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Fall 2002

Effects of Occupational Ultrasonic Noise Exposureon Hearing of Dental Hygienists: A Pilot StudyJennifer Dunning Wilson

Michele Leonardi DarbyOld Dominion University

Susan L. TolleOld Dominion University, stolle@odu.edu

Joseph C. Sever Jr.Old Dominion University, jsever@odu.edu

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Repository CitationWilson, Jennifer Dunning; Darby, Michele Leonardi; Tolle, Susan L.; and Sever, Joseph C. Jr., "Effects of Occupational UltrasonicNoise Exposure on Hearing of Dental Hygienists: A Pilot Study" (2002). Dental Hygiene Faculty Publications. Paper 12.http://digitalcommons.odu.edu/dentalhygiene_fac_pubs/12

Original Publication CitationWilson, J.D., Darby, M.L., Tolle, S.L., & Sever, J.C. (2002). Effects of occupational ultrasonic noise exposure on hearing of dentalhygienists: A pilot study. Journal of Dental Hygiene, 76(4), 262-269.

Effects of Occupational Ultrasonic Noise Exposure onHearing of Dental Hygienists: A Pilot StudyJennifer Dunning Wilson, BSDH; Michele Leonardi Darby, BSDH, MS;S. Lynn Toile, BSDH, MS; Joseph C. Sever, Jr., PhD

Introduction

More than 30 million Americansare exposed on a regular basis tohazardous noise levels.' Occupa-tional noise exposure contributes tooverstimulation of the hearing,whieh in turn, can lead to perma-nent hearing loss. Persons can dif-fer in their host susceptibility tonoise damage. Unfortunately, oncethe damage occurs, hearing prob-lems are irreversible. Tn privatedental offices, dental hygienistscontinually use low-speed band-pieees, sonic and peizoelectricsealers, and ultrasonic cleaners andsealers in the proeess of citre. Ultra-sonic devices are the biggest poten-tial noise hazard affecting hearingin dental hygienists.- Ultrasonicsealers ean produce 68 to 75 dBAwhen used. Although tbis deeibelrange does not fall into the cate-gory of damaging, with therepeated use of an instrument emit-ting these decibel levels, hearingdamage may be eaused.' Moreover,the literature supports the expandeduse of ultrasonic instrumentation totreat periodontal disease nonsurgi-cally and to minimize eumulativetrauma disorders of the skeleto-muscular system in practitioners.Therefore, the use of ultrasonicsealers is expected to escalate. Inlarge group oral health care prac-tices, multiple practitioners usethese instruments, further inereas-ing occupational noise levels andthe risk for hearing loss amongworkers in this environment. Littleresearch has been conducted onhearing loss in dental hygienists andresults have been mixed.

AbstractPurpose. The purpose of this case-control study was to determinewhether long-term ultrasonic noise exposure via the dental office envi-ronment is related to dental hygienists' hearing status.

Methods. Registered dental hygienists (N - 698) who live in the Hamp-ton Roads areas of Virginia were mailed a Dental Hygiene Wori< His-tory Questionnaire to determine who would meet the inclusion criteriaand would be willing to participate in the study. Consenting subjectswere categorized into one of two groups, according to ultrasonic sealerusage rate, and matched on age. Persons with known hearing loss dueto infection, disease, or congenital defect were excluded from the study.The final sample consisted of 20 dental hygienists with a high ultrasonicusage rate and a matched group of 20 dental hygienists who had a lowultrasonic usage rate. Once the groups were formed, a certified audi-ologist tested subjects' hearing in each ear via the pure-tone audiome-ter. Audiometric data were analyzed using the analysis of variance forrepeated measures procedure to determine if degree of ultrasonicsealer noise exposure in the dental office environment was significantlyrelated to hearing status in these dental hygienists.

Results. Results revealed that the right and left ears were not statisti-cally different in the hearing threshold levels, regardless of group sta-tus. However, there was a significant difference in the high ultrasonicusage group and the low ultrasonic usage group at the 3000 Hz. No dif-ferences were found at the frequencies of 500, 1000, 2000, 4000,6000, and 8000 Hz.

Conclusions. Based on these outcomes, the ultrasonic sealer is notconsidered to have a negative effect on the hearing of dental hygien-ists at 500,1000, 2000, 4000, 6000, and 8000 Hz, but may be relatedto hearing loss at 3000 Hz. Ultrasonic noise may in fact be affectingdental hygienists' hearing at 3000 Hz, but loss of hearing observed atthe higher frequencies may be attributed to other unidentified factorspresent in both groups.

