Normally, braces should never make your tooth weak, loose, and fallout, as long as proper orthodontic treatment is followed. Your teeth may feel slightly loose for 2-3 days after braces are tightened, which is temporary. An excessive force might cause your teeth to fall out. This may never happen when you see a qualified orthodontist. However, braces may weaken your tooth or cause permanent loosening rarely if you have weak periodontal health due to the conditions like periodontal diseases.
Note: There is a strong relationship between your periodontal health and braces. Periodontium is the supporting structure for your tooth. It consists of gums, bone, cementum (root portion of the tooth), and periodontal ligaments. Periodontal ligaments are fibre or thread-like structures that are attached between alveolar bone and cementum. These fibres and gums are important in tooth movement because they must have the ability to bear the pressure given with wire/elastic through braces.