Initial and late treatment effects of headgear-Herbst appliance with mandibular step-by-step advancement

Treatment effects of Herbst appliance in skeletal Class II cases during pre-pubertal and post-pubertal periods: a cone-beam computed tomographic study

In the present study, Thirty-six Class patients II (A condition in which the upper jaw is larger than the lower jaw) were randomly selected and assigned to one of two groups based on their maturation stage: the pre-pubertal group (18 patients, mean age 9.15 ± 1.5 years) and post-pubertal group (18 patients, mean age 16.3 ± 1.0 years). All patients were treated with a metallic splint-supported Herbst IV appliance (An appliance that acts like artificial joint working between the upper and power jaws that keeps the lower jaw in a forward position, thus improving the Class II condition). Pretreatment (T1) and post-Herbst IV treatment (T2) scans were obtained for both groups. Dental and skeletal measurements were made on the scans and statistically analyzed using paired and independent t-tests. The study hypothesis was that; the dentoskeletal changes in Class II malocclusion treatment using Herbst appliance in the Pre-pubertal is more than the Post-pubertal growth stage due to the remaining growth potential for the pre-pubertal patients. The comparison between the two groups revealed statistically significant differences in horizontal skeletal parameters in the lower jaw only, while other readings were similar.

Long-term stability of Class II malocclusion treatment with the cantilever bite jumper

INTRODUCTION

This study aimed to assess the long-term stability of Class II malocclusion treatment with the Cantilever Bite Jumper (CBJ) after 13 years of follow-up.

METHODS

The treatment group comprised 10 Class II Division 1 malocclusion patients treated with the CBJ, followed by fixed appliances, analyzed at 3 stages: pretreatment (aged 11.56-14.32 years), posttreatment (aged 16.34-19.58 years), and long-term posttreatment (aged 29.04-32.33 years). The control group included 15 subjects with normal occlusion. Intragroup treatment changes comparison was performed with repeated measures and analysis of variance followed by Tukey tests. Intergroup comparisons regarding the long-term posttreatment changes were performed with t tests.

RESULTS

No statistically significant relapse was observed during the follow-up period. Morever, the treated group presented a significantly smaller increase in lower anterior facial height and greater retrusion of the lower lip than the control group in the posttreatment period.

CONCLUSIONS

Treatment with the CBJ, followed by fixed appliances, is a stable alternative for Class II Division 1 malocclusion correction. The dentoskeletal and soft-tissue changes obtained during treatment remained stable in the long-term posttreatment follow-up.

Evaluation of mandibular changes after rapid maxillary expansion: a CBCT study in youngsters with unilateral posterior crossbite using a surface-to-surface matching technique

OBJECTIVES

The purpose of this study was to evaluate mandibular asymmetry in youngsters with posterior unilateral crossbite (PUXB), through cone-beam computed tomography and reverse engineering technique, before and after rapid maxillary expansion (RME) treatment.

MATERIALS AND METHODS

Forty cone-beam computed tomography (CBCT) images were obtained from all patients at two time points, namely T0 acquired before the placement of a Hyrax expander and T1 after appliance removal. The CBCT scans were segmented and volume rendered into a surface there-dimensional (3D) mesh model. Thereafter, mandibular models were digitally registered by using a "best-fit" algorithm. Surface and volumetric changes, between T0 and T1, were compared by using Student's t tests.

RESULTS

A slight increase of 0.45 cm3 of the total mandibular volume was found at T1 when compared with T0 (p < 0.001). The mandibular hemi-volume on the crossbite side (CB) was slightly smaller than the non-crossbite side both at T0 and T1. However, the mean differences of hemi-volume from the CB (crossbite) and non-CB side between T0 and T1 show a decrease of 0.26 cm3 (p < 0.001). Findings for the surface-to-surface deviation analysis demonstrated a fine percentage of matching at T0 which slightly improved at T1 (p < 0.001).

CONCLUSIONS

Youngsters affected by PUXB showed a very slight and not statistically significant volumetric and morphological asymmetry between CB side and non-CB side at T0. However, the change in mean differences of 0.26 cm cannot be considered clinically relevant.

