2015.www14dddcom

ARTICLEOPENHearinglossanditsassociationwithoccupationalnoiseexposureamongSaudidentists:across-sectionalstudyBanderMAlabdulwahhab1,RaneemIAlduraiby2,MayAAhmed2,LamyaIAlbatli2,MaramSAlhumain2,NadaASoftah2andShazaSaleh3OBJECTIVES/AIMS:Dentalpractitionersarepronetohearinglossduetonoiseexposureencounteredindentalclinics.
Theaimofthisstudywastodeterminewhetherthepersistenthigh-frequencysoundsproducedbythedentalequipmentcouldcausehearingdecrementamongtheSaudidentalpractitioners.
MATERIALSANDMETHODS:Thiscross-sectionalstudyincluded38randomlyselectedSaudidentistsfromdifferentspecialtieswhowereexposedtonoiseduringworkinghoursand38individualsasacontrolgroup.
Theparticipantsunderwentfouraudiometricteststhatincludedanotoscopicexamination,tympanometry,puretoneaudiometryandthedistortionproductotoacousticemissions(DPOAE)test.
RESULTS:Thedatarevealedthat~15.
8%ofthedentistsand2.
6%ofthecontrolgrouphadsomehearingloss.
Nosignicantdifferencewasfoundbetweenthetwogroupsinthepuretoneaudiometrytest;however,qualitativeanalysisrevealedahigherpercentageofhearinglossamongthedentists'groupascomparedwiththeircontrolcounterparts.
AstatisticallysignicantdifferencewasfoundinDPOAEsbetweenthetwogroupsintheleftear(P=0.
002),andbetweentherightandleftears(P=0.
005).
DISCUSSION:Inthepresentcross-sectionalstudy,theprevalenceofhearinglossamongdentistsasassessedwiththepuretoneaudiometrytestwas15.
8%.
WhichwasinaccordancewithapreviousstudyperformedbyKhaimooketal.
,whichrevealedtheprevalenceofhearinglossindentalpersonneltobe17.
7%;however,nosignicantdifferenceswereobservedcomparedtothecontrolgroupinbothstudies.
Theotoacousticemissiontestintheleftearexhibitedsignicantchanges.
Thesechangescouldhavebeenduetothepresenceandcontinuityofthesoundsproducedbyhigh-andlow-velocitysuctiondevicesontheleftsideofthedentalunitknowingthat97%ofthedentistsarerighthanded.
CONCLUSION:Evidencesuggeststhatnoisefromdentalclinicscancausehearingproblems,whichhadagreatereffectontheleftearthantheright;however,theseproblemsarenotsevereinnature.
Noise-inducedhearinglosswasmoreprevalentamongthedentiststhanthecontrolgroup.
BDJopen(2016)2,16006;doi:10.
1038/bdjopen.
2016.
6;publishedonline4November2016INTRODUCTIONAccordingtothenationalinstituteforoccupationalsafetyandhealth,noisehasbeenidentiedasoneofthe10leadingcausesofwork-relateddiseasesorinjuries.
1Theamountofdamagedependsprimarilyontheintensityofthenoiseandthedurationoftheexposure.
Noise-inducedhearinglosscanbetemporaryfollowingshort-termexposuretonoise,withthereturnofnormalhearingafteraperiodofrest.
2Injurytotheearduetonoiseoccursintwodifferentmannersthatdependonthetypeofexposure.
High-levelshort-durationexposurestomorethan140decibel(dB,i.
e.
,aunitthatmeasuressoundintensity)canstretchthedelicateinnereartissuesbeyondtheirelasticlimitsandthenriportearthemapart.
Thistypeofdamage(acoustictrauma)developsrapidlyandcausesanimmediateandpermanenthearingloss.
Thesecondtypeofinjuryoccursbecauseofexposuretonoisebetween90and140dB,whichcausesmetabolicratherthanmechanicaldamagetothecochlea,andthisdamageisrelatedtothelevelanddurationofexposure.
3Thefactorsthataffectthedegreeandextentofhearingimpairmentincludetheintensityandtypeofnoise,theperiodofexposureeachday,totalworkduration,distancefromthesource,andindividualageandsusceptibility.
