IL-1 gene polymorphisms, secretion in gingival crevicular fluid, and speed of human orthodontic tooth movement

Biological characteristics of microRNAs secreted by exosomes of periodontal ligament stem cells due to mechanical force

BACKGROUND

Orthodontic tooth movement (OTM) has previously been considered an inflammatory process. However, recent studies suggest that exosomes may play an important role in the cellular microenvironment of OTM. microRNAs (miRNAs) are one of the major constituents of exosomes. This study aims to investigate the biological characteristics of miRNAs secreted by exosomes of periodontal ligament stem cells (PDLSCs) due to mechanical forces.

MATERIALS AND METHODS

First, we established a mechanical stress model. The PDLSCs were loaded under different force values and exosomes were extracted after 48 h. High-throughput sequencing of exosomal miRNAs was performed to further evaluate their biological functions and underlying mechanisms.

RESULTS

The morphology and functions of exosomes were not significantly different between the loading and non-loading PDLSC groups. The optimal loading time and force were 48 h and 1 g/cm2, respectively. After sequencing, gene ontology (GO) and Kyoto encyclopaedia of genes and genomes (KEGG) pathway and network analyses were performed and 10 differentially expressed miRNAs were identified according to a literature search. These are miR-99a-5p, miR-485-3P, miR-29a-3p,miR-21-5p, miR-146a-5p, miR140-3p, miR-1306-5p, miR-126-5p, miR-125a-5p, and miR-23a-3p.

LIMITATIONS

Extracting exosomes needs a large amount of PDLSCs. More functional experiments need to be done to confirm the exact mechanism of exosomal miRNAs of PDLSCs due to mechanical force.

CONCLUSIONS

The expression levels of miRNAs secreted by PDLSC-derived exosomes due to mechanical force were very different compared to PDLSC-derived exosomes under nonmechanical stress. The function of many of the identified exosomal miRNAs was found to be related to osteoblasts and osteoclasts. Further validation is required. A functional investigation of these miRNA could provide novel insights into their mechanism.

Differential gene expression and protein-protein interaction networks of human periodontal ligament stromal cells under mechanical tension

Orthodontic treatment is based on complex strategies and takes up to years until a desired therapeutic outcome is accomplished, implying long periods of high costs and discomfort for the patient. Choosing the optimal settings for force intensities in the initial phase of orthodontic tooth movement is the key to successful orthodontic treatment. It is known that orthodontic tooth movement is mainly mediated by tensile and compressive forces that are communicated to the alveolar bone via the periodontal ligament. While the revelation of the complex molecular network was already approached by transcriptomic analysis of compressed periodontal ligament cells, the entity of molecular key players activated by tensile forces remains elusive. Therefore, the aim of this study was to assess the effect of mechanical tensile forces on the gene expression profile of human primary periodontal ligament stromal cells, mimicking the initial phase of orthodontic tooth movement. A transcriptomic analysis of tension-treated and untreated periodontal ligament stromal cells yielded 543 upregulated and 793 downregulated differentially expressed genes. Finally, six highly significant genes were found in the transcriptome that are related to biological processes with relevance to orthodontic tooth movement, including apelin, fibroblast growth factor receptor 2, noggin, sulfatase 1, secreted frizzled-related protein 4 and stanniocalcin 1. Additionally, differences of gene expression profiles between individual cell donors showed a high effect size. Closer understanding of the roles of the identified candidates in the initial phase of orthodontic tooth movement could help to clarify the underlying mechanisms, which will be essential for the development of personalized treatment strategies in orthodontics.

Orthodontics Surgical Assistance (Piezosurgery®): Experimental Evidence According to Clinical Results

Orthodontic tooth movement (OTM) is based on intermitted or continuous forces applied to teeth, changing the mechanical loading of the system and arousing a cellular response that leads to bone adaptation. The traditional orthodontic movement causes a remodeling of the alveolar bone and changes in the periodontal structures that lead to tooth movement. The use of a piezoelectric instrument in orthodontic surgery has already shown great advantages. The purpose of this study is to rank the behavior of inflammatory mediators in accelerating orthodontic tooth movement. Ten patients with malocclusion underwent orthodontic surgical treatment, which included a first stage of surgically guided orthodontic movement (monocortical tooth dislocation and ligament distraction, MTDLD) to accelerate orthodontic movements. In all cases, corticotomy was performed by Piezosurgery. Bone and dental biopsy was executed to evaluate changes in the cytokines IL-1beta, TNF-alpha and IL-2 in different time intervals (1, 2, 7, 14 and 28 days). The molecular mediators are IL-1 beta, TNF-alpha and IL-2. Immediately after the surgical procedure there was a mild expression of the three molecular markers, while the assertion of IL-1 beta and TNF-alpha reached the maximum value after 24 h and 48 h, indicating a strong activation of the treated tissues. The Piezosurgery® surgical technique induces an evident stress in short times, within 24–48 h from the treatment, but it decreases significantly during the follow-up.

