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Calcitonin (CT) is a well-known inhibitor of osteoclastic bone resorption both in vivo and in vitro. The effect is mediated by activation of adenylate cyclase and subsequent increased levels of cyclic AMP (cAMP). We report here that CT-induced (30 nmol/liter) accumulation of cAMP in cultured neonatal mouse calvaria is enhanced two-fold by 12-O-tetradecanoylphorbol-13-acetate (TPA; 100 nmol/liter) and phorbol 12,13-dibutyrate (PDBU; 100 nmol/liter), two protein kinase C (PKC)-activating phorbol esters, whereas phorbol 13-monoacetate (phorb-13; 100 nmol/liter), a related compound that does not activate PKC, has no effect. The ability of TPA and PDBU to enhance CT-stimulated cAMP accumulation was obtained also in the presence of indomethacin (1 mumol/liter). Kinetic studies revealed that TPA enhanced the cAMP response to CT at all the time points at which CT had a significant effect per se and that TPA did not alter the time-course of the cAMP response to CT. Treatment with pertussis toxin (100 ng/ml) enhanced cAMP response to parathyroid hormone (10 nmol/liter) and prostaglandin E2, but not to CT. From these data it is concluded that PKC, but not pertussis toxin-sensitive guanyl nucleotide-binding proteins (G-proteins), can interact with and modify the signal transducing system for CT in osteoclasts. [ABSTRACT FROM AUTHOR]

The effect of prostaglandin E2 (PGE2) on the kinetic of bone resorption in vitro was assessed by following the release of minerals and degradation of matrix in cultured mouse calvarial bones. PGE2 (1 and 3 mumol/liter) caused an initial inhibition of the release of 45Ca, stable calcium, and inorganic phosphate from unstimulated calvarial bones. The effect was transient and after 24 and 48 hours the release of 45Ca, stable calcium, and inorganic phosphate from PGE2-treated bones was enhanced. 0.3 mumol/liter of PGE2 stimulated the release of 45Ca after 24 hours, but at this concentration no initial inhibition was observed. The initial inhibitory effect of PGE2 (1 mumol/liter) could be further increased by three structurally different inhibitors of cyclic AMP breakdown. PGE2 (1 mumol/liter) caused not only an initial inhibition of mineral release but also an initial inhibition of matrix degradation, as assessed by the release of 3H from [3H]-proline labeled bones. In addition, PGE2 (3 mumol/liter), in the presence of the phosphodiesterase inhibitor isobutylmethylxanthine, caused a rapid (6 hours) inhibition of the release of the lysosomal enzymes beta-glucuronidase and beta-N-acetyl-glucosaminidase, without affecting the release of the cytosolic enzyme lactate dehydrogenase. Similar specific initial inhibition of lysosomal enzyme release was also seen in the presence of calcitonin and dibutyryl cyclic AMP, but not in the presence of parathyroid hormone (PTH). Neither PGE2 nor the phosphodiesterase inhibitors rolipram and Ro 20.1724, could inhibit the initial stages of PTH-induced 45Ca release. Nor did PGE2 inhibit the stimulation of radioactive calcium mobilization induced by 1 alpha (OH)-vitamin D3.(ABSTRACT TRUNCATED AT 250 WORDS) [ABSTRACT FROM AUTHOR]

The effects of mouse recombinant γ-interferon ( γ-IFN) and indomethacin on bone resorption stimulated by bradykinin, Lys-bradykinin, Met-Lys-bradykinin, des-Arg-bradykinin and prostaglandin E (PGE) have been studied using cultures of neonatal calvarial bones and analyzing the release ofCa from prelabelled bones as a paramenter of bone resorption. In addition, the effects of γ-IFN and indomethacin on formation of PGE in bone cultures stimulated by bradykinin was analyzed. Indomethacin (1 μmol/l) totally abolished bradykinin (1 μmol/l) inducedCa release. The inhibitory effect of indomethacin could be fully reversed by addition of PGE (1 μmol/l). γ-IFN (1000 U/ml) almost totally inhibitedCa release stimulated by bradykinin (1 μmol/l), but the inhibitory effect could only be partially overcome by PGE. γ-IFN and indomethacin also inhibited the stimulatory effects of Lys-bradykinin, Met-Lys-bradykinin and des-Arg-bradykinin (1 μmol/l) onCa release. The stimulatory effects of PGE (1 μmol/l) on radioactive calcium mobilization was partially inhibited by γ-IFN (1000 U/ml), whereas indomethacin (1 μmol/l) was without effect. The inhibitory effect of γ-IFN onCa release stimulated by bradykinin and PGE was dose-dependent with threshold for action at 3-30 U/ml. Comparative dose-response curves showed that γ-IFN was most potent as inhibitor of bradykinin inducedCa release. Bradykinin (1 μmol/l) significantly stimulated PGE formation by a mechanism that was completely inhibited by indomethacin (1 μmol/l). γ-IFN (1000 U/ml) partially inhibited the stimulatory effect of bradykinin on PGE formation. These data show that i) γ-IFN is a potent inhibitor of bone resorption induced by bradykinin and bradykinin analogues and ii) that the mechanism of action can be mainly explained by an inhibition of kinin induced prostaglandin biosynthesis. The results, however, also show that γ-IFN can inhibit bone resorption by mechanisms unrelated to prostaglandin formation. [ABSTRACT FROM AUTHOR]

