tooth preparation for all-ceramic crowns

TOOTH PREPARATION to receive Porcelain Jacket Crown{All-Ceramic / Metal-Free Crown} on Maxillary Central Incisor. : 

TOOTH PREPARATION to receive Porcelain Jacket Crown{All-Ceramic / Metal-Free Crown} on Maxillary Central Incisor. P V Badwaik

All – Ceramic Crowns : 

All – Ceramic Crowns Not cast in Gold / Some other metal Produces best cosmetic effect But Ceramic is a brittle substance, so more susceptible to fracture Newer development – porcelain reinforced with Alumina, Dicor cast glass ceramic, Hi-ceram, In-ceram & IPS Empress

PREPARATION : 

PREPARATION Should be as long as possible --- to give maximum support to porcelain Overshortened Preparation ---- will create stress concentrations in labiogingival area Incisal edge – flat & placed at a slight inclination toward the linguogingival area – to meet forces on the incisal edge & prevent shearing All sharp angles should be rounded – to reduce the danger of fracture (by points of stress concentrations )

Principles of Tooth Preparation : 

Principles of Tooth Preparation Concave Cingulum Reduction (Structural Durability) Flat Incisal Edge & Rounded Angles (Structural Durability) Vertical Lingual Wall (Retention & Resistance ) Radial Shoulder (Marginal Integrity) (Periodontal preservation) (Structural Durability) (Resistance) Axial Reduction (Retention & Resistance) (Structural Durability)

MARGIN / GINGIVAL FINISH LINE : 

MARGIN / GINGIVAL FINISH LINE Shoulder (d) of uniform width (approx – 1 mm) is used as a gingival finish line --- to provide flat seat to resist forces directed from the incisal area. a) Knife edge, b) Bevel, c) Chamfer, d) Shoulder, e) Shoulder with bevel

ARMAMENTARIUM : 

ARMAMENTARIUM Micro motor with Control box Handpiece Flat-end tapered diamond Small wheel diamond End cutting diamond

Method of Tooth Preparation : 

Method of Tooth Preparation Depth-orientation grooves are placed on Incisal & Labial Surfaces ----- to gauge the depth of preparation Labial grooves – 1.2 – 1.4 mm 3 grooves parallel to gingival one-third. 2 grooves parallel to incisal two-third Two plane reduction to achieve good esthetics without encroaching the pulp Incisal grooves – 2.0 mm

Incisal reduction : 

Incisal reduction Done with flat-end tapered diamond Incisal edge – flat & placed at a slight inclination toward the linguogingival area – to meet forces on the incisal edge & prevent shearing

Labial reduction : 

Labial reduction First incisal two third preparation Then the one-third, : this reduction extends around the labioproximal line angles End of diamond point will create shoulder finish line, while axial reduction is done by sides of the diamond

Lingual reduction : 

Lingual reduction Is done by Small Wheel diamond Should not over reduce the junction between the cingulum & the lingual wall Overshortening the lingual wall will decrease the retention of the preparation Lingual Axial Reduction ---- is done by Flat-end tapered diamond Radial Shoulder margin (1mm)--- smooth continuation of labial & proximal shoulder

To SummarizePrinciples of Tooth Preparation : 

To SummarizePrinciples of Tooth Preparation Concave Cingulum Reduction (Structural Durability) Flat Incisal Edge & Rounded Angles (Structural Durability) Vertical Lingual Wall (Retention & Resistance ) Radial Shoulder (Marginal Integrity) (Periodontal preservation) (Structural Durability) (Resistance) Axial Reduction (Retention & Resistance) (Structural Durability)