Effects of aging on RANKL and OPG levels in gingival crevicular fluid during orthodontic tooth movement

The age-related effects on orthodontic tooth movement and the surrounding periodontal environment

Orthodontic treatment in adults is often related to longer treatment time as well as higher periodontal risks compared to adolescents. The aim of this review is to explore the influence of age-related chages on orthodontic tooth movement (OTM) from macro and micro perspectives. Adults tend to show slower tooth movement speed compared to adolescence, especially during the early phase. Under orthodontic forces, the biological responses of the periodontal ligament (PDL) and alveolar bone is different between adult and adolescents. The adult PDL shows extended disorganization time, increased cell senescence, less cell signaling and a more inflammatory microenvironment than the adolescent PDL. In addition, the blood vessel surface area is reduced during the late movement phase, and fiber elasticity decreases. At the same time, adult alveolar bone shows a higher density, as well as a reduced osteoblast and osteoclast activation, under orthodontic forces. The local cytokine expression also differs between adults and adolescents. Side-effects, such as excessive root resorption, greater orthodontic pain, and reduced pulpal blood flow, also occur more frequently in adults than in adolescents.

Age-related alveolar bone maladaptation in adult orthodontics: finding new ways out

Compared with teenage patients, adult patients generally show a slower rate of tooth movement and more pronounced alveolar bone loss during orthodontic treatment, indicating the maladaptation of alveolar bone homeostasis under orthodontic force. However, this phenomenon is not well-elucidated to date, leading to increased treatment difficulties and unsatisfactory treatment outcomes in adult orthodontics. Aiming to provide a comprehensive knowledge and further inspire insightful understanding towards this issue, this review summarizes the current evidence and underlying mechanisms. The age-related abatements in mechanosensing and mechanotransduction in adult cells and periodontal tissue may contribute to retarded and unbalanced bone metabolism, thus hindering alveolar bone reconstruction during orthodontic treatment. To this end, periodontal surgery, physical and chemical cues are being developed to reactivate or rejuvenate the aging periodontium and restore the dynamic equilibrium of orthodontic-mediated alveolar bone metabolism. We anticipate that this review will present a general overview of the role that aging plays in orthodontic alveolar bone metabolism and shed new light on the prospective ways out of the impasse.

Effect of autophagy on aging-related changes in orthodontic tooth movement in rats

BACKGROUND

The number of adult orthodontic patients is increasing, and studies have shown that autophagy is involved in regulating orthodontic tooth movement and plays an important role in aging-related changes. Therefore, we aimed to explore the role of autophagy in aging-related changes during orthodontic tooth movement by establishing a rat orthodontic tooth movement model.

METHODS

Forty-five 6-week-old and sixty-five 8-month-old male Sprague-Dawley rats were selected to represent adolescents and adults and establish orthodontic tooth movement model. They were sacrificed on days 0,1,3,7 and 14. Immunohistochemistry, immunofluorescence and tartrate resistant acid phosphatase (TRAP) staining were applied to measure the expression level of osteogenesis, autophagy, aging factors and osteoclast number in periodontal membrane of left upper first molar during orthodontic tooth movement. Then, we regulated the autophagy level by injecting autophagy activator rapamycin during orthodontic tooth movement and measured these factors and tooth movement distance by micro-computed tomography.

RESULTS

Aging factor levels in the periodontal membrane were higher in adult rats than in adolescent rats and the autophagy factor levels were lower. The levels of osteogenic factors were lower on the tension side in adult rats than in adolescent rats. The peak osteoclast number on the pressure side occurred later in adult rats than in adolescent rats. The injection of rapamycin increased autophagy, accelerated orthodontic tooth movement in adult rats, and reduced the levels of aging factors. The levels of osteogenic factors were higher and reached those in adolescent rats at some time points. The number of osteoclasts increased significantly in the early stage.

CONCLUSIONS

Autophagy may play a substantial role in regulating aging-related changes in orthodontic tooth movement.

Comparison of the Effects of Ketorolac and Acetaminophen on RANK-L Levels in the Gingival Crevicular Fluid during Orthodontic Tooth Movement: A Pilot Study

Background: Patients usually present pain due to the release of different inflammatory mediators such as prostaglandin E2 and RANK-L. Analgesics such as acetaminophen and ketorolac can inhibit RANK-L expression and this can affect orthodontic treatment by decreasing bone remodeling and slowing orthodontic dental movement. Several studies have reported a decrease in dental movement after administering some non-steroidal anti-inflammatory drugs. Proposal: The objective was to evaluate the RANK-L levels and a possible modulation by administering acetaminophen and ketorolac in patients starting orthodontic treatment. Methodology: A double-blind, randomized clinical trial was carried out with 24 subjects divided into three study groups: calcined magnesia as a placebo, acetaminophen, and ketorolac. Gingival crevicular fluid was obtained at four time points: before pharmacological intervention, at 24 h, at 48 h, and on the 5th day. RANK-L concentrations were evaluated through ELISA analysis. Also, interproximal space generated by the elastic separator at the end of the study was recorded in the different study groups using the visual analog scale. Results: An increase in RANK-L at 24 h was observed in the placebo group compared to the ketorolac and acetaminophen groups. However, no significant differences were observed in the interproximal space at day 5 in the three study groups. Conclusion: Patients who do not take analgesics at the start of orthodontic treatment have higher levels of RANK-L. Therefore, the use of ketorolac or acetaminophen could decrease bone remodeling and interfere with orthodontic dental movement.

Changes in alveolar bone structure during orthodontic tooth movement in adolescent and adult rats: A microcomputed tomography study

BACKGROUND

Increasing number of adults are willing to seek orthodontic treatment, but treatment duration for them is commonly longer. Although there have been studies on molecular biological changes during tooth movement, few have focused on microstructural changes in alveolar bone.

OBJECTIVE

This study aims to compare the microstructural changes in alveolar bone during orthodontic tooth movement in adolescent and adult rats.

METHODS

25 6-week-old and 25 8-month-old male Sprague-Dawley (SD) rats were used to build orthodontic tooth-movement models. On Days 0, 1, 3, 7 and 14, the rats were sacrificed. Microcomputed tomography was used to evaluate tooth movement, alveolar crest height loss and microstructural parameters of alveolar bone (bone volume fraction, trabecular thickness, trabecular separation and trabecular number).

RESULTS

Tooth movement in the adult group was slower than in the adolescent group. Alveolar bone crest height in adults was lower than it was in adolescents on Day 0. Under orthodontic force, the alveolar crest in both groups decreased and the degree of decrease are higher at early stage in adolescents. The microstructural parameters indicated that the alveolar bone was originally denser in the adult rats. With orthodontic force, it tended to be looser.

CONCLUSIONS

Under orthodontic force, changes in alveolar bone differ between adolescent and adult rats. Tooth movements in adults are slower, and the decrease in alveolar bone density are more severe.

