Cytokine measurements in gingival crevicular fluid and periodontal ligament: Are they correlated?

Biological alterations associated with the orthodontic treatment with conventional appliances and aligners: A systematic review of clinical and preclinical evidence

Background&objectives

Mechanical forces applied during an orthodontic tooth movement (OTM) propel several biochemical and molecular responses in the periodontal ligament and alveolar bone. Here, we compile the existing clinical and preclinical evidence on these biological changes, aiming to provide a comprehensive discussion on the influence of the mechanical parameters of the OTM in the biological profile of the periodontium.

Material and methods

This systematic integrative review was conducted according to PICOS strategy and PRISMA guidelines. A bibliographic search was performed in three electronic databases (PubMed, Scopus, and Web of Science) to find research articles published until 2023 and written in English. This search resulted in a total of 2279 publications, which were independently assessed by two evaluators using appropriate tools.

Results

Forty-six studies were selected for this review. These revealed that compression, and stretching of the periodontal ligament fibers and cells are observed in the initial phase of the OTM. Specifically, on the tension side, high levels of IL-1β, OPG, and TIMPs are identified. On the compression side, an increase of RANKL, RANK, and MMPs levels predominate.

Conclusion

This paper describes the release profile of common biomarkers according to the orthodontic protocol, suggesting the most appropriate parameters to keep the teeth and their supporting structures healthy. Overall, this manuscript provides a better understanding of the OTM-associated biological phenomena, also highlighting the importance of early evaluation of oral health, and thus it contributes as a fundamental basis for the development of more effective and safe orthodontic treatments with conventional appliances and aligners.

Evaluation of periodontal parameters and gingival crevicular fluid cytokines in children with anterior open bite receiving passive orthodontic treatment with a spur

Objective

To evaluate clinical parameters and gingival crevicular fluid (GCF) cytokines in children with anterior open bite receiving passive orthodontic treatment with spurs.

Methods

Twenty children with indications for interceptive orthodontic treatment, an anterior open bite, and good oral hygiene and periodontal health were included in this study. GCF samples were collected from the mandibular and maxillary central incisors before (baseline) and 24 hours and 7 days after spur bonding. Clinical and periodontal examinations and cytokine analyses were performed.

Results

At 7 days after spur attachment, gingival bleeding in the mandibular group was increased relative to that in the maxillary group. Visible plaque was correlated with gingival bleeding at 7 days and the GCF volume at 24 hours after spur attachment. Compared with those at baseline, interleukin (IL)-8 levels in the maxillary group and IL-1β levels in both tooth groups increased at both 24 hours and 7 days and at 7 days, respectively. At 24 hours, IL-8, IL-1β, and IL-6 levels were higher in the maxillary group than in the mandibular group. Cytokine production was positively correlated with increased GCF volume, but not with gingival bleeding, visible plaque, or probing depth.

Conclusions

Although orthodontic treatment with spurs in children resulted in increased gingival bleeding around the mandibular incisors, IL levels were higher around the maxillary incisors and not correlated with periodontal parameters. Increased cytokine levels in GCF may be associated with the initial tooth movement during open bite correction with a passive orthodontic appliance in children.

Open bite

Immune Changes Induced by Orthodontic Forces: A Critical Review

Orthodontic tooth movement (OTM) is generated by a mechanical force that induces an aseptic inflammatory response in the periodontal tissues and a subsequent coordinated process of bone resorption and apposition. In this review, we critically summarize the current knowledge on the immune processes involved in OTM inflammation and provide a novel insight into the relationship between classical inflammation and clinical OTM phases. We found that most studies focused on the acute inflammatory process, which ignites the initial alveolar bone resorption. However, the exact mechanisms and the immune reactions involved in the following OTM phases remain obscure. Recent studies highlight the existence of a typical innate response of resident and extravasated immune cells, including granulocytes and natural killer (NK), dendritic, and γδT cells. Based on few available studies, we shed light on an active, albeit incomplete, process of resolution in the lag phase, supported by continuously elevated ratios of M1/M2 macrophage and receptor activator of nuclear factor κB ligand/osteoprotegerin ratio. This partial resolution enables tissue formation and creates the appropriate environment for a transition between the innate and adaptive arms of the immune system, essential for the tissue's return to homeostasis. Nevertheless, as the mechanical trigger persists, the resolution turns into a low-grade chronic inflammation, which underlies the next, acceleration/linear OTM phase. In this stage, the acute inflammation dampens, and a simultaneous process of bone resorption and formation occurs, driven by B and T cells of the adaptive immune arm. Excessive orthodontic forces or tooth movement in periodontally affected inflamed tissues may hamper resolution, leading to "maladaptive homeostasis" and tissue loss due to uncoupled bone resorption and formation. The review ends with a brief description of the translational studies on OTM immunomodulation. Future studies are necessary for further uncovering cellular and molecular immune targets and developing novel strategies for controlling OTM by local and sustained tuning of the inflammatory process.

Expression of cytokines in gingival crevicular fluid associated with tooth movement induced by aligners: a pilot study

Introduction:

The search for more aesthetic and comfortable orthodontic devices has led to an increase in the use of clear aligners.

Objective:

To increase knowledge on biological mechanisms of orthodontic tooth movement using Invisalign aligners.

