A Cochrane review [withdrawn from publication] included 2 studies with a total of 40 subjects. No primary outcome measures like self expressed or organoleptic scores were reported. Secondary outcomes expressed as volatile sulfur compound (VSC) levels were assessed by a portable sulfide monitor in both trials. One trial showed reductions of VSC levels of 42% with the tongue cleaner, 40% with the tongue scraper and 33% with the toothbrush (p<0.05). Reduced VSC levels persisted longer with the tongue cleaner than the toothbrush and could not be detected for more than 30 minutes after the intervention in any of the groups. The second trial showed a reduction of VSC levels compared with baseline measurements of 75% with the tongue scraper and 45% with the toothbrush (p<0.01). Six (60%) of the participants complained of nausea and one participant of tongue trauma only with the toothbrush but all participants were receptive to the tongue scraper.
Comment: The quality of evidence is downgraded by sparse data and indirectness.
An RCT with a cross-over study design included 21 subjects. No halitosis at day 14 was identified in 12/21 subjects with active rinse alone, in 10/21 with adjunct use of tongue scraper, in 1/21 for negative control rinse alone, and in 3/21 in the control and tongue scraping sequence. At day 14, significantly lower counts were identified only in the active rinse sequence (p < 0.001) for 15/78 species of bacteria. A decrease in bacteria from baseline to day 14 was found in successfully treated subjects for 9/74 species. The use of a tongue scraper combined with active rinse did not change the levels of VSC compared to rinsing alone.