Randomized clinical trial on the effect of intermittent vibrational force application during orthodontic treatment with aligners on RANKL and OPG concentrations in crevicular fluid

Application of intermittent forces by vibration is proposed as an easy-to-use accelerator of dental movement. The purpose of this study was to determine the effect of intermittent vibrational force application during orthodontic aligner treatment on receptor activator of nuclear factor-kappa B ligand (RANKL) and osteoprotegerin (OPG) concentrations in crevicular fluid as markers of bone remodeling. This three-arm parallel randomized clinical trial included 45 candidates for malocclusion treatment with aligners, randomly assigned to: Group A (vibrational forces from onset of treatment); Group B (vibrational forces at 6 weeks after treatment onset); or Group C (no vibration). The frequency of aligner adjustment also differed among groups. At different time points, a paper tip was used to draw crevicular fluid samples from a moving lower incisor for RANKL and OPG analysis using ELISA kits. Mixed-model ANOVA found no significant differences in RANKL (A: p = 0.31, B: p = 0.8, C: p = 0.49) or OPG (A: p = 0.24, B: p = 0.58, C: p = 0.59) over time in any group or as a function of the application/non-application of vibration or the frequency of aligner adjustments. Application of this accelerator device did not significantly affect bone remodeling in patients undergoing orthodontic treatment with aligners. However, a nonsignificant improvement in biomarker concentrations was observed when aligners were changed every 7 days and vibration was also applied. Further research is warranted to establish protocols for the application of vibration and the timing of aligner adjustments.

Effect of leukocyte-platelet-rich fibrin (L-PRF) on the rate of orthodontic tooth movement and expression of various biomarkers in gingival crevicular fluid

OBJECTIVES

To assess the outcome of leukocyte-platelet-rich fibrin (L-PRF) on the rate of maxillary canine retraction and its correlation with the levels of Receptor activator of nuclear factor kappa-B ligand (RANKL), osteoprotegerin (OPG), and RANKL:OPG in the gingival crevicular fluid (GCF) during comprehensive orthodontic treatment.

SUBJECTS AND METHODS

Eighteen females who required all 1st premolars extraction for the correction of their class I bimaxillary protrusion malocclusions were included. The L-PRF plugs were placed in the experimental side 1st premolar extraction sockets. Canine retraction was performed by sliding mechanics. Canine retraction was assessed from the maxillary study models prepared just before the extraction (T₀) and then at 1 week (T₁), 2 weeks (T₂), 4 weeks (T₃), and 8 weeks (T₄) after the 1st premolar extraction and placement of L-PRF plugs. The concentrations of RANKL and OPG in the GCF were evaluated at T₀, T₁, T₂, T₃, and T₄.

RESULTS

In experimental sides, the amount of canine retraction was statistically more during the T₀-T₁, T₁-T₂, and T₂-T₃ periods. The mean concentration of RANKL at T₁, T₂, and T₃ was significantly more in the experimental sides. The mean concentration of OPG was significantly less in the experimental sides at T₂, T₃, and T₄. The RANKL:OPG was significantly more in the experimental sides at T₁, T₂, T₃, and T₄. No significant correlation was found between amount of canine retraction and concentration of RANKL and OPG and RANKL to OPG ratio in GCF.

CONCLUSIONS

The L-PRF accelerated the rate of maxillary canine retraction by 0.28 mm over an 8-week period. The L-PRF favored the local osteoclastogenesis by enhancing the RANKL and suppressing the OPG concentrations. There was no significant correlation between the rate of maxillary canine retraction and expression of RANKL, OPG, and RANKL:OPG in GCF.

TRIAL REGISTRATION

The Clinical Trials Registry of India (Reg. No. CTRI/2020/10/028390, Date-13.10.2020).

Effects of autologous leukocyte-platelet rich fibrin (L-PRF) on the rate of maxillary canine retraction and various biomarkers in gingival crevicular fluid (GCF): A split mouth randomized controlled trial

OBJECTIVES

Primary objective: To evaluate the effect of L-PRF on the rate of maxillary canine retraction.

SECONDARY OBJECTIVE

To validate the rate of maxillary canine retraction by identifying the levels of Interleukin-1β (IL-1β) and Tumour Necrosis Factor-α (TNF-α) in the Gingival Crevicular Fluid (GCF).

MATERIALS AND METHOD

Fifteen females (age range, 18-25 years) with Class I bimaxillary dentoalveolar protrusion malocclusions were included. After levelling and alignment of maxillary arches, 1st premolars were extracted from both sides. Canines were retracted immediately after the extraction of 1st premolars in control sides and placement of L-PRF plugs in the experimental sides. The amount of canine retraction was evaluated from study models recorded before the extraction of 1st premolars (T₀) and at 1-week (T₁), 2-weeks (T₂), 4-weeks (T₃), and 8-weeks (T₄) after the beginning of canine retraction by using digital model superimpositions. The concentrations of IL-1β and TNF-α were evaluated from the GCF collected at T₀, T₁, T₂, T₃, and T₄ by using commercially available human IL-1β and TNF-α ELISA kits.

RESULTS

The amount of canine retraction in the experimental sides was statistically greater during T₀-T₁ (P=0.038),T₁-T₂ (P=0.002), and T₂-T₃ (P=0.011) periods. Total canine retraction during T₀-T₄ was statistically greater in experimental sides (2.43±0.46mm) than control sides (2.08±0.28mm) (P=0.001). The concentration of IL-1β increased significantly in the experimental sides at T₁ (P=0.000),T₂ (P=0.000), and T₃ (P=0.032). The concentration of TNF-α increased both in the control and experimental sides, but it was statistically greater in the experimental sides compared to control sides at T₁ (P=0.000) and T₂ (P=0.006). A positive but not statistically significant correlation was noted between the rate of canine retraction and the concentrations of cytokines such as IL-1β and TNF-α in GCF.

CONCLUSION

Over an 8-week period, autologous L-PRF statistically accelerated the rate of maxillary canine retraction, but only by 0.35mm. This small acceleration occurred mainly in the first 4 weeks. During the following 4 weeks, the amount of canine retraction was comparable on the experimental and control sides.

Effect of customized vibratory device on orthodontic tooth movement: A prospective randomized control trial

AIMS:

The primary purpose of the present trial was to evaluate the effect of low-frequency (30Hz) vibrations on the rate of canine retraction.

SETTING AND DESIGN:

Single-center, split mouth prospective randomized controlled clinical trial

METHODS AND MATERIAL:

100 screened subjects (aged18–25 years) were selected; out of which 30 subjects having Class I bimaxillary protrusion or Class II div 1 malocclusion, requiring upper 1^st premolar therapeutic extractions, were selected for the study. A split-mouth study design was prepared for the maxillary arch of each selected individual and was randomly allocated into vibration and nonvibration side (control) groups. A customized vibratory device was fabricated for each subject to deliver low-frequency vibrations (30 Hz). Scanned 3D models were prepared sequentially to assess the amount of tooth movement from baseline (T0),(T1), (T2), (T3), and (T4)-4^th month of canine retraction.

STATISTICAL ANALYSIS USED:

Independent “t” test.

RESULTS:

There was no statistically significant differencein the rate of individual canine retraction among the experimental and control groups when the intergroup comparison was done using independent “t” test at T1-T0, (P = 0.954), T2-T1 (P = 0.244), T3-T2 (P = 0.357), and T4-T3 (P = 0.189).

