Despite of recent advances in orthodontic bracket manufacturing technology and prescription, and the new era of customizing brackets to suit a specific malocclusion treatment, despite of that, the need for perfecting the basic knowledge and skills of generating 1st, 2nd and 3rd order couples to solve various orthodontic problems have never ended. understanding the biomechanics of cantilevers and couples in three planes of spaces ,and how these couples work, allow orthodontist to control tooth movement and solve several orthodontic problems that existed initially or that emerging during treatment progress.
Straight wire mechanics rarely enable clinicians to meet treatment objectives. Situation like deep curve of spee ,specially in skeletal deep bite cases, necissate employment of segmental mechanics and intrusion arches which utilize a second order couple at molar tubes. On the other hand , generation of a 3rd order couple, by adding twists to the wire , is sometimes necessary to avoid dumping of the incisors during retraction, 3rd order couples are also very useful when fabricating cantilevers to achieve forced eruption of palatally impacted canines and others. Cantilevers which are activated in 1st order direction are useful means to get a tooth or a segment out of crossbite and and can correct mild midline discrepancy. In general the lecture will focus on the clinical use if cantilevers to solve different problems that clinician meet in everyday practice.
Objectives
1-Understanding the biomechanics of creating different types of couples in orthodontics.
2- Differentiating one couple and two couple systems.
3-Demonstrating segmental mechanics and spee curve correction using intrusion arches in deep bite cases.
4-Demonstrating canine disimpaction mechanics using cantilevers .
5-Understanding the different ways of controlling incisors inclination during retraction.