Clinical Application of Tissue Reflectance Spectrophotometry to Periodontal Disease

Rapid, accurate, and non-invasive measurements of hemodynamics and oxygen utilization in gingiva are clinically important in evaluation of the severity of the inflammatory response in periodontal disease. In the present study, tissue reflectance spectrophotometry was used to examine gingiva in vivo to estimate hemoglobin concentration (Hb index) and the oxygen saturation level of hemoglobin in gingiva (HbSO 2 index). Reflectance spectrophotometry was also used to examine these parameters in experimental periodontitis in dogs, and in patients with periodontal disease. Both in vitro and in vivo experiments confirmed that the Hb index was positively correlated with hemoglobin concentration in gingival tissue. The relationship between the HbSO 2 index and PO 2 in gingiva was a sigmoid curve resembling the hemoglobin-oxygen dissociation curve. In rapidly advancing periodontitis resulting from ligature placement in dogs, the Hb index was significantly enhanced, but the HbSO 2 index was reduced. This reduction corresponded to increases in gingival inflammation during the experiments. Furthermore, in humans, the Hb index was significantly higher in inflamed gingiva than in clinically healthy gingiva. A lower HbSO 2 index was also found in inflamed gingiva. These findings are consistent with congested blood vessels, impaired venous return, and localized hypoxia in inflamed gingival tissue. Tissue reflectance spectrophotometry is clinically useful in estimating blood volume and oxygen saturation in diseased gingiva.