Which of the following is not a recognized method of replacing missing teeth?

The functional appliance is not a recognized method of replacing missing teeth. Functional appliances are typically used in orthodontics to correct jaw alignment or retain dental positions rather than to replace lost teeth. They work by encouraging the growth and movement of teeth and the jaws.

On the other hand, a bridge, denture, and implant are all well-established options for tooth replacement. A bridge uses adjacent teeth to support a prosthetic tooth, while a denture provides a removable solution for multiple missing teeth. Implants involve a surgical procedure to insert a titanium post into the jawbone, providing a solid foundation for a crown that mimics the function and appearance of a natural tooth.

Thus, among the options listed, the functional appliance stands apart because it does not serve the primary purpose of tooth replacement.