Overcoming Common Dental Crown Seat Problems

As dentists, a crown seat problem is common place. We often encounter a range of complexities when it comes to cementing dental crowns. While dental crowns are effective solutions for restoring severely damaged or decayed teeth, the process can sometimes be riddled with issues that can compromise the crown’s longevity and the patient’s comfort. In this blog post, we will explore some of the common problems that arise during the cementation of dental crowns, including margin fit issues, interproximal tightness, and other less common issue and what steps can be taken to address these challenges.

1. Crown Margin Not Fitting Properly

One of the most significant challenges dentists face when cementing crowns is achieving a proper margin fit. A poorly fitting margin can lead to several complications, such as microleakage, secondary caries, and eventual crown failure. If the margin is not right then there is nothing that can be done and you will need to have the crown remade and usually re-prepare the crown and take a new impression. Often times when this occurs a wider margin or better impression will solve the problem even when there is a lab error. The lab is more likely to make an error if your margin or impression is not excellent and very clear.

Possible causes of this crown seat problem:

• Impression Error: An inaccurate impression can result from improper technique or inadequate material handling. Always ensure that the impression material is mixed and set according to manufacturer instructions.
• Laboratory Error: Your laboratory can mess up on any of the steps from scanning the impression in, to trimming the die, designing the crown, milling the crown, and polishing and finishing the margin.
  
• Tooth Preparation: Over-reduction or undercuts in the tooth preparation may prevent the crown from seating correctly or from a nice margin even existing.
• Interproximal contacts are too tight: This is one of the most common causes and should be

Solutions for a bad dental crown margin:

• The best solution is to take your time and ensure your preparation’s margins are clean and you take an excellent impression.
• Don’t use cheap labs or labs you do not have a relationship with. Consistently good lab work will not be the cheapest crowns.
• Allow your retraction cord and/or retraction paste to sit longer.
• Use a product designed to stop bleeding on the gingiva to help ensure cleaner impression.
• Increase magnification. This is good for both dentist and lab.
• Regularly evaluate the tooth prep to ensure optimal contours and margins.

2. Interproximal Tightness or Open Interproximal Contact

Another frequent problem is interproximal tightness, where the crown is either too tight or too open in the contact area with an adjacent teeth. This issue can lead to patient discomfort and may complicate hygiene efforts. Fortunately this is an issue you can fix without having the crown remade or making the patient come back.

Possible causes of this crown seat problem:

• Interproximal Contacts: Shrinkage and expansion of dental materials.
• Crown Contour: Poor crown design

Solutions:

• When checking for interproximal fit, use dental floss to assess the contact points. If the floss tears or is too tight, adjustments are necessary.
• .If contact is open can add material. Depending on if porcelain or zirconia can perform different steps to bond small amounts of flowable composite to area.

3. Occlusal Contact During Crown Seat

Achieving proper occlusal contact is essential when cementing dental crowns. A crown that is either too high or too low can lead to a variety of complications, including discomfort for the patient, compromised occlusion leading to further dental issues, and potential crown dislodgement over time. Proper occlusal adjustment is critical to ensure both patient comfort and the longevity of the restoration.

Possible causes of this crown seat problem:

• Improper mounting: There are many ways that both the dentist and the laboratory can slightly alter the bite and result in a dental crown being too low or too high. One way that is more common to result in a bite discrepency is if the posterior or both posterior teeth are getting crowns. The lack of the posterior stop makes it more difficult to get the bite right.
• Temporary Crown: If a temporary crown isn’t correct the bite will change in the course of the couple of weeks. The patient is usually numb and has been open for an long time when the temporary is fitted. This can result in the patient not biting how they normally do and thus the temporary is not correct.
• Material selection: All of the materials we use have known error variations in expansion and contraction. Sometimes you get more than other times.
• Failure to capture enough teeth in the initial impression. Posterior teeth, especially if doing multiple teeth, require full arch impressions for the lab to mount the case properly. Single crowns may require past the canine for the lab to know what excursive interferences may exist.
• Deficient reduction: This can occur due to failure to reduce enough, a build up that is built back too high, or if a posterior stop, from the jaw resetting.

Solutions:

• Pre-Operative Occlusal Records: Take occlusal records before preparing the tooth/teeth in larger cases. This strategy helps ensure you understand the patient’s original bite, allowing you to replicate it as closely as possible in the finished crown.
• Trial Seating: Before trying in the crown, perform a check bite. Ask the patient to remember how this bite feels as it should not change. Listen to how the teeth hit together. Sound can be a good indication of an interference.
• Articulating paper: Use articulating paper to visualize any high points on the crown compared to the opposing dental arch. This is as much an art as it is a science. Using a very thin articulating paper such as Troll foil is better.
• Check lateral excursions: If there is a worn down canine this can be an issue. Especially if that canine was not in the impression, the lab would have no idea how to design for lateral excursion.
• Recheck the bite after seating: If the crown feels high upon seating, adjust further.
• Deficient occlusion: Often will be okay as the patient’s teeth will supra-erupt into occlusion. Rather have it perfect but minor deficiencies will typically fix themselves.

Crown seat problems no more!

While there are several other problems that come with a crown seating, understanding these common pitfalls and implementing effective strategies can significantly improve outcomes. The main other issue we do not discuss is color or esthetics. However, by focusing on precise impressions, ensuring optimal tooth preparations, adjusting interproximal contacts, and carefully evaluating occlusion, dentists can enhance their skill set in successfully cementing crowns.

Ultimately, addressing these issues not only ensures a successful restoration but also boosts patient satisfaction, leading to better overall oral health. Remember, practice makes perfect, and continual learning is the key to overcoming these challenges. Happy cementing!