CLINICAL RELEVANCE

Mandibles in young PUXB patients exhibit only a very mild mandibular asymmetry. Although the statistically significant mean change found right after RME removal cannot be considered clinically relevant, a more consistent sample and a longer follow-up could be of interest in explaining the short-term findings.

Effects of Class II division 1 malocclusion treatment with three types of fixed functional appliances

Objective:

This study aimed at comparing the dentoskeletal changes in patients with Class II division 1 malocclusion, treated with three types of fixed functional appliances.

Methods:

A sample comprising 95 patients with the same malocclusion, retrospectively selected, and divided into four groups, was used: G1 consisted of 25 patients (mean age 12.77 ± 1.24 years) treated with Jasper Jumper appliance; G2, with 25 patients (mean age 12.58 ± 1.65 years) treated with the Herbst appliance; G3, with 23 patients (mean age 12.37 ± 1.72 years) treated with the Mandibular Protraction Appliance (MPA); and a Control Group (CG) comprised of 22 untreated subjects (mean age 12.66 ± 1.12 years). Intergroup comparison was performed with ANOVA, followed by Tukey test.

Results:

The Jasper Jumper and the Herbst group showed significantly greater maxillary anterior displacement restriction. The Jasper Jumper demonstrated significantly greater increase in the mandibular plane angle, as compared to the control group. The MPA group demonstrated significantly greater palatal inclination of the maxillary incisors. Vertical development of the maxillary molars was significantly greater in the Herbst group.

Conclusions:

Despite some intergroup differences in the amount of dentoskeletal changes, the appliances were effective in correcting the main features of Class II malocclusions.

Long-term stability of Class II treatment with the Jasper jumper appliance

INTRODUCTION

Treatment of Class II Division 1 malocclusion with orthopedic devices combined with fixed orthodontic appliances has shown excellent results when used in growing patients. We aimed to evaluate the long-term stability of the cephalometric changes obtained during Class II malocclusion correction with the Jasper jumper associated with fixed appliances.

METHODS

The treatment group comprised 24 patients who were evaluated at 3 stages: pretreatment, posttreatment, and long-term posttreatment. The control group comprised 15 subjects with normal occlusion. Intratreatment group comparisons among the 3 stages were performed with repeated measures analysis of variance, followed by Tukey tests. Intergroup comparisons of posttreatment changes and normal growth changes of the treatment group were performed with t tests.

RESULTS

Apical base relationship, maxillary incisor anteroposterior position, and overjet demonstrated significant relapses in relation to the control group.

CONCLUSIONS

Most dentoalveolar changes obtained with the Jasper jumper followed by fixed appliances during treatment remained stable in the long term. However, apical base relationship, maxillary incisor anteroposterior position, and overjet demonstrated significant relapses in relation to the control group. Therefore, active retention time should be increased in the posttreatment period.

Treatment effects of skeletally anchored Forsus FRD EZ and Herbst appliances: A retrospective clinical study

OBJECTIVE

To evaluate the skeletal, dentoalveolar, and soft tissue effects of the Forsus FRD appliance with miniplate anchorage inserted in the mandibular symphyses and to compare the findings with a well-matched control group treated with a Herbst appliance for the correction of a skeletal Class II malocclusion due to mandibular retrusion.

MATERIALS AND METHODS

The sample consisted of 32 Class II subjects divided into two groups. Group I consisted of 16 patients (10 females and 6 males; mean age, 13.20 ± 1.33 years) treated using the Forsus FRD EZ appliance with miniplate anchorage inserted in the mandibular symphyses. Group II consisted of 16 patients (9 females and 7 males; mean age, 13.56 ± 1.27 years) treated using the Herbst appliance. Seventeen linear and 10 angular measurements were performed to evaluate and compare the skeletal, dentoalveolar, and soft tissue effects of the appliances using paired and Student's t-tests.

RESULTS

Both appliances were effective in correcting skeletal class II malocclusion and showed similar skeletal and soft tissue changes. The maxillary incisor was statistically significantly more retruded in the skeletally anchored Forsus FRD group (P < .01). The mandibular incisor was retruded in the skeletally anchored Forsus FRD group (-4.09° ± 5.12°), while it was protruded in the Herbst group (7.50° ± 3.98°) (P < .001).

