Volume 32 Issue 3 Article 2

2020

Clinical Effectiveness of Using in Orthodontic Treatment

Chih-Ling Lin Department of Craniofacial , Chang Gung Memorial Hospital, Taipei, Taiwan

Yi-Chin Wang Department of Craniofacial Orthodontics, Chang Gung Memorial Hospital, Taipei, Taiwan.

Yuh-Jia Hsieh Graduate Institute of Craniofacial and Dental Science, Chang Gung University, Taiwan; Craniofacial Research Center, Chang Gung Memorial Hospital, Linkou, Taiwan; Department of Craniofacial Orthodontics, Chang Gung Memorial Hospital, Taoyuan, Taiwan

Yun-Fang Chen Department of Craniofacial Orthodontics, Chang Gung Memorial Hospital, Taipei, Taiwan; Graduate Institute of Craniofacial and Dental Science, Chang Gung University, Taiwan; Craniofacial Center, Chang Gung Memorial Hospital, Taoyuan, Taiwan; Craniofacial Research Center, Chang Gung Memorial Hospital, Linkou, Taiwan

Yu-Chih Wang FDeparollowtment this and of Cr additionalaniofacial works Orthodontics, at: https:/ Chang/www.tjo.or Gungg.tw/tjo Memorial Hospital, Taipei, Taiwan; Graduate Institute of Craniofacial and Dental Science, Chang Gung University, Taiwan; Craniofacial Center, Chang Gung Par Memorialt of the Or Hospital,thodontics Tao andyuan, Or Tthodontaiwan; ologyCraniofacial Commons Resear ch Center, Chang Gung Memorial Hospital, Linkou, Taiwan

Recommended Citation Lin, Chih-Ling; Wang, Yi-Chin; Hsieh, Yuh-Jia; Chen, Yun-Fang; and Wang, Yu-Chih (2020) "Clinical Effectiveness of Using Clear Aligners in Orthodontic Treatment," Taiwanese Journal of Orthodontics: Vol. 32 : Iss. 3 , Article 2. DOI: 10.38209/2708-2636.1001 Available at: https://www.tjo.org.tw/tjo/vol32/iss3/2

This Review Article is brought to you for free and open access by Taiwanese Journal of Orthodontics. It has been accepted for inclusion in Taiwanese Journal of Orthodontics by an authorized editor of Taiwanese Journal of Orthodontics. REVIEW ARTICLE Clinical Effectiveness of Using Clear Aligners in Orthodontic Treatment

Chih-Ling Lin a,b,e, Yi-Chin Wang a,b,c,d, Yuh-Jia Hsieh b,c,d,f, Yun-Fang Chen a,b,c,d, Yu-Chih Wang a,b,c,d,* a Department of Craniofacial Orthodontics, Chang Gung Memorial Hospital, Taipei, Taiwan b Graduate Institute of Craniofacial and Dental Science, Chang Gung University, Taiwan c Craniofacial Center, Chang Gung Memorial Hospital, Taoyuan, Taiwan d Craniofacial Research Center, Chang Gung Memorial Hospital, Linkou, Taiwan e Department of Orthodontics, New Taipei Municipal Tucheng Hospital, New Taipei, Taiwan f Department of Craniofacial Orthodontics, Chang Gung Memorial Hospital, Taoyuan, Taiwan

ABSTRACT

Purpose: To assess the clinical treatment effectiveness of clear aligners in orthodontic tooth movements. Methods: The database of Cochrane Central Register of Controlled Trials, Embase, PubMed, Web of Science, and Scopus were searched from Jan 2015 to Jan 2020. The National Institute for Health and Clinical Excellence assessment tool was used for the methodological quality of included studies. Results: The literature review yielded 166 articles after removal of duplicates, and an additional 2 articles were included from hand search of the bibliographies of included articles and relevant reviews. Fifteen studies were included in the systematic review. One study was randomized controlled trial, one study was prospective caseecontrol study, two studies were retrospective caseecontrol and eleven studies were retrospective cohort studies. Conclusion: The clear aligner treatment (CAT) is effective in managing minor . CAT could achieve a comparable treatment outcome to that of the fixed orthodontic appliance in nongrowing patients with mild malocclusion. There are weak evidences to support the efficacy of CAT in extraction orthodontics. The results should be interpreted with caution due to heterogeneity in studies.

