Long-term mandibular adaptations to protrusive function: an experimental study in Macaca mulatta

Evaluation of modified clear Twin Block aligner in treating adolescents with skeletal class II malocclusion: A two-centre cephalometric study

INTRODUCTION

The purpose of this study was to evaluate the therapeutic effect of modified clear Twin Block (CTB) aligner and traditional twin block (TB) appliance from skeletal, dentoalveolar and soft tissue changes in adolescents with skeletal class II malocclusion.

METHODS

A total of 80 adolescents, included in this study from two medical centres, were distributed into CTB group, TB group and control group based on the treatment they received. Lateral cephalograms at pre-treatment (T1) and post-treatment (T2) were measured by modified Pancherz's cephalometric analysis, and dentoskeletal and soft tissue changes were analysed by independent-sample t-test, paired-sample t-test, ANOVA test and Scheffe's Post Hoc test.

RESULTS

Seventy-five adolescents completed the study, including 32 in the CTB group, 32 in the TB group and 11 in the control group. Both CTB and TB treatment showed significant differences in most dentoskeletal and soft tissue measurements. Compared with the control group, improvements were observed in class II molar relationship through significant different in S Vert/Ms-S Vert/Mi in the CTB group (P < .01) and the TB group (P < .001), as well as deep overjet through significant different in S Vert/Is-S Vert/Ii in the CTB group (P < .001) and the TB group (P < .001). Besides, the CTB group also showed less protrusion of lower incisors and resulted in a more significant improvement in profile with fewer adverse effects on speaking, eating and social activities.

CONCLUSIONS

For adolescents with skeletal class II malocclusion, CTB appliance was as effective as TB on improving dentoskeletal and soft tissue measurements, featuring more reliable teeth control and patient acceptance.

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.

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.

Effects of functional orthopedic treatment on mandibular trabecular bone in class II patients using fractal analysis

PURPOSE

The aim of this retrospective study was to evaluate the effects of functional orthopedic treatment on mandibular bone structure using fractal dimension (FD) analysis of panoramic radiographs.

METHODS

The study material consisted of the pre- and posttreatment digital panoramic radiographs of 80 patients (mean age 10.1 ± 2.01 years; 45 girls, 35 boys) with class II malocclusion who were treated with the monoblock or twin block appliances. The following regions of interest (ROI) were selected: ROI1, condylar process; ROI2, angulus mandibulae; ROI3, corpus mandibulae; and ROI4, mental foramen. Pre- and posttreatment FD values were compared for each ROI.

RESULTS

FD values of the mandibular condyle did not change with the functional orthodontic treatment. FD values of the mandibular corpus region had the highest pretreatment values and significantly decreased with treatment (p < 0.05).

CONCLUSION

Functional orthopedic treatment altered the trabeculation of the mandibular bone, but it is speculated that the changes in the occlusal forces seemed to be of primary significance for this effect.

3D Evaluation of Upper Airway Morphological Changes in Growing Patients with Class II Malocclusion Using Sander Bite Jumping Appliance

Class II malocclusion due to mandibular retrognathia is associated with a posterior positioning of the tongue and the hyoid bone, reducing the oropharyngeal volume. This could be a contributing factor to the development of respiratory and cardiovascular problems. This study evaluates the oropharyngeal volume variation in 13 patients with class II malocclusion undergoing functional orthopedic treatment with Sander Bite Jumping Appliance (SBJ). CBCT scans were performed before treatment (T0) and approximately after 12.5 months (T1): the retropalatal volume and retroglossal volume were quantified in mm3 using a segmentation software. At T1, the retropalatal volume increased in 2523 ± 2088 mm3, and the retroglossal volume increased in 2258 ± 1717 mm3. Both values were statistically significant (p < 0.05). This widening of the airways may allow prevention and treatment of sleep-disordered breathing, including obstructive sleep apnea syndrome.

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.

Evaluation of architectural changes in mandibular trabecular and cortical bone pattern after functional treatment

Purpose:

To assess the changes in mandibular trabecular and cortical bone following functional appliance treatment through fractal dimension (FD) and cortical thickness (CorT) measurements.

Material and methods

The study was performed on 45 mandibular retrognathia cases. While the treatment group (T) comprised 30 patients treated using a functional appliance for one year during puberty, the control group (C) consisted of 15 patients who did not receive any orthodontic treatment due to insufficient oral hygiene. FD and CorT analyses were bilaterally evaluated for each mandible. FD measurements were performed on the condylar process, the antegonial notch, and ramus regions on panoramic radiographs. A paired t-test was applied for group analysis, before (T1) and after treatment (T2) and, correspondingly, before (C1) and after (C2) controls. In addition, an independent t-test was used to determine differences between the treatment (∆T = T2−T1) and the control group (∆C = C2−C1).

Results

Statistically significant differences were found in the treatment group between the initial and post-treatment FD values of the right (p < 0.05) and left condyles (p < 0.05), and the CorT measurements on the right (p < 0.01) and the left sides (p < 0.05). There was no statistically significant difference in FD parameters in the control group and a significant difference was only found in the left CorT (p < 0.05). A comparison of the treatment and control groups revealed that the changes in FD and CorT measurements were not statistically significantly different between the groups (p > 0.05).

