Morphological and quantitative study of collagen fibers in healthy and diseased human gingival tissues

Objectives: This study aimed to evaluate types I, III and IV collagen in healthy gingival tissue and to compare them to gingival tissues suffering from chronic gingivitis and chronic periodontitis. Materials and Methods: Thirty-two man patients were selected. The patients belonged to three diagnostic categories: healthy gingiva (HG), chronic gingivitis (CG) and chronic periodontitis (CP), based on clinical and radiographical criteria. Gingival tissue samples were obtained from patients who underwent periodontal surgery procedures. Hematoxylin and Eosin (HE), Picrosirius red, indirect immunofluorescence by confocal microscopy and quantitative analyses were performed to identify the presence and location of types I, III and IV collagen. Statistical significance was verified using the Kruskal-Wallis test. Results: Samples from HG group showed thick collagen fibers arranged in a parallel pattern. Samples from CG group showed dilated blood vessels; collagen fibers and inflammatory cells were found dispersed throughout the tissue. Samples from CP group showed the extracellular matrix severely damaged, disorganized collagen fibers and large amount of inflammatory cells. The HG group showed an apparent higher expression of type I collagen, when compared to tissues with CG and CP, however no statistical differences were detected (p=0.064). The types III and IV collagen fibers showed no difference in expression in tissues with gingivitis and periodontitis. Conclusions: Following the periodontal disease there was a morphological destruction of the extracellular matrix with lower expression of collagen, which led to a change in tissue architecture that might compromise its functional capacity. There were differences in type I collagen expression among healthy, chronic gingivitis and chronic periodontitis tissue samples.