Dental glossary — terms beginning with U

Overbite, the position of the upper front teeth relative to the lower ones when the upper incisors overlap the lower.

Ultrasound, in dentistry ultrasound is used during professional tooth cleaning to remove calculus and soft or hard deposits above or below the gum margin. Removing calculus with ultrasound at the dentist is generally not painful.

Ultrasonic toothbrush, most of the oscillating electric toothbrushes on the market are wrongly described as ultrasonic brushes; they are sonic toothbrushes. In a sonic brush the head usually oscillates at around 250 to 350 Hz, whereas ultrasonic brushes work from about 20,000 Hz upwards. Because the frequency is so high, the user feels no vibration at all. In the end both sonic and ultrasonic toothbrushes deliver clean and healthy teeth, using fundamentally different technologies.

Uvula, the small fleshy projection at the back of the soft palate.