Apolipoprotein E is an effective biomarker for orthodontic tooth movement in patients treated with transmission straight wire appliances

INTRODUCTION

Orthodontic tooth movement (OTM) is the core component of orthodontic treatment and is increasingly popular for treating malocclusions. In this study, we aimed to investigate the role of apolipoprotein E (ApoE) in OTM.

METHODS

Thirty patients treated with transmission straight wire technology were selected and longitudinally tracked at 2 different stages of orthodontic treatment (initial 2 months and 12 months of orthodontic treatment). Total saliva was collected and analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Western blotting was used to detect the difference in ApoE expression in the saliva samples of the 2 groups. The expression of ApoE was further verified by immunohistochemical staining in a mouse model of tooth movement.

RESULTS

The results of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry showed significant differences in the components of the salivary peptides in the 2 groups and peptides with a molecular weight of 2010.7 Da were predicted to be ApoE by database analysis. Western blotting further verified a significant difference in the expression of salivary ApoE in the 2 groups. In addition, an OTM model was successfully constructed in mice. The immunohistochemical staining results showed that ApoE expression significantly increased after force loading in the OTM model.

CONCLUSIONS

This study indicated that ApoE participated in and played a role during OTM in patients treated with transmission straight wire technology. This relationship might be related to alveolar bone reconstruction and root resorption. The results provide new ideas for research on the mechanism of tooth movement using precision medicine based on saliva detection.

Comparison of cytokine level changes in gingival crevicular fluid between the aligner and pendulum appliance during early molar distalization : A single-center, prospective, observational study

PURPOSE

There is currently a lack of evidence pertaining to gingival crevicular fluid cytokine levels in patients treated with the pendulum appliance. This study aimed to compare changes in cytokine secretion levels in gingival crevicular fluid (GFC) between the aligner and pendulum appliance in patients undergoing molar distalization.

METHODS

GFC samples were collected from 28 participants with asymmetrical dental class II malocclusion who were undergoing molar distalization using aligners or pendulum appliances. An enzyme-linked immunosorbent assay was used to detect cytokine secretion levels during asymmetrical molar distalization for up to 14 days. Periodontal health indices and tooth movements were also assessed.

RESULTS

No significant difference was found for the distalization distance between the two appliances. The Silness and Loe Plaque Index and Lobene Modified Gingival Index increased in the pendulum group but not in the aligner group at 14 days. Interleukin-1β and tumor necrosis factor‑α were upregulated in both groups. In the pendulum group, receptor activator of nuclear factor kappa‑Β ligand and osteoprotegerin secretion levels were significantly upregulated and downregulated, respectively; smaller changes in these two cytokines were observed in the aligner group.

CONCLUSIONS

Pendulum appliances exert stronger forces than aligners, which cause more changes in the secretion of inflammatory mediators in young patients.

The effect of genetic polymorphisms on treatment duration following premolar extraction

To elucidate genetic factors affecting orthodontic treatment duration, we employed targeted next-generation sequencing on DNA from the saliva of 117 patients undergoing orthodontic treatment after premolar extraction. The clinical characteristics of patients are summarized, and the association of clinical variables with treatment duration was assessed. Patients whose treatment duration deviated from the average were classified into an extreme long group or an extreme short group. We identified nine single nucleotide polymorphisms (SNPs) of six genes that significantly differed in the two groups via targeted sequencing. The frequency of the CC genotypes of WNT3A, SPP1 (rs4754, rs9138), and TNFSF11, TT genotype of SPP1 (rs1126616), and GG genotype of SFRP2 was significantly higher in the extreme long group than in the short group. In the extreme short group, the TC genotype of SPP1, AA genotype of P2RX7, CT genotype of TNFSF11, and AG genotype of TNFRSF11A tended to exhibit higher frequency than in the long group. Taken together, we identified genetic polymorphisms related to treatment duration in Korean orthodontic patients undergoing premolar extraction. Our findings could lead to further studies predicting the prolongation of the orthodontic treatment duration, and will be of great aid to patients as well as orthodontists.

Comparison of the efficacy of two-time versus one-time micro-osteoperforation on maxillary canine retraction in orthodontic patients: A split-mouth randomized controlled clinical trial

BACKGROUND

Micro-osteoperforation (MOP), a minimally invasive technique for accelerating the rate of orthodontic tooth movement has been research extensively, but with varied clinical results.

OBJECTIVE

To compare the efficacy of one-time versus two-time micro-osteoperforation on the rate of maxillary canine retraction, its influence on anchorage loss, canine angulation and the levels of interleukin (IL-1β) in gingival crevicular fluid (GCF).

MATERIALS AND METHODS

The split-mouth study included 16 patients in which the left and right sides were randomly allocated to the control side (one-time MOP) and experimental side (two-time MOP). MOP was performed on both sides distal to the maxillary canines and canine retraction was carried out using NiTi closed coil springs (150gm) and direct anchorage with miniscrew implants. The second MOP was performed on experimental side one month after the first MOP. The rate of canine movement was assessed using 3D model superimposition over a period of six months. The type of tooth movement, anchorage loss and levels of IL-1β were also evaluated.

