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

Topical and intermittent application of parathyroid hormone recovers alveolar bone loss in rat experimental periodontitis

BACKGROUND AND OBJECTIVE

Periodontitis is characterized by periodontal tissue inflammation and alveolar bone loss. The intermittent administration of parathyroid hormone (PTH), a major regulator of bone remodeling, has been demonstrated to stimulate osteoblastic activity. Although the systemic administration of PTH has been reported to protect against periodontitis-associated bone loss, the effect of the topical administration of PTH is unclear. In this study, the effect of intermittent administration of PTH on osteoblastic differentiation was examined in cultured calvaria cells and then the effect of topical and intermittent administration of PTH was determined by measuring the recovery of alveolar bone loss after inducing experimental periodontitis in rats.

MATERIAL AND METHODS

Alkaline phosphatase activity and bone nodule formation were measured in fetal rat calvaria cells. Experimental periodontitis was induced by placing nylon ligature around rat maxillary molars for 20 d. After ligature removal (day 0), PTH was topically injected into buccal gingiva three times a week for 10 wk. Micro-computed tomography analysis and histological examination were performed on days 35 and 70.

RESULTS

Intermittent exposure of PTH in calvaria cells increased alkaline phosphatase activity and bone nodule formation by 1.4- and 2.4-fold, respectively. Ligature procedures induced marked alveolar bone loss around the molars on day 0 and greater bone recovery was observed in the PTH-treated rats on day 70. An increase in osteoid formation on the surface of alveolar bone was detected in the PTH-treated rats.

CONCLUSION

Intermittent treatment with PTH stimulated osteoblastic differentiation in fetal rat calvaria cell cultures, and topical and intermittent administration of PTH recovered alveolar bone loss in rat experimental periodontitis.

Effect of teriparatide on induced tooth displacement in ovariectomized rats: a histomorphometric analysis

INTRODUCTION

The aim of this study was to evaluate morphologically the effect of teriparatide on induced orthodontic movement of the maxillary first molars in ovariectomized rats.

METHODS

Ovariectomized Wistar rats (n = 16), ovariectomized rats treated with teriparatide (n = 16), and nonovariectomized rats (n = 16) had orthodontic tooth movement for 5 and 7 days. The group treated with teriparatide received a subcutaneous injection (Forteo, Eli Lilly, Indianapolis, Ind; 30 μg/kg/day) for 90 days after the ovariectomy. Histologic sections obtained from the maxilla were prepared for the morphometric analysis of dental movement, the thickness of the periodontal ligament, and the number of osteoclasts in the pressure and tension areas of the apex of the root and alveolar crest in the distal root of the maxillary first molars.

RESULTS

The ovariectomized rats treated with teriparatide had similar responses at 5 and 7 days after the induced dental movements compared with the untreated ovariectomized group. Both ovariectomized groups had greater molar movement on day 7 day compared with the controls (P <0.05). There were no statistically significant differences between groups in the spacing of the periodontal ligament or the number of osteoclasts in the areas studied.

CONCLUSIONS

These data suggest that the treatment of osteoporosis with teriparatide is a good alternative for patients undergoing orthodontic treatment.

A review of the clinical implications of bisphosphonates in dentistry

Bisphosphonates are drugs that suppress bone turnover and are commonly prescribed to prevent skeletal related events in malignancy and for benign bone diseases such as osteoporosis. Bisphosphonate associated jaw osteonecrosis (ONJ) is a potentially debilitating, yet poorly understood condition. A literature review was undertaken to review the dental clinical implications of bisphosphonates. The present paper briefly describes the postulated pathophysiology of ONJ and conditions with similar clinical presentations. The implications of bisphosphonates for implantology, periodontology, orthodontics and endodontics are reviewed. Whilst bisphosphonates have potential positive applications in some clinical settings, periodontology particularly, further clinical research is limited by the risk of ONJ. Prevention and management are reviewed, including guidelines for reducing cumulative intravenous bisphosphonate dose, cessation of bisphosphonates prior to invasive dental treatment or after ONJ development, and the use of serum beta-CTX-1 in assessing risk. In the context of substantial uncertainty, the implications of bisphosphonate use in the dental clinical setting are still being determined.

Effects of clodronate on early alveolar bone remodeling and root resorption related to orthodontic forces: a histomorphometric analysis

INTRODUCTION

The objective of this study was to evaluate the short-term effects of clodronate, a first-generation bisphosphonate, on early alveolar bone remodeling and root resorption related to orthodontic tooth movement.

METHODS

The samples consisted of 54 sex-matched Wistar rats (weight, 180-230 g) allocated to the 2.5 mmol/L clodronate, 10 mmol/L clodronate, and control groups (n = 18 for each group). After application of a nickel-titanium closed-coil spring (force, 60 g) between the maxillary central incisor and first molar, 2.5 mmol/L of clodronate, 10 mmol/L of clodronate, or saline solution was injected into the subperiosteum adjacent to the maxillary first molar every third day. All animals received tetracycline, calcein, and alizarin red by intraperitoneal injection at 1, 6, and 14 days, respectively. The amounts of tooth movement were measured at 3, 6, 9, 12, and 15 days. The animals were killed at 4, 7, and 17 days. Histomorphometric analyses of bone mineral appositional rate, labeled surface, percentage of root resorption area, and number of root resorption lacunae of the mesiobuccal root of the maxillary first molar at 4, 7, and 17 days were done. One-way analysis of variance (ANOVA) with the post-hoc test were done for statistical analyses.

RESULTS

Rats in the 10 mmol/L clodronate group had significant decreases of tooth movement (12 and 15 days, P <0.05) and percentages of root resorption area and numbers of root resorption lacunae (7 day, P <0.05), and increases of labeled surface and mineral appositional rates (17 day, P <0.05) over those of the 2.5 mmol/L clodronate and control groups.

CONCLUSIONS

Although clodronate might decrease root resorption related to orthodontic tooth movement, patients should be informed about a possible decrease in the amount of tooth movement and a prolonged period of orthodontic treatment.

