Marginal adaptation and mechanical strength of endocrowns with different materials and tooth prepration design: a review

The endocrown, a modified overlay or crown, is considered to have the advantages of adhesive retention and mechanical retention. Marginal adaptation and mechanical strength are common criteria for evaluating endocrowns. This review studied these aspects of endocrowns to guide further clinical application. Results from previous academic studies indicate that endocrowns made of different materials, such as glass-based ceramics, zirconia-based ceramics and resin-based ceramics, exhibit clinically acceptable marginal adaptation. Zirconia is a common dental material, but when used in endocrowns, it tends to present a risk of irreparable tooth root fractures. Compared with products manufactured with zirconia, endocrowns manufactured with resin-based ceramics and glass-based ceramics, such as lithium disilicate ceramics, do not tend to cause irreparable results, such as tooth root fracture, but their mechanical strengths are not as good as those of zirconia. At the same time, the tooth prepration design such as the types of endocrowns, the pulp chamber extension depth and angles, the endocrown thickness can influence the mechanical strength of endocrowns as well. Compared with traditional zirconia, self-glazed zirconia, a new type of material used to restore defective teeth, has the similar elasticity modulus (210 GPa) and better aesthetic advantages, and is suitable for short crown patients with insufficient occlusal space. Further study is warranted to improve the performance of endocrowns made from ceramic materials to prevent root fracture.