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The aim of this study was to evaluate the stability of treatment with a Herbst appliance associated with Hyrax expander (Stage I), followed by fixed appliances (Stage II) and follow-up for an average of 4 years after Stage II, on dentoskeletal facial structures.This study involved 50 adolescents with Angle Class II division 1 malocclusion associated with mandibular retrognathism: Treated Group (TG-25) and Control Group (CG-25). Lateral cephalometric radiographs were taken: T1, immediately before Stage I (TG) or at the beginning of the follow-up period (CG); T2, at the end of Stage I (TG) or the follow-up period (CG); T3, at the end of Stage II (TG); and T4, on average, 4 years after Stage II (TG). Enlow's counterpart analysis and some cephalometric measurements were evaluated. Parametric and non-parametric tests were used (P ≤ 0.05).The ramus alignment variables (P 0.001), SNB (0.040), ANB (0.001), 1.PP (P = 0.015), 1.MP (P 0.001), ms/RLp (P 0.001), mi/RLp (P 0.001) and S-LS (P = 0.005) showed differences between TG and CG from T1 to T2. Longitudinally, there were differences in ramus alignment, P = 0.003, T1 T2 T3 = T4; SNB, P = 0.016, T1 T2 = T3 = T4; ANB, P 0.001, T1 T2 = T3 = T4; 1.MP, P 0.001, T1 T2 = T3 = T4; ms/RLp, P = 0.002, T1 = T2 T3 = T4; mi/RLp, P 0.001, T1 T2 = T3 = T4; S-LS, P 0.001, T1 T2 = T3 = T4 and S-LI, P = 0.003, T1 = T2 = T3 T4.The nasomaxillary complex (MCF/PM alignment) tended to a retrusive effect to compensate the degree of mandibular retrusion. The protrusive effect of the lower facial third was evident after the Herbst stage and did not remain stable in the follow-up. The dentoalveolar compensation and improvement in facial profile remained stable.

Introduction: Obstructive sleep apnea syndrome is a common condition in childhood and if left untreated can result in many health problems. An accurate diagnosis of the etiology is crucial for obstructive sleep apnea treatment success. Functional orthodontic appliances that stimulate mandibular growth by forward mandibular positioning are an alternative therapeutic option in growing patients. Objective: To perform a literature review about the effects of functional orthodontic appliances used to correct the mandibular deficiency in obstructive sleep apnea treatment. Methods: The literature search was conducted in June 2020 using Cochrane Library; PubMed, EBSCO (Dentistry & Oral Sciences Source), LILACS Ovid; SciELO Web of Science; EMBASE Bireme and BBO Bireme electronic databases. The search included papers published in English, until June 2020, whose methodology referred to the types and effects of functional orthopedic appliances on obstructive sleep apnea treatment in children. Results: The search strategy identified thirteen articles; only four articles were randomized clinical studies. All studies using the oral appliances or functional orthopedic appliances for obstructive sleep apnea in children resulted in improvements in the apnea-hypopnea index score. The cephalometric (2D) and tomographic (3D) evaluations revealed enlargement of the upper airway and increase in the upper airspace, improving the respiratory function in the short term. Conclusion: Functional appliances may bean alternative treatment for obstructive sleep apnea, but it cannot be concluded that they are effective in treating pediatric obstructive sleep apnea. There are significant deficiencies in the existing evidence, mainly due to absence of control groups, small sample sizes, lack of randomization and no long-term results. Resumo Introdução: A síndrome da apneia obstrutiva do sono é uma condição comum na infância e, se não tratada, pode resultar em muitos problemas de saúde. Um diagnóstico preciso da etiologia é crucial para o sucesso do tratamento dessa condição clínica. Aparelhos ortodônticos funcionais que estimulam o crescimento mandibular através do anteroposicionamento mandibular são uma opção terapêutica para pacientes em crescimento. Objetivo: Fazer uma revisão da literatura sobre os efeitos do aparelho ortodôntico funcional usado para corrigir a deficiência mandibular no tratamento da apneia obstrutiva do sono. Método: A pesquisa bibliográfica foi feita em junho de 2020 nos os bancos de dados eletrônicos da Cochrane Library; PubMed, EBSCO (Dentistry & Oral Sciences Source), Lilacs Ovid; SciELO Web of Science; Embase Bireme e BBO Bireme. A busca incluiu artigos publicados em inglês, até junho de 2020, cuja metodologia referia-se aos tipos e efeitos dos aparelhos ortopédicos funcionais no tratamento da apneia obstrutiva do sono em crianças. Resultados: A estratégia de busca identificou 19 artigos; apenas quatro eram estudos clínicos randomizados. Todos os estudos que usaram aparelhos orais ou aparelhos ortopédicos funcionais para apneia obstrutiva do sono em crianças resultaram em melhorias no índice de apneia-hipopneia. As avaliações cefalométrica (2D) e tomográfica (3D) mostraram alargamento das vias aéreas superiores e aumento do espaço das vias aéreas superiores, que melhoraram a função respiratória em curto prazo. Conclusão: Os aparelhos funcionais podem ser um tratamento opcional para apneia obstrutiva do sono, mas não é possível concluir que sejam eficazes na população pediátrica. Existem deficiências significativas nas evidências existentes, principalmente devido à ausência de grupos de controle, tamanho pequeno das amostras, falta de randomização e ausência de resultados em longo prazo.

Summary Background Surface treatment of miniscrews was implemented to determine whether its application increased bone-to-surface contact and enhanced the interlock between the device and the surrounding bone. Objectives To compare the success rate of surface-treated and non-treated orthodontic miniscrews used as reinforcement of anchorage during treatment with the Herbst appliance. Trial design Split-mouth design with an allocation ratio of 1:1. Methods Eligibility criteria to enrol patients were skeletal and dental class II patients with a retrusive chin, use of the Herbst appliance to correct malocclusion, need for skeletal anchorage using a miniscrew both in the left and right side of the mouth, absence of systemic diseases, absence of using drugs that alter bone metabolism, and good oral hygiene. Patients received self-drilling miniscrews without surface treatment and with surface treatment. Both types presented a 1.4 or 1.2 mm diameter. Miniscrews were inserted between the first molar and second premolars or between the two premolars. The force applied to the screws was an elastic chain from the head of the miniscrews to a direct button applied on the canines. The success rate of each type of miniscrew was considered the primary outcome, and the association of success with demographical, clinical, and geometrical characteristics was investigated. Differences were tested by the generalised linear mixed effects model for the split-mouth design. Differences with a P-value < 0.05 were selected as significant. Randomisation A randomisation list was created for the mouth side assignment. Blinding The study was single blinded with regard to the statistical analysis. Results Thirty-nine miniscrews of the non-treated type and 39 miniscrews of the surface-treated type were inserted in 39 patients (23 female and 16 male, mean age: 15.55 ± 7.91) recruited between March 2018 and December 2020 with a split-mouth study design. The mean therapy duration was 9.3 months (SD = 1.31). No differences in failure rate were observed between miniscrew types. No serious harm was observed. Conclusions The success rate of surface-treated and non-treated miniscrews showed no significant differences. Registration This trial was not registered.

