Class II correction using clear aligners: a scoping review

Six databases were searched in November 2023 using keywords and index terms related to “Class II Malocclusions” and “Clear Aligners”. In addition to peer-reviewed studies, a grey literature search was conducted using analogous keywords. No restrictions were placed on study design, nor country of origin; however, only papers in English were considered. The search strategy was first developed for PubMed and then adapted according to the design required for EMBASE (Ovid), Web of Science, Scopus, ProQuest Central, and the DOSS (Dentistry and Oral Sciences Source) databases (Appendix I). The grey literature was searched including all global orthodontic website links (obtained through the Australian Society of Orthodontics website)¹⁴ (Appendix II) as well as clear aligner company websites¹⁵ using the search terms “Class II Malocclusions” and “Clear Aligners” (Appendix III).

Texts were uploaded to COVIDENCE (Veritas Health Innovation Ltd, Melbourne, Australia) following which duplicates were removed. Three independent reviewers (S.W.C.J, L.M.S, E.D.J) screened the titles and abstracts from the initial search of the databases and grey literature sites. Any relevant articles flagged during this process underwent a full-text review. The texts were screened using the inclusion and exclusion criteria (Table I). Inter-reviewer conflicts on a particular decision regarding inclusion/exclusion were resolved via discussion between the reviewers. For each conflict, a justification from each reviewer was required and discussed. This was independently reviewed by a third reviewer before a final decision.

Data were extracted and organized into a piloted extraction form by the reviewers (L.M.S, S.W.C.J, E.D.J). Extracted data included the author’s names, the year of article publication, the geographical location of the study, the study aims and design, the population characteristics, intervention(s), the techniques/modalities used, the use of overcorrection, the efficacy of treatment and its measurement, refinements required, and the benefits/limitations of the CAT/modality in the treatment of Class II malocclusions. If any additional trends were noted, a new search was conducted throughout all of the papers to determine if a concept/term was discussed within the study. Data were categorically synthesized and tabulated according to the growth status of included individuals (<18 years “growing,” and ≥ 18 years “non-growing”).

Location and age: Table II presents a summary of the characteristics of the 37 included studies of growing individuals. Countries of affiliation of the first author included the USA (n=9),^{18,20,23,26,29,35,36,50,51} Italy (n=8),^{22,24,31,39,41,44,45,48} Canada (n=7),^{16,28,32,42,43,47,49} China (n=6),^{17,25,27,37,46,52} Saudi Arabia (n=2),^19,33 Germany (n=1),²¹ UAE (n=1),³⁰ Greece (n=1),³⁴ Slovakia (n=1),³⁸ Singapore (n=1).⁴⁰ A total of 482 individuals had a Class II malocclusion treated using CAT across all studies. The mean age of the treated patients was 14.1 years.

Duration and efficacy: the mean treatment duration was 18 months. There were seven studies that showed a treatment duration or allocated treatment time ≤12 months.^{20–22,30,35,41,47} There was a combination of skeletal, dental, unilateral and bilateral cases. Thirty-three of the 37 studies demonstrated the success/efficacy of CAT in treating Class II malocclusions: 10 retrospective cohort studies,^{16,19,22,25,26,31,38,45,46,49} four prospective cohort studies,^24,36,48,50 and 19 case reports^{17,18,20,21,23,29,32–35,37,39–44,47,52} showed success in reaching the treatment objectives and/or achieving a Class I molar relationship. However, one case report mentioned that success only occurred for “modest Class II correction”,³⁵ and one study still had a Class II canine relationship remaining on the right side after 28 months of treatment.²⁷

Techniques and adjuncts: broadly, there were three categories of CAT described as CAT alone, CAT plus mandibular advancement (MA; i.e. precision wings) and CAT plus arch distalization (sequential distalization of the upper dentition) (Table III). Any studies that mentioned Invisalign “First” or Invisalign “Teen” were considered to be part of the general CAT category as the principals of design and use were not uniquely different from techniques used within a general course of CAT. Within the CAT plus distalization reports, two texts specifically mentioned the “DF2 protocol”, which involved a short preliminary phase of sagittal correction followed by full arch CAT to correct any remaining malalignments.^20,26 One text specifically mentioned that the DF2 protocol may be beneficial in cases which require significant Class II correction.²⁶ As this was not definitively stated, it was omitted from the table. Elastics were used in treatment by 21 studies^{16–18,20–22,24,26,32,34–38,41–44,47,49,52} (Table III). Mostly this was in the form of Class II elastics, but the use of vertical elastics³⁷ and Class III elastics was noted.³² Bite ramps were used in four studies in a CAT plus MA case^37,42,43 and a CAT case alone.³⁵ Overcorrection was utilized in a number of reports^17,23,43,44 and one study mentioned that it may be routinely required.²⁶ Additional aligners (mentioned as “refinement”) were required in 14 studies.^{17,20,21,23,24,29,32,33,35,37,40,44,48,52}

