Full Gold Crown

Question 1

What are the indications for a FGC?

Answer 1

• 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
• Heavy bruxism

Question 2

What are some pre-operative factors to consider for a FGC (also applies with other crowns)

Answer 2

• 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

Question 3

What are some potential issues that could arise when preparing an FGC?

Answer 3

• 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

Question 4

What are the steps/reductions and burs used for an FGC?

Answer 4

Occlusal
-Non-functional: 1.0mm
-Functional: 1.5mm
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)

Question 5

How many types of gold are there and what are they used for? What percentage of gold in each one?

Answer 5

4 types
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)

Question 6

How do the following metals modify gold alloys?
Copper
Silver
Platinum
Palladium
Zinc

Answer 6

Copper: Hardener
Silver: Reduces melting temperature, modifies red colour
Platinum: reduces Co-efficient of Thermal Expansion (CTE)
Palladium: increases hardness, whitening, improves castability
Zinc: improves castability

Question 7

What are the advantages of gold?

Answer 7

• 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)

Question 8

What are some advantages and disadvantages with gold-free alloys?

Answer 8

• Even harder than type 4 gold
• Decreased cost (increased affordability)
• Less ductile
• Casting discrepancies (poorer control over metal oxide layer thickness)
• Less corrosion resistance
• Increased risk of allergy
• Toxicity

Question 9

What are some disadvantages of FGC’s?

Answer 9

• 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)
• Not aesthetic
• Future pulp testing difficult
• Iatrogenic damage (again applies for all crowns)
• Galvanic current
• Cost

Question 10

What are some extra retentive features possible for FGC’s?

Answer 10

Buccal seating groove (increase resistance/retention)
Boxes
Cast pins
Additional grooves
*Should follow same path of insertion without creating undercuts