Contemporary Orthodontics & Dentofacial Orthopedics
Board Certified Treatment for Children, Teens and Adults ______________________________________
Does Invisalign work?
(And should I believe all the Advertising?)
Evidence Based Conclusions
Modern technology has been assisting medical and dental care for many years; orthodontic treatment is no exception. From bonding materials contrived by modern chemistry to alloys used in modern wires which arose from the recent space age, we all benefit from advances in science. The most recent technological change has been the advent of digital imaging and digital scanning with three dimensional lasers. Creating a digital copy of our teeth has allowed computers to reproduce our teeth and manipulate angles/position of teeth in the digital world which then led to producing three dimensional printings of the teeth with incremental “movements”. Clear aligner trays can then be made with a vacuum machine over the digitally printed models with the intention of moving the teeth as trays are worn. Each tray would have a slightly increased movement until a tooth (or teeth) moved to a new/corrected position. This is the idea and mechanism of all aligner systems such as Invisalign, Orchestrate, Clear Correct, and others.
As this new technology became commercially available and the companies (Invisalign in particular) went public (Align Technologies), treatment shifted from a doctor-planned and driven treatment to a patient/corporate driven treatment. Now, companies like Invisalign advertise directly to the public referring patients to “trained” experts in their product (training that takes just a single day), even when most of the providers are not even orthodontists. Over the last few years, this advertising has taken a toll on the traditional standards of Orthodontics stressing esthetics of the smile over the function of the occlusion. Research has been slow to catch up with or verify claims from these companies. Even worse, due to the power of advertising and the money put forward into promoting their product, it is becoming increasingly difficult to find un-biased studies which can show the true efficacy of the products. Even now, when Invisalign is googled, you get pages of sponsored (and usually biased) links with heavy salesmanship and Invisalign-sponsored or authored efforts to combat the hidden limitations (what they refer to as the “Myths of Invisalign”) of the product.
“Over the last few years, this advertising has taken a toll on the traditional standards of Orthodontics stressing esthetics of the smile over the function of the occlusion.”
Unfortunately it is quite difficult to combat something that the public has been told they want and told that it works as if it IS “Orthodontics”, the same as traditional braces; I even see it advertised as “Invisible Braces” which it certainly is not. Because dentists can take an afternoon course for certification, and because dentists have generally seen patients before they are referred to Orthodontists, Invisalign and other companies are changing (I would argue negatively) the dynamics and the very standards of modern dental treatment. General dentists that provide aligners do not have near the education in growth and development to properly diagnose an orthodontic case which in turn leads to many treatments that are incomplete, incorrect or even detrimental (see the studies on efficacy of movements in the studies below). Now with Invisalign for teens, you have general dentists holding off on referring children for orthodontic evaluation/treatment because they want to offer Invisalign themselves later; this can easily lead to poor outcomes due to changes in growth which cannot be accounted for in aligners without multiple scans throughout treatment (and costly remaking of future trays over and over) and incomplete corrections due to waiting too late for optimal correction which may require treatment before all of the permanent teeth are erupted; in some of these cases, waiting to treat will also lead to a significant risk of surgery (underbites, openbites and crossbites).
So does Invisalign “work”? Well in some cases (and in some degree), yes. Unfortunately it continues to fall short of complete correction on average with success of tooth movements ranging from a dismal 20% to 57% (in school we call this an F) and can cause significant malocclusion in patients by leaving the posterior teeth out of occlusion (see research below) thereby placing front teeth into hyper-occlusion. Some studies have concluded that cases treated by Invisalign simply could not be completed without additional treatment including traditional braces. Personally, I have found that in minor cases (those of which Invisalign or other clear aligner systems are best suited), braces could have treated the same teeth more reliably, cheaper and with less time versus starting with aligner trays only to have to finish in braces to fully upright cuspids or reduce overjet (but some people still will want the clear aligners for esthetics, seeing them worth the extra time and cost). Dentists usually won’t have this option since they are not trained at all with braces so patients will just get what they get.
As an Orthodontist, I see many parents of kids I have in treatment that have chosen Invisalign or other aligner systems recommended by their general dentists because they were told it could fix their bite; many come in after their treatment with complete lack of contact on back teeth and multiple teeth that are leaning one direction or the other. This is not to say aligners aren’t a great option for correcting mild crowding or closing spaces where the bite allows for closure and esthetics are of great concern during treatment however Invisalign (Align Technologies) has expanded their reach farther and farther into the public’s and general dentists’ imaginations and I am seeing more and more incomplete corrections.
So what exactly does non-biased, professional and juried research show when it is performed and published by non-Invisalign experts in the field? To answer this, I will be referencing (and including) summaries of actual research published over the last several years by some of the top academic Orthodontic researchers across the Country, research appearing in the prestigious Journal of the American Association of Orthodontics & Dentofacial Orthopedics; the governing literature for certified Orthodontists.
