This morning I was finishing up a maxillary premolar e.max crown in a very easy-going patient. We were cleaning up some extra cement right after it began to gel. I pulled the cord and the gingiva began to bleed a bit. Remembering back to a lecture I attended a long time ago, the question was asked, “When during the bonding process is it OK if you begin to get some bleeding?” Essentially, the questioner wanted to know when is it OK to break your isolation and not be concerned with contamination anymore?

The lecturer said, “When the viscosity of blood and saliva is unable to displace the curing cement.” He went on to add that as soon as the gel stage begins, you should be fine if there is bleeding and saliva contamination. Technically, it's not contamination anymore, as it should do nothing deleterious to our developing bond. I have been following this advice for years with good results and still do believe that his advice is correct.

Today while cementing that premolar crown, I had an experience that makes you really think just how important not good, but great isolation is. I began to floss the contacts while the cement was still gelling. My assistant was holding the crown with her finger and I was flossing away. Then my heart sank, I thought I saw the crown lift just a little. More of a sensation than something visual and probably a fraction of a millimeter. I immediately pushed the crown back down and it confirmed my fear. It dropped down into place ever so slightly.

Realizing that this was very bad, I gripped the crown and removed it before the cement was able to set more. What I saw next was what really amazed me. The inside of the crown was filled with blood. It was everywhere. Not big old drops but a layer of blood mixed with the still-setting cement. I was horrified thinking of what would have happened had I not felt that slight movement. How many times could it have happened and I missed it?

This experience reinforced for me just how technique-sensitive the bonding process is. There are so many variables. Most we can control through knowledge, training and experience. Others may come down to a little bit of luck, and that's what worries me most. We can overcome luck with vigilance and staying alert. Never let down your guard. Encourage your assistant to tell you right away if she sees something odd that occurs. She can save you and your patient some trouble down the line.  It's great to be able to learn from our mistakes, after being aggravated, of course.