Neuropathy in female dental personnel exposed to high frequency vibrations

A Review of Hand-Arm Vibration Studies Conducted by US NIOSH since 2000

Studies on hand-transmitted vibration exposure, biodynamic responses, and biological effects were conducted by researchers at the Health Effects Laboratory Division (HELD) of the National Institute for Occupational Safety and Health (NIOSH) during the last 20 years. These studies are systematically reviewed in this report, along with the identification of areas where additional research is needed. The majority of the studies cover the following aspects: (i) the methods and techniques for measuring hand-transmitted vibration exposure; (ii) vibration biodynamics of the hand-arm system and the quantification of vibration exposure; (iii) biological effects of hand-transmitted vibration exposure; (iv) measurements of vibration-induced health effects; (iv) quantification of influencing biomechanical effects; and (v) intervention methods and technologies for controlling hand-transmitted vibration exposure. The major findings of the studies are summarized and discussed.

Vibration-induced injuries in workers exposed to transient and high frequency vibrations

Background

The risk of developing vibration white fingers and neurosensory symptoms increases with the duration and intensity of the exposure. The aim of this study was to investigate the risk of developing vibration white fingers (VWF), neurosensory symptoms and musculoskeletal disorders among workers exposed to transient and high frequency vibrations.

Methods

The study included 38 vibration exposed workers from a loader assembly plant in Sweden (30 males and 8 females). All participants answered questionnaires and had a structured interview about work and medical history. A following medical examination included the determination of vibration and temperature perception thresholds and musculoskeletal symptoms in the neck, shoulder, elbow and hands. The individual vibration exposure expressed as A (8)-values and vibration exposure in minutes per day, were obtained from questionnaires answered by the participants.

Results

The prevalence of VWF was 30% among the male workers and 50% among the females. The corresponding prevalence of neurosensory symptoms was 70% among the males and 88% among the females. Musculoskeletal findings were common among the male workers. Dominant symptoms/syndromes were tension neck syndrome, biceps tendinitis, carpal tunnel syndrome and ulnar entrapment in hand/wrist. A total of 32 diagnoses were observed among the male workers and four diagnoses among the female workers. Numbness in fingers and age had the strongest impact on perceived work ability.

Conclusions

ISO 5349-1 considerably underestimates the risks of VWF for this group of workers exposed to transient and high frequency vibrations. It is therefore important to develop a risk assessment standard also covering this frequency range.

Awareness of ergonomics & work-related musculoskeletal disorders among dental professionals and students in Riyadh, Saudi Arabia

[Purpose] The present research was undertaken to investigate the awareness of ergonomics and prevalence of musculoskeletal disorders among dental professionals and students in Riyadh, Saudi Arabia and to find a mean to decrease the prevalence of musculoskeletal disorders in the future. [Subjects and Methods] A self-administered survey was prepared and disseminated to dental professionals and students in Riyadh, Saudi Arabia. The questionnaire was focused on the awareness of ergonomics and musculoskeletal disorders. Five hundred and sixty-one participants were included in this survey. [Results] Within the present study, significant differences were noticed among specialists, general practitioners and undergraduate students. Work load (risk factors) had great influence on musculoskeletal disorders in all dental practitioners, and lower back pain was the most common reported disorder among all practitioners. [Conclusion] Most of the respondent dentists seem to work in conditions that aggravate disorders of the musculoskeletal system, the increased prophylactic remedies were directly associated with the increase of the musculoskeletal disorders symptoms. All dentists regardless of their dental specialties, are recommended to apply principles of ergonomics in their daily practice. Moreover, dental ergonomics should be taught to undergraduate students and strictly implemented in the clinics to provide comfortable working environment for all dental professionals.

The effects of physical and psychosocial factors and ergonomic conditions on the prevalence of musculoskeletal disorders among dentists in Malaysia

BACKGROUND

Musculoskeletal disorders (MSDs) have been recognized as one of the main occupational health problems for dentists. Many studies have suggested that dentists experience work-related pain or discomfort in the neck, shoulder, and back, as well as in other parts of the body.

OBJECTIVE

This study aimed to examine the relationship between specific physical and psychosocial factors and/or ergonomic conditions on MSD symptoms among dentists in Malaysia.

METHODS

A group of 85 dentists was asked to complete a questionnaire to determine whether their complaints were related to physical and psychosocial factors and/or ergonomic conditions in their practices.

RESULTS

Among the nine reviewed body areas, the shoulders were most often affected by symptoms of MSDs (92.7%). Moreover, MSDs of the neck and upper back were most likely to prevent these practitioners from engaging in normal activities (32.9%). In general, no significant differences were found in the prevalence of MSD symptoms in relation to gender, age, body mass index, years in practice, number of patients, and frequency of breaks.

CONCLUSIONS

Our results were consistent with those reported in other studies that focused on MSD problems among dentists in other countries. To reduce the prevalence of MSDs, more attention should be paid to instituting ergonomically sensible approaches in the dental practice setting.

Health effects associated with occupational exposure to hand-arm or whole body vibration

Workers in a number of different occupational sectors are exposed to workplace vibration on a daily basis. This exposure may arise through the use of powered-hand tools or hand-transmitted vibration (HTV). Workers might also be exposed to whole body vibration (WBV) by driving delivery vehicles, earth moving equipment, or through use of tools that generate vibration at low dominant frequencies and high amplitudes, such as jackhammers. Occupational exposure to vibration has been associated with an increased risk of musculoskeletal pain in the back, neck, hands, shoulders, and hips. Occupational exposure may also contribute to the development of peripheral and cardiovascular disorders and gastrointestinal problems. In addition, there are more recent data suggesting that occupational exposure to vibration may enhance the risk of developing certain cancers. The aim of this review is to provide an assessment of the occupations where exposure to vibration is most prevalent, and a description of the adverse health effects associated with occupational exposure to vibration. This review will examine (1) various experimental methods used to measure and describe the characteristics of vibration generated by various tools and vehicles, (2) the etiology of vibration-induced disorders, and (3) how these data were employed to assess and improve intervention strategies and equipment that reduces the transmission of vibration to the body. Finally, there is a discussion of the research gaps that need to be investigated to further reduction in the incidence of vibration-induced illnesses and injuries.

Musculoskeletal Disorders and Mental Health-related Issues as Occupational Hazards among Dental Practitioners in Salem City: A Cross-sectional Study

Background:

Like in any other profession, dental surgeons are also afflicted by many occupational health hazards such as Musculoskeletal disorders (MSD) and mental health related issues.

Aims:

To assess the distribution of MSD and mental health related issues amidst dentists in Salem City according to age, sex and number of working hours per week.