Objectives To assess the objective compliance levels in skeletal Class II patients with mandibular retrognathia wearing monoblock and twin-block appliances. Materials and Methods A prospective clinical study was conducted with 30 patients between 10 and 15 years old who were equally divided into two study groups. Group 1 was treated with monoblock, and group 2 was treated with twin-block appliances. The patients were instructed to wear their appliance for 15 hours per day. Wear times were monitored by a microsensor. (TheraMon; MCTechnology, Hargelsberg, Austria) for an average of six appointments. Patients were also instructed to record their wear times on a chart, and this record was admitted as subjective wear time. Statistical analysis was performed with the data derived from both the patients' charts and the monitoring records. Results The mean wear time by the patients was 10.67 ± 3.93 hours, which was less than the 15 hours prescribed by the orthodontist, with no difference between the two appliances (P > .05). The regular use rate, which included the days with a wear time of 8 hours or more per day, was 75%. Compliance levels decreased by 35% throughout the six control appointments. Patients declared that their wear time was more than their objective wear time by an average of 3.76 hours. Conclusions Despite their different designs, there was no significant difference between the monoblock and twin-block appliances in terms of compliance.

This research aimed to compare treatment effects of functional appliances between children with and without morphologic deviations in the upper spine and analyze associations between Atlas dimensions and the short- and long-term treatment effects.Sixty-eight prepubertal or pubertal children (35 boys and 33 girls; mean age, 11.47 ± 1.39 years) treated with Class II functional appliances were included. Lateral cephalograms were taken at pretreatment (T1), postfunctional appliance treatment (T2), and after retention at postpuberty (T3). Upper spine morphology and Atlas dimensions were evaluated at T1. T1-T2 and T1-T3 lateral cephalograms were superimposed using a structural method. Changes in the jaws were compared with multiple linear regression analysis between children with and without deviations in the upper spine. Associations between the changes and Atlas dimensions were analyzed by partial correlation.Children with morphologic deviations in the upper spine showed significantly more backward rotation of the mandible (P 0.01) and increased inclination of the jaws (P 0.05, P 0.01) from T1-T2 and significantly smaller condylar growth (P 0.01) from T1-T3 compared with children without the deviations. Atlas height was significantly associated with vertical and rotational changes in the mandible (P 0.01) from T1-T2 and condylar growth (P 0.05) from T1-T2 and T1-T3.Morphologic deviations in the upper spine and low Atlas height were significantly associated with smaller condylar growth induced by functional appliances in the long term. Upper spine morphology and the Atlas dimension may be valuable in phenotypic differentiation in children with Class II malocclusion for optimal treatment outcome.

Background and objectives Class II malocclusion is one of the most common orthodontic problems. The Twin Block appliance has proven to be the most popular appliance for the correction of these malocclusions. Although randomized controlled trials (RCTs) on the Twin Block appliance have reported the changes to be mainly dentoalveolar, several nonrandomized studies have reported a significant skeletal improvement in these patients. Hence, the aim of this study was to compare the effectiveness of Twin Block appliance evaluated using an RCT or retrospectively selected cases (RSC) for the treatment of Class II Division 1 malocclusion in an adolescent population. Methods This was a retrospective study. The results for an RCT were selected from a UK Class II multicenter study. Sixty-three patients from the trial were included. This group was matched with retrospectively selected Class II cases treated with a Twin Block functional appliance and their results submitted for Membership in Orthodontics examination in the United Kingdom, from four centers. The primary outcome was skeletal measurement ANB (A point, nasion, B point). Secondary outcomes included final peer assessment rating (PAR) scores and final overjet. Intrarater reliability of measurements was assessed. Independent samples t-test was carried out to look at the difference between the groups. Results The reliability assessment showed excellent agreement for all measurements. The data were normally distributed. There was a statistically significant difference favoring the RSC group for final overjet (mean difference [MD] = 1.068, 95% confidence interval [CI] −0.67 to 1.47, P = 0.000) and final PAR (MD = 4.0, 95% CI −0.79 to 5.5, P = 0.000). There was no significant difference in the scores for final ANB (MD = 0.34, 95% CI −0.39 to 1.07, P = 0.33). Conclusion The RSCs show significantly improved overjet and PAR scores at the end of treatment and no statistically significant difference for skeletal change. The study raises the question of a potential role of observational studies in evaluating the effect of an intervention in orthodontics.

Summary Objective To analyze the stress distribution in the hard and soft tissue structures of craniomandibular complex during mandibular advancement with miniplate anchored rigid fixed functional appliance (FFA) using Finite Element Analysis (FEA). Material and methods The virtual model consisting of all the maxillofacial bones (up to calvaria), the mandible and temporomandibular joint (TMJ) was generated using the volumetric data from pre-treatment CBCT-scan of a growing patient. The masticatory muscles, other soft tissues, Herbst appliance and plate geometry were modelled mathematically. Force vectors simulating muscle contraction at rest and advanced mandibular positions, with protraction force of 8 N were applied. The final model was imported into ANSYS for analysis after assigning material properties. Results The maximum von Mises stress of 11.69 MPa and 11.96 MPa magnitude was observed in the region of pterygoid plates and at the bone-miniplate interface respectively, with the mandibular advancement of 7 mm. Stress patterns were also noted at the condylar neck. The stress values observed in the medial and lateral pterygoid muscles were of 10.42 MPa and 4.16 MPa magnitude, respectively. Stress was noted in the bucco-cervical region of the upper posterior teeth, but negligible change was seen on the lower anterior teeth and periodontal ligament. Conclusion Miniplate Anchored Herbst Appliance brought about Class II skeletal correction in growing children as it was accompanied by minimal changes in the inclination of the lower incisors. Soft tissue structures like pterygoid muscles and discal ligaments exhibited increased stress whereas masseter muscle displayed reduction in stresses.

