What does the term 'adontia' refer to?

Adontia specifically refers to a condition where one or more teeth are congenitally missing, meaning that these teeth never developed due to genetic factors or other reasons present from birth. This term encompasses both complete adontia, where all teeth are absent, and partial adontia, where some teeth are missing. It is important to distinguish adontia from other terms related to missing teeth, as it directly points to congenital absence rather than loss due to external factors like decay or hygiene issues.

In comparison, the other options relate to different conditions concerning teeth. Missing teeth due to poor hygiene suggests an acquired condition often resulting from periodontal disease or caries, which leads to tooth loss after they have formed. Teeth that are impacted refers specifically to teeth that are obstructed from emerging fully into the dental arch, such as wisdom teeth, but they are still present within the mouth. Fallen out due to decay addresses a scenario where deterioration of dental tissues leads to loss, which also is an acquired situation. Therefore, the context of adontia being about congenital absence makes option B the accurate choice in this scenario.