EDITORIAL

Clinical trials needed to answer questionsabout InvisalignDavid L. Turpin, Editor-in-Chief

Seattle, Wash

One of the subjects I am asked about most oftenis the effectiveness of Invisalign treatment andwhat research has been published to verify

Align Technology’s marketing approach. After a face-to-face meeting between the President and CEO ofAlign Technology, Thomas M. Prescott, and the AAOBoard of Trustees a few months ago, I became hopefulthat some common concerns can be resolved. This wasa productive meeting, with opportunity to discussconsumer advertising and referral programs, the degreeof commitment to patient care, and the increased use ofInvisalign.

When reflecting on concerns raised by your editor,Mr Prescott expressed surprise at questions about thelack of substantive controlled clinical trials, noting that“more than 45 articles have been published in profes-sional journals and publications around the world.” Myown Medline search, limited to English articles pub-lished during the past 15 years, yielded 2 clinical trials,6 case reports, 11 descriptive technical articles, and 8assorted abstracts or commentaries. This does notrepresent an overwhelming volume of science uponwhich to base the treatment of more than 200,000patients.

The manufacturer makes it clear that Invisalign isindicated for patients with mild to moderate crowding(1-6 mm), mild to moderate spacing (1-6 mm), andnonskeletal constricted arches, and those who haveexperienced relapse after fixed appliance therapy. Thefact that each clinician is responsible for the treatmentresults achieved in every patient makes it important toconduct more clinical studies.

Of greatest interest to me are the only 2 clinicaltrials published so far; they are very familiar to mebecause they were conducted over nearly 4 years hereat the University of Washington and published in theAJO-DO. The first study, by Bollen et al,1 examined theeffects of activation time and material stiffness on thepatient’s ability to complete a prescribed series ofaligners. With respect to activation times, the 2-week

Am J Orthod Dentofacial Orthop 2005;127:157-80889-5406/$30.00Copyright © 2005 by the American Association of Orthodontists.

doi:10.1016/j.ajodo.2004.12.009

activation period almost doubled the likelihood for asuccessful completion of the initial series of aligners,compared with the 1-week activation. High PAR scoresand planned extractions substantially decreased thelikelihood that the initial series of aligners would becompleted. As it turned out, all subjects who completedtheir initial series of aligners underwent further refine-ment with an additional series of aligners or fixedappliances. The overall completion of the initial align-ers for patients requiring the extraction of 2 or morepremolars was 29%. In a clinical setting where theclinician is not bound by a protocol, this completionrate would most likely be greater. The completion ratewas highest (46%) among patients with PAR scoresless than 15 and no planned extractions, and lowest(0%) among subjects who had 2 or more premolarsextracted. This study tends to support Align Technol-ogy’s current recommendations for a 2-week activationtime in patients who do not require premolar extrac-tions.

The second clinical trial, by Clements et al,2 mea-sured the effects of activation time and material stiff-ness on the quality of treatment as measured by changein PAR scores. When the different components of PARscores were examined, the aligners were most success-ful in improving anterior alignment and least successfulin improving buccal occlusion, transverse relationships,and overbite. They were moderately successful atimproving the midline and overjet. Because the studywas designed for a specific purpose, it presented manydifferent situations than one would expect in clinicalpractice. And neither of the materials used in this studywas identical to the material commercially available asInvisalign. One benefit was observed: treatment withaligners appeared to have no adverse effects on gingivalhealth.

Because these 2 clinical trials were published overa year ago and the aligners are made of a differentmaterial now, it is easy to minimize their importance.We need 2 or 3 well-designed cohort studies comparingthe long-term treatment results in 2 groups of patients:an Invisalign group and a braces group. The discrep-

ancy index3 of the ABO phase III clinical examination

157

American Journal of Orthodontics and Dentofacial OrthopedicsFebruary 2005

158 Editorial

could be used to match the pretreatment severity in bothgroups. Study casts and panoramic radiographs couldbe evaluated posttreatment with the ABO’s objectivegrading system,4 which has become the gold standardfor systematic evaluation of treatment outcomes sinceits introduction in 1999. Because ABO certificationrepresents the highest achievement in orthodontic cre-dentials, it is appropriate to use these indexes to assessthe treatment outcome of Invisalign, relative to conven-tional braces.

The data complied from these new studies wouldhelp clinicians answer several critical questions. Whattype of patients can be treated successfully with Invis-align? Are the results the same for properly selectedpatients treated with either Invisalign or fixed appli-ances? Are treatment times the same? What do weknow about patient acceptance and discomfort? Areoral hygiene complications significantly reduced withthe use of aligners? And perhaps most important of all,what are the treatment limitations of Invisalign?

Some advances in the use of 3-dimensional tech-

nology pioneered by Align Technology are formidable

and will have applications throughout the health careindustry. It will be interesting to see how widespreadthe use of computerized diagnostic setups and theindirect bonding of fixed appliances will become as aresult of these innovations. But to establish a broadbase of support within the profession, we need morewell-designed clinical trials.

REFERENCES

1. Bollen AM, Huang G, King G, Hujoel P, Ma T. Activation timeand material stiffness of sequential removable orthodontic appli-ances. Part 1: ability to complete treatment. Am J OrthodDentofacial Orthop 2003;124:496-501.

2. Clements KM, Bollen AM, Huang G, King G, Hujoel P, Ma T.Activation time and material stiffness of sequential removableorthodontic appliances. Part 2: dental improvements. Am J OrthodDentofacial Orthop 2003;124:502-8.

3. Cangialosi TJ, Riolo ML, Owens SE, Dykhouse VJ, Moffitt AH,Grubb JE, et al. The ABO discrepancy index: a measure of casecomplexity. Am J Orthod Dentofacial Orthop 2004;125:270-8.

4. Casko JS, Vaden JL, Kokich VG, Damone J, James RD, Cangia-losi TJ, et al. Objective grading system for dental casts andpanoramic radiographs. Am J Orthod Dentofacial Orthop 1998;

114:589-99