Comparison and conventional methods: of the 16 cohort studies, nine had specific comparison groups: one of non-treated individuals,¹⁹ one comparing a fixed bracket group,³⁸ one treated using the Herbst appliance,¹⁶ one with the pendulum appliance,²⁴ four with the twin block (TB),^28,31,45,49 and one study compared CAT with a control, vanBeek appliance, Herbst appliance, and TB groups.⁴⁶ Compared to a control of non-treated individuals, one study found that CAT plus MA produced predominantly skeletal changes in favour of Class II correction.¹⁹ Compared to fixed appliances, CAT was found to produce a similar correction of sagittal discrepancies but with better control of the lower incisors.³⁸ CAT and Herbst appliance cases were found to produce similar results with CAT having better vertical and lower incisor control.¹⁶ Compared with the pendulum appliance, CAT was found to have less clockwise mandibular rotation (pendulum +2.8 degrees versus CAT -4.2 degrees) and a better ability to control the vertical dimension.²⁴ Compared to the TB appliance, three studies found comparable results between CAT and the TB; however of these, one found CAT to have better control of the upper anterior teeth,³¹ one found CAT to have better control of the lower incisors,⁴⁹ and one study found the TB encouraged greater forward growth of the soft tissue chin.⁴⁵ One qualitative study and survey found that individuals reported CAT plus MA as less intimidating, less noticeable and easier to insert; however, it was also associated with more tooth pain, and soft tissue soreness.²⁸ Compared to control, vanBeek and Herbst appliance cases, CAT was found to have solid control of the lower incisors although the vanBeek appliance was found to have the greatest skeletal effect.⁴⁶

Benefits and limitations: overall, the common benefits reported, which also pertained to CAT in general, included the advantage of aesthetics,^{17,19–23,26,32,33,37,40,44,46,49,50} comfort,^{17,21–23,27,33,36,37,44,46,50–52} improved patient hygiene^18,33,51 and the ease/simplicity of use of the appliance and/or the process.^{18,27,28,44,51} Regarding aesthetics, one study mentioned that CAT was less noticeable than the TB appliance.²⁸

Twelve studies reported the benefit that enabled CAT to perform simultaneous or multiple movements of teeth and/or in conjunction with MA.^{17,20,23,29,35,36,39,42,45,46,51,52}

Common benefits that pertain more specifically to Class II correction using CAT reported good/beneficial control of the mandibular incisors,^{16–18,26,30,34,36,38,46,47,49} good/beneficial control of the maxillary incisors,^23,31 general good/beneficial control of the incisors^20,45,52 and good/beneficial vertical control.^{16,17,20,23,24,27,36,41,44,45,48,49} An additional common noted benefit was the effective advancement of the mandible and/or beneficial skeletal changes.^{16,17,19,22,23,25,30–34,37,39,41} One paper reported successful skeletal changes but only when treatment by CAT plus MA occurred during the pubertal growth spurt.⁵⁰ It should be noted that one study reported vertical control in relation to the premolars rather than vertical dimension control, and control of the incisors from a general three-dimensional control of the dentition.²⁰ Lesser reported benefits included good mandibular plane angle control,¹⁸ 3D control,²⁰ molar extrusion control,³⁶ root axis control,⁴⁰ and increased accuracy.⁴⁶

Common appliance limitations included difficulty in engaging or adjusting the precision wings in CAT plus MA treatment,^23,36,43 and a resulting temporary posterior/lateral open bite during treatment.^{17,23,24,33,34,40,42} One study discussed the poor predictability of tooth movement.³⁷ An additional study that compared the TB appliance and CAT plus MA treatment noted that individuals undergoing CAT plus MA found it less noticeable and easier to insert than the TB; however, greater tooth discomfort was experienced compared to the TB group.²⁸ Similarly, an additional study also mentioned discomfort/pain although clarified that it was minor and not consistent, as patients stated “sometimes” or “never” in regard to their discomfort.³⁶