Conclusion:

Mandibular protraction appliances do not produce trabecular bone alteration in the mandibular condyles, the antegonial notch and ramus over a 12-month time period.

Motor learning might contribute to a therapeutic anterior shift of the habitual mandibular position-An exploratory study

BACKGROUND

Passive mandibular advancement with functional appliances is commonly used to treat juvenile patients with mandibular retrognathism.

OBJECTIVE

The aim of this study was to investigate whether active repetitive training of the mandible into an anterior position would result in a shift of the habitual mandibular position (HMP).

METHODS

Twenty adult healthy subjects were randomly assigned to one of two groups: a training group receiving six supervised functional training sessions of 10 min each and a control group without training. Bonded lateral biteplates disengaged occlusion among both groups throughout the 15-day experiment. Customised registration-training appliances consisted of a maxillary component with an anterior plane and a mandibular component with an attached metal sphere. Training sessions consisted of repeated mouth-opening/closing cycles (frequency: 30/min) to hit an anteriorly positioned hemispherical target notch with this metal sphere. The HMP was registered at defined times during the experiment.

RESULTS

The HMP in the training group showed a statistically significant anterior shift of 1.6 mm (interquartile range [IQR]: 1.2 mm), compared with a significant posterior shift of -0.8 mm (IQR: 2.8 mm) in the control group (p < .05). Although the anterior shift among the training group showed a partial relapse 4 days after the first training block, it then advanced slightly in the 4-day interval after the second training block, which might indicate neuroplasticity of the masticatory motor system.

CONCLUSIONS

Motor learning by repetitive training of the mandible into an anterior position might help to improve the results of functional appliance therapy among patients with mandibular retrognathism.

Evaluating the effects of functional orthodontic treatment on mandibular osseous structure using fractal dimension analysis of dental panoramic radiographs

OBJECTIVE

To evaluate the effects of functional appliance treatment on mandibular trabecular structure using fractal dimension (FD) analysis of dental panoramic radiographs.

MATERIALS AND METHODS

This study was conducted using digital panoramic radiographs of 45 patients with Class II malocclusion treated with functional appliances (treatment group, mean age: 11.39 ± 0.97 years; 23 girls, 22 boys) acquired before (T0) and after (T1) treatment and the panoramic radiographs of 45 control subjects who had undergone no orthodontic treatment (control group, mean age: 11.31 ± 0.87 years; 23 girls, 22 boys). FD values in the condylar process, mandibular corpus, and mandibular angle were analyzed from the panoramic radiographs of both groups.

RESULTS

Analysis of changes in FD between T0 and T1 revealed significant increases in the FD values of the right and left condylar processes and right mandibular corpus in the treatment group (P < .001) and in the right condylar process in the control group (P < .05). Between-group comparisons demonstrated that the treatment group showed greater changes in the condylar process (right, P < .001; left, P < .05) and right mandibular corpus (P < .05) compared to controls. Correlation analysis between the cephalometric and FD changes in the treatment group showed the right condylar process changes were negatively correlated with GoGn/SN angle (P < .05) and positively correlated with Co-Go (P < .05), although these correlations were weak.

CONCLUSIONS

FD analysis demonstrated significant changes in trabeculation of the condyle and mandibular corpus in the treatment group compared to the control group. Functional appliance treatment may lead to skeletal correction by altering skeletal form and trabeculation of the mandibular bone.

Effect of Strontium Ranelate on Condylar Growth during Mandibular Advancement in Rats

Objective

Strontium ranelate (SR), unlike other anti-osteoporotic agents, might not only prevent bone resorption but also might induce bone formation. The aim of this experimental study was to evaluate the effects of systemic SR on condylar growth during mandibular advancement (MA) in growing rats.

Methods

Fifty-six, 8-week-old Wistar male rats weighting 160-190 g were randomly divided into four groups; one control (n=14) and three experimental (n=14). Group 1: Control group, Group 2: SR (900mg/kg daily dose), Group 3: MA, Group 4: SR +MA. The amount and direction of mandibular growth were assessed by linear measurements on the computed tomography (CT) images taken on days 1, 15, and 30. For immunohistochemical evaluation, half of the subjects in the groups were sacrificed on the 15th day (early phase) and the rest of them on the 30th day (late phase). New cartilage and bone formation areas on the condyle were analyzed by using Sox9 and Osteopontin antibodies.

Results

Early and late CT images measurements showed no significant difference between the groups (p<0.05). However, there were significant differences between the control and experimental groups in the immunohistochemical assessment. Severe immunolocalization of SOX9 and Osteopontin was observed in Group 4, while the immunolocalization scores were moderate in Group 2 and Group 3. In addition, early histological findings were similar to late results in all groups.

Conclusion

In mandibular advancement therapy, Strontium ranelate could be therapeutically effective in avoiding relapse and reducing the duration of retention.

