Cutting into the wrong tooth

 I had a mishap just a couple of days ago where I had to remove a crown to perform endodontic therapy as the crown eventually required replacement. It was a lower central incisor and all the lower teeth had been crowned with the same white, monotone, textureless ceramic.I was very paranoid about cutting into the wrong tooth as all the teeth appeared the same. I counted mesial to distal, correlating the tooth to the xrays, counted, and then counted again. Finally, I made a bur mark into the tooth to mark it and got into cutting.

Somehow, I still managed to cut into the wrong tooth and ended up sectioning halfway through the contralateral central incisor before I realised my mistake. This is a very real risk in these situations and I put it half down to how uniform the teeth looked, half down to my stupidity and carelessness. 

In the future, in a situation like this, I will be making a mark on the tooth with an indelible marker before double checking and triple checking the tooth. The issue here was checking the teeth multiple times before making a mark so that when I looked away to pick up the handpiece and reset my vision, I lost track of which was the actual tooth. An indelible mark is a non destructive way to mark the tooth and it will be impossible to lose track of which tooth is the one in question.