An Animal Model of Pulpitis Based on an Outbred Mice Strain and Its Histological Analysis

The Naval Medical Research Institute (NMRI) mice have not been reported previously for creating a dental pulp inflammation model. In this protocol, we present an animal model employing NMRI mice and provide detailed histological procedures for the pulpitis model to ensure reproducibility. We included 70 NMRI mice that were randomly assigned to two groups: Group A (n=35), in which pulpitis was induced by the pulp exposure alone, and Group B (n=35), which received pulp exposure followed by Zymosan application. After the pulp exposure of the right maxillary molar, animals were sacrificed at designated time intervals (0, 6, 9, 12, 24, 48, and 72 h). The maxillary jaw was obtained for histology and quantitative histomorphological analysis. A time-dependent gradual increase in inflammation was observed in histological analysis for both groups. Both animal models allowed the study of inflammation up to 72 h. The technique presented in this paper is reproducible and will help standardize the histological study of pulpitis.