Keywords: Orthodontic tooth movement; Clear aligner treatment (CAT); Aligners; Treatment effectiveness

INTRODUCTION efforts to use transparent overlays to achieve minor tooth movements. With the advent of ith the increasing esthetic and comfort- dental materials and hi-tech 3D technology, the W able demands in patients seeking for or- Invisalign@ system (Align Technology@, Santa thodontic treatment, CAT nowadays has been a Clara, Calif) was commercially released to the popular alternative to traditional fixed orthodon- orthodontic market to treat misaligned teeth in tic appliances in orthodontic society. The modern 1998. The modern computer-aided design/com- CAT has been considered a modified form which puter-aided manufacturing (CAD/CAM) system, could be to date back 1940s. Kesling first intro- incorporating orthodontic virtual planning and duced a series of clear tooth positioners which stereolithographic prototyping technology, man- could progressively align minor mispositioned ufactures a series of individualized thermoplastic teeth after fixed orthodontic treatment.1 Later, clear aligners. The custom-made aligner was many experts adopted the concept and tried their

Conflicts of interest: The authors declare that they have no competing interests. The authors received no financial support for this study.

Received 19 June 2020; revised 30 September 2020; accepted 4 October 2020. Available online 1 December 2020

* Corresponding author at: Department of Craniofacial Orthodontics, Chang Gung Memorial Hospital, 6F, No.199, Tung Hwa N. Road, Sunshan District, Taipei, 105, Taiwan. Fax.: þ02 25148246. E-mail address: [email protected] (Y.-C. Wang). https://doi.org/10.38209/2708-2636.1001 2708-2636/© 2020 Taiwan Association of Orthodontist. Taiwanese Journal of Orthodontics C.-L. LIN ET AL 2020;32(3):138e148 CLINICAL EFFECTIVENESS OF CLEAR ALIGNERS

programmed to move a tooth or a small group of of review articles and all the studies included for teeth by 0.25e0.33 mm in every 14 days.2 Since data extraction were searched. the patent of Invisalign@ expired in 2017, to date, numerous clear aligner systems, even some Inclusion and exclusion criteria without the intervention of a dental profession are 3 The inclusion criteria were as follows: (1) pro- available in the orthodontic market. All those spective and retrospective studies including ran- orthodontic treatment with removable trans- domized clinical trials, controlled clinical trials and parent aligners is characterized as CAT. cohort studies; (2) studies on human subjects with Clear aligners were initially introduced to resolve permanent teeth; (3) studies on individuals under- mild to moderate dental crowding and close mild going extraction or non-extraction orthodontic spacing. At present, there are numerous publica- treatment with CAT; (4) studies that providing data tions and experts’ experiences showed in more regarding to dental movement or treatment complex malocclusion such as extraction cases, outcome assessment by evaluating dental models, could be corrected with CAT. Advantages of CAT radiographs, or validated scoring system. The were reported for better aesthetics, comfort at early exclusion criteria were as follows: (1) case series, stage, easier oral hygiene maintenance, improved case reports, review articles; (2) studies on subjects periodontal health, and less root resorption as with craniofacial anomalies or syndromes, or those e compared with fixed appliances.4 6 In addition to who were medically compromised; (3) in vitro aforementioned issues, the treatment efficiency is studies. another one major concern for orthodontic pro- fessions. Recently, there have been many in- Data extraction vestigations and few reviews conducted to assess the predictability of tooth movement with CAT. The following data were extracted: authors, pub- With the continually evolution in the field of mate- lication date, study design, number and groupings rials, algorithms of tooth movement planning and of study subjects, types of malocclusion, compara- the apparatus design of CAT are constantly updat- tive groups, types of intervention, time points of ing. The aim of this review was to investigate the measurements, methodology of outcome assess- latest relevant evidences about the precision of tooth ment, outcomes, and key findings. movement and clinical effectiveness with CAT. Assessment of methodological quality MATERIAL AND METHODS The National Institute for Health and Clinical Study design Excellence (NICE) was used to assess the method- ological quality of included studies.8 The instrument The implement of this study was in accordance consists of eight items that are assessed for the in- with the Preferred Reporting Items for Systematic dividual study. Review and Meta-analysis (PRISMA) guidelines.7 The main question guided the systematic search of the literature was: what's the clinical effectiveness of RESULTS clear aligners in orthodontic treatment? After removal of duplicates, the database search yielded 127 articles. Hand search of the bibliogra- Search strategy phies of the selected articles and relevant reviews identified one additional article. After screening The Cochrane Central Register of Controlled full-text articles, fifteen relevant studies met the Trials, Embase, PubMed, Web of Science, and Sco- eligible criteria were included in the analysis. pus databases were searched for relevant English- Figure 1 provided the details of the search strategy. language literature from Jan 2015 to Jan 2020 using the following keywords: “clear aligner” OR “invis- Characteristics of included studies ible orthodontic” OR “Invisalign” OR “Clear Aligner” OR “clear aligner therapy” OR “CAT” AND The characteristics and details of the included “effectiveness” OR “efficacy” OR “accuracy” OR fifteen studies presented in Table 1. In terms of “treatment effectiveness” OR “treatment outcome”. study design, one study was randomized controlled Unpublished literature was searched using Google trial, one study was prospective caseecontrol study, or Google Scholar search engine. The bibliographies two studies were retrospective caseecontrol and