3D assessment of mandibular skeletal effects produced by the Herbst appliance

BACKGROUND

A functional appliance is commonly used to optimize the development of the facial skeleton in the treatment of Class II malocclusion. Recent three-dimensional(3D) image-based analysis offers numerous advantages in quantitative measurement and visualization in orthodontics. The aim of this study was to localize in 3D the skeletal effect produced by the Herbst appliance on the mandible using the geometric morphometric technique.

METHODS

Twenty patients treated with a Herbst appliance and subsequent fixed appliances were included. Cone-beam computed tomography (CBCT) images were taken before treatment (T1), 8 weeks after Herbst appliance removal (T2), and after subsequent fixed appliance treatment (T3). Spatially dense morphometric techniques were used to establish the corresponding points of the mandible. The mandibular morphological changes from T1-T2, T2-T3, and T1-T3 were calculated for each patient by superimposing two mandibular models at two time points with robust Procrustes superimposition. These changes were then compared to the morphological changes estimated from normative mandibular growth curves over the same period. The proportion of cases exceeding the growth expression for controls was compared to a normal population using a one tailed binomial test.

RESULTS

Approximately 1.5-2 mm greater condylar changes and 0.5 mm greater changes in the chin occurred from Tl to T2. This effect lasted until the completion of treatment (T1-T3), but there was no obvious skeletal effect during the orthodontic phase (T2-T3). Approximately 40-50% of the patient sample exceeded condylar growth by > 1.5 mm compared to untreated controls (p < .05). However, changes at the chin were not statistically significant.

CONCLUSIONS

The principal skeletal effect of Herbst appliance treatment was additional increase in condylar length for about half of the sample. This inconsistency may relate to the degree of mandibular growth suppression associated with a specific malocclusion.

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.

Evaluation of temporomandibular joint, masticatory muscle, and brain cortex activity in patients treated by removable functional appliances: a prospective fMRI study

OBJECTIVES

The aim of this study is to evaluate the effects of functional orthodontic appliances on the masticatory muscles, temporomandibular joint (TMJ), and brain to determine whether using functional appliances full-time or only at night yields different results.

METHODS

16 patients with Class II malocclusion were included in this study. Eight patients were instructed to wear their appliances (monoblock/twinblock) full-time and the other eight patients were instructed to wear them at night while sleeping. An additional 10 patients with Class II malocclusion were later included as a pre-treatment control group. Signal intensity ratios (SIR) of TMJ structures and morphological evaluations of the masticatory muscles were done for all patients. Functional MRI (fMRI) data were also obtained from the patients while performing chewing and biting movements.

RESULTS

ANB angle was reduced significantly in both the full-time and night wear groups, by values of 1.17° and 1.35°, respectively (p < 0.05). MRI showed that SIRs were significantly increased in both groups in the masticatory muscles, retrodiscal pad, condylar process, and articular disc (p < 0.05). Both resting and task-based fMRI evaluation revealed significant increases in blood oxygen level dependent signals in several regions of the brain in both groups (p < 0.05).

CONCLUSIONS

The cephalometric and MRI findings of this study indicate that the treatment effects were similar for both wear schedules. Functional appliances should be regarded not as simple devices that treat Class II malocclusion through skeletal and dental correction alone, but as exercise devices that lead to neuromuscular changes by facilitating muscle adaptation and activating various brain regions.

[Mandibular repositioning in adult patients. An alternative to surgery in some patients? A two-year follow-up]

INTRODUCTION

A number of adult patients with skeletal discrepancies refuse surgical intervention.

AIMS

The aim was to assess the reaction to mandibular repositioning in simulating a skeletal correction in such patients.

MATERIALS AND METHODS

32 consecutive patients without any signs of temporo-mandibular dysfunction (TMD) were offered mandibular repositioning, as a non-invasive alternative and it was explained to them that the approach was based on the results described in case reports. Before initiating any treatment initial records, headfilms, study casts and photos were taken (T₀) and the mandible was repositioned to camouflage the skeletal discrepancy by means of an occlusal built-up in Triad^® Gel.

RESULTS

Three months later (T₁) 23 patients had adapted to the new occlusion reflected in absence of functional problems and lack of fracture of the built-up. In these patients the mandibular position was maintained by orthodontics adjusting the occlusion to the built-up position (T₁). The skeletal changes occurring during repositioning were assessed on sagittal and frontal head films while intra-articular changes occurring during a 2-year follow-up period (T₂) were evaluated on images constructed from CBCT images. No significant changes, neither in the direction of a relapse nor in the direction of further normalization of the condylar positioning, were observed during the 2-year observation period.

CONCLUSIONS

Repositioning is a non-invasive intervention and may be considered a valid alternative to surgery in some patients. Morphological variables from the radiographs taken at T₀ and the results of the initial clinical evaluation of dysfunction yielded only vague and insignificant indications regarding the predictability of adaptation to the repositioning.

