The road to orthodontic treatment often is paved with a lot of jargon and lingo that you as a patient or parent may find confusing.

You shouldn’t have to complete an orthodontic residency to understand what orthodontists and their assistants are talking about when they discuss malocclusion and whether it falls under Class I, Class II or Class III.

The kids are back in school for a new year, and now it’s time for you to pull up a chair. Class is in session!

First, a definition: malocclusion means a “bad bite,” or the imperfect positioning of the teeth when the jaws are closed.

Types of malocclusion that can benefit from orthodontic treatment include (click on the hyperlinked terms to read articles we’ve previously written on these topics):

  • Crowded teeth– Not enough room between teeth for them to align properly in relationship to each other.
  • Diastema– Spaces between teeth.
  • Overjet– The upper front teeth protrude disproportionately in front of the lower front teeth.
  • Open bite– The upper front teeth don’t properly overlap the lower front teeth.
  • Overbite– The front teeth in the upper jaw overlap the front teeth in the lower jaw too much.
  • Underbite– The lower jaw juts forward of the upper jaw and causes the teeth in the lower jaw to overlap the upper front teeth.
  • Crossbite– One or more teeth are closer to the cheek or the tongue than their counterparts in the opposite dental arch.
  • Scissors bite– The lower molars are positioned too far inward in relation to the upper molars, or vice versa.
  • Misplaced midline- The maxillary midline is where your upper front two teeth meet. The line created by their meeting should align with the center of your lip and nose. When that midline appears off center, it is “misplaced.”
  • Rotated teeth- Teeth that are next to each other aren’t aligned because one or more are turned.
  • Transposed teeth- Two teeth that have erupted in each other’s proper position, such as a canine that erupts into a premolar’s position.

These types of malocclusion fit into one of three classes, and these classes identify the relationship between the upper and lower jaw, as well as teeth positioning and spacing.

Class Icrowded teeth

In this malocclusion category, the upper and lower molars and the canine teeth are positioned properly. However, the teeth are too crowded, have too much space between them, or other localized tooth problems are present.

Other problems may be present in a more severe Class I case such as an open bite or a crossbite.

Each treatment case is different, but generally speaking, treatment of Class I malocclusion may include expanding the upper arch to correct a crossbite, to create more space for crowded teeth, or to correct a misplaced midline. Treatment of Class I cases may also call for closing diastemas and aligning rotated teeth.

Class IIProtruding teeth

This classification is marked by upper molars that are positioned slightly forward of the lower molars, and canines that are not properly positioned to each other. It gets further broken down into divisions.

Division 1 includes orthodontic cases where the lower jaw may be underdeveloped, and the teeth in the upper jaw protrude to create overjet. The upper arch often is narrow in these cases, and it may be difficult for the patient to comfortably close the lips without straining.

Division 2 cases are those that include deep overbite, but the upper arch is broad and the lips can be closed comfortably without straining.

In addition to braces, other orthodontic appliances often are used to correct Class II malocclusion. They include:

  • Headgear- This removable appliance provides extra anchorage that we often need to move teeth into their optimum positions. It also inhibits upper jaw growth to correct overjet.
  • Herbst appliance- A fixed appliance patients cannot remove, it helps correct overbite by pushing the lower jaw forward and the upper molars backward. Patients typically wear this for about one year.
  • Twin block appliance- This appliance features upper and lower acrylic bite blocks that guide the lower jaw forward and downward.

Other treatment methods include the use of elastics, and in more severe cases, tooth extraction or orthognathic surgery.

Class IIIIMG_0032[1]

Orthodontic cases of this classification feature upper molars that are positioned farther behind the lower molars than they should be, and the lower front teeth jut forward of the upper front teeth to create an underbite.

True Class III malocclusion is chalked up to genetics and is caused by a combination of a larger-than-normal lower jaw or an upper jaw that is underdeveloped.

Sometimes patients have an underbite, but don’t have a true Class III malocclusion. This “pseudo” Class III malocclusion is caused by incisors or canine teeth that make contact prematurely, which causes the lower jaw to move forward.

Treatment of Class III malocclusion is most effective when the patient is a child who is still growing. We can put the patient’s growth to work for us. This way, we correct the problem while hopefully avoiding the need for surgical procedures.

To that end, we use a variety of appliances in addition to braces with brackets and arch wires. They include:

  • Maxillary expander – Placed in the roof of the mouth and slightly widened daily by inserting a key and turning it.
  • Reverse-pull headgear- Worn at night to promote upper jaw growth.
  • Chin cap – Worn to inhibit lower jaw growth.

Some cases require orthognathic surgery to correct the jaw discrepancy, particularly if the patient is an adult whose growth is complete.

I hope this lesson in terminology helps you better understand what is discussed at the next orthodontic appointment for yourself or your child. It’s easier to get your treatment-related questions answered with you have a bit of foundational knowledge under your belt.

I invite you to check out other articles on our blog for additional information. In addition to sharing news about what’s going on in our office and announcing contests, we post a great deal of information related to orthodontic treatment in an effort to make the entire treatment process more relatable.

As always, we welcome your questions and information requests.

1 Comment

  1. Very interesting and comprehensive post Dr.Sanders.
    I took my youngest son who is almost 4 to his routine dental cleaning yesterday and his dentist noticed a unilateral posterior cross bite. Up till now, nobody had noticed it, not even his dentist at his previous cleanings.
    My understanding is that crossbite needs to be addressed at a very young age so my son is coming to see you in a couple of years when he is 6-7 years old.
    My oldest son who is 8 has no bite issues. His dentist says there is no indication for early orthodontic treatment for him but he will probably need braces later on.

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