Keywords. Ultrasonic noise, hearing loss, occupational hazards.

Significance of theProblem

Occupational noise exposure isthe most common oecupational dis-ease in the United States.' Peopleare unaware of their hearing lossuntil they have lost 28%, or 30

dBHL. of hearing ability.-* In addi-tion to unrecognized hearing loss,problems created by oecupationalhearing loss include 1) reducedquality of life because of social iso-lation and unielenting ringing in theears (tinnitus): 2) impaired commu-nication with family members, the

262 The Journal of Dental Hygiene Volume 76 IssucIV Fall 2002

public, and co-workers; 3) dimin-ished ability to monitor the workenvironment such as warning signsor equipment sounds: 4) lost pro-ductivity and increased accidentsresulting from impaired communi-cation and isolalion: and 5)expenses ibr workers" compensationand hearing aids.' Oral health careprofessionals need to be aware ofthe potential dangers of occupa-tional noi.se exposure, the leadingcause of noise-induced hearing lossin the country.

Review of theLiterature

Effects of Occupational Noiseon Oral Health Care Profession-als' Hearing Status

Moller. Grevstad. and Kristoi-fersen studied ultrasonic scaling ofthe maxillary teeth to determine Hitcaused tinnitus and temporary hear-ing shifts.' Many oral health eareprofessionals reported experiencingtinnitus or a ringing in the ear. Tin-nitus is iVequently associated withnoise induced hearing loss, and isnature'.s warning that noise levelsare dangerously high.^ Moller,Grevstad. and Kristoffersen' foundthat half of the subjects in the studyexperienced- temporary hearingshift and tinnitus when their maxil-lary teeth were sealed with the ultra-sonic sealer.

For 30 years, noi.se in dentaloffices has been suspected of eon-tributing to hearing loss." If a noiseis intense enough, or if one isexposed to it long enough, and/or ifone's hearing meehanism is suscep-tible enough, any noise ean causehearing loss. Given these eonditions.hair cells in the cochlea will be dam-aged and eause hearing loss. Noisecauses unwanted masking of sounds.interference with speech and eom-munication. pain and injury, andtemporary or permanent loss ofhearing. Physiologically, noiseincrea.ses blood pressure, quiekenspulse, and constricts blood vessels.Researchers have documented that

hand-reflex time to stimuli waslengthened alter human subjects hadbeen exposed to noise and that pre-cision movements of hands andarms were also affeeted."* Noise hasalso been found to eause emotionalproblems, nervousness. Indigestion,headaehe. deereased overall elfi-eiency, and decreased ability to per-form eomplex or multiple tasks.These findings suggest that signiti-cant noise levels in the oral healtheare environment might affect skillperformance of dentists and dentalhygienists, thereby, affeeting thequality of eare rendered.

Zubick and Tolentino conductedresearch on the hearing differencesamong 137 dentists and 80 physi-cians.' In pure tone air eonduetionevaluations, physieians had betterhearing threshold levels than den-tists, espeeially around the frequencyof 4000 Hz. Zubick and Tolentinoalso discovered that right-handeddentists showed greater hearing lossin their left ear. probably related totheir positioning aiid proximity to thenoise. Those dentists working in aspecialty area also showed hearingloss in the same pattern as generalpractice dentists. Zubick andTolentino concluded that there maybe a cause and effect relationshipbetween hearing loss and the use ofthe high-speed dental handpiece.^ Inwork on minimizing health hazardsin the dental workplace, Baratz alsostated that repetitive handpiece noiseproduces permanent high-freequencyhearing loss."

Although sound exposures poten-tially hazardous to hearing are usu-ally defined in terms of sound levels,frequency bandwidths, and duration.hearing experts agree that otherexposures may be hazardous. Forexample, if the sound is appreciablylouder than conversational levels lora sufficient period of lime, it ispotentially harmful. Furthermore,noise may be hazardous if the lis-tener experiences difficulty eommu-nieating while "in" the sound, hastinnitus alter exposure to the sound,or if sound seems muffled after leav-ing the exposure area.

Noise Levels Produced byUltrasonic Sealer

The term ultrasonic describes arange of aeoustical vibrations thatcannot be heard by the human ear. Indentistry, the ultrasonic frequenciesrange from approximately 20.000vibrations per second to 50,000vibrations per second. These ultra-sonie vibrations are a unit of fre-quency often referred to as eyelesper second (eps) or Hertz (Hz).Some ultrasonic units are alreadypreset for these different levels,while other units are adjustable.