In recent years, the early orthodontic treatment of malocclusion has become a hot issue in the field of orthodontics. Some new phenomena and new problems that have emerged require in-depth analysis and discussion, and need to be given correct guidance and norms. Malocclusion refers to the deformities of teeth, jaws, and craniofacial bones caused by genetic and environmental factors during growth and development. Based on the accurate judgment of the etiology and diagnosis, choosing the right time and suitable indications, with the advantage of growth and development, the most suitable appliance can be selected in the early stage of malocclusion to fix malocclusion, and to effectively prevent and block the formation and development of malocclusion. This article will discuss how to timely and appropriately carry out the early prevention and treatment of malocclusion with six aspects, including methods of performing early orthodontic treatment, the basis and guarantee of early orthodontic treatment, correctly understanding early orthodontic treatment, the issues that should be paid attention to in carrying out early orthodontic treatment, actively advocating multidisciplinary cooperation during early orthodontic treatment and understanding face management in a serious way.近年，错（牙合）畸形的早期矫治成为正畸领域的热点问题，随之出现的一些新现象和新问题需要深入分析和讨论，更需要给予正确的引导和规范。错（牙合）畸形是指在生长发育过程中，由遗传和环境因素导致的牙齿、颌骨、颅面畸形。临床可在准确分析病因和正确诊断的基础上，选择合适的时机和适合的适应证，借助生长发育优势，在错（牙合）畸形形成初期选择合适的矫治器，纠正错（牙合）畸形，有效预防和阻断错（牙合）畸形的形成与发展。本文从如何开展正畸治疗、开展早期矫治的基础和保障、如何正确理解和认识错（牙合）畸形早期矫治、开展早期矫治应关注的问题、积极倡导错（牙合）畸形早期矫治的多学科合作与协作，以及以科学和严谨的态度看待“颜面管理”六方面，探讨如何适时、适宜、适度地开展错（牙合）畸形的早期防与治。.

Class II malocclusion is one of the most common malocclusion with varied prevalence. Functional therapy with appliances like Twin Block or Fixed functional appliances forms the mainstay of treatment in growing Class II patients. These patients might demonstrate narrow airway due to the retrognathic position of the mandible. This study investigated the effects of twin block and fixed functional appliance therapy (Forsus™ FRD) on the pharyngeal airway space in skeletal Class II patients.Forty patients with Class II malocclusion were selected and divided into two equal groups of 20 patients each for both Twin block and Forsus group. Lateral cephalograms were obtained before and after the functional appliance therapy. Evaluation was done for changes in hyoid bone position, pharyngeal airway dimensions and tongue position.The variables of the study showed better hyoid position in both the groups. In Twin Block group, an increase in hy-apw2 and hy-PoFH suggested anterior positioning of hyoid and a decrease in H-MP and hy-ML indicated superior positioning. In Forsus group an increase in H-H', hy-FH, hy-ML, hy-NL, hy-NSL and hy-OL suggested inferior positioning of hyoid, while an increase in hy-apw2, hy-CVT, hy-PoFH, hy-RL and hy'-tgo indicated anterior positioning of hyoid bone after functional therapy.Both the twin block and Forsus™ FRD improved the position of the hyoid bone after the functional appliance therapy however the changes were not statistically significant. Twin block and Forsus™ had similar effect on the hyoid bone position, pharyngeal dimensions and the tongue position.

This study aimed to determine the influence of Clark's twin block (CTB) appliance therapy on achieving golden proportion in post-treatment facial profiles in skeletal Class II patients.A retrospective longitudinal study was conducted on a sample of 44 skeletal Class II subjects treated with CTB, followed by nonextraction mechanotherapy. Ricketts' 13 dentoskeletal ratios were measured on pre- and post-treatment lateral cephalograms. Paired Student's t test was used to analyze the existence of golden proportion in the values of the pre- and post-treatment ratios. The influence of pretreatment variables was tested on post-treatment ratio 4 using simple and multiple linear regression analyses.A statistically significant difference in pre- and post-treatment values was found for ratios 4 (P = 0.02), 9 (P = 0.04), 10 (P0.001), and 13 (P = 0.01). Ratios 4, 9, and 13 moved closer to the golden proportion, whereas ratio 10 moved away from the golden proportion after CTB therapy. Simple linear regression analysis showed a statistically significant association of post-treatment ratio 4 with pretreatment ratios 1, 4, 8, 9, and 12. Multiple linear regression analysis showed a statistically significant association of post-treatment ratio 4 with pretreatment ratios 4 and 12.Treatment with CTB appliance may well move various facial ratios in individual patients toward the published Ricketts ideals. Ricketts' published golden proportion may be used as one guide when planning for attempted dentofacial change in individual patients.

Summary Objectives The aim of this retrospective investigation was to generate representative data on the efficiency and outcome quality of Class II:2 Herbst-Multibracket appliance (Herbst-MBA) treatment. Subjects and methods All Class II:2 patients who had started Herbst-MBA treatment at the study centre since 1986 were included. Study casts from before treatment, after Herbst-MBA treatment, and (if available) after ≥24 months of follow-up were evaluated using standard occlusal variables, the Peer Assessment Rating (PAR)-Index, and the Ahlgren-Scale. Results During treatment, the pre-treatment PAR score was reduced from 23.6 ± 7.66 to 5.6 ± 3.85 (n = 192); during the follow-up period, a slight increase to 6.0 ± 3.60 occurred (n = 127). The percentage of patients who could be assigned to the PAR category ‘greatly improved’ was 30% after treatment and 33% after follow-up; only 1%, respectively, 2% had to be assigned to the category ‘worse/no different’. The outcome ratings according to the Ahlgren-Scale revealed 20% excellent, 32% good, 46% acceptable, and 2% unsuccessful results. Limitations Retrospective study design with follow-up data not available from all subjects and no data from untreated controls. Conclusions Herbst-MBA is an efficient treatment approach in orthodontic care of Class II:2 malocclusions. High-quality results (mean/median PAR score: 5.6/5.0) with very good short-term stability (2.2 years’ follow-up) were achieved. Unfortunately, no appropriate control group or groups, where other treatment approaches had been applied, exist.

