Lecture on Designing a Single Unit Posterior Crown

Introduction

• Objective: Walkthrough the basics of designing a single unit posterior crown
• Goals:
  • Efficient design techniques
  • Perfect contacts and occlusion
  • Discuss stain and glaze techniques
  • Choosing shade for Emax crown

Model Axis Alignment

• Align occlusal plane along horizontal lines
• Incline jaw slightly to match natural position
• Set model axis important for anterior cases, less for posterior
• Ensure arch fits within the outlined shape

Marking Margins

• Skip trim die process, usually leave untrimmed
• Important to have color in the impression to see margins
• Two options: Auto vs. Manual
  • Auto: For distinct ledges and supergingival margins
  • Manual: For areas where margin meets tissue
  • Switch between them for efficiency
• Verify margins from multiple angles to ensure no undercuts

Insertion Axis Phase

• Minimize yellow on the prep
  • Yellow indicates undercuts
  • Avoid yellow near the margin

Initial Proposal and Parameters

• CEREC software gives an initial proposal in the design phase
• Bypass undesired phases to gain control over proposals
• Set parameters for Emax posterior crown:
  • Spacer: 100-140 (120 as medium)
  • Occlusal & Dynamic Contact Strength: -175
  • Minimal Thickness: Set to actual minimum (e.g., 500 microns)
  • Marginal Thickness: Increase to 90 to prevent chipping
• Adjust parameters to fit your needs, unlock if necessary

Position Phase

• Key for better control over the design
• Align tooth shell to prep and margins
• Use Scale and Position tools to adjust fitting
• Make occlusion red for easier further adjustments
• Uncheck Constrained Adoption for final proposal based on position phase

Designing with Biogeneric Variation Tool

• Use tool for proper tooth morphology
  • Adjust tool to add anatomical features
• Use Positioning Tool for big movements
  • Disable Keep Contacts for smoother adjustments
• Use Anatomical Two-Directional Tool for finer adjustments
  • Ensure contacts and occlusal alignment are correct

Adjusting Occlusion and Contacts

• Use Adjust Contacts tool for optimal tooth contacts
  • Set occlusal strength to -175 as established earlier
  • Mesial contact adjustments as needed
  • Aim for green contacts and accurate occlusion
• Final checks: ensure no marshmallow-like appearance

Shade Selection

• Match to the lightest portion of the tooth when choosing shade
  • Avoiding a too-dark final result
• Use lighter shade blocks for translucent effects
  • E.g., BL1 for HT to get closest match

Stain and Glaze Techniques

• Apply consistent thin layer of glaze
• Mix stain with glaze (50/50) for color application
• Apply stain-glaze mix where needed before baking
• Alternative: Stain first, then glaze for more control
• Monochromatic teeth: MT and polish
• Concepts valuable for achieving realistic restorations

Conclusion

• Replay video for comprehension
• Effective use of techniques leads to perfect posterior restorations.

Feedback

• Comments and feedback encouraged for improvement