Orthodontic treatment, just like any other dental, medical, or pharmacological treatment, has side effects. Because it is elective in nature, the risks of orthodontic treatment have to be weighed against the benefits.  

Orthodontic tooth movement is a rather destructive process by nature. Orthodontic appliances, be it braces or clear aligners, put force on the teeth, and this initiates an inflammatory process in the periodontal ligament space around the teeth. The result is the release of osteoclasts, specialized cells that resorb or destroy the bone on the side to which the force is directed, and osteoblasts, which cause bone formation on the opposite side. This bone remodeling allows the teeth to move. 

The orthodontic movement has to be carefully monitored by an orthodontist. Excessive, or uncontrolled inflammation coupled with poor tissue metabolism and impaired regeneration abilities can cause serious damage. 

Risks of orthodontic treatment fall into several major categories:

Damage to the roots of the teeth and surrounding tissues

Orthodontic movement may cause roots of some teeth to become shorter, the process called root resorption. It is not known what exactly causes root resorption, and it is impossible to predict which patients will experience more of it. The inflammatory nature of the tooth movement that dissolves bone around the teeth may affect the roots as well. However, the resorbed roots do not grow back like the the bone does. The orthodontist will monitor for root resorption by taking progress radiographs every 6-12 months, or more frequently if indicated, throughout the treatment.

If root resorption is noted, the treatment may have to be paused. Temporarily reducing the force acting on the teeth may halt the process of resorption. In some cases, it may be prudent to discontinue the treatment entirely. Do not panic if your orthodontist informs you of root shortening. Most teeth with mild to moderate root resorption can still be vital and may last the whole lifetime. Severe resorption, however, may compromise the support of the tooth. 

Periodontal disease, an infectious process affecting gums and bones around the teeth, may develop or become worse during orthodontic treatment. Even though the orthodontic appliances themselves do not cause periodontal disease, poor oral hygiene during the treatment can worsen bacterial overgrowth. As is true with any infections disease, periodontal disease causes inflammation and in turn bone loss. When this is coupled with poor healing mechanisms and additional inflammation from orthodontic movement, uncontrolled bone loss can occur and may result in tooth loss. If you have a history of periodontal disease, ask for a referral to a periodontist to make sure it is properly controlled before starting orthodontic treatment. 

Other issues affecting gums are gum recession and formation of dark triangles. If gum tissue is thin and lacks proper keratinized layer (lighter pink durable layer), it is more susceptible to recession from orthodontic movement. Poor oral hygiene, periodontal disease and inflammation can all worsen it and make your teeth sensitive. Existing recession should be evaluated by a periodontist prior to orthodontic treatment. 

Dark triangles are spaces between the part of the teeth closest to the gums. Most teeth are somewhat triangular in shape, they are wider at the top and become narrower near the gum line. If gum tissue doesn’t fill the area between the teeth completely, these dark triangles become apparent. During orthodontic treatment, when previously crowded overlapping teeth become properly aligned, dark triangles may appear if gum tissue doesn’t regenerate and doesn’t adjust to the new position of the teeth. This may especially happen in adults with periodontal disease, gum recession and bone loss. 

Damage resulting from poor oral hygiene

Damage described in this section is actually not caused by braces directly, but rather by the patient’s failure to take proper care of oral hygiene. In fact, the area of the tooth under a bracket is sealed and therefore protected from bacteria, acid, sugar. However, presence of braces, wires and auxiliary attachments makes it more difficult to brush and floss thoroughly. Excellent oral hygiene and regular dentist visits are required during orthodontic treatment. Inadequate hygiene may result in cavities and white spots (areas of weakened enamel) around the brackets and along the gum line, as well as inflammation of the gums. Poor oral hygiene may cause these problems even in the absence of orthodontic treatment, but the risk is higher when braces are in place. 

Injury and discomfort from appliances. 

Some discomfort is to be expected after introduction of orthodontic appliances. During the first few days or weeks, as your mouth is adjusting to the metal wires or clear aligners, some irritation and cuts to the gum tissues are common. Teeth often feel sore during this period and eating harder and chewy foods may feel uncomfortable. There is a lot of individual variation in how much discomfort patients experience: some report none and some report being in pain for weeks. Eventually, though, the mouth and the teeth adjust. 

Sometimes during the treatment you may experience a broken bracket. Biting too hard, eating certain foods, being hit in the mouth during sports can all cause a wire to break or bracket to loosen, or separate from the tooth. The loosened bracket may be swallowed or aspirated. If swallowed, most likely it will pass with stool. However, if you suspect you inhaled a bracket and experience difficulty breathing, contact an emergency medical service immediately. 

During removal of the braces or attachments used with clear aligners, enamel of teeth may become chipped, scratched, or otherwise damaged. If a bracket is bonded to a crown, veneer or composite build up, those restorations may fracture during the removal process and may need to be replaced by your dentist. 

