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Typical Class Three orthodontic problem: deficient upper jaw or prognathic lower jaw
Genetic profile problems with the lower jaw
A Class three skeletal pattern is characterized by the lower jaw protruding forward of the lower jaw. It is typically a genetic problem, but may also be a functional result of the upper jaw being too small.
Normal Class One skeletal vs the Class Three prognathic skeletal pattern
What is a Class Three? The true genetic Class III growth pattern is the opposite of the most common orthodontic problem which is retrusion of the lower jaw. In the Class III the lower jaw is protrusive and it may be mistakenly referred to as an "under bite". In reality, the lower jaw is too long relative to the rest of the face, and the chin appears to protrude too far in front of the rest of the face. Think of Jay Leno...! There is commonly a problem with the width of the upper jaw associated with this condition.
The true Class III is a genetically directed problem which may express itself at an early age, but usually becomes more apparent as the child approaches the teenage growth spurt. Generally, you will find a parent or grandparent with the exact same problem on one side of the family. It is helpful to review pictures of older family members and play detective to discover "which" side of the family the problem originates.
The true Class III is not an all or none problem. There are varying degrees in the amount of abnormal growth which can occur in the lower jaw. Once the lower teeth move out in front of the upper incisors, the muscles influence their position and the size of the chin comes into play to determine how "bad" the condition looks. If there is full genetic expression where the lower jaw is obviously very protrusive, then a combination of braces and jaw surgery is the best treatment. The surgery results are excellent and only involve an approach through the mouth to set the jaw back to normal position. Surgery should only be done on a non-growing patient, so we usually wait until after age sixteen on females and eighteen for males.
There is a condition called a pseudo (fake) Class III which mimics the true genetic condition, and is caused by an artificial forward positioning of the lower jaw due to the bite being forced forward at an early age by abnormal eruption of the front teeth. This condition is easy to diagnose and much easier to correct. The test is to see if the lower jaw slides forward on closing, and if the patient can actively bring the lower front teeth back behind the upper teeth.
A pseudo Class III due to a deficient maxilla (upper jaw) in concert with a constriction of the palate.
Another variation of the Class III is lack of upper jaw growth. Typically this patient will appear to lack cheek bones, the nose is depressed, and the face appears dished-in due to lack of mid-facial growth. Generally there is a cross-bite associated with the problem. Treatment is more difficult with this type of patient, but is correctable given enough time and growth. The need for growth indicates the need for early treatment with these mid-face deficient patients. Non-growers or adult patients are generally a surgical candidate with mid-facial problems. Typically Class III elastics are a protracting headgear may be used with these maxillary deficient patients. Below is the type of maxillary advancing headgear we use in our practice. It rests on the forehead and chin and then elastics are attached to a crossbow in the front of the mouth and then to the upper archwire. The applies a light force to advance the maxilla forward.
Since there are variations in degree of protrusion, sometimes a minor, early Class III will respond to orthodontic intervention with braces and elastic wear. The problem is to diagnose correctly because a true Class III will commonly become progressively worse as the child grows. There are many clues to the degree of growth. Each patient has to be evaluated over a long period of time with progressive x-rays and models of the teeth and jaws.
In the late teens or adult, treatment for the true, full blown, genetic Class III is best achieved by a combination of preliminary orthodontic alignment of the teeth, and then repositioning of the lower jaw surgically by an Oral Surgeon. There are generally excellent results with this procedure and surgery fees are usually covered by medical insurance. Orthodontic fees are not covered by medical insurance unless you have specific orthodontic coverage.
What should you do first? Dr. Richards or Dr. Kriger will advise you on timing treatment and will recommend when it is appropriate to take records and visit the Oral Surgeon for pre-treatment consultations. This type of treatment occurs over a long period of time. There is no hurry to make decisions unless interceptive treatment is recommended.
TREATMENT MECHANICS FOR CLASS III:
The ideal treatment assumes enough room is available or can be made to avoid extraction of permanent teeth. The assumption is also made that this is a true genetic class three which will be treated with a combined orthodontic-surgical approach.
- If the upper jaw is too narrow, a palatal expander will be used to expand the upper jaw to a more normal width. This procedure takes about four months to accomplish. After the expander is removed, full braces will be placed.
- Typical non-extraction orthodontic treatment of the class three will involve placing highly detailed braces on all the upper and lower teeth. The braces are designed with a slot in the front of the metal attachment which precisely accepts a wire. The slot is rectangular in shape, with the front of the rectangle open to accept the wire. The wire diameter can vary from rectangular to round in various diameters and stiffness. Recent wire technology has given the orthodontist the ability to move teeth in half the time that it used to take to gain the initial alignment of the teeth.
- The first months of treatment are dedicated to moving the front teeth forward and gaining symmetrical alignment of the right and left sides of the dental arches by using small diameter, flexible wires. These first wires are made of a nickel-titanium alloy which is very flexible, exerts low force, but is long acting. These wires remain in the braces from one to four months before they complete their job. The time depends on how crowded or out of align the teeth are initially.
- When there are teeth which are unerupted, it will take time to allow these teeth to erupt and space must be made and maintained to allow normal eruption.
- Next comes leveling of the vertical aspects of the teeth to conform to larger nickel-titanium wires which fully engage the diameter of the slot of the braces. The first objectives are to gain a normal curvature, angulate and parallel the roots of the teeth, and to achieve coordination of the shape of the upper arch to the lower arch. You may expect to see the lower teeth move forward significantly since they usually have been tipped backward by the lower lip. This is the usual method of pre-surgical alignment.
- After initial alignment, larger stainless steel wires are placed which again fully engage the inside diameter of the braces. This is the stabilization phase of the braces. During this phase, if adjustments to the bite are needed, then elastics are applied. The elastics are a light force to shift midlines or tooth positions. The force and use of the elastics are highly variable depending on how much movement is needed.
- Once the teeth are aligned, impressions are made to check the bite and consultations are made with the surgeon to discuss objectives and final alignment. Once the surgery is completed, then final adjustments are necessary to compensate for any surgical limitation or malpositions remaining. The time for this final phase is unpredictable.
- After the teeth are deemed to be stable in their alignment, the braces are removed and a fixed retainer is placed on the back of the lower teeth to hold them in place. The upper teeth are held with a removable retainer. Retainers are worn for two or more years depending on the original problem. The lower retainer should be worn as long as possible as the highest rate of relapse will be with the lower front teeth.
This section contains information on orthodontic treatment, however orthodontic treatment is highly personalized and varies from patient to patient depending on the situation and doctor.
