A 42-year-old man needs an indirect composite onlay on tooth 36. After removal of an old restoration and caries, the distal cervical margin lies about 1.5 mm below the gingival margin, but a bitewing shows it is still about 2.5 mm coronal to the alveolar crest. Rubber dam can be placed and a matrix band seals well below the margin. What is the most appropriate way to manage this margin before the impression?