Objective The objective of this study was to evaluate the effect of combined temporomandibular joint (TMJ) disk repositioning by suturing through open incision and orthodontic functional appliance (OFA) treatment for adolescents with mandibular asymmetry. Study Design Adolescent patients (12-20 years old) with mandibular asymmetry combined with unilateral TMJ disk displacement without reduction were treated with disk repositioning by suturing through open incision with and without postoperative OFA. Magnetic resonance imaging and posteroanterior cephalometric radiographs (PA) were used to measure and compare the changes in condylar height, joint space, and menton deviation pre- and postoperatively. Results Twenty-six patients were included in the study. Joint space was significantly increased postoperatively and new bone mostly formed at the superior or posterior superior part of the condyle after 6 to 18 months in all surgically treated joints. Fourteen patients with OFA had a significant increase in condylar height and menton deviation compared to 12 patients without OFA (2.29 ± 0.91 mm vs 1.22 ± 0.69 mm, P = .003; 4.56 ± 1.48 mm vs 2.01 ± 0.74 mm, P = .000). Conclusions Combined treatment with TMJ disk repositioning by suturing through open incision and OFA can promote condylar growth and correct mandibular deviation in adolescent patients. Postoperative OFA can maintain the increased joint space created by disk repositioning and promote new bone formation at the superior and posterior parts of the condyle.

Introduction The purpose of this prospective clinical trial is to evaluate the changes of soft tissues and designate the esthetic perceptions of children with Class II malocclusion after Herbst appliance therapy and maxillary molar distalization using stereophotogrammetry. Methods Thirty patients were allocated either to Herbst (6 boys and 9 girls; mean age = 11.60 ± 0.82 years) or distalization (4 boys and 11 girls; mean age = 11.46 ± 1.30 years) groups. Dentoskeletal and soft-tissue treatment changes were examined objectively by cephalometric analysis and stereophotogrammetry, respectively. Pre- and posttreatment profile views were evaluated subjectively by orthodontists and laypeople using the 7-point Likert scale. Intra- and intergroup comparisons for the repeated measurements were performed with 2-way variance analysis. Bonferroni test was used for multiple comparisons (P ≤0.05). Results Greater skeletal changes were observed in the Herbst group than in the distalization group. Maxillary incisor retrusion and mandibular incisor protrusion were observed in the distalization and Herbst groups, respectively. Stereophotogrammetric measurements showed that mandibular body length and lower and anterior facial height increased in both treatment groups. Convexity angle (P = 0.020) and labiomental angle (P = 0.033) were greater in the Herbst group than the distalization group. Conclusions The skeletal contribution to correction of maxillomandibular discrepancy was greater in the Herbst group than the distalization group. Significant profile improvements were recorded for both groups with treatment. After both treatments, orthodontists were found to have higher rates of detection in the profiles than laypeople. The esthetic contribution of treatments to the facial profile was found similar in both groups.

Objectives To determine factors that could predict Class II/1 malocclusion patient compliance during functional treatment. Materials and Methods The sample consisted of 77 subjects (aged 11–13 years; 47% girls) presenting with Class II/1 malocclusion. Inclusion criteria were distal molar relationship, overjet greater than 5 mm, and confirmed pubertal growth spurt. Removable functional appliances (62% Twin Block [TB], 38% Sander Bite Jumping [BJ]) with built-in maxillary expansion screws were used. Follow-up period was 1 year. Patients and parents independently filled out the Child Perception Questionnaire, Parental/Caregiver Perception Questionnaire, and Family Impact Scale to assess emotional and social well-being, oral symptoms, functional limitations, parental emotions, family activities, conflicts, and financial burden as possible predictors of compliance during treatment. Sex, overjet, and appliance type were also analyzed. Results There were more noncompliant than compliant patients (55% vs 45%). Parental perception of altered emotional well-being of their children was the strongest predictor, increasing compliance odds 3.4 times (95% confidence interval [CI], 1.2–9.4; P = .017). Patients were 3.2 times (95% CI, 1.1–9.3; P = .033) more likely to cooperate with TB compared with BJ appliance. OJ ≥ 8 mm increased compliance odds 3.1 times (95% CI, 1.0–9.4; P = .044). Conclusions Parental perception of child's emotional well-being alteration, severity of malocclusion, and type of appliance are major predictors of compliance. Psychosocial issues and oral function limitations reported by children and family impact are of negligible influence.

Background: The purpose of this study was to analyze the relationship between body posture and sagittal dental overjet in children before and after early orthodontic treatment with removable functional orthodontic appliances. Methods: Angle Class II patients (mean age 8.2 ± 1.2 years; 29 males and 25 females) with a distinctly enlarged overjet (> 9 mm) were retrospectively examined regarding body posture parameters before and after early orthodontic treatment. In addition, changes in overjet were investigated with the aid of plaster models. Forms of transverse dysgnathism (crossbite, lateral malocclusions) and open bite cases were excluded. Body posture parameters kyphosis, lordosis, surface rotation, pelvic tilt, pelvic torsion and trunk imbalance were analyzed by means of rasterstereographical photogrammetry to determine, if the orthodontic overjet correction is associated with specific changes in posture patterns. Results: In nearly all patients an overjet correction and an improvement regarding all body posture and back parameters could be noted after early orthodontic treatment. Overjet reduction (− 3.9 mm ± 2.1 mm) and pelvic torsion (− 1.28° ± 0,44°) were significantly (p < 0.05) and moderately correlated (R = 0.338) with no significant associations found for the other posture and back parameters (p > 0.05). Conclusion: Overjet reduction during early orthodontic treatment may be associated with a detectable effect on pelvic torsion., Finanziert über die DEAL-Vereinbarung mit Wiley 2019-2022.

This study aimed to compare cephalometrically the pharyngeal airway, hyoid bone, and soft palate (SP) changes after Class II malocclusion treatments using Twin-block (TWB) and Forsus Fatigue Resistant Device (FFRD) (3M Unitek Corp, 3M Dental Products, Monrovia, Calif) during the postpeak growth period.Forty-two patients with Class II malocclusion treated during the postpeak growth period were randomly and retrospectively included in this study. These patients were divided into 2 treatment groups: TWB and FFRD. The skeletal, dental, pharyngeal airway, hyoid bone position, and SP measurements were obtained from the lateral cephalometric radiographs taken at the beginning and at the end of the treatment. Paired-samples and independent-samples t tests were used for the intragroup and intergroup comparisons, respectively.In the TWB group, the SNB (°), Md1-NB (mm), Md1-NB (°), and McNamara upper and lower pharyngeal airway dimensions significantly increased, whereas the ANB (°), AD1-Ba (mm), AD2-H (mm), adenoidal nasopharyngeal area, and SP angle decreased (P 0.05). In the FFRD group, the SNB (°), Md1-NB (mm), Md1-NB (°), Ptm-Ba (mm), and McNamara upper airway dimensions significantly increased, whereas the ANB (°), AD2-H (mm), and interincisor angle decreased (P 0.05). Moreover, there were statistically significant differences in the Md1-NB angles and SP thicknesses between the 2 groups (P 0.05).The effects of TWB and FFRD treatment on the airway during the postpeak growth period were similar. However, the FFRD caused a greater mandibular incisor protrusion.