Some of the frequencies that theultrasonic produces may reach thepatient's inner ear by bone or airconduction. Moller. Gravstad, andKristofferson set out to measureultrasonie sealing effects of maxil-lary teeth on the inner ears ofhealthy young adulis by means ofaudiometry.^ Twenty healthy sub-jects with at least 13 erupted maxil-lary teeth participated in the study:ages ranged from 22 to 36 with 9females and I I males. Resultsshowed a shift in patients' hearingthresholds after ultrasonic sealing ineight participants (40%). The thresh-old shifts ranged from 10 to 20 deci-bels and persisted for as long as 30minutes after the ultrasonie scalingwas terminated. Five of the partici-pants had a threshold shift in theright ear and two showed shifts inthe left ear. Seven participantsshowed a threshold shift at 7(){)() Hzor at 8()()() Hz or boih: three partici-pants showed a shift for sevetal fre-quencies. Moller. Grevstad, andKristoffersen concluded that theelfeets of the ultrasonic sealer weretemporary, and should not preventthe use of ultrasonie instruments.*^However, it should be noted that inthe 1970s, ultrasonie instrumenta-tion was less IVequently used than inthe 21st century. The rate of ultra-sonie instrument usage todaydemands a more critical attitudetowards their frequent and repeatedapplication and their potentialeffects on hearing.

Holmberg, Landstrom, and Nord-strom set out to evaluate the sensa-

VolLmie76 ksuc IV Fall 2002 The Journal of Dental Hygiene 263

tion of annoyance as well as the sen-sation of discomfort during expo-sure to the high-frequency soundand ultrasound from an ultrasonicwasher.̂ The study included 10 sub-jects and consisted of five men, aged23 to 38, and five women, aged 23to 44. Based on a pre-study audio-metric evaluation, none of the sub-jects presented with hearing loss.The subjects were exposed to thenoise while proof reading a text,simulating the work in an office.Afterwards they were asked to ratetheir sensation of annoyance (men-tal effect) and discomfort (effectlocated at the ear) on a 100 mmscale with verbal labels. The relatedlevels of annoyance were high at allamounts of exposure. The groupaverage for the noise level of 96dBA was 63 mm, which corre-sponds to "rather annoying" and"quite annoying." Holmberg. Land-strom, and Nordstrom concludedthat the ratings of annoyance anddiscomfort among participants in theinvestigation must be consideredhigh enough to recommend anavoidance of even the lowest levelof noise from the washer at 70 dBA/

Methods

The protocol was reviewed andapproved by the Old Dominion Uni-versity Institutional Review Boardfor the Protection of Human Sub-jects. A prescrecning instrument,titled the Dental Hygiene Work His-tory Questionnaire, was mailed toall registered dental hygienists in theHampton Roads area of Virginia(N = 698) to determine those meet-ing the inclusion/exclusion criteria(Figure 1). Inclusion criteria statedthat the subject must be 21 years ofage and a regislered dental hygien-ist. This included both practicingand nonpraclicing dental hygienistsfrom the list of registered dentalhygienists obtained through the Vir-ginia Board of Dentistry Web site inFebruary 2001 (http//www.vbd.org).If the subjects had a histoiy of hear-ing loss due to infection, disease, orcongenital defects, they were

excluded from the study. The dentalhygienists that agreed to participatewere matched on age. The final sam-ple consisted of 20 matched pairs ofdental hygienists. All participantswere female. The overall samplehad a mean age of 42.7 and a mean

of \5.1 years in practice. Twentydental hygienists that had a highultrasonic sealer usage score werematched with 20 dental hygienistswho had a low ultrasonic sealerusage score. The high ultrasonicusage group had a mean age of

Directions,' Please complete the following 11 questions by filling in the blank or circlingthe response that best reflects your characteristics and experiences. This information willbe used to identify dental hygienists for a hearing loss study. Your cooperation is appre-ciated and may contribute to improvement in occupational safety for dentai hygienists.Piease return the questionnaire by March 1, 2001.

