ORIGINAL ARTICLE
Evaluation of Invisalign treatment effectiveness and efficiency compared with conventional fixed appliances using the Peer Assessment Rating index Jiafeng Gu,a Jack Shengyu Tang,b Brennan Skulski,c Henry W. Fields, Jr,a F. Michael Beck,d Allen R. Firestone,a Do-Gyoon Kim,a and Toru Deguchia Columbus and Mason, Ohio
Introduction: The purpose of this retrospective case-control study was to compare the treatment effectiveness and efficiency of the Invisalign system with conventional fixed appliances in treating orthodontic patients with mild to moderate malocclusion in a graduate orthodontic clinic. Methods: Using the peer assessment rating (PAR) index, we evaluated pretreatment and posttreatment records of 48 Invisalign patients and 48 fixed appliances patients. The 2 groups of patients were controlled for general characteristics and initial severity of malocclusion. We analyzed treatment outcome, duration, and improvement between the Invisalign and fixed appliances groups. Results: The average pretreatment PAR scores (United Kingdom weighting) were 20.81 for Invisalign and 22.79 for fixed appliances (P 5 1.0000). Posttreatment weighted PAR scores between Invisalign and fixed appliances were not statistically different (P 5 0.7420). On average, the Invisalign patients finished 5.7 months faster than did those with fixed appliances (P 5 0.0040). The weighted PAR score reduction with treatment was not statistically different between the Invisalign and fixed appliances groups (P 5 0.4573). All patients in both groups had more than a 30% reduction in the PAR scores. Logistic regression analysis indicated that the odds of achieving “great improvement” in the Invisalign group were 0.329 times the odds of achieving “great improvement” in the fixed appliances group after controlling for age (P 5 0.0150). Conclusions: Our data showed that both Invisalign and fixed appliances were able to improve the malocclusion. Invisalign patients finished treatment faster than did those with fixed appliances. However, it appears that Invisalign may not be as effective as fixed appliances in achieving “great improvement” in a malocclusion. This study might help clinicians to determine appropriate patients for Invisalign treatment. (Am J Orthod Dentofacial Orthop 2017;151:259-66)
T
he Invisalign system, introduced by Align Technology (Santa Clara, Calif) in 1999, involves moving teeth in increments with a series of removable clear polyurethane trays (aligners). Over the past few years, Align Technology has seen significant growth, with
a Division of Orthodontics, College of Dentistry, The Ohio State University, Columbus, Ohio. b Division of Dental Hygiene, College of Dentistry, The Ohio state University, Mason, Ohio. c College of Dentistry, The Ohio State University, Columbus, Ohio. d Division of Oral Biology, College of Dentistry, The Ohio State University, Columbus, Ohio. All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest, and none were reported. Address correspondence to: Toru Deguchi, Ohio State University College of Dentistry, 4088 Postle Hall, 305 W 12th Ave, Columbus, OH 43210; e-mail,
[email protected]. Submitted, February 2016; revised and accepted, June 2016. 0889-5406/$36.00 Ó 2017 by the American Association of Orthodontists. All rights reserved. http://dx.doi.org/10.1016/j.ajodo.2016.06.041
more than 3 million patients treated with Invisalign worldwide.1 Patients prefer Invisalign treatment over conventional fixed appliances because of its superior esthetics2 and comfort.3 However, in the era of evidence-based dentistry, the scientific evidence on which to choose the treatment of more than 3 million patients is limited. The most recent systematic review of clear aligners only identified 11 relevant scientific articles.4 Of those, 6 were published more than 5 years ago, and no evidence-based conclusions can be drawn from those studies due to poor quality levels.4 Randomized clinical trials have been conducted by a research group to evaluate the effects of aligner material stiffness and activation frequency on Invisalign treatment completion and outcome.5-7 The authors concluded that patients with a 2-week activation protocol, no extractions, and a low initial Peer Assessment Rating (PAR) score were more likely to complete their initial series of aligners.5 This study supports Align Technology's 2-week activation time 259
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recommendation and also suggests that Invisalign is not suitable for extraction patients and those with complex treatment plans. Furthermore, the authors reported that fixed appliances will be needed in premolar extraction patients treated with aligners to correct dental tipping.7 They also concluded that the aligners were most successful in improving anterior alignment, transverse relationships, and overbite; moderately successful in improving midline and overjet; and least successful in improving buccal occlusion.6 Two retrospective cohort studies compared the treatment results of Invisalign patients with those with fixed appliances using the American Board of Orthodontics objective grading system.8,9 The authors reported that Invisalign patients lost 13 more objective grading system points on average than did fixed appliances