Three-dimensional skeletal, dentoalveolar and temporomandibular joint changes produced by Twin Block functional appliance

Different treatment strategies for monozygotic twins with Class II division 1 malocclusion: 10-year follow-up study

BACKGROUND

Early-stage growth modification has been demonstrated effective in treating prepubertal patients with Class II division 1 malocclusion. Since monozygotic twins are genetically identical, environmental factors, including oral habits and treatment strategies, may contribute to different treatment outcomes. To date, few reported comparisons of different treatment strategies in monozygotic twins with Class II division 1 malocclusion exist.

CASE DESCRIPTION

In this case report, we compare the effects of different functional appliances and extraction strategies in a pair of prepubertal monozygotic twins. Different compliance and treatment protocols may have different effects on their early changes in facial profile. Customized treatment plans are necessary for optimal treatment outcomes. Both twins achieved favourable improvements in facial profile, and their long-term stability of functional occlusion was also maintained after a ten-year follow-up.

PRACTICAL IMPLICATIONS

With the outcome of the case, we acknowledged that functional appliance therapy can affect the potentiality of mandibular growth. Individualized protocols should be approached aside from different functional appliances.

Effect of Mandibular Advancement on Condylar Remodelling of Class II Malocclusion Adolescent Patients With or Without Anterior Disc Displacement: A Retrospective Study

OBJECTIVE

To compare condylar remodelling in Class II malocclusion adolescents with or without anterior disc displacement (ADD) before and after treatment with mandibular advancement.

METHODS

CBCT data were collected from 20 Class II division 1 malocclusion adolescent patients with normal disc-condyle relationships and 20 Class II division 1 malocclusion adolescent patients with ADD, before and after mandibular advancement. All the TMJs were classified into three types: normal disc-condyle relationship joint, anterior disc displacement with reduction (ADDwR) joint, and anterior disc displacement without reduction (ADDwoR) joint. 3D Slicer 5.0.3 software was used to compare the quantitative index changes before and after treatment, including condylar volume, superficial area, morphological index, maximum cross-sectional area, width, depth, height and length. In addition, three-dimensional reconstructions and superimpositions of the condyle-glenoid fossa were performed to visualise condylar remodelling, and the condylar osseous change during treatment was evaluated qualitatively.

RESULTS

Before treatment, the morphological index and depth of the condyle were smaller in the ADDwoR joint. After treatment, condylar dimensions increased in all three types. The amount of increase in various indices of the ADDwR joint was comparable to that of the normal joint, with the highest rate of condylar repair and regeneration observed in the ADDwR joint. Specifically, the condylar volume changes in the normal joint (95% CI: 187.59 ± 107.05) and the ADDwR joint (95% CI: 199.97 ± 135.32) showed no significant difference (p = 0.672). The increase in condylar volume (p < 0.05), superficial area (p < 0.01) and length (p < 0.01) in the ADDwoR joint was lower than that in the normal joint. Three-dimensional reconstructions showed posterior and superior condylar growth in all three types.

CONCLUSION

Mandibular advancement significantly promotes condylar remodelling in Class II malocclusion adolescent patients, with or without ADD, effectively promoting the backward growth of the condyle. Condylar growth of ADDwR joints was comparable to that of normal joints, while the condylar growth of ADDwoR joints was less.

Expert consensus on orthodontic treatment of protrusive facial deformities

Protrusive facial deformities, characterized by the forward displacement of the teeth and/or jaws beyond the normal range, affect a considerable portion of the population. The manifestations and morphological mechanisms of protrusive facial deformities are complex and diverse, requiring orthodontists to possess a high level of theoretical knowledge and practical experience in the relevant orthodontic field. To further optimize the correction of protrusive facial deformities, this consensus proposes that the morphological mechanisms and diagnosis of protrusive facial deformities should be analyzed and judged from multiple dimensions and factors to accurately formulate treatment plans. It emphasizes the use of orthodontic strategies, including jaw growth modification, tooth extraction or non-extraction for anterior teeth retraction, and maxillofacial vertical control. These strategies aim to reduce anterior teeth and lip protrusion, increase chin prominence, harmonize nasolabial and chin-lip relationships, and improve the facial profile of patients with protrusive facial deformities. For severe skeletal protrusive facial deformities, orthodontic-orthognathic combined treatment may be suggested. This consensus summarizes the theoretical knowledge and clinical experience of numerous renowned oral experts nationwide, offering reference strategies for the correction of protrusive facial deformities.

A finite element study comparing Advansync® and Twin Block in mandibular anterior repositioning

OBJECTIVE

This study aims to utilize the finite element method (FEM) to compare the dentoalveolar and mandibular effects associated with anterior mandibular repositioning using AdvanSync® (ADV) and Twin Block (TB).

METHODS

A patient with Class II skeletal malocclusion and mandibular retrognathism was selected. A TB appliance was subsequently applied. Computed Tomography (CT) scans were acquired at the beginning of treatment (T1) and 8 months later (T2). Concurrently, a numerical TB model was validated through FEM simulations, which were compared with the T2 results. The ADV appliance was virtually simulated to evaluate stress and deformation on the condyle, symphysis, first lower molar and lower central incisors.

RESULTS

Both simulations demonstrated significant mandibular advancement. However, ADV led to less incisor proclination and more molar intrusion compared to TB. ADV exhibited increased stress in the lower molar area, while TB had higher stress in the lower incisor region. Stress and deformations in the condyle and mandibular symphysis were similar in both simulations, with the highest stress observed at the condylar neck and the lowest at the upper pole of the condylar head.

CONCLUSIONS

Both appliances achieved similar levels of mandibular advancement, with greater proclination of the lower central incisors and more widespread distribution of stress and molar intrusion when using ADV compared to TB.

The combination of odontogenic stem cells and mandibular advancement promotes the length of the mandible in adult rats by facilitating the development of condylar cartilage

BACKGROUND

Mandibular retraction is a prevalent dental and maxillofacial deformity that negatively affects patients' functional health and facial aesthetics. It has been challenging to achieve optimal outcomes for patients who have passed the peak of growth and development using only functional orthopedic treatment. There is a pressing need to explore innovative methods to promote the adaptive remodeling of adult condylar cartilage and the mandible in response to external stimuli. This study aimed to investigate the impact of varying injection frequencies of stem cells from the apical papilla (SCAPs) on the growth and development of condylar cartilage and the mandible, as well as their potential for adaptive remodeling.

METHODS

The study was conducted on 8-week-old adult male Sprague-Dawley rats. The effects of SCAPs injection and different durations of mandibular advancement (MA) on the adaptive remodeling of condylar cartilage and the mandible were assessed. After the initial experimental findings, various injection frequencies of SCAPs were applied to determine the most effective conditions for promoting the growth and adaptive remodeling of condylar cartilage and the mandible during an 8-week period of mandibular advancement.