RESULTS

Sixteen patients (mean age, 17.87±3.34 years) were analysed for a rate of canine retraction, anchorage loss, and type of tooth movement, while 15 patients were analysed for IL-1β. The rate was significantly higher on two-time MOP side after two months (P<0.001). No statistical difference was found in anchorage loss and controlled tipping of canines was observed. The IL-1β levels immediately after 2^nd MOP were significantly higher than 1^st MOP (P<0.001).

CONCLUSION

The two-time intervention of MOP is more efficacious than one-time MOP in accelerating tooth movement.

Relationship between the polymorphism in the interleukin 1-β and the treatment time of patients subjected to a modified piezocision technique

Aim:

We aimed to evaluate the correlation between the polymorphism of the interleukin 1-Beta (IL1-β, +3954 C>T) and tooth movement, in a group of Colombian patients undergoing surgically accelerated orthodontic tooth movement.

Methods:

The study was nested to a controlled clinical trial. Blood samples were taken from 11 women and 29 healthy Colombian male volunteers between 18 and 40 years old, after 1 year of starting orthodontic treatment. The patients presented malocclusion class I, with grade II or III. To detect the genetic polymorphism of the nucleotide +3954 C to T in the IL-1β gene, we used a real-time PCR assay.

Results:

Eleven individuals presented the allele 2 (T) heterozygous with the allele 1 (T/C) and 19 individuals were homozygous for the allele 1 (C/C). When analyzing the presence of the SNP, no significant differences were found in any of the variables. The best treatment was reflected in Group 3 (selective upper and lower alveolar decortication and 3D collagen matrix) and Group 4 (only selective alveolar decortication in the upper arch, with 3D collagen matrix), with 27% and 35% more speed respectively than in the control group.

Conclusions:

Our analyses indicated that a reduction in the total treatment time can be mostly potentiated by using decortication and collagen matrices and not for the presence of the allele 2 in the IL-1β. Nevertheless, it is important that further studies investigate if the polymorphism could be associated with the speed of tooth movement and analyze the baseline protein levels.

Optimal force magnitude for bodily orthodontic tooth movement with fixed appliances: A systematic review

INTRODUCTION

There is a high degree of uncertainty regarding the appropriate force level that should be applied during orthodontic tooth movement (OTM). As a result, orthodontic treatments may take longer than necessary, leading to unwanted side effects. This review aimed to identify an optimal force range with the rate of OTM as the primary outcome. External apical root resorption and pain were evaluated as secondary outcomes, and the influence of growth was examined.

METHODS

Five electronic databases were searched (MEDLINE [via PubMed], Embase [via OVID], Cochrane Library, CINAHL, and Web of Science) with no publication date or language restrictions. Inclusion eligibility screening, quality assessment, and data extraction were performed by 3 investigators. Each retrieved record was assessed by 2 observers independently. Only randomized controlled trials and randomized split-mouth studies were included.

RESULTS

A total of 12 articles satisfied the inclusion criteria-two randomized controlled trials and 10 randomized split-mouth studies. Only 1 study showed a low risk of bias, whereas the remaining 11 were unclear. The qualitative analysis showed that forces between 50 cN and 250 cN produced a similar OTM rate; forces >250 cN yielded a slightly higher rate but were accompanied by adverse effects. Because of considerable heterogeneity in methodology, clinical diversity with varying forces between 18 cN and 360 cN, and poor statistical reporting, a meta-analysis was deemed inappropriate.

CONCLUSIONS

Forces between 50 cN and 100 cN seem optimal for OTM, patient comfort and potentially exhibit fewer side effects. Nevertheless, careful data interpretation is necessary because of the lack of strong evidence. Protocol registration: PROSPERO CRD42016039985.

Assessment of salivary interleukin-1β (IL-1β), prostaglandin E2 (PGE2) levels and pain intensity in children and adults during initial orthodontic treatment

OBJECTIVES

To investigate pain intensity, interleukin-1β and prostaglandin E₂ values in saliva during initial orthodontic treatment among varying age groups and their correlation between these mediators.

MATERIALS AND METHODS

Twenty healthy patients distributed equally in age and gender groups were chosen. Unstimulated saliva was collected before the placement of orthodontic fixed appliance (T₀), 1 hour after the placement of the appliance with 0.014" nickel titanium archwire (T₁), 1 month after the first visit (T₂), and 1 hour after the placement of 0.016" nickel titanium archwire (T₃). The saliva samples were then analyzed for prostaglandin E₂ and interleukin-1β using enzyme-linked immunosorbent assay. Pain intensity was measured using a numerical rating scale.

