AO-AIIS 951 SCHOOL. OF AEROSPACE MEDICINE OROES AFS TX /65

W.ThASONJC CLEMENRS. (UlOAR U 5 A MAY15. 5 J SUM,~ .J N POWELL

WiCLASSIFIED SAM-AEROMEDICAL REVIEW-1-M

1111L2 LA 132

11II11 III II 1.6

MICROCOPY RESOLUTION TEST CHARTNATIONAL BUREAU Of STANDARDS 963-A

Review 1-82 (2

AEROMEDICAL REVIEW

ULTRASONIC CLEANERS

Bruce A. Matis, Lieutenant Colonel, USAF, DCBrian J. Smith, Staff Sergeant,_USAFJoseph M. Powell, Colonel, USAF, DC

Laurence P. Crigger, Major, USAF, DC

John M. Young, Colonel, USAF, DC

March 1982

DT!CJN 1 19820

A

C36 Approved for public release; distribution unlimited.

C->

USAF SCHOOL OF AEROSPACE MEDICINEAerospace Medical Division (AFSC)

C., Brooks Air Force Base, Texas 78235

8 2 0 6 01032

NOTICES

This final report was submitted by the Dental Investigation ServiceBranch, Clinical Sciences Division, USAF School of Aerospace Medicine, Aero-space Medical Division, AFSC, Brooks Air Force Base, Texas, under job ordernumber DSB38200.

When U.S. Government drawings, specifications, or other data are used forany purpose other than a definitely related Government procurement operation,the Government thereby incurs no responsibility nor any obligation whatsoever;and the fact that the Government may have formulated, furnished, or in any waysupplied the said drawings, specifications, or other data is not to be re-garded by implication or otherwise, as in any manner licensing the holder orany other person or corporation, or conveying any rights or permission to man-ufacture, use, or sell any patented invention that may in any way be relatedthereto.

This report has been reviewed by the Office of Public Affairs (PA) and isreleasable to the National Technical Information Service (NTIS). At NTIS, itwill be available to the general public, including foreign nations.

This report has been reviewed and is approved for publication.

LAURENCE P. CRIGGER, Major, USAF, DC OHN MY.U G, Colionel, USAF, DCProject Scientist ,)Supervisor' .

ROY L. DEHARTColonel, USAF, MCCommander

A . aL

,. ,. :;StiOI-

A Ctr O. -

w 1 Lc i o

UNCLASSIFIlEDSECURITY CLASSIFICATION OF THIS PAGE (fien Date Entered)

REPOT DCUMNTATON AGEREAD INSTRUCTIONS______ REPORT_______________________PAGE_ BEFORE COMPLETING FORM

I. REPORT NUMBER 12. GOVT ACCESSION No. 3. RECIPIENrs CATALOG NUMBER

-Aeromedical Review-1-82 //~( 1C4 ?ILE (ni Subeti) S. TYPE OF REPORT A PERIOD COVERED

ULTRASONIC CLEANERS Final ReportAugust 1980 - July 1981S. PERFORIMING 01G. REPORT NUMBER

_________________________________________S AM- TR- 82-97. AUTHOR() Bruce A. Matis, Lieutenant Colonel, USAF, 8. CONTRACT OR GRANT NUMBER(*)

DC; Brian J. Smith, Staff Sergeant, USAF; Joseph M.Powell, Colonel, USAF, DC; Laurence P. Crigger,Major, USAF, DC; John M. Young, Colonel, USAF. DC

9. PERFORMING ORGANIZATION NAME -AND ADDRESS 10. PROGRAM ELEMENT. PR~OJECT. TASKUSAF School of Aerospace Medicine (NGD) AREA A WORK UNIT NUMBERS

Aerospace Medical Division (AFSC) 87714FBrooks Air Force Base, Texas 78235 DS838200

OFCE NAME AN 1 4 2 EOTGT

e ros pace Vflcne(NGD) March 1982Aerospace Medical Division (AFSC) 13. NUMBER OF PAGES

Brooks Air Force Base, Texas 78235 1614. MONITORING AGENCY NAME & ADDRESS(Ul different from Controlitng Office) IS. SECURITY CLASS. (of this report)

Unclassified

ISa. DECLASSIFICATION/ DOWN GRAOINGSCHEDULE

16. DISTRIBUTION STATEMENT (of this Report)

Approved for public release; distribution unlimited.