Bone inductive proteins to enhance postorthodontic stability

OBJECTIVES

To evaluate the use of bone morphogenetic proteins to enhance postorthodontic stability in sheep and to develop a biological method of postorthodontic retention.

MATERIALS AND METHODS

First incisors were extracted in four mature and healthy sheep, and the second incisors were tipped reciprocally toward the midline and then retained. Dried bone matrix was injected into the distal periodontal space of the left second incisor. The right second incisor was left as a control. Both incisors were retained in the tipped position for 4 weeks. Then, the orthodontic appliance was removed and the teeth were left without retention. Six weeks later, the animals were killed and serial sections were prepared for histologic observation.

RESULTS

Unlike the control, the experimental second incisor maintained its tipped position with minimal relapse. On the distal periodontal space of the experimental tooth, areas of focal fusion between newly formed bone and newly formed areas of hypercementosis were observed. In the distal periodontal space of the control tooth, osteoclastic activity was observed along most of the socket wall, and the periodontal space appeared narrow and compressed. This brought the tooth close to the boundary of the alveolar bone, confirming the relapse observed on that side.

CONCLUSION

This study proposes a new method of retention in which a biologically safe osteoinductive material is used to retain the teeth via induction of points of approximation between the cementum and alveolar bone.

Influence of bisphosphonates on orthodontic tooth movement in mice

Mechanical stress such as orthodontic tooth movement induces osteoclastogenesis. Sometimes, excessive mechanical stress results in root resorption during orthodontic tooth movement. It has been reported that bisphosphonate inhibits osteoclastogenesis. Recently, there have been concerns for orthodontic patients receiving bisphosphonates. Thus, the aim of this study was to investigate the effect of bisphosphonates on orthodontic tooth movement and root resorption in mice. A nickel-titanium (Ni-Ti) closed coil spring delivering a force of 10 g was inserted between the upper anterior alveolar bone and the first molar in 8-week-old male C57BL/6 mice. Bisphosphonate (2 microg/20 microl) was injected daily into a local site adjacent to the upper molar. After 12 days, the distance the tooth had moved was measured. The number of tartrate-resistant acid phosphatase (TRAP)-positive cells was counted as osteoclasts in histological sections. Root resorption was assessed by scanning electron microscopy. The data were analysed with a Student's t-test. The orthodontic appliance increased the number of osteoclasts on the pressure side and mesial movement of the first molar. Bisphosphonates reduced the amount of tooth movement and the number of osteoclasts. In addition, they also reduced root resorption on the pressure side. Bisphosphonates inhibit orthodontic tooth movement and prevent root resorption during orthodontic tooth movement in mice. These results suggest that bisphosphonates might have an inhibiting effect on root resorption during orthodontic tooth movement in humans and that they may interrupt tooth movement in orthodontic patients undergoing treatment, thus altering the outcome of treatment.

Local delivery of EGF-liposome mediated bone modeling in orthodontic tooth movement by increasing RANKL expression

AIMS

It has long been demonstrated that epidermal growth factor (EGF) has catabolic effects on bone. Thus, we examined the role of EGF in regulating mechanically induced bone modeling in a rat model of orthodontic tooth movement.

MAIN METHODS

The maxillary first molars of rats were moved mesially using an orthodontic appliance attached to the maxillary incisor teeth. Rats were randomly divided into 4 groups: (G1) administration of PBS (phosphate buffer saline) solution (n=24); (G2) administration of empty liposomes (n=24); (G3) administration 20ng of EGF solution (n=24); and (G4) 20ng of EGF-liposomes solution (n=24). Each solution was injected in the mucosa of the left first molar adjacent to the appliance. At days 5, 10, 14 and 21 after drug administration, 6 animals of each group were sacrificed. Histomorphometric analysis was used to quantify osteoclasts (Tartrate-resistant acid phosphatase (TRAP)+cells) and tooth movement. Using immunohistochemistry assay we evaluated the RANKL (receptor activator of nuclear factor kappaB ligand) and epidermal growth factor receptor (EGFR) expression.

KEY FINDINGS

The EGF-liposome administration showed an increased tooth movement and osteoclast numbers compared to controls (p<0.05). This was correlated with intense RANKL expression. Both osteoblasts and osteoclasts expressed EGFR.

SIGNIFICANCE

Local delivery of EGF-liposome stimulates osteoclastogenesis and tooth movement.

Modulation of murine bone marrow-derived CFU-F and CFU-OB by in vivo bisphosphonate and fluoride treatments

OBJECTIVES

Bisphosphonates (BPN) have actions on a variety of cell types including: osteoclasts, osteoblasts, osteocytes, and endothelial cells. The objectives of this report are to review the current state of understanding of the effects of BPNs on orthodontic tooth movement and to provide evidence on BPN's in vivo effects on bone marrow-derived osteoprogenitor cells.

MATERIAL AND METHODS

Mice from the C3H/HeJ (C3H), C57BL/6J (B6), FVB/NJ (FVB), and BALB/cByJ (BALB) strains were treated for 3 weeks with 0, 3, 30, or 150 mcg/kg/week alendronate (ALN) administered subcutaneous alone or in combination with 50 ppm fluoride (F). Bone marrow cells were harvested and subjected to in vitro colony-forming unit fibroblast (CFU-F) and colony-forming unit osteoblasts (CFU-OB) assays.

RESULTS

Baseline differences in CFU-F, CFU-OB/ALP+, and CFU-OB/total were observed among the four strains. Strain-specific responses to ALN and F treatments were observed for CFU-F, CFU-OB/ALP+, and CFU-OB/total. F treatment alone resulted in decreases in CFU-F (p = 0.013), CFU-OB/ALP+ (p = 0.005), and CFU-OB/total (p = 0.003) in the C3H strain. CFU-F (p = 0.036) were decreased by F in the B6 strain. No significant (NS) effects of F were observed for FVB and BALB. ALN treatment resulted in a significant decrease in CFU-F (p = 0.0014) and CFU-OB/total (p = 0.028) in C3H only. ALN treatment had NS effect on CFU-OB/ALP+ in all four strains.

CONCLUSION

Genetic factors appear to play a role in ALN's effects on CFU-F and CFU-OB/total but not on CFU-OB/ALP+.