4TheOccupationalSafetyandHealthAdministrationoftheUnitedStateDepartmentofLabordemandsthatemployersdevelopandimplementanoise-monitoringprogrammewhenemployeesareexposedtonoiseequaltoorexceeding85dBformorethaneightworkinghours.
Ifthissituationoccurs,OccupationalSafetyandHealthAdministrationrequiresemployerstoinformemployeestoestablishandmaintainanaudiometrictestingprotocol,andtotrainworkershowtopreventoccupationalhearingloss.
Whenhazardousnoisehavenotyetbeeneliminated,OccupationalSafetyandHealthAdministrationalsorequiresemployerstoprovidehearingprotectionandtoensurethattheworkersutilisethatprotection.
2Puretoneaudiometryisgenerallytherstquantitativehearingtestthatisperformedtoassessthenatureanddegreeofhearinglossinadultsandchildrenover4yearsofagetoproperlyplanthemostappropriateinterventionbecausethistestdeterminesthefaintesttonesapersoncanhearatselectedfrequenciesfromlowtohigh.
5,61RestorativeDepartment,RoyalClinicsDepartmentofDentalServices,PartTimeFacultyatRiyadhCollegesofDentistryandPharmacy,Riyadh,SaudiArabia;2RiyadhCollegesofDentistryandPharmacy,Riyadh,SaudiArabiaand3KingFaisalSpecialistHospitalandResearchCentre,Riyadh,SaudiArabia.
Correspondence:LIAlbatli(lamyaalbatli@live.
com)Received21April2016;accepted27July2016www.
nature.
com/bdjopenOtoacousticemissions(OAEs)permittheearlydetectionofinnerearabnormalitiesthatareassociatedwithawidevarietyofdiseasesanddisorders,includingnon-pathologicetiologies,suchasnoiseexposureandaging.
Changesinouterhaircelllengthgenerateenergywithinthecochleathatcontributestohearingsensitivityandtheabilitytodistinguishsmalldifferencesinthefrequenciesofsounds.
7Peopleareaccustomedtoeverydaynormalnoisethatisconstantlypresentallaroundthem.
Similartootherworkingprofessionals,dentalpractitionersareexposedtomanyoccupa-tionalhazards;hearinglossisdenitelyonesuchoccupationalhazardduetothenoisethatisconstantlypresentduringtheirwork.
8Instrumentsinthedentalofce,suchashigh-speedturbinehandpieces,low-speedhandpiecesandhigh-velocitysuctiondevices,producedangerouslyloudnoisesthatmaycontributetohearingloss.
Long-termexposuretonoiselevelsofgreaterthan80–85dBisassociatedwithanincreasedriskofhearingloss.
9Kilpatrick10providedalistofthedBratingsofdifferentofceinstrumentsandequipmentandreportedlevelsof70–92dBforhigh-speedturbinehandpieces,86dBforultrasonicscalersand74dBforlow-speedhandpieces.
ApreviousstudybyAlwazzanetal.
11thatsoughttodeterminetheprevalenceofhearingproblemsamongdentistsinSaudiArabiaconcludedthatalldentalpersonnelexhibitroughlythesameincidenceofsymptoms,whichincludetinnitus,speechdiscriminationdifcultiesanddifcultieswithspeechdiscriminationinthepresenceofbackgroundnoise;moreover,dentaltechnicianswerefoundtobethemostaffectedgroup.
Theaimofthisstudywastodeterminewhetherthepersistenthigh-frequencysoundsproducedbythedentalequipmentcouldcausehearingdecrementamongtheSaudidentalpractitioners.
MATERIALSANDMETHODSStudygroupThiscross-sectionalstudywasconductedfromMarchtoDecember2015.
Thirty-eightdentistsfromdifferentspecialtieswhoworkatvariousgovernmentalhospitalsandprivateclinicsthatwereexposedtooccupationalnoiseandacontrolgroupofthirty-eightmatchednon-dentalprofessionalswererecruited;matchingwasdonebasedonage,genderandwhetherthatparticipantwasasmoker/non-smoker.
