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.     

Long-term efficacy of reverse pull headgear therapy

OBJECTIVE: To add to the data for long-term reverse pull headgear (RPHG) outcomes and further explore possible variables that could be predictors of long-term failure. MATERIALS AND METHODS: Cephalometric radiographs of 41 Class III malocclusion children treated with RPHG (face mask) were evaluated before and immediately after treatment; at 5 years posttreatment; and, for 18 patients, at 10 years posttreatment. Patients were assigned to success or failure groups according to positive or negative overjet at the longest available recall. RESULTS: Seventy-five percent of the patients maintained positive overjet, whereas 25% outgrew the correction. In a stepwise discriminant analysis, a large mandible and vertical positioning of the maxilla and mandible so that mandibular growth would be projected more horizontally were the major indicators of unfavorable later mandibular growth. Patients who experienced downward-backward rotation of the mandible during RPHG treatment were more likely to be categorized in the failure group. The age at which treatment began had no effect on long-term success and failure for patients younger than 10 years, but the percentage of successful treatment decreased after that age. CONCLUSIONS: When RPHG treatment is used for all but the most obviously prognathic children to correct anterior cross-bite in the early mixed dentition, positive overjet is maintained long-term in 70%-75% of cases, whereas 25%-30% of cases relapse into reverse overjet mainly because of increased horizontally directed and often late mandibular growth. Up to age 10, the time at which RPHG treatment began does not appear to be a major factor in long-term success in maintaining positive overjet.     

Treatment and posttreatment changes with combined headgear therapy

OBJECTIVE: To determine the effects of combined headgear treatment in high-angle patients and to evaluate the differences 2 years after treatment. MATERIALS AND METHODS: The study material consisted of lateral cephalograms of 21 patients (13 girls and eight boys; mean age 10 years 3 months) with Class II dental relationship. Only extraoral combined traction that was applied to maxillary first molars was used in the treatment of all patients. The patients were instructed to wear the appliance 20 hours per day until the molar relationship was corrected. The treatment time was approximately 5 months. At the beginning (T0), at the end (T1), and approximately 2 years after (T2) combined headgear treatment, lateral cephalometric radiographs were obtained. RESULTS: SNA and ANB angles and convexity decreased significantly during treatment (T0-T1; P<.05 and P<.01, respectively), and the net changes (T0-T2) in ANB angle and convexity were also found to be statistically significant (P<.01). During treatment, significant distal movement was found in the upper first molar, and the second premolar and molar were also distalized significantly (P<.001). At the end of 2 years, there was a significant mesial migration of the upper molars and the second premolar during the posttreatment period, but all of them were positioned more distally compared to the beginning of treatment (P<.001). The decrease in molar relation was statistically significant during the T0-T1 and T0-T2 periods (P<.001).     

Maxillary features following protraction headgear therapy in skeletal Class III patients

The objective of the research was to scrutinize maxillary alteration of skeletal Class III patients following protraction headgear therapy. The sample comprised of 15 patients (6 males, 9 females) aged 8-13 years. According to Sassouni Analysis, the maxilla was retrognathism whereas the mandible was prognathism. All of them were treated with fixed appliance and protraction headgear. Orthopedic force system included maxillary protraction with 400 gram force, mandibular retraction with 1000 gram for 12-14 hours per day. Alteration of the maxilla was scrutinized from consecutive lateral cephalograms prior to orthodontic treatment, immediate posttreatment and 2 years of follow up. The result indicated that orthopedic force enhanced the anterior portion of the maxilla to move downward and forward significantly, without rotation and relapse.     

Cervical headgear therapy as a factor in obstructive sleep apnea syndrome

PURPOSE: Obstructive sleep apnea syndrome (OSAS) has been a subject of increasing interest from the orthodontic point of view, but less attention has been paid to the possible influence of orthodontic treatment on its occurrence. The aim here was to study possible associations between the use of cervical headgear and nocturnal cessations of airflow and the severity of the latter. METHODS: The subjects were 30 children (12 boys, 18 girls, mean age 8.2, sd 1.61 years), divided into three groups: a group of 10 children undergoing headgear therapy, selected for this examination because of symptoms of OSAS while using headgear, an age-matched control group of 10 healthy children and a group of 10 with OSAS. Standard cephalograms of the headgear group prior to the orthodontic therapy and the corresponding cephalograms of healthy controls were analysed. A polygraphic (PG) sleep evaluation was used to assess the tendency for OSAS. Apnea and hypopnea periods were summated as apnea index (AI) and number of desaturations as desaturation index (ODI). All the subjects spent one night sleeping under laboratory conditions, those with orthodontic treatment spending the first half of the night with the headgear and the latter half without. RESULTS: The position of the mandible was found to be slightly more posterior in the headgear group than in the control group. The children in the headgear group were found to have significantly more apnea/hypopnea periods during the hours when the appliance was used, and the ODI-index showed increased values in this group. CONCLUSIONS: We suggest that headgear therapy may contribute to the occurrence of sleep apnea, when a strong predisposition, such as mandibular retrognathia to the development of upper airway occlusion already exists.     