Bisphosphonate-associated osteomyelitis of the jaw: guidelines for practicing clinicians

OBJECTIVE

To evaluate the literature and discuss the risk factors, mechanisms, pathophysiologic aspects, and recommended management of bisphosphonate-associated osteomyelitis of the jaw (BAOMJ).

METHODS

More than 350 published articles, case reports mentioning BAOMJ, and independent histology slides from BAOMJ lesions were reviewed critically. The most pertinent publications are cited and discussed.

RESULTS

The incidence of BAOMJ increases after extraction of teeth, dentoalveolar surgical procedures, or recent oral trauma leading to exposed maxillary or mandibular bone. Contributory factors include poor oral hygiene, oral infections, periodontal disease; recent or ongoing corticosteroid administration or chemotherapy; compromised immune status; diabetes or vascular insufficiency; old age; chronic diseases; and malignancies. On average, 1 of every 100,000 patients treated with bisphosphonates orally for osteoporosis or Paget disease of bone may develop BAOMJ-like lesions. Patients with cancer often receive bisphosphonate doses 10 times or higher, and also more frequently, than those used in patients with osteoporosis or Paget disease of bone. Therefore, greater frequency of administration of bisphosphonates, higher dosages, and prolonged use (that is, for more than 2 years) are likely to be factors triggering BAOMJ.

CONCLUSION

The association of bisphosphonate therapy with BAOMJ is rare in noncancer patients and is likely to be a class effect that may occur with use of any bisphosphonate. Whether patients with cancer require such a high frequency of intravenously administered bisphosphonates needs to be investigated. Following established guidelines can decrease the risks of BAOMJ in vulnerable patients. Rather than necrotic bone, current evidence supports an infectious and perhaps immunologic underlying cause for BAOMJ. The estimated incidence of BAOMJ among noncancer patients receiving bisphosphonates is about 0.001%, whereas among patients with cancer receiving intravenous bisphosphonate therapy the incidence is between 0.5% and 4%, depending on the dose, frequency, and duration of therapy (on average, approximately 2%). Nevertheless, the benefits of bisphosphonates far outweigh the risks.

Medication effects on the rate of orthodontic tooth movement: a systematic literature review

INTRODUCTION

Recently, several reviews have been published on the effects of medications on bone physiology and the clinical side effects in orthodontics. However, the effects of medications on the rate of orthodontic tooth movement have not been evaluated.

METHODS

A systematic literature review on the effects of medications and dietary supplements on the rate of experimental tooth movement was performed by using PubMed (1953-Oct 2007), Web of Science, and Biosis, complemented by a hand search.

RESULTS

Forty-nine articles were included in the review, but their interpretation was hindered by the variability in experimental design, magnitude of force applied during tooth movement, and medication regimens. Therapeutic administration of eicosanoids resulted in increased tooth movement, whereas their blocking led to a decrease. Nonsteroidal anti-inflammatory drugs (NSAIDs) decreased tooth movement, but non-NSAID analgesics, such as paracetamol (acetaminophen), had no effect. Corticosteroid hormones, parathyroid hormone, and thyroxin have all been shown to increase tooth movement. Estrogens probably reduce tooth movement, although no direct evidence is available. Vitamin D3 stimulates tooth movement, and dietary calcium seemed to reduce it. Bisphosphonates had a strong inhibitory effect.

CONCLUSIONS

Medications might have an important influence on the rate of tooth movement, and information on their consumption is essential to adequately discuss treatment planning with patients.

Pharmacovigilance and reporting oversight in US FDA fast-track process: bisphosphonates and osteonecrosis of the jaw

More than half of all serious adverse reactions are identified 7 or more years after a drug receives approval from the US Food and Drug Administration (FDA). In 2002, 9 months after the intravenous bisphosphonate zoledronic acid received regulatory approval for marketing, the FDA received reports of nine patients with cancer, who were treated with zoledronic acid, who unexpectedly developed osteonecrosis of the jaw. During the next 2 years, three oral surgeons described 104 patients with cancer with osteonecrosis of the jaw in the medical literature and identified intravenous bisphosphonate therapy as being common to the care of these patients. In subspecialty medical, radiology, and dental journals, case reports and case series described clinical features of osteonecrosis of the jaw in patients with cancer who were treated with bisphosphonates. Manufacturer-sponsored epidemiological studies reported the first estimates of the incidence of this toxic effect, ranging from 0.1% to 1.8%. By contrast, independent epidemiological efforts from clinicians and the International Myeloma Foundation reported incidence estimates between 5% and 10%. Between 2003 and 2005, warnings about the risks of bisphosphonate-associated osteonecrosis were disseminated by national regulatory agencies, the manufacturers of bisphosphonates, and the International Myeloma Foundation. From 2006, independent clinical recommendations for diagnosis, prevention, and treatment of this toxic effect have been disseminated by manufacturers, national regulatory authorities, the International Myeloma Foundation, and medical specialty organisations. Furthermore, independent efforts by pharmaceutical manufacturers, dental and medical professionals, a non-profit organisation (the International Myeloma Foundation), patients, and regulatory authorities has led to the rapid identification and dissemination of safety information for this serious adverse reaction. Better coordination of safety-related pharmacovigilance initiatives is now needed.

Effects of estrogen deficiency on tooth movement after force application: an experimental study in ovariectomized rats

OBJECTIVE

The aim of this study was to investigate the effects of estrogen deficiency on tooth movement in ovariectomized rats.

MATERIAL AND METHODS

Forty-two adult female Sprague-Dawley rats were assigned at random to one of the following groups: test group (n=20), ovariectomized rats (or estrogen-deficient rats); control group (n=22), non-ovariectomized rats. Two months after ovariectomy, expansion springs exerting 10 g of force were inserted between the upper central incisors in both groups. The amount of movement was measured daily until tooth movement began and then at intervals of 3 days. The rats were sacrificed 18 days after applying the expansion spring and histomorphometric analysis was performed along the left upper central incisor root towards the apex of the alveolar bone.

