Periodontal Bone Loss in Rice Rats

Objective:   The purpose of this study was to quantify naturally occurring periodontal disease in Rice (Oryzomy palustris) rats.

Methods:    Thirty, ~ 1 year old, female rice rats, were anesthetized and micro CT scans were obtained (Inveon microCT, Siemens, Malvern, PA).  The DICOM images were imported into Dolphin Imaging (Chatsworth, CA) 3D. Measurements of root length (CEJ to root apex) and existing bone levels were made in both the coronal and sagittal sections along all maxillary and mandibular tooth roots.  Percent bone loss (PBL) was calculated based on the root length and existing bone levels.  The data was analyzed using analysis of variance (ANOVA) and Tukey-Kramer method.

Results:  The PBL was found to be greater than 90% in 10.3% of the root measurements made from the sagittal slices. The greatest mean (SD) PBL by tooth occurred at the maxillary second molar (PBL = 40.98%, ± 30.19) and was not significantly (p = 0.75) different from the maxillary third molar (PBL = 39.21%, ± 39.20).  The greatest mean PBL by root type in the coronal and sagittal slices was found on the palatal (PBL = 47.77%, 95% CI: 38.99-56.55) and the mesiobuccal root (PBL = 65.46%, 95% CI: 50.24-80.69), respectively of the maxillary right third molar.  The lowest mean PBL by root type in the coronal (PBL = 13.24%, 95% CI: 12.48-14.00) and sagittal (PBL = 15.78%, 95% CI: 13.60-17.95) slices was found at the distobuccal root of the mandibular left second molar.  Localized areas of severe bone loss and resulting pathologic migration of the teeth was observed. Limitation of this study is that bone loss is reported relative to the CEJ, as it served as a reliable identification landmark.

Conclusions:   The rice rat demonstrated evidence of bone loss and may serve as an animal model for investigations relating to periodontal disease.