Prosth Flashcards
Zinc-oxide eugenol setting time can be accelerated by adding ____. It sets through a(an) ____ reaction that yields ____.
Water
Acid-base
Zinc eugenolate chelate
What material provides the most accurate means of evaluating centric occlusion and/or occlusal interferences on fixed prostheses?
Shim stock
True or false… light sources have an effect on the perception of color because light sources must contain the wavelength of the color to be matched if the color is to be seen by the eye
True
____ is the matching of the apparent color of objects with different spectral power distributions. Colors that match this was are called ___
Metamerism
Metamers
The ___ articulators contains the condylar element attached to the lower member and condylar guidance attached to the upper member to correctly resemble human anatomy. ___ records should be utilized in order to achieve both medial and superior condylar guides.
ARCON
Lateral interocclusal
Wax patterns for cast restorations should be invested as soon as possible after they are completed to minimize distortion caused by ___
The relaxation of the internal stress of the wax pattern which results in distortion of the shape and contour of the wax and may decrease the accuracy of the fit of the restoration
True or false.. an impression tray should not extend past the vibrating line in a maxillary diagnostic impression
False. It should slightly extend beyond the vibrating line
What is the most important reason zinc oxide eugenol cements are better than zinc phosphate cements for crown delivery?
Because zinc oxide cements have decreased potential to irritate the pulp. In fact, zinc oxide eugenol actually has a sedative effect to the pulp.
Zinc phosphate cement uses phosphoric acid for its chemical reaction and is irritating to the pulp
What is the most common operatory error that makes it difficult for the lab to fabricate PFM crowns?
Insufficient tooth reduction
Name the four types of elastomeric impression materials
Polysulfides
Condensation silicones
Addition silicones
Polyethers
Elastomeric impression material works best when the tooth preparation is ___
Free of moisture
What happens if you increase the proportion of water to class 4 gypsum die stone?
Less expansion and less strength
Define tensile strength
The maximum stress that a material can withstand while being stretched or pulled when falling or breaking. It is an important property of a restorative material
Define elastic modulus
The ability to sustain deformation without permanent change in size or shape
Define flexural strength
The ability of a material to resist fracture under bending loads
Define fracture toughness
The ability to resist the propagation of a crack
Changing the vertical dimension of occlusion through fixed restorations require the mounting of patients’ casts in a ____
True hinge position
A true hinge axis is a line that passes through the ___ and ___ and coincides with ___
Left and right mandibular condyles
Center of rotation of the mandible
PFM crowns with high-noble base typically have the highest percentage of what metal?
Gold
What is the advantage of high noble metals?
Highly resistant to corrosion and oxidation
What describes the physical property which gives cast gold the ability to be burnished?
Percentage elongation
It describes the increase in length of a material when subjected to tensile forces divided by the original length
Modulus of elasticity describes tensile elasticity, or the tendency of an object to deform along an axis when opposing forces are applied along that axis; it is defined as the ratio of ___ to ___
Tensile stress
Tensile strain
Gold can be easily burnished into and against margins to accomplish what 3 things?
Improve adaptation of the restoration
Decrease marginal leakage
Increase cleansibility
The main drawback to using polyether impression material is ___ which often leads to ___. The material is sometimes difficult to remove when compared to other materials. It is [more/less] expensive than other materials except for addition silicones. It has an adequate ___ and can be poured multiple times. The ___ nature of polyethers makes it work to use in ___ conditions.
High stiffness
Tearing
Less
Tear strength
Hydrophilic
Wet
What contributes to the dimensional instability of condensation silicones?
Evaporation of volatile by-products results in shrinkage of the impression (alcohols)
An impression made with condensation silicones should be poured immediately to prevent its shrinkage
Addition silicones do not produce by-products
When casting chrome-cobalt, how much shrinkage should you expect?
2.2%
What is CrCo (chrome-cobalt) used for?
