Final answer:
A 4-mm reading is recorded for the mesial-facial of tooth #12. The type of pocket present at this location is a mesial-facial pocket, which is typically seen in cases of moderate gum disease.
Step-by-step explanation:
The type of pocket present at the location described is called a mesial-facial pocket.
A pocket is a space between the teeth and gums that is created as a result of gum disease. In this case, the 4-mm reading indicates that there is some loss of attachment between the gum tissue and the tooth. The gingival margin being located slightly apical to the cementoenamel junction means that the gums are positioned slightly below the point where the tooth's enamel meets the cementum.
This type of pocket is typically seen in cases of moderate gum disease, where there is inflammation and some loss of bone support around the tooth. It is important to seek treatment to prevent further progression of the disease and maintain oral health.