The document discusses various classification systems for cavity preparation in dentistry. It describes G.V. Black's original classification system of Classes I-V which categorize cavities based on their location. It also discusses modifications to Black's system proposed by Charbeneu, Sturdevant, Finn, and others. Finally, it introduces the Mount and Hume classification system which defines the extent and complexity of cavities based on the site of carious lesions and their size.