[The mobility of the anterior teeth after the direct bonding of lingual retainers. A comparison of in-vitro and in-vivo measurements].

Lingual retainers are today widely used in the long-term stabilization of incisors. In that they are left in place for a period of years, the question arises to what extent lingual retainers allow sufficient physiological movement. To answer this question first an in-vitro study of the inflexibility of various retainers under horizontal and vertical load was carried out. Next the retainer which limited physiological movement to the least degree was studied in-vivo. Both dynamic and static mobility measurements of the lower jaw front teeth were carried out on 5 patients before and after bonding the retainers. A self developed measuring instrument was used to make the static measurements and a periotest device was employed in the dynamic measurements. The in-vitro tests indicated that, with the exception of the retainer made of multistranded 0.0155" wire or glass fiber, a significant reduction in tooth mobility can be expected with all the retainers. However, the static in-vivo measurement carried out with the 0.0155" wire resulted in a distinct reduction in tooth movement. The dynamic measurements using the periotest device confirmed this finding. With regard to clinical practice within the framework of long-term retention, highly flexible retainers appear to be the most suitable and are to be recommended.