RESULTS

The study found that rats with extended mandibular lead times (8 weeks) or an appropriately increased frequency of mandibular leading time (once every 2 weeks or once every 1 week) exhibited increased lengths of the mandibular body and ascending branch, and a thickened full layer of condylar cartilage. The highest proportions of the proliferative layer, mature layer, and hypertrophic layer were observed in these rats. Additionally, there was a significant increase in the expression levels of SOX9 and COL2A1.

CONCLUSION

The data from this study suggest that adult rats, even after missing their peak growth period, retain the potential for continued growth and development of their condylar cartilage. By prolonging the duration of mandibular advancement and administering injections of stem cells from the apical papilla (SCAPs), it is possible to stimulate the growth and development of the mandibular condyle.

Biomechanical effects of functional clear aligners on the stomatognathic system in teens with class II malocclusion: a new model through finite element analysis

OBJECTIVES

The Functional Clear Aligner (FCA) is a novel orthodontic appliance designed for the treatment of Class II malocclusion with mandibular retrognathia in adolescents. The aim of this study was to investigate the biomechanical characteristics of the masticatory muscles, jawbone, and temporomandibular joint (TMJ) during mandibular advancement using either FCA or Class II elastics combined with clear aligner (Class II elastics) through finite element analysis.

MATERIALS AND METHODS

A 3D finite element model of the 'muscle-jawbone-TMJ-appliance' system was constructed based on CBCT and MRI images of a boy with skeletal Class II malocclusion. Masticatory muscles included masseter, temporal, medial pterygoid, and lateral pterygoid muscles. The TMJ consists of the temporal bone's glenoid fossa, disc, and mandibular condyle. To observe the biomechanical characteristics of the muscles and TMJ during orthodontic appliance wearing and the retention phase, two different protocols were used: Model 1: The mandibular advancement using FCA; Model 2: The mandibular advancement using Class II elastics.

RESULTS

The FCA group produced greater and more coordinated masticatory muscle forces compared to the Class II elastics group. Temporal and masseter muscles exhibited the most pronounced variation in muscle strength during mandibular advancement. The FCA group exhibited greater TMJ region stress compared to the Class II elastics group. Interestingly, the stress on the articular discs in both models decreased over time. Tensile stresses were observed in both the condyle and the posterior region of the articular fossa.

CONCLUSION

During skeletal Class II malocclusion treatment, masticatory muscle forces and stress on the TMJ were higher in the FCA group compared to the Class II elastics group. In both models, stress cushioning was provided by the articular disc.

Management of Patients Receiving Anticoagulation Therapy in Dental Practice: A Systematic Review

BACKGROUND

Anticoagulant drugs are a valuable tool for minimizing thrombotic risks in at-risk patients. The purpose of this study is to conduct a literature review highlighting the management of these drugs during daily clinical dental practice.

MATERIALS AND METHODS

We limited our search to English-language papers published between 1 January 1989, and 7 March 2024, in PubMed, Scopus and Web of Science that were relevant to our topic. In the search approach, the Boolean keywords "anticoagulant AND dentistry" were used.

RESULTS

Twenty-five clinical trials were included for final review from 623 articles obtained from the databases Web of Science (83), PubMed (382), and Scopus (158), eliminating duplicates and 79 off-topic items, resulting in 419 articles after removing 315 entries and confirming eligibility. Overall, these studies support the use of local hemostatic measures to manage the risk of bleeding in patients on anticoagulant therapy undergoing dental procedures and highlight the importance of greater education and collaboration among healthcare professionals.

CONCLUSIONS

Research and clinical investigation have improved understanding and management of dental procedures in patients undergoing anticoagulant or antiplatelet therapy. Hemostatic agents, clinical protocols, risk factors, and continuous education are essential for navigating the complexities of anticoagulant therapy, ensuring optimal outcomes and enhancing patient well-being.

Recommendations for standard criteria for the positional and morphological evaluation of temporomandibular joint osseous structures using cone-beam CT: a systematic review

OBJECTIVE

This systematic review aimed to appraise the reliability and comprehensiveness of imaging methods in studies that used three-dimensional assessment of the temporomandibular joint (TMJ) in order to propose a standardized imaging method.

METHODS

Six databases/search engines were searched up until September 2022. The outcomes of interest included measurements of the mandibular condyle, glenoid fossa, joint spaces, or the entire TMJ. Two checklists were utilized: one to assess the risk of bias, with a maximum score of 37, and the other, a pre-designed checklist consisting of 22 items to evaluate the comprehensiveness of the methods used, with a maximum score of 33.

RESULTS

Out of the 2567 records retrieved, only 14 studies, which used cone bean computed tomography (CBCT), were deemed eligible and thus included in the qualitative analysis. Three studies were deemed of low risk of bias, while the remaining studies were rated as moderate to high risk of bias, primarily due to improper reporting of inter-observer agreement, varying reliability values, and a limited number of cases included in the reliability analysis. Regarding the comprehensiveness of the methods used, only four studies achieved relatively high scores. The deficiencies observed were related to the reporting of variables such as slice thickness and voxel size, absence of or improper reporting of intra- and inter-examiner reliability analyses, and failure to assess all osseous components of the TMJ.

CONCLUSION

CBCT-based methods used to assess the positions and morphology of TMJ bony structures appear to be imperfect and lacking in comprehensiveness. Hence, criteria for a standardized assessment method of these TMJ structures are proposed.

CLINICAL RELEVANCE STATEMENT

Accurately, comprehensively, and reliably assessing the osseous structures of the temporomandibular joint will provide valid and valuable diagnostic features of the normal temporomandibular joint, and help establish potential associations between these osseous features and temporomandibular disorders.

REGISTRATION

The protocol for this systematic review was registered at the International Prospective Register of Systematic Reviews (PROSPERO, No.: CRD42020199792).

KEY POINTS

•Although many methods have been introduced to assess the osseous structure of the temporomandibular joint, they yielded inconsistent findings. •None of the published studies comprehensively assessed the temporomandibular joint. •Recommendations for a comprehensive temporomandibular joint osseous assessment method were suggested for better validity and reliability of future research.

Skeletal, dentoalveolar and soft tissue changes after stabilization splint treatment for patients with temporomandibular joint disorders

BACKGROUND

Temporomandibular disorder (TMD) is a grouping of heterogeneous disorders with multifactorial origins. Stabilization splints (SS) have demonstrated an acceptable treatment effect in TMD. The possible changes at the skeletal, dental, and soft tissue levels need to be addressed to evaluate the benefit/risk ratio of this therapeutic procedure. Accordingly, this study aimed to three‑dimensionally evaluate skeletal, dentoalveolar and soft tissue changes after SS treatment for patients with TMD.