Objectives:

A survey was organized to check the rate of occurrence of these occupational health hazards among dental practitioners in Salem city.

Materials and Methods:

The study was conducted among one hundred and fifty dentists practicing in Salem City in the form of questionnaire. Dentists were asked about any occupational disease that they suffered related to a musculo–skeletal pain and its location whether in the back, upper limbs or lower limbs. In addition to this, dentists were asked about mental stress that they had experienced.

Results:

MSD showed higher rate of prevalence compared to mental health related issues.

Conclusion:

The application of preventive measures is necessary, in view of the high rate of these disorders in the society of dental practitioners.

Do dental students have a neutral working posture?

BACKGROUND

Dentists are susceptible to Musculoskeletal Disorders (MSDs) due to prolonged static postures. To prevent MSDs, working postures of dental students should be assessed and corrected in early career life.

OBJECTIVE

This study estimated the risk of developing musculoskeletal disorders in dental students using Rapid Upper Limb Assessment (RULA) tool.

METHODS

A number of 103 undergraduate dental students from fourth and fifth academic years participated. Postures of these students were assessed using RULA tool while working in the dental clinic. They also answered a questionnaire regarding their knowledge about postural dental ergonomic principles.

RESULTS

The majority of the students (66%) were at intermediate and high risk levels to develop MSDs and their postures needed to be corrected. There was no significant correlation between RULA score and gender, academic year and different wards of dental clinics. There was no significant correlation between knowledge and RULA scores.

CONCLUSIONS

Dental students did not have favorable working postures. They were at an intermediate to high risk for developing MSDs which calls for a change in their working postures. Therefore students should be trained with ergonomic principles and to achieve the best results, ergonomic lessons should be accompanied by practice and periodical evaluations.

"Musculoskeletal problem": Its prevalence among Iranian dentists

Objectives:

Musculoskeletal problems (MSPs) are a major complication for practitioners in the field of dentistry. The present study is designed to define the prevalence of MSPs among Iranian dentists.

Materials and Methods:

This was a cross-sectional survey conducted on 600 dentists. The questions were about demographic characteristics, headache, and physical problems of different parts of the body. Data were analyzed using logistic regression analysis.

Results:

Of all dentists studied, 67.5% had physical problems. These MSPs were observed in neck (51.87%), wrist (92.96%), waist (11.11%), and shoulder (7.40%) of the practitioners. Some practitioners took leave of absence (18.52%), while others (7.40%) underwent medical care. There was a direct correlation between age (P = 0.0001), high body mass index (BMI; P = 0.021), total number of daily under-care patients (P = 0.002), and little physical activity (P = 0.0001) with MSPs.

Conclusion:

The prevalence of MSPs is very high among dentists. Awareness about preventive care is necessary for dentists. The dental curriculum also should address ergonomic issues for dental educators.

Removal of simulated biofilm: a preclinical ergonomic comparison of instruments and operators

BACKGROUND

Periodontal scaling might cause musculoskeletal disorders, and scaling instruments might not only have different effectiveness and efficiency but also differ in their ergonomic properties. The present study assessed ergonomic working patterns of experienced (EO) and less experienced operators (LO) when using hand and powered devices for periodontal scaling and root planning.

METHODS

In an experimental study using periodontally affected manikins, sonic (AIR), ultrasonic (TIG) and hand instruments (GRA) were used by 11 operators (7 EO/4 LO) during simulated supportive periodontal therapy. Using an electronic motion monitoring system, we objectively assessed the working frequency and positioning of hand, neck and head. Operators' subjective evaluation of the instruments was recorded using a questionnaire.

RESULTS

Hand instruments were used with the lowest frequency (2.57 ± 1.08 s(-1)) but greatest wrist deviation (59.57 ± 53.94°). EO used instruments more specifically than LO, and generally worked more ergonomically, with less inclination of head and neck in both the frontal and sagittal planes, especially when using hand instruments. All groups found hand instruments more tiring and difficult to use than powered instruments.

CONCLUSION

Regardless of operators' experience, powered instruments were used more ergonomically and were subjectively preferred compared to hand instruments.

CLINICAL RELEVANCE

The use of hand instruments has potential ergonomic disadvantages. However, with increasing experience, operators are able to recognise and mitigate possible risks.

Prevalence of Upper Extremity Musculoskeletal Disorders in Dentists: Symptoms and Risk Factors

Aim. The purpose of the present research was to examine the factors that lead to musculoskeletal disorders in dentists by assessing their posture using RULA method. Materials and Methods. In this cross-sectional study, 130 dentists (84 male and 46 female) participated. The posture of the subjects during their normal workload was recorded by using the RULA method, and the range of musculoskeletal pains by using the Nordic Musculoskeletal Questionnaire (NMQ), and individual and professional data was assessed by a demographics questionnaire. All tests were performed at the P < 0.05 level. Results. Assessment of the physical status of the subjects showed that 82.8% of subjects were at high risk of musculoskeletal disorders. The majority of musculoskeletal pains were in the neck (55.9%) and the shoulder (43.8%). Moreover, 68.9% of the subjects had experienced pain at least once over the last year. Significant relationships were observed between musculoskeletal pain and daily work hours (P = 0.07) and number of patients (P = 0.02), but the pain was not significantly associated with BMI and experience. Conclusion. The present findings showed that unsuitable posture of dentists during work has a considerable effect on musculoskeletal disorders. Therefore, further investigation is required to avoid the detrimental effects of wrong posture.

Work-related musculoskeletal disorders among dental professionals in Saudi Arabia

[Purpose] Musculoskeletal disorders are common causes of work-related disability in different professions involving the frequent practice of lifting, stooping, twisting, prolonged sitting, or standing. The dental profession is one such profession. Our aim was to determine the prevalence of work-related musculoskeletal disorders among dental professionals in Saudi Arabia, the factors associated with them, and their consequences and to propose preventive measures for them. [Subjects and Methods] A self-administered online questionnaire was sent to 225 members of the Saudi Dental Association. It included questions on demographic and professional characteristics, general medical history, and history of work-related musculoskeletal disorders before and after joining the dental profession. [Results] The questionnaire was completed by 65% of the respondents. Among them 85% reported that they had developed some pain due to work after joining the dental profession, and 42% reported that they were suffering pain at the time of the survey. Besides lower back, shoulder, and neck regions, the hands, upper back, and other regions like the elbows, buttocks, thighs, leg, and feet were areas in which they pain. [Conclusion] The prevalence of work-related musculoskeletal disorders among dental professionals in Saudi Arabia is high, affecting their daily activities, sometimes even forcing them to change their work setting. Age, gender, specialty of work, work setting, number of contact hours with patients, etc., were all found to be related to their work-related pain. We need to emphasize the role of ergonomics, counseling, proper techniques of patient handling, etc., during the training of dental professionals so that they can work efficiently.