Early in the introduction of Invisalign, the American Journal of Orthodontics & Dentofacial Orthopedics (AJODO, http://dx.doi.org/10.1016/j.ajodo.2004.05.002 ) published a report criticizing the advertising practices of the newly public company stating:
“Despite Align Technology's claims, orthodontic treatment and Invisalign therapy are not the same thing. The misrepresentation of orthodontic treatment in the marketing of Invisalign is a disservice to our patients. It is also at odds with the mission of the AAO, the ABO, and other well-respected orthodontic professional organizations. By emphasizing Invisalign's ability to achieve straight teeth, without mentioning the importance of a functional occlusion, ideal overbite and overjet, aligned marginal ridges, and long-term stability, Align Technology has effectively reduced the role of the orthodontist from that of a “knowledgeable dental specialist and professional” to that of an “esthetician.”
This article continued to reports that “Align Technology has blurred the distinction between general dentists and orthodontists about expertise in dental movement. By equating the experience of doctors using Invisalign to the return search list of recommended doctors found on Align Technology's website, orthodontic specialty training has been rendered inconsequential to the prospective Invisalign patient.”
As Invisalign became more widespread with general dentists, the specialty of Orthodontics began to study treatment with aligners and in 2007 the AJODO published a paper detailing exactly how effective Invisalign was at moving teeth; the summary is below.
How well does Invisalign work? A prospective clinical study evaluating the efficacy of tooth movement with Invisalign
The purpose of this prospective clinical study was to evaluate the efficacy of tooth movement with removable polyurethane aligners (Invisalign, Align Technology, Santa Clara, Calif).
The study sample included 37 patients treated with Anterior Invisalign. Four hundred one anterior teeth (198 maxillary and 203 mandibular) were measured on the virtual Treat models. The virtual model of the predicted tooth position was superimposed over the virtual model of the achieved tooth position, created from the posttreatment impression, and the 2 models were superimposed over their stationary posterior teeth by using ToothMeasure, Invisalign's proprietary superimposition software. The amount of tooth movement predicted was compared with the amount achieved after treatment. The types of movements studied were expansion, constriction, intrusion, extrusion, mesiodistal tip, labiolingual tip, and rotation.
The mean accuracy of tooth movement with Invisalign was 41%. The most accurate movement was lingual constriction (47.1%), and the least accurate movement was extrusion (29.6%)— specifically, extrusion of the maxillary (18.3%) and mandibular (24.5%) central incisors, followed by mesiodistal tipping of the mandibular canines (26.9%). The accuracy of canine rotation was significantly lower than that of all other teeth, with the exception of the maxillary lateral incisors. At rotational movements greater than 15°, the accuracy of rotation for the maxillary canines fell significantly. Lingual crown tip was significantly more accurate than labial crown tip, particularly for the maxillary incisors. There was no statistical difference in accuracy between maxillary and mandibular teeth of the same tooth type for any movements studied.
“The mean accuracy of tooth movement with Invisalign was 41%. The most accurate movement was lingual constriction (47.1%), and the least accurate movement was extrusion (29.6%)— specifically, extrusion of the maxillary (18.3%) and mandibular (24.5%) central incisors, followed by mesiodistal tipping of the mandibular canines (26.9%).”
We still have much to learn regarding the biomechanics and efficacy of the Invisalign system. A better understanding of Invisalign's ability to move teeth might help the clinician select suitable patients for treatment, guide the proper sequencing of movement, and reduce the need for case refinement.
From this article it is very clear that Invisalign cannot completely move teeth as planned. Much of the movements were so poor that if you predict even a mild amount of relapse, there would essentially be no significant correction at all. The research revealed that pulling teeth inward was most successful but still only 47.1% accurate. Closing the bite through extrusion was particularly ineffective with only an 18.3% upper and 24.5% lower correction; since this movement typically will relapse to some degree no matter how you move the teeth, it is logical to assume there will be little correction of any openbite through Invisalign. And since movement of posterior teeth in any other dimension will, according to the Laws of Physics, have a tendency to extrude (opening the bite), many cases will open and the aligners will be unable to accurately close the bites back.
Other studies continue to confirm these findings with only slight improvement (41% average in 2007 up to 57% in 2013) of Invisalign:
Variables affecting orthodontic tooth movement with clear aligners
In this study, we examined the impacts of age, sex, root length, bone levels, and bone quality on orthodontic tooth movement.
Clear aligners were programmed to move 1 central incisor 1 mm over the course of 8 weeks. Thirty subjects, ages 19 to 64, were enrolled, and measurements were made on digital models (percentage of tooth movement goal achieved). Morphometric features and bone quality were assessed with cone-beam computed tomography. Data from this study were combined with data from 2 similar studies to increase the power for some analyses.