Context: Silicon (Si), which is present in the diet in the bioavailable form of orthosilicic acid (OSA) and is detected as a dissolution product of certain bone-substitute materials, is suggested to promote bone health, and enhance bone healing, respectively. Silicon has been shown to stimulate osteoblastic cell differentiation and function, although the effect of Si on human osteoclasts is unclear., Aim: The present study investigated the direct effects of Si on human osteoclast differentiation, gene expression, and bone resorption., Material & Methods: Human CD14+ monocytes were isolated from buffy coats and cultured with M-CSF and RANKL in medium without or with Si (50 μg/ml; constituting 75% OSA). The effects of Si on osteoclast differentiation were evaluated by TRAP-staining and the expression levels of CtsK, CalcR, TRAP, and DC-STAMP measured by RT-qPCR. The effect of Si on the expression level of AQP9, which encodes a potential Si transporter, was also analyzed. Bone resorption was determined based on the number of resorption pits formed when the RANKL-stimulated monocytes were cultured on bone slices, and by the levels of type I collagen fragments released into the cell culture medium., Results: Silicon significantly inhibited the number of TRAP+ multinucleated cells and the expression of osteoclast related genes but increased the late expression of AQP9. Furthermore, Si significantly inhibited the number of resorption pits and the amount of collagen fragments in the medium when cells were cultured on bone slices., Conclusion: Our results demonstrate that OSA inhibits RANKL-stimulated human osteoclast differentiation, gene expression of osteoclast phenotypic markers, and bone resorption., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Magnusson, Ransjö. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Purpose: The aim was to assess skeletal stability after maxillary advancement using either distraction osteogenesis (DO) or conventional Le Fort I osteotomy (CO) in patients with cleft lip and palate (CLP) or cleft palate (CP) utilising a new superimposition-based cephalometric method., Method: This retrospective study included patients who were treated with DO (N = 12) or CO (N = 9). Sagittal and vertical changes after surgery, and skeletal stability at 18 months post-operatively were assessed with superimposition-based cephalometry, comparing lateral cephalograms performed pre-operatively (T0), post-operatively after CO or immediately after completed distraction in DO (T1), and at 18 months of follow-up (T2)., Results: The mean sagittal movements from T0 to T2 in the DO and CO groups were 5.9 mm and 2.2 mm, respectively, with a skeletal relapse rate of 16% in the DO group and 15% in the CO group between T1 and T2. The vertical mean movement from T0 to T2 in the DO and CO groups was 2.8 mm and 2.0 mm, respectively, and the skeletal relapse rate between T1 and T2 was 36% in the DO group and 32% in the CO group., Conclusion: Sagittal advancement of the maxilla was stable, in contrast to the vertical downward movement, which showed more-extensive relapse in both groups. Despite more-extensive maxillary advancement in the DO group, the rates of skeletal relapse were similar., (© 2024. The Author(s).)

Silicon (Si) may be a mineral beneficial for bone health. Pregnancy and lactation have major impacts on maternal bone metabolism as bone minerals, including calcium (Ca), are required for growth of the foetus and for milk production. Like urinary Ca excretion, Si excretion has been reported to be high in pregnant women, but there are no data post-partum and during lactation. The aim of the present study was to investigate the urinary excretion of Si (U-Si), from the third trimester of pregnancy until 18 months post-partum, and in relation to the length of lactation, to determine if changes in U-Si are associated with changes in areal bone mineral density (aBMD). This longitudinal study included 81 pregnant women, of whom 56 completed the study. Spot urine samples were collected at the third trimester and at 0.5, 4, 12, and 18 months post-partum and were analysed for Si and Ca by ICP-OES. The aBMD was measured post-partum at lumbar spine and femoral neck by dual-energy x-ray absorptiometry. Women lactating for 4-8.9 and ≥ 9 months had significantly higher U-Si at 4 months post-partum, compared with the third trimester. No significant longitudinal differences in U-Si were found after correcting for creatinine. Changes in U-Si and in aBMD were not correlated, except at the lumbar spine from 0.5 to 12 months post-partum in the women lactating for 4-8.9 months. Taken together, our results suggest that there is a possibility that U-Si increases post-partum in women lactating for 4 months or longer, although it is not related to changes in aBMD., (© 2024. The Author(s).)

