Alveolar Bone Remodeling Research Articles

To beam or not to beam: that is the question: Author response

In response to the letter by Aps1 concerning our papers published in DMFR2 and the September 2012 issue of the European Journal of Paediatric Dentistry (EJPD),3 we would like to provide clarification and evidence of the careful approach taken to the orthodontic and radiological procedures employed in these studies. Importantly, we would like to clarify that the authors do not use ionizing radiation as a daily orthodontic diagnostic tool. Careful dosage and ionizing radiation should be used only in specific clinical conditions such as impacted canines, supernumerary teeth and temporomandibular joint arthritis, and in planning orthognathic surgery.4 As was reported clearly in the article and could be seen easily in the figures, all patients in the study sample presented with severely displaced maxillary canines. Canine impaction is one of the clinical conditions in orthodontics for which evidence-based research for the clinical application of three-dimensional (3D) imaging exists. Thus, the primary indication for the low-dose CT was to evaluate the position of displaced intraosseus canines in the maxilla. These data cannot be detected using dental casts. While it is true that the position of the crown determines the surgical approach and direction of traction, the direction of eruption and location of the root apex play important roles in the orthodontic mechanics, avoiding damage to adjacent teeth and improving the effectiveness of canine traction.5 Hofmann et al6 developed a system on 3D imaging that allows for accurate evaluation of the position of the displaced canines relative to three spatial planes. The Department of Orthodontics at the University of Rome “Tor Vergata” is specialized in the treatment of impacted canines often associated with other dental anomalies such as supernumerary teeth and missing or peg-shaped lateral incisors.7,8 Consequently, we applied the protocol reported in several papers9–12 demonstrating that rapid maxillary expansion (RME) is an orthopaedic procedure that improves the initial intraosseus position of the canines and increases the rate of eruption of palatally displaced maxillary canines compared with an untreated control group. The present study sample is a very unique sample in the literature, and it allowed for scientific investigation of the skeletal, dental and periodontal effects of RME, one of the procedures most commonly applied and most debated in orthodontics. All of these effects (which cannot be derived using dental casts only) were analysed using the same sample in different publications by our research group.2,13–16 The imaging protocol in the present study was carefully planned with our radiologist to minimize patient dosage in low-resolution and small field of view (FOV) image acquisitions. The trained radiology technician reduced the voltage to the lowest possible level (80 kV) and restricted the area investigated strictly to the maxilla, adapting the FOV from a minimum of 6 cm to a maximum of 13 cm. Despite this, the accuracy of the measurements performed was not compromized. With this careful imaging protocol, the radiation dosage of three low-dose CT scans, considering their stochastic effect, is much smaller and not comparable to one multislice skull CT. The two images published in the EJPD demonstrate, contrary to what is claimed by Professor Aps, the high level of standardization involved where imaging acquisition was carried out by a single radiographer at the same scanner console, and the careful positioning of the patients' heads. Head position was standardized using perpendicular light beams, and the axial CT images were reconstructed always as parallel to the palatal plane and passing through the trifurcation of the right upper first molar, with the same method reported in numerous previous articles.17–28 For this reason, it was not necessary to add a figure; in addition, with the device in situ, it was possible to draw clearly the circle area because the expander was located in a more occlusal position at crown level, while the axial images were at the root level of anchored tooth. We thank Professor Aps for sharing the link to Image Gently, which is an initiative we certainly applaud. We absolutely agree that imaging as gently as possible, keeping the patient benefits and risks in mind, is our most sincere goal. In summary, as paediatric dentists, we are guarding over the health of our young patients, and as orthodontists, it is our duty to plan a treatment as conservative as possible, especially in clinical cases that need a combined surgical–orthodontic approach. Thus, all subjects of the study sample benefited from this research protocol and achieved successful treatment outcomes thanks to adequate treatment planning based on careful use of the right diagnostic tools.

