Comparison of Two Protocols for the Treatment of Class 2 Malocclusion

Purpose: The purpose of this study was to compare the outcomes of the treatment with the twin block and modified twin block appliances in growing patients with Class 2 malocclusion. Materials and Methods: A cephalometric analysis was performed in 51 patients. The twin block sample consisted of 23 patients, 10-girls and 13-boys (mean age 10.46±0.71 years at the start of treatment, T1, and 12.84±0.78 years at the end of active treatment, T2). The modified twin block sample consisted of 28 patients, 18 girls and 15 boys (mean age 11.78±0.91 years at T1, and 13.32±0.56 years at T2). The twin block activators were used during the day, except for eating time, and the modified ones were used only at night. Duration of the treatment was 16-20 months. The changes from T2 to T1 and the differences between the groups were compared with the analysis of variance. Results: SNB angle in the twin block group showed 1.25±1.39 degrees change and in the modified twin block group, it exhibited 3.69±1.01 degrees change. Overjet in the group with twin block decreased 4.58±1.59 mm, and in the group with modified twin block it decreased 4.43±1.41 mm. In the modified twin block group, there was more retrusion of upper incisors in comparison with the twin block group. Accordingly, under the effect of modified twin block, retrusion of the upper lip was observed. Conclusion: Through modifying the twin block appliance, it is possible to ensure the comfort of the patients by reducing the daily usage, to reposition the mandibula forward and to correct overjet and sagittal dento-skeletal relationships without increasing facial height and to improve positions of upper incisors and lips.

Comparison of AdvanSync2® and Twin Block Appliances in Treatment of Class II Malocclusion With Retrognathic Mandible—An Observational Retrospective Study

Objectives: To evaluate the treatment outcomes between Twin Block and AdvanSync2® appliances by comparing the skeletal, dentoalveolar, and soft tissue changes. Materials and Methods: Radiographic data of 20 patients were retrospectively analyzed. Data were selected from patients in their skeletal growth spurt as evaluated by the cervical vertebral maturation method (CVMI 2, 3, and 4), with class II malocclusion characterized with retrognathic mandible (ANB > 4°, SNB < 77°, FMA = 25 ± 5°, overjet > 5 mm). There were 10 patients in each group that underwent orthodontic correction for class II malocclusion: either using Twin Block or AdvanSync2®. Independent t test and Paired t test and chi-square tests were used for the data analysis. The level of statistical significance was set at P value ≤.05. Results: The chronological and skeletal age were similar in both the groups. Records were taken for the functional treatment with mean treatment span of 8 ± 1 month. Changes in SNB (group I = 1.59°, group II = 3.11°) ( P < .01), Co-Gn (group I = 2.89 mm, group II = 5.34 mm), and U1-L1° (group I = −1.51°, group II = 2.97°) showed statistically different outcome between the groups, when the pre-post data were studied. Rest of the variables—cranial base, maxillary skeletal, mandibular skeletal, intermaxillary, vertical skeletal, maxillary dentoalveolar, mandibular dentoalveolar, and soft tissue—showed similar outcome ( P > .05). Conclusion: Both appliances lead to desirable outcomes in the correction of class II malocclusion. AdvanSync2® resulted in inducing more of changes in SNB and effective mandibular length as compared to Twin Block. Overjet and molar relation improved significantly with both the appliances. Both the appliances resulted in similar skeletal, dentoalveolar, and soft tissue changes.

Comparative Analysis of Dentoskeletal Changes of the Twin Block Appliance and the AdvanSync2 Appliance in Treatment of Skeletal Class-II Malocclusion in Pakistani Population: A Randomized Clinical Trial

Objective This study aimed to compare dentoskeletal changes in skeletal class-II malocclusion with removable twin block appliance and fixed AdvanSync2 appliance. Materials and Methods A prospective randomized clinical trial was conducted over a span of 1 year at AFID at Rawalpindi. Thirty patients with skeletal class-II malocclusion, 16 males (53.3%) and 14 females (46.6%), were randomly selected and divided in two equal groups (15 each) to be treated with either fixed functional appliances (FFAs) or with removable functional appliances (RFAs). Out of 30 patients, 15 between cervical vertebral maturation (CVM) stages of 2 and 3 were treated with RFA (twin block appliances) and remaining 15 between CVM stages of 4 and 5 were treated with FFA (AdvanSync2 appliances). Pretreatment (T1) and posttreatment (T2), angular variable, and linear variable were measured to compare the dentoskeletal effects between the two groups. Statitical Analysis Paired sample t-test was used to assess significant difference between variables at T1 (Pre-treatment) and T2 (Post-treatment) stage for both RFA and FFA group. Comparison among the RFA and FFA group was made using non-parametric Mann-Whitney U Test. IBM SPSS version 25.0 was used for evaluation. Results No significant difference was found in angular variables between the RFA and FFA groups (p > 0.05) with the exception of linear variables. Sella-posterior nasal spine (S-PNS) length significantly increased and Jarabak's ratio significantly decreased for FFA group (p = 0.010 and 0.045, respectively), when compared with RFA group. Conclusion Both the appliances, twin block (RFA) and AdvanSync2 (FFA), are effective for correction of skeletal class-II malocclusion. Both the appliances produced similar effects in the sagittal plane but for better vertical control twin block should be the appliance of choice. AdvanSync2 appliance could be preferred over twin block appliance when dentoalveolar and slight retrusive effect on the maxilla is desired especially for individuals in postpubertal growth spurt.

