Which of the following microorganisms are commonly present in large percentage of root canal treated teeth that present with persistent periradicular lesions indicative of failed treatment?
**Core Concept**
The presence of microorganisms in root canal treated teeth is a common cause of persistent periradicular lesions, indicating failed treatment. The most commonly implicated microorganisms are those that are resistant to disinfection and have the ability to survive in a biofilm within the root canal system.
**Why the Correct Answer is Right**
The correct answer is Candida albicans, which is a type of fungus that can form a biofilm within the root canal system. Candida albicans is known to be resistant to many disinfectants and can survive in the presence of low oxygen levels, making it a common cause of persistent periradicular lesions. The biofilm formed by Candida albicans can also make it difficult to eradicate the microorganism using conventional root canal treatment methods.
**Why Each Wrong Option is Incorrect**
**Option A:** Enterococcus faecalis is a type of bacteria that can also be present in root canal treated teeth, but it is not as commonly implicated in persistent periradicular lesions as Candida albicans.
**Option B:** Streptococcus mutans is a type of bacteria that is commonly associated with tooth decay, but it is not typically found in root canal treated teeth.
**Option C:** Actinobacillus actinomycetemcomitans is a type of bacteria that is associated with periodontal disease, but it is not commonly implicated in root canal treated teeth.
**Clinical Pearl / High-Yield Fact**
Candida albicans can form a biofilm within the root canal system, making it resistant to disinfection and a common cause of persistent periradicular lesions. This is an important consideration for dentists and endodontists when treating root canal infections.
**Correct Answer: C. Candida albicans**