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For the construction of a porcelain
jacket crown it is essential that there is a clearance of 1.5mm between the
root preparation and the opposing teeth in all positions of the mandible, otherwise
the crown will be weak or contact the opposing teeth and will break. Always
supply a bite and opposing model.
Remove sufficient tooth substance
labially to allow a good covering of porcelain, otherwise the cement will show
through and the crown will be weak.
Always make a good cervical ledge
for a jacket crown, or the porcelain will chip or crack. Use free flowing material,
otherwise you may burst your crown when cementing it. Bonded crown preparations
should have cervical ledges buccally and interstitially. Buccal edgeless preparations
should be subgingival to allow for a narrow metal collar.
Do make sure that silicone putty
is fully set and dry prior to taking the perfecting wash impression.
A temporary auto-polymerised acrylic
splint should be used to prevent migration and over eruption of the abutment
teeth whilst bridges are being made.
Review Precision Attachments
and Crown and bridgework
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