week 6- Cementation Flashcards
what are the steps for delivering the final prostheses before seeing the patient
- evaluate the framework/final prosthesis
- any need for remake or alteration
- may any adjustments prior to the patient appointment
- check the prosthesis for:
- proximal contacts
- internal surface
- marginal adaptation
- inter abutment stability
- occlusal contacts
- occlusal anatomy and finish
- axial contours
- overall design
- clean the prosthetic for patient try in
what should you look for in your framework prior to patient appointment
- metal ceramic finish lines
- framework design to support porcelain
- pontic contours
- connector location; dimension, contour
- adequate cut back for porcelain
- adequate metal thickness in areas to be veneered
what frameworks is it necessary to try in to ensure the fit prior to porcelain veneering
metal ceramic or zirconia based
framework is tried in to check:
- proximal contacts
- internal fit
- marginal integrity
- stability
- occlusion
when is shade selection confirmed
at the framework try in appointment
once ceramic is veneered at try in you should check:
- same things as when framework was tried in
- any adjustments needed like occlusion or contacts
- patient approval and acceptance and consent for cementation
before removing the temporary what should you do
take an impression of the temporary to save you time just in case you need to remake a temp, especially if you adjusted the first temp a lot. it also might help remove the old temp
how should you remove the temporary
- using curved hemostat gently rock the temporary back and forth to break the current seal
- grasp the temporary in a manner in which the temporary is not likely to break
- clean out the inside of the temp, disinfect it and set aside
before removing the temporary always make sure you have either:
the temporary matrix or take a new one
if the temp doesnt come off what do you do
section it off
how should you take a temp off teeth with an RCT, post or build up
section it off and cut it off with a bur
if the temporary does not come off easily or you are concerned at all about the materials and their stability under the temp what should you do
section it off
how should you section a temp bridge off and what should you use
use a very thin tapered diamond to section M-D and B-L and then gently remove the sections by applied lateral force in between the criss crossed lines you just made
once the temporary is removed:
-clean off any excess cement chunks
- clean the tooth preparations with pumice slurry
if the framework wobbles or rocks on the preparations what should you check
- proximal contacts
- internal surface
- margin adaptation
how should you evaluate proximal contacts
- evaluate visually and with floss or shimstock
- mark areas and adjust as needed if contact is inhibiting full seat
how should you check the internal surface
- use “fit checker” or similar to check internal surface
- adjust any “positive” areas
- only minor adjustments should be made in the internal surface
what does a positive defect in checking the margin mean
there is too much framework material and this can be polished away with a stone or rubber wheel to see if this allows the rock to disappear
what does a negative defect means when checking the marginal adaptation
you have an open margin and a new impression will need to be taken
if the framework is still rocking, the contacts are appropriate and the internal surface is not hindering the seat then what is wrong with it
the framework may be distorted
what should you do if the framework is distorted
- section the framework through a connector
- evaluate each retainer separately
- if individually each retainer fits, move forward with solder technique
- if individually either retainer still wobbles or rocks, take a new impression
if the framework is sectioned the cut should be:
- at least 0.2mm wide
- flat
- have parallel sides
what do you do after you section the distorted framework
- to make sure retainers are solidly placed and stationary make a Duralay relation
- once Duralay has set, evaluate framework to make sure rocking or wobble has been removed
- make a plaster “pick up” index after duralay is set to stabilize the framework as you send it to the lab
once framework returns from soldering at the lab what should you evaluate on the framework-
- proximal contacts
- internal fit
- marginal integrity
- stability
- occlusion
if the permanent prosthesis seats properly what should you do
- first take a pre veneering radiograph to confirm margins
- then take a shade and send it back to the lab for porcelain veneering
what are the phases in the lab script
- please pour impression, pin and section cast, articulate master cast with enclosed opposing cast using interocclusal record. return for die trimming and evaluation of articulation
