Answer:
experimental
Explanation:
Based on the information provided within the question it can be said that the research method that was used was experimental research design. This is a research method which follows the scientific method, meaning that it has a hypothesis, a manipulated variable, as well as other variables that are measurable, while the whole is experiment is completely controlled. Which seems to be the case in this scenario since there are controlled groups as well as a manipulated variable such as the oral punch biopsy given to some of the groups.