BothsamplegroupswereselectedrandomlywhileobservingthematchingcriteriaforthecontrolgrouponlyTheinclusioncriteriafortheexperimentalgroupincludeddentistswhohadbeenpracticingdentistryformorethan5years,whichincludes2yearsofpreclinicalpractice.
Forthecontrolgroup,theinclusioncriterionwasindividualswhohadnotbeenexposedtonoiseduringworkhours.
Bothsamplegroupsincludedindividualsbetweentheagesof25and40years.
Theexclusioncriteriaforbothgroupsincludeddailyloudmusicexposureformorethan3h,12historyofchroniceardisease,earsurgery,eartrauma,ototoxicdrugs,diabetes,previoussensorineuralhearingloss,anyhereditaryfactorsandtreatmentwithradiationorchemotherapy.
SampledesignThisstudyhasreceivedaformalreviewandapprovalfromtheethicscommitteeofRiyadhCollegesofDentistryandPharmacy.
Thepotentialparticipantswereapproachedeitherbytelephoneorinpersontoexplaintheeffectsofinstrumentnoiseonhearingandwereaskedtobepartofthiscross-sectionalstudy.
Afterprovidingwritteninformedconsent,theparticipantsunderwentanotoscopicexaminationandtympanometrybyanaudiologyspecialistatMagrabiHospitalsandCenters.
Ifabnormalndingswereobserved,theindividualwasexcludedfromfurthertesting.
Subsequently,theparticipantswhofullledtheinclusioncriteriacom-pletedademographicquestionnaireandunderwentpuretoneaudiometryanddistortionproductotoacousticemission(DPOAE)testing.
Thecollecteddataincludedagegroup(25–28,29–32,33–36and37–40yearsofage),gender,yearsofpractice(5–8,9–12or13years),actualnumberofhoursexposedtoloudnoiseeachweek(27,28–36or37h),daysofexposureperweek(3,4,5or6days)andwhetherthedentistsareleft-handedorright-handed(Table1).
TestbatteryPuretoneaudiometry.
Theaudiometricexaminationswereperformedusinganaudiometer(GSI61,GrasonStadler,Minneapolis,MN,USA)ina2*2mdouble-walledsoundbooththatwascalibratedaccordingtothestandardsoftheInternationalStandardOrganization(1964).
Airconduc-tionhearingthresholdsweremeasuredbypuretoneaudiometryatthefollowingfrequencies:250Hz,500Hz,750Hz,1kHz,2kHz,3kHz,4kHz,6kHzand8kHz.
Thepuretoneaveragesat4,6and8kHzreectthefrequencyrangethatismostsusceptibletonoise-inducedhearingloss.
Lossesofmorethan25dBinthesefrequenciesareusuallyconsideredabnormal(seeFigure1).
DistortionProductOtoacousticEmissions.
Otoacousticemissiontests(DPOAE,OAESystem,Pleasanton,CA,USA)areusedtodeterminecochlearstatusandparticularlyhaircellfunction.
13StatisticalanalysisTheIBMSPSScomputersoftware(StatisticalPackagefortheSocialSciences,version20.
0,SPSSInc.
,Chicago,IL,USA)forWindowswasusedtoperformtheanalyses.
The3PowerG3.
1software(G*Power:StatisticalPowerAnalysesHeinrich-Heine-UniversityDüsseldorf,Düsseldorf,Germany)wasusedtoconductpoweranalysisanddeterminethenumberoftherequiredsamplesize,whichwas25.
WilcoxontestwasusedtodeterminewhetherthedifferencesinthepuretoneaudiometryandOAEtestresultsweresignicantlydifferentbetweenthedentistsandthecontrolgroup.
Thelevelofsignicancewasdenedasequaltoorlessthan0.
05.
QualitativeanalysisofpuretoneaudiometryresultswasconductedbasedonthecharacterisationcriteriaproposedbyJensenetal.
,14whichwasusedtoinvestigatenoise-inducedhearinglossamongmusiciansofsymphonyorchestras.
Theyadoptedaratherstrictcriterionfornormalhearing,andmorespeciccriteriaforthedegreeofthenoisenotchifpresent(seeFigure2).
