Twin-block Treatment Research Articles

Prediction on the chin advancement of the twin block functional appliance in growing Chinese patients using the cephalometric markers: a retrospective study.

In spite of the widespread use of functional appliances, broad variations were applied the treatment response. The aim of this study is to investigate the pre-treatment cephalometric predictors on the chin advancement of twin-block in growing Chinese patients with class II malocclusion. After screening, 90 patients treated by twin-block were included in the study. The treatment outcome was assessed by the alterations in the distance of skeletal pogonion (Pog) to the vertical reference plane perpendicular to the Frankfurt plane (ΔPog-VRP). Moreover, ΔPog-VRP was divided by the cranial growth indicated by the Nasion to Basion changes (ΔN-Ba) to minimize the growth discrepancy among individuals (adjΔPog-VRP). Patients with ΔPog-VRP/adjΔPog-VRP above the median value were categorized into good response group (GRG/adjGRG, N = 45), while the rest were poor response group (PRG/adjPRG, N = 45). Independent t-test was used to compare the pre-treatment cephalometric measurements between GRG/adjGRG and PRG/adjPRG. Stepwise multivariate regression models were used to determine the pre-treatment cephalometric predictors for the chin advancement. Generally, there were not any significant differences between GRG/adjGRG and PRG/adjPRG regarding age, gender and cervical stage before twin-block treatment. Patients from GRG had significantly reduced cephalometric measurements in the vertical dimensions, including ∠N-Go-Me, ∠Mandibular plane-Occlusal plane (∠MP-OP) and the sum of angles (p < 0.05) in comparison to PRG. When the individual growth was taken account, similar findings were observed. The patients from adjGRG had a significantly lower ∠Sella Nasion line-MP (∠SN-MP), ∠Ar-Go-Me and ∠N-Go-Me, as well as an increased Posterior facial height (PFH)/Anterior facial height (AFH) (p < 0.05) compared with their counterparts. ∠N-Go-Me variable was the independent predictor on Pog advancement with (β = -0.26, 95% CI: -0.06 to -0.01, p = 0.01) and without (β = -0.29, 95% CI: -0.06 to -0.01, p < 0.01) adjustments on individual growth. The results of this study showed that patients with a reduced N-Go-Me angle are more likely to experience a greater chin advancement following twin-block treatment.

Functional therapy and adenotonsillectomy clinical trial for class II malocclusion (FACT-II): protocol for a randomised controlled trial

IntroductionClass II malocclusion with mandibular retrognathia is a common complication of paediatric obstructive sleep apnoea (OSA), often accompanied by transverse maxillary deficiency. In early orthodontic treatment, a twin block (TB)...

Evaluation of the External Soft Tissue Changes Following the Correction of Class II Skeletal Malocclusion in the Adolescence Period Using Removable and Fixed Functional Appliances: A Systematic Review and Meta-Analysis.

In this systematic review, we aimed to assess the current evidence regarding the effectiveness of functional treatment with both removable and fixed appliances to normalize the external soft tissue for skeletal class II adolescent individuals. We performed a broad electronic search to retrieve relevant studies from nine databases to identify randomized controlled trials (RCTs) and controlled clinical trials (CCTs) that investigated soft tissue changes following functional treatment and evaluated the changes using 2D lateral cephalometric radiographsand 3D-optical surface laser scanning. A total of three RCTs and eight CCTs were included. Ages ranged from 11 to 16 years with the fixed functional appliances, and from eight to 12 years with the removable ones, including 689 skeletal class II patients. Version 2 of Cochran's risk-of-bias (RoB2), and the risk of bias in non-randomized studies of interventions (ROBIN-I) were used to assess the risk of bias for the included papers. Of the 11 eligible studies, three studies were included in the meta-analysis to assess the upper and lower lip position in relation to the E-line (Ricketts's aesthetic line) in addition to the nasolabial angle. The meta-analysis showed that the upper lip retracted after functional treatment with Twin-block in relation to E-line (mean difference (MD) = -1.93; 95% CI: -2.37, -1.50; p < 0.00001; χ² = 5.43; p = 0.07; I2 = 63%), while the lower lip position did not change after functional treatment with Twin-block in relation to E-line (MD = 0.03; 95% CI: -0.56, 0.61; p = 0.92; χ² = 1.74; p = 0.42; I2 = 0%). The nasolabial angle increased after Twin-block treatment (MD = 5.75; 95% CI: 4.57, 6.93;p < 0.00001; χ² = 6.77; p = 0.03; I2 = 70%). The mentolabial angle and Z-angle also increased after functional therapy, where the facial convexity angle decreased, regardless of the functional devices used. On the other hand, using the 3D-optical surface laser scanning showed that the upper lip length and the commissural width did not change following therapy, but the lower lip increased in length, as well as the total face height. More high-quality RCTs are required to obtain accurate evidence in this field.