1. What is your age at the time of your last birthday?

2. How many days a week do you work in a dental office providing client care? (circleone response) 0 days 1 day 2 days 3 days

4 days 5 days 6 days

3. How long have you worked in a dental office providing direct client care? {circle oneresponse)

<3 years >5-10 years >15-20 years3-5 years >10-15 years >20 years

4, in your total dental hygiene practice career, how many years have you practiced?Full time (defined as 4 or more days per week)Part time (defined as less than 4 days per week) _______

5, On how many patients per day, on average, do you use the ultrasonic sealer?(specify)

6, On the average, how many years have you used or been using the ultrasonic sealeron patients? (specify)

7. Have you had any previous hearing problems that have been diagnosed by a physi-cian or audiotogist?

Yes (If yes, answer item 8 on back)No (if no, go directly to item 9 on back)

What is the cause of your hearing loss? (check all that apply)Infection Congenital defect OtherDisease Loud noise exposure (specify)

9. Do you have a family history of hearing loss?Yes (If Yes, please answer item 10)No (If No, pfease go directly to item 11)

10. Who in your family has had a history of hearing loss? (circle all that apply)ryiother SiblingsFather Other

11. Are you exposed to any loud noises outside of the dental office?(i.e., concerts, noise at home) Yes (please specify source of noise)

No .

If you would like to participate in this study, please sign below and fill in your telephonenumber. If you meet the requirements for the study, you will be called to schedule a freehearing test appointment at Old Dominion University. Thank you,

^No, I am not interested (no need to sign your name, just return the questionnaire)

__Yes, I am interested, piease contact me based on the information provided below.

Print name: Telephone number: ^___ .

Preferred time for hearing test: days/time evenings time „Signature: Date:Please return this form in the stamped envelope provided to:

School of Dentai HygieneOld Dominion UniversityTechnology BIdg.47th Street and Hampton Blvd.Norfolk, VA 23529-0499Attn. Jennifer Dunning, BSDH

Figure 1. Dental hygiene work history questionnaire

264 The Journal of Dental Hygiene Volume 76 bsucIV P;ill 2002

42.75 and a mean of 18.65 years inpractice; the low ultrasonie usagegroup had a mean age of 42.65 andmean of 11.8 years in practice.

The usage score was determinedby an equation that comprised theself-reported number of patientstreated per day with the ultrasonicsealer multiplied by the number ofyears the dental hygienist had usedthe ultrasonic sealer. For example,if the dental hygienist reported usingthe ultrasonic sealer on five patientsper day and had been in practice for13 years, the usage score was 65.

A certified audiologist tested sub-jeets' hearing in each ear via thepure-tone audiometer. Testing atseven frequencies look place at theOld Dominion University, LionsChild Study Center. Audiometry, ata minimum, consisted of pure-toneair-eonduetion threshold of eaeh earat 500, 1000, 2000, 3000, 4000.6000, and 80(){) Hz. The test wasgiven in a standard sound-attenuat-ing room. At eaeh frequency, theheiuing threshold recorded for an earwas the lowe.st decibel hearing level(dBHL) at which the individualresponded to two of three trials. Apure-tone audiometer test uses sim-ple vibrations of various frequenciesand intensities to measure hearing.Hearing threshold levels wererecorded in increments of 5 dBHL.Tympanometry followed ihe pure-tone testing only if the partieipantshowed hearing loss in the lower fre-quencies. Only one participant in thehigh usage rate group was requiredto have a tympanogram. Upon eval-uation, the paiiicipant presented witha normal tympanogram suggestingthat there was no middle-ear pathol-ogy. Of the 40 partieipants, 10 whohad threshholds 30 dBHL or higherat any frequency were asked toreturn for a repeated test free ofcharge. This was done to reevaluatethe hearing thresholds for changes.Fifty percent of the subjects thatneeded to be re-tested were in thehigh frequency of ultrasonic use, and50% of the subjects were in the lowfrequency of ultrasonic use. Datawere analyzed using the analysis ofvariance for repeated measures.

Between and within group audio-metric data were analyzed using theanalysis of varianee for repeatedmeasures so that the main effect ofultrasonic usage, as well as the inter-action effects of ultrasonie usage atthe seven different frequency levels,could be determined. All hypothe-ses were tested at the 0.05 level.Because data were not normally dis-tributed, data was subjected to a logtransformation to ensure that analy-sis of varianee could be used legiti-mately. The computerized SAS sys-tem was used for data analysis.

Results

Hypothesis One. The firsthypothesis .stated that there was nodifference in the hearing status ofmatched groups of high and lowultrasonie sealer users, as measuredby pure-tone audiometry. Theanalysis of variance for repeated

measures revealed a statisticallysignificant differenee in the hearingof dental hygienists who were highultrasonic sealer users us comparedwith dental hygienists who werelow ultrasonic sealer users (F =2.79, df= 6, P = 0.01). High-ultra-sonic users have signifieantlypoorer hearing status than low-ultrasonic users. Therefore, hearingstatus appeared to be negativelyaffected by high-ultrasonic sealerusage in dental hygiene praetice(Table I and Figure 2).

