Mechanobiology of orthodontic tooth movement: An update

TNF reduces osteogenic cell fate in PDL cells at transcriptional and functional levels without alteration of periodontal proliferative capacity

AIMS

To investigate the effect of tumor necrosis factor (TNF) on the growth of human periodontal ligament (PDL) cells, their osteogenic differentiation and modulation of their matrix secretion in vitro.

METHODS

The influence of 10 ng/ml TNF on proliferation and metabolic activity of PDL cells was analyzed by cell counting (DAPI [4',6-diamidino-2-phenylindole] staining) and the MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay. In addition, cells were cultured under control conditions and osteogenic conditions (media containing 10 mM β-glycerophosphate). Quantitative expression analysis of genes encoding the osteogenic markers alkaline phosphatase (ALP), collagen type I alpha 1 chain (COL1A1), osteoprotegerin (OPG), and osteopontin (OPN) was performed after 7 and 14 days of cultivation. Calcium deposits were stained with alizarin red.

RESULTS

Our studies showed that 10 ng/ml TNF did not affect the survival and metabolic activity of PDL cells. Quantitative expression analysis revealed that long-term cultures with TNF impaired osteogenic cell fate at early and late developmental stages. Furthermore, TNF significantly reduced matrix secretion in PDL cells.

CONCLUSION

The present data confirm TNF as a regulatory factor of proinflammatory remodeling that influences the differentiation behavior but not the metabolism and cell proliferation of the periodontium. Therefore, TNF represents an interesting target for the regulation of orthodontic remodeling processes in the periodontium.

Exploring biological mechanisms in orthodontic tooth movement: Bridging the gap between basic research experiments and clinical applications - A comprehensive review

OBJECTIVES

The molecular mechanisms behind orthodontic tooth movements (OTM) were investigated by clarifying the role of chemical messengers released by cells.

METHODS

Using the Cochrane library, Google scholar, and PubMed databases, a literature search was conducted, and studies published from 1984 to 2024 were considered.

RESULTS

Both bone growth and remodeling may occur when a tooth is subjected to mechanical stress. These chemicals have a significant effect on the stimulation and regulation of osteoblasts, osteoclasts, and osteocytes during alveolar bone remodeling. This regulation can take place in pathological conditions, such as periodontal diseases, or during OTM alone. This comprehensive review outlines key molecular mechanisms underlying OTM and explores various clinical assumptions associated with specific molecules and their functional domains during this process. Furthermore, clinical applications of certain molecules such as relaxin, prostaglandin E (PGE), and interleukin-1β (IL-1β) in accelerating OTM have been reported. Our findings underscore the existing gap between OTM clinical applications and basic research investigations.

CONCLUSION

A comprehensive understanding of orthodontic treatment is enriched by insights into biological systems. We reported the activation of osteoblasts, osteoclast precursor cells, osteoclasts, and osteocytes in response to mechanical stress, leading to targeted cellular and molecular interventions and facilitating rapid and regulated alveolar bone remodeling during tooth movement. Despite the shortcomings of clinical studies in accelerating OTM, this review highlights the crucial role of biological agents in this process and advocates for prioritizing high-quality human studies in future research to gain further insights from clinical trials.

The effect of cacao bean extracts on the prevention of periodontal tissue breakdown in diabetic rats with orthodontic tooth movements

Objective

Proper management of orthodontic treatment in diabetic patients is essential due to the heightened risk of periodontal tissue breakdown associated with hyperglycemia. Cacao bean extracts (CBE) are known to reduce the inflammatory response and increase synthesis and angiogenesis in periodontitis. Therefore, this study aims to examine the effect of CBE on preventing periodontal tissue breakdown in diabetes with orthodontic force.

Methods

A total of 25 Wistar rats were divided randomly into 5 groups, including non-diabetes, diabetes, diabetes cacao 125, 250, and 500 mg/kg BW. Diabetic rats were induced with the stratified dose of Streptozotocin, and a 30-g-force from orthodontic device was applied in all groups. Diabetes cacao group was given CBE for 7 days using a gastric probe. GCF samples were used to analyze the eNOS level through the ELISA method. NFκB, Collagen-1, and FGF-2 expression were then assessed using the immunohistochemical method, while the number of fibroblasts and blood vessels was observed using hematoxylin-eosin stained tissue. The data obtained were analyzed with one-way ANOVA and post hoc tests, with p < 0.05.