17. DISTRIBUTION STATEMENT (of the abstract entered In Block 20, if different from, Repot)

III. SUPPLEMENTARY NOTES

It. KEY WORDS (Continue on reverse side if necessary and Identify by block nitutber)

Ultrasonic cleanersUltrasonicsDental sterilizationDental disinfection

20. ABSTRACT (Continue an reverse side If necessary mid identify by block number)

This document discusses the rationale for using ultrasonic cleaners in aninfection control regimen, and it briefly describes the principles of cavita-tion. Seven units are compared based on the following criteria: cost, alumi-num foil erosion, pitting of type IV stone, heat production in 3 hours, noiselevels, weight, basket water drainage, fit of lid, presence or absence ofexternally accessible fuse, and cement removal in 1 minute. Guidelines for

oroar ue ar orvided.DD I1JiAN73 1473 EDITION OF I1NOV 69 IS OBSOLETE UNCLASSIFIED

L~SI-CUITY CLASSIFICATION OF THIS PAGE ("en Dore Entered)

SECURITY CLASIFICATION OF THIS PAG(Wha Doe Entered)

SECURITY CLASSIFICATION OF THIS PAGE (MO DOfMe tnoeteed)

ULTRASONIC CLEANERS

INTRODUCTION

The selection of an ultrasonic cleaner for use in Air Force dental facil-ities depends on several factors. Determining the primary use of the unitprior to purchase is important because different units may be better suited todifferent tasks. Traditionally, dental laboratories use ultrasonic cleanersto remove cements, polishing compounds, and waxes from prostheses. Theseunits, however, can also be used to clean contaminated dental instruments,thus reducing the chances of cross-contamination. Hinged instruments andaspirator tips often have foreign material build up in arcas inaccessible orj'difficult to clean. According to the American Dental Association -l-7iaITpractical methods of sterilization or disinfection can be overchallenged bysoiled or heavily contaminated instruments.

Because they reduce the likelihood of injury and infection of the hands,ultrasonic cleaners are safer than manua , scrubbing. They are 16 times moreeffective in their cleaning ability a2-rand significantly reduce the aerosoli-zation of potentially pathogenic organisms during the instrument-cleaningprocess.

The purpose of this report is to help base dental surgeons decide whichultrasonic cleaner(s) will best suit their needs. All units were evaluatedwith the concept of dental treatment room use.

NATURE OF ULTRASONIC CLEANING

An ultrasonic cleaning system consists of an electronic generator whichgenerates an alternating current of the desired frequency anid a transducerizedtank to contain the cleaning solution. The cleaning tank is the heart of thesystem and is the only truly ultrasonic part of it.

The term "ultrasonic" is used to describe sound above the audible range.Most humans can hear sounds up to about 16,000 Hz. The normal frequency rangefor ultrasonic cleaning is from 20,000 to 90,000 Hz.

The generator creates an electrical current at a selected frequency.

" This electrical energy is then changed into mechanical energy by transducers* that expand and contract in frequency with the alternating current. These

transducers, bonded to the bottom or side of the tank, set up alternating

1. American Dental Association Accepted Dental Therapeutics, 1979, p. 55.2. Sandord, J. E. Cleaning with ultrasonics. Am. Machinist 110:87-98

(1966).

--- , ,,, " " I | i i1

pressure waves which create the so-called cavitation phenomenon--the formationand collapse of microscopic cavities (bubbles) in liquid, creating a scrubbingaction.

A sound wave passing through liquid carries high pressure ahead of it andlow pressure in back of it. As the wave passes, the trailing low pressure isbelow that of the liquid, and millions of bubbles or cavities are formed.Almost immediately, the high-pressure area in front of the next wave causesthe bubbles to implode (collapse inward), releasing a very intense level ofenergy impingement by the cleaning liquid against the submerged ware. Thisresults in the scrubbing action, which is given the term "ultrasonic clean-ing."