CONCLUSION

Although both appliances were successful in correcting the skeletal Class II malocclusion, the skeletally anchored Forsus FRD EZ appliance did so without protruding the mandibular incisors.

Change of mandibular position during two-phase orthodontic treatment of skeletal class II in the Chinese population

The aim of this study was to evaluate the change in mandibular position during a two-phase orthodontic treatment of skeletal Class II malocclusion. Thirty consecutively treated Chinese male adolescents who had undergone two-phase treatment with Herbst appliance and fixed appliance and fulfilled the specific selection criteria were sampled. Cephalograms taken at T0 (before treatment), T1 (at the end of functional appliance treatment), and T2 (at the end of fixed appliance treatment) were analyzed. The change in sagittal positioning of the mandible was 6.8±3.44 mm in phase I (T0-T1), 0.4±2.79 mm in phase II (T1-T2), and 7.2±4.61 mm in total. The mandible came forward in 100% of the patients at T1. In phase II, it came forward in one-third (positive group) remained unchanged in one-third (stable group) and went backward in one-third (negative group) of the patients. At T2, it came forward twice as much in the positive group compared to the negative group. Mandibular length was significantly increased in 100% of the patients in both phases. In conclusion, during the treatment with functional appliance, the mandibular prognathism increases in all patients, whereas during the treatment with fixed appliance there is no significant change in mandibular prognathism.

The short-term skeleto-dental effects of a new spring for the intrusion of maxillary posterior teeth in open bite patients

BACKGROUND

The technology surrounding temporary skeletal anchorage devices has improved in leaps and bounds. However, no specific auxiliary exists for the intrusion of molars in conjunction with these devices and currently clinicians are forced to make do with available force delivery materials. A new intrusion auxiliary, the Sydney Intrusion Spring (SIS), was designed to facilitate intrusion without frequent need for reactivation or tissue irritation.

METHODS

The subjects consisted of 16 adolescent patients (12 females and 4 males) with an average age of 13.1 years (range 12.2 to 14.3 years). All patients were in the permanent dentition with an anterior open bite of ≥2 mm. Four self-drilling miniscrews were placed into the posterior maxillary buccal alveolar bone. The intrusion appliance consisted of a bonded acrylic appliance and the SIS, activated to produce an initial intrusive force of 500 g. Cone beam computed tomograms were taken after miniscrew placement and at the end of active intrusion. Rendered lateral cephalograms were produced and measurements were taken and compared.

RESULTS

All study objectives were achieved in 4.91 months (range 2.5 to 7.75 months). The mean molar intrusion was 2.9±0.8 mm (P<.001), resulting in over bite increase of 3.0±1.5 mm (P<.001). The intrusion led to a 2.6°±1.3° (P<.001) clockwise occlusal plane rotation and a 1.2°±1.3° (P<.01) counter-clockwise rotation of the mandible. Dental measurements showed a significant uprighting and elongation of the incisors. There was no significant extrusion of the lower molars.

CONCLUSION

The SIS is an effective appliance for the intrusion of maxillary posterior teeth, in conjunction with miniscrews.

Skeletal and dental outcomes of a new magnetic functional appliance, the Sydney Magnoglide, in Class II correction

INTRODUCTION

The purpose of this prospective study was to evaluate the dentoskeletal effects of a new magnetic functional appliance, the Sydney Magnoglide (Macono Orthodontic Lab, Sydney, Australia), after both active treatment with the appliance and comprehensive fixed appliance therapy, compared with a group of untreated Class II controls.

METHODS

Thirty-four consecutively treated Class II Division 1 patients treated with the Sydney Magnoglide followed by fixed appliances were compared with 30 untreated Class II controls with the same initial dentoskeletal Class II features and matched for age and sex. Lateral cephalograms were taken before treatment, immediately after functional appliance therapy, and after comprehensive fixed appliance therapy. Cephalometric analyses included the Pancherz analysis and linear and angular measurements. The comparisons were made with Student t tests (P <0.05). There were 3 dropouts, for a final sample for statistical analysis of 31 subjects.

