Which method is NOT effective for achieving proper penetration of gel etch?

Brushing is not considered an effective method for achieving proper penetration of gel etch because it can lead to uneven application and might not allow the etching gel to properly engage with the surface of the enamel. The goal of using gel etch is to create a controlled, rough surface that can improve bond strength between the tooth structure and bonding agents. Brushing can introduce bubbles and cause the gel to spread too thin, which diminishes its etching capability.

Conversely, methods like dabbing, using an applicator, and applying in small sections are effective because they allow for a more controlled application. Dabbing ensures that the etch can adequately penetrate the pits and fissures of the enamel, while the use of an applicator can help target specific areas without over-spreading the gel. Applying in small sections allows for more precise control, ensuring that each area is effectively etched before the gel dries or evaporates. These methods help achieve the desired surface characteristics for optimal bonding in dental procedures.