Biomechanical and biological responses of periodontium in orthodontic tooth movement: up-date in a new decade

Abstract

Nowadays, orthodontic treatment has become increasingly popular. However, the biological mechanisms of orthodontic tooth movement (OTM) have not been fully elucidated. We were aiming to summarize the evidences regarding the mechanisms of OTM. Firstly, we introduced the research models as a basis for further discussion of mechanisms. Secondly, we proposed a new hypothesis regarding the primary roles of periodontal ligament cells (PDLCs) and osteocytes involved in OTM mechanisms and summarized the biomechanical and biological responses of the periodontium in OTM through four steps, basically in OTM temporal sequences, as follows: (1) Extracellular mechanobiology of periodontium: biological, mechanical, and material changes of acellular components in periodontium under orthodontic forces were introduced. (2) Cell strain: the sensing, transduction, and regulation of mechanical stimuli in PDLCs and osteocytes. (3) Cell activation and differentiation: the activation and differentiation mechanisms of osteoblast and osteoclast, the force-induced sterile inflammation, and the communication networks consisting of sensors and effectors. (4) Tissue remodeling: the remodeling of bone and periodontal ligament (PDL) in the compression side and tension side responding to mechanical stimuli and root resorption. Lastly, we talked about the clinical implications of the updated OTM mechanisms, regarding optimal orthodontic force (OOF), acceleration of OTM, and prevention of root resorption.

Immunomodulatory Activities of Periodontal Ligament Stem Cells in Orthodontic Forces-Induced Inflammatory Processes: Current Views and Future Perspectives

“…Among other tissue-resident cells, immune cells, such as neutrophiles, macrophages, T and B lymphocytes, may contribute to increased levels of various immune factors in the periodontium, such as various chemokines, growth factors, cytokines [e.g., interleukin-(IL)-1β, IL-6, IL-8, tumor necrosis factor-(TNF)-α, interferon-(IFN)-γ], and prostaglandin E 2 (PGE 2 ). All these inflammatory mediators contribute to the regulation of osteoclast- and osteogenesis and the activities of bone remodeling cells (osteoclasts and osteoblasts) [ 1 , 5 ]. Hence, the inflammatory environment is directly involved in orchestrating the interconnected catabolic (bone resorption) and anabolic (bone formation) processes within the periodontium, which finally leads to alveolar bone turnover and tooth movement [ 6 ].…”

Impact of Myeloid p38α/MAPK on Orthodontic Tooth Movement

“…The application of an orthodontic force to a tooth creates pressure and tension zones in the periodontal ligament. Osteoclastic bone resorption processes predominantly take place at the pressure zones, while new bone is formed by osteoblasts at the tension side [ 1 , 2 ]. These bone remodelling processes are regulated by the cells in the periodontal ligament through the release of proinflammatory mediators such as cytokines and chemokines.…”

“…Numerous signal transduction pathways, such as the mitogen-activated kinase pathway (MAPK), also play a mediating role in orthodontic tooth movement [ 1 , 9 ]. The MAPK signalling pathway consists of a number of Ser/Thr kinases, such as extracellular signal-regulated kinase (ERK)1/2, c-Jun N-terminal kinase (JNK), ERK5 subfamilies, and p38 [ 10 , 11 ].…”

“…Playing a regulatory role in both osteoblast and osteoclast differentiation, the p38/MAPK pathway is closely associated with bone resorption and formation [ 12 , 13 ]. In addition, p38/MAPKs are activated by numerous growth factors and cytokines such as receptor activator of NFkB ligand (RANKL) and TNF [ 11 , 14 ], which are also increasingly released during orthodontic tooth movement [ 1 , 4 ]. Cell culture studies have also shown that mechanical stress activates ERK1/2 and p38/MAPK in periodontal ligament fibroblasts [ 15 , 16 , 17 ].…”

Systemic rosiglitazone administration leads to cementocytes apoptosis in wild type mice

“…Also, it is well described that osteocytes play an important role in the pathogenesis of bone diseases, such as osteoporosis and osteoarthritis [4,5]. Also, there are few evidence describing the role of these cells during oral processes and diseases [6,7].…”