Efficacy of a modified twin block appliance compared with the traditional twin block appliance in children with hyperdivergent mandibular retrognathia: protocol for a single-centre, single-blind, randomised controlled trial

IntroductionCompensatory mouth breathing, caused by nasopharyngeal obstructive diseases, is the main cause of hyperdivergent mandibular retrognathia in children. Such deformities require effective growth guidance before pubertal growth peaks. The traditional...

Fixed vs Removable Twin-block Treatment in Skeletal Class II Malocclusion

Fixed vs Removable Twin-block Treatment in Skeletal Class II Malocclusion

Evaluation of Changes in Soft and Hard Tissues of TMJ among Class II Division 2 Patients after Prefunctional Orthodontics and Twin Block Functional Appliance Therapy: A Prospective MRI Study.

No study has been conducted to explore soft and hard tissue changes brought by functional appliances within the temporomandibular joint (TMJ) after correction of class II division 2 (div 2) malocclusion. Hence, we planned this study to evaluate the mandibular condyle disk-fossa relationship before and after prefunctional and twin block therapy using a magnetic resonance imaging (MRI) scan. This prospective observational study was conducted among 14 males treated with prefunctional appliances for 3-6 months, followed by 6-9 months of fixed mechanotherapy. MRI scan was evaluated for changes in the TMJ at baseline after completion of prefunctional phase and after completion of functional appliance therapy. At pretreatment, there was a flat contour on the posterosuperior surface of the condyles and a notch-like projection on its anterior surface. After functional appliance therapy, slight convexity appeared on the posterosuperior surface of the condyle and the prominence of the notch was reduced. There was a statistically significant anterior shift of condyles both after prefunctional and twin block treatment. The meniscus on both sides had significantly shifted posteriorly over three stages with respect to the posterior condylar (PC) plane and Frankfort horizontal (FH) plane. The superior joint space had significantly increased with significant linear glenoid fossa displacement between pre and posttreatment stages. Prefunctional orthodontics induced favorable changes in TMJ soft and hard tissues of patients, but they were not sufficient to place the soft and hard tissues in their normal positions. A functional appliance phase is needed to place the TMJ in their respective normal positions. Patel B, Kukreja MK, Gupta A, et al. Evaluation of Changes in Soft and Hard Tissues of TMJ among Class II Division 2 Patients after Prefunctional Orthodontics and Twin Block Functional Appliance Therapy: A Prospective MRI Study. Int J Clin Pediatr Dent 2022;15(5):479-488.

Comparison of the effects of removable functional appliance therapy applied in pubertal and postpubertal periods: A retrospective cephalometric and fractal analyses study

In this study, we compared the effects of functional treatment with Twin-block appliance on the bony architectures of the maxilla and mandible by fractal dimension (FD) analysis, and the skeletal and dentoalveolar effects by cephalometric analysis, in pubertal and postpubertal patients with Class II malocclusion. This study comprised 60 patients who underwent Twin-block treatment. Group 1 consisted of 30 patients in the pubertal period (6 boys and 24 girls; mean age 12.27 ± 1.35 years), whereas group 2 consisted of 30 patients in the postpubertal period (6 boys and 24 girls; mean age 13.73 ± 1.51 years). FD analysis was performed on the patients before and after Twin-block panoramic and lateral cephalometric radiographs. Cephalometric analysis was also conducted. Paired and Student t tests were used to compare the parametric data, and Wilcoxon signed rank and Mann-Whitney U tests were conducted to compare the nonparametric data. SNB, Pg-N, N-Me, ANS-Me, IMPA, L1/NB, Co-Gn, Go-Gn, S-Go, Co-Go, and Go-Me significantly increased in both groups after treatment. FD values of tuber, condyle, and molar regions significantly decreased in group 1, whereas no significant differences were observed in group 2 after treatment. In the pubertal period, the Twin-block appliance resulted in skeletal correction by causing bone remodeling and reshaping in both jaws along with the dentoalveolar correction. In the postpubertal period, Twin-block had no significant effect on the bone trabecular arrangement in the investigated areas but produced cephalometric improvement to a certain extent with lower skeletal and higher dental impact.