[Not Available]

James A. McNamara, diplômé de l’Université de Californie de Berkeley, a suivi ses études de dentisterie et d’orthodontie au sein de l’Université de Californie de San Francisco, et a obtenu un doctorat en anatomie à l’Université du Michigan. Il est titulaire actif de la chaire de professeur émérite Thomas M. and Doris Graber dans le département d’orthodontie et d’odontologie pédiatrique. Il est également professeur émérite de biologie cellulaire et du développement à la faculté de médecine de l’Université du Michigan, et professeur émérite chargé de recherche au Centre de la croissance et du développement humains. Il est l’auteur (avec l’artiste William L. Brudon) de Orthodontics and Dentofacial Orthopedics, manuel très largement utilisé.

The use of functional appliances in contemporary orthodontic practice

Functional appliances have been used for over 100 years in orthodontics to correct Class II malocclusion. During this time numerous different systems have been developed often accompanied by claims of modification and enhancement of growth. Recent clinical evidence has questioned whether they really have a lasting influence on facial growth, their skeletal effects appearing to be short term. However, despite these findings, the clinical effectiveness of these appliances is acknowledged and they can be very useful in the correction of sagittal arch discrepancies. This article will discuss the clinical use of functional appliances, the underlying evidence for their use and their limitations.

Treatment of a mandibular functional shift in an adolescent boy with temporomandibular disorder and crossbites

A mandibular functional shift usually poses a challenge for orthodontists, especially when it is accompanied by a temporomandibular disorder (TMD). Accurate diagnosis and complete elimination of the etiologic factors are the keys to an esthetic and stable outcome. This article describes the treatment of a teenager with a mandibular functional shift, TMD symptoms, and facial asymmetry resulting from an asymmetric maxillary arch form and multiple crossbites as occlusal interferences. The treatment alternatives and effective orthodontic techniques are described. To optimize the treatment results and prevent the recurrence of the TMD after treatment, the displaced mandible was repositioned by full-time wearing of a splint for 10 months. Adhesive bite-blocks were used to maintain the newly acquired mandibular position during fixed appliance treatment. A series of nickel-titanium and stainless steel rectangular archwires was placed in the maxillary arch to reshape it for 8 months after alignment. Finally, the displaced mandible was steadily seated into its physiologic position with fine occlusion. The TMD symptoms disappeared and never relapsed after treatment. At 2 years 3 months of retention, there was good stability. The combined splint and fixed appliance approach resolved an intractable clinical problem and avoided using additional appliances. An esthetic, functional, and stable outcome was achieved that satisfied both the patient and his parents.

The effects of altered maxillary growth on patterns of mandibular rotation in a pig model

OBJECTIVES

A thorough understanding of influence of maxillary growth on patterns of mandibular rotation during development is important with regard to the treatment of skeletal discrepancies. In the present study, we examined whether experimentally altered maxillary position has a significant influence on patterns of mandibular rotation in a pig model.

DESIGN

Maxillary growth was altered in a sample of n=10 domestic pigs via surgical fixation of the circummaxillary sutures. We compared the experimental group to control and surgical sham samples and assessed the effects of altered maxillary growth on mandibular form using geometric morphometric techniques. We tested for significant differences in mandibular shape between our samples and examined axes of morphological variation. Additionally, we examined whether altered mandibular shape resulting from altered maxillary position was predictably associated with morphological changes to the condylar region.

RESULTS

There was a statistically significant difference in mandibular shape between the experimental and control/sham groups. As a result of vertical displacement of the snout, mandibles in the experimental sample resulted in greater anterior rotation when compared to the control/sham pigs. Variation in rotation was correlated with morphological changes in the condyle including the shape of the articular surface and condylar orientation indicative of greater anterior mandibular rotation.

CONCLUSIONS

Vertical displacement of the maxilla had a significant effect on mandibular shape by encouraging anterior mandibular rotation. This result has important implications for understanding the effects of altered mandibular posture on condylar remodeling the treatment of skeletal discrepancies such as the correction of hyperdivegent mandibular growth.

Treatment effects of myofunctional appliances in different jaw rotations in Class II division 1 malocclusion

Aim

This retrospective study was conducted to determine skeletal, dentoalveolar changes in children treated with Twin Block or activator for the treatment of Class II Division 1 malocclusion with different jaw rotations.

Materials and Methods

Standardized lateral cephalograms of 32 patients (18 boys, 14 girls) between the ages of 11 and 14 years were chosen and divided into two groups, high angle (FMA >27) and low angle (FMA <20). Cephalograms were taken at T1 (pre-treatment) and T2 (after one year of myofunctional therapy).These were manually traced and analysed.

Results

The results showed statistically significant increase in SNB angle, VRP-Pog due to forward movement of the mandible. The overjet reduced significantly due to retroclination of upper incisors and proclination of lower incisors in both groups.

Conclusion

It was concluded that both high angle and low angle groups responded equally well to myofunctional therapy showing significant skeletal and dentoalveolar changes.

Treatment effects of removable functional appliances in patients with Class II malocclusion: a systematic review and meta-analysis

OBJECTIVE

To assess the treatment effects of removable functional appliances (RFAs) in treated versus untreated patients with Class II malocclusion by means of lateral cephalometric radiographs.

SEARCH METHODS

Unrestricted electronic search of 18 databases and manual searches up to October 2013.

