Final answer:
An impression tray must be painted with an adhesive before use, and antiseptic is suitable for microbial control on living tissues to prevent infection.
Step-by-step explanation:
An impression tray with a smooth surface must be painted with an adhesive substance before use. The adhesive helps in creating a strong bond between the impression material and the tray, ensuring that the material does not move or shift during the impression-taking process, which could result in a distorted impression.
When it comes to microbial control on tissues to prevent infection, antiseptic is the suitable choice. Antiseptics are gentle enough to be used on living tissues and are effective in reducing the presence of microorganisms that could cause infection.