Traditional restorative dental treatment has many shortcomings and has not been shown to be an effective method for managing caries. In spite of this, many dentists continue to be powered by an aggressive restorative approach which may result in unnecessary treatment and which must now be seen as inappropriate. There is a pressing need for a greater understanding as to the precise criteria that dictate the need for both non-invasive (reversible) preventive measures and invasive (irreversible) restorative treatment. This paper examines these criteria and provides decision trees with respect to the clinical management of carious lesions and teeth with existing restorations, showing when, and what type of, intervention is required. The assessment and management of fissured tooth surfaces receives special attention. It is demonstrated that while many clinical situations warrant clinical intervention, often this should be entirely preventive and of a non-invasive type.