Removal of crowns

Question 1

How to avoid adjustments

Answer 1

Ideally none necessary if accurate imps and interocclusal records
Check on model and check occlusion in all excursions before cementation
Check pt happy

Question 2

Minimal adjustments

Answer 2

Before cementation (can re-polish in lab)
-using diamond burs for ceramic
-using TC burs for metal
Use calipers to measure crown - must not cut too thin or make a hole
Check prep - enough space? Do you need to re-prepare, imp and re-make?
Occlusal indicator wax - 0.5mm
Polish - rubber points, greenies and brownies, special kits

Question 3

Causes of crown failure

Answer 3

Biological
Mechanical
Aesthetic
Allergy

Question 4

Biological causes of crown failure

Answer 4

Caries
Endo treatment or re-treatment
Periodontal
Occlusion

Question 5

Mechanical causes of crown failure

Answer 5

Cementation failure
Defective margins
Fracture

Question 6

Factors to consider with crown failure

Answer 6

Caries status
Periodontal status
Endodontic status
Occlusion
Restorability - status of core
What type of crown - materials
Cement type
Access

Question 7

Methods of crown removal

Answer 7

Sectioning with burs
Crown removers (‘sliding hammer’ type)
Ultrasonics
Many devices on market - wamkey; crown tractor
Need to be as conservative as possible
Warning - resin luting agents bond to tooth structure

Question 8

Sectioning crowns

Answer 8

Protect airway
Vertical groove made mid-point of buccal surface just through to cement
-diamond bur for ceramic
-TC ‘jet’ bur for metal
Cut just through to cement
Tooth coloured cements - may cut too far through causing iatrogenic damage
Place instrument in groove and gently twist - do not want to damage core
May need to cut through lingual/ palatal surface just through to cement
May need to section into smaller pieces just through to cement
Avoid trauma to gingiva and soft tissues

Question 9

Temporary crown removal

Answer 9

Temporary luting agent
Gently loose cement at margin with straight excavator/ Mitchell’s trimmer
Care not to cause trauma to gingiva or soft tissues
Aim to keep intact so can reuse if definitive restoration needs to be returned to lab for re-make or adjustment
May need to section or use crown remover if cannot loosen by hand
Clear all temp cement away