Agreement, correlation, and kinetics of the alveolar bone-loss measurement methodologies in a ligature-induced periodontitis animal model

Periodontal research involves the use of animal models to better understand the biological processes of periodontal diseases and the potential of new or existing therapies. Currently, ligature-induced periodontitis in rats is the main model used in periodontal research, in this model, alveolar bone loss (ABL) is the main parameter evaluated by radiographic, morphometric, and histological techniques. Interestingly, although these methodologies are widely used, it is not totally clarified neither the kinetics of ABL over the induction time nor the agreement degree (repeatability and reproducibility) of these techniques. Objective: To characterize ABL kinetics at 0, 3, 7, 15, 30, and 60 days after ABL induction by ligature and to evaluate the intra- (repeatability) and inter-examiner (reproducibility) agreement and the correlation among the radiographic, morphometric, and histological methodologies. Material and Methods: 60 male Wistar rats with induced ABL were randomly divided into 6 experimental groups (n = 10 animals/group). After 0, 3, 7, 15, 30, and 60 days, the animals were euthanized and their hemimandibles were removed for ABL determination using radiographic, morphometric and histological techniques. Results: Radiographic and morphometric/linear techniques allowed the detection of statistically significant ABL on the third day, while histological and morphometric/area techniques could only detect ABL after the seventh day (ANOVA/Tukey, p<0.05). After the fifteenth day, except for histological analysis, the ABL was stabilized. Concerning the agreement of the methodologies, Bland Altman's test (intra and inter-examiner evaluations) showed no difference among the measurements (p>0.05). In addition, high correlations (Pearson's test, r2>0.9, p<0.05) were observed. Conclusion: The results indicated that the minimum time for ABL induction could vary from 3 to 7 days, according to the chosen analysis methodology. Agreement and correlation data support the comparison of results between studies with same induction time.