da Rosa Moreira Bastos RT, et al. - Researchers assessed the data from PubMed (MEDLINE), Cochrane Library, Scopus, Web of Science, Virtual Health Library, Google Scholar, and OpenGrey to examine the periodontal side effects of rapid and slow maxillary expansion. They used a Haas expander with different protocols in 2 studies whereas one study used a Haas expander in comparison with a quad-helix appliance. They observed periodontal parameters and periodontal indices by clinical examination with a millimeter probe. They also used computed tomography images in one study. They noticed a "low" risk of bias in 2 studies. They graded the evidence as moderate quality for alveolar bone level, tooth displacement, and inclination and very low for all other outcomes. They found no significant variances to facilitate a sound conclusion about the type of maxillary expansion having the least periodontal side effects.