Confocal microscope analysis of depth of etch between self-limiting and traditional etchant systems

To see whether there is an advantage to using a self-limiting phosphoric acid etchant versus a traditional 34% phosphoric acid etchant for bonding by measuring the depth of etch at multiple time intervals.

A total of 25 bovine teeth were mounted and etched on the facial surface with two different etchants: standard 34% phosphoric acid and a self-limiting 35% phosphoric acid etchant at varied time intervals of 15, 30, 60, 90, and 120 seconds. Teeth were scanned using a three-dimensional laser confocal scanning microscope prior to etching and scanned again after etching to determine the depth of enamel etched compared to the baseline enamel surface prior to etching.

The 34% phosphoric acid etchant etched significantly deeper than the self-limiting etch. Etch times exceeding 30 seconds also etched significantly deeper for both types of etchant.

The etch depth of the self-limiting etchant was consistently less than the standard etchant. Both types of etchant etched deeper after 30 seconds, but the depth of etch at 120 seconds was not different than at 60 seconds, indicating that both etchants are somewhat self-limiting in depth. Therefore, there is no advantage to using the self-limiting etchant.