patients and achieved a passing rate 27% lower than for fixed appliances.8 The study indicated that Invisalign and fixed appliances are similar in correcting rotations, marginal ridge heights, space closure, and root alignment, but fixed appliances are superior in correcting occlusal contacts, posterior torque, and anteroposterior discrepancies.8 In their follow-up study on postretention dental changes of treated Invisalign patients, the authors reported that patients treated with Invisalign relapsed more than did those treated with fixed appliances, particularly in maxillary anterior alignment.9 Many of those studies were conducted several years ago before Align Technology introduced changes to the tray material, attachments, and treatment algorithms. After 2008, improved technologies such as Precision Cuts, Precision Bite Ramps, and Smart Force Attachments led to innovations of Invisalign G3, G4, and G5 that resulted in a possibly wider range and more precision for tooth movement. It seems reasonable to reevaluate the effectiveness and efficiency of this popular treatment system after the introduction of what the company calls significant advances in materials. Therefore, well-designed clinical trials are needed to provide evidence for contemporary Invisalign treatment. An assessment of orthodontic treatment outcomes with a quantitative index helps to establish goals, evaluate effectiveness, and achieve a measureable finish for completed patients. Several quantitative indexes have been developed to evaluate the malocclusion severity and orthodontic treatment need or treatment outcome.10-14 One index, the PAR, has been used widely for evaluating the effects of treatment in a variety of circumstances.15-17 The PAR is an occlusal index that not only measures how much a patient deviates from ideal occlusion, but also quantitatively evaluates orthodontic treatment outcomes by comparing pretreatment and posttreatment casts.13,14
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The purpose of this retrospective case-control study was to determine the effectiveness and efficiency of the Invisalign system compared with conventional fixed appliances in treating orthodontic patients with mild to moderate malocclusion using the PAR index. The specific aims were to compare patients treated with Invisalign and fixed appliances for (1) posttreatment PAR scores, (2) posttreatment reduction in PAR scores, (3) treatment duration, and (4) malocclusion improvement between Invisalign and fixed appliances patients after establishing 2 groups of Invisalign and fixed appliances patients with comparable pretreatment characteristics. See Supplemental Materials for a short video presentation about this study. MATERIAL AND METHODS
The study protocol was reviewed and approved by the Ohio State University Institutional Review Board. The sample for this retrospective case-control study was selected from approximately 1500 conventional orthodontic patients and 250 Invisalign patients in the archives of the Division of Orthodontics at Ohio State University College of Dentistry. All patients were started and completed by orthodontic faculty and residents between 2009 and 2014. The patients were chosen without regard to their history or final treatment results. Selection was based on the following criteria: (1) available pretreatment and posttreatment records including digital models (OrthoCad) and photos; (2) age, 16 years or older when treatment started; (3) no auxiliary appliances other than elastics used during treatment; (4) no extraction patients; (5) no orthognathic surgery or syndromic patients; and (6) full permanent dentition except third molars. The only patients not included were those who were debonded early or terminated (Invisalign patients, because of compliance, hygiene, or transfer). After the initial review, 62 fixed appliances patients and 61 Invisalign patients met the criteria. To match the pretreatment malocclusions between the 2 groups and eliminate any early termination patients, 48 subjects from each group were selected. With a nondirectional alpha risk of 0.05 and an estimated standard deviation of 4.316, our power to detect a difference of 63 units of weighted post-PAR score was 0.92. Patients in the fixed appliances group were treated with fixed orthodontic appliances with various prescriptions, but all appliances were straight-wire edgewise appliances. The PAR index (United Kingdom weighted PAR, which includes the mandibular anterior18) was used in this study to assess 8 components: maxillary anterior segment alignment, mandibular anterior segment
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Table I. Comparison of baseline characteristics between Invisalign and fixed appliances groups Treatment groups
Variable Age (y) Sex Female Male Race/ethnicity African American Asian White Hispanic Class I molars Retreatment
All
Invisalign
Fixed appliances
(n 5 96) 24.0 (SD, 9.0)
(n 5 48) 26.0 (SD, 9.7)
(n 5 48) 22.1 (SD, 7.9)
62 (65%) 34 (35%)
32 (67%) 16 (33%)
30 (63%) 18 (37%)
16 (17%) 4 (4%) 73 (76%) 3 (3%) 65 (68%) 7 (7%)
7 (15%) 2 (4%) 38 (79%) 1 (2%) 35 (73%) 4 (8%)
9 (19%) 2 (4%) 35 (73%) 2 (4%) 30 (63%) 3 (6%)
P value 0.0374* 0.6695
0.8813
0.2751 1.0000
*Significant difference between groups (P\0.05).