SELECTION CRITERIA

Prospective randomized and non-randomized controlled trials reporting on cephalometric angular measurements of Class II patients treated with RFAs and their matched controls.

DATA COLLECTION AND ANALYSIS

Skeletal, dental, and soft tissue changes were annualized and stratified to short- and long-term effects. Methodological limitations were evaluated with the Cochrane Risk of Bias tool and the Downs and Black checklist. Mean differences (MDs) with their 95% confidence intervals (CIs) were calculated from random-effects meta-analyses. Patient- or appliance-related subgroup analyses and sensitivity analyses were performed with mixed-effects models.

RESULTS

Seventeen studies were included (1031 patients; mean age: 10.6 years), with most of them originating from university clinics and reporting short-term effects (directly after the removal of RFAs). Treatment was associated with minimal reduction of SNA angle (11 studies, MD = -0.28 degree/year, 95% CI: -0.44 to -0.12 degree/year), minimal increase of SNB angle (11 studies, MD = 0.62 degree/year, 95% CI: 0.36-0.88 degree/year), and small decrease of ANB angle (10 studies, MD = -1.14 degree/year, 95% CI: -1.52 to -0.77 degree/year) compared to untreated Class II patients. RFAs caused significant dentoalveolar changes (predominantly retroclination of the upper incisors) and significant soft tissue changes. Skeletal changes were more pronounced with the Twin Block appliance. Various patient- or appliance-related factors influenced the results of the subgroup analyses, while the sensitivity analyses indicated robustness. Existing evidence was inadequate to assess the long-term effectiveness of RFAs.

CONCLUSIONS

The short-term evidence indicates that RFAs are effective in improving Class II malocclusion, although their effects are mainly dentoalveolar, rather than skeletal.

Three-dimensional treatment outcomes in Class II patients treated with the Herbst appliance: a pilot study

INTRODUCTION

The aims of this study were to analyze 3-dimensional skeletal changes in subjects with Class II malocclusion treated with the Herbst appliance and to compare these changes with treated Class II controls using 3-dimensional superimposition techniques.

METHODS

Seven consecutive Herbst patients and 7 Class II controls treated with Class II elastics who met the inclusion criteria had cone-beam computed tomographs taken before treatment, and either after Herbst removal or at posttreatment for the control subjects. Three-dimensional models were generated from the cone-beam computed tomography images, registered on the anterior cranial bases, and analyzed using color maps and point-to-point measurements.

RESULTS

The Herbst patients demonstrated anterior translation of the glenoid fossae and condyles (right anterior fossa, 1.69 ± 0.62 mm; left anterior fossa, 1.43 ± 0.71 mm; right anterior condyle, 1.20 ± 0.41 mm; left anterior condyle, 1.29 ± 0.57 mm), whereas posterior displacement predominated in the controls (right anterior fossa, -1.51 ± 0.68 mm; left anterior fossa, -1.31 ± 0.61 mm; right anterior condyle, -1.20 ± 0.41 mm; left anterior condyle, -1.29 ± 0.57 mm; P <0.001). There was more anterior projection of B-point in the Herbst patients (2.62 ± 1.08 mm vs 1.49 ± 0.79 mm; P <0.05). Anterior displacement of A-point was more predominant in the controls when compared with the Herbst patients (1.20 ± 0.53 mm vs -1.22 ± 0.43 mm; P <0.001).

CONCLUSIONS

Class II patients treated with the Herbst appliance demonstrated anterior displacement of the condyles and glenoid fossae along with maxillary restraint when compared with the treated Class II controls; this might result in more anterior mandibular projection.

Vertical facial height and its correlation with facial width and depth: Three dimensional cone beam computed tomography evaluation based on dry skulls

Introduction

The aim of the present study was to evaluate how vertical facial height correlates with mandibular plane angle, facial width and depth from a three dimensional (3D) viewing angle.

Methods

In this study 3D cephalometric landmarks were identified and measurements from 43 randomly selected cone beam computed tomography (CBCT) images of dry skulls from the Weisbach collection of Vienna Natural History Museum were analyzed. Pearson correlation coefficients of facial height measurements and mandibular plane angle and the correlation coefficients of height-width and height-depth were calculated, respectively.

Results

The mandibular plane angle (MP-SN) significantly correlated with ramus height (Co-Go) and posterior facial height (PFH) but not with anterior lower face height (ALFH) or anterior total face height (ATFH). The ALFH and ATFH showed significant correlation with anterior cranial base length (S-N), whereas PFH showed significant correlation with the mandible (S-B) and maxilla (S-A) anteroposterior position.

Conclusions

High or low mandibular plane angle might not necessarily be accompanied by long or short anterior face height, respectively. The PFH rather than AFH is assumed to play a key role in the vertical facial type whereas AFH seems to undergo relatively intrinsic growth.

The effects of gradually induced backward movement of the mandible by a Twin Inclined Plane Device in rats

OBJECTIVE

To develop a model of gradually induced backward movement of the mandible under normal masticatory action and to examine morphological changes in the mandible and condylar cartilage in rats.