The mean percentage of tooth movement goal achieved was 57% overall. Linear regression modeling indicated a cubic relationship between age and tooth movement, with a decreasing rate of movement from ages 18 to 35 years, a slightly increasing rate from ages 35 to 50, and a decreasing rate from ages 50 to 70. The final decreasing trend was not apparent for women. As would be expected, the correlation was significant between the percentage of the goal achieved and the cone-beam computed tomography superimposed linear measures of tooth movement. A significant negative correlation was found between tooth movement and the measurement apex to the center of rotation, but bone quality, as measured by fractal dimension, was not correlated with movement.
“The mean percentage of tooth movement goal achieved was 57% overall”
The relationship between age and tooth movement is complex and might differ for male and female patients. Limited correlations with cone-beam computed tomography morphology and rate of tooth movement were detected.
This is similar to my own experiences with aligner trays and the reason I use a system that gives me more control between each aligner (Orchestrate; https://www.orchestrate3d.com). Other researchers actually compared Invisalign to traditional braces, publishing findings again in the AJODO:
Outcome assessment of Invisalign and traditional orthodontic treatment compared with the American Board of Orthodontics objective grading system
Introduction: This treatment-outcome assessment objectively compares Invisalign (Align Technology, Santa Clara, Calif) treatment with braces.
Methods: This study, a retrospective cohort analysis, was conducted in New York, NY, in 2004. Records from 2 groups of 48 patients (Invisalign and braces groups) were evaluated by using methods from the American Board of Orthodontics Phase III examination. The discrepancy index was used to analyze pretreatment records to control for initial severity of malocclusion. The objective grading system (OGS) was used to systematically grade posttreatment records. Statistical analyses evaluated treatment outcome, duration, and strengths and weaknesses of Invisalign compared with braces.
Results: The Invisalign group lost 13 OGS points more than the braces group on average, and the OGS passing rate for Invisalign was 27% lower than that for braces. Invisalign scores were consistently lower than braces scores for buccolingual inclination, occlusal contacts, occlusal relationships, and overjet. Invisalign’s OGS scores were negatively correlated to initial overjet, occlusion, and buccal posterior crossbite. Invisalign patients finished 4 months sooner than those with fixed appliances on average. P < .05 was used to determine statistically significant differences.
Conclusions: According to the OGS, Invisalign did not treat malocclusions as well as braces in this sample. Invisalign was especially deficient in its ability to correct large anteroposterior discrepancies and occlusal contacts. The strengths of Invisalign were its ability to close spaces and correct anterior rotations and marginal ridge heights. This study might help clinicians to determine which patients are best suited for Invisalign treatment.
“According to the OGS, Invisalign did not treat malocclusions as well as braces … Invisalign was especially deficient in its ability to correct large anteroposterior discrepancies and occlusal contacts.”
Again, in a study which looked at results of Invisalign cases to determine success:
Evaluation of Invisalign treatment utilizing the American Board of Orthodontics Objective Grading System for dental casts
The purpose of this study was to evaluate the treatment outcome of patients treated with Invisalign aligners by using the American Board of Orthodontics Objective Grading System (OGS) for dental casts. The dental cast component of the OGS scores 7 categories for discrepancies from ideal related to tooth alignment and occlusion. Depending on the magnitude of the discrepancy, up to 2 points can be scored in each category; thus the fewer the points scored, the more ideal the result. A total of 135 patients treated with the Invisalign system and having pretreatment and posttreatment records were identified from 7 orthodontic private practices. If patients met the selection criteria, the dental cast component of the OGS was performed on the pretreatment and posttreatment casts. The selection criteria were (1) no missing teeth (other than previous premolar extractions), (2) Invisalign treatment exclusively, and (3) available pretreatment and posttreatment models of diagnostic quality. Pretreatment and posttreatment OGS scores were compared, and the differences were analyzed by using paired t tests.
Results showed that, of the 135 subjects, 65 (48%) met the inclusion criteria. These were evaluated with the OGS. For those not included in the OGS analysis, 33 (24% of the 135) required fixed appliances or spring aligners to finish the treatment, 25 (19%) had poor or missing records, and 12 (9%) had missing teeth. For the 65 subjects analyzed, the mean age was 31.1 (± SD 12.5) years, the duration of treatment was 12.5 (± 4.1) months, and the patients wore 17.9 (± 7.3) maxillary and 17.7 (±6.9) mandibular Invisalign aligners. The pretreatment total OGS score (dental component only) was 47.0 (± 16.5), and the posttreatment OGS score was 36.4 (± 16.0; P ≤ .001). Comparison of the categories in the OGS showed that significant improvements occurred in tooth alignment (pretreatment mean: 21.5 points vs posttreatment: 7.0 points (P ≤ .001), buccolingual inclination (4.7 vs 4.1 points, P = .001), and interproximal spaces (1.3 vs 0.0 points; P ≤ .05). On the other hand, there was a negative change in posterior occlusal contacts (4.0 vs 10.3 points; P ≤ .001). The remaining categories, including marginal ridge relationships, occlusal relationships (eg, posterior interdigitation), and overjet (anterior and posterior), showed no significant change. Thus, for this sample treated with the Invisalign system, the greatest positive change as measured by the OGS point system was in the alignment of teeth, followed by closure of interproximal space. An undesirable change was found with a decline in posterior occlusal contacts. The score for the latter category had a negative impact on the overall changes as measured with the OGS method. The results of the OGS show that treatment with Invisalign aligners had adverse effects on posterior occlusal contacts and positive effects on tooth alignment, buccolingual inclination, and interproximal spaces.
