Classification of halitosis by malodor intensities measured with electronic nose

Objectives: For halitosis to be diagnosed, oral malodor is assessed with the organoleptic test and/or gas chromatograph. However, these two measurements do not necessarily give concordant results. We previously reported that various volatile organic compounds measured with electronic nose (EN) contributed to oral malodor. The purpose of this investigation was to classify halitosis patients by cluster analysis using malodor intensities of various volatile organic compounds in breath air as measured with EN.

Methods: Sixty-three patients who complained of oral malodor participated. Oral malodor was assessed by the malodor-intensity values of seven category-gases using EN. Cluster analysis was performed by Ward's method using the malodor intensities measured with EN. Oral health status was evaluated as probing pocket depth (PPD), tongue coating score (TCS) and plaque index (PLI). Additionally, the proportion of total six anaerobes in saliva was assessed by real-time PCR method.

Results: Based on the malodor-intensity values of seven gases, the halitosis patients were classified into four clusters. All of the malodor intensities were high in cluster 1, the intensities of hydrogen sulfide and methyl mercaptan were high in cluster 2, the intensities of five gases except for hydrogen sulfide and methyl mercaptan showed high level in cluster 3 and the intensities of all gases were low in cluster 4. In addition, % teeth of PPD of 4mm or greater, TCS and PLI in cluster 1 were significantly higher than those in cluster 4. TCS in cluster 2 was significantly higher than that of cluster 4. PLI in cluster 3 showed significantly higher than that in cluster 2 or cluster 4. The proportions of total six anaerobes in cluster 1 and 2 were significantly higher than those in cluster 4.

Conclusion: The classification of halitosis using various malodor intensities measured with EN may be useful for diagnosis of oral malodor.