Aims SARS‐CoV‐2 RNA has been recovered from different sites in the human body, including the mouth. The present study aimed to investigate the presence of SARS‐CoV‐2 RNA in the dental biofilm of symptomatic patients who tested positive in nasopharyngeal and oropharyngeal (NASO/ORO) samples. Materials & Methods An observational clinical study of individuals with flu‐like symptoms was conducted between July and September 2020. Dental biofilm (BIO) samples were collected and analysed using real‐time quantitative polymerase chain reaction (RT‐qPCR) to determine the virus's presence. Results Seventy participants (40 ± 9.8 years of age, 71.4% female) tested positive for SARS‐CoV‐2 RNA in NASO/ORO samples and were included in the study. Among them, 13 tested positive in BIO samples (18.6%; 95% CI: [9.5, 27.7]). The median and interquartile range of cycle quantification (Cq) for NASO/ORO and BIO samples were 15.9 [6.9] and 35.9 [4.0] (p = .001), respectively. BIO‐positive participants showed a higher virus load in NASO/ORO samples (p = .012) than those testing negative (Cq = 20.4 [6.1]). Conclusions Dental biofilms from symptomatic COVID‐19 patients harbour SARS‐CoV‐2 RNA and might be a potential reservoir with an essential role in COVID‐19 transmission.

Background Saliva, salivary glands, gingival crevicular fluid, and supragingival biofilms may harbor SARS‐CoV‐2 RNA. This observational study aimed to investigate the presence and load of SARS‐CoV‐2 RNA in supragingival, and subgingival biofilms obtained from intensive care unit (ICU) patients. Methods A convenience sample, composed of 52 COVID‐19+ participants (48.6 ± 14.8 years, 26.9% females), were evaluated for pre‐existing comorbidities, number of teeth, and periodontal data [visible plaque (VPI), bleeding on probing (BOP), periodontal probing depth (PPD), and attachment loss (AL)]. Supragingival and subgingival samples (SubDeep: four sites with the deepest PPD; SubRemain: remaining shallower sites) were analyzed by RT‐qPCR with corresponding cycle quantification (Cq). Statistical analyses considered the individual ( P = 5%). Results Twenty‐six participants tested positive for dental biofilms (Biofilm+) with 96.2% of them being positive for subgingival samples. Pre‐existing comorbidities, number of teeth examined, VPI, PPD, AL, and BOP were similar between Biofilm+ and Biofilm‐. SubDeep PPD (3.72 ± 0.86), AL (4.34 ± 1.33), and % of BOP (66.0 ± 31.1) values were significantly greater compared to SubRemain values (2.84 ± 0.48, 3.37 ± 0.34, and 20.4 ± 24.1, respectively). Biofilm+ Cqs showed no association with the periodontal condition. Cqs from Nasopharynx/Oropharynx (Naso/Oro; n = 36) were similar between Biofilm+ and Biofilm‐ participants. Length of time since ICU intake, last Naso/Oro RT‐qPCR readings, onset of COVID‐19 symptoms, and biofilm samplings were greater for Biofilm‐. Conclusions ICU patients harbored SARS‐CoV‐2 RNA in supragingival and subgingival biofilms, irrespective of the periodontal condition, and systemic viral load. The high number of positive patients highlights the need to better understand this habit to provide adequate oral care.