Message Boards
Today's Active Topics Today's Active Cases Browse Forum Categories My Recent Activity My Messages Private Groups My Marked Threads My Subscriptions
Today's Active Images Today's Active Polls Most Active Topics Global Townie Map Advanced Message Board Search Message Board Terms of Use

Straight Talk Clark D. Colville, DDS, MS

Start Discussion More by this author (3)
 
Class II Correction with Invisalign Branded Clear Aligners
by Clark D. Colville, DDS, MS

The evolution of the Invisalign system of clear aligner therapy has made quite an impression in orthodontic mechanotherapy throughout the past 10 years. At its inception in 1999, Invisalign clear aligners were designed and marketed to the adult patient who wished to have straight teeth without wearing traditional braces. From there, the appliance has evolved steadily into a product that has wide usage in both adolescents and adults.

Within the past several years the product enhancements have been prodigious. The technical advances in the many proprietary software applications provide specific measurable forces with resulting moments which cause tooth movements that are both efficient and effective. Individual tooth movements that were once thought to be difficult to achieve are now routinely achieved with surprising accuracy.

In October, the latest round of product enhancements has come online. In addition to the new look and feel of the Web site, now called the Invisalign Doctor Site (formerly VIP), the aligners can now be manufactured with cutouts and precision cuts in the aligners to allow planned use of Class II and Class III interarch forces with elastics.

In recent years several anecdotal case reports have been reported in the literature in an effort to expand and define the range of types of malocclusions that can effectively be treated with clear aligners.¹ The literature provides little guidance to help determine the range of malocclusions that can be successfully treated with clear aligners. There is no question that the experience of the practitioner still plays a large role in achieving quality outcomes. The steady stream of Invisalign product enhancements require ongoing continuing education to keep up with the latest improvements in the ClinCheck software that is used by the clinician to develop the desired tooth movement that will ultimately correct the malocclusion. This experience allows the clinician to develop a sense of what is realistic tooth movement versus what can loosely be described as "cartoonadontics."

Cartoonadontics is a term that can describe both tooth movements and the correction of skeletal malocclusions that look entirely realistic when viewed on the computer, but have no chance to occur in the real world constraints of bone morphology and physiology of tooth movement. A perfect example is a ClinCheck which shows a lower molar that translates – both bodily and distally – to alleviate crowding, while at the same time the lower incisors stay completely stationary. Looks great on the screen, eliminates crowding and corrects occlusion, but has no basis in reality. In every case of cartoonadontics Newton's Laws of motion and physics are violated in egregious fashion. It requires a very discerning eye, as well as a thorough understanding of the principles of tooth movement to avoid being mesmerized as one watches the most treacherous Class II malocclusions bloom into a beautiful Class I ideal dental relationship in the ClinCheck software application.

The introduction of simultaneous staging in 2005, where all the teeth in an arch move at the same time from the start of treatment until the completion of treatment, had a profound effect in the evolution of Invisalign branded clear aligners. This staging pattern, first introduced by Dr. David Paquette and now considered a best practices standard, more closely mimics the movement of teeth as seen with traditional fixed orthodontic appliances. Subsequently, it has proven to be the most efficient method to move teeth with clear aligners. Simultaneous tooth movement was further enhanced in software updates in 2009 so that correction of interarch relationships can be shown, if directed by the clinician in the prescription form, which are intended to simulate the effect of Class II/III elastic wear. As a result, the clinician is required to discern those Class II corrections that are realistic and achievable as opposed to those that are unobtainable, regardless of how beautiful the tooth movement is depicted on the screen. One needs to remember that the tooth movement shown on the screen is a lab technician's interpretation of the doctor's request on the treatment prescription. The technician is not tasked with deciding whether the movement is realistic or achievable. They are only required to deliver the occlusion that is requested, within the defaults of the proprietary software developed by Align Technologies, Inc.

So what can one reasonably expect to achieve in terms of Class II molar correction with the Invisalign branded clear aligners? First, it is important to understand that the same principles which apply to fixed appliances also apply to clear aligner treatment. The basic mechanics required to make a correction from a Class II molar relationship to a Class I molar relationship are as follows: maxillary distal molar rotation, maxillary distal molar movement, mandibular growth with a sagittal component, mandibular autorotation as a result of vertical control of the posterior molar teeth, and utilization of interarch forces. (The use of temporary anchorage devices will not be discussed in the context of this article, but is acknowledged to be an additional consideration in Class II correction.) Each of the components listed can ultimately be a contributing factor in achieving Class II correction. In addition, careful evaluation of pre- and post-treatment models along with carefully traced superimpositions of pre- and post-treatment cephalometric X-rays can be used to determine which of the five factors were significant in achieving the final outcome.

Invisalign branded clear aligners have the ability to directly produce three of the basic mechanical movements required to correct many Class II malocclusions. Distal molar rotation is, in many instances, the simplest mechanical correction required to move molars from an end on relationship to a full Class I relationship. When the mesial lingual cusp of the maxillary first molar is seated in the central fossae of the lower first molar, a distal rotational moment around the palatal root of the first molar can be achieved using aligners, with or without a specific attachment on the buccal surface of the tooth. While this movement is routinely achieved with fixed appliances due to the built-in distal rotation of many of the leading bracket prescriptions, it is quite often absent in the initial ClinCheck set up. This movement can be produced by the technician, but generally requires modification of the ClinCheck to produce this particular movement.