Effect of alendronate on bone remodeling around implant in the rat

PURPOSEThe purpose of this study was to evaluate the effect of alendronates on bone remodeling around titanium implant in the maxilla of rats.MATERIALS AND METHODSThe maxillary first molars were extracted and customized-titanium implants were placed immediately in thirty male Sprague-Dawley rats. The rats were divided into experimental (bisphosphonate) group and control group. At 4 weeks after implantation, the rats in the bisphosphonate group were subcutaneously injected with alendronate three times a week for 6 weeks where as the rats in control group were injected with saline. The rats were sacrificed at 1, 2, 3, 4, or 6 weeks after starting of injection and maxillary bones were collected subsequently. Alveolar bone remodeling around the implants were evaluated by radiographic and histologic analysis. Microarray analysis and immunohistomorphologic analysis were also performed on one rat, sacrificed at 6 weeks after starting of injection, from each group. Statistical analysis was performed using repeated measures analysis of variance and independent t test at a significance level of 5%.RESULTSThere was no statistically significant difference in the bone area (%) around implant between the bisphosphonate group and the control group. However, the amount of empty lacuna was significantly increased in the bisphosphonate group, especially in the rats sacrificed at 4 weeks after starting of injection compared to that of the corresponding control group. The bisphosphonate group showed the same level of TRAP positive cell count, osteocalcin and angiopoietin 1 as the control group.CONCLUSIONAlendronate may not decrease the amount of osteoclast. However, the significantly increased amount of empty lacuna in the bisphosphonate group may explain the suppression of bone remodeling in the bisphosphonate group.

Effect of orthodontic tooth movement on salivary levels of Interleukin-1beta, Tumor Necrosis Factor-alpha, and C- reactive protein

Orthodontic force is considered to stimulate cells in the periodontium to release many mediators such as cytokines which play a responsible role for periodontal and alveolar bone remodeling, bone resorption and new bone deposition. Aim of this study was carried out to estimate changes of the (interleukin-one beta, tumor necrosis factor - alpha and C-reactive protein) levels in unstimulated whole saliva during the leveling stage of orthodontic tooth movement. Materials and methods: The sample consisted of thirty adult patients (12 males and 18 females) with ages ranges (19- 23) years. Each sample had Class I and Class II malocclusion dental classification and required bilateral extraction of their maxillary first premolars, underwent a session of professional oral hygiene and received oral hygiene instructions before and during the period of study, one month later fixed orthodontic appliance were placed in the upper arch by using 0.014 nickel titanium arch wire. The unstimulated whole saliva was taken from each sample immediately before placement of the appliance (baseline), and at (after1hour, after one week and after two week) following placement of the fixed orthodontic appliance. In addition the plaque index and gingival index were recorded during the interval periods of this study to assess oral cleanliness. The interleukin - one beta and tumor necrosis factor- alpha were determined by enzyme linked immunosorbent assay, while the C-reactive protein was determined by latex agglutination. Results: The results of the present study found the mean value of both salivary (interleukin-one beta and tumor necrosis factor -alpha) were highest at (after1hour) followed by at (after one week) then at (after two week) than the baseline with highly statistical significant differences (P 0.05). While the mean values of C-reactive protein were higher at (after 1hour) only with highly significant differences (P< 0.01) among females and total samples while only significant difference (P<0.05) for males, in addition there were no statistical significant differences between males and females. Regarding the correlation between salivary (interleukin - one beta and tumor necrosis factor -alpha), there were positive correlation between them at all periods of study. Moreover there were positive correlation between salivary (interleukin - one beta and tumor necrosis factor -alpha) and salivary C- reactive protein. On the other hand there were no association between the salivary (interleukin - one beta and tumor necrosis factor -alpha and C-reactive protein) and clinical parameter (plaque index and gingival index). Conclusion: From this clinical study we conclude that orthodontic force induces increasing the levels of (interleukin - one beta, tumor necrosis factor -alpha, C-reactive protein) in unstimulated whole saliva during orthodontic tooth