CONCLUSION:

The low-frequency vibratory stimulation of 30 Hz using a customized vibratory device did not significantly accelerate the rate of orthodontic tooth movement.

TRIAL REGISTRATION:

Registered at ctri.nic.in (CTRI/2019/05/019043).

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.

Clinical research: low-level laser therapy in accelerating orthodontic tooth movement

Background

The present study aimed to investigate the effects of low-level laser therapy (LLLT) on orthodontic tooth movement and its correlation with the levels of interleukin-1β (IL-1β), receptor activator of nuclear factor kappa B ligand (RANKL) and osteoprotegerin (OPG) in gingival crevicular fluid (GCF).

Methods

This split-mouth design study included 12 patients scheduled for the extraction of both upper first premolars. Patients were randomly selected for experimental group that received left- or right-side radiation with a diode laser (810 nm wavelength, 100 mW power output, 6.29 J/cm² energy density). Laser treatment was applied on days 0, 7, 14, and 21, after loading the canine retraction forces. GCF concentrations of IL-1β, RANKL, and OPG were analyzed. The upper arch of each patient was scanned with an intraoral scanner to assess tooth movement.

Results

The cumulative tooth movement over 28 days was significantly higher in the laser group than in the control group. We observed significant reductions in OPG levels and increases in IL-1β and RANKL levels in GCF samples on the experimental sides.

Conclusion

With the parameter settings used in this study, LLLT could, to some extent, lead to changes in bone metabolism, which could accelerate orthodontic tooth movement.

Trial registration: Chinese Clinical Trial Registry, ChiCTR2000039594. Registered 2 November 2020—Retrospectively registered, www.chictr.org.cn/edit.aspx?pid=62465&htm=4.

Effect of micro-osteoperforations on rate of space closure by mini-implant supported maxillary anterior en-masse retraction: A randomized clinical trial

Background

Micro-osteoperforations is one of the non-invasive surgical techniques used in attempt to accelerate OTM. Conflicting reports on its effectiveness has been reported in the literature.

Objectives

The objectives of this trial were to investigate the effect of micro-osteoperforations on the rate of space closure and on molar anchorage loss during mini-implant supported maxillary anterior en-masse retraction.

Trial design

A single center, parallel arm, randomized controlled trial was conducted.

Method

Sixty, male and female subjects (age range 16-25 years) having Class I bimaxillary protrusion or Class II div 1 malocclusion, who required fixed mechanotherapy with either upper 1st premolar or all four 1st premolar extractions were allocated into two groups using 1:1 allocation ratio. The allocation was done by block randomization method with a block size of 6. In the experimental group, 5 MOPs per side were performed only once just before the en-masse anterior retraction. Mini-screws were placed in order to obtain maximum anchorage. Impressions were taken every month till 4 months and rate of space closure was measured on 3D study models.

Results

Data of 27 subjects in control (attrition ​= ​3) and 28 subjects in experimental group (attrition ​= ​2) were analyzed at the end of this trial. There was a statistically significant increase in the rate of en-masse retraction for the 1st month(p ​= ​0.001,95%CI, 0.17, 0.37 ​mm) but there was no statistically significant difference for the subsequent 2nd (p ​= ​0.450,95%CI,0.13,0.43 ​mm), 3rd(p ​= ​0.204,95%CI,0.23,0.47 ​mm) and 4th month (p ​= ​0.680,95%CI,0.21,0.41 ​mm) between experimental and control groups. There was also no difference (p ​> ​0.05) in molar anchorage loss between both groups at all time intervals.

Conclusion

Micro-osteoperforations (MOPs) did not accelerate the rate of anterior en-masse retraction over a period of 4 months; however, it temporarily increases the rate of retraction only for first month and no affect on molar anchorage.

Trial registration

The trial was registered at www.ctri.nic.in with CTRI No- CTRI/2019/03/018140).

The preventive effect of medicinal herbal extract and gelatin sponge on alveolar osteitis: An in vivo micro-computed tomography and immunohistochemical analysis in rats

OBJECTIVE

The purpose of this study was to evaluate the preventive effect of medicinal herbal extract (MHE) and gelatin sponge on alveolar osteitis (AO) in an experimental rat model.

DESIGN

Twenty-one Sprague-Dawley male rats with a mean age of 12 weeks were used. After extraction of the maxillary right first molar, an AO model was created for each animal. The animals were randomly separated to three equal groups. Group I served as a control, Group II was subjected to an intra-alveolar MHE application, and gelatin sponge was left in the sockets of Group III. On the 7th post-extraction day, the animals were sacrificed. The specimens were analyzed by micro-computed tomography (micro-CT), histopathologically and immunohistochemically.

RESULTS

Macroscopic evaluation revealed mild to intense signs of AO in all groups, but the difference was not significant (p < 0.05). Micro-CT analysis showed that bone formation was the highest in Group III (bone volume/total volume; 10.63 ± 4.9 %), whereas bone mineral density was the highest in Group I (2.05 ± 0.2 g/cm³). The difference was not significant (p > 0.05). In Group III, only 16.7 % of specimens showed no signal of inflammatory response (p < 0.01). The difference was not significant between the positive labeling for receptor activator of nuclear kappa-β (RANK), receptor activator of nuclear kappa-β ligand (RANKL), osteoprotegerin and osteopontin, but the intensity of Groups II and III was higher than the Group I for osteopontin (p < 0.01).

CONCLUSIONS

MHE and gelatin sponge were not effective enough to prevent alveolar osteitis, but positive results were obtained in bone healing.

Age effect on orthodontic tooth movement rate and the composition of gingival crevicular fluid : A literature review

PURPOSE

To evaluate and form a comprehensive understanding of the effect of patient age on bone remodeling and consequently on the rate of orthodontic tooth movement (OTM).

METHODS

A systematic search in PubMed and Embase from 1990 to December 2017 was performed and completed by a hand search. Prospective clinical trials which investigated the rate of OTM and/or studies assessing age-related changes in the composition of gingival crevicular fluid (GCF) in older compared to younger study groups were included. Study selection, data extraction and risk of bias were assessed by two authors.

RESULTS

Eight studies fulfilled the inclusion criteria. Among them, four evaluated the rate of OTM and six investigated mediators in the GCF (prostaglandin E₂, interleukin [IL]-1β, IL‑6, IL‑1 receptor antagonist, receptor activator of nuclear factor kappa‑Β ligand, osteoprotegerin, granulocyte-macrophage colony-stimulating factor, pentraxin 3). Patient age ranged between 16 and 43 years for older and <16 years for younger groups. In most of the studies, the younger patients showed faster OTM in the first phase of treatment and more pronounced cytokine levels. Older patients had a delayed reaction to orthodontic forces.

CONCLUSION

The small number of included studies and large heterogeneity in study design give limited clinical evidence that the older patients are less responsive to orthodontic force in comparison to younger patients. The initial cellular response to orthodontic force is expected to be delayed in older patients. Control intervals during orthodontic treatment should be adjusted to the individual's treatment response.

