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ePaper created 2018-02-16, 10:54:19 | version 1.38.0
lighting opinion | Table 1: Comparison and evaluation of very basic parameters of illumination. Parameter Overall surgery illumination Overall uniformity Patient illumination Instruments illumination Material preparation area illumination Nurse’s desk illumination Doctor’s desk illumination Background illumination General colour rendering index Compliance with Standard Fig. 1 Fig. 2 20–500 lx (cid:31) 600–1,500 lx (cid:29) poor (cid:31) 300–500 lx (cid:31) 500–700 lx (cid:29) 50–200 lx (cid:31) very good (cid:29) 1,000–3,000 lx (cid:29) 500–700 lx (cid:29) 500–750 lx (cid:29) 20–200 lx (cid:31) 30–100 lx (cid:31) 20–500 lx (cid:31) 600–1,000 lx (cid:29) 500–750 lx (cid:29) 700–800 lx (cid:29) 70–80 (cid:31) NO (cid:31) > 90 (cid:29) YES (cid:29) The model surgery has dimensions 5 x 6 m and ceiling height of 2.8 m. The luminaire above the chair is suspended in the height of 2.2 m above the floor. Positions of the additional luminaires are a compro- mise between functionality and aesthetics. Besides the visual task in the mouth cavity, many other facets exist in the dental surgery that need to be illuminated in order to carry out tasks: instrument trays, controls and displays of diagnostic instru- ments, material preparation areas, PC table, filing cabinet etc. Illumination requirements have to be ful- filled at all these places, too. A minimum overall room illumination of 500 lx has to be maintained as well. One of the principal items in the updated standard is the background surrounding the dentist’s work- space, which is a stripe aligned to the surrounding area of the dentist’s workspace, at least 3 m wide, within the size of the room. According to the stand- ard, this has to be illuminated 1/3 of the illumination of the surrounding area. Installations according to the older standard rarely meet this requirement. A luminance of 5,000 lx directed at the patient can be measured under a powerful luminaire. The back- ground lighting in this case would be 1,670 lx, which is quite expensive to achieve. This requirement has not been met in any of tens of surgeries measured where a powerful directional pendant luminaire was placed above the chair. The updated standard helps us to understand the room as a whole, not just a set of task areas. Not only the illumination of the patient, but also the uniformity and acceptable contrast in the whole space is important. The focused beam of the operating light provides illumination of about 15,000 lx that is necessary for the dentist’s task in the mouth cavity. The high- output directional/indirectional panel luminaire above the chair provides illumination of the task background area of about 3,000 lx, providing a 1 : 5 contrast, which is already an acceptable level. Colder tones of light further improve the perceived contrast to about 1 : 4. Besides illuminating the patient, the high-output directional/indirectional panel luminaire serves as an ergonomic aid to ease the visually demanding task of the dentist. Measurements carried out in dental surgeries across some Eastern European countries5 clearly Meaning Purpose Overall illumination Patient illumination 500 lx 1,000 lx Symbol Em UGRL Uo Ra – Maintained Illuminance Adequate level of light Limit of Glare index UGR Glare limitation, acceptable contrast Minimum illuminance uniformity Acceptable distribution of light Minimum general colour rendering index Required color discrimination 19 0.6 90 Special requirements According to selected task or area Light should not dazzle the patient – 0.7 90 – Table 2: Requirements on lighting in dental surgeries, according to table 5.48 of the standard.1 cosmetic dentistry 1 2017 11