Causes
- Periapical radiograph shows carious lesion in distal of lower right second molar
- Extensive periodontal defect present in the same tooth
- Difficult to determine which process occurred first and caused pulp death
- Combined periodontic-endodontic lesions can originate from two distinct locations
- Infection can spread from pulp tissue or periodontal pocket

Classification
- Endo-Perio subclassification: infection from pulp tissue spreads into bone surrounding tooth root, forming periapical abscess
- Infection may then spread through periodontal ligament to communicate with alveolar bone and oral cavity
- Perio-Endo subclassification: infection from periodontal pocket proliferates into root canal, causing pulpal inflammation
- Accessory canals may allow bacterial penetration into root canal
- Fractured tooth can also result in combined lesion

Treatment
- Conventional endodontic therapy followed by conventional periodontal therapy
- Severe lesions may require tooth extraction
- Treatment outcome and prognosis not dependent on infection source

References
- American Academy of Periodontology provides parameter on acute periodontal diseases
- J. Periodontol article discusses periodontic-endodontic lesions
- Consensus report by American Academy of Periodontology on the topic
- Various authors including Preston D. Miller and Carl E. Misch have written on the subject
- Capnocytophaga sp. is mentioned as a reference

Additional Information
- Combined lesions can be diagnosed through radiographs and clinical examination
- Proper diagnosis and treatment planning are crucial for successful management
- Regular dental check-ups and good oral hygiene can help prevent combined lesions
- Research is ongoing to explore new treatment modalities for these lesions
- Collaboration between endodontists and periodontists is often needed for optimal care