Dental Crown Preparation

Axial Reduction

• Remove remaining tooth structure while placing chamfer margin, reducing half of axial surface first and leaving the other as reference.
• Take care not to injure adjacent tooth in interproximal area.
• Use enamel lip technique: cut into proximal area from both sides until a few mm of interproximal island remains, then remove contact with a fine needle diamond.

Protecting Adjacent Tooth

• If adjacent proximal surface is damaged, polish with white stone, silicon stones, and prophylaxis paste.
• Apply fluoride to prevent demineralization.

Finishing

• Use fine grit diamond or carbide bur for finishing, operating at reduced speed or with low speed handpiece.
• Smooth internal line angles, chamfer finish line should be glassy smooth.
• Add non-functional cusp bevel if necessary, and additional retention features with tapered carbide bar if needed.

Evaluation

• Evaluate preparation for smooth, even, and continuous chamfer finish line.
• Check for 6° taper, gradual transition between prepared surfaces, and no undercuts.
• Assess occlusal and proximal clearance.

Occlusal/Incisal Reduction

• Reduce incisal edge by 2mm for adequate material thickness and translucency.
• Posterior teeth require less reduction (1.5mm).

Buccal/Labial Reduction

• Divide facial surface into 2 imaginary parts: 1/3 cervical and 2/3 incisal.
• Place 3 grooves: mesial, distal, and middle, with a depth of 1.3 mm.
• Cervical grooves and reduction are parallel to the long axis of the tooth and/or the intended path of insertion.
• Incisal grooves are parallel to the facial contour.

Shoulder Finish Line

• Place shoulder finish line 1 mm above the gingival crest.
• Retract gingiva using a retraction cord to place the finish line more apically.
• Manipulate gingival tissue to prevent recession and exposure of metal collar.

Axial Reduction of Proximal and Lingual Surfaces

• Remove sufficient tooth structure to provide a distinct, smooth chamfer finish line (0.5 mm in width).
• Use round-end tapered diamond bur held parallel to the intended path of insertion.
• Place guiding grooves on anterior teeth and remove concavity with wheel or football diamond bur.
• Follow gingival contour for interproximal margin and extend lingual chamfer buccally to blend with interproximal area.

This quiz covers the preparation steps for a complete metal crown, including axial reduction and protection of adjacent teeth.