Flashcards in Full Gold Crown Deck (10):
What are the indications for a FGC?
-Protection of remaining coronal tissue in broken down, heavily filled posterior teeth where CR and amalgam inadequate
-Retainer for fixed bridgework or reshaping denture abutment tooth
-Splinting periodontally mobile posterior teeth
-Eliminate occlusal interferences by re-contouring tilted molars
-Insufficient interocclusal distance for alternatives
What are some pre-operative factors to consider for a FGC (also applies with other crowns)
-Assess need for posts/cores for adequate retention
-Periodontal management: electrosurgery to relocate crown margins from sub to supragingival
-If occlusal adjustments needed to correct overerupted teeth and prevent premature contact, do this before crown prep
-Orthodontics: consider to move tilted bridge abutments to more favourable alignment and simplify prep + improve prognosis
What are some potential issues that could arise when preparing an FGC?
-Iatrogenic pulp damage due to overreduction, overheating or poor fitting temp crown
-Damage during impression/cementation procedure (e.g. hydrostatic pressure on fluid contents of cut dentine tubules)
-Inadequate contours/open contacts
-Poor margins leading to micro-leakage, pulpitis, recurrent caries
What are the steps/reductions and burs used for an FGC?
Burs: Jet 330 for depth cut + Technik 856
Depth cuts: 0.8mm non F; 1.0mm F
Functional cusp lateral reduction: 1.5mm
Bur: Technik 847
Depth cut: 1.2mm
Buccal: 1.0mm mid bucally, decrease to 0.5mm at chamfer margin
Bur: Komet 8877
Proximal: 1.0mm at marginal ridge, decrease to 0.5mm at chamfer margin; 6-10 degree taper
Bur: Komet L10 then 8877
Lingual: 0.8mm in occlusal third, 0.5mm at chamfer margin
(reduce in one plane, tilt of bur will cause more reduction occlusally)
Bur: Komet 8877, light chamfer margin
(Go to long axis of tooth/parallel to buccal gingival 1/3)
How many types of gold are there and what are they used for? What percentage of gold in each one?
Type I (softest): 85% (inlays)
Type 2: 75% (inlays and some onlays)
Type3: 60-70% (gold crowns)
Type 4 (hardest): <60% (gold post-cores, PBM metal component)
How do the following metals modify gold alloys?
Silver: Reduces melting temperature, modifies red colour
Platinum: reduces Co-efficient of Thermal Expansion (CTE)
Palladium: increases hardness, whitening, improves castability
Zinc: improves castability
What are the advantages of gold?
-High strength even in thin sectionsallows minimum thickness 0.5mm
-Ductile (can be burnished at margins to improve seal)
-Resists oxidation, acid stable
-Better control over thickness of oxide layer
-Good Retention + resistance (due to not having to remove too much tooth structure)
-Longevity (94-96% can last from 30=40+ years depending on fabrication)
What are some advantages and disadvantages with gold-free alloys?
-Even harder than type 4 gold
-Decreased cost (increased affordability)
-Casting discrepancies (poorer control over metal oxide layer thickness)
-Less corrosion resistance
-Increased risk of allergy
What are some disadvantages of FGC's?
-Extensive removal of tooth structure (more conservative than PBM and PBZ crowns but crowns in general are unconservative compared to direct CR, amalgams, inlays, onlays)
-Future pulp testing difficult
-Iatrogenic damage (again applies for all crowns)