Comparative evaluation of newer devices and technics for the removal of tooth structure: vibration characteristics and patient reaction

72 • THE JO U R N A L OF THE A M E R IC A N DENTAL A SSO C IA T IO N

4. Maver, M. E., and Wells, H. G . Studies on the biochemistry and chemotherapy of tuberculosis. X X III. Chemical composition of calcified tuberculous lesions. Am. Rev. Tuberc. 6:649 Oct. 1922. 5. Radasch, H. E. Determination of the percentage of the organic content of compact bone. Anat. Record 21:153 May 1921.

9. Wells, H. G. Chemical pathology, ed. 5. Phila­ delphia, W . B. Saunders Co., 1925, p. 486-493. JO. Lichtwitz, L. Über die Bedeutung der Koloide für die Konkrementbilding und die Verkalkung. Deut, med. Wschr. 36:704, 1910. 11. Howland, John. Etioloqy and pathogenesis of rickets. Medicine 2:349 Nov. 1923. 12. Stern, R. Über Lungensteine. Deut. med. Wschr. 6. Disturbances of mineral metabolism. InPathology, 30:1414, 1904. Anderson, W . A. D., editor. St. Louis, C. V. Mosey Co., 1948, p. 85-87. 13. BLirgi, Emil, über Lungensteine. Deut. med. Wschr. 32:798, 1906. 7. Wells, H. G . Metastatic calcification. Arch. Int. Med. 15:574, 1915. 14. McCarthy, Justin. Case of tonsillar calculus. Brit. M. J. 2:1062 Oct. 28, 1911. 3. Meyer, A. W., and Cajon, F. A. Anatomic and chemical report on a unique case of myeloma. Arch. 15. Prinz, Hermann. Oriqin of salivary calculus. D. Int. Med. 33:581 May 1924. Cosmos 63:231 March 1921.

Com parative evaluation of newer devices and technics fo r the rem oval of tooth structure: vibration characteristics and patient reaction

Jack L . Hartley * D .D .S .; Donald C. H udson,f D .D .S ., and Francis A . Brogan, B.A.,% Randolph Air Force Base, Texas

N ewer devices for removing tooth struc­ ture were compared and evaluated with respect to annoyance and discomfort to the patient. T h e number 10 was assigned to the conventional low-speed m ethod of cutting. T h e annoyance factor was deter­ mined to be 2 for the ultrasonic hand­ p iece; 3 for the air turbine handpiece with diamond cylinder; 4 for the air tur­ bine handpiece with no. 5 5 8 carbide bur, and so forth. Audiometric tests indicated no significant temporary loss in hearing in patients as a result of cutting with any of the handpieces studied.

Comprehensive studies o f the newer m e­ chanical instruments for the removal o f tooth structure which have recently been m ade available to the dental profes­ sion indicate that these devices are indeed

very effective. Increase in cutting effi­ ciency, ease o f operation, better control and reduction in pressure and heat p ro­ duction, however, should be considered as approaching the ultimate only when accom plished with an absolute m inimum o f patient annoyance and discom fort. Studies o f effectiveness, therefore, should include the factor o f patient response. A recent study1 has indicated that there is an unquestionable decrease in patient annoyance and discom fort when tooth structure is rem oved by any o f the newer instruments as com pared to the low speed handpieces. T h ere is, however, a significant variation in the degree o f an­ noyance produced by cutting with the newer devices, and some instruments ap­ pear to introduce new factors o f discom ­ fort. It is therefore desirable to evaluate the instruments com paratively with re­

