Effects of topical administration of a bisphosphonate (risedronate) on orthodontic tooth movements in rats

Medications and Orthodontic Tooth Movement: What Accelerates and Diminishes Tooth Movement?

The biological aspect of orthodontic tooth movement is influenced by the magnitude and duration of the applied force. This initiates signaling cascades essential for bone remodeling, which involve activating various cell signaling pathways that enhance the metabolism of the periodontal ligament, leading to localized bone resorption and deposition. This process facilitates tooth movement on the pressure side and promotes healing on the tension side. The remodeling associated with orthodontic tooth movement is an inflammatory reaction involving mediators. Key components in this process include hormones, systemic influences, cyclic adenosine monophosphate, specific cytokines like interleukin 1, colony-stimulating factors, calcium, collagenase, and prostaglandins, all of which are essential for the biological adjustments necessary for tooth movement. Medications that influence molecular pathways critical for the homeostasis of periodontal tissues or that affect changes during orthodontic tooth movement and clastic cell regulation can potentially modulate tooth movement. With the recent increase in prescription medication use, it is essential for clinicians to be aware of medication consumption in prospective patients and understand its potential impact on orthodontic treatment. This review aimed to explore the effects of commonly prescribed medications on the rate of orthodontic tooth movement, thoroughly review the existing evidence on this topic, and identify potential areas for future research.

Influence of risedronate on orthodontic tooth movement in rodents: a systematic review and case report

INTRODUCTION

Bisphosphonates have an inhibitory impact on osteoclastic activity, reducing bone resorption. However, the influence of risedronate on tooth movement is not well-defined.

OBJECTIVE

This systematic review assessed the effect of risedronate intake on orthodontic tooth movement. A case report was also provided.

METHODS

Two independent reviewers searched six databases (PubMed, Web of Science, Ovid, Lilacs, Scopus, and Open Grey). The searches were carried out in April/2020, and an update was set in place in June/2023. Therefore, the searches considered a timeline from the databases' inception date until June/2023, with no publication date and/or language restrictions. The clinical question focused on evaluating the orthodontic tooth movement and relapse movement (Outcome) in animals (Population) exposed to risedronate (Exposure), compared to control groups (Comparison). The Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines were applied, and the protocol was registered in PROSPERO (CRD42020168581). The risk of bias was determined using the Systematic Review Centre for Laboratory Animal Experimentation protocol (SYRCLE).

RESULTS

Two studies in rats and one in guinea pigs were included in the systematic review. The studies reported a decrease in orthodontic tooth movement, a reduction in the relapse movement, and a reduced number of positive tartrate-resistant acid phosphatase (TRAP) cells, with a significantly reduced number of bone gaps after the administration of risedronate in rats. A case report illustrated the effects of risedronate administration in one patient.

CONCLUSION

Based on the systematic review, risedronate seems to impair orthodontic tooth movement and relapse due to a decrease in bone resorption cells.

Under pressure-mechanisms and risk factors for orthodontically induced inflammatory root resorption: a systematic review

BACKGROUND

The application of orthodontic forces causes root resorption of variable severity with potentially severe clinical ramifications.

OBJECTIVE

To systematically review reports on the pathophysiological mechanisms of orthodontically induced inflammatory root resorption (OIIRR) and the associated risk factors based on in vitro, experimental, and in vivo studies.

SEARCH METHODS

We undertook an electronic search of four databases and a separate hand-search.

SELECTION CRITERIA

Studies reporting on the effect of orthodontic forces with/without the addition of potential risk factors on OIIRR, including (1) gene expression in in-vitro studies, the incidence root resorption in (2) animal studies, and (3) human studies.

DATA COLLECTION AND ANALYSIS

Potential hits underwent a two-step selection, data extraction, quality assessment, and systematic appraisal performed by duplicate examiners.

RESULTS

One hundred and eighteen articles met the eligibility criteria. Studies varied considerably in methodology, reporting of results, and variable risk of bias judgements.In summary, the variable evidence identified supports the notion that the application of orthodontic forces leads to (1) characteristic alterations of molecular expression profiles in vitro, (2) an increased rate of OIIRR in animal models, as well as (3) in human studies. Importantly, the additional presence of risk factors such as malocclusion, previous trauma, and medications like corticosteroids increased the severity of OIIRR, whilst other factors decreased its severity, including oral contraceptives, baicalin, and high caffeine.

CONCLUSIONS

Based on the systematically reviewed evidence, OIIRR seems to be an inevitable consequence of the application of orthodontic forces-with different risk factors modifying its severity. Our review has identified several molecular mechanisms that can help explain this link between orthodontic forces and OIIRR. Nevertheless, it must be noted that the available eligible literature was in part significantly confounded by bias and was characterized by substantial methodological heterogeneity, suggesting that the results of this systematic review should be interpreted with caution.

REGISTRATION

PROSPERO (CRD42021243431).

Effect of vitamin D deficiency on postorthodontic relapse: An animal study

OBJECTIVES

This study aims to evaluate the effect of vitamin D deficiency (VDD) on orthodontic tooth movement (OTM), retention, and relapse and to assess the effect of systemic administration of vitamin D (VD) in a rat model.

MATERIALS AND METHODS

A total of 32 male Wistar rats were divided into two groups, a control group of 11 rats and an experimental group of 21 rats with VDD, after enhancement using a custom diet. Of the VDD group, 11 rats were supplemented with systemic vitamin D3 and categorized as vitamin (VD supplement [VDS]) groups. The VDS group received 40,000 IU/kg via intramuscular injection on Days 1 and 15 of the orthodontic treatment period. A modified orthodontic appliance was fitted to apply 0.5 N of force to move the maxillary right first molars mesially for 14 days, followed by retention and relapse periods for 7 days. Space created during OTM was measured and reassessed after the retention and relapse periods. The relapse ratio was estimated, and histomorphometric analysis was performed to assess the number of osteoblasts, osteoclast bone cells, and bone area.

RESULTS

A significant increase in the relapse ratio and a reduction in osteoblast cells and bone area were observed in the VDD group. By contrast, the amount of tooth movement was significantly higher together with osteoblast cells and bone marrow in VDS with a significant reduction in relapse ratio.

CONCLUSION

VDD was associated with a significant reduction in osteoblast cell count and total bone area in addition to a significant increase in relapse ratio. Routine screening of VD may be beneficial before commencing orthodontic treatment.

