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.     

Temporomandibular joint growth changes in hyperdivergent and hypodivergent Herbst subjects. A long-term roentgenographic cephalometric study.

The aim of this long-term study was to assess the amount and direction of glenoid fossa displacement, condylar growth, and "effective" temporomandibular joint (TMJ) changes (= the sum of glenoid fossa displacement, condylar growth, and condylar position changes in the fossa) in 3 vertical facial-type groups of Class II Division 1 malocclusions treated with the Herbst appliance. A comparison was made between 38 normodivergent (ML/NSL= 26.5 degrees -36.5 degrees), 17 hypodivergent (ML/NSL or= 37 degrees ) subjects. Lateral headfilms from before, after, and 5 years after treatment were scrutinized. Glenoid fossa displacement, condylar growth, and "effective" TMJ changes were analyzed. Treatment changes: in all facial-type groups, the glenoid fossa was displaced anteriorly and inferiorly. No differences existed between the 3 groups. Condylar growth and "effective" TMJ changes were directed posteriorly and superiorly. The changes in posterior direction were more apparent in the hyperdivergent group than in the normodivergent and hypodivergent groups. Posttreatment changes: in all facial-type groups, the fossa was displaced posteriorly. No differences existed between the 3 groups. Condylar growth and "effective" TMJ changes were directed more vertically compared with the treatment changes. The changes in posterior direction were more pronounced in the hyperdivergent group than in the other 2 groups. It was found that the amount and direction of TMJ growth changes (fossa displacement, condylar growth, and "effective" TMJ changes) were only temporarily affected favorably in the sagittal direction by Herbst treatment. Condylar growth and "effective" TMJ changes were directed more posteriorly in hyperdivergent than in hypodivergent Herbst subjects. This was true for both treatment and posttreatment period changes.     

Amount and direction of temporomandibular joint growth changes in Herbst treatment: a cephalometric long-term investigation

The amount and direction of condylar growth, glenoid fossa displacement, and "effective" temporomandibular joint (TMJ) changes (a summation of condylar growth, glenoid fossa displacement, and condylar position changes within the fossa) were analyzed in 35 Class II, Division 1 malocclusions (23 boys and 12 girls) treated with the Herbst appliance. Lateral head films in habitual occlusion and with the mouth wide open from before (T1) and after 7.5 months of Herbst treatment (T2) as well as 7.5 months (T3) and three years (T4) after treatment were evaluated. As a control group, a sample of 12 untreated male Class II Division I malocclusions was used during a 7.5-month time period corresponding to the treatment period (T2-T1) of the Herbst cases. The results revealed that during the treatment period (T2-T1) condylar growth was directed posteriorly about twice the amount as in the control subjects, and the fossa was displaced in an anterior inferior direction. The effective TMJ changes showed a pattern similar to condylar growth but were more pronounced. During the first posttreatment period (T3-T2), all TMJ changes reverted. The glenoid fossa was displaced backward; the amount of condylar growth and effective TMJ changes was reduced, and the changes were more superiorly directed. During the second posttreatment period (T4-T3), all TMJ changes were considered physiological. Conclusion: During Herbst treatment, the amount and direction of TMJ changes (condylar growth, fossa displacement, and effective TMJ changes) were only temporarily affected favorably by Herbst treatment.     

Changes in temporomandibular joint disc position and form following Herbst and fixed orthodontic treatment

Objective:To determine the changes in the position and form of the temporomandibular joint articular disc in adolescents with Class II division 1 malocclusion and mandibular retrognathism treated with the Herbst appliance (phase I) and fixed orthodontic appliance (phase II).Materials and Methods:Thirty-two consecutive adolescents went through phase I of treatment and 23 completed phase II. The temporomandibular joints were evaluated qualitatively by means of magnetic resonance images at the beginning of treatment (T1), during phase I (T2), at the end of phase I (T3), and at the end of phase II (T4).Results:Significant changes in disc position were not observed with the mouth closed between T1 × T3 (P  =  .317), T3 × T4 (P  =  .287), or T1 × T4 (P  =  .261). At T2, on average, the disc was positioned regressively. With the mouth open, no difference was observed between T1 × T3 (P  =  .223) or T1 × T4 (P  =  .082). We did observe a significant difference between T3 × T4 (P < .05). Significant changes in the disc form were found with the mouth closed between T1 × T2 (P < .001) and T2 × T3 (P < .001).Conclusions:At the end of the two-phase treatment, in general terms, the position and form of the initial articular discs were maintained; however, in some temporomandibular joints some seemingly adverse effects were observed at T4.     

肌激动器治疗前后关节盘矢状位置与颞下颌关节临床症状和体征的关系

目的 探讨功能矫治中关节盘矢状位置对颞下颌关节临床功能的影响.方法 选择20个AngleⅡ1错(牙合)患者,采用Activator功能矫治器治疗.用MRI检查治疗前后关节盘位置, Helkimo指数评价功能矫形前后的颞下颌关节功能.探讨治疗前后关节盘位置的改变及其与颞下颌关节症状之间的关系.结果 治疗前关节盘位置正常者,治疗后临床检查指数有下降趋势;治疗前关节盘前移位者,治疗后临床检查指数升高.结论 功能矫形虽然不会导致关节盘前移位的发生,但对于治疗前已经存在关节盘前移位者,治疗后可能会引发或加重其TMD症状和体征.     