Denture framework
All metal restorations
PFMs
Other base metal alloys used in dentistry are nickel-chromium-beryllium and nickel-chromium alloys
What is the purpose of flux in the soldering process? (3 purposes)
To displace gasses and dissolve corrosion products
Acts to dissolve oxides along the adjoining metal surface and become a protective barrier against oxygen
Flux dissolves oxides and facilitates the wetting of the surface of the molten metal which makes the metal joint stronger and more durable
Back pressure porosity is suggested by ___
The presence of rounded edges of the casting instead of sharp and angled edges
Rounded edges of the casting suggests gas was still present within that area, prohibiting the fluid from flowing in
Too short of a sprue can also cause back-pressure porosity since inadequate length causes incomplete venting of gas
Define flexural strength
Property of a material to resist fracture under bending
It is a property of a material which is critical in thin layers such as margins.
The main significance of flexural strength in restorative dentistry is observed in class 5 cervical caries
Cervical flexure in class 5 preparations is the major reason for the failure of these restorations
What is the Bennett angle?
The angle that is formed by the non-working condyle and the sagital plane during lateral movements (it is anterior and mesial to the original position)
What is a Bennett shift?
The lateral movement of the mandible towards the working side during lateral excursions
What is a Bennett movement?
The left and right condylar motions caused by lateral movements of the mandible
___ implants are the most popular used endosseous implants today
Root-form
What are endosseous implants?
They are placed directly into the bone and act as an anchor or root that will hold the crown, bridge, or implant supported denture in place
True or false… transosteal implants are commonly used.
False. They are Less likely to be used because of the complicated and very extensive surgical procedure that the patient undergoes.
____ implants are indicated for patients who want implants but have inadequate bone height and width. The placement of these implants is highly technique sensitive and is quite expensive.
Subperiosteal
The most common esthetic problem associated with porcelain veneers is their ____
Lack of color differentiation between the gingival and incisal portions of the restoration
Orange stains are commonly used to change the hue of porcelain
Staining methods are used to transform monochromatic porcelain veneers into polychromatic restorations to have natural beauty
What mistake should be avoided to prevent production of porous porcelain?
Inadequate condensation of porcelain. This would cause voids between particles, causing porosity.
Controlled and gentle mechanical condensation of porcelain allow sthe particles to settle and become closer, eliminating voids
Surface tension condensation allows the drawing of porcelain particles together by draining the excess fluid from the mixture
When preparing a partial veneer for tooth #8, the proximal grooves are placed parallel to ___. This ensures that ___
The incisal 2/3 of the facial axial wall
There is only one path of insertion
Proximal grooves created in a proper way also relieve the tooth of unsupported enamel
True or false… the narrowing of the occlusal table of the Pontic of a bridge can lessen the force exerted by its antagonist
True
True or false… osseointegrated implants should NOT be partnered with a natural tooth as an abutment for FPDs. Why?
True
Because they have different type of bone support and degree of physiologic mobility
If one of the abutments DO NOT show any degree of mobility, like that found in an implant, the force exerted on the natural abutment tooth will elicit a cantilevering effect to the implant, breaking the cement seal.
Osseointegrated iimplants do not have a PDL. If one abutment complensates for the occlusal load and the other does not, the torque force between the abutments is increased
What may occur as a result of enamelplasty on #11 that results in the unilateral loss of canine guidance?
Decreased clearance on the right side and a greater possibility of a non-working contact
The decrease in clearance occurs due to the placement of the crown on the left upper canine without restoring the canine guidance. The change to group function occlusion will create a decades in the vertical clearance on the right side because the teeth will not separate as much as when the patient was in canine guidance
What is the most common reason for a crown not to fully seat upon delivery?
Excessive proximal contacts
What is the best reason why the liquid component of a cement should be dispensed immediately before mixing is commenced?
To prevent evaporation of the volatile components
having deficient liquid in proportion to cement powder results in a __ consistency and ___ setting of the cement mixture
Grainy
Premature
What is the primary reason why adjacent abutment teeth are splinted in an FPD?
To improve the distribution of the occlusal load
What is the ideal incisal reduction for a PFM preparation
2mm
The PFM crown requires a minimum of __ incisal reduction to provide adequate thickness of metal and porcelain. Porcelain thickness can be __ to __ thick, while the metal thickness should be ___ to ___ minimally.
