This document discusses furcation involvement in multi-rooted teeth. It begins with introductions and definitions, then describes the anatomy of furcated teeth. Several classifications of furcation involvement are presented based on horizontal and vertical bone loss. Potential etiologies include dental plaque, local anatomic factors like furcation dimensions and root concavities, developmental anomalies, trauma, caries, and pulpal pathology. Diagnosis and various treatment options are also covered, along with prognostic factors and conclusions.