## 1 Introduction
In several studies between 1970 and 1975, air filtration systems (Electrostatic filters) were tested and proved to reduce microorganism concentration in the dental office air [17; 18]. A study conducted by [PERSON] in 2009 in a hospital dental clinic showed that only 36.7% of the dental personnel rigorously respected the decontamination, disinfection and sterilization protocols, leading to an increased occupational risk [19]. More recent studies (2018) also focused on the sterilization protocols and their efficiency (surfaces, instruments, air etc. ), showing less than optimal outcomes. The authors of the article suggest the implementation of biologic monitoringprotocols [20]. Several other studies that were conducted in the past few decades tend to show the high level of air contamination in dental offices, especially during dental procedures and the importance of biologic monitoring and strict disinfection and sterilization protocols [21,22]. The bacterial contamination of the dental office is a valuable indicator in the evaluation of the infective risk, both for dental personnel and patients entering the office [23]. Although, during the past few months, the focus was mostly shifted towards viral infections, evaluation of the viral load is more difficult and presents a higher contamination risk. The prevalence of Hepatitis C virus (HCV) was measured by [PERSON] and his team on different surfaces in the dental office by harvesting samples in order to identify HCV-RNA strands and analyze them by polymerase chain reaction (PCR) [24]. Positive HCV patients took part in that study. Such a testing protocol would have been unethical to conduct with SARS-CoV-2 patients because of the extremely high risks involved. National and international guides were elaborated during the pandemic in order to reduce the risk of cross contamination and medical personnel infection. Each country outlined their own set of indications, but most of them were common throughout the world. One of the most important recommendations was related to oral cavity rinsing with antiseptic solutions before aerosol inducing procedures. The efficiency of this measure in reducing the bacterial load of oral cavities has been well-documented for a long time. Some studies suggest a decrease of the bacterial load in aerosols by up to 92%. Scribs, coats or other medical uniforms are also a reservoir of bacteria resulted from aerosol inducing procedures; therefore, changing scrubs between patients is considered a good way to prevent cross contamination [14]. During this period, impermeable, single use overalls were recommended to avoid such risks. PPE also included FFP2/3 face masks (N95 or above). Their efficiency has been determined to be very high, if used correctly: 99.7% for influenza A virus, rhinovirus 14 and _S. Aureus_, and 99.3% for surrogate particulates (paraffin oil and sodium chloride) [25]. Face shields and protective spectacles were also included in the mandatory PPE list, since their efficiency has also been proven for a long time [8]. Although it is not part of the PPE per se, the dental dam was one of the most effective ways to control the spread of pathogens through aerosols. Intraoral radiographs were forbidden for several months, using panoramic scans and CT (CBCT) scans as an alternative. The recommendations for air disinfections included natural or forced ventilation, Ultraviolet C (UVC) light and dry aerosols. A study from 1994 conducted in Italy by [PERSON] recommended the use of a dry aerosol producing machine that vaporizes phenols or chlorbreaking for environmental disinfection. This method seemed to remove all salivary microorganisms from the dental office. The authors suggested the use of this device at the end of every workday [26]. Other studies recommended fumigation of the office at least once a month [27]. Little information, though, has been offered regarding the used substances, concentrations, particle sizes etc.