Chemical vapor deposition diamond dental burs for high speed air turbine handpieces

Background: The objectives were, establishment of diamond coating using Chemical Vapor Deposition (CVD) on tungsten carbide burs and, assessment of diamond film adherence at 250,000 rpm after cavity preparations on teeth. Methods: Hot Filament CVD (HFCVD) was used to deposit a thin diamond film on tungsten carbide burs using 1-1.5% methane in excess hydrogen at 1800-2200 degrees C and 2700 - 6700 Pa pressure. Consistent and repeated film deposition of Microcrystalline diamond (MCD) and Nano crystalline diamond (NCD) could be achieved. Raman spectrometry and scanning electron microscopy (SEM) were used to confirm diamond deposition. Adherence of the films was checked after cavity preparations on human teeth at speeds of similar to 250,000 rpm, and flank wear was determined using SEM. Results: SEM images confirmed presence of microcrystalline and nanocrystalline forms. MCD had a 3-7 mu m cubooctahedral crystal formation. NCD was seen as 25-50 nm cuboidal facets in columnar formation. Raman spectrometry corroborated these findings. SEM of NCD showed no loss of diamond film or blunting of blades after three cavity preparations followed by a maximum loss of 33 mu m after nine repeated cavity preparations. MCD showed partial loss of diamond film after third cavity with a maximum loss of 91 mu m after nine repeated cavities. Conclusion: Successful deposition of uniform diamond coating on tungsten carbide burs that remain adherent even at high rotational speeds was achieved and NCD coating adhered better compared to MCD. Practical implication: The newly developed dental bur which combines the cutting action of bladed instruments and the hardness of diamond and provides a new area of clinical application.