Background: Orthodontic treatments have evolved significantly, with clear aligners becoming increasingly popular due to their aesthetic appeal and ease of use. This study systematically reviewed the impact of clear aligners in the changes in the oral microbiota compared to traditional fixed appliances. Methods: Following PRISMA guidelines, a systematic review was conducted using two databases such as Scopus, Web of Science, and the PubMed search engine. The studies included were those published between 2010 and 2023, involving adults over 18 years using clear aligners and fixed appliances. The data on oral microbiota changes were extracted and analyzed. Results: The review included eight studies, highlighting the differences in microbial changes associated with clear aligners versus fixed appliances. Clear aligners were associated with fewer detrimental changes in the oral microbiota, potentially due to their removable nature allowing for better hygiene. Fixed appliances showed a tendency to harbor more pathogenic bacteria, which is likely due to their difficulty to clean. Conclusions: Clear aligners may offer a better alternative to fixed appliances in terms of maintaining a healthier oral microbiota. Their design and ease of hygiene contribute to less accumulation of pathogenic bacteria, showing a more positive impact on maintaining a balanced oral microbiota when compared to fixed appliances.

Background/Objectives: Resin 3D printing is widely used to fabricate orthodontic diagnostic models, but the practical performance of commercial desktop workflows compared to dental-certified workflows is still debated. This study compared the dimensional accuracy and 7-day stability of maxillary orthodontic models printed from the same master STL file using a dental-certified workflow versus two commercial desktop workflows. Methods: An ISO 20896-1:2019-based reference cast with four 6 mm calibration spheres was used to generate a master STL file. Fifteen models were printed (n = 5 per workflow) using Primeprint™ (dental-certified workflow) and two commercial desktop printers (Anycubic Photon Mono M5s; Phrozen Sonic Mighty 14K REVO). The models were digitized at baseline (T0, ≤48 h) and after 7 days (T7) using a laboratory scanner. Surface superimposition in CloudCompare^® calculated the RMS (root mean square) surface deviation and mean signed deviation, and two calibrated operators performed independent extractions. Results: The mean RMS deviations were 0.05), and the inter-operator agreement was excellent (ICC 0.991–0.999). Conclusions: Under the tested workflows, dental-certified and commercial desktop resin printing produced orthodontic models with a comparable global surface accuracy and short-term dimensional stability.