139 C.-L. LIN ET AL Taiwanese Journal of Orthodontics CLINICAL EFFECTIVENESS OF CLEAR ALIGNERS 2020;32(3):138e148

Figure 1. PRISMA flow diagram demonstrating the results of the systematic literature search.

e eleven studies were retrospective cohort studies.9 23 (accuracy ¼ 100% - [(jpredicted e achievedj)/ Three of them were comparative studies to investi- jachievedj]x100%); and (3) scores with the grading gate the differences between CAT and conventional tools. Among them, only one study reported the result fixed appliances. Invisalign@ was used in twelve of extraction cases with CAT. studies, and Clear aligners@, F22@ and Nuvola@ were applied in the other studies. Methodological quality of the included studies Regarding to the methodology of outcome assess- ment: (1) two study analyzed plaster models with All the fifteen included studies satisfied five to validated grading tools, which were American Board seven of the eight NICE quality assessment tool of Orthodontics (ABO) Objective Grading System items (Table 2). The limits of evidences and sources (OGS) scores or Peer Assessment Rating (PAR) index; of bias were as follows: (1) investigations conducted (2) five studies investigated the tooth movement from in a single institution or not reported; (2) the data lateral cephalogram; (3) nine studies studied super- were not collected prospectively; (3) the studies did imposed digital models; and (4) one study inspected not report that patients were recruited the reconstructed 3D craniofacial models with a consecutively. combination of the digital dental model and cone- beam computed tomography (CBCT) data. Mean- Results of CAT interventions while, the data representation which was varied among different studies included (1) size of difference Anteroposterior dimension between predicted and achieved dental movements in Sfondrini et al. compared the buccolingual incli- millimeters or degrees; (2) percentage of accuracy nation of upper incisor treated with CAT,

140 Table 1. Characteristics of included studies. 2020;32(3):138 Orthodontics of Journal Taiwanese Study Study design N, age Appliance Type of Time points Method Measures Result malocclusion 14 @ Buschang Prospective case 27, NR Invisalign NR Pre (T0), post (T1), Plaster models, ABO-OGS score: 1. CC models do e 148 econtrol setup (Ts) software (CC) alignment, not accurately marginal ridge, reflect final inclination, occlusal occlusion. contact, OJ, 2. CC interproximal overestimated contact alignment, BL inclination, occlusal contacts, and occlusal relations 3. The vertical components (marginal ridges and occlusal contacts) showed the largest differences. Zhang15 Retrospective 32, 26.7 Clear aligners@ Complete Pre (T0), post (T1), CBCT, scanned Crown and root Crowns but not cohort study permanent setup (Ts) PVS impression, position of anterior roots can be moved dentition, nEXT, software (OrthoDS teeth to designated 141 Angle Class I or no 4.6/EA) positions by tilting AP change motion Duncan16 Retrospective 61, NR Invisalign@ Md crowding, Pre (T0), post (T1) Digital models Md incisor position, 1. Md incisors tend cohort study nEXT (iTero), LA ceph arch width, OB, OJ to procline and protrude in severe crowding cases 2. Buccal arch expansion and IPR have significant ALIGNERS CLEAR OF EFFECTIVENESS CLINICAL effect on resolution of crowding Henessay17 RCT 44, 26.4 Invisalign@ and C Mild md crowding Pre (T0), post (T1) LA ceph Lower incisor No difference in <4 mm, nEXT, ANB inclination Md incisor 1-4 proclination produced by CAT and C in mild crowding cases. (continued on next page) .L I TAL ET LIN C.-L. Table 1. (continued) ALIGNERS CLEAR OF EFFECTIVENESS CLINICAL AL ET LIN C.-L. Study Study design N, age Appliance Type of Time points Method Measures Result malocclusion Houle18 Retrospective 64, 31.2 Invisalign@ nEXT Pre (T0), post (T1), Digital models Intercanine width, 1. The accuracy of cohort study setup (Ts) (iTero), software interpremolar expansion with (CC) width, intermolar CAT was 72.8% for widths Mx and 87.7% for Md. 2. Less accuracy toward the posterior region 3. More dental tipping than bodily movement. Ravera19 Retrospective 20, 29.7 Invisalign@ Bilateral molar Pre (T0), post (T1) LA ceph Cephalometric CAT is effective in cohort study Class II end-on, values distalizing Mx skeletal Class I ~ II, molars 2e3mm normal divergent, without significant Mx mild crowding vertical and tipping (<4 mm) movements. Grünheid20 Retrospective 30, 21.6 Invisalign@ Full permanent Post (T1), setup (Ts) Scanned alginate MD, BL, OG 1. Mx arch cohort study dentition, nEXT impression (3- position (mm); tip, expansion was not shape), software torque, rotation (o) fully achieved 142 (Orthoanalyzer/3 2. More occlusal shape) position of Md incisors 3. Incomplete rotation of round teeth Gu21 Retrospective case 96, 24.0 Invisalign@ and C Full permanent Pre (T0), post (T1) PAR index PAR index: upper 1. Final occlusal econtrol dentition, nEXT anterior/lower scored di not differ anterior alignment, between the 2 AP, transverse, systems vertical, OB, OJ, 2. CAT finished midline 30% faster (5.7 months) than C Khosravi22 Retrospective 120, 33.0 Invisalign@ nEXT Pre (T0), post (T1) LA ceph , 1. CAT is relatively awns ora fOrthodontics of Journal Taiwanese cohort study cephalometric successful in values managing OB 2. CAT improved deep bites primarily by proclination of Md 2020;32(3):138 incisors. e 148 2020;32(3):138 Orthodontics of Journal Taiwanese Lombardo23 Retrospective 16, 28.0 F22@ Crowding < 5mm/ Pre (T0), post (T1), Digital models (3- BL tip and MD tip 1. The mean cohort study arch, no rotation setup (Ts) shape), software of anterior teeth, accuracy was 73.6% >35o, no diastema > (Orthoanalyzer/3 rotation 2. MD tipping was

