ORE Masterclass
Metal-Ceramic (PFM) Crown Preparation Upper Incisor

ORE Instructions

METAL CERAMIC CROWN PREPARATION. Prepare the tooth indicated to receive a metal ceramic crown. The tooth should be prepared for:

• a metal margin all round the tooth;
• for a molar tooth for the porcelain to cover the buccal surface, and extend over the buccal cusp to just short of the central fossa;
• for an anterior tooth for the porcelain to cover the labial, incisal, and proximal surfaces of the tooth up to contact points.

The laboratory instructions may also need to be completed.

ORE Desirable Features

1. Index Preparation

• Sectioned once in the middle of the tooth

2. Occlusal Reduction

• 2.0 mm over occlusal surface / incisally for metal and porcelain
• Otherwise 0.75 - 1 mm

3. Axial Reduction

• Sufficient to give 6° - 20° taper
• 1.2 mm labially and 0.5 - 1.0 mm lingually

4. Margin

• Continuous around the tooth
• 0.5 - 0.75 mm chamfer palatally and extending to just buccal to the contact point
• ~1.2 mm labial shoulder
• 1mm above gingival margin
• Contact cleared with adjacent teeth by ~ 0.5mm

5. Surface Finish

• Smooth with no sharp angles

6. Path of Insertion

• Perpendicular to the occlusal plane
• Does not conflict with adjacent teeth

ORE Undesirable Features

1. Index Preparation

• Not used
• Reveals inappropriate reduction

2. Occlusal Reduction

• Too great / too little reduction occlusally
• No functional cusp bevel

3. Axial Reduction

• Too great / too little axial reduction
• Too great / too little taper
• Undercut regions present

4. Margin

• Too wide or shoulder or inverted
• Too narrow or absent so not continuous
• Too far above / below gingival margin
• Not cleared contact with adjacent tooth

5. Surface Finish

• Rough and pitted

6. Path of Insertion

• In conflict with tooth structure of adjacent teeth
• Seating groove incorrectly placed / angled

7. Other

• Damage to adjacent teeth other than minor grazing