METHODS

This retrospective study included 74 adult patients with myofascial and/or intra-articular disorders (25 males and 49 females), with an average age of 22.88 ± 4.8 years, who underwent SS treatment. Pre- and post-treatment Cone beam computed tomography were analysed using Invivo 6.0.3 software. The primary outcome was the vertical skeletal and dentoalveolar changes, while the secondary outcomes were the anteroposterior skeletal, dentoalveolar and soft tissue changes. Paired t-test and Wilcoxon rank sum test were used for statistical analyses.

RESULTS

For the primary outcome; skeletally, there was a significant increase in mandibular plane inclination (difference: 0.82°±1.37), decrease facial height ratio (difference: 0.45%±1.07) and at the dentoalveolar level, the inclination of the functional (FOP-SN, FOP-FH) and bisecting (BOP-SN, BOP-FH) occlusal planes exhibited a significant increase too (difference: 0.38 ± 1.43°, 0.49 ± 1.62°, 0.44 ± 1.29° and 0.41 ± 1.17°, respectively) and also a decrease in the overbite (difference: -0.54 ± 0.83). For the secondary outcomes; there was a significant decrease in mandibular position (SNB) (difference: 1.60 ± 1.36°) and increase in the overjet (difference: 0.93 ± 1.04, p < 0.001) and a significant lower lip retrusion (difference: 0.33 ± 1.01 mm p < 0.01), was observed too.

CONCLUSIONS

SS therapy resulted in significant vertical skeletal and dentoalveolar changes that were manifested mainly by facial height ratio, mandibular and occlusal plane changes, and to a lesser extent, significant anteroposterior skeletal, dentoalveolar, and soft tissue changes in the form of mandibular position, increased overjet and a more retrusive lower lip. These changes should be considered during patients' selection prior to initiating SS therapy.

A Three-Dimensional Evaluation of Skeletal and Dentoalveolar Changes in Growing Class II Patients after Functional Appliance Therapy: A Retrospective Case-Control Study

Background: The aim was to assess three-dimensionally mandibular and maxillary changes in growing Class II patients treated with removable functional appliances followed by fixed appliances. Methods: Twenty-four Class II patients (age range: 9 to 14, mean: 12.1 ± 1.1 years) treated with removable functional appliances followed by fixed appliances (functional appliance group-FAG) were retrospectively selected and compared to an age-matched control group (CG) treated with fixed appliances only. To be included in the study, pre- and post-treatment CBCT scans had to be available. The CBCTs were used to analyze, in 3D, the changes following treatment and growth. Results: Before treatment, overjet (FAG: 9 mm ± 2.8 (mean ± standard deviation); CG: 4 mm ± 1.7), ANB (FAG: 5.7° ± 2.0; CG: 3.2° ± 1.4), and effective mandibular length (FAG: 113.0 mm ± 4.1; CG: 116.6 mm ± 5.9) were statistically significantly different between the two groups. After treatment, overjet (FAG: -6.8 mm ± 2.8; CG: -1.8 mm ± 1.8) and effective mandibular length (FAG: 6.3 mm ± 2.6; CG: 3.9 mm ± 2.6) statistically significantly changed. There was a significant difference in the treatment effect between the FAG and the CG in overjet, ANB, and effective mandibular length. Conclusions: The results indicate that functional appliances are effective in correcting Class II malocclusions. The growth modification in the FAG resulted in an increase in mandibular length. Yet, the final length of the mandible in the FAG was smaller when compared to the CG.

Impact of initial lip competence on the outcome of class II functional appliances therapy

OBJECTIVES

The aim of this prospective clinical study was to evaluate the impact of initial lip position on class II functional appliance therapy.

MATERIALS AND METHODS

In total, 34 class II division 1 patients (23 females, 19 males; mean age 12.4 ± 0.9 years) that met the inclusion criteria (> ½ class II molar relationship, overjet > 6 mm, ANB > 4°, neutral or horizontal growth pattern, cervical vertebral maturation stage (CVMS) II - III, mean wear-time > 10 h/day) were consecutively divided into two groups (lip incompetence (LI); lip competence (LC)). All patients were treated with the Sander bite jumping appliance (BJA). Wear time was microelectronically measured. Lateral cephalograms were taken at the beginning (T0) and after 1 year of treatment (T1). An untreated class II group served as a control (CG). Inter-group comparisons were determined with Mann-Whitney U tests for independent samples.

RESULTS

Significant skeletal treatment effects were found in both treated groups when compared to the CG with significantly more pronounced mandibular skeletal effects in the LI than in the LC group (mandibular base length p < 0.001, composite mandibular base length p < 0.001, condylar head growth p = 0.002, co-pg p < 0.00, go-pg p = 0.003, reduction of the ANB angle p = 0.009, and Wits appraisal p < 0.001).

CONCLUSION

The more pronounced mandibular effects in the LI group were composed of the functional orthopedic effect plus harmonization of the lip competence.

CLINICAL RELEVANCE

Functional harmonization of lip incompetence with BJA enhances mandibular growth stimulation. Lip incompetence seems to impede mandibular growth and its harmonization seems to be a preventive approach.

Three-dimensional spatial analysis of temporomandibular joint in adolescent Class II division 1 malocclusion patients: comparison of Twin-Block and clear functional aligner

BACKGROUND

Our study aimed to use three-dimensional (3D) spatial morphological measurement methods to compare the influence of Twin-Block and clear functional aligners on the temporomandibular joint (TMJ) of adolescent Class II division 1 malocclusion mandibular retraction patients. We also aimed to explore the similarities and differences in the effects on the TMJ upon using Twin-Block and clear functional aligner.

METHODS

Cone-beam computed tomography (CBCT) data of 49 patients with Class II division 1 malocclusion (Twin-Block group: 24; clear functional aligner group: 25) were collected before and after functional orthodontic treatment, and a 3D model of the TMJ was reconstructed using MIMICS 21.0 software. Eighteen measurement parameters, including the anterior, superior, and posterior joint spaces, were measured and compared using the 3D model.

RESULTS

After the two groups underwent functional appliance treatment, the height, volume, and surface area of the condyle, length of the mandibular ramus and mandibular length increased; The retro-displaced condyle moved to the middle position of the articular fossa, while the rest of the condylar position did not change significantly. Remodeling of the articular fossa after treatment was not evident. The superior joint space of the clear functional aligner group increased, but there was no significant change after Twin-Block appliances treatment.

CONCLUSIONS

Both appliances promote condylar growth and sagittal and vertical development of the mandible in adolescent Class II division 1 malocclusion mandibular retraction patients. The length of the mandibular ramus showed a more significant increase following treatment with the Twin-Block appliances than with clear function aligners.