Impact of pharmacologic inhibition of tooth movement on periodontal and tooth root tissues during orthodontic force application

OBJECTIVE

The goal of this study was to investigate potential negative sequelae of orthodontic force application ±delivery of an osteoclast inhibitor, recombinant osteoprotegerin protein (OPG-Fc), on periodontal tissues.

SETTING AND SAMPLE POPULATION

Sprague Dawley rats from a commercial supplier were investigated in a laboratory setting.

MATERIALS AND METHODS

Rats were randomly divided into four groups (n = 7 each): one group with no orthodontic appliances and injected once prior to the experimental period with empty polymer microspheres, one group with orthodontic appliances and injected once with empty microspheres, one group with orthodontic appliances and injected once with polymer microspheres containing 1 mg/kg of OPG-Fc, and one group with orthodontic appliances and injected with non-encapsulated 5 mg/kg of OPG-Fc every 3 days during the experimental period. The animals were euthanized after 28 days of tooth movement for histomorphometric analyses.

RESULTS

Root resorption, PDL area and widths were similar in animals without appliances and animals with appliances plus high-dose OPG-Fc. PDL blood vessels were compressed and decreased in number in all animals that received orthodontic appliances, regardless of OPG-Fc. Hyalinization was significantly increased only in animals with orthodontic appliances plus multiple injections of 5 mg/kg non-encapsulated OPG-Fc when compared to animals without appliances.

CONCLUSIONS

Results of this study indicate that while pharmacological modulation of tooth movement through osteoclast inhibition is feasible when delivered in a locally controlled low-dose manner, high-dose levels that completely prevent tooth movement through bone may decrease local blood flow and increase the incidence of hyalinization.

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.

Microsphere controlled drug delivery for local control of tooth movement

Background

Because orthodontic tooth movement is dependent upon osteoclast-mediated resorption of alveolar bone adjacent to the pressure side of tooth roots, biologic mediators that regulate osteoclasts can be utilized to control tooth movement.

Objectives

To develop a novel method to locally enhance orthodontic anchorage.

Methods

We encapsulated osteoprotegerin (OPG) in polymer microspheres and tested the effectiveness of microsphere encapsulated versus non-encapsulated OPG for enhancing orthodontic anchorage in a rodent model of tooth movement. A single injection of 1 mg/kg non-encapsulated or microsphere encapsulated OPG was delivered into the palatal mucosa mesial to the first maxillary molar 1 day prior to tooth movement. A positive control group received injections of 5 mg/kg non-encapsulated OPG every 3 days during tooth movement. After 28 days of tooth movement, hemi-maxillae and femurs were dissected. Molar mesial and incisor distal tooth movement was measured using stone casts that were scanned and magnified. Local alveolar, distant femur bone, and tooth root volumes were analyzed by micro computed tomography. Serum OPG levels were measured by ELISA. Osteoclast numbers were quantified by histomorphometry.

Results

The single injection of microsphere encapsulated OPG significantly enhanced orthodontic anchorage, while the single injection of non-encapsulated OPG did not. Injection of encapsulated OPG inhibited molar mesial movement but did not inhibit incisor tooth movement, and did not alter alveolar or femur bone volume fraction, density, or mineral content. Multiple injections of 5 mg/kg non-encapsulated OPG enhanced orthodontic anchorage, but also inhibited incisor retraction and altered alveolar and femur bone quality parameters. Increased OPG levels were found only in animals receiving multiple injections of non-encapsulated 5 mg/kg OPG. Osteoclast numbers were higher upon tooth movement in animals that did not receive OPG. Osteoclast numbers in OPG injected animals were variable within groups.

Conclusions

Microsphere encapsulation of OPG allows for controlled drug release, and enhances site-specific orthodontic anchorage without systemic side effects. With additional refinements, this drug delivery system could be applicable to a broad array of potential biologic orthodontic therapeutics.

Single Local Injection of Epigallocatechin Gallate-Modified Gelatin Attenuates Bone Resorption and Orthodontic Tooth Movement in Mice

Osteoclastic bone resorption enables orthodontic tooth movement (OTM) in orthodontic treatment. Previously, we demonstrated that local epigallocatechin gallate (EGCG) injection successfully slowed the rate of OTM; however, repeat injections were required. In the present study, we produced a liquid form of EGCG-modified gelatin (EGCG-GL) and examined the properties of EGCG-GL with respect to prolonging EGCG release, NF-E2-related factor 2 (Nrf2) activation, osteoclastogenesis inhibition, bone destruction, and OTM. We found EGCG-GL both prolonged the release of EGCG and induced the expression of antioxidant enzyme genes, such as heme oxygenase 1 (Hmox1) and glutamate-cysteine ligase (Gclc), in the mouse macrophage cell line, RAW264.7. EGCG-GL attenuated intracellular reactive oxygen species (ROS) levels were induced by the receptor activator of nuclear factor-kB ligand (RANKL) and inhibited RANKL-mediated osteoclastogenesis in vitro. An animal model of bone destruction, induced by repeat Lipopolysaccharide (LPS)-injections into the calvaria of male BALB/c mice, revealed that a single injection of EGCG-GL on day-1 could successfully inhibit LPS-mediated bone destruction. Additionally, experimental OTM of maxillary first molars in male mice was attenuated by a single EGCG-GL injection on day-1. In conclusion, EGCG-GL prolongs the release of EGCG and inhibits osteoclastogenesis via the attenuation of intracellular ROS signaling through the increased expression of antioxidant enzymes. These results indicate EGCG-GL would be a beneficial therapeutic approach both in destructive bone disease and in controlling alveolar bone metabolism.

RANK/RANKL/OPG Expression in Rapid Maxillary Expansion

The aim of this study was to evaluate osteoclastogenesis signaling in midpalatal suture after rapid maxillary expansion (RME) in rats. Thirty male Wistar rats were randomly assigned to two groups with 15 animals each: control (C) and RME group. RME was performed by inserting a 1.5-mm-thick circular metal ring between the maxillary incisors. The animals were euthanized at 3, 7 and 10 days after RME. qRT-PCR was used to evaluate expression of Tnfsf11 (RANKL), Tnfrsf11a (RANK) and Tnfrsf11b (OPG). Data were submitted to statistical analysis using two-way ANOVA followed by Tukey test (a=0.05). There was an upregulation of RANK and RANKL genes at 7 and 10 days and an upregulation of the OPG gene at 3 and 7 days of healing. Interestingly, an increased in expression of all genes was observed over time in both RME and C groups. The RANKL/OPG ratio showed an increased signaling favoring bone resorption on RME compared to C at 3 and 7 days. Signaling against bone resorption was observed, as well as an upregulation of OPG gene expression in RME group, compared to C group at 10 days. The results of this study concluded that the RANK, RANK-L and OPG system participates in bone remodeling after RME.

Age-dependent biologic response to orthodontic forces

INTRODUCTION

Orthodontic tooth movement results from increased inflammation and osteoclast activation. Since patients of all ages now routinely seek orthodontics treatment, we investigated whether age-dependent biologic responses to orthodontic force correlate with the rate of tooth movement.