Local use of iontophoresis with traditional Chinese herbal medicine, e.g., Gu-Sui-Bu (Rhizoma Drynariae) may accelerate orthodontic tooth movement

Introduction: Mechanical force is not the only means to cause tooth movement, but just one kind of stimuli for it. Biological stimuli, with potential of accelerating alveolar bone remodeling, other than mechanical force, have been attracted by orthodontists who are combating prolonged treatment duration. It has been approved that some traditional Chinese medicines, such as Gu-Sui-Bu (Rhizoma Drynaria), affect the process of bone remodeling. The Hypothesis: We make the hypothesis that local use of iontophoresis with Gu-Sui-Bu (Rhizoma Drynaria) as a non-invasive and safe drug delivery system with no trauma, risk of infection or damage to patients is a new potential approach for accelerating orthodontic tooth movement, and shorten the orthodontic treatment time. Evaluation of the Hypothesis: Gu-Sui-Bu is effective at inducing bone remodeling, and iontophoresis as a non-invasive technique for drug delivery, is suitable for the transmission of some traditional Chinese herbal medicines into periodontal tissues.

Periodontal effects with self ligating appliances and laser biostimulation.

Background:Recently, various biostimulation's effects of low energy laser irradiation have been reported. The present study was designed to examine the effects of low-energy laser irradiation on alveolar bone remodelling during orthodontic tooth movement and finally on formation of new keratinized gingiva.Materials and Methods:22 patients and 27 teeth in vestibular mucosal without keratinized gingiva were selected. Every patient was treated with self ligating appliances. In every orthodontic session the patient was treated with Diode laser biostimulation. At the moment of debonding, 27 teeth involved in the research were evaluated in terms of quality and quantity of attached gingiva. BOP and CAL loss were investigated.Results:Every tooth considered at the end of orthodontic treatment showed an attached gingiva around the crown: The average of keratinized gingiva at the end of the study was 3.10 mm and the mean increasing at each month was 0,49 mm.Conclusions:The combination between self ligating appliances and laser's biostimulation could improve the differentiation of periodontal ligaments stem cells in fibroblasts, able to promote attached gingiva around the crown of the teeth erupted in oral vestibular mucosa.

Effects of vascular endothelial cells on osteogenic differentiation of noncontact co‐cultured periodontal ligament stem cells under hypoxia

During periodontitis or orthodontic tooth movement, the periodontal vasculature is severely impaired by chronic inflammation or excessive mechanical force. This leads to a hypoxic microenvironment of the periodontal cells and enhances the expression of various cytokines and growth factors that may regulate angiogenesis and alveolar bone remodeling. However, the role of hypoxia in regulating the communication between endothelial cells (ECs) and osteoblast progenitors during the remodeling and repair of periodontal tissue is still poorly defined. The aim of this study was to investigate the effects of vascular ECs on osteogenic differentiation, mineralization and the paracrine function of noncontact co-cultured periodontal ligament stem cells (PDLSCs) under hypoxia, and further reveal the involvement of MEK/ERK and p38 MAPK pathways in the process. First, PDLSCs were obtained and a noncontact co-culture system of PDLSCs and human umbilical vein endothelial cells was established. Second, the effects of different time-periods of hypoxia (2% O(2) ) on the osteogenic potential, mineralization and paracrine function of co-cultured PDLSCs were investigated. Third, ERK1/2 and p38 MAPK activities of PDLSCs under hypoxia were measured by western blotting. Finally, we employed specific MAPK inhibitors (PD98059 and SB20350) to investigate the involvement of ERK1/2 and p38 MAPK in PDLSC osteogenesis under hypoxia. We observed further increased osteogenic differentiation of co-cultured PDLSCs, manifested by markedly enhanced alkaline phosphatase (ALP) activity and prostaglandin E(2) (PGE(2)) levels, vascular endothelial growth factor (VEGF) release, runt-related transcription factor 2 (Runx2) and Sp7 transcriptional and protein levels and mineralized nodule formation, compared with PDLSCs cultured alone. ERK1/2 was phosphorylated in a rapid but transient manner, whereas p38 MAPK was activated in a slow and sustained way under hypoxia. Furthermore, hypoxia-stimulated transcription and expression of osteogenic regulators (hypoxia-inducible factor-1α, ALP, Runx2, Sp7, PGE(2) and VEGF) were also inhibited by PD98059 and SB203580 to different degrees. Further increased osteogenic differentiation and mineralization of co-cultured PDLSCs under hypoxia were regulated by MEK/ERK and p38 MAPK pathways. And the ECs-mediated paracrine of PGE(2) and VEGF may facilitate the unidirectional PDLSC-EC communication and promote PDLSCs osteogenesis.

