*4.2. Strengths and Limitations of the Study*

The most important strength of the study is that the results covered a great gap in scientific information related to the impact of fear of COVID-19 on mental health of medical professionals, especially of dentists. One of the limitations of the research is that the present study did not identify personality traits (according to the Big Five model, for example, which associated the presence of insomnia with neuroticism). Insomnia was more present in people with sleep vulnerability and introversion because all these were found to be linked to low gray matter density in the orbitofrontal cortex. Therefore, as Dekker et al. showed [59], introverts may be more vulnerable to COVID-19 fear and score higher on the insomnia scale.

Another limitation of the research is given by the small number of subjects. Thus, although the results are interesting, they cannot be generalized to the entire population of dentists, together with the geographical context related to the impact of the pandemic. So results cannot be generalized, and no causality is provided.

A third limitation of the research which should not be ignored is related to the fact that this study was conducted during the first part of the pandemic, when stress was connected to the fact that dentists did not have satisfactory access to protective materials or to complete information about the transmission of the virus, and were financially affected due to the closure of medical offices and the drastic decrease in financial profits. Therefore, sleep disorders could be strongly influenced by a combination of factors and not just by the fear of virus infection, and can affect quality of life [60].

The fourth limitation of the study is caused by the fact that the respondents were considered mentally healthy, no psychological or psychiatric diagnostic was obtained, and no supplementary psychological scale was applied. The presence of mental chronic diseases or various comorbidities could lead to a more pronounced presence of insomnia.