alignment, anteroposterior discrepancy, transverse discrepancy, vertical discrepancy, overjet, overbite, and midline. Digital models were used to determine the PAR scores. Previous research has demonstrated that PAR index scores derived from digital models are valid and reliable measures of malocclusion.19 One investigator (J.S.T.) was trained and calibrated for the PAR index and performed all the PAR measurements. This investigator was blinded to the group assignment (Invisalign or fixed appliances) to which the models belonged. Intraexaminer reliability was assessed with intraclass correlation coefficients determined by duplicate scoring of 12 randomly selected subjects from each category (total of 24) 2 months after initial data collection. In their original article to evaluate the PAR index, Richmond et al13 determined that “at least a 30 percent reduction in PAR score was required for a case to be considered as improved and a change of 22 PAR points brought about great improvement.” However, not every patient starts with s PAR score above 22. To include all subjects, we redefined “great improvement” as either (1)weighted PAR score reduction of 22 points or more or (2), if the initial PAR score was less than 22, a weighted PAR score after treatment equal to 0. Statistical analysis
All statistical analyses were performed with software (version 9.3 SAS, Cary, NC). Subject characteristics were compared for the 2 treatment groups using chi-square or Fisher exact tests for categorical variables and randomization tests for continuous variables. Multiple comparisons were adjusted using the step-down Bonferroni method of Holm. The Fisher exact test was also used to compare the distribution of percent
reduction of weighted PAR scores between the 2 groups. Logistic regression was used to evaluate differences in great improvement outcome due to treatment group after controlling for age. The level of statistical significance for all analyses was set at a 5 0.05. RESULTS
The calibrated examiner demonstrated good intraexaminer reliability. (The intraclass correlation coefficient scores ranged from 0.66 for posttreatment overbite to $0.98 for the remaining variables.) The basic sample description and characteristics are presented in Table I. The Invisalign group had a mean pretreatment age of 26.0 6 9.7 years (average 6 standard deviation), and the fixed appliances group had a pretreatment age of 22.1 6 7.9 years. This difference was statistically significant (P 5 0.0374). The differences between the 2 groups for the following variables were not statistically different: sex, race/ethnicity, percentage of Class I molar patients, or percentage of retreatment patients (previous orthodontic treatment) (P .0.05; Table I). The mean weighted pretreatment PAR scores between the Invisalign and fixed appliances groups were not statistically different (P 5 1.0000; Table II). There were no statistically significant differences between the 2 groups for the 8 individual components of pretreatment PAR scores (Table II). After treatment, weighted PAR scores for both groups were less than 5 and did not differ significantly (P 5 0.7420; Table III). None of the 8 individual components of posttreatment PAR scores differed significantly between the groups (Table III). Neither of the weighted PAR reduction scores after treatment or the reduction scores of the 8 individual
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Table II. Pretreatment PAR scores between Invisalign and fixed appliances groups Invisalign (n 5 48) Variable UANT LANT AP TRANS VERT OJ OB MID PREWPAR
Mean 5.25 4.65 2.48 0.17 0.02 5.75 1.92 0.58 20.81
SD 2.07 2.41 1.34 0.66 0.14 5.25 1.65 1.65 6.79
Minimum 1 0 0 0 0 0 0 0 9
Fixed appliances (n 5 48) Maximum 10 10 4 3 1 24 8 8 43
Mean 6.23 5.13 2.44 0.33 0 4.88 2.54 1.25 22.79
SD 2.09 2.45 1.29 0.81 0 6.27 2.36 2.05 7.72
Minimum 1 0 0 0 0 0 0 0 9
Maximum 11 9 4 3 0 24 10 8 38
P value 0.2313 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000
UANT, Maxillary anterior segment alignment; LANT, mandibular anterior segment alignment; AP, anteroposterior discrepancy; TRANS, transverse discrepancy; VERT, vertical discrepancy; OJ, overjet; OB, overbite.; MID, midline; PREWPAR, pretreatment weighted PAR.
Table III. Posttreatment PAR scores between Invisalign and fixed appliances groups Invisalign (n 5 48) Variable PUANT PLANT PAP PTRANS PVERT POJ POB PMID POSTWPAR
Mean 0.44 0.04 2.06 0.06 0 0.75 0.56 0.17 4.08
SD 0.94 0.2 1.29 0.43 0 2.94 0.9 0.81 4.35
Minimum 0 0 0 0 0 0 0 0 0
Fixed appliances (n 5 48) Maximum 5 1 4 3 0 12 2 4 19
Mean 0.42 0.08 1.69 0.06 0.02 0 0.17 0.25 2.69
SD 0.79 0.35 1.27 0.43 0.14 0 0.56 0.98 2.23
Minimum 0 0 0 0 0 0 0 0 0
Maximum 3 2 4 3 1 0 2 4 9
P value 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 0.3060 1.0000 0.7420
PUANT, Posttreatment maxillary anterior segment alignment; PLANT, posttreatment mandibular anterior segment alignment; PAP, posttreatment anteroposterior discrepancy; PTRANS, posttreatment transverse discrepancy; PVERT, posttreatment vertical discrepancy; POJ, posttreatment overjet; POB, posttreatment overbite; PMID, posttreatment midline; POSTWPAR, posttreatment weighted PAR.
PAR components was statistically different between the 2 groups (Table IV). The treatment time for the Invisalign group (13.35 months) was significantly shorter than that for the fixed appliances group (19.08 months) (P 5 0.0040; Table IV). To compare the treatment efficiency of the groups, we evaluated the weighted PAR reduction per month. The Invisalign group was not significantly different compared with the fixed appliances group in reducing the weighted PAR score per month of treatment (P 5 0.2318; Table IV). In our study, all patients in both groups were improved; ie, there was at least a 30% reduction in the PAR score. However, logistic regression analysis indicated that, using our definition of “great improvement” as either a reduction in PAR score of 22 points or a final PAR score of 0, the odds of achieving “great improvement” in the Invisalign group were 0.329 times the odds of achieving “great improvement” in the fixed appliances group after controlling for age (95% confidence interval, 0.1330.815; P 5 0.015; Table V). We further analyzed the
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distribution of the percent reduction in weighted PAR scores between the 2 groups. Our data indicated that fixed appliances are significantly more effective to reduce weighted PAR scores than Invisalign (P 5 0.0322; Fig). DISCUSSION
In our study, the patients in the Invisalign group were significantly older than those in the fixed appliances group, 26.0 and 22.1 years, respectively. This might indicate that older people tend to prefer the cosmetic benefit of the Invisalign system and also that older people might feel more confident that they could wear their trays as directed. Walton et al2 reported that older subjects tended to rate clear orthodontic appliances higher than did younger subjects. However, there is also potential selection bias that attending faculty in our program possibly placed higher consideration in the Invisalign treatment option to older patients. In our study, both the Invisalign and the fixed appliances patients were older than 16 years, and had generally finished growth, so that it was unlikely that growth played a significant role in the treatment
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Table IV. PAR score reduction after treatment and improvement between Invisalign and fixed appliances groups Invisalign (n 5 48) Variable DWPAR MOS DWPAR/MOS DUANT DLANT DAP DTRANS DVERT DOJ DOB DMID Improved Great improvement
Mean 16.73 13.35 1.55 4.81 4.6 0.42 0.1 0.02 5 1.35 0.42
SD 6.78 8.63 0.8 2.09 2.44 1.18 0.52 0.14 4.85 1.76 1.7
Minimum 5 4 0.25 1 0 2 0 0 0 2 4 48/48 (100%) 11/48 (22.9%)
Fixed appliances (n 5 48) Maximum 38 48 3.5 10 10 3 3 1 24 8 8
Mean 20.1 19.08 1.16 5.81 5.04 0.75 0.27 0.02 4.88 2.38 1
SD 8.06 5.92 0.69 2.21 2.42 1.34 0.71 0.14 6.27 2.53 2.1
Minimum 7 6 0.43 1 0 2 0 1 0 2 4 48/48 (100%) 22/48 (45.8%)
Maximum 38 31 4.33 11 9 4 3 0 24 10 8
P value 0.4573 0.0040* 0.2318 0.4573 1.0000 1.0000 1.0000 1.0000 1.0000 0.4573 1.0000 1.0000 0.0150*
DWPAR, Weighted PAR score reduction; MOS, months in treatment; DWPAR/MOS, average weighted PAR score reduction per month; DUANT, maxillary anterior segment alignment score reduction; DLANT, mandibular anterior segment alignment score reduction; DAP, anteroposterior discrepancy score reduction; DTRANS, transverse discrepancy score reduction; DVERT, vertical discrepancy score reduction; DOJ, overjet score reduction; DOB, overbite score reduction; DMID, midline score reduction; Improved, subjects with at least a 30% reduction in PAR score; Great improvement, either weighted PAR score reduction of 22 points or more, or weighted PAR score after treatment equal to 0. *Significant difference between groups (P\0.05).
Table V. Logistic regression analysis for “great improve-
ment” (either PAR reduction of 22 points or to 0 if initial PAR \22) with patient age as a random variable Pr Effect Num DF Den DF Chi-square .chi-square Type III tests of fixed effects Group 1 93 5.92 0.015 Comparison Estimate DF Odds ratio estimates Group Invisalign 0.329 93 vs fixed
95% confidence limits 0.133
0.815
Num DF, numerator degrees of freedom; Den DF, denominator degrees of freedom; Pr, probability.
outcome. Djeu et al8 also found that Invisalign patients were relatively older than fixed appliances patients. Otherwise, our treatment groups were balanced for all other demographic components (sex, race/ethnicity, Class I molar relationship, and retreatment percentage). Previous research indicated that more female patients choose Invisalign treatment; however, in our study there was no statistical difference in sex between Invisalign and fixed appliances patients (P 5 0.6695).20 Our 2 treatment groups were comparable in malocclusion severity with regard to pretreatment weighted PAR scores and all 8 individual components (Table II). The average weighted pretreatment PAR scores of our Invisalign and fixed appliances patients were similar to those in the study by Miller et al,21 although only some
of their patients were from a university clinic. Our fixed appliances patient weighted pretreatment PAR score was also comparable with previously reported dental school orthodontic patients.22 Thus, our sample seemed consistent with other reported groups of orthodontically treated patients. The Invisalign and fixed appliances patients in this study were treated by orthodontic residents under supervision of different orthodontic faculty. In contrast, Djeu et al8 analyzed only the first 50 Invisalign patients treated by 1 orthodontist. Therefore, our study provides greater generalizability. The average weighted posttreatment PAR score of the Invisalign group was higher than that of the fixed appliances group by less than 2 points; this was not statistically different. None of the individual components of posttreatment PAR scores demonstrated a significant difference between the Invisalign group and the fixed appliances group. However, regarding deep overbite correction with either posterior extrusion or anterior intrusion, previous reports only recommend Invisalign to treat simple malocclusions with small overbite discrepancies4 and indicate that significant correction of a deep overbite with Invisalign appears unlikely.6,23 Recently, Align Technology introduced Invisalign G5 with optimized attachments and precision bite ramps to improve deep overbite correction. However, this innovation was introduced after the time period covered in this sample, so its effect on the results of deepbite treatment is unknown. The PAR index does not differentiate between deep overbite and open bite. Boyd24 and Boyd et al25 reported that
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Fig. Distribution of percent reduction in weighted PAR scores (WPAR) between the Invisalign and fixed appliances groups.