Background: The long-term effects on dentofacial morphology of interceptive treatment with premolar extractions, in the absence of subsequent orthodontic treatment, have not been fully explored., Objective: The aim was to investigate the effects of premolar extractions (without subsequent orthodontic treatment) on the dentoskeletal and soft tissue profile of patients aged between 12 and 62 years with Class I malocclusion with severe crowding, as compared to untreated controls., Materials and Methods: The Extraction group (N = 30 with Class I crowding malocclusion) had their first premolars removed in early adolescence without subsequent orthodontic treatment. The Control group included 30 untreated subjects with Class I normal occlusion. Cephalograms were taken at 12 (T1), 15 (T2), 30 (T3), and 62 (T4) years of age. A superimposition-based cephalometric method was used to assess the dentoskeletal and soft tissue changes., Results: There were no significant differences between the Extraction and Control groups in terms of skeletal sagittal relation, incisor inclination, and protrusion, or most of the soft tissue parameters throughout the observation period. However, significant differences were observed between the groups with respect to the vertical relations in T2-T3, such that the Extraction group showed more-pronounced decreases in the ML/NSL, ML/NL, and Gonial angles and more-pronounced increases in facial heights., Conclusions and Implications: Treatment for subjects with Class I malocclusion with severe crowding by the extraction of four premolars, without subsequent orthodontic treatment, does not affect the long-term dentoskeletal and soft tissue profile, as compared to an untreated Control group. The degree of crowding, rather than changes in dentofacial morphology, is crucial in deciding on extraction therapy., (© The Author(s) 2022. Published by Oxford University Press on behalf of the European Orthodontic Society.)

Background: In long-term studies of orthodontic, orthognathic, and prosthodontic treatments, control subjects are needed for comparison., Objectives: To study the craniofacial (skeletal, soft tissue, and dental) changes that occur in untreated subjects with normal occlusion between 13 and 62 years of age., Materials/methods: Thirty subjects with a Class I normal occlusion and harmonious facial profile were studied. X-ray examinations were performed at 13 (T1), 16 (T2), 31 (T3), and 62 (T4) years of age, and data were obtained from cephalograms. In total, 53 angular and linear parameters were measured using superimposition-based and conventional cephalometric methods to describe the craniofacial changes., Results: The jaws showed significant anterior growth from T1 to T2, and significant retrognathism from T3 to T4. The anterior face height and jaw dimensions increased significantly until T3. Significant posterior rotation of the mandible and opening of the vertical jaw relation, in addition to significant retroclination of the incisors and straightening of the facial profile, were found from T3 to T4., Limitations: Given the small sample size at T4, it was not possible to analyse the gender dimension., Conclusions/implications: Craniofacial changes continue up to the sixth decade of life. These changes are consistent, albeit to a lesser extent, with the adolescent growth patterns for most of the studied parameters, with the exceptions of incisor inclination, sagittal jaw position, vertical jaw relation and inclination, and posterior face height., (© The Author(s) 2022. Published by Oxford University Press on behalf of the European Orthodontic Society.)

Numerous studies have reported on the positive effects of silicon (Si) on bone metabolism, particularly on the stimulatory effects of Si on osteoblast cells and on bone formation. Inhibitory effects of Si on osteoclast formation and bone resorption have also been demonstrated in vitro and are suggested to be mediated indirectly via stromal and osteoblast cells. Direct effects of Si on osteoclasts have been less studied and mostly using soluble Si, but no characterisation of the Si treatment solutions are provided. The aims of the present study were to (a) further investigate the direct inhibitory effects of Si on osteoclastogenesis in RANKL-stimulated RAW264.7 cells, (b) determine at what stage during osteoclastogenesis Si acts upon, and (c) determine if these effects can be attributed to the biologically relevant soluble orthosilicic acid specie. Our results demonstrate that silicon, at 50 μg/ml (or 1.8 mM), does not affect cell viability but directly inhibits the formation of TRAP+ multinucleated cells and the expression of osteoclast phenotypic genes in RAW264.7 cells. The inhibitory effect of Si was clearly associated with the early stages (first 24 hr) of osteoclastogenesis. Moreover, these effects can be attributed to the soluble orthosilicic acid specie., (© 2021 The Authors. Journal of Biomedical Materials Research Part A published by Wiley Periodicals LLC.)

Objective: Descriptions of the craniofacial morphology in Saethre-Chotzen syndrome (SCS) are primarily based on case reports or visual assessments of affected families. The aim of this study was to compare cephalometric measurements of the craniofacial skeleton in a cohort of individuals with SCS and age- and sex-matched individuals without craniofacial anomalies., Design: Retrospective case series., Patients: Eight girls and 4 boys with SCS (age range, 7.0-19.2 years)., Methods: Cephalometric measurements were performed using lateral and frontal cephalograms., Results: Most of the individuals with Saethre-Chotzen syndrome exhibited lower values for SNA, SNB, s-n and s-ar, while their NSL/NL, NSL/ML, NL/ML, and n-s-ba values were higher than the respective mean reference values for healthy individuals. In comparison with age- and sex-matched individuals without craniofacial anomalies, the individuals with SCS showed higher values for the maxillary and mandibular angular measurements, as well as for the menton midline angle., Conclusions: This sample of 12 unrelated individuals with SCS is the largest collected to date for cephalometric measurements. We found that the syndrome is associated with bimaxillary retrognathism, posterior maxillary and mandibular inclination, neutral sagittal relation as well as a tendency toward an open vertical skeletal relation, a short and flattened skull base, and facial asymmetry, as compared to individuals without the syndrome.