Hypothesis Two. The secondhypothesis stated that there was nostatistically signifieant differenee inthe hearing sLatus of high and Iow ofultrasonic sealer users at the 500,1000, 2000, 3000, 4000, 6000, and8000 Hz as measured by pure-toneaudiometry. Analysis of variance forrepeated measures revealed a statis-tically signifieant difference in highand low usage groups at 3000 Hz(F = 5.81, df = ),P =0.02), but no

o

i" 2-o(D

> 1 •

0 -

Plot of Mean Log Response vs. Frequency LevelsFor the Two Groups

1000—I—2000

—I—3000 4000

1—5000

1—6000 7000 8000

Frequency (Hz)

Group •-•-• 1

Group 1= Low-ultrasonic usage group.Group 2 = High-ultrasonic usage group.Note: Higher mean log responses indicate poorer hearing.

Figure 2. Change in hearing ability of two matched groups of dentalhygienists (High-ultrasonic usage verses low-ultrasonic usage) atseven frequencies

Voliimt!76 l.s.suelV Rill 2002 The Journal of Dental Hygiene 265

statistically significant differencesat 500, 1000, 2000.4000, 6000, and8000 Hz. Dental hygienists withhigh usage rates had significantlypoorer hearing at 3000 Hz. whilethose in the low usage group hadsignificantly better healing at 3000Hz. Therefore, hearing status at3000 Hz appeared to be negativelyaffected by frequency of ultrasonicsealer usage (Table II).

Hypothesis Three. The thirdhypothesis stated that there was nointeraction between usage levels ofthe ultrasonic sealer (high and lowusage) and the IVequeneies (500,,1000. 2000, 3000. 4000, 6000. and8000 Hz). Analysis of variance forrepeated measures revealed thatdental hygienists with high usagelevels had a higher hearing thresholdlevel documented at 3000 Hz butnot at the other frequencies(F =37.62. df =6. P=0.0001). There-fore, there was significant interac-tion between high usage rate andhearing threshold^at 3000 Hz (TableIII). Results revealed that as fre-quency increased, hearing gotpoorer for both groups, but this dif-ference in hearing status betweenthe groups was not statistically sig-nificant (Figures 2 and 3).

Hypothesis Four. The fourthhypothesis stated that there was nosignifieant differenee in the hearingstatus of the right and left ears ofdental hygienists in either the high-or low-ultrasonie sealer usagegroups. Analysis of variance forrepeated measure results revealedno statistically significant differeneein the hearing thresholds of the rightand left ears (F = 3.61. df= \.P =0.057). regardless of high- or low-ultrasonic usage group status. Theright and left ears showed little vari-ation in the hearing patterns as aresult of ultrasonic sealer usage indental hygienists (Table III and Fig-ure 3).

In general, the percentages ofpersons in both matched groupswith normal hearing and hearingdefieits are presented in Table V.Although the percentages were nothypothesized, it is interesting to notethe overall similarities in both

Table I. Analysis of variance comparison of high-and low-ultrasonic sealer usage levels in twomatched groups of dental hygienistsSource

GroupSubject

Frequency

Group and frequency

DF1

38

6

6

SS4.48

138,47

226.78

16.84

Mean Square

4.48

3.64

37.79

2.80

F value4.50

3.65

37.90

2.82

Probability0.0334*

0.0001 *

o.ooor0.0105** aigniticance

Table II. Analysis of variance comparison offrequencies for high- and low-ultrasonic sealer usagegroups of dental hygienists

Frequency3000HZ

500 Hz

lOOOHz

2000HZ

4000HZ

6000HZ

8000HZ

SourceGroup

Group

Group

Group

Group

Group

Group

DF1

1

1

1

1

1

1

Type 1 SS14.86

2.77

0.03

0.76

2.03

0.51

0.34

Mean Square

14.86

2.77

0.03

0.76

2.03

0.51

0.34

F value

5.81

1.73

0.04

0.32

0.90

0.41

0.41

Probability0.02*

0.19

0.84

0.57

0.34

0.52

0.52* Significance

3-

(/)coQ.

0)niCToen2

2-

1 -

0-

Plot of Mean Log Response vs. Frequency LevelsFor Combinations of Group and Ear

1000—I—2000 3000

—I—4000

1—5000 6000

—I—7000 8000

Frequency (Hz)

Group Ear • -^-•GIEI •-•-•G1E

Gl El = Low-ultrasonic usage group tested in the right earGl E2 = Low-ultrasonic usage group tested in the left earG2E1 = High-ultrasonic usage group tested in the right earG2E2 = High-ultrasonic usage group tested in the left earNote: Higher mean log responses indicate poorer hearing.

