Early Transverse Treatment

Predictability of maxillary dentoalveolar expansion with clear aligners in patients with mixed dentition

Objective

This prospective study evaluated the effectiveness of clear aligner treatment (CAT) in achieving dentoalveolar upper arch expansion in patients with mixed dentition and transverse maxillary deficiency.

Methods

Forty patients with mixed dentition and a transverse discrepancy of ≤ 5 mm were treated using clear aligners. Pre- and post-treatment digital dental models were measured using specific landmarks and compared with the programmed expansion in the virtual treatment plan. Statistical analyses included the inter-class correlation coefficient to evaluate inter-rater reliability. A paired t test was employed to compare pre- and post-treatment values and to examine the significance of the changes. Multiple regression analysis was conducted to estimate the relationship between the prescribed and observed measurements, stratified by inter-dental measurements (deciduous canines, first deciduous molars, and permanent molars, at cusp and gingival levels).

Results

Excellent measurement reproducibility was observed. The accuracy of dentoalveolar maxillary arch expansion varied among different tooth regions. The inter-canine accuracy was 87.7% at the cusp level and 82.7% at the gingival level. The inter-first deciduous molars exhibited accuracies of 84.9% (cusp level) and 80.5% (gingival level). The inter-first molars showed accuracies of 77.8% (cusp level) and 67.9% (gingival level). Significant differences were observed between the planned and obtained measurements for specific tooth regions.

Conclusions

CAT demonstrated reliable predictability in achieving dentoalveolar expansion of the maxillary arch in patients with mixed dentition. A higher accuracy was observed in the anterior region than in the posterior region. These findings suggest that CAT could be an effective option for treating transverse maxillary deficiencies in patients with mixed dentition with moderate inter-arch transverse discrepancies, considering tooth-specific predictability differences.

Impact of Invisalign® first system on molar width and incisor torque in malocclusion during the mixed dentition period

In orthodontic treatment of patients during the mixed dentition period, arch expansion and opening deep overbite are one of the objectives to achieve proper alignment of the teeth and correction of sagittal and vertical discrepancies. However, the expected outcomes of most therapeutic regimens are not clear, making it impossible to standardize early treatment effects. Therefore, this study was designed to evaluate the impact of the Invisalign® First System on the dental arch circumference and incisor inclination in patients during the mixed dentition period. A total of 21 children during the mixed dentition period (10 females and 11 males, with an average age of 8.76 years) were included in this study. The patients received non-extraction treatment through Invisalign® First System clear aligners, and no other auxiliary devices were used except Invisalign® accessories. Subsequently, the cooperation degree of patients during treatment and the oral measurement parameters at the beginning (T1) and the end (T2) of treatment were collected. All patients showed moderate/good cooperation degree during treatment. Besides, horizontal width of the maxillary first molar increased significantly; the designed arch expansion was 4.1 mm (±1.4 mm), while the actual arch expansion was 3.0 mm (±1.7 mm). Furthermore, the torque expression rate of upper anterior teeth reached 56.53%. Invisalign® First System clear aligners can effectively correct the teeth of patients during the mixed dentition period, widen the circumference of dental arch, and control the torque of incisors.

Evaluation of maxillary dimensional changes in the mixed dentition: clear aligners vs acrylic expanders

OBJECTIVES

To compare changes in upper arch dimension and molar inclination between Invisalign First (IF) and removable acrylic expander (RE) treatments during the mixed dentition period.

MATERIALS AND METHODS

Seventeen patients meeting inclusion criteria underwent IF treatment and were age matched with a group that received treatment with a removable acrylic expander (RE). Intercanine width (ICW), intermolar width, arch depth, buccolingual inclination of the first molars (MI), surface area (SA) and volume (VAP) of the anterior palate, and expansion were compared before and after treatment. The predictability of expansion was calculated for the IF group. Analysis of variance and Kruskal-Wallis tests were used to assess differences.

RESULTS

The ICW increased significantly by 2.14 mm in the IF group and 3.49 mm in the RE group, with no significant intergroup difference. Both groups exhibited significant increases in intermolar width (P < .05), except for intermolar distopalatal width in the IF group (P = .246). Mesiobuccal rotation of the first molar was observed with IF treatment. Although SA and VAP increased in both groups, the changes were not significant for the IF group (P > .05). The RE group exhibited significantly higher increases (P < .05), with an SA increase of 34.32 mm2 and VAP increase of 119.15 mm3. MI changes were in the opposite directions. The prediction accuracy of expansion was 70.28% for canines and 34.12% for first molars.

