According to Black's classification, decay diagnosed on the incisal edge of anterior teeth and the cusp tips of posterior teeth is class:

Black's classification of caries categorizes dental cavities into specific classes based on their location. In this classification, Class VI refers specifically to cavities that occur on the incisal edges of anterior teeth and the cusp tips of posterior teeth. This is significant because the incisal edges and cusp tips are areas that are often subjected to high stress during chewing, making them susceptible to decay.

Class IV pertains to cavities located on the interproximal surfaces of anterior teeth, particularly involving the incisal edge, but it does not encompass the cusp tips of posterior teeth. Class II focuses on cavities on the interproximal surfaces of posterior teeth, which are typically affected by decay due to plaque accumulation between adjacent teeth. Class V includes cavities located in the cervical area of all teeth, typically found at the gum line.

Understanding these classifications helps dental professionals diagnose and plan for the treatment of dental caries effectively. Thus, the identification of decay on the incisal edge of anterior teeth and cusp tips of posterior teeth as Class VI is correct within the context of Black's classification framework.