RESULTS

The amount and speed of movement was observed to be greater in ovariectomized rats. On histomorphometric analysis, osteoblast and osteocyte counts on the pressure side were higher in the non-ovariectomized group than in the ovariectomized group (p<0.001). In contrast, the osteoclast count was significantly higher (p<0.01) in the ovariectomized group than in the non-ovariectomized group. The osteoblast and osteocyte counts were significantly higher (p<0.001) on tension side in the non-ovariectomized group than in the ovariectomized group.

CONCLUSION

Estrogen deficiency increased orthodontic tooth movements but counts of osteoblasts, which are responsible for new bone formation, were lower in regions of tension and of pressure.

Local delivery of osteoprotegerin inhibits mechanically mediated bone modeling in orthodontic tooth movement

INTRODUCTION

The RANKL-OPG axis is a key regulator of osteoclastogenesis and bone turnover activity. Its contribution to bone resorption under altered mechanical states, however, has not been fully elucidated. Here we examined the role of OPG in regulating mechanically induced bone modeling in a rat model of orthodontic tooth movement.

METHODS

The maxillary first molars of male Sprague-Dawley rats were moved mesially using a calibrated nickel-titanium spring attached to the maxillary incisor teeth. Two different doses (0.5 mg/kg, 5.0 mg/kg) of a recombinant fusion protein (OPG-Fc), were injected twice weekly mesial to the first molars. Tooth movement was measured using stone casts that were scanned and magnified. Changes in bone quantity were measured using micro-computed tomography and histomorphometric analysis was used to quantify osteoclasts and volumetric parameters. Finally, circulating levels of TRAP-5b (a bone resorption marker) was measured using enzyme-linked immunosorbent assay.

RESULTS

The 5.0 mg/kg OPG-Fc dose showed a potent reduction in mesial molar movement and osteoclast numbers compared to controls (p<0.01). The molar movement was inhibited by 45.7%, 70.6%, and 78.7% compared to controls at days 7, 14, and 21 respectively, with the high dose of OPG. The 0.5 mg dose also significantly (p<0.05) inhibited molar movement at days 7 (43.8%) and 14 (31.8%). While incisor retraction was also decreased by OPG-Fc, the ratio of incisor to molar tooth movement was markedly better in the high-dose OPG group (5.2:1, p<0.001) compared to the control group (2.3:1) and the low-dose OPG group (2.0:1).

CONCLUSIONS

Local delivery of OPG-Fc inhibits osteoclastogenesis and tooth movement at targeted dental sites.

Inhibition of tooth movement by osteoprotegerin vs. pamidronate under conditions of constant orthodontic force

The undesired movement of anchor teeth, and relapse of previously moved teeth, are major clinical problems in orthodontics. Dental implants are increasingly used to preserve anchorage, but these are costly and require invasive surgical procedures. An alternative strategy for maintaining anchorage may be the use of biological inhibitors of osteoclastic bone resorption. In the present study, we investigated the relative efficacy of pamidronate vs. osteoprotegerin (OPG) in inhibiting bone resorption and tooth movement, using a new orthodontic model in mice in which maxillary molars are moved for prolonged periods by near-constant, clinically relevant forces. Osteoclast influx to compression sites was initiated on day 3, was maximal on day 4, and persisted until at least day 12 after force application. Tooth movement paralleled osteoclast numbers. Minimal osteoclast apoptosis was observed, suggesting that recruitment, rather than programmed cell death, is a critical regulatory mechanism under conditions of constant force. Osteoclasts were reduced at compression sites by both OPG (95%) and pamidronate (70%); tooth movement was more dramatically inhibited by OPG (77% vs. 34%). Our findings indicate that constant orthodontic force regulates the recruitment, activation, and viability of osteoclasts, and that OPG could have clinical utility in preventing undesired tooth movement.

Physical properties of root cementum: Part 9. Effect of systemic fluoride intake on root resorption in rats

INTRODUCTION

Orthodontically induced inflammatory root resorption is a common complication in orthodontic treatment. Fluoride has been reported to have a beneficial effect against root resorption in dental traumatology. The effect of fluoride on orthodontically induced inflammatory root resorption has not been investigated. This study was undertaken to investigate the effect of fluoride on the incidence of root resorption.

METHODS

Thirty-two female 8-week-old Wistar rats were separated into 4 groups. Two groups (6 rats per group) were controls; they did not undergo orthodontic tooth movement. The other 2 groups (10 rats per group) had orthodontic tooth movement consisting of activated 100-g closing nickel-titanium coils (NiTi 10-000-06, GAC International, Bohemia, NY) connecting the mandibular first molar to the incisors. Fluoridated water (100 ppm) was given ad libitum to 1 control and 1 experimental group. The other 2 groups received deionized water. After 2 weeks, the animals were killed, and the samples were harvested. Resorption craters were scanned with a Micro CT (SkyScan 1072, Aartselaar, Belgium). Software analysis of the scanned samples provided a volumetric measurement of the resorption craters on the mandibular molar cementum surface.

RESULTS

Resorption sites were found in the control samples, especially on the distal surfaces; this could be attributed to normal physiological tooth drift. Resorption sites were significantly (P <.05) increased in the groups receiving orthodontic tooth movement.

CONCLUSIONS

Fluoride reduces the size of resorption craters, but the effect is variable and not statistically significant (P >.05).

The effect of drugs on orthodontic tooth movement

OBJECTIVE

Molecules produced in various diseased tissues, or drugs and nutrients consumed regularly by patients, can reach the mechanically stressed paradental tissues through the circulation, and interact with local target cells. The combined effect of mechanical forces and one or more of these agents may be inhibitory, additive or synergistic. The objective of this review is to outline the mechanisms of action and effects of some commonly used drugs on tissue remodeling and orthodontic tooth movement.

DESIGN

All the existing published literature on the effects of various drugs that are prescribed by orthodontists, which are consumed by patients for systemic diseases and those that are known to promote and retard the tooth movement process was obtained and subjected to thorough review process.

RESULTS

All the drugs reviewed have therapeutic effects, as well as side effects, that may influence the cells targeted by orthodontic forces. Therefore, it is imperative that the orthodontist pays close attention to the drug consumption history of each and every patient, before and during the course of orthodontic treatment. When the use of drugs is revealed, their effects and side effects on tissue systems should be explored, to determine their potential influence on the outcome of mechanotherapy.