The Use of Polymers to Enhance Post-Orthodontic Tooth Stability

Relapse after orthodontic treatment occurs at a rate of about 70 to 90%, and this phenomenon is an orthodontic issue that has not yet been resolved. Retention devices are one attempt at prevention, but they require a considerable amount of time. Most orthodontists continue to find it challenging to manage orthodontic relapse; therefore, additional research is required. In line with existing knowledge regarding the biological basis of relapse, biomedical engineering approaches to relapse regulation show promise. With so many possible uses in biomedical engineering, polymeric materials have long been at the forefront of the materials world. Orthodontics is an emerging field, and scientists are paying a great deal of attention to polymers because of their potential applications in this area. In recent years, the controlled release of bisphosphonate risedronate using a topically applied gelatin hydrogel has been demonstrated to be effective in reducing relapse. Simvastatin encapsulation in exosomes generated from periodontal ligament stem cells can promote simvastatin solubility and increase the inhibitory action of orthodontic relapse. Moreover, the local injection of epigallocatechin gallate-modified gelatin suppresses osteoclastogenesis and could be developed as a novel treatment method to modify tooth movement and inhibit orthodontic relapse. Furthermore, the intrasulcular administration of hydrogel carbonated hydroxyapatite-incorporated advanced platelet-rich fibrin has been shown to minimize orthodontic relapse. The objective of this review was to provide an overview of the use of polymer materials to reduce post-orthodontic relapse. We assume that bone remodeling is a crucial factor even though the exact process by which orthodontic correction is lost after retention is not fully known. Delivery of a polymer containing elements that altered osteoclast activity inhibited osteoclastogenesis and blocking orthodontic relapse. The most promising polymeric materials and their potential orthodontic uses for the prevention of orthodontic relapse are also discussed.

Ability of piezocision to retain orthodontically moved teeth in a goat model: A split-mouth study

OBJECTIVES:

to evaluate the effectiveness of piezocision in enhancing retention when performed after orthodontic tooth movement.

METHODS:

Four mature goats had their second incisors removed bilaterally. For each goat, the two sides of the mandible were either treated with piezocision or served as a positive control. Using fixed orthodontic appliance, the first and third incisors on each side were approximated and then retained in place for two weeks. Relapse was measured by the amount of space developed between the approximated incisors after six weeks from the end of the retention period. The periodontal ligament of all incisors was assessed histologically with micro computed tomography and regular hematoxylin and eosin staining.

RESULTS:

A significantly less relapse was observed in the piezocision group than in the control group (p ≤ 0.05). Bone formation occurs in the vicinity and periphery of the periodontal ligament and thus results in the narrowing of the periodontal ligament.

CONCLUSION:

A protocol of post-orthodontic retention involving piezocision can be promising to enhance stability of orthodontic treatment outcome.

Effect of local administration of bisphosphonate on orthodontic anchorage – A systematic review of animal studies

BACKGROUND:

Pharmacological means of anchorage control can improve patient compliance. Bisphosphonates could be helpful in orthodontic anchorage control if their actions could be localized to limit (or control) unwanted tooth movement while not interfering with the desired tooth movement.

OBJECTIVE:

This systematic review aimed to examine and evaluate the quality of all animal studies that reported the effect of locally administered bisphosphonate on limiting orthodontic tooth movement.

DATA SOURCES:

An electronic search was conducted in the PubMed-Medline, Scopus, Google Scholar, and Cochrane databases till May 2022, using the keywords anchorage, anchorage loss, molar movement, posterior tooth movement, incisor movement, incisor retraction, anterior retraction, unwanted tooth movement, tooth displacement, tooth movement forward, bisphosphonate, local bisphosphonate administration, bisphosphonate injection, and bbisphosphonate vestibular induction. Only studies involving localized bisphosphonate administration for anchorage purposes were taken into account.

DATA SELECTION:

Animal studies that simulated orthodontic tooth movement after localized injection of bisphosphonate and evaluated the rate of tooth movement were included in the review.

DATA EXTRACTION AND ANALYSIS:

The quality of the studies was assessed by using ARRIVE guidelines (Animal Research: Reporting of In Vivo Experiments). Bias in the studies was analyzed by SYRCLE's tool (Systematic Review Centre for Laboratory Animal Experimentation) for risk of bias.

RESULTS:

The search strategy yielded 925 titles. After screening, 908 articles were discarded because they did not fulfill the inclusion/exclusion criteria based on the title and abstract. The remaining 16 articles were read entirely, of which nine were excluded as they involved systemic administration of bisphosphonates. Finally, after careful consideration, seven papers that met our inclusion criteria were included in the qualitative analysis. The majority of studies were assessed to have an uncertain risk of bias, with just one deemed low risk of bias.

CONCLUSION:

This systematic review found that bisphosphonates limit orthodontic tooth movement around the application site without affecting adjacent sites. More potent bisphosphonates in smaller doses or less potent bisphosphonates in higher frequencies have been proposed to improve outcomes. However, the data quality is insufficient to recommend a protocol for bisphosphonate administration for anchoring control. Long-term studies evaluating various types, frequencies, and dosages of bisphosphonates are required to clarify the effects on orthodontic tooth movement.

REGISTRATION NUMBER FOR PROSPERO:

CRD42021224033

Effect of Strontium Ranelate on Condylar Growth during Mandibular Advancement in Rats

Objective

Strontium ranelate (SR), unlike other anti-osteoporotic agents, might not only prevent bone resorption but also might induce bone formation. The aim of this experimental study was to evaluate the effects of systemic SR on condylar growth during mandibular advancement (MA) in growing rats.

Methods

Fifty-six, 8-week-old Wistar male rats weighting 160-190 g were randomly divided into four groups; one control (n=14) and three experimental (n=14). Group 1: Control group, Group 2: SR (900mg/kg daily dose), Group 3: MA, Group 4: SR +MA. The amount and direction of mandibular growth were assessed by linear measurements on the computed tomography (CT) images taken on days 1, 15, and 30. For immunohistochemical evaluation, half of the subjects in the groups were sacrificed on the 15th day (early phase) and the rest of them on the 30th day (late phase). New cartilage and bone formation areas on the condyle were analyzed by using Sox9 and Osteopontin antibodies.

Results

Early and late CT images measurements showed no significant difference between the groups (p<0.05). However, there were significant differences between the control and experimental groups in the immunohistochemical assessment. Severe immunolocalization of SOX9 and Osteopontin was observed in Group 4, while the immunolocalization scores were moderate in Group 2 and Group 3. In addition, early histological findings were similar to late results in all groups.

Conclusion

In mandibular advancement therapy, Strontium ranelate could be therapeutically effective in avoiding relapse and reducing the duration of retention.

The risk of osteonecrosis of the jaw and adverse outcomes in patients using antiresorptive drugs undergoing orthodontic treatment: A systematic review

Objectives

Medication-related osteonecrosis of the jaw (MRONJ) is rare. It is a serious adverse effect of certain drugs, of which bisphosphonates (BPs) are the most widely known. The aim of this systematic review was to analyze all published evidence for the reported adverse outcomes as a result of orthodontic treatment in patients undergoing antiresorptive therapy.