Insights into ergonomics among dental professionals of a dental institute and private practitioners in hubli-dharwad twin cities, India

Background

To assess the knowledge, attitude, and practice of ergonomics among dental professionals of Hubli–Dharwad twin cities, India.

Methods

Investigator-developed, self-administered, closed-ended questionnaire assessing knowledge, attitude, and practices regarding ergonomics during dental practice was filled in by undergraduates, house surgeons, postgraduates, and faculty members of dental institutions and private practitioners from Hubli–Dharwad twin cities.

Results

Data were collected from a total of 250 participants, 50 belonging to each academic group. Overall mean knowledge, attitude, and practice scores were 52%, 75%, and 55%, respectively. Significant correlation was found for age with attitude (χ² = 10.734, p = 0.030) and behavior (χ² = 12.984, p = 0.011). Marital status was significantly associated with all the three domains; knowledge (χ² = 29.369, p = 0.000), attitude (χ² = 29.023, p = 0.000), and practices (χ² = 13.648, p = 0.009).

Conclusion

Participants had considerable awareness and behavior toward ergonomics in dental practice. The high attitude score indicates stronger acceptance of ergonomics principles and guidelines during routine dental procedures. The current study highlights the situation of ergonomics in dental practice in the form of knowledge, attitude, and practices.

Mechanized scaling with ultrasonics: Perils and proactive measures

Mechanized scaling for plaque removal is a routine procedure in the practice of periodontics. Though it appears innocuous by itself, there are retinues of hazards associated with it on various organ systems in the body. Some of these unwanted effects and measures to avoid or ameliorate the same are elaborated here. Exposure to ultrasonic scaling is inevitable before any other treatment procedure. Aerosol contamination, vibrational hazards, thermal effects on the dental pulp, altered vascular dynamics, disruption in electromagnetic device, diminished hearing and dental unit waterline contamination are some of the probable off-shoots a patient has to bear. Uses of barrier devices, proper attention to usage of equipment, protection for ear and water treatment are few of solutions for the same. Though documented evidence for the existence of all effects is lacking, it is never the less significant for the overall safety of the patient. A conscientious clinician should therefore inculcate the available steps to overcome the hazards of ultrasonic scaling.

Musculoskeletal pain reports among Mashhad dental students, Iran

Dental practitioners are susceptible to Musculoskeletal Disorders (MSDs). The symptoms may begin from education courses. The aim of this study was to assess prevalence of musculoskeletal pain reports and correlated factors among the Mashhad Dental School students, Iran. A total of 177 undergraduate and postgraduate dental students, who were involved in educational clinical training, completed a questionnaire focusing on pain reports of different body anatomical regions. Variables such as gender, academic grade, academic year, clinical working hour, regular exercise times and also pain characteristics including pain duration intensity and frequency were evaluated. As results 82% of undergraduate students and 90% of postgraduate students reported body pain in at least one region. The most prevalent pain locations were: chest/shoulder (46.9%), head/neck (41.8%), middle back (33.9%) and right hand (25.4%). Severity of reported pain was increased due to performing dental work, increased working stress and working fatigue. Regular exercise was associated with alleviated some pain characteristics. As conclusions musculoskeletal pain reports were highly prevalent among dental students. Attention to prevention of musculoskeletal disorders should be considered as priority in dental schools. For dental students exercise training courses for strengthening muscles of shoulder/chest, neck and back are necessary.

Physical workload in neck, shoulders and wrists/hands in dental hygienists during a work-day

Physical workload was recorded by electromyography, inclinometry and goniometry for twelve female dental hygienists during authentic work. Their work was, in relation to other types of work, characterised by pronounced head flexion (90th percentile 46°), high loads on the forearm extensor muscles (90th percentile 23% and 18% of maximal EMG (MVE), for the right and left sides, respectively), average loads on trapezius muscles (90th percentile 15% and 14% MVE), average arm elevation (99th percentile 83° and 72°) and average wrist flexion and velocities (50th percentiles 17° of extension and 7.3°/s, for the right side). Manual scaling and machinery (use of ultrasonic scaling and hand-pieces) showed higher loads on the trapezius muscles, regarding muscular rest, as well as the 10th and 50th percentiles, than the other tasks, and for the forearm extensor muscles, an almost complete lack of muscular rest (0.1% time), and much higher loads regarding the 10th and 50th percentiles. Further, more pronounced head flexion and lower head and upper arm velocities were found, indicating more constrained postures for the neck and shoulders for the manual scaling and machinery. Use of ultrasonic scaler reduced the 50th percentile loads on the right forearm extensor muscles, but had no effect on the fraction of muscular rest and on the 10th percentile load. These findings are consistent with the high prevalences of musculoskeletal disorders among dental hygienists.

Analysis of kinematic, kinetic and electromyographic patterns during root canal preparation with rotary and manual instruments

Objective

This study assessed the muscular activity during root canal preparation through kinematics, kinetics, and electromyography (EMG).

Material and Methods

The operators prepared one canal with RaCe rotary instruments and another with Flexo-files. The kinematics of the major joints was reconstructed using an optoelectronic system and electromyographic responses of the flexor carpi radialis, extensor carpi radialis, brachioradialis, biceps brachii, triceps brachii, middle deltoid, and upper trapezius were recorded. The joint torques of the shoulder, elbow and wrist were calculated using inverse dynamics. In the kinematic analysis, angular movements of the wrist and elbow were classified as low risk factors for work-related musculoskeletal disorders. With respect to the shoulder, the classification was medium-risk.

Results

There was no significant difference revealed by the kinetic reports. The EMG results showed that for the middle deltoid and upper trapezius the rotary instrumentation elicited higher values. The flexor carpi radialis and extensor carpi radialis, as well as the brachioradialis showed a higher value with the manual method.

Conclusion

The muscular recruitment for accomplishment of articular movements for root canal preparation with either the rotary or manual techniques is distinct. Nevertheless, the rotary instrument presented less difficulty in the generation of the joint torque in each articulation, thus, presenting a greater uniformity of joint torques.