CONCLUSION

Drug-consumption history must be an integral part of every orthodontic diagnosis and treatment plan.

Effects of human relaxin on orthodontic tooth movement and periodontal ligaments in rats

INTRODUCTION

The rate-limiting step in orthodontic treatment is often the rapidity with which teeth move. Using biological agents to modify the rate of tooth movement has been shown to be effective in animals. Relaxin is a hormone present in both males and females. Its main action is to increase the turnover of fibrous connective tissues. Thus, relaxin might increase the amount and rate of tooth movement through its effect on the periodontal ligament (PDL). The purpose of this study was to measure the effect of relaxin on orthodontic tooth movement and PDL structures.

METHODS

Bilateral orthodontic appliances designed to tip maxillary molars mesially with a force of 40 cN were placed in 96 rats. At day 0, the animals were randomized to either relaxin or vehicle treatment. Twelve rats in each group were killed at 2, 4, 7, and 9 days after appliance activation. Cephalograms were taken at appliance placement and when the rats were killed. Tooth movement was measured cephalometrically in relation to palatal implants. Fractal analysis and visual analog scale assessments were used to evaluate the effect of relaxin on PDL fiber organization at the tension sites in histologic sections. The in-vitro testing for PDL mechanical strength and tooth mobility was performed by using tissue from an additional 20 rats that had previously received the same relaxin or vehicle treatments for 1 or 3 days (n = 5).

RESULTS

Both groups had statistically significant tooth movement as functions of time. However, relaxin did not stimulate significantly greater or more rapid tooth movement. Fractal and visual analog scale analyses implied that relaxin reduced PDL fiber organization. In-vitro mechanical testing and tooth mobility assessments indicated that the PDL of the mandibular incisors in the relaxin-treated rats had reduced yield load, strain, and stiffness. Moreover, the range of tooth mobility of the maxillary first molars increased to 130% to 170%, over vehicle-treated rats at day 1.

CONCLUSIONS

Human relaxin does not accelerate orthodontic tooth movement in rats; it can reduce the level of PDL organization, reduce PDL mechanical strength, and increase tooth mobility at early time points.

Trabecular and cortical bone as risk factors for orthodontic relapse

INTRODUCTION

Dental relapse of the mandibular incisors after orthodontic treatment is a common problem, and few risk factors have been identified. The purpose of this case-control study was to evaluate whether the amount or the structure of mandibular bone affects the potential for postorthodontic mandibular incisor relapse.

METHODS

The subject sample was selected from the postretention database at the University of Washington. Subjects were chosen based on the availability of lateral cephalograms and mandibular periapical radiographs taken approximately 10 years postretention (T3). The mandibular incisor irregularity index (II) was measured on the T3 casts. Two groups were identified: subjects with the II greater than 6 mm (relapse or case) and those with the II less than 3.5 mm (stable or control). Once the case/control status was determined, the II was measured on models taken at the initial orthodontic examination (T1) and at the end of treatment (T2). Sixty relapse and 263 stable subjects were identified. Mandibular cortical thickness measured on both panoramic and lateral cephalometric radiographs was used to assess the amount of mandibular bone, and fractal analysis was used to analyze the trabecular bone structure around the mandibular incisors on the periapical radiographs. Logistic regression analyses were used to determine the association between dental relapse and significant bone parameters. The models were adjusted for potentially confounding variables (initial II, sex, age, and postretention time).

RESULTS

The relapse subjects had a larger mean II at T1 and a longer postretention time than the stable subjects. The mean cephalometric mandibular cortical thickness was significantly smaller in the relapse group than in the stable group at T1, T2, and T3. There were no statistically significant differences in the trabecular structure of bone, as measured with fractal analyses, between the relapse and stable groups.

CONCLUSIONS

These results indicate that patients with thinner mandibular cortices are at increased risk for dental relapse.

Expression of genes for gelatinases and tissue inhibitors of metalloproteinases in periodontal tissues during orthodontic tooth movement

Orthodontic tooth movement progresses by a combination of periodontal ligament (PDL) tissue and alveolar bone remodeling processes. Besides the remodeling of alveolar bone around the moving teeth, the major extracellular matrix (ECM) components of PDLs, collagens, are degenerated, degraded, and restructured. Matrix metalloproteinases (MMPs) and their specific inhibitors, tissue inhibitors of metalloproteinases (TIMPs), act in a co-ordinated fashion to regulate the remodeling of periodontal tissues. We hypothesized that the expression levels of the genes for MMP-2, MMP-9, and TIMPs 1-3 are increased transiently in the periodontal tissue during orthodontic tooth movement. To test this hypothesis, we employed an animal model of tooth movement using rats, as well as in situ hybridization to analyze the expression levels of Mmp-2, Mmp-9, and Timps 1-3. The expression levels of these genes increased transiently in cells of periodontal tissues, which include cementoblasts, fibroblasts, osteoblasts, and osteoclasts, at the compression side of the moving teeth. The transient increases in gene expression at the tension side were mainly limited to osteoblasts and cementoblasts. In conclusion, the expression levels of Mmp-2, Mmp-9, and Timps 1-3 increase transiently during orthodontic tooth movement at both the tension and compression sides. The expression of these genes is regulated differentially in the periodontal tissue of the tension side and compression side. This altered pattern of gene expression may determine the rate and extent of remodeling of the collagenous ECM in periodontal tissues during orthodontic tooth movement.

Progressive, generalized, apical idiopathic root resorption and hypercementosis

BACKGROUND

Root resorption is a multifactorial process that results in loss of tooth structure. The causes of root resorption may vary, leading to several types of resorptions. Some factors have been identified and may be categorized into physiological resorption, local factors, systemic conditions, and idiopathic resorptions. The objective of this report was to present a case of a 17-year-old white female with progressive, generalized, apical idiopathic root resorption followed up for 34 months.

