Causes and Solutions for Post-Operative Sensitivity

Post-operative sensitivity from composite restorations is a complication most clinicians would like to avoid. Unfortunately, it happens a lot more often than most dentists and patients would like. Common causes exist for post-operative in composite restorations. Here are a few of them and how you can avoid them in your restorations.

Per Dental Update, post-operative sensitivity is more likely in complex restorative procedures, like those that require etching of enamel and dentine or that need acidic adhesive monomers. Moreover, the pain patients feel is caused by dentinal fluid movement stimulating the nerves in the tubules, which causes the mechanoreceptors near the dental pulp's outer surface to react. The authors of the 2018 review article suggest that the remaining dentine thickness, the tubule diameters and the sealing of them, and the tooth's overall pulp status may cause the sensitivity. They also categorize the technique factors that contribute to post-operative sensitivity in the general areas of:¹

• Cavity preparation that damages dental tissues
• The type of adhesive system you use, self-etch vs. total-etch
• Not utilizing a desensitizer on the dentine surface
• Incomplete polymerization of the material because of curing
• The use of improper technique when placing materials into the cavity

Post-operative sensitivity occurs in up to 50% of composite restorations, per some studies, and is especially prevalent in posterior teeth and Class II restorations, but not limited to them. Post-operative sensitivity could have various causes. Per The International Research Journal of Dentistry (IRJD, post-operative sensitivity results from the interaction between:²

• The clinician's technique
• The health of the pulp and enamel
• The restorative material

Dentists can't do anything about the tooth's health (at this point, anyway) or the restorative materials' makeup. However, clinicians can refine their technique, and this is where the most significant opportunity to prevent post-operative sensitivity lies.

Some of the Most Common Causes of Post -Operative Sensitivity

Tim Bizga, DDS, FAGD, a private practice dentist outside of Cleveland, Ohio, and lecturer for the dental industry, says that dental material science has reached a point where most post-operative sensitivity comes from operator error and things that clinicians overlook. The updates to the materials and the advances in science have resulted in excellent materials that address the potential for post-operative sensitivity. However, if a doctor rushes the process or doesn't understand what the materials can do, it can lead to problems after restoration.

"There are knowledge gaps regarding materials and which ones to choose," Dr. Bizga says.

White fillings with bonding involved have the most sensitivity post-operatively, Dr. Bizga says. In his experience, Dr. Bizga resolved the issues by reviewing his technique and comparing it to thought leaders in the industry, particularly Mark Latta, DMD, MS, and associate dean of Research at Creighton University School of Dentistry, who lectures on bonding. Dr. Bizga identifies the following causes of post-operative sensitivity and how he solves it in his technique.

• Cause #1: Over etching Over-etching is a cause of sensitivity. When you leave the etching agent on the tooth too long, Dr. Bizga explains that the bonding agent physically can't penetrate the depth dentists etched the tooth and creates a demineralization zone.
  • Solution: "We have changed our opinion on how we etch," Dr. Bizga says. "People need to pay attention to what the current thoughts are on etch time."
    
    For example, you can etch on enamel for 10-20 seconds, Dr. Bizga says. However, living tissue has different needs than enamel. When etching living tissue, like the dentin, he thinks it would be best not to etch it for longer than five to eight seconds.
• Cause #2: Not removing the solvent Dr. Bizga identified another common problem as not removing the solvents in the drying step. If they are still present upon curing, solvents can cause sensitivity.
  • Solution: Dr. Bizga says to ensure the solvent is completely evaporated before curing.
• Cause #3: Under curing Dr. Bizga says that one of the leading causes of post-operative sensitivity is under curing. Under curing can happen for several reasons, including not knowing the length of time to cure the materials with the curing light or the distance you should hold it from the material when curing, or not curing to the depth of the preparation, among others.
  • Solution: Dr. Bizga thinks paying closer attention to the details when curing is essential to avoiding post-operative sensitivity. In everything from maintaining the curing light regularly to re-reading the manufacturer's instructions, you should be vigilant about the details in curing materials.
    
