Histochemical characterization of collagen fibers in fibrous overgrowth (irritation fibroma) of the oral mucosa: effect of age and duration of lesion

In a study of 43 specimens of oral mucosa irritation fibroma, polarization colours of collagen thin (0.8 μm) and thick (1.6-2.4 μm) fibers were recorded in formalin-fixed and paraffinembedded sections stained with Picrosirius red. Examination of polarization colours of both the 'thin' and 'thick' collagen fibers revealed an increase of yellowish-orange and orange fibers as a function of age in patients over 30 years old (P < 0.05 only in thick fibers). When the polarization colours of thin and thick collagen fibers were recorded as a function of duration of the lesion, there was an increase in the number of yellowish-orange and orange fibers and a decrease in blue-green and green fibers in both thin (P < 0.1) and thick (P < 0.05) populations as the lesion matured. These findings show that increments in both the patient's age and the duration of the lesions increase the amount of collagen fibers which exhibit yellowish-orange and orange polarization colours indicating tighter packing and better alignment of the microfibrils, similar to normal mature collagen. These differences may have an effect on the timing of the surgical excision.