CONCLUSIONS

Both appliances effectively expanded the intercanine region in growing patients. Expansion predictability was lower in first molars than in canines for the IF group. Removable acrylic expanders could be a choice of preference for expansion targeted to the molar region.

Predictability of expansion movements performed by clear aligners in mixed dentition in both arches: a retrospective study on digital casts

BACKGROUND

to evaluate the predictability of expansion achieved in patients in early mixed dentition treated with Clear Aligners (CA), analyzing the efficiency of the expansion at the end of the first set of aligners and at the end of the therapy in the upper and lower arch.

METHODS

36 patients (20 F, 16 M; mean age 8.3 ± 1.5 years) were selected retrospectively from the Department of Orthodontics of the Hospital of Rome "Tor Vergata". All subjects were treated with CA with no other auxiliaries than attachments. For each patient a standardized sequential expansion protocol was planned for both arches. Digital dental casts were created at three observation periods from an intraoral scanner: prior to treatment (T0), at the end of the first set of aligners (T1), at the end of treatment (T2). The 3D models in planned position determined by the first Clincheck (CC) were obtained for comparison with T1 and T2. Six linear transversal measurements were used to evaluate the dimensional changes and the predictability of expansion movements, comparing T1-CC and T2-CC.

RESULTS

a statistically significant increase within the pre-treatment and the final outcomes for all the variables examined was found. In the upper arch, the greatest level of predictability was detected at the level of the first (46.44%) and second deciduous molar width (44.95%) at T1. The analysis of T2-CC changes showed a significant increase in the percentage of predictability of expansion at the level of the first permanent molars, at mesial (54.86%) and distal (58.92%) width. In the lower arch, a higher percentage of predictability than the upper arch was reported at T1-CC and T2-CC, with the greatest values at the level of second (T1-CC: 48.70%; T2-CC: 75.32%) and first deciduous molar width (T1-CC: 45.71%; T2-CC: 72.75%).

CONCLUSIONS

CA can induce significant transversal increments. The predictability of expansion is variable, but it did not exceed the 50% during the first set of aligners. It was necessary to apply refinement set to achieve a good predictability for expansion of about 70%. The expansion in the lower arch was observed to be more predictable than in the upper arch.

Three-dimensional evaluation of the temporomandibular joints after unilateral surgically assisted rapid maxillary expansion in adults: A preliminary retrospective study

BACKGROUND

Unilateral surgically assisted rapid maxillary expansion (U-SARME) is a successful method for correction of true unilateral posterior crossbite (TUPC).

OBJECTIVES

This retrospective preliminary study aimed to evaluate the position and morphology of condyles in TUPC cases and the effects of U-SARME on condyle with the help of cone beam computed tomography (CBCT).

METHODS

Fifteen patients (mean age: 18.69 ± 1.59 years) who were diagnosed as TUPC and undergone U-SARME were selected. Preoperative (T0) and after 6-month retention (T1) DICOM data of CBCT images were evaluated with MIMICs version 19.0 software. Condylar morphology (medio-lateral and antero-posterior dimensions) and position (anterior, posterior, medial and lateral joint spaces, frontal/axial axis angles, the ratio of posterior to anterior joint space and the percentage of posterior to anterior joint space) were evaluated. Student's t-test was used for intergroup (crossbite, normal) comparisons. Paired-samples t-test was used for intra-group comparisons (p = .05).

RESULTS

There were no positional or dimensional asymmetry of the condyles between crossbite and normal sides initially and after expansion. Regarding T0-T1 changes, while significant increase was determined in medial (0.3 ± 0.29 mm; p = .001) and superior (0.39 ± 0.7 mm; p = .045) joint spaces on crossbite side, posterior (0.79 ± 0.99 mm; p = .008), superior (0.5 ± 0.79 mm; p = .029) and lateral joint spaces (0.31 ± 0.54 mm; p = .042) presented significant increases on normal side. However, no significant changes were found between crossbite and normal sides at T0 and T1.

CONCLUSIONS

Condyles were symmetrical in true unilateral posterior crossbite cases and the symmetry were not disrupted following U-SARME.

