An umbrella review of systematic reviews of the evidence of a causal relationship between periodontal microbes and respiratory diseases: Position paper from the Canadian Dental Hygienists Association.

Previous position papers have confirmed to varying degrees associations between periodontal microbes and respiratory tract infections such as nosocomial or hospital-acquired pneumonia (HAP), ventilator-associated pneumonia (VAP), and chronic obstructive pulmonary diseases (COPD). Causal relationships have not been confirmed and have been the source of much confusion for the medical and oral health professions. Aim: To investigate whether sufficient evidence exists for a causal relationship between periodontal microbes and respiratory diseases, with a focus on HAP and VAP. Methods: The PICO question was "For patients in hospitals, nursing homes or long-term care facilities who are at high risk for respiratory infections, will an oral care intervention such as toothbrushing, administration of antimicrobial agents, and/or professional care, as compared to no oral care intervention (or usual oral care) reduce the risk for respiratory infections?" Only systematic reviews (SRs) with or without a meta-analysis (MA) of randomized controlled trials published in the English language between 2007 and 2019 were included. Databases searched included PubMed, MEDLINE, EbscoHost, CINAHL, Scopus, Cochrane Registry of Systematic reviews, and Clinical Trials Registry. Quality assessments were conducted by both authors using the PRISMA checklist. The Bradford Hill criteria were used to determine evidence for causality. Results: Of 47 respiratory studies retrieved, after elimination of duplicates and studies not meeting inclusion criteria, 10 SRs were selected, 9 of which included MAs. Although there was evidence that administration of chlorhexidine gluconate (CHX) reduced the risk for VAP, none existed for HAP. Limitations included inconsistencies among studies in population groups, CHX concentration, frequency of administration, number of applications, and insufficient evidence for use of povidone iodine or toothbrushing in ventilated patients. While some studies reported other patient-centred outcomes (i.e., ICU mortality, length of ICU stay or duration of mechanical ventilation), findings were positive only for cardiac surgery ventilated patients, who did not meet the inclusion criteria. Conclusions: Bradford Hill criteria analysis failed to support a causal relationship between periodontal microbes/oral health care and respiratory diseases such as pneumonia.