The concept of compliance was mentioned in 22 studies.^{17–20,22–24,26,28,29,32,33,36,38–41,44,45,48,50,52} Of these, compliance was acknowledged either as a general comment of CAT’s reliance on patient co-operation for success, specifically making compliance an inclusion criterion of their study, and/or acknowledging the compliance of the individual(s) within the study. One study mentioned no issue related to compliance,⁵¹ although it was a promotional communication, while one study found no differences in compliance between CAT and the TB groups.⁴⁹ An additional study further stated that the discreteness and comfort of CAT may promote compliance over other removable appliances such as the TB.⁴⁶

Location and age: a total of 21 studies discussed CAT for Class II correction in non-growing individuals (Table IV). Countries of affiliation of the first author included USA (n=7),^{53,54,58,63,69,70,73} Italy (n=4),^59,60,66,67 Brazil (n=2),^61,68 China (n=2),^56,65 India (n=2),^55,71 Australia (n=1),⁵⁷ Bolivia (n=1),⁶² Canada (n=1),⁶⁴ and Taiwan (n=1).⁷² The mean age of non-growing patients was 25.9 years.

Duration and efficacy: the mean treatment time for non-growing patients was 18.8 months. Several studies reported a treatment time of ≤12 months.^{55,58,60,64,68} Of the five relevant articles, three described cases that were unilateral Class II molar in nature,^55,60,68 one reported a bilateral half-unit (end-to-end molar) Class II case,⁶⁴ and one article described cases of mixed/non-specific Class II severities, and whose treatment time was standardised.⁵⁸ Of the 21 studies, the efficacy of CAT in Class II correction/treatment objective(s) was achieved in 17 studies (i.e. success in Class II correction and or mention of CAT ability to correct Class II malocclusions).^{53–57,59,60,62–69,71,72}

Techniques and adjuncts: treatment approaches included both extraction^53,62 and non-extraction plans^{54,57,59–61,63,65,66,68,69,71–73} in addition to CAT alone, CAT plus arch distalisation, CAT plus MA and CAT plus temporary anchorage devices (TADs). One study included extraction and non-extraction cases.⁵⁸ Class II elastics were prescribed in 15 studies^{53,54,57–63,65,66,68,69,72,73} (Table V). Typically, the elastics were placed from the upper canine tooth to the lower first molar and attached to the clear aligners by a variety of mechanisms. Where specified, the elastic attachments included TADs, hooks, buttons, or a combination (Table V). Overcorrection was mentioned in five texts.^{57,62–64,70} Additional aligners (refinement) were mentioned in 10 studies.^{53,56–58,62–64,66,70,72} Two additional studies mentioned that refinements would be required in their cases.^61,67

Comparison and conventional methods: of the 11 cohort studies within the non-growing population articles, four had comparison groups: two studies compared CAT in Class I versus Class II cases^58,70 and two studies compared CAT with fixed appliance cases.^56,69

Benefits and limitations: the reported common benefits which relate to general CAT, include comfort,^60,62,65 aesthetics,^{54,55,57,60,62,63,65,67–70} and improved oral hygiene.^{55,60,62,68,69} Common highlighted benefits which specifically pertained to Class II correction by CAT included good/beneficial control of the incisors (either mandibular/maxillary)^{59,60,66,68,69,71} and good/beneficial vertical control.^{54,55,60,69,71,72} Three studies also discussed the simplicity, ease or convenience of the appliance and/or treatment planning or process.^57,62,65 Less common benefits were in relation to the efficacy of distalisation; one study concluded that CAT was able to provide reliable upper molar distalisation.⁵⁴ A recent systematic review determined that arch distalisation using CAT was the most effective movement when compared to all other tooth movement mechanics.⁷¹ The study also mentioned the benefit of good control over mesio-distal tipping.⁷¹ An additional study indicated that CAT was able to distalise molars without significant tipping of their crowns.⁶⁶ Additional minor benefits mentioned were in relation to extrusion control,⁵⁹ advantageous molar intrusion,⁶³ and the benefit of implementing simultaneous tooth movements.^57,63 Two papers mentioned that there may be too many simultaneous tooth movements which may be a disadvantage.^58,61 One study mentioned that using CAT for Class II correction may lead to a reduced occurrence of root resorption and bone fenestration, but was not included in the table as the concept was theoretical and not conclusive as the study only stated that it “could reduce” root resorption/fenestration).⁵⁶ Common treatment limitations included poor efficacy or less than ideal predictability of tooth movement.^{58,61,65,67,70,72} Five of the studies were in relation to sequential distalisation.^{58,61,65,67,72} Three studies mentioned poor predictability/efficacy of tooth movement following a comparison of pre-treatment and either predicted or post-treatment results by the American Board of Orthodontics Objective Grading System (ABO OGS),^58,61,70 and three studies discussed a discrepancy between the predicted and the actual outcome.^65,67,72 One study stated the possible need for further refinements due to a posterior open bite created during treatment.⁵⁸