HARTLEY— H U D SO N — BROGAN . . .V O L U M E 59, JULY 1959*- 73

spect to these annoyance or discom fort factors. METHOD

M u ch o f the discom fort in a dental p ro­ cedure involving rem oval o f tooth struc­ ture is caused by vibrations transmitted through the bones o f the skull to the hearing mechanism. This is a frequent com plaint o f the patient, even though he may be anesthetized. In order to evaluate objectively the noise produ ced by the various cutting m ethods, tape recordings were m ade o f the vibrations transmitted through the skull during actual removal o f tooth structure. A sensitive bone conduction m icro­ phone, nonresonant in the audible fre­ quency range, em ploying a barium titanate crystal, was placed over the frontal bone o f the patient and held firmly by an elastic bandage. T h e m icrophone output was recorded on tape at 15 inches per second, full track, for optim um high fre­ quency response, on an “ A m pex” m odel 350-2 studio recorder which provided the necessary broad frequency response and freedom from flutter and w ow . A re­ corder gain control setting was estab­ lished whereby m inim um and m axim um signal levels fell within the range o f the V U meter and that position was fixed for all recordings. Thus, the amplitudes o f vibration prod u ced by cutting with each type o f handpiece and technic could be com pared. T a p e playback through an octave ban d noise analyzer (G eneral R a dio C om pany, type 1550-A ) permitted analysis o f the skull vibrations in the frequency range o f 20 to 10,000 cycles per second. This instrument selectively filtered ou t all frequencies except those needed for determination o f am plitude o f each harm onic band, in decibels. T h e over-all level o f vibration fo r the co m ­ plete range o f from 20 to 10,000 cps also was determined. Photographs were m ade o f the skull vibrations as they were displayed on an

oscilloscope, w hich was also adjusted to a constant level fo r all handpieces evalu-' ated. T h e trace heights, therefore, repre­ sent the intensity o f the vibration trans­ m itted to the skull during cutting with the various handpieces and cutting in­ struments. Preliminary discussion with the audiology departm ent o f the School o f Aviation M edicine, U nited States A ir F orce, indi­ cated that the intensity and frequency o f vibrations characteristic o f some o f the new er devices conceivably could produce tem porary loss o f hearing o f certain fre­ quencies. A utom atic audiom eter tests therefore were given each patient before and immediately after cavity preparation with the various handpieces. T w o audiom eter tests were perform ed before the operative procedure, one to familiarize the patient with the testing procedures and another to obtain a pre­ operative hearing level determination. DETERMINATION OF HANDPIECE NOISE

T h e relative intensity o f air-borne noise originating from the instruments evalu­ ated in this study was determ ined by the use o f a H erm an H osm er Scott sound level meter, m odel 410-C. A ll measure­ ments were on the “ C ” scale at three inches from the handpiece. Sound pres­ sure levels o f the newer handpieces were fou n d to be higher than those o f conven­ tional instruments. DETERMINATION OF ANNOYANCE FACTOR NUMBERS

Preliminary studies indicated that a nu­ m erical indication o f the degree o f an­ noyance created by the various instru­ ments cou ld be assigned on a tentative basis. This num ber was assigned, based on subjective response o f the patient to a particular handpiece, and correlated with the measured intensity o f vibrations recorded from the skull.1 T h e number,

74 ••THE JO U R N A L OF THE A M E R IC A N DENTAL A SSO C IA TIO N

10, was assigned to the conventional lowspeed m ethod o f cutting, on the basis o f adverse subjective responses to cutting by this m ethod and high amplitudes o f vibration recorded. A num ber relative to 10 was assigned each o f the other hand­ pieces evaluated. Previous studies em ploying tape record­ ings o f skull vibrations have indicated a significant difference between the use o f burs and diam ond points in the newer handpieces. O n this basis, an annoyance factor also was determined for the type o f instrument in the handpiece being evaluated. Frequency does not appear to be the sole criterion for the determination o f degree o f annoyance. T h e classic work o f W alsh and Symmons2 in a study o f vi­ bration and its effect on dental patients indicated certain frequencies w hich were most bothersome to the patient. H udson3 added the factor o f amplitude in the study o f bur eccentricities. A t low rota­ tional speeds, pressures required to cut adequately are excessive; the com bina­ tion o f low -frequency, high-am plitude vi­ brations is extremely annoying to the patient. As rotational speeds increase, cut­ ting becom es m ore effective with reduced pressure; the frequencies are higher, am ­ plitudes are lower. This results in less dis­ com fort during rem oval o f tooth struc­ ture. It was our purpose then, to evaluate this frequency versus amplitude response in an attempt to seek an instrument which is not only very efficient, but is effective in accom plishing rem oval o f tooth struc­ ture with a m inim um o f discom fort and annoyance. PROCEDURE