RESULTS

There was no statistically significant difference between the treated and control groups before treatment. Treatment with the Sydney Magnoglide and comprehensive fixed appliance therapy normalized the overjet and corrected the Class II relationship in all treated subjects. The ANB angle showed a reduction of 1.0°, as opposed to an increase of 0.3° in the untreated controls, and was associated with a statically significant improvement in the SNB angle (P <0.05). There was a significant gain of 2.3 mm in mandibular length in the treated group compared with the control group (P <0.01).

CONCLUSIONS

The outcomes of this prospective study demonstrate that the compliance-free Sydney Magnoglide is an effective functional appliance for Class II correction.

A prospective study on the clinical effectiveness of the stainless steel crown Herbst appliance

OBJECTIVES

To evaluate the clinical performance of the stainless steel crown Herbst (cHerbst) used as a single appliance for a single phase therapy.

MATERIALS AND METHODS

A total of 180 consecutive Class II patients were treated with cHerbst for one year and followed up one year after the end of treatment.

RESULTS

Class I relationship was achieved in all 175 patients who finished the functional phase of treatment, 58 patients continued treatment with fixed appliances while 21 patients (12%) showed relapse. Seventy two patients (41.1%) obtained and maintained stable Class I relationship one year after treatment with the cHerbst appliance used as a single appliance. Altogether 46 episodes of appliance breakages were observed and most of them could be repaired at the chair side. Patients' questionnaire revealed that in general the appliance was easy to tolerate and did not cause esthetic or functional problems.

CONCLUSIONS

The crown Herbst appliance is a viable therapeutical option in patients with Class II malocclusions and it is characterized by low complication rate along with good patient compliance.

Tratamento de más oclusões de Classe II graves com aparelhos funcionais removíveis e ortodônticos sequenciais: um caso para a avaliação do MOrthRCSEd

INTRODUÇÃO: o aparelho funcional é uma forma eficaz de tratar as más oclusões de Classe II esqueléticas em crianças e adolescentes. Um protocolo de avanço mandibular progressivo de 12 meses já demonstrou ser capaz de aumentar o crescimento condilar e melhorar o prognatismo mandibular utilizando o aparelho de Herbst. OBJETIVO: relatar o caso clínico (apresentado como um dos requisitos para aprovação no Exame de Ortodontia para Filiação ao Royal College of Surgeons de Edimburgo*) de uma menina chinesa de 11 anos de idade, com 11mm de sobressaliência, tratada na Fase I da terapia de modificação do crescimento, ao longo de 12 meses, utilizando o aparelho Twin Block com um expansor palatal Hyrax e um extrabucal de puxada alta, em um protocolo de avanço mandibular progressivo, seguido pela Fase II da terapia, com um aparelho Edgewise pré-ajustado.

Stability of Class II treatment with an edgewise crowned Herbst appliance in the early mixed dentition: Skeletal and dental changes

INTRODUCTION

The objectives of this research were to assess skeletal and dental changes in patients with Class II malocclusion treated with the edgewise crowned Herbst appliance in the early mixed dentition and to measure the stability of treatment after a second phase of fixed appliance therapy.

METHODS

Twenty-two patients (ages, 8.4 ± 1.0 years) with Class II Division 1 malocclusion treated consecutively with the edgewise crowned Herbst appliance in the early mixed dentition were studied. Lateral cephalograms were taken before Herbst treatment, immediately after Herbst treatment, and after a second phase of fixed appliance therapy. The results were compared with a control group of untreated Class II subjects selected from the Bolton-Brush study, matched by age, sex, and craniofacial morphology. A total of 37 sagittal, vertical, and angular cephalometric variables were evaluated. Changes in overjet and molar relationship were calculated. Changes due to growth were subtracted to obtain the net changes due to treatment. The data were analyzed by using analysis of variance (ANOVA) and the t tests.