"Effective" TMJ and chin position changes in Class II treatment

OBJECTIVE: To evaluate the "effective" temporomandibular joint (TMJ) changes (the sum of condylar modeling, glenoid fossa modeling, and condylar position changes within the fossa), and their influence on chin position in patients with a Class II division 1 malocclusion treated orthodontically with a multibracket appliance and Class II elastics (Tip-Edge) and orthopedically with a fixed functional appliance (Herbst). MATERIALS AND METHODS: Two groups of successfully treated subjects were evaluated: Tip-Edge (n = 24) and Herbst (n = 40). The Bolton Standards served as a control group. Lateral head films obtained before treatment and after an observation period of 2.6 years (Herbst also after 0.6-year period) were analyzed. RESULTS: In comparison with the Herbst and control groups, the Tip-Edge group exhibited less favorable sagittal "effective" TMJ growth and chin position changes necessary for skeletal Class II correction. CONCLUSIONS: Orthodontic therapy with a multibracket appliance and Class II elastics seems not to have any favorable sagittal orthopedic effect on the mandible, while bite jumping with the Herbst appliance has a favorable sagittal orthopedic effect on a short-time basis.     

Herbst双期拔牙矫治对颞下颌关节位置影响的CBCT研究

目的:探讨Herbst双期拔牙矫治对颞下颌关节位置关系的影响.方法:纳入15例恒牙列早期安氏Ⅱ类错(牙合)下颌后缩患者,一期矫治采用Herbst矫治器,然后拔除每位患者的4个前磨牙;二期矫治采用edgewise固定矫治器.在Herbst矫治器矫治前两周(T1期)、Herbst矫治器初戴入矫治时(T2期)、Herbst矫治器拆除时(T3期)及二期固定矫治器拆除时(T4期)分别拍摄锥形束CT(cone beam computed tomography,CBCT).应用InvivoDental软件对CBCT图像进行三维重建,再对颞下颌关节间隙进行测量,并进行统计分析.结果:T1-T2-T3期,关节前间隙先减小后增大,关节上间隙、关节后间隙先增大后减小;T3-T4期,关节上、后间隙进一步减小,关节前间隙无明显变化;与T1期比,T4各关节间隙的变化均无明显差异.结论:髁突在关节窝中的位置在Herbst矫治开始时向前下移位,一期功能矫治结束时尤其双期矫治结束时几乎回到了治疗前的位置.     

Long-term effects of Herbst treatment in relation to normal growth development: a cephalometric study.

The aim of this study was to evaluate the short- and long-term effects of Herbst appliance treatment in relation to normal growth and development. The sample consisted of 32 subjects (16 boys and 16 girls) with a Class II, division 1 malocclusion treated successfully with the Herbst appliance for an average period of 7 months. The patients were reinvestigated 6 months post-treatment when the occlusion had settled and at the end of the growth period, an average of 6.7 years (SD = 1.1 years) after therapy. The control group comprised of 32 subjects (16 boys and 16 girls) with excellent occlusion (Bolton Standards). Sagittal, skeletal, and dental changes occurring during three observation periods were evaluated on lateral cephalograms in centric occlusion. On a long-term basis, Herbst treatment improved the sagittal jaw base relationship, but did not normalize it. The sagittal dental arch relationship, on the other hand, was almost normalized.     

Activator矫治对颞下颌关节的影响及其与颞下颌关节紊乱病的关系

Activator矫治器是较早用于临床的功能矫治器,由Andresen于1908年设计,对安氏Ⅱ类1分类错(牙合)畸形患者有良好的治疗效果,通过前移下颌刺激下颌骨的生长且抑制上颌矢状向生长,从而调节上下颌骨矢状向的关系.目前,关于Activator矫治器的矫治原理还存在较多的分歧,其中之一就有Activator是否能刺...     

Activator versus cervical headgear: superimpositional cephalometric comparison.

Clinical trials comparing activator and headgear treatment have shown comparable effectiveness in the total result achieved, but the mechanism of correction is still uncertain. Most studies have used conventional cephalometric methods to evaluate treatment effects, and this might be a factor for the inconclusive results. The aim of this retrospective investigation was to compare the effects of activator and cervical headgear treatment with a superimpositional cephalometric method that could discern between vertical and horizontal effects as well as skeletal, dental, and rotational treatment results. The sample consisted of 2 groups of Class II Division 1 patients, treated without extraction by the same clinician (22 patients were treated with a modified activator-type functional appliance, and 30 patients were treated with a combination of cervical headgear and fixed edgewise appliances). Lateral cephalometric radiographs taken at the beginning of treatment and after Class II molar correction were evaluated conventionally and with a superimpositional method. Regarding the conventional cephalometric measurements, the only difference in the anteroposterior dimension between the 2 treatment modalities was the significantly reduced SNA angle in the headgear group. Both appliances appeared to produce minimal changes in FMA and GoGn-SN angles, and there were no statistically significant differences between the treatment groups. Regional superimpositions showed differences in the movement of molars: the maxillary molar was found to move more posteriorly and inferiorly in the headgear group. Conversely, the mandibular molar was found to move toward the occlusal plane more in the activator group. Assessment of mandibular skeletal changes showed that the mandible moved anteriorly by approximately 1 mm more in the activator than in the headgear group. The overall effect of the 2 appliances was found to be clinically comparable. However, the individual components of change showed differences characteristic of each appliance.     