In non-growing populations, the issue of “compliance” was acknowledged in 11 studies.^{53,54,56–59,65–67,69,70} The studies mentioned compliance as an explicit disadvantage of CAT and/or were mentioned as part of their inclusion or exclusion criteria (i.e. “good compliance” as part of their inclusion criteria). Two studies specifically mentioned that their cases had good compliance throughout CAT,^62,63 while one study specifically mentioned poor compliance.⁵³

Prior to CAT plus MA treatment, fixed or removable functional appliances provided a method for the early management of a Class II malocclusion. Nine of the 16 cohort studies had comparison groups which provided valuable insight into the efficacy and mechanisms of CAT compared to traditional functional appliances. Comparing their test group to a control of non-treated individuals, Al Subaie et al. corroborated the findings of several of the previous case reports and determined that CAT plus MA produced a predominantly skeletal change in favour of Class II correction.¹⁹ However, compared to the TB appliance, CAT plus MA showed slight variances in efficacy and in the end result. Caruso et al. noted that while both appliances effectively reduced ANB values and overjet, the TB “demonstrated a higher efficacy in increasing mandibular dimensions”; however, CAT provided better control of the upper incisors.³¹ Blackham’s retrospective cohort study found that while there were few significant differences in the skeletal changes produced by a TB versus CAT plus MA, increased mandibular growth in the TB group occurred compared to the CAT plus MA and control groups.⁴⁹ It was further noted that treatment using CAT plus MA resulted in less tipping of the lower incisors.⁴⁹ A comprehensive analysis by Wu et al. compared CAT to the vanBeek appliance, the Herbst appliance and the TB.⁴⁶ The comparison showed that all were effective in Class II correction by inducing forward growth of the mandible; however, it was the vanBeek appliance that produced the greatest skeletal effects and also exhibited significant lower incisor control.⁴⁶ The Herbst appliance showed skeletal change with effective upper molar distalisation, while the TB showed both skeletal and dental changes and lower incisor proclination. Although CAT plus MA corrected an overjet mainly via dentoalveolar effects, it also provided good lower incisor control and the ability to perform multiple alignments in conjunction with MA.⁴⁶

Comparisons of the numerous studies between CAT modalities and traditional functional appliances, determined that functional appliances may produce a greater skeletal effect, and forward growth of the mandible, and therefore, may be beneficial in retrognathic Class II cases. However, the projected growth of an individual must be considered along with the appliance’s potential to worsen the mandibular plane angle or contribute to a clockwise mandibular rotation, in which case, CAT may prove to be a preferred option. Greater demands for aesthetics, lower incisor control as well as vertical control may also favour the use of CAT.

The treatment of growing patients produced a wider range of CAT treatment approaches, perhaps due to the growth potential. Upper molar distalisation using the “DF2 protocol” comprised of a treatment course of two distinct phases, was reported in several studies.^20,26 The primary stage focused on sagittal alignment using Class II elastics, to rotate and distalise the upper molars; the second phase involved full arch CAT to correct other malalignments that may be present.^20,26 The main benefit noted was better vertical control during sagittal correction compared to the Carriere Distalizer (Henry Schein Orthodontics, NY USA). Otis found that poor correlation between the amount of Class II correction and treatment duration might indicate the advantages of the DF2 protocol in cases that required significant Class II correction.²⁶ Ferris and Rungcharassaeng,²⁰ noted that the use of the DF2 protocol resulted in a headgear treatment effect, in which a backward force applied to the maxilla restricted its growth.⁷⁵ This may be advantageous in individuals with a hyperplastic maxilla, but it was also noted that there was a lack of discernible change in sagittal mandibular position. This may indicate a difference in effect between DF2 and functional appliances.

