Dental occlusion (Angle classifications)

The mouth is made up of two key bones: the mandible, which is the bone beneath the bottom row of teeth; and the maxilla, which is the bone above the top row of teeth.

The bones are lined by the gums and have an alveolus, or socket, for each tooth.

Since the mouth is symmetrically divided down the middle, let’s look at one side of a mouth containing the permanent, or adult, teeth. The teeth that pair up vertically have the same names.

Starting in the center, first, there are the central incisors and then the lateral incisors.

And incisors are used for cutting into something like a juicy peach.

Next, are the canines, which get their name from being the same teeth that are extra long and sharp in dogs.

They’re also called the cuspids, which comes from the word cusp, meaning point.

These are used for gripping and tearing into food like a piece of meat.

Then, there are the first and second premolars or bicuspids which have two cusps each.

Next comes the first permanent molars and the second permanent molars.

Molars usually have four to five cusps, and are great for crushing and grinding food.

Lastly, there are the third permanent molars, or wisdom teeth, which, in some people, never erupt at all.

All together, that makes 32 permanent teeth.The front teeth from canine to canine are called anterior teeth.

The rest are called the posterior teeth.

Each tooth has five surfaces that are named based on their location and function.

Each tooth has one chewing surface.

The chewing surface of posterior teeth are called occlusal surfaces, and the cutting edges of anterior teeth are called incisal edges.

Each tooth has two proximal surfaces which are surfaces that face adjacent teeth.

Proximal surfaces are mesial when they are closer to the midline of the mouth and distal when they are away from the midline.

Tooth surfaces next to the face, the ones resting next to cheek or lips, on the upper and lower teeth are called facial surfaces.

Facial surfaces of posterior teeth are sometimes called buccal surfaces.

The facial surfaces of anterior teeth that face the lip are called Labial surfaces.

Surfaces that face the tongue on lower teeth are called lingual surfaces and the surfaces that face the palate on the upper teeth are called palatal surfaces.

Each anterior tooth, including the central and lateral incisors and the canines, has a cingulum, which is the name of the little hump about one-third of the way from the gums toward the occlusal surface of the tooth.

The occlusal surface of the molars and premolars, have a central fossa and ridges - like a mountain ridge - that arise from cusps.

The marginal ridges connect the buccal and lingual or palatal cusps, and the triangular ridges start at cusp tip and terminate in the central groove.

Transverse ridges connect facial and lingual cusps through the center of the tooth and oblique ridges, which are only seen in upper molars, connect the distobuccal cusp to mesiopalatal cusp.

The intersection of two ridges forms a groove and the intersection of three or four ridges forms a pit.

There are also multiple grooves or valleys that run between cusps and each one is named for its location.

For example, the valley running across the length of the tooth is called the central groove, and the one running outward from the center in the section of the tooth where the mesial and buccal sides collide is called the mesiobuccal groove.

Now, the point or plane where a tooth touches an adjacent tooth to the side of it is called a proximal contact.

Embrasures are the V-shaped spaces that occur between teeth, right next to where side-by-side teeth make contact with each other.

Finally, there’s the incline, which refers to the steep planes of teeth, including the canines, that lead up to the cusp or point of the tooth, kind of like the side of a mountain leading up to the peak.

Dental occlusion refers to the way in which the teeth line up with each other as the jaw goes from open to closed.

So malocclusion is when the teeth don’t line up properly, and Angle’s classification of malocclusion is a system used to categorize that.

The system bases everything on the position of the maxillary first permanent molar. And it was designed this way because its creator, Edward Angle, believed that the maxillary first molar reliably stayed where it was after eruption while the other teeth tended to have a bit more movement.

In people who don’t have maxillary first molars, he based the system on the location of the canines instead.