Marginal Integrity – FINISH LINES

a) Finish line — the junction between prepared and unprepared position — should be at contra bevel — core
b) Position of the finish line;
 Supra — best, hygienic maintenance
 Equi — for gold crowns only, gingival 1/3rd
 Subgingival — gingival 1/5th

Shoulder – 1.0-1.5mm thick
o All-ceramic crowns, coz edge strength of porcelain is low- so need but joint, 90 degree
o For the labial side of Anterior PFM also, as it maximizes the aesthetics by eliminating the display of metal.
o Bur used is – diamond end cutting bur


Light Chamfer – 0.3-0.5mm thick
o Mostly for gold crowns & Metal crowns
o rarely in PFM
o Preferred finish line For cast Gold restorations
o Leaves adequate bulk for marginal strength with acute angle & produces minimal stress at the margin.


Heavy chamfer - 1.0-1.5mm thick
o Best for PFM, esp in posteriors
o And some all-ceramic crowns
o If not given enough thickness at the finish line, the lab will be forced to over contour the crown – means to increase the thickness at the margin – it will stick- bacteria will accumulate and eventually affect the gingiva
o metal-ceramic labial only


Knife edge
o — SS crowns (subgingival)
 Most important aspect of FPD abutment complex is its finish line.
 margin of crown if brokn — causes caries
 if caries at margin
----o marginal leakage
----o unsupported crown
----o redo crown
 Failure of marginal caries — crown margin damage
 Failure of margin of crown —caries