MATERIALS AND METHODS

The newly developed Twin Inclined Plane Device (TIPD) was composed of upper and lower posterior metal crowns with a long inclined plane on both sides separately and was applied in experimental groups of 6-week-old male Wister rats. After 3, 14, 30, and 60 days, the rats were euthanatized and samples were collected. Various measurements and hematoxylin-and-eosin stains were performed.

RESULTS

From day 30 on, the length of the condylar process was shorter in the TIPD groups than in the control groups (P < .05). The angulation of the condylar process axis to the mandibular plane was greater in the TIPD groups (P < .01). The thickness of the condylar cartilage in the posterior part of the posterior region was thinner in the TIPD groups (P < .05) on day 30 and even thinner (P < .01) on day 60; from day 30 on, the thickness in the anterior part of the posterior region was thicker in the TIPD groups (P < .01).

CONCLUSION

TIPD can successfully induce backward movement of the mandible under normal masticatory action. TIPD can cause region-specific changes in condylar cartilage and leads to a continuous remodeling.

[Orthodontic treatment of nongrowing patient with Class II Division 2 malocclusion by Herbst appliance]

BACKGROUND

Inheritance is most casual etiological factor of Class II division 2 malocclusion. This kind of malocclusion is very difficult for treatment specially in older patients.

CASE REPORT

In the female patient, 20 years old, at the beginning of the treatment at the School of Dentistry in Belgrade, lateral cephalogram showed skeletal and dentoalveolar Class II division 2 malocclusion. She was in the Herbst treatment for 8 months and 12 months more with a fixed multibracket appliance. The measurements were performed on lateral cephalograms before and after the treatment: ii, is, mi, ms, Pg and ss. The distance from these points to occlusal perpendicular line (Olp) were measured and compared from cephalogram before to cephalogram after the treatment. Temporomandibular joint (TMJ) tomograms were compared from before and after the treatment by superimposition. Correction was found in molar and incisor relation, overjet and overbite. There were found sagital skeletal changes and soft tissue profile improvement.

CONCLUSION

Herbst appliance is effective in the treatment of Class II malocclusions, even in adult patients. Dental and skeletal changes as a result of Herbst treatment could be good choice instead of camouflage orthodontics or surgical decision.

Differential gene expression in the perichondrium and cartilage of the neonatal mouse temporomandibular joint

Our goal was to discover genes differentially expressed in the perichondrium (PC) of the mandibular condylar cartilage (MCC) that might enhance regenerative medicine or orthopaedic therapies directed at the tissues of the temporomandibular joint. We used targeted gene arrays (osteogenesis, stem cell) to identify genes preferentially expressed in the PC and the cartilaginous (C) portions of the MCC in 2-day-old mice. Genes with higher expression in the PC sample related to growth factor ligand-receptor interactions [FGF-13 (6.4x), FGF-18 (4x), NCAM (2x); PGDF receptors, transforming growth factor (TGF)-beta and IGF-1], the Notch isoforms (especially Notch 3 and 4) and their ligands or structural proteins/proteoglycans [collagen XIV (21x), collagen XVIII (4x), decorin (2.5x)]. Genes with higher expression in the C sample consisted mostly of known cartilage-specific genes [aggrecan (11x), procollagens X (33x), XI (14x), IX (4.5x), Sox 9 (4.4x) and Indian hedgehog (6.7x)]. However, the functional or structural roles of several genes that were expressed at higher levels in the PC sample are unclear [myogenic factor (Myf) 9 (9x), tooth-related genes such as tuftelin (2.5x) and dentin sialophosphoprotein (1.6x), VEGF-B (2x) and its receptors (3-4x) and sclerostin (1.7x)]. FGF, Notch and TGF-beta signalling may be important regulators of MCC proliferation and differentiation; the relatively high expression of genes such as Myf6 and VEGF-B and its receptors suggests a degree of unsuspected plasticity in PC cells.

Mandibular functional positioning only in vertical dimension contributes to condylar adaptation evidenced by concomitant expressions of L-Sox5 and type II collagen

OBJECTIVE

Concerted expressions of L-Sox5 and type II collagen play an important part in osteogenic transition in epiphyseal cartilage. This study was designed to elucidate the role of mandibular vertical functional positioning in condylar adaptive remodelling by examining L-Sox5 and type II collagen expressions in condylar cartilage.

DESIGN

40 female Sprague-Dawley rats at age of 5 weeks were randomly divided into the experimental (n=20) and control groups (n=20). Bite plates were fitted on the upper posterior teeth of the experimental animals to induce functional repositioning of mandible in vertical dimension. The animals in both experimental and matched control groups were sacrificed on days 3, 6, 9 and 12, respectively. Tissue sections were cut in the sagittal plane through the mandibular condyles and processed with histomorphological examination for cellular response and immunohistochemical test for expressions of L-Sox5 and type II collagen. Quantitative assessment was conducted with computer-assisted imaging system to reveal the correlation between these two factors.

