In this post, we will explore the principles behind tooth movement and the mechanisms orthodontists use to achieve desired outcomes. A basic understanding of this process will inform your treatment decisions and aid you in understanding your orthodontist’s recommendations, which may include the following tools:
- precision braces, such as LightForce
- aligners, such as Invisalign and/or
- an invisible, lingual appliance such as Brava
For instance, while aligner/Invisalign treatment can be very appealing to many orthodontic patients, it may or may not be mechanically appropriate for a given case. Understanding the biological processes involved in orthodontic tooth movement is helpful in grasping why.
Teeth are rooted in the alveolar bone within the jaws and are held in place by the periodontal ligament (PDL), a thin layer of connective tissue surrounding the tooth root and attaching it to the bone. The PDL plays a crucial role in transmitting forces applied to the tooth and facilitating its movement. Each orthodontic appliance applies force in a unique way, impacting the PDL differently than other appliances.
When orthodontic forces are exerted, the periodontal ligament or PDL undergoes remodeling, leading to changes in the bone surrounding the tooth root. These changes include bone resorption where the force is applied and bone deposition on the opposite side of the tooth. This remodeling process allows the tooth to move in the desired direction.
Did you know?
It takes approximately six hours of light, directed force to elicit biochemical responses in the periodontal ligament (PDL) that initiate orthodontic tooth movement, yet it takes only two hours, once the force is removed, for the six-hour-long process to reverse!
To apply these forces, orthodontists use a variety of orthodontic appliances and techniques, including braces, clear plastic aligners such as Invisalign, and invisible applications to the back of the teeth such as the Brava appliance (see below) or lingual braces (brackets and wires). Let’s briefly review these methods to illustrate their mechanical differences and why one treatment modality may be superior to another in a particular case.
Braces: Orthodontics with Wire and Brackets
An appliance with which most people are familiar is braces, which consist of small metal or clear brackets bonded to the teeth and connected by what are called archwires. These wires provide a continuous force that acts on the teeth, guiding them into proper alignment. The orthodontist adjusts the archwires periodically to control the direction and magnitude of the applied forces, facilitating the desired tooth movement. Archwires vary in material, shape, thickness, and other properties, allowing the orthodontist to customize forces for specific situations. Archwires may also be hand-bent to further facilitate fine detailing.
Braces are able to move teeth over relatively long distances in a slow, sweeping motion, applying continuous force to the tooth and PDL. Interestingly, fixed appliances, such as traditional braces and the Brava appliance, can deliver a stronger continuous force than that of removable appliances such as aligners, and can, therefore, move roots of teeth in the supporting bone much more effectively and efficiently. Precision appliances such as custom brackets and doctor-customized wires, only increase this efficiency. This factor becomes more important the greater the required movement of roots, especially that of molars.
The disadvantages of braces include visibility and hygiene. Some patients, both youth and adult, are comfortable with the appearance of braces, but others are not. Likewise, some are comfortable brushing around braces and flossing under wires, while others find both challenging.
Invisalign: Orthodontics with Clear Aligners
Due to aesthetic concerns with traditional braces, a popular alternative over the last ten years has been and continues to be the use of clear plastic aligners, such as those under the trade name Invisalign. Aligners are removable trays that are custom-fabricated to the orthodontist’s specifications in order to apply controlled forces to the teeth. Each aligner in the series is designed to move the teeth incrementally, and patients typically begin a new aligner each week or more frequently. The aligners combine direct movement, tipping, rotation, and other forces to gradually shift teeth into the desired positions.
Aligners are made of relatively thin, flexible plastic and move teeth via the forces created by the stretched plastic combined with fixed, tooth-color attachments that are specified and positioned by the orthodontist. When the attachments are engaged by the plastic aligner, the direction and amount of force is altered according to the orthodontist’s treatment plan.
Each new aligner must fit the teeth intimately. If the fit is insufficient, the forces needed to move the teeth will not be produced. As a result, each new aligner must represent an incremental change in tooth position. Consequently, the range of motion for an aligner is very limited compared to the sweeping motion of braces or the Brava appliance. As a result, the length of treatment for moderately complex or highly complex orthodontic cases may be greater with aligner treatment.