2. A high-speed handpiece powered by a conventional dental engine which had been prepared to deliver speeds at the bur o f 12,000 to 16,000 rpm with carbide burs and diam ond points. T h e K err “ Im perator” contra-angle fo r con ­ ventional bur shanks. 3. A hydraulic turbine handpiece, em ­ ploying diam ond points. T h e Bowan “ T urbo-Jet.” C arbide burs were not rec­ om m ended by the m anufacturer although they are available. Speed o f rotation: 45,000 rpm. 4. T w o brands o f superspeed hand­ pieces w hich obtained the increase in revolutions per minute by means o f m ini­ ature ball-bearing pulleys and a belt con ­ tained within the handpiece sheath. T he conventional dental unit was altered by removal o f the high-speed resistance shunt and the use o f a large diameter pu l­ ley on the m otor. Speeds were from 80,000 to 120,000- rpm. T h e Page-Chayes and the K err “ Super-Speed” instruments. T h e cutting instruments were carbide burs and diam ond points. 5. Five brands o f ultraspeed hand­ pieces, driven by a self-contained air tur­ bine; speed was from 150,000 to 200,000 rpm. T h e Borden “ A irotor” by R itter; the D ensco “ A ero-T u rb ex” ; the W eber “ A T -2 0 0 ” ; the Star “ Star Flite” ; the M idwest “ A ir-D rive 400.” Cutting in­ struments were carbide burs and dia­ m ond points. 6. T h e ultrasonic handpiece. Cutting is produced by an aluminum oxide slurry directed upon the tip w hich vibrates at a frequency o f 29,000 cycles per second. T h e C avitron instrument.

In order to control the possible varia­ T h e instruments em ployed in this evalu­ bles from tooth to tooth in this type of ation were: 1. A standard handpiece and dental study, recordings o f each handpiece were m ade on the same patient and the same engine with conventional steel and car­ tooth. T h e level o f the recorder gain con ­ bide burs. R otational speed at the bur trol was maintained at a fixed level for was 4,500 to 6,000 rpm. T h e S.S. W hite all recordings o f each type o f handpiece “ R evelation” with contra-angle.

HARTLEY— H U D SO N — BROGAN . . .V O L U M E 59, JULY 1959 • 75

and cutting instrument. A representative sample o f each recording was cut from the master tape and spliced into a loop for continuous playback, to permit octave band noise analysis and oscilloscope study and photography. Vibrations recorded from the skull showed variation in intensity and fre­ quency from those calculated mathemati­ cally as arising from an instrument o f a known diam eter, rotational speed and pressure. T h e recording m icrophone de­ signed for this project had a flat response o f from 20 cps to 35,000 cps; the fre­ quency response o f the tape recorder lim ­ ited the high frequency response to 15,000 cps. T h e dam ping factor o f the hard and soft tissues o f the skull appeared to further reduce the frequency o f vibra­ tions concerned in this experiment, to 10.000 cps. T h e range o f frequencies which was o f concern in the study o f skull vibrations induced by drilling therefore appeared to be from 20 to 10.000 cps. T h e oscilliscope tracings indicated variation in amplitude from the most intense, produ ced by the con ­ ventional low-speed handpiece and a steel no. 558 bur, to the least intense, produced by the air turbine handpiece with a 1 /1 6 inch diam ond cylinder, (Fig. 1, 2 ) . T h e oscilloscope tracings in Figures 1 and 2 are o f skull vibrations during cutting on the' same tooth and patient. T h e recorder and oscilloscope were at a constant level in order to show amplitude and frequency variations o f the instru­ ments evaluated in this study. T he ultrasonic instrument frequency o f 29,000 cps is above the audible range, yet definite low frequency vibrations were produced in the skull o f the patient when this instrument was used fo r cutting. These low frequencies are thought to result from the m ovem ent o f the alumi­ num oxide particles against the tooth as they cut. T h e am plitude o f these low fre­ quency vibrations was higher than that produced by cutting with the air turbine instrument.

