It has been propagated by the dental care professionals to start toothbrushing the lingual aspect of teeth first. In general, it is assumed that these surfaces of teeth are more difficult to clean. The evidence to support this recommendation is sparse.
In this randomized controlled clinical trial using a split-mouth design, 46 students were included. Before the visit, the participants were requested to refrain from any oral hygiene procedure for 48 h. First, the plaque index (PI) score was assessed full mouth. Two randomly chosen contra-lateral quadrants were used to start brushing from the lingual aspect first. The opposing two quadrants were used to start brushing from the buccal aspect. After the brushing exercise was completed, full-mouth PI was scored again. Subanalyses were performed for the buccal, lingual and approximal surfaces.
At baseline, there was no statistically significant difference between the two sets of contra-lateral quadrants (P = 0.770). Starting at the lingual aspect of the lower jaw resulted in a 55% reduction of plaque scores in comparison with 57% when the brushing exercise was started buccally. The difference in mean plaque scores between brushing orders was 0.04, which was not significant (P = 0.219). None of the subanalyses revealed any significant differences for the isolated surfaces.
Using a manual toothbrush reduced the plaque scores between 55 and 58% with no difference between brushing from either the lingual or buccal aspect first. Within the limitations of this study, a recommendation to start toothbrushing the lingual aspect is not supported by the outcome in this young student population.