Purpose To assess a potential association between lower incisor (LI) position changes during Herbst–multibracket appliance (Herbst–MBA) treatment and the development of labial gingival recessions (LGR). Methods All class II patients (Department of Orthodontics, University of Giessen, Giessen, Germany) who had undergone Herbst–MBA treatment until 2015 with study models and lateral cephalograms available from before (T0) and after treatment plus ≥24 months of retention (T3) were included (n = 259). Lateral cephalograms were evaluated regarding LI position changes: iiL/ML (angle between LI long axis and mandibular plane [MP]), ii-MLPg (distance between LI incisal edge and a line perpendicular to MP through pogonion), apex-MLPg (distance between LI apex and a line perpendicular to MP through pogonion), ii-MLii (distance between LI incisal edge and MP on a line perpendicular to MP through incisal edge). Using study models the distance between the cementoenamel junction and the deepest point of the gingival margin was defined as LGR. Results The following cephalometric mean changes were recorded (T0–T3): iiL/ML +5.9 ± 5.76° (p = 0.929), ii-MLPg −0.2 ± 0.25 mm (p = 0.430), apex-MLPg +0.1 ± 0.32 mm (p = 0.363), ii-MLii +0.1 ± 0.36 mm (p = 0.206). The mean increase of LGR magnitude measured on the study models was 0.1 ± 0.35 mm. However, no association with the cephalometric LI position changes was found (|R| ≤ 0.2). Conclusion There is no association between the amount of LI position changes and the development of LGR during Herbst–MBA treatment plus retention. Nevertheless, individual predisposition or excessive treatment changes and extraordinary treatment approaches, respectively, might still lead to development of LGR.

Objectives To determine dentoalveolar and skeletal effects produced in mature patients by the Carriere Motion Class III (CM3) appliance followed by fixed appliances. Materials and Methods This retrospective study evaluated 32 patients at three time points: T1 (initial), T2 (removal of CM3), and T3 (posttreatment). Serial cephalograms were traced and digitized, and best-fit regional superimpositions were constructed. Eleven linear and 7 angular variables were measured. The starting forms of the CM3 patients were compared with a sample of untreated subjects with normal occlusions and well-balanced faces. Results The CM3 phase lasted 6.3 months, followed by a phase of fixed appliances lasting 12.9 months; the total duration of treatment was 19.2 months. Minimal skeletal changes were measured sagittally, with only a slight increase in lower anterior facial height observed during treatment. Most treatment changes were dentoalveolar in nature. Wits appraisal increased 4.0 mm during treatment. The molar relationship improved by 6.0 mm during phase I, a value that rebounded slightly during phase II, resulting in an improvement toward Class I of 4.8 mm. Best-fit regional superimpositions revealed anterior movement of upper molars relative to the maxilla and posterior movement of lower molars relative to the mandible. Conclusions The Carriere Motion Class III appliance is an effective and efficient method of resolving occlusal problems in minimally growing Class III patients. Primary treatment effects are dentoalveolar in nature with minimal skeletal alterations.

Angle Class II malocclusions including a retrognathic mandible are the most frequent orthodontic problems. Both removable and fixed functional appliances can be used for mandibular advancement. Mandibular advancement after treatment with any fixed functional appliance has numerous therapeutic effects, such as stretching of masticatory muscles, ligaments, membranes and surrounding soft tissues, thus causing positional changes of the hyoid bone and epiglottis. This retrospective study investigates and compares treatment effects upon epiglottis- and hyoid bone position and posterior airway space in class II patients who received mandibular advancement through two different cast splint fixed functional appliances. Two groups of 21 patients each (‘Functional Mandibular Advancer’ (FMA) and Herbst appliance) were investigated. The same experienced orthodontist performed the treatment in all patients, employing a single-step advancement protocol. The mandible always received initial protrusion into an edge-to-edge position. Conventional lateral cephalograms were available pre-treatment (T1) and immediately after appliance removal (T2) for all patients. The measurements comprised (I) hyoid bone, (II) epiglottis or (III) posterior airway space. Treatment-related changes were analysed with one-sample Student’s t tests for intragroup comparisons and independent Student’s t tests for intergroup comparisons. Statistical significance was set at p

To investigate whether fixed functional therapy for mandibular advancement with the Forsus™ appliance would produce any changes in the cervical spine posture.This prospective clinical exploratory study was conducted on 12 patients (six females and six males) with a mean age of 15 ± 1.3 years, having mandibular retrusion, Class II malocclusion, who were treated with the Forsus™ appliance. Lateral cephalogram was taken twice, once at the baseline (T1) before the commencement of the treatment and once following termination of fixed functional treatment (T2). Eleven measurements representing the vertical and the sagittal craniofacial proportions, and the head posture, were taken into account. Data were analyzed using SPSS version 22. The variations between before and after treatment measurements were collated using paired t-test.No significant differences were noticed in the angle linking the horizontal lines of the head and the superior crest of the spinal column before and after the treatment, with P = 0.73. The cervical curvature angle also failed to show any significant difference with P = 0.14.Fixed functional therapy with the Forsus™ device resulted in dentoalveolar and soft tissue alterations alone but did not alter the cervical spine posture.