5 mm, nEXT shape) the most e predictable 148 movement (82.5%) 3. The least predictable movement was rotation of lower canines (54.2%) Charalampaski24 Retrospective 20, 37.6 Invisalign@ NR Pre (T0), post (T1), Digital models, Horizontal, vertical, Rotations of cohort study setup (Ts) software (CC) width, rotation canines and intrusions of incisors were the most inaccurate movements. Sfondrini25 Retrospective case 75, 25.5 Invisalign@, C and SLB Permanent teeth, Pre (T0), post (T1) LA ceph Cephalometric All the three econtrol dental Class I or values systems showed mild Class II & III good clinical reliability in the upper incisor torque control 143 Tepedino26 Retrospective 39, 30.0 Nuvola@ Crowding up to Pre (T0), post (T1), Digital models (3- Inclination of Nuvola@ produce cohort study 6 mm, nEXT setup (Ts) Shape), software anterior teeth outcome (Maestro 3D Ortho comparable to Ts in Studio) pt up to 6 mm crowding Caruso27 Retrospective 10, 22.7 Invisalign@ Bilateral Class II Pre (T0), post (T1) LA ceph Cephalometric Mx molar cohort study molar or End-on values distalization allow (needs Mx molar good control of

distalization), mild vertical dimension ALIGNERS CLEAR OF EFFECTIVENESS CLINICAL Mx crowding and Is torque Dai, 201928 Retrospective 30, 19.4 Invisalign@ Extraction first Post (T1), setup (Ts) Scanned alginate Mx incisors and In first premolar cohort study premolars impression (iTero), first premolars extraction cases software position and with CAT, first (Orthoanalyzer/3 angulation molar shape) control and central incisor retraction were not fully achieved N, number of patients; NR, not reported; pre, pre-treatment; post, post-treatment; CC, ClinCheck; nEXT, non-extraction; CBCT, cone-beam CT; PVS, polyvinyl siloxane; Md, fi

mandibular; LA ceph, lateral cephalogram; C, conventional xed labial appliance; AP, anterioposterior; MD, mesiodistal; BL, buccolingual; OG, occlusogingival AL ET LIN C.-L. C.-L. LIN ET AL Taiwanese Journal of Orthodontics CLINICAL EFFECTIVENESS OF CLEAR ALIGNERS 2020;32(3):138e148

