AIMS: The main purpose of the study was to find out how the oral health of critically ill patients affected the chances of bad outcomes such as longer hospital stays and death while taking into account possible confounders such as how often the critically ill patients used chlorhexidine mouthwash each week and their sequential organ failure assessment scores. METHODS: We conducted a retrospective observational study on 4,999 critically ill patients admitted to the King Hussein Medical Centre in Amman, Jordan, from January 2018 to May 2022. The patients were adults and the elderly, with a minimum of three consecutive days of admission. The study encompassed both mechanically ventilated and non-ventilated patients. We divided the cohort into two groups, Group I, based on favorable adverse outcomes, and Group II, based on unfavorable adverse outcomes. We examined the weekly administration of chlorhexidine mouthwash during critical care admissions as the principal variable. We conducted multiple logistic regression analyses to evaluate the correlation between weekly mouthwash usage and the likelihood of poorer outcomes while accounting for oral health conditions and the risk of critical illness. RESULTS: A retrospective study of 4,999 critically ill patients revealed that 2,370 patients (47.41%) achieved improved composite outcomes of interest (cOI), while 2,629 patients (52.26%) fell into the inferior cOI group. The overall mortality rate in the lower socioeconomic category was 1,920 patients (73%), compared to 709 patients (27%) in the survival rate. A study using multiple logistic regression showed a strong link between critically ill patients' oral health statuses (OHS), how often they used mouthwash each week (WMW), and their sequential organ failure assessment (SOFA) scores. The regression association for OHS relative to poorer cOI was positive, indicating a higher risk for poorer OHS compared to better OHS. The multivariate logistic regression model showed a predictive variability range of 69.5%-92.7%, with sensitivity indices of 98.6% for specificity, 96.7% for sensitivity, and 97.6% for accuracy. CONCLUSION: The study found a significant association between poor OHS and adverse outcomes. Other factors in critically ill patients, such as the weekly application of chlorohexidine gluconate mouthwash and SOFA, significantly influenced this independent variable, which had a high propensity risk of 180.965. The optimal threshold for a weekly chlorhexidine mouthwash application was 15.5 times per week.