A Study on the Posture of the Operator in Dental Treatment

Field: Health Professions (Health Sciences)

There has been much literature published on the subject of working postures of various operators, which are regarded as being important from human engineering and industrial medicine points of view. However, studies on working postures of the dentist are scanty. In view of the fact that individual dentists assume their own particular postures, the author carried out the present study as part of a series of researches on the occupational and hygienic study of the dentist, conducted for a long time by the Department of Hygiene and Public Dental Health where the author belongs. In the belief that the working posture of a dentist might exert some influence on his spinal column, observations were mode of the occlusal plane angle, inclination of the back of dental chair and position assumed in terms of various treatment spots and contents. As the same time, radiograms were taken of the spinal column and photographs were also taken of various working postures. An artificial spinal column was constructed from these data and careful analyses of changes in the artificial spinal column revealed the following conclusions:1) Angles of the occlusal plane.On the average, 27.1° and 23.8° were respectively measured for the treatment of upper and lower jaws in a standing position. In a sitting position, on the other hand, the measured values were 46.6° for the upper and 37.4° for the lower jaw respectively. In either position, the angles were found to be larger in the treatment of the upper jaw.2) Inclination of the chair back.On the average, 130.8° and 128.8° were respectively measured for the treatment of upper and lower jaws in a standing position. In a sitting position, on the other hand, the inclinations were 155.8° for the upper and 252.9° for the lower jaw. Here again, upper jaw revealed the tendency of a slight increase over the lower jaw.3) Treatment positions.In a standing position, 8.8 o'clock and 9.0 o'clock were measured for the upper and lower jaws respectively. On the other hand, in a sitting position the measured values were 9.8 o'clock and 9.9 o'clock for the upper and lower jaws. In either case, the lower jaw revealed somewhat higher values.4) As for the lateral curvature of the spinal colum on the part of dentists, those who were above 4° gave an incidence of 52.2%. Distorsion of the spinal column was seen in 87.0% of dentists. The distorsion in many cases was either to the right or in the form of an S and, for this reason, it was thought that unnatural or constrained posture assumed in dental treatment had some bearing on this phenomenon.5) About 5.9 vertebrae per dentist suffered from the lateral curvature and these were chiefly concentrated around Th, 8 and Th, 9 thoracal vertebrae.6) The simulation of various movements revealed the following facts. That is, at a standing position the body tended to incline itself forward to the right around the Th, 7 thoracal vertebra, while a distorsion made the cervical region turn to the left. In a sitting position, on the other hand, there was observed a tendency that a backward bending occurred from the Th, 12 thoracal vertebra to the lumbar region.7) From these findings, it is urged that those conditions should be established which willmaintain the safety of spinal column on the part of dentists engaged in treatment.8) From a standpoint of health control of dentists, it is thought desirable that some kind of exercises to rotate and extend the spinal column should be routinely performed.