This study aimed to review the oral hygiene status, oral care guidelines, and outcomes of oral care in intensive care unit (ICU) patients from a dental perspective for effective oral care. A literature search using the keywords “Hospital dentistry” OR “Oral care” OR “Intensive care unit” OR “Hospital inpatient” OR “Hospitalization” OR “Emergency service” AND “Oral health” OR “Oral hygiene” OR “Dental plaque” was conducted in PubMed, Medline, and Google Scholar to identify publications reporting on the oral care of the patients admitted to ICUs. A total of 17,400 articles were initially identified. Of these, 58 were selected and classified into three categories for critical review. Seven of these studies evaluated the oral status of ICU patients, and most of the studies indicated that ICU patients had poor oral hygiene or required active dental treatment. Thirty-three of these studies evaluated oral care methods for ICU patients, and in general, oral care methods using chlorhexidine as adjuncts along with tooth brushing were recommended. However, there were insufficient studies to evaluate oral hygiene through effective assessment tools from a dental perspective. In 36 studies on the outcomes of oral care in ICU patients, interventions by dental professionals showed effective results in preventing hospital-acquired infection. This review highlights the importance of establishing guidelines for the evaluation of oral status in ICU patients and summarizes data that may be useful for future studies. Further studies on maintaining good oral hygiene among ICU patients are needed.