I. Principles of Tooth Preparation

• Biologic: Maintain oral tissue health
• Mechanical: Ensure integrity and durability of the restoration
• Esthetic: Meet patient’s appearance expectations

II. Preparation Guidelines by Restoration Type

🔹 Full Cast Crown

• Occlusal reduction: 1.5 mm (functional), 1.0mm (non-functional)
• Axial reduction: 0.5-1.0 mm

🔹 Ceramo-Metal Crown

• Incisal clearance: 2.0 mm
• Porcelain: 1.5 mm
• Metal: 1.0 mm
• Functional Cusp: 1.5-2.0 mm
• Non-functional cusp: 1.0mm-1.5mm

🔹 All-Ceramic Crown

• Incisal: 1.5-2.0 mm
• Axial: 1.2–1.5 mm
• Finish line: 1.0 mm
• Occlusal reduction: 2.0mm (Functional), 1.5mm (non-functional)

🔹 Monolithic Zirconia

• Occlusal Reduction: 1.0 to 1.5 mm  (functional) 1.0mm (nonfunctional)  
• Gingival Chamfer: 0.5 mm reduction. 
• Axial: 0.8 to 1.0 mm. 
• Marginal Design: 0.8 mm chamfer. 
• Incisal Reduction (anterior): 1.8 to 2.0 mm. 
• 0.8mm is minimal thickness

III. Preparation Sequence

1. Occlusal/Incisal Reduction
   • Use depth grooves
   • Add functional bevel
2. Axial Reduction
   • Buccal-lingual and mesial-distal
   • Two-plane reduction
3. Finish Line Design
   • Chamfer or shoulder
4. Secondary Retention
   • Grooves or boxes if needed

IV. Retention & Resistance (R&R)

• Minimum Height:
  • Premolars: 3 mm
  • Molars: 4 mm
• Convergence Angle:
  • Ideal: 10–20°
  • Resistance decreases with increased taper
• Enhancing R&R:
  • Increase height (restorative or crown lengthening)
  • Add grooves or boxes

V. Biologic Width

• Maintain ~2.04 mm (CT + JE)
• Avoid subgingival margins deeper than ½ sulcus depth
• Crown Lengthening as needed

I. Interim Restoration – Definition

A temporary prosthesis used to evaluate esthetics, function, and stability before final restoration.

II. Requirements

• Protect prepared teeth
• Maintain periodontal health
• Preserve occlusal stability
• Restore function and esthetics

III. Types of Interim Restorations

• Prefabricated: Polycarbonate, aluminum, stainless steel
• Custom Molded: Vacuum-formed, silicone, alginate
• Digital: Milled from scans

IV. Materials

Protemp Instructions

Interim Crown Fabrication with PMMA.ppt

V. Fabrication Techniques

• Direct: Chairside, fast but risk of irritation
• Indirect: Lab-based, safer and more accurate
• Indirect-Direct: Combines both for optimal fit and comfort
• Digital: CAD/CAM workflow for long-term provisionals

VI. Cementation

1. Apply petroleum jelly externally
2. Dry teeth, isolate
3. Seat interim, allow cement to set
4. Remove excess, floss contacts, give OHI

VII. Special Scenarios

• Endodontically Treated Teeth: Use prefabricated crowns with post support
• Digital Workflow: Ideal for full-arch or long-term provisionals