RESULTS

Overcorrection with the Herbst appliance resulted in an average reduction in overjet of 7.0 mm and a change in molar relationship of 6.6 mm. Several factors contributed to the change in overjet: restraint of the forward movement of the maxilla (0.4 mm), forward movement of the mandible (2.0 mm), backward movement of the maxillary incisors (3.7 mm), and forward movement of the mandibular incisors (0.9 mm). Skeletal changes together with a 3.1-mm backward movement of the maxillary molars and a 1.1-mm forward movement of the mandibular molars contributed to the changes in molar relationship. After the second phase of fixed appliance therapy, the change in overjet was reduced to 2.8 mm. Most of the remaining overjet corrections were contributed by the restraint of maxillary growth (2.8 mm). The mandible moved posteriorly by 1.6 mm, and the mandibular incisors moved forward by 0.2 mm. Change in molar relationship was reduced to 2.2 mm. The maxillary molars moved backward by 0.2 mm, and the mandibular molars moved forward by 0.8 mm.

CONCLUSIONS

Overcorrection of Class II malocclusion with the edgewise crowned Herbst appliance in the early mixed dentition resulted in a significant reduction in overjet and correction of the molar relationship. A portion of the correction was maintained after a second phase of fixed appliance therapy because of the continuous restraint of maxillary growth and the dentoalveolar adaptations.

The biological mechanisms of PCNA and BMP in TMJ adaptive remodeling

OBJECTIVES

To histologically and immunohistochemically assess the pattern of expression of bone morphogenic proteins 2 and 4 (BMP2/4) and proliferating cell nuclear antigen (PCNA) in response to bite jumping appliances in the condylar cartilage and the glenoid fossa.

MATERIALS AND METHODS

Fifty-five 4-week-old female Sprague-Dawley rats were randomly divided into four experimental and four control groups. Bite-jumping appliances were fitted to the experimental animals. The rats were sacrificed at 3, 14, 21, and 30 days, and the temporomandibular structures were analyzed histologically and immunohistochemically.

RESULTS

The expression of BMP2/4 in response to bite-jumping appliances was statistically significant in the condylar cartilage and the glenoid fossa. Cell proliferation was not significant.

CONCLUSION

BMP2/4 plays an important role in bone formation in response to mandibular advancement by accelerating and enhancing the differentiation of mesenchymal cells into bone-forming cells.

Sagittal and vertical occlusal cephalometric analyses of Pancherz: Norms for Chinese children

INTRODUCTION

The aims of this research were to establish norms for the sagittal and vertical occlusal cephalometric analyses of Pancherz for Chinese children and compare them with those of a matched white sample.

METHODS

The material comprised lateral cephalograms of a random sample of 405 southern Chinese children (age, 12 years; 200 boys, 205 girls) and an additional sample of 86 British white children (age, 12 years; 43 boys, 43 girls) in Hong Kong. The radiographs were digitized twice.

RESULTS

Statistically significant sex differences were found for 9 of 11 parameters in the sagittal occlusal analysis, and 6 of 10 in the vertical occlusal analysis in the Chinese sample, whereas there were no sex differences in the sagittal occlusal analysis and only 2 differences in the vertical occlusal analysis in the white sample. Statistically significant ethnic differences were found for 5 parameters in boys and 8 in girls of the 11 parameters in the sagittal analysis. For the vertical analysis, 7 of 10 parameters in both sexes differed significantly.

CONCLUSIONS

For the sagittal and vertical occlusal analyses of Pancherz, separate sex-specific standards are needed for Chinese and white children.

Management of Severe Class II Malocclusion With Sequential Fixed Functional and Orthodontic Appliances: A Case for MOrthRCSEd Examination

Fixed functional appliance is an effective way of treating skeletal Class II malocclusion in children and adolescents. The following case report documented a 13-year-old boy with 15 mm overjet treated by a phase I 12-month growth modification therapy using Herbst appliance with Hyrax palatal expander and high pull headgear in a stepwise mandibular advancement protocol followed by a phase II pre-adjusted edgewise appliance therapy. It is one of the cases submitted for the Membership of Orthodontics Examination of the Royal College of Surgeons of Edinburgh.

Condylar growth and mandibular positioning with stepwise vs maximum advancement

INTRODUCTION

The aim of this study was to compare the effects of several Class II malocclusion treatments on condylar growth and positioning of the mandible.

