Study sample
tooth
EVENTS, RECRUITMENT
Study participants were recruited via an internal mailing list of the Justus-Liebig-University Giessen and via online announcements of a regional newspaper. Inclusion criteria were being a student-resident of Giessen aged at least 18 to a maximum of 35 years as well as the predominant use of a manual toothbrush for at least six months (at least two-thirds of all tooth brushing events). Exclusion criteria were fixed orthodontic appliances, removable prostheses/dentures, oral piercings or dental jewelry, dental prophylaxis within the previous four months, pregnancy/lactation or use of antibiotics within the previous three months, and any training in a dental or medical profession. Sample size was calculated using G*Power 3, a free available power analysis program [
Flow diagram of participant recruitment, randomization, follow-up, and analysis