TMJ discomfort

Contrary to what orthodontists believed for decades, new research suggests that orthodontic treatment has very little to do with Temporomandibular Joint Dysfunction, it neither causes it, nor treats it. Occlusion, or the bite, is only one of the many factors that affects the jaw. The other factors may include trauma, arthritis, heredity, tooth grinding or clenching, and many other medical conditions. Having said that, it should be noted that symptoms of existing jaw problem may become worse during orthodontics. Compromised jaw joint may be very sensitive to slight changes in the bite, pull of elastics, and movement of the teeth. Pain, popping, difficulty opening and closing may develop during the treatment. Referral to a jaw specialist may be needed, and treatment discontinuation is sometimes warranted. 

Allergies to appliances

Some people may be allergic to certain components in orthodontic appliances. Metal braces and wires often contain nickel and elastic rubber bands contain latex, both of which are common allergens. Some people allergic to plastics may also develop a reaction to Invisalign aligners. Let your orthodontist know if you are aware of any allergies. If you develop a reaction, discuss this with your orthodontist. A change of treatment plan or discontinuation of treatment may be necessary. If the reaction to dental materials is severe, medical intervention may be required. 

Duration and results of treatment     

Despite what a colorful marketing blurb depicting happy people and promising a perfect smile in no time might make you believe, neither the results, nor the duration of orthodontic treatment can be guaranteed. Every orthodontist intends to do everything possible to achieve the best result. However, the biological response to orthodontic movement is unique for each patient and teeth might move slower or faster than expected, or not at all, if they are ankylosed, or fused to the bone, for example.

The movement may have to be slowed down, suspended, or stopped completely, if periodontal disease, root resorption, or any other adverse effects develop. Treatment may be lengthened and additional appliances may need to be used if unanticipated growth occurs or jaws don’t grow as expected in an adolescent. Poor cooperation, such as not coming to appointments, not wearing Invisalign aligners properly, breaking brackets, or not following all of your orthodontist’s instructions may slow down treatment. 

Even if the treatment proceeds to completion as planned, there is no guarantee you will be completely satisfied. If the teeth have irregular shape, too big, or too narrow, they may not look good even if perfectly straight. Sometimes restorative dental treatment is needed after orthodontics, such as veneers, esthetic bonding, gum tissue recontouring, to give you the best smile. Orthodontists are limited by the individual biological constraints: the sizes of the patient’s teeth and the shape of the patient’s jaws. 

The bottom line to remember is that when orthodontists estimate duration of treatment, it is usually based on an average time that a similar case usually takes assuming full patient cooperation and absence of any adverse effects. 

Adverse effects from not following directions

Successful orthodontic treatment requires substantial patient cooperation. Not following your orthodontist’s instructions may prolong treatment and even cause undesirable movement of the teeth. 

One example of when poor cooperation affects treatment is not wearing the appliances as instructed. Let’s say the orthodontists initiates the elastic wear. The rubber bands are designed to bring upper and lower teeth together to establish proper bite. If you wear them sporadically, really well one month, but not that well the next, the treatment will take longer. If you don’t wear them enough hours in a day they might not be effective at all, so your bite will not be corrected. 

Another area of cooperation is coming to appointments. At each visit, the orthodontist evaluates the progress of the teeth movement and decides on the course of action: continue with the same strategy, change it, or maybe reverse it entirely. Let’s say the orthodontist places a spring to open space for a blocked out tooth and wants to evaluate the progress in six weeks. At that time the spring may be activated, or removed, if the desired space is achieved. If you miss that appointment and don’t come back for two months, the spring may remain active and may push the teeth too much to one side, which will take more time to correct. Or let’s say the orthodontist tells you to wear elastics and wants to evaluate the progress in a month. If you miss the appointment, but continue to wear the rubber bands, they may overcorrect too much and your overbite may turn into underbite. 

Relapse

After the treatment is completed, retainers will be required to preserve the new tooth position. Without retainers teeth can move out of alignment quickly. Protocols related to wear of retainers vary from orthodontist to orthodontist. Commonly, full time wear is recommended for a period of time, after which night time wear is sufficient. Long term retention is essential and more and more orthodontists advise life time wear. However, even with proper retainer use, the results cannot be guaranteed forever. Some degree of relapse is expected, especially in the lower front area. Habits, such as mouth breathing and tongue thrust, may affect future position of the teeth as well as age related bone changes. 

Risks associated with radiation

To properly diagnose and monitor the orthodontic movement X-rays are taken before, after, and during the orthodontic treatment. The amount of radiation associated with these radiographs is minimal, and therefore the risks are minimal too. However, if you are concerned about extra radiation, orthodontic treatment may not be for you. If you refuse X-rays, your orthodontist may decline to treat you or may suspend the treatment. If you are pregnant, or thinking about getting pregnant and are concerned about radiation exposure to the fetus, it may be best to postpone the treatment.