Final answer:
The most likely explanation for Samara's periodontal condition is the systemic effect of lupus.
Step-by-step explanation:
The most likely explanation for Samara's periodontal condition, given that she has good oral hygiene, is the systemic effect of lupus. Systemic lupus erythematosus (SLE) is an autoimmune disease that can cause body-wide tissue damage, including the oral tissues. The immune dysfunction in SLE can lead to chronic inflammation and damage to the gums and supporting structures, resulting in periodontal disease.