TEST AREAS AND EVALUATION

A protocol identified ten specific areas to be evaluated for each of the

following instruments:

Unit Manufacturer Telephone

Steele's SS-4 Columbus Dental Co. (614) 445-8192634 Wager StreetColumbus OH 43206

Health Aids T3.3B Health Sonics Corp. (415) 828-58036575 Trinity Ct.P.O. Box 2698Dublin CA 94566

Vector 55 J. F. Jelenko (800) 431-1785Dental Health Products99 Business Park DriveArmonk NY 10504

Buffalo 773 Buffalo Dental Mfg. Co., Inc. (212) 277-54002911 Atlantic AvenueBrooklyn NY 11207

L&R T-14 L&R Manufacturing Company (201) 991-5330577 Elm StreetKearny NJ 07032

Vibraclean 100 MDT Corporation (213) 516-0516Suite 1175, One Continental Plaza101 Continental BoulevardEl Segundo CA 90245

Vale-1 Esmadent Chemicals Inc. (314) 433-6116P.O. Box 162Highland Park IL 60035

2

Scores were assigned on the basis of 1 through 7 for each area evaluated, with1 being the best or most desirable. The results are explained individually inthe succeeding sections and then summarized in Tables 1 and 2. Theinstruments--with results of some evaluations--are shown at the end of thissection (Figs. 2-8).

(1) Cost: All costs were current as of 28 May 1981. The Steele's,Buffalo, LX-'and Vale have basket and/or lid listed as accessory equipment,but all costs shown here include an ultrasonic unit with a basket and lid.Jelenko's main emphasis In ultrasonic cleaners has been for laboratory use andthey manufacture only a double-beaker holder, so the Vector price includes theBuffalo lid and basket. All machines are covered by a 12-month warranty ex-cept the Health Aids which has an 18-month warranty.

Rating: 1 2 3 4 5 6 7Steele's Health Aids Vector Buffalo L&R Vibraclean Vale-1$177.75 $185.30 $238.64 $249.62 $262.95 $341.25 $425.00

(2) Aluminum Foil Erosion: A sheet of heavy-duty aluminum foil was se-cured horizontally 3.18 cm (1.25 in) above the tank floor and touching thewalls of the tank. Ultrasonic cleaning solution was added to bring the levelof the fluid to a height of 9.52 cm (3.75 in). the ultrasonic unit was turnedon for 4 minutes. Erosion of foil illustrates intensity and distribution ofenergy. A score of 1 was given to the cleaner exhibiting the greatest amountof erosion, as measured by voids and wrinkling of aluminum foil (see "f" ininstrument illustration).

Rating: 1 2 3 4 5 6 7Health Aids Buffalo Steele's Vibraclean L&R Vector Vale-1

(3) Pitting of Diekeen Stone: According to manufacturer's instructions,50 mg of type IV stone (Diekeen Stone: Modern Materials, Columbus Dental Co.,St. Louis, Mo.) was vacuum spatulated with 22 cc of distilled water. The pre-pared stone was vibrated into a 5- x 7.5-cm mold. All seven molds were allow-ed to set overnight. When removed from the molds, the stone casts were 7 mmthick.

Deionized/distilled water was added to the ultrasonic tank to a level7.62 cm (3 in) above the bottom of the basket. The stone cast was placed inthe center of the basket, and the machine was turned on for 5 minutes of cavi-tation.

Pitting by implosion indicates the power of an ultrasonic cleaner. Uni-form distribution of pitting is desirable because it indicates equal cavita-tion throughout the tank. The evenness and depth of pitting were subjectivelyevaluated. A score of 1 was given to the unit exhibiting the deepest and mostuniform pitting of the same blocks (see "b" and "d" in instrument illustra-tions).

Rating: 1 2 3 4 5 6 1Steel's Vector Buffalo Health Aids Vale-1 Vibraclean L&R

3

(4) Heating: All units were filled with 2000 ml of ultrasonic cleaningfluid and were adjusted to run continuously for 3 hours. A thermometer wasplaced inside each tank, and periodic temperature readings were recorded.Elevated temperatures cause more rapid deterioration of the solid-state com-ponents (i.e., transistors, diodes, and transducers). A score of 1 was givento the coolest unit after 3 hours of continuous testing (see "e" in instrumentillustrations).

