Psychological Impact of COVID-19 in the Setting of Dentistry: A Review Article

The worldwide pandemic has exposed healthcare professionals to a high risk of infection, exacerbating the situation of uncertainty caused by COVID-19. The objective of this review was to evaluate the psychological impact of the COVID-19 pandemic on dental professionals and their patients. A literature review was conducted using Medline-Pubmed, Web of Science, and Scopus databases, excluding systematic reviews, narratives, meta-analyses, case reports, book chapters, short communications, and congress papers. A modified version of the Newcastle-Ottawa Scale (NOS) was used to evaluate the quality of the selected studies. The search retrieved 3879 articles, and 123 of these were selected for the review (7 longitudinal and 116 cross-sectional studies). Elevated anxiety levels were observed in dental professionals, especially in younger and female professionals. Except for orthodontic treatments, patients reported a high level of fear that reduced their demand for dentist treatment to emergency cases alone. The results suggest that the COVID-19 pandemic has had psychological and emotional consequences for dental professionals and their patients. Further research is necessary to evaluate the persistence of this problem over time.


Introduction
COVID-19 produced a state of generalized fear that has been studied in various social settings reviewed in [1]. The risk of infection affects the whole population but is greater among healthcare workers due to their frequent close contact with infected symptomatic or asymptomatic individuals [2], making them especially vulnerable to the impact of the pandemic [3].
Among healthcare professionals, dentists in particular have had to introduce numerous modifications in their daily clinical practice [4]. COVID-19 is known to be transmitted via aerosols and droplets [5], to which dentists are exposed in oral interventions, when they are in close proximity to the oropharynx of the patient [6]. These circumstances have increased the work stress levels of dentists and their fear of infecting family members. Some countries almost completely halted activity in dental clinics during certain phases of the pandemic [7]. These restrictions and changes have exacerbated feelings of so-called "dental phobia" that can often be responsible for delaying or avoiding non-emergency treatments [8]. Such delays can lead to dental emergencies that require procedures carrying a greater risk of infection by SARS-CoV-2 [9].
Since the beginning of 2020, numerous studies have investigated the psychological disorders produced by this situation in dental professionals and their patients. Two systematic reviews have addressed this issue [10,11], but they were limited to the first few months of the pandemic and only included articles studying the psychological impact on dental professionals. An updated review is warranted to include the numerous studies published since their publication and which also address the effect on the patients.
With this background, the objective of this study was to review studies on the psychological consequences of the COVID-19 pandemic for dental professionals and patients as well as the factors associated with the psychological impact.

Search Strategy and Selection Criteria
The search of this review was conducted in Medline-PubMed, Web of Science, and Scopus databases. The objective of this review was to address the question: "What emotional consequences has the COVID-19 pandemic had for dental professionals and their patients?". The search strategy was: (COVID- 19  The following review inclusion criteria were established: (1) studies analyzing anxiety, fear, or stress caused by the COVID-19 pandemic in dentists and/or their patients; (2) studies written in English, Italian, or Spanish; and (3) studies published between 1 December 2019 and 1 January 2022. Exclusion criteria were: (1) systematic reviews, narratives, or meta-analyses; and (2) case reports, book chapters, short communications, and congress communications.
After eliminating duplicates, the titles and abstracts of retrieved articles were screened to exclude non-eligible items. The whole text of the remaining articles was then reviewed to establish their eligibility for the review. A reverse search of reference lists from all the relevant original articles and previous systematic reviews and meta-analyses was also done.

Data Extraction and Quality Evaluation
The following data were gathered from each article: (1) first author and year of publication; (2) country of study population; (3) sample size; (4) professional category/treatment undergone by patients; (5) demographic characteristics of the sample; (6) variables of interest analyzed and sources of information; and (7) main results.