RESULTS

Prostaglandin E₂ and interleukin-1β levels had increased at T₁ followed by a drop at T₂ and a subsequent increase at T₃. The prostaglandin E₂ and interleukin-1β levels were higher in adults than children. There was an insignificant correlation between the interleukin-1β and prostaglandin E₂ changes in all the patients. No significant differences were seen in pain scores between adults and children. Insignificant correlation was seen between pain scores and prostaglandin E₂ and interleukin-1β.

CONCLUSION

Prostaglandin E₂ and interleukin-1β can be detected in saliva and are increased in during the initial orthodontic treatment but are higher in adults than children. Pain intensity was not significantly different between adults and children.

Cytokine levels in gingival crevicular fluid during orthodontic treatment with aligners compared to conventional labial fixed appliances: a 3-week clinical study

Objective: To test the hypothesis that the levels of IL-1ß and TNF-α increased more and IL-1α, IL-2, IL-6, IL-8 increased less, after 3 weeks of treatment with conventional labial fixed appliance and with aligners. Material and methods: Forty patients who were treated either with labial brackets (n = 20) or aligners (n = 20). Gingival crevicular fluid (GCF) samples were collected at baseline and after 21 days. Cytokine levels were evaluated by enzyme-linked immune sorbent assay (ELISA). Plaque index (PI), gingival index (GI), and bleeding on probing (POB) were also examined. Results: The levels of IL-1α, IL-1ß, IL-2, IL-6, IL-8 and TNF-α in the GCF were significantly increased in both groups. The levels of IL-2, IL-6, IL-8 increased more in patients treated with aligners compared to those treated by labial fixed appliances. There was a statistically significant difference in change of the mean cytokine levels of IL-1α, IL-2, IL-6, IL-8 and TNF-α compared to labial fixed appliances and aligners. Conclusions: The levels of the six studied cytokines in GCF (IL-1α, IL-1ß, IL-2, IL-6, IL-8 and TNF-α) increased after 3 weeks both after treatment with conventional labial fixed appliance and with aligners. IL-1ß and TNF-α showed a prominent increase compared to the other cytokines in the GCF of teeth by both the labial fixed appliance and aligners. However, there were only minor differences in the changes of the cytokine levels from baseline to 3 weeks between the two groups. There were no differences between the groups regarding PI, GI or POB.

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.

Elevated levels of Interleukin (IL)-1β, IL-6, tumor necrosis factor-α, epidermal growth factor, and β2-microglobulin levels in gingival crevicular fluid during human Orthodontic tooth movement (OTM)

Aim

The aim of this study was to identify and quantify the various cytokines in human gingival crevicular fluid (GCF), and to investigate the changes in their levels during orthodontic tooth movement (OTM).

Materials and Methods

A statistically significant no. of subjects (n = 10 and mean age = 15.6 years) were included in the study. A maxillary cuspid of each subject having one treatment for distal orthodontic tooth movement served as the experimental tooth, whereas the contralateral cuspids were used as controls. Gingival crevicular fluid (GCF) around the experimental and the two control teeth was collected from each subject immediately before activation, and at 1, 24, and 168 hours after the initiation of tooth movement.

Result

ELISAs were used to determine cytokine levels. The concentrations of interleukin (IL)-1lβ, IL-6, tumor necrosis factor-α, epidermal growth factor, and β2-microglobulin were significantly higher in the experimental group than in the controls at 24 hr after the experiment was initiated. All the cytokines remained at baseline levels throughout the experiment for the control groups.

Conclusion

Since all cytokines in GCF play an important role in the bone remodelling processes in vivo, the present results indicate that the changes in cytokines in GCF are associated with OTM.

The effect of compressive force combined with mechanical vibration on human alveolar bone osteoblasts

Objective

This study aimed to investigate the effects of compressive force combined with mechanical vibration on the expression of pro-inflammatory cytokines that promote osteoclastogenesis and related to orthodontic tooth movement acceleration in human alveolar bone osteoblasts in vitro.

Methods

Osteoblasts were subjected to compressive force (C), mechanical vibration (V), compressive force combined with mechanical vibration (CV), or no force as a control for 12, 24 and 48 h. Interleukin-1 beta (IL-1β), interleukin-6 (IL-6), receptor activator of nuclear factor kappa-Β ligand (RANKL) and osteoprotegerin (OPG) mRNA and protein expression were assessed using quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent assays.

Results

In C and CV groups, IL-1β and IL-6 mRNA and protein expression were significantly higher and OPG mRNA and protein expression were significantly lower than control and V groups. However, the expressions were not different between C and CV groups. RANKL mRNA and protein expression were not different between any groups. While, OPG mRNA and protein expression in V group were significantly higher than control group.

Conclusions

Vibration neither enhanced nor inhibited the expression of IL-1β, IL-6, RANKL and OPG in compressed human alveolar bone osteoblasts.

Speed of human tooth movement in growers and non-growers: Selection of applied stress matters

OBJECTIVES

To test that the speed of tooth translation is not affected by stress magnitude and growth status.

