Review Questions/ Objectives The objective of this review is to synthesize the best available evidence for the effectiveness of daily oral use of propolis to improve oral health by reducing oral plaque, oral ulcer and oral infection. Specific questions to be answered are: 1. What is the effectiveness of propolis mouthwash or gel on the plaque index for adult population? 2. What is the effectiveness of propolis mouthwash or gel on the frequency of ulcers for adult population? 3. What is the effectiveness of propolis mouthwash or gel on the severity of oral infection for adult population? Inclusion criteria Types of Participants Adults over 18 years old of either gender who are in-patient and out-patient settings are included in the review. Types of Interventions Daily orally taken propolis mouthwash or gel Comparator: placebo or other mouthwash Types of Outcome The outcome measures will include: (1) The score of supragingival dental plaque measured by the Plaque Index(PI) (2) The number of ulcers in one year measured by the frequency of mouth ulcers (3) The severity of oral infection by culture to estimate the existence or counts of bacteria or fungi