METHODS

Two panoramic radiographs, 14 and 34 months after initial clinical and radiological examinations, showed the rapid progression of apical root resorption. Two molars, teeth #15 and #16, which had to be extracted, and a bone sample from the distal aspect of tooth #15 were processed for histologic analysis.

RESULTS

Two millimeters apical to the cemento-enamel junction, an abrupt increase in the cementum thickness was noted, amounting to 300 and 800 microm in teeth #15 and #16, respectively. The thickening of the cementum layer was due to an accelerated deposition of cellular intrinsic fiber cementum. An unusually high number of mineralization foci were observed in association with acellular extrinsic fiber cementum, and both free and fused cementicles were seen. In contrast to tooth #16, tooth #15 revealed extensive dentin replacement by a bone-like and a cementum-like tissue. Furthermore, ankylosis was demonstrated in tooth #15 and confirmed in the bone sample.

CONCLUSIONS

At present, there is no preventive or therapeutic regimen for the type of root resorption seen in this case report. Treatment usually consists of the extraction of teeth with advanced lesions.

Effect of Topical Administration of Monosodium Olpadronate on Experimental Periodontitis in Rats

BACKGROUND

Periodontitis is characterized by gingival inflammation, periodontal pocket formation, and bacterial plaque that lead to alveolar bone destruction. Research studies have recently begun to evaluate the effect of antiresorptive agents using experimental models of periodontitis. Bisphosphonates are the most frequently tested antiresorptive agents; their main effect is inhibition of bone resorption. The aim of this study was to perform a histomorphometric evaluation of the preventive effect of monosodium olpadronate (OPD), an aminobisphosphonate, on experimental periodontitis (EP).

METHODS

Twenty male Wistar rats were used in this experiment. The animals were assigned to one of two groups: group I: EP; and group II: EP plus topical administration of OPD (EP + OPD). The contralateral side in both groups served as untreated controls (CI and CII), respectively. Mesio-distally oriented sections of each lower first molar were obtained for histomorphometric evaluation.

RESULTS

The treated group (EP + OPD) exhibited marked inhibition of bone loss; interradicular bone volume was significantly greater than that observed in the EP group. The height of the periodontal ligament in the interradicular alveolar bone, which served as an indirect measure of bone loss, was found to be significantly increased in the EP group as compared to the EP + OPD group. Osteoclasts in the OPD treated group were detached from the bone surface, were round in shape, and exhibited a loss of polarity and lack of ruffled borders.

CONCLUSIONS

The dose used herein was found to inhibit bone loss and to cause marked morphologic changes in osteoclasts. The drug effectively prevented bone loss caused by periodontitis.

A influência de medicamentos na movimentação ortodôntica: uma análise crítica da literatura

Neste trabalho analisou-se criteriosamente a literatura pertinente sobre a influência de medicamentos na movimentação dentária induzida, avaliando os métodos experimentais para correlacioná-los com a aplicabilidade e extrapolação para a clínica ortodôntica. Devido aos trabalhos experimentais serem feitos em animais, que têm um tempo de vida curto, as doses dos medicamentos são elevadas e os períodos de administração muito longos. Portanto, não se pode afirmar sobre qualquer alteração na movimentação dentária induzida causada por algum tipo de medicamento que o paciente faça uso durante o tratamento ortodôntico.

Local OPG gene transfer to periodontal tissue inhibits orthodontic tooth movement

Previously, we discovered that RANKL expression is induced in compressed periodontal ligament cells, and that this promotes osteoclastogenesis on the compression side in orthodontic tooth movement. We hypothesized that local OPG gene transfer to the periodontium would neutralize the RANKL activity induced by mechanical compressive force, thereby inhibiting osteoclastogenesis and diminishing tooth movement. The upper first molars of six-week-old male Wistar rats were moved palatally by means of a fixed-orthodontic wire. A mouse OPG expression plasmid [pcDNA3.1(+)-mOPG] was constructed, and the production of functional OPG protein was confirmed in vitro. The inactivated HVJ envelope vector containing pcDNA3.1(+)-mOPG or PBS was injected periodically into the palatal periodontal tissue of upper first molars. When this local OPG gene transfer was performed, OPG production was induced, and osteoclastogenesis was inhibited. Local OPG gene transfer significantly diminished tooth movement. In this study, we report that OPG gene transfer to periodontal tissue inhibited RANKL-mediated osteoclastogenesis and inhibited experimental tooth movement.

Tissue reaction to orthodontic tooth movement in acute and chronic corticosteroid treatment*

OBJECTIVES

To study tissue reaction to orthodontic loading during the course of short- and long-term corticosteroid administration.

DESIGN

'Split-mouth' design to perform orthodontic tooth movement in 64 six-month-old male rats divided into groups: no drug administration (n = 19), acute (n = 22) and chronic (n = 23) 8 mg/kg/day corticosteroid treatment. Performed in the Department of Orthodontics at Aarhus University.

EXPERIMENTAL VARIABLE

The upper left first molar was moved for 21 days. Bone markers were administered at 7 and 2 days before sacrifice. Histological sections were cut at the coronal level.

OUTCOME MEASURE

Tooth movement rate, alveolar socket area, the relative extension of alveolar wall with erosion, and the mineralizing surfaces were measured and compared in the three groups.

RESULTS

Tooth movement rate increased in the chronic group. The mechanical load induced an enlargement of the alveolar wall that was less pronounced in both medicated groups. In the acute group the drug suppressed bone resorption and formation without mechanical stimulus. Force application resulted in significant increase in the relative extension of resorption and formation in both drug groups; it was particularly pronounced in the chronic group.

CONCLUSION

Because acute corticosteroid ingestion reduces bone turnover, in these patients orthodontic treatment might best be postponed until a time the patient is free of the drug. Chronic steroid ingestion leads to an increased biological reaction to mechanical perturbation indicating that the orthodontic force level should be reduced and controlled more frequently in patients on chronic steroid treatment.

Tissue reaction to orthodontic tooth movement in different bone turnover conditions

OBJECTIVES

To study the tissue reaction to orthodontic load in normal, high, and low bone turnover states.

