The History of Accelerating Orthodontic Treatment and the OrthoAccel® Technology

 OrthoAccel®’s Technology is predicated on the application of pulsating, low magnitude forces (cyclic forces) to the teeth and surrounding bone as a means of accelerating orthodontic tooth movement. It is important to understand the history of this science and technology.

Let’s first consider past attempts at speeding up tooth movement, and then take a lesson from similar, well-understood scientific concepts in long bones as the ideal solution …
 

 Faster Tooth Movement is Not a New Goal

Many different approaches to faster tooth movement have been employed in the past. And given all of the disadvantages associated with wearing braces for a lengthy duration, this fact is not a huge surprise. Some attempts have been more creative than others. Irradiation with lasers has been used. Pharmacological approaches have been employed (injection of prostaglandins and peptide hormones around the teeth). But they have all come along with different sets of problems, such as pain, severe root resorption, and drug-induced side effects. One invention back in the 1970’s even involved powered brackets … each with a tiny working motor. Talk about a mouthful! For obvious reasons, these “braces” were never marketed. The quest for faster tooth movement continued and eventually came to include Dr. Jeremy Mao’s work (Chairman, OrthoAccel® Scientific Advisory Board). The big step taken here was that vibratory forces could actually complement the existing braces. An initial design based on preliminary work involved placing the motor inside the mouth. So much for comfort! And through the years, various other ultrasonic (very high frequency vibration) and magnetic approaches have been attempted … none with any degree of success.

Has There Been Any Success in Shortening Orthodontic Treatment?

In a word, absolutely. One of the biggest breakthroughs has come with the resurgence of self-ligating brackets. Although the first self-ligating fixed appliances were invented over thirty years ago, this category of innovation has really only become “mainstream” in the last five – ten years. Through reducing friction at the bracket-archwire interface, self-ligation certainly achieves reduced treatment time through more efficient biomechanics. These appliances, however, do nothing to speed up the physiological rate of tooth movement. Probably the most interesting (and dramatically successful) approach has come with the recent emergence of surgical-based orthodontics. Interestingly, surgically-assisted orthodontic tooth movement has been used since the 1800s. In the past 50 years, there have been infrequent reports of its successful use as a procedure for shortening orthodontic treatment duration. More recently, in the early 2000’s, Drs. Thomas and William Wilcko modified the traditional corticotomy-assisted technique with the addition of alveolar augmentation. In fact, this procedure was even patented and branded as “Wilckodontics.” The results have been remarkable … treatment times have typically been reduced one-third to one-fourth that of traditional treatment. It does necessitate a surgical procedure and therefore the involvement of an oral surgeon or periodontist.

Let’s Take a Look at Bone Biology Outside of the Mouth

Mechanical loading of bone is necessary for maintaining bone mass. Bone adapts to natural mechanical strain (weight bearing via walking) and therapeutic mechanical strain (orthodontic braces). For example, increased bone formation has been observed in the favored arms of tennis players, but not in the contralateral arm, as a result of loading. In contrast, loss of loading, as is experienced during immobilization or spaceflight, can decrease bone formation and increase bone resorption, resulting in bone loss. The adaptation of bone to mechanical forces has been recognized for well over one hundred years. Wolff was the first to note the association between bone remodeling and mechanical forces. Wolff’s Law (1892) states that “every change in the form and function of bones or of their function alone is followed by certain definite changes in their internal architecture, and equally definite alterations in their external conformation.” In other words, applying force to bones in different ways can induce different responses. Clint Rubin, Ph.D. (OrthoAccel® Scientific Advisory Board) found that if very low magnitude strains at high frequency-vibrations were applied for only 20 minutes a day to sheep, a 34% increase in trabecular femur bone density resulted. These findings were the basis for the commercialization of a technology for treatment of osteoporosis. Cyclic forces have also long been shown to accelerate the rate of fracture-healing in long bones.

More Does Not Always Mean Better

Increased duration of loading, however, does not cause increased bone formation. In fact, it has been shown by a number of studies that, as loading duration is increased, the bone formation response tends to saturate or reach a point of diminishing returns. Under continued stimulation, bone is desensitized to mechanical stimuli. Furthermore, it has been shown that if bone is given a sufficient recovery period between loading regimens (eight hours, for example), it is able to regain its mechanosensitivity. Many of the paramount experiments in this area were conducted by Charles Turner, PhD (OrthoAccel®, Scientific Advisory Board) and his team.

Now Back To The Mouth

More recently, work out of Dr. Jeremy Mao’s laboratory (Chairman, OrthoAccel® Scientific Advisory Board) demonstrated accelerated bone remodeling in the growth of craniofacial structures in a variety of animal models. This research was groundbreaking, because it was an application in the craniofacial region, or in other words … above the neck. There are many important differences between the craniofacial skeleton and the appendicular skeleton, for example, they are derived from different embryological origins. Dr. Mao’s work then was the first to suggest that an orthodontic tooth movement application could be feasible. In early 2008, a confirmatory paper was published in the American Journal of Orthodontics and Dentofacial Orthopaedics out of Tohoku University, Sendai, Japan using a rodent model. The results were clear: the treatment group received cyclic forces once per week for just eight minutes, and showed significantly accelerated tooth movement when compared to the control group. And we know what you are thinking … yes, braces can actually be fit to rats!

So How Does It Work Exactly

It is believed that cyclic forces increase the cellular signaling that regulates bone remodeling, thus enhancing the rate of orthodontic tooth movement. Moving teeth with braces requires external forces (applied by the braces) to be converted to cellular signals or factors that result in coordinated bone remodeling. Factors that increase the rate of bone remodeling have been shown to increase the rate of tooth movement. In a number of studies it has been shown that prostaglandins are involved in the bone removal component of orthodontic tooth movement. In addition, inhibitors to prostaglandin production, (cyclooxygenase, or COX, inhibitors) are known to decrease the amount of orthodontic tooth movement. Similarly, it has been shown that administration of certain prostaglandins locally caused an increase in orthodontic bone resorption and tooth movement. Parathyroid hormone (PTH) is a potent bone-remodeling factor. Continuous infusion of PTH has been shown to cause a 2 fold increase in the rate of orthodontic tooth movement in rats. The hypothesis, then, is that the pulsating force up-regulates and down-regulates certain cellular signaling pathways, resulting in faster tooth movement. Dental researchers have long postulated that a pulsating force might also be used to successfully move teeth and alleviate the discomfort associated with traditional orthodontics. A number of different devices have been marketed in the past which use various means of vibrating the teeth, although none were designed with the clinical benefit of faster tooth movement in mind … periodontal disease and treatment through increased blood flow to the gums has been a popular indication. Typically, these products employed such cumbersome designs as external power sources, fluid-based mechanics, and even a radio and speaker set to generate vibration! And all were mounted on extraoral headgear and face bow designs.

An Intersection of Two Worlds

In some sense, OrthoAccel®’s science and technology are nothing new. The company is essentially addressing an old problem (how can teeth be moved faster) with an old technology (vibrating bone to speed up its biology) but in a new way.