Changes in Angulation and Eruption Space of Developing Mandibular Third Molars Following Twin Block Treatment

The aim of this study was to assess the effects of twin block functional appliance three dimensionally on mandibular third molars angulation and eruption space. This retrospective study included cone beam computer tomography (CBCTs) of 34 Class II females (11.84 ± 0.94 years) who were divided into 2 groups. The first group received a standard twin block appliance (intervention group), while the other was considered as a control. CBCT images were obtained for all patients before the start of the intervention (T0) and after the active phase (9.4 ± 1.33 months) in the intervention group and at the beginning (T0) and after the observation period (T1) in the control group (8.12 ± 2.72 months). Measurements for the retromolar space were performed on the axial views, while those for molar angulation were performed on sagittal views as well as CBCT panoramic reformatted images. Both twin block and control groups showed non-significant changes in the angular measurements (sagittal L8/MP° and panoramic L8/MP°) denoting lack of change in the angulation of the third molars in relation to the mandibular plane after treatment. On the other hand, retromolar spaces showed a statistically significant increase (P ≤ .05) in both groups. The change was much significant for the twin block group, measuring 1.95 mm and 1.56 mm on the right and left sides, respectively, as compared to the control group which revealed less than 1 mm increase in the retromolar space on both the right and left sides. In spite of their positive impact on the retromolar space, twin block bite jumping appliances have a non-significant influence on the angulation of the developing mandibular third molars.

Effect of Twin-block Appliance on Pharyngeal Airway, Sleep Patterns, and Lung Volume in Children with Class II Malocclusion

In this study, we sought to evaluate the effect of the twin-block appliance on pharyngeal airway dimensions, sleep patterns, and lung volumes in growing children with class II malocclusion with a retrognathic mandible. Twenty children aged 9-12 years with class II malocclusion with a retrognathic mandible participated in the study. A validated sleep questionnaire assessed the sleep patterns and the sleep problems of the children. The pre-treatment cephalometric variables and the pharyngeal airway passage (PAP) dimensions were analyzed. Spirometry tests were performed to evaluate lung volumes. A custom-made twin-block appliance was fabricated, and children were instructed to wear it for a minimum of 10 months. All variables including sleep problems, cephalometric variables, and pharyngeal airway measurements were evaluated post-treatment. Spirometry tests were re-evaluated at the end of the twin-block treatment. All data were statistically analyzed. Post-twin-block appliance treatment, there was a definite decrease in snoring, noisy breathing, and sleeping with mouth open. The sella-nasion to B point angle (SNB), mandibular length, the depths of oropharynx, nasopharynx, and hypopharynx as well as the height of nasopharynx (HNP) were significantly increased post-treatment (p <0.001). The length and thickness of soft palate (SPI) increased significantly (p <0.001), while its inclination decreased significantly (p <0.001). We found improvements in forced vital capacity (FVC) and forced expiratory volume at 1 second (FEV1); however, the changes were statistically not significant (p = 0.88 and p = 0.78). Twin-block appliance significantly increased the pharyngeal airway dimensions and improved the length and thickness of the soft palate in children with class II malocclusion. Post-twin-block treatment showed a considerable reduction in the sleep problems of the children. The lung volume measurements showed improvement; however, it was not statistically significant. Twin block may be used not only to correct the facial disharmony of children with a retrognathic mandible but also to improve the airway dimensions and lung volume as well as to reduce the sleep-disordered symptoms.

Comparison of the effects of activator and twin block treatment on skeletal, dental and soft tissues

Background: The aim of this study was to evaluate the effects of activator and Twin Block appliances on the patient’s profile. To evaluate skeletal, dental and soft tissue changes after treatment of Class II division 1 malocclusion with activator and Twin block appliances. Methods: The study included 30 skeletal Class II patients, 15 girls and 15 boys, mean age: 10.5 ± 0.15 years who were randomly allocated to one of two functional appliance treatment groups. Pretreatment (T0) and post functional appliance therapy (T1) lateral cephalograms of 30 patients were evaluated. The skeletal, dentoalveolar and soft tissue changes were evaluated in both groups on standardized lateral cephalograms taken with the same cephalostat before (T0) and after (T1) functional appliance therapy. The groups were compared at T0 and T1 using analysis of variance, and treatment/observation differences (T1−T0) were evaluated with the Kruskal–Wallis test. The Student’s t test was used, with a significance level of P

Development of a Prediction Model for Short-Term Success of Functional Treatment of Class II Malocclusion.