Alveolar Bone Remodeling Around Immediate Implants Placed in Accordance With the Extraction Socket Classification: A Three‐Dimensional Microcomputed Tomography Analysis

Previous studies assessed bone remodeling after a single tooth extraction; however, the effect of multiple contiguous teeth extractions around immediate implant remains unknown. The aim of this microcomputed tomographic investigation is to analyze the alveolar bone remodeling around immediate implants placed in accordance with the extraction socket classification (ESC). Under general anesthesia, 10 beagle dogs underwent atraumatic tooth extractions. Animals were randomly divided into three groups, with 16 sites per group: 1) ESC-1, single tooth extraction; 2) ESC-2, two contiguous teeth extraction; and 3) ESC-3, more than two contiguous teeth extractions. Immediate implants were inserted in each socket, and postoperative plaque control measures were undertaken. After euthanasia, the jaw segments were evaluated for bone thickness, marginal bone loss (MBL), and bone-to-implant contact (BIC) using microcomputed tomography. The mean buccal bone thickness (P <0.05) and MBL (P <0.05) was compromised in jaws in ESC-3 compared to those in ESC-1 and ESC-2. The BIC was significantly higher among jaws in ESC-1 compared to those in ESC-2 and ESC-3 (P <0.05). There was no significant difference in the buccal bone thickness, MBL, and BIC among the groups in the maxilla and mandible. Lingual bone remodeling did not reveal any significant differences among the groups in either jaw. Buccal bone remodeling is significantly more extensive around immediate implants placed in multiple contiguous tooth extraction sites compared to immediate implants placed in single tooth extraction sites.

Effects of insulin‐like growth factor I on alveolar bone remodeling in diabetic rats

Diabetes is a chronic hyperglycemic disorder and results in a tendency to develop osteoporosis. Furthermore, the delayed healing of tooth-extraction wounds, the activation of alveolar resorption and the suppressed formation of bone around implants are difficult for dentists to resolve. In diabetes, insulin-like growth factor I (IGF-I) appears to enhance the differentiation of osteoblasts and to activate the mineralization of bone. Hence, the aim of this study was to investigate the effects of insulin-like growth factor I on the remodeling of alveolar bone in diabetic rats. Diabetes was induced in 40 male Sprague-Dawley rats by intravenous administration of alloxan. The teeth of the rats were extracted to investigate remodeling of alveolar bone. Insulin-like growth factor I was administered, via intraperitoneal injection, to diabetic rats following tooth extraction. The remodeling of alveolar bone was determined using radiographic data, histological analyses and tetracycline fluorescence labeling. Compared with the control group, diabetes decreased alveolar bone formation. The height of alveolar bone and the bone-formation rate was significantly lower in the untreated diabetic group than in the control group or in the treated rats. Treatment with insulin-like growth factor I not only regulated abnormal blood glucose levels but also increased the height of the alveolar bone and increased the bone-formation rate relative to the results in diabetic animals. Furthermore, the expression of glucose transporter-1, the main transporter of glucose, was changed by hyperglycemia. The results suggest that insulin-like growth factor I treatment increases the volume of newly formed bone following tooth extraction and normalizes the expression of glucose transporter-1 in diabetic rats, which may play an important role in bone formation and mineralization.