    "And if it's a deeper prep, you should cure the material longer than is even on the manufacturer's instructions because they do those in ideal conditions, and the mouth is anything but," Dr. Bizga says.
• Cause #4: Over drying If you over-dry the tooth in the etch and rinse step, then the bonding agent cannot work correctly, Dr. Bizga says.
  • Solution: To avoid drying the dentin too much, review the instructions on the materials, Dr. Bizga says.
    "If you read the instructions, many of them call for or recommend a moist-bonding technique," Dr. Bizga says.

These are the four most common clinician-technique-based mistakes that can cause post-operative sensitivity in bonded restorations that everyone who is doing bonding needs to be continuously aware of, Dr. Bizga says. However, there is one more that is less commonly thought of but may cause sensitivity too.

• Cause #5: Insufficient isolation When bonding, Dr. Bizga says, everything must be as close to ideal conditions as you can manage. Your working field needs to be free of saliva, blood, and crevicular fluids, if possible.
  • Solution: Dr. Bizga recommends using a rubber dam or an isolation device, like a Zyris product (Isolite®, Isodry®, or Isovac®) or DryShield®.

Many other areas contribute to post-operative sensitivity, which includes pathology. Secondary caries, cracks from bruxism or other forces, and gum recession can cause sensitivity after restorative work. Also, if you aren't using a composite or glass ionomer for restorative work, there can be sensitivity with metal restorations, like gold. In those cases, Dr. Bizga likes to use desensitizing agents underneath the restoration.

"There are some unbelievable desensitizers you can put down before you do your cementation protocol that can really mitigate it," Dr. Bizga says.

How to Improve Technique to Avoid Post-Operative Sensitivity

If Dr. Bizga had one piece of advice in terms of avoiding post-operative sensitivity for bonded restorations, it would be to re-read the manufacturers' instructions for your particular bonding agent. It's a simple action, but one that could make a significant difference in your restoration outcomes.

"Just read them," Dr. Bizga says. "It's amazing how you think you are using the material the way they ask you to, but you aren't. Understanding the nuances of the bonding agent/system that you are using is important."

Following a review of the materials' particular instructions, Dr. Bizga would also advise reviewing your process and protocols mentally before you do it. Dr. Bizga visualizes going through each step before placing a restoration.

"I like to presume before I ever do a procedure that I've already done it in my head," Dr. Bizga says of his mental run-through. "It's good to revisit those steps."

Sensitivity is the sign that there is a problem somewhere, Dr. Bizga says. If you are having issues with your restorations and patients complain about sensitivity, it's likely something you are missing in your technique that can be corrected and resolved. Having made these mistakes before and addressing them for himself, Dr. Bizga recommends reviewing the five areas he mentioned to see if there is anything that stands out as an opportunity for adjustments in your technique.

"A lot of the materials are forgiving, so if you still having problems, it's got to be something that you're missing. A lot of times, it is curing or lack thereof. With curing, it is easy to become lackadaisical and cut corners," Dr. Bizga says, adding that when he trained his assistant to cure that he told her to "cure it like it was her mom in the chair."

Trying to do it right the first time and put yourself out of business is a good mindset, Dr. Bizga says. He approaches restorations as if he is building them to last and never revisit them.

"I'm doing it right now, so hopefully I won’t have to do it again," Dr. Bizga says.

References

1. Sabbagh J, Fahd JC, Mcconnell. Post-operative sensitivity and posterior composite resin restorations: A review. Dental Update. March 2018. Accessed February 11, 2021. researchgate.net. https://www.researchgate.net/publication/323763472_Post-operative_sensitivity_and_posterior_composite_resin_restorations_A_review
2. Porto I. Post-operative sensitivity on direct resin composite restorations: Clinical practice guidelines. International Research Journal of Dentistry. 2012. Accessed February 9, 2021.