RESULTS

(1) Both L-Sox5 and type II collagen were expressed in prechondroblastic cells and chondroblastic cells. (2) When mandible was downward positioned, the amount of L-Sox5 expression was significantly higher by 16.1% (day 9) and 24.2% (day 12) than that of the control (P<0.05); Similarly, type II collagen expression in the experimental group was also significantly stronger by 9.3% (day 9) and 12.3% (day 12) than control group (P<0.05), indicating an enhanced osteogenic transition occurring in condylar cartilage. (3) There was a similarity in temporospatial patterns between the expressions of these two factors, indicating their integral functions in facilitating condylar adaptation.

CONCLUSIONS

It is suggested that L-Sox5 plays a key role in adaptive remodelling of condylar cartilage resulting from downward positioning of the mandible. Integration with type II collagen enables L-Sox5 to induce osteogenic transition and consequently to encourage endochondral ossification.

Gene Therapy to Enhance Condylar Growth Using rAAV-VEGF

Objective: To test the hypothesis that the introduction of specific vascular growth inducting genes would favorably affect mandibular condylar growth in Sprague-Dawley (SD) rats over a limited experimental period. Therefore, the aim of this study is to examine the effect of gene therapy on condylar growth by means of a morphological assessment.

Materials and Methods: Ninety 35-day-old female SD rats were randomly divided into three groups, which received any of the injections of recombinant adeno-associated virus mediated vascular endothelial growth factor (rAAV-VEGF), rAAV mediated enhanced green fluorescence protein (rAAV-eGFP), or phosphate-buffered saline (PBS) into both mandibular condyles. Each group of rats was sacrificed on the following experimental days: 7, 14, 21, 30, and 60. Left halves of the mandibles were isolated and digital pictures were obtained in a standardized manner.

Results: The length of condylar process (B-F) as well as mandibular length (A-F) significantly increased on day 30 and continued to increase until the end of the experiment. Moreover, the width of condyle (Q-R) had increased significantly from day 30 and lasted to day 60. Condylar length (C-D) was found to be significantly longer on day 60.

Conclusions: Gene therapy with VEGF stimulates condylar growth at will. The rAAV-VEGF is an excellent candidate for future gene therapy to induce mandibular growth.

Mandibular Growth Changes and Cervical Vertebral Maturation

Objective: To evaluate mandibular dimensional changes and regional remodeling occurring during five intervals of circumpubertal growth.

Materials and Methods: This investigation evaluated a unique sample of subjects in whom tantalum implants were placed into the craniofacial complex during childhood. The sample was obtained from the Mathews and Ware implant study originally conducted at the University of California San Francisco in the 1970s, with longitudinal cephalometric records of 20 subjects (13 female, 7 male) available for evaluation. Cephalograms at six consecutive stages of cervical vertebral maturation (CS1 through CS6) were analyzed.

Results: Peak mandibular growth was noted during the interval from CS3 to CS4. Forward rotation of the mandible was due to greater mandibular growth posteriorly than anteriorly. Progressive closure of the condylar-ramus-occlusal (CRO) angle resulted in a forward and upward orientation of the ramus relative to the corpus of the mandible due to increased vertical growth of the condyle.

Conclusions: A peak in mandibular growth at puberty was substantiated. Mandibular remodeling and condylar rotation continue to occur after the growth spurt.

Remodeling the dentofacial skeleton: the biological basis of orthodontics and dentofacial orthopedics

Orthodontic tooth movement is dependent upon the remodeling of the periodontal ligament and alveolar bone by mechanical means. Facial sutures are also fibrous articulations, and by remodeling these joints, one can alter the positional relationships of the bones of the facial skeleton. As might be expected from the structure and mobility of the temporomandibular joint (TMJ), this articulation is more resistant to mechanical deformation, and whether functional mandibular displacement can alter the growth of the condyle remains controversial. Clinical investigations of the effects of the Andresen activator and its variants on dentofacial growth suggest that the changes are essentially dento-alveolar. However, with the popularity of active functional appliances, such as the Herbst and twin-block based on 'jumping the bite', attention has focused on how they achieve dentofacial change. Animal experimentation enables informed decisions to be made regarding the effects of orthodontic treatment on the facial skeleton at the tissue, cellular, and molecular levels. Both rat and monkey models have been widely used, and the following conclusions can be drawn from such experimentation: (1) Facial sutures readily respond to changes in their mechanical environment; (2) anterior mandibular displacement in rat models does not increase the mitotic activity of cells within the condyle to be of clinical significance, and (3) mandibular displacement in non-human primates initiates remodeling activity within the TMJ and can alter condylar growth direction. This last conclusion may have clinical utility, particularly in an actively growing child.