Treatment of Class II Malocclusion With Removable Functional Appliances: A Narrative Review

Around half of all malocclusions that need orthodontic treatment are class II in nature. Patients with class II malocclusion primarily seek treatment for aesthetic improvement. Most of the skeletal class II malocclusions are because of mandibular deficiency, and can be best treated during the growing phase of development by removable functional appliances. The objective of this review is to evaluate and compare skeletal and dentoalveolar effects of various removable functional appliances in the treatment of class II malocclusion. Manual and electronic databases were searched, and out of 5,711 articles, 221 abstracts were shortlisted and reviewed. A total of 19 articles that fulfilled the selection criteria were then retrieved and analyzed. A significant increase in mandibular length and dentoalveolar effects with an increase in vertical dimension in a short time were observed with Twin-Block appliance treatment, followed by Bionator appliance treatment. The long-term stability of results achieved with Twin-Block appliance treatment is still questionable. In addition, Frankel appliance treatment effects are more skeletal in nature, with better control in the vertical dimension. However, it takes a more extended treatment duration to produce similar effects. Based on available evidence, we are convinced that removable functional appliances are valuable tools for correction of the class II malocclusion at a growing age with horizontal growth pattern.

Dentoskeletal effects of Twin Block appliance in patients with Class II malocclusion

Background and aim. Class II malocclusions are most commonly seen in orthodontic practice and in the recent times Twin Block appliance has been the most popular and widely used among removable functional appliances for the correction of Class II malocclusion in growing patients. The aim of this retrospective study was to evaluate the dentoskeletal effects produced by the Twin Block appliance for the correction of Class II division 1 malocclusion with retrognathic mandible. Methods. Pre-treatment (T1) and post-treatment (T2) lateral cephalograms of 30 patients treated with Twin Block appliance (mean age = 10.8 ± 1.2 years) for the correction of class II division 1 malocclusion were compared with the 30 untreated class II control patients (mean age 11.2 ± 0.8 years) who did not undergo any treatment during this period. Both the groups were evaluated for the dentoskeletal changes using 24 angular and linear cephalometric measurements. The differences between the pre and post-treatment were calculated using a paired t-test. Results. The cephalometric analysis revealed that the Twin Block appliance stimulated mandibular growth and statistically significant differences were found between the two groups. Twin Block patients showed a statistically very high significant (p<0.001) increase in mandibular length (6.02 mm) compared with the control group (0.3 mm). ‘Headgear effect’ on the maxilla, increase in lower anterior facial height, significant reduction of overjet, overbite and Class I molar relationship was achieved in the Twin Block group. However, no significant changes appeared in the control group. Conclusion: The results of the present study conclude that the Twin Block appliance is effective in the treatment of Class II malocclusion and this is due to a combination of skeletal and dentoalveolar changes in both the arches.

Debonding Analysis and Identification of the Interface Between Sleeper and Track Slab for Twin-Block Slab Tracks

For China Railway Track System (CRTS) I twin-block slab tracks, the interface between the sleeper and track slab is susceptible to damage under the coupled effect of long-term train load and external environment factors. In order to analyze the damage behavior and identify the type of debonding at the interface, this paper established a three-dimensional finite element model and introduced the cohesion zone model and concrete damaged plasticity model to simulate the interface damage and the inner-layer damage of the track slab, respectively. The interface debonding induced by the temperature effect was analyzed, and the debonding types were identified based on the obtained vertical vibration responses of the sleeper surface under the train load. The results reveal that the damage mainly occurs on the bottom and lateral sides at the interface under the temperature load. The track model can be refined further to obtain higher analysis accuracy with acceptable calculation time using the sequential loading method. The 26 damage features derived from the time domain, frequency domain, and time–frequency domain are in good representativeness in reflecting the damage information hidden in the vibration signals. Among them, the peak values (maximum vertical acceleration of the sleeper) are 55.0, 56.7, 60.3, and 61.6[Formula: see text]m/s2 for no debonding, debonding on the lateral side, debonding at the bottom, and debonding on the longitudinal side of the interface under train load, respectively. Moreover, the identification accuracy of the debonding type can reach 93.75% combining the particle swarm algorithm and support vector machine. It indicates that the proposed identification method is effective and reliable to provide theoretical guidance for developing scientific maintenance and repair strategies for twin-block slab tracks.