Sabine Ruf

Temporomandibular joint remodeling in adolescents and young adults during Herbst treatment: A prospective longitudinal magnetic resonance imaging and cephalometric radiographic investigation

The aim of this prospective study was to analyze and compare the temporomandibular joint adaptive mechanisms in 25 adolescent and 14 young adult Class II malocclusions treated with the Herbst appliance. Temporomandibular joint remodeling was analyzed by magnetic resonance imaging. In each subject, 4 magnetic resonance images of both temporomandibular joints were available: before treatment, at the start of treatment (when the Herbst appliance was placed), during treatment (6 to 12 weeks after appliance placement), and after treatment (when the appliance was removed). Furthermore, effective temporomandibular joint changes (the sum of condylar remodeling, fossa remodeling, and condyle-fossa relationship changes) were analyzed with the aid of lateral cephalometric radiographs from before and after treatment. All subjects were treated to Class I or overcorrected Class I dental arch relationships, and their mandibles became significantly (P <.001) more prognathic. After 6 to 12 weeks of Herbst treatment, signs of condylar remodeling were seen at the posterosuperior border in 48 of the 50 adolescent condyles and in 26 of the 28 young adult condyles. Bilateral remodeling of the mandibular ramus could be detected in 1 adolescent and 2 young adult patients. Signs of glenoid fossa remodeling at the anterior surface of the postglenoid spine were noted in 36 adolescent and 22 young adult temporomandibular joints. Effective temporomandibular joint changes during treatment were more horizontally directed and larger in both adolescents and young adult patients treated with the Herbst appliance than in an untreated group of subjects with ideal occlusion (Bolton standards). The increase in mandibular prognathism accomplished by Herbst therapy in both adolescents and young adults seems, in particular, to be a result of condylar and glenoid fossa remodeling. Because the Herbst appliance is most successful in Class II patients also at the end of the growth period, the treatment method could be an alternative to orthognathic surgery in borderline skeletal Class II cases. Magnetic resonance imaging renders an excellent opportunity to visualize the temporomandibular joint remodeling growth processes.

Does orthodontic proclination of lower incisors in children and adolescents cause gingival recession

In this investigation we sought to assess the effect of orthodontic proclination of lower incisors in children and adolescents with respect to the possible development of gingival recession. Ninety-eight children with a mean +/- SD start-of-treatment age of 12.8 +/- 1.4 years, treated with the Herbst appliance, were surveyed, for a total of 392 lower incisors. Lateral head films, dental casts and intraoral photographs were analyzed with respect to the degree of orthodontic proclination, crown height, and gingival recession. In all subjects, Herbst treatment resulted in varying degrees of lower-incisor proclination (mean = 8.9 degrees, range = 0.5 degrees to 19.5 degrees). In 380 of the surveyed teeth (97%), either no recession developed or preexisting recession remained unchanged during Herbst therapy. In only 12 teeth (3%) did recession develop or preexisting recession deteriorate during treatment. No interrelation was found between the amount of incisor proclination and the development of gingival recession. In conclusion, orthodontic proclination of lower incisors in children and adolescents seems not to result in gingival recession.

Dentoskeletal effects and facial profile changes in young adults treated with the Herbst appliance

This prospective Herbst study analyzed the sagittal dental and skeletal changes contributing to Class II correction in young adults. Additionally, the alteration in skeletal and soft tissue convexity occurring during treatment was assessed. Early adolescent subjects in the permanent dentition who had been treated with the Herbst appliance were used for comparison. Lateral headfilms from before and after an average treatment period of 8.5 months for the young adults and 7.1 months for the adolescents were evaluated. All adult and adolescent subjects were treated to either Class I or overcorrected Class I occlusal relationships. In both groups the improvement in sagittal incisor and molar relationships was achieved more by dental changes than by skeletal ones. The amount of skeletal change contributing to overjet and molar correction was smaller in the young adult group (22% and 25%, respectively) than in the early adolescent group (39% and 41%, respectively). Skeletal and soft tissue facial profile convexity was reduced in adults and adolescents. Facial profile improvement did not differ between the two groups. The results of this study revealed that the Herbst appliance is most effective in the treatment of Class II malocclusion in young adults. It is suggested that this treatment method could be an alternative to orthognathic surgery in borderline Class II cases.