Data

All types of studies involving patients undergoing orthodontic treatment and treated with antiresorptive drugs were considered. A meta-analysis was not conducted due to the high amount of variability and heterogeneity in the reporting and presentation of data among the studies meeting the inclusion criteria.

Sources

A systematic search was performed using 4 databases (PubMed, MEDLINE, EMBASE and CINAHL).

Study selection

Seven studies matched the inclusion criteria for this review, reporting a total of 29 patients. MRONJ was only reported in 1 patient. The adverse outcomes following orthodontic treatment included difficulty achieving root parallelism (n = 4), difficulty achieving complete space closure (n = 3), exaggerated tooth mobility post-debond (n = 2), increased duration of orthodontic treatment beyond expected completion (n = 1), sclerotic alveolar bone changes seen on post-op radiographic images (n = 2), and an increased amount of root resorption (n = 1).

Conclusions

The high amount of heterogeneity and limited evidence precluded a valid interpretation and analysis of the results through pooling of data. Additional data with sufficient quality, a reduction of bias, and a greater prospective cohort of patients is crucial to assess adverse effects, mechanisms of action, and associated risk factors in at-risk patients.

Clinical significance

Based on the limited evidence available in the literature, it is unclear whether orthodontic treatment alone can precipitate MRONJ. However, antiresorptive drug therapy may be associated with a sub-optimal treatment outcome.

Metabolic activities affect femur and lumbar vertebrae remodeling, and anti-resorptive risedronate disturbs femoral cortical bone remodeling

Metabolic activities are closely correlated with bone remodeling and long-term anti-resorptive bisphosphonate treatment frequently causes atypical femoral fractures through unclear mechanisms. To explore whether metabolic alterations affect bone remodeling in femurs and lumbar vertebrae and whether anti-osteoporotic bisphosphonates perturb their reconstruction, we studied three mouse strains with different fat and lean body masses (BALB/c, C57BL6, and C3H mice). These mice displayed variable physical activity, food and drink intake, energy expenditure, and respiratory quotients. Following intraperitoneal calcein injection, double calcein labeling of the femoral diaphysis, as well as serum levels of the bone-formation marker procollagen type-I N-terminal propeptide and the bone-resorption marker C-terminal telopeptide of type-I collagen, revealed increased bone turnover in mice in the following order: C3H > BALB/c ≥ C57BL6 mice. In addition, bone reconstitution in femurs was distinct from that in lumbar vertebrae in both healthy control and estrogen-deficient osteoporotic mice with metabolic perturbation, particularly in terms of femoral trabecular and cortical bone remodeling in CH3 mice. Interestingly, subcutaneous administration of bisphosphonate risedronate to C3H mice with normal femoral bone density led to enlarged femoral cortical bones with a low bone mineral density, resulting in bone fragility; however, this phenomenon was not observed in mice with ovariectomy-induced femoral cortical bone loss. Together, these results suggest that diverse metabolic activities support various forms of bone remodeling and that femur remodeling differs from lumbar vertebra remodeling. Moreover, our findings imply that the adverse effect of bisphosphonate agents on femoral cortical bone remodeling should be considered when prescribing them to osteoporotic patients.

The effects of calcitonin on post-orthodontic relapse in rats

Objectives

To determine the effects of systematic calcitonin administration on post‐orthodontic relapse in rat model.

Material and methods

This experimental animal model involved 36 male Wister rats. The maxillary right first molars were moved mesially, using a modified orthodontic appliance delivered 50 gm, for 14 days, retained for 4 days and left to relapse for 10 days. The study group was divided into three subgroups in which a single injection of calcitonin (20 IU/Kg), three injections of calcitonin (20 IU/Kg), each every other day, and normal saline were administered subcutaneously after orthodontic tooth movement has finished. The relapse ratio, histomorphometric analysis including osteoblasts, osteoclasts numbers and bone area and immunohistochemical analysis including the expression of receptor activator of nuclear factor kappa Β (RANK), receptor activator of nuclear factor kappa Β ligand (RANKL) and osteoprotegerin (OPG) were measured and assessed.

Results

The relapse ratio was significantly reduced in the three‐dose calcitonin group (28%) compared to the single dose calcitonin group (34%) and the control group (46%). This was accompanied by a nonsignificant increase in osteoblasts number and bone area in three‐dose calcitonin group and a nonsignificant reduction in osteoclast number. However, the immune histochemical expression of RANK, RANKL and OPG did not show statistically significant difference at the end of relapse period.

Conclusions

Systemic administration of three doses of calcitonin may minimize the relapse ratio in experimentally moved rat molars.

Potential and limitations of orthodontic biomechanics: recognizing the gaps between knowledge and practice

The perennial goals of efficient biomechanics are to obtain more controlled and faster movement and using more discrete appliances. The most recent technological advances have buttressed these goals. Temporary anchorage devices have revolutionized orthodontic practice and loom as a solid cornerstone of orthodontic science, along with the use of light forces, facilitated by "smart" archwires for optimal tooth movement. Accelerated tooth movement with decortication has been successful because of decreasing the resistance of cortical bone but micro-osteoperforation has not matched the same results. Clear aligners and preprogrammed regular or lingual appliances reflect the importance of three-dimensional technology in appliance design based on treatment outcome. These mechanical developments have inched the science closer to the traditional goals, but advances lack regarding their enhancement by biomaterials in a system where the physical stimulus is exerted on the teeth but the expression of tooth displacement is through the biological processes within the surrounding tissues. In this article, present tenets, applications, and advances are explored along with the gaps between knowledge and practice and the possibilities to bridge them. Anchorage control remains the major widely used development but slower is the development of faster noninvasive treatment.

Could medications and biologic factors affect post-orthodontic tooth movement changes? A systematic review of animal studies

Immediately after the removal of orthodontic appliances, the teeth might start to drift away from their corrected position in an attempt to reach a new equilibrium. Medications and biologic factors could potentially modulate these processes. The objective of the present systematic review is to systematically investigate and appraise the quality of the evidence regarding the effect of various medications and biologic factors on the rate of relapse following active tooth movement. Search without restrictions in eight databases and hand searching until April 2020 were conducted. Studies performed on animal models investigating the effects of medication and biologic factors on the rate of relapse following orthodontic tooth movement were considered. Following study retrieval and selection, relevant data were extracted and the risk of bias was assessed. Seventeen studies were finally identified, mostly at either high or unclear risk of bias. Ketorolac did not show any significant effects on relapse, while the administration of tetracycline, atorvastatin, psoralen and raloxifene decreased it. Overall, the same result was observed with bisphosphonates with the exception of low dosage of risedronate, which did not have an effect. Osteoprotegerin and strontium resulted in reduced relapse, but not in the immediate post-administration period. Inconsistent or conflicting effects were noted after the use of simvastatin and relaxin. The quality of the available evidence was considered at best as low. It can be concluded that specific medications and biologic factors may have an effect on the rate of relapse following tooth movement. The orthodontist should be knowledgeable about the substances potentially affecting retention.