Summary Objectives This controlled study aimed to evaluate the effects of Herbst therapy on the trabecular structure of the condyle and angulus mandible using fractal dimension analysis (FD-A) accompanied by skeletal cephalometric changes. Material and method The panoramic and cephalometric radiographs of 30 patients with skeletal Class II malocclusion treated with the Herbst appliance (C II-H group, mean age: 15.23 ± 1.08), 30 patients with skeletal Class II malocclusion that received fixed orthodontic treatment (C II-C group, mean age: 15.73 ± 1.38), and 30 patients with skeletal Class I malocclusion (C I-C group, mean age: 15.90 ± 1.30) were selected. FD-A was performed on the superoposterior region (C-SP) and centre of the condyles (C-C) and the mandibular angulus (Ang) on the panoramic radiographs taken at the pretreatment (T0), intermediate stage of treatment (T1), and posttreatment (T2) timepoints just like cephalometric analysis. Results Herbst therapy provided a statistically significant increase in SNB, ANS-Me, Na-Me, S-Go, Co-Gn and a decrease in ANB and overjet (P < 0.05). All skeletal changes remained stable during the fixed appliance treatment after Herbst. The FD values in C-C increased (P < 0.05), and C-SP values decreased (P < 0.05) during Herbst therapy, while after removal of the Herbst appliance, no significant change was observed despite an increase in C-SP. The Ang value did not change during Herbst treatment, but then increased significantly (P < 0.05). There was no significant change in the FD values of the C I-C and C II-C groups at any stage of treatment. The C-C and C-SP changes at T1–T0 period, C-SP and Ang changes at T2–T1 period, and C-C, C-SP, and Ang values at T2–T0 period were found higher in C II-H group compared with the C II-C group significantly (P < 0.05). Conclusion Herbst therapy changed the trabecular structure of the condyles in different directions at the superoposterior and central regions of the condyles, while the structural complexity of the angulus mandible, which did not change during the Herbst treatment, increased during the fixed orthodontic treatment after Herbst.

Aim: To evaluate the effects produced by functional orthodontic appliances at dental and skeletal level in relation to the level of skeletal maturation in class II patients. Study design: Longitudinal and observational study. Patients selected for the study had been wearing Sander Bite Jumping Appliance (SBJA) for at least 12 months; they were first diagnosed (T1) with skeletal class II according to Ricketts’ cephalometric analysis, and had had lateral cephalograms taken before and after orthopaedic treatment (T2). Variables studied at T1 and T2 were: facial convexity, inclination of the upper and lower incisors, and facial depth. Results were compared between T1 and T2 for each variable and in relation to cervical maturation stage (CVS) according to the Lamparski analysis. Statistical analysis was performed using Shapiro–Wilk, t-student, Analysis of Variance (ANOVA) and multiple comparison tests, taking as statistically significant a p-value Results: A final sample of 235 patients was obtained. Statistically significant differences were found in the inclination of the mandibular incisors between T1 and T2 and among the different cervical stages when the functional appliances were placed in CVS1 (p = 0.000), CVS2 (p = 0.04) or CVS5 (p = 0.048). For the remaining variables, significant differences were also found between T1 and T2, but these differences were similar in all cervical stages. Conclusions: A significant proclination of the mandibular incisors was found when the functional appliance was placed during CVS1, CVS2, or CVS5. Time of placement of the functional appliances was not statistically significant for the remaining variables studied.

Summary Background Patients with dental and skeletal Class II growth patterns present typical facial characteristics. Functional appliance (FA) therapy is one of the conventional orthodontic treatment modalities used to harmonize these facial imbalances. Objectives The aim of this systematic review was to investigate and summarize the effects of FAs on the facial soft tissues captured in three dimensions. Search methods A systematic search was conducted up to December 2020. Databases Medline (via PubMed), Embase (via Ovid), Web of Science, and Cochrane Central were searched without language restrictions. Selection criteria Randomized clinical trial (RCT)’s investigating the influence of FA therapy on the facial soft tissues in a non-cephalometric and three-dimensional (3D) manner, were included. Data collection and analysis Data extraction was independently undertaken by two authors. In case of conflict, a third author was consulted. RoB 2.0 tool was used to assess the risk of bias. A meta-analysis was performed for total facial height, upper lip length, lower lip length, commissural width, and facial depth. The single-step activation versus incremental approach was compared using a random effects model. Results Five studies were included in the qualitative synthesis of the systematic review. Facial height increased after FA therapy. Three studies met the criteria for the meta-analysis. The mean facial depth increased significantly (P Conclusions Current evidence suggests a positive influence of the FA therapy on the soft tissues in Class II patients. However, conclusions were drawn based on a two-dimensional analysis of 3D images, suggesting that more controlled studies using a comprehensive 3D analysis are necessary to confirm these results. Registration PROSPERO registration (CRD 42021224016).

Summary Background No reliable predictive factors for treatment (Tx) success and outcome quality in Class II:1 Tx have been identified yet. Objective To assess the influence of pre-Tx Class II severity and skeletal maturity on outcome quality after Herbst-multibracket appliance (MBA) Tx. Subjects and methods All Class II:1 patients who completed Herbst-MBA Tx between 1986 and 2014 at University of Giessen, Germany. Pre-Tx (T0), post-Tx (T1), and (if available) post-retention (≥24 months; T2) study casts were evaluated using the Peer Assessment Rating (PAR) index and the Ahlgren scale. Three occlusal severity (mild, moderate, and severe) and four skeletal maturity (pre-peak, peak, post-peak, and adult) subgroup categories were defined. Results Four hundred eight-five patients (age at T0: 14.4 ± 3.2 years) could be evaluated; post-retention (T3) data were available for 230 patients. For the total sample, the median PAR score was 32.4 ± 8.85 at T0, 8.0 ± 4.52 at T1, and 8.8 ± 5.11 at T2. Very low correlations between the subgroup categories (occlusal severity/skeletal maturity) and PAR-score reduction were detected both during Tx (r = 0.12/r = 0.05) and the total observation period (r = 0.17/r = 0.03). The overall outcome quality according to Ahlgren was: 17.0% excellent, 34.8% good, 43.8% acceptable, 2.2% unacceptable, and 2.2% not assessable. The association with the subgroup categories was: p = 0.019 (occlusal severity)/p = 0.820 (skeletal maturity). Limitations Retrospective study design with follow-up data was not available from all subjects and no data from untreated controls. Tx was performed by several physicians using different kind of MBAs. Conclusion Class II:1 Herbst-MBA Tx is an effective and successful Tx approach irrespective of pre-Tx skeletal maturity but dependent—to a certain extent—on Class II severity. Thus, when considering a Herbst appliance for Class II correction, neither of the two variables should considerably limit the indication.

