A Study on the Air Pollution in Dental Clinics from a Hygienic Point of View with Reference to the Dust and Aerial Bacteria Particles

Abstract

In the modern buildings, where the natural ventilation is far from satisfactory as viewed from environ mental hygiene, various air-conditioning devices have been developed to date. But some of them leave much room for improvement. This is particularly true of medical and dental clinics, where the installation of defective air-conditioners may perniciously affect other rooms and laboratories that will produce the so-called intramural infection.In dental clinics, the airturbine engine makes it possible to cut the teeth effectively but, on the other hand, it creates a main cause of the air pollution by scattering the cutting dust and bacterial particles.In the present study, the author was concerned with comparative analyses of the aerial dust and bacterial particles at two different dental clinics or installations which were equipped with different types of air-conditioning devices.By way of study method, a dental clinic (to be referred to as Y) and another dental section of general hospital (to be referred to as Z), including the treatment room, dental laboratory and waiting room, were subjected to the collection of air-borne dust and bacterial particles near the dental chairs, center of dental laboratory, both air inlet and outlet of the respective treatment rooms. The study consisted of the following 6 items, including i) the count of dust and bacterial particles at the three intervals of initiating the daily treatment (9 a. m.), during treatment (11 a. m.) and concluding treatment for the day (3 p. m.), ii) the aerial dust particles larger than 0.3μ were classified into 15 different size classes by use of the Royco 202 air-borne particle monitor of light diffusion system and then measured, iii) for the measurement of aerial bacterial particles, air at the measurement site was collected 50l/2min. and was cultivated by tryptosoy-agar medium (Eiken) for colony count with conjoint observations by means of DHL medium (Eiken) and, at the same time, the Andersen sampler was used to classify the aerial bacteria into 6 classes according to size, iv) correlative coefficients were calculated between the different sizes of dust particles and the number of persons present in a given room, v) correlative coefficients were also calculated between the size of different dust particles and the number of aerial bacteria, and finally vi) for determining the degree of instrument contamination, the reception counter at the clinic and bracket table (5×5cm2) were wiped and subjected to examinations, also including the surface of hand-pieces.As a result of these comprehensive examinations, the author arrived at the following conclusions:1. The count of dust particles.a. In the treatment room, dental laboratory and air inlet, the total count in Y was 48.8×104-58.9×104 pieces/l and, in the case of Z, it was 4.8×104-9.9×104 pieces/l the former giving the value of about 5 to 10 times than that of the latter.At the air outlet, Y gave 45.4×104-49.2×104 pieces/l and, on the other hand, Z gave 3.3×104-3.9×104 pieces/l, the difference between the two sets of values being as large as about 12 to 17 times.b. When examined in terms of sizes, the dust particles smaller than 0.3 to 0.4μ accounted for the majority both in Y and Z institutions. The number of dust particles decreased proportionately to their size and those larger than 1.0μ were about 1%.At the Z institution where the pre- and after-filters were used, there were found no dust particles larger than 1.5μ at the air outlet.