What type of portable unit is used at chairside to provide a flame?

The alcohol burner is a commonly used portable unit in chairside dental practices for providing a controlled flame. It operates by burning denatured alcohol, which creates a steady flame useful for various purposes, such as softening materials or sterilizing instruments. Its portability makes it ideal for use in a clinical environment, where it's essential to have a reliable and easily manageable source of heat.

While other options may also provide a flame, they differ in functionality and application. For example, a portable flame unit is not a standard term used in dental practices; it is less specific than an alcohol burner and does not clearly define its method of operation. A soldering torch typically produces a hotter, more focused flame, which is more suitable for metalwork rather than the softer applications usually required in a dental chairside setting. Lastly, a gas burner generally requires a more complex setup and is less portable, making it impractical for direct chairside use. Thus, the alcohol burner stands out as the most appropriate choice for providing a flame in the context of chairside lab practice.