This study compared the biocompatibility of new bone substitutes, Mega-oss and Mega-TCP, with Bio-Oss using osteoblast and osteoclast cells fixed with alginate gel. Results showed better cell spreading on Mega-oss and Mega-TCP than on Bio-Oss. MTT assays indicated good viability for all materials, with Mega-oss and Mega-TCP showing similar osteoblast differentiation ability to Bio-Oss. Mega-TCP and Mega-oss exhibited higher resorption rates than Bio-Oss. The authors conclude that Mega-oss and Mega-TCP may be viable alternatives to Bio-Oss, and that alginate gel fixation is a useful method for in vitro bone material experiments.