Invisalign may have advantages in correcting mild anterior open bite because of the intrusive effect on the posterior teeth from the double thickness of the aligner trays. Another point to note is posttreatment overjet, although there were no statistical differences between the 2 groups. Fixed appliances corrected overjet in all patients, but Invisalign still left some patients with significant overjet (maximum score, 12.00; Table III). This result agrees with previous observations on overjet and anteroposterior correction by Invisalign.6,8 To overcome Invisalign's deficiency in overjet and anteroposterior correction, auxiliary appliances might be used. We further evaluated efficiency between Invisalign and fixed appliances by considering treatment duration. In our study, there was a statistically significant difference between the treatment duration of the 2 groups: Invisalign treatment was on average 5.7 months faster than that of the fixed appliances group (Table IV). This result was comparable with previous reports between Invisalign and fixed appliances on nonextraction treatment with mild to moderate malocclusion.8,20 One study indicated that there is no detailing or finishing phase for Invisalign patients that might have resulted in less treatment time. Although there was no statistically significant difference in the post-PAR scores between the Invisalign (4.1) and fixed appliance (2.7) groups, this difference may be more obvious when analyzing more severe cases, which may result worse PAR scores in Invisalign patients who did not require finishing and detailing. The other suggested reasons for
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shorter treatment durations for Invisalign patients may be related to the difference in the method of tooth movement. In patients with Invisalign, the occlusal force would be much greater than the orthodontic force and result in faster tooth movement than that of the tooth positioner. However, the average reduction in weighted PAR score was not significantly different between the 2 groups; neither was treatment efficiency. Richmond et al13 reported that at least a 30% reduction in PAR score is required for a patient to be considered as “improved.” All subjects in our Invisalign and fixed appliances groups improved by at least 30% (Table IV and Fig). The mean PAR score percentage reduction in our Invisalign and fixed appliances groups were 80.3% and 87.0%, respectively. However, a change of 22 PAR points is needed to be considered a “great improvement.”13 Since not every patient has more than 22 PAR points at pretreatment, to include more subjects, we redefined “great improvement” to include those with a pretreatment PAR score less than 22 points if their posttreatment PAR score was 0. Using this definition of “great improvement,” significantly more subjects were classified as “greatly improved” in the fixed appliances group (P 5 0.0150; Table IV). Even if we considered only subjects with the original definition of “great improvement”—a change of 22 PAR points—there were 9 of 48 subjects in the Invisalign group and 19 of 48 subjects in the fixed appliances group who met this definition. However, this difference did not reach statistical significance (P 5 0.0628). The distribution of percent reduction in
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weighted PAR scores between the 2 groups further indicated that fixed appliances are significantly more effective at reducing weighted PAR scores than Invisalign (P 5 0.0322; Fig), and it appears that Invisalign may be about half as effective as fixed appliances. Previously, the mean accuracy of tooth movement with Invisalign was reported to be about 41%,23 and those authors also reported that 70% to 80% of clinicians need either midcourse correction, refinement, or conversion to fixed appliances to finish treatment. Recently, Simon et al26 reported that overall mean efficacy of tooth movement was 59%. They also demonstrated that incisor torque, premolar derotation, and molar distalization can be performed using Invisalign. In our study, the