Stress distribution of the modified clear twin-block aligner on the temporomandibular joint, alveolar bone and teeth: A finite element analysis

OBJECTIVE

The modified clear twin-block aligner (CTBA) was developed to provide a mandibular advancement appliance for the treatment of mandibular retrognathia. The objective of this study was to analyse the stress distribution changes of CTBA with 45°, 60° and 70° bite blocks.

MATERIAL AND METHODS

A three-dimensional model of the craniomaxillofacial bones and teeth was generated from a spiral computed tomography (CT) scan. The models of the articular disc, capsule, periodontal ligament and CTBA were constructed mathematically. After assigning the appropriate material properties and the boundary condition using ABAQUS software, we simulated the CTBA with different bite blocks to analyse the mechanical effects.

RESULTS

In the temporomandibular joint (TMJ) region, the posterior aspect of the condyle and glenoid fossa experienced tensile stress that was approximately about 22 times greater at 70° than at 45°. The Von Mises stress distribution on the articular disc tended to be uniform. The strain direction of the condyle was backward. In the maxillary bone, the stress on the labial alveolar bone was about 5.83MPa at 70° and greater than that on the lingual side. The resulting displacement of the dentition revealed a tendency for the upper teeth to shift backward and the lower teeth to move forward by 0.46 to 0.49mm. The foregoing stress and displacement rose as the angle of the bite blocks increased.

CONCLUSIONS

CTBA with 70° bite blocks constituted an advantageous biomechanical setting for the treatment of mandibular retrognathia in teenagers and provided a superior therapeutic effect.

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

INTRODUCTION

Compensatory 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 mandibular advancement device, twin block (TB), can guide the forward development of the mandible. However, the side effect of increasing the vertical dimension of the lower facial third, worsens the facial profile of children with divergent growth trends. To solve this problem, a modified TB (LLTB) appliance was designed to control the vertical dimension by intruding incisors and inhibiting the elongation of posterior teeth during the advancement of the mandible, which could avoid the side effects of traditional appliances and effectively guide the growth of the mandible in a normal direction.

METHODS AND ANALYSIS

The study was designed as a single-centre, single-blind, randomised, parallel controlled trial. We aim to enrol 60 children aged 9-14 years with hyperdivergent skeletal class II malocclusion, using a 1:1 allocation ratio. The participants were will be randomly assigned to receive either the TB or LLTB treatment. The primary outcome will be a change in the angle of the mandibular plane relative to the anterior cranial base. The secondary outcomes will include changes in the sagittal maxillomandibular relation, occlusal plane, facial height, morphology of the mandible and upper airway width. Safety endpoints will also be evaluated.

ETHICS AND DISSEMINATION

Ethical approval was obtained from the ethics committee of Shanghai Stomatological Hospital. Both participants and their guardians will be fully informed of the study and sign an informed consent form before participating in the trial. The results will be publicly available in peer-reviewed scientific journals.

TRIAL REGISTRATION NUMBER

ChiCTR2000035882.

Skeletal Class II Malocclusion: From Clinical Treatment Strategies to the Roadmap in Identifying the Genetic Bases of Development in Humans with the Support of the Collaborative Cross Mouse Population

Depending on how severe it is, malocclusion, which may involve misaligned teeth, jaws, or a combination of the two, can hurt a person's overall facial aesthetics. The maxillary molar develops before the mandibular molar in class II malocclusion, which affects 15% of the population in the United States. With a retrusive mandible, patients typically have a convex profile. The goal of this study is to classify the skeletal and dental variability present in class II malocclusion, to reduce heterogeneity, present the current clinical treatment strategies, to summarize the previously published findings of genetic analysis, discuss these findings and their constraints, and finally, propose a comprehensive roadmap to facilitate investigations aimed at determining the genetic bases of malocclusion development using a variety of genomic approaches. To further comprehend the hereditary components involved in the onset and progression of class II malocclusion, a novel animal model for class II malocclusion should be developed while considering the variety of the human population. To overcome the constraints of the previous studies, here, we propose to conduct novel research on humans with the support of mouse models to produce contentious findings. We believe that carrying out a genome-wide association study (GWAS) on a large human cohort to search for significant genes and their modifiers; an epigenetics-wide association study (EWAS); RNA-seq analysis; integrating GWAS and the expression of quantitative trait loci (eQTL); and the testing of microRNAs, small RNAs, and long noncoding RNAs in tissues related to the skeletal class II malocclusion (SCIIMO) phenotype, such as mandibular bone, gum, and jaw in humans and the collaborative cross (CC) mouse model, will identify novel genes and genetic factors affecting this phenotype. We anticipate discovering novel genetic elements to advance our knowledge of how this malocclusion phenotype develops and open the venue for the early identification of patients carrying the susceptible genetic factors so that we can offer early prevention treatment strategies.

Treatment of severe open bite and mandibular condyle anterior displacement by mini-screws and four second molars extraction: A case report

BACKGROUND

Temporomandibular joint (TMJ) disorders are closely related to high-angle and skeletal Class II malocclusion. Sometimes pathological changes in the mandibular condyle can cause open bite to occur after growth is complete.

CASE SUMMARY

This article is about the treatment of an adult male patient with a severe hyperdivergent skeletal Class II base, an unusual and gradually occurring open bite and an abnormal mandibular condyle anterior displacement. Because the patient refused surgery, four second molars with cavities and root canal therapy were extracted, and four mini-screws were used for intrusion of the posterior teeth. The treatment duration was 22 mo, and after the treatment, the open bite was corrected and the displaced mandibular condyles were seated back to the articular fossa as shown by cone-beam computed tomography (CBCT). Based on the patient’s open bite history, the result of clinical examinations and CBCT comparisons, we believe it is possible that the occlusion interference was eliminated after the four second molars were extracted and the posterior teeth were intruded, and the patient's condyle spontaneously returned to its physiologic position. Finally, a normal overbite was established, and stable occlusion was achieved.

CONCLUSION

This case report suggested that identifying the cause of open bite is essential, and the TMJ factors for hyperdivergent skeletal Class II cases should be particularly examined. For these cases, intruding posterior teeth may place the condyle in a more appropriate position and provide an environment suitable for TMJ recovery.

Efficacy of invisible advancement correction for mandibular retraction in adolescents based on Pancherz analysis

BACKGROUND

Mandibular retraction is the main etiological mechanism of class II malocclusion in China and the subsequent distal molar relationship can cause functional discomfort in mastication, breathing and the temporomandibular joint. The use of mandibular advancement (MA) devices has recently emerged as an adolescent mandibular retraction treatment; however, current studies regarding the effect thereof are relatively few, and there is lack of sufficient clinical support.

AIM

To investigate the clinical effect of invisalign MA on the treatment of mandibular retraction in adolescents.

