7/28/2019 prostho retention of CD

1/4

7/28/2019 prostho retention of CD

2/4

J. Pros. Den.Nov.-Dec.. 1958

is high-speed dentistry. A glaring example was in an advertisement in one ofthe free commercial Journals which goes to virtually every dentist in the UnitedStates. This advertiser, who had shown such discretion in bringing forth the Air-brasive equipment, referred to the Airotor with speeds of 100,000 r.p.m. up to250,000 r.p.m. as a great contribution to highpeed dentistry. To realize theseriousness of this connotation high-speed, it is onlv necessary to mingle inthe crowd about one of the commercial exhibits demonstrating one of these iii-struments and listen to the discussion. The concern seems to be almost exclusivel>in how short a time a preparation may be completed, not how well.

,4 number of highly competent dentists have admitted to a sense of necessar)haste when first using more rapidly rotatin g cutting instruments for operativeprocedures. In most instances, these experiences were with belt-driven, more orless conventional equipment. If such operators can be affected in this way, whatmay we expect from less expert and possibly careless dentists, thoroughly confusedby the application of the term high speed ?TYPES OF ROTATIXG IKSTRLTMENTS

Some consideration of the characteristics of the various rotating instrumentsis indicated. Kilpatrick divides them into three methods : ( 1) gear-driven equip-ment including straight handpieces and contra-angle handpieces, (2) belt-drivencontra-angle handpieces, and (3 ) turbine-driven contra-angle handpieces.

It is recognized that there will always be a need for a dental handpiece usableat formerly conventional speeds upon occasion. For this reason, ball-bearing hand-pieces developed by several manufacturers meet a dual need in that they may beopera.ted at speeds, varying from the usual 6,000 r.p.m. peak achievable withstandard equipment, up through perhaps 24,000 r.p.m. with relatively simple ad-justments. Such a handpiece, through the use of an oversize driving pulley onthe unit motor, may perhaps be stepped up to 12,000 r.p.m. A switch arrange-ment allowing the cutting out of resistance to the motor will usually double thespeed to 24,000 r.p.m. \arious types of double-belt arrangements and, in some,gears, likewise, have been used with varying degrees of satisfaction, according tothe dentists desires. The development of ball-bearing handpieces, both for straightand contra-angle, has been a great boon to operative dentistry, even if used with-out increased rotating speeds, Among other improvements, it has required manu-facturers to develop more accurately balanced cutting points.PURPOSE OF INCREASED ROTATING SPEEDS

The purpose of increased speed of the rotating instrument is to increase cut-ting efficiency. This should mean to cut more rapidly, with less vibration, andto cut with less pressure, with resultant lower heat production, for the safety ofthe dental pulp. With each increase in rotating speed has come a correspondingreduction in torque. This is a decided safety factor and soon teaches the desir-ability of light pressure application, since excessive pressure Lvill stall the revolv-ing point. With the realization of the safety of the low stalling pressure, due tolowered torque, and the relatively lower frictional temperatures developed, it is

7/28/2019 prostho retention of CD

3/4

\-olume YKunher 6 SUBJECT OF HIGH SPEED 1033startling to recall that in a recent article in Life Magazine, devoted entirely to one ofthe high-speed mechanical handpieces and its inventor, the inventor is quoted as be-availing the loss of torque in his equipment and promising a future development\vhich will produce a torque value similar to that of the conventional equipmentrotating at 1,000 to 6,000 r.p.m. It would appear that this inventor should be anearly candidate for some instruction in operative technique. The deplorable effectsof such misinformation in lay publications will be obvious.

The hydraulically driven instrument now manufactured as Turbojet appearsto have been the first departure from the mechanical drive principle in rotary cut-ting instruments. It has the desirable quality of very low torque, as well as sup-plying its own coolant to the revolving point. The torque on this instrument is solow that, running at better than 50,000 r.p.m., it has been demonstrated to be pos-sible to stall a small diamond wheel on the wrist without laceration.A more recent instrument available to the profession is the Airotor, which asits name implies is an air-driven turbine. This instrument has even lower torquethan the hydraulically driven one. This equipment possesses certain advantagesin size over the hydraulic turbine, but it brings in the complication of variable airpressures in most professional buildings. The turbine type cutting instrumentsdefinitely are adjuncts to the standard belt-driven type of handpiece. They un-doubtedly supply the most effective cutting of tooth substance now known, and incapable hands, they have a strong safety factor in their low torque. The rapidit)of their cutting action, however, presents a distinct hazard, especially in areas ofdifficult access. Control is dependent upon visibility- alone. since the tactile senseis missing.IMPORTANCE TO DENTAL PRACTICE