Table1.
Participants'demographicdataDemographicsn*=38;%GenderFemale15(39.
47)Male23(60.
52)Age(years)25–2817(44.
73)29–3211(28.
94)33–366(15.
78)37–404(10.
52)Workingdaysperweek32(5.
26)411(28.
94)519(50)66(15.
78)Workinghoursperweek(h)18–2713(34.
21)28–3611(28.
94)37h14(36.
84)Yearsofexperience5–819(50)9–1211(28.
94)138(21.
05)HandinessRight-handed37(97%)Left-handed1(3%)Abbreviation:n*,numberofdentists.
TheassociationofhearinglosswithoccupationalnoiseexposureBMAlabdulwahhabetal2BDJopen(2016)16006RESULTSTheagesofthe38dentistsandthe38participantsofthecontrolgrouprangedfrom25to40years,andthesampleincluded23(61%)malesand15(39%)females(Table1).
Theprevalenceofhearingloss(asassessedbyanydecreaseinhearingofmorethan25dBHLinthepuretoneaudiometrytests)wassixparticipantsinthegroupof38dentists(15.
8%)andoneparticipantinthecontrolgroupof38participants(2.
6%).
Whenthemorestringentcriteriaof15dBhearingloss(HL)14wasapplied,itrevealedthat29ofthedentists(76%)and23participantsfromthecontrolgroup(60%)hadsometypeofhearingloss.
Nosignicantdifferencewasobservedbetweenthetwogroupsinthepuretoneaudiometryresultsatthefollowingfrequencies:500Hz,1kHz,2kHz,4kHz,6kHz,and8kHz.
Moreover,therewerenosignicantdifferencesbetweendentistsandthematchedcontrolgroupintermsofnoise-inducedhearinglossintherightandleftearsseparatelyorinbothearscombined(Table2).
Theassessmentsofnoise-inducedhearinglosswiththeDPOAEtestsrevealednosignicantdifferencesbetweenthetwogroupsintherightear(P=0.
355),butasignicantdifferencewasfoundfortheleftear(P=0.
002)andinbothearscombined(P=0.
005)(Table2).
ThemeanvaluesforthepuretoneaudiometryandtheDPOAEtestsforbothdentistsandtheircontrolcounterpartsareillustratedinTables3and4.
QualitativeanalysisoftheaudiogramsasproposedbyJensenetal.
14showeddifferentpatternsamongthedentistsascomparedtotheircontrolcounterparts.
Fortherightear,5.
2%ofthedentistsexhibitedslopingloss,and60.
5%hadatloss.
Fortheleftear,7.
8%hadamoderatenotch,and50%hadatloss.
Ontheotherhand,42.
1%ofthecontrolgroupshowednormalhearingintherightear,and52.
6%hadnormalhearingintheleftear(seeTable5).
DISCUSSIONOccupationalnoise-inducedhearinglossisdenedasbilateralsensorineuralhearinglossthatdevelopsgraduallyoveraperiodofseveralyearsbecauseofexposuretocontinuousorintermittentloudnoiseintheworkplace.
15Hearinglossduetoagingorgeneticfactorsisnotpreventable.
Incontrast,noise-inducedhearinglosscanbepreventedbytheuseofprotectiveequipmentinnoisyenvironments,includingearFigure1.
Audiogramsshowingresultsmorethan25dBinhighfrequenciesintherightandleftear.
Figure2.
Criteriaforthecharacterizationofthepure-toneaudiogramsandthedegreeofthenoisenotchadaptedfromJensenetal.
14Table2.
Thedifferencebetweenthedentistsandthecontrolgroupinthepuretoneaudiometryand(DPOAE)resultsEarofparticipantDentist(n*=38)Control(n*=38)PuretoneaudiometryOtoacousticemissionP*-valueP*-valueLowfrequencyHighfrequencyRight38380.
3870.
3210.
355Left38380.
2930.
2170.
003Bothears(rightandleft)38380.
1730.
1320.
005Abbreviations:DOAE,distortionproductotoacousticemission;n*,numberofparticipants;P*,levelofsignicanceo0.
05.