(1) Background: The nature of the changes that contribute to Class II correction with functional appliances is still controversial. A broad variation in treatment responses has been reported. The purpose of this study was to find cephalometric predictors for individual patient responsiveness to twin-block treatment in patients with Class II Division 1 malocclusion; (2) Methods: The study was performed on a sample of 39 pubertal patients (21 females, 18 males) treated with the twin block appliance. Lateral cephalograms were available at the start of the treatment (T1) and at the end of functional therapy (T2). The outcome variable was the T2–T1 change in the sagittal position of the soft tissue pogonion with respect to the vertical line perpendicular to the Frankfort plane and passing through point subnasale. The predictive variables were age, gender at T1, and all the cephalometric parameters measured T1. Forward stepwise linear regression with p value to enter 0.05 and p value to leave 0.10 was applied; (3) Results: The only significant predictive variable that was selected was the Co–Go–Me angle (p = 0.000); (4) Conclusions: A greater advancement of the soft tissue chin on the profile is expected with smaller pretreatment values of Co–Go–Me angle.

Three-dimensional cone beam computed tomography analysis of temporomandibular joint response to the Twin-block functional appliance.

ObjectiveTo propose a three-dimensional (3D) method for evaluating temporomandibular joint (TMJ) changes during Twin-block treatment.MethodsSeventeen patients with Class II division 1 malocclusion treated using Twin-block and nine untreated patients with a similar malocclusion were included in this research. We collected their cone beam computed tomography (CBCT) data from before and 8 months after treatment. Segmentations were constructed using ITK-SNAP. Condylar volume and superficial area were measured using 3D Slicer. The 3D landmarks were identified on CBCT images by using Dolphin software to assess the condylar positional relationship. 3D models of the mandible and glenoid fossa of the patients were constructed and registered via voxel-based superimposition using 3D Slicer. Thereafter, skeletal changes could be visualized using 3DMeshMetric in any direction of the superimposition on a color-coded map. All the superimpositions were measured using the same scale on the distance color-coded map, in which red color represents overgrowth and blue color represents resorption.ResultsSignificant differences were observed in condylar volume, superficial area, and condylar position in both groups after 8 months. Compared with the control group (CG), the Twin-block group exhibited more obvious condyle-fossa modifications and joint positional changes. Moreover, on the color-coded map, more obvious condyle-fossa modifications could be observed in the posterior and superior directions in the Twin-block group than in the CG.ConclusionsWe successfully established a 3D method for measuring and evaluating TMJ changes caused by Twin-block treatment. The treatment produced a larger condylar size and caused condylar positional changes.

Changes in soft tissue facial profile of class II skeletal malocclusion patients with retrognathic mandible treated with twin block appliance

Introduction: The soft tissue aspect in orthodontics treatment has gained attention in the last few years. The soft tissue profile is said to reflect the underlying skeletal profile, which causes a convex profile in patients with class II skeletal malocclusion. This research was aimed to determine the changes in the soft tissue facial profile of class II skeletal malocclusion patients with retrognathic mandible after twin block treatment. Methods: The type of research used in this study was retrospective descriptive research with paired t-test. The population was children aged 10-13 years old with class II skeletal malocclusion that were treated with twin block appliance in the Faculty of Dentistry Universitas Padjadjaran, Indonesia. The results of soft tissue changes before and after twin block treatment were compared. Results: There was an insignificant increase in soft tissue profile angle and Holdaway’s soft tissue angle after twin block treatment (p &gt; 0.05). Whereas, Holdaway’s H-angle was decreasing and Merrifield’s Z-angle was increasing after twin block treatment, with statistically significant difference (p &lt; 0.05). Conclusion: There was a decrease of H-angle, indicates a reduction in facial convexity and improvement of the facial profile after twin block treatment, but no difference in soft tissue profile angle and Holdaway’s soft tissue angle after twin block treatment. Keywords: Facial soft tissue profile, class II skeletal malocclusion, retrognathic mandible, twin block appliance

Evaluation of changes in the upper airway after Twin Block treatment in patients with Class II malocclusion.