G2E2

Figure 3. Change in hearing status in right and left ears of twomatched groups of dental hygienists at seven frequencies

The Journal of Dental Hygiene Volume 76 Issue IV Fall 2002

groups. These percentages werecomputed by calculating the per-centage of the participants that pre-sented with a hearing threshold of25 dBHL or higher and 24 dBHLor lower. The subjects presentingwith 25 dBHL or higher have agreater hearing deficit than thosewho tested with a threshold levelless than 25 dBHL.

Discussion

Hypothesis One. The analysis ofmean differences in the overall hear-ing evaluation revealed statisticalsignificance between those dentalhygienisls who had a high frequencyof ultrasonic usage as compared tothose dental hygienists who hadlow-uitrasonic sealer usage{P = 0.01). Results suggest that den-tal hygienists with high-ultrasonieusage rates had poorer hearing thanthose with low-usage rates.Although there is statistical signifi-

cance, the clinical difference showsonly minimal variation in dBHL lev-els. This implies that heavy use ofthe ultrasonic sealer may be eon-tributing to noise-induced hearingloss in Ihe oral health care workenvironment. The means for eachgroup in the study are displayed inTable TV.

As compared to other dentaloffice noises, the ultrasonic mightbe a source of damaging noise. Asreported by Setcos and Muahyud-dan, the ultrasonic sealer wasrecorded as emitting some of thehighest intensities of dental officenoises {ranges of 75 to 88 dBA).**The Hazardous and Solid WasteAmendment (HSWA) states that allworkers who are exposed to sound85 dBA or above should be givenadequate information about the riskinvolved by their employers. TheEPA has also stated that if a personin a 24-hour period is exposed tonoise levels maintained at 70 dBA orbelow, for the most part, hearing

TabiG III. Analysis of variance of between andwithin group data for high- and low-ultrasonic usergroups, at seven frequencies, in both earsSourceBetween group subjectWithin groupfrequencyEar

DF38

61

SS138.47

226.783.63

Mean Square3.64

37,793.63

F value3.63

37.623.61

Probabilityo,ooor

o,ooor0.0579

* Significance

Table IV. Sums and averages of the dBHL at theseven frequencies for both low- and high-ultrasonicuser groups

Low usageSumAverage25 dBHL orgreater

High usageSumAverage25 dBHL orgreater

Differenceof sums

500HZ

205

5

0

150

3.750

-55

1000HZ

205

5.1250

2105.25

0

5

2000HZ

12030

185

4,6251

65

3000HZ

1604

1

310

7.750

150

4000HZ

290

7.252

390

9,752

100

6000HZ

555

13.8756

675

16.8757

120

8000HZ

720

18

9

820

20.511

100

Note: Higher values denote poorer hearing.

loss will not occur. All of the soundsrecorded from the ultrasonic sealerin this study were above 70 dBA.Dental hygienists are not exposed tothis noise for 24 hours, but therepeated exposure appears to bedamaging. Findings of this studyand that of Setcos and Mahyuddinsuggest that dental hygienists thatuse the ultrasonic sealer frequentlyin practice might want to useearplugs or ear muffs lo protect theirhearing and prevent the accumulatedtrauma associated with repeatedexposure to ultrasonic noise."*

Hypothesis Two. Statistical analy-sis revealed that the ability to heardifferent frequencies yields unusualresults when comparing the hearingof high-ultra.sonie sealer users andlow-ultrasonic sealer users. At 500,1000, 2000, 4()(){), 6000, and 8000Hz, there was no statistically signif-icant difference in the hearing statusof the low frequency and high-fre-quency groups (F = 1.73. df = 1,P = 0.19); (F=0.04, df = \. P =0.84); (F = 0.32, df=\.P = 0.5765);(F =0.90, df = I. P = 0.34),(F ^0 .41, df = 1, P = 0.52),(F =0.41, df = I, P = 0.52). respec-tively. In contrast, statistically sig-nificant differences were found at3OOOH/(F = 5.81,df= \.P=0.02).The bearing threshold levels in thedental hygienists with high-ultra-sonic sealer usage was found to behigher than the threshold levels indental hygienists with a low-ultra-sonic sealer usage al the same fre-quency. This suggests a hearing lossassociated with ultrasonic usage at3000 Hz. The reason 3000 Hz isunique cannot be explained by thesedata. Frequencies ranging from3000 to 8000 Hz are most suscepti-ble to noise-induced hearing loss.