SETTING AND SAMPLE POPULATION

Advanced Education Orthodontic clinics at the Universities of Nebraska Medical Center and Missouri-Kansas City. Forty-six consenting subjects with orthodontic treatment plans involving maxillary first premolar extractions.

MATERIALS AND METHODS

This randomized split-mouth study used segmental mechanics with definitive posterior anchorage and individual vertical-loop maxillary canine retraction appliances and measured three-dimensional tooth movements. Height and cephalometric superimposition changes determined growing (G) and non-growing (NG) subjects. Subjects were appointed for 9-11 visits over 84 days for maxillary dental impressions to measure three-dimensional tooth movement and to ensure retraction forces were continuously applied via calibrated nitinol coil springs. Springs were custom selected to apply two different stresses of 4, 13, 26, 52 or 78 kPa to maxillary canines in each subject. Statistical analyses (α=0.050) included ANOVA, effect size (partial η² ) and Tukey's Honest Significant Difference (HSD) and two-group t tests.

RESULTS

Distolateral translation speeds were 0.034±0.015, 0.047±0.019, 0.066±0.025, 0.068±0.016 and 0.079±0.030 mm/d for 4, 13, 26, 52 and 78 kPa, respectively. Stress significantly affected speed and partial η² =0.376. Overall, more distopalatal rotation was shown by teeth moved by 78 kPa (18.03±9.50º) compared to other stresses (3.86±6.83º), and speeds were significantly higher (P=.001) in G (0.062±0.026 mm/d) than NG subjects (0.041±0.019 mm/d).

CONCLUSIONS

Stress magnitude and growth status significantly affected the speed of tooth translation. Optimal applied stresses were 26-52 kPa, and overall speeds were 1.5-fold faster in G compared to NG subjects.

Saturation of the biological response to orthodontic forces and its effect on the rate of tooth movement

OBJECTIVES

Investigate the expression and activity of inflammatory markers in response to different magnitudes of orthodontic forces and correlate this response with other molecular and cellular events during orthodontic tooth movement.

SETTING AND SAMPLE POPULATION

CTOR Laboratory; 245 Sprague Dawley male rats.

METHODS AND MATERIALS

Control, sham, and 5 different experimental groups received different magnitudes of force on the right maxillary first molar using a coil spring. In the sham group, the spring was not activated. Control group did not receive any appliance. At days 1, 3, 7, 14, and 28, the maxillae were collected for RNA and protein analysis, immunohistochemistry, and micro-CT.

RESULTS

There was a linear relation between the force and the level of cytokine expression at lower magnitudes of force. Higher magnitudes of force did not increase the expression of cytokines. Activity of CCL2, CCL5, IL-1, TNF-α, RANKL, and number of osteoclasts reached a saturation point in response to higher magnitudes of force, with unchanged rate of tooth movement.

CONCLUSION

After a certain magnitude of force, there is a saturation in the biological response, and higher forces do not increase inflammatory markers, osteoclasts, nor the amount of tooth movement. Therefore, higher forces to accelerate the rate of tooth movement are not justified.

The osteoimmunology of alveolar bone loss

The mineralized structure of bone undergoes constant remodeling by the balanced actions of bone-producing osteoblasts and bone-resorbing osteoclasts (OCLs). Physiologic bone remodeling occurs in response to the body's need to respond to changes in electrolyte levels, or mechanical forces on bone. There are many pathological conditions, however, that cause an imbalance between bone production and resorption due to excessive OCL action that results in net bone loss. Situations involving chronic or acute inflammation are often associated with net bone loss, and research into understanding the mechanisms regulating this bone loss has led to the development of the field of osteoimmunology. It is now evident that the skeletal and immune systems are functionally linked and share common cells and signaling molecules. This review discusses the signaling system of immune cells and cytokines regulating aberrant OCL differentiation and activity. The role of these cells and cytokines in the bone loss occurring in periodontal disease (PD) (chronic inflammation) and orthodontic tooth movement (OTM) (acute inflammation) is then described. The review finishes with an exploration of the emerging role of Notch signaling in the development of the immune cells and OCLs that are involved in osteoimmunological bone loss and the research into Notch signaling in OTM and PD.

Immunoassay analysis of proteins in gingival crevicular fluid samples from resorbing teeth

Objective: 

To carry out an immunoassay analysis of biomarkers expressed in gingival crevicular fluid (GCF) with the main goal of finding a useful diagnostic pattern to distinguish between resorbing deciduous teeth and nonresorbing controls.

Materials and Methods: 

A split-mouth design was used in this study with a total of 22 GCF samples collected from 11 patients in the mixed dentition. For each child, one deciduous molar with radiographic evidence of root resorption was used as the test tooth whereas the contralateral first permanent molar with formed roots was used as the control tooth. Samples were processed with immunoassays using a panel of selected biomarkers including interleukin-1 beta (IL-1b), interleukin-1 receptor antagonist (IL-1RA), nuclear factor kappa B ligand (RANKL), osteoprotegerin (OPG), matrix metalloproteinase-9 (MMP-9), and dentin sialoprotein (DSP).

