Clear aligners are removable orthodontic appliances that cover the tooth surface. The microbial composition and pH of the inner surface of aligners directly affect the enamel health. In this study, eight subjects who used the same type of clear aligners were instructed to brush their teeth normally and to not clean their aligners until sampling. Saliva and the contents of the inner surface of the aligners (liquid and plaque) were collected at 0 h (T0), 4 h (T4), 8 h (T8), 12 h (T12), and 24 h (T24) after usage, and pH values and microbial compositions were measured. The microbial composition was analyzed with 16S rRNA gene sequencing, and changes were assessed based on operational taxonomic unit abundance. The pH, alpha diversity values, and abundance of specific microbes on the inner surface of the aligners gradually decreased from T0 to T24 ( P < 0.05). An insignificant increase in microbial community beta diversity was observed from T0 to T24. Principal component analysis revealed that the microbial composition at T0 was different from at T12 and T24. The relative abundances of phylum Firmicutes ( P < 0.01) , orders Lactobacillales and Bacteroidales ( P < 0.05) , and genus Streptococcus and species Streptococcus infantis increased significantly, while those of genera Actinomyces and Rothia and species Rothia aeria decreased significantly at T24 ( P < 0.05). These findings reveal that uncleaned aligners might lead to enamel damage, especially after continuous usage for 12 h. Thus, clear aligners should be cleaned after 12 h of usage or at least within 24 h of usage.

中文翻译：

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透明矫正器不同使用期后内表面微生物群的变化

透明矫正器是覆盖牙齿表面的可拆卸正畸器具。矫正器内表面的微生物组成和pH值直接影响牙釉质的健康。在这项研究中，八名使用相同类型透明矫正器的受试者被要求正常刷牙，并且在取样前不要清洁矫正器。在 0 小时 (T0)、4 小时 (T4)、8 小时 (T8)、12 小时 (T1​​2) 和 24 小时 (T24) 后收集唾液和矫正器内表面的内容物（液体和牙菌斑）使用情况，测量 pH 值和微生物组成。通过 16S rRNA 基因测序分析微生物组成，并根据操作分类单元丰度评估变化。pH、alpha 多样性值、矫治器内表面特定微生物的丰度从 T0 到 T24 逐渐减少（ P < 0.05）。从 T0 到 T24，观察到微生物群落 Beta 多样性的增加不显着。主成分分析表明，T0 时的微生物组成与 T12 和 T24 时不同。T24 时厚壁菌门 ( P < 0.01) 、乳杆菌目和拟杆菌目 ( P < 0.05) 以及链球菌属和婴儿链球菌属的相对丰度显着增加，而放线菌属和 Rothia 属以及 Rothia aeria 种的相对丰度显着降低 ( P < 0.05) 0.05）。这些发现表明，未清洁的矫正器可能会导致牙釉质损坏，尤其是在连续使用 12 小时后。因此，透明矫正器应在使用 12 小时后或至少在使用后 24 小时内清洁。