Long-term changes in pharyngeal airway dimensions following activator-headgear and fixed appliance treatment

Abstract

The aim of this study was to evaluate changes in the pharyngeal airway in growing children and adolescents and to compare these with a group of children who received activator-headgear Class II treatment. The sample consisted of 64 children (32 males and 32 females), 32 had a combined activator-headgear appliance for at least 9 months (study group) followed by fixed appliance therapy in most patients, while the other half received only minor orthodontic treatment (control group). Lateral cephalograms before treatment (T1, mean age 10.4 years), at the end of active treatment (T2, mean age 14.5 years), and at the long-term follow-up (T3, mean age 22.1 years) were traced and digitized. To reveal the influence of somatic growth, body height measurements were also taken into consideration. A two-sample t-test was applied in order to determine differences between the groups. At T1, the study group had a smaller pharynx length (P = 0.030) and a greater ANB angle (P < 0.001) than the controls. The pharyngeal area and the smallest distance between the tongue and the posterior pharyngeal wall also tended to be smaller in the study group. During treatment (T1-T2), significant growth differences between the two groups were present: the study group had a greater reduction in ANB (P < 0.001) and showed a greater increase in pharyngeal area (P = 0.007), pharyngeal length (P < 0.001) and the smallest distance between the tongue and the posterior pharyngeal wall (P = 0.038). At T2, the values for the study group were similar to those of the control group and remained stable throughout the post-treatment interval (T2-T3). Activator-headgear therapy has the potential to increase pharyngeal airway dimensions, such as the smallest distance between the tongue and the posterior pharyngeal wall or the pharyngeal area. Importantly, this increase seems to be maintained long term, up to 22 years on average in the present study. This benefit may result in a reduced risk of developing long-term impaired respiratory function.

Effectiveness of twin-block and Mandibular Protraction Appliance-IV in the improvement of pharyngeal airway passage dimensions in Class II malocclusion subjects with a retrognathic mandible

“…20 In Class II controls, the PAP dimensions did not change significantly during the follow-up period. Hä nggi et al 12 also did not find any change in PAP dimensions during adolescence. In our Class II subjects, the soft palate was thinner, longer, and more inclined compared to that of Class I subjects.…”

“…The positive impact of functional appliance therapy on the airway dimension cannot be explained simply by the established skeletal change; the difference in the posture of the tongue caused by increased genioglossus muscle tonus or soft tissue changes may play an important role and is probably induced by forward positioning of the mandible during the treatment. 12 Another possible explanation for the improvement could be ''catch-up growth,' whereby children with small oropharyngeal dimensions would have a greater intrinsic stimulus to increase their capacity for respiratory function.…”

“…9,10 Although there are numerous studies those have evaluated the nature of Class II correction by various functional appliances in growing skeletal Class II children, there are only a few studies that mention the PAP dimension changes following functional appliance treatment. Studies have been conducted to evaluate the effect of the Harvold activator, 11 an activator with high-pull headgear, 12 cervical headgear, 6 the Farmand appliance, 13 the modified bionator, 14 the Klammt appliance, 15 the Herbst appliance, 16 and rapid maxillary expansion with Herbst appliance therapy 17 on the PAP in Class II patients. However, to our knowledge there is no study in the literature mentioning the effect of the most commonly used functional appliance, that is, the twinblock appliance, in the improvement of PAP dimension among subjects with Class II malocclusion.…”

Effects of Functional Appliance Therapy on the Depth of the Pharyngeal Airways: Activator vs. Forsus

“…Eventually, the main objective of our study, i.e., subsequent effects of these appliances on the dimensions of pharyngeal airways, will be addressed. Having reviewed the literature, there are very few published studies [4,[10][11][12][13][14] that have investigated the effect of functional appliances on the dimensions of awake pharyngeal airways. Of these studies, four have included either headgear [4,10,12] or maxillary expansion [11] appliances in combination with functional appliances, and the other two studies have used only removable [13] The sample was then divided into two groups.…”

“…Having reviewed the literature, there are very few published studies [4,[10][11][12][13][14] that have investigated the effect of functional appliances on the dimensions of awake pharyngeal airways. Of these studies, four have included either headgear [4,10,12] or maxillary expansion [11] appliances in combination with functional appliances, and the other two studies have used only removable [13] The sample was then divided into two groups. The first group consisted of the subjects who were treated with removable functional appliances (Activator type), and the second group consisted of those who were treated with fixed functional appliances, Forsus Fatigue Resistant Device (FRD) (3M Unitek Corp, Monrovia, Calif).The sex and age distribution of the treatment groups are shown in Table 1.…”