In the webinar presentation, Prof. Dahl talked about two specific tests for evaluating repair bond strength; measurements of shear bond strength and tensile strength.
In the Q&A session around half of the questions were focused on adhesive products and their properties as well as details on the adhesive treatment. The other half of the questions from the Q&A session focused on composites and the repair process.
Based on the Q&A following the webinar, here is a list of ten tips and insights:
- The use of a bonding product is mandatory for composite repair.
- For both old and new composite restorations the use of silane improves repair bond strength.
- Another important point is to apply the silane after using a diamond bur to roughen the surface of the failed restoration.
- The best way to “silanize” an old restoration is to use a two-part silane that is mixed before application or a bonding product that contains silane.
- Leaving the bonding layer uncured when bonding to another composite increases tensile strength. These findings are quite new, so the exact reasons are still untested. We still don’t know if this is also the case for binding to dentin or enamel.
- NIOM studies have shown that repairing any composite with any other kind of composite is fine as long they are both metacrylate-based composites.
- Sandblasting on dental amalgam increases micromechanical retention; an alternative is roughening the dental amalgam with a diamond bur.
- In cases when the repair involves enamel and dentin, we recommend the selective edge procedure and a two-step self etch.
- Two-step self-etch bonding products are more resistant to hydrolytic degradation.
- Crown vs composite on an endodontically treated tooth must be decided on the amount of remaining tooth substance. The most important aspect is to get a tight seal to the endodontic restoration.