What is the role of varnishing a cavity before filling?

Varnishing a cavity before filling plays a crucial role in ensuring good marginal seals. When a dental varnish is applied, it acts as a protective layer between the tooth structure and the filling material. This layer helps to create a more effective bond by reducing microleakage around the margins of the restoration. Good marginal seals are essential for the longevity of the filling, as they prevent bacteria and moisture from penetrating under the filling, which can lead to secondary caries and compromise the success of the treatment.

Additionally, while varnishing may provide some benefits related to tooth sensitivity, such as sealing dentinal tubules, its primary purpose is not centered around addressing sensitivity directly but more toward facilitating a successful and durable restoration with an effective seal. Therefore, the emphasis on achieving good marginal seals is key to maintaining the integrity of both the filling and the underlying tooth structure.