Mandibular articular disk position changes during Herbst treatment: A prospective longitudinal MRI study ☆ ☆☆

The aim of this prospective longitudinal study of 15 consecutively treated Class II malocclusions was to assess any possible changes in the relative position of the articular disk to the condyle during different phases of Herbst therapy. Using a disk position index, parasagittal MRIs (central, medial and lateral slices) of the right and left TMJ were analyzed at five occasions: before Herbst treatment (T1), at start of treatment when the appliance was placed (T2), after 6 weeks of treatment (T3), after 13 weeks of treatment (T4), and after 7 months of treatment when the appliance was removed (T5). In all subjects Herbst treatment resulted in Class I or overcorrected Class I dental arch relationships. Condyle position was on average unchanged during Herbst treatment (T1 to T5). Before treatment (T1) the articular disk was in a slight protrusive position relative to the condyle. At start of treatment (T2) the mandible was advanced to an incisal edge to edge position. Because of the physiologic relative movement of disk and condyle on mandibular protrusion the disk attained a pronounced retrusive position. At the end of treatment (T5), the disk had almost returned to its original pretreatment position. In several cases, however, a slight retrusive disk position prevailed. In conclusion, Herbst treatment did not result in any adverse changes in articular disk position. On the contrary, the Herbst appliance could possibly be useful in the therapy of patients with anterior disk displacement.

Does Bite-Jumping Damage the TMJ? A Prospective Longitudinal Clinical and MRI Study of Herbst Patients

The aim of this prospective longitudinal study of 62 consecutively treated Class II malocclusions was to determine whether bite-jumping causes temporomandibular disorders (TMD). The function of the temporomandibular joint (TMJ) was assessed anamnestically, clinically, and by means of magnetic resonance images (MRIs) taken before (T1), after (T2), and 1 year after (T3) Herbst treatment. Average treatment time with the Herbst appliance was 7.2 months. In all subjects, Herbst treatment resulted in a Class I or overcorrected Class I dental arch relationship. Thereafter, treatment was continued with a multibracket appliance. The condyle was positioned significantly forward during treatment but returned to its original position after removal of the Herbst appliance. A temporary capsulitis of the inferior stratum of the posterior attachment was induced during treatment. Over the entire observation period from before treatment to 1 year after treatment, bite-jumping with the Herbst appliance: (1) did not result in any muscular TMD; (2) reduced the prevalence of capsulitis and structural condylar bony changes; (3) did not induce disc displacement in subjects with a physiologic pretreatment disc position; (4) resulted in a stable repositioning of the disc in subjects with a pretreatment partial disc displacement with reduction; and (5) could not recapture the disc in subjects with a pretreatment total disc displacement with or without reduction. A pretreatment total disc displacement with or without reduction did not, however, seem to be a contraindication for Herbst treatment. In conclusion, bite-jumping using the Herbst appliance does not have a deleterious effect on TMJ function and does not induce TMD on a short-term basis.

The compensatory mechanism in high-angle malocclusions: A comparison of subjects in the mixed and permanent dentition

Dentoskeletal morphology was assessed in 191 untreated and unselected children with a hyperdivergent (high-angle) mandibular plane (ML/NSL > or =40 degrees) by analyzing lateral roentgenographic cephalograms. The subjects were divided into mixed dentition and permanent dentition groups, and further divided into subgroups based on the amount of overbite (OB) as a measure of dentoalveolar compensation of jaw base hyperdivergency: OB < 0 mm (openbite) = insufficient/no compensation; OB 0 to 4 mm (normal overbite) = acceptable compensation; OB > 4 mm (deepbite) = overcompensation. Openbite was observed in 20% of the children, normal overbite in 50%, and deepbite in 30%. Skeletally, the deepbite mixed dentition group was characterized by a relatively posterior inclination of the maxilla, while the deepbite permanent dentition group had a relatively anterior inclination of the mandible. Dentoalveolar compensation was accomplished by relative increases in maxillary and mandibular anterior dentoalveolar heights in the mixed dentition group and by relative decreases in maxillary and mandibular posterior dentoalveolar heights in the permanent dentition. Positive overbite was found in the majority (80%) of children with high-angle morphology. Thus, mandibular hyperdivergency is frequently compensated for. Skeletal characteristics and dentoalveolar compensatory mechanisms differ with dental maturity and seem to be influenced by mouth breathing and other oral habits.

The effect of Herbst appliance treatment on the mandibular plane angle: a cephalometric roentgenographic study.

