A vital bleaching tray is constructed with:

A vital bleaching tray is typically constructed using lighter-gauge plastic because this material allows for better comfort and adaptability in the patient's mouth. Lighter materials are generally more flexible, which helps the tray to conform to the contours of the patient's teeth and gums, ensuring an even distribution of the bleaching agent. This flexibility is essential for creating a snug fit, which minimizes the chance of leakage and maximizes the effectiveness of the bleaching process.

Using rigid or heavy-gauge materials can result in a tray that is uncomfortable for the patient and may not create the necessary close contact with the teeth to achieve optimal results. The absence of additional components like a spacer or handle in the correct answer reflects the simplicity and efficiency of the design specifically for the bleaching procedure, which aims for effectiveness rather than unnecessary complexity. Thus, lighter-gauge plastic strikes the right balance between comfort and functionality needed for achieving the desired whitening effects during treatment.