Which method is effective in preventing pulp injuries during preparation?

Preventing pulp injuries during tooth preparation is crucial for maintaining dental health and comfort. Using a water spray handpiece is effective in this context as it helps to keep the tooth cooler during the preparation process. The heat generated from the bur can lead to pulpal necrosis if not managed properly. The water spray provides cooling and also helps to flush away debris, which can further minimize the risk of damaging the pulp during the procedure.

While other methods, such as choosing the correct size of bur or the design of the margin, may have their benefits in tooth preparation, they do not directly address the heat and potential damage to the pulp that can occur during the mechanical preparation of the tooth. Applying a dental dam is important for maintaining a clean working area and preventing contamination, but it does not specifically target the prevention of pulpal injuries caused by heat or friction during preparation. Thus, using a water spread hand device is the most effective method for reducing the risk of pulp injury during dental procedures.