The Newcastle-Ottawa Scale (NOS) was used to evaluate the quality of the reviewed studies [12], assigning a score (stars) based on three quality parameters: sample selection, comparability, and results evaluation. Studies are classified as: very good quality (9-10 stars), good (7-8 stars), satisfactory (5-6 stars), or unsatisfactory (<5 stars). This scale was originally designed for longitudinal studies but it has been modified to evaluate cross-sectional studies in previous studies [13,14]. We have done an additional adaptation for this study: the point 4 of 'Selection' section is referred to the validity of measurement tool. The studies selected in this review used the tools to evaluate the psychological impact as a result (consequence of the pandemic) and not as an exposure. So, this point was moved to 'Outcome' section ("Assessment of the outcome II"). Nevertheless, the final score remained unchanged (Supplementary Materials S1).

Results
The search strategy retrieved 3879 articles, of which 982 were excluded as duplicates. Titles and abstracts of the remaining 2897 articles were then reviewed, and 2759 were excluded. After reading the whole text of the remaining 138 articles, 16 were excluded and a further article was added by reverse search (Figure 1). Finally, 123 studies were included in the review, 80 focusing on dental professionals  and 43 on patients .
The search strategy retrieved 3879 articles, of which 982 were excluded Titles and abstracts of the remaining 2897 articles were then reviewed, and cluded. After reading the whole text of the remaining 138 articles, 16 were a further article was added by reverse search (Figure 1). Finally, 123 studies in the review, 80 focusing on dental professionals  and 43 on patien

Characteristics of Studies
The main characteristics and results of the studies are summarized which have been divided according to the use of validated questionnaires ( fessionals and Table 3 in patients) and non-validated ones ( Table 2 in pro  Table 4 in patients). The percentage of studies using validated questionna in professionals and 55.8% in patients.

Characteristics of Studies
The main characteristics and results of the studies are summarized in Tables 1-4, which have been divided according to the use of validated questionnaires ( Table 1 in  professionals and Table 3 in patients) and non-validated ones ( Table 2 in professionals and  Table 4 in patients). The percentage of studies using validated questionnaires was 52.5% in professionals and 55.8% in patients. Depression, anxiety and stress  Dentists living with someone at high risk for COVID-19, who did not practice leisure activities, working on the frontline, and those who suffered changes in their eating habits, sleep quality and physical health during this period obtained the highest scores for anxiety, depression and stress. Dentists had the highest out-of-work prevalence (32.3%) and the lowest prevalence of remote work (20.2%) among healthcare professionals. Regarding the psychological variables, the prevalence of depression, anxiety and stress symptoms was higher in dentists than in physicians, nurses and psychologists. 25% of professionals reported moderate to severe anxiety levels, and only 14% had post-traumatic stress disorder. About 26% were willing to treat patients, and higher anxiety and stress levels were associated with females, older age, and living with the close ones. Both fear of COVID-19 and perceived job insecurity were positively associated with depressive symptoms. Among those dentists who showed low fear levels of COVID-19, the effect of perceived job insecurity on these symptoms was weaker. There was a strong positive correlation between the total scores of insomnia and fear of COVID-19. The more the professionals were afraid of patients lying about their health, or getting infected from their co-workers or while taking off their personal protective equipment, the more severe their insomnia was. It was observed that the anxiety level of professionals increased significantly on the day that the high-risk procedures were restarted. This increase was significant for females, dentists working in endodontics and restorative dental care, and nurses. 63.4% of dentists had a score greater than 40 on the anxiety scale from 0 (no anxiety) to 100 (highest anxiety). 44.1% were willing to continue treating their patients during this period, and more than 50% worried about not being able to do it in the personal way as before. The positive association between subjective overload and psychological distress suggested a higher rate of intensity in Italy, when compared to the rest of the countries. The interaction variable between both of them was significantly associated with the UK and with those dentists who reported fear of contracting COVID-19 from patients, or their families becoming infected. (2) Sources of stress [Non-validated questionnaire] Perceived stress increased by more than two points (on a scale of 40) from phase I (before the onset of SARS-CoV-2 spread) to phase II (in the month immediately following the nationwide lockdown) of the pandemic. Lack of family time due to long working hours was the main stressor (90%) among professionals during phase I, and concern about getting infected was the most frequent (  There was a statistically significant association of higher scores of psychological distress with age, gender, practice and education. The odds of stress were two times higher among males. General anxiety decreased over the weeks, with significant differences between strict and partial confinement. Endodontists showed higher levels of anxiety during anesthesia inoculation, and dental assistants during dental unit's disinfection. Most dental professionals showed greater levels of stress, being significantly higher in those working in the filiation service (identification and management of possible COVID-19 cases). In addition, 34.4% of them reported occupational burnout, compared to 17.6% of those not working in that service.  