Effect of Herbst treatment on temporomandibular joint morphology: a systematic literature review.

The purpose of this systematic review was to evaluate the effect of Herbst appliance therapy on temporomandibular joint (TMJ) morphology, with special reference to glenoid fossa remodeling, condylar remodeling, condylar position, and articular disc position. Publications of controlled trials of Herbst treatment of Class II patients using magnetic resonance imaging (MRI), computerized tomography scans, or tomography to assess TMJ morphology were identified with Medline (1966-2001), Best Evidence (1991-2001), Cochrane Database of Systematic Reviews (second quarter, 2001), and Embase (1998-2001). Case reports were excluded. Based on our search, only 5 studies met the selection criteria. All studies used internal controls with pretreatment and posttreatment imaging. Four studies used MRI, and 1 used tomograms. The 4 MRI studies used overlapping patient samples and were not considered as independent evidence. The MRI studies did not provide conclusive evidence of osseous remodeling or condyle position change. The tomography study demonstrated minor condyle position change. Methodological deficiencies prevented major conclusions regarding disc position. The reviewed studies highlight the importance of further research. Prospective controlled studies using serial MRI and tomography are required to establish the effect of Herbst treatment on TMJ morphology.     

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.     

Long-term effects of the Herbst appliance in relation to the treatment growth period: a cephalometric study.

The aim of this study was to analyse the long-term effects of Herbst treatment on the dentofacial complex with special reference to the growth period in which the patients were treated. The sample consisted of 40 male subjects with a Class II, division 1 malocclusion treated successfully with the Herbst appliance for an average period of 7 months. The patients were reinvestigated at the end of the growth period, on average 6.6 years (SD = 1.0 years) after therapy. Nineteen patients were treated before the maximum of pubertal growth (prepeak), 15 at the maximum (peak) and 6 after the pubertal growth maximum (post-peak). Sagittal skeletal and dental changes occurring during and after Herbst treatment were evaluated on lateral radiographs in centric occlusion. At the time of follow-up examination no group differences were seen in sagittal dental arch relationships. During the follow-up period after Herbst treatment maxillary and mandibular growth development were favourable and comparable in all three groups: mandibular growth exceeding maxillary growth by an average of 4.3 mm (SD = 2.4 mm). For natural reasons, however, the amount of jaw growth during the follow-up period was larger in the subjects treated before the maximum of pubertal growth than in the subjects treated at the later stages. The conclusion of this study was that the growth period in which Herbst treatment was performed did not seem to have any conclusive effect on the long-term results. However, in order to favour occlusal stability after treatment and to reduce the time of post-treatment retention, Herbst therapy in the permanent dentition at or just after peak height velocity of growth is recommended.     

A cephalometric and tomographic evaluation of Herbst treatment in the mixed dentition.

This study describes combined treatment and posttreatment effects for patients treated with the Herbst appliance in the mixed dentition followed by retention with a prefabricated positioner. The sample included 24 female and 16 male patients with Class II malocclusions. Posttreatment lateral cephalograms were taken an average of 17 months after Herbst removal, when the patients presented for phase II comprehensive orthodontics. The cumulative treatment and retention effects were compared with a sample of untreated Class II controls matched for age, sex, and mandibular plane angle. The overjet and molar relationship were corrected by 3. 4 and 3.3 mm, respectively. A headgear effect of Herbst therapy was observed, as anterior maxillary displacement was reduced by 1.2 mm. Condylar growth was redirected to produce 2.0 mm greater posterior growth in the treatment group. These effects produced significantly greater decreases in SNA (0.8 degrees ) and ANB (1.4 degrees ), and a tendency toward an increase in SNB (0.5 degrees ) Mandibular orthopedic effects resulted in an increase in anterior facial height (1.6 mm) and inferior displacement of the chin. Minimal changes in the displacement of condylion in relation to stable cranial base structures suggest that glenoid fossa displacement does not contribute in a clinically significant way to Class II correction. Pretreatment, immediate posttreatment, and postretention corrected temporomandibular joint tomograms demonstrated a tendency for the condyle to be slightly forward (0.2 mm) at the end of treatment and then to fall back after treatment. Statistically significant joint space changes were limited to the posttreatment period. We conclude that Herbst treatment in the mixed dentition, in combination with retention, produces significant long-term improvements in dental and skeletal relationships as a result of dentoalveolar changes and orthopedic effects in both jaws.