Objective: To compare the reliability of digital occlusal contacts quantification and the validity of digital occlusal contacts quantification with traditional methods used for occlusal contact determination., Subjects and Methods: Thirty participants, all of whom were students at the Sahlgrenska Academy, University of Gothenburg in Gothenburg, Sweden, were included in the study. Three different methods were used to evaluate occlusal contacts: (I) a digital examination of the patients' casts, using the Ortho 3D Models (O3DM) software and measuring the total occlusal contact area in square millimeters (DE); (II) an examination involving the measurement of the total number of occlusal contacts on stone casts mounted in an articulator (AE); and (III) a clinical examination with the measurement of the total number of occlusal contacts with 8 μm-thick articulating foil (CE)., Results: The repeated digital measurements (same casts scanned multiple times) showed a significant correlation of 0.85 ( p < 0.01), which shows a diagnostic consistency. Furthermore, there was a significant correlation between the results obtained with the DE method and the AE of 0.41 ( p < 0.05), and between those acquired with the AE method and the CE of 0.37 ( p < 0.05). However, no significant correlation was found between the DE method and the CE method with a correlation coefficient of 0.10 ( p > 0.05)., Conclusions: Digital casts can be used for quantification of the total occlusal contact area (in mm 2 ) owing to the high reliability of repeated measurements and the strong validity of the method compared to traditionally employed stone cast measurements.

To assess the craniofacial changes related to growth and/or to orthodontic and orthognathic treatments, it is necessary to superimpose serial radiographs on stable structures. However, conventional superimposition provides only a graphical illustration of these changes. To increase the precision of growth and treatment evaluations, it is desirable to quantitate these craniofacial changes. The aims of this study were to (1) evaluate a superimposition-based cephalometric method to process numerical data for craniofacial growth changes and (2) identify a valid, reliable, and feasible method for superimposition. Forty pairs of cephalograms were analyzed at T1 and T2 (mean age 9.9 and 15.0 years, respectively). The superimposition-based cephalometric method involved relating the sagittal and vertical measurements on the T2 radiographs to the nasion and sella landmarks on the T1 radiographs. Validity and reliability were evaluated for three superimposition methods: the sella-nasion (SN); the tuberculum sella-wing (TW); and Björk's structural. Superimposition-based cephalometrics can be used to quantify craniofacial changes digitally. The numerical data from the superimposition-based cephalometrics reflected a graphical illustration of superimposition and differed significantly from the data acquired through conventional cephalometrics. Superimposition using the TW method is recommended as it is valid, reliable, and feasible.

Objective: The aim of this study was to evaluate if delayed dental development is a cause of postponed care for patients with impacted maxillary canine (IMC)., Materials and Methods: This case-control study was based on 403,355 children and adolescents in Region Västra Götaland, Sweden. The subjects, who were in the age range of 9-16 years during the period of 2011-2013, underwent surgical exposure or removal of a maxillary canine. Demirjian's dental age assessment was carried out on panoramic radiographs., Results: In total, 1028 patients, 514 with IMC and 514 age- and gender-matched controls, were enrolled. The patients with IMC exhibited a dental development delay of 0.2 years compared to the control group. In the impaction sub-groups, the female patients, patients in the chronological age group of 12-13 years, and patients with palatally positioned IMC had a significantly lower dental age than their paired-control subjects., Conclusions: Overall, the difference in dental age between patients with or without IMC is significant but small, and as such is likely of minor clinical relevance. Therefore, the timing of preventive care and treatment for patients with IMC should be the same as that for patients with normally erupting canines.

