- Minimum of 2 accessible non-adjacent teeth (incisors, canines, pre-molars), preferably in different quadrants, that meet all of the following criteria: Signs of facial/cervical gingival recession and/or signs of erosion or abrasion (EAR), Tooth with MGI score =0 adjacent to the test area (exposed dentine) only [Lobene, 1986] and a clinical mobility of ≤1, Tooth with signs of sensitivity measured by qualifying evaporative air assessment (Y/N response)