Oral conditions among workers in the Danish granite industry.

The purpose of the study was to evaluate the oral health situation of workers in the Danish granite industry, in particular, to describe the prevalence and severity of dental abrasion. Measurements of the work environment showed that the workers were exposed to abrasive quartz dust. A total of 39 workers (72%) completed a questionnaire on their dental health, work environment, and symptoms from the masticatory system. Only 10% had been treated by school dental services, and only 51% made regular visits to the dentist. Consequently, the clinical examinations revealed a high prevalence of dental caries (mean number of decayed, missing, and filled surfaces 87.2). The workers' periodontal conditions were poor; the mean percentage of teeth with gingivitis, calculus and pockets deeper than 5 mm was 13.4. The prevalence of dental abrasion was 100%; in particular, abrasion was observed on the front teeth. The severity of abrasion and the affection ratio increased by duration of exposure to dust. In conclusion, dental abrasion induced by work-related dust should be considered an occupational disease.

Oral cav ity injuries which occ ur as a direct result of an occup at ion are rath er commo n . The inj urio us effect of occupational ha zards may manifest them selves in the teeth, jaw bones, periodonta l tissues, tongue , lips, and or al mucosa. Th e effects of th e various etiologic agent s responsible for oral occupational disease depend on their specific chemical, phy sical and bacterial nature, their ph ysical state, and th eir mode of ent ry (13). Work in mines (3,12), metal work (6), and work in th e chemical industry (4,8) ma y affect the pattern of disease in the periodont ium and the oral muco sa (14). Other studies ha ve show n that work in bakeries (2) and in the ca ndy indu str y (I) increases the prevalence of den tal ca ries. A recent Danish study amo ng choco late wor kers (17) demonstrated an increase in the risk of dent al caries and per iodontal diseases because of a high level of sugar du st in the work environment . As a con sequence of th e study, the Dan ish social authorities now recognize " sugar caries" as an occupational disease (18,20).
Dent al abrasio n is a co ndition in which too th su bstance is lost by friction al effec ts other th an thos e associated with mastication. It involves a for eign object or sub stan ce repeatedly contact ing th e teeth . Abras ive co mpo nents exist in several wo rk en vironments. Th e purpose of the pre sent study was to evaluat e the or al health situat ion of workers in th e Danish gra nite industry, in particular, to describe the pr evalence and Repr int requ ests to: Dr PE Petersen, Institut e for Co mmunit y Dent istry and Graduate Studies, Ro yal Dental Co llege, 20 Norre AIle, DK-2200 Co penhagen N, Denma rk. 328 severity of dental a brasion in relation to expo sur e to qua rtz du st.

Subjects and methods
The survey too k place in 1986-1 987. The target gro up co nsisted of all wor kers (N = 55) employed, currentl y or for merly , in a Danish granite industr y (Ronne, Bo rnh olm ). Th e study population comprised 39 male wo rkers with a mean age of 55 (ran ge 28-75) yea rs. Th is number co rre spo nds to a response rate of 72 %. Twenty-fi ve of the wor kers had been empl oyed for mor e than 10 yea rs, nin e of the wo rkers for 5-10 year s, a nd five fo r less than five yea rs. The study was preceded by dust meas ure ments perform ed by the Labor Inspe ction Serv ice. At th e time of th e investigation the con centration of quartz (abrasive du st) at th e cru shing mill varied from 2.24 to 2.38 mg/m ' .
A questionnaire was used to collect data on residence, edu cat ion , wor k condition s, dental health behavior , self-assess ment of dent al health status, and symptoms fro m the temp orom and ibular joint s and mu scles. Informati on about or al health status was based on clinical o bservations . Den tal caries and removable dentures were recor ded as described by the Wo rld Health Orga nization (21). Th e assessment of per iodontal sta tus was based on the Periodontal T reatment Need System (10,15). Th e periodontal registr ation s included all teeth present. The dental abrasion of each tooth was recorded according to recommended criteria (21). Th e followin g coding was used : 0 = no abrasio n, I = abrasio n o f the enamel -cusp still visible, 2 = dentin e expose d, 3 = occlusal relief worn away leaving a peripheral rim of enamel , and 4 = crown worn down close to th e cementoena me l junction. Finall y, Table 1. Percentag e of workers who reported having been exposed to various work co nditions (N = 39). Table 2. The percent age of respondents wit h symptoms (daily) from the mastica tory 'system (N = 39).