- please fabricate metal- ceramic framework using noble alloy as follows. return in one piece for framework try in:
- phase 3: please add porcelain to complete FPD according to above specifications
what are the steps in delivering the final prostheses with the metal and porcelain
- remove the temp, clean and prepare teeth for seating by making sure all temporary cement is removed and tooth has been pumiced
- try in framework and check for marginal adaptation, pontic adequacy and any rock or wobble
- take a pre cement radiograph to confirm margins
what is fit chekcer used for
to determine if any part of the prep or intalgio surface needs to be adjusted to enable full seating of bridge
what would you do with an open proximal contact
send back to the lab to add on more porcelain
what tissue contact with the pontic should you be looking for
- passive contact with the tissue
- slight blanching of the tissue is acceptable
- more than slight blanching adjust the pontic/tissue contact
- if adjustment is made this tissue portion needs to be highly polished
when the bridge fully seats, has floss and pontic fit is acceptable next is:
occlusion
check occlusion in:
MI, lateral and protrusive movements
- canine guidance should be maintained
anterior bridges need to have appropriate length in protrusive to protect against:
porcelain chipping
how should esthetics of the final prostheses be evaluated
- look at the angulation of the facial
- step back and view the patient from several feet away
when do you ask the patient if they are happy with the esthetics
after you, the dentist, are happy with the esthetics
when is the patients approval signed as consent signed
prior to cementation
final step prior to cementing is:
polishing and finishing
how are metals polished
brown and green polishers
- green polishers work very well
- brown is course
- green is fine
- two step polishing
what do you need to stay away from when polishing and why
at the ceramic metal junction because the colors can stay in the porcelain and contaminate the porcelain porosities, it will look ugly
if it is necessary to smooth or polish at the metal- ceramic junction:
the burr/stone should be help perpendicular to the junction otherwise, the metal particles contaminate the porcelain decreasing the esthetics
- and move side to side not up and down
- if you have to move up and down make sure the bur is spinning away from the incisal edge
how should you polish porcelain
margin adjustment should be made perpendicular to the margin and rotation of polisher should be toward bulk of material
which material is easiest to polish prior to cementation
porcelain
how should you adjust ceramic
- use gentle forces when inserting and testing the fit of the bridge
- do not overheat/create excess vibration. this leads to microcracks and tends toward fracture
- use fine diamonds
- use separate instruments for metal and porcelain
- polish porcelain with diamond rubber points and then a fine diamond impregnated polishing paste
why is it important to keep as much anatomy as possible while adjusting metal or porcelain
it can lead to poor occlusion in other areas and can cause occlusal disharmony
what is another name for conventional cements
luting cements
what are the conventional cements
- zinc-oxide eugenol (temporary cement): Temp bond
- zinc polycarboxylate (temporary cement): Durelon
- zinc phosphate cement: gold standard all cements are compared to
- glass ionomer cement
- resin modified glass ionomer: Rely-X-Luting
what does luting mean
the use of a moldable substance to seal a space or to cement two components together
what are the advantages and disadvantages of luting cements
- A: adhesion to tooth substance and alloys, easy manipulation, strength, solubility, firm thickness properties comparable to zinc phosphate, fluoride release
- D: needs accurate proportioning, critical manipulation, lower compressive strength, greater viscoelasticity than zinc phosphate, short walking time, clean surfaces needed for best adhesion
what is another name for resin based cements
adhesive cements
what are the resin based cements
- adhesive resin cement with dentin bonding agent: total or selective etch
- self etch: self etching primer with no extra dentin bonding agent
- self-adhesive: no etch, no additional dentin bonding agent needed but does require a primer
which resin cements bond to the tooth
self etch and self adhesive
- SpeedCem Plus
what are the advantages and disadvantages with resin based cements
- A: high strength, low oral solubility, high micromechanical bonding to dentin, alloys and ceramic surfaces
- D: need for meticulous and critical technique, more difficult sealing, higher film thickness, possible leakage, pulpal sensitivity, difficulty in removal of excess cement
describe adhesive resin cement
- requires use of dentin bonding agent
