Objectives: This review aimed to compare the effectiveness of using a dental water jet (WJ) to manual tooth brushing (MTB) alone or when combined with flossing (MTB + F) in improving plaque index (PI), bleeding index (BI), and gingival index (GI) in regular and orthodontic patients. Materials and Method: This review was registered with the PROSPERO registry (CRD42022296752). Three reviewers conducted a comprehensive search of MEDLINE, the Cochrane Library, and Google Scholar for studies published between 1990 and July 2022. Eligible studies were randomized clinical trials, excluding those involving peri-implantitis, patients with impaired manual dexterity, or powered brushes. The outcomes of interest (PI, BI, and GI) were measured across short-, intermediate-, and long-term periods. Results: Eighteen RCTs were included in this review. PI: in regular patients, use of a WJ showed no additional improvement over flossing, and the results were inconsistent when compared to MTB alone. For orthodontic patients, use of a WJ provided a slight improvement over flossing in the short term and MTB alone in the intermediate term. BI: use of a WJ demonstrated a slight improvement over flossing and MTB alone in both patient groups at different time points. GI: use of a WJ was comparable to flossing but showed slight benefits over MTB alone in the short term for regular patients and in the intermediate term for orthodontic patients. Conclusions: use of a WJ may provide slight benefits in BI and GI compared to flossing or MTB alone, especially for orthodontic patients. Clinical relevance: incorporating a WJ into the daily oral hygiene routine is recommended due to its potential benefits over brushing alone and its user-friendly alternative to flossing.