The purpose of this prospective case control study is to describe in growing patients with mandibular hypoplasia, treatment outcomes following functional therapy in terms of volumetric changes in nasopharynx and oropharynx, that is, upper and lower pharynx. We recruited 60 study participants aged between 8 and 12 years having mandibular Class II malocclusion and a reduced upper airway (UA) size, as determined by McNamara cephalometric analyses. Forty patients received Twin Block treatment, whereas the remaining 20 patients did not receive treatment, thus constituting the control group. The control group included patients who did not start treatment after their first visit but returned for a consultation one or 2 years later. All patients underwent an initial teleradiography examination of the skull and a final teleradiography examination to measure changes using McNamara cephalometric analysis of the UA. Pretreatment and posttreatment changes were assessed using Student's t test for independent samples with a significance level of 0.05. Both anatomical structures analyzed—the upper pharynx (nasopharynx) and lower pharynx (oropharynx)—showed significant increases after treatment regardless of whether the patients were boys or girls. The controls showed a decrease in UA size on average after approximately 2 years of growth. A clear relationship exists between the mandibular advancement achieved with TB treatment and an increased UA size. Therefore, the appliance is considered suitable for improving the respiratory quality of growing patients with a decreased UA size.

Predictors of favorable soft tissue profile outcomes following Class II Twin-block treatment.

ObjectiveThe aim of this study was to determine cephalometric factors that help predict favorable soft-tissue profile outcomes following treatment with the Class II Twin-block appliance.MethodsPre- and post-treatment lateral cephalograms of 45 patients treated with the Class II Twin-block appliance were retrospectively analyzed. Profile silhouettes were drawn from the cephalograms and evaluated by three orthodontists in order to determine the extent of improvement. Samples were divided into a favorable group (upper 30% of visual analogue scale [VAS] scores, n = 14) and an unfavorable group (lower 30% of VAS scores, n = 14). Skeletal and soft-tissue measurements were performed on the cephalograms and an intergroup comparison was conducted.ResultsAn independent t-test revealed that the following pre-treatment values were lower in the favorable group compared to the unfavorable group: lower incisor to mandibular plane angle, lower incisor to pogonion distance, point A-nasion-point B angle, sella-nasion line (SN) to maxillary plane angle, SN to mandibular plane angle, gonial angle, and symphysis inclination. The favorable group had a larger incisor inclination to occlusal plane. Moreover, the favorable group showed larger post-treatment changes in gonial angle, B point projection, and pogonion projection than did the unfavorable group.ConclusionsClass II malocclusion patients with a low divergent skeletal pattern and reduced lower incisor protrusions are likely to show more improvement in soft-tissue profile outcomes following Class II Twin-block treatment.

Twin Block appliance with acrylic capping does not have a significant inhibitory effect on lower incisor proclination.

To investigate the effect of acrylic capping, treatment duration, overjet, and lower incisor inclination on the posttreatment tooth position in patients treated with 2 Twin Block (TB) appliance versions. Cephalograms of 56 patients with Class II malocclusion (21 boys, 35 girls; mean age before treatment [T1] = 12.5 years; standard deviation, 0.7) treated with a TB appliance with either acrylic capping or ball-ended clasps on lower incisors were retrospectively collected and traced. Lower incisor inclination (L1-GoGn, L1-GoMe, L1-MP) was measured at T1 and after TB appliance removal (T2). Regression analysis was performed to evaluate the effect on the lower incisor inclination of appliance type, overjet, lower incisor inclination at T1, and treatment duration after adjusting for baseline measurements. Appliance design was not a significant predictor for either incisor inclination measurement (P< .05). Pretreatment lower incisor inclination was the only factor significantly associated with final tooth inclination (L1-GoGn: β = 0.57, 95% confidence interval [CI] = 0.30, 0.84, P < .001; L1-GoMe: β = 0.56, 95% CI = 0.28, 0.84, P < .001; L1-MP: β = 0.46, 95% CI = 0.17, 0.75, P = .003). There was weak evidence that treatment duration excluding L1-MP (95% CI = -1.85, -0.02; P = .045) and overjet might be associated with inclination of lower incisors at T2. TB appliance design with acrylic capping on lower incisors appears not to significantly control incisor proclination. Pretreatment lower incisor inclination may be significantly associated with tooth inclination after active TB treatment and should be considered in treatment planning.

Comparison of Activator-Headgear and Twin Block Treatment Approaches in Class II Division 1 Malocclusion.

