Purpose: The aim of the present retrospective clinical study was to compare the efficacy of two piezoelectric cutting inserts for the incidence, size, and types of sinus membrane perforations, and to evaluate their various advantages for lateral window osteotomy. Materials and Methods: The study consisted of 127 maxillary sinus augmentation procedures performed at two centers. A bony window was made on the lateral wall of the maxillary sinus with either the piezoelectric saw or the round diamond insert and repositioned over the bone graft as a homologous bony barrier. The rate of membrane perforation during sinus augmentation between the two groups was compared and analyzed statistically by the chi-square test and the two-sample t test. Results: Seven perforations were seen in the 127 maxillary sinus procedures in this study (5.51%). Six perforations in 84 cases (7.14%) occurred with the piezoelectric saw and one perforation in 43 sites (2.32%) occurred while using the round insert. No statistically significant difference was found between the rates of membrane perforation between the two inserts. Conclusion: The lateral bony window was created effectively with either of the two kinds of piezoelectric inserts. The membrane perforation rate was not significantly affected by the type of piezoelectric insert. The piezoelectric saw insert was more advantageous than the round diamond due to its greater precision and easier repositioning of the lateral bony window as a barrier. Keywords: maxillary sinus augmentation, piezoelectric round diamond insert, piezoelectric saw, replaceable bony window, sinus membrane perforation