METHODS

The material comprised series of lateral cephalograms obtained at the start, after about 6 months, and after about 12 months of treatment from 3 groups of consecutively treated patients who used a headgear-activator with stepwise mandibular advancement (HGA-S), a headgear-activator with maximum jumping of the mandible (HGA-M), and a headgear-Herbst appliance with stepwise advancement (HGH-S), respectively. Six-month growth data from matched controls were used to calculate the net treatment effects.

RESULTS

Mandibular prognathism was enhanced after stepwise advancement but not after maximum jumping, and only during the initial phase of therapy; the effect was significantly greater for the fixed functional appliance than for the removable functional appliance. Lower-facial height was increased by the HGA-S, unchanged by the HGA-M, and restrained by the HGH-S. The low construction bite of the HGH-S meant that the extent of bone apposition on the posterior and superior parts of the condyle was similar, whereas the high construction bite of the HGA-S and the HGA-M meant that the effect on the superior part was greater, but only significantly so after stepwise advancement.

CONCLUSIONS

The mode of jumping, the vertical opening, and whether the functional appliance is fixed or removable affect the amount and pattern of condylar growth, and the position of the mandible.

Does the degree of advancement during functional appliance therapy matter?

The aim of this study was to assess the effect of varied degrees of mandibular advancement on condylar growth. Three hundred and thirty five 35-day-old female Sprague-Dawley rats were randomly divided into 10 experimental groups (n = 10) and five control groups (n = 5) for analysis of new bone formation and 10 experimental groups (n = 14) and five control groups (n = 14) for molecular analysis. The experimental animals were fitted with bite-jumping appliance to advance the mandible 2 and 4 mm. The rats were sacrificed on days 3, 7, 14, 21, and 30. A computer-assisted image analysing system was used to assess the quantity of new condylar bone formation. Molecular analysis utilizing real-time reverse transcription-polymerase chain reaction was used to assess the different levels of mRNA expression of different growth markers in the condyle. One-way analysis of variance (ANOVA), with a Bonferroni multiple comparison test, showed significantly more newly formed bone in the 4 mm group compared with the 2 mm and control groups on days 21 and 30 (P < 0.05). Most of the examined growth markers demonstrated a significant increase during the 4 mm advancement (P < 0.05). Indian hedgehog (Ihh) mRNA showed a 7- and 5-fold change, parathyroid hormone-related peptide (PTHrP) a 5.2- and 3-fold change and type II collagen a 9.6- and 3.7-fold change in the 4 and 2 mm advancement groups, respectively. Varied degrees of mandibular advancement result in different quantities of new bone formation and levels of expression of growth members: Ihh, PTHrP, and type II collagen.

Stepwise advancement versus maximum jumping with headgear activator

The aim of this study was to compare the effects of stepwise mandibular advancement versus maximum jumping and extended treatment versus early retention. The material was obtained prospectively and consisted of lateral cephalograms taken at the start (T0), after initial (T1), and at the end (T2) of treatment, from two groups of consecutively treated skeletal Class II patients who had undergone therapy with headgear activators. The first headgear activator group, HGA-S (n=24; mean age 11.9 +/- 1.2 years), was treated for 13 months and had 4-mm mandibular advancement every 3 months. The second headgear activator group, HGA-M (n=31; mean age 11.2 +/- 1.5 years), had maximum jumping, 6-8 mm interincisal opening, for a total of 15.4 months, and with reduced wear for the last 6.9 months. The dropout over 12 months was 41 and 46 per cent, respectively. Pre-treatment growth changes were obtained as a reference. An independent t-test was used to determine differences in baseline dentofacial morphology between the groups, a paired t-test for intra-group comparisons, and an independent t-test to evaluate differences between the groups. The results, in both groups, showed enhanced mandibular prognathism during the initial phase (T0-T1), followed by normal growth (T1-T2), and lower face height enhancement throughout treatment (T0-T2). For both groups, the mandibular plane and occlusal angle increased, possibly enhanced by 'extrusion' of the lower molars. For both groups, maxillary forward growth was restrained only during the initial phase, but the effect remained significant at T2 for the HGA-S group. In the HGA-M group, the lower incisors were protruded, while in the HGA-S group, they were unaffected. The findings indicate that both modes of mandibular jumping resulted in skeletal and dental effects. The length of active treatment seemed to be decisive in maintaining the treatment effects; stepwise advancement had less dental effects.

