I am looking for references to serious research articles on the subject, whether confirming or refuting. (Or articles referring to such, but not articles without peer refereed references.)
To avoid any confusion, by "serious" I only mean reputable peer refereed journals.
Here are some examples of such articles, taken from https://www.reddit.com/r/C_S_T/comments/6t6wot/oil_pulling_and_why_the_skeptics_are_wrong/, (some of which seem to confirm the positive effects of the oil pulling but do not seem to study the specific problem in the question):
https://www.johcd.org/doi/pdf/10.5005/johcd-1-1-12 https://www.ncbi.nlm.nih.gov/pubmed/27084861 https://www.ncbi.nlm.nih.gov/pubmed/11890570 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3853744/ https://www.ncbi.nlm.nih.gov/pubmed/25838632 https://www.ncbi.nlm.nih.gov/pubmed/21911944 https://www.nature.com/articles/sj.bdj.2012.856?foxtrotcallback=true
Many sources recommend to spend 15-20 minutes for oil pulling, however those numbers look randomly chosen with no justification provided. It is conceivable that 15-20 minutes have been chosen by popular practitioners for reasons of their personal comfort, while other sources have simply repeated the figure. It is also conceivable that longer pulling may increase the benefits, even if it feels less comfortable to some practitioners. Or, conversely, are there side effects of any prolonged oil pulling?
My question is, where is the science and where are people's personal convenience choices? Has any research been conducted to study effects of the oil pulling over different periods?