Interaction of periodontitis and orthodontic tooth movement-an in vitro and in vivo study

Abstract

Objectives: The aim of this in vitro and in vivo study was to investigate the interaction of periodontitis and orthodontic tooth movement on interleukin (IL)-6 and C-X-C motif chemokine 2 (CXCL2).

Materials and methods: The effect of periodontitis and/or orthodontic tooth movement (OTM) on alveolar bone and gingival IL-6 and CXCL2 expressions was studied in rats by histology and RT-PCR, respectively. The animals were assigned to four groups (control, periodontitis, OTM, and combination of periodontitis and OTM). The IL-6 and CXCL2 levels were also studied in human gingival biopsies from periodontally healthy and periodontitis subjects by RT-PCR and immunohistochemistry. Additionally, the synthesis of IL-6 and CXCL2 in response to the periodontopathogen Fusobacterium nucleatum and/or mechanical strain was studied in periodontal fibroblasts by RT-PCR and ELISA.

Results: Periodontitis caused an increase in gingival levels of IL-6 and CXCL2 in the animal model. Moreover, orthodontic tooth movement further enhanced the bacteria-induced periodontal destruction and gingival IL-6 gene expression. Elevated IL-6 and CXCL2 gingival levels were also found in human periodontitis. Furthermore, mechanical strain increased the stimulatory effect of F. nucleatum on IL-6 protein in vitro.

Conclusions: Our study suggests that orthodontic tooth movement can enhance bacteria-induced periodontal inflammation and thus destruction and that IL-6 may play a pivotal role in this process.

Clinical relevance: Orthodontic tooth movement should only be performed after periodontal therapy. In case of periodontitis relapse, orthodontic therapy should be suspended until the periodontal inflammation has been successfully treated and thus the periodontal disease is controlled again.

Keywords: Fusobacterium nucleatum; Orthodontic tooth movement; Periodontitis; Periodontium.

Fig. 1

Experimental periodontitis and/or orthodontic tooth movement in rats. An animal model was used to study the influence of periodontitis and/or orthodontic tooth movement on periodontal tissues. Experimental periodontitis was induced by cotton ligatures, which were tied around the cervical region of the maxillary first molars (a and b). Orthodontic tooth movement was accomplished by a closed nickel-titanium coil spring placed between the maxillary first molars and central incisors (c)

Fig. 2

IL-6 and CXCL2 levels in human gingival biopsies. Levels of IL-6 mRNA (a) and CXCL2 mRNA (b) in gingival biopsies from periodontally healthy (n = 7) and periodontitis (n = 7) subjects, as measured by real-time PCR. *Significant (p<0.05) difference between groups. IL-6 and CXCL2 protein (c) in gingival biopsies from periodontally healthy and periodontitis subjects, as assessed by immunohistochemistry. Representative histological sections are shown

Fig. 3

The effect of experimental periodontitis and/or orthodontic tooth movement (OTM) on alveolar bone loss as well as IL-6 and CXCL2 levels in rat gingival biopsies. Representative histological sections (a) and percentage area of unmineralized tissue (b) in the furcation region of first maxillary molars of rats in which experimental periodontitis was induced and/or OTM was performed (n = 4 rats/group). First maxillary molars from rats without periodontitis and OTM served as control. Levels of IL-6 mRNA (c) and CXCL2 mRNA (d) in gingival biopsies from first maxillary molars of rats in which experimental periodontitis was induced and/or OTM was performed (n = 4 rats/group). First maxillary molars from rats without periodontitis and OTM served as control. * Significant (p<0.05) difference between groups

Fig. 4

Synthesis of IL-6 and CXCL2 in response to F. nucleatum (Fn) and/or constant tensile strain (CTS) in periodontal fibroblasts. IL-6 mRNA (a) and protein (b) levels and CXLC2 mRNA (c) and protein (d) levels in cultures of periodontal fibroblasts stimulated with F. nucleatum (Fn) and/or subjected to constant tensile strain (CTS), as analyzed by real-time PCR (n = 6) and ELISA (n = 12), respectively. Untreated cells served as control. IL-6 (a) and CXCL2 (c) mRNA levels of treated and control cells, which had been pre-incubated with a specific MEK1/2 inhibitor (Inh), are also shown. * Significant (p<0.05) difference between groups