Table 2. Methodological quality of included studies. sequential distalization protocol. There was no sig- Study Methodological quality of included nificant tipping and vertical movement of the studiesa crown.14 Caruso et al. followed the sequential dis- 1 2345678 talization protocol of maxillary molars described by Buschang et al.14 NR Y N Y Y Y Y Y Ravera et al., presented the outcome could be Duncan et al.15 NYYYNNYYensured by concomitantly using Class II and Zhang et al.16 NYYYNNYYrectangular attachments on the upper molars and 17 Hennessy et al. NR Y Y Y Y N Y Y premolars in maxillary arch distalization.22 The re- Houle et al.18 NYYYNNYY Ravera et al.19 NR Y Y Y N N Y Y sults indicated that orthodontic aligners could Grunheid et al.20 NYYYNYYYperform a bodily distal movement of maxillary Gu et al.21 NYYYNNYYmolars up to 2e3 mm in the control of vertical Khosravi et al.22 YYYYNYYYdimension. Meanwhile, the axis of upper incisors 23 Lombardo et al. NYYYNNYYshowed a significant reduction of 13.2. Charalampakis et al.24 NYYYNNYY Sfondrini et al.25 NR Y Y Y N N Y Y Tepedino et al.26 YYYYNNYYTransverse dimension @ Caruso et al.27 NR Y Y Y N N Y Y Grunheid et al. documented that Invisalign was Dai et al.28 NYYYNNYYable to achieve predicted tooth positions in non- NR, not reported; Y, Yes; N, No. extraction individuals with 2±2 mm crowding other a Quality Assessment of cases series studies checklist from than rotation of mandibular lateral incisor, canine, National Institute for Health and Clinical Excellence (NICE): 1) and premolars.15 The molar torque may not be fully Was the case series collected in more than one center, i.e. multicenter study? 2) Is the hypothesis/aim/objective of the study achieved. However, only maxillary second molars clearly described? 3) Are the inclusion and exclusion criteria (case had the clinically relevant magnitude of more buccal definition) clearly reported? 4) Is there a clear definition of the crown torque than predicted (2.3 ±4.9 , 95% CI outcomes reported? 5) Were data collected prospectively? 6) Is [-2.85, 1.41], P < 0.05). The maxillary molar was there an explicit statement that patients were recruited consecu- positioned more lingually. Houle et al. reported that tively? 7) Are the main findings of the study clearly described? 8) Are outcomes stratified? (e.g., by abnormal results, disease stage, dental tipping rather than bodily movement was patient characteristics). observed following dentoalveolar arch expansion with [email protected] The average accuracy of arch conventional fixed brackets, and self-ligating transversal expansion from canine to first molar was brackets in nonextraction cases. All the three tech- 82.9% at the cusp tip and 62.7% at the gingival niques showed good clinical reliability in the upper margin. In the mandibular arch, there was an incisor torque and no significant difference was average accuracy of 98.9% at the cusp tip and 76.4% 20 found among the various techniques. Tepedino at the gingival margin. In average, the errors existed @ et al. stated Nuvola produced clinical outcomes between the predicted and achieved arch expansion comparable to the planning of digital setup relative at the gingival margin of maxillary first molar was to torque movements of anterior teeth in patients 1.42 mm (SD, 1.9 mm; 95% CI [0.95, 1.90]) as an 21 with moderate crowding up to 6 mm. Henessay average 3.02 mm of bucco-lingual movement was et al. founded that there was no statistically signifi- prescribed. Meanwhile, Invisalign@ for arch expan- cant difference in the mandibular incisor proclina- sion became less accurate going from the anterior to tion of the mild mandibular crowding patients the posterior region. Zhang et al. assessed the in- (<4 mm) underwent the orthodontic treatment tegrated 3D craniofacial composite models with the @ course either with Invisalign or conventional fixed CBCT data and the digitized dental model.10 The 12 orthodontic appliances. Duncan et al. further results indicated that the tooth movement with CAT indicated when there was <6 mm of mandibular was a tilting motion rather than a bodily movement. @ crowding, Invisalign appliance used in non- The crowns but not roots could be moved to extraction non-growing patients could successfully designated position. relieve crowding under a good control of lower incisor position and proclination. The buccal arch Vertical dimension expansion and dominated Khosravi et al. indicated that the Invisalign@ 11 the relief of mandibular crowding. Moreover, appliance was relatively successful in managing lower incisors tended to procline and protrude overbite.17 The revealed the when the crowding is more than 6 mm. overbite remained stable in patients with normal In matter of the efficacy of with pretreatment overbite. A median 1.5 mm of overbite CAT. Ravera et al. reported the maxillary molar reduction in patients with deep bite and a similar could be averagely distalize 2.5 mm in the increase of overbite in patients with open bite