1Yhat has the phrase high speed meant to the practice of dentistry? Toskillful and studious dentists, it has brought reduced fatigue, increased efficiency,and economy of time. To their patients, it has meant increased comfort, chieflythrough reduced irritating noise and shorter operation periods. It will be notedthat nothing is said here of reduced pain. Dentists of the type described have longyears ago eliminated the pain of operative dentistry for their patients throughstandard, accepted methods of analgesia or anesthesia. To them, time has alwaysbeen of importance, but always subordinate to patient comfort and welfare.

In the hands of the dentist lvho has depended for his knowledge upon adver-tising, the detail man, and the throw-away publicationst it is to be feared that theterm high speed has increased his vulnerability to malpractice actions. Whilesuperficially it appears to have increased his production, it has nevertheless laidupon him some headaches and worries that would make a migraine sufferer gloatin his freedom from pain. For the patients of this latter type of dentist, it hasmeant catastrophies to an innumerable host of dental pulps and a rapid approach tocomplete dentures.FITLL COVERAGE RESTORATIONS

A trend which has appeared to permeate the profession with the introductionof high-speed rotary equipment is the increased application of so-called full cover-

7/28/2019 prostho retention of CD

4/4

J. Pros. Den.Nov.-Dec., 1958age operative procedure. This is most notable when fixed prosthodontics are in-volved. Possibly in days of greater operative difficulty, full crown restorationswere avoided at times when they might have been the indication of protective choice.Today, however, it appears that the rapid and easy reduction of tooth substanceand contour has led many dentists into unwarranted destruction of tooth sub-stance. An example is a man recently examined, approximately 30 years ofage, an actor, who within the year had had twenty-eight crowns placed on histeeth. This work had been done in a large New York clinic. It was quite welldone. The occlusion and color were good. The hinge axis had been determined,and proper jaw relations had been established to produce a very creditable result.The porcelain on the mandibular right second molar had fractured, leaving atroublesome sharp place. This patient had applied for treatment in New Yorkoriginally to correct a diastema and somewhat protruded maxillary incisors. By hisreport, dental decay had not been excessive. He was persuaded to have the entiretwenty-eight teeth treated in this manner in order to prevent any further tooth de-cay. The improved appearance was a factor, of course, but it was minimized, in theopinion given supporting the full mouth reconstruction, as being secondary to thepreservation from future tooth decay. The gingival tissues about most of the teethshowed passive congestion, hypertrophy, and a flabby tone. Ko effort whatsoeverhad been made to educate the patient to proper daily maintenance.

It was pointed out to the patient that, unless he undertook vigorous personalhygiene measures, he would soon experience further bony absorption with theexposure of all of the cervical margins of the restorations. It is a very rare instancewhen one sees this many crowns in a mouth, without finding gingival inflammatoryconditions about some of them. There is no artificial material tolerated by thegingival tissues as well as is natural tooth substance. Undoubtedly, gold foil, cor-rectlq- inserted, is the best tolerated of the artificial materials. It seems highlyprobable that had preparation of these twenty-eight teeth been as difficult in 1957as it was in 1937, the patient would not have had twenty-eight full crowns in hismouth.CONCLUSION

Unless steps are taken to bring adequate instruction to the vast majority ofdentists who are influenced to use high-speed rotary instruments, it may be an-ticipated that an era of slovenly cavity preparation will plague dentistry for sometime to come. The effect on the public esteem for high quality operative dentistry,which we have all striven to establish, is unpleasant to contemplate.REFERENCE1. Kilpatrick, H. C.: An Evaluation of Rotational High Speed and Coolant Equipment for

Speeds up to 200,000 R.P.M. A Progress Report III. Bul. Alabama D. A. 41:7-16,1957.409 N. CAMDEN DR.BEVERLY HILLS, CALIF.