Several studies have indicated that dietary silicon (Si) is beneficial for bone homeostasis and skeletal health. Furthermore, Si-containing bioactive glass biomaterials have positive effects on bone regeneration when used for repair of bone defects. Si has been demonstrated to stimulate osteoblast differentiation and bone mineralisation in vitro. However, the mechanisms underlying these effects of Si are not well understood. The aim of the present study was to investigate the effects of soluble Si on osteogenic differentiation and connexin 43 (CX43) gap junction communication in cultured pluripotent cells from human dental follicles (hDFC). Neutral Red uptake assay demonstrated that 25 μg/ml of Si significantly stimulated hDFC cell proliferation. Dosages of Si above 100 μg/ml decreased cell proliferation. Alizarin Red staining showed that osteogenic induction medium (OIM) by itself and in combination with Si (25 μg/ml) significantly increased mineralisation in hDFC cultures, although Si alone had no such effect. The expression of osteoblast-related markers in hDFC was analysed with RT-qPCR. OSX, RUNX2, BMP2, ALP, OCN, BSP and CX43 genes were expressed in hDFC cultured for 1, 7, 14 and 21 days. Expression levels of BMP-2 and BSP were significantly upregulated by OIM and Si (25 μg/ml) and were also induced by Si alone. Notably, the expression levels of OCN and CX43 on Day 21 were significantly increased only in the Si group. Flow cytometric measurements revealed that Si (50 μg/ml) significantly increased CX43 protein expression and gap junction communication in hDFC. Next-generation sequencing (NGS) and bioinformatics processing were used for the identification of differentially regulated genes and pathways. The influence of OIM over the cell differentiation profile was more prominent than the influence of Si alone. However, Si in combination with OIM increased the magnitude of expression (up or down) of the differentially regulated genes. The gene for cartilage oligomeric matrix protein (COMP) was the most significantly upregulated. Genes for the regulator of G protein signalling 4 (RGS4), regulator of G protein signalling 2 (RGS2), and matrix metalloproteinases (MMPs) 1, 8, and 10 were also strongly upregulated. Our findings reveal that soluble Si stimulates Cx43 gap junction communication in hDFC and induces gene expression patterns associated with osteogenic differentiation. Taken together, the results support the conclusion that Si is beneficial for bone health.

Silicon is a trace element found mainly in plant-based food and proposed to be beneficial for bone health. Urinary excretion of Si has been shown to be a surrogate measure of its uptake in the gastrointestinal tract. The objective of this study was to describe and compare the levels of urinary Si excretion, and consequently Si uptake, in Swedish men, non-pregnant women, and pregnant women. No formal assessment of dietary Si intake was carried out in this study. This cross-sectional study included 89 men, 42 non-pregnant women, and 60 pregnant women. The subjects collected urine over a 24-h period and the samples were assayed for total Si using inductively coupled plasma optical emission spectrometry. The excretion levels of creatinine were used to validate the completeness of the urine sample collections. The mean 24-h urinary excretions of Si were 7.8 mg for the cohort of young men, 7.6 mg for the cohort of non-pregnant women, and 12.4 mg for the cohort of pregnant women. Creatinine excretion was similar between pregnant and non-pregnant women (10.4 vs. 10.8 mmol/day) and significantly higher in men (15.4 mmol/day). The pregnant women excreted significantly higher levels of Si than the young men and non-pregnant women, respectively (p < 0.05). The higher urinary excretion of Si by pregnant women compared with men and non-pregnant women is a novel finding possibly caused by temporary physiological changes during pregnancy such as increased gastrointestinal uptake of Si, altered bone metabolism, and increased renal excretion of Si.

Background: In dentistry, epidemiological studies are important for establishing high-quality care for the individual patient as well as for socio-economic reasons., Objective: The aim of this epidemiological study was to evaluate the prevalence of impacted maxillary canines in a geographical region in which interceptive treatment is implemented systematically. Furthermore, the aim was to study the age and gender of the patients, and the location and surgical technique used for the impacted maxillary canine., Method: The study was based on 54 716 adolescents in the Region Västra Götaland, Sweden who were born in the period 1996-98. All patients in the three cohorts who had impacted maxillary canines treated with surgical exposure or surgical removal were identified in the dental record system used in the region., Results: The prevalence of impacted maxillary canines when interceptive treatment was systematically implemented was 1.1% (N = 601). Overall, the cohorts of patients with impacted canines comprised 65% girls and 35% boys. Most of the canines were palatally impacted and the most common surgical technique was closed exposure., Conclusion: The prevalence of impacted maxillary canines in a geographical area in which interceptive treatment is systematically implemented is lower than that reported previously. The distributions of impacted canines with respect to gender and location are in accordance with those reported previously in similar studies., (© The Author(s) 2019. Published by Oxford University Press on behalf of the European Orthodontic Society. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

We sought to investigate site-specific expression of bone-regulatory factors expressed by human dental follicles and to compare the stimulated expression of tumour necrosis factor (ligand) superfamily, member 11/tumour necrosis factor receptor superfamily, member 11b (RANKL/OPG) in human dental follicle cells (HDFCs) from different patients. Analysis of bone-regulatory markers in follicles from 12 different study participants was performed using RT-qPCR and immunofluorescence; apical and coronal segments from each dental follicle were processed independently. Four additional dental follicles were used for cell cultures; HDFCs were precultured in osteogenic medium to initiate differentiation and thereafter cultured with 10 -6 M forskolin (FSK) to activate the protein kinase cAMP (PKA/cAMP) signalling pathway and induce RANKL/OPG expression. We demonstrate that RANKL expression is significantly higher in the coronal part of follicles than in the apical part. High levels of collagen type 1 (COL1), alkaline phosphatase (ALP) and Gap-junction protein, alpha 1, 43 kDa (CX43) were expressed, whereas expression of Sp7 transcription factor (OSX), bone morphogenetic protein 2 (BMP2), colony-stimulating factor 1 (CSF-1), chemokine (C-C motif) ligand 2 (MCP1), and OPG was low in all samples. The immunofluorescence localization of CSF-1, MCP1, osteocalcin (OCN), RANKL, and BMP2 was not specific for either part of the follicles. In conclusion, a consistently high expression of CX43 suggests that gap-junction communication in HDFCs is essential for the eruption process. Furthermore, the induced expression of RANKL in HDFCs varies significantly between individuals and may relate to clinical variations in tooth eruption., (© 2018 The Authors. Eur J Oral Sci published by John Wiley & Sons Ltd.)