- 5
- 2 - 1.5
- 5-0.3
What is the minimum amount of occlusal clearance necessary for a non-functional cusp of a posterior PFM? What is the minimum clearance for functional cusps?
1.5mm = nonfunctional
2-2.5 = functional
What is the next step after evaluating the occlusion of a full gold FPD?
Cement the FPD with temporary cement and reassess the fit
The thickness of the denture flange in the maxillary buccal vestibule needs to be reduced due to the presence of ___ in the mandible.
Coronoid process
When border molding the lingual border of the mandibular final impression for a complete denture, the contractions of which muscles are being accounted for?
Palatoglossus
Superior pharyngeal constrictor
Mylohyoid
Genioglossus
The ___ muscle and ___ muscle both help in elevating the tongue. The ____ muscle protrudes the tongue
Palatoglossus
Mylohyoid
Genioglossus
The __ is a stable landmark that does not change position within the palate. It is used as a guid in placing and positioning of the maxillary anterior teeth during denture tooth placement. It is expected to be ____ positioned between the maxillary central incisors. The most labial surface of the maxillary central incisor denture tooth should be placed approximately ___mm anterior to the ___
Incisive papilla
Lingually
8-10mm anterior to the incisive papilla
What is combination syndrome? What are 7 symptoms?
Observed in patients with a maxilla complete denture occluding against a Kennedy class 1 partial denture
Bone loss in the premaxilla
Hypertrophy of the posterior maxillary tuberosities
Extrusion of the lower anterior teeth
Posterior bone loss in the mandible under RPD
Papillary hyperplasia of the maxilla
Decreased VDO
Facial esthetics often altered
Combination syndrome is a condition that usually occurs when ___ oppose ___
Mandibular anterior teeth
A maxillary complete denture
The path of the condyles in mandibular movements is regulated by what 3 factors?
Size and shape of the fossa
Size and shape of the menisci
Muscular influences and movements
True or false… compromised endodontically treated teeth should NOT be used as abutments because of the lack of pulp vitality
False. Although they do become weaker, it is because the removed dentin makes them weaker.
What is the ideal crown to root ratio? What is realistic?
1: 2
2: 3
What is the minimum crown to root ratio for abutments?
1: 1
2: 1 should not be used for abutments
What is Ante’s law?
The PDL surface area of the abutment teeth should be equal to or greater than the imaginary PDL surface area of the missing teeth
Splinting teeth serves what purpose?
Distributes occlusal forces
When is splinting teeth recommended?
Where the periodontal surface of an abutment tooth is not sufficient to support the bridge (failure of Ante’s law)
When replacing a canine, the central and lateral should be splinted together to prevent lateral drifting of the bridge
True or false… when replacing a maxillary canine with a Pontic, the central and lateral should be splinted together to prevent lateral drifting of the bridge
True
What kinds of roots are best for bridge abutments?
Divergent, multiple, curved, and broad roots
Not fused, single, conical, and round roots
In what 4 circumstances are partial dentures recommended?
Distal extension
Long span
Bone loss around potential abutments
Bridge or implant is too expensive
When is a complete maxillary denture contraindicated?
When only the mandibular anterior teeth are present because severe damage to opposing premaxilla occurs (combination syndrome)
What is combination syndrome?
When a complete maxillary denture is present with only mandibular anterior teeth are present. It causes damage to the premaxilla
Which is more economical, cement retained or screw retained implants?
Cement-retained
Which allows for minor angle correction, cement or screw retained implants
Cement retained
Which, cement or screw retained implants are easier to use in small teeth?
Cement retained
Name three draw backs to cement-retained implants
Requires more chair time
Has some propensity to loosen
Excess cement can cause peri-implantitis
Name one major advantage of screw-retained implants
Retrievability allows for crown removal and good maintenance
Name two draw-backs to the screw retained implant
Access hole is through occlusal of posterior teeth and lingual of anterior teeth
Screw may loosen during function
Alginate is an ___ hydrocolloid that is composted of sodium or potassium salts of ____ which react chemically with ___ to produce ___.
