Final answer:
In teeth with pulp necrosis, the periapical area is involved if there is pain on percussion. Pulp necrosis indicates that the dental pulp is dead, and unlike with vital pulp, there wouldn't be a response to thermal stimuli or electric pulp testing under such a condition.
Step-by-step explanation:
In teeth with pulp necrosis, the periapical area is involved if there is pain on percussion. Pulp necrosis is a condition where the dental pulp, a part of the tooth that contains nerves and blood vessels, has died. Pain to thermal stimuli or responses to electric pulp testing is indicative of vital pulp, whereas necrotic pulp would not respond to such tests. When a patient experiences pain while lying down, it may suggest the spread of infection from the root canals into the surrounding tissues, potentially forming an abscess, but it does not specifically diagnose the involvement of the periapical area, which refers to the region around the apex of a tooth's root.
Dental caries, if untreated, can lead to pulp necrosis. Tooth decay is primarily caused by microbes like Streptococcus mutans, which is a cariogenic bacteria responsible for the majority of dental caries.
Pain on percussion of a tooth usually indicates that inflammation has extended to the periapical tissues, potentially leading to abscess formation.