Final answer:
Internal resorption is typically the most challenging pulpal or periapical condition to diagnose, as it can remain asymptomatic without radiographic evidence, unlike conditions with visible clinical signs like necrotic pulp or chronic pulpitis.
Step-by-step explanation:
Among the options provided, internal resorption is often the most difficult pulpal or periapical pathosis to diagnose. Unlike acute apical abscesses or chronic suppurative apical periodontitis, which show more evident clinical signs and symptoms, internal resorption can often go undetected without the use of radiographs.
It occurs when the body starts to resorb the tooth structure from within, and it may not cause pain or visible changes until it is quite advanced. Conditions like necrotic pulp and chronic pulpitis are relatively easier to identify based on the patient's symptoms and the results of clinical exams.