Upper arch dimensional changes with clear aligners in the early mixed dentition : A prospective study

BACKGROUND

One goal of orthodontic treatment in mixed dentition is to expand the maxillary arch to allow proper tooth alignment and a correction of sagittal and vertical malocclusions. However, for most treatment protocols, expected outcome is not really clear to allow for a standardization of phase I orthodontic treatments. This lack of information makes it difficult for clinicians to predict tooth movements, including transverse expansion efficacy with Invisalign® (Align Technology, Santa Clara, CA, USA) in children. Therefore, the aim of the present study was to evaluate the transverse maxillary arch development with the Invisalign First System® in growing subjects.

METHODS

The study group included 23 subjects (9 females, 14 males, mean age 9.4 ± 1.2 years). Patients were treated nonextraction with Invisalign First System® clear aligners with no auxiliaries other than Invisalign® attachments. Transverse interdental widths were measured only in the upper arch on each model at the start (T1) and at the end (T2) of treatment. A paired t‑test was chosen to compare T2-T1 changes. The level of significance was set at 5%.

RESULTS

The greatest increase of maxillary width was detected at the level of the upper first deciduous molars (+3.7 ± 1.4 mm; P < 0.001), followed by the level of the second deciduous molars (+3.4 ± 1.6 mm; P < 0.001) and by the deciduous canine (+2.6 ± 2.0 mm; P < 0.001). Upper first molars showed a greater expansion in the intermolar mesial width (+3.2 ± 1.2 mm; P < 0.001) than in the intermolar distal (+1.7 ± 1.2 mm; P < 0.001) and transpalatal width (+1.2 ± 1.2 mm; P < 0.01).

CONCLUSIONS

The Invisalign First System® can be considered effective in growing patients who require maxillary arch development. The greatest net increase was detected at the level of upper first deciduous molars, whereas the upper first molars showed a greater expansion in the intermolar mesial width due to a rotation that occurs around its palatal root.

A Novel Mathematical Method to Diagnose the Transverse Growth Deficit of the Nasomaxillary Complex

The diagnosis of transverse growth deficit of the maxilla in daily clinical practice is carried out mainly through the experience of a well-trained clinician, which implies a lack of objective criteria applicable in a protocolized manner. The objective of this study was to establish a mathematical method to diagnose maxillary compression in relation to the dimensions of the skull and mandible. Methods: Records of 97 cases with an overall mean age of 9.8 ± 2.6 years were analyzed by three experienced orthodontists. The group of transverse compression was comprised of 62 cases and the control group of 35 cases. The main measurements of the widths were made on a frontal teleradiography of the skull (cranial, zygomatic, orbital, maxillary, bigonial and biantegonial width) and a lateral teleradiography of the skull (facial axis, mandibular plane, SNA, SNB, ANB and Wits). It was established that from the cranial width it is possible to predict the group to which each subject studied belongs—the compression group or the control group. A mathematical formula was obtained in the form of logistic regression that allows for the diagnosis of the presence of maxillary compression based on the cranial, maxillary and orbital widths with a sensitivity of 88.7% and a specificity of 77.1%.

The Diagnosis Methods and Management Modalities of Maxillary Transverse Discrepancy

Transverse deficiency of the maxilla (TDM) is the most common skeletal change that involves the maxilla. The craniofacial skeletal assessment as early as possible is critical, as the early diagnosis of TDM influences the effectiveness of treatment. Methods for treating TDM have been reported since the mid-19th century and continue to evolve. This article puts forward a literature review on the topic, investigating the diagnosis and management of TDM, as well as stability after surgical and nonsurgical interventions. We conducted a literature search using a logical combination of the terms “palatal extension,” “maxillary transverse deficiency,” “diagnosis,” and “management.” More recent approaches include three-dimensional imaging, which has allowed for accurate depictions of the craniofacial region to be examined, allowing for evaluation of the spatial relationships between the jaw elements. The success of nonsurgical management compared to surgical management depends on the growth stage of the patient. Unfortunately, data comparing the stability of surgical and nonsurgical management is still lacking. However, for surgical intervention, surgically assisted palatal expansion (SARPE) appears to be the appropriate choice, especially when a large expansion is needed.