Dentists reported a lack of interest in social relationships, mood swings and emotional exhaustion. Fear of aerosol propagation and financial insecurity increased the probability of higher levels of perceived stress and distress, while years of practice and age seemed to be protective factors. 16.7% of orthodontists were anxious, with a statistically significant difference between the working place and the level of anxiety. Thus, the odds of having anxiety above the threshold were higher among those working in public institutions and organizations (60% The prevalence of poor sleep quality was 42.3% in dentists, the lowest as compared to doctors (55.4%) and nurses (67.3%). High levels of social and family support were identified as protective factors, and poor sleep quality was significantly associated with working in hospitals and high post-traumatic stress levels. Frontline dental professionals were 4.3 times more likely to suffer anxiety than the general public.    91% of dentists reported being afraid of becoming infected in the clinical environment, and 98% changed habits due to fear of infecting their relatives.
Dentists were more anxious than physicians, and their relationship with patients was also more influenced by the pandemic.  Anxiety of contracting COVID-19 was reported by more than 80% of professionals. The level of anxiety was higher among females and younger dentists, and no significant differences were found in anxiety levels between fields of practice.    The mean fear and anxiety score obtained was high (6.57 ± 2.07, in a range from 0 to 9), but 58.31% of dentists showed a low level. Those between 41-60 years of age or with individual practices presented greater scores of fear. The mean level of anxiety was 3.35 ± 1.18 (in a range from 0 to 5). 83.1% thought that neither the protective equipment nor the precautions taken would protect them from becoming infected, while only 16% of dental professionals considered them to be really effective. All of the studies had a cross-sectional design, except those marked with *. The prevalence of dental anxiety was 5.1%, and higher scores were significantly associated with female gender, patients who reported severe pain, and those who felt very or extremely anxious about visiting a dental clinic during the pandemic. Those with previous diagnosis of anxiety/depression (18%) showed an increase in their symptoms. (

3) Dental anxiety [S-DAI]
There was an association between trait anxiety and dental fear with the frequency of spontaneous hand-to-face self-contact of patients in the waiting room. Facial self-contact was higher in women, but it also rose in men as dental fear increased. 46.3% of patients reported being anxious, with a higher level among females. A significant association was observed between the level of anxiety and the willingness to attend a dental appointment, and the greatest concern of patients was a delay in completion of treatment.  Respondents with higher fear scores began brushing and using oral care products more regularly, and reported increased consumption of sugary food. Despite the high prevalence of dental problems, these patients hesitated to visit the dentist. The prevalence of psychological distress was 38%, and higher odds ratios were associated with female gender, missed appointments, and residing in Hubei. The type of orthodontic appliance was positively associated with anxiety, due to its implication in a longer treatment duration. Significantly higher levels of anxiety were observed in women, and there was a positive correlation with age. The most anxious patients considered dental clinics as risky environments for the spread of SARS-CoV-2, and preferred to resume their treatment once the pandemic was over.  Fear of getting infected and attitude towards dental treatment [Non-validated questionnaire] A significant association was observed between parents' willingness to take their children to the dentist with the level of fear, and 66.6% of parents would only seek urgent dental care. 61.5% stated that their diet had changed during the pandemic period. Willingness and barriers to visiting a dentist [Professional validation] 83% of mothers did not request dental care for their children, and 24% of those who already had an appointment did not allow their children to attend. 80% reported that the main barrier to visit the dental clinic was fear of being infected by SARS-CoV-2 from someone there. The more informed the participants were, the higher was the risk of missing dental appointments. The two most reliable communication channels were journals and websites for healthcare professionals. Women were more active in collecting information and relying on less secure channels.