Summary Objective To compare the skeletal and dentoalveolar changes in Angle Class II malocclusion subjects treated with the banded Mandibular Anterior Repositioning Appliance (Ba-MARA) and crowned MARA (Cr-MARA). Materials and methods This retrospective cohort study included 40 consecutively treated pubertal adolescents with Class II division 1 malocclusion who received full-fixed orthodontic appliances with a phase of orthopedic treatment using Ba-MARA (n = 20) or Cr-MARA (n = 20). The samples were compared with 20 untreated Class II controls obtained from the Michigan Growth Study. Lateral cephalograms were obtained pre-treatment (T1), post-MARA removal (T2), and post-full-fixed orthodontic treatment (T3). Results After MARA removal (T2-T1), the total mandibular length increased only in the Cr-MARA group compared to controls (Co-Gn = 5.4 mm; post-hoc P = 0.042). Overall dentoskeletal changes were less significant during the T3-T2 timepoint. After full-fixed orthodontic treatment (T3-T1), and after controlling for normal growth, both Ba- and Cr-MARA groups increased the total mandibular length by 3.1 mm and 3.8 mm respectively. Overjet decreased by 2.2 mm in Ba-MARA and 2.9 mm in Cr-MARA. The mandibular molars erupted and moved mesially in both treatment groups. The mandibular incisors proclined significantly in the Cr-MARA group in comparison to controls (IMPA = 7.1o, post-hoc P = 0.002). Conclusions Both MARA designs were effective in correcting the malocclusion by a combination of small skeletal and dental changes. Although significant differences in dentoskeletal outcomes were observed between the MARA groups and the controls, the differences between the two MARA designs were small and did not achieve statistical/clinical significance.

To systematically review the effects of functional appliances (FA) using incremental vs maximal mandibular advancement regarding cephalometric measurements in class II malocclusion individuals and to assess patient-centred-outcomes. Six electronic databases were searched without restrictions up to April 2020. We included randomized and non-randomized controlled trials using identical FA. Trials involving participants who used adjunct appliances, inter-maxillary elastics, who received surgical treatment or that recruited individuals with cleft lip/palate or craniofacial deformity/syndrome were excluded. Risks of bias assessments were performed using the Cochrane risk of bias tool-2 and ROBINS-I tools. Mean differences (MD) with their 95% confidence intervals were calculated from random-effects meta-analyses. The GRADE tool was used to assess the certainty of the evidence. Six studies were included. Low to very low certainty of evidence indicated that incremental mandibular advancement resulted in greater gains in mandibular length (MD = 0.89 [0.38, 1.34], P = .0005), anterior mandibular displacement (MD = 0.73 [0.40, 1.06], P .0001) and SNB angle (MD = 0.44 [0.02, 0.85], P = .04). No significant differences were found for maxillary, dento-alveolar and upper airway outcomes between construction bite protocols (P .05). Study design and appliance-related factors influenced the results of the subgroup analyses. Existing evidence is inadequate to assess patient-related response and long-term outcome could not be assessed. Currently, there are a heterogeneous number of studies with low quality and methodological issues can lead to biases that strongly limit an evidence-based conclusion. Weak evidence suggests gains in mandibular skeletal parameters in the short term using FA with incremental mandibular advancement. Randomized trials evaluating key topics such as patient-centred outcomes need to be conducted to guide clinical management. PROSPERO (CRD42019147436).

Difference in the functional orthopedic effect between stepwise mandibular advancement (SWA) and single-step mandibular advancement (SSA) in Angle class II patients remains unclarified.To compare the treatment effects of SWA and SSA on skeletal and dentoalveolar changes in class II patients.Randomized controlled trials (RCTs) and nonrandomized studies that compared differences in skeletal and dentoalveolar effects on class II patients between SWA and SSA were identified in PubMed, Embase, CENTRAL, and Web of Science. The grey literature was also searched. The primary outcomes were the mandibular length, L1-MP, and (ANB). Secondary outcomes included Pog sagittal, SNB, overjet, and mandibular plane angle.Seven studies, including three RCTs and four cohort studies, were retrieved. Meta-analyses revealed pooled mean differences (95% confidence interval) of 0.79 mm (0.45 to 1.12 mm) for Pog sagittal, 0.53° (0.19 to 0.87°) for SNB, -0.51° (-0.83 to -0.20°) for ANB, -0.17° (-0.72 to 0.39°) for the mandibular plane angle, -0.41 mm (-0.90 to 0.09 mm) for overjet, -1.87° (-3.23 to -0.52°) for L1-MP, and 1.03 mm (0.63 to 1.42 mm) for the mandibular length. Publication bias was not observed, except for Pog sagittal. The quality of evidence for each outcome was judged as low (mandibular length, SNB and overjet) and very low (Pog sagittal, ANB, L1-MP and mandibular plane angle).Although the magnitude of differences in clinical practice was limited, SWA might be more appropriate because it produces a greater skeletal change and less dental compensation than SSA. As the level of current evidence is low, more high-quality RCTs are needed.HINTERGRUND: Der Unterschied in der funktionskieferorthopädischen Wirkung zwischen der schrittweisen (SWA) und der einstufigen Unterkiefervorverlagerung (SSA) bei Patienten der Angle-Klasse II ist nach wie vor nicht geklärt. ZIEL: Vergleich der Behandlungseffekte von SWA und SSA auf skelettale und dentoalveoläre Veränderungen bei Klasse-II-Patienten.In PubMed, Embase, CENTRAL und Web of Science wurden randomisierte kontrollierte Studien (RCTs) und nichtrandomisierte Studien identifiziert, welche die Effekte von SWA und SSA auf das Skelett und die dentoalveolären Strukturen bei Patienten der Klasse II miteinander verglichen. Auch graue Literatur wurde durchsucht. Die primären Endpunkte waren Unterkieferlänge, L1-MP und ANB, zu den sekundären Endpunkten zählten Pog sagittal, SNB, Overjet und Unterkieferebenenwinkel.Sieben Studien, darunter 3 RCTs und 4 Kohortenstudien, wurden eingeschlossen. Metaanalysen ergaben gepoolte mittlere Unterschiede (95% Konfidenzintervall) von 0,79 mm (0,45 bis 1,12 mm) für Pog sagittal, 0,53° (0,19 bis 0,87°) für SNB, −0,51° (−0,83 bis −0,20°) für ANB, -0,17° (−0,72 bis 0,39°) für den Unterkieferebenenwinkel, −0,41 mm (−0,90 bis 0,09 mm) für den Overjet, −1,87° (−3,23 bis −0,52°) für L1-MP und 1,03 mm (0,63 bis 1,42 mm) für die Unterkieferlänge. Ein Publikationsbias wurde mit Ausnahme von Pog sagittal nicht beobachtet. Die Qualität der Evidenz für jedes Ergebnis wurde als gering (Länge des Unterkiefers, SNB und Overjet) bzw. sehr gering (Pog sagittal, ANB, L1-MP und Winkel der Unterkieferebene) beurteilt.Auch wenn das Ausmaß der Unterschiede in der klinischen Praxis begrenzt war, könnte die SWA geeigneter sein, da sie eine größere skelettale Veränderung und weniger dentale Kompensation als die SSA bewirkt. Da das Niveau der aktuellen Evidenz gering ist, sind mehr qualitativ hochwertige RCTs erforderlich.

