Effect of Water and Chemo-mechanical Coolant Flow Rates on Carbide Bur Cutting

Objectives: Irrigation with dilute mouthwash solutions and higher coolant flow rates enhance diamond bur cutting rates through chemomechanical effects (CMEs). The present study was undertaken to evaluate combined CMEs and irrigant flow rates for carbide burs. Methods: Cutting studies were performed on Macor machinable ceramic. A highspeed KaVo 649B handpiece was used at a load of 147.5 g and rotation speed of 350 krpm and coolant flow rates of 15, 25 and 35 ml/min using water and 1:5 mouthwash:water mix. Six 702-016 carbide burs were used for each irrigant and flow rate to make 6 cuts, 3 mm in length, through 13 mm of Macor. Cutting rates (CRs) were determined as the time to transect the Macor block and data were analyzed by 1-way ANOVA with post-hoc Scheffé tests Results: Cutting rates with water increased 50% at 25 ml/min and 100% at 35 ml/min compared to 15 ml/min over 6 cuts (p<0.01) but there was no difference in CR at 25 and 35 ml/min (p>0.05). The addition of a commercial mouthwash at a 1:5 dilution in water had no significant effect on the cutting rates at any of the 3 irrigant flow rates (p>0.05). Conclusions: CRs are increased through higher coolant flow rates for carbide burs. However, unlike the CMEs found at lower bur speeds (120 krpm), no chemo-mechanically enhanced cutting rates were found with ultra-highspeed (350,000 rpm) handpieces.