Repairing an incisal fracture is one of the most rewarding things I have found in my practice. A patient comes in having chipped their tooth opening a package, biting on a dessert fork or clinking it against a wine bottle. (That actually happened.) The repair rarely necessitates a local anesthetic, and often is done over just a few minutes. With a good color match, the patients are always happy considering the repair comes out invisible.
I always roughen the surface and create a slight bevel for the repair. The bevel helps not only with increasing the surface area for bonding, but aiding with color transition as well. At some point though, I am wrapping a thin veneer of composite on unprepared enamel, and the last thing I want is a stained, peeling edge down the road. In recent years, we have switched over to self-etching adhesives due to their superiority in reducing post-op sensitivity. Total etch technique has always worked well since the fractures are often mostly in enamel. The question then becomes this, "Is the etch in a self-etching adhesive strong enough, or do I still need to etch any unprepared enamel?" I have still used phosphoric acid etch in these cases, motivated less by any real evidence, more by paranoia for that perfect bond.
A recent study shed light on this question. Researchers looked at Clearfil SE Bond, often considered the gold standard in self etching adhesives. They measured sheer bond strength of resin tags to etched and un-etched enamel. Additionally, they used a scanning electron microscope to look at resin penetration to enamel in these samples.
Their results showed that etching the unprepared enamel not only showed higher strengths in the sheer bond test, but deeper penetration of the resin tags as well. Essentially, the acid of the self etching adhesive may be strong enough to get a decent bond, but the best long term choice to achieve superior bonding is to simply etch the tooth first.
You can see the abstract and study here. Once again, a simple experiment helps us to become better at what we do every day. As always, if you have a simple tip or trick you have learned in your practice, drop a comment below.