144 Taiwanese Journal of Orthodontics C.-L. LIN ET AL 2020;32(3):138e148 CLINICAL EFFECTIVENESS OF CLEAR ALIGNERS

patients were reported. Furthermore, the posterior posttreatment models lost 2 more points on average vertical dimension remained stable (for molar than the respective ClinCheck model (p < 0.001).9 extrusion < 0.5 mm) in patients either with pre- Gu et al. compared the CAT with fixed appliances treatment normal overbite, deep-bite, and open bite. by using the Peer Assessment Rating (PAR) index. Charalampakis et al. indicated vertical movements The data concluded the final occlusal scores did not and particularly intrusions of maxillary central in- differ between the two systems.16 Posttreatment cisors were less accurate in all linear measurements, weighted PAR scores were 4.08 ± 4.35 in the Invis- with a median difference of 1.5 mm (P < 0.001) be- align patients and were 2.69 ± 2.23 in fixed appli- tween the predicted and the achieved amount.19 The ances patients (p ¼ 0.7420). maxillary incisor showed a tendency of extrusion. On the other hand, Grünheid et al. found the DISCUSSION mandibular incisors tended to be positioned more 15 In the present analysis, the achieved tooth occlusally than predicted. movement was inconsistent with prescribed move- ment by CAT. Since the mechanical properties of Rotation thickness and stiffness of clinical aligners, mismatch Regarding to the rotational movement, Lombardo et al. reported the least predictable movement was of the force system transmitted to the teeth and the 18 biomechanical response of the affected teeth were rotation of the lower canines (54.2%). The predic- quite diverse to be predicted as we manipulate tooth tion errors were 6.9 ± 5.4 at lower canines, movement in the specific software. Meanwhile, we 3.4 ± 2.5 at lower incisors, and 2.0 ± 1.8 at lower could not neglect the influences of manufacturing molars (p < 0.05). The result was in accordance with errors, staging of tooth movement, attachment the study conducted by Grünheid et al. that design, or aging and distortion of each aligner after rounded teeth such as mandibular canines and e continually wearing.24 28 In terms of patient-asso- premolars, the rotation could not be fully cor- ' rected.15 Charalampakis et al. reported that all ciated factors, patient s compliance and anatomic characteristics e.g. density and morphology of achieved rotations were significantly smaller than alveolar bone, or crown and root morphology of predicted ones. The median differences ranged < teeth were proposed to be related to the precision of from 0.9 on maxillary premolars to 3.05 (P 0.001) 29,30 19 tooth movement. The difference between the on maxillary canines. prescribed and real amount of IPR performed by the clinician could not be overlooked.31 In the in-vitro CAT in extraction cases study, Simon et al. reported the initial force systems Dai et al. superimposed 4 digital composite models to assess the precision of tooth movement in between consecutive aligners could show great va- 23 riety even though constant tooth movements were extraction cases by Invisalign. They concluded planned. Thus, the resulting tooth movement might both upper first molar control and central incisor be inconstant with the predicted tooth movement.32 retraction did not fully achieve the predicted posi- The current data agreed with previous reviews tions without using additional refinements, other that the orthodontic tooth movement was predict- fixed appliance or auxiliary appliances. Although able in nongrowing patients with mild to moderate maximum anchorage was planned (an average malocclusion undergoing CAT. For those cases, the predicted mesial translation of 0.87 mm on the first molar) in their subjects, the first molars actually clear aligners could reposition the misaligned teeth through the mechanism of arch expansion, inter- moved mesially by an average of 3.16 mm. proximal reduction and distalization of maxillary molar. Undoubtedly, the arch expansion was mostly Scores in grading tools achieved by a tipping movement. Therefore, the greater success is obtained with Invisalign@ when Buschang et al. evaluated the predictability of @ treating nonskeletal arch constriction as concluded ClinCheck model of Invisalign with ABO's OGS. by Phan and Ling.33 Although the reported mean They reported that there was a significant overall OGS point deduction in posttreatment model as accuracy of maxillary and mandibular expansion was 72.8% and 87.7% respectively, 2 mm of trans- comparing with the ClinCheck models (24 vs 15, versal expansion was more predictable overall. The p ¼ 0.16). Among them, the vertical components of IPR procedure provided the space required to pre- the OGS system, including marginal ridges and vent excessive proclination of incisors in non- occlusal contacts, showed largest differences be- extraction orthodontic tooth movement. For all that tween the predicted treatment outcome and the clinicians could expect 2e3 mm of maxillary molar post-treatment model. For both components, the

