Post-mortem Drug Analysis of Plaque Samples in Seven Intoxication Cases

Objectives: Non-mineralized dental biofilm (plaque) as material for drug analysis might extend the spectrum of common matrices (e.g. blood, urine, hair) used in forensic toxicology, especially in post-mortem drug analysis. So far, the retention of extraneous substances in plaque has been investigated only sparsely. Hence, post-mortem plaque samples from seven intoxication cases were analyzed on illicit and medicinal drugs. Since opioids show a high prevalence in intoxications, findings for morphine and codeine (also metabolites of street heroin) are presented here.
Methods: Plaque samples were obtained post-mortem in seven cases using a dental scaler. The samples were air-dried, extracted by ultrasonication with acetonitrile and quantitatively analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results were compared to those of routinely analyzed hair and body fluid (femoral blood, urine) samples.
Results: Morphine has been detected in all plaque samples with concentrations ranging from 5.8-8,100 pg/mg (median: 90 pg/mg), whereas codeine has been found in 4/7 cases with concentrations ranging from 2.8-400 pg/mg (median: 167 pg/mg).
In two cases morphine could not be detected in body fluids but only in hair and plaque. In one case morphine has not been found in any routinely investigated material, but in plaque (90 pg/mg).
Conclusions: The results are showing that opiates are retained in plaque and can be detected using the presented method. Compared to other matrices (especially body fluids), plaque may offer a larger window of detection in three of seven cases. In one case morphine was exclusively found in plaque confirming a morphine uptake missed by routinely analyzed matrices. Therefore plaque might be a suitable additional alternative matrix in forensic toxicology especially if other material is not available.