Results

CBE at a dose of 250 mg/kg BW significantly increased eNOS level, Collagen-1, and FGF-2 expression, and the number of fibroblasts and blood vessels in diabetes groups. Meanwhile, the treatment decreased NFκB expression in diabetes groups (p < 0.05).

Conclusion

This study proved that CBE increased periodontal ligament synthesis and angiogenesis and decreased inflammatory response, thereby preventing periodontal tissue breakdown in diabetic rat models with tooth movement.

Efficacy of microchips and 3D sensors for orthodontic force measurement: A systematic review of in vitro studies

OBJECTIVE

To evaluate the efficacy of microchips and 3D microsensors in the measurement of orthodontic forces.

METHODS

Through September 2023, comprehensive searches were conducted on PubMed/MEDLINE, SCOPUS and SCIELO without restrictions.

RESULTS

After removing duplicate entries and applying the eligibility criteria, 23 studies were included for analysis. All the studies were conducted in vitro, and slightly more than half of them were centred on evaluating orthodontic forces exerted by aligners. Eight utilized microchips as measurement tools, while the remaining studies made use of 3D microsensors for their assessments. In the context of fixed appliances, key findings included a high level of agreement in 3-dimensional orthodontic force detection between simulation results and actual applied forces. Incorporating critical force-moment combinations during smart bracket calibration reduced measurement errors for most components. Translational tooth movement revealed a moment-to-force ratio, aligning with the bracket's centre of resistance. The primary findings in relation to aligners revealed several significant factors affecting the forces exerted by them. Notably, the foil thickness and staging were found to have a considerable impact on these forces, with optimal force transmission occurring at a layer height of 150 μm. Furthermore, the type of material used in 3D-printing aligners influenced the force levels, with attachments proving effective in generating extrusive forces. Deliberate adjustments in aligner thickness were observed to alter the forces and moments generated.

CONCLUSIONS

Microchips and 3D sensors provide precise and quantitative measurements of orthodontic forces in in vitro studies, enabling accurate monitoring and control of tooth movement.

GDF15 Contributes to the Regulation of the Mechanosensitive Responses of PdL Fibroblasts through the Modulation of IL-37

During orthodontic tooth movement (OTM), areas of compressive and tensile forces are generated in the periodontal ligament (PdL), a mechanoreactive connective tissue between the teeth and alveolar bone. Mechanically stimulated PdL fibroblasts (PdLFs), the main cell type of PdL, express significantly increased levels of growth differentiation factor 15 (GDF15). In compressed PdL areas, GDF15 plays a fundamental role in modulating relevant OTM processes, including inflammation and osteoclast activation. However, the specific function of this factor in tensile areas has not yet been investigated. Thus, the aim of this study was to investigate the role of GDF15 in the mechanoresponse of human PdLFs (hPdLFs) that were exposed to biaxial tensile forces in vitro. Using siRNA-mediated knockdown experiments, we demonstrated that GDF15 had no impact on the anti-inflammatory force response of elongated hPdLFs. Although the anti-inflammatory markers IL1RN and IL10, as well as the activation of immune cells remained unaffected, we demonstrated an inhibitory role of GDF15 for the IL-37 expression. By analyzing osteogenic markers, including ALPL and RUNX2, along with an assessment of alkaline phosphatase activation, we further showed that the regulation of IL-37 by GDF15 modulates the osteogenic differentiation potential of hPdLFs. Despite bone resorption in tensile areas being rather limited, GDF15 was also found to positively modulate osteoclast activation in those areas, potentially by adjusting the IL-37 levels. In light of our new findings, we hypothesize that GDF15 modulates force-induced processes in tissue and bone remodeling through its various intra- and extracellular signaling pathways as well as interaction partners. Potentially acting as a master regulator, the modulation of GDF15 levels may hold relevance for clinical implications.