Effect of spray air settings of speed-increasing contra-angle handpieces on intrapulpal temperatures, drilling times, and coolant spray pattern

Abstract

Objectives Decreasing aerosol leaks are of great interest, especially in the recent era of COVID-19. The aim was to investigate intrapulpal heat development, coolant spray patterns, and the preparation efficiency of speed-increasing contra-angle handpieces with the spray air on (mist) or off (water jet) settings during restorative cavity preparations. Methods Standard-sized cavities were prepared in 80 extracted intact human molar teeth using diamond cylindrical drills with a 1:5 speed-increasing contra-angle handpiece. A custom-made device maintained the standardized lateral drilling force (3 N) and predetermined depth. Temperatures were measured using intrapulpal thermocouple probes. The four experimental groups were as follows: mist cooling mode at 15 mL/min (AIR15), water jet cooling mode at 15 mL/min (JET15), mist cooling mode at 30 mL/min (AIR30), and water jet cooling mode at 30 mL/min (JET30). The coolant spray pattern was captured using macro-photo imaging. Results The JET15 group had the highest increase in temperature (ΔT = 6.02 °C), while JET30 (ΔT = 2.24 °C; p < 0.001), AIR15 (ΔT = 3.34 °C; p = 0.042), and AIR30 (ΔT = 2.95 °C; p = 0.003) had significantly lower increases in temperature. Fine mist aerosol was formed in the AIR15 and AIR30 preparations but not in the JET15 and JET30 preparations (p < 0.001). The irrigation mode had no influence on the preparation time (p = 0.672). Conclusions Water jet irrigation using coolant at 30 mL/min appeared to be the optimal mode. Considering the safe intrapulpal temperatures and the absence of fine mist aerosols, this mode can be recommended for restorative cavity preparations. Clinical significance To increase infection control in dental practices, the water jet irrigation mode of speed-increasing handpieces with coolant flow rates of 30 mL/min should be considered for restorative cavity preparations.

Effect of Ceramic and Dentin Thicknesses and Type of Resin-Based Luting Agents on Intrapulpal Temperature Changes during Luting of Ceramic Inlays

“…However, during cavity preparation for direct or indirect restorations, the enamel and DEJ are partially removed, and the dentin thickness is reduced according to the extent of the caries or depending on the special cavity design. Hard tissue removal during cavity preparation and several steps of the adhesive restorative procedure (i.e., polymerization of the adhesive layer and the RBC/adhesive luting agent, and the polishing procedure) may cause thermal damage due to the weakened thermal insulation effect, especially in younger patients with wider dentinal tubules [ 63 , 64 ]. The present study investigated four thicknesses (1.0 mm, 1.5 mm, 2.0 mm, and 2.5 mm) of the remaining dentin layer.…”

Dental high-speed handpiece and ultrasonic scaler aerosol generation levels and the effect of suction and air supply

“…Although the new ‘no chip air’ function is innovative, whether the absence of air spray could affect the pulpal temperature of the drilled tooth remains unknown. More recently, Lempel and Szalma 38 found that effective ‘no chip air’–mediated reduction of aerosol is possible while maintaining a thermally safe environment for the tooth.…”

Increased Handpiece Speeds without Air Coolant: Aerosols and Thermal Impact

“…At a 15-mL min −1 water flow rate, concern has been expressed that a change of 5.5°C (the threshold to protect the pulp) can be exceeded with 1 mm remaining dentine thickness. Therefore, 30 mL min −1 was advised when using 200,000 rpm (Lempel and Szalma 2021). In that study, temperature was measured via a thermocouple, which also risks the peak temperature being missed compared to recording an area of interest as seen with the thermograph in this study.…”

“…Modern HSCAHs use air and water to cool, lubricate, and clean the cutting bur, thus reducing energy transfer to the tooth. One recent study indicated that the use of an HSCAH with only water coolant can result in acceptable temperature increases (Lempel and Szalma 2021). This was reported as highly dependent on the water flow rate when the remaining dentine thickness was 1 mm.…”