Problem 1: Suboptimal Tooth Preparation
Many times, conditions are less than ideal when prepping a tooth for a crown. That said, it's critical to avoid jagged edges, undercuts, and unclear margins for a well-fitting crown. Good prep not only ensures a well-fitted crown but also helps a dental technician correctly identify and trim/mark the margin.
Takeaway: It all starts with the prep!
Problem 2: Insufficient Records or Impressions
An accurate snapshot of the patient’s mouth is crucial for creating a crown that fits perfectly. Inaccurate impressions can occur due to:
⦁ Incomplete coverage of prep, margin, or other crucial areas by the impression material.
⦁ Removal of the impression material before it's fully set.
⦁ The patient doesn’t bite down properly.
⦁ Failure of the impression material to capture margin or interproximal.
⦁ Poor fluid control, especially with digital impressions.
Takeaway: The final crown will only be as good as the impression.
Problem 3: Teeth Movement Due to Poor Temporization
Fact: Teeth can physiologically drift or erupt up to .5mm per day.
⦁ Creating and fitting the temporary crown is a critical yet often overlooked step in the crown-making process. Regardless of how perfect your preparation and record capture (digital or PVS) may be, the whole process can be ruined if the temporary crown is not made to fit correctly.
⦁ For example, if the temporary crown is out of occlusion, or if the interproximal contacts are open, adjacent teeth may drift inward and opposing teeth could erupt and fill the space. This can occur at rates up to 0.5mm per day and significantly alter the teeth's position from the initial records and leading to a permanent crown that does not fit.
Takeaway: After careful preparation and diligently capturing an accurate snapshot of your patient's mouth, it’s paramount to maintain the exact state of the teeth until the permanent crown is placed.
Problem 4: Choosing the Wrong Material/Shade
Restorative dentistry is both a science and an art, full of subjective decisions. This is why it’s so important to be objective when possible.
⦁ Choosing the right material for a crown is crucial. The decision should be based on the translucency of a patient's existing teeth. If a patient has translucent teeth and the crown will be visible when they smile, pick a material that matches this translucency. Pick porcelain, not a full monolithic opaque zirconia. Or pick a high translucent zirconia at the very least. If the crown isn't visible in the smile line, material choice may not be as critical.
⦁ Next, ensure that you and your lab use the same shade guide. Avoid using direct light when choosing the shade; natural light is preferable. Additionally, gather a few opinions for a more rounded decision. If the shade selection becomes complex, consider sending the patient to your lab for a custom shade.
Takeaway: Making an informed choice of material and shade can significantly enhance the natural look of the crown and patient satisfaction.