Initial responses of osteoblasts derived from human alveolar bone to various compressive forces

Mechanical stress generated by orthodontic force is recognized as a major factor in the modulation of alveolar bone remodeling. During this process, osteoblasts play a crucial role, not only by participating in bone formation but also by promoting osteoclastogenesis. The aim of this study was to investigate how continuous compressive force (CF) affects human primary osteoblasts (HOBs) in terms of cell proliferation, apoptosis, and expression of interleukin-6 (IL-6) and chemokine CXC ligand 8 (CXCL8). Human primary osteoblasts, isolated from human mandibular bone pieces, were cultured with or without CF (1-4 g cm(-2)) for up to 72 h. Cell viability and proliferation were evaluated using the MTT assay. RT-PCR was used to determine the levels of expression of KI67 (a proliferation marker), BAX (a pro-apoptotic marker), BCL2 (an apoptotic inhibitor), IL6, and CXCL8 mRNAs, while a multiplexed bead immunoassay was used to measure the release of IL-6 and CXCL8. The results revealed that CF decreased cell viability and proliferation in a time- and force-dependent manner. After applying CF for 24 h, the mRNA expression of KI67 was markedly inhibited, whereas the mRNA expression of BAX and BCL2 was unaltered. In addition, CF enhanced the levels of IL6 and CXCL8 mRNAs in a force-dependent manner, whereas the levels of the corresponding proteins were reduced in the compressed HOBs.

A methodological approach to assessing alveolar ridge preservation procedures in humans: hard tissue profile

Multiple surgical protocols using biomaterials have been proposed to limit the typical post-extraction bone resorption. However, because of the heterogeneity of the studies, particularly the differences in assessment methods, it is difficult to determine the superiority of one technique over another. The objective of this study was to describe a new radiographic method to draw a map of alveolar bone remodelling after alveolar ridge preservation procedures to compare different surgical techniques more accurately. The newly developed measuring method was applied to a case series describing a specific preservation technique. Fourteen extraction sites (in 14 patients) located in the upper anterior maxilla were treated with bovine hydroxyapatite (0.25- to 1-mm particles) and a saddled connective tissue graft. A radiographic three-dimensional assessment of the hard tissues was performed at baseline and 3months after the procedure. Standardized horizontal measurements were taken at three corono-apical levels (-2, -5 and -9mm) and at three mesio-distal levels (mesial, centre and distal) in the buccal and palatal aspects. Vertical measurements were also recorded in nine regions superior to the alveolar crest. The measurements were performed by two independent observers and intra- and inter-observer effects were evaluated. No inter- and intra-observer effects were found when analysing the measurements from these two observers. The horizontal dimension of the crest decreased by 1.6mm (20%) in the cervical regions (-2mm level), decreased moderately, by 1mm (12%), at the -5mm level and decreased very little, 0.5mm (6%), at the apical (-8mm) level. The losses were always significantly higher in the buccal than in the palatal aspect. Buccally, the maximal bone remodelling at the cervical level remained below 1mm. Vertical bone resorption was homogeneous and<1mm in the nine measured regions. The radiographic measuring methodology proved to be reproducible. It can be applied in other clinical settings. It successfully assessed the alveolar ridge preservation technique (BHA+saddle connective tissue graft).

