Abstract
PurposeMany adult orthodontic patients suffer from periodontitis, which is caused by oral pathogens such as the gram-negative Aggregatibacter actinomycetemcomitans (Agac). Like orthodontic tooth movement, periodontitis is associated with inflammation and alveolar bone remodelling thereby affecting orthodontic treatment. Interactions of both processes, however, are not sufficiently explored, particularly with regard to oxidative stress.MethodsAfter preincubation with Agac lysate for 24 h periodontal ligament fibroblasts (PDLF) were either stretched or compressed for further 48 h simulating orthodontic forces in vitro. We analysed the expression of genes and proteins involved in the formation of reactive oxygen species (NOX-4, ROS) and nitric oxide (NOS-2), inflammation (TNF, IL-6, PTGS-2) and bone remodelling (OPG, RANKL).ResultsAgac lysate elevated the expression of NOX-4, NOS-2, inflammatory IL-6 and PTGS-2 and the bone-remodelling RANKL/OPG ratio during compressive, but not tensile mechanical strain. Agac lysate stimulated pressure-induced inflammatory signalling, whereas surprisingly ROS formation was reduced. Pressure-induced downregulation of OPG expression was inhibited by Agac lysate.ConclusionsAgac lysate impact on the expression of genes and proteins involved in inflammation and bone remodelling as well as ROS formation, when PDLF were subjected to mechanical forces occurring during orthodontic tooth movement.
Highlights
Orthodontic treatment prevents and corrects dysfunctions, malocclusions and jaw malposition
Impact of Aggregatibacter actinomycetemcomitans (Agac) lysate and tensile strain on protein expression of NADPH oxidase‐4 (NOX‐4) and nitric oxide synthase‐2 (NOS‐2) After assessment of cell number and lactate dehydrogenase (LDH) release, which revealed a cytotoxic effect of Agac lysate and mechanical strain (Additional file 1: Figure S2), we investigated the effects of Agac lysate in combination with tensile strain on protein expression of NOX-4 and NOS-2
Impact of Agac lysate and tensile strain on expression of inflammatory genes we investigated the effect of Agac lysate and tensile strain on the gene expression of the inflammatory genes tumor necrose factor (TNF), interleukin-6 (IL-6) and prostaglandin-endoperoxide synthase-2 (PTGS-2)
Summary
Orthodontic treatment prevents and corrects dysfunctions, malocclusions and jaw malposition. An uncontrolled inflammatory process during orthodontic treatment in a periodontally challenged dentition can result in orthodontically induced root resorption, including destruction of the periodontal tissue [7]. In contrast to the pathophysiological inflammation and destruction of periodontal tissue that can be detected as signs and symptoms of periodontitis [6, 8], a local so-called controlled sterile inflammatory cascade is activated during orthodontic tooth movement inducing bone remodelling [7, 9]. Cells in the periodontal ligament are subjected to compressive and tensile strain [7, 9, 10], resulting in bone deposition by osteoblasts at tension and bone resorption by osteoclasts at pressure areas [11]. In a healthy periodontal condition, orthodontic treatment does not induce gingival recessions, alveolar bone loss or increased pocket depths to a clinically relevant extent [14], whereas this is true for orthodontic treatment during active periodontitis [15]
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