Background Functional appliances has been used for treatment of skeletal Class II malocclusion for a long time; however, the real skeletal effects, mandibular growth particularly, remain insufficient. Several auxiliary approaches have been attempted with the hope of enhancing treatment effects. In this review, we summarize and discuss the use of additional nutrition and hormones to assist the functional appliance treatment on patients with skeletal Class II malocclusion. Methods Relevant articles were identified by electronic research in MEDLINE Ovid using keywords such as “nutrition,” “hormone,” “functional appliance,” “orthodontics,” “maxillofacial development,” and “maxillofacial abnormalities.” References of related articles were assessed for relevant studies to identify additional published references. Results The literature search yielded 239 studies. According to the current literature, use of additional nutrition and hormones, including growth hormones, sex hormones, insulin, and insulin-like growth factor I, seem to improve the effects of functional appliance treatment on patients with skeletal Class II malocclusion. Conclusions The current evidence indicates that additional nutrition or hormones might improve the treatment effects on mandibular hypoplasia compared with the functional appliance alone, which is a promising approach and calls for further studies.

Objectives To determine the prevalence, incidence, and changes in magnitude of labial gingival recessions (LGR) in class II:2 patients during Herbst-Multibracket appliance (Herbst-MBA) treatment (Tx) plus retention. Subjects and methods All class II:2 patients of the Department of Orthodontics, University of Giessen, Germany who completed Herbst-MBA Tx (mean pre-Tx age 15.6 years). The cohort had undergone a Herbst phase (mean 8.1 months) as well as a subsequent MBA phase (mean 14.4 months). Study casts were evaluated from pre-Tx and after Herbst-MBA Tx plus ≥ 24 months of retention. Results Ratable pre-Tx and post-retention study casts (total observation period 53.5 ± 10.3 months) were available from 94 out of 173 patients. No significant difference existed regarding pre-Tx LGR data between patients with and without complete records. The prevalence for teeth with LGR ≥ 0.5 mm was 1.4% pre-Tx respectively 6.7% post-retention. The highest values of up to 5.3% (pre-Tx) and 20.2% (post-retention) were determined for the upper first premolars and lower central incisors. Incidence values of 4.7% (all teeth) and up to 14.9% (upper first right premolars) respectively 11.1% (lower central incisors) were calculated (LGR ≥ 0.5 mm). The overall LGR mean magnitudes were 0.01 mm pre-Tx respectively 0.06 mm post-retention. Conclusions For the prevalence of LGR ≥ 0.5 mm an average increase of 5.3% was determined during ≈ 4.5 years of Herbst-MBA Tx plus retention. The highest incidence was seen for lower central incisors and upper right premolars (11.1/14.9%). The overall LGR mean magnitude increased by 0.05 mm. Clinical relevance Herbst-MBA Tx is a common approach for class II:2 malocclusions. Very little, however, is known regarding LGR development in respective patients.

Objective To evaluate the esthetic perceptions of orthodontists and laypersons for facial profile changes after orthodontic treatment using Herbst or Forsus appliances. Materials and Methods Pre- and posttreatment facial profile contour images of 20 Class II patients treated with Herbst (group H; n = 10) and Forsus (group F; n = 10) appliances were analyzed by 30 orthodontists and 30 laypersons, who graded them from 1 (unattractive) to 10 (very attractive) using a visual analog scale. Two assessments were carried out with a 15 day-interval. In the first evaluation, 40 images were presented in a random sequence. In the second evaluation, initial and final facial profile images of each patient were randomly presented side by side. To compare groups in relation to treatment method, Mann-Whitney tests were used. To evaluate differences between time points, Wilcoxon tests were used. Results In the first evaluation, there was a significant difference between initial and final images only for group H, for both laypersons (P = .017) and orthodontists (P = .037). There was also a significant difference between laypersons and orthodontists in their ratings of posttreatment Herbst appliance profiles (P = .028). There was no significant difference between initial and final facial profile images for group F and no significant differences between or within evaluator groups in their ratings of initial or final Forsus appliance profiles. In the second evaluation, there was a significant difference between appliance groups only for laypersons, who considered cases treated with the Herbst appliance more attractive than those treated with the Forsus (P = .031). Laypersons also considered Herbst profiles more attractive than did orthodontists (P = .047). Conclusions Class II malocclusion treatment using the Herbst appliance may produce a more esthetically improved facial profile silhouette compared with Forsus appliances. The magnitude of perceived changes may not be considered clinically relevant.

To investigate if treatment outcome in patients with Class II division 1 malocclusion treated by a variety of approaches is affected by masticatory muscle capacity.Seventy-four children with Class II division 1 malocclusion were included in the present study. These were divided into 54 children (10.4 ± 1.6 years of age) treated with fixed appliances including headgear and/or Class II intermaxillary elastics, 12 children (9.9 ± 1.9 years of age) treated with functional appliances and 8 children treated with fixed appliances and other means of treatment. Ultrasonographic masseter muscle thickness measurements were taken before treatment, while lateral cephalograms were taken before and after treatment.Multivariate linear regression analysis was used to assess the association between masseter muscle thickness and treatment outcomes, as well as the gonial angle and treatment outcomes.In children with Class II division 1 malocclusion treated by means other than functional appliances, treatment outcome is not associated with masseter thickness. This may be the case since the application of intermaxillary forces and torque application may offset the functional component in tooth movement. Outcomes following functional appliance treatment may be partly determined by the masticatory muscles. During functional treatment, children with a weaker masticatory system show greater dentoalveolar compensation. This is however not maintained during the second phase of fixed appliance treatment.