METHODS

This study included 30 adolescent patients who underwent treatment with the MA appliances from December 2017 to June 2021. The lateral cephalometric data before and after treatment were collected and imported into Dolphin Imaging software. The changes were measured by linear measurement superimposed with lateral cephalometric trajectory based on the Pancherz technology.

RESULTS

There was no significant difference in the length and position of maxilla before and after the treatment. The position of the mandible moved 3.13 mm, the length increased 4.14 mm, the mandibular ramus length increased 4.09 mm, the body length increased 4.25 mm, and the position of the condyle moved 1.03 mm forward after treatment. Additionally, changes in the incisor sagittal position and labial inclination were observed. The position of the upper incisor point moved back 1.33 mm, without statistical difference, the inclination and tooth angle decreased by 3.44° and 4.06°, respectively; the position of the lower incisor point was moved 2.98 mm, and the inclination and tooth angle increased by 2.62° and 1.23°, respectively. Furthermore, changes in the incisor overjet and molar relationship were seen. Overjet decreased by 4.31 mm, of which 1.78 mm was due to dental factors, accounting for 41.3% of the effect as opposed to 58.7% due to skeletal factors. Molar relationship improved 3.87 mm, with 1.34 mm due to dental factors, and dental and skeletal factors were accounted for 34.6% and 65.4% of the effect, respectively.

CONCLUSION

For adolescent patients with mandible retraction, invisalign MA can effectively promote the mandible growth, and it was proven to be mainly due to skeletal effects.

Evaluation of Local Application of Glucosamine Sulfate and Chondroitin Sulfate on Temporomandibular Joint Response and Alleviation of Pain and Tension During the Functional Treatment of Skeletal Class II Patients: A Randomized Control Clinical Trial

OBJECTIVE

 This study was conducted to assess the effects of applying a gel of combined glucosamine sulfate and chondroitin sulfate on the temporomandibular joint (TMJ) area in patients with skeletal Class II malocclusion treated by removable functional appliances in terms of TMJ internal proportions, levels of pain, and tension.

MATERIALS AND METHODS

The study included 36 patients aged 10-13 years with skeletal Class II malocclusion due to retrusion of the mandible characterized by: 4-8 degrees of the sagittal skeletal discrepancy (ANB) angle, 4-7 mm of overjet, 72-76 degrees of the sagittal mandibular positioning (SNB) angle, and a bone maturity stage located at pubertal growth spurt. Patients were distributed to the experimental group (Twin-Block appliance + Jointance® gel) or the control group (conventional treatment with the Twin-Block appliance). An allocation ratio of 1:1 was employed. Pre- and post-treatment digital lateral cephalometric radiograms were taken, and the TMJ joint spaces were measured using the Viewbox software (dHAL Software, Kifissia, Greece). The pain and discomfort levels were evaluated using a questionnaire with a four-point Likert scale at three assessment times.

RESULTS

 The anterior and posterior glenoid and anterior condylar distances to the pterygoid vertical (PTV) reference plane significantly decreased after treatment (p<.001), and the anterior joint space decreased significantly (p<.001). In contrast, the superior distance of the condyle to the Frankfort horizontal reference plane increased significantly after treatment, and the same results were found for the posterior and superior joint spaces (p<.05). There were no significant differences between the two groups in the evaluated linear variables. No significant differences were found when comparing pain and tension levels between the two groups at each assessment time. A gradual decrease in pain and tension levels was observed between the three evaluation times in both groups.

CONCLUSIONS

 A combination of glucosamine sulfate and chondroitin sulfate did not affect the temporomandibular joint spaces, pain, and tension levels in patients with skeletal Class II malocclusions treated by removable functional appliances.

Comparative Evaluation of Twin Block Appliance and Fixed Orthodontic Appliance in Early Class II Malocclusion Treatment: A Randomized Controlled Trial

AIMS

To compare skeletal, dentoalveolar, and soft tissue changes between Twin block and early fixed orthodontic appliance for class II division 1 malocclusion treatment through a randomized controlled trial.

MATERIALS AND METHODS

Sample and randomization: This study was a randomized controlled trial with a 1:1 allocation ratio in which 40 patients were divided equally into two groups: control and experimental; each group had an equal number of boys and girls. Randomization was achieved using random blocks of 20 patients with allocation concealed in sequentially numbered, opaque, and sealed envelopes. Blinding was only applicable for data analysis of radiographic measurements. Intervention: Twin block appliance was used in the experimental group for 1 year. However, control group was treated with fixed appliance. Inclusion criteria: Skeletal class II division 1 malocclusion with mandibular retrognathism; cephalometric angular measurements: SNA ≥ 82, SNB ≤ 78, ANB ≥ 4; overjet ≥6 mm; and patient in circumpubertal stage cervical vertebral maturation (CVM2 and CVM3). Parameters for evaluation: Cephalometric skeletal, dental, and soft tissue angular and linear measurements were used for evaluation.

RESULTS

SNB increased remarkably by 4° in the Twin block group, but only by 0.68 in the control group. There was a significant decrease in vertical dimensions (SN-GoGn) in the Twin block group compared to control group (p = 0.002). Significant enhancement in the facial profile of the patients was observed.

CONCLUSIONS

The Twin block appliance induced significant skeletal and dental changes. These changes were more obvious relative to the slight changes induced by natural growth.

CLINICAL SIGNIFICANCE

Early treatment of Class II due to mandibular retrusion with Twin block functional appliance is recommended due to its favourable skeletal effect. Early treatment with fixed appliance affects mainly the dentoalveolar component. Long term follow-up is needed for further insights.

Skeletal and dentoalveolar effects of class II malocclusion treatment using bi-maxillary skeletal anchorage: a systematic review

BACKGROUND

The goal of this systematic review was to assess the available evidence regarding the skeletal and dentoalveolar effects of bi-maxillary skeletal anchorage devices (BMSADs) used in treating growing class II malocclusion patients.

METHODS

A comprehensive search was conducted on PubMed, Scopus, Science Direct, Web of Science, Cochrane, and LILACS up to November 2021, which was augmented by a manual search. The studies included were clinical trials (RCTs) and/or follow-up observational studies (retrospective and prospective). The outcomes of interest were the skeletal, dentoalveolar, and occlusal treatment-induced changes obtained from pre- and post-cephalometric measurements. The risks of bias of the included studies were assessed using an assessment tool from previous publications.

RESULTS

Out of 742 screened articles, only 4 were eligible and thus included in the qualitative synthesis. They showed a moderate overall risk of bias. The results are presented as mean changes in both the study and control groups. All studies reported retrusion of the maxillary base and advancement of the mandible (meaning reduced ANB angle). Three of the included studies reported an increase in the vertical jaw relation, which was contrary to what the fourth study reported. Three studies reported an increase in the maxillary incisors' inclination or position, while one study reported their retroclination. Proclination of the mandibular incisors happened in two studies, whereas the other two studies reported retroclination. The overjet was reduced in all included studies.

