Orthodontics 101

Orthodontics is not just about the teeth, it’s the bone too!

Teeth are actually held in sockets in the bone. Specifically, the type of bone that holds teeth is called alveolar bone. The upper teeth are embedded in the maxilla, and the lower teeth are embedded in the mandible. Teeth are surrounded on top by gum tissue (also called Gingiva). Under the gum tissue, the Periodontal Ligament (also called the PDL) encases the bottom portion of the tooth and attaches to the adjacent bone.

When braces put pressure on your teeth, the periodontal membrane stretches on one side and is compressed on the other. This loosens the tooth. The bone then grows in to support the tooth in its new position.

Teeth and the surrounding bone in which they are embedded respond physiologically to the forces that are applied to them. The controlling biological process is known as bone remodeling. It is actually a biomechanical phenomenon. Loading bones with pressure – or applying force – actually has the effect of making the bone tissue stronger. Inversely, the absence of loading on bone tissue results in weaker bone. Bones are made of cells called osteocytes. Other cells also participate in the bone remodeling process: osteoclasts resorb or “tear down” existing bone, and osteoblasts deposit or “build” new bone.

The load increase causes a proliferation of osteoclasts which break down bone in response to the load. When the load is removed, osteoblasts are created which deposit new bony cells. This process is repeated through repetitive motion and eventually the bone density increases.

The PDL is an interesting structure with many unique characteristics not found in other ligaments throughout the body. In some sense, it serves as a means of communication between the teeth and surrounding alveolar bony. Pressure between the PDL and bone causes the bone to create osteoclasts and break down the bone tissue as to restore the normal spacing between the teeth and bone. The corresponding tension on the PDL behind the movement causes the bone to create osteoblasts, effectively building new bone to fill in the vacated space left behind and restore the normal spacing between teeth and bone.

Clinicians know that the osteoclastic (breakdown or resorption) process takes about 72 hours to really take off, and the osteoblast (rebuilding or deposition) process takes about 90 days. Stabilizing the result can take up to a year. This long duration is the reason it is so important to wear retainers following treatment … to avoid a relapse, or in other words have the teeth return to their original, crooked positions.

So what are “braces” and how do they work?

The term “braces” typically refers to a combination or system of two hardware components: brackets and archwires. Brackets are the part of the braces that are affixed directly to the teeth. A commonly used analogy is that they are the “handles” that help an orthodontist or dental professional control movement of the teeth. Additionally the braces require an archwire that connects through the brackets and provides the forces to steer the teeth in a desired direction. The interaction of brackets and archwires enables the doctor to have three-dimensional control over the movement of the teeth. In many cases, additional forces are needed to help ensure that the upper teeth and lower teeth occlude – or bite together – correctly. These additional forces are oftentimes delivered by adjunctive appliances or components of the “braces” system such as elastics or rubber bands, headgear, functional appliances, and even palatal expanders.

And not surprisingly, all braces are not created equal. Brackets differ from one another in a number of important ways. There are even differences in where they anatomically attach to the teeth … most attach on the facial (cheek side) of the teeth, others attach on the lingual (tongue side) although these lingual braces are not as common. Braces also vary in appearance. Some brackets are fabricated from ceramic or some other clear material. Others are fabricated from stainless steel and may or may not have colored elastics around them.

For a complete orthodontic glossary of terms, as well as more helpful and educational information, visit the website of the American Association of Orthodontists: http://www.braces.org

A high degree of variability exists as it relates to the total duration of treatment – or amount of time that the braces must be worn. Important factors include the complexity of the orthodontic problem to be corrected, growth, tissue response to treatment, and patient compliance or cooperation. Generally, the length of comprehensive orthodontic treatment can range from approximately 18 months to 30 months, depending on treatment options and individual characteristics. An average treatment time of 24 months was reported in a recent survey.

What is the benefit of wearing braces anyway?

A nice smile is an esthetic asset that many people desire. Of course, what constitutes a “nice smile” can vary from one person’s opinion to another. Many people consider whiter teeth to be more appealing. In the case of the benefit from wearing braces, straight teeth contribute to a nicer smile. Orthodontics go beyond just the mouth, however. Proper treatment can bring the teeth and lips into proportion with the jaws and face. Many studies have shown that an attractive smile and facial appearance contributes to self-esteem which is important at any age. For children, the development of a positive self-image can carry forward throughout life. For adults, self-esteem is critically important in many professional settings and social situations.

As important as appearance can be, however, the benefit of braces is not limited only to esthetics. Straight teeth help an individual more effectively bite, chew, and even speak. It may come as a surprise that straight teeth contribute to healthy teeth and gums. But think about it … it makes sense that straighter teeth are easier to brush, clean, and floss! The ability to take better care of the teeth through oral hygiene also helps prevent future cavities and periodontal disease. This latter problem is of particular concern because over time it can lead to destruction of the bone that holds the teeth in place.

Properly aligned teeth and jaws may also alleviate unnecessary wear and grinding. It is known that malocclusion – or a “bad bite” – can lead to problems with the TMJ (temporomandibular joint) and even ineffective chewing and digestion problems. In extreme cases, chronic headaches and back or neck pain can result.

Furthermore, straight teeth are less prone to injury. Protruding upper teeth are more likely to be broken or traumatized in an accident. Once repositioned and aligned, these teeth are at a decreased risk of being fractured. So in many ways, an attractive smile is a pleasant “side effect” of orthodontic treatment … although many patients actually view it as the primary benefit.

Treatment by an orthodontist to correct a problem early in life is almost always less costly than the restorative dental care required to treat more serious problems that can develop in later years.

Orthodontists recommend that all children get a check-up no later than age seven. Although only a few orthodontic problems need to be corrected at that age, an early exam allows the orthodontist to offer advice and guidance as to when the appropriate age to start treatment would be.

What about invisible braces?

This type of system consists of strong plastic trays that are fabricated individually for each patient and fit over the teeth to exert pressure instead of affixing brackets and an archwire. At the first visit, a full set of customized aligners is prescribed using a software-based predictive representation of the full treatment course.

The patient wears each aligner for a period of a few weeks, allowing the teeth to gradually move as the pressure causes the bone to remodel in the same way as traditional braces. Therefore, the “total” treatment consists of some number (typically around 20 or so) of customized trays. The aligners feel tight at the beginning of each two-week period and then steadily fit better as the teeth move to conform to the aligner. They should be worn continuously and should only be removed to eat and brush. Aligner-based treatments typically work best with certain types of cases and are oftentimes recommended for patients with minor tooth movement.