The intrasulcular application effect of bisphosphonate hydrogel toward osteoclast activity and relapse movement

Introduction

Orthodontic relapse occurs after orthodontic treatment and shifting of teeth to unfavorable positions. Bisphosphonates’ effects on bone resorption and relapse prevention have been extensively investigated. However, topical administration, which results in local effect, is still a problem.

Objective

This study aimed to investigate the effect of risedronate with gelatin hydrogel as a carrier to prevent relapse movement by inhibiting osteoclast activity.

Methods

Lower incisors of 75 guinea pigs were moved distally using an orthodontic appliance until ±3 mm length. Gelatin hydrogel was fabricated to obtain a semisolid controlled release of 250 (Bis-CR250) and 500 mmol/L risedronate (Bis-CR500) and then applied intrasulcularly into the mesial subperiosteal area of 50 guinea pigs (25 in each group) every 3 days; the rest were the control (Bis-CR000). After 14 days of stabilization, the apparatus was removed. The distance decrease between incisors and the osteoclast number with TRAP staining at 0, 3, 7, 14, and 21 days were measured. ANOVA was used to determine the differences among the different time and experimental groups.

Results

Both treatments showed significantly less relapse movement compared to the control (p < 0.05) at 14 and 21 days. Bis-CR500 more effectively inhibited the relapse movement than Bis-CR250 on day 21, indicating a dose dependency in the inhibition. Both treatments showed less osteoclast numbers than control (p < 0.05).

Conclusion

Controlled release of bisphosphonate risedronate with a topically administered gelatin hydrogel has shown to be effective in decreasing the tooth relapse movement and osteoclast activity.

The role of bisphosphonates in orthodontic tooth movement-A review

The present study has reviewed and put insights on the reports and recent literatures confined to the effects of bisphosphonate (BP) medication on orthodontic tooth movement (OTM). Pharmacological anchorage control plays a vital role in orthodontic treatment planning to the required patients. BPs inhibit bone resorption by involving increased activity of mineral adsorption on the bone surfaces where BPs tend to target osteoclasts. The present study reviewed on the latest report and examined cases relating to the impact of BPs in OTM. Clinical implication, chemical formulation, and mode of action of BPs have been discussed. This reviewspecifically focused on various kinds of BPs used in medication for bone adsorption in OTM therapy. Furthermore, it tries to explore the rare adverse and side effects of BPs observed based on the literatures. A systematic literature search was attempted in the Medline database (PubMed) using appropriate keywords, such as orthodontic tooth movement, bisphosphonates, and manual hand look was more overdone. On the basis of reports examined, BP treatments in OTM have posed an increased trend toward the benefit and interfere with osteoclastic resorption. In many cases, they may be advantageous for mooring strategies and encourage long-term planned randomized controlled trials to evaluate conceivable benefits and antagonistic impacts of BP treatments for OTM, before initiating remedial use.

Biological aspects of orthodontic tooth movement: A review of literature

This review of literature describes the cellular and molecular biology of orthodontic tooth movement, including various theories and effect of chemical mediators on tooth movement. The better understanding of the tooth movement mechanism will inspire the clinicians to design and implement effective appliances that will result in maximum benefits and minimum tissue damage to the patients. This paper also emphasizes the applied aspect of different medication and hormones, during orthodontic treatment, on the signaling molecules which produce bone remodeling.

Effect of local injection of Zolena, zoledronic acid made in Iran, on orthodontic tooth movement and root and bone resorption in rats

Background. Anchorage control is an essential part of orthodontic treatment planning, especially in adult patients who demand a more convenient treatment. Zoledronic acid (ZA) is an effective choice to address this problem. It is the most potent member of the bisphosphonates family that has an inhibitory effect on bone resorption by suppressing osteoclast function. Therefore, ZA might be a good option for orthodontic anchorage control. The current study evaluated the effect of local administration of Zolena (ZA made in Iran) on orthodontic tooth movement (OTM) and root and bone resorption. Methods. The experimental group consisted of 30 rats in 3 subgroups (n=10). Anesthesia was induced, and one closed NiTi coil spring was installed between the first molar and central incisor unilaterally, except for the negative control group. The positive control group received vestibular injection of 0.01 mL of saline next to the maxillary first molar, and 0.01 mL of the solution was injected at the same site in the ZA group. After 21 days, the rats were sacrificed and the distance between the first and second molars was measured with a leaf gauge. Histological analysis was conducted by a blind pathologist for the number of Howship's lacunae, blood vessels, osteoclast-like cells and root resorption lacunae. Data were analyzed with ANOVA, Tukey test and t-test. Results. There were no significant differences in OTM between the force-applied groups. ZA significantly inhibited bone/root resorption and angiogenesis compared to the positive control group. Conclusion. Zolena did not decrease OTM but significantly inhibited bone and root resorption. Zolena might be less potent than its foreign counterparts.

Zoledronic acid and alendronate sodium and the implications in orthodontic movement

OBJECTIVE

To evaluate orthodontic tooth movement (OTM) in rats treated with two types of bisphosphonates (BPs), alendronate sodium (A) and zoledronic acid (Z).

DESIGN

In all, 15 male Wistar rats were randomly divided into three groups. Group OTM+A: orthodontic tooth movement and subcutaneous administration of alendronate sodium (2.5 mg/kg); Group OTM+Z: orthodontic tooth movement and subcutaneous administration of zoledronic acid (0.02 mg/kg), and Group OTM: orthodontic tooth movement and subcutaneous injection of saline. The BPs were administered once a day during 25 days before OTM started and during 10 days of OTM. The left upper first molar was moved with a stainless-steel closed coil spring which delivered an initial force of 0.4N. OTM was measured with a digital caliper comparing the moved and the contralateral side. The histomorphometric analysis counted the number of osteoclasts, inflammatory cells, blood vessels and fibroblasts (n/10⁴  m² ) in periodontal ligament (PDL) of the distobuccal root.

RESULTS

A reduction of 58.3% of OTM was found in Group OTM+A and 99.6% in Group OTM+Z, when compared with Group OTM. There was a significant decrease of osteoclasts and inflammatory cells in BP-treated groups. Blood vessels and fibroblastic cells decreased mainly in Group OTM+Z.

CONCLUSION

Alendronate sodium and zoledronic acid have similar effects on the periodontal tissue during orthodontic treatment in rats. Especially, zoledronic acid can affect orthodontic tooth movement.

