Mylar strips are placed __________ acid etch.

Mylar strips are placed before the acid etch to create a seamless interface between the composite material and the tooth structure while also ensuring proper adaptation of the composite material to the surrounding tooth surface. This procedural step allows for the desired contour and proximal contact to be formed effectively. When mylar strips are positioned prior to the etching process, they help facilitate the subsequent application of the bonding agent and composite resin, leading to improved aesthetic outcomes and a more effective bonding procedure. By embedding the strips beforehand, the technician can ensure that the final contour of the restoration aligns properly with the adjacent teeth and maintains the necessary contact points, which is crucial for the longevity and function of the dental restoration.