CLINICAL CROWN PREPARATION IN FPD (Fixed Prosthodontics)

TOPIC: CLINICAL CROWN PREPARARTION IN FPD

🎯 KEY POINTS:

🔺Functional cusp bevel is given on the lingual inclines of the maxillary lingual cusps and buccal inclines of the mandibular buccal cusps.

🔺Finish line of choice in cast metal is chamfer, in all-ceramic is shoulder, in PFM is shoulder with bevel on labial surface and chamfer on lingual and proximal surfaces, shoulder with bevel is proximal box of inlay and onlay.

🔺Knife-edged finish line is advocated in lingually tilted mandibular posterior teeth.

🔺Truss effect is provided to enhance the structural durability.

🔺Half-moon fracture is produced in the labiogingival area of all-ceramic crown due to overshortening of the preparation.

🔺All-ceramic crowns should be avoided in edge-to-edge occlusion cases and deep overbite.

🔺Disadvantage of porcelain is high firing shrinkage.

🔺In winged preparation for PFM, the shoulder finish line should be lingual to the proximal contact.

🔺Porcelain bonded to metal is strongest when it is fired under compression.

🔺Proximal grooves in anterior partial veneer crown should be placed parallel to the incisal two-thirds of the facial surface.

🔺In posterior partial veneer crown, the proximal grooves should be
parallel to the long axis of the tooth.

🔺Grooves should have definite lingual walls to resist displacement in partial veneer crown.

🔺Reverse three-quarter crown is used on mandibular molars to preserve intact lingual surface in cases of severe lingual inclination.

🔺Proximal half-crown is a three-quarter crown which preserves the distal surface as the tooth is rotated by 90°.

🔺Vertical lingual wall in anterior partial veneer crown is essential for retention.

🔺In partial veneer crown, contrabevel is never placed on the incisor because of aesthetic concern.

🔺Minnesota ditch is a ‘V’-shaped groove at the junction of axial wall and gingival floor in proximo-occlusal inlays used to enhance resistance to displacement by occlusal forces.

🔺Principle of substitution is used to compensate for mutilated or missing cusps or when clinical crown length is inadequate.

🔺Shade tabs should be moistened during shade selection.

🔺First all-ceramic crown was developed by Charles H. Land in 1886 and called it as PJC.

🔺Dicor was the first commercially castable ceramic material used.

🔺Dr Charles Pincus first used porcelain veneers to improve aesthetics.

🔺Periodontal bridge is the most common cause of missing tooth in a dental arch.

🔺Full veneer crown has the maximum retention among all the retainers.

🔺Richmond crown was the first crown on which porcelain facing was given.

🔺Davis crown is an all-ceramic crown which is attached to the tooth by means of post.