TheassociationofhearinglosswithoccupationalnoiseexposureBMAlabdulwahhabetal3BDJopen(2016)16006plugsandearmuffs.
16Unfortunately,noneoftheparticipantsinthisstudywereusinganytypeofearprotection,potentiallyduetodiscomfort,fearthattheprotectivedevicemayinterferewithcommunication,inconvenience,negativefeedbackfromco-workersorpatientsandthebeliefthatnoiselevelsfromdentalinstrumentswillnotdamagetheirhearing.
16AstudythatsoughttodeterminetheprevalenceofhearingproblemsamongdentistsinSaudiArabiaconcludedthatalldentalpersonnelexhibitroughlysimilarincidencesofsymptoms;i.
e.
,16.
6%hadtinnitus,14.
7%hadspeechdiscriminationdifcultiesand63%hadproblemswithspeechdiscriminationinthepresenceofbackgroundnoise.
Theincidencesofsymptomweresimilarbecausealldentalpersonnelareexposedtosimilarnoiselevels.
11Theoccurrenceofhearinglossduetoprolongedexposuretonoiselevelsgreaterthan85dBwithouttheuseofanytypeofearprotectioniswelldocumentedintheliterature.
17–19Therefore,thenoisegeneratedinthedentalclinicshouldnotbeunderestimated.
20Thesourcesofdentalsoundsthatcanbetreatedaspotentiallydamagingtohearingincludehigh-speedturbinehandpieces,high-velocitysuctiondevices,ultrasonicscalersandothermixingdevices.
8Altinozetal.
21notedthatpersonnelwhoworkinnoisyenvironmentsshouldnotengageinnoisyactivitiesimmediatelyfollowingtheworkday.
Theseauthorsstatedthat'theearbeginstorecoveritshearingabilitywhenitisallowedtorest'.
Theprevalenceofnoise-inducedhearinglossamongdentalpersonnelhasbeenreportedtorangefrom7to16%intheliterature.
22–24ThestudyperformedbyKhaimooketal.
15revealedtheprevalenceofhearinglossindentalpersonneltobe17.
7%;however,nosignicantdifferenceswereobservedcomparedwiththecontrolgroup.
Inthepresentcross-sectionalstudy,theprevalenceofhearinglossamongdentistsasassessedwiththepuretoneaudiometrytestwas15.
8%,whichdidnotsignicantlydifferfromtheresultsobservedinthecontrolgroup.
Prevalencewithmorestringentcriteriaamongdentistswas76%.
Asignicantdifferencemayhavebeenobservedwithalargersample.
RegardingtheDPOAEsthatwereusedtocomparethetwogroups,theleftearexhibitedsignicantchangesthatcouldhavebeenduetochangesintheouterhaircelllengths.
Thesechangescouldalsohavebeenduetothepresenceandcontinuityofthesoundsproducedbyhigh-andlow-velocitysuctiondevicesontheleftsideofthedentalunit,consideringthat97%ofthedentistsinthisstudywereright-handed.
Undoubtedly,thedegreeofrisktothedentalpractitionerdependsuponcertainfactorssuchastheintensityofthesoundandthedurationofexposure.
8,25InanarticlewrittenbyKhaimooketal.
,15theauthorsstatedthatriskfactorsincludingtheyearsofexperienceandtheworkinghoursperweekinuencehearing.
Furtherstudyisrecommendedinthefuturetorevealriskfactorsrelatedtodentalspecialty,workinghoursandyearsofexperience.
Table3.
IllustratesdescriptivestatisticsofallthevariablesforthedentistsEarofparticipantDentist(n*=38)PuretoneaudiometryOtoacousticemissionLowfrequencyHighfrequencyStdMeanStdMeanStdMeanRight385.
9607711.
29166.
9284011.
64298.
1146712.
6194Left386.
242689.
93798.
0043411.
56007.
9547513.
5362Bothears(rightandleft)386.
1007010.
61477.
4357711.
60148.
0415813.
0778Abbreviation:n*,numberofdentists.
Table4.
