What are misaligned teeth and jaws?

Our teeth are embedded in small “tooth sockets” in the jawbones known as dental alveoli. They are arranged in a semicircle, with the teeth in the upper and lower jaw forming two arches.

When you close your mouth, the two arches come together. The back teeth (molars) have wide chewing surfaces with raised cusps and small grooves. When you bite, the cusps of the upper teeth fit into the grooves of the lower teeth, and vice versa.

The front teeth don’t have chewing surfaces: The canines have pointy tips and the incisors have a narrow edge. When you bite, the lower incisors fit behind the upper incisors. This biting position of the teeth is known as a normal bite or an ideal bite.

A misalignment may affect just one tooth or the whole jaw.

For instance, one single tooth might

• be crooked,
• lean towards the cheek or tongue,
• be “out of line” with the other teeth,
• stay in the bone (known as an impacted tooth) or
• be missing.

Sometimes more than one tooth is affected. For example, several teeth might be out of line or crooked if there isn’t enough room in the jaw – perhaps because there are too many teeth or the jawbone is too small. If there’s too much room – for instance, because some teeth are missing – the teeth may be too far apart, leading to tooth gaps.

The position and size of the upper or lower jaw is sometimes different to normal, too, affecting how the teeth come together. Common examples include:

• Overbite
• Underbite
• Open bite
• Crossbite

Sometimes the two jawbones meet at the wrong angle or overlap sideways. Misaligned teeth and jaws can also occur as a result of severe birth defects such as a cleft lip and cleft palate.

It is normal for the upper front teeth to slightly overlap the lower front teeth. People are only considered to have an overbite if there’s a gap of more than 3 millimeters between their upper and lower front teeth. This is more noticeable when looking at the teeth from the side. The position of the upper jaw is then too far forward or – more commonly – the lower jaw is too far back.

When someone has an overbite, their upper front teeth might stick out (“buck teeth”) and sometimes even cover their lower lip. But the teeth may also be straight, or point slightly inwards. Viewed from the front, the upper front teeth then often completely cover the lower front teeth. This type of overbite is known as a “deep overbite.” Sometimes the bite is so deep that the upper front teeth touch the gums of the lower jaw.

An overbite doesn’t only affect the front teeth. The upper back teeth (molars) are also slightly further forward than the lower back teeth when you bite. The raised cusps of the upper molars then fit into the grooves of teeth that are further forward. But sometimes the biting edges of the upper teeth bite directly onto the biting edges of the lower teeth. This is known as an “edge-to-edge” bite of the molars.

An underbite is basically the opposite of an overbite: The lower front teeth are too far forward. When you close your mouth, the edges of the upper and lower front teeth come together (edge-to-edge bite of the front teeth). In more pronounced underbites, the lower front teeth might even be in front of the upper front teeth when the person closes their mouth.

Underbites are usually caused by a protruding lower jaw. But they can also occur if the upper front teeth point too far inwards or if the lower front teeth point too far outwards.

Like with overbites, the position of the molars (back teeth) is important here: When someone who has an underbite closes their mouth, their upper back teeth (molars) are slightly further back than their lower molars. The raised cusps of the upper molars then fit into the grooves of lower molars that are further back in the mouth or – if the person also has an edge-to-edge bite in that area – the raised cusps of the upper molars bite directly onto the raised cusps of the lower molars.

When you bite, the upper and lower arches of teeth usually close off your mouth. In people who have an open bite, there’s still a small space between the upper and lower teeth when they bite. The open space often occurs between the upper and lower front teeth (anterior open bite). But it might also occur between the upper and lower teeth at the side or back of the mouth (posterior open bite). Open bites are sometimes a result of thumb sucking. They can also be caused by birth defects affecting the jawbone, or by an unusual size and position of the tongue.

A crossbite is where one or more of the upper teeth at the side of your mouth fit behind your lower teeth (are closer to your tongue) when you bite.

If this makes the raised cusps on the upper and lower back teeth come together when you bite, it is a crossbite with an edge-to-edge bite. If the crossbite is very extreme, the teeth might even miss each other completely when biting. This can happen on one or both sides of the mouth. It may develop as a result of misalignments of individual teeth – or because the jawbones don’t fit together properly due to their shape and size.