Effect of Reveromycin A on Experimental Tooth Movement in OPG−/− Mice

In osteoprotegerin-deficient (OPG−/−) mice, osteoclast activity causes bone resorption to outpace bone formation, leading to the development of severe osteoporosis. Such mice are therefore useful for investigating the alveolar bone of patients with osteoporosis. Reveromycin A (RM-A) was recently identified as the unique agent acting on osteoclast activation. This study aimed to analyze the effect of RM-A on the orthodontic treatment of OPG−/− mice (a model of osteoporosis patients with high levels of bone turnover). We examined alveolar bone remodeling in OPG−/− and wild-type (WT) mice during continuous tooth movement. The orthodontic force was induced by means of a Ni-Ti closed-coil spring to move the maxillary first molar for 14 days. RM-A sodium salt (1 mg/kg) was administered intraperitoneally twice daily. In OPG−/− mice, the tooth movement distance was longer, alveolar bone resorption was enhanced, the osteoclast count was greater, and serum alkaline phosphatase and tartrate-resistant acid phosphatase levels were higher relative to those in WT mice. However, the administration of RM-A in OPG−/− mice reduced these parameters. We conclude that RM-A normalizes bone metabolism and loss of alveolar bone during continuous tooth movement in OPG−/− mice.

Magnetic bead-based salivary peptidome profiling analysis during orthodontic treatment durations

Orthodontic treatment induces various biological responses, including tooth movement and remodeling of alveolar bone. Although some studies have investigated the contribution of orthodontic procedures to changes in saliva conditions, little is known about the effects of different treatment durations on the saliva proteome. To identify the discriminating protein profiles in unstimulated whole saliva of orthodontic patients with different treatment durations, we used matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) combined with magnetic bead, and peptide mass fingerprints were created by scanning MS signals. Saliva samples from 40 patients (10 in each of four groups: the group without an appliance and groups under treatment for 2, 7, and 12months) were analyzed. The results showed eight mass peaks with significant differences. Furthermore, mass peak intensities at proteins 1817.7, 2010.7, 2744 and 2710.2Da represented a steady time-dependent increasing trend, whereas protein 4134Da exhibited a decreasing tendency. Differential expression of the peptidome profile also occurred in the multiple comparisons, and we established a fitting model. Thus, the potential discriminating biomarkers investigated in this study reflected the complicated changes in periodontal tissues during orthodontic treatment and indicated dynamic interactions between orthodontic treatment and the saliva proteome. The results provide novel insights into alterations in salivary proteins due to different orthodontic treatment durations and may lead to the development of a therapeutic monitoring strategy for orthodontics.

Numeric simulation of functional remodeling of the anterior alveolar bone

To study the remodeling of the anterior alveolar bone with parodontium under physiology loading using finite element method (FEM) and theory of bone remodeling. A FEM model of the maxillary central incisor with parodontium was established, and the change of bone density during the remodeling of alveolar bone was investigated under physiology loading (60 - 150 N) based on the theory of bone remodeling about strain energy density (SED). The finite element analysis software Abaqus user material subroutine (UMAT) were used. With the increase of physiology loading, the pressure stress on the buccal cervical margin increased gradually while the density was decreased gradually. The cortical bone was lower than its initial density 1.74 g/cm(3), which was 1.74 - 1.63 g/cm(3). The density of cancellous bone was 0.90 - 0.77 g/cm(3), which was lower than its intial density 0.90 g/cm(3). The lingual cervical margin was under tensile stress which also increased with loading, the density had no significant change. When the achieve to 120 N, the density of cortical bone was 1.74 - 1.73 g/cm(3). No significant change was found in the cancellous bone. The simulation of the perodontium remodeling is achieved and proved to be effective by the relevant research based on the method of the study. And the result will be helpful to form the basis of analysis bone remodeling process and predict the results in the clinical work.