refinement rate for Invisalign was 37.5%, which is much lower than reported previously.23 This significant difference may reflect the improvements of the aligner material and attachment features, or also indicate increased clinician experience with the system. Refinement features with the Invisalign system may partially account for the disparity in treatment effectiveness between Invisalign and fixed appliances. Treatment with fixed appliances is continuous. In contrast, treatment with Invisalign may be interrupted by requesting midcourse correction or refinement. Patients who choose Invisalign for esthetic reasons may well also prefer shorter treatment times, and thus be more likely to prefer to avoid refinement or any fixed appliance treatment to complete difficult tooth movement. The higher PAR scores and shorter treatment times may indicate greater patient autonomy with Invisalign treatment. The PAR index was developed based on the judgment of dental professionals and may not be fully coincident with patient values. There are several shortcomings with this study. Most significantly, it is a retrospective study. This introduces selection bias. Only subjects with complete records were included, so early termination patients because of poor cooperation or hygiene were excluded. Additionally, the residents who delivered care had greater experience with fixed appliances. Furthermore, whereas developments in materials and protocols with fixed appliance systems have been modest during and after the time period encompassed in this investigation, there have been major changes in materials and protocols to the Invisalign system since 2009, and the results of this study do not reflect them. Like fixed appliances, Invisalign can achieve outstanding outcomes with appropriate patients. However, the clinician's orthodontic knowledge and clinical experience, as well as the patient's compliance and motivation, all play significant roles in the process.
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Practitioners with limited experience with Invisalign should be conservative in patient selection with this system. Further research with randomized clinical trials is warranted to compare the treatment outcomes between Invisalign and fixed appliances. CONCLUSIONS
In this study, we examined the treatment effectiveness and treatment efficiency between Invisalign and fixed appliances with the weighted PAR index. We made the following conclusions. 1. 2. 3.
4.
Final occlusal scores did not differ between the 2 systems. Fixed appliances improved malocclusion more effectively than did Invisalign. Treatment with Invisalign was finished on average 30% (5.7 months) faster than treatment with fixed appliances. However, the likelihood of achieving “great improvement” in a malocclusion appears to be better with fixed appliances.
SUPPLEMENTARY DATA
Supplementary data related to this article can be found online at http://dx.doi.org/10.1016/j.ajodo.2016. 06.041. REFERENCES 1. Align Technology. Invisaline for adults and teens. Available at: www.invisalign.com/braces-for-adults-and-teens. Accessed on August 25, 2015. 2. Walton DK, Fields HW, Johnston WM, Rosenstiel SF, Firestone AR, Christensen JC. Orthodontic appliance preferences of children and adolescents. Am J Orthod Dentofacial Orthop 2010;138: 698.e1-12: discussion, 698-9. 3. Fujiyama K, Honjo T, Suzuki M, Matsuoka S, Deguchi T. Analysis of pain level in cases treated with Invisalign aligner: comparison with fixed edgewise appliance therapy. Prog Orthod 2014;15:64. 4. Rossini G, Parrini S, Castroflorio T, Deregibus A, Debernardi CL. Efficacy of clear aligners in controlling orthodontic tooth movement: a systematic review. Angle Orthod 2015;85:881-9. 5. Bollen AM, Huang G, King G, Hujoel P, Ma T. Activation time and material stiffness of sequential removable orthodontic appliances. Part 1: ability to complete treatment. Am J Orthod Dentofacial Orthop 2003;124:496-501. 6. Clements KM, Bollen AM, Huang G, King G, Hujoel P, Ma T. Activation time and material stiffness of sequential removable orthodontic appliances. Part 2: dental improvements. Am J Orthod Dentofacial Orthop 2003;124:502-8. 7. Baldwin DK, King G, Ramsay DS, Huang G, Bollen AM. Activation time and material stiffness of sequential removable orthodontic appliances. Part 3: premolar extraction patients. Am J Orthod Dentofacial Orthop 2008;133:837-45. 8. Djeu G, Shelton C, Maganzini A. Outcome assessment of Invisalign and traditional orthodontic treatment compared with the