ASDS: Acute Stress
Hajek 63.6% of respondents reported fear of visiting the dentist, and 66.2% thought that they would become infected in the dental office. Women were more anxious, as well as participants with an infected family member. Significant differences were found according to age and educational level. Older age was positively associated with perceived susceptibility to contracting COVID-19 in a dental clinic. Confirmation by public health officials of the safety of dental settings was reported as the most important factor for returning to routine dental visits. The greatest concern of participants was infecting a family member. The restrictive measures that forced people to stay at home led to an increased consumption of cariogenic foods. Patients felt safe when visiting the dentist, and asked for introducing telemedicine in similar situations in the future. Children who required dental care during quarantine did not show a significantly higher level of anxiety as compared to the pre-pandemic control group. Caregiver anxiety levels were higher in the pandemic group, revealing stronger correlations with dental anxiety in children.  All of the studies had a cross-sectional design.
All except for seven longitudinal studies [30,48,55,61,110,121,127] had a cross-sectional design. Online questionnaires served as the source of information in 107 of the 116 crosssectional studies. The year of publication was 2020 in 33 studies (26.8%). The research was most frequently conducted in India (n = 20), followed by Turkey (n = 13), Saudi Arabia (n = 12), Italy (n = 11), and Brazil (n = 10) [ Table S1 for further information]. The psychological aspects most frequently evaluated were anxiety (n = 58), fear (n = 38), stress (n = 30), and depression (n = 22). The sample size ranged between 15 and 5170 individuals. Patients were most frequently in the 30-50-year age group; there was a slight predominance of female sex in 86 studies, and the majority of dental professionals worked in a private practice.
Comparing the results of the studies using validated and non-validated questionnaires, there were differences in the percentage of dentists suffering from anxiety, with higher frequencies in those studies carried out with non-validated questionnaires (ranging from 7.1 to 71% with validated questionnaires [71,83] vs. 25.6 to 89% with non-validated questionnaires [64,81]). This was also observed in the studies that analysed adult patients under general treatment (ranging from 4.5 to 5.1% with validated questionnaires [100,108] vs. 9.5 to 62.4% with non-validated questionnaires [76,133]). Similarly, studies analyzing the percentage of patients presenting fear reported higher values with validated questionnaires (from 45 to 45.7% [100,120]) than with the non-validated ones (62.4 to 63.6% [115,133]).
The data collection period of the studies covered from November 2019 to July 2021, and the pandemic moment in each one of the countries [138] is summarized in Supplementary Tables S2 and S3. The vaccination process was not initiated in most part of the studies by the time of data collection. The pandemic situation was instead very different within the studies, with some recruiting participants during the first and second waves, and therefore at times of high rate of cases and deaths, and some of them recruiting at timings of low incidence of COVID-19 [138].

Quality Evaluation
Supplementary Materials, Tables S4 and S5 exhibit the NOS scores assigned to the studies: 10 studies (8.1%) had very good quality (9 stars), 52 (42.3%) good (7-8 stars), 56 (45.5%) satisfactory (5-6 stars), and only 5 (4.1%) unsatisfactory (4 stars). The main study limitations were the failure to calculate the required sample size and the lack of control for potential confounders in the data gathering or results analysis.
The main study variable in investigations on general dentists was anxiety (n = 35). Elevated anxiety levels about the possible contraction of COVID-19 from patients was observed in up to 89% of professionals [81], ranging from 1.7 to 23% those reporting severe anxiety [29,42]. Distrust about the effectiveness of protective measures and equipment during the first phase of the pandemic was expressed by 83.1% of professionals [84], and clinical activity was suspended at some point by 71.2% [86]. The subsequent resumption of activity was associated with increased anxiety levels, especially in professionals performing procedures with high aerosol generation [48]. Various studies found that a higher anxiety level was significantly associated with younger age and female sex of the dentist [28,36,43,48,50,52].
