Fluctuation of bone turnover markers' levels in samples of gingival crevicular fluid after orthodontic stimulus: a systematic review

BACKGROUND

The aim of the present study was to provide an overview of gingival crevicular fluid (GCF) bone turnover markers (BTMs) concerning the physiology of orthodontic tooth movement (OTM) and assess their potential contributions to regulating bone remodeling, that could prove useful in designing future approaches to modulating orthodontic tooth movement.

METHODS

Multiple electronic databases (MEDLINE/PubMed, Ovid MEDLINE, Ovid Embase, LILACS, and Cochrane Library) were searched up to October 1st, 2020. Randomized controlled trials (RCTs), controlled clinical trials, observational studies of prospective and retrospective designs, and cross-sectional studies reporting on levels of BTMs in GCF were eligible for inclusion. The quality of the included RCTs was assessed per the revised Cochrane risk of bias tool for randomized trials (RoB 2.0), whereas the risk of bias of the included cohort studies was assessed using the Risk Of Bias In Non-randomized Studies of Interventions tool.

RESULTS

Five RCTs, 9 prospective cohort studies, and 1 cross-sectional study fulfilled the inclusion criteria. The risk of bias was deemed as high for the RCTs and 4 of the prospective studies and moderate for the rest of the studies. The following biomarkers for bone formation were assessed: bone alcaline phosphatase (BALP), alcaline phosphatase (ALP), and osteocalcin (OC). For bone resorption, the following BTMs were assessed: deoxypyridinoline (DPD) and pyridinoline (PYD), N-terminal telopeptide (NTX), osteopontin (OPN), and tartrate-resistant acid phosphatase (TRAP). The follow-up period ranged mainly from baseline to 45 days, although one study had an expanded follow-up period of up to 16 months. The results of the included studies comparing different BTMs were heterogeneous and qualitatively reported.

CONCLUSIONS

Current evidence continues to support the potential for BTMs to provide clinically useful information particularly for adjusting or standardizing the orthodontic stimulus. The present systematic review has retrieved studies of high, overall, risk of bias, and has unveiled a substantial clinical and methodological heterogeneity among included studies. Further data of the relationships between the clinical assays and the physiological or pre-analytical factors contributing to variability in BTMs' concentrations are required.

SYSTEMATIC REVIEW REGISTRATION

CRD42020212056 .

Oxidative stress inhibits the proliferation, induces premature senescence and promotes a catabolic phenotype in human nucleus pulposus intervertebral disc cells

Aged and degenerated intervertebral discs are characterised by a significant increase in the number of senescent cells, which may be associated with the deterioration of this tissue due to their catabolic phenotype. On the other hand, carboxymethyl-lysine has been found to be accumulated with ageing in the proteins of the disc, evidencing the existence of oxidative stress in this tissue. Accordingly, here we investigated the effect of oxidative stress on the physiology of human nucleus pulposus cells. Hydrogen peroxide (H2O2) at subcytotoxic concentrations transiently increased the intracellular levels of reactive oxygen species, activated the p38 MAPK, ERKs, JNKs and Akt signalling pathways and induced the nuclear translocation of NF-κΒ and Nrf2. It also provoked DNA damage and triggered a DNA repair response by activating the ATM-Chk2-p53-p21(WAF1)-pRb pathway, ultimately resulting in a G1 cell cycle delay and the decrease of cells' proliferation. Prolonged exposure to H2O2 led to premature cellular senescence, as characterised by the inhibition of proliferation, the enhanced senescence-associated β galactosidase staining and the over-expression of known molecular markers, without though a significant decrease in the chromosome telomere length. H2O2-senescent cells were found to possess a catabolic phenotype, mainly characterised by the up-regulation of extracellular matrix-degrading enzymes (MMP-1, -2, -9 and ADAMTS-5) and the down-regulation of their inhibitors (TIMPs), as well as of several proteoglycans, including aggrecan, the major component of the nucleus pulposus. The senescent phenotype could be reversed by N-acetyl-L-cysteine, supporting the use of antioxidants for the improvement of disc physiology and the deceleration of disc degeneration.

Effect of blue light on the proliferation of human gingival fibroblasts

OBJECTIVES

Previous studies have reported that blue light, under conditions similar to those used for orthodontic bonding, influences several aspects of cellular physiology. The purpose of this study was to investigate the effect of the exposure to blue light curing sources, i.e. halogen, light emitting diode (LED) and plasma arc irradiation, on the proliferation of human gingival fibroblasts.

METHODS

Primary cultures of human gingival fibroblasts were exposed to halogen, LED and plasma arc irradiation for 240, 180 and 120 s, respectively. The effect of blue light on DNA synthesis and cell proliferation was estimated by tritiated thymidine incorporation and direct cell counting, respectively. The possible involvement of an oxidative stress on the effect of blue light irradiation was studied by using N-acetyl-cysteine. Finally the formation of DNA double-strand breaks after irradiation was studied by immunofluorescence with an antibody against histone H2A.x phosphorylated in Ser139.

RESULTS

Blue light showed no immediate effect on the regulation of DNA synthesis. However, exposure of cells to these light sources inhibits cell proliferation measured one week after irradiation. This phenomenon is not attributed to the formation of DNA double strand breaks and cannot be annulled by N-acetyl-cysteine.

SIGNIFICANCE

The results presented here indicate a mild inhibition of gingival fibroblasts' proliferation after exposure to blue light and necessitate further study to clarify the exact mechanism underlying this effect.