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Authors:Dr. Divya S. Dr. Arun S. Urala Dr. Siddharth Mehta

This article reviews the comparison between segmented arch mechanics and continuous arch mechanics. Introduction:

Biomechanics is the application of mechanical principles to living organisms, such as humans, animals, plants and the functional basic units of life, the cells. As force is the medicine in orthodontics we need to understand the basic laws of mechanics and its effects on living cells.
Today's orthodontist needs a working knowledge of both segmented and continuous arch mechanics. There are indications for both, and therefore a practitioner should not be limited to one or the other. Following are the various criteria which differentiate between segmented and continuous arch mechanics.
  1. Definition,
  2. Case selection criteria,
  3. Possibilities,
  4. Treatment time sequencing,
  5. Advantages and disadvantages,
  6. Pearls and pitfalls.

Segmented arch mechanics

Continuous arch mechanics

- Orthodontic mechanotherapy in which not all teeth within an arch are included in the same arch wire, but rather anchorage and active segments are created by consolidating teeth together using wire segments.

-It consists of an archwire that engages only few teeth within an arch (only four incisors or only the teeth in a posterior dental segment)


-Orthodontic mechanotherapy utilizing continuous arch wires in the entire dental arch. (As opposed to segments of arch wires encompassing segments of teeth)

-It consists of an archwire that engages, through crown attachments (brackets and tubes), many or all of the erupted teeth in the maxillary or mandibular dental arch. (molar to molar)



Continuous arch mechanics

Segmented arch mechanics

Generalized spacing



Mild crowding(Non Extraction)






Surgical cases



Open bite cases

Moderate to severe crowding (Extraction)



Differential anchorage desired



Severe canine or premolar root angulations



Asymmetric cases



Multiple missing teeth



Periodontal health compromised



Desired to perform multiple stages of treatment



3. Possibilities of segmented arch mechanics and continuous arch mechanics:
  • Deep bite correction
  • Open bite correction
  • Space closure: En masse retraction

Canine retraction

Deep bite correction


Segmented arch mechanics11

Continuous arch mechanics8


Deep bite can be corrected by

intrusion of the incisors with intrusion arches.

  • Rickets utility arch ( 2x4 appliance

  • Continuous intrusion arch

  • Burstone’s three piece intrusion utility arch




Deep bite can be corrected by using

  • Bite plates

  • Reverse curve of spee

  • Step bend in the arch wire


Open bite correction


Segmented arch mechanics12

Continuous arch mechanics8


Extrusion arches

  • The extrusion arch is the reverse of the intrusion arch.

  • Used to correct upper and lower occlusal planes that diverge anterior to the first premolars.




  1. Vertical elastics

  2. Multiloop Edgewise Arch Wire.

  • Correcting the inclination of the occlusal planes.

  • Aligning the maxillary incisors relative to the lip line.

  • Uprighting the axial inclinations of the posterior teeth.



Space closure mechanics


Segmented arch mechanics13,14,15

Continuous arch mechanics8

En masse retraction:


  1. Four Incisors: PG spring, Utility arch, Omega loop

  2. Six anteriors: T loop, opus loop


Simultaneous intrusion and retraction:

  1. Four incisors: K SIR loop

  2. Six anteriors: Burstone’s three piece intrusion arch, Rickets retraction and intrusion utility arch


Single Canine retraction:


Poul Gjessing spring, Burstone’s T loop


  • E chain

  • Sliding mechanics with light forces:

Active tie backs

Passive tie backs: Elastomeric modules, Nickel titanium coil springs



4.Treatment stages7


Segmented Arch Mechanics


Continuous Arch Mechanics

Retraction of canine


Leveling and Aligning


Retraction of incisor and Intrusion

Retraction of canine


Align and Level


Retraction of incisor


Coordination, Detailing and Finishing


Coordination, Detailing and Finishing



5. Segmented arch mechanics5




  • One of the major advantages of segmented mechanics is that a known force system is delivered to teeth because there is no dissipation of force by friction.

  • Precise control over the anterior and posterior anchorage.

  • It is fail safe; the tooth will move only to the limit to which the loop is activated.

  • Differential tooth movement is possible.

  • Retraction loops or springs offer more controlled tooth movement than continuous mechanics.


  • A good understanding of mechanics is required when using retraction loops or springs because minor errors in mechanics can result in major errors in tooth movement.

  • More wire bending skill and chair time is required as compared to friction mechanics.

  • Retraction loops may be uncomfortable to some patients, especially with less vestibular depth.

  • Can lead to gingival irritation because of the loops.



Continuous arch mechanics8




  • Complicated wire configuration is not required.

  • Initial wire placement is less time consuming.

  • Enhances patient comfort.


  • Confusion regarding the ideal force levels. There are no essential guidelines concerning the amount of force to be used during space closure.

  • Tendency for initial over activation of elastic and spring forces, causing initial tipping and inadequate rebound time for uprighting.

  • Limited ability to produce differential anchorage, optimal tooth movements or control for adverse responses in complex cases.


6. Pearls and Pitfalls7


Continuous arch wire

Segmented arch wire






Appliance system is simple

Force system cannot be determined (Indeterminate system)

Force systems can be determined (Determinate system)

Decreased ability to delegate

Arch coordination is easy

Unable to avoid adverse tooth movements

Precise spring design

Arch coordination is difficult





Chair side time is reduced

Causes incisor proclination and round tripping

Minimizes adverse tooth movements

Chair side time is increased

Minimal or no loops



Patient discomfort (loops)

Maintaining oral hygiene is easier



Maintaining oral hygiene is difficult


To obtain optimal and efficient treatment, the clinician must select the ideal mechanical approach for the individual patient and the arch. A well-considered proactive selection of optimal biomechanics, careful appliance design, and implementation of strategies to minimize adverse tooth movements are likely to produce the most desirable and efficient results in any orthodontic patient.

  1. 1. Glossary of Orthodontic Terms.  Daskalogiannakis J, editor. 2000, Quintessence Books.
  2. 2. Contemporary Orthodontics. Profitt W.R, Fields W.H, Sarver D.M, editors. 4th edition 2007, Mosby Elsevier.
  3. 3. Biomechanics in Orthodontics. Marcotte M.R, editor. 1st edition 1990, B.C. Decker publisher.
  4. 4. Biomechanics in Clinical Orthodontics. Nanda R, editor. 1st edition 1997, Saunders.
  5. 5. Modern Edgewise mechanics and the segmented arch technique. Burstone C.J, Steenbergen E.V, Hanley K.J, editors. 1st edition 1995.
  6. 6. Biomechanics and Esthetic strategies in clinical orthodontics. Nanda R, editor. 1st edition 2005, Elsevier Saunders.
  7. 7. Current therapy in Orthodontics. Nanda R, Kapila S.D, editors. 1st edition 2010, Mosby Elsevier.
  8. 8. Systemized Orthodontic Treatment Mechanics – McLaughlin R.P, Bennett J.C, Trevisi H.J, editors. 2001, Mosby.
  9. 9. Burstone C.J. Rationale of the Segmented arch. Am J Orthod Dentofac Orthop 1962;48:805-822.
  10. 10. Burstone C.J. Deep overbite correction by intrusion. Am J Orthod Dentofac Orthop 1977;72:1-22.

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