EXPERIMENTAL BILIRUBIN PIGMENTATION OF RAT DENTIN AND ITS DETECTION BY A QUALITATIVE ANALYTICAL METHOD

An animal model of bilirubinemia was used to determine whether bilirub in present in pigmented teeth can be extracted and qualitatively analy sed. The bile ducts of 10 Long-Evans Agouti rats were ligated and bili rubin (14 mg/kg per day) was injected intraperitoneally for 4 days. Wh en the animals were killed 2 weeks later, pigmented lower incisors wer e observed in three animals. These teeth were dried, powdered and bili rubin was extracted with chloroform/methanol/acetic acid, 30:10:0.5, v /v for 10 min under sonication. After centrifugation, the supernatant was collected and evaporated. The residue was dissolved in chloroform and its absorption spectrum measured before and after diazo reaction. This resulted in a shift of the absorption maximum from 450 to 540 nm and indicated the presence of bilirubin in pigmented teeth. No bilirub in was found in the lower incisors of untreated control rats. This tec hnique may be useful in distinguishing bilirubin staining from other i ntrinsic discolorations of teeth. Copyright (C) 1996 Elsevier Science Ltd.