Dental practice and musculoskeletal disorders association: a look at the evidence

Disorders localized to the musculoskeletal system are a common problem among dental personnel. This study has the aim of surveying epidemiological studies reporting positive associations between dental practice and musculoskeletal disorders (MSKDs). The focus was to evaluate the size of reported risk increase and the extent to what alternative causal explanations were considered. Reports with significant links (p value <.05) were systematically selected from 2 electronic databases. Twenty-five studies were identified. Risk measures were reported in 8 studies, and all of them presented weak associations. The impact of at least 1 competing explanations was analyzed in 32% of studies, but adjustment was considered not adequate in half of them. The evidence on dentistry as a profession with potential risk for development of MSKDs remains questionable. Further research is needed to more carefully elucidate the risk and the impact of MSKDs in this particular occupational group.

Prevalence and correlates of musculoskeletal disorders among Australian dental hygiene students

INTRODUCTION

Although musculoskeletal disorders (MSD) have been identified as a significant occupational health issue for dental hygienists, few studies have explored this problem among the dental hygiene student population.

AIM

The aim of this study was to investigate the prevalence and correlates of MSD among a selection of undergraduate dental hygiene students in Australia.

METHODOLOGY

A self-reporting questionnaire was distributed to dental hygiene students at an Australian university during 2008, from which a response rate of approximately 72% was achieved.

RESULTS

Musculoskeletal disorders were most commonly reported by students at the neck (64.29%), lower back (57.94%) and shoulder (48.41%) regions. Logistic regression indicated various correlations with MSD. Students who did not undertake regular exercise every week experienced an increased risk of lower back pain [Odds Ratio (OR): 4.88, 95% Confidence Interval (CI): 1.75-14.9]. Students undertaking 16-20 h of desk-based study per week were much more likely to report neck pain (OR: 19.7, 95% CI: 1.34-378.94). Working 6-10 h on a computer each week was a risk factor for shoulder (OR: 7.03, 95% CI: 1.42-39.49) and upper back pain (OR: 5.29, 95% CI: 1.21-25.56).

CONCLUSIONS

Overall, this study suggests that MSD are a reasonably common problem for dental hygiene students in Australia. As such, further studies are required to establish epidemiological patterns of MSD, and our profession will need to carefully consider preventive strategies to help minimize the impact of this important occupational health issue on the next generation of dental hygienists.

Assessment of dental student posture in two seating conditions using RULA methodology - a pilot study

OBJECTIVES

To assess dental students' posture on two different seats in order to determine if one seat predisposes to a difference in working posture.

DESIGN

A between-subject experimental design was selected.

SETTING

The study was undertaken at the University of Birmingham School of Dentistry in 2006. Subjects (materials) and methods Sixty second year dental students at the University of Birmingham who were attending their fi rst classes in the phantom head laboratory were randomly selected and allocated to two different seats (30 Bambach Saddle Seats and 30 conventional seats). Students were trained in the use of the seats. After ten weeks, the students were observed, photographs were taken by the researcher and these were assessed using Rapid Upper Limb Assessment (RULA).

MAIN OUTCOME MEASURES

The posture of the students was assessed using the RULA. Each student was given a risk score. A Mann Whitney test was used for statistical analysis.

RESULTS

The results indicated that the students using the conventional seat recorded significantly higher risk scores (p <0.05) when compared with the students using Bambach Saddle Seat, suggesting an improvement in posture when using the Bambach Saddle Seat.

CONCLUSION

RULA has identified that dental students using a Bambach Saddle Seat were able to maintain an acceptable working posture during simulated dental treatment and this seating may reduce the development of work-related musculoskeletal disorders.

Occupational health problems in modern dentistry: a review

Despite numerous technical advances in recent years, many occupational health problems still persist in modern dentistry. These include percutaneous exposure incidents (PEI); exposure to infectious diseases (including bioaerosols), radiation, dental materials, and noise; musculoskeletal disorders; dermatitis and respiratory disorders; eye injuries; and psychological problems. PEI remain a particular concern, as there is an almost constant risk of exposure to serious infectious agents. Strategies to minimise PEI and their consequences should continue to be employed, including sound infection control practices, continuing education and hepatitis B immunisation. As part of any infection control protocols, dentists should continue to utilise personal protective measures and appropriate sterilisation or other high-level disinfection techniques. Aside from biological hazards, dentists continue to suffer a high prevalence of musculoskeletal disorders (MSD), especially of the back, neck and shoulders. To fully understand the nature of these problems, further studies are needed to identify causative factors and other correlates of MSD. Continuing education and investigation of appropriate interventions to help reduce the prevalence of MSD and contact dermatitis are also needed. For these reasons, it is therefore important that dentists remain constantly informed regarding up-to-date measures on how to deal with newer technologies and dental materials.

Scapholunate dislocation: A rare occupational hazard

Dentists and their assistants are at risk of physical injuries during dental operations. The most common injuries are musculoskeletal. The need to work in a fixed working position using continuous repetitive movements can predispose dentists to wrist ache, lower backache, and neckache. We encountered a rare case of scapholunate dislocation with ligamentous injury, an unusual complication of extraction of teeth.

The Hand-Arm Vibration International Consortium (HAVIC): Prospective Studies on the Relationship Between Power Tool Exposure and Health Effects

OBJECTIVES

The Hand-Arm Vibration International Consortium (HAVIC) is a collaboration of investigators from Europe and North America studying health effects from hand-arm vibration (HAV). Features include prospective design, cross-cohort exposure, and health assessment methods.

METHODS

Two new cohorts (dental hygienists and dental hygiene students), two existing cohorts (Finnish forest workers, and Swedish truck cab assemblers), and a previous population (US shipyard workers) are included. Instruments include surveys, quantitative medical tests, physical examination, and work simulation and data logging to assess exposure. New methods were developed for nerve conduction and data logging.

RESULTS

Findings on the relationship between nerve conduction and skin temperature in HAV-exposed subjects resulted in a new approach to subject warming.

CONCLUSIONS

Integrating established cohorts has advantages over de novo cohort construction. Complex laboratory tests can be successfully adapted for field use.

Nerve conduction and sensorineural function in dental hygienists using high frequency ultrasound handpieces

BACKGROUND

Oscillatory vibration from industrial power tools poses a well-recognized risk of peripheral nerve injury. There have been reports of elevated vibrotactile perception thresholds (VPT) among dentists, dental technicians, and dental hygienists, using rotary devices and ultrasonics. Elevated VPTs are an indicator of small fiber nerve or mechanoreceptor injury, but the high frequencies associated with dental instruments are presumed by the ISO to exceed physiological response upper thresholds. This study examines nerve conduction and sensorineural deficits in dental hygienists.

