A Comparison of Two Models of Experimental Periodontitis in Rats

Abstract

Rats are being used in models of experimental periodontitis because the periodontal anatomy in the molar  region bears much resemblance to that of man. Furthermore, rats are available with different genomes and  microbial status. 

The main purpose of the study was to compare two different methods of inducing experimental periodontitis  in rats, by ligature or LPS injection. 

Rats were bred and housed on wire-mesh floor with no bedding material and fed a special diet to avoid  periodontal destruction caused by impaction of bedding and dietary fibers interdentally. Because no bedding  was used it was suggested that in future studies PVC tubes (diameter: 7 cm, length: 12-15 cm) be  placed in the cages to improve the environment for the rats. The possible effect of doing so was therefore  also examined in this study. 

Periodontitis was established either with peridental silk ligatures for 1 or 4 weeks or with gingival injections  of lipopolysaccharide (LPS) every other day for a 6-day-period to provoke inflammation. For each  experimental group a corresponding control group was established. In all groups the number of rats was  14. In addition 10 rats receiving no treatment were placed in cages with PVC-tubes. Alveolar bone loss was  measured by means of morphometrical and radiographical methodologies. 

A previously described method for breeding and housing periodontitis-free rats was reproduced. The access  to PVC-tubes did not result in differences in alveolar bone destruction when compared to the 4-week control  group and therefore, PVC-tubes may be used as an environmental improvement for the rats in future  studies. 

Compared to the control groups significantly more alveolar bone loss was established in the ligated rats  both after 1 and 4 weeks, with the 4-weeks-ligature group having significantly more alveolar bone destruction  than the 1-week-ligature group. No effect of LPS injections could be demonstrated and therefore, the  study did not confirm earlier findings of significant effect of LPS injection on alveolar bone destruction  as compared to saline injection.