Keywords
occupational noise - work environment - odontology - odontological instruments - hearing
loss
Palavras-chave
ruído ocupacional - ambiente de trabalho - odontologia - instrumentos odontológicos
- perda auditiva
Introduction
The noise induced hearing loss (NIHL) is a neurosensorial hearing loss predominantly
cochlear and of irreversible. This disease occurs due to a prolonged history of high
intensity noise exposure and has a gradual and progressive evolution. The hearing
loss occurs when it is not an impossibility of sound reception by lesion of the hair
cells of the cochlea and starts in high frequencies, generally in 4000 Hz (four kilohertz).
After noise exposure, the hearing loss tends to stabilize.
The NIHL achieves acute frequencies and the main difficulties include hearing bells
and telephone calls. With the further advance of the disease, there comes difficulties
in all frequencies, therefore the diagnosis is many times delayed.
This is the occupational disease of highest incidence and the major evitable cause
of hearing loss worldwide, according to Lopes Filho and Campos
[1]. The exposed individuals periodical controls and the sound intensity levels permitted
by 8 hours of daily exposure to the noise are maximally of 85 decibels and are well
regulated according to Annex I of the regulating standards of numbers 7 and 15 of
the Brazilian Labor Law as provided in [Table 1]
[2]
[3].
Table 1.
Annex I of the Regulating Standard no. 15: limits of tolerance for continuous or intermittent
noise.
|
Level of noise dB (NA)
|
Maximum daily exposure permitted
|
|
85
|
8 hours
|
|
86
|
7 hours
|
|
87
|
6 hours
|
|
88
|
5 hours
|
|
89
|
4 h and 30 min
|
|
90
|
4 hours
|
|
91
|
3 h and 30 min
|
|
92
|
3 hours
|
|
93
|
2 h and 40 min
|
|
94
|
2 h and 15 min
|
|
95
|
2 hours
|
|
96
|
1 h and 45 min
|
|
98
|
1 h and 15 min
|
|
100
|
1 hour
|
|
102
|
45 minutes
|
|
104
|
35 minutes
|
|
105
|
30 minutes
|
|
106
|
25 minutes
|
|
108
|
20 minutes
|
The dentists are health professionals exposed in their offices to several noises produced
and emitted by high and low rotation pens, suction tube, compressor, spitter, straight
piece, photopolymerizer, autoclave and air-conditioning, however, the first ones are
considered to have a major harmful potential to the human ear. Therefore, different
studies have analyzed the relationship between the intensity of the noises in the
dental office, the professional hours, the time of professional activity and the hearing
loss in these professionals[4]. What we confirm in most of them is that even exposed to sound intensity levels
lower than 85 decibels, but with a time of professional exercise over five years,
they present with hearing losses[5]
[6].
To prevent the unleashing or aggravation of occupational hearing loss an annual audiologic
control through at least one audiometry, in addition to individual protection should
be performed. [Table 1] below shows Annex I of the Regulating Standard number 15 that establishes the tolerance
limits for continuous and intermittent noise[3].
The objectives of this work are: 1) measuring the noise intensities in public and
private dental offices, from pens driven by high rotation engine and the environment
basal noise, checking whether these have harmful intensities for the human ear; 2)
comparing the results obtained between the public and private service.
Method
The measurement places were dental offices of Health Basic Units (UBS) or other public
services and private offices in Jundiaí, State of São Paulo, Brazil, in which the
professional, the assistant and the patient are daily exposed after contact and agreement
of the participants. Received at SISNEP, the work was approved by the Ethics Committee
in Research of the Teaching Institution under number 314/2008. The noise intensity
measurement was made in four dental offices of the public health system and at four
private offices. For measurement, we used a Minipa® decibelimeter, model MSL-1352C, from USA, set up as follows: Slow response time that
measured the level of noise in decibels (dBNA), with scale of 30 to 130 dB, for a
period of five minutes at a distance of twenty centimeters from the pen and the high
rotation engine, of the Dabi Atlante®, Kavo®, and Micro Dente ®, used by different professionals in their offices. The environmental intensity was
initially measured in each office, during five minutes and this value was called Basal.
Then we carried out the measurement of the intensity of the noise emitted by the above
mentioned equipment, also for five minutes. In these two scenarios, the average in
decibels of the noise intensity was calculated.
No statistical analysis of the results was carried out due to the type of graphic
register of the decibelimeter used and the fact that the main objective of the study
was that of determining if the intensities measured would be lesive for the human
ear.
Results
Dental offices of the public health system of Jundiaí ([Graphic 1]):
Graphic 1. Average intensities in decibels of the basal noise and the high rotation engines
measured in four odontological offices of the public service in Jundiaí - SP.