The purpose of this investigation was to assess the individual reaction pattern and the long-term effect of Herbst appliance treatment on the vertical jaw base relationship, as expressed by the mandibular plane angle (ML/NSL). In the evaluation special reference was given to the pretreatment vertical jaw base relationship (hypodivergent, normodivergent or hyperdivergent). Lateral head films of 80 patients (47 males and 33 females) from before, at start (when the appliance was placed) and at the end of Herbst treatment (when the appliance was removed) as well as 6 months and 4.5 to 5 years posttreatment were analyzed. The ML/NSL angle was on the average unaffected by Herbst therapy. Posttreatment, a continuous decrease in the ML/NSL took place. Male subjects showed a larger angular decrease than female subjects. However, a large interindividual variation existed. No statistically significant differences were found between hypodivergent, normodivergent, and hyperdivergent subjects.

Effective condylar growth and chin position changes in activator treatment: a cephalometric roentgenographic study.

Effective condylar growth (a summation of condylar remodeling, glenoid fossa remodeling, and condylar position changes within the fossa) and its influence on the position of the chin was analyzed in 40 class II, division I malocclusions treated successfully with activators. Additionally, the amount of mandibular rotation was assessed. Lateral head films in habitual occlusion from before and after an average treatment period of 2.6 years were evaluated. The Bolton Standards (32 untreated individuals with ideal occlusion) served as controls. Two different treatment effects were evaluated: overall growth change and treatment effects (overall growth changes minus age-related Bolton values). In comparison with the Bolton group, the activator patients exhibited an increase in the amount of vertical effective condylar growth (3.0 mm; P < .001), a decrease in the amount of sagittal effective condylar growth (0.6 mm; P < .05), and an increase in the amount of vertical development of the chin (1.8 mm; P < .001). No group differences could be found for sagittal development of the chin. In the Bolton group, the mandible rotated posteriorly, and in the activator group it rotated anteriorly (2.7 degrees; P < .001). The present investigation revealed that effective condylar growth can be increased and the chin position can be changed by activator treatment. Thus activator treatment induces skeletal changes, although not always in the desired (sagittal) therapeutic direction.

The mechanism of Class II correction during Herbst therapy in relation to the vertical jaw base relationship: a cephalometric roentgenographic study.

This retrospective Herbst study analyzes and compares the sagittal dental and skeletal effects contributing to Class II correction in subjects with small or large pretreatment mandibular plane angles. Lateral headfilms of 15 hypodivergent (ML/NSL < or = 26 degrees) and 16 hyperdivergent (ML/NSL > 39 degrees) Class II subjects treated to a Class I occlusal relationship with the Herbst appliance were analyzed. Radiographs were taken before and after an average treatment period of 7 months. Cephalograms were evaluated according to the method of Pancherz. In both groups, impprovements in sagittal incisor and molar relationships were achieved by greater dental than skeletal changes. The amount of skeletal changes contributing to overjet and molar correction was larger in the hyperdivergent group (37% and 44%, respectively) than in the hypodivergent group (25% and 25%, respectively). Dental and skeletal changes contributing to Class II correction were found to be independent of the vertical jaw base relationship. Thus, a hyperdivergent jaw base relationship did not affect the treatment response unfavorably.

Temporomandibular Joint Effects of Activator Treatment: A Prospective Longitudinal Magnetic Resonance Imaging and Clinical Study

The aim of this prospective longitudinal clinical and magnetic resonance imaging (MRI) study was to analyze the effect of Activator treatment on the disc-condyle complex and the posterior attachment of the temporomandibular joint (TMJ) considering the degree of compliance in the evaluation. The material was comprised of 30 class II, division I patients (nine girls and 21 boys) who underwent Activator treatment. The average pretreatment age of the subjects was 11.4 years. Parasagittal MRIs in closed mouth position from before and after one year of Activator treatment were analyzed metrically. Possible clinical and subclinical soft tissue lesions of the posterior attachment of the TMJ were assessed by passive joint loading before, after six months, and after one year of Activator treatment. The overjet was continuously documented as a clinical measure for treatment reaction. To assess patient compliance, the subjects had to perform daily wearing-time records. Furthermore, the Activator was clinically inspected for fitting accuracy and signs of wear. The results revealed the following: (1) during the one-year treatment period the sagittal dental arch relationship improved, but a class I occlusion could not be achieved in all patients; (2) on average, a physiologic position of disc, condyle, and fossa was present both before and after one year of Activator treatment; (3) a pretreatment physiologic disc-condyle relationship was unaffected by Activator therapy; 4) a pretreatment disc displacement could not be repositioned during Activator treatment; (5) the prevalence of a subclinical capsulitis of the inferior stratum of the posterior attachment increased during Activator treatment; and (6) the degree of compliance had no influence on the disc-condyle relationship or the reaction of the posterior attachment of the TMJ.