A common clinical scenario we face is closing an endo access opening through a crown. We now have a variety of ceramic materials and metals to restore and we have to consider each material when going through a protocol for bonding composite to it.
Whether it is a PFM or e.max (monolithic or layered), I follow the same technique when closing an endo access hole.
I bevel back the ceramic edge (approximately 1mm) as the endodontist will generally leave a butt joint where the opening is made. Then I use ceramic etch but, note that depending on your ceramic you will need different etch times and different strengths. E.max crowns etch with a 5 percent hydrofluoric acid for 20 seconds and Feldspathic porcelain etches 9 percent for one to two minutes. NOTE: You need to have both percentages in your supplies.
Also, please know that hydrofluoric acid will require rubber dam placement or a really well-isolated environment. I personally always apply one or the other depending on the tooth site, tissues and risk of tongue involvement.
Then silane is applied followed by an adhesive and then the composite material. Yes, it takes a few additional minutes for the ceramic etch to be effective, and another minute for the silane to dry; it might be easy to skip these steps but it reassures me that the composite will bond well and reduce the incidence of leakage over time.
Since many of us are now using zirconia restorations, what is the protocol for closing access openings on these restorations?
I spoke with Dr. Robert Winter whose lab fabricates all of my restorations and he suggested that the endo access opening NOT be beveled but microair- abraded. The reason you don’t want to bevel is that composite resin does not bond well to zirconia so if the ceramic has a long bevel with a resulting thin layer of composite extending to the margin, it will be more likely to break down or chip off.
Remember that the entire occlusal surface may receive the abrasion, so the entire occlusal surface needs to be polished after placing the composite.
Then the endo access opening should be silanated. Both Dr. Winter and I use Monobond Plus for one minute, adhesive and finally the composite placed.
Summary of endo access opening
Zirconia restorations: No Ceramic etch and no bevel, but do microetch. For PFM, Feldspathic and e.max restorations: No microetch/air abrasion, but do bevel and use ceramic etch and silane. Remember, pay attention to what kind of ceramic you have before you select your etch.
I hope this is helpful to all of us needing to complete this procedure in a dental material world where protocols followed will make a big difference in outcomes.
(Click this link to read more dentistry articles by Dr. Mary Anne Salcetti.)
Mary Anne Salcetti, DDS, Spear Visiting Faculty and Contributing Author. www.maryannesalcettidds.com