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American Board of Orthodontics objective grading system. Am J Orthod Dentofacial Orthop 2005;128:292-8. Kuncio D, Maganzini A, Shelton C, Freeman K. Invisalign and traditional orthodontic treatment postretention outcomes compared using the American Board of Orthodontics objective grading system. Angle Orthod 2007;77:864-9. Cangialosi TJ, Riolo ML, Owens SE Jr, Dykhouse VJ, Moffitt AH, Grubb JE, et al. The ABO discrepancy index: a measure of case complexity. Am J Orthod Dentofacial Orthop 2004;125:270-8. Casko JS, Vaden JL, Kokich VG, Damone J, James RD, Cangialosi TJ, et al. Objective grading system for dental casts and panoramic radiographs. American Board of Orthodontics. Am J Orthod Dentofacial Orthop 1998;114:589-99. Little RM. The irregularity index: a quantitative score of mandibular anterior alignment. Am J Orthod 1975;68:554-63. Richmond S, Shaw WC, Roberts CT, Andrews M. The PAR index (peer assessment rating): methods to determine outcome of orthodontic treatment in terms of improvement and standards. Eur J Orthod 1992;14:180-7. Richmond S, Shaw WC, O'Brien KD, Buchanan IB, Jones R, Stephens CD, et al. The development of the PAR index (peer assessment rating): reliability and validity. Eur J Orthod 1992;14: 125-39. Firestone AR, Beck FM, Beglin FM, Vig KW. Evaluation of the peer assessment rating (PAR) index as an index of orthodontic treatment need. Am J Orthod Dentofacial Orthop 2002;122: 463-9. Deguchi T, Honjo T, Fukunaga T, Miyawaki S, Roberts WE, Takano-Yamamoto T. Clinical assessment of orthodontic outcomes with the peer assessment rating, discrepancy index, objective grading system, and comprehensive clinical assessment. Am J Orthod Dentofacial Orthop 2005;127:434-43.
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17. Dyken RA, Sadowsky PL, Hurst D. Orthodontic outcomes assessment using the peer assessment rating index. Angle Orthod 2001;71:164-9. 18. DeGuzman L, Bahiraei D, Vig KW, Vig PS, Weyant RJ, O'Brien K. The validation of the Peer Assessment Rating index for malocclusion severity and treatment difficulty. Am J Orthod Dentofacial Orthop 1995;107:172-6. 19. Mayers M, Firestone AR, Rashid R, Vig KW. Comparison of peer assessment rating (PAR) index scores of plaster and computer-based digital models. Am J Orthod Dentofacial Orthop 2005;128:431-4. 20. Buschang PH, Shaw SG, Ross M, Crosby D, Campbell PM. Comparative time efficiency of aligner therapy and conventional edgewise braces. Angle Orthod 2014;84:391-6. 21. Miller KB, McGorray SP, Womack R, Quintero JC, Perelmuter M, Gibson J, et al. A comparison of treatment impacts between Invisalign aligner and fixed appliance therapy during the first week of treatment. Am J Orthod Dentofacial Orthop 2007;131:302.e1-9. 22. Firestone AR, Hasler RU, Ingervall B. Treatment results in dental school orthodontic patients in 1983 and 1993. Angle Orthod 1999;69:19-26. 23. Kravitz ND, Kusnoto B, BeGole E, Obrez A, Agran B. How well does Invisalign work? A prospective clinical study evaluating the efficacy of tooth movement with Invisalign. Am J Orthod Dentofacial Orthop 2009;135:27-35. 24. Boyd RL. Esthetic orthodontic treatment using the Invisalign appliance for moderate to complex malocclusions. J Dent Educ 2008;72:948-67. 25. Boyd RL, Oh H, Fallah M, Vlaskalic V. An update on present and future considerations of aligners. J Calif Dent Assoc 2006;34:793-805. 26. Simon M, Keilig L, Schwarze J, Jung BA, Bourauel C. Treatment outcome and efficacy of an aligner technique—regarding incisor torque, premolar derotation and molar distalization. BMC Oral Health 2014;14:68.
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