Treatment effects of the edgewise Herbst appliance: A cephalometric and tomographic investigation

INTRODUCTION

The crown Herbst appliance was introduced in the late 1980s because of shortcomings of the banded Herbst. In edgewise Herbst treatment, a fixed appliance is used with the crown Herbst to maximize the skeletal effects of treatment. Treatment response to the edgewise Herbst appliance has not been reported in the literature. Our objective was to investigate skeletal and dental changes in patients with Class II malocclusions treated with the edgewise Herbst appliance.

METHODS

Fifty-two consecutive patients were treated with the edgewise Herbst appliance; 32 (18 girls, 14 boys) met the criterion of 16 months out of Herbst treatment and were included in the study. Mean treatment time with this appliance was 8.0 +/- 1.8 months. Patients in the mixed dentition received additional treatment with 2 x 4 appliances until proper overbite, overjet, and torque on the incisors and permanent first molars were achieved. Patients in the permanent dentition were treated with full appliances to finalize the occlusion. Cephalometric measurements were taken at pretreatment, posttreatment, and 16 months after removal of the Herbst appliance, and the results were compared with 32 untreated Class II subjects from the Bolton Brush Study, matched for sex, age, and cephalometric dentofacial morphology. Data were analyzed with ANOVA, Tukey-Kramer multiple comparison tests, and 2-tailed t tests.

RESULTS

After 8 months of Herbst treatment, incisal relationship was overcorrected to an end-to-end incisal relationship and improved 8.4 mm, compared with the control group. The maxilla moved backward 1.4 mm at Point A, and the mandible moved forward 1.7 mm. The maxillary incisors moved lingually 1.7 mm, and the mandibular incisors were proclined 3.6 mm. The molars were corrected to a Class III relationship with a change of 7.2 mm compared with the control group. The mandible moved downward and forward. However, the condyle showed only 0.2 mm forward movement in the fossa. Sixteen months after appliance removal, the molars had relapsed into a Class I relationship, for a net change of 2.4 mm compared with the control group. Net overjet gain was 2.7 mm. Net restraint of maxillary growth was 1.3 mm, and net forward movement of the mandible was 1.0 mm. The maxillary incisors had no net movement, and the mandibular incisors had a net forward movement of 0.3 mm. Overall, skeletal change contributed 85% of the net overjet correction.

CONCLUSIONS

Class II treatment with the edgewise Herbst appliance is accompanied by both skeletal and dental changes. The changes are stable, with significant skeletal differences remaining 16 months after appliance removal. The forward and downward movement of the mandible with minimal changes in the position of the condyles in the fossae suggests a combination of condylar growth and remodeling of the glenoid fossa with treatment.

The Dynamax system: a new orthopaedic appliance and case report

The Dynamax appliance is a treatment modality for the correction of the Skeletal II malocclusion characterized by a mandibular retrusion. Progressive mandibular advancement, maxillary expansion, control of maxillary growth, incisor torque and control of vertical facial development are incorporated into a two-part appliance. The design facilitates laboratory construction, clinical handling and patient acceptability. A prefabricated spring module forms the basis of the appliance, allowing both maxillary expansion and mandibular advancement. An easily adjustable progressive forward position of the lower jaw makes a construction bite unnecessary. The spring module provides most of the structure of the appliance so that minimal acrylic is required and the appliance is fully contained within the freeway space. Contact between the upper and lower parts of the appliance occurs posteriorly in the lingual sulcus. Here the depth permits an extended vertical contact, to maintain a protrusive mandibular position throughout the range of mandibular opening, including during sleep. The lower portion of the appliance may be fixed or removable and multibracket treatment can be carried out in one or both arches at the same time as the orthopaedics.

Identification of temporal pattern of mandibular condylar growth: a molecular and biochemical experiment

OBJECTIVES

Based on the phenomenon that expression of type X collagen and capillary endothelium correlates with endochondral ossification, the prime aim of this study was to establish the temporal pattern of condylar growth in Sprague-Dawley rats by biochemically identifying the expression of these two factors.