METHODS

We studied 18 healthy subjects, adolescents (11-14 years) and adults (21-45 years), with Class II Division 1 malocclusion requiring 4 first premolar extractions. Canines were retracted with a constant force of 50 cN. Gingival crevicular fluid was collected before orthodontic treatment and at days 1, 7, 14, and 28 after the canine retraction. Cytokine (IL-1β, CCL2, TNF-α) and osteoclast markers (RANKL and MMP-9) were measured using antibody-based protein assays. Pain and discomfort were monitored with a numeric rating scale. The canine retraction rate was measured from study models taken at days 28 and 56.

RESULTS

Although the cytokine and osteoclast markers increased significantly in both age groups at days 1, 7, and 14, the increases were greater in adults than in adolescents. Interestingly, the rate of tooth movement in adults was significantly slower than in adolescents over the 56-day study period. Adults also reported significantly more discomfort and pain.

CONCLUSIONS

Age is a significant variable contributing to the biologic response to orthodontic tooth movement. Adults exhibited a significantly higher level of cytokine and osteoclasts activity but, counterintuitively, had a significantly slower rate of tooth movement.

Gingival crevicular fluid bone turnover biomarkers: How postmenopausal women respond to orthodontic activation

INTRODUCTION

Bone turnover associated with orthodontic tooth movement is evidenced by increased bone turnover markers in gingival crevicular fluid (GCF). Postmenopausal women have an increased concentration of serum bone turnover markers. The filtrate of this serum makes up GCF, but little is known of the bone turnover around teeth in this cohort. The objective of this investigation was to compare the GCF bone turnover markers in premenopausal vs postmenopausal women receiving orthodontic treatment at baseline and at orthodontic activation.

METHODS

Twenty-eight women were enrolled in the study and separated into 2 groups: premenopausal (16) and postmenopausal (12). Bone turnover was evaluated by GCF at baseline and 24 hours after orthodontic appliance activation. GCF concentrations of RANKL and OPN were measured using ELISA. Baseline and change in concentrations were compared between groups.

RESULTS

Baseline RANKL and OPN were significantly different between the premenopausal and postmenopausal groups (P <0.05). Both markers increased significantly from baseline to 24 hours after orthodontic appliance activation in both groups (P <0.05). However, the response to orthodontic activation was not significantly different between groups.

CONCLUSIONS

Although postmenopausal women have a different bone turnover profile at baseline than do their premenopausal counterparts, there is no difference in their response to orthodontic activation. This confers a level of security associated with orthodontic activation. Future studies are warranted to construct biomarker curves throughout orthodontic therapy.

RANK/RANKL/OPG Signalization Implication in Periodontitis: New Evidence from a RANK Transgenic Mouse Model

Periodontitis is based on a complex inflammatory over-response combined with possible genetic predisposition factors. The RANKL/RANK/OPG signaling pathway is implicated in bone resorption through its key function in osteoclast differentiation and activation, as well as in the inflammatory response. This central element of osteo-immunology has been suggested to be perturbed in several diseases, including periodontitis, as it is a predisposing factor for this disease. The aim of the present study was to validate this hypothesis using a transgenic mouse line, which over-expresses RANK (R^Tg) and develops a periodontitis-like phenotype at 5 months of age. R^Tg mice exhibited severe alveolar bone loss, an increased number of TRAP positive cells, and disorganization of periodontal ligaments. This phenotype was more pronounced in females. We also observed dental root resorption lacunas. Hyperplasia of the gingival epithelium, including Malassez epithelial rests, was visible as early as 25 days, preceding any other symptoms. These results demonstrate that perturbations of the RANKL/RANK/OPG system constitute a core element of periodontitis, and more globally, osteo-immune diseases.

The Gingival Crevicular Fluid as a Source of Biomarkers to Enhance Efficiency of Orthodontic and Functional Treatment of Growing Patients

Gingival crevicular fluid (GCF) is a biological exudate and quantification of its constituents is a current method to identify specific biomarkers with reasonable sensitivity for several biological events. Studies are being performed to evaluate whether the GCF biomarkers in growing subjects reflect both the stages of individual skeletal maturation and the local tissue remodeling triggered by orthodontic force. Present evidence is still little regarding whether and which GCF biomarkers are correlated with the growth phase (mainly pubertal growth spurt), while huge investigations have been reported on several GCF biomarkers (for inflammation, tissue damage, bone deposition and resorption, and other biological processes) in relation to the orthodontic tooth movement. In spite of these investigations, the clinical applicability of the method is still limited with further data needed to reach a full diagnostic utility of specific GCF biomarkers in orthodontics. Future studies are warranted to elucidate the role of main GCF biomarkers and how they can be used to enhance functional treatment, optimize orthodontic force intensity, or prevent major tissue damage consequent to orthodontic treatment.

The "Mechanostat Theory" of Frost and the OPG/RANKL/RANK System

Frost's great interest to elucidate the principles of action underlying skeletal deformities, during, and after growth, urged him to undertake an extensive study of the mammalian skeleton. He suggested that survival of the skeleton (but also of other tissues, such as fibrous tissue, hyaline cartilage, fibrocartilage, cementum, or dentin) requires the functional coordination of modeling and remodeling. Modeling adapts bone to overloads, by enhancing additions of new bone and by changing bone architecture, and remodeling adapts bone to underloads by removing bone next to marrow and conserving normally used bone. There exists a mechanism that monitors bone metabolism (longitudinal growth, bone modeling, and remodeling activities) in relation to mechanical usage, the "mechanostat." Recent literature has presented new information regarding the physiological procedure of osteoclast and osteoblast activation. It has been understood that the OPG/RANKL/RANK proteinic system regulates bone metabolism by exerting biological effects on osteoblasts or osteoclasts. The same proteinic network, also regulates alveolar remodeling during tooth movement, as well as physiological root resorption and root resorption during orthodontic tooth movement. The aim of the present review is the presentation and evaluation of recent information in the field of osteoclast and osteoblast biology, as regards to the "mechanostat theory" of Frost. An attempt will be made to elucidate, whether recent data can support this remarkable theory and reveal the biological mechanisms behind it.

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.

Expression and Presence of OPG and RANKL mRNA and Protein in Human Periodontal Ligament with Orthodontic Force

OBJECTIVE

The objective of this study is to investigate the expression and concentration of ligand receptor activator of NFkB (RANKL) and osteoprotegerin (OPG) in human periodontal ligament (hPDL) with orthodontic forces of different magnitudes.

METHODS

Right premolars in 32 patients were loaded with 4oz or 7oz of orthodontic force for 7 days. Left first premolars were not loaded. After 7 days, premolars were extracted for treatment as indicated. OPG and RANKL mRNA expressions were measured by quantitative reverse transcription polymerase chain reaction (qRT-PCR), and ELISA was used to assess OPG and RANKL protein concentration in compression and tension sides of PDL. Data were subjected to analysis of variance and Tukey tests.

RESULTS

There was statistically significant difference in RANKL concentration on comparing control teeth with tension and compression sides of the experimental teeth (P < 0.0001). The expression of mRNA RANKL was increased in the tension and compression sides with 4oz (P < 0.0001). OPG did not show statistically significant association with any group. Changes in RANKL/OPG protein ratio in experimental and control groups showed statistically significant difference (P < 0.0001).

