This study reports the cross-sectional associations of work stress, according to the ERI, with dental caries, periodontal disease, and tooth loss. ERI was associated with a low number of dental caries and tooth loss, and an increased risk for periodontitis.
This study has two strengths. First, work stress was assessed using a widely accepted measure. Previous studies on work stress and oral diseases have often used nonspecific questionnaires.19 This study captured work stress more accurately than previous studies. Second, this study included potential confounders such as socioeconomic status and work-related variables. Our review revealed only two studies among the 11 studies included in the systematic review considered the potential confounders sufficiently.19 Our study is superior to previous studies in terms of these two points. However, our study had three limitations. First, periodontal status was assessed using a self-reported questionnaire. It is possible that participants with work stress exaggerated responses for questions on periodontitis screening. However, as the questionnaire about periodontitis has been validated among workers, there can be no significant bias. In the second source population survey, DMFT was estimated using intraoral photographs with mobile phones. Although an early study indicated the usefulness of intraoral photographs with mobile phones for assessment of oral conditions,30 some decayed and filled teeth could be missed because our study included fewer photographs than the previous study. Therefore, DMFT can be underestimated. However, the results in the second source population were consistent with those in the first source population, for which DMFT was assessed on clinical examination. Second, in the two-source population, many participants had a high socioeconomic status. More than 70% of participants had university degrees or higher. The social gradients of oral diseases have been reported.31,32 Additionally, blue-collar workers were also small. Participants in the two-source population had a better oral condition than those in the national survey.33 The results of people with low socioeconomic status and blue-collar workers might have been underestimated in this study. Finally, this study was cross-sectional; therefore, a temporal association was not established. Further cohort studies are required.
The current results show a negative association between work stress and the number of decayed or filled teeth (caries experienced teeth). There is only one previous study on work stress and the number of teeth with caries.19,34 In a previous study, work stress was assessed using the demand-control model, and the dependent variable was DMF tooth surfaces. One unit increases in work mental demand and work control score were associated with 0.19 (95%CI = -0.91, 1.29) and 0.87 (95% CI = 0.18, 1.91) increases in DMF teeth surfaces.34 This inconsistency might be due to the DMFT and DMF teeth surfaces which included caries experiences that occurred before exposure to work stress. For a more accurate understanding of the association between work stress and dental caries, the incidence of dental caries should be measured.
In the present study, work stress was negatively associated with tooth loss. There were two previous cross-sectional studies in which the dependent variables were self-reported tooth loss and having four or more lost teeth.19,35,36 Two studies have reported an increased risk of tooth loss due to work stress. Our results are inconsistent with those of the two previous studies. In this study, the number of tooth losses were few. Furthermore, as with dental caries, this inconsistency might be due to the characteristic of the dependent variable, missing teeth, which included tooth loss that occurred before exposure to work stress. Owing to these limitations, it is difficult to derive conclusions from the current results. The incidence of tooth loss should be used as an outcome in future research.
Work stress was associated with an increased risk of severe periodontitis, which is consistent with previous studies.19 Eight of nine previous studies reported a significant association between work stress and periodontal status, but only one study used the accepted measure for work stress and adjusted for potential confounders.19,34 Our results provide additional evidence based on the more accurate work stress status considering the potential confounders.
Work stress was associated with a risk of severe periodontitis and not with dental caries and tooth loss. According to previous reviews,37,38 periodontal disease seems to be more sensitive to psychological stress than dental caries. Work stress brings about uncontrolled metabolism and impaired immune system, which can exacerbate periodontal disease.14 Besides, the definition of periodontal disease is based on current inflammation activities in the supporting structures of the teeth.39 The above features might facilitate the observation of the cross-sectional association between work stress and severe periodontitis than dental caries and tooth loss.