For the perfect deep purification I use sand drill to clean the pits and fissures as the powder particles will easily reach the bottom of the fissures. Debridement needs 27 micron aluminium oxide powder. If there is a minor decay I use 100 micron powder. Larger caries -like in that case - needs burs. In the case presented probably the inappropriate sealing (besides the awful modern nutrition) is the cause for the caries. I knew I had to drill, so I made transparent stamp to accelerate the restorative part of my work.