Effect of cyclic mechanical loading on osteoclast recruitment in periodontal tissue.
OBJECTIVE
It is well accepted that cyclic mechanical loading induces osteoclastogenesis in periodontal tissue, but its molecular mechanisms are not well understood, in part because of a lack of appropriate models. In this study, we investigated a novel device that allows cyclic mechanical loading to be performed in a well-controlled manner. Furthermore, by employing this model, the effect of cyclic loading on osteoclast recruitment in the periodontal tissue was described.


METHODS
By using a newly developed device, the cyclic loading of 20 n (reference loading corresponding to the fracture hardness of dietary pellets) and two excessive loadings (i.e. 30 and 40 n) were applied to maxillary right molars in rats for up to 7 d, and osteoclast recruitment in the periodontal tissue was evaluated by analyzing relevant marker proteins using immunohistochemistry.


RESULTS
Osteoclastogenesis was induced by day 3 within alveolar bone subjected to a compression force of 30 n. With both 30 and 40 n loadings, cells that were positive to for tartrate-resistant acid phosphate, receptor activator of nuclear factor-kappaB ligand and osteoprotegerin were significantly increased in the alveolar bone/periodontal ligament in a time-dependent manner.


CONCLUSIONS
A new device was developed that allows various levels of cyclic mechanical loading to be exerted. By using this device in rats, early events of osteoclast recruitment in the periodontal tissues were observed with excessive loadings in a time-dependent manner, indicating the usefulness of this model.
Nozaki
K
K
Fixed Prosthodontics, Department of Restorative Sciences, Graduate School of Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan.
Kaku
M
M
Yamashita
Y
Y
Yamauchi
M
M
Miura
H
H
D000135:Acid Phosphatase / Q000032:analysis; D000539:Alveolar Process / Q000166:cytology; D000818:Animals; D015415:Biomarkers / Q000032:analysis; D001696:Biomechanical Phenomena; D001732:Bite Force; D002452:Cell Count; D002465:Cell Movement; D003094:Collagen; D003799:Dental Stress Analysis / Q000295:instrumentation; D005502:Food; D006244:Hardness; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000032:analysis; D008297:Male; D008963:Molar; D010010:Osteoclasts / Q000502:physiology*; D053244:Osteoprotegerin / Q000032:analysis; D010513:Periodontal Ligament / Q000166:cytology; D010519:Periodontium / Q000166:cytology*; D011312:Pressure; D053245:RANK Ligand / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D013314:Stress, Mechanical; D000071681:Tartrate-Resistant Acid Phosphatase; D013997:Time Factors
D015415:Biomarkers; D007527:Isoenzymes; D053244:Osteoprotegerin; D053245:RANK Ligand; D003094:Collagen; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase