaginary line traced from the ala of the nose to the tragus of the ear
campers line (helps in establishing the plane of occlusion)
the ___ line is in the traverse plane and is an imaginary line drawn between the pupils of the eyes
interpupillary line (helps in establishing the plane of occlusion)
fricative or labiodental sounds f, v, ph are made between the maxillary incisors contacting the wet/dry lip line of the mandibular lip and help determine what in the complete denture patient?
the position of the incisal edges of the maxillary anterior teeth
linguoalveolar sounds or sibilants (sharp sounds s, z, sh, ch, and j) are made with the tip of the tongue and the most anterior part of the palate or lingual surface of the teeth. these sounds help determine ___ in the complete denture patient
the vertical length and overlap of the anterior teeth
in the complete denture patient, what is a whistling sound indicative of?
having a posterior dental arch form that is too narrow
linguodental sounds (tip of the tongue slighltly between the maxillary and mandibular teeth, such as “this” “that” and “those”) helps determine ___ in the complete denture patient. the “th” sound provides information regarding the ___
- the labiolingual position of the anterior teeth
- labiolingual position of the anterior teeth
in the complete denture patient, vertical dimension is evaluated during pronunciation of what sound? the interincisal separation should be ___mm. what is this space called?
- the s sound
- 1-1.5mm
- the closest speaking space
in the complete denture patient, what are the limiting structures of the maxillary denture?
- anterior region: labial vestibule and buccal vestibules
- posterior region: limit extends to junctions of movable and immovable tissue (coincides with the line drawn through the hamular notches and approx. 2mm anterior to the foveae palatina (vibrating line)
support for a maxillary complete denture is provided by the ___ and ___
maxillary and palatine bones
in the complete denture patient, what are the limiting structures of the mandibular denture?
- anterior labial area, which extends from the labial frenum to the right and left buccal frenums
- buccal vestibules
- retromolar pad
- lingual frenum
- sublingual gland area
- mylohyoid area
- retromylohyoid area
the ___ marks the distal termination of the mandibular edentulous ridge
retromolar pad
how do the buccinator and masseter muscles limit/displace mandibular complete dentures?
- buccinator muscle fibers run in an oblique fashion and have little displacing action
- masseter muscle limits the denture in a lateral direction
maxillary and mandibular lip support in a patient with complete dentures is provided by ___ and ___
facial surfaces of teeth and the denture base
denture ___ refers to resistance to vertical seating forces
denture support
denture ___ is necessary to resist dislodgment of a denture in the horizontal direction
stability
denture ___ is the ability of the denture to withstand dislodging forces exerted in the vertical plane
retention
what are the surfaces of a denture that play a part in retention?
- intimate contact of the denture base and its basal seat
- teeth - no occlusal prematurities to break retention
- design of the labial, buccal, and lingual polished surfaces
what is the primary retentive force for dentures?
saliva to denture and tissues (adhesion)
what is the favorable type of saliva for denture adhesion? what is the unfavorable type?
- favorable type is watery (greater retention)
- unfavorable type is thick and ropy
how is abnormal mucoperiosteum beneath dentures treated?
complete removal of the dentures until the tissues return to a normal size, shape, color, consistency, and texture
candida albicans is normal in the oral cavity, but under trauma or antibiotic usage, it may cause generalized inflammation (candidiasis). it may involve the corners of the mouth (angular cheilitis) which is common in patients with diminished ___
vertical dimension
what is the nystatin rinse prescription regimen for candidiasis infections?
- nystatin oral suspension contains sugary (caution with diabetic patients)
- dispense 60mL of 100,000 units/mL
- take 4mL 3x/day; after each meal, hold in mouth for 2 minutes then expectorate
what is the nystatin cream prescription regimen for candidiasis infections?
- nystatin w/triamcinolone acetonide cream (used for angular cheilitis)
- dispense 15g tube
- instructions: apply to affected area a small amount 4x/day (after meals and bedtime) for 14 days
what are the advantages of retaining roots when planning for overdentures?
- decreases bone resorption
- maintains the proprioceptive fibers within the PDL
what is cheek biting with dentures due to? how can the problem be solved?
- insufficient horizontal overlap between maxillary and mandibular teeth
- reducing the facial of mandibular posterior teeth in question can solve the problem
in denture cases, overextension usually causes ___
dislodgment of the denture
which kennedy classification is described as bilateral edentulous areas located posterior tot he remaining natural teeth?
class I
which kennedy classification is described as a unilateral edentulous area located posterior to the remaining natural teeth?
class II
which kennedy classification is described as a unilateral edentulous area with nautral teeth remaining both anterior and posterior to it?
class III
which kennedy classification is described as a single, but bilateral (crossing the midline), edentulous area located anterior to the remaining teeth?
class IV
how are kennedy classifications determined in cases where extractions are needed?
classifications should follow rather than precede any extractions of teeth that might alter the original classification
what are the rules for kennedy classifications in terms of third molars?
- if a third molar is missing and not to be replaced, it is not considered in the classification
- if a third molar is present and is to be used as an abutment, it is considered in the classification
if a second molar is missing and is not to be replaced, is it considered in the kennedy classification?
no
the most ___ edentulous area determines the kennedy classification
posterior
what are kennedy classification modifications?
- edentulous areas other than those determining the classification
- they are designated by the number of additional edentulous areas, not the extent of modification
which kennedy classification cannot have any modifications?
class IV
what is the function of a major connector?
- to connect all the RPD components on one side of the arch with the opposite side to unite them
- provides stability to resist displacement while in function
should major connectors be flexible or rigid? what tissues should they not be placed on?
- rigid
- not placed on movable tissue
- undercut areas and soft and bony prominences (tori, median palatal suture) should be avoided, removed, or relieved, depending on the severity
which kennedy classifications are anterior-posterior palatal straps useful for?
all classes, especially class II and IV
should major connectors cross the midline at right angles or diagonal?
right angles
what kennedy classifications are single palatal straps useful for? how should they be designed?
- kennedy class III with bilateral, short-span edentulous areas
- palatal strap should be wide and thin for strength and comfort
- anterior border should be posterior to the rugae
describe palatal plate designs. which kennedy classifications are they useful for?
- can be designed as a wide palatal strap short of the rugae area for distal extension RPD where more than the anterior teeth are present (kennedy class I)
- complete palatal strap (most rigid of all major connectors) is indicated when all posterior teeth are missing bilaterally, in a kennedy class I mod I, and for periodontally compromised teeth, shallow vault, small mouth, or flat or flabby ridges
which situations are u-shaped palatal (horseshoe) major connectors useful for?
- used only when other, more rigid designs cannot be used
- commonly used when large, inoperable palatal torus exists or when anterior teeth need replacement
which major connector is the least rigid of all maxillary connectors?
u-shaped palatal (horseshoe)
a palatal bar is less than ___mm in width
8mm (this is because a palatal strap is greater than 8mm in width)
a palatal bar must be centrally located in the framework and needs ___ to be rigid to provide the needed cross-arch support
bulk
describe anterior-posterior palatal bars
- similar to the single bar, configured similarly to the anterior-posterior palatal strap
- main disadvantage is the bars needed bulk
what are the options for mandibular major connectors?
lingual bar, lingual plate, and labial bar (swinglock)
which is the simplest and most commonly used mandibular major connector?
lingual bar
for a lingual bar mandibular major connector, the depth of the vestibule should exceed ___mm
7-8mm
what situations are lingual plate mandibular major connectors useful for?
- when the depth of the lingual vestibule is less than 7mm
- when additional loss of teeth is anticipated
- when lingual tori are present
- when all posterior teeth are to be replaced bilaterally
describe the labial bar (swinglock) mandibular major connector
a hinged continuous labial bar located buccal and distal to the remaining dentition, with a latching mechanism opposite to the hinge
which cases are labial bar (swinglock) mandibular major connectors indicated for?
- when anterior teeth are missing, including a canine
- where there are unfavorable tooth or soft tissue contours
- when there are teeth with questionable periodontal prognosis
a ___ is a rigid component of an RPD that connects the major connector or base with other components of the partial denture such as rests, indirect retainers, and clasps
minor connector
___ is a procedure of scribing a rounded groove (0.05mm) outlining the anterior and posterior borders of a maxillary major connector
beading
what are the benefits of beading an RPD?
adds strength to the major connector and maintains tissue contact to prevent food impaction
what is the purpose of a clasp in an RPD design?
to retain the RPD by means of the abutments
what are the features of clasps that provide, retention, stability, and support?
- retention from the retentive arm
- stability from the minor connector and rest
- support from the rest
when designing clasps, how do you ensure that horizontal movement of the clasp is prevented?
clasps need adequate encirclement (greater than 1/2 the tooth circumference)
retentive clasps should become active only when ___
dislodging forces are applied to them
what are the two types of direct retainers?
intracoronal and extracoronal
describe intracoronal direct retainers
-composed of a prefabricated machined key and keyway (precision attachment)
are intracoronal or extracoronal direct retainers more esthetic? which ones are more common?
- intracoronal are more esthetic
- extracoronal are more common
what are the two types of extracoronal direct retainers?
suprabulge (originate above the survey line) and infrabulge (originate below the survey line)
what are examples of suprabulge extracoronal direct retainers?
circumferential clasp, ring clasp, combination clasp, and embrasure clasp
what are examples of infrabulge extracoronal direct retainers?
I bar, T bar, bar type, and Y type
what kennedy classifications are RPI (rest, proximal plate, I bar) and RPD/RPA (rest, proximal plate, cast circumferential clasp or akers clasp) useful for?
class I and II
how is reduction in the torqueing force on abutment teeth achieved? when is it indicated?
- with the use of wrought wire clasp system
- indicated for periodontally weakened teeth or endodontically treated teeth
a ___ wire direct retainer is indicated if retention is placed on the opposite side of the fulcrum line from the edentulous ridge
wrought
in a distal extension situation, what is the order of preference of use of clasp assembly?
- RPI (rest, proximal plate, I bar)
- RPC (rest, proximal plate, cast circumferential clasp/ akers clasp)
- wrought wire
the reciprocal/stabilizing clasp contacts the tooth where? what does this allow? where are reciprocal/stabilizing clasps typically placed (lingual/palatal or buccal)?
- should contact the tooth on or above the height of contour
- allows for insertion and removal with passive force
- placed on the lingual/palatal side
the ___ is the component of the RPD located on the opposite side of the fulcrum line to the extension base, and assists the direct retainer to prevent displacement of the denture base in an occlusal direction
indirect retainer
the indirect retainer should always be placed as far as possible from the ___
distal extension base
rests are critical for the health of which structures?
the soft tissues underlying the denture resin base and the minor and major connectors
rests should prevent ___ action and should direct forces through the ___
- tilting
- long axis of the abutment tooth
what is the shape/outline for of occlusal rests? how wide and deep should they be? what is the angle formed with the vertical minor connector?
- rounded (semicircular) outline form
- 1/3 the facial lingual width, and 1/2 the width between the cusps
- 1.5mm for base metal
- floor inclines apically toward the center, so that the angle formed with the vertical minor connector is less than 90 degrees
what is the shape for cingulum rests? what is the mesiodistal length, labiolingual width, and incisoapical depth? which teeth are they generally contraindicated for?
- inverted “V” or “U” shape
- mesiodistal length of 2.5-3mm
- labiolingual width of 2mm
- incisoapical depth of 1.5mm
- contraindicated for mandibular central and lateral incisors
what is the shape for incisal rests? how wide and how deep should they be? how does it compare to lingual rests?
- rounded notch at an incisal angle
- 2.5mm wide, 1.5mm deep
- less favorable than a lingual rest and is rarely used because of esthetic compromise
a ___ is a metal plate that contacts the proximal surface or guide plane of an abutment tooth
proximal plate
___ are two or more parallel surfaces in the abutment teeth that provide a path of insertion and removal and can contribute to the retention of an RPD
guide planes
how wide should guide planes be?
should be about 1/3 of the buccolingual width of the tooth and extend 2-3mm vertically from the marginal ridge in the cervical direction
how does the molecular weight of acrylic resin denture bases affect the hardness of it?
the greater the molecular weight, the better the polymerization, and the harder the resin
shrinkage of acrylic resin always occurs, but what increases it?
- when excessive monomer is incorporated into the polymer during the mixture
- the volumetric monomer/polymer ratio is 1:3
what causes porosity of an acrylic resin denture base?
underpacking with resin at the time of processing, or a thick denture base heated to rapidly
what affect does cold-working have on cobalt-chromium RPDs?
- reduces the percentage elongation, causing an increase in hardness which makes the alloy more susceptible to fracture
- a low percent elongation is directly related to greater brittleness
cobalt chromium alloy RPDs are known to shrink approximately ___%
2.3%
are cobalt-chromium alloys more or less rigid compared with gold? what about palladium alloys?
more rigid than both
T or F:
in fixed prosthodontics, conservation of tooth structure by partial coverage instead of complete coverage whenever possible is preferred
true
in fixed prosthodontics, what does minimal taper accomplish?
enhances resistance and retention (6-degree taper between walls is recommended
when prepping a tooth for a cast fixed prosthetic, the labial reduction should be in two planes to avoid ___
overtapering or lack of occlusal clearance or insufficient space for porcelain
when prepping a tooth for a cast fixed prosthetic, where should margins ideally be placed and why?
supragingivally or at the gingival crest whenever possible, for maintenance care, ease of preparation, and impression
in fixed prosthodontics, what can surgical crown lengthening accomplish?
- can improve the outcome of a short clinical crown or when the placement of a margin impinges on the normal soft tissue attachment
- it is important to maintain the biologic width
what are factors that affect retention of fixed prosthetics?
- magnitude of the dislodging forces (sticky food)
- geometry of the tooth preparation
- roughness of the fitting surface of the restoration
- the materials being cemented
- the film thickness of the luting agent
what can be added to the preparation to add additional retention and resistance in short clinical crowns or when retention is compromised?
grooves
how can grooves or boxes affect a preparation that already has good retention?
- don’t really increase retention significantly if retention is already good
- where a groove limits the path of withdrawal, retention is improved
how do teeth with large surfaces areas affect retention?
more retentive (long axial walls vs short, molars vs premolars, etc)
can root canal treated teeth be used as abutments? what about teeth with short roots or little remaining coronal structure?
- root canal treated teeth restored with core buildups or post and cores can serve as abutments
- teeth with short roots or little remaining coronal structure are not recommended because failures can occur
when prepping a tooth for a fixed prosthetic, axial contours should correspond to the emergence profile (usually flat or concave) of the tooth to prevent what 3 things?
plaque accumulation, gingival inflammation, and bone loss
which type of occlusal contacts between opposing teeth are preferred for fixed prosthetics?
occlusal point contacts are preferred over broad, flat occlusal contacts to prevent wear
which two occlusal schemes are recognized in fixed prosthodontics?
cusp-marginal ridge and cusp-fossa
which occlusal scheme is typically seen with class I occlusion?
cusp-marginal ridge scheme
which occlusal scheme is typically seen with class II malocclusion?
cusp-fossa
which type of gold alloys are used for intracoronal cast restorations?
type I and II
which type of gold alloys are used for crowns and fixed dental prostheses?
type III and IV gold alloys or an alternative to gold alloy
when preparing a tooth for a cast restoration, a minimal metal thickness of ___mm over centric or occlusal bearing cusps and ___mm over nonbearing or noncentric cusps is needed to withstand occlusal forces when metal along is used, and ___mm when porcelain is used
- 1.5mm
- 1.0mm
- 2.0mm
when prepping a tooth for a cast restoration, how much space at the margin is required to prevent distortion during function and construction of the restoration?
0.5mm
when constructing a PFM restoration, what is considered adequate porcelain thickness needed to obtain good esthetic results?
1.5mm
a pontic design can be classified in which two categories?
mucosal contact and nonmucosal contact pontics
what are examples of mucosal pontics?
- ridge lap, modified ridge lap, ovate, conical, or bullet shape
- all of these pontics should be concave and passively contact the ridge
what are examples of nonmucosal pontics?
- sanitary (hygienic) and modified sanitary (hygienic)
- these are generally used in nonesthetic areas
which pontic design covers the ridge labiolingually, forming a concave area that is not cleansable and therefore is not used?
saddle pontic design
what are examples or rigid connectors for fixed dental prostheses?
cast (one-piece casting) and soldered
when are nonrigid FDP connectors indicated?
when it is impossible to obtain a common path of insertion between FDP abutments
which medications can act as antisialogogues?
- atropine, propantheline, hyoscyamine, and glycopyrrolate
- can be useful during tissue management when taking impressions
- should be used with caution
how do cords impregnated with chemicals containing aluminum or iron salts provide better sulcus displacement? what are examples of these chemicals?
- they cause transient ischemia and shrinkage of the gingival tissue and absorb seepage of gingival fluid
- aluminum chloride, aluminum sulfate, ferric sulfate, and ferric chloride
cords impregnated with ___ should be avoided because they can cause tachycardia
epinephrine
when a cord by itself might not achieve the desired tissue displacement, ___ is indicated
electrosurgery
when using electrosurgery to achieve the desired tissue displacement, what patients is it contraindicated in?
patients using medical devices such as cardiac pacemakers, a transcutaneous electrical nerve stimulation unit, or an insulin pump and in patients with delayed healing
which type of attached gingiva should electrosurgery not be used for?
thin
when performing electrosurgery, why should you use plastic instruments instead of metal?
to prevent burning and tissue destruction of the surface contacted
when cutting using electrosurgery, intervals of what time frame should be used?
5 seconds
when performing electrosurgery, the electrode should not contact metallic restorations or tooth structure because this may cause ___
irreversible pulp damage
elastic impression materials for final impressions for fixed restorations include ___
reversible hydrocolloid, polysulfide, condensation silicone, polyether, and additional silicone
which impression materials are agar hydrocolloids that, when heated, change from gel to sol between 71-99 degrees C; on cooling, they return to the gel state at 30 degrees C
reversible hydrocolloids
which impression material has a base paste main component that is a polysulfide polymer, a filler to add strength (titanium dioxide), a plasticizer (dibutyl phthalate), and an accelerator (sulfur)?
polysulfide polymer
with polysulfide polymers, the reactor (catalyst) contains ___ and the same filler found in the base, and a retarder to control the setting reaction (___ or ___)
- lead dioxide
- oleic acid or steric acid
which impression material releases water as a by-product on polymerization, which causes dimensional contraction?
polysulfide polymer
which impression material’s main component int he base is polydimethylsiloxane with fillers such as calcium carbonate or silica, and the accelerator may be stannous octate suspension and alkyl silicate?
condensation silicone
which impression material releases alcohol as a by-product on polymerization, which causes dimensional contraction?
condensation silicone
which impression material’s base paste contains a polyether polymer, colloidal silica as a filler, triglycerides, and nonphthalate plasticizer?
polyether
which impression material’s accelerator paste contains an alkyl-aromatic sulfonate, filler, and plasticizer?
polyether
which impression material has excellent dimensional stability owing to the fact that no volatile by-products are formed?
polyether
polyether impression material is very susceptible to change by ___
water absorption
which impression material does not develop any reaction by-products, but hydrogen gas release may occur if a reaction between moisture and residual hydrides of the base polymer occurs? what is added by the manufacturer to act as a scavenger for the hydrogen gas?
- addition silicone (vinyl polysiloxane)
- the result is a cast with small voids if the impression is poured soon after removal from the mouth
- platinum or palladium is added to act as a scavenger (another option is to wait an hour before pouring to allow the release of gas)
what are the advantages and disadvantages of irreversible hydrocolloid?
- advantages: rapid set, straightforward technique, low cost
- disadvantages: poor accuracy and surface detail
what are the advantages and disadvantages of reversible hydrocolloid?
- advantages: hydrophilic, long working time, low material cost, no custom tray required
- disadvantages: low tear resistance, low stability, equipment needed
what are the advantages and disadvantages of polysulfide polymer?
- advantages: high tear strength, easier to pour than other elastomers
- disadvantages: messy, unpleasant odor, long setting time, stability only fair
what are the advantages and disadvantages of condensation silicone?
- advantages: pleasant to use, short setting time
- disadvantages: hydrophobic, poor wetting, low stability
what are the advantages and disadvantages of addition silicone?
