The dentist who originally put in my side bondings said no drilling was necessary and that acid etiching was sufficient. After about one year, one of them came out and I had it replaced by a new dentist. The new dentist insisted that "roughening" the tooth surface with a drill was necessary in addition to acid etching (this is on the actual tooth surface, as I have gum recession that exposes the tooth below the enamel). There is still ~4mm tooth structure left--is this sustainable? Opinions?