Animal studies suggest that the dental follicle (DF) plays a major role in tooth eruption. However, the role of the DF during tooth impaction and related root resorptions in adjacent teeth is not clear. The hypothesis for the present study is that expression of regulatory factors involved in the bone remodelling process necessary for tooth eruption may differ between dental follicles from teeth with different clinical situations. We have analysed the gene expression profiles in the DF obtained from impacted canines, with (N = 3) or without (N = 5) signs of root resorption, and from control teeth (normal erupting teeth, mesiodens) (N = 3). DF from 11 patients (mean age: 13 years) obtains at the time of surgical exposure of the tooth. Due to the surgical time point, all teeth were in a late developmental stage. Gene expression related to osteoblast activation/bone formation, osteoclast recruitment and activation was analysed by RTqPCR. Genes related to bone formation (RUNX2, OSX, ALP, OCN, CX43) were highly expressed in all the samples, but osteoclast recruitment/activation markers (OPG, RANKL, MCP-1, CSF-1) were negligible. No apparent patterns or significant differences in gene expression were found between impacted canines, with or without signs of root resorption, or when compared to control teeth. Our results suggest the DF regulation of osteoclastic activity is limited in the late pre-emergent stage of tooth development, irrespective if the tooth is normally erupting or impacted. We suggest that the follicle may have an important regulatory function for alveolar bone formation in the final eruption process and CX43-gap junction communication could be an important signalling pathway.

Background: Ectopic eruption and/or impaction of maxillary permanent canines is a frequent problem in clinical dentistry. Previous studies aimed to identify potential associated factors and predictors for impacted maxillary canines have only used conventional univariate statistics, which does not allow the analysis of the interaction between and within variables. Multivariate data analysis (MVDA) is a better and more powerful tool for the integration and interpretation of complex datasets., Aim: The aim of this study was to validate previously explored predictors of permanent maxillary canine impaction using MVDA., Subjects and Methods: This cohort study included all the patients referred during 2011 to Mölndal Hospital, Sweden for surgical exposure of impacted canines (N = 45). Age- and gender-matched orthodontic patients (N = 45) with normally erupting canines comprised the control group. The age range for both groups was 11-17 years. The positions of the canine teeth (orthopantograms), the skeletal variables (profile radiographs), and dentoalveolar traits (casts) were evaluated as potential predictive factors for impaction., Results: None of the parameters evaluated with either profile radiography or casts were positively correlated with impacted maxillary canines, with the exception of the location of the already impacted canines, as identified by orthopantogram., Conclusion: No correlation between clinical variables and impaction was found using MVDA. Therefore, these variables could not be used as predictors of canine impaction. Other types of parameters, such as inheritance and molecular factors that regulate the biological mechanisms of the eruption process, need to be further investigated., (© The Author 2016. Published by Oxford University Press on behalf of the European Orthodontic Society. All rights reserved. For permissions, please email: journals.permissions@oup.com)

