Purpose : The purpose of this study was to determine a conversion coefficient for Hounsfield Units(HU) to material density ($g;cm^{-3}$) obtained from cone-beam computed tomography ($CBMercuRay^{TM}$) data and to measure the hard tissue density based on the Hounsfield scale on dental head phantom. Materials and Methods : CT Scanner Phantom (AAPM) equipped with CT Number Insert consists of five cylindrical pins of materials with different densities and teflon ring was scanned by using the $CBMercuRay^{TM}$ (Hitachi, Tokyo, Japan) volume scanner. The raw data were converted into DICOM format and the HU of different areas of CT number insert measured by using $CBWorks^{TM}$. Linear regression analysis and Student t-test were performed statistically. Results : There was no significant difference (P > 0.54) between real densities and measured densities. A linear regression was performed using the density, $ ho$($g;cm^{-3}$), as the dependent variable in terms of the HU (H). The regression equation obtained was $ ho=0.00072H-0.01588$ with an $R^2$ value of 0.9968. Density values based on the Hounsfield scale was $1697.1{pm}24.9;HU$ in cortical bone, $526.5{pm}44.4;HU$ in trabecular bone, $2639.1{pm}48.7;HU$ in enamel, $1246.1{pm}39.4;HU$ in dentin of dental head phantom. Conclusion : CBCT provides an effective option for determination of material density expressed as Hounsfield Units.