IllustratesdescriptivestatisticsofallthevariablesforthecontrolgroupEarofparticipantControl(n*=38)PuretoneaudiometryOtoacousticemissionLowfrequencyHighfrequencyStdMeanStdMeanStdMeanRight385.
0061310.
40554.
8540510.
02298.
1629513.
2664Left385.
452268.
40117.
116119.
24167.
6838614.
9819Bothears(rightandleft)385.
295939.
40336.
063039.
63227.
9668814.
1242Abbreviation:n*,numberofcontrol.
Table5.
TheaudiogramresultsforbothgroupsaccordingtothecriteriaproposedbyJensenetal.
14forcharacterisationofthepuretoneaudiogramsEarofparticipantDentist,n=38(%)Control,n=38(%)NormalNotchmoderateNotchprofoundSlopinglossFlatlossRestNormalNotchmoderateNotchprofoundSlopinglossFlatlossRestRightear13(34.
2%)0(0%)0(0%)2(5.
2%)23(60.
5%)0(0%)16(42.
1%)0(0%)0(0%)1(2.
6%)21(55.
2%)0(0%)Leftear15(39.
4%)3(7.
8%)0(0%)0(0%)19(50%)0(0%)20(52.
6%)0(0%)0(0%)0(0%)18(47.
3%)0(0%)TheassociationofhearinglosswithoccupationalnoiseexposureBMAlabdulwahhabetal4BDJopen(2016)16006Todecreasetheriskofdevelopingnoise-inducedhearingloss,dentalpractitionersareencouragedtofollowtherecommenda-tionoftheADAcouncilondentalmaterialsanddevices,whichincludethefollowing:Preventivemeasuresfornoiseattenuationshouldbedirectedinthreeareas:optimummaintenanceofrotaryequipment,reductionoftheambientnoiselevelintheoperatoryandpersonalprotectionthroughtheuseofearplugs.
26Dentistsareadvisedtoperformregularannualaudiometrycheck-ups.
26Thisregulartestingshouldidentifythosewhohavebeguntolosetheirhearingbeforetheyacquiresignicantauditoryimpairments.
4,21,27Itisnecessarytoproducedentalhandpieceswithadditionalnoisecontrol.
Manufacturesareurgedtoimprovequalityintermsofdecreasingthesoundlevelsproducedbyhigh-speeddentalhandpieces.
Furthermore,frictionincreasesinoldandwornmachinery,whichresultsinincreasesinsoundlevelsandhighlightstheimportanceofmaintenanceandperiodicreplacement.
27Duringtheconstructionanddesignofthedentalclinic,considerationoftheuseofsound-absorbingmaterialsisalsorecommendedtodecreasethenoiselevel.
21Continuingeducationprogrammeswouldbebenecialintermsofdecreasingtheriskofnoise-inducedhearinglossamongdentalpersonnel.
Moreover,dentalschoolcurriculaoughttoincludeeducationaboutthedifferentoccupationalhazards.
11CONCLUSIONWithinthelimitationsofthisstudy,evidencesuggeststhatnoisefromdentalclinicscancausehearingproblems,whichhadagreatereffectontheleftearthantheright;however,theseproblemsarenotsevereinnature.
Noise-inducedhearinglosswasmoreprevalentamongthedentiststhanthecontrolgroup.
ACKNOWLEDGEMENTSThisresearchwassupportedbyAlbirCharityCenterinRiyadh.
TheauthorsthankRiyadhCollegesofDentistryandPharmacyfortheircontributionandsupport.
AswellasallofthedentistsfromKingFaisalSpecialistHospital&ResearchCenter,PrinceSultanMilitaryMedicalCentreandRiyadhCollegesofDentistryandPharmacyfortheircooperationandparticipationinthisresearchandwouldalsoliketoexpressdeepgratitudetoMagrabiHospitalsandCenters,Riyadhfortheirsupportandcollaboration.
TheauthorsareimmenselygratefultoDrAzizaAlJohar,SectionHeadandConsultantPediatricDentist,andMedicalDirectorofthecleftLipcraniofacialprogrammeKFSHRCforsharingherpearlsofwisdomduringthecourseofthisresearch.
COMPETINGINTERESTSTheauthorsdeclarenoconictofinterest.
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