145 C.-L. LIN ET AL Taiwanese Journal of Orthodontics CLINICAL EFFECTIVENESS OF CLEAR ALIGNERS 2020;32(3):138e148

distalization as well as anterior retraction with good as predicted. The loss of first molar anchorage vertical control of posterior teeth, the rectangular showed as a moderate anchorage type with 3 mm of attachments at the posterior teeth and usage of mesial translation. The inherent feature of auxiliary appliances, e.g. Class II elastics were rec- anchorage with CAT is comparable to the traditional ommended. On the contrary, Simon et al. indicated edgewise orthodontic treatment in first premolar the overall accuracy of upper molar distalization extraction cases.37 Consequently, utilization of without the support of attachment were comparable auxiliary appliances e.g. mini-implants, prescribed to that with the attachment. Nevertheless, the in- horizontal attachment, and overcorrection with a fluence of attachment on the movement pattern of setting of 6.6 distal tipping on the first molar could molar distalization, which is either bodily move- be considered as the maximum anchorage control ment or tipping movement, could not be clarified.34 was required in extraction orthodontic treatment Regarding to the effectiveness of vertical tooth with CAT.23 Interestingly, the current data revealed movement with CAT, Rossini et al. in the systemic that CAT provided a good posterior vertical control review indicated that CAT could be only recom- in patients undergoing maxillary molar distaliza- mended for mild deep overbite correction but not tion, nonextraction, or even extraction orthodontic for treatment of open bite. CAT had less effects on treatment. Hence, it could be assumed that CAT was controlling the vertical movement of incisors.35 viable for posterior vertical control in patients with Charalampakis et al. agreed that of in- hyperdivergent facial patten. cisors was the most unpredictable linear tooth The accuracy of individual tooth movement with movement and showed a tendency of extrusion CAT could not fully reflect the treatment effective- even though intrusion was planned.19 On the basis ness from the clinical perspective. Several quanti- of overbite changes, the present evidences sup- tative indexes have been developed to evaluate the ported the expected efficacy of managing deep malocclusion severity and orthodontic treatment overbite and open bite with CAT was 1.5 mm need or treatment outcome.38,39 Differing from improvement. Overbite overcorrection, leveling the previous investigations, Buschchang et al.40 indi- curve of Spee, and virtual bite ramp might be cated the average actual posttreatment model scores considered in the planning strategy of deep bite fell at the high end of the acceptable range of the correction. By the contrast, extrusion attachments ABO's OGS.9 Moreover, both Invisalign@ and fixed could be prescribed to extrude incisors. However, appliances had the similar clinical treatment effec- according to the cephalometric analysis, changes in tiveness to improve the malocclusion in non- the incisor position, either by proclination of extraction patients based on the PAR scores.16 mandibular incisors or extrusion of incisors, were In terms of treatment efficiency, the current evi- responsible for the most improvements in the deep dences represented that the treatment duration was bite and open bite. Therefore, the potential of averagely 5.7 month less for Invisalign patients than achieving true vertical movement of incisors with for fixed appliance patients with mild to moderate CAT merits further investigation. crowding. However, the result of treatment effi- In 2015, Align Technology, Inc. introduced Invis- ciency should be interpreted with caution. The alignG6 system incorporating with SmartForce lower patient's expectation, lack of detailing and (optimized anchorage attachment on posterior teeth finishing stages, higher occlusal force, and less and optimized retraction attachment on the canine) severity of malocclusion have been proposed to features and SmartStage (optimized tooth move- explain a shorter treatment duration for Invisalign ment stage) technology claimed to achieve predict- patients. Currently, there are no ample evidences to able tooth movement and improve clinical outcomes conclude that CAT increases the treatment effi- in cases with severe crowding and extraction or- ciency and particularly for more complicated cases, thodontics.36 The evidences for extraction cases with e.g. extraction treatment. CAT were relatively weak to date. There was only Interestingly, Gu et al. showed the refinement rate one study reported the predictability of tooth was half of previous report and decreased to 37.5% movement in first premolar extraction cases with in their study subjects.16 The result might exhibit the Invisalign@. As the result showed, notable mesial improvement in aligner material, attachment fea- tilting and translation of molars after the first serials tures, and planning algorithm, or indicate the cli- of aligners without using any fixed appliance and nicians should have more experiences with the auxiliary appliance. In the meantime, upper incisors system. showed loss of torque control and more lingual It was not surprising that up-to-date evidences tipping. The anchorage control of first molar and agreed that CAT had difficulties in achieving retraction of central incisor were not fully achieved adequate occlusal contacts and deficiencies in