Introduction: Fixed retainers are widely used after orthodontic treatment, sometimes for extended periods, despite insufficient knowledge of their possible long-term adverse effects on the periodontium. The aim of this study was to evaluate whether bonded orthodontic retainers have an adverse long-term effect on the marginal bone levels of the mandibular front teeth., Methods: The study included 62 consecutive patients in 3 groups: (1) patients who underwent orthodontic treatment and wore a fixed retainer for 10 years, (2) patients who underwent orthodontic treatment but did not have a fixed retainer, and (3) untreated controls. The marginal bone levels were measured by cone-beam computed tomography 10 years after treatment. Additionally, multivariate data analysis was used to analyze possible correlations between the marginal bone levels at 10 years and the variables obtained from the study casts and profile radiographs., Results: The results demonstrated a significantly lower marginal bone level on the buccal side of the mandibular front teeth in the orthodontically treated patients compared with the orthodontically untreated group. There was no difference in the marginal bone levels between the retainer group and the no-retainer group. Multivariate analysis indicated that a low marginal bone level was correlated with a basal open vertical relationship, posterior rotation of the mandible, pretreatment of the incisor protrusion, and extraction therapy., Conclusions: Within the limits of this research design, the long-term retention phase in general does not seem to cause any adverse effects on the marginal bone levels after 10 years., (Copyright © 2017 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The introduction of digital cast models is inevitable in the otherwise digitized everyday life of orthodontics. The introduction of this new technology, however, is not straightforward, and selecting an appropriate system can be difficult. The aim of the study was to compare 4 orthodontic digital software systems regarding service, features, and usability., Methods: Information regarding service offered by the companies was obtained from questionnaires and Web sites. The features of each software system were collected by exploring the user manuals and the software programs. Replicas of pretreatment casts were sent to Cadent (OrthoCAD; Cadent, Carlstadt, NJ), OthoLab (O3DM; OrthoLab, Poznan, Poland), OrthoProof (DigiModel; OrthoProof, Nieuwegein, The Netherlands), and 3Shape (OrthoAnalyzer; 3Shape, Copenhagen, Denmark). The usability of the programs was assessed by experts in interaction design and usability using the "enhanced cognitive walkthrough" method: 4 tasks were defined and performed by a group of domain experts while they were observed by usability experts., Results: The services provided by the companies were similar. Regarding the features, all 4 systems were able to perform basic measurements; however, not all provided the peer assessment rating index or the American Board of Orthodontics analysis, simulation of the treatment with braces, or digital articulation of the casts. All systems demonstrated weaknesses in usability. However, OrthoCAD and 03DM were considered to be easier to learn for first-time users., Conclusions: In general, the usability of these programs was poor and needs to be further developed. Hands-on training supervised by the program experts is recommended for beginners., (Copyright © 2015 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.)

Objective: To evaluate the effects of rapid maxillary expansion (RME) on nocturnal enuresis (NE) related to the nasal airway, nasal breathing, and plasma osmolality (as an indicator for antidiuretic hormone)., Materials and Methods: Nineteen patients with monosymptomatic primary NE, aged 6-15 years, were treated with RME for 10-15 days. To exclude a placebo effect of the RME appliance, seven patients were first treated with a passive appliance. Computed tomography of nasal cavity, rhinomanometric, and plasma osmolality measurements were made 2-3 days before and 2-3 months after the RME period. RME effects on NE were followed for three more years., Results: Two to three months after the expansion there were significant improvements in the breathing function and a decrease in the plasma osmolality. NE decreased significantly in all patients after the RME period, and all patients showed full dryness after 3 years., Conclusions: This study demonstrates that RME causes complete dryness in all patients, with significant effects on pathophysiological mechanisms related to NE.

Purpose: It is important to predict and prevent the impaction of canines. The aim of this study was to estimate the prevalence of impacted canines in patients with unilateral cleft lip and palate (UCLP) and to identify factors associated with impaction., Materials and Methods: This retrospective cohort study included patients with nonsyndromic UCLP. The predictors were pre-eruptive inclination angle, deviation in tooth number (agenesis or supernumerary lateral incisors), and reoperation of bone transplant. The outcome variable was impacted and surgically exposed canines., Results: The prevalence of impacted and surgically exposed canines in the 68 consecutive patients with UCLP was 20.6%. The pre-eruptive inclination angle was significantly larger (34.4°) for the impacted canines on the cleft side compared with the spontaneously erupted canines on the cleft and non-cleft sides (25.5° vs 15.4; P < .05). Reoperation of the bone transplant significantly increased canine impaction (50%; P < .05)., Conclusion: The eruption of maxillary canines needs to be supervised carefully in patients with UCLP, because the prevalence of impaction is 10 times higher compared with the general population. Factors associated with canine impaction are a pre-eruptive inclination larger than 30° and reoperation of the bone transplant., (Copyright © 2014 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.)

