Fixed functional appliances are crucial orthodontic devices used to correct discrepancies in jaw relationships, particularly when addressing class II malocclusions. These malocclusions often involve the upper jaw protruding relative to the lower jaw, leading to an overbite. Fixed functional appliances work by stimulating growth in the lower jaw while restraining growth in the upper jaw, ultimately aligning the jaws into a more harmonious position.One of the most commonly used fixed functional appliances is the Herbst appliance. This device consists of metal tubes and rods that connect the upper and lower jaws, allowing for controlled movement and positioning over time. The Herbst appliance is fixed to the teeth, ensuring constant pressure and continuous adjustment as the jaw structure gradually adapts.Patients undergoing treatment with fixed functional appliances typically experience a period of adjustment. Initially, they may notice changes in speech and eating habits as their mouths accommodate the new appliance. However, these challenges usually diminish as the patient becomes accustomed to wearing the device.