- advantages: dimensional stability, pleasant to use, short setting time, automix available
- disadvantages: hydrophobic, poor wetting, some materials release H2
what are the advantages and disadvantages of polyether?
- advantages: dimensional stability, accuracy, short setting time, automix available
- disadvantages: set material very stiff, imbibition, short working time
what are the noble metals?
gold (Au), platinum (Pt), and palladium (Pd)
high noble alloys have a noble metal content of ___% weight or greater and a gold content of ___% or greater
- 60%
- 40%
- old term was precious metal
noble alloys have a noble metal content of ___% or greater.
- 25%
- old term was semiprecious metal
T or F:
silver is considered a noble metal
false, it is reactive and improves castability but can cause porcelain “greening”
base metal alloys contain less than ___% noble metals
- 25%
- old term was nonprecious metal
what are the desirable mechanical properties of alloys for metal-ceramic restorations?
- high yield strength
- high modulus of elasticity (stiffness)
- casting accuracy
- biologic compatibility
- corrosion resistance
- the metal coefficient of thermal expansion should be higher than the porcelain to leave the porcelain in compression in a stronger state
why is it important to select a less dense base metal for a long-span FDP?
weigh less
the tooth preparation reduction for metal-ceramic restorations must provide space for metal and porcelain. what are the reduction measurements?
- total 1.5-2mm (occlusal contacts should be at least 1.5mm away from the porcelain-metal junction)
- allow 0.5mm for metal and 1.0-1.5mm for porcelain
in PFM restorations, the metal substructures provides ___ and increases the ___ of the porcelain
provides support and increases the strength of the porcelain
in the bonding of porcelain to metal, ___ formation is necessary for metal-ceramic bond
- metal oxide formation
- oxidation of a metal is accomplished by heating the metal structure in a furnace before the application of porcelain
porcelain is stronger under ___ forces than it is under ___ forces
- compressive
- tensile
how many layers of porcelain are used to build a ceramic restoration?
3
describe the 3 layers of porcelain used to build a ceramic restoration
- opaque porcelain masks the dark oxide color and provides the porcelain-metal bond (minimum thickness if 0.1mm)
- body or dentin porcelain contains most of the color or shade and is used generally to build most of the crown
- incisal porcelain is the most translucent layer of porcelain
describe hue, chroma, and value
- hue refers to the shade or color (red, green, yellow) and should be selected first
- chroma is the saturation or intensity of the color or shade and is selected second
- value is the relative lightness or darkness of a color
is it better to choose a shade with a higher or lower chroma?
- lower because it is easier to alter with surface colorant modifiers
- too high a chroma is impossible to decrease in hue or increase in value
___ is the phenomenon where a color match under a lighting condition appears different under a different lighting condition
metamerism
___ is the art of reproducing natural defects; this can be particularly successful in making a crown blend with the adjacent natural teeth
characterization
the hue of a natural tooth always lies in the ___ to ___ range
yellow-red to yellow range
when adjusting value, adding a ___ color can reduce value
complementary
___ can cause a loss of fluorescence in the finished restoration and an increase in the metameric effect
staining
glazing must be performed without ___
vacuum
describe the adhesive failure modes responsible for metal-ceramic failures
- porcelain-metal interface: oxide was not formed
- oxide-metal interface: contamination of metal
- porcelain-oxide interface: contamination of oxide surface
describe the cohesive failure modes responsible for metal-ceramic failures
- porcelain-porcelain: inclusions or voids (this is the preferred type of failure)
- oxide-oxide: oxide layer too thick
- fracture of a porcelain fused to metal restoration can usually be attributed to inadequate framework design
long-span metal-ceramic FDPs may be subjected to bending and may cause cracking or fracture of the porcelain because of its ___
low ductility
ceramic inlays and onlays have better ___ resistance than composite resins
abrasion
all-ceramic crowns that are glass infiltrated (feldspathic, leucite, lithium disilicate) are etched with diluted ___ and treated with a ___ agent and bonded to the tooth
- hydrofluoric acid
- silane-coupling agent
all-ceramic crowns with no glass content (zirconia and alumina) are luted to the tooth with ___ or ___
conventional or resin cements
machine grinding of ceramics can induce ___
surface cracks
what are the materials used for provisional restorations?
