[Performance of orthodontic aligners in the aging process: systematic review and in vitro study]

The objective of this study was to evaluate, through a systematic review of the literature and an in vitro study, the alteration of the mechanical and chemical properties of aligners after aging in artificial saliva and in the oral cavity.

A systematic literature review was carried out, through an electronic consultation of three databases: PubMed, EBSCO and Sciencedirect, between September 2018 and January 2020. The search was guided by the use of several specific keywords. In our in vitro study, the mechanical properties of our sample of aligners were evaluated using the 3-point bending test after a water immersion.

Of the 189 articles found, only six articles met our inclusion criteria. In the light of the studies selected in this systematic review and of our in vitro study, it can be concluded that the orthodontic aligners undergo an alteration in their mechanical properties after stay in the mouth. However, the real impact of these modifications on their clinical performance remains to be demonstrated and it is difficult to make a final judgment on their chemical stability. Other controlled clinical studies, with protocols better suited to the clinical criteria studied, are necessary to objectively assess the aging phenomenon of orthodontic aligners.