Other psychological factors studied included depression (n = 15), stress (n = 22), distress (n = 6), and burnout (n = 4). Depression-related symptoms were found in up to 60% of general dentists [71], having severe depression up to 22% [27]. Fear of infection and perceived work insecurity were positively associated with more depressive symptoms [39,83] and with the presence of some type of underlying disease [29,53,83]. Stress had a prevalence of up to 92% in professionals [71] and the severe stress ranged from 0.7 to 45% [29,71]. It was observed that stress was significantly increased among dentists during the first few weeks of the pandemic (from 18.61 ± 6.87 to 20.72 ± 1.95 on a 40-point scale; p < 0.0001) [55]. Clinical symptoms of post-traumatic stress disorder were recorded in 1.1 up to 32.3% of professionals [29,40]. Mild-severe distress was observed in 11.5-57.8% of general dentists [31,79], with a higher prevalence among females and under 40-year-olds [58]. Other distress-related factors were the presence of underlying disease, fear of infection by patients, and work overload [79], with 55.6% of professionals describing states of emotional exhaustion [40].
Studies of orthodontists mainly evaluated anxiety (n = 2), which was almost five-fold more frequent among those working in public versus private settings (60% vs. 12.6%, respectively; p = 0.034) [91]. Elevated distress levels were associated with the resumption of daily practice after the lockdown period, and 31.2% of orthodontists with higher distress were in favor of interrupting their work activity. Their main fear was the possibility of infecting a family member, which was greater than the concerns about their own death (48.2% vs. 26.9%, respectively) [51].
Finally, some of the studies comparing the impact of the pandemic on dental professionals with respect to other healthcare groups (as physicians or nurses) showed a higher prevalence of anxiety symptoms in dentists, and a greater reduction in their work activity [25,33]. On the other hand, it has also been described that financial uncertainty appears to have negatively influenced the emotional state of dental practitioners [40,53,65,78]. The evaluation over time of this financial insecurity and its impact on professionals was not analysed in any study.
Among adult patients receiving general dental treatment (restoration, extraction, cleaning, etc.), the main study variable analyzed was the fear of visiting the dentist during the pandemic (n = 11), reaching up to 63.6% of these patients [115]. Various studies [95,100,[110][111][112][113]115] found a greater reluctance to seek dental treatment and a more marked tendency to postpone appointments among female patients and among over 60-year-olds who had a systemic disease. The delay in dental care, mainly due to restrictive measures, was associated with depression in adults of middle age (Odds Ratio (OR): 2.05, 95% confidence interval (CI): 1.04-4.03) and in those over 65 years old (OR: 3.08, 95% CI: 1.07-8.87) [114].
Most orthodontic patients appeared willing to continue their treatment, with 69% reporting that the sole reason for its interruption was the closing of their dental clinic [102]. A possible delay in their treatment was found to be the main concern of these patients [105,118,137]. Anxiety was described in almost half of them, observing that females were more prone to suffer both anxiety (5.35 ± 2.48 vs. 4.29 ± 2.18 in males on a 10-point scale; p < 0.001) [105] and psychological distress (OR: 1.77, 95% CI: 1.07-2.93) [136].
Studies in the pediatric setting confirmed that parents were less willing to take their children to the dentists when their fear of COVID-19 infection was greater, and 66% of parents only sought dental care when emergency treatment was required [103]. A higher level of anxiety about visiting the dentist was shown by children during the pandemic, although it was not significantly greater than pre-pandemic levels evaluated in 2018, and their anxiety was lesser with older age. Anxiety levels in caregivers were also higher than those observed in 2018 and were more strongly correlated (close to 1) with the anxiety of the children [122].