Several studies have suggested that silicon (Si) may be essential for the normal development of connective tissue and the skeleton. Positive effects of Si from the diet as well as from Si-containing biomaterials, such as bioactive glass 45S5 (BG), have been demonstrated. Studies have reported that Si stimulates osteoblast proliferation and differentiation. However, the effects of Si on osteoclasts have not been directly addressed. The purpose of the present in vitro study was to clarify if Si has regulatory effects on osteoclast formation and bone resorption. The effects of BG, BG dissolution extracts and Si containing cell culture medium were investigated in a mouse calvarial bone resorption assay and osteoclast formation assays (mouse bone marrow cultures and RAW264.7 cell cultures). We conclude from our results that Si causes significant inhibition of osteoclast phenotypic gene expressions, osteoclast formation and bone resorption in vitro. In conclusion, the present study suggests that Si has a dual nature in bone metabolism with stimulatory effects on osteoblasts and inhibitory effects on osteoclasts. This suggested property of Si might be interesting to further explore in future biomaterials for treatments of bone defects in patients., (Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Porphyromonas gingivalis strongly correlates with periodontitis, but the underlying mechanisms causing dentoalveolar bone resorption are not fully understood. As contradictory effects of P. gingivalis on osteoclastogenesis have been reported, this study investigates the effect of P. gingivalis extract on osteoclast formation. Osteoclast formation in mouse bone marrow (MBM) cell cultures and RAW 264.7 cells was stimulated by nuclear factor-κB ligand (RANKL) or parathyroid hormone (PTH). Cells were cultured with and without P. gingivalis surface-associated material and phenotypic characteristics were examined using microscopy, flow cytometry, and RT-PCR. P. gingivalis significantly decreased osteoclast formation and the expression of osteoclast phenotypic markers in PTH-stimulated MBM cultures. Additionally, P. gingivalis inhibited expression of osteoclast differentiation factors and stimulated expression of the mouse macrophage marker F4/80. The presence of P. gingivalis in RANKL-stimulated MBM cultures and RAW 264.7 cells inhibited osteoclastogenesis. Interestingly, a transient exposure with P. gingivalis before PTH stimulation increased osteoclastogenesis in MBM cultures. Flow cytometric analyses of cells transiently exposed to P. gingivalis demonstrated an increased proportion of potential osteoclast precursor cells. We conclude that a transient exposure of MBM cultures to P. gingivalis increases the number of osteoclast precursors and osteoclast formation, whereas a prolonged exposure completely abolishes osteoclastogenesis.

Objectives: To systematically investigate the biological interface of Bio-Oss by analysing dissolution-precipitation behaviour and osteogenic responses using in vitro experimental systems., Material and Methods: Different concentrations (1-100 mg/ml) of Bio-Oss were incubated in cell culture medium for 24 h before elemental concentrations for calcium, phosphorus and silicon in the medium were analysed with inductive coupled plasma-optical emission spectroscopy. Radioactive calcium-45 isotope labelling technique was used to study possible precipitation of calcium on the Bio-Oss particle. Biological interface of Bio-Oss was studied in osteogenic experiments using mineralization medium and three different sources of cells (primary mouse bone marrow stromal cells, primary rat calvarial cells and MC3T3-E1 mouse pre-osteoblast cell line). Cells were fixed and stained with Toulidine blue, von Kossa or Alizarin Red staining for confirmation of extracellular matrix mineralization., Results: Elemental analysis of the cell culture medium demonstrated a significant decrease of calcium and phosphorus and a dose-dependent release of silicon to the medium after incubation with Bio-Oss. A significant decrease of calcium and phosphorus in the medium occurred even at low concentrations of Bio-Oss. Uptake of calcium on the Bio-Oss particle was confirmed with radioactive calcium-45 isotope labelling technique. In osteogenic experiments with Bio-Oss (<1 mg/ml), matrix mineralization around the Bio-Oss particles were demonstrated in all three cell types with von Kossa and Alizarin Red staining., Conclusion: Dissolution-precipitation reactions occur at the surface of Bio-Oss, and osteogenic responses are seen at the biological interface. The concentration of Bio-Oss is a key factor for the experimental in vitro results, and may also have implications for the clinic., (© 2011 John Wiley & Sons A/S.)

Objectives: The aim of this work was to investigate the release of inorganic ionic products from specimens of the polyacid-modified composite resin Dyract AP (DAP) and furthermore, to analyze the biological effect of DAP and the medium extract in human periodontal ligament (PDL) cells and mouse bone marrow cell (BMC) cultures., Methods: Ion release from DAP specimens immersed in cell culture medium was analyzed with inductively coupled plasma optical emission spectroscopy (ICP-OES). Cells were cultured with either DAP specimens or with DAP media extract and effects on cell proliferation, osteoblastic gene expression and mineralization capacity were analyzed with direct-contact tests, neutral red (NR) uptake, quantitative real-time PCR and a bone nodule formation assay., Results: ICP-OES analysis of DAP extract demonstrated a significant increase in fluoride, strontium and silica. PDL cells demonstrated normal growth pattern in the direct-contact tests with the material. DAP extracts produced a dose-dependent stimulation of cell proliferation and concomitant inhibition of osteoblast specific markers and nodule formation., Significance: The compomer may have possible bioactive properties due to ions leaching out from the filler component.

Receptor activator of NF-kappaB ligand (RANKL) is crucial in osteoclastogenesis but signaling events involved in osteoclast differentiation are far from complete and other signals may play a role in osteoclastogenesis. A more direct pathway for cellular crosstalk is provided by gap junction intercellular channel, which allows adjacent cells to exchange second messengers, ions, and cellular metabolites. Here we have investigated the role of gap junction communication in osteoclastogenesis in mouse bone marrow cultures. Immunoreactive sites for the gap junction protein connexin 43 (Cx43) were detected in the marrow stromal cells and in mature osteoclasts. Carbenoxolone (CBX) functionally blocked gap junction communication as demonstrated by a scrape loading Lucifer Yellow dye transfer technique. CBX caused a dose-dependent inhibition (significant > or = 90 microM) of the number of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells formed in 7- to 