eISSN: 2956-7548
ISSN: 1734-1558
Forum Ortodontyczne / Orthodontic Forum
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vol. 19
Review article

The concept of directional force mechanics – a literature review

Katarzyna Regulska
Dennis Michael Ward
Małgorzata Zadurska

Prywatna praktyka, Stany Zjednoczone

Private practice, USA
Zakład Ortodoncji, Warszawski Uniwersytet Medyczny

Department of Orthodontics, Medical University of Warsaw
Forum Ortod 2023; 19 (3): 95-100
Online publish date: 2024/01/30
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The concept of orthodontic treatment with directional force mechanics is a method that has been used for many years. This concept makes it possible to control the vertical dimension and the mandibular plane, allowing the counterclockwise mandibular response. This is particularly useful in the treatment of high-angle Class II cases.

The purpose of the paper is to present the concept of directional force mechanics according to the Tweed-Merriefield philosophy.

Material and methods.
Using electronic PubMed databases, 41 articles from 1966–2022 were analysed with the following keywords: Tweed-Merrifield, Tweed sequential, Tweed mandibular rotation. Twelve works were included in the review.

Conducting treatment according to the directional force mechanics allows monitoring of treatment at each stage and enables control of vertical height, prevents extrusion of lateral teeth, and allows control of counterclockwise mandibular rotation. This is especially important when treating high-angle patients with Class II malocclusions. As a result of this positive rotation, the patient’s occlusal conditions and facial aesthetics improve.

Treating Class II malocclusions in high-angle patients according to the Tweed-Merriefield approach makes it possible to achieve good treatment outcomes through the desired control of the vertical dimension and counterclockwise mandibular rotation. The result of this approach is a harmonious appearance of the patient’s soft tissue profile and face, which improves the patient’s self-esteem and well-being. Cases of patients treated with this technique are available on the Charles H. Tweed Foundation website.


Tweed-Merrifield, Tweed sequence, Tweed mandibular rotation