Zubiek and Tolentino looked atthe differences of hearing thresholdsin dentists and physieians.' Theyfound a statistically significant dif-ference in the thresholds in dentistsat 40()() Hz. Although dental officeequipment noises range from 20.000to 50,000 Hz, the frequency of thenoise emitted from the ultrasonic orother dental equipment will effectthe hearing thresholds around 3000

Volume 76 Issue IV Rili 2002 The Journal of Dental Hygiene 267

10 8000 Hz which falls into the com-munication range of frequency. Thisfinding was documented in iheresearch by Moller, Grevstad, andKristofferson^ on temporary thresh-old .shifts after exposure to ultra-sonic noise.

Hypothesis Three. Statisticalanalysis revealed that the dentalhygienists with high-ultrasonic usehad higher hearing thresholds whencompared to the dental hygienistswith low-Ieveis of ultrasonic use at3000 Hz. The finding suggests thathigh-ultrasonic .sealer usage isrelated to a hearing loss detected at3000 Hz but not at the other fre-quencies. Thi.s could be due to thesmall sample size that did not rep-resent the total range of possiblehigh- and low-usage scores thatcould occur in a larger sample orin the population of dental hygien-ists. When examining mean differ-ences of the high-ultrasonic usagegroup compared to the low-ultra-sonic usage group, the meansincreased in distance as the fre-quencies increased, except lor500 Hz (Table IV)

Hypothesis Four. Analysisrevealed no statistically significantdifference in the hearing when com-paring the subjects' right and leftears (F = 3.61, df= 1,P = 0.0579).This result may have been differentif more subjects participated,because the lack of significance isborderline. Perhaps the background-noise level plus the ultrasonic noisein the dental office is sufficient toeffect both ears similarly. Also,Zubick and Tolentino found that indentists, the ear closest to the noiseemitted from the dental hand pieceswas the ear that presented with ahigher threshold change.^ For exam-ple, a dentist that is right-handedwill have closer proximity to thesound in the left ear. and hence,greater hearing loss in the left ear.Since left- verses right-handednessof the subjects was not a variablecollected on the Dental HygieneWork History Questionnaire, thisfinding cannot be interpreted withconfidence. Right- verses Icft-hand-edness may have implications for

TabiG V. Summary of hearing status of dentalhygienists in the high-usage (N=20) and low-usage(N=20) Group

Low-usageGroup% of normalhearing% of hearingdeficits

High-usagegroup% of normalhearing% of hearingdeficits

500HZ

100%

0%

100%

0%

1000HZ

100%

0%

100%

0%

2000HZ

100%

0%

95%

5%

3000HZ

95%

5%

100%

0%

4000HZ

90%

10%

90%

10%

6000HZ

70%

30%

65%

35%

SOOOHz

55%

45%

45%

55%

differential hearing loss in dentalhygienists, and this variable needsto be explored in future research.

Conclusions

Based on the results and inter-pretation of this investigation, thefollowing conclusions are made:

1. Dental hygienists with a high fre-quency of ultrasonic sealer usehave a greater chance of experi-encing hearing loss than dentalhygienists with a low frequencyof ultrasonic sealer usage at3000 Hz.

2. Dental hygienists need to protecttheir hearing if the ultrasonic isused over an extended period oftime and/or if it is used frequentlyin practice.

3. At higher frequencies (>3000Hz), dental hygienists showdeclines in hearing status, regard-less of their ultrasonic sealerusage rates.

4. Both ears of dental hygienistsseem to be affected similarly bynoise exposure.

Considering the limitations anddesign of this study, future researchis needed using a larger sample ofdental hygienists and less than 5dBHL increments during hearingevaluations. Also, future researchers

should screen the dental hygienistsfor temporary threshold changes thatmight occur as a result of ultrasonicsealer noise exposure, and deter-mine hearing shifts that occur indental hygienists immediately afterultrasonic sealer use. It would alsobe valuable to test the effect of noisefrom ultrasonic sealer use on psy-chomotor skills and tactile sensitiv-ity. Other studies might include thedevelopment of a method lo meas-ure the cumulative effect of ultra-.sonic noise on dental hygienists thatuse mechanized instruments, deter-mination of how the source of ultra-sonic noise affects the hearing in theright and left ears differentially, andif wearing earplugs during ultra-sonic sealer use reduces temporarythreshold changes.