RESU LTS

T h e determination o f degree o f annoy­ ance was accom plished follow ing the p ro ­ cedure described in a previous paper.1 In the present study, we obtained the follow ­ ing results. 1. T h e conventional low -speed hand­ piece, 4,500 to 6,000 rpm with a steel no. 558 bu r: 10 2. T h e high-speed handpiece, 12,000 to 16,000 rpm with a carbide no. 558 b u r: 9 3. T h e high-speed handpiece, 12,000 to 16,000 rpm with a 1 /1 6 inch diam ond cylinder: 8 4. T h e water turbine handpiece, 45,000 rpm with a 1 /1 6 inch diam ond cylin­ der: 6 5. T h e superspeed handpiece, (PageChayes) 80,000 to 120,000 rpm with car­ bide no. 558 bur : 6 6. T h e superspeed handpiece (PageChayes) 80,000 to 120,000 rpm, 1 /1 6 inch diam ond cylinder: 5 7. T h e superspeed handpiece (K e r r ), 80.000 to 120,000 rpm carbide no. 558 bu r: 5 8. A ir turbine handpiece, 150,000 to 200.000 rpm , 1 /1 6 inch diam ond cylin­ der: 3 9. A ir turbine handpiece, 150,000 to 200.000 rpm carbide no. 558 b u r: 4 • 10. Ultrasonic h andpiece:

2

T h e annoyance factor num ber, if based on amplitude alone, w ould have been designated tentatively as 2 fo r the air turbine handpiece with diam ond instru­ ment and 3 fo r the air turbine handpiece with carbide instrument; the high air­ borne noise, however, created by these instruments resulted in raising the an­ noyance factor num ber one degree higher fo r each instrument. A com parison o f the air-borne noise produced by the handpiece while the in­ strument is rotating but not cutting, indi­

76 • THE JO U R N A L OF THE A M E R IC A N DENTAL A SSO C IA T IO N

Fig. I • Oscilloscope tracings. A bove left: Conventional handpiece, 4,500 rpm; no. 558 steel bur. Dominant frequency, 300 to 600 cps; skull vibration. Above right: High speed handpiece, 12,000 to 16,000 rpm; no. 558 carbide bur. Dominant frequency, 600 to 1,200 cps; skull vibration. Below left: H igh speed handpiece, 12,000 to 16,000 rpm; diamond cylinder. Dominant frequency, 300 to 600 cps; skull vibration. Below right: W ater turbine handpiece, 45,000 rpm; diamond cylinder. Dominant frequency, 600 to 1,200 cps; skull vibration

cated that the air-turbine handpiece was the loudest, and the conventional and high-speed instruments, the quietest (Figs. 3, 4 ) . O ctave band analysis graphs were plotted to show the over-all level o f noise p roduced in the skull by cutting with the various handpieces and the intensity o f vibrations by frequency bands from 20-75 cps to 4,800-10,000 cps. Gain was ad­ justed at the octave band analyzer so that the highest noise level produced by any o f the instruments studied indicated zero decibels. A ll other levels were rela­ tive to this; thus all signals below zero decibles appeared as minus values as their intensity decreased (Figs. 5 -9 ). T he

graphs presented as Figures 5 through 9 were plotted from recordings o f cutting the same tooth in the same patient. Analysis o f the use o f burs and diam ond points in all speed ranges indicates that the ultraspeed instruments, because o f the extremely light pressure and reduced time o f contact with the tooth, last in ­ definitely. This reduces the replacement cost o f cutting instruments as well as the num ber o f instruments required in the clinical armamentarium. T h e conventional low-speed instru­ m ent, rotating at 4,500 to 6,000 rpm, because o f the heavy pressures and pro­ longed contact necessary fo r effective cutting, wears dow n steel burs, fractures

HARTLEY— H U D SO N — BROGAN . .. VO LUM E 59, JULY 1959 • 77

carbide burs and strips diam ond abrasive from points and wheels at an excessive rate. This ineffective cutting also re­ quires a large selection o f specifically shaped burs and diam ond instruments. It is not unusual to use new burs o f sev­ eral shapes in order to com plete a prepa­ ration properly, nor is it unusual fo r a diam ond point or wheel o f m oderate-tosmall size to becom e com pletely ineffec­ tive at the point o f most frequent con ­ tact with the tooth. Large disks will last

longer because their peripheral speed is increased, thus requiring less pressure for effective cutting. As rotational speeds increase, the pres­ sures required to cut effectively are re­ duced. T h e time o f contact with the tooth is likewise decreased with increased rotary speeds. These factors prolong cutting in ­ strument life. W ith rotary speeds in the range o f 180,000 to 225,000 rpm and above, burs and diam ond points last in­ definitely. Carbide instruments d o not