- poly ethyl methacrylate
- polymethyl methacrylate
- microfilled composite
- light cured
the thickness of the cement (luting agent) film at the margins should be minimized to reduce ___ of the luting agent
dissolution
what are the factors that increase the cement space for crowns?
- use of die spacers
- increased expansion of the investment mold
which luting agent is useful for cast crown, metal-ceramic crown, and partial FDP?
adhesive resin, composite resin, glass ionomer, reinforced ZOE, resin ionomer, zinc phosphate, and zinc polycarboxylate
which luting agent is useful for crown or partial FDP with poor retention?
adhesive resin
which luting agent is useful for metal-ceramic crowns with porcelain margins?
adhesive resin, composite resin, glass ionomer, reinforced ZOE, resin ionomer, zinc phosphate, and zinc polycarboxylate
which luting agent is useful for casting on patient with history of posttreatment sensitivity?
consider reinforced ZOE or zinc polycarboxylate
which luting agent is useful for pressed, high-leucite, ceramic crowns?
adhesive resin or composite resin
which luting agent is useful for slip-cast alumina crowns?
adhesive resin, composite resin, glass ionomer, reinforced ZOE, zinc phosphate, and zinc polycarboxylate
which luting agent is useful for ceramic inlays?
adhesive resin or composite resin
which luting agent is useful for ceramic veneers?
adhesive resin or composite resin
which luting agent is useful for resin-retained partial FDP?
adhesive resin or composite resin
which luting agent is useful for cast post and core?
adhesive resin, composite resin, glass ionomer, resin ionomer, and zinc phosphate
___ forces on teeth are the most destructive to the periodontium
horizontal
nonworking interferences generally occur on what areas of teeth?
inner aspects of the facial cusps of mandibular teeth
in selective grinding or occlusal equilibration, how should cusp tips be treated?
- they should not be reduced
- they can be narrowed, or the opposing fossa or marginal ridge can be adjusted
in centric relation, the mandible can rotate around the horizontal axis ___mm. where is it measured?
- 20-25mm
- it is measured between the maxillary and mandibular incisal edges of the teeth
translation is the motion of a body in which all of its points move in the same direction at the same time. where does translation of the mandible occur?
within the superior cavity of the joint between the disc-condyle complex and the articular fossa
which muscle is responsible for condylar translation?
the lateral pterygoid
___ is seen when the maxillary and mandibular teeth of multiple posterior teeth contact in lateral excursive movements on the working side
group function occlusion
how do the physical properties of composite compare to amalgam?
moisture and thermal expansion properties of composite are inferior to that of amalgam
what are the drawbacks of complete ceramic restorations?
fracture potential and in some ceramic materials, marginal fit
the setting expansion of any gypsum product is a function of ___
calcium sulfate hihydrate crystal growth
describe the 5 types of dental gypsum
- type I: plaster, impression plaster
- type II: model plaster
- type III: dental stone
- type IV: dental stone, high strength (die stone)
- type V: high strength
which types of dental stones require higher water/powder ratio?
types I and II require higher water/powder ratio than type III and IV stones
increasing water/powder ratio of dental gypsum increases ___ and decreases ___ and ___
increases setting time and decreases strength and setting expansion
which chemicals accelerate setting of gypsum and which slow the setting?
- potassium sulfate and sodium chloride accelerate setting of gypsum
- sodium citrate and borax slow setting
T or F:
investments shrink during setting when heated
false, they expand
gypsum-bonded investments are used for casting alloys containing ___% to ___% gold
65-75%
phosphate-bonded investments are used for casting ___ alloys
metal-ceramic
silica-bonded investments are used for casting ___ alloys
base metal alloys (for frameworks for dental prostheses)
___ is the procedure performed on a metal when it is brought to an elevated temperature and is cooled rapidly; it softens the alloy owing to change in the phase structure of the alloy, making it more malleable for finishing procedures.
quenching
T or F:
sprues should always be larger in diameter than the cross-section area of the patterns where they are attached
true
T or F:
crucibles can be used with multiple types of alloy
false, they should always be used with only one type of alloy to prevent contamination
