A histologic assessment of low-torque, ultrahigh-speed cutting technique

Abstract

lh 11 e pu pa response to rotary cutting instruments is influenced by several factors: speed of the cutting instrument, type and size of the cutting instrument (bur or diamond), torque capability of the driving instrument, technique employed by the dentist, cooling armamentarium, and proximity to the pulp. At ultrahigh speeds, with the low-torque air turbines available, studies of rotational speed and torque indicated parameters of cutting speeds for most efficient removal of tooth structure with minimal frictional trauma.‘-” Excessive cutting pressure causes stalling, with large bites and inefficient frequency; while the reverse (low pressure) allows high rotational speed and minimal bite. Varying the bur or diamond size, bur design, and bur sharpness at compared torques can produce different cutting efficiencies with resultant varying frictional response.ls li, ; In other studies, torque capabilities of the turbines and the technique employed by the dentist were again related to cutting efficiency and frictional and vibratory responses resulting in varying pulpal responsesy-” It has been found that optimum operating technique, at ultrahigh speeds with low torque, allows efficient removal of tooth structure with short periods of instrument-tooth contact and less friction, in contrast to a technique utilizing high torque at ultrahigh and low speeds.“-I’; It has been documented that excessive heat can be transmitted to the dental pulp with resultant significant cellular damage.“-‘7 Maintenance of almost normal intrapulpal temperature can be accomplished by water or water-air spray or air and the aforementioned factors; however, the question of desiccation resulting from use of air as a coolant has not been resolved.“S-“a The clinical advantages and success of a flexible cooling armamentarium have been reported.l”, ‘(is 35 The action of any coolant at ultrahigh rotational speeds is one of cooling the entire coronal portion of the tooth.“’ Photographing at a rate of 250,000 frames per second, wherein a rotating bur and the spray can be observed in a portion of a