Expansion in the absence of crossbite – rationale and protocol

Transverse maxillomandibular discrepancies are a major component of several malocclusions. Clinically, posterior crossbite is a common and valid indicator of maxillary transverse problems and orthopedic and orthodontic forces are routinely used to correct maxillary transverse deficiency. However, crossbite and transverse discrepancies are not a homologous group but must be viewed as a continuum with varying degree of abnormality. The etiology, diagnostic protocol, rationale, and procedures employed for correcting maxillary transverse discrepancy in the absence of crossbite are discussed in the article.

Three-dimensional evaluation of surgically assisted asymmetric rapid maxillary expansion

INTRODUCTION

Unilateral posterior crossbite is classified as true unilateral posterior crossbite (TUPC) or functional posterior crossbite (FPC). The differential diagnosis between TUPC and FPC is of utmost importance for the decision of expansion protocol because conventional expansion methods have some shortcomings for TUPC. The aim of this retrospective study was to 3-dimensionally evaluate the effects of asymmetric rapid maxillary expansion combined with unilateral osteotomy.

METHODS

This study sample comprised 16 patients (mean age 18.38 ± 1.45) with TUPC. A Hyrax acrylic cap included the maxillary premolars and molars on the constricted side, and all teeth up to the central incisor were included on the other side to increase anchorage. Unilateral surgically assisted rapid maxillary expansion was performed and included anterior (aperture piriformis), lateral (zygomatic buttress), and posterior (pterygomaxillary junction) osteotomies on the constricted side and separation of the midpalatal suture. Cone-beam computed tomographic scans taken just before the operation and after 6 months of retention were used to assess skeletal, dental, and periodontal changes.

RESULTS

Expansion was seen on both sides; however, the amount of expansion and tipping was higher on the osteotomy+ side. Because the canines were not included in the acrylic cap on the osteotomy+ side, they did not present the same amount of tipping as the ipsilateral posterior teeth. More teeth were affected periodontally on the osteotomy- side; however, there were no clinically significant differences between the osteotomy+ and osteotomy- sides (mean differences range +0.54 to -0.57 mm). The aperture piriformis width increased significantly on the osteotomy+ side.

CONCLUSIONS

The treatment mechanics had no clinically detrimental effects on the supporting alveolar bone of the maxilla on either side, and it was thought to be effective in cases with TUPC; however, case selection is crucial.

Mandibular response after rapid maxillary expansion in class II growing patients: a pilot randomized controlled trial

Background

The aim of this pilot randomized controlled trial (RCT) was to evaluate the sagittal mandibular response induced by rapid maxillary expansion (RME) therapy in mixed dentition patients with class II malocclusion, comparing the effects of bonded RME and banded RME with a matched untreated class II control group.

Methods

This RCT was designed in parallel with an allocation ratio of 1:1:1. The sample consisted of 30 children with a mean age of 8.1 ± 0.6 years who were randomly assigned to three groups: group 1 treated with bonded RME, group 2 treated with banded RME, and group 3 the untreated control group. All patients met the following inclusion criteria: early mixed dentition, class II molar relationship, transverse discrepancy ≥ 4 mm, overjet ≥ 5 mm, and prepubertal skeletal maturity stage (CS1–CS2). The expansion screw was activated one quarter of a turn per day (0.25 mm) until overcorrection was reached. For each subject, lateral cephalograms and plaster casts were obtained before treatment (T1) and after 1 year (T2). A randomization list was created for the group assignment, with an allocation ratio of 1:1:1. The observer who performed all the measurements was blinded to group assignment. The study was single-blinded in regard to statistical analysis.

Results

RME was effective in the correction of maxillary deficiency. Class II patients treated with both types of RME showed no significant improvement of the anteroposterior relationship of the maxilla and the mandible at both skeletal and occlusal levels. The acrylic splint RME had significant effects on reducing the skeletal vertical dimension and the gonial angle.

Conclusions

The orthopedic expansion did not affect the sagittal relationship of class II patients treated in the early mixed dentition when compared with the untreated control group. Additional studies with a larger sample are warranted to elucidate individual variations in dento-skeletal mandibular response to the maxillary expansion protocol in class-II-growing patients.

Trial registration

ClinicalTrials.govNCT03159962.

