Try in Flashcards
What are the features of the ideal crown?
Easily seated
Stable
Accurate occlusal contact
Adequate proximal contacts
Accurate marginal fit (for longevity of restoration)
Aesthetic
What should be checked during the try in?
Seating
Fitting
Contact points
How is the tooth assessed systematically?
1) Evaluation of the crown on the die
2) Seating the crown on the prepared tooth
3) Assessment of the seated crown
What are the aims of evaluation of the crown on the die?
Detection of fabrication errors (laboratory related)
prior to the clinical appointment
Save critical chair time
Anticipation of problems before clinical appointment
Consider good lighting and magnification
In case of problem, consult with the dental laboratory
What issues can arise when evaluating the crown on the die?
Poor pouring
Overtrimming
Fracture
Scratches
Wear
Casting problems: air bubbles
Casting nodules or blebs
Ideally, the casting should touch the die at the margins only
Overall fit could potentially be loose and can have an excessive gap.
Marginal fit can be poor with open margins, overhangs or underextensions.
Occlusion (Centric contacts, eccentric contacts and interferences)
What features should be checked when evaluating the crown on the die?
Internal surface
External surface
Overall fit and resistance
Marginal fit
Occlusion
How should the crown be seated ideally?
Crown should seat on the prepared tooth without forcing it.
What can cause the crown not to sit properly?
Proximal contacts
Internal fit
Inaccurate margins / over extensions
Retained temporary cements
Trapped gingival tissue.
What can cause FPD to not sit properly?
Same as for single crown
Tissue contacts under pontics
Location and shape of connectors could produce another issue.
What kind of forces should be applied when removing a crown?
Only apply vertical forces when removing the crown do not use torsion movements as this can break the crown or the tooth structure.
If crown doesn’t come off easily, it is a good idea to section the crown.
What tools can be used for removal of a crown?
Excavator, sickle probe
Hemostat, backhaus forceps, and pliers
Crown remover: Back-action remover, automatic crown remover, and Richwill crown remover
How are proximal contacts checked when seating the crown?
Assess tightness with dental floss
Articulating paper, marking liquid, or spays can be used to determine contact points.
How should the crown feel when being seated on the tooth?
There should be some tightness with the dental floss but not too difficult.
What kind of contact point do we need in anterior and posterior teeth?
Anterior teeth need a small contact point. Posterior teeth need a larger contact area
How should the crown fit onto the tooth?
The restoration should seat completely without interference of the occlusal or axial surfaces
How can the internal fit be identified and fixed?
Using a disclosing medium or aerosol indicator. Then can be fixed with a diamond bur.
What mistakes with impression taking can cause problems with the internal fit?
Early impression removal
Distortion of the impression
Latex contamination
Incorrect mixing tip
IF THIS HAPPENS USE A NEW IMPRESSION
What are the features of poor marginal adaptation?
Overextension
Underextension
Overhanging
Open margin
What are the potential effects of poor marginal fit?
Sensitivity (exposed dentin)
Dissolution of cement leading to plaque retention and caries as well as gingival inflammation
What leads to poor marginal fit?
Can be due to inability to read the finish line by the technician.
What should be done if the margin has overhangs/overextension, underextension, or gaps?
Can be adjusted
Underextension and Gap require remake
What is checked when the seated crown is assessed?
Stability
Contour
Occlusion
Aesthetics
Confirming the crown is suitable for cementation
How is the stability of a crown assessed?
Restoration should not rotate when the force is applied.
Instability causes failure in function.
What causes internal surface misfit?
Disruption in impression or fabrication process
Why should the crown’s contour be adequate?
Improper contour may impair gingival health and affects the natural appearance
They must be adjusted before cementation
When should occlusal adjustments be done to the seated crown?
Crown should be fully seated
Major adjustments should be done prior to cementation
Minor adjustments can be completed after cementation
What causes inadequate occlusal contacts?
Poor occlusal recording
Poor articulation
What is a shim stock used for?
The shim stock will determine if an occlusal
contact is present
Assess the occlusion on all teeth with and
without the prosthesis
Assess the occlusion on the crown
How is articulating paper used for occlusion assessment?
Mark heavy contacts or interferences in
centric and eccentric
Articulating paper will locate the contact area
Use different colors for different movements
How should occlusion be adjusted if there is a premature contact in centric?
Adjust grooves or cusp
inclines
Never the tip of cusp
How should occlusion be adjusted if there are interferences in eccentric movements?
Adjust cusp inclines
Tip of cusps if necessary
How can the thickness of the prosthesis be measured?
Using a thickness gauge (Svensen gauge) to know how much you can adjust of the crown.
What is the aim of occlusal distribution?
Completed adjustment
Well distributed occlusal contacts
Posterior teeth: the prosthesis and the remaining dentition should have the same occlusal contact and hold shim stock
Anterior teeth: the prosthesis should lightly hold the shim stock if other anterior teeth do
How are the aesthetics of the crown assessed?
Patient approval should be obtained prior to
cementation
Shade and morphology
- Lighter shade: can be stained and glazed
- Darker shade: should be cut back and followed
by new ceramic application
Modify the morphology with diamond burs and
soflex discs
- Send back for glazing
Consider temporary cementation
How is the crown finished?
Metal: rubber polishing wheels and points
Ceramic: Rough ceramic will wear the opposing teeth:
Composite finishing rubber burs should be used to smoothen it
- Rubber cup and diamond polishing paste
- Or send to laboratory for reglazing
