The aim was to assess the extent of enamel damage sandblasting might cause and to identify a combination of sandblasting durations and MicroEtcher nozzle-tooth surface distance (NTD) resulting in the least enamel damage.

Lingual surfaces of 30 human teeth were sandblasted with 2 different distances: 1, 2mm and 3 different durations: 1, 2, 3s and photographed using a light microscope. The cavity depth and diameter of the sandblasted teeth were measured on the light microscope's pictures. A pilot study was performed to minimize possible combinations of sandblasting durations and distances. To validate the measurement method, sandblasted teeth were ground cut for comparison. Inter-examiner reliability was assessed with Bland-Altman analysis. Mann-Whitney U-test was used to detect cavity and diameter changes for every sandblasting duration and NTD combination.

From the pilot study sandblasting durations 1,2 and 3s and NTD<2mm were chosen. The cavity diameter of the sandblasted area did not change with increased sandblasting duration nor NTD (P>0.05). The cavity depth of the sandblasted area increased statistically with an increased sandblasting duration (P<0.05) but did not increase with an increase NTD (P>0.05). The 95% limits of inter-examiner agreement were narrow.

All distance and duration combinations tested caused enamel damage. Sandblasting duration had greater impact on the cavity depth than the NTD. The blasting duration should, therefore, not exceed 2s and the NTD should be held at maximum 2mm to minimize the risk of unintentional spread.