Page 64 - REMOVABLE ORTHODONTIC APPLIANCES
P. 64

56 Removable Orthodontic Appliances
                                                       Figure 7.10  An  appliance to expand the  upper
                                                       arch. Adams' clasps 64|46  (0.7 mm), a  mid-line
                                                       screw and  molar capping to eliminate
                                                       mandibular  displacement.



















             •  to help seat the appliance, particularly  after  Rotations
               activation.
                                                    A  mildly  rotated  upper  central  incisor  can  be
             Anchorage                              corrected  with  a  removable  appliance.  Rota-
             The  arch  is  to  be  expanded  symmetrically,  so  tions  of other teeth  and multiple  rotations can
             anchorage is reciprocal.               only  be  corrected  by  using  a  fixed  appliance.
                                                    Many rotations are  associated with an element
             Points to note                         of  apical  displacement  and  will  be  difficult  to
             The patient should open the screw by one quar-  correct  with  a removable  appliance.  Rotations
             ter-turn each week.  If the appliance is adjusted   are also particularly liable to relapse.
             more frequently it may not seat home  fully and
             will  become  difficult  to  wear.  The  molar  An  appliance  to  derotate  an  upper central
             capping should be removed after the expansion   incisor (Figure 7.11)
             has been  completed  and  the  appliance  should
             continue  to be worn  as  a retainer  for at least 3   Active  component
             months. It is wise to cover the screw with cold-  A  force-couple  must  be  applied  to  the  tooth.
             cured  acrylic  to  prevent  any  unwanted  move-  A  labial  bow  and  a  palatal  spring  can  gener-
             ment during this stage.                ate  this.  If  the  palatal  aspect  of  the  tooth  is
                                                    already  in  the  line  of  the  arch,  contact  with

             Upper  arch  contraction
             Only if there  is a buccal crossbite  of the upper
             teeth  will  contraction  of  the  upper  arch  be
             necessary. This is an unusual finding associated
             with  a  broad  maxillary  base  and  a  narrow
             mandibular  base.  Treatment  is  difficult  and  is
             best  left  to  the  orthodontic  specialist.  It  may
             involve the use of an upper appliance similar to
             that  for  upper  arch  expansion  except  that  the  Figure 7.11  A rotated  |l  to be aligned with a 'U'
             screw  is  opened  before  it  is  incorporated  into  loop labial bow (0.7 mm). The labial bow is activated
                                                    progressively. The acrylic must be cleared away from
             the  appliance  and  is  closed  by  the  patient.
                                                    the  mesial  aspect  of the  central  but maintained  in
             Simultaneous expansion  of the  lower arch  will  contact with the disto-palatal aspect of the central
             usually be  required.                  incisor.
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