Evaluation of dental handpieces for high speed operations

Abstract

During the past 70 or 75 years there has been little significant change in the basic design of the dental handpiece for rotat­ ing instruments, because the original de­ sign of this instrument was generally satisfactory. During this same period, however, numerous refinements have been made in the basic instrument which have permitted greater flexibility and better functioning of the instrument dur­ ing the cutting of tooth tissue. Most of these developments were associated with the contemporary advances that have oc­ curred in the field of machine tool manu­ facture and the general production of precision instruments. One of the most recent refinements in dental handpieces is the development of instruments which are capable of being operated at increased speeds of rotation. The speed of rotation, of course, is rela­ tive. Speeds which were previously con­ sidered slow, medium and high now are considered to be in the slower ranges of rotation. The present optimum and maxi­ mum speeds of rotation likewise may change within a few years because of further refinements and changes in in­ strument design. At the present time there is little agree­ ment among either the manufacturers of dental engines and handpieces or dentists who use the handpiece, regarding the possible optimum and maximum speeds of rotation. It is agreed, however, that faster speeds of instrument rotation are now practical and possible when com­ pared to instruments available ten years ago. For example, until recently, manu­ facturers of engines and handpieces made available instruments that operated within the accepted range of 4,000 to 6,000 rpm. Standard equipment is now obtainable which operates at speeds from 10,000 to 20,000 rpm, and experi­ mental studies are being conducted with instruments operating at speeds of 30,000 to 75,000 rpm. The clinical or laboratory justification for speeds over 15,000 to 20,000 rpm has not been fully established. Many prob­ lems of production and manufacture of a well balanced instrument with a po­ tential long life when operated at exces­ sive speeds have not been solved. The care and maintenance of both the hand­ pieces and motor units when operated at speeds of more than 15,000 rpm con­ tinue to be a problem of importance.