In CAT plus MA, clear aligners either included posterior precision wings to posture the mandible forward, or they relied on incisor position; the F22 Young Appliance (Sweden and Martina, Due Carrare (PD), Italy) consisted of a clear aligner with a “customisable block” on the palatal surface of the upper incisors to fit behind the lower aligner and advance the mandible.²² The F22 Young Appliance may be used in conjunction with other techniques and appliances such as a rapid palatal expander.²² Invisalign Teen (Align Technology, Inc., Santa Clara, CA, USA) was used in studies that involved distalisation and/or MA/precision wings^28,41,51 although the clear aligners were identical to those used in other Invisalign treatment plans, the aligners included a compliance indicator component and treatment plans tended to allow for tooth eruption and also include a mostly elastic-free option.^41,51

Two concerns related to CAT were identified which included difficulty in engaging the precision wings in CAT plus MA appliances and a resulting temporary open bite (either posterior or lateral) during treatment. The issue of compliance during CAT was seen as a common disadvantage of treatment.^76,77 Furthermore, elastics as an auxiliary in Class II correction also required compliance.⁷⁸ The precision wing engagement has further potential implications regarding patient compliance and may ultimately affect treatment time and efficacy. Temporary open bites may require further aligners which may also increase treatment time.

Prior to design advancements in CAT, functional appliances were the main treatment option for Class II correction. Within the non-growing patient studies, two reports compared CAT to conventional therapies of Class II correction. While data on treatment time and efficacy between the two groups were not specifically mentioned, Bajaj provided valuable insight into the dento-skeletal changes between the two groups as their study found that there were less vertical tooth moments in the CAT group compared to the fixed appliance group.⁶⁹ Additionally, the findings showed increased incisor intrusion in the CAT group compared to increased protrusion and the extrusion seen in the fixed appliance group.⁶⁹ The findings support the benefits of vertical and lower incisor control identified in numerous studies. However, it was noted that the results of the CAT group were obtained from one practitioner compared to the results of the fixed appliance group which were obtained from multiple sources, implying differences in treatment execution and techniques.⁶⁹

The advancements and progression of techniques have enhanced the efficacy of CAT when applied in the treatment of Class II malocclusions. Of the studies of non-growing patients, 17 achieved the treatment objectives or mentioned correction to Class I. No single treatment method was shown to be superior, as there were multiple treatment options which achieved the planned objectives,^{54–56,59,60,63,69} and recorded as CAT (mandibular jump),⁵⁷ CAT (sequential distalisation),^{57,65–68,71,72} CAT plus surgery plus TADs,⁵³ CAT plus TADs,⁶² CAT plus MA (with photobiomodulation (PBM)).⁶⁴ Three of the five studies which showed a treatment time of ≤12 months assessed unilateral Class II cases,^55,60,68 while one was a bilateral half-unit (end-to-end molar) Class II case.⁶⁴ However, within the five studies, there were two which employed CAT,^55,60 two with CAT (sequential distalisation),^58,68 and one with CAT plus MA with PBM.⁶⁴ While it is evident that less complex cases may lead to shorter treatment times, there were no obvious advantages between treatment modalities and efficacy/treatment times.

General alignment of the arches and sequential distalisation were more commonly employed rather than CAT plus MA due to a lack of growth potential in adult patients. However, a case report described the successful treatment of an adult patient who presented with a Class II malocclusion by using CAT plus MA and PBM.⁶⁴ The combination of clear aligners with MA wings and the use of a PBM device worn for five minutes in each arch daily (10 minutes in total), led to successful aligner changes every three to four days. The total active treatment time was seven months, resulting in a Class I occlusion as well as a Class I skeletal relationship (verified by lateral cephalometric measurements).⁶⁴ Although further research is needed to corroborate the findings, this pioneering technique may prove to be a solution to overcome the challenge of treating skeletal Class II cases in non-growing patients.

