Which device is used in dental units to remove saliva and fluids?

The device specifically designed for removing saliva and fluids in dental units is the salivary ejector. This tool typically consists of a thin, flexible tube that can be positioned comfortably in the patient's mouth to effectively suck away excess saliva, blood, or other fluids during dental procedures.

Salivary ejectors are vital in maintaining a dry and clean working environment, allowing the dentist to focus on the procedure without the interference of fluids. They often operate on a low suction strength, which is gentle and safe for patients.

While other devices mentioned also have their uses in a dental setting, they serve different purposes. An ultrasonic scaler is primarily used for cleaning and removing plaque from teeth, while a dental suction machine is a broader category that can refer to various suction devices, including the salivary ejector. A high-speed handpiece, on the other hand, is a tool used for drilling and cutting teeth, not for fluid removal. Thus, the salivary ejector is the most suitable answer to the question about managing saliva and fluids in dental procedures.