Fig. 2 • Oscilloscope tracings. Above left: Superspeed handpiece ( Page-Chayes), 80,000 to 120,000 rpm; no. 558 carbide bur. Dominant frequency, 1,200 to 2,400 cps; skull vibration. Above right: Superspeed handpiece (Page-Chayes), 80,000 to 120,000 rpm; diamond cylinder. Dominant fre­ quency, 1,200 to 2,400 cps; skull vibration. Center left: Superspeed handpiece (Kerr), 80,000 to 120.000 rpm; carbide bur. Dominant frequency, 1,200 to 2,400 cps; skull vibration. Center right: Air turbine handpiece, 150,000 to 200,000 rpm; no. 558 carbide bur. Dominant frequency, 2,400 to 4,800 cps; skull vibration. Below left: A ir turbine handpiece, 150,000 to 200,000 rpm; diamond cylinder. Dominant frequency, 2,400 to 4,800 cps; skull vibration. Below right: Ultrasonic handpiece, 29.000 cps. Dominant frequency, 300 to 600 cps; skull vibration

78 • THE JO U R N A L OF THE A M E R IC A N DENTAL A SSO C IA TIO N

INSIDE B -29 AIRCRAFT 160 M PH

ORDINARY CONVERSATION AT 5 FEET

10 7 10® to 9 INCREASE IN ACOUSTIC POWER

Fig. 3 • Relative sound pressure levels of den­ tal handpieces (at 3 inches from meter). C om ­ parative levels of air-borne noise originating from the handpieces evaluated in this study. The relative noise levels of conversation and that created within an aircraft are indicated at their corresponding sound pressure levels

11

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Fig. 4 * Relative sound pressure levels of air turbine handpieces (at 3 inches from meter). Comparative levels of air-borne noise originat­ ing from the five air turbine handpieces evalu­ ated in this study

OCTAVE BAND FREQUENCY IN CPS

Fig. 5 • Handpiece evaluation— vibrations trans­ mitted to the skull. The conventional, low-speed handpiece, 4,500 rpm, and the air turbine hand­ piece with a diamond cylinder (1/16 inch diam­ eter), 150,000 to 200,000 rpm

leg en d : ;

db 0

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75 150 300 600 1200 2400 4800 150 300 600 1200 2400 480010000 Kc OCTAVE BAND FREQUENCY IN CPS

Fig. 6 • Handpiece evaluation— vibrations trans­ mitted to the skull. Octave band analysis of vibrations created by cutting with the high speed handpiece, 12,000 to 16,000 rpm, with a no. 558 carbide bur and a 1/16 inch diamond cylinder

HARTLEY— H U D SO N — BROGAN . . . VO LUM E 59, JULY 1959 • 79

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75 150 300 6 00 1200 2400 480 0 150 3 0 0 6 0 0 1200 2 4 0 0 4 8 0 0 lOOOOKc OCTAVE BAND FREQUENCY IN CPS

Fig. 9 • Handpiece evaluation— vibrations trans­ mitted to the skull. The air turbine handpiece, 150,000 to 200,000 rpm, with a no. 558 carbide bur, and the ultrasonic instrument, are com­ pared with handpieces which produced the highest and lowest noise levels

-10 -20 -3 0 -4 0 -5 0 -6 0

20 75

75 150 3 0 0 6 00 1200 240 0 4 8 0 0 150 3 0 0 6 0 0 1200 2 4 0 0 4 8 0 0 1 0 0 0 0 Kc OCTAVE BAND FREQUENCY IN C P S

Fig. 7 • Handpiece evaluation— vibrations trans­ mitted to the skull. W ater turbine handpiece, 45,000 rpm, with a 1/16 inch diamond cylinder; the superspeed handpiece, 80,000 to 120,000 rpm, with a no. 558 carbide bur

•----- »CONVENTIONAL I FPFHn- *------P A G E-C H A Y ES-D IA M O N D •-----»KERR SUPER SPEED -C ARBIDE 0----- °AIR TURBINE- DIAMOND