METHODS

A cross-sectional study of 94 experienced dental hygienists was conducted to assess peripheral nerve function and clinical signs and symptoms. Specialized testing included measurement of VPTs for three different categories of mechanoreceptors, sensory nerve conduction tests with fractionated digit and palmar segments, and measurement of calibrated pinch force with force sensitive resistors (FSRs) during a simulated procedure.

RESULTS

Chronic hand paresthesias were described by 44.7% of experienced dental hygienists. Sensory nerve conduction velocity (SNCV) across the wrist-palm segment of the median nerve. VPTs were particularly elevated at the FAII mechanoreceptor among experienced dental hygienists. Compared to participants without carpal tunnel syndrome (CTS), as defined by study criteria, 14 experienced hygienists with diagnosed CTS had almost twice the average weekly use of vibratory instruments -8.3 hr versus 4.5 hr, and had SNCV deficits along the digit -47.11 m/sec (+8.70) versus 42.57 m/sec (+8.25), and across the wrist -44.04 m/sec (+7.15) versus 41.36 m/sec (+9.27). There was a distinct subset of dental hygienists (27%) with a combination of low calibrated pinch force in simulations, subjective loss of strength and elevated VPTs, especially in the FAII mechanoreceptor population -110.82 db (+8.57) versus 104.84 db (+6.80) in the rest of the cohort. This subset also had a higher prevalence of paresthesias (67% vs. 39%) and greater cumulative vibration exposure (OR = 1.206 [CI 1.005-1.448]), than other hygienists.

CONCLUSIONS

The high levels of paresthesias observed among dental hygienists appear to be attributable to several pathophysiological mechanisms, including, sensory nerve demyelination at the carpal tunnel and intrinsic to the digits, and dysfunction of fingertip mechanoreceptors. A distinct sub-population appears to exhibit a high level of accumulated abnormality.

A Meta-Analysis of the Neuropsychological Effects of Occupational Exposure to Mercury

This paper reports a meta-analysis of 36 peer-reviewed published studies of the neuropsychological effects of occupational exposure to mercury, which yielded 43 independent samples. These studies included 2,512 exposed participants and 1,846 controls, for a total sample size of 4,358. Because the independent variables defining mercury exposure varied across studies, effect sizes were calculated for exposed versus non-exposed workers. Dose-response relations were considered for measures of mercury levels in urine (81% of studies reported), blood (42% of studies reported), and air samples (33% of studies reported). Level of exposure was also estimated by reported years of exposure (M = 11.3, SD = 5.6). Cohen's d statistic yielded a statistically significant weighted study-mean effect size of -.23, p < .0001 for occupational mercury exposure. However, an effect this small is typically undetectable when evaluating individuals because it is smaller than the typical 95% confidence interval used for most neuropsychological measures. None of the exposure variables analyzed reached statistical significance. The magnitude of self-reported symptoms (-.30) was slightly larger than that obtained from objective test scores (-.22), though the difference was not statistically significant. Also, the weighted mean effect size for psychomotor skills (-.34) was the largest in magnitude, whereas the weighted mean effect size for verbal comprehension measures had the smallest (-.06). However, an analysis of the differential effects of mercury exposure across cognitive domains found significant differences between verbal comprehension measures and all other domains. None of the other domains were significantly different from one another. The weighted study-mean effect size suggests that the prevalence of neuropsychological deficits due to occupational exposure to mercury is small and difficult to detect on an individual case-by-case basis.

Hand-arm vibration exposure of dentists

OBJECTIVES

The use of dental handpieces exposes the dental personnel to high-frequency vibration. Dentists have been shown to have a high frequency of finger-related and other upper limb symptoms and a high prevalence of osteoarthrosis in the distal interphalangeal joints.

METHODS

The vibration of 22 dental handpieces was measured during normal work with accelerometer. The weighted vibration according to the standard ISO 5349-1 and the total acceleration of high frequency vibration ("ultravibration") in the frequency range of 1.6-10 kHz were analyzed. In order to compare non-contact vibration measurement method for dental handpieces, vibration of 12 handpieces was measured during idling with Portable Digital Vibrometer and simultaneously with the accelerometer. A group of 295 female dentists aged 45-63 years responded to a questionnaire on working conditions, lifestyle, and health.

RESULTS

The vibration measurements of air-turbine and micromotor handpieces showed that daily vibration exposure of dentists was below the exposure action value of the Vibration Directive of European Union. The highest vibration levels of the handpieces exist in the frequency range above 1,250 Hz. The traditional method and the laser method gave highly similar values. A long work history in dental filling and root treatment as well as high BMI seem to be associated with frequent finger symptoms perceived as vibration-related by the dentists.

CONCLUSIONS

The vibration exposure of dentists is low determined according to European legislation. However, a long work history in dental filling and root treatment seems to be associated with the risk of frequent finger symptoms of dentists. Therefore, when "pinch-gripping" is used, the effects of vibration on fingers should be comprehensively studied.

Structure and biomechanics of peripheral nerves: nerve responses to physical stresses and implications for physical therapist practice

The structural organization of peripheral nerves enables them to function while tolerating and adapting to stresses placed upon them by postures and movements of the trunk, head, and limbs. They are exposed to combinations of tensile, shear, and compressive stresses that result in nerve excursion, strain, and transverse contraction. The purpose of this appraisal is to review the structural and biomechanical modifications seen in peripheral nerves exposed to various levels of physical stress. We have followed the primary tenet of the Physical Stress Theory presented by Mueller and Maluf (2002), specifically, that the level of physical stress placed upon biological tissue determines the adaptive response of the tissue. A thorough understanding of the biomechanical properties of normal and injured nerves and the stresses placed upon them in daily activities will help guide physical therapists in making diagnoses and decisions regarding interventions.

The European vibration directive – how will it affect the dental profession?

On 6 July 2005, the EU Physical Agents (Vibration) Directive (2002) came into force across all member states. This will mean that legally enforceable limits on hand-arm vibration exposures will be introduced and that risk management must be set in place at work. This article briefly describes the content of the Directive, how this will affect the dental profession and what measures will be required to ensure compliance.

An 18-month follow-up study on vibrotactile sense, muscle strength and symptoms in computer users with and without symptoms

OBJECTIVES

The aim was to explore whether symptoms, sensory perception and muscle strength among computer users with and without symptoms in forearm or hand had changed after 18 months.

METHODS

Twenty-six out of 30 females, experienced computer users, from a baseline study participated in the follow-up. In addition, five control subjects participated. The subjects completed a questionnaire regarding exposure to computer work, prevalence and severity of symptoms, health status and physical activity. Perceived thresholds for vibration were measured twice with 3 h in between on the right hand on four different sites innervated by the radial, median or ulnar nerve. Furthermore, sensory perception was measured on the left hand on two sites innervated by the median and ulnar nerve, respectively. Skin temperature was measured at each site prior to sensory perception measurements. Maximal handgrip strength and maximal pinch-grip strength were measured for both hands.

