yilmaz. FPD Flashcards
is alteration of speech a result of tooth loss
yes, alteration of speech can be a result of tooth loss
what is Ante’s law?
Ante’s law says for an FPD (a bridge spanning an edentulous space), that the peri-cemental area of abutments (the amount of root/cementum of abutments) MUST be more than the peri-cemental area replaced by the FPD (as in, if 2 abutment teeth, these generally can’t support a 3-pontic span). must look at quality of roots and teeth to really make a determination
what is the mathematical expression for the effect of length (span of pontic) on deflection of the FPD? what does it mean?
The mathematical expression relating the length of the pontic (spanning edentulous area) to the amount of deflection seen is
D=L^3. so, deflection is seen as a cubed amount of the lenght.. so even a short seeming length will undergo an exponential amount of deflection
describe and explain the mathematical expression for the effect of the connector height on deflection
the math. expression showing the effect f connector height on deflection is
D=(1/ H^3). So if the connector height is reduced by half, you will see 8x the amount of deflection (so thinning hte connectors will result in large amounts of deflection felt by the pontic span)
in a metal ceramic crown, describe how the two different materials of porcelain and metal relate
the relationship of hte porcelain to the metal is very importnat since these two must fuse togehter to form a cohesive unit. metal has a higher thermal expansion rate than does porcelain, .. so potassium oxide is added to feldspar porcelian which then allows for leucite to precipitate.. the amount of leucite determines the amt of thermal expansion and allows material manipultion to bring procelains thermal expansion closer to that od the metal alloy. there are many metal choices, but the ingredients of galliun, indium, and copper provide for the necessary oxidation of the metal that binds the porcelain to the metal ((this oxide layer via ions- allows the porcelain to “wet”the surface of the metal))
name three aspects bny which to evaluate teeth form their potential as abutements
3 qualities ealuated in choosing appropriate abutments include:
- the clinical crown-root ration (ideally 2:3;; a minimium of 1:1)
- the root form
- tooth angulation
in terms of selecting abutments, with other aspects equal, are teeth with single or multiple roots prefered? why?
teeth with multiple roots are preferred to single roots in selection of an abutment. this is bc SURFACE AREA of the root is key.. so more roots = more surface area
generally speaking .. order these from most to least desirable as an abutment choice:
incisor
canine
premolar
generally:
canines are excellent abutment choices, then premolars, and rarely incisors
when comparing multiroot teeth for abutment choice, are straight or cirved roots preferred? divergent or convergent roots?
when evaluating multi-rooted teeth , teeth with Curved and Divergent roots are preferred to the qualities of straight and/or convergent.
for what preparation difficulty would you consider using precision attachments?
precision attachments are an option of dealing with teeth with very different path of withdrawals (recall, for FPD< common POW = paramount importance).. so preceision attachment allows for 1 abutment to be made as a separate piece to be attached via a special (though weaker and less lasting) attachment to the second piece containing thepontic and the abutment
A ridge lap shaped pontic (aka, saddle) is not a recommended shape – why?
the saddle pontic has the contours and emergence profile of the missing tooth, however, it is difficult to clean the mucosal surface (where food and bacteria get trapped) and therefore not recommended due to unhygenic enviro created
is a hygenic-styled pontic appropriate for use anywhere?
no! of course not (dental choices NEVER a one size fits all!) . the hygenic pontic is basically floating – has 1-2 mm lcearnace of the mucosal surface (ridge) everywhere. this is not good for the maxillary arch where the clearance is like a shelf for food to get stuck, and it is not esthetically pleasing on the highly visible MAX arch.
it is an option for the MAND arch, especially broadly shaped ridges (vs sharply shaped) . good in areas of low visibility - such as posterior
what is the most common design for pontic shaping?
the most common design for pontic shaping the the modified ridge lap (the same as we made for class). this has a “T” shaped contact w buccal mucosa as the anterior region extends a bit gingivally for esthetics. is easy to clean. the lingual portion has 1.5 mm clearance over the entire mucosal surface/ridge
where can a bullet shaped pontic be used?
a bullet pontic is like a hygenic pontic is that it floating. however , the bullet pontic is more heart shaped (more pointed at hte cervical region) and is better suited for sharp arches (sharp-shaped ridges) . also very hygeinic bc is a floating pontic w mucosal clearnace all-around
what is an ovate pontic?
an ovate pontic has a egg-shape finish at the cervical region and is meant to sit in the socket of the evacuated tooth. for this sort of pontic to work, the socket of the missing tooth needs to be maintained or surgically created.
what is a cantilevered pontic and where can this be used?
a cantilevered pontic is a pontic design where the pontic only has an abutment on one side (and no connectors/abutment ont he other). this is an option suitable when the missing tooth is mesial to the abutments.
the abutment teeth should have No periodontal problems.
-the pontic should be MESIAL to the abutment so that the abutment can better handle the oclcusal loads (when the cantilever is distal to the abutment = very unfavorable occlusal loads on the abutment)
if the lateral incisor is missing, could a cantilever pontic be a good option?
yes! if the lateral incisor is missing, a cantilever pontic could be a great option – esp since (helathy) canine are a good abutment choice, the pontic would be mesial to the abutment, and the lateral incisor does not receive a lot of occlusal force. further, this set-up would allow for preservation of the central maxilary incisor = Great
should the pontic have ridge contact?
no. the pontic should not have ridge contact. such contact w the ridge mucosa will irritate the tissue and cause ulceration and inflammation
should the pontic contact the gingival surface on the buccal aspect. ?
depending on the pontic design- yes. esthetically, shaping the pontic to contact the buccal gingical tissue makes the pontic appear to be naturally emerging from the gingiva - which is good bc a natural appearnace
are only 3 unit bridges possible?
no. larger spans of FPD are possible.. there can be an internal abutment with a pontic on wither side and then anchoring abutments. (5 tooth span, replacing 2 missing teeth).. // this middle abutment is called a PIER ABUTMENT. or there can be creativitiy mixing and matching cantilevers, non-rigid connetors, etc
what are the top 3 causes for FPD failure?
1) caries - 23%
2) procelain fracture - 16%
3) uncemented, 15%
should porcelain-to-gold contact be avoided or sought?
porcelain to gold occlusion contact should be AVOIDED (per rosentsteil)
patient allergy to nickel can be high, what metal alloy could be used as the metal portion of MC/ FPD?
a cobalt chromium alloy is an alternative to nickel-chromium alloy. gold and palladium options exist as well, but are expensive
what component bonds the porcelain to the metal alloy understructure in a FPD/MCC?
an oxide layer of the metal (gallium, indium, and copper are added to alloys to provide for this necesary oxidation) is needed for porcelain to metal bonding
for an FPD, how thick should the metal portion be minimally?
the metal framework of an FPD should minimally be 0.3mm thick
T/F enamel can withstand tension better, while dentin can better withstand compression forces
False. the opposite is true:
enamel can better withstand compression while dentin can better withstand tensile forces
why are metals alloyed versus just using pure forms?
alloying metal confers STRENGTH. pure metals are too soft and deform ..alloying, solid solution hardening, and grain refining are processes to strengthen the metal
T/F fine grain structure resists deformation
True. fine grains tructure of metals resists deforation – especially, the grain boundaries. small amounts of Ir and Ru are added to produce metals with very fine grains . the grain boundaries act to block dislocation movements