- dentin bonding agent bonds to tooth and resin
- cement bonds to dentin bonding agent
- most esthetic cement system
- most retentive
- used for veneer restorations mostly
describe self etch adhesive resin
cement does not require a separate dentin bonding agent but requires tooth pre treatment in the form of a primer
describe self adhesive resin
cement requires no dentin bonding agent nor does it require a self etch primer pre treatment
- resin cement interacts directly with the tooth surface
- generally creates higher bonds to dentin
what are the considerations when using resin cements on all ceramic restorations
- resin cements require a moisutre free environment
- required for low strength glass ceramics
what are the considerations for RMGI with all ceramic restorations
- RMGI cements are contraindicated with low strength glass ceramics
- the RMGI ceramics absorb water and expand as they set which could cause fracture of ceramics especially at margins
- need adequate retentive preps
- RMGI is great with metal, PFM and zirconia restorations
why are RMGI cements recommended for eMax crowns
to offset the brittle nature of glass ceramic
when are RMGI cements used
with IPS eMax when tooth preparations are sufficiently deep axially and with margin thickness of at least 1mm, retentive mechanically, and patients are highly caries prone
what are the steps to determine which type of cement to use
- type of material
- design of material
- tooth prep and location - retentive vs non retentive prep
- additional factors: caries prone patients, weird occlusion, moisture isolation, clencher or grinder
what cement has the most to least amount of steps
adhesive cements > self adhesive cements > conventional cements
what cement requires the most retentive prep to least
conventional cements > self adhesive cements > adhesive cements
In PFM cementation with adequate preparation retentive features what cements can be used and what is the most commonly used
- zinc phosphate
- glass ionomer
- RMGI - most common
in PFM cementation without totally adequate preparation retentive features, wacky occlusion, or bruxer what cement is used
resin cement - either dual cure or self cure
what is the cement of choice with glass ceramics
resin cement- dual cure or self cure
what is the restoration pre cementation treatment for ceramics
- internal surface: HF acid etch to roughen for micromechanical retention for eMax or feldspathic porcelain. done by lab. sandblasting or diamond bur roughening would damage the surface of these ceramics
- silane treatment in internal surface to enhance the chemical bond between glass/ceramic/resin cement
what cement is used in zirconia cementation with adequate preparation retentive features and what is most commonly used
- zinc phosphate
- glass ionomer
- RMGI - most common
what cement should be used in zirconia cementation without totally adequate preparation retentive features, wonky occlusion or bruxer
resin cement
what is the internal surface pre treatment for zirconia
- abrasion needed. lab leaves internal too smooth
- air abrasion or diamond bur leaving horizontal roughened lines on internal walls
in zirconia cementation adhesive promoting agent can be used but must contain:
MDP
what is the adhesive promoting agent made of in zirconia cementation
methacryloyloxydecyl dihydrogren phosphate
what is the downside of eugenol
inhibits polymerization of any composite resin
what removes eugenol residue
acid etchant
what does provisional cement residue do
occludes tubules and decreases effective bonding
what does cleaning the tooth with pumice do
removes the temporary cement residue
what should the patient close down on to seat the crown
soft cotton roll, not anything hard because it leads to fracturing
if occlusion does not permit solid pressure for crown seating:
firm pressure from finger is used to fully seat the crown until cement has cured on its own or it has been light cured
when using a curing light for resin cement, seat the crown full of cement and:
tack the cement
what is tacking the cement and why do we do it
- turn on your curing light while on the facial margin and immediately turn it off
- place the curing light on the lingual and turn it on and immediately turn it off
- this allows you to partially cure the cement so it peels away
what happens if you cure fully with too much excess
it will be very challenging to be able to remove all the cement
- youll need high speed handpieces
once excess cement is removed with hand pieces:
floss to remove interproximal excess
- once all cleaned, fully cure on facial and lingual and move light around to cure interproximal areas too
now that prosthesis is cementeD:
-Recheck occlusion
- adjust if necessary: use a fine diamond to avoid excess heat
- polish with diamond impregnanted discs or points
- take a post cementation radiograph
- discuss OHI with patient