RESULTS

Eighty-three percent of the subjects who had symptoms at baseline still had symptoms and 21% of the subjects who did not have symptoms at baseline experienced symptoms at follow-up. The first and the second sensory perception measurement were highly correlated. Vibrotactile sensory threshold representing the radial nerve was increased since baseline among the subjects who originally had symptoms. At follow-up, the vibrotactile sense for the computer users who reported symptoms in forearm or hand at baseline was deteriorated for the sites representing the median, ulnar and radial nerves compared to the control group. Among the original symptom free subjects with intensive computer work increases in vibrotactile perception thresholds were found for the sites representing the median and ulnar nerves. Handgrip muscle strength remained unchanged for all groups.

CONCLUSIONS

The study indicates that sensory dysfunctions as well as symptoms in forearm and hand among computer users to a high degree are persistent. Muscle strength seems to be well maintained.

Work Environment and Occupational Health of Dental Hygienists: A Qualitative Assessment

OBJECTIVE

We sought to characterize the work environment and identify factors that influence the occupational health of dental hygienists.

METHODS

We conducted a qualitative analysis of dental hygiene work based on five national focus groups.

RESULTS

We found that musculoskeletal symptoms are common, particularly after 10 years; common ergonomic problems included instruments and chairs. Important non-physical workplace problems include role ambiguity (eg, employee vs. independent practitioner), inadequate recognition, role identity (eg, distinction from dental assistants), role conflict (eg, with dentists and spousal office managers), and social isolation.

CONCLUSIONS

Work organizational factors (eg, frequent part-time work, inadequate breaks, perception as a "second team" distinct from the dentist and dental-assistant team) impede the remediation of ergonomics and other problems. Job flexibility encourages hygienists to change work hours or location rather than deal with work conditions. Occupational health interventions should address social environment and work organization.

Work-related disorders of the upper limb in female workers using orbital sanders

OBJECTIVES

To investigate the prevalence of vascular, neurological and musculoskeletal disorders of the upper limb in a group of female workers performing either mechanical or hand sanding in the furniture industry (n=100) and in a control group of female office workers (n=100). A further aim was to study the possible adverse effects of exposure to a combination of vibration and ergonomic risk factors in female workers.

METHODS

All female workers underwent a medical interview and a complete physical investigation. The clinical diagnoses of Raynaud's phenomenon and carpal tunnel syndrome (CTS) were made according to international consensus criteria. Hand-transmitted vibration from orbital sanders was measured according to International Organization for Standardization (ISO) recommendations. Daily vibration exposure was assessed in terms of 8-h energy-equivalent frequency-weighted acceleration [A(8)] according to the European Directive on physical agents. Ergonomic load on the upper limbs was estimated by means of strain index methodology.

RESULTS

There was no significant difference in the prevalence of Raynaud's phenomenon between the furniture workers (4%) and the controls (8%). The prevalence of CTS, peripheral sensorineural disturbances (after exclusion of CTS cases) and upper-limb musculoskeletal complaints was significantly greater in the furniture workers than in the controls. CTS was clinically diagnosed in 19% of the furniture workers and 8% of the controls. A log-binomial regression analysis showed that the occurrence of soft-tissue disorders of the upper limb increased significantly with the increase of both daily vibration exposure and the strain index score. It was estimated that the risk for CTS increased by a factor of 1.30 (95% CI 1.11-1.53) for each unit of increase in A(8) (ms(-2)), and by 1.09 (95% CI 1.02-1.15) for each unit of increase in the strain index score.

CONCLUSIONS

Even though the cross-sectional design of this epidemiological study does not allow aetiological considerations, our findings suggest a significant association between occupational use of vibratory tools and soft-tissue disorders in the upper limbs of female workers. Quantitative estimation of vibration exposure and ergonomic stress showed that these physical risk factors seem to contribute in a multiplicative way to the occurrence of chronic nerve and musculoskeletal disorders in female workers operating hand-held vibrating tools in the furniture industry.

Hand muscle pathology after long-term vibration exposure

The morphology of the abductor pollicis brevis muscle was studied in 20 patients suffering from hand-arm vibration syndrome. The main morphological changes observed were centrally located myonuclei and fibre type grouping (found in all 20 muscle biopsies), angulated muscle fibres (found in 19 biopsies), ring fibres and regenerating fibres (found in 18 biopsies) and fibrosis (found in 17 biopsies). The observed abnormalities are believed to reflect damage to both the muscle fibres and the motor nerve. The changes were related to different vibration exposure parameters. The number of fibres demonstrating centrally located nuclei correlated significantly with the cumulative vibration exposure, while the number of angulated fibres correlated significantly with the total vibration exposure time. This indicates that the vibrating tools may cause direct damage to muscle fibres as well as nerves.

Amalgam toxicity--environmental and occupational hazards

OBJECTIVES

To discuss briefly the recent developments in mercury production, consumption and waste handling especially in relation to the use of mercury in dentistry. Furthermore, to discuss the toxicological and reproductive aspects of the mercury body burden of dental personnel.

DATA, SOURCES AND STUDY SELECTION

The data discussed are primarily based on published scientific studies and on publications and reviews from governmental and other official authorities which have been published within the last 10 years, References have been traced manually or by MEDLINE.

CONCLUSIONS

Global production and consumption of mercury is decreasing, as is the production of amalgam fillings in some countries. By proper measures it is possible to further reduce the environmental burden of mercury from dental clinics. In general, the mercury body burden of the dental personnel can be kept below the normally accepted toxicological limits and reproductive effects have not been proven provided a proper mercury hygiene regimen is adopted.

Prevalence of musculoskeletal disorders in dentists

Background

The prevalence of musculoskeletal complaints in dentists is high although relatively few studies had focus in this profession. The aim of this study was to investigate the relations between physical, psychosocial, and individual characteristics and different endpoints of musculoskeletal complaints of low back, neck, shoulders and hand/wrist.

Methods

A questionnaire survey was carried out among 430 dentists (response 88%) in Thessaloniki, Greece. Questions include data on physical and psychosocial workload, need for recovery, perceived general health and (i) the occurrence of musculoskeletal complaints in the past 12 months, (ii) chronic complaints during at least 1 month, complaints which led to (iii) sickness absence, and (iv) medical care seeking. In logistic regression analysis odds ratios were estimated for all relevant risk factors.