Results: 

There were no statistically significant differences in levels of IL-1b, OPG, and MMP-9 between test and control sites (P &gt; .05). IL-1RA was the only biomarker to show a significant down-regulation (P  =  .04) in GCF samples collected from resorbing teeth. RANKL data showed a heavily skewed distribution and was deemed unreliable. Only one deciduous GCF sample had detectable levels of DSP; therefore, no further statistical calculation was applicable because of the limited amount of data for this biomarker.

Conclusions: 

This study indicated that IL1-RA is down-regulated in GCF from resorbing primary molars, thus suggesting this cytokine as a potential analyte to be included in a panel that can discriminate between resorbing and nonresorbing teeth.

Biomarkers of Orthodontic Tooth Movement in Gingival Crevicular Fluid: A Systematic Review

BACKGROUND

The analysis of gingival crevicular fluid (GCF) may be an acceptable way to examine the ongoing biochemical processes associated with bone turnover during orthodontic tooth movement. If it is possible to biologically monitor and predict the outcome of orthodontic forces, then the management of appliances could be based on individual tissue responses, and the effectiveness of the treatment could be improved.

METHODOLOGY

A literature search was carried out in major databases, such as medline, EMBASE, cochrane library, web of science, google scholar and scopus for relevant studies. Publications in English between 2000 and 2014 which estimated GCF markers as indicators of orthodontic tooth movement were included.

RESULTS

The list of biomarkers available to date was compiled and presented in table format. Each biomarker is discussed separately based on the available evidence.

CONCLUSION

Several sensitive GCF markers are available to detect the biomechanical changes occurring during orthodontic tooth movement. Further focused research might help to analyze the sensitivity and reliability of these indicators, which in turn can lead to the development of chairside tests to assess the outcome of orthodontic therapy.

Effect of orthodontic forces on cytokine and receptor levels in gingival crevicular fluid: a systematic review

This systematic review aimed to generate evidence on role of potent markers of inflammation [cytokines, chemokines, their associated receptors and antagonists] following the application of orthodontic forces. Subsequent to registration with PROSPERO, literature search followed a predetermined search strategy to key databases along with hand search (HS). Seventy-seven articles from PubMed (P), 637 from Scopus (S), 51 from Embase (E), and 3 from hand search (HS) were identified. A total of 39 articles were shortlisted that met strict inclusion and exclusion criteria and quality assessment. Each study was evaluated for participant characteristics, study design, oral hygiene regimen, and gingival crevicular fluid (GCF) handling. Among these studies, biomarkers in the order of frequency were interleukin (IL)-1β (N = 21), tumor necrosis factor (TNF)-α (N = 10), IL-8,IL-6(N=8), receptor activator of nuclear factor kappa-B ligand (RANKL) (N = 7), monocyte chemoattractant protein (MCP)-1 (N = 3), IL-2 (N=4), IL-4, IL-10, RANTES (N = 2), IL-1, IL-5, IL-1α, IP-10, osteopontin (OPN) (N = 1) and receptors and their antagonists in the order of osteoprotegerin (OPG) (N = 8), IL-1RA (N = 5), and RANK (N = 1). Results revealed an immediate release of inflammatory bone-resorptive mediators, IL-1β and TNF-α, where IL-1β increased as early as 1 min to 1 h reaching peak at 24 h while TNF-α increased at 1 h or 1 day. This was accompanied by a fall in bone-protective mediator (OPG) levels at 1 h and 24 h after orthodontic force application. Continuous forces were accompanied by a decrease in mediator levels after attaining peak levels (most commonly at 24 h) while repeated activations in interrupted force upregulated their secretion. Significant correlations of IL-1β levels with pain intensity, rate of orthodontic tooth movement (OTM) and of activity index (AI) (IL-1β/IL-1RA) with velocity of tooth movement and growth status of individuals have also been deduced. A greater AI and RANKL/OPG ratio was seen in juveniles as compared to adults or non-growers that were associated with faster rate of OTM in juveniles. None of the studies addressed the effect of estrous cycle in female subjects. Lack of homogeneity in several parameters calls for a better controlled research on the biology of OTM.