20 75

75 150 3 0 0 6 0 0 1200 240 0 4 8 0 0 150 3 0 0 6 0 0 1200 2 4 0 0 4 8 0 0 lOOOOKc OCTAVE BAND FREQUENCY IN C PS

Fig. 8 • Handpiece evaluation— vibrations trans­ mitted to the skull. Superspeed handpieces, 80,000 to 120,000 rpm, one with a 1/16 inch diamond cylinder and another with a no. 558 carbide bur, are compared with handpieces which produced the highest and lowest noise levels. Note shift to higher frequencies and reduction in noise level

Fig. 10 • Recommended group of carbide instru­ ments required for most routine ultraspeed prepa­ rations. Above: no. I/2 or no. I round; no. 35 or no. 37 inverted cone. Below: no. 57 to no. 59 straight fissure; no. 70 or no. 71 tapered fissure; extra-long tapered fissure. All are 1/16 shankfriction grip type

80 • THE JO URNAL OF THE A M E R IC A N DENTAL A SSO C IA T IO N

Fig. I I • Recommended diamond instrument group. All are 1/16 inch shank-friction grip type, and are entirely adequate for routine preparations employing air turbine handpieces

dull when they are properly cleaned and sterilized, and have been known to last so long as to suffer vibrational fatigue. T h e increase in cutting effectiveness derived from the ultraspeed rotary instru­ ments has drastically reduced the num ­ ber o f burs and diam ond instruments re­ quired to perform routine or specific cuts. T h e inherent low torque o f the air tur­ bine instruments will not permit fullspeed rotation o f any but the smallest o f burs and diam ond points. ( I f full-speed rotation is not attained, cutting will not be effective.) T here is no need for large diam eter instruments since the primary need for large size was to obtain sufficient peripheral speed. T h e small diam ond points and burs il­ lustrated (Figs. 10, 11) represent our recomm endations for consideration as a com plete set o f cutting instruments fo r the air turbine handpieces. These are drawn to approxim ate scale; the burs are: no. 35 or no. 37 inverted con e; no. 70 or no. 71 tapered fissure; no. Yi or no. 1 rou n d ; no. 57 to no. 59 straight fissure, and an extra-long, endcuttingj tapered fissure.

These instruments are not cross-cut ; they have been found to have a less traumatic effect and to cut a smoother surface. H and instrumentation in the classic manner should be continued; in­ creased emphasis upon this (in con ju n c­ tion with ultraspeed instrumentation) will produ ce superior preparations with a m inim um o f trauma to the patient and m inimal operator fatigue. C linical interpretation o f the audio­ metric tests indicated no significant tem ­ porary loss in hearing as a result o f cut­ ting with any o f the handpieces, under the conditions o f this experiment. D e ­ pression o f hearing may originally result from tem porary fatigue, with subsequent recovery. D uration o f exposure as well as the intervals between exposures are fa c­ tors concerned in the production o f hear­ ing loss.4 W ith the reduced time o f exposure o f the patient to the air or boneconducted noise when the newer super­ speed instruments are used, it is p rob­ able that the exposure was insufficient to produce tem porary loss o f hearing. T he possibility o f temporary high tone hear­ ing loss still remains, however, when ex­ posure is prolonged and repeated at fre­ quent intervals.

Presented as part of a panel discussion, "Clinical evaluation of new high-speed equipment," in the Forum on Dental Practice Part III, ninety-ninth annual session, American Dental Association, Dallas, Texas, November 12, 1958. *M ajort> U. S. A ir Force Dental Corps; head, restora­ tive dentistry section, Air University, School of Aviation Medicine. fColonel, U. S. Air Force Dental Corps; chief, dental sciences division, Air University, School of Aviation Medicine. ^Electronic engineer, department of ear, nose and throat, Air University, School of Aviation Medicine. 1. Hartley, Jack L. Comparative evaluation of newer devices and techniques for the removal of tooth struc­ ture. J. Pros. Den. 8:170 Jan. 1958. 2. Walsh, J. P., and Symmons, H. F. Vibration per­ ception and frequencies. New Zealand D. J. 45:106 April 1949. 3. Hudson, D. C., and others. Factors influencing the cutting characteristics of rotating dental instruments. J.A.D.A. 50:377 April 1955. 4. Aviation otolaryngology, School of Aviation M edi­ cine textbook no. 4. Air University, School of Aviation Medicine, U. S. Air Force, April 1956.