Results

62% of dentists reported at least one musculoskeletal complaint, 30% chronic complaints, 16% had spells of absence and, 32% sought medical care. Self-reported factors of physical load were associated with the occurrence of back pain (OR = 1.59), shoulder pain (OR = 2.57) and, hand/wrist pain (OR = 3.46). With the exception of hand/wrist complaints, the physical factors were not associated with chronic complaints and musculoskeletal sickness absence. Physical load showed a trend with the number of musculoskeletal complaints with ORs of 2.50, 3.07 and 4.40 for two, three and four musculoskeletal complaints, respectively. No consistent influence of psychosocial factors on complaints, chronicity, sickness absence and medical care seeking was observed. A perceived moderate general health was a significant factor for chronic complaints, comorbidity and medical care seeking where high perceived exertion was significant for absenteeism. Living alone was also related with increased absenteeism due to shoulder pain (OR = 5.01) and hand/wrist (OR = 4.07).

Conclusions

The physical load among dentists seems to put them at risk for the occurrence of musculoskeletal disorders. More than one and severe complaints are related to perceived general health while high perceived exertion and social characteristics are associated with sickness absence. Chronic symptoms seem to determine medical care seeking. Ergonomic interventions may have a greater impact in prevention of hand/wrist complaints. When investigating the influence of work-related risk factors on musculoskeletal health, psychosocial and other personal characteristics should be taken into account.

Ultrasonic dental scaler: associated hazards

BACKGROUND

The ultrasonic dental scaler is a valuable tool in the prevention of periodontal disease; however, this equipment has a number of hazards with which it is associated. These include heating of the tooth during scaling, vibrational hazards causing cell disruption, possible platelet damage by cavitation, associated electromagnetic fields that can interrupt pacemakers, auditory damage to patient and clinician and the release of aerosols containing dangerous bacteria.

OBJECTIVE

To collate the research reported on the various hazards associated with the ultrasonic dental scaler and discuss possible future research areas.

DATA SOURCES

The scientific literature was searched using Web of Science, EMBASE and Medline, and the results of these were then hand-searched to eliminate nonrelevant papers.

CONCLUSIONS

This review outlines some of the research conducted into these areas of associated hazard in order to assess their significance in the clinical situation, and discusses ideas for future research. Suggestions of recommendations are given, which have been previously investigated for their aid in reducing possible hazards, to ensure the safe working of ultrasonic scalers in the dental practice.

Hand-arm-vibration syndrome (HAVS): is there a central nervous component? An fMRI study

Hand-held vibrating tools may result in neuromuscular dysfunction and vasospastic problems of the hand. Sensory and motor dysfunction can be explained by injury to peripheral structures, but could also be due to changes in cortical somatotopic mapping of the hand in the brain. The purpose of the present study was to use functional magnetic resonance imaging (fMRI) to assess the somatotopic cortical representation of the hands of workers subjected to occupational vibration. The study included six men with severe vibration exposures who were suffering from hand-arm-vibration syndrome (HAVS) and six controls. The analysis focused on the pattern and degree of activation of contra- and ipsilateral hemispheres of the brain with tactile stimulation and motor activation of the hand. These stimulations resulted in well-defined activation of the contralateral, and to a lesser extent the ipsilateral hemisphere. Statistical analysis of this limited patient material did not indicate any significant somatotopic cortical changes following long-term exposure to vibrating hand-held tools, although there was a tendency to a shift of activation towards the more cranial parts of the cortex in the patient group.

Self-reported and measured time of vibration exposure at ultrasonic scaling in dental hygienists

In the present study, our objective was to quantify the daily duration of vibration exposure from ultrasonic scaling in dental hygienists and to compare different methods of self-estimates to time-recorded measurements. The exposure time was self-estimated by use of diary and interview methods in 10 subjects. We found that the measured total daily exposure time was limited, only on average 12min, with a great variation, however, between and within the subjects. Self-assessed duration of exposure was overestimated, on average three times higher with a diary and even more at an interview (8 times). In conclusion, the objectively measured exposure time was short and clearly overestimated in self-reports.

[Occupational activity and prevalence of osteomuscular pain among dentists in Belo Horizonte, Minas Gerais State, Brazil: a contribution to the debate on work-related musculoskeletal disorders]

The objective was to determine the prevalence of upper-limb and back pain among dentists (n = 358) and factors associated with these symptoms. Dentists were interviewed using a self-administered questionnaire containing data on sociodemographic, occupational, lifestyle, and psychosocial factors and presence, site, and characteristics of pain. Participation rate was 92.3%. 58% reported upper limb pain, with 22, 21, 20, and 17% for the arm, back, neck, and shoulder, respectively. 26% reported daily frequency and 40% classified pain as moderate or severe. In the multivariate analysis (multiple logistic regression), the factors associated with pain were: neck: anxiety/depression (OR = 2.3; CI95%: 1.2-4.5), compressor in the office (OR = 2.1; CI95%: 1.2-3.7), job satisfaction (OR = 0.3; CI95%: 0.1-0.9), and use of indirect vision (OR = 0.5; CI95%: 0.3-0.9); shoulder: income > 20 minimum wage (OR = 2.9; CI95%: 1.2-6.7), greater productivity (OR = 3.3; CI95%: 1.3-8.4), height > or = 160cm (OR = 0.3; CI95%: 0.2-0.7), and age 30-49 years (OR = 0.3; CI95%: 0.1-0.8); back: anxiety/depression (OR = 2.3; CI95%: 1.2-4.5), manual activity (OR = 0.4; CI95%: 0.2-0.9), and being married (OR = 0.5; CI95%: 0.3-0.9); arms: manual activity (OR = 1.8; CI95%: 1.0-3.2).

Ocular sequelae of pneumatic drills

PURPOSE

To determine the ocular sequelae of rock-drilling.

METHODS

Nineteen rock-drillers and 20 age-, sex- and race-matched control subjects underwent ocular examination in a prospective manner.

RESULTS

Subepithelial corneal opacities were found in 12 drillers (63%) and none of the controls; pigmented trabecular meshwork was noted in 13 drillers (68%) and 1 control (5%); low-tension glaucoma was diagnosed in 1 driller (5%); vitreous liquefaction was present in 17 of 17 drillers (100%) examined by a retina specialist and 9 of 20 controls (45%).

CONCLUSIONS

The sequelae of drilling include corneal scars from projectile pieces of drilled stone as well as vibration-induced pigment deposition in the trabecular meshwork and vitreous liquefaction. Wearing of safety glasses is recommended.

