Week 5- Pontics Flashcards
what dimension does bone loss of the alveolar ridge occur in after extraction
horizontal dimension and buccally
what percentage of alveolar bone dimension can be lost after tooth extraction
50%
alveolar bone loss has been reported to be up to _____
6-7mm
two thirds of loss of bone volume can occur within the ______ of tooth extraction
first three months
reductions of _____ in vertical ridge height have been noted
2-4mm
what is the pattern of vertical bone resorption often accompanied by
a ridge that has moved in a palatal/lingual direction and has atrophied vertically
sockets that were preserved with bone grafting and/or membrane on average lost _____ less of ridge with and _____ less of ridge height
2mm; 1mm
sockets that were grafted had _____ more bone volume when compared to sockets that were not grafted
20%
maxillary sites lost ____ bone than mandibular sites
less
what percentage of patients have a normal ridge after extraction
8%
what percentage of patients have a class III ridge after extraction and what is a class III ridge
- 56%
- F-L and OG height affected
what percentage of patients have a class II ridge after extraction and describe a class II ridge
- 3%
- O-G height is affected
what percentage of patients have a class I ridge after extraction and describe a class I ridge
-32%
- FL width is affected
what is the most common class of alveolar ridge deformity after extraction
class III
what does the pre-treatment assessment include
- evaluate the dimensions of the edentulous space
- evaluate the positions of the abutment teeth to assess the favorability for a bridge
- evaluate the possible occlusal outcomes
- is there a need to reposition the teeth orthodontically prior to fixed work
- wax up!!
what materials are used for pontics
- cast metal
- metal-ceramic
- zirconia or all ceramic
when two materials are used, the finish line for their joining should not be on the:
edentulous ridge
what are the ideal characteristics we look for in a pontic design
- esthetic
- biologic
- mechanical
what are the esthetic characteristics we look for in pontic design
- apperance of replacement
- replication of emergence from ridge
what are the biologic characteristics we look for in pontic design
- ability for the patient to clean well around the bridge/pontic area
- allows for healthy tissue
- patient comfort of the bridge
- harmonious occlusion
what are the mechanical characteristics we look for in pontic design
rigid framework to resist deformation or fracture
ideally, a pontic should have the same _____ height as the original or neighboring teeth
inciso- gingival
when resorption of bone has taken place, the pontic does what
changes shape in order to keep in contact with the ridge concavity
contour of the pontic needs to be blended smoothly to avoid:
a ledge at the cervical
contour in apical half should approximate:
the length of the adjacent teeth
the facial surface is altered to curve:
from the gingival-facial to the middle of the facial surface
what happens when the pontic doesnt adapt to the ridge well
esthetics, speaking and food impaction can become troublesome
pontic ridge contact should ideally be on what kind of tissue
keratinized
when pontic contact is on non-keratinized tissue:
ulceration and constant irritation can occur
pontic contact with ridge should not:
inflict pressure on the tissue
pontic shape in contact with tissue should also be:
convex
what happens when the pontic contact is too heavy
tissue/bone resorption
what happens when the pontic contact is too light
food impaction, esthetics compromised
convex shape of the gingival aspect of pontic allows for:
easier cleaning for patient
what keeps out food and debris from being trapped under the pontic
fullness of pontic shape and proper gingival embrasures
what tools can be used to keep up oral hygiene under pontics
- floss threader
- super floss
- proxabrush
- rubber tip
- water pik
what size of pontic connectors are necessary for strength
-4mm OG
- 3-4mm FL
what is the order of material strength from greatest to least
metal > zirconia > porcelain > acrylic
pontic connectors should not impinge on:
embrasures
do you want occlusion on pontics
yes just should be equal to or lighter than adjacent teeth
what pontic position creates torque on connectors and abutments leading to failure
pontics placed outside of the inter-abutment axis
what is the number 1 reason for bridge failure
occlusion
occlusion development with a bridge should replace ideal occlusion:
MI contacts, working and non-working contacts in lateral excursions, protrusive contacts and canine guidance
what are the types of pontic design
- ridge lap (saddle)
- modified ridge lap
- hygenic-perel modification
- conical
- ovate
describe a ridge lap pontic and what is is also known as
- AKA saddle pontic
- not used any longer
- forms a large concave contact area with ridge
- patient not able to clean
- creates tissue inflammation leading to tissue ischemia and necrosis
describe the hygenic pontic and what is it also known as
- AKA sanitary pontic
- no contact with ridge
- at least 2-3mm of space between the ridge and pontic
- patient can easily clean without the pontic being a food trap
- only for use in non-esthetic areas
- design and shape is convex in all directions
what is the modified hygenic pontic used for
- to increase strength of bridge in connectors with hygienic pontic
what is the issue that is created with modified hygienic pontics and what can be done to overcome that
- deflection is increased with less occlusal gingival height
- make connectors larger
describe conical pontics
- passive contact with ridge crest
- rounded and cleansable
- triangular embrasure space can trap food
- best suited for thin mandibular ridges
- also not best for esthetic areas
describe the modified ridge lap pontic
- passive contact facial side of ridge crest
- can appear very esthetic
- convex tissue surface contact
- used frequently in the esthetic areas
- shape can help keep food from trapping
- cleansability much easier for patients
what is the most common pontic design
modified ridge laps
describe the shape of modified ridge lap pontics
- convex in all directions except for a small concavity on the lingual side of the F-G aspect of the pontic
- contact area is meant to be minimal
- lingual side needs to be smooth and highly polished
- tissue contact okay but should not put pressure on the tissue
- keep tissue contact on keratinized tissue
