Removable Orthodontic Appliances

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CONTENTS

INTRODUCTION

      

        As the name suggests, these are appliances that can be removed by the patient without any supervision by the orthodontist. Removable orthodontic appliances are useful in a variety of situations but present the inherent disadvantage of the treatment being in the control of the patient.

DEFINITION

       Device that can be inserted into and removed from the oral cavity by the patient  at will .

HISTORY

·         Early 20^th century  Victor Hugo Jackson use  Vulcanite bases & precious metals

·         Early  1900s,  George  Crozat  developed  a removable  appliance  fabricated  entirely of precious metal

              

  

INDICATIONS OF REMOVABLE

1. Tipping type of tooth movement
2. Overbite reduction
3. Growth modification during mixed dentition
4. Retention following orthodontic treatment
5. Adjunct to fixed orthodontic appliances
6. Interfere with  or prevent the development of abnormal orofacial habits

CONTRA INDICATIONS

1. Uncooperated patient  like mental retarded, etc
2. Patient with multiple rotation of teeth
3. In case requiring extraction , it is difficult to close residual space by forward movement of posterior teeth
4.  Class II malocclusion with unfavorable growth pattern
5. Class III malocclusion with unfavorable growth pattern

ADVANTAGES

1. Maintain good oral hygiene during orthodontic therapy
2. ROA was fabricted in the lab so reducing the dentist’s chair time
3. ROA take less chair side time , the orthodontist can handle more number of patient
4. Less expensive than fixed appliance
5. As it need less chair time and are less expensive an be used in community based programs
6. ROA can be used by general practitioners , so  the specialists to concentrate  on more difficult cases
7.  Fabrication of ROA  need less inventory

8. ROA are less conspicuous than fixed appliance
9. Damaged appliances that apply undesirable forces can be removed by the patient

DISADVANTAGES

1. Patient cooperation  is vitally important for the success of the treatment
2. Removable appliances are capable of only tipping tooth movement
3. Whenever multiple tooth movements are to be carried out, it should be done one at a time
4. Treatment duration is prolonged in case of severe malocclusion
5. Multiple rotation are difficult to treat using ROA
6. In cases requiring extraction , it is very difficult to close residual space by forward movement of posterior teeth
7. Greater chance of patient  misplacing or damaging ROA
8. Patient should exhibit enough skill to remove and replace the appliance without distorting them
9. ROA cannot be used to treat severe cases of class II and class III malocclusion with unfavorable growth pattern

PARTS OF REMOVABLE ORTHODONTIC APPLIANCE

1. Rententive component
2. Active component
3. Base plate

RETENTIVE COMPONENT

·         Help to retain the appliance in place and resist displacement due to active components.

·         Effectiveness of the active components is dependent on retention of the appliance

·         Good fixation will help patient compliance, anchorage and tooth movement

 CLASPS

·         These are the retentive components of most removable orthodontic appliances.

·         They are supposed to hold the teeth in such a manner so as to resist the displacement of the appliance

TYPES OF CLASPS

                 

        C Clasp                         Jackson clasp                  Schwartz clasp

                         

      Southern end                      Triangular                           Ball end                   

             clasp                                 clasp                                  clasp                      

                                       

                                              Crozatz clasp

ADAM’S CLASP

·            Also known as modified arrowhead, Universal and Liverpool clasp

·            Devised by Professor C Philip Adams in 1948,

·            It makes use of the mesial and distal proximal undercuts of the first permanent molars

·            It is made from 0.7mm round SS wire.

·            This clasp offers maximum retention as it engages the undercuts on the mesial and distal embrasures of first

     The Adams' clasp has a lot of advantages over other clasps,  

  which are:

1.     It is simple, strong and easily constructed.

2.     It offers excellent retention.

3.     It can be used on any tooth be it incisor, premolars or molars.

4.     It is neat and unobtrusive and it makes an appliance easy to   insert and remove using the bridges of the clasp.

5.     Good patient compliance as it is comfortable to wear and resistant to breakage.

6.     It can be used on both deciduous and permanent teeth.

7.     A number of modifications enable its use in a wide variety of appliances.

MODIFICATIONS OF ADAMS' CLASP

                           

     Adams Clasp with                  Adams Clasp with                   Adams Clasp with

           arrow head                       additional arrow head                distal extension

                      

    Adams Clasp with                     Adams Clasp with                  Adams Clasp with       

          J hook                                         buccal tube                                  helix       

                 

                                                  

                                                         Adams clasp on 

                                                              anteriors                                  

ACTIVE COMPONENT

·            Apply forces to the teeth to bring about the desired tooth movement.

·            Active components include:

1.       Springs 

2.       Bows   

3.       Screws

4.       Elastics

SPRING

           

       Finger Spring                   Z Spring                       T Spring                       Helical Spring

                                             

           Buccal Retractor                   Helical Retractor                      Palatal Retractor

BOWS

          

    Short Labial bow             Long Labial bow             Split Labial bow              Robert’s Retractor     

           

 Reverse Labial bow        High Labial bow with           Mills  Labial bow               Fitted Labial Bow

                                                  apron spring

SCREWS & ELASTICS

                   

    Removable appliances for            Removable appliances for                              Elastics

        buccal movement of a                distal movement of teeth

                group of teeth

BASE PLATE

·         Bulk of removable appliance is made up of the acrylic plate

·         Material used is cold cure or heat cure acrylic.