CONCLUSION

Apart from the protrusive effects on the mandible, retrusive effects on the maxilla, and the consequent reduction of the overjet, BMSADs results in inconsistent skeletal and dentoalveolar effects. However, the current evidence is limited due to the variability in the biomechanics of the intermaxillary components, type of anchorage, and comparable groups in the included studies. Further RCTs with more standardized methodologies are highly encouraged.

CLINICAL RELEVANCE

BMSADs (using miniscrews or miniplates on both jaws) induces more skeletal than dentoalveolar effects. However, this must be practiced with caution, based on the benefit to risk (surgical insertion) ratio, and the limited evidence available in hand so far. Registration The protocol for this systematic review was registered at the International Prospective Register of Systematic Reviews (PROSPERO, No.: CRD42020199601).

Effects of the advanced mandibular spring on mandibular retrognathia treatment: a three-dimensional finite element study

Background

The Advanced Mandibular Spring (AMS) was newly developed as a dentofacial orthopedic appliance in conjunctive use of clear aligners to treat Class II malocclusion with mandibular retrognathia in adolescents. This study aimed to launch a biomechanical assessment and evaluate whether the stress patterns generated by AMS promote mandibular growth.

Methods

A three-dimensional finite element model was constructed using images of CBCT and spiral CT. The model consisted of craniomaxillofacial bones, articular discs, retrodiscal elastic stratum, masticatory muscle, teeth, periodontal ligament, aligner and AMS. Mechanical effects were analyzed in three types of models: mandibular postural position, mandibular advancement with AMS, and mandibular advancement with only muscular force.

Results

The stress generated by AMS was distributed to all teeth and periodontal ligament, pushing mandibular teeth forward and maxillary teeth backward. In the temporomandibular joint area, the pressure in the superior and posterior aspects of the condyle was reduced, which conformed to the stress pattern promoting condylar and mandibular growth. Stress distribution became even in the anterior aspect of the condyle and the articular disc. Significant tensile stress was generated in the posterior aspect of the glenoid fossa, which conformed to the stress pattern stimulating the remodeling of the fossa.

Conclusions

AMS created a favorable biomechanical environment for treating mandibular retrognathia in adolescents.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-022-02308-w.

Three-Dimensional Assessment of the Temporomandibular Joint Changes Following Reversed Twin Block Therapy of Patients With Skeletal Class III Malocclusion in Conjunction With the Photobiomodulation Therapy: A Randomized Controlled Clinical Trial

BACKGROUND

Despite the positive effect of the photobiomodulation therapy (PBMT) application on animals, the primary role of this technique on the human condyle is still unclear. Several experimental reports have shown the efficacy of PBMT in inducing cellular changes in the temporomandibular joint (TMJ) region during functional treatment of patients with skeletal deformities. Still, the lack of information about its effects on human condyles requires further studies.

OBJECTIVES

This study aimed to evaluate the effect of PBMT on the TMJ components following Class III treatment with the reversed twin block (RTB) appliance in growing patients.  Materials and Method: Forty children (12 females, 28 males) between the age of nine and eleven years with skeletal Class III were assigned randomly to the RTB group with photobiomodulation (RTB+PBMT) or the control group (RTB). The PBMT was applied to the TMJ region using an 808-nm wavelength Ga-Al-As semiconductor laser device with 5 Joules/cm2 energydensity on days 1, 3, 7, and 14 of the first month. Afterwards, the irradiation was conducted every 15 days until the end of the treatment. Cone-beam computerized tomography (CBCT) images were taken before (T1) treatment and following the end of treatment (T2) to assess TMJ and skeletal changes.

RESULTS

Condylar volume was significantly increased in the RTB group only by a mean of 287.97 mm3 (p<0.001). The significantly backward and upward condylar movement was observed in the RTB and RTB+PBMT groups (superior joint space (SJS): 0.26 mm, 0.15 mm; posterior joint space (PJS): 0.42mm, 0.11mm, respectively). The RTB group showed the most remarkable changes. Significant improvement of the sagittal maxilla-mandibular relationship was greater in the RTB+PBMT group compared to the RTB group (p=0.02).

CONCLUSION

There were no considerable differences in the condylar position after Class III treatment between the RTB and the RTB+PBMT groups. But a difference in the condylar volume was noticed between the two group.

Effect of low-level laser therapy on condylar growth in children treated with functional appliance: a preliminary study

Purpose

This study aimed to evaluate the skeletal and dentoalveolar changes achieved by combining low-level laser irradiation applied on the condyle area with twin-block therapy in growing class II malocclusion patients.

Methods

Fourteen patients (9 males, 5 females; mean age, 11.4 ± 2 years) with skeletal class II mandibular deficiency were recruited. They were divided into two groups (G 1: twin-block + low-level laser therapy, G 2: twin-block only). A semiconductor diode laser with a wavelength of 940 nm was applied on the condyle area (100 mW, 2.5 J, 3.9 J/cm²). The laser was applied twice a week in the first month and once a week in the second and third months, totalizing 16 sessions. Skeletal, dental, and soft-tissue cephalometric parameters were measured and compared at different treatment points.

Results

Mandibular length (Co-Gn) was significantly increased by 3.6 mm in the experiment group (3.16 SD) and 4.3 mm (4.4 SD) in the control group, with no significant difference between groups at every time point (P-value 0.949 at T2). Similarly, a statistically significant positive effect of treatment was found in both groups on ramus height (Co-Go), upper lip to E-Line, SNA angle, ANB angle, and U1/SN angle with no significant difference between groups.

Conclusion

Based on the results of this preliminary study, low-level laser irradiation with the used parameters seems to have no synergetic impact on the skeletal and dental outcomes of twin-block therapy over 9 months. However, more studies are needed to investigate the effect of low-level laser therapy on condylar growth during functional orthodontic treatment.

Supplementary Information

The online version contains supplementary material available at 10.1007/s41547-022-00158-x.

The effect of functional mandibular advancement for adolescent patients with skeletal class II malocclusion on the TMJ: a systematic review and meta-analysis

OBJECTIVES

This study aimed to assess whether functional mandibular advancement (FMA) will cause temporomandibular joint disorders (TMD) or have side effects on temporomandibular joint (TMJ) in adolescent patients.

METHODS

All searched databases, including PubMed, Web of Science, EMBASE, Cochrane Central Register of Controlled Trails and Scopus were searched. Gray literature and unpublished literature was also searched. Randomized controlled trails (RCT) and non-randomized studies of the effects of interventions (NRSI) directly observe the condition of adolescent patients' TMJ after finishing treatment will be considered to include in our study. According to Cochrane Handbook, Cochrane Collaboration risk of bias tool was used to assess the quality of included RCTs, and Risk of Bias In Non-randomized Studies of Interventions (ROBINS-I) tool was used to assess the quality of included NRSIs.