The purpose was to compare the treatment effects of functional appliances activator-headgear (AH) and Twin Block (TB) on skeletal, dental, and soft-tissue structures in class II division 1 malocclusion with normal growth changes in untreated subjects. The sample included 50 subjects (56% females) aged 8–13 years with class II division 1 malocclusion treated with either AH (n = 25) or TB (n = 25) appliances. Pre- and posttreatment lateral cephalograms were evaluated and compared to 50 untreated class II division 1 cases matched by age, gender, ANB angle, and skeletal maturity. A paired sample, independent samples tests and discriminant analysis were performed for intra- and intergroup analysis. Treatment with both appliances resulted in significant reduction of skeletal and soft-tissue facial convexity, the overjet, and the prominence of the upper lip in comparison to untreated individuals (p < 0.001). Retroclination of maxillary incisors and proclination of mandibular incisors were seen, the latter being significantly more evident in the TB group (p < 0.05). Increase of effective mandibular length was more pronounced in the TB group. In conclusion, both AH and TB appliances contributed successfully to the correction of class II division 1 malocclusion when compared to the untreated subjects with predominantly dentoalveolar changes.

Patient's Psychological Response to Twin-block Therapy

ABSTRACT Aims and objectives To determine the psychological response of the patient to twin-block therapy. To design and formulate a questionnaire to patient on twin-block therapy in the orthodontic clinic and the result will be evaluated. Materials and methods A total of 14 patients within the age group of 12 to 14 years on twin-block therapy for treatment of skeletal class II malocclusion with a mandibular deficiency in the Department of Orthodontics were selected. A questionnaire was formulated at the end of twin-block therapy. The completed questionnaire was analyzed and the patient responses to the different aspects of twin-block treatment were recorded. Results Of the 14 patients, 12 patients liked wearing the appliance. All the patients wore it comfortably full time. About 3 out of 14 had pain, 1 had ulcer, 9 14 had difficulty in eating, 6 patients had altered taste, and 3 had altered speech. A total of 13 patients observed improvement in lower jaw position. A total of 13 patients considered recommending the appliance to families and friends. Conclusion The response of the patient to twin-block appliance was positive. The twin block appears to be well accepted by the patients despite their age. Clinical significance Patient compliance directly affects the treatment outcome of the appliance. How to cite this article Thirumurthi AS, Felicita AS, Jain RK. Patient's Psychological Response to Twin-block Therapy. World J Dent 2017;8(4):327-330.

Meta-analysis of the condylar position changes produced by functional appliances in class Ⅱ malocclusion

This study aimed to analyze the condylar position changes produced by functional appliances in class Ⅱ malocclusion by systematic review. Electronic search was conducted using Chinese Biomedical Literature Database, China National Knowledge Infrastructure, VIP Database for Chinese Technical Periodicals, Medline, Embase, Pubmed, and Cochrane Central Register of Controlled Trials. Studies on condylar position changes produced by functional appliances in class Ⅱ malocclusion were included. Risk of bias assessment and data extraction of included studies were conducted by two reviewers independently. The meta-analysis was carried out using Revman 5.1. Six studies were included (five high quality and one low quality). The condylar position showed no changes after Herbst treatment. The condylar posterior space after Twin-block treatment averagely increased by 0.31 mm (P<0.000 01), whereas the condylar anterior space averagely reduced by 0.32 mm (P<0.000 01). Twin-block appliance enables forward movement of the condylar position. This result contributes to the correction of class Ⅱ malocclusion.

The changes of horizontal distance condyle to nasal septum after the Twin-block treatment on class II division 1 with retrognathic mandible

Introduction: Twin-block appliance is simple removable bite block mostly used in the management of Class II malocclusion. It can modify the occlusal inclined plane to guide the mandible protrusion. Hence, when the patients are wearing the Twin-block appliances, this altered biomechanical environment and will stimulate the growth of the secondary cartilage of condyle and will caused the condyle to change in size, volume or position the in long term. The aim of this study was to investigate the changes of horizontal distance from condyle to nasal septum after the Twin-block treatment on Class II division 1 with retrognathic mandible. Methods: There were total 5 samples of panoramic radiograph before Twin-block treatment and 5 samples of panoramic radiograph after Twin-block treatment. The panoramic radiographs were traced to identify the changes of horizontal distance from condyle to nasal septum after the Twin-block treatment. The distance from the middle of nasal septum to the most superior surface of condyle head for right region and left region were measured, then the differences were statistically analyzed. Results: The horizontal distance from the middle of nasal septum to the most superior surface of condyle head after the Twin-block treatment increased. The difference of condyle position before and after the treatment of Twin-block.was slight (p-value &gt; 0.05). Conclusion: There is no significant difference in horizontal distance from the most superior surface of condyle head to the middle of nasal septum before and after treatment of Twin-block.