The early phase response of rat alveolar bone to traumatic occlusion

ObjectivesOcclusal trauma is an important factor to influence alveolar bone remodelling, the effect of which includes many cytokines and signalling pathways. However, the exact mechanism of the traumatic stimulus for alveolar remodelling is still unclear. The purpose of the present study was to investigate the early responses of alveolar osteocytes to occlusal trauma through genome-wide microarray. MethodsThe occlusal surface of the upper left first molar of rat was raised by placing a stainless steel wire to induce occlusal trauma in the lower left first molar. After 24h, we took out the alveolar bone tissue of the first molars at the both sides of rats’ lower jaws under anaesthesia. The different gene expressions were showed by genome-wide microarray, which comprises about 27,000 genes and the results were examined by quantitative RT-PCR. ResultOf the approximately 27,000 genes, the expression of 586 genes was strongly changed. These findings clearly demonstrated that in the early response of the alveolar bone to occlusal trauma, the expression of osteoblast, collagens, bone mineralization, bone remodelling and WNT, TGF-β pathway related cytokines decreased, and osteoclast-specific cytokines have no significant changes in expression. ConclusionThese results suggested that at early phase of the occlusal trauma, osteogenesis in rat's alveolar bone was inhibited, and osteoclastogenesis was not significant.

Enhanced alveolar bone loss in a model of non‐invasive periodontitis in rice rats

The rice rat (Oryzomys palustris) develops periodontitis-like lesions when fed a diet rich in sucrose and casein (H-SC). We aimed to establish whether this model can accurately mimic the development of human periodontitis. For this purpose, 28-day-old rice rats (15/group) were assigned to standard (STD) or H-SC diets and sacrificed after 6, 12, and 18 weeks. Jaws were processed for morphometric, histometric, histologic, histomorphometric, and micro-CT analyses. We found a progressive increase in horizontal alveolar bone loss (ABL) with age in maxillae of rats fed the STD diet as determined by morphometry. The H-SC diet exacerbated horizontal ABL at the palatal surface at 12 and 18 weeks. Furthermore, increased vertical ABL was detected in mandibles and maxillae of rats fed the H-SC diet for 12 and/or 18 weeks by histometry and micro-CT. Remarkably, the H-SC diet significantly increased bone remodeling at the interproximal alveolar bone of mandibles from rats fed for 6 weeks, but not in those fed for longer periods. These findings indicate that the H-SC diet induced a transient increase in alveolar bone remodeling, which is followed by ABL characteristic of moderate periodontitis.

Biological evaluation of alveolar bone remodeling in methylprednisolone treated –rats during orthodontic tooth movement

Background: Bone remodeling and metabolism associated with orthodontic tooth movement are regulated by a large number of local and systemic factors. The widespread useof therapeutic corticosteroids (GCs) today raise concerns with regard to their effects on mineralized tissue metabolism. This study aimed to investigate the effect of Methylprednisolone treatment on alveolar bone remodeling during orthodontic tooth movement. Materials and Methods: A twenty-six 12-weeks old male Wistar albino rats were divided into 2 groups; control group (n = 13) without any drug administration during the study and steroidal group (n = 13) which received 5 mg/kg/day of methylprednisolone for 3 weeks. A split- mouth design was used performing orthodontic tooth movement on the upper right 1st molar by applying 20 g of mesial force using superelastic closed-coil spring attached to the incisors for 21 days while the upper left side served as the non-appliance side. Orthodontic tooth movement was evaluated on weekly basis using digital caliber. The rats were sacrificed after 3 weeks and alveolar bone remodeling process was evaluated by counting the number of osteoblast and osteoclast cells at the compression and tension sites at the coronal and apical levels of the mesiobuccal root of upper 1st molar in both appliance and non-appliance sides using digital microscope at 400× magnification. At day of sacrifice serum measurements for alkaline phosphatase (ALP) and acid phosphatase (ACP) activity were carried out. Results: Showed that in the steroid group there was significantly greater amount of orthodontic tooth movement, greater reduction of bone formation and an increase in bone resorption with the presence of orthodontic appliance, increase in serum ACP activity and reduction of serum ALP activity as compared with the control group,(P ≤ 0.05). Conclusion: The Methylprednisolone therapy in low-medium doses elicits a noticeable change in the bone turnover rate during orthodontic tooth movement.