Rating: 1 2&3 4 5 6 7Vale-1 Vector & L&R Health Aids Buffalo Steele's Vibraclean38% 45% 500C 53°C 54% 590C

I

(5) Noise: Noise levels on ultrasonic cleaners with proper levels ofdegassed distilled water were measured using two different methods. Thefirst was a subjective evaluation conducted independently by four health carepractitioners. The second was a decibel-scale reading measured with a cali-brated instrument. According to AFR 161-35, the maximum allowable Air Forcelevel is an 84-dBA average for an 8-hour day. The USAF Occupational and Envi-ronmental Health Laboratory/ECH measured decibel levels using the A-weightedband on a General Radio 1982 sound-level meter (calibrated 9 Mar 81). Themeter was at a height horizontal to an operator's ear (1.22 m (4 ft) abovefloor level) and 0.28 m (11 in) from the top of the ultrasonic unit. (TheVale unit was not available for the second evaluation--the dBA measurement.)A score of 1 was given the unit that produced the noise level deemed by thehealth care practitioners to be least objectionable to dental patients.

Rating: 1 2 3 4 5 6 7Subjective: L&R Vector Vibraclean Steele's Health Aids Buffalo Vale-1dB Levels: Vector L&R Health Aids Buffalo & Vibraclean Steele's

70 dBA 71dBA 73 dBA both 74 dBA 80 dBA

(6) Weight: A lightweight ultrasonic unit has an advantage because ofthe periodic need to empty solution from the tank and to move the unit forcleanup purposes. Weight is not as critical in units that have a drain(i.e., Vibraclean and Health Aids). A score of 1 was given to the unitlightest in weight.

Rating: 1 2-4 5 6 7Health Aids Steele's, Buffalo, Vector L&R Vibraclean Vale-16 lbs 8 lbs 8.5 lbs 14 lbs 15.5 lbs

(7) Water Drainage from Baskets: A basket should drain rapidly whenlifted out of an ultrasonic cleaning tank filled with solution. Solution isapt to spill with slow draining baskets because most baskets have minimalclearance from the inside of the tank. A score of 1 was given to the unitwhose basket drained of cleaning solution most rapidly when lifted from theultrasonic cleaner.

Rating: 182 3&4 5 6 7Vale-1 & L&R Health Aids & Buffalo Steele's Vibraclean Vector

4

(8) Fit of Lid: Ultrasonic units should be operated with the lid inplace because the solution will aerosolize during operation. The fit of thelid was subjectively evaluated. A score of I was given to the unit with thebest fitting lid (see "a" in instrument illustration).

Rating: 1 2&3 4&5 6 7Steele's Vibraclean & Buffalo Health Aids & L&P Vector Vale-1

(9) External Access to Fuse: The first item to fail in an ultiasonicunit will probably be the fuse. External access to the fuse allows convenentreplacement. One ultrasonic unit (Buffaln) has a circuit breaker that isexternally accessible.

Rating: Yes NoL&R, Vibraclean, Health Aids, Buffalo Steele's, Vale-1, Vector

(10) Removal of Dental Cement: Zinc phosphate cement (Fleck's Cement,Mizzy Inc., Clifton Forge, Va.) was mixed according to manufacttrer's in-structions. The facts of scv'en b13ck #2 condense- point, (2 mi: in diareter,"were filled with cem:ient. The cement was a]lwio to - for 48 hours 'se-Fig. 1). The cond,,','sers were identified by multicolored bands and plar-Ca -ultrasonic units that were activated for minute. All units rero'v,! thecement (also blood dried overnight on cotton forceps) wihin 1 minute.

Spherical dental aralgan was condensed into the black -2 condenser ro ,tsand allowed to set overnight. ."4une of the ultrasonic cleaners was able tcdislodge the amalgam in 10 minutes on sonication.

Rating: Cement removal by all units within 1 minute.

Ir

Figure 1. Condenser point before filling with cement, after cementwas hardened, and after I minute of sonication (left toright).