- tissue contact shaped like a T
what is the one part of the modified ridge lap pontic that is concave
the area of contact
describe the ovate pontic
- blunt rounded pontic shape that is set into a concavity in the tissue of the edentulous ridge
- generally requires planning
- cleansable by well educated and motivated patients
- highly esthetic
what type of planning do ovate pontics require
- pre-prosthetic surgery via immediate provisionalization after extraction
- surgery/modification with provisional to develop tissue shape and contour
- ovate pontics keep a slight pressure on the tissue to maintain the effect of emerging from the ridge
which are the esthetic pontic designs
- modified ridge lap
- ovate
what is the most common pontic and why
modified ridge lap because it is esthetic but requires less effort for the patient and doctor
is sx required with modified ridge lap
no
what are the typical connector dimensions
- height: 3-4mm
- width: 3-4mm
what shape is better for gingival embrasures: U shape or Vs haped
U shaped
connectors are shaped to be concave in the:
- buccal lingual and the mesial distal toward the ridge
connector U shape from:
occlusal to gingival
why is the U shape connector preferred over the V shape
- U shape is stronger
- U shape less likely to fracture
if you increase the height by 2x you increase the strength by:
a cube
what shape are anterior connectors
tear drop
anterior connectors are placed more ______ for esthetics
lingually
anterior connectors are longer _____ for strength
inciso-gingivally
metal connectors can be ____ in height
3mm
in posterior connectors occluso-gingival height is more important than _____ for strength
buccal lingual width
posterior connector is what shape
heart shaped
in all ceramic bridges the connector size is at least _____
4mm and possibly needs to be larger
in all ceramic bridges, U shaped connectors need a ________ at the gingival embrasure
large radius
full strength zirconia shows ____ fracture resistance compared to all ceramic
increased
what is the difference in connector size between all ceramic and full strength zirconia
none they need to be the same size
metal frameworks are assembled in two ways:
- cast/milled as one piece
- two or more pieces are soldered together
when can laser welding be used
in titanium alloy situations
when can CAD/CAM be used
to make a one piece bridge framework with ceramics/zirconia
what is the issue with single piece casting
distortion- greater the length, the increased distortion
longer span bridges are often:
cast in multiple pieces and soldered together
what can you do if a FPD metal framework does not fit due to distortion
you can cut between a pontic and retainer, re-seat each smaller piece to verify the individual fit and capture the new seating with acrylic. this is then sent to the lab to solder the new pieces together
what is soldering and explain the process
joining of metals by fusion of filler metal bonding to each of the parts being joined
- the bond is created by wetting the surface of parent metals with liquefied solder
- the metal framework does not melt during this
what is brazing
a specific form of soldering when the filler material has a melting temperature above 450 degrees celsius
what do we want solder to do for us
- resists tarnish and corrosion
- the fusion temperature 100-150 degrees farenheit below that of the substrate metal
- free flow when melted
- resists pitting
- is strong
- matches color of the two parts being joined
solder is classified by:
fineness
describe fineness
- fineness is the parts per thousand of gold in a solder
- 560 fine = 650 parts gold per thousand parts
higher fineness ____ the melting range
increases
higher fineness ____ resistance to tarnish or corrosion
increases
higher fineness results in____ hardness
decreased
what does more gold do to fineness
lower it will melt and more flexibility, less hardness
what factors affect the accuracy and prognosis of soldered connectors
- connector space
- metal surface preparation
- indexing technique for investment
what does a proper connector space allow for in solder accuracy
- allows the solder to flow in between
- allows for thermal expansion and shrinkage of the solder
- small enough to minimize distortion from the solder shrinkage as it cools
- large enough to allow for a strong connector
- parallel and flat with a space for thickness the size of a business card- 0.2mm
how should the metal surface be prepared for soldering
- needs to be clean and uncontaminated
- needs to have a satin finish instead of highly polished
describe the indexing technique for investment
- flow auto-polymerizing acrylic resin into space to hold two pieces together. each side should be fully seated with margin integrity checked and verified
- make an occlusal plaster index to send to the lab for soldering. framework should be solidly planted in plaster index so that enough of the coronal portion is covered so framework can be held in place
what is flux and what does it contain
- enables solder to wet and spread over clean metal surfaces
- removes oxides and prevents further oxide formation
- contains borate
what does anti-flux do and what does it contain
- limits the spread of the solder
- contains graphite or rouge
what are the two types of soldering
- pre-ceramic veneer soldering
- post- ceramic veneer soldering
describe pre-ceramic veneer soldering
- uniting components of the same alloy before porcelain is fired
- uses high fusing solder and is stronger
- melt solder with a torch
- solder has lower melting temp than alloy, but higher melting temp that porcelain firing temperature
- less technique sensitive
describe post ceramic veneer soldering
- uniting components of the same allow AFTER porcelain is fired
- uses low- fusing solder and is not as strong
- melt solder in oven
- solder has lower melting temp than alloy and porcelain
- more technique sensitive
- can compensate for slight discrepancies or distortions that occur after the porcelain is fired
- porcelain can crack in area of solder joint during solder process
why cant you add porcelain after post- ceramic veneer soldering
temperature of porcelain firing is too high and you’d melt the low fusing solder
when would you use the post ceramic veneer soldering
ideally you dont want to unless you absolutely have to
what do you do if you have open contact with an all metal or PFM crown
- addition soldering
- add metal to contact area
- smooth and shape contact area
