A root assembly includes an implant body and a positioning device connected to the implant body. The implant body has a positioning hole formed through one end thereof and an engaging portion opposite to the positioning hole. The positioning hole has an end edge. The positioning device has a positioning seat where an artificial tooth is attached and a positioning unit extending through and out of the positioning seat. A first recognition portion is formed on the positioning seat. The location of the first recognition portion of the positioning seat corresponding to the end edge of the positioning hole can recognize that the positioning device is exactly positioned on the implant body, thereby preventing the positioning device from loosening.
