Overjet vs Overbite — What's the Difference?

What is overjet?

Overjet is the horizontal distance between the front edge of the upper front teeth and the front edge of the lower front teeth when the mouth is closed. A normal overjet is 2 to 4 mm. An increased overjet — where the upper front teeth protrude significantly ahead of the lower — is what is colloquially called buck teeth. It is associated with Class II Division 1 malocclusion and is measured in the horizontal plane: how far forward the upper teeth stick out relative to the lower.

What is overbite?

Overbite is the vertical overlap of the upper front teeth over the lower front teeth when biting. A normal overbite is 2 to 4 mm, where the upper teeth cover approximately one third of the lower front teeth. A deep overbite occurs when the upper teeth cover more than half of the lower front teeth. In severe cases, the lower incisors bite into the gum tissue behind the upper front teeth, which can cause damage to both teeth and gum. Overbite is measured vertically — how far down the upper front teeth overlap the lower.

Can you have both?

Yes, and it is common. Class II Division 1 malocclusion typically presents with both increased overjet and increased overbite. Thumb sucking and dummy use beyond age 3 to 4 can increase overjet while also deepening the overbite. An underdeveloped lower jaw tends to increase both measurements together. It is important to distinguish the two because the treatment mechanics required to address each are different even when both are present in the same patient.

How overjet is treated

Overjet correction requires retracting the upper front teeth, advancing the lower front teeth, or a combination of both. In growing patients, functional appliances such as twin blocks or Herbst appliances guide lower jaw growth forward, reducing overjet by influencing skeletal development. In non-growing adults with a skeletal component, jaw surgery may be required for the best functional and aesthetic result. Where the overjet is purely dental — teeth rather than jaws — fixed braces or clear aligners with or without extractions can correct the tooth position.

How deep overbite is treated

Deep overbite treatment involves intruding the upper or lower front teeth, extruding the back teeth to open the bite, or a combination. Bite turbos — small pads bonded to the upper front teeth or lower back teeth — disengage the bite and allow the teeth to move freely. Deep overbite is one of the more technically demanding movements to achieve with clear aligners; specialist planning with attachments is essential. Fixed braces can be more reliable for severe cases. Correcting a deep overbite is important not just aesthetically but to prevent ongoing trauma to the gum behind the upper front teeth.

Useful related pages

This guide is for general information only. It is not a diagnosis, treatment plan, or substitute for advice from a registered dentist or orthodontist.