RESULT

Finally 18 researches were evaluated as eligible to include in this study. 5 of the studies were RCTs, 8 were NRSIs and 5 were systematic reviews. The data of RCTs and NRSIs were statistically pooled in meta-analysis. The number of samples under investigated among primary studies was 579 individuals,there were 80 patients who developed temporomandibular symptoms during or after treatment. But all the subjective symptoms disappeared during follow-up time. The statistical outcomes proved that patients received FMA didn't show more tendency to develop temporomandibular symptoms [I2 = 27%, OR = 0.54, 95%CI (0.33,0.87), p = 0.01].

CONCLUSION

(1) TMJ symptoms may occur during the functional oral appliance wearing, but the symptoms will release or disappear after treatment or during the follow-up period. (2) Less convincing evidence indicates that slightly previous TMD and condyle-glenoid fossa relationship will be improved after treatment. (3) There is TMJ disc anterior displacement observed during treatment, but most of them will return to the normal position later. (4) Moderate evidence support that FMA will not have side effects on TMJ of adolescent patients.

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.

Three-Dimensional Evaluation of Condyle-Glenoid Fossa Complex Following Treatment with Herbst Appliance

The purpose of the present retrospective observational study was to compare the effects of treatment with Herbst appliance and fixed therapy with elastics on the condyle and glenoid fossa complex. Thirty patients aged between twelve and sixteen years with skeletal Class II malocclusion who met the inclusion criteria were included in the study: fifteen patients treated with Herbst appliance (Group 1), and fifteen patients treated with orthodontic camouflage using MBT prescription (MBT^TM Versatile+ Appliance System) (Group 2). For Group 2, patients had CBCT scans taken before treatment either after Herbst appliance removal or at the end of treatment. CBCT scans were evaluated for changes in condyle-glenoid fossa complex using the In Vivo Dental 5.1 software. Statistical significance was set at p ≤ 0.05. On inter-group comparison, the Herbst group showed statistically significant increases in the condylar height of 1.35 mm (p ≤ 0.001) on the right and 1.21 mm (p ≤ 0.01) on the left side, and a condylar volume of 111.03 mm³ (p ≤ 0.01) on the right and 127.80 mm³ (p ≤ 0.001) on the left side. The Herbst group showed anterior remodelling on the postero-superior aspect of glenoid fossa. Herbst appliance treatment induced growth at the condylar head and anterior remodelling of glenoid fossa, thereby improving the maxilla-mandibular relationship in growing skeletal Class II patients.

Cone beam computed tomographic evaluation of the changes in condylar position in growing patients with unilateral posterior crossbite undergoing rapid maxillary expansion followed by fixed orthodontic therapy

PURPOSE

This study aimed at assessing changes in condylar position (CP) in growing patients with unilateral posterior crossbite (UPC) undergoing rapid maxillary expansion (RME) followed by fixed orthodontic treatment (FOT) (experimental-group); and growing patients without posterior crossbite (PC) treated with FOT alone (control-group).

METHODS

Cone beam computed tomography (CBCT) images were obtained before treatment (T0), 6 months after RME (T1) and after FOT (T2) for the experimental-group (n = 19); and at T0 and T2 for the control-group (n = 22). Condylar position-related measurements including the anterior joint space (AJS), superior joint space (SJS), posterior joint space (PJS), lateral position of condyle (LC) and condylar angle (CA) were measured. Non-parametric tests were used.

RESULTS

On the crossbite side, significant increases were found in LC (P = 0.039) and CA (P = 0.007), and on the non-crossbite side significant increases were observed in SJS (P = 0.027) and LC (P = 0.001) between T0, T1 and T2 in patients with UPC. On the right and left sides in the control-group, significant increases were identified in LC (P < 0.001 and P = 0.012, respectively) between T0 and T2.

CONCLUSIONS

In growing patients with UPC, RME followed by FOT is associated with significant changes in CP-related measurements.

Three-dimensional morphological and positional analysis of the temporomandibular joint in adults with posterior crossbite: A cross-sectional comparative study

OBJECTIVES

The purpose of this study was to three-dimensionally (3D) evaluate the morphological and positional features of the temporomandibular joint (TMJ) in adults with unilateral and bilateral posterior crossbite compared with aligned control subjects.

MATERIALS AND METHODS

This cross-sectional comparative study analysed cone beam computed tomography (CBCT) images of 90 adult subjects' divided into three equal groups: bilateral posterior crossbite (BCG), unilateral posterior crossbite (UCG) and control group (CG). 3D measurements of the TMJ included the following: (a) position, angulation and inclination of the mandibular condyles; (b) centralisation of the condyles in their respective mandibular fossae; and (c) volumetric measurements of the TMJ spaces. Intra- and intergroup differences were identified using the paired Student's t test and an analysis of variance (ANOVA) followed by Tukey's post hoc test, respectively.

RESULTS

Regarding the intra-group side-based comparisons, there were significant differences in the anterior and superior joint spaces and the anteroposterior condylar joint position in the UCG. Intergroup comparisons revealed significant differences in the vertical condylar inclination, medial condylar position, condylar width and height, and volumetric joint space between the unaffected side of the UCG and left sides of the other groups. There were significant differences in the anteroposterior condylar inclination, medial condylar position, condylar width and height, anterior, posterior, superior and volumetric joint spaces, and anteroposterior condylar joint position between the crossbite side of the UCG and the right sides of the other groups.

CONCLUSION

Skeletal crossbite accompanied with characteristic morphological and positional TMJ features associated with unilateral posterior crossbite and are associated with side-specific TMJ asymmetry.

Three-Dimensional Assessment of Mandibular Condylar Volume and Position Subsequent to Twin Block Functional Therapy of Skeletal Class II Malocclusion Accompanied by Low-Level Laser Therapy

This study aimed to evaluate and compare the effect of low-level laser therapy (LLLT) on mandibular condylar volume and position following treatment of a Class II malocclusion with a twin block (TB) appliance employing cone beam computed tomography (CBCT). Twenty-four growing patients, aged 9–12 years, were randomly allocated into control and laser groups. All patients were treated with a TB appliance. The patients in the laser group were treated weekly with a gallium–aluminum–arsenide (GaAlAs) diode laser around the temporomandibular joint (TMJ) region for three months. CBCT images were obtained before and after TB therapy and the changes in TMJ and skeletal variables were evaluated and compared among and between the groups. In the laser group, the condylar volume of the right and left sides significantly increased by 213.3 mm³ and 231.2 mm³, respectively (p < 0.05), whereas in the control group it significantly increased by 225.2 mm³, and 244.2 mm³, respectively (p < 0.05), with forward and lateral positioning of both sides. Furthermore, effective mandibular, ramus, and corpus lengths were increased, which were not significant between the groups. Low-Level Laser therapy accomplished no considerable effect on mandibular condylar volume and position following the functional orthopedic treatment of skeletal Class II malocclusions using a TB appliance.