DESIGN

'Split mouth' design performing orthodontic tooth movement in 52, 6-month-old male rats with: normal (n = 19), high (n = 16), and low bone turnover (n = 17), the latter two being obtained by induction of hyperthyroidism and hypothyroidism, respectively. Performed at the Department of Orthodontics at Aarhus University.

EXPERIMENTAL VARIABLE

The upper left first molar was moved for 21 days. Bone markers were administered 7 and 2 days before killing. Histological sections were cut at the coronal and apical levels.

OUTCOME MEASURE

Alveolar socket area, periodontal ligament width, the relative extension of alveolar wall with erosion surfaces, and the mineralizing surfaces were measured and compared in the three groups.

RESULTS

Alveolar socket, periodontal ligament width, and erosion surface were larger on the treated than on the control side in the three groups. The normal and hypothyroid groups showed a wider periodontal ligament at the bucco-distal site at the coronal level, while the hyperthyroid group showed a widening which was not spatially oriented. The normal and hyperthyroid groups showed higher erosion at the corono-mesial site. The mineralizing surfaces were larger on the treated than on the control side in the normal and hypothyroid groups, but not in the hyperthyroid group.

CONCLUSION

In the hyperthyroid group, the widening of the periodontal ligament was not spatially oriented and the increased erosion was not accompanied by increased formation, as observed in the normal and hypothyroid groups.

Involvement of nitric oxide in orthodontic tooth movement in rats

Nitric oxide (NO) is an important regulatory molecule in bone formation and resorption. The purpose of this study was to examine the role of NO in orthodontic tooth movement in rats. We used specific inhibitors of NO synthases (NOS). Upper first molars of 9-week-old male Wistar rats were moved buccally for 21 days. The local administration of N(G)-nitro-L-arginine methyl ester. HCl (L-NAME), a general inhibitor of NOS activity, significantly reduced tooth movement. On the other hand, N(6)-(1-iminoethyl)-L-lysine. 2HCl (L-NIL), a selective inhibitor of the inducible isoform of NOS, had no effect. These results suggest that NO is an important biochemical mediator in the response of periodontal tissue to orthodontic force and is produced primarily through the activity of constitutive NOS.

Estrous-cycle-dependent variation in orthodontic tooth movement

Sex hormones, including estradiol, play important physiological roles in bone metabolism. The purpose of this study was to investigate whether there is estrous-cycle-dependent variation in orthodontic tooth movement, and, if so, to determine the mechanism. Ten-week-old female Wistar rats were used. They received repeated orthodontic force during specific phases in the estrous cycle. Tooth movement in animals that received force principally in estrus was about 33% greater than that in animals that received such force principally in pro-estrus (p < 0.05). Serum estradiol levels also varied according to the estrous cycle, with a peak during pro-estrus and a nadir during estrus, and were inversely related to tooth movement. Furthermore, there were negative correlations between estradiol and both serum TRAP activity and pyridinoline (r = -0.42, p < 0.05; r = -0.59, p < 0.001). These results suggest that cyclic changes in the estradiol level may be associated with the estrous-cycle-dependent variation in tooth movement through its effects on bone resorption.

Effects of topical administration of clodronate on alveolar bone resorption in rats with experimental periodontitis

BACKGROUND

We examined whether topical administration of a bisphosphonate clodronate could prevent alveolar bone loss in rats with experimental periodontitis.

METHODS

On day 0, elastic rings were placed around the cervix of the right and left maxillary first molars (M1) to induce inflammatory periodontitis. Fifty microl of clodronate solution at a concentration of either 0 (0.9% NaCl), 20, 40, or 60 mM was injected into the subperiosteal palatal area adjacent to the interdental area between M1 and M2 on either the left or right (experimental) side on days 0, 2, 4, and 6. The contralateral side served as a control and received 0.9% NaCl solution without clodronate. The animals were sacrificed on day 7.

RESULTS

Histological examination and determination of bone mineral density in the interdental alveolar bone area between M1 and M2 revealed that placement of an elastic ring caused severe vertical and horizontal bone resorption on the control side, while the topical administration of clodronate significantly prevented such alveolar bone loss. The number of osteoclasts on the experimental side was decreased compared with the control side. Furthermore, many of the osteoclasts on the experimental side were detached from the surface of the alveolar bone and had degenerated appearances, such as rounded shapes and a loss of polarity.

CONCLUSIONS

These results suggest that topical administration of clodronate may be effective in preventing osteoclastic bone resorption in periodontitis.

Review of risedronate in the treatment of osteoporosis

Risedronate (Actonel, Procter & Gamble and Aventis) is a novel, orally administered pyridinyl bisphosphonate. Preclinical studies have shown that risedronate is a potent inhibitor of osteoclasts. Risedronate inhibited bone resorption and increased bone density in the spine and hip. Prospective, randomised, placebo-controlled trials (RCTs) in patients with postmenopausal osteoporosis (PMO) have demonstrated that risedronate decreased the risk of vertebral fractures by up to 49% and of non-vertebral fractures by up to 39% over 3 years in postmenopausal women with one or more prevalent vertebral fractures. This reduction of the risk for vertebral fractures was significant from the first year of treatment (risk reduction up to 65%). Risedronate was the first bisphosphonate to be studied in a large RCT with prevention of hip fracture as the primary end point. In this study, risedronate reduced the risk of hip fracture by 40% in elderly women with low hip bone density and one clinical risk factor for hip fracture and by 60% in women with low bone density and a prevalent vertebral fracture at baseline. Risedronate was also effective in the prevention and treatment of bone loss in glucocorticoid-induced osteoporosis (GIO), with a positive effect on vertebral fractures within the first year. Risedronate was well-tolerated with a safety profile comparable to placebo in all clinical studies. Patients with a previous or current history of upper GI illness or who were taking NSAIDs or aspirin were not excluded from these studies. Importantly, the upper GI safety profile of risedronate was shown to be similar to that of placebo in endoscopic studies. There was no evidence of acute-phase reactions or primary mineralisation defects. The most appropriate dose of risedronate was 5 mg/day.

