Increased Cutting Efficiency of Diamond Burs With Chemomechanical Sprays

CAD/CAM units are becoming increasingly popular for milling all ceramic restorations from ceramic blocks.  The solution used to spray the diamond cutting instrument also lubricates the diamond, which may not only prolong the cutting life of the diamond instrument but also provide smoother cuts on the ceramic block. Objective: To compare the cutting efficiency of diamond burs on ceramic blocks by measuring the weight loss produced by each cut and the length of each cut in a CAD/CAM milling device with 4 solutions.  Methods: 12 Empress CAD blocks, 34 fine diamond burs, 3 solutions and distilled water were used. Each bur made four, 4 mm deep cuts in the ceramic blocks for 4 minutes per cut.  The burs were placed in an E4D milling head operating at 40,000 rpm.  The blocks were mounted in a testing apparatus that pulled a moveable table at a load of 200g against the diamond bur. The blocks and burs were weighed before and after each cut and after acetone ultrasonic cleaning between cuts. The length of each cut was measured.  Weight loss was analyzed with ANOVA and Tukey Kramer analysis.  Results:  The four solutions produced significantly different diamond cutting effectiveness (p<.05). Solution number 2 with additives provided significantly longer cutting lengths and increased weight loss of the ceramic block compared to the other solutions(p<.05). Distilled water was the least effective of the solutions tested.  The length of cut of the burs decreased with each cut of the diamond but the burs using solution two had longer cuts with each of the 4 cuts.  Conclusion:  This study demonstrates that the cutting effectiveness of diamond instruments can be significantly improved by using solutions with additives thereby reducing cutting time for the CAD/CAM system.