High and low torque handpieces: cutting dynamics, enamel cracking and tooth temperature

Area of Science:

• Dental Materials Science
• Biomaterials Engineering
• Operative Dentistry

Background:

• Dental handpieces are crucial for cavity preparation.
• High-speed, low-torque (air-turbine) and high-speed, high-torque (speed-increasing) handpieces differ in operational dynamics.
• Understanding their impact on tooth structure and temperature is vital for clinical practice.

Purpose of the Study:

• To compare the cutting dynamics of high-speed, high-torque and air-turbine handpieces.
• To evaluate the effect of handpiece torque and bur type on sub-surface enamel cracking.
• To measure temperature changes in the pulp chamber during cavity preparation.

Main Methods:

• Confocal microscopy captured dynamic interactions between burs and enamel.
• Cutting load, rate, sub-surface enamel cracking, and pulp chamber temperature were recorded.
• Diamond and tungsten carbide (TC) burs were used with both handpiece types.

Main Results:

• High-torque handpieces maintained cutting performance under heavy loads, unlike air-turbine handpieces which tended to stall.
• No significant differences were observed in sub-surface enamel cracking between handpiece types or bur types.
• Temperature rise in the pulp chamber was comparable for both high-torque and air-turbine handpieces.

Conclusions:

• Speed-increasing (high-torque) handpieces exhibit superior cutting efficiency at increased loads.
• Neither high-torque nor air-turbine handpieces caused increased tooth cracking or pulp chamber heating.
• High-torque handpieces do not appear to have deleterious effects on tooth structure.