Methods:

This study included 11 patients with a mean age of 23.6 ± 4.8 years. Cases planning included alignment and leveling of lower incisors using Invisalign aligners. Gingival crevicular fluid samples were collected from the lower incisors on the day of delivery of aligner number 1 (T0) and after 1 (T24h), 7 (T7d), and 21 (T21d) days. During the observation period of the study, the patients used only the aligner number 1. Levels of nine cytokines were quantified using Luminex’s multi-analysis technology. Non-parametric tests were used for comparisons between cytokine expression levels over time.

Results:

Cytokine expression levels remained constant after 21 days of orthodontic activation, except those of MIP-1β, which presented a statistical difference between T24h and T21d with a decrease in the concentration levels. IL-8, GM-CSF, IL-1β, MIP-1β, and TNF-α showed the highest concentrations over time.

Conclusions:

The different behavior in the levels of the investigated cytokines indicates a role of these biomarkers in the tissue remodeling induced by Invisalign.

Tumor Necrosis Factor-alpha in Gingival Crevicular Fluid as a Diagnostic Marker for Periodontal Diseases: A Systematic Review

OBJECTIVES

The aim of this systematic review was to evaluate human gingival crevicular fluid (GCF) tumor necrosis factor-alpha (TNF-α) as a potential biomarker for diagnosis of periodontal disease (International prospective register of systematic reviews [PROSPERO] number: CRD42015020199).

METHODS

An electronic search for TNF-α in human GCF was conducted until May 17, 2018. Data from systemically healthy patients with healthy periodontium or periodontal disease were incorporated. Risk bias was assessed by Newcastle-Ottawa Scale for case-control studies and Jadad scale for clinical trials.

RESULTS

Twenty-six studies were included (12 case-control studies, 7 clinical trials, and 7 randomized controlled trials). Most case-control studies showed increased TNF-α concentration in GCF of patients with periodontal disease. The clinical trials and randomized controlled trials demonstrated no consistent modification of TNF-α level after periodontal intervention.

CONCLUSION

The present data support the use of TNF-α in GCF as a potential biomarker for diagnosis of periodontal disease but not to monitor the healing after therapy.

Effect of orthodontic force on expression levels of ten cytokines in gingival crevicular fluid

Various types of inflammatory mediators are involved in the cascade of biological events behind tissue remodeling allowing orthodontic tooth movement. This split-mouth longitudinal study aimed to evaluate the gingival crevicular fluid (GCF) levels of ten cytokines, IL-6, IL-8, IL-10, IL-13, IL-17, IFN-γ, GM-CSF, MCP-1, MIP-1β and TNF-α, during initial orthodontic treatment. The sample comprised 15 healthy patients (9 males and 6 females, 13.9±2.5 years). The lower (test) incisors were moved using fixed appliance carrying a 0.014-inch nickel titanium wire, whereas the upper (control) incisors were bonded without any force. The GCF was collected from the test and control teeth before fixed appliance mounting (baseline) and after 1, 7 and 21days. In 6 sites per tooth, from canine to canine, periodontal conditions were defined as the percentage of sites with visible plaque and bleeding on probing. The total GCF cytokines levels were quantified using multianalysis Luminex technology. Throughout the experimental term, and for both test and control teeth, the mean percentage of sites with visible plaque and bleeding on probing were generally below 25% and 15%, respectively, although variability was also seen. In the test teeth, the GCF levels of all the cytokines remained constant throughout the experimental term. On the contrary, significant reductions were seen in the control teeth for each cytokine. Moreover, significantly greater levels of IL-6, GM-CSF, MCP-1 and TNFα were seen in the test teeth as compared to the control teeth at 7days. The reasons for the differential behavior in the levels of all the investigated cytokines between the test and control teeth may be related to the presence of orthodontic forces and/or subclinical tissue inflammation. Further investigation is needed to elucidate potential roles for these biomarkers in the tissue remodeling incident to orthodontic tooth movement.

Biochemical markers of bone metabolism during early orthodontic tooth movement with aligners

OBJECTIVE

To evaluate the expression of receptor activator of nuclear factor-kappa ligand (RANKL), osteoprotegerin (OPG), osteopontin (OPN), interleukin 1β (IL-1β), and transforming growth factor ß1 (TGF-ß1) in the gingival crevicular fluid (GCF) of teeth subjected to orthodontic forces released by aligners.

MATERIALS AND METHODS

A total of 10 healthy, adult patients were selected to participate in this split-mouth study. The treatment plan was designed to obtain only one movement with the first aligner: distalization of a second molar. GCF samples were obtained from pressure and tension sites of the test tooth and from the mesiobuccal and distobuccal sites of the control tooth. The GCF sample volumes were measured using a Periotron 8000. Levels of TGF-β, IL-1β, RANKL, OPG, and OPN were measured by enzyme-linked immunosorbent assay.

RESULTS

IL-1β showed a significant increase at the pressure sites after 1 week and 3 weeks with respect to baseline (P < .05) compared with control sites. The kinetics of TGF-1β and OPN were characterized by a significant increase at the tension sites of the test teeth (P < .05) after 3 weeks from the application of orthodontic force. The RANKL level was significantly increased at pressure and tension sites after 1 hour and after 1 week from the application of the orthodontic forces (P = .023 and P = .043, respectively).

CONCLUSIONS

An increased concentration of bone modeling and remodeling mediators at the pressure sites (IL-1β, RANKL) and tension sites (TGF-1β, OPN) was observed. These scenarios are compatible with previous in vivo and in vitro studies investigating the biological effects of orthodontic tooth movement.