Review articles

By Dr. Diana Jamshir , Dr. Leda Valentini , Dr. Roberta Scarola , Mr. Enrico Pompeo , Dr. Anazoly Chudan Poma , Dr. Emanuele Fantasia
Corresponding Author Dr. Diana Jamshir
La Sapienza University, - Italy
Submitting Author Dr. Diana Jamshir
Other Authors Dr. Leda Valentini
La Sapienza University, - Italy

Dr. Roberta Scarola
University of Bari, - Italy

Mr. Enrico Pompeo
La Sapienza University, - Italy

Dr. Anazoly Chudan Poma
La Sapienza University, - Italy

Dr. Emanuele Fantasia
La Sapienza University, - Italy


Twin Block; functional therapy; Class II malocclusion; skeletal effects; dental effects.

Jamshir D, Valentini L, Scarola R, Pompeo E, Chudan Poma A, Fantasia E. Skeletal and dentoalveolar effects in patients with Class II malocclusions using Twin Block appliance A review of literature. WebmedCentral ORTHODONTICS 2019;10(2):WMC005552

This is an open-access article distributed under the terms of the Creative Commons Attribution License(CC-BY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Submitted on: 18 Feb 2019 10:26:46 PM GMT
Published on: 19 Feb 2019 07:21:00 AM GMT


Functional appliances therapy have been shown to be an effective treatment protocol for growing Class II patients, through a combination of skeletal and dentoalveolar effects. Many literature studies revealed a significant increase in mandibular length and a minimum restriction on the maxillary growth in Class II malocclusion after Twin Block therapy. Reduction of overjet, palatal tipping of the upper incisors, labial tipping of the mandibular incisors, vertical and sagittal correction of the molar relationship are dentoalveolar effects produced by Twin Block appliance.


Class II malocclusion is a common dysgnathia in orthodontic practice and studies reveal it is found in one-third of the population. Class II functional therapy includes a wide variety of orthodontic devices that stimulate multiple muscle groups responsible for the function and mandibular position. The result is an adaptive skeletal growth to correct the skeletal discrepancy.

The Twin Block appliance was introduced by William Clark in 1988 and it is the most popular functional appliance in the United Kingdom. Twin Block appliance can be realized with many modifications depending on the characteristics of the malocclusion.     It consists of maxillary and mandibular removable plates with acrylic bite blocks that contact at an angle of 70 degrees posturing mandible in the correct position. These two unattached plates would make Twin Block more acceptable to patients than other removable functional appliances, which are generally monoblocks, considering more freedom they have in mandibular movements. Delta claps improve the retention of the appliance. A labial bow is rarely required to prevent retraction of upper incisors by the lips.


Our review was conducted on the electronic literature database, Pubmed, using specific keywords. The period considered was from 1998 to 2016. Keywords: Twin Block; functional therapy; Class II malocclusion; skeletal effects; dental effects.


The main objective of functional therapy in Class II malocclusion is the achievement of an adequate intermaxillary relationship by promoting the mandibular growth. Many authors have found a significant increase in mandibular length measured from distance Art-Pg, Art-B (3,4,5,10), Co-Po, Co-B (10) and Co-Gn (17) and forward movement of point Pg. Lund and Sandler and other authors claim that it is impossible to know whether the raise in Art-Pg depends on the increase in mandibular length or on the repositioning of the mandible (3,12). The mandibular growth can be demonstrated also by the significant increase in SNB angle in patients treated with Twin Block appliance (3,4,5,11,15) and the reduction in ANB angle (3,7).  

According to some authors Twin Block appliance would be able to limit the growth of the maxilla (15). However, several studies reveal that a restraining effect by Twin Block on the maxilla could not be demonstrated (3).

Many studies showed that Twin Block appliance produce a significant reduction of overjet in Class II, Division 1 malocclusions, through a combination of skeletal and dentoalveolar effects. Dentoalveolr changes produced by Twin Block therapy consist in retroclination of the maxillary incisors and proclination of the mandibular incisors, distal movement of upper molars and mesial movement of lower molars for the correction of a Class II molar relationship. An acrylic capping to cover the edges of mandibular incisors minimizes the tipping of incisors and promotes skeletal effects (4).

The versatility of Twin Block appliance consists in the ability to promote or not the eruption of molars depending on the facial divergence (3). Some authors found an increase in vertical facial dimension after Twin Block therapy, but the ratio lower anterior facial height/ total anterior facial height remained generally unchanged (4,5).


Twin Block appliance produces a significant increase in mandibular length. Dentoalveolar changes mainly consist in the reduction of overjet and in the improvement of the molar relationship.


  1. Comparison of 2 modifications of the Twinblock appliance in matched Class II samples. Nicola Ann Parkin, Helen Fiona McKeown and Paul Jonathan Sandler. Am J Orthod Dentofacial Orthop 2001; (119:572-7).
  2. Treatment with Twin-block appliance followed by fixed appliance therapy in a growing Class II patient. Keun-Young Lee, Jae Hyun Park,  Kiyoshi Tai, and Jong-Moon Chae. Am J Orthod Dentofacial 2016; (150:847-63).
  3. The effects of Twin Blocks: A prospective controlled study. David Ian Lund and Paul Jonathan Sandler. Am J Orthod Dentofacial Orthop 1998; (113:104-10.)
  4. Clinical Effectiveness of the Twin Block Appliance in the Treatment of Class II Division 1 Malocclusion. Antanas Šidlauskas. Stomatologija, Baltic Dental and Maxillofacial Journal, 7:7-10, 2005
  5. The effects of the Twin-block appliance treatment on the skeletal and dentolaveolar changes in Class II Division 1 malocclusion. Antanas Šidlauskas. Clinic of Orthodontics, Kaunas University of Medicine, Lithuania. Medicina (Kaunas) 2005; 41(5).
  6. Cephalometric evaluation of the effects of the Twin Block appliance in subjects with Class II, Division 1 malocclusion amongst different cervical vertebral maturation stages. Aisha Khoja, Mubassar Fida, Attiya Shaikh. Dental Press J Orthod. 2016 May-June; 21(3):73-84.
  7. Cephalometric study to test the reliability of anteroposterior skeletal discrepancy indicators using the twin block appliance. Rahul Trivedi, Amit Bhattacharya, Falguni Mehta, Dolly Patel, Harshik Parekh1 and Vaibhav Gandhi. Trivedi et al. Progress in Orthodontics (2015) 16:3.
  8. Use of the Clark Twin Block functional appliance with and without an upperlabial bow: a randomized controlled trial. Omar Yaqoob; Andrew T. DiBiase; Padhraig S. Fleming; Martyn T. Cobourne. Angle Orthodontist, Vol 82, No 2, 2012.
  9. Treatment Effects of Twin-Block and Mandibular Protraction Appliance-IV in the Correction of Class II Malocclusion. Ashok Kumar Jena;Ritu Duggal. Angle Orthodontist, Vol 80, No 3, 2010.
  10. Proportional changes in cephalometric distances during Twin Block appliance therapy. M.J. Trenouth. Department of Oral and Maxillo Facial Surgery and Orthodontics Royal Preston Hospital, Lancashire, UK. European Journal of Orthodontics 24 (2002) 485-491.
  11. Treatment effects of the R-appliance and twin block in Class II division 1 malocclusion. Abdolreza Jamilian, Rahman Showkatbakhsh and Shabnam Sheikholeslam Amiri. Departments of Orthodontics, Universities of  Islamic Azad University and  Shahid Beheshti, Tehran, Iran.  European Journal of Orthodontics 33 (2011) 354–358.
  12. An extended period of functional appliance therapy: a controlled clinical trial comparing the Twin Block and Dynamax appliances. Robert T. Lee, Emma Barnes, Andrew DiBiase, Ravichandram Govender and Usman Qureshi. Department of Orthodontics, Bart’s & The London NHS Trust, London, East Kent Hospitals University NHS Foundation Trust, Department of Orthodontics, Q.M.U.L., London, UK. European Journal of Orthodontics 36 (2014) 512–521.
  13. Dentoskeletal effects of Twin Block and Herbst appliances in patients with Class II division 1 mandibular retrognathy. Asl? Baysal and Tancan Uysal. Department of Orthodontics, Faculty of Dentistry, Izmir Katip Celebi University, Turk. European Journal of Orthodontics 36 (2014) 164–172.
  14. Systematic review: Short-term treatment effects produced by the Twin-block appliance: a systematic review and meta-analysis. Sayeh Ehsani, Brian Nebbe, David Normando, Manuel O. Lagravere and Carlos Flores-Mir. Private Practice in Vancouver, British Columbia, Canada, Private Practice in Edmonton, Alberta, Canada, Faculty of Dentistry, University of Para, Belem, Brazil, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada. European Journal of Orthodontics, 2015, 170–176.
  15. Randomized controlled trial: Dentoskeletal effects of the Bite-Jumping Appliance and the Twin-Block Appliance in the treatment of skeletal Class II malocclusion: a randomized controlled trial. Ahmad S. Burhan and Fehmieh R. Nawaya. Orthodontic Department, Faculty of Dentistry, Al-Baath University, Homs, Pediatric Dentistry Department, Faculty of Dentistry, Syrian Private University, Damascus Countryside, Syria.
  16. Design and management of Twin Blocks: reflections after 30 years of clinical use. William Clark. Journal of Orthodontics, Vol. 37, 2010, 209–216.
  17. Dentoskeletal effects of Class II malocclusion treatment with the Twin Block appliance in a Brazilian sample: A prospective study. Luciano Zilio Saikoski, Rodrigo Hermont Cançado, Fabrício Pinelli Valarelli, Karina Maria Salvatore de Freitas.  Dental Press J Orthod. 2014 Jan-Feb;19(1):36-45.
  18. Twin-block Re-activation. J. A. Brennan Mosman, Sydney, Australia S. J. Littlewood. Department of Orthodontics, St Luke’s Hospital, Bradford, UK. Journal of Orthodontics, Vol. 33, 2006, 3–6.

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