Original sentence: A study using a tea tree oil solution as a mouth rinse found no positive effect on the quantity or quality of supragingival plaque.Different oils, for instance soy oil have also been tried regarding their anti-plaque effect,  with or without other substances (PMID 12799117, PMID 7817156, PMID 7634134)
Edited sentence: Different oils , for instance soy oil have also been tried regarding their anti-plaque effect,  with or without other substances (PMID 12799117, PMID 7817156, PMID 7634134) A study using a tea tree oil solution as a mouth rinse found no positive effect on the quantity or quality of supragingival plaque