Effects of Herbst Appliance Therapy to Improve Airway Dimension
Condition: Angle Class II
MeSH terms: Malocclusion, Angle Class II; Overbite
Study type: Interventional

Summary: 
      Herbst appliance is one of the most popular fixed functional appliances to treat orthodontic
      patients with small lower jaws. Since small lower jaws are reported to be one of the main
      reasons to induce sleep disordered breathing(SDB) of children, Herbst appliance can be used
      to treat SDB children. Previously no study compared the effects of Herbst appliance therapy
      with removable functional appliance on airway dimension, so it still remains unclear which
      kinds of functional appliance is more suitable for improving airway dimension. This study
      will assess the effect of Herbst appliance on airway dimension and compare the effects with
      those of twin block appliance (a popular 24 hours used removable functional appliance, and
      also commonly used to treat adult sleep apnea).
    

Detailed description: 
      Sleep disordered breathing (SDB) is an important paediatric problem. It is estimated that
      3.2% to 12.1% of children have habitual snoring and 0.7% to 10.3% have obstructive sleep
      apnea syndrome (OSAS). Children OSAS is associated with a series of daytime and nighttime
      signs and symptoms. Nighttime symptoms include heavy snoring, restless sleep, heavy seating
      and enuresis, etc. Daytime symptoms include excessive daytime sleepiness and abnormal
      behavior such as aggressiveness and hyperactivity, etc. Untreated OSAS was reported to result
      in serious morbidity, such as failure to thrive, poor learning, attention deficit and
      hyperactivity disorder, etc.

      There is an increasing concern related to sleep disordered breathing(SDB) of children by
      orthodontists. Since not only the tonsilar and adenoid hypertrophy is the main cause of
      paediatric OSA, but also craniofacial anomalies such as retrognathic mandible, narrow
      maxillary palatal arch and increased lower facial height can also contribute to it,
      orthopedic treatment such as rapid maxillary expansion (RME) and mandibular advancement
      device (MAD) may potentially permanently cure the children OSA. RME which is used to widen
      maxilla, thus increasing the nasal cavity and improving the nasal flow, has been thoroughly
      researched. However, only a few previous studies focused on the treatment effect of MAD for
      treating OSA children. These studies showed sorts of MAD such as jaw-positioning appliance,
      mono-block, and Herbst appliance were effective to OSA children, but it remains unclear how
      to choose a functional appliance, and if there is any treatment difference between removable
      functional appliance and fixed functional appliance for improving airway dimension.
    

Intervention name(s): The Herbst appliance; Twin block appliance
Intervention type(s): Device; Device
Intervention description(s): Orthodontic functional appliance; Orthodontic functional appliance
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Outcomes Assessor)
Primary purpose: Treatment