Note the cavitation.
-In the U.S. tradition was to restore dental caries when it reaches the
D.E. junction or slightly into dentin.
-Internationally this is considered as radical treatment. It has been recommend that a restoration should be placed only after penetration of 60% into dentin..
( Pitts N, Lond FR. Current methods and criteria for caries diagnosis in Europe. J Dent Educ 1993;57 (6):409-14.)