“there was a negative change in posterior occlusal contacts (4.0 vs 10.3 points; P ≤ .001). The remaining categories, including marginal ridge relationships, occlusal relationships (eg, posterior interdigitation), and overjet (anterior and posterior), showed no significant change….”
“The results of the OGS show that treatment with Invisalign aligners had adverse effects on posterior occlusal contacts”
The public has been led to believe through aggressive advertising (not unlike many drugs that are mega-advertised) that a pretty smile is just simple alignment of the front teeth when in fact alignment at the expense of function is actually a net-negative which can lead to extensive problems down the road. What may seem like only partial failures of Invisalign and other aligner systems (with “acceptable” limitations in some dimensions of movement) is can actually cause an inability to restore posterior occlusion which can lead to TMD (Chronic muscle and jaw pain), relapse of tooth alignment/spacing, and excessive wear of teeth as well as other issues detrimental to the overall oral health. In the opinion of most Board Certified Orthodontists, it would be malpractice to align teeth for esthetics but knowingly place them in poor occlusion that will lead to significant risks in the future. In fact, a doctor could easily and successfully be sued if he or she creates a malocclusion that leads to damage to the dentition/supporting tissues; this goes for traditional braces, restorative crowns or Invisalign clear aligners.
So is Invisalign right for you? Can you trust your doctor? Will it work?
I believe today the best way to evaluate whether Invisalign is right for you is:
1. Find a specialist that is fully trained in Orthodontics (a true Orthodontist, member of the American Association of Orthodontists (AAO) and if possible, a diplomate of the American Board of Orthodontics (ABO) as there are no other true specialty organizations for Orthodontists).
2. Make sure the Orthodontist isn’t exclusively using Invisalign; they should be able to make a calculated and realistic appraisal of treatment and be literate to the research showing the limitations of Invisalign; anyone treating exclusively with aligner trays is not providing or offering the best (and sometimes not even an adequate option) that Orthodontics has to offer and if they are not admitting just that, then you should seek another opinion.
3. Ask the right questions; don’t try to lead your doctor with answers you may WANT to hear; listen to what you NEED to hear. Realize that poor treatment is the most expensive treatment as it may fail, cause more problems/damage to the dentition or simply have to be re-performed later.
4. Realize that Invisalign is a publicly traded business, they are not your doctor and not governed by the rules and ethical obligations of a certified doctor; to them you are a potential profit. Realize that dentists and Orthodontists are not beauticians; we are highly trained doctors; medical professionals that are responsible and obliged to provide the highest standard of care even if it is not the product you want.
5. Hold your doctor accountable: If they promise success with aligners equal to traditional braces, and they cannot provide what they promised, report it to your State’s Dental Board. If your bite is poor or you have problems following aligner treatment, seek a second opinion from a Board Certified Specialist. Aligners can be a valuable armament in the treatments available to you by your orthodontist but only if we, as patients and doctors, hold anyone who abuses the technology responsible for their actions.
If you have questions or comments concerning this or any orthodontic question, please feel free to make a complimentary new-patient appointment at either my Steiner Ranch location or my North-central Austin location on West 35th street and MoPac.
Dr. James R. Waters is a 1996 graduate from UTHSC Dental School in San Antonio, 1997 graduate of Advanced Dentistry from the UNMC in Nebraska and the 2001 Valedictorian graduate from the prestigious Saint Louis University Orthodontic Program receiving the J.P. Marshall award for clinical excellence in 2001. He holds a Bachelor’s Degree in Science, Doctorate in Dental Surgery, a post-doctorate certificate in Advanced Dentistry, post-doctorate Degree in Orthodontics & Dentofacial Orthopedics and a Master of Science Degree in Orthodontics. Dr. Waters and his wife of 20 years live in Austin, TX with their 4 children where he has a thriving, multi-faceted Specialist practice with locations in Steiner Ranch and North-Central Austin. You can learn more about Dr. Waters at BracesAustin.com.
1814 W. 35th Street
Austin, TX 78703
4302 N. Quinlan Park
Austin, TX 78732