External apical root resorption concurrent with orthodontic forces: the genetic influence

Root resorption is a pathological process of multifactorial origin related to the permanent loss of dental root structure in response to a mechanical, inflammatory, autoimmune or infectious stimulus. External apical root resorption (EARR) is a frequent clinical complication secondary to orthodontic tooth movement; apart from variables related to treatment, environmental factors and/or interindividual genetic variations can confer susceptibility or resistance to its occurrence. In this context, genetic predisposition has been described as an etiological factor, together with mechanical factors derived from orthodontic treatment. In recent years, international research groups have determined the degree of influence of some genetic biomarkers in defining increased/reduced susceptibility to postorthodontic EARR. The influences of the IL1 gene cluster (IL1B, IL1A, IL1RN, IL6), P2RX7, CASP1, OPG (TNFRSF11B), RANK (TNFRSF11A), Osteopontin (OPN), TNFα, the vitamin D receptor (TaqI), TNSALP and IRAK1 have been analyzed. The objective of the present review study was to compile and analyze the latest information about the genetic background predisposing to EARR during orthodontic treatment. Genetics-based studies along with other basic science research in the field might help to clarify the exact nature of EARR, the influence of genetic inheritance and possibly lead to the prevention or even eradication of this phenomenon during orthodontic treatment.

Dose- and time-dependent effects of clodronate on orthodontic tooth movement

Orthodontic tooth movement is the result of bone remodeling that occurs in periodontal ligament and alveolar bone tissue as a response to mechanical loading of the tooth. The aim of this study is to investigate the time- and dose-response effects of locally administered clodronate on tooth movement. Sixty Wistar rats were randomly assigned to 4 groups of 15 specimens: E1 - application of 10 mMol of clodronate in 3-day intervals; E2 - application of 2.5 mMol of clodronate in 3-day intervals; E3 - application of 10 mMol of clodronate in 7-day intervals; E4 - application of 2.5 mMol of clodronate in 7-day intervals. A 50 μL clodronate solution was injected into a subperiosteal area to the right maxillary incisor. The left maxillary incisor served as a control, with an injection of saline solution. In 3-day interval application regime, there was no effect of clodronate dosing on tooth movement. In 7-day interval application regime, decreased tooth movement was observed with 10 mMol compared with 2.5 mMol clodronate concentration. However, decreased tooth movement was also observed when 2.5 mMol of clodronate was applied in 7-versus 3-day intervals. Conversely, no difference was observed when 10 mMol concentration was applied in 3- versus 7-day intervals. When clodronate is applied subperiosteally in the root area, it decreases the tooth movement. Tooth movement is impeded by the higher clodronate dosing, as well as by shorter application interval even with lower dosing. The purpose of future trials should, therefore, be to determine a safe therapeutic dose/interval application of clodronate in humans and their potential side effects.

Bone-site-specific responses to zoledronic acid

OBJECTIVES

Bisphosphonates are widely used to treat bone diseases such as osteoporosis. However, they may cause osteonecrosis of the jaw. Here, we investigated whether in vivo exposure to bisphosphonates has a different effect on long bone and jaw osteoclasts, and on the turnover of these different bones.

MATERIALS AND METHODS

Zoledronic acid (0.5 mg kg^-1 weekly) was administered intraperitoneally to 3-month-old female mice for up to 6 months. The effects on the number of osteoclasts, bone mineralization and bone formation were measured in the long bones and in the jaw.

RESULTS

Long-term treatment with zoledronic acid reduced the number of jaw bone marrow cells, without affecting the number of long bone marrow cells. Zoledronic acid treatment did not affect the number of osteoclasts in vivo. Yet, the bisphosphonate increased bone volume and mineral density of both long bone and jaw. Interestingly, 6 months of treatment suppressed bone formation in the long bones without affecting the jaw. Unexpectedly, we showed that bisphosphonates can cause molar root resorption, mediated by active osteoclasts.

CONCLUSIONS

Our findings provide more insight into bone-site-specific effects of bisphosphonates and into the aetiology of osteonecrosis of the jaw. We demonstrated that bisphosphonates can stimulate osteoclast activity at the molar roots.

Randomised trial of bisphosphonate-coated dental implants: Radiographic follow-up after five years of loading

The results of a randomised trial with bisphosphonate-coated dental implants have been reported previously. Each patient received one coated and one uncoated implant in a double-blind split-mouth design study. After 6 months of osseointegration, resonance frequency analysis indicated better fixation of the coated implants. Reduced marginal bone resorption was also shown. However, it was not known whether the advantage of the bisphosphonate coating would persist over time. The radiographic results at 5 years after implant installation are reported herein. A blinded investigator measured marginal resorption on fresh radiographs obtained for 14 of the 16 patients (two had died) and compared these with the post-implantation images. Non-parametric statistics were used. All implants functioned well. The median marginal bone loss for control implants was found to be 0.70mm, which is less than usually reported in the literature. The bisphosphonate-coated implants showed even less resorption (median 0.20mm). The median difference within each pair of implants after 5 years of use was 0.34mm (95% confidence interval 0.00-0.75mm; P=0.04). The present data suggest that bisphosphonate-coated implants enable prolonged preservation of the marginal bone.

PDL Progenitor-Mediated PDL Recovery Contributes to Orthodontic Relapse

Periodontal ligament (PDL) is subjected to mechanical force during physiologic activities. PDL stem /: progenitor cells are the main mesenchymal stem cells in PDL. However, how PDL progenitors participate in PDL homeostasis upon and after mechanical force is largely unknown. In this study, force-triggered orthodontic tooth movement and the following relapse were used as models to demonstrate the response of PDL progenitors and their role in PDL remodeling upon and after mechanical force. Upon orthodontic force, PDL collagen on the compression side significantly degraded, showing a broken and disorganized pattern. After force withdrawal, the degraded PDL collagen recovered during the early stage of relapse. Correspondingly, increased CD90(+) PDL progenitors with suppressed expression of type I collagen (Col-I) were observed upon orthodontic force, whereas these cells accumulated at the degradation regions and regained Col-I expression after force withdrawal during early relapse. Our results further showed that compressive force altered cell morphology and repressed collagen expression in cultured PDL progenitors, which both recovered after force withdrawal. Force withdrawal-induced recovery of collagen expression in cultured PDL progenitors could be regulated by transforming growth factor-β (TGF-β), a key molecule for tissue homeostasis and extracellular matrix remodeling. More interesting, inhibiting the regained Col-I expression in CD90(+) PDL progenitors by blocking TGF-β interrupted PDL collagen recovery and partially inhibited the early relapse. These data suggest that PDL progenitors can respond to mechanical force and may process intrinsic stability to recover to original status after force withdrawal. PDL progenitors with intrinsic stability are required for PDL recovery and consequently contribute to early orthodontic relapse, which can be regulated by TGF-β signaling.

Locally limited inhibition of bone resorption and orthodontic relapse by recombinant osteoprotegerin protein

OBJECTIVES

To determine minimal dose levels required for local inhibition of orthodontic relapse by recombinant OPG protein (OPG-Fc), while also determining effects of injected OPG-Fc on alveolar bone and long bone.

