Laser Doppler measurement of gingival blood flow in dogs with increasing and decreasing inflammation

Dramatic changes in vessel morphology and vascularization are associated with early clinical signs of gingivitis in the dog; there is conflicting evidence of both increased and decreased blood flow in the inflamed gingiva. The blood-flow rates were compared in treated and untreated gingivitis in dogs by a new, non-invasive technique, the laser Doppler flow meter (LDF). The LDF measures blood flow in 1 mm 3 of the gingival margin by back-scattered light. Four adult mongrel dogs with generalized mild gingivitis were fed a dental-plaque-inducing diet. Teeth on the left were scaled and polished at zero and four weeks and brushed six times a week during the seven-week experimental period; teeth on the right were left untreated. Test teeth were the upper canines through to the fourth premolars, and lower second premolars through to the first molars. On the facial aspect of these teeth, plaque index (PlI), gingival index (GI), and gingival crevicular fluid (GCF) were assessed at weeks zero, one, four and seven. Blood flow at the gingival margin was measured with LDF at weeks one, four and seven. Acrylic appliances were used to reposition the fibre-optic probe in the same place at each follow-up examination. In a conditional binary logistic regression model, PlI, GI and GCF were significantly related to treatment ( p < 0.01), but LDF blood flow was not ( p = 0.01). Blood flow increased slightly with time on the untreated side, but there was no significant decrease in blood flow with the resolution of inflammation on the treated side. Thus microvascular changes in gingival inflammation may not quickly, if ever, be reversed.