Final answer:
Exodontic therapy is recommended for a crown fracture with pulp exposure, where the structural damage is severe and could lead to infection if untreated. Microbes like Streptococcus mutants contribute to tooth decay by producing acids, highlighting the need for regular dental care.
Step-by-step explanation:
Exodontic therapy, or tooth extraction, should be recommended when the condition of a tooth cannot be restored or when its damage is irreversible. In the given options, exodontic therapy is most appropriate for a crown fracture with pulp exposure (option B). This condition presents with significant structural damage to the tooth, exposing the pulp which contains nerves and blood vessels, and can lead to severe infection or abscess if not promptly treated. Other scenarios provided, such as a subluxation of the root or fractures without pulp exposure, may have alternative treatments that aim to preserve the tooth.
Microbes play a role in tooth decay by metabolizing sugars from food remnants in the mouth and producing acids that erode dental enamel. The most important cariogenic species of bacteria is Streptococcus mutans, which is particularly adept at creating biofilms and producing acid in the dental environment. Regular oral hygiene and prompt dental care, including fillings or root canals, are essential in preventing and addressing the harmful effects of these microbes.