·         Base plate acts as a support for pressure sources and distributes the reaction of these forces to the anchorage areas

USES OF BASE PLATE

1. It incorporates both the retentive and active components into a single functional unit
2. It helps in anchorage and retention of the appliance in the mouth
3. It helps resist unwanted drift during tooth movement
4. It distributes the forces from the active components over a large area
5. It protects the palatal springs against distortion in the mouth
6. Bite planes can be incorporated into the base plate and used to treat specific problems

MODIFICATION OF  BITE PLANE

„  Anterior Bite plane

„  Posterior Bite plane

ANTERIOR BITE PLANE

·            Used for overbite reduction

·            Are made behind the incisors and canines

·            Bite plane should be flat and not inclined to avoid proclining forces on the mandibular incisor teeth

·            Thickness should be sufficient to open the bite in the premolar region by 4 to 5 mm

·            As the overbite reduces, additional acrylic can be added to raise the platform and continue overbitereduction.

·            Grooves can be provided in the anterior bite

·            An inclined guide plane can also be provided as a modification of the anterior bite plane

                                    

POSTERIOR BITE PLANE

„  Are used mainly when teeth have to be pushed over the bite.

„  Height of the platform should be sufficient enough to free the teeth, that are to be moved, from occlusal interference with the opposing teeth.

    It is better to adjust the posterior bite planes to obliterate the freeway space to aid compliance

                             

REMOVABLE RETAINERS

HAWLEY’S RETAINER

•         Most common removable retainer

•         Designed in 1920s  by Charles Hawley

Design of Appliance

„  Wire used  : 19 gauge wire

„  Labial bow is positioned in middle third of teeth

„  Clasps on molars, palatal coverage, and labial bow with adjustment loops

„  Base plate is extended to embrasures

„   It can incorporate biteplate for deep bite patients

            

HAWLEY'S RETAINER WITH LONG LABIAL BOW

●        The labial bow has 'u' loops on the premolar distal to the canine

●        This modification allows the closure of spaces distal to the canine

HAWLEY'S RETAINER WITH CONTINUOUS LABIAL  BOW SOLDERED TO CLASPS

●        This allows for space closure in the anterior as well as the extraction or premolar region

●         It is well tolerated by the patient

●        Prevents spaces opening up in the region where the extractions were undertaken

MODIFIED HAWLEY'S RETAINER WITH LIGHT ELASTIC REPLACING THE LABIAL BOW

●        This retainer is rarely used nowadays.

●        The use of elastics in the anterior region put unnecessary forces on these teeth and has a tendency to flatten the arch

BEGG RETAINER

·         It is  introduced by  P R Begg

·         It is ideal for cases where settling of occlusion is required; especially in the posterior segments, as there is no wire framework crossing the occlusion.

Design of Appliance

·         Labial wire that extends the last erupted molar and curves around it to get embedded in acrylic that spans the palate

                         

SINGLE ARROWHEAD PARTIAL WRAPAROUNDS RETAINER

●        This retainer is a modification of the Begg's retainer and is advocated in case with partially erupted third or second molars.

●        The wire bending can be tedious

SPRING RETAINER

●        The spring retainer or the spring realigner was designed to be used exclusively in the anterior segments.

●        It is capable of aligning as well as retaining the corrected alignment of these teeth.

KESLING'S TOOTH POSITIONER

●        In 1945 ,  H.D. Kesling developed the tooth positioner

●         It is made up of thermoplastic rubber material

●        It covers the upper and lower clinical crowns and part of the adjacent gingiva

●        Patient is unable to speak with the appliance in place.

●        Minor adjustments for settling of occlusion can be made with this appliance.

OSAMU'S INVISIBLE RETAINERS

●        These retainers are made of thin thermoplastic sheets.

●        They are relatively inconspicuous and well accepted by all patients.

●        The material fully covers the clinical crown and extends partly on to the adjacent gingiva.

HABIT  BREAKING APPLIANCES

ORAL SCREEN

     It is a myofunctional appliance that is easy to fabricate and wear.

  It is used

·            To intercept mouth breathing habit

·            To intercept thumb sucking , tongue thrusting , lip biting and cheek biting

·            To decreases the anterior proclination of incisor

EXPANSION APPLIANCES

COFFIN SPRING

·               Appliance was designed by Walter Coffin

·               Capable of slow dento alveolar expansion

·               Design of appliance

·               Consist of omega shaped wire of  1.25 mm thickness

·               Placed in mid – palatal region

·               Free ends of omega wire are embedded in acrylic covering the slopes of the palate

·               Spring is activated by pulling the two sides apart manually

REFERENCE

1.     Contemporary Orthodontics                         :   W R  Proffit

2.     Textbook of orthodontics                              :  Gurkeerat singh

3.     Orthodontics  the art and science                :  S I Bhalajhi