Background: Plaque is the cause of dental caries and periodontal disease. Food colouring with the pink rose colour can be used as a disclosing solution and it is better than common liquid used for plaque detection. It is not yet known the exact concentration of food coloring that can be absorbed to expose the plaque clearly. 

Aim: To determine the most effective concentration of the food colouring to visualize the plaque as an alternative for plaque detector and the most comfortable concentration for the respondents. The benefits of research is finding the optimal concentration of food coloring as a disclosing solution to improve oral hygiene community.

Methode: This was an experimental research using rose pink food colouring powder   that available in the market. The object of this research was 10 students of the Department of Dental Nursing, divided into two groups, the treatment group and the control group. Common disclosing solution were used for control group, while a solution of food colouring with a concentration of 2.5gr/20ml (A), 5 gr/20 ml (B) and 10gr/20ml (C) without sweeteners and 2.5gr/20ml(D), 5 gr/20 ml (E) and 10gr/20ml (F) with sweeteners (1,25 gr, 2,5 gr and 5 gr of sugar respectively) were used for treatment group. Mann Whitney test were used to define which concentration of the food colouring solution were similar or better than common disclosing solution. 

Results: Significant difference were found on colour intensity between treatment and control group except for concentration 2,5 gr/20 ml (p=0,222). But the most intense colour and the most acceptable taste perception were at concentration 2,5gr/20 ml of food colouring with the 1,25 gr (p=0,04)

Conclusion: Solution  of 25gr food colouring powder + 1.25 gr sugar / 20 ml is the most optimal concentration as a plaque detector and as the most acceptable taste of respondents.

Key words:  Food colouring, disclosing solution, plaque