<qa>  What is the minimum of 2 accessible non-adjacent teeth?- Minimum of 2 accessible non-adjacent teeth incisors, canines, pre-molars, preferably in different quadrants that meet all of the following criteria: Signs of facialcervical gingival recession andor signs of erosion or abrasion EAR Tooth with MGI score 0 adjacent to the test area exposed dentine only and a clinical mobility of less than or equal to 1 and Tooth with signs of sensitivity measured by qualifying evaporative air assessment YYesNNo response screening 