Newly developed ultrasonic diamond-coated tips (UDT) have been created for sulcus penetration and intracrevicular finish line preparation and polishing. One hundred forty-two freshly extracted premolars and molars were employed for a cutting efficiency test. Dentin surface roughness was analyzed with an optical profilometer and a scanning electron microscope. Within a reasonable cutting time, the UDTs possessed sufficient dentin-cutting capacity. The surface roughness of dentin prepared with the UDT can be improved by using a smaller grit size UDT or a smooth tip set at lower power, and the roughness approaches that of dentin prepared with a referenced red diamond bur. A clinical protocol of ultrasonic sulcus penetration with these developed UDTs is proposed.