Annotation Effect of Lithium Upon Plaque and Gingivitis in the Beagle Dog JAMES L. MCDONALD, JR., BRUCE R. SCHEMEHORN, and GEORGE K. STOOKEY Oral Health Research Institute, Indiana University School of Dentistry, 410 Beauty Avenue, Indianapolis, Indiana 46202, USA J Dent Res 57 (3) :474, March 1978. This is a report on the influence of lithium upon plaque and gingivitis in the Beagle dog. Twenty male Beagle dogs (20 to 30 lbs: 23 months of age) were used. One week before initiation of the study, all dogs received a thorough dental prophylaxis including manual scaling and polishing with a flour of pumice slurry. Twenty-four hours before the study initiation, baseline gingivitis scores were obtained and all buccal plaque accumulations removed with a rubber prophylactic cup and flour of pumice. On the basis of the gingivitis scores the dogs were then divided into 3 groups. The various groups were as follows: A, deionized water; B, deionized water containing 25 ppm lithium added as LiCl; and C, deionized water containing 100 ppm lithium added as LiCl. The dogs were provided their respective drinking water ad libitum during the study and were individually provided twice daily approximately 300 gm of a moistened commercial dog ration with the appropriate drinking water. Following 4 weeks on this regimen the dogs were anesthetized and evaluated for plaque and gingivitis. During this study, 22 different buccal gingival areas were clinically evaluated for gingivitis (I3, C4, P, 13, P4, M', bilaterally) using the following criteria: 0, no apparent inflammation; 0.5, mild inflammation not extending completely around the scored surface; 2, moderate inflammation with hemorrhaging on gentle probing; and, 3, severe inflammation with spontaneous hemorrhaging. The scores for each gingival area were totaled and the sum divided by the total number of surfaces scored to give an average per area gingivitis score for each animal. Plaque was scored visually on the corresponding tooth surfaces after staining with 0.075% fuchsin using the following criteria: 0, no observable plaque; 1, scattered plaque covReceived for publication October 3, 1977. Accepted for publication February 1, 1978.

ering less than 10% of the buccal tooth surface; 2, plaque covering between 10 and 33% of the buccal surface; 3, plaque covering between 33 and 66 % of the buccal tooth surface; and, 4, plaque covering more than 66% of the buccal tooth surface. The individual tooth scores were then totalled and the sum divided by the total number of teeth scored to give a mean per surface plaque score for each dog. In order to maintain blindness the two examiners remained unaware of the nature of the assigned treatments and were not involved in the treatment phase of the studies. The data were initially analyzed for homeogeneity of variance using the Bartlett chi-square test (at a = 0.10) and a one-way analysis of variance was utilized (at a = 0.05). Two weeks after initiation of the study, several dogs in Group C showed signs of weight loss with 2 dogs refusing to eat. Subsequently, one dog (No. 20) died. All dogs in Group C were taken off the 100 ppm lithium water approximately 20 days into the study. A blood test of dog No. 20 showed a markedly elevated blood urea nitrogen (200 versus a normal 10 to 20 mg%). This was suggestive of acute renal failure. A subsequent histologic evaluation of the kidneys revealed acute tubular necrosis of the proximal convoluted tubules. The pathologist's conclusion was that the lithium chloride was nephrotoxic in this particular animal-in other words that it was an idiosyncracy. The results of the experiment are presented in the following table. Neither examiner found any significant difference in plaque or gingivitis between the water group and the group provided 25 ppm lithium in the water. The group receiving 100 ppm lithium in the drinking water was stopped midway through the experiment because of the possible toxic manifestations. In conclusion, the presence of 25 ppm lithium did not influence plaque or gingivitis in this experimental model. By means of comparison, the use of chlorhexidine treatments in this model in repeated experiments resulted in reductions of plaque and gingivitis ranging from 44 to 53%.

TABLE PLAQUE AND GINGIVITIS SCORES Experimental Regimen

Number Dogs

Examiner No. 1 (JLM) Plaque

0.10j*t

Deionized water

6

2.66 ±

Lithium, 25 ppm

7

2.66 ± 0.10

Lithium, 100 ppm

7

*

Gingivitis

Examiner No. 2 (BRS) Plaque Gingivitis

0.56 +

0.121

2.65 ±

0.46 ±

0.061

2.73 -+ 0.11

0.101

0.51 ± 0.10

0.49

0.07

Group Discontinued

Standard error of the mean.

t Values within brackets do not differ significantly (P < 0.05).

474

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