Based on this study's findings,ultrasonic sealer instrumentationhas some effect on hearing status ofdental hygienists. With increaseduse of ultrasonic instrumentation,more research should be conductedto determine if the ultrasonic sealercauses hearing loss and if so, atwhat rate. The findings in the .studydo not warrant the elimination oftbe ultrasonic sealer; the findingsunderscore the need for moreresearch to understand the risk ofhearing loss in dental hygienists thatuse mechanized instruments.

The Journal of Dental Hygiene Volume 76 Issue [V Fall 2002

Acknowledgement

This investigation was supportedin part by the American DentalHygienists' Association Institute forOral Health. The authors also thankDr. Dayanand N. Naik, Professor,Department of Mathematies andStatistics, Old Dominion University,for his expertise in data analysis.

References

Jennifer Dunning Wilson, BSDH,is a private practitioner, Suffolk,Virginia. Michele Leonardi Darby,BSDH, MS, is Eminent Scholar,university professor and gradu-ate program director at the GeneW. Hirschfeld School of DentalHygiene; S. Lynn Tolle, BSDH,MS, is a professor at the GeneW. Hirschfeld School of Dental

Hygiene; Joseph C. Sever, Jr,PhD, is an associate professor inthe Department of Early Child-hood, Speech Pathology andSpecial Education, alt at OldDominion University, Norfolk,Virginia.

1, National Institute of Occupational Research Agenda(1999), Hearing Loss. Available at: http://www.cdc.gov/niosh. Accessed August 7, 2001.

2, Stevens, M: An Earful: Is someone listening to the din ofoccupational noise exposure in dentistry? RDH1999:19:34-85.

3, Merrel HB, Claggett K: Noise pollution and hearing loss inthe dental office. Dental Assisting Journal^\992\6^i3):6•9.

4, Setcos JC, Mahyuddin A: Noise levels encountered indental clinical and laboratory practice, Int J Prosthodont1998:11:150-157.

5, Moller P, Grevstad A, Kristoffersen, T: Ultrasonic scalingof maxillary teeth causing tinnitus and temporary hearingshifts. J Clin Periodontol 1976;3:123-127.

6. Mittleman JS: The dental practitioner and hearing. JAmerDentAssoc 1965;58:56-58.

7. Zubiek T: Hearing loss and the high-speed dental hand-piece. Am J Public Health ^980\ 70: 633-5.

8. Baratz, R: Minimizing health hazards in the dental work-place a critical review. Dentistry 1990:10:9-5.

9. Holmberg, K, Landstrom, U, and Nordstrom, B: Annoy-ance and discomfort during exposure to high-frequencynoise from an ultrasonic washer. Percep Mot Skills1995;81:819-827.

ADHA Distance Research Student Internship/Faculty Fellowship

ADHA is pleased to announce the Distance Student Internship/Faculty Fellowship program for eligiblemembers during the 2002-2003 academic year. The purpose of the non-compensated position is to providean opportunity for a novice researcher to collaborate with central office staff in order to develop individualresearch abilities. In turn, this will increase the body of dental hygiene research and the corps of researchers.

ADHA will provide for one distance student intern/faculty fellowship during the 2002-2003 academicyear. While research will be conducted off-site, ADHA will provide the selected student intern or faculty mem-ber with research tools such as SPSS 10 software and the ADHA Research Database packet. ADHA alsowill provide research assistance with respect to survey design and data analysis. Conversely, the studentintern or faculty member will be expected to assist ADHA with survey studies, research analysis, and build-ing/expanding the ADHA research database. Research topics are related to, but not limited to, the ADHANational Research Agenda.

Applicants for the ADHA Student Internship/Faculty Fellowship are required to have Internet access andmust have taken a basic statistical course. An intern/fellow is required to complete research/educational proj-ects using SPSS windows software and thus should be familiar with this package. The applicants shouldeither have access to an SPSS program, or own a personal computer which meets the following require-ments: Windows 98/2000 Professional or NT 4.0 Workstation (Service Pack 5 and above) and above;586/P90 processor. For Windows 98 machines - 32 MB RAM (min, at least 64 MB are recommended); forWindows NT or 2000 - 64 MB RAM, min; 70 MB hard disk space; and SVGA monitor.

If you are interested in this unique opportunity, please contact ADHA and request an application form ordownload the form from the "Members Only" section of ADHA's Web site, www.adha.org. Send the com-pleted form and a copy of your resume to: Division of Research, American Dental Hygienists' Association,444 N. Michigan Avenue, Suite 3400, Chicago, IL 60611 or FAX to 312-467-1806.

The deadline for the application is January 2, 2003.

VolLimc76 Issue iV Fall 2002 The Journal of Dental Hygiene 269