Irreversible
Alginic acid
Calcium sulfate
Insoluble calcium alginate
____ adds strength to alginate
____ controls the setting rate of alginate
Diatomaceous earth
Trisodium phosphate**
MI and CR coincide in only ___% of the population
10%
Casts are mounted in __ when ___ can be maintained such as in ___
MI
MI
Singled fixed procedure
Casts are mounted in ___ when ___ is impossible to maintain such as in ___
CR
MI
Complete dentures, or multiple teeth being restored or replaced
What is the objective of the facebow record?
Objective is to duplicate on the articulator relationship of the maxillary arch to the skull and the mandible to the rotational center of the TMJs that exist for that particular patient
The arbitrary facebow orients the maxillary cast to the skul via ___ to stabilize the bow.
With a kinematic facebow, it is placed on the ___ of the ___
Auditory meatus.
Hinge axis of the mandible
True or false… the non adjustable articulator does not reproduce full range of movement and the distance between hinge and teeth is significantly shorter than in the patient
May result in premature contacts and incorrect ridge and groove direction of restorations
True
In a semi adjustable articular, such as ___, it allows you to set the Bennett angle (___degrees) and the HCI (___ degrees)
Arcon
15
30
What is the difference between arcon and non arcon semiadjustable articulator?
Arcon = condyles are a part of the lower member, fossa are a part of the upper member
Nonarcon = upper and lower members are rigidly attached
Casts poured from alginate are more accurately mounted with __ records. Casts poured from elastomeric materials are more accurately mounted with ____ materials
Wax
Elastomeric (PVS or ZOE paste)
Condylar guidance is distinguished by the ____. It is represented by __ on the articulator. It is the ___ determinant of occlusion
Slope of articular eminence
HCI
Posterior
Incisal guidance is determined by _____. It is represented by the ____ on the articulator. It is the ___ determinant of occlusion
Incisal edges of lower incisors against lingual slopes of upper incisors
Pin and guide table on articulator
Anterior
Define canine guidance
When in lateral movements, all posterior teeth are immediately disclosed as contact occurs solely between upper and lower canine on the working side.
Define anterior guidance
Refers to both incisal and canine guidance
During protrusive, incisal and condylar guidance provide clearance for all posterior teeth
During lateral, canines on working side and condyle on balancing side provide clearance for posterior teeth on balancing side
Anterior guidance must be preserved when restorative procedures change the surfaces of any ___ teeth
“Guiding” (anterior)
What is the difference between mechanical incisal guide table and custom?
Mechanical incisal guid table gives insufficient information to reproduce lingual contours of maxillary anterior natural teeth
Custom incisal guide table is made out of acrylic resin and provides this information
Define mutual protection
Front teeth protect teeth - front teeth disclose posterior teeth during protrusive and lateral movements
Back teeth protect front teeth - back teeth have flat occlusal surfaces and strong roots to help protect anterior teeth from bite forces
Define the labial vestibule and buccal vestibule
Labial vestibule goes from labial frenum to buccal frenum.
Buccal vestibule goes from buccal frenum posterior to the hamular notch
The hamular notch is formed at the junction of the ____ and the ___ of the ___
Maxilla
Hamular process
Sphenoid bone
Where is the vibrating line located?
From hamular notch to hamular notch
2mm away from fovea palatini
It has a “butterfly line” appearance (the vibrating line is slightly posterior to it)
What is the valsava procedure?
Hold your nose and try to push air through the nose.
It would balloon the soft palate down, to help you identify the “butterfly line”
The vibrating line to “butterfly line”is a critical area for denture fabrication called the ___
Posterior palatal seal
The coronoid notch refers to the ___ are of the impression/denture
Coronoid notch
In order to identify the coronoid notch in border modeling, you have the patient move their jaw in what direction?
Left to right
The pterygomandibular raphe connects what two muscles?
What movement do you have the patient do to identify this anatomy?
Buccinator and superior pharyngeal constricter
Open their mouth wide
