Journal of Dental Medicine

Statement of Problem: Musculoskeletal disorders (MSDs) are major parts of the occupational diseases in workplaces. Protection from such diseases is dependent on assessment and improvement of job postures by using job analysis methods in ergonomics.

Purpose: This study was aimed to evaluate ergonomic conditions in dental professions by rapid entire body assessment (REBA) in Birjand city and also to assess the relation between MSDS in different parts of the body and work conditions.

Materials and Methods: This study was a descriptive-analytical approach performed on 48 persons working at different professions by using REBA method. The prevalence of MSDs was obtained by using Nordic Musculoskeletal Questionnaire (NMQ). The data were analyzed by independent t-test, Chi-square and Fisher tests with P<0.05 as the limit of significance.

Results: In this investigation, the prevalence of disorders for different parts of the body was as follows: 65% for neck, 60% for back, 38% for shoulders, and 31% for wrist. These disorders were higher in women than men except for the back. There were significant correlation between disorders of femur and foreleg with work history, ankle and sole with body mass index (BMI), and MSDs with work conditions (P<0.05).

Conclusion: It is concluded that the work conditions and postures need to be improved. In addition the level of dental professional education regarding biomechanical hazardous effects as well as correct work conditions and postures should be increased.

Background and Aim: Dentists are exposed to mercury from dental amalgam in their routine occupational practice. Excess exposure to mercury is harmful and the measurement of mercury content of urine is a reliable and valid assessment of the level of mercury exposure from dental amalgam. The aim of this study was the measurement of urine mercury in dentists of Tehran and assessment of some possible related factors.

Materials and Methods: This cross-sectional study was performed randomly on 211 dentists in all regions in Tehran city (center, north, south, west, and east) between 1381 and 1383. Dentists were asked to give a sample of urine in the day of visit and to complete a questionnaire consisting of variables such as age, working history, handling of amalgam, environmental parameters and general health situation. Urine samples were analyzed by cold vapour atomic absorption spectrophotometry. Data were analyzed by Kruskall Walis, Kendall and Mann Whitney tests, with p<0.05 as the limit of significance.

Results: The mean of urine mercury content in Tehran dentists was 3.1 (± 3.95) which was lower than the international TLV (Threshold Limit Value). There was a significant relation between urine mercury level and working hours per day (P=0.006). This relation was observed with working hours per week too (P=0.006). In general dentists, there was a positive relation between urine mercury and age (0.008) as well as the practicing years (P=0.034). A significant relation was found between urine mercury and the number of amalgam repairs and replacements in restorative specialists (p=0.039). There was a significant relation between the number of amalgam fillings in the mouth and urine mercury in general practitioners (p=0.027). The type of amalgam (predosed capsules or bulk powder) had a significant effect on the urine mercury content (P=0.001). There was no significant relation between urine mercury and other variables of the study such as the squeezing of triturated amalgam, storage method of residual amalgam, method of storing mercury and office ventilation.

Conclusion: Based on the results of this study, the mean urine mercury content of dentists of Tehran was below the international TLV. The use of precapsulated amalgams had significant effect on the urine mercury. Most of the dentists were working in public or semiprivate clinics, so it is concluded that the level of general hygiene and specially mercury hygiene in these centers seems to be acceptable.

Background and Aim: Dental Amalgam is a common restorative material for posterior teeth. Because of Hg content in the composition of amalgam, during the handling of material, mercury may release as vapor in the environment. Excess amount of mercury vapor can cause serious health problems in dental personnel. The aim of this investigation was to determine mercury vapor concentration in working environment of dentists in Tehran.

Materials and Methods: 211 dental clinics were participated in this cross-sectional study. The clinics were randomly selected from different regions of Tehran (north, center, south, east and west). The dentists were asked to complete a questionnaire including items on demographic characteristics such as age, sex and work history, method of handling of amalgam, environmental characteristics and general health conditions. Environmental measurements of mercury vapor in dentists’ offices were done by mercury absorption tubes (Hydrar) and personal pumps (SKC, 222-3, England) as suggested in NIOSH method. Analysis of air samples was done by atomic absorption spectrophotometery (cold vapor). The data were analyzed by non-parametric tests (Kruskall Wallis, Mann-Whitney and Kendall).P<0.05 as the level of significance.

Results: The mean mercury vapor concentration in dentists’ offices was 8.39(±9.68) µg/m³.There was no significant relationship between the urine mercury of dentists (3.107±3.95) and the air Hg vapor concentration of their offices. Using precapsulated amalgam showed significantly less Hg vapor than bulk amalgam (P=0.034). Also the surface area of working room and air Hg vapor (P=0.009) had a significant relationship (P=0.009 r=0.81). There was not any significant correlation between mercury vapor and other factors such as working hours per day and working days per week, squeezing of triturated amalgam or not, storage medium of set amalgam (water or fixer solution), mercury storage method and type of ventilation.

Conclusion: The concentration of mercury vapor in dental offices' environment was lower than threshold limit value. Based on this study the type of amalgam (precapsulated or not) and area of the working room had significant effect on the mercury vapor concentration of environment.