The overriding advantage of aligner/Invisalign treatment for many patients is the freedom, both aesthetically and hygienically, afforded by removable appliances that are less visible than braces. The disadvantage, however, is that, for some patients, this freedom results in an insufficient wearing of aligners, leading to longer or less successful treatment.
(Knowing and communicating your likely tendencies and preferences to the orthodontist is important in determining if aligner treatment is right for you, as are the movements that will be required for your teeth and the ability of aligners to create that movement. I have treated thousands of patients successfully with Invisalign, but it is not always the most effective choice.)
Brava: Orthodontics with an Invisible Appliance
The Brava appliance allows for an alternative mode of treatment that offers the mechanical advantages of fixed orthodontic appliances and an even greater aesthetic advantage than that of aligners. Brava is a plastic-free, fixed orthodontic appliance placed on the tongue side of the teeth, making it invisible. Treatment with the Brava appliance is not equivalent to lingual (tongue-side) braces, however.
The Brava appliance differs from braces in that each tooth moves independently (not bound by its neighbor through an archwire). The site-specific effect on the PDL and resulting movement of each tooth leads to treatment lengths roughly half as long as other methods in many cases.
The Brava appliance does not use an archwire; rather, independent arms are attached to each tooth from a wire band that sits on the gum. Tooth and gumline hygiene is not inhibited by a wire as with braces.
The disadvantage of the Brava appliance is that, for some patients, it may be a few weeks before it’s presence becomes completely comfortable to the tongue. Also, patients with large bony growths on the tongue side of the teeth cannot wear the Brava appliance, which will not fit properly.
Note: In addition to aligners, braces, and lingual appliances such as Brava, orthodontists may use auxiliary appliances, such as elastics or springs, to apply additional forces or modify the direction of tooth movement. Elastics, for example, can be attached to braces, aligners, or Brava to exert force between upper and lower teeth, correcting bite discrepancies.
Remote Monitoring: Checkups without Appointments
Regardless of the orthodontic appliance used, regular monitoring by an orthodontist is essential, allowing the orthodontist to make necessary adjustments as the treatment proceeds.
My practice (Keith B. Wong, DDS, MS, Specialist in Orthodontics) uses remote monitoring of the teeth to assess progress and advise patients. Remote monitoring involves scans made by the patients using their cell phones and a specialized application. These scans are reviewed by both staff members and myself, with the patient contacted when an office visit is needed.
Remote monitoring increases care, supervision, and communication while minimizing in-person office visits. Gone are the days of monthly trips to the orthodontist! Patients can be seen in our office as infrequently as every four months, and for non-local or international patients, this can be extended even further with adherence to the treatment protocol. With remote monitoring, the importance of proximity of the orthodontist’s office is greatly reduced, allowing the patient greater choice in choosing a practitioner.
With remote monitoring, the importance of proximity of the orthodontist’s office is greatly reduced, allowing the patient greater choice in choosing a practitioner.
Where to Begin: A Thorough Orthodontic Examination
The patient’s first visit is devoted to a thorough, complimentary examination and a discussion of desires and preferences. The exam is concluded with an initial treatment recommendation, including choice of appliances, and the anticipated treatment length and its associated fee. If the patient wishes to proceed at that time, flexible financial arrangements are discussed and, in many cases, treatment can be initiated that day if the patient desires. If the patient prefers additional time or information, a second consultation may be arranged.
Treatment recommendations are based upon a multitude of factors, including the presenting facial structure, age/anticipated growth, tooth position and bite, and patient goals and preferences. Recommendations are informed by the orthodontist’s thorough understanding of tooth movement, which enable him or her to plan and execute treatment effectively, resulting in improved dental aesthetics, function, and overall oral health.
When considering the options presented to you, recall that appliances differ in their abilities to move teeth, especially roots, and that you or your child’s experience with each appliance will also differ. An option not previously considered may prove to be the best choice for effective treatment.
If you would like to learn more or schedule a consultation, please feel free to contact my office or use our online scheduling application.
I hope this post has been informative!