SETTING AND SAMPLE POPULATION

The Department of Orthodontics and Pediatric Dentistry at the University of Michigan. Eighteen male Sprague Dawley rats.

MATERIALS & METHODS

Maxillary molars were moved with nickel-titanium springs and then allowed to relapse in Sprague Dawley rats. Upon appliance removal, animals were injected with a single dose of 1.0 mg/kg OPG-Fc, 0.1 mg/kg OPG-Fc, or phosphate-buffered saline (vehicle) just distal to the molar teeth. Tooth movement measurements were made from stone casts, which were scanned and digitally measured. Alveolar tissues were examined by histology. Micro-computed tomography was used to quantify changes in alveolar and femur bone.

RESULTS

Local injection of OPG-Fc inhibited molar but not incisor relapse, when compared to vehicle-injected animals. No significant differences in alveolar or femur bone were seen between the three treatment groups after 24 days of relapse.

CONCLUSIONS

Our results demonstrate that a single local injection of OPG-Fc effectively inhibits orthodontic relapse, with minimal systemic bone metabolic effects. Our results also show that a single injection of OPG-Fc will influence tooth movement only in teeth close to the injection site. These findings indicate that OPG-Fc has potential as a safe and effective pharmacological means to locally control osteoclasts, for uses such as maintaining anchorage during orthodontic tooth movement and preventing orthodontic relapse in humans.

Osteoprotegerin and zoledronate bone effects during orthodontic tooth movement

OBJECTIVES

To assess the effects of local delivery of recombinant fusion protein osteoprotegerin (OPG-Fc) and bisphosphonate zoledronate on bone and periodontal ligament in a rat tooth movement model.

MATERIALS AND METHODS

Maxillary first molars of 36 male Sprague-Dawley rats were displaced mesially using a calibrated spring connected to an anterior mini-screw. Two different drugs were used: a single dose of Zoledronate (16 μg) and a twice-weekly dose of OPG-Fc (5.0 mg/kg) were injected. Tooth movement was measured on scanned plaster casts. Structural and immunohistochemical analysis of the orthodontic-induced changes in bone included receptor activator of nuclear factor ĸ (RANK), Runx, type 1 collagen, matrix metalloproteinases (MMPs) 2 and 9, tissue inhibitors of metalloproteinases (TIMPs) 1 and 2, and vimentin.

RESULTS

Both groups showed a reduction in mesial molar displacement. Animals receiving OPG-Fc demonstrated only 52%, 31%, and 21% of the total mesial molar displacement compared to control rats at 7, 14, and 21 days, respectively (*p < 0.001). For rats receiving zoledronate tooth displacement decreased significantly with 52%, 46% and 30%, respectively (*p < 0.001). At 14 and 21 days, OPG-Fc group showed significantly less molar displacement than the zoledronate group (*p < 0.001). RANK, Runx, vimentin, MMP-9 and tissues-inhibitor metalloproteinase 1 immunoreactivity were reduced in zoledronate treated animals and even more in OPG treated animals.

CONCLUSION

Local delivery of OPG-Fc or zoledronate inhibits bone resorption and therefore tooth movement. OPG-Fc was more effective than zoledronate in blocking the action of osteoclasts.

The effect of simvastatin on relapse of tooth movement and bone mineral density in rats measured by a new method using microtomography

PURPOSE

To evaluate the effect of simvastatin on relapse of tooth movement in rats using microtomography (micro CT), as well as the correlation of bone density with the orthodontic relapse.

METHODS

Twenty-five adult male Wistar rats, divided into two groups, had stainless steel springs installed on left maxillary first molar. The molars were moved for 18 days, and after removing the springs, were applied by oral gavage, 5mg/kg of simvastatin in the experimental group for 20 days. Tooth relapse was assessed with a micro CT scanner, and the images chosen through the Data Viewer software 1.5.0.0 had their measurement guides made and checked by the software Image ProR plus 5.1, and compared by Mann-Whitney test. After rats were sacrificed, bone mineral density was evaluated by micro CT through the software CT Analyzer 1.13 and compared by independent T-test, as well as by Spearman correlation test.

RESULTS

Relapse and bone mineral density (BMD) was lower in the experimental group than in the control group, however without a statistically significant difference.

CONCLUSION

Simvastatin did not inhibit the relapse of tooth movement in rats, and there was no correlation between bone density and orthodontic relapse.

Recombinant osteoprotegerin effects during orthodontic movement in a rat model

BACKGROUND AND OBJECTIVES

Anchorage is one of the most challenging sides in orthodontics. The use of biological modulators that inhibit osteoclasts could be a solution to address these problems and provide new adjunctive approaches. The aim of this study was to assess the effectiveness of recombinant osteoprotegerin fusion protein (OPG-Fc) in orthodontic anchorage.

MATERIALS AND METHODS

Two groups of male Sprague-Dawley rats were utilized. The animals in the experimental group received twice-weekly injections with high dose of OPG-Fc (5.0mg/kg) in mesial and distal mucosa of the first molars, and those in the control group received no drugs. Right first maxillary molars were mesialized using a calibrated nickel-titanium spring connected to an anterior mini-screw. Tooth movement was measured by two blinded observers using scanned and magnified stone casts. Receptor activator of nuclear factor κB (RANK), run-related transcription factor 2 (Runx2), type I collagen, vimentin, matrix metalloproteinases 2 and 9, S100 protein and the putative mechanoproteins acid-sensing ion channel (ASIC2) and transient receptor potential vainilloid 4 (TRPV4) were evaluated using immunohistochemistry.

RESULTS

OPG-Fc group showed an important decreased in mesial molar movement with only 52%, 31%, and 22% of the total mesial molar movement compared with control group at Days 7, 14, and 21, respectively (P < 0.001). RANK ligand and Runx2 positive cells were severely reduced after OPG-Fc treatment. Periodontal ligament architecture, cell arrangement, and immunohistochemical patter for vimentin, type I collagen and the mechanoproteins TRPV4 and ASIC2 were altered by tooth movement and all these parameters altered by the applied treatment.

CONCLUSIONS

OPG-Fc effectively inhibits osteoclastogenesis resulting in improved bone quantity and orthodontic anchorage. Based on present results, OPG-Fc could have clinical utility in preventing undesired tooth movements.

Effect of bisphosphonates on orthodontic tooth movement-an update

Bisphosphonates are a synthetic class of pyrophosphate analogues that are powerful inhibitors of bone resorption which are commonly used as a medication for the prevention and therapy of osteoporosis and osteopenia, also used to treat tumor diseases. As it affects bone metabolism, it is said to have an influence on orthodontic treatment and tooth movement. Also, this review gives an insight into the reported effects of Bisphosphonate medication in literature highlighting the status quo of scientific research regarding effects of Bisphosphonates on orthodontic tooth movement. A systematic literature search was done in Medline database (Pubmed) for the appropriate keywords. Manual handsearch was also done. From the available evidence it can be concluded that the duration of orthodontic treatment is increased for patients under Bisphosphonate therapy as they interfere with the osteoclastic resorption. However, they may be beneficial for anchorage procedures. Further long term prospective randomized controlled trials are required to assess possible benefits and adverse effects of bisphosphonate treatment, before Bisphosphonates can be therapeutically used in orthodontics.