Hand function in workers with hand-arm vibration syndrome

Hand-arm vibration syndrome has been specially addressed in the Scandinavian countries in recent years, but the syndrome is still not sufficiently recognized in many countries. The object of this preliminary study was to describe the nature and character of vibration-induced impairment in the hands of exposed workers. Twenty symptomatic male workers (aged 28 to 65 years) subjected to vibration by hand-held tools were interviewed about subjective symptoms and activities of daily living and were assessed with a battery of objective tests for sensibility, dexterity, grip function, and grip strength. The test results were compared with normative data. The majority of patients complained of cold intolerance, numbness, pain, sensory impairment, and difficulties in handling manual tools and in handwriting. The various objective tests showed considerable variation in indications of pathologic outcome, revealing differences in sensitivity to detect impaired hand function. Semmes-Weinstein monofilament testing for perception of light touch-deep pressure sensation, the small-object shape identification test, and moving two-point discrimination testing for functional sensibility provided the most indications of pathologic outcomes. The authors conclude that vibration-exposed patients present considerable impairment in hand function.

A new tactile gnosis instrument in sensibility testing

A new quantitative test instrument for the assessment of tactile gnosis--the ability to identify shapes and textures without vision--is introduced. Introductory investigations of validity and reliability are presented. Fifty-four patients (60 hands) with carpal tunnel syndrome, vibration-induced neuropathy, or nerve repair at distal forearm level, and a matched asymptomatic control group were initially examined. After establishing the cut-off limit for normal tactile gnosis, sensitivity and specificity were calculated to determine the discriminative power of the new instrument. A high sensitivity (1.0) of the new shape/texture identification test was found in the group of patients with nerve repair. Given a cut-off limit, the sensitivity was lower in the groups with vibration-induced neuropathy and carpal tunnel syndrome (0.65 and 0.40, respectively), and the specificity of the test was 0.90 to 0.95. In a second step, a group of 52 patients who had had nerve repair at the distal forearm level were examined. Test-retest reliability was good, with a weighted kappa value of 0.79 to 0.81. Good reliability was also shown in the internal consistency of test items, with a Cronbach alpha value of 0.78. These introductory results indicate that the new shape/texture identification test can be useful in the assessment of tactile gnosis.

Vibrotactile sense and hand symptoms in blue collar workers in a manufacturing industry

OBJECTIVES

To study whether vibrotactile sense combined with questionnaires (subjective complaints) and a clinical examination (including scoring of the Stockholm workshop scale (sensorineural staging)) could serve as a screening procedure, in the health care service, for sensorineural symptoms. A group of blue collar workers exposed to vibration in a manufacturing industry (rock crushing plants) was used as the study group. Another group of workers not exposed to vibration but subjected to heavy manual work served as the control group.

METHODS

Vibrotactile sense was determined. The index and the little fingers of both hands were investigated. A clinical examination was performed. Questionnaires were used for exposure data and for assessment of symptoms.

RESULTS

Important findings were that impairment in vibrotactile sense correlated with impairment in grip force, cold sensitivity, and other sensorineural symptoms--such as numbness and tendency to drop items. Clinical findings such as Phalen's test and two point discrimination were related only in those workers with the poorest vibrotactile sense. There was a relation between vibrotactile sense and the Stockholm workshop scale (sensorineural staging) for the sensorineural symptoms. Muscle and joint problems were more often seen in workers with decreased vibrotactile sense.

CONCLUSIONS

Tactilometry for assessment of vibrotactile sense is a useful tool in assessing and evaluating the severity of vibration induced neuromuscular symptoms and verifying the patients' clinical complaints. Heavy manual work without exposure to vibration may contribute to impairment of vibrotactile sense. The relation between impairment in vibrotactile sense and grip strength indicates that impaired sensory feedback may contribute to muscle weakness.

Changes over a workshift in aesthesiometric and vibrotactile perception thresholds of workers exposed to intermittent hand transmitted vibration from impact wrenches

OBJECTIVES

To investigate the changes over a workshift in fingertip tactile perception thresholds in users of impact wrenches exposed to intermittent hand transmitted vibration. A further aim was to assess the relation between acute changes in tactile sensation, sensorineural disorders, and vibration dose.

METHODS

The study populations consisted of 30 workers exposed to vibration (16 men and 14 women) and 25 control manual workers (10 men and 15 women). Sensorineural disorders in the fingers and hands were graded according to the staging system of the Stockholm workshop scale. Tactile function was tested by measuring aesthesiometric thresholds (two point discrimination and depth sense perception) and vibrotactile perception thresholds at 16, 31.5, and 125 Hz before and after a workshift. Temporary threshold shift was then calculated as the difference between threshold measures before and after the shift. The measurement and assessment of exposure to vibration were made according to the international standard ISO 5349. The vibration dose accumulated over a workshift (m2s-4h) was estimated for each user of impact wrenches. Daily exposure to vibration was also expressed in terms of eight hour energy equivalent frequency weighted acceleration ((ahw)eq(8) in ms-2 rms).

RESULTS

After adjustment for age and alcohol consumption, vibrotactile perception thresholds before exposure were greater in the workers exposed to vibration than in the controls. No differences in aesthesiometric thresholds before the shift were found between the study groups. Sensorineural disorders were mild in the workers exposed to vibration and minor neurological abnormalities were detected at the physical examination. Owing to the intermittent use of impact wrenches, the estimated mean (ahw)eq(8) for the subjects exposed to vibration was low (1.3 ms-2 rms). A significant temporary threshold shift in vibration perception at all test frequencies was found in the workers exposed to vibration but not in the controls. A significant increase in depth sense perception thresholds was found in the men exposed to vibration. The temporary threshold shift in vibration perception at 125 Hz, and to a lesser extent at 16 and 31.5 Hz, was associated with the severity of sensorineural disorders. In the workers exposed to vibration the temporary threshold shift in vibration sense at all test frequencies was positively related to the estimated dose of vibration received over a workshift. No significant relation was found between aesthesiometric threshold changes and vibration dose.

CONCLUSIONS

Intermittent exposure to hand transmitted vibration over a workshift can cause a deterioration of tactile perception in the fingers of users of impact wrenches. Acute tactile dysfunction was related to both the estimated dose of vibration and the severity of sensorineural symptoms. The temporary threshold shift in vibration perception suggested that fast adapting skin mechanoreceptors such as Pacinian and Meissner corpuscles were mainly involved in the acute sensory impairment to the fingertips of the workers exposed to vibration. Changes in tactile perception can occur in workers with daily exposure to vibration that is considered to be associated with a minimal risk of adverse health effects induced by vibration.