Discussion
In Denmark , the gra nite industry is only found on the island of Bornholm . However, the dental health problems in term s o f abrasion may also occur in comparable industries. For example, stone cutters, sand blowers, and construction workers sho uld be consid-A brasion. All th e den tate workers were affected by dental abrasion. As shown in tabl e 3 and illustrated in figure I, abrasion was frequent on the front teeth (incisor s, cuspids). A severe pattern of abrasion was observed for workers with exposure to dust for 10 years or mor e. Furthermore, the affection rat io (number o f teeth with abras ion/number of teeth present) increased as the duration of exposure increased (table 4). Clicking or grating in jaw joint Tendern ess of teeth Tendern esslfatigu e in cheeks Difficult ies in openin g mouth Locking of jaw Grind ing of teeth Wor k con dition 11.9, and DMF-S = 82. 1. The number of untreated dental caries among the 28to 54-year-olds was high (D-S = 8.0). The total caries index increased to 87.2 when the edentulous persons were included. The mean number of teeth present varied from 23. 1 among the 28-to 54-year-olds to 12.0 amon g the 55-to 75-yearold s. The mean percentage of teeth with a healthy periodontium was 6.8, the percentage of teeth with gingivitis without calculus was 48.3, the percentage of teeth with gingivitis and calculus was 31.5, while the percentage of teeth with pockets deeper than 5 mm or looseness of the third degree was 13.4. The clinical examinations revealed that no workers suffered from muscle symptoms and that the mean size of the mouth opening was 46.5 mm.
Sympt om Data analysis. Caries experien ce was describ ed by the DMF-S index, ie, the number o f decayed (D), missing due to caries (M), and filled (F) tooth surface s (5). The periodontal status was expressed by the following varia bles: (i) the percentage of present teeth with health y periodontium (0), (ii) the percentage of teeth with gingivitis without calculus (A), (iii) the percentage of teeth with gingivitis and calculu s (B), (iv) the percenta ge of teeth with gingivitis, calculus, and pockets deeper than 5 mm (C) , and (v) the percentage of teeth with gingivitis, calculus, pockets deeper tha n 5 mm , and loo seness of the third degree (D). The means were computed for the caries experience and periodontal variables. For the description of dental abrasion, the number of teeth with various affections was calculated, and the means were computed . the presence or absence of pain or tenderness from the temporal and ma sseter muscles was record ed according to the results of a palp ation test (5), and the wor ker's cap acity to open his mou th was measured in millimete rs.

Results
Work conditions. Most of the workers had had seven years of schoo ling. Half of them were unskilled workers, one-four th were semi-skilled, and one-fou rth were skilled. Shift work was reported by 15 010. Various disturbing or embarrassing work conditions were reported frequently (table 1) Dental health. Only 10 0J0 of the respondents had been treated by school dental services, and only 51 % visited the denti st regularly. While 70 % of the participants claimed to bru sh their teeth twice a da y or more, only 5 0J0 repo rted daily toothbrushin g at work . A tot al of six persons were edentulous and had dentures in both jaws; six persons had a denture for the maxilla only; and three persons had a denture for the mandible only. Among the dentate respondents, one-tenth claimed to have teeth in good condition, while 84 0J0 declared that the ir teeth were bad or fairly good . Health y gingival conditions were reported by one-fourth, and two-thirds reported bad or fairly good gingival cond ition s. Sixty percent answered that they were in need of dental treatment. On e-third claimed to have had a great deal of trouble in their lifetime with their teeth or gums, and these problems were related to the work enviro nment. The results of the question s on function of the masticatory system are shown in tabl e 2. Headache (daily/ weekly) was claimed by 18 % , and 15 0J0 reported using anal gesics against head ache or facial pain daily or weekly.
Among the dentate gra nite workers the mean caries index was as follows: D-S=4.5, M-S =65.7 , F-S= Table 3. Mean number of teeth wit h abrasio n at different levels in relati on to toot h type and age.  ered risk groups. This survey comprised both active workers and pensioners and an acceptable response rate was obtained. In comparison to similar studies of indu strial wor kers (15,16), our investigation showed that granite workers had rather poor dental conditions. Ho wever , this finding was explained by the more irregular dental care habits since only a few persons had been treated by school dent al services and a low proportion of the workers mad e regular visits to the denti st in adult life. Th e survey also showed that most of the granite workers were awa re of their poor dental health status , and man y related their dental probl ems to the work environment. Po or work conditions, including exposure to dust , were reported. The con centration of quartz dust was con siderably higher than the concent rat ion recommended as a maximum for indust ria l hygiene in Denm ark (0.1 mg/ rn') .
In general population s, extremely worn dentit ion s are uncommon. Loss of too th structure due to causes 330 othe r than dental caries may be associated with physiological and/or pathological pro cesses, usually classified as being the result of erosion, attrition, or abrasion. Dental erosion is defined as the loss of tooth substan ce by a simple chemical proce ss and is frequently the result of exposure to acids. Indu strial environmental factors have been reported to cause dental erosion (19). Attrition refers to the ph ysiological wearing awa y of tooth substance as a result of toothto-tooth cont act. Grinding and/or clench ing of teeth due to hyperactivity in the masticatory muscles are considered to be necessary for the development of path ological att rition.
In the present study attrition may be excluded as an explanation of dental wear since only a few participants report ed symptoms from the masticatory system. The level of repo rted symptoms corresponds to similar Danish findings (11). Furthermore, the findings on selfreported disorders of the masticator y system were supported by the clinical ob servations. In accordance with previous reports (7,9) the observed dental wear amo ng the granite workers should therefore be ascribed to the abrasive compo nents of the work environment. Th is phenomenon was also demon strated by the dose-effect relationship (table 4).
First of all, dental abrasion am ong gra nite work ers and similar occupational group s ought to be prevented through the reduction of the dust level. How ever, until such a reduction is achieved, the use of face guards and regular toothbrushing at work should be recommended . In cases of extremely worn dentition s dental recon stru ction is not only a difficult clinical problem but also very expensive, due to the fact that complicated treatments (crowns, bridges, etc) are not covered by the Nat ional Health Insurance. Since this type of severe denta l abras io n is closely related to the wor k environment, the lesion should be considered an occupa tional disease. Consequently, dental abr asion ought to be entitled to compen sation in Denmark accor ding to the Indu strial Inju ries Insuran ce Act.