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

Objective

To propose a three-dimensional (3D) method for evaluating temporomandibular joint (TMJ) changes during Twin-block treatment.

Methods

Seventeen 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.

Results

Significant 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.

Conclusions

We 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.

What effect does functional appliance treatment have on the temporomandibular joint? A systematic review with meta-analysis

BACKGROUND

The aim of the current systematic review was to compare the radiologic effects of functional appliance Class II treatment compared to no treatment on the temporomandibular joint and its components.

METHODS

Nine databases were searched up to June 2019 for randomized or prospective non-randomized clinical trials comparing Class II patients treated with functional appliances to untreated patients. After duplicate study selection, data extraction, and risk of bias assessment with the Cochrane tool and the ROBINS-I tool, random effects meta-analyses of mean differences (MDs) and their 95% confidence intervals (CIs) were performed, followed by the assessment of the quality of evidence with GRADE.

RESULTS

A total of 11 papers on 8 unique trials with 377 patients (39.8% male; average age 10.3 years) were finally included. Limited evidence indicated that compared to untreated growing patients functional appliance treatment was associated with increased condylar width (2 studies; MD 1.1 mm; 95% CI 0.1 to 2.2 mm; very low evidence quality), decreased anterior joint space (2 studies; MD - 0.7 mm; 95% CI - 0.5 to - 0.9 mm; very low evidence quality), increased superior joint space (2 studies; MD 0.7 mm; 95% CI 0.5 to 1.0 mm; very low evidence quality), increased posterior joint space (2 studies; MD 1.0 mm; 95% CI 0.9 to 1.2 mm; very low evidence quality), and vertical displacement of the glenoid fossa (2 studies; MD 0.4 mm; 95% CI 0.1 to 0.7 mm; very low evidence quality). The main limitations affecting the validity of the present findings were the inclusion of non-randomized studies with methodological issues, imprecision due to limited samples of the included studies, and inconsistencies among studies.

CONCLUSIONS

Currently existing evidence from controlled clinical studies on humans indicates that functional appliance treatment is associated with positional and skeletal alterations of the temporomandibular joint in the short term compared to untreated controls. However, the clinical relevance of these changes remains unclear, while the quality of existing evidence is low due to methodological issues of existing studies.

REVIEW REGISTRATION

PROSPERO, CRD42018109271.

Cone-beam CT evaluation of temporomandibular joint in permanent dentition according to Angle's classification

OBJECTIVES

To compare characteristics of temporomandibular joint (TMJ) and related structures according to Angle class I, II¹, II², and III.

METHODS

123 Chinese patients (13-36 years old, 60 males, and 63 females) were classified in four groups according to Angle's classification: skeletal class I (31 patients), skeletal class II division 1 (30 patients), skeletal class II division 2 (30 patients), and skeletal class III (32 patients). Left and right TMJs of each subject were evaluated independently with cone-beam computed tomography (CBCT). The position of condyle in the joint fossa was analyzed according to Pullinger.

RESULTS

There were significant differences between class III subjects and class I, II¹, II² in the superior joint space (p < 0.05). Compared with class II¹, II², and III subjects, the height and diameter of condyle in class I was significantly larger (p < 0.05). The width of joint fossa was significantly larger in Angle class III than in Angle class I, II¹, and II², while the depth was significantly smaller. The condyle position in class III subjects was more anteriorly displaced compared with that in class I subjects. In class II² patients, the condyle position was mainly concentric and posterior.

CONCLUSIONS

There are significant differences in condylar morphology, joint space, joint fossa morphology, and condylar position between different Angle classifications.

Dentoalveolar compensation in different anterioposterior and vertical skeletal malocclusions

Background

To evaluate the position and inclination of maxillary and mandibular incisors in adults with different anteroposterior and vertical skeletal malocclusions.

Material and Methods

In this retrospective study, lateral cephalometry of 272 adults (134 males and 138 females) who met the selection criteria were digitally analyzed. They were classified based on both linear and angular measurements, anterioposteriorly into skeletal Class I, Class II and Class III and vertically into hypodivergent, normodivergent and hyperdivergent individuals. Sixteen linear and angular measurements were used to assess both positions and inclinations of maxillary base, mandibular base, maxillary incisors, mandibular incisors, and inter-incisors relationship. Descriptive statistics were calculated and presented. The intra-class correlation coefficient (ICC) was applied for the reliability of measurements. Pearson correlation was used to present the degree of correlation between all variables. A P value of < 0.05 was considered significant.

Results

There was a significant correlation between anteroposterior skeletal discrepancy and maxillary and mandibular dentoalveolar compensation (P<0.001). There was significant correlation between vertical skeletal discrepancy and maxillary and mandibular dentoalveolar compensation except for maxillary incisor position. Anterioposterior skeletal jaw position had greater significant effect on the dentoalveolar changes than the vertical skeletal jaw inclination did with variant degree.

Conclusions

There may be an association between dentoalveolar changes and the skeletal anteroposterior and vertical positions, inclinations and intermaxillary relation. Key words:Dentoalveolar compensation, anteroposterior, vertical, skeletal malocclusions, Cephalometry.

Expression of lubricin in rat posterior mandibular condylar cartilage following functional mandibular forward repositioning

PURPOSE

The aim of the present study was to investigate the effects of mandibular forward repositioning on expression of lubricin in rat posterior condylar cartilage.

METHODS

In total, fifty 5‑week-old female Sprague Dawley rats were divided randomly into experimental groups and control groups. The animals in the experimental groups were fitted with modified acrylic inclined planes to advance the mandible, whereas rats in the normal control groups were left intact. Rats were sacrificed on days 3, 7, 14, 21, and 30, and temporomandibular joint (TMJ) samples were collected. The expression of lubricin of the posterior mandibular condylar cartilage was evaluated by immunohistochemistry.

RESULTS

In the control groups, higher expression of lubricin was observed in the proliferative zone of the posterior mandibular condylar cartilage compared with the hypertrophic zone during the experimental period. Compared with the control group, the positive signals for lubricin of the posterior mandibular condylar cartilage in the experimental animals were significantly higher on days 7, 14, and 21; however, no statistical difference was found on day 3 or 30.

CONCLUSIONS

Data analyses suggest that the bite jumping appliance temporarily enhanced lubricin expression, providing a good mechanical environment for the physiologic growth of the condyle and mandible, and contributes to TMJ remodeling by the regulation of condylar chondrocyte proliferation.