146 Taiwanese Journal of Orthodontics C.-L. LIN ET AL 2020;32(3):138e148 CLINICAL EFFECTIVENESS OF CLEAR ALIGNERS

overjet and anteroposterior correction. Additionally, 4. Lin F, Yao L, Bhikoo C, Guo J. Impact of fixed orthodontic CAT had less efficacy in controlling orthodontic appliance or clear-aligner on daily performance, in adult patients with moderate need for treatment. Patient Prefer tooth movement of rotation and incisor intrusion. Adherence 2016;10:1639e45. Consequently, clinicians might need auxiliary ap- 5. Rossini G, Parrini S, Castroflorio T, Deregibus A, pliances (e.g. interarch elastics, temporary Debernardi CL. Periodontal health during clear aligners treatment: a systematic review. Eur J Orthod 2015;37:539e43. anchorage devices), midcourse correction, re- 6. Root resorption in orthodontic treatment with clear aligners: a finements, or even conversion to fixed orthodontic systematic review and meta-analysis. Orthod Craniofac Res fi 2019;22:259e69. appliances to nish treatment. 7. Moher DSL, Clarke M, Ghersi D, Liberati A, Petticrew M, There were several limitations of the review Shekelle P, et al. Preferred reporting items for systematic article. First, most of the included studies were review and meta-analysis protocols (PRISMA-P) 2015 state- retrospective studies which having difficulties to ment. Syst Rev 2015;4:1. 9,11,13,15e19,21,23 8. London: National Institute for Health and Care Excellence eliminate the confounding factors. To (NICE). Methods for the development of NICE public health elucidate the real effects, a well-controlled subgroup guidance. 3rd ed. 2012. 9. Buschang PH, Ross M, Shaw SG, Crosby D, Campbell PM. comparison is required. Second, the methodology Predicted and actual end-of-treatment occlusion produced for accuracy assessment could be the source of bias with aligner therapy. Angle Orthod 2015;85:723e7. since the serial digital images were superimposed 10. Zhang XJ, He L, Guo HM, Tian J, Bai YX, Li S. Integrated e on the posterior teeth.15,17 19 Although the reference three-dimensional digital assessment of accuracy of anterior tooth movement using clear aligners. Korean J Orthod 2015;45: teeth were assumed to be “stable”, the forces from 275e81. the flexibility of the material might exert certain 11. Duncan LO, Piedade L, Lekic M, Cunha RS, Wiltshire WA. Changes in mandibular incisor position and arch form reaction forces on the reference tooth. The assess- resulting from Invisalign correction of the crowded dentition ment of tooth movement based on the superimpo- treated nonextraction. Angle Orthod 2016;86:577e83. sition on stable structures could be conducted in 12. Hennessy J, Garvey T, Al-Awadhi EA. A randomized clinical future investigations. To the best of our knowledge, trial comparing mandibular incisor proclination produced by fixed labial appliances and clear aligners. Angle Orthod 2016; there are still lack of evidences to support the long- 86:706e12. term stability of CAT. 13. Houle JP, Piedade L, Todescan Jr R, Pinheiro FH. The pre- dictability of transverse changes with invisalign. Angle Orthod 2017;87:19e24. CONCLUSIONS 14. Ravera S, Castroflorio T, Garino F, Daher S, Cugliari G, Deregibus A. Maxillary molar distalization with aligners in Based on the available evidences, CAT is effective adult patients: a multicenter retrospective study. Prog Orthod in managing minor malocclusion. CAT could ach- 2016;17:12. 15. Grünheid T, Loh C, Larson BE. How accurate is Invisalign in ieve comparable treatment outcome to that of the nonextraction cases? Are predicted tooth positions achieved? fixed orthodontic appliance in nongrowing patients Angle Orthod 2017;87:809e15. with mild malocclusion. However, the fixed appli- 16. Gu J, Tang JS, Skulski B, Fields Jr HW, Beck FM, Firestone AR, et al. Evaluation of Invisalign treatment effectiveness and ances are more effective in great improvement, efficiency compared with conventional fixed appliances using including adequate occlusal contacts than CAT. the Peer Assessment Rating index. Am J Orthod Dentofacial CAT is more effective in control of incisor extrusion Orthop 2017;151:259e66. 17. Khosravi R, Cohanim B, Hujoel P, Daher S, Neal M, Liu W, than in control of incisor intrusion and rotation of et al. Management of overbite with the Invisalign appliance. lower canine and premolar. Arch expansion with Am J Orthod Dentofacial Orthop 2017;151:691e699.e2. CAT primarily achieved by crown tipping and ex- 18. Lombardo L, Arreghini A, Ramina F, Ghislanzoni LTH, Siciliani G. Predictability of orthodontic movement with or- hibits less accuracy on second molars. There is no thodontic aligners: a retrospective study. Prog Orthod 2017;18:35. consensus about the efficacy of CAT for complex 19. Charalampakis O, Iliadi A, Ueno H, Oliver DR, Kim KB. Ac- malocclusion e.g. extraction. Well-controlled pro- curacy of clear aligners: a retrospective study of patients who needed refinement. Am J Orthod Dentofacial Orthop 2018;154: spective studies and randomized control trials with 47e54. rigorous methodology, proper sample size and 20. Sfondrini MF, Gandini P, Castroflorio T, Garino F, Mergati L, recruitment should be conducted to increase the D'Anca K, et al. Buccolingual inclination control of upper central incisors of aligners: a comparison with conventional strength of evidence level for a more persuasive and self-ligating brackets. BioMed Res Int 2018;29:9341821. conclusion. 21. Tepedino M, Paoloni V, Cozza P, Chimenti C. Movement of anterior teeth using clear aligners: a three-dimensional, retrospective evaluation. Prog Orthod 2018;19:9. REFERENCES 22. Caruso S, Nota A, Ehsani S, Maddalone E, Ojima K, Tecco S. Impact of molar teeth distalization with clear aligners on 1. 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