Which class of cavity affects the pits and fissures occlusally on molars and premolars?

A Class I cavity specifically refers to decay that occurs in the pits and fissures of the occlusal surfaces of molars and premolars. These areas are particularly susceptible to cavities due to their complex anatomy that can trap food particles and bacteria. This type of cavity typically affects the chewing surfaces that are prominent in molars and premolars, making it a common site for dental caries.

The other classes of cavities do not pertain to the occlusal aspects of molars and premolars. For instance, Class II cavities are found on the proximal surfaces of premolars and molars; Class III cavities affect the proximal surfaces of incisors and canines but do not involve the incisal edge; and Class IV cavities also occur on anterior teeth but involve the incisal edge and proximal surfaces. Hence, the definition of these cavity classes helps clarify why Class I is the correct answer in this context.