This book evaluates the predictability of tooth movements with clear aligners in first premolar extraction cases, focusing on factors influencing outcomes, the accuracy of predicted versus actual movements, and the effectiveness of aligners in managing space closure and alignment. A systematic review following PRISMA guidelines was conducted from January 2008 to March 2023. Databases searched included EMBASE, Web of Science, ResearchGate, PubMed CENTRAL, Cochrane Library, Google Scholar, and grey literature. Three reviewers assessed the studies, evaluating the quality of in vivo studies using the ROBIN-I tool for bias. Out of 257 identified articles, 10 met the inclusion criteria. Study types included one comparative study, one prospective study, two observational studies, three retrospective studies, and three case reports. Most studies focused on the predictability of tooth movements with clear aligners in premolar extraction cases. Sample sizes ranged from 1 to 31. The aligners used were Invisalign(R) with ClinChek software.