Mandibular advancement and morphological changes in the mandibles of female mice of different ages

Mandibular advancement (MA) by means of functional orthopedic techniques is currently used in young patients to stimulate mandibular growth. The aim of this study was to evaluate the morphological changes in the mandibles of 2-, 7-, and 16-month-old female mice after MA. Every 3 days during 1 month, the lower incisors were trimmed by 1mm to induce protrusion when the animal was feeding. The left mandibles of the 30 experimental and 28 control individuals were subsequently dissected and digital images were obtained to analyze nine linear/angular measurements. The condylar microstructure was also analyzed by scanning electron microscopy (SEM). The linear/angular measurements showed a growth response in different mandibular regions in 2- and 16-month-old individuals. SEM showed that, in the 7-month-old mice, the condylar cartilage had regenerated in the treated individuals but not in the controls. The results suggest that MA produces mandibular growth in 2- and 16-month-old female mice. Although there was no mandibular growth in 7-month-old mice, regeneration of the condylar cartilage was detected, thus demonstrating that different responses to the MA stimulus occur in female mice of different ages.

Growth modification of the mandible with ultrasound in baboons: a preliminary report

INTRODUCTION

Growth modification for patients with skeletal Class II malocclusions due to mandibular deficiency is controversial. Low-intensity pulsed ultrasound (LIPUS) can modify mandibular growth in growing rabbits. Before applying this treatment to humans, we must study the effect on mandibular growth in higher animal models. The objective of this study was to evaluate the effect of LIPUS on mandibular growth in baboons.

METHODS

Fourteen juvenile male hamadryas baboons were divided into 2 groups of 7 each. One group received bite-jumping appliances (jumper group), and the other group did not (control group). In both groups, the left temporomandibular joint area received LIPUS (stimulated), and the right side served as the control (unstimulated). Four months after the start of treatment, the baboons were injected with 99-mTc methylene diphosphonate and killed. They were decapitated and scanned for bone growth by using a dual head gamma camera. The mandibles were dissected, sectioned into halves, and radiographed for anthropometric measurements. The condyles were harvested and processed for histological examinations.

RESULTS

LIPUS increased mandibular length and growth activity in all treated sides (P<.001), especially in the jumper group.

CONCLUSIONS

LIPUS enhances mandibular growth in growing baboons, especially when combined with anterior mandibular jumping appliances.

Long-term comparison of treatment outcome and stability of Class II patients treated with functional appliances versus bilateral sagittal split ramus osteotomy

PURPOSE

The objective of this study was to compare the treatment outcomes and stability of patients with Class II malocclusion treated with either functional appliances or surgical mandibular advancement.

MATERIAL

The early-treatment group consisted of 30 patients (15 girls, 15 boys), with a mean age of 10 years 4 months (range, 7 years 5 months to 12 years 5 months), who received either Fränkel II (15 patients) or Herbst appliances (15 patients). The surgical group consisted of 30 patients (23 female, 7 male), with a mean age of 27 years 2 months (range, 13 years 0 months to 53 years 10 months). They were treated with bilateral sagittal split ramus osteotomies with rigid fixation. Lateral cephalograms were taken for the early-treatment group at T1 (initial records), T2 (completion of functional appliance treatment), and Tf (completion of comprehensive treatment). In the surgical group, lateral cephalograms were taken at T1 (initial records), T2 (presurgery), T3 (postsurgery), and Tf (completion of comprehensive treatment). The average times from the completion of functional appliance treatment or surgery to the final cephalograms were 35.8 months and 34.9 months, respectively. A mixed-design analysis of variance was used to compare changes within and between groups.

RESULTS

In the functional appliance group, the mandible continued to grow in a favorable direction even after discontinuation of the functional appliance. Both groups had stable results over time. Both groups finished treatment with the same cephalometric measurements. Significant skeletal and soft tissue changes were noted in the treatment groups due to either functional or surgical advancement of the mandible. More vertical relapse was noted in the surgical group than in the functional group.

CONCLUSIONS

This study suggests that early correction of Class II dentoskeletal malocclusions with functional appliances yields favorable results without the possible deleterious effects of surgery.

Condyle-fossa modifications and muscle interactions during Herbst treatment, Part 2. Results and conclusions

Herbst appliances were activated progressively in growing nonhuman primates, and the results were compared with primate and human controls. The methods and materials of this research are explained in Part 1 of this study. The results are discussed here in Part 2. All experimental subjects developed large super Class I malocclusions, the result of many factors including posterior movement of the maxilla and the maxillary teeth, an increased horizontal component of condylar growth, and anterior displacement of the mandible and the mandibular teeth. The growth modification measured in the glenoid fossa was in an inferior and anterior direction. Restriction of the downward and backward growth of the fossa observed in the control subjects might additionally contribute to the overall super Class I malocclusion. Clinically, these combined effects could be significant at the fossa. The restriction of local temporal bone (fossa) growth cannot be observed clinically; thus, these results might also clarify some Class II correction effects that cannot be explained with functional appliances. Differences in the area and maximum thickness of new bone formation in the glenoid fossa and in condylar growth were statistically significant. The bony changes in the condyle and the glenoid fossa were correlated with decreased postural electromyographic activity during the experimental period. Results from permanently implanted electromyographic sensors demonstrated that lateral pterygoid muscle hyperactivity was not associated with condyle-glenoid fossa growth modification with functional appliances, and that other factors, such as reciprocal stretch forces and subsequent transduction along the fibrocartilage between the displaced condyle and fossa, might play a more significant role in new bone formation. These results support the growth relativity concept.