Objective As a new kind of reinforcing filler, ultrafine diamon（d UFD）is added into photocurable composite core materials. The properties of the materials are then measured to see if there is any improvement. Methods Different content of barium glass and UFD were added into resin matrix to fabricate six groups of photocurable composite core materials. For each group of the materials, the flexural strength, Vicker′s micro- hardness and depth of cure were measured. Data of the flexural strength and Vicker′s micro- hardness was then collected and analyzed by One-Way ANOVA. Results For the two kinds of composites with barium glass of 60% and 70%, only a small quantity of modified UFD with 0.2% weight percentage could improve the flexural strength of the composites by 34% and 21% respectively, the microhardness was improved by 23% and 30% respectively. The depth of cure of the composite core materials were more than 2 mm, which had reached the demand of the corresponding ISO criteria. The addition of UFD could make the composite core materials darker and grayer. Conclusion Micro- quantity of UFD can improve the mechanical properties of composite resins notably, and it will not affect the curability of the materials, but the defect in the color need to be reformed.