Enhancement of orthodontic anchorage and retention by the local injection of strontium: An experimental study in rats

OBJECTIVES

To examine the clinical and histological effects of locally injected strontium on the anchoring unit of a rat model of an experimental relapsed tooth movement.

MATERIALS AND METHODS

Thirty-six 10-week-old male Wister rats were randomly divided into two groups of 18 animals that were then randomly divided into three subgroups of six animals corresponding to three observation periods: T1 = 1 week, T2 = 2 weeks, and T3 = 3 weeks. In the first experiment, both the right and left maxillary first molars were moved buccally with a standardized expansive spring. Strontium chloride solution was injected every 2 days into the subperiosteal area buccal to the left maxillary first molar (the experimental side). The right-sided first molar was injected with distilled water as a control. In the second experiment, maxillary first molars were moved buccally with the spring. After 3 weeks, the spring was removed. Two days before the spring removal, strontium chloride was injected into the palatal side of left-sided maxillary first molar and distilled water was injected into the palatal side of the right-sided maxillary first molar as in experiment 1.

RESULTS

At the end of the experimental period, significant levels of inhibition were noted in terms of both tooth movement and relapse movement in strontium-injected sides. Histological examinations showed that strontium enhanced the number of osteoblasts and reduced the number of osteoclasts.

CONCLUSION

The local injection of strontium can inhibit the degree of experimental and relapsed tooth movement in a rat model.

Administration of bisphosphonate (ibandronate) impedes molar tooth movement in rabbits: A radiographic assessment

Introduction:

Bisphosphonate (Bp)-ibandronate is a pharmacological agent, exhibits antiosteoclastic or antiresorptive activity and used to treat osteolytic or osteopenic disorders. BP-ibandronate may also interfere during orthodontic tooth movement. The aim of this study was to examine the influence of locally administered Bp-ibandronate on experimental tooth movement in rabbits.

Materials and Methods:

Twenty rabbits were divided into two groups- “10” served as Group-1 (control) and other “10” as Group-2 (experimental). Both groups received nickel-titanium closed coil springs with 100 g force between mandibular molar and incisors. Group-1 animals received 1 ml normal saline and Group-2 animals received ibandronate solution (0.3 mg/kg body weight) locally, mesial to the mandibular molar on the 1^st, 7^th, and 14^th day of the experiment. A total of “40” lateral cephalograms were taken from both groups on the 1^st and 21^st day using a digital X-ray unit (Siemens X-ray systems, 300 mA Pleomophos analog, 2008, Germany). Individually, each animal's radiograph was traced manually and superimposed. The molar tooth movement was measured with the help of a standard metric scale.

Results:

The Student's t-test has been done to compare the mean values of Group-1 (4.650 ± 0.363) and Group-2 (2.030 ± 0.291) and the difference was statistically significant (P < 0.001).

Conclusion:

The retarded molar tooth movement was noticed in local drug administered rabbits, which could be beneficial in orthodontics to control the undesired tooth movement.

Mechanical loading influences the effects of bisphosphonates on human periodontal ligament fibroblasts

OBJECTIVES

There is increasing evidence that bisphosphonates affect orthodontic tooth movement. The object of the study was to investigate the changes produced by tensile strain on human periodontal ligament fibroblasts (HPdLFs) treated with clodronate or zoledronate.

MATERIALS AND METHODS

HPdLF were cultured with 5 and 50 μM clodronate or zoledronate for 48 h and applied to tensile strain (TS) (5 and 10 %) for 12 h in vitro. Viability was verified by MTT assay and apoptosis rate via caspase 3/7 assay. Gene expression of receptor activator of nuclear factor kappa-B ligand (RANKL) and osteoprotegerin (OPG) was investigated using real-time PCR. OPG was also analyzed by ELISA and RANKL by immunocytochemical staining.

RESULTS

Zoledronate (50 μM) reduced the viability of HPdLF (76 vs 100 %) and combined with 5 % TS to 53 %. TS of 10 % and clodronate reduced viability to 79 % with increased caspase 3/7 activity. Clodronate (5 μM) led to a slight increase of OPG gene expression, zoledronate (5 μM) to a slight decrease. Combined with 5 % TS, both increased OPG gene expression (2-3-fold) and OPG synthesis. Zoledronate increased gene expression of RANKL (4-fold). Combined with 5 % of TS, this increase was abolished. TS of 10 % in combination amplified increase of RANKL ending up with a 9-fold gene expression by clodronate and high RANKL protein synthesis.

CONCLUSIONS

This study shows for the first time that mechanical loading alters the effects of bisphosphonates on viability, apoptosis rate, and OPG/RANKL system of HPdLF dependent on the applied strength. Low forces and bisphosphonates increase factors for bone apposition, whereas high forces combined with bisphosphonates stimulate osteoclastogenesis.

CLINICAL RELEVANCE

Mechanical loading of periodontal ligament with high strengths should be avoided during bisphosphonate therapy.

Lithium chloride attenuates root resorption during orthodontic tooth movement in rats

Root resorption is a common side effect of orthodontic treatment. In the current study, lithium chloride (LiCl), a Wnt signaling activator, was examined to determine its effect on root resorption. In total, 10 Sprague Dawley rats were randomly allocated into the experimental group (EG) and control group (CG). Each group consisted of five subjects. By using closed nickel-titanium coil springs, a 50-g force was applied between the upper incisors and the maxillary right first molars in order to mimic orthodontic biomechanics in the EG and CG for 14 days. During the 14 days, the EG rats were gavage-fed 200 mg/kg LiCl every 48 h. Next, digital radiographs were captured using a micro-computational tomography scanner. The movement of the maxillary first molars and the root resorption area ratio were measured electronically on the digital radiographs. The outcomes were analyzed using ANOVA. Following 14 days of experimental force application, all rats had spaces of varying sizes between the first and second right maxillary molars. The average distance measured in the CG was slightly higher than in the EG, however, the difference was not found to be statistically significant (P=0.224). Root resorption craters were observed in the groups following the experiment. Rough cementum areas were observed on the mesial surface of the distobuccal and distopalatal roots. The mean root resorption area ratio of CG was significantly greater than EG (P<0.05). Results of the present study indicate that LiCl can attenuate orthodontically induce root resorption during orthodontic tooth movement. The effect of LiCl on tooth movement is insignificant.

The effect of bone morphometric changes on orthodontic tooth movement in an osteoporotic animal model

OBJECTIVE

To elucidate the effect of bone morphometric changes on orthodontic tooth movement (OTM) in zoledronic acid-treated ovariectomized rats.