Occlusal Relations in Patients With Scaphocephaly

Scaphocephaly results from a premature fusion of the sagittal suture. Usually, cranial vault corrective surgery is performed during the first year of life. There is currently no scientific data regarding occlusion of scaphocephalic patients, or the potential effect of craniovault surgery on the occlusion. The aims were to describe occlusion in scaphocephalic patients and compare with a general pediatric population, and to compare the difference in occlusion of surgically versus unoperated treated scaphocephalic subgroup. A total of 91 scaphocephalic patients (71 boys aged between 2 and 11 y) seen at the Craniofacial Clinic of CHU Ste-Justine's formed the experimental group. All patients received an orthodontic assessment. Among them, 44 underwent craniovault surgery, whereas 47 remained unoperated. Thirty-eight (33 boys; 17 operated) had lateral cephalometric radiographies, some of them also had cephalometric growth follow-ups. Clinical values for dental classification and overjet indicate an increased prevalence of class II malocclusions in scaphocephalic patients. However, interestingly enough, cephalometric values indicative of skeletal class II malocclusions (ie, N-A perp HP, N-B perp HP, N-Pog perp HP, Wits, N-A-Pog) remained within normal limits. Some cephalometric values present statistically significant differences between operated and unoperated patients (ANS-PNS t2, P = 0.025; /1-FH t2, P = 0.028), but these are individual variations not related to scaphocephaly. Maxillary width of scaphocephalic children remains within normal limits. Scaphocephalic patients clinically presented more class II malocclusions compared with normal children. Radiographic values remain, however, within normal limits for both anteroposterior and transverse dimensions. Corrective craniovault surgery did not affect occlusion in these patients.

Alveolar bone changes after asymmetric rapid maxillary expansion

OBJECTIVE

To quantitatively evaluate the effects of asymmetric rapid maxillary expansion (ARME) on cortical bone thickness and buccal alveolar bone height (BABH), and to determine the formation of dehiscence and fenestration in the alveolar bone surrounding the posterior teeth, using cone-beam computed tomography (CBCT).

MATERIALS AND METHODS

The CBCT records of 23 patients with true unilateral posterior skeletal crossbite (10 boys, 14.06 ± 1.08 years old, and 13 girls, 13.64 ± 1.32 years old) who had undergone ARME were selected from our clinic archives. The bonded acrylic ARME appliance, including an occlusal stopper, was used on all patients. CBCT records had been taken before ARME (T1) and after the 3-month retention period (T2). Axial slices of the CBCT images at 3 vertical levels were used to evaluate the buccal and palatal aspects of the canines, first and second premolars, and first molars. Paired samples and independent sample t-tests were used for statistical comparison.

RESULTS

The results suggest that buccal cortical bone thickness of the affected side was significantly more affected by the expansion than was the unaffected side (P < .05). ARME significantly reduced the BABH of the canines (P < .01) and the first and second premolars (P < .05) on the affected side. ARME also increased the incidence of dehiscence and fenestration on the affected side.

CONCLUSIONS

ARME may quantitatively decrease buccal cortical bone thickness and height on the affected side.

Three-dimensional assessment of the temporomandibular joint and mandibular dimensions after early correction of the maxillary arch form in patients with Class II division 1 or division 2 malocclusion

Objective

This study aimed to assess three-dimensional changes in the temporomandibular joint positions and mandibular dimensions after correction of dental factors restricting mandibular growth in patients with Class II division 1 or division 2 malocclusion in the pubertal growth period.

Methods

This prospective clinical study included 14 patients each with Class II division 1 (group I) and Class II division 2 (group II) malocclusions. The quad-helix was used for maxillary expansion, while utility arches were used for intrusion (group I) or protrusion and intrusion (group II) of the maxillary incisors. After approximately 2 months of treatment, an adequate maxillary arch width and acceptable maxillary incisor inclination were obtained. The patients were followed for an average of 6 months. Intraoral and extraoral photographs, plaster models, and cone-beam computed tomography (CBCT) images were obtained before and after treatment. Lateral cephalometric and temporomandibular joint measurements were made from the CBCT images.

Results

The mandibular dimensions increased in both groups, although mandibular positional changes were also found in group II. There were no differences in the condylar position within the mandibular fossa or the condylar dimensions. The mandibular fossa depth and condylar positions were symmetrical at treatment initiation and completion.

Conclusions

Class II malocclusion can be partially corrected by achieving an ideal maxillary arch form, particularly in patients with Class II division 2 malocclusion. Restrictions of the mandible in the transverse or sagittal plane do not affect the temporomandibular joint positions in these patients because of the high adaptability of this joint.