CONCLUSIONS

RANKL protein levels are elevated in hPDL loaded with orthodontic forces, suggesting that RANKL protein contributes to bone modeling in response to the initial placement of orthodontic force.

Slow and fast orthodontic tooth movement: an experimental study on humans

INTRODUCTION

The aim of this study was to investigate the variation in the amount of the orthodontically induced tooth movement in humans and potential associations between the amount of tooth movement with age and location in the mandible or maxilla.

SUBJECTS AND METHODS

This study included 11 participants (7 females, 4 males) with an age range of 11.3-28.6 years. In a standardized experimental orthodontic tooth movement protocol, two premolars of each participant were moved buccally during 8 weeks with the use of 1 N force. No functional or localized obstacles were affecting the displacement. Plaster models before and after the experimental tooth movement were constructed, digitized, and superimposed, to evaluate the amount of tooth movement of each tooth. Random effects linear regression analysis was performed to examine associations between tooth displacement, age, and tooth location.

RESULTS

The mean displacement of the teeth was 2.7±1.4mm. The range of tooth movement varied substantially between individuals (0.6-5.8mm). The displacement of the teeth within the same individual was highly correlated (R (2) = 0.78, P < 0.001). The tooth displacement decreased with age; however, this finding did not reach statistical significance (β = -0.11, 95% CI: -0.28, 0.05, P = 0.172). The tooth movement was higher in the maxilla than in the mandible (β = 0.47, 95% CI: 0.81, 0.86, P = 0.018).

CONCLUSION

Wide range of tooth displacement revealed slow and fast movers in this sample. Larger displacements were recorded in the maxilla compared to the mandible and in younger individuals.

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.

Hypertension modifies OPG, RANK, and RANKL expression during the dental socket bone healing process in spontaneously hypertensive rats

OBJECTIVE

The aim of this study was to evaluate the dental socket bone healing process by histomorphometric and immunohistochemical analysis of osteoprotegerin (OPG), receptor activator of nuclear factor-κβ (RANK), and receptor activator of nuclear factor-κβ ligand (RANKL) proteins in spontaneously hypertensive rats (SHR).

MATERIALS AND METHODS

Under general anesthesia, 25 Wistar rats and 25 SHRs underwent upper right incisor extraction. Rats were euthanized after 7, 14, 21, 28, or 42 days of dental extractions. Histomorphometric and immunohistochemical analyses of OPG, RANK, and RANKL proteins were performed.

RESULTS

Histomorphometric results showed decreased bone healing and reduced bone trabecular thickness in SHRs. Immunohistochemical reactions showed intense RANKL and RANK immunolabeling at 14 and 28 postoperative days and mild OPG immunolabeling at 7, 14, and 21 days after surgery in SHRs.

CONCLUSION

The results of this study show that RANK, RANKL, and OPG immunolabeling was altered in SHRs, and these results are associated with bone healing delay and decreased trabecular thickness in SHRs.

CLINICAL RELEVANCE

Hypertension alters the expression of RANK, RANKL, and OPG and delays the socket bone healing process. These alterations could influence some dental procedures such as orthodontic treatment and implant placement.

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.

Nitric oxide in human gingival crevicular fluid after orthodontic force application

Nitric oxide (NO) is involved in bone remodelling and has been shown to play a role in regulating the rate of orthodontic tooth movement (OTM) in rat models. In humans, however, the role of NO in OTM remains less clear. In this study, NO concentration in gingival crevicular fluid (GCF) was measured in patients undergoing orthodontic treatment. Thirteen male participants (ages 11-18 years) planned for non-extraction fixed orthodontic therapy were recruited. Samples of GCF were collected from each maxillary central incisor and first and second molar immediately before (T0), 1h after (T1), and 3-4 days after (T2) application of light orthodontic forces. The maxillary second molars were not included in the appliance and served as controls. Measureable NO levels were consistently obtained from all sampled sites. Total NO levels showed significantly higher NO levels (p<0.05) at T1 at the buccal surfaces of the central incisors when compared to the first and second molars. The results indicate a possible role for NO in OTM at the pressure sites of incisors at early time points. Further studies are required to determine whether NO levels in the periodontal ligament tissues of human teeth during OTM are affected by a force gradient and the magnitude of the applied force.

Effects of low-level laser therapy on orthodontics: rate of tooth movement, pain, and release of RANKL and OPG in GCF

The aim of the study was evaluate tooth movement, receptor activator of nuclear factor KB ligand (RANKL), osteoprotegerin (OPG), and RANKL/OPG ratio in gingival crevicular fluid (GCF) in compression side and pain level during initial orthodontic tooth treatment to determine the efficacy of low-level laser therapy (LLLT). Ten volunteers who required fixed appliance positioned from the upper first premolars to upper first molars were selected. For each patient, the upper first premolar of the quadrant 1 was chosen to be irradiated with a laser diode at 670 nm, 200 mW, and 6.37 W/cm(2), applied on the distal, buccal, and lingual sides during 9 min on days 0, 1, 2, 3, 4, and 7. The same procedure was applied in the first premolar of the contralateral quadrant inserting the tip but without laser emission. Samples of GCF from the compression side of the upper first premolars to distalize were collected at baseline and after 2, 7, 30, and 45 days posttreatment for determination of RANKL and OPG by enzyme-linked immunosorbent assay. In addition, tooth movement was assessed by scanning models and pain intensity was assessed using a visual analog scale. There was improvement in the parameters studied (pain, tooth movement, levels of RANKL in GCF, and RANKL/OPG ratio) in the laser group when compared to the control group, although differences were not statistically significant. The accumulated retraction of the upper premolar at 30 days was higher in the laser group, and this difference was statistically significant between groups. LLLT delivered in repeated doses (six times in the initial 2 weeks) leads in some extent to a slight orthodontical improvement.

Factors related to the rate of orthodontically induced tooth movement

INTRODUCTION

The purpose of this study was to investigate the variations of orthodontically induced tooth movement in the maxillary and mandibular arches between patients and the factors such as age, sex, and presence of an interference that might influence the amount of tooth displacement.

METHODS

By using a standardized experimental orthodontic tooth movement in 30 subjects, 57 premolars were moved buccally during 8 weeks with the application of a 1-N force. Forty-four contralateral premolars not subjected to orthodontic tooth movement served as the controls. Plaster models from before and after the experimental tooth movement were digitized and superimposed to evaluate the amounts of tooth movement. Differences in tooth movement between the experimental and control groups were tested by an unpaired t test. For the experimental teeth, subject-related factors (age and sex) and tooth-related factors (location in the maxillary or mandibular dental arch, and the presence or absence of an intra-arch or interarch obstacle such as neighboring touching teeth or teeth interfering with the occlusion) were examined with analysis of variance. Multiple linear regression analysis was performed to determine correlations between tooth displacement, age, sex, tooth location, and presence of an interference.

