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20 GENERAL DENTISTRY Dental Tribune Middle East & Africa Edition | 6/2017 Lighting in dental surgeries —frequently neglected requirements of the standard on illumination By Antonín Fuksa, Czech Republic Proper illumination plays an impor- tant role in most of our activities, as we acquire more than 80 per cent of information by sight. Precious val- ues such as health and wellbeing are intrinsic in health care. Lighting in dental surgeries is gov- erned by EN 12464-1:2011 standard1 specifying minimum lighting re- quirements for workplaces. National versions of this harmonized stand- ard are made mandatory by country regulations in EC countries.2 The current standard is effective as of 2011. Some of the illumination sys- tems designed according to the pre- vious edition (2002) are therefore no longer compliant. The requirements of the standard should be under- stood as the absolute hygienic mini- mum, as they are a compromise be- tween average physiological needs and average economic potential. According to ergonomic research, most people prefer their workplaces to be illuminated to 1,000 lx or more, while the standard-prescribed mini- mum is 500 lx. The standard pre- scribes the maintained illumination Em. When the real average illumina- tion E falls under Em, maintenance is to be performed: luminaires to be cleaned up, lamps to be replaced, walls to be repainted etc. Adequate illumination of the operat- ing area is vital to perform surgical tasks. The standard3 for dental oper- ating lights requires the operating field illumination to be in the range of 8,000 to 20,000 lx in ellipsis of size 50 × 25 mm (visual task area); but only 60 mm up from the centre of the ellipsis, a maximum of 1,200 lx is allowed to prevent the patient from being dazzled. Constant re-adaptation of the eye between very bright and dark ar- eas leads to eye fatigue, and finally to overall fatigue for the dentist. A powerful luminaire above the chair meets or exceeds the minimum prescribed illumination of the pa- tient, which is 1,000 lx (co-responds to immediate surrounding area of the visual task: a stripe at least 0.5 m around visual task area). Lower con- trast means better visual comfort for the dentist. Fig. 2a: 3-D visualisation of situation from Fig. 1a. Lighting is designed using require- ments for office workplaces. The installation does not respect additional task areas. Fig. 1a: Typical situation in dental surgeries in Eastern Europe:5 lighting is designed using requirements for office workplaces. Most of the requirements are not met, see Table 1 Fig. 1b: Balanced illumination of dental surgery employing a di- rectional/ indirectional panel luminaire above the chair and us- ing additional ceiling and furniture luminaires, see Table 2. Cold tones of light are preferred as peripheral vision is more sensi- tive to the blue component of light. This leads to a decrease of perceived contrast. The standard requires light with high colour rendering index Ra ≥ 90. Patients looking directly into the luminaire prefer matt luminous surfaces. The model surgery has dimensions 5 x 6 m and ceiling height of 2.8 m. The luminaire above the chair is sus- pended in the height of 2.2 m above the floor. Positions of the additional luminaires are a compromise be- tween 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 instruments, material preparation areas, PC table, filing cabinet etc. Illumination re- quirements have to be fulfilled 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 standard, this has to be illuminated 1/3 of the illumination of the sur- rounding area. Installations accord- ing 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 direc- tional pendant luminaire was placed above the chair. The updated stand- ard helps us to understand the room as a whole, not just a set of task areas. Not only the illumination of the pa- tient, but also the uniformity and ac- ceptable 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 highoutput directional/indirec- tional 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. Be- 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) Table 1: Comparison and evaluation of very basic parameters of illumination. Fig. 2b: 3-D visualisation of situation from Fig. 1b. An insight into a model room with a directional/indirectional panel luminaire and additional luminaires to respect addi- tional task areas. Table 2: Requirements on lighting in dental surgeries, according to table 5.48 of the standard.1 surgery equipment luminaires visual task areas task surrounding area task background area sides illuminating the patient, the high-output directional/indirec- tional 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 Eu- ropean countries5 clearly show that even the very basic requirement of task illumination is often neglected. Also task background and overall illumination are often far too low, which has both eye and overall fa- tigue implications. As little as 30 lx have been repeat- edly measured on the material prep- aration areas and computer desks. Many surgeries installed in existing buildings kept the original (office) luminaires, not quite following the lighting project. These systems were often projected according to an old standard that required as little as 300 lx for office work. Savings on lighting tend to generate much larg- er expenses later. The need for light grows with age. Other parameters of lighting like uniformity, glare, colour rendering or non-visual effects of light and lighting control will be discussed later in a dedicated article. Lighting the surgery with office lu- minaires only is not sufficient to fulfil basic requirements. Lighting using a single, powerful central lu- minaire provides enough light in the visual task area, but may easily fail to meet additional requirements. That is why additional luminaires are needed to provide background area illumination and uniformity. References 1. EN 12464-1:2011 Light and light- ing—Lighting of work places—Part 1: Indoor work places. 2. Czech Government Regulation No. 361/2007 establishing the conditions of occupational health protection. 3. EN ISO 9680:2007 Dentistry—Op- erating lights (repl. 2014). 4. FUKSA, Antonín. Lighting in dental surgeries. StomaTeam. 2/2014. ISSN 1214-147X. 5. SVOBODA, Filip. Lighting in dental surgeries in Romania—a summary report. Personal communication, 2015. Antonín Fuksa graduated (MSc) in 2000 at the Czech Technical University in Prague, Faculty of Electrical Engineering in the field of study Measurement and instrumentation. He currently works as a developer of intelligent luminaires, smart lighting systems and chronobiological phototherapy devices in NASLI.