A significant issue when treating Class II deep bite cases is the challenge of creating and preserving anchorage. While temporary anchorage devices (TADs) have established use alongside fixed appliances,⁷⁹ it is a relatively newer technique in cases treated using CAT.^53,62 Further complications can arise when treating extraction cases due to the tooth tipping characteristic of CAT, bodily movements can be a challenge in extraction cases and may even contribute to lengthier treatment times than fixed appliances.⁸ A case report addressed both of these issues and presented a deep bite extraction case in which treatment consisted of the removal of the upper first premolars and the bilateral placement of TADs between the upper lateral incisors and canines. Buttons on the upper lateral incisors provided attachments for elastics looped to the TADs. Supplemental elastics were also attached between hooks on the upper canines and buttons on the lower first molars. The authors noted that the deep-bite and a slight right-side canine Class II relationship persisted after the initial 21 months of treatment but after 31 months, all the treatment objectives were met.⁶² While there has been an increase in the use of novel adjuncts, further research of these newer techniques is required to broaden their scope and applicability.

While compliance is a well-known issue across any removable appliance, the known disadvantage of CAT within non-growing individuals was poor efficacy of tooth movement.⁵⁹ Clear aligners are created using a digital scan and online planning, which inherently involves a significant reliance on technology. Software programs such as the Invisalign ClinCheck system (Align Technology, Inc., Santa Clara, CA) provide an online platform for practitioners to plan their case and desired outcome and subsequently produce aligners based on the digitally predicted outcome.⁷⁰ While the success of orthodontic treatment is usually evaluated clinically by a finished Class I occlusion,¹ the American Board of Orthodontics Objective Grading System (ABO OGS) provides a more thorough and objective measurement of treatment success.⁸⁰ Three studies mentioned poor predictability/efficacy of tooth movement following a comparison of pre-treatment and either predicted or post-treatment results by the ABO-OGS.^58,61,70 Alternatively, while predictions and actual outcomes may be compared through software programs, three studies discussed an inconsistency between the predicted versus the actual outcome.^65,67,72 Of the six studies which discussed poor efficacy/predictability of tooth movement,^{58,61,65,67,70,72} five were in relation to sequential distalisation.^{58,61,65,67,72} This implies that sequential distalisation alone may be inadequate for correcting a Class II malocclusion. Two studies discussed a discrepancy between the predicted and actual outcome^65,72 and other studies included planned overcorrection to try to avoid these discrepancies.⁷⁰ Overcorrection is not a novel concept and is commonly planned into aligner treatment to increase treatment efficacy.⁸¹ A failure to meet treatment objectives due to poor tooth movement may also add to the need for additional aligners. One study from the USA included a mix of growing and non-growing individuals⁸² and discussed creative adjuncts including traditional TADs (particularly in adult patients in whom more anchorage may be required due to the lack of growth potential), as well as a palatal TADs with a mesially extending “power arm” incorporating a closed coil retraction spring to help guide the clear aligner tray to distalise an entire quadrant.⁸² The general findings were consistent with previous studies in stating the benefit of aesthetics but also mentioning the major issue of compliance.⁸² However, the study also recommended the use of TADs to increase distalisation predictability.⁸² Further research on this technique and the issue of predictability may therefore be beneficial. Predictability within growing patients was not reported in depth which also creates a demanding area of future research, particularly as growth patterns may be a compounding treatment factor.

As a removable appliance, the issue of compliance with CAT cannot be ignored and was mentioned in 11 of the 21 studies of non-growing populations. Poor compliance may result in failed treatment outcomes, a need for further refinements, and/or a prolonged treatment duration.

There are a number of limitations associated with the present study. Firstly, individual growth rates differ and it is difficult to account for this in Class II treatment unless the growth stage of an individual is determined.⁸³ Growth status using the cervical vertebral maturation (CVM) method was not always stated in each text and so studies were divided into growing and non-growing patients based on whether participants were above or below 18 years of age. A number of studies may have therefore been unnecessarily excluded when there was mixed data pertaining to growing and non-growing individuals. Secondly, studies in which CAT was used for Class II correction with adjuncts (such as surgery/functional appliances) were only included if the individual/population still had a Class II malocclusion prior to the commencement of the CAT treatment phase. If an adjunct such as surgery or a functional appliance was used to completely correct the Class II malocclusion prior to CAT, the study was excluded. Finally, separation by severity, dental or skeletal, or division of a Class II malocclusion may yield valuable results and may help improve the orthodontic understanding of Class II correction using CAT.