Contemporary Orthodontics & Dentofacial Orthopedics
James
R. Waters,
DDS, MSD , PA
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
Introduction
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).
Methods
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.
Results
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%).”
Conclusions
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
Introduction
In this study, we examined the impacts of age, sex, root
length, bone levels, and bone quality on orthodontic tooth movement.
Methods
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.
Results
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”
Conclusions
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.
Central Austin
1814 W. 35th
Street
Austin, TX 78703
(512) 451-6457
Steiner Ranch
4302 N. Quinlan Park
Austin, TX 78732
(512) 266-8585
BracesAustin.com