Discussion
This review evidences the high levels of anxiety experienced by dental professionals during the COVID-19 pandemic, similarly to the findings of previous reviews [10,11], mainly caused by fears of infection and of work insecurity. Professionals who were younger and female appeared more vulnerable to these concerns. Fears raised by the pandemic also had a psychological impact on patients, leading them to avoid or postpone dental treatments.
As it has been described previously, it was found a greater reduction in the work activity of dentists in comparison to physicians and nurses, among others [25,33]. The relationship of dentists with patients and colleagues was also more strongly affected by the pandemic, attributed to a lesser feeling of safety and preparation for the treatment of possibly infected patients [33]. Although dentists and physicians both expressed major worries about the risk of infecting their family members, these appeared to be greater among dental professionals [33]. In this regard, it has been observed that work-related stress levels are higher among dentists than among other healthcare professionals under "normal" (non-pandemic) conditions [139]. In fact, studies have suggested that dentists are more prone to professional burnout, anxiety and depression, even when they are still dental students [140][141][142][143]. Nevertheless, these studies showed a maximum prevalence of both variables that did not reach 45%, while a large number of studies included in this review far exceed that percentage, presumably as a consequence of the COVID-19 pandemic.
Dental professionals frequently described a lack of agreement on the effectiveness of available preventive measures (e.g., air purifiers, ozone generators, etc.), exacerbating the psychological problems observed. In this context, a key factor during the early phase of the pandemic was the difficulty obtaining personal protection equipment or material (e.g., surgical masks, safety glasses, face shields, etc.) [144]. Some professionals even asked acquaintances with 3D printers to manufacture protective shields [145]. The insecurity generated by this shortage was one of the most frequent complaints cited by professionals in the reviewed studies.
Consistent with previously described results [11], the financial insecurity generated by the pandemic also appears to have influenced the emotional state of dentists. Dental offices had to adapt to the new situation, investing heavily in all types of protective measures for clinicians and patients. Being an eminently private profession, this added expense may have further impacted on the psychological stability of dentists. Furthermore, although there was a smaller volume of patients than before the pandemic, protective measures inevitably increased the time devoted to each one. The correct disinfection and ventilation of the dental office, completion of an exhaustive questionnaire to identify possible symptoms, and other associated administrative tasks were responsible for work overload in all members of the clinical team, with a higher risk of burnout syndrome [40,54,63,67,79]. Moreover, increased anxiety, stress and burnout were detected among dental professionals working in hospitals [18,29,50,63], not because of an increase in workload during the pandemic due to the reduced private clinical activity [8] but rather attributable to greater contact with possible carriers of SARS-CoV-2 in the hospital setting [146,147].
The studies reporting significant differences in psychological disorders as a function of sex or age were of high methodological quality and indicated that anxiety and depression were more frequent among the younger age groups, similar to the finding of a previous review [11], and female dentists. One explanation may be that younger professionals tend to have a higher workload and to be less financially stable, as previously observed in other types of healthcare professionals [148]. Regarding the apparently greater effect on female professionals, it should be born in mind that females are considered two-fold more likely to suffer from anxiety than males in the general population [149]. Fears about the possibility of virus transmission to their children may also have been greater in dentists who were mothers [50].
Many patients perceived the dental office as an unsafe environment and expressed high levels of fear about possible infection in the waiting room or during treatment [95,104,111,115,133]. As with all diseases, a delay in dental treatment can have negative health consequences [150,151], and the increased consumption of sugar observed during the pandemic [119,130] would further contribute to a worsening of oral and general health. In this regard, it has been suggested that the presence of periodontal disease in patients diagnosed with COVID-19 may be related to higher complication and mortality rates [152]. It is essential to warn populations about the negative effects of postponing dental treatments due to COVID-19 and to assure them that the dental office is a safe setting.
Unlike general dental care, most patients receiving orthodontic therapy wanted it to be continued without interruption. Although the treatment is non-invasive, aerosols can be generated by some procedures such as debonding [153]; however, patients may be unwilling to disrupt a long-term orthodontics plan that has already been started. It is also possible that patients establish a more direct relationship with their orthodontists, especially via mobile apps; in fact, the marked increase in "teledentistry" during the pandemic has demonstrated its usefulness to enhance the relationship between patient and healthcare professional [154].