5

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TABLE 2. MECHANICAL EVALUATION OF UNITS BY BIOMEDICAL EQUIPMENTMAINTENANCE PERSONNEL

Disadvantages Advantages

Steele's *Soldered-in fuses. *Components Modular board replace-SS-4 difficult to reach for trouble- able. RF-output tunable.

shooting. Strain relief poorlyengineered. Pads glued on bottomand front metal plate.

Health Aids Strain relief improperly sized Modular circuit replace-T3.3B with respect to power cord. Tank able. No water seepage

not removable without PVC drain possible. Fuse rating ondestruction. panel.

Vector 55 Internal fuse with leads on Heavy-duty input wiring.end--odd item. Serial number Tank well-sealed to onetaped on. ID plate glued with piece top panel. Clampsfoam tape. No light with hold attach tank to bottombutton. panel for heat and sound-

conduction control.

Buffalo 773 *Power transistors in back not Transistors plug in.protected. Gap of 1.3-1.4 cm(1/2- 3/4 in) between lower andupper control panel. Unit diffi-cult to clean because of wrinklepainting. Potential for waterseepage--may cause RF shock.

Vibraclean Front panel glued on. Timer knob Power transistors plug100 could allow moisture to enter in. Tank insulated well

unit. Solution trap around joint for noise.of pan to tank. Heat sink heldon by two screws. Drain pipecould break off easily. Marginaldrain plug.

Vale-1 *Very difficult to troubleshoot Unit can be power tunedbecause of short leads. Seepage externally by visualaround top tank and top panel means. Heat control farthrough raised edges. Strain in unit. Integratedrelief had 0.6-1.3 cm (1/4-1/2 circuits plug in.in) gap where solution couldenter internal compartment. Fusevery difficult to change.

*Major disadvantages which Biomedical Equipment Maintenance personnel feel

will increase downtime to repair or reservice the specified units.

7

gup . U U 1

Figure 2. Steele's SS-4 ultrasonic unit:a - Ultrasonic cleaner with basket and lid in place.b - Superior surface of type IV stone slab placed in cleaner

5 mm.c - Basket.d - Inferior surface of stone slab showing effect of sonication

through basket.e - Temperature elevation during 3 hr of continued use.f - Erosion of aluminum foil after 4 min of sonication.

8

Omon1

mm . U 1 II U

Figure 3. Health Aids T3.3B ultrasonic unit:a - Ultrasonic cleaner with basket and lid in place.b- Superior surface of type IV stone slab placed in cleaner

5 min.c - Basket.d - Inferior surface of stone slab showing effect of sonication

through basket.e - Temperature elevation during 3 hr of continued use.f - Erosion of aluminum foil after 4 min of sonication.

9

Figure 4. Vector 55 ultrasonic unit:a - Ultrasonic cleaner with basket and lid in place.b - Superior surface of type IV stone slab placed in cleaner

5 min.c - Basket.d - Inferior surface of stone slab showing effect of sonication

through basket.e - Temperature elevation during 3 hr of continued use.f - Erosion of aluminum foil after 4 min of sonication.

10

en-

~ -30 m

A. A.--

Figure 5. Buffalo 773 ultrasonic unit:

11

a - Ultrasonic cleaner with basket and lid in place.b -Superior surface of type IV stone slab placed in cleaner

5 min.c- Basket.d -Inferior surface of stone slab showing effect of sonication

I through basket.e - Temperature elevation during 3 hr of continued use.

f - Erosion of aluminum foil after 4 min of sonication.throughbasket

?T

e [-50 -_

i

40

30

2100 10 15 30 45 N 90 120 in S

Figure 6. L&R T-14 ultrasonic unit:a - Ultrasonic cleaner with basket and lid in place.b - Superior surface of type IV stone slab placed in cleaner

5 min.c - Basket.d - Inferior surface of stone slab showing effect of sonication

through basket.e -Temperature elevation during 3 hr of continued use.

f -Erosion of aluminum foil after 4 min of sonication.

12

100~

- -

T. (M.)

Figure 7. Vibraclean 100 ultrasonic unit:a - Ultrasonic cleaner with basket and lid in place.b - Superior surface of type IV stone slab placed in cleaner

5 min.c - Basket.d - Inferior surface of stone slab showing effect of sonication

through basket.e - Temperature elevation during 3 hr of continued use.f - Erosion of aluminum foil after 4 mn of sonication.

