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Updated: Aug 9, 2026
Robust Ligature-Induced Model of Murine Periodontitis for the Evaluation of Oral Neutrophils
Published on: January 21, 2020
Nitric oxide synthase expression is increased by occlusal force in rat periodontal ligament
1Orthodontic Science, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan. warita.orts@tmd.ac.jp
Objectives:
The goal of this study was to investigate the role of nitric oxide synthase (NOS) in occlusal force-induced signal transduction in rat periodontal ligament (PDL).
Design:
Rats were fitted with a bite plate and a metal cap to the maxillary and mandibular incisors, respectively, to eliminate the occlusal forces on rat molars. One group was sacrificed at 7 days (exclusion group), while the remaining rats had their appliances removed to reestablish molar occlusal contact (reload group) and were sacrificed 7 days thereafter. Another group of rats (normal group) were left completely untreated. Frozen cross sections of the upper first molars were stained with NADPH-diaphorase to quantify NOS activity. The distal sides of the disto-palatal roots of the upper first molars were examined, and the number and the area of stained cells in the PDL were measured.
Results:
In the normal group, NOS expression was detected in blood vessels, monocyte-macrophages, fibroblastic cells and osteoclastic cells. NOS expression was lower in the exclusion group when compared with the normal group or the reload group (p < 0.05), and the exclusion group exhibited occluded blood vessels and a narrowing of PDL. In contrast, in the reload group the PDL and blood vessel structure had recovered and NOS expression was increased to the level of the controls.
Conclusion:
Occlusal force resulted in increased NOS expression. NO may mediate changes in PDL structure in response to occlusal force.