A visit to the dentist frequently produces anxiety in children [155], and high anxiety levels have been strongly correlated with those of their parents, known to play a key role in the potential development of anxiety disorders in their children [156]. At the beginning of the pandemic, little was known about COVID-19 impact on children and reports were controversial, ranging from the possibility to develop Kawasaki syndrome [157] to assurance that symptoms were mild in children, with a good prognosis [158]. This uncertainty may have increased the reluctance of parents to seek non-emergency dental care for their children. One way to reduce anxiety is for professionals to convince patients that it is safe to come to the office and receive treatment [122].
Despite data collection occurring at different pandemic moments (high and low incidences of COVID-19 depending on the study), it is unlikely that this had impact on the psychological impact since the vaccination process had not been initiated in the majority of them and the fear due to this lack of protection may be generalized for all studies included in this review [159]. Indeed, in one of the few studies that included vaccinated healthcare professionals, receipt of vaccination was associated with a reduction of fear and anxiety levels in 35.6% of participants [160]. Vaccinated patients may also be more willing to seek treatment, and Vohra et al. [133] reported that 62.4% of patients were ready to receive treatment after their vaccination.
Of note, the percentage of subjects with anxiety and fear was usually higher in those studies that were performed with non-validated questionnaires. This is relevant regarding the confidence in the results obtained by means of non-validated tools as they may be subject to measurement error, as it has been suggested in other areas [161].
There is a need for longitudinal studies to determine the persistence of these psychological effects of the pandemic and to investigate possible associated factors. Data obtained could assist to the development of psychological support protocols that allow healthcare professionals to carry out early interventions to prevent the worsening of anxiety, depression, or stress.
Limitations of this review include that the comparisons of results among studies are hampered by their utilization of distinct instruments and methodologies to evaluate each psychological aspect, although most studies used validated scales relatively frequently applied in the field of psychology. It would be advantageous to unify criteria in future investigations, prioritizing instruments that specifically evaluate the relationship between COVID-19 and its possible emotional consequences, such as the "Fear of COVID-19 Scale, FCV-19S" [162] and "COVID-19 Peri-Traumatic Distress Index, CPDI" [163] described in this review. Quantification of the results obtained was also limited by the heterogeneity of the analytical methodologies applied. In addition, the data on which studies were based were self-reported by the individuals and therefore subjective, potentially differing from a potential professional psychological diagnosis. Finally, most of the evidence found was based on cross-sectional studies, with only seven having a longitudinal design, prevent-ing confirmation that the psychological/emotional disorders observed were caused by the pandemic.
One strength of this review is that it is the first to jointly consider the emotional impact of the pandemic on professionals and patients, offering a more global view of clinical dentistry. The external validity of the review may be supported by the fact that the studies were conducted in numerous different countries and did not focus on a specific epidemiological area or context, obtaining a methodological quality score > 4 stars in 96%. Finally, no article was excluded due to its language, despite being an inclusion criteria, which may imply a lower selection bias.

Conclusions
The COVID-19 pandemic had a major impact on dental practice, raising the anxiety levels of the professionals, increasing the patients' fear of visiting their dentist, and being responsible for multiple psychological disorders in both groups. Further studies are needed to evaluate the possible persistence of these disorders over time and once the vaccination process has been widely established.
Supplementary Materials: The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/ijerph192316216/s1, Supplementary Materials S1: Modified Newcastle-Ottawa Scale (NOS). Adaptation for cross-sectional studies based on surveys; Table S1: Number of studies from each country; Table S2: Vaccination and pandemic moment of the studies on dental professionals; Table S3: Vaccination and pandemic moment of the studies on dental patients; Table S4: Quality assessment of studies on dental professionals using the modified Newcastle-Ottawa Scale; Table S5: Quality assessment of studies on dental patients using the modified Newcastle-Ottawa Scale.