In this study, it was identified that the number of victims of facial fractures was lower in the prevailing period of social distancing by COVID-19, with a 54.5% reduction (n=279 in 2019 and n=127 in 2020), according to the literature [9, 11, 14]. This result was expected, as there was a 70% reduction in parks movement, 71% in commercial activities, 64% in leisure, and 34% reduction in mobility in relation to people who were unable to work in person [19].

The most affected age group by facial fractures was between 19 and 29 years, in both cohorts (2019 and 2020), with an average age of 34 and 28 years for men and women, which corroborates with the literature [14, 20]. This data may be the reason why individuals are more active in social, professional, and sporting environments at this age and are prone to facial fractures [15].

Facial fractures were more frequent in males in both cohorts, 84.2% in 2019 and 81.19% in 2020, corroborating with other authors [16, 21]. Activities performed by men are more likely to incidents, high-risk driving, interpersonal conflicts, and radical sports, leading to greater risks of facial fractures [7, 22].

The highest frequency of facial fractures was found in the urban zone, n=87.1% in 2019 and 90.6% in 2020, corroborating published data [7, 17]. This outcome may be explained by population aggregation in urban environment, predisposing to accidents and conflicts among individuals, contributing to the increased incidence of facial fractures [7, 23].

Motorcycle accident was the main etiological factor of the middle third fractures of the face, in both cohorts, 39.4% in 2019 and 42.5% in 2020, with a growing proportion in social isolation period by COVID-19, corroborating with other authors in relation to the great frequency of traffic accidents in developing countries [16, 24, 25].

The growth in the number of motorcycle accidents during the pandemic may be explained by the increase in online shopping, resulting in a greater distribution of motorized deliverymen in urban regions [26, 27]. However, our study identified a statistically significant association between physical aggression and age between 30 and 39 in 2019, in agreement with previous results that highlight more fractures by aggression in this age [28, 29]. In 2020, no statistical significance was observed between age groups and trauma etiologies (x² (28) = 35.24; p=0.163; Table 3), contradicting the study by Canzi et al. [30] in 2021 in Milan, in which there was an increase in the average age of trauma in 2020 during the Lockdown period. It is believed that these results can be explained by the large reduction in the frequency of facial fractures in the studied population, as it was an atypical period in society, causing discrepancies between the cohorts analyzed. Furthermore, differences in the social context, legislation, and culture in different regions of Brazil may present heterogeneous epidemiological data compared to international literature [1, 30].

In relation to the main etiological factor approached in contrast to other findings [17, 21, 31], they demonstrate that the main etiological factor of facial fractures was physical aggression. These facts may be explained by the differences in legislation, culture, economy, and politics of each region [22]. Moreover, a proportionately significant association was found (p<0.05) between falls and age from 50 to 100 in the 2019 cohort, demonstrating that the elderly are predisposed to falls [17]. In the 2020 cohort, there was an increase in the number of physical aggression, being the second most frequent cause during the COVID-19 pandemic [32].

Zygomatic bone fractures were the most frequent type of facial fractures in both years, 47.3% (2019) and 43.3% (2020), corroborating with studies in Brazil and other countries [14, 25]. The results showed the statistical significance of zygomatic bone fractures in relation to motorcycle accidents and physical aggression in the 2019 cohort (p<0.05). Also, in 2020, data demonstrated a statistically significant proportion of zygomatic bone in motorcycle accidents which is also reported by other authors [2, 14, 27]. Zygomatic bone is the side pillar of the face and absorbs a large part of the traumatic force in traffic accidents and physical aggressions, as they have a high kinetic load on impact [25].

Different from the results presented, other authors demonstrate a higher frequency of fractures, such as mandible and nasal bones ones, in which this research corresponded to the second and third types of fracture, in both years [31, 33]. The nasal bone is placed in the sagittal area of the face and has less bone thickness, making it less resistant to trauma impact [26]. The nasal bone tissue is susceptible to low-speed fractures or high kinetic load; in this case, it causes quadrangular cartilage fractures, so such factors contribute to the increased incidence of fractures in this area [27, 28].

It was observed that mandible fractures were mainly related to motorcycle accidents. The mandible is the only facial mobile bone and has an exacerbated prominence, being directly exposed in cases of facial trauma [28]. However, the results of Cohn et al. [31] and Juncar et al. [10] emphasize that mandible fractures are more frequent in victims of physical aggression. These differences may be explained by cultural, economic, and sociopolitical variations in the epidemiological pattern of fractures of each area [10].

The inferential statistical data in 2020, a period of social isolation due to COVID, highlight a statistically significant proportion of nasal fractures in physical aggressions and fractures by shock (p<0.05) compared to 2019 (p>0.05). The growth in the number of nasal fractures due to interpersonal violence, in this atypical period, may be related to social isolation, sociopolitical conflicts, economic stress, and family issues [17, 29, 34].

The severity of facial fractures was higher in the 2019 cohort (2.48—2019 versus 2.44—2020), in comparison to the COVID-19 pandemic period. In opposite to our findings, Ludwig et al. [32] demonstrated that the severity of traumatic injuries was higher during the social isolation period by COVID-19. These results must be carefully analyzed, because the difference in the proportion of fractures between the studied years is a factor which influences the statistical analysis of data. In addition, there are few publications in relation to the severity of injuries in a comparative form, before the pandemic and the period of social isolation; therefore, our data represent a promisor scientific and clinical impact for the community.

The main etiological factor before and during social isolation by COVID-19 were the motorcycle accidents, mainly in individuals from the urban zone. The frequency and severity of facial fractures were lower during the pandemic period. The main bone affected by facial fractures was the zygomatic in both years. Thus, this study may contribute to epidemiological knowledge and management of facial fractures in future situations and educational campaigns in traffic, for greater public awareness.