-
Basal, with environmental noise (conversation): average of 56.4 dB. High rotation
engine (Dabi Atlante®, time of use of four and a half years, time of exposure of 3 hours a day), average
of 77.2 dB;
-
Basal, with environmental noise (conversation, fan and consultation at the chair beside):
average of 61.7 dB. High rotation engine (Dabi Atlante®, time of use of four years, time of exposure of 4 hours a day), average of 73.7 dB;
-
Basal, with environmental noise (conversation): average of 67.1 dB. High rotation
engine (Kavo®, time of indefinite use, time of exposure, one third of the professional hours),
average of 75.0 dB;
-
Basal, with environmental noise (radio and fan): average of 63.6 dB. High rotation
engine (Kavo®, time of use longer than one year, indefinite exposure time), average of 77.3 dB.
Private dental offices of Jundiaí ([Graphic 2]):
Graphic 2. Average intensities in decibels of the basal noise and the high rotation engines
measured in four private dental offices in Jundiaí - SP.
-
Basal, with environmental noise (conversation, suction tube, ambient noise): average
of 60.7 dB. High rotation engine (Kavo®, time of use of one year, time of exposure of three hours a day), average of 79.1 dB;
-
Basal, with environmental noise (conversation, suction tube, ambient noise): average
of 60.7 dB. High rotation engine (Kavo®, time of use of one year, time of exposure of three hours a day), average of 83.1 dB;
-
Basal, with environmental noise (Air-conditioning, suction tube and conversation):
average of 58.4 dB. High rotation engine (Kavo®, time of use of two years, time of exposure of three hours a day), average of 75.5 dB;
-
Basal, with environmental noise (environmental noise, conversation, suction tube):
average of 63.0 dB. High rotation engine (Micro Dente®, time of use of five years, time of exposure of 4 hours a day), average of 76.0 dB.
Discussion
The concern with the hearing losses of occupational origin is due to the fact that
this disease is the occupational disease of the highest incidence and evitable cause
of hearing loss worldwide. After the noise exposure is over it tends to stabilize,
and the detection is its most effective preventive action. Noises emitted by household
appliances that caused the authorities' concern in the past as for the maintenance
of the auditory health in the houses, restaurants and other places where such appliances
are used have been reduced with technological enhancement[7]. Therefore, the old high rotation engines of dental use also presented a sound limit
over 85 decibels and there are many works in the literature confirming hearing losses
in these professionals; however, the modern engines, under periodical technical maintenance
and suitably lubricated have a noise level lower than 85 decibels; according to Scully et al[5], this finding corresponds to what we noticed in the equipment analyzed. [Graphic 1] shows the mean intensities in decibels of basal noise and of the high rotation engines
measured in the dental offices of the public service of the city of Jundiaí - SP,
and [Graphic 2] shows the same findings in private dental offices in the city of Jundiaí - SP, and
none of the values extrapolates the limit of 85 dB. Even taking into account that
the professionals may have other operating sites and these findings correspond to
a single work period, the maximum provided by the Standard, that is of 85 dB, is regarded
for 8 hours of ongoing exposure. Such findings encourages us for they are according
to the Brazilian Law. Such confirmation sets our minds at ease under the preventive
aspect of the occupational auditory losses in professionals of the dental area, that
some years ago used to be a reason for large concern of the professionals in the preventive
medicine field[4]. As regards to all the averages of basal noise and the high rotation engines, [Graphics 3] and [4] compare the findings in the dental offices of private and public services in the
city of Jundiaí - SP, that certifies the mean basal noise was 2.4% higher than the
public service due to the elevated environmental noise, while the average noise of
the high rotation engines was 3.3% higher in the private clinic offices. For this
reason, efforts must be taken to abandon and replace the archaic dental equipment.
Graphic 3. Comparison between the total of the averages of the basal noise of dental offices
of private and public services in Jundiaí - SP.
Graphic 4. Comparison between the total of the averages of high rotation engines of dental offices
of private and public services in Jundiaí - SP.
Despite there are works that suggest hearing losses in dentists exposed to noises
lower than 85 dB, the noises emitted by the equipment measured in this work are within
the limits accepted for not to use NIHL, according to the Brazilian Law, that enables
professional re-adaptations as their time of exposure.
Conclusions
-
The measured noise intensities from equipment used in both public and private dental
offices are below the limits considered to be harmful to the hearing health.
-
In the public service, the basal medium noise intensity is higher than that of the
private clinics, however the one of the high rotation motors is higher in the private
clinics.