Bisphosphonate administration alters subcellular localization of vacuolar-type H(+)-ATPase and cathepsin K in osteoclasts during experimental movement of rat molars

This study was designed to clarify the effects of bisphosphonate (BP) administration on structure and functions of osteoclasts in alveolar bone resorption during experimental movement of rat molars. To produce orthodontic force, elastic band was inserted between the upper first and second molars for 4 days, and dissected maxillae were then examined by means of light and electron microscopic immunocytochemistry for vacuolar-type H(+)-ATPase and lysosomal cystein proteinase, cathepsin K in osteoclasts. Vacuolar-type H(+)-ATPase and cathepsin K in osteoclasts are the most important enzymes for demineralization of apatite crystals and degradation of bone type-I collagen, respectively. At 1 day before elastic band insertion, BP was administered intraperitoneally. Control rats received the same volume of physiologic saline. In BP-administered rats, most osteoclasts exhibited either irregularly-formed ruffled borders and clear zones or only clear zones of various degrees of extension. Subcellular localization and expression of both vacuolar-type H(+)-ATPase and cathepsin K was significantly decreased in such osteoclasts with impaired ruffled borders and/or only clear zones by BP administration. In particular, cathepsin K secretion by osteoclasts towards resorption lacunae was markedly inhibited by BP administration. Our results indicate for the first time that BP administration significantly impair the osteoclast structure and reduces expression of both vacuolar-type H(+)-ATPase and cathepsin K in osteoclasts during tooth movement.

An ultrastructural study of the effects of bisphosphonate administration on osteoclastic bone resorption during relapse of experimentally moved rat molars

This study was designed to clarify the effects of systemic administration of bisphosphonate, pamidronate, on the bone resorbing activity of osteoclasts during relapse of rat molars, after experimental movement. An elastic band was inserted between the upper first and second molars of 7-week-old rats and removed 21 days later. At 1 day before elastic band removal, bisphosphonate was administered via a tail vein. After elastic band removal, the rats were further maintained for 0, 5, or 10 days. The relapse of the first molars was studied by means of light and scanning-electron and transmission-electron microscopy. When an elastic band was removed, the mean interdental distance between the first and second molars in all rats was approximately 435 micrometer. In the control rats, it had decreased to 108 micrometer by day 5 and 57 micrometer by day 10. In these control rats, numerous osteoclasts appeared along the alveolar bone surface in the compressed side of the periodontal ligament of first molars. Administration of bisphosphonate significantly inhibited the prominent decrease in interdental distance. In these rats, it averaged 313 micrometer at day 5 and 115 micrometer at day 10. In bisphosphonate-treated rats, osteoclasts aggregated mainly in vascular canals of alveolar bone but were occasionally observed along the alveolar bone surfaces facing the periodontal ligament. Administration of bisphosphonate also induced structural changes, such as disappearance of ruffled borders and cytoplasmic polarity, in osteoclasts. A degenerated osteoclast was also observed in a bisphosphonate-treated rat. However, bisphosphonate induced no structural changes in osteoblasts, osteocytes, or periodontal ligament fibroblasts. These results suggest that a single systemic administration of bisphosphonate decreases the extent of initial relapse in experimentally moved rat molars via a mechanism involving impairment of the structure and resorptive functions of osteoclasts.

Inhibitory effect of the topical administration of a bisphosphonate (risedronate) on root resorption incident to orthodontic tooth movement in rats

Root resorption associated with tooth movement is an unsolved problem in orthodontics. If such root resorption could be prevented, it would be an important contribution toward reducing risk factors in orthodontic treatment. The purpose of this study was to examine the effects of the topical administration of a bisphosphonate, risedronate, which is known to be a potent blocker of bone resorption, on root resorption during tooth movement and on the repair of the resorbed root surface after tooth movement in rats. In the first experiment, both the right and left upper first molars were moved buccally with a standardized expansion spring under administration of risedronate. After day 7, extensive root resorption had occurred on the control side, and the area of root resorption reached a maximum on day 14. The topical administration of risedronate caused a significant and dose-dependent inhibition of root resorption after the orthodontic force was applied. In the second experiment, the right and left upper molars were first moved buccally for 3 weeks. Risedronate treatment began on the day the spring was removed. After the force was withdrawn, the resorbed root surfaces on both the control and risedronate-treated sides were gradually restored by apposition of repair cementum (cementoid). The topical administration of risedronate did not appear to inhibit the repair process of root resorption. These results suggest that the topical administration of risedronate may be useful in preventing root resorption of teeth during orthodontic treatment.

Localization of glycosaminoglycans in periodontal ligament during physiological and experimental tooth movement

Localization of chondroitin sulphates in periodontal ligaments (PDL) of rat molar roots during physiological and experimental tooth movement were analysed immunohistochemically with the use of monoclonal antibodies, 3B3 and 2B6, specific to chondroitin 6-sulphate (CH-6S) and chondroitin 4-sulphate/dermatan sulfate (CH-4S/DS), respectively. The maxillary first molars of experimental animals were forced to move laterally with a 10 g weight by U-shaped wires for 3 and 7 d. In control animals, 3B3 epitope was seen in the PDL near to the bone surface facing the distal half of roots, which corresponded to the compressive side during physiological tooth movement. Immunoreactivity for 2B6 was weak or negative in the PDL. Both epitopes were present at osteoid, precementum, lacunae and canaliculli of osteocytes and cementocytes. In 3-d-treated animals, the early stage of hyalinization characterized with visible cells and fibres was observed in the PDL at the buccal side of the mesial root, which showed intense immunoreactivity for 3B3. Further 3B3 positive area seen in control animals changed its position from the distal to the buccal side of the PDL. Immunoreactivity for 2B6 did not change in the PDL of 3-d-treated animals. In 7-d-treated animals, the typical hyalinization characterized with no visible cells and fibres was seen in the PDL at the buccal sides of both mesial and disto-buccal roots, where both epitopes were present at the peripheral part of the tissue. Observation of serial sections suggested that the 3B3-positive area was present at the peripheral part of the 2B6-positive area. The present results suggest that the expression of CH-6S is related to the compressive force in non-hyalinized and hyalinized PDL, whereas that of CH-4S/DS is not influenced by the mechanical stress.