13

6A

V %

Figure 8. Vale-i ultrasonic unit:a Ultrasonic cleaner with basket and lid in place.

b Superior surface of type IV stone slab placed in cleaner5 min.

c Basket.d Inferior surface of stone slab showing effect of sonication

through basket.e - Temperature elevation during 3 hr of continued use.f - Erosion of aluminum foil after 4 min of sonication.

14

USE OF ULTRASONIC UNITS

Ultrasonic units should be placed close to the sink but far enough awayto allow only minimal splashing onto or pooling underneath the unit bywater, soaps, etc. Select a location close to a grounded outlet since allultrasonic cleaners must be grounded.

Liquid must always be in the stainless-steel tank before the ultrasoniccleaner is turned on. Pour only room- tempe ratu re liquid into a cool unit.The solution should be placed in the tank to at least a three-quarters-fulllevel. The units should not be operated with less than a half-full tank.Do not change solution immediately after heavy use of the unit, while theunit is hot. After prolonged use, an empty tank, without solution todissipate the heat, will significantly shorten the life of the transistors.

Allow a tank of fresh solution to degas by operating the unit for5 minutes before processing soiled instruments. This will let the implo-sions occur on the surface of instruments instead of on entrapped air pock-ets. Rinse gross debris from instruments before placing them in the ultra-sonic cleaner basket. Instruments are cleaned much faster when rinsed andplaced in solution before saliva or other contaminants dry. The recommendedtime of ultrasonic action for instruments that have been immersed immledi-ately in the basket or in other holding solution is only 3 to 5 minutes(3). A large load will increase the time required for cleaning.

instruments should be suspended in the solution, not allowed to sit onthe bottom of the tank. Items placed on the bottom of the tank will inter-fere with the transducer action. Any flat surface placed against the solidsurface of a basket will not be cleaned properly because implosion, orscrubbing action, cannot take place.

Before placement into the ultrasonic cleaner, small dental instrumentssuch as burs and reamers can be put on magnetic strips or into separate con-tainers such as-bur blocks or beakers. Also, a liquid disinfectant (e.g.,glutaraldehyde) can be placed in an auxiliary container, covering only theitems to be cleaned. When this container is placed in the main tank, cavi-tation will occur in the disinfectant as well as in the tank's solution.

When baskets are removed from the ultrasonic cleaner, care should betaken not to spill and drip solution from the main tank onto the units andcountertops. The basket should be taken to the sink and the instrumentscarefully rinsed. The instruments can be dried by dipping them in an alco-hol solution or patting them dry with a towel. Only dry instruments shouldbe placed in the sterilizer, especially a chemical vapor sterilizer.

The ultrasonic cleaning solution should be changed approximately once aweek in the average treatment room. Solutions will not readily break down

3. Palenik, C. J., and C. H. Miller. Use of an ultrasonic cleaner inthe dental office. J Ind Dent Assoc 59:11-12 (1980).

15

chemically when used, but they will become contaminated and less effective.The solution can be filtered through medium filter paper to reduce foreigndebris. The mechanism of ultrasonic cleaning can operate in liquids thatare completely neutral, such as water, but detergents are usually added toreinforce dissolving action (4). When changing the solution, avoid sub-merging the unit in water or allowing splatter onto the louvers. Any liquidin the casing will shorten the useful life of the ultrasonic unit consider-ably.

Remember, ultrasonic cleaners do not sterilize; they only prepare in-struments for sterilization.

SELECTION OF EQUIPMENT

Base dental surgeons should use the comparison rating for each crite-rion as well as the evaluation by Biomedical Equipment Maintenance Personnelto choose a unit that best suits their needs.

Any questions concerning this technical review should be directed tothe Dental Investigation Service, USAFSAM/NGD, Brooks AFB TX 78235, AUTOVON240-3502, Commercial (512) 536-3502.

4. Eames, W. B., S. 0. Byrington, and N. B. Suway. A comparison ofeight ultrasonic cleaners. Operative Dentistry 5:118-124(1980).

16

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