Research reports about the etiologies of breath malodor agree that the vast majority of halitosis originates with the anaerobic bacterial degradation of sulfur containing amino acids within the oral cavity, resulting in the emission of hydrogen sulfide (H2S), methyl mercaptan (CH3SH), and dimethyl sulfide (CH3SCH3), collectively referred to as volatile sulfur compounds (VSC).
The Halimeter® responds to all three volatile sulfur compounds, and gives a reading of total VSC’s.
Here are the electrochemical reactions in the sensor:
H2S 2H+ + S0 + 2e–
2CH3SH CH3 – S – S – CH3 + 2H+ + 2e–
CH3 – S – CH3 + 2H2O 2CH3OH + S0 + 2H+ + 2e–
To be rigorous, the Halimeter® does not respond equally to all three compounds, nor are all three compounds present in the same proportion in all patients—or even in the same patient—at all times. The relative amounts of these compounds are affected by diet, and the extent of anaerobic bacterial growth.
Elucidating the precise breakdown of the three compounds in an oral malodor sample requires a gas chromatograph, an instrument clearly beyond the scope of the typical dental office, and rare enough even in academic dental research settings. Fortunately, the additive reading provided by the Halimeter® correlates extremely well with organoleptic panels of trained human olfactory evaluators, and compares admirably with chromatographic testing.
At levels of 200-300 ppb, oral malodor is noticeable by an observer standing close to the patient.
At 350-400 ppb, the odor is noticeable by an observer standing several feet away from the patient.
At 500-700 ppb the odor is more noticeable not because it is “stronger,” but because it is more foul.
At over 1000 ppb, the odor will linger for several minutes after the patient leaves the room.
As in all biological parameters, Halimeter® readings should be used not so much as absolute standards, but as relative indicators of a condition. That is, a “normal” blood pressure reading is said to be 120/80. While 180/110 would be an indication that the patient should look into his condition, a reading of 130/82 would not.