MATERIALS AND METHODS

Twenty-one 10-week-old female Wistar rats were divided into ovariectomy (OVX), OVX with zoledronic acid administration (OVX + ZOL), and sham operation (control) groups. Two weeks after OVX, ZOL administration was initiated. Twelve weeks after OVX, a nickel-titanium closed-coil spring of 25-g force was applied mesially to the maxillary left first molar. In vivo micro-computed tomography (CT) of the left proximal tibia was performed for bone morphometric analysis every 2 weeks after OVX. In addition, OTM was investigated using micro-CT at 0, 12, and 14 weeks after OVX.

RESULTS

There were significant differences in the bone mineral content (BMC), bone volume (BV), BMC to tissue volume ratio (BMC/TV), and BV to TV ratio of trabecular bone between the control and OVX groups and also between the OVX + ZOL and OVX groups. In the OVX + ZOL group, increased BMC and BV in the cortical bone and increased bone mineral density (BMD) in the trabecular bone were observed. Interestingly, OTM in the OVX group was almost two times more than that in the control and OVX + ZOL groups. Moreover, OTM was correlated with BMD, BMC, BV, and BMC/TV in the trabecular bone.

CONCLUSIONS

OVX accelerated OTM, while ZOL suppressed it. OTM demonstrated a significant negative relationship with trabecular bone mass.

What you need to know about bisphosphonates: an overview and general recommendations for orthodontic treatment

The orthodontic treatment of patients on bisphosphonates is becoming an increasing aspect of contemporary practice. This article will draw attention to the chemical structure and effects of these drugs on bone and will provide the latest recommendations to avoid potential sequelae.

Icariin enhances the healing of rapid palatal expansion induced root resorption in rats

Icariin has been reported to enhance bone healing and treat osteoporosis. In this study, we examined the effect of Icariin on rapid palatal expansion induced root resorption in rats. Our hypothesis is that Icariin can enhance the healing of rapid palatal expansion induced root resorption. Forty-eight male Wistar rats were divided randomly and equally into three groups (n=16 rats each). The rats were untreated (negative control) or treated with rapid palatal expansion without (positive control) or with Icariin at 2.5 mg/kg day (Icariin-treated groups). An initial force of 50×g was applied to the areas between the right and left upper first molars of the rats for 21 days. Eight rats were randomly chosen from each group, and the root resorption index (RRI) was determined with scanning electron microscopy (SEM). Upper first molar-centered buccal- lingual tissue slices were generated from the upper first molars and peridentium of the remaining eight rats from each group. Specimen slices were analyzed with HE and tararate-resistant acid phosphatase staining, osteoprotegerin (OPG) and receptor activator of nuclear factor kappa-B ligand (RANKL) immunohistochemistry, and optical microscopy. Analyses of cell number, densitometry, and one-way analysis of variance were performed. The Icariin-treated groups displayed decreased RRI values, decreased osteoclast numbers and activity levels, and increased OPG/RANKL expression ratios. High-power SEM revealed reparative cementum in the Icariin-treated samples. Icariin regulates osteoclast differentiation via the OPG/RANKL ratio, evoking a reparative effect on rapid palatal expansion induced root resorption in rats.

Orthodontic tooth movement and root resorption in ovariectomized rats treated by systemic administration of zoledronic acid

INTRODUCTION

The effect of zoledronic acid, a potent and novel bisphosphonate, on tooth movement and orthodontically induced root resorption in osteoporotic animals systemically treated with zoledronic acid as similarly used in postmenopausal patients has not been elucidated. Therefore, this study was undertaken.

METHODS

Fifteen 10-week-old female Wistar rats were divided into 3 groups: ovariectomy, ovariectomy + zoledronic acid, and control. Only the ovariectomy and ovariectomy + zoledronic acid groups underwent ovariectomies. Two weeks after the ovariectomy, zoledronic acid was administered only to the ovariectomy + zoledronic acid group. Four weeks after the ovariectomy, 25-g nickel-titanium closed-coil springs were applied to observe tooth movement and orthodontically induced root resorption.

RESULTS

There were significant differences in the amounts of tooth movement and orthodontically induced root resorption between the ovariectomy and the control groups, and also between the ovariectomy and the ovariectomy + zoledronic acid groups. There was no statistically significant difference in tooth movement and orthodontically induced root resorption between the ovariectomy + zoledronic acid and the control groups. Zoledronic acid inhibited significantly more tooth movement and significantly reduced the severity of orthodontically induced root resorption in the ovariectomized rats. The ovariectomy + zoledronic acid group showed almost the same results as did the control group in both tooth movement and orthodontically induced root resorption.

CONCLUSIONS

Zoledronic acid inhibits excessive orthodontic tooth movement and also reduces the risk of severe orthodontically induced root resorption in ovariectomized rats.

[Accelerated tooth movement by alveolar corticotomy or piezocision]

The relatively recent introduction of corticotomies and piezocision has made it possible for orthodontists to accelerate tooth movement and thereby to shorten the length of orthodontic treatment. Specialists emphasizing a mechanistic concept have been debating the underlying basic biological mechanics of these new therapeutic tools with opposing specialists who support a biological conception. Our analysis of different publications on the subject suggests that the biological explanation, with its emphasis on the Regional Acceleratory Phenomenon (RAP), is correct. However, the majority of studies in this field are not based on the principle of evidence based medicine (EBM).

Effect of cyclosporine-A on orthodontic tooth movement in rats

OBJECTIVE

The objective of this study is to examine the effect of cyclosporine-A (CsA) on the rate of orthodontic tooth movement in rats.

SETTING AND SAMPLE POPULATION

This is a randomized controlled trial with a split-mouth design in Sprague-Dawley rats.

MATERIAL AND METHODS

Eighteen rats, divided at random in two groups, were fed with 8 mg/kg CsA (experiment) or mineral oil (control) daily after initial healing of bilateral maxillary second molar removal. All rats received orthodontic coil springs (10 cN) secured to the maxillary incisors and first molars at the rights side, while no springs were placed at the left. Distances between first and third molars were measured on days 0, 3, 6, and 12. After sacrificing on day 12, the alveolar ridges of the maxillae were sectioned and blood samples were collected for serum tartrate-resistant acid phosphatase (TRAP)-5b level detection and for histology, respectively.

RESULTS

Significantly larger changes in intermolar distances were found after orthodontic force application in the CsA group at days 3 and 12 when compared with the control group. The inter-radicular dental alveolus of CSA-fed rats was osteopenic. Significantly increased TRAP-5b serum level was noted in the CsA group when compared with the control group.

CONCLUSIONS

We suggest that CsA enhanced the rate of orthodontic tooth movement. The osteopenia and the increased osteoclastic activity could be the underlying factors.