Distal molar movement, combining both tipping and minor bodily movement, is the second element in Class II correction and is routinely depicted in ClinCheck setups. This movement is predictable, within limits, and generally requires attachments on the buccal surface of the maxillary molars, as well as Class II elastics. Conceptually, technicians understand this movement and consistently show this in the ClinCheck setup when requested. Randomized clinical trials do not exist to determine the amount of molar distalization that can be achieved. However, case reports by Dr. Sam Daher, with cephalometric superimpositions pre- and post-treatment have been provided in the literature which reported molar distalization to be, on average, 1.8 mm.²

As mentioned above, and the third element in Class II correction, interarch Class II elastics can be routinely incorporated with clear aligner mechanotherapy. Class II elastics can be worn directly to the aligners, or to buttons attached to the teeth where the aligners have been modified by cutting away aligner material on the buccal surface. Both methods have proven to be effective. The recent introductions of precision cuts and cut outs will make elastic wear much easier to incorporate interarch elastics during the course of treatment. The aligners will be manufactured with precision cuts or cut outs according to online prescription form submitted by the doctor. Class II elastics should be used in conjunction with distal rotation and bodily distalization any time those movements are depicted in a ClinCheck. The optimal force level has not been determined, so one should use elastics similar to those used in fixed appliances. In most cases, a 5/16, medium force, between 4 and 6 ounces, is sufficient to provide a Class II force vector.

The fourth element in Class II correction is vertical control of the posterior molar teeth. Dr. Fred Schudy wrote extensively on the concept of the vertical dimension and its effect on sagittal correction of Class II malocclusions. Vertical control, and more specifically, preventing vertical eruption of both the maxillary and mandibular molar teeth has traditionally been one of the more challenging aspects in orthodontic treatment. Variable-pull and high-pull headgears, chin cups, transpalatal bars with large midpalatal pads and temporary anchorage devices have all been used by orthodontists for many years in an attempt to control the vertical eruption of posterior teeth. Final superimposition tracings have shown that vertical eruption can be minimized during Invisalign treatment.

Invisalign aligners have a distinct and significant advantage over traditional fixed appliances in this particular area. When wearing both upper and lower aligners concurrently, full time, the aligners act as a posterior bite splint and prevent the passive eruption of molar teeth. In a growing patient, this can be a significant factor in achieving Class II correction. In a non-growing patient it will be less significant, but nonetheless a positive factor in the treatment outcome. This is the reason that mild anterior open bite malocclusions are ideally suited to be treated with clear aligners, and conversely, low mandibular plane angle, deep overbite malocclusions are not amenable to significant overbite correction when treated with clear aligners. The relative posterior intrusion of the molar teeth can often be seen at the end of treatment in routine, Class I, crowded cases. Settling of the posterior teeth into a final functional occlusion usually occurs over a period of 6 to 24 weeks as long as both arches are not retained with full coverage essix-type appliances.

The last, and probably the greatest element in Class II correction, is favorable mandibular growth. There is no question that without favorable growth, Class II correction is difficult to achieve; even with the best mechanics. On the other hand, poor mechanics can be made to look brilliant with favorable growth of the mandible, counterclockwise direction with a significant sagittal component. Ask any board examiner and they will likely tell you that the one consistent feature of all well treated Class II malocclusions is an excellent growth pattern.

So we go back to the original question – to what extent can Invisalign predictably correct a Class II malocclusion to a Class I malocclusion? Where no randomized clinical trials exist, one can make a reasonable guess that only minimal Class II malocclusions can be corrected to full Class I with aligners as a stand alone product. Indeed, this has been my experience clinically, having treated over 300 patients. The key to having clinical success in treating these types of patients is to incorporate as many of the five listed elements as possible. Case selection is critical. Growing adolescent patients who require minimal Class II correction would be the best candidates to successfully treat with clear aligner therapy. In addition, incorporating as many of the five elements of Class II correction into the ClinCheck setup is the responsibility of the treating doctor, prior to accepting the ClinCheck. Careful planning for proper attachment placement, planned elastic wear and interproximal reduction, in addition to making sure tooth movements are not in the realm of cartoonadontics, are all necessary steps in the development of the final ClinCheck. Failure to incorporate one or more of the elements will decrease the chances for maximum correction of the malocclusion.

References
1. Eckhart, JCO Volume XLIII, number 7 pp. 439-448, Schupp ,et al, JCO Volume XLIV number 1, pp. 28-35
2. Daher, Class II Corrections - Handout, Invisalign Summit, November 2008
Orthotown Magazine
September 2025
Orthotown Magazine September 2025 Read Current Issue Read Archived Issues
Sponsors
Townie® Poll
Do you have a dedicated insurance coordinator in your office?
  
Site Menu
Message Boards Magazine Continuing Education Podcasts Blogs Classifieds News Events Townie® Poll Ebooks Townie Choice Awards
Company Info
Contact Us Advertise With Us Howard Farran DDS, MBA Policies and Agreements
Site Help
Sally Gross, Member Services Specialist
Phone: +1-480-445-9710
Email: sally@farranmedia.com
©2025 Orthotown, a division of Farran Media • All Rights Reserved
9633 S. 48th Street Suite 200 • Phoenix, AZ 85044 • Phone:+1-480-598-0001 • Fax:+1-480-598-3450