Cytokines and VEGF Induction in Orthodontic Movement in Animal Models

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

Sclerostin: A Novel Key to Bone and Dental Treatment

Problem statement: Tooth loss can induce dramatical remodeling of alveolar bone because of mechanical loading impairment and strategies to help maintain adequate bone levels for subsequent therapies are sorely needed. Recent discoveries have shown that osteocytes, matrix-embedded cells in bone, respond to mechanical stimulation by modulating the expression of the Sost gene, which encodes for the protein sclerostin. This protein can oppose the WNT canonical pathway, a signaling cascade which regulates osteoblastic differentiation and bone homeostasis and thus orchestrate bone turn-over according to the skeleton’s mechanical needs. Conclusion: Experimental attempts at Sclerostin inhibition have provided interesting data on a novel approach to decrease bone resorption and promote bone formation, with important implications for the orthopedic and dental field.

Effect of Single and Contiguous Teeth Extractions on Alveolar Bone Remodeling: A Study in Dogs

Tooth extraction is associated with dimensional changes in the alveolar ridge. The aim was to examine the effect of single versus contiguous teeth extractions on the alveolar ridge remodeling. Five female beagle dogs were randomly divided into three groups on the basis of location (anterior or posterior) and number of teeth extracted - exctraction socket classification: group 1 (one dog): single-tooth extraction; group 2 (two dogs): extraction of two teeth; and group 3 (two dogs): extraction of three teeth in four anterior sites and four posterior sites in both jaws. The dogs were sacrificed after 4 months. Sagittal sectioning of each extraction site was performed and evaluated using microcomputed tomography. Buccolingual or palatal bone loss was observed 4 months after extraction in all three groups. The mean of the alveolar ridge width loss in group 1 (single-tooth extraction) was significantly less than those in groups 2 and 3 (p < .001) (multiple teeth extraction). Three-teeth extraction (group 3) had significantly more alveolar bone loss than two-teeth extraction (group 2) (p < .001). The three-teeth extraction group in the upper and lower showed more obvious resorption on the palatal/lingual side especially in the lower group posterior locations. Contiguous teeth extraction caused significantly more alveolar ridge bone loss as compared with when a single tooth is extracted.

Bone remodeling‐associated salivary biomarker MIP‐1α distinguishes periodontal disease from health

The field of salivary diagnostics lacks an accepted and validated biomarker of alveolar bone remodeling. To address this, we examined levels of salivary biomolecules specifically associated with biological aspects of bone remodeling in subjects with chronic periodontitis in a case-control study. Levels of macrophage inflammatory protein-1α (MIP-1α), osteoprotegerin, C-telopeptide pyridinoline cross-links of type I collagen and β-C-terminal type I collagen telopeptide in unstimulated whole saliva of 80 subjects (40 subjects with moderate to severe chronic periodontitis and 40 sex- and age-matched healthy control subjects) were measured using enzyme immunosorbent assays. Saliva was collected before clinical examination, which included probing depth, clinical attachment loss and bleeding on probing. The mean level of MIP-1α in subjects with periodontitis was 18-fold higher than in healthy subjects (p < 0.0001). Clinical periodontal indices correlated significantly with MIP-1α levels (p < 0.0001). Of the biomolecules examined, MIP-1α demonstrated the greatest ability to discriminate between periodontal disease and health as determined by the area under the curve (0.94) and classification and regression tree analysis (sensitivity 94% and specificity 92.7%). Osteoprotegerin levels were elevated 1.6-fold (p = 0.055), whereas C-telopeptide pyridinoline cross-links of type I collagen and β-C-terminal type I collagen telopeptide levels were below the level of detection in the majority of subjects. These findings suggest that the chemokine MIP-1α may aid in identifying periodontitis. Future longitudinal studies are warranted to determine whether this biomarker can help in ascertaining the progression of bone loss in subjects with periodontal disease.