头帽肌激动器与双[牙合]板矫治器矫治安氏Ⅱ^1类错[牙合]的比较研究

目的对比研究头帽 Activator 及 Twin-block 功能矫治器矫治安氏Ⅱ类错(牙合)的机理。方法应用 Clark 教授设计的 Twin-block 矫治器及 Vanbeek 设计的 Activator 治疗Ⅱ~1类错(牙合)22例(年龄10-13岁)。根据骨龄、错(牙合)严重程度等条件基本对等平均分成两组,分别戴用 Twin-block 或头帽 Activator 矫治器进行矫治。每位患者均拍摄术前、术后头颅侧位定位片、全颌曲面断层片及左手腕骨 X 光片,以 X 线头影测晕方法评价疗效。结果头帽 Activator 对上颌牛生抑制作用强于 Twin-block 矫治器,而 Twin-block 矫治器刺激下颌生长,尤其是水平向生长优于头帽 Activator;头帽 Activator 内收压入上前牙效果明显,对下前牙的唇倾控制也较好。结论头帽 Activator 更适于矫治上颌矢状及垂直向发育过度的Ⅱ类错殆。而 Twin-block 矫治器适于矫治下颌发育不足的Ⅱ类错(牙合)。     

Safety headgear products

A survey of safety products in the U.K. demonstrates that the orthodontic companies have responded to the need for improvements, and consequently there is a wide choice available. Laboratory tests have shown that there is a large difference in the effectiveness of safety release headgear systems. Further work is needed on safety facebow design to develop a version which meets both the requirements of increased safety, and ease of use. Such a safety facebow, used in conjunction with an effective 'breakaway' headcap will produce a safer system. The safety elements are an integral part of breakaway headgears and safety facebows, and when they are used together--no additional cooperation is required from the patient to increase the margin of safety.     

Adherence to instructions and fluctuation of force magnitude in cervical headgear therapy

Objectives:To investigate how patients adhere to instructions and how force magnitude fluctuates and influences the use of cervical headgear (CHG) therapy.Materials and Methods:In this controlled clinical trial, subjects (n = 40) were treated with CHG with light (L, 300 g) or heavy (H, 500 g) force. Patients were asked to wear CHG for 10 hours per day for 10 months (ie, during sleep), but the importance for treatment of wearing CHG also in the evening hours was emphasized. Adherence to instructions and force magnitude in CHG use were monitored by electronic module (Smartgear, Swissorthodontics, Switzerland).Results:Force magnitude can be set at a certain level, L or H, even if great individual variability is seen in all subjects (0–900 g). Children in the L group used CHG longer per day than those in the H group (9.3 hours ±1.5 hours and 7.8 hours ± 2.1 hours, respectively, P = .002). During evening hours, CHG was used more (P = .02) in the L group than in the H group. In both groups, CHG was used less in the evening hours during school breaks than in the evening hours during school (P < .001).Conclusions:Children with lower force in CHG seem to adhere better to the instructions for CHG use. Daily rhythm also influences the time of appliance use regardless of force magnitude. The force can be set to a certain magnitude level, even though there is substantial individual variability.     

A cephalometric evaluation of high-pull molar headgear and face-bow neck strap therapy.

The effects of two different extraoral appliances were evaluated over a 1-year period. Of the thirty-seven cases selected for study, twenty were treated with a face-bow neck strap and seventeen were treated with a high-pull molar headgear. Patients ranged in age from 10.10 to 16.6 years and averaged 13.4 years. The appliances exerted less than 600 Gm. of force per side and were worn for 12 to 16 hours per day. All cases were fully banded, and extraction and nonextraction treatment were included. An analysis of pretreatment data revealed a high degree of selection. Patients selected for high-pull treatment generally exhibited larger anterior face heights, steeper mandibular plane angles, and a greater amount of tooth eruption of the upper first molars than the patients selected for neck strap therapy. A control group of ten untreated subjects was matched to each treatment group to permit assessment of the impact of treatment on growth. Relative to normal growth, treatment with face-bow neck strap traction tended to direct the maxilla and mandible downward and backward. The palatal plane was lowered anteriorly and point A was retracted. The maxillary molars were extruded, and concomitantly an increase in anterior face height and mandibular plane angle was observed. On the other hand, the high-pull molar headgear traction resulted only in increased mandibular molar eruption. However, there was also a nonsignificant tendency for point A to be held back and for lower anterior face height to increase. The comparison of the two treatment samples revealed that the functional occlusal plane was tipped down at the back as the maxillary molars were more extruded in the neck strap sample. In the high-pull sample, the functional occlusal plane was unchanged and the mandibular molars were more extruded than they were in the neck strap group.     

Upper headgear versus lower headgear, yokes, and class III elastics.

The use of a lower headgear-yoke-Class II mechanism on an average works faster than a maxillary headgear. The distal tipping of the molars is greater with HGY-II which may be the result of the quicker tooth movement. The speed of distalization is probably due to the effect of the constant force of the Class II elastics. An orthopedic change on the maxilla could be seen if one can draw any conclusions from a change of only 1 degrees. A reduction of the SNA angle and a slight clockwise rotation of the palatal plane was noticed. These results agree with earlier investigations about cephalometric changes with headgear therapy. We have come to the conclusion that both methods are indicated. We use the upper headgear especially at a time when a complete therapy is not possible because of noneruption of the permanent teeth. The HGY-II mechanism is indicated when most permanent teeth are available and thus the therapy can be completed in one treatment period.