DESIGN

Sprague-Dawley rats were divided into five groups representing five different stages during somatic pubertal growth. In situ hybridization and immunoperoxidase were performed to examine expression of type X collagen in hypertrophic zone and capillary endothelium in erosive zone of condylar cartilage. Computer-assisted imaging analyses were conducted to allow for a quantitative assessment of the expression of these two factors, from which the temporal pattern of condylar growth was inferred.

RESULTS

(1) Synthesis of type X collagen and emergence of capillary endothelium were critical factors during the transition of condylar cartilage from chondrogenesis into osteogenesis, a biological pathway that leads to endochondral bone formation, the mode through which the condyle grows. (2) Quantitative analyses revealed the temporal pattern of the expression of these two factors, indicating that the thrust of natural growth of the condyle in the rats occurred in concomitance with somatic pubertal growth, featured by an acceleration starting from day 38, a maximum growth rate on day 56, followed by a decrease afterwards.

CONCLUSION

It is suggested that the biochemical examination of growth markers, such as type X collagen, might be a new approach to accurately depict temporal pattern of condylar growth which is too delicate to be reflected by gross measurement not only in Sprague-Dawley rats but potentially also in other species.

Skeletal effects of bite jumping therapy on the mandible - removable vs. fixed functional appliances

AUTHORS: Shen G, Hagg U, Darendeliler MA.

OBJECTIVE

Based on an extensive review of the literature, the aim of this study was to explore the mainstream consensus on the controversial topic of whether the bite jumping treatment could enhance mandibular growth.

DESIGN

The data for removable and fixed functional appliances were respectively comprehended and analyzed with regard to their attributes in mandibular growth modification. Furthermore, numerous reported findings were assessed by relating them to some important factors influencing the effects of bite jumping, such as treatment timing, treatment duration and post-treatment follow-up, to allow for a more objective and accurate evaluation.

RESULTS

The key differences between removable and fixed appliances are working hours (intermittent vs. continuous), length of treatment time (long vs. short), optimal treatment timing (before puberty growth vs. at or after puberty spurt), and mode of bite-jumping (considerable vertical opening vs. limited vertical opening). These different features lead to different treatment effects on mandibular and TMJ growth, such as the intensity of possibly increased growth (clinically less significant vs. significant), the direction of enhanced growth (vertical vs. horizontal), and the stability of treatment changes (unstable vs. stable). The short-term or long-term post-treatment relapse mainly relates to the rebound of dental position.

CONCLUSION

The immediate effects of bite jumping functional appliances on the mandibular growth enhancement are convincing during actual treatment. This extra gain of growth might be sustainable during the short-term and long-term post-treatment period.

Vascular endothelial growth factor expression and bone formation in posterior glenoid fossa during stepwise mandibular advancement

This study assessed the amount of vascular endothelial growth factor (VEGF) expression and related the findings to new bone formation in the posterior glenoid fossa during stepwise mandibular advancement. A total of 250 female Sprague-Dawley rats, 35 days old, were randomly divided into 10 groups, each including 5 control and 20 experimental rats. Within each group, 10 experimental rats were fitted with functional appliances with a 1-step advancement of 3.5 mm. Another 10 were fitted with stepwise appliances with an initial advancement of 2 mm and a subsequent increase to 3.5 mm on day 30. The rats in the experimental groups were killed on days 3, 7, 14, 21, 30, 33, 37, 44, 51, and 60, respectively. The matched controls were killed on the same time points. Sections (7 microm) were cut through the glenoid fossa sagittally and stained with anti-VEGF antibody. VEGF expression in the posterior glenoid fossa was evaluated with a computer-assisted image-analyzing system. Both VEGF expression and new bone formation were greater in the experimental rats than in the controls. During stepwise advancement, initial VEGF expression was less than that of 1-step advancement, but the second advancement elicited another peak on day 44. New bone formation was also less than that of 1-step advancement during early stages of stepwise advancement but then began to increase from day 37 onward. The maximum increase was observed on day 60. Stepwise advancement of the mandible delivers mechanical stimuli that produce a series of tissue responses that lead to increased vascularization and bone formation.