Use of Chlorhexidine Gluconate to Prevent Bone Resorption in the Rice Rat

The purpose of this study was to observe the effect of daily swabbing with 2% chlorhexidine on the accumulation of dental plaque and on the loss of alveolar bone in the rice rat model. Weanling male rice rats (Oryzomys palustris) were placed on Teklad powdered diet 2000 and divided into three groups. One group of 14 animals was swabbed once each day, five times per week, with 2% aqueous chlorhexidine gluconate* applied by cotton-tipped applicator. The cotton tips were dipped in the chlorhexidine solution and then applied to the tooth surfaces of one side by a gentle rolling motion from the buccal over and on to the lingual surfaces of both the maxillary and mandibular arches. A fresh applicator was used to complete the other half of the jaws. A second group of 10 animals was swabbed similarly, but with applicators dipped in deionized water. A third group of 10 animals remained untreated. Food and deionized water were provided ad libitum. The experiment was terminated after 60 + 2 days. The animals were humanely killed and the maxillary and mandibular bone segments were dissected free. A plaque-disclosing agent containing erythrocin was applied to the teeth and the surrounding soft tissues. After a 2-second water rinse, buccal and lingual photographs were made using a dissecting microscope. The photographic images of each quadrant were projected at a fixed magniflcation. With the aid of a reference grid, the plaque area and total tooth surface area were then determined. The buccal and lingual scores were combined into a maxillary and a mandibular score, and these in turn were combined to yield a total score for each animal. The mandibles were defleshed, and alveolar bone loss was measured under a dissecting microscope equipped with a micrometer eyepiece. In a modification of the method of Keyes and Gold (Oral Surg, 8:492, 1955), eight sites were measured along the buccal and lingual surfaces from the cemento-enamel junction to the crest of the alveolar bone. The measurements were totaled to estimate the resorption. for each quadrant. Chlorhexidine swabbing reduced plaque accumulation significantly in comparison with either the swabbed or unswabbed controls (Table 1). Similarly, the results of analyses by Welch's t-test (Brownlee, Statistical Theory and Methodology, New York, John Wiley and Sons, Inc., 1965, p. 299) revealed significantly less alveolar bone loss in the chlorhexidine recipient group than either of the control groups. This finding confirms an earlier observation first reported by Morrison, Rosen and App (J Dent Res, 53:124, 1974) and further documents the role of chlorhexidine in preventing the loss of alveolar bone as well as its antiplaque activity. A comparison of control groups (Table 1) shows a statistically significant difference in the swabbed animals as compared to the unswabbed controls. This suggests that the swabbing itself appears to have had a beneficial influence in lessening the accumulation of plaque and in lessening the amount of bone loss in the model. Lastly, while the chlorhexidine and control groups showed no (statistically) significant difference with respect to body weight, the two control groups did show a significant difference (p < 0.02).