Force-induced Adrb2 in periodontal ligament cells promotes tooth movement

The sympathetic nervous system (SNS) regulates bone resorption through β-2 adrenergic receptor (Adrb2). In orthodontic tooth movement (OTM), mechanical force induces and regulates alveolar bone remodeling. Compressive force-associated osteoclast differentiation and alveolar bone resorption are the rate-limiting steps of tooth movement. However, whether mechanical force can activate Adrb2 and thus contribute to OTM remains unknown. In this study, orthodontic nickel-titanium springs were applied to the upper first molars of rats and Adrb1/2(-/-) mice to confirm the role of SNS and Adrb2 in OTM. The results showed that blockage of SNS activity in the jawbones of rats by means of superior cervical ganglion ectomy reduced OTM distance from 860 to 540 μm after 14 d of force application. In addition, the injection of nonselective Adrb2 agonist isoproterenol activated the downstream signaling of SNS to accelerate OTM from 300 to 540 μm after 7 d of force application. Adrb1/2(-/-) mice showed significantly reduced OTM distance (19.5 μm) compared with the wild-type mice (107.6 μm) after 7 d of force application. Histopathologic analysis showed that the number of Adrb2-positive cells increased in the compressive region of periodontal ligament after orthodontic force was applied on rats. Mechanistically, mechanical compressive force upregulated Adrb2 expression in primary-cultured human periodontal ligament cells (PDLCs) through the elevation of intracellular Ca(2+) concentration. Activation of Adrb2 in PDLCs increased the RANKL/OPG ratio and promoted the peripheral blood mononuclear cell differentiation to osteoclasts in the cocultured system. Upregulation of Adrb2 in PDLCs promoted osteoclastogenesis, which accelerated OTM through Adrb2-enhanced bone resorption. In summary, this study suggests that mechanical force-induced Adrb2 activation in PDLCs contributes to SNS-regulated OTM.

Effects of mechanical stress and growth on the velocity of tooth movement

INTRODUCTION

In this study, we investigated the effects of the magnitudes of applied stress and growth status on the speed of tooth movement.

METHODS

Eighty-two maxillary canines in 41 subjects were retracted for 84 days by estimated stresses of 4, 13, 26, 52, or 78 kPa applied continuously via segmental mechanics. Dental impressions made at intervals of 1 to 14 days resulted in 9 or 10 dental casts per subject. Three-dimensional tooth movements were quantified using these casts, custom reference templates, and a measuring microscope. Serial height and cephalometric measurements determined growth status.

RESULTS

Distal tooth movement was linear with no lag phase in 96% of the teeth. Speeds averaged 0.028, 0.040, 0.050, 0.054, and 0.061 mm per day (standard errors, ± 0.004) for 4, 13, 26, 52, and 78 kPa, respectively. The maximum difference in speed between teeth was 9:1. Teeth moved significantly faster (P <0.0001) in growing compared with nongrowing subjects, on average by 1.6-fold. Stress and speed of tooth movement were logarithmically related in growing (R(2) = 0.47) and nongrowing (R(2) = 0.34) subjects. Other tooth movements were relatively small, except for the distopalatal rotation of teeth moved by 78 kPa that averaged more than 19°.

CONCLUSIONS

The speed of retraction was logarithmically related to the applied stress and was significantly faster in actively growing subjects compared with those who were not growing.

Evaluation of oxidative stress biomarkers in patients with fixed orthodontic appliances

AIM

The aim of this study was to examine the changes in the levels of interleukine-1 beta (IL-1 β ), tumor necrosis factor alpha (TNF- α ), malondialdehyde (MDA), nitric oxide (NO), and 8-hydroxydeoxyguanosine (8-OHdG) in saliva and IL-1 β , TNF- α , and NO in gingival crevicular fluid (GCF) samples of patients with fixed orthodontic appliances.

MATERIAL AND METHOD

The subject population consisted of 50 volunteers who were in need of orthodontic treatment with fixed orthodontic appliances. GCF and saliva samples were obtained from all individuals before treatment, at 1st month of treatment and at 6th month of treatment. Periodontal clinical parameters were measured. Samples were investigated to detect IL-1 β , TNF- α , and 8-OHdG levels using ELISA method and NO and MDA levels using spectrophotometric method.

RESULTS

Since IL-1 β level detected in GCF at the 6th month of orthodontic treatment is statistically significant according to baseline (P < 0.05), all other biochemical parameters detected both in saliva and in GCF did not show any significant change at any measurement periods.

CONCLUSION

Orthodontic tooth movement and orthodontic materials used in orthodontic treatment do not lead to a change above the physiological limits that is suggestive of oxidative damage in both GCF and saliva.

Human tooth movement by continuous high and low stresses

Objective:

To compare three-dimensional tooth movements resulting from relatively higher and lower stresses in a split-mouth design.

Materials and Methods:

Eight volunteers whose maxillary first premolars were removed for orthodontic treatment participated. Each subject's maxillary canines were retracted by randomly assigned constant stresses of 78 kPa and 4 kPa via segmental mechanics. Dental casts depicting 8–10 visits per subject over 84 days and a three-axis microscope were used to measure movements serially. Descriptive statistics and mixed linear modeling were applied for data analyses (α  =  .05).

Results:

Teeth moved by 78 kPa had significantly faster (P  =  .0005) distal movement (0.066 ± 0.020 mm/day) compared to teeth moved by 4 kPa (0.031 ± 0.012 mm/day). Lateral movement and distopalatal rotation were also significantly faster (fourfold and 10-fold, respectively) with higher than with lower stress (P &lt; .0001). Average extrusion-intrusion, crown torque, and tip were small (≤ |0.25| mm, |2.29|°, and |1.98|°, respectively), fluctuated, and not significantly different between high and low stresses. No lag phase of tooth movement was evident.

Conclusions:

Maxillary canines were retracted faster by 78 kPa than by 4 kPa. Controlled translation was possible with 4 kPa, but 78 kPa outstripped appliance constraints, causing distopalatal rotation.

Validation of a modified McGill Pain Questionnaire for orthodontic patients

OBJECTIVE

To assess better and more efficiently the aspects of pain experienced by adolescent orthodontic patients, the McGill Pain Questionnaire-Short Form (MPQ-SF) was modified (MMPQ-SF) and validated.

MATERIALS AND METHODS

Internal and external expert panels developed a MMPQ-SF with 15 descriptors and 4-point Likert severity scales (MMPQ-SF15). Seventy-five subjects undergoing orthodontic treatment gave informed consent. Sixty-one subjects completed the MMPQ-SF15, a visual analogue scale (VAS), and the present pain index (PPI) 24 hours after an orthodontic visit. Respondents were grouped by gender and treatment stage: initial (15 female, 7 male), middle (10 female, 7 male), and end (16 female, 6 male). MMPQ-SF, VAS, and PPI scores were compared by Spearman correlation analysis. Underlying constructs were explored by factor analyses. Construct validity of the MMPQ-SF was tested by analysis of variance.

RESULTS

MMPQ-SF15 and VAS (r = 0.78, r(2)s = 0.61, P < .0001), MMPQ-SF15 and PPI (r = 0.84, r(2)s = 0.71, P < .0001), and VAS and PPI (r = 0.70, r(2)s = 0.48, P < .0001) were correlated positively and significantly. A two-factor solution (localized and generalized/emotional pain; Kaiser-Meyer-Olkin = 0.88) showed that 11 descriptors (MMPQ-SF11) accounted for 64% of response variability. Generalized/emotional pain values were significantly higher during the initial stage of treatment compared to the middle (P = .011) and end stages (P = .014).

CONCLUSIONS

MMPQ-SF, particularly MMPQ-SF11, demonstrated utility in assessment of localized and generalized/emotional aspects of pain in adolescent orthodontic patients and correlated well with VAS and PPI. Future application of the MMPQ-SF11 to measure orthodontic pain more specifically could lead to more appropriate management of this important facet of therapy.

Archwire vibration and stick-slip behavior at the bracket-archwire interface

INTRODUCTION

It is unknown whether or not intraoral vibrations affect stick-slip behavior at orthodontic bracket-archwire interfaces. In this study, we evaluated bracket-archwire stick-slip behavior as a function of ligation method and archwire vibration.

METHODS

In-vivo archwire vibrations were measured to obtain frequencies and amplitudes for ex-vivo testing. A piezoresistive accelerometer ligated to the maxillary right canines of 6 subjects transduced the intraoral vibrations. All subjects gave informed consent to participate. Amplitude and frequency of the vibrations were quantified and used in a bench-top friction testing apparatus. Active and passive ligation methods were compared for 9 vibration scenarios. The amount of time to move the bracket along a stainless steel wire was recorded in 90 trials. Analysis of variance and post-hoc tests were used for statistical analyses of the data.

RESULTS

During carrot biting, orthodontic wire vibrations had a mean frequency of 98 Hz and a peak-to-peak mean amplitude of 151 mV. The bench-top stick-slip measurement trials containing medium (150 mV) and high (190 mV) amplitude vibrations had significantly less friction (ln, s), 4.81 ± 2.08 and 4.67 ± 2.00, respectively, than those subjected to low (110 mV) amplitudes, 5.80 ± 1.39 (P = 0.04). There were no significant differences between passive and active ligation methods.

CONCLUSIONS

Amplitudes of archwire vibrations affect stick-slip behavior at the bracket-archwire interfaces.

Cytokines and VEGF induction in orthodontic movement in animal models

Orthodontics is a branch of dentistry that aims at the resolution of dental malocclusions. The specialist carries out the treatment using intraoral or extraoral orthodontic appliances that require forces of a given load level to obtain a tooth movement in a certain direction in dental arches. Orthodontic tooth movement is dependent on efficient remodeling of periodontal ligament and alveolar bone, correlated with several biological and mechanical responses of the tissues surrounding the teeth. A periodontal ligament placed under pressure will result in bone resorption whereas a periodontal ligament under tension results in bone formation. In the primary stage of the application of orthodontic forces, an acute inflammation occurs in periodontium. Several proinflammatory cytokines are produced by immune-competent cells migrating by means of dilated capillaries. In this paper we summarize, also through the utilization of animal models, the role of some of these molecules, namely, interleukin-1β and vascular endothelial growth factor, that are some proliferation markers of osteoclasts and osteoblasts, and the macrophage colony stimulating factor.