Cone-beam computed tomography evaluation of dentoskeletal changes after asymmetric rapid maxillary expansion

INTRODUCTION

The aims of this study were to quantitatively evaluate the changes in arch widths and buccolingual inclinations of the posterior teeth after asymmetric rapid maxillary expansion (ARME) and to compare the measurements between the crossbite and the noncrossbite sides with cone-beam computed tomography (CBCT).

METHODS

From our clinic archives, we selected the CBCT records of 30 patients with unilateral skeletal crossbite (13 boys, 14.2 ± 1.3 years old; 17 girls, 13.8 ± 1.3 years old) who underwent ARME treatment. A modified acrylic bonded rapid maxillary expansion appliance including an occlusal locking mechanism was used in all patients. CBCT records had been taken before ARME treatment and after a 3-month retention period. Fourteen angular and 80 linear measurements were taken for the maxilla and the mandible. Frontally clipped CBCT images were used for the evaluation. Paired sample and independent sample t tests were used for statistical comparisons.

RESULTS

Comparisons of the before-treatment and after-retention measurements showed that the arch widths and buccolingual inclinations of the posterior teeth increased significantly on the crossbite side of the maxilla and on the noncrossbite side of the mandible (P <0.05). Comparison of the 2 sides showed statistically significant differences in both the maxilla and the mandible (P <0.05).

CONCLUSIONS

After ARME treatment, the crossbite side of the maxilla and the noncrossbite side of the mandible were more affected than were the opposite sides.

Asymmetric rapid maxillary expansion in true unilateral crossbite malocclusion: a prospective controlled clinical study

OBJECTIVE

To investigate the short-term effects of the asymmetric rapid maxillary (ARME) appliance on the vertical, sagittal, and transverse planes in patients with true unilateral posterior crossbite.

MATERIALS AND METHODS

Subjects were divided into two groups. The treatment group was comprised of 21 patients with unilateral posterior crossbite (mean age  =  13.3 ± 2.1 years). Members of this group were treated with the ARME appliance. The control group was comprised of 17 patients with Angle Class I who were kept under observation (mean age  =  12.3 ± 0.8 years). Lateral and frontal cephalograms were taken before the expansion (T1), immediately after expansion (T2), and at postexpansion retention (T3) in the treatment group and at preobservation (T1) and postobservation (T2) in the control group. A total of 34 measurements were assessed on cephalograms. For statistical analysis, the Wilcoxon test and analysis of covariance were used.

RESULTS

The ARME appliance produced significant increases in nasal, maxillary base, upper arch, and lower arch dimensions (P < .01) and a clockwise rotation of the occlusal plane (P  =  .001).

CONCLUSION

The ARME appliance created asymmetric increments in the transversal dimensions of the nose, maxilla, and upper arch in the short term. Asymmetric expansion therapy for subjects with unilateral maxillary deficiency may provide satisfactory outcomes in adolescents, with the exception of mandibular arch expansion. The triangular pattern of expansion caused clockwise rotation of the mandible and the occlusal plane and produced significant alterations in the vertical facial dimensions, whereas it created no displacement in maxilla in the sagittal plane.

Palatal configuration in Class II Division 1 malocclusion: a longitudinal study

INTRODUCTION

The purpose of this study was to evaluate palatal contours in nonextraction orthodontic treatment and long-term stability in patients with Class II Division 1 malocclusions.

METHODS

Data were obtained from maxillary study models before treatment, after treatment, and at least 5 years postretention. Data were collected with a digital pantograph in the canine, second premolar, and first molar regions. Palatal width, base width, palatal height, and alveolar angle were evaluated.

RESULTS

During treatment, the canine region was stable; in the premolar and molar regions, there were statistically significant increases in transverse (palatal and base widths) and palatal height measurements, whereas the alveolar angle decreased. In the postretention evaluation, the canine region showed the greatest modifications, except for alveolar angulation, which was stable. The premolar region showed stability, but, in the molar region, palatal width and alveolar angulation decreased.

CONCLUSIONS

In analyzing alterations in the geometry of palatal configuration, we concluded that a favorable transverse gain of the palatal base, from growth or orthodontics, was important for stability. The transverse gain of palatal base width during Class II treatment is important to compensate for the expected transverse loss in the cervical region and the decrease of alveolar angle in the long term.