-
Orthodontic Class Two skeletal or retrusive lower jaw profile
Typical profile of the child who has sucked the thumb or has a genetic tendency toward retrusion of the lower jaw. Generally there is protrusion of the upper teeth also.
Normal or Class One skeletal pattern vs retrusive Class Two profile
What is a Class Two bite?
Sometimes called an over-bite or protrusive-bite, it is basically the upper teeth protruding forward of the lower teeth. Both the front and back teeth are one-step forward of the lower teeth. The child's profile is usually described by a parent as "not having a good chin" or "the lower jaw is receded." Frequently these children are teased by their peers for being different..."bucky beaver". The face is generally long, narrow and mouth breathing is frequently noted.
This is the typical orthodontic patient whose front teeth may stick out and over the lower lip. The obvious cosmetic problem is that the front teeth stick out, but the real problem is the lower jaw is set back, not fully developed and the back teeth do not fit together normally. There is a functional problem with swallowing, chewing, and sometimes speech. Frequently these patients have jaw joint popping, will complain of frequent headaches, and display stomach distress due to inability to chew properly.
Variations and complications of the Class Two bite are as follows:
- DEEP BITE: the bottom front teeth erupt onto the palate and are hidden from view during a smile. The biggest problem is the lower jaw can't grow forward because it is held back against the roof of the mouth.
- OPEN BITE: the front teeth do not touch when the back teeth are together. These patients usually are mouth breathers, sucked their thumbs and are tongue thrusters. There is little or no ability to "bite" using the front teeth.
- CROSS BITE: the width of the upper jaw is too narrow to fit properly against the lower jaw. Cross bites involve bone and require treatment beyond normal braces.
- BLOCKED OUT TEETH: teeth which erupted earlier will use up the room needed for teeth which erupt at a later age. Typically these teeth will remain in the bone.
- CROWDING: the permanent teeth are large and the jaw is too small to accommodate all the teeth. Removal of permanent teeth may become necessary to make room for correct alignment, but every effort is made to avoid extractions. If treatment is started too late, and the teeth have crowded, removal of permanent teeth may become necessary to make room for correct alignment.
Causes: Approximately 60% of our orthodontic patients are some variation of the Class two problem. Class two patterns are the result of a combination of one or more influences:
- AIRWAY PROBLEMS: The inability to breath through the nose, causes abnormal positioning of the jaw and tongue. These patients usually have a long narrow face, with the lower lip rolled over and thick. They may be observed at night with the tongue hanging out of the mouth while mouth breathing during sleep. Allergies, adenoids, and tonsilar problems may contribute to the problem.
- GENETICS: One or more parents have the same problem. Sometimes we see a whole family with the similar growth pattern. The receded lower jaw and no chin are typical.
- ABNORMAL SWALLOW: Usually caused by a tongue thrust. The biggest factor in Class two.
- HABITS: Thumb and finger habits which distort the jaws and growth.
- ABNORMAL ERUPTION OF THE TEETH: Due to early loss of the baby teeth. This has decreased as a cause with better dental care and the reduction of cavities.
What can be done to correct a Class two problem? Usually treatment will consist of full braces starting before the time the last baby teeth are lost or at approximately age eleven. Normal treatment time is approximately 18 to 24 months in braces.
Sometimes with younger children, who have severe problems, treatment is divided into two phases. The idea behind two phase treatment is to correct the jaws as early as possible to allow normal growth patterns to occur. Phase one is best done between age 8 to 10 and phase two at age 11 to 13.
When should treatment begin? You want to begin treatment early enough to take advantage of the growth spurts, but not so early that treatment is extended beyond normal. If treatment is started too late, the jaws may not be able to grow and a normal profile will not be obtained. Late treatment usually requires extractions, where as starting at the best time during growth of the child may help avoid removing permanent teeth and keep treatment time to a minimum. It may be necessary to take x-rays and impressions of the teeth to help us decide the best time to start. See the section on How Kids Grow to better understand growth and orthodontics.
Will this problem self-correct? No! A casual look at older people walking around the mall will find more Class two problems than you can believe. Those retrusive lower jaws never catch up unless treated orthodontically.
How long do we have to wait to start treatment? Because different children have different rates of growth and tooth eruption, all are not started in treatment at the same age. The reason we want to see your child at about age 7 for their first visit is to select those patients who need early treatment or place them on a recall program to watch their growth and development. The idea is to time treatment during the ideal growth period to obtain the best results with the least time in braces.
TREATMENT MECHANICS FOR CLASS II, DIVISION ONE CHILD WITH GROWTH AVAILABLE:
A Division One Class II is a generalization of the most common type Class II. There are multiple variations of the Class II and each requires a variation of the treatment plan.
The ideal treatment assumes enough room can be made to avoid extraction of permanent teeth. There must also be adequate growth remaining in the face and jaw joints.
- Typical non-extraction orthodontic treatment for this problem will involve placing highly detailed braces on all the upper and lower teeth. Frequently, only the upper braces will be placed to start treatment in order to effect rapid movement of the upper teeth. After the initial alignment occurs, and there is clearance to place brackets on the lower front teeth, then the lower braces will be placed. 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 few months of treatment are dedicated to 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.
- 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 of the arches, parallel the roots of the teeth, and to achieve coordination of the shape of the upper arch to the lower arch.
- 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 where the lower arch is used as an anchor to pull elastics against the upper arch. The elastics are a light force to tease the lower teeth forward and allow growth of the lower jaw. They also retard the growth of the upper jaw. The force and use of the elastics are highly variable depending on how much movement or growth is needed.
- The main force working against the elastics is the muscle of the tongue and lips. The tongue works negatively in the form of an abnormal swallow or tongue thrust. Since the front teeth are pushed forward by the tongue, the elastics are the only force which moves them back. Eliminate the tongue thrust and the elastics work easily to retract the front teeth. Treatment time is directly proportional to growth and cooperation.
- 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.