RESULTS

Each subject contributed at least 2 experimental premolars and 1 control premolar. The displacement of the orthodontically moved teeth was 2.42 mm (range, 0.3-5.8 mm). Younger subjects (<16 years; n = 19; number of teeth, 36) had significantly greater amounts of tooth displacement compared with older subjects (≥16 years; n = 11; number of teeth, 21): 2.6 ± 1.3 mm vs 1.8 ± 0.8 mm; P <0.01. When an interarch or intra-arch obstacle was present, the amount of tooth movement was significantly less (2.6 ± 1.3 mm vs 1.8 ± 0.8 mm) (P <0.05). Neither sex nor the location of the experimental teeth in the mandible or the maxilla had any effect.

CONCLUSIONS

Younger patients showed greater tooth movement velocity than did older ones. An interarch or intra-arch obstacle decreased the amount of tooth displacement.

Differences in the gingival crevicular fluid composition between adults and adolescents undergoing orthodontic treatment

OBJECTIVES

To investigate differences in the gingival crevicular fluid (GCF) composition between adolescent and adult patients undergoing orthodontic treatment with fixed appliances.

MATERIALS AND METHODS

Ten adolescents (14.4 ± 1.43) and 10 adults (28.5 ± 7.83) with Class I malocclusions and minor upper incisor crowding were allocated to two different age groups. Brackets were bonded only in the upper arch over the 20-week period of the experiment. Samples of GCF were collected from the labial sides of the upper incisors (experimental sites) and lower incisors (control sites) of each subject at five time points. Aliquots from diluted GCF were screened for the presence of receptor activator of nuclear factor kappa B ligand (RANKL), osteoprotegerin (OPG), interleukin-1 (IL-1), interleukin-1 receptor antagonist (IL-1RA), and metalloproteinase-9 (MMP-9) using a microarray technique. The values were statistically analyzed.

RESULTS

In adults, the ratio of IL-1 to IL-1RA decreased significantly (P  =  .033) in experimental sites 3 weeks after appliance placement and first archwire activation. In adolescents, the ratio of RANKL to OPG peaked 6 weeks after the insertion of the first rectangular archwire. This ratio peak found in adolescents was a consequence of a decrease in the mean concentration of OPG. No significant changes over time were observed in the concentration of MMP-9.

CONCLUSION

This study demonstrates age trends in the GCF levels of IL-1, IL-1RA, RANKL, and OPG that may be used to track differences in tissue response between adults and adolescents undergoing orthodontic treatment.

Biochemical markers of bone metabolism in gingival crevicular fluid during early orthodontic tooth movement

OBJECTIVE

To evaluate the expression of an activator of nuclear factor-kappa (RANK), osteoprotegerin (OPG), osteopontin (OPN), and transforming growth factor ß1 (TGF-ß1) in gingival crevicular fluid (GCF) of teeth subjected to orthodontic forces.

MATERIALS AND METHODS

A randomized, pilot clinical trial including 10 healthy volunteers was conducted using a split-mouth design. Orthodontic elastic separators were placed between the second premolar and first molar, with the contralateral quadrant serving as a control. The GCF samples were collected from the tension and compression sites at baseline, 24 hours, and 7 days after the placement of separators. The GCF sample volumes were measured using a Periotron 8000, and total protein concentrations were determined. Levels of RANK, OPG, OPN, and TGF-ß1 were also analyzed using a multiplex enzyme-linked immunosorbent assay.

RESULTS

The control sites remained unchanged throughout the study. In contrast, the concentration of OPG significantly decreased at the compression site by 24 hours, and the amount and concentration of RANK differed significantly between the control, compression, and tension sites after 7 days. A significant increase in absolute TGF-ß1 levels was also detected at the compression site versus the control and tension sites after 7 days.

CONCLUSION

Bone metabolism is affected by application of force to the teeth by elastic separators. Both increased expression of bone resorptive mediators (eg, RANK and TGF-ß1) and decreased expression of a bone-forming mediator (eg, OPG) on the compression side were detected.

Immunohistochemical expression of RANKL, RANK and OPG in gingival tissue of patients with periodontitis

OBJECTIVES

To evaluate the expression of the receptor activator of NF-κB (RANK), the receptor activator of NF-κB ligand (RANKL) and osteoprotegerin (OPG), in the gingival tissue of patients with periodontitis.

MATERIALS AND METHODS

Gingival tissue was obtained from 14 systemically healthy subjects with chronic periodontitis during conventional periodontal surgery. Immunohistochemistry was used to detect the expression of RANK, RANKL and OPG in the oral and periodontal pocket epithelium as well as in the connective tissue cells.

RESULTS

RANKL was negatively expressed in both oral and periodontal pocket epithelium. OPG was also negative or weakly positive in the whole epithelium. RANK showed moderate/strong positive staining mainly in the basal and suprabasal layer of oral and periodontal pocket epithelium. In most of the cases, more than 60% of the inflammatory cell infiltrate stained for RANK and RANKL. In these cases the intensity of the stained cells ranged from moderate-to-strong. In less than half of the cases, OPG was positive in more than 60% of the stained cells of the inflammatory cell infiltrate.

CONCLUSION

The RANK, RANKL and OPG proteins are differentially expressed in periodontal tissues and may play a major role in the bone loss occurring in periodontitis.

Induction of cytokines, MMP9, TIMPs, RANKL and OPG during orthodontic tooth movement

This controlled longitudinal intervention study investigated changes in cytokines and biomarkers of bone and tissue metabolism within gingival crevicular fluid (GCF) from patients undergoing orthodontic treatment. GCF was collected on Periopaper™ strips (Oraflow Inc., USA) from 20 volunteers at baseline, before tooth extraction and appliance placement and then at intervals during orthodontic treatment. Samples were taken 10 weeks following first appliance placement: at four hours; 7 days; and 42 days after application of distalising forces to maxillary canine teeth. Cytokines (GM-CSF, interferon-gamma, IL-1beta, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10 and TNFalpha), tissue biomarkers (MMP-9, TIMP-1 & 2) and bone metabolism indicators (RANKL and OPG) were measured in GCF using multiplex assays. Tension sites adjacent to canines showed significant increases in IL-1beta, IL-8, TNFalpha, MMP-9 and TIMPs 1 and 2 across all time points following force application, while compression sites exhibited increases in IL-1beta and IL-8 after 4 hours, MMP-9 after 7 and 42 days and RANKL after 42 days. These data demonstrate that high levels of pro-inflammatory cytokines and biomarkers of tissue and bone metabolism in GCF are associated with orthodontic force application. Elevated levels were evident at 4 hours but continued for periods of up to 6 weeks. The data suggest that GCF biomarker analysis may help optimise orthodontic forces for individual patients.

Mechanical loading activates β-catenin signaling in periodontal ligament cells

OBJECTIVE

To determine whether β-catenin signaling is responsive to mechanical loading in periodontal ligament (PDL) cells.

MATERIALS AND METHODS

To determine whether Wnt/β-catenin signaling pathway components are present and functional, PDL cells were treated with lithium chloride or Wnt3a-conditioned media. To determine whether mechanical strain activates β-catenin signaling, PDL cells were subjected to compressive loading. Activation of the β-catenin signaling pathway was determined by immunofluorescence, Western immunoblotting, and TOPflash assay.

RESULTS

Mimicking Wnt signaling stimulates β-catenin nuclear translocation and T-cell factor/lymphoid enhancer binding factor-dependent transcriptional activation in PDL cells. Mechanical loading stimulates a transient accumulation of dephosphorylated β-catenin in the cytoplasm and its translocation to the nucleus. This effect of strain acts through activation of protein kinase B and phosphorylation of glycogen synthase kinase-3 beta. These strain-related changes do not involve the low-density lipoprotein receptor-related protein 5/Wnt receptor.

CONCLUSIONS

The Wnt/β-catenin signaling pathway components are functional and activated by mechanical loading in PDL cells. β-catenin serves as an effector of mechanical signals in PDL cells.

[Orthodontic tooth displacement: histology, biology and iatrogenic effects]

Iatrogenic effects of orthodontic forces, in particular root resorption, are described in the literature. However, our knowledge on the risk of osseous defects induced by orthodontic treatment is still scarce. After an overview of histological and biological principles of orthodontically-induced tooth movement, this study focuses on the recent data concerning the occurrence and the treatment of bone resorption associated with orthodontic treatment.

Root resorption and the OPG/RANKL/RANK system: a mini review

Odontoclastic root resorption is a significant clinical issue in relation to orthodontic tooth movement, and resorption of the roots of primary teeth is an intriguing biological phenomenon. The functional coordination of the OPG/RANKL/RANK system seems to contribute not only to alveolar remodeling, but also to resorption during orthodontic tooth movement and physiological root resorption. Serum OPG and s-RANKL are related to regulation of bone homeostasis by the OPG/RANKL/RANK system, and determination of their concentrations might be useful for predicting the rate of bone remodeling during orthodontic tooth movement, the net effect between bone remodeling and root resorption, and the degree of root resorption. It is therefore rational to speculate that a study of the levels of OPG and s-RANKL in blood and GCF, in relation to the degree of root resorption during orthodontic tooth movement, using healthy experimental animals and a carefully planned and organized experimental design, may be able to answer this intriguing question.

Osteoprotegerin in Gingival Crevicular Fluid under Long-term Continuous Orthodontic Force Application

Objective: To investigate the level of osteoprotegerin (OPG) in gingival crevicular fluid (GCF) during tooth movement.

Materials and Methods: Twelve patients (13–17 years of age) requiring canine distalization participated in the study. GCF sampling was done at baseline, 1 hour, 24 hours, 168 hours, 1 month, and 3 months from the distal sites of the test and with control teeth after the application of mechanical stress. OPG concentration was detected by enzyme-linked immunosorbent assay.

Results: OPG concentrations in distal sites of the test teeth were decreased in a time-dependent manner. Decreasing is significant when compared with the baseline measurements (P = .038). Variability was detected in the levels of OPG concentration in the distal sites of the control tooth throughout the experimental period.

Conclusion: OPG is one of the key mediators responsible for alveolar bone remodeling during tooth movement.

Cytokines in crevicular fluid and orthodontic tooth movement

This review aimed to evaluate studies on cytokines in the gingival crevicular fluid (GCF) during orthodontic treatment, summarizing the regulation patterns of the most commonly studied cytokines and exploring their clinical implications. To achieve this, a number of key databases were searched using MESH terms and free text terms. An additional search was made by reference tracking. The procedures suggested by the QUOROM statement were followed. Data from the included studies were extracted into orthodontic mechanics, GCF sampling/handling methods, and cytokine measurements. From the 85 relevant studies identified, 23 studies could be included. Common drawbacks consisted mainly of inadequacies in the study design (e.g. short duration and small number of study subjects). The most consistent result was a peak of cytokine levels at 24 h. Associations existed between prostaglandin E(2) (PGE(2)) and interleukin-1beta (IL-1beta) and pain, velocity of tooth movement, and treatment mechanics. Interleukin-1beta and PGE(2) showed different patterns of up-regulation, with IL-1beta being more responsive to mechanical stress and PGE(2) more responsive to synergistic regulation of IL-1beta and mechanical force. The results might be taken to support, at the cellular level, the use of light continuous forces for orthodontic treatment.

Regulation of RANKL and OPG gene expression in human gingival fibroblasts and periodontal ligament cells by Porphyromonas gingivalis: a putative role of the Arg-gingipains

Porphyromonas gingivalis is highly implicated in the pathogenesis of periodontitis, which is characterized by the destruction of periodontal connective tissues and the supporting alveolar bone. Receptor Activator of NF-kappaB Ligand (RANKL) stimulates bone resorption, whereas osteoprotegerin (OPG) blocks its action, and this bi-molecular system is implicated in periodontitis. The aim of this work was (a) to investigate the regulation of RANKL and OPG gene expression in human periodontal ligament (PDL) cells and gingival fibroblasts (GF), in response to P. gingivalis culture supernatants, by quantitative real-time PCR and (b) to attempt to identify putative virulence factors involved in this process. The results indicated that P. gingivalis induced RANKL and reduced OPG mRNA expression by the studied cells, resulting in an increased RANKL/OPG expression ratio. Heat-inactivation of P. gingivalis resulted in significant reduction of RANKL mRNA expression. A Lys-gingipain mutant strain did not affect, whereas an Arg-gingipain mutant strain further enhanced RANKL mRNA expression, compared to their parental wild-type strain. In conclusion, P. gingivalis up-regulates the RANKL/OPG expression ratio in GF and PDL cells, denoting an enhanced osteoclastogenic potential by the cells. The component mainly responsible for RANKL induction appears to be proteinaceous, and it may be regulated by the Arg-gingipains.

Gingival crevicular fluid levels of RANKL and OPG in periodontal diseases: implications of their relative ratio

AIM

Receptor activator of NF-kappaB ligand (RANKL) and osteoprotegerin (OPG) are a system of molecules that regulate bone resorption. This study aims to compare the levels of RANKL, OPG and their relative ratio in gingival crevicular fluid (GCF) of healthy and periodontal disease subjects.

MATERIAL AND METHODS

GCF was obtained from healthy (n=21), gingivitis (n=22), chronic periodontitis (n=28), generalized aggressive periodontitis (n=25) and chronic periodontitis subjects under immunosuppressant therapy (n=11). RANKL and OPG concentrations in GCF were measured by enzyme-linked immunosorbent assays.

RESULTS

RANKL levels were low in health and gingivitis groups, but increased in all three forms of periodontitis. OPG levels were higher in health than all three periodontitis, or gingivitis groups. There were no differences in RANKL and OPG levels between chronic and generalized aggressive periodontitis groups, whereas these were lower in the immunosuppressed chronic periodontitis group. The RANKL/OPG ratio was significantly elevated in all three periodontitis forms, compared with health or gingivitis, and positively correlated to probing pocket depth and clinical attachment level.

CONCLUSION

GCF RANKL and OPG levels were oppositely regulated in periodontitis, but not gingivitis, resulting in an enhanced RANKL/OPG ratio. This ratio was similar in all three periodontitis groups and may therefore predict disease occurrence.