Bonded Orthodontic Retainers

Orthodontic retainers are used at the end of an orthodontic treatment to retain the achieved tooth position. Without a phase of retention, there is a tendency for the teeth to relapse towards their initial position after treatment. The aetiology of relapse is not fully understood but relates to a number of factors that involves periodontal and occlusal aspects, possibly soft tissue pressures and physiological growth. Retention, which refers to the fixation of the achieved orthodontic result, can be accomplished using removable or fixed retainers. Due to the advances in adhesive technologies, the use of fixed retainers bonded to lingual or palatal surfaces of the incisors has been widely used. Debonding of these retainers is however one of the most frequently reported failure types in orthodontics and has a multifactorial cause. This thesis was conducted in an attempt to identify some of the possible debonding factors causing these failures. Therefore, failures were analyzed in clinical retrospect as well as bond strenght comparison of different retainer types and materials. Comparison of the fatigue resistance, debonding force, and failure type of different retainer materials in vitro was conducted as well as a prospective evaluation of the survival of multi-stranded stainless steel bonded retainers using different resin composite types. At last the evaluation of anterior tooth movement with and without bonded retainers under incremental loading conditions using 3D reconstruction was done. Debonding of these retainers remains unsolved and multicausal, yet aspects such as age, gender, operator, resin composite type could be disclosed.