A study of the cutting efficiency of dental burs for the straight handpiece.

IN THE preparation of cavities through the use of rotating instruments utilizing burs and stones, the ideal condition of design and operation has been described as the one which will remove the most material with the least patient discomfort due to heat, vibration, and pressure, and which also produces the longest life of the operating instrument. Some have recommended new and ingenious methods of material removal. The Air-Dent method is one example,' while Walsh and Symmons2 in New Zealand have advocated the use of a dental bur at a speed of 60,000 r.p.m. Others advocate the use of diamond pointed instruments at high speed. The use of diamond instruments, however, is not recommended for soft materials. According to one investigator, they should not be used against amalgams and metals. This material should be removed by burs.4 Studies on some causes of heat and vibration have been conducted and reported.5' 6 A third study, namely, the amount of material removed or efficiency of the instrument, is in order and a portion of that study is reported at this time. The amount of material removed is a function of several variables, such as the instrument design, material to be cut, speed, and pressure. The composition of the bur is also a variable, particularly when the active life of the bur is considered. It is therefore necessary at the outset to establish the limits that will be considered in this portion of the study. The first is the material to be cut. This report will be limited to results obtained through the use of Ivoryene, a synthetic ivory, having a hardness somewhat comparable to dentin. It has the advantage over actual tooth material of being more uniform and homogeneous. A second condition is the active life of the bur. To overcome this variable, each test (except for carbide burs, stones, and diamond points) was conducted with a new bur. Therefore, no consideration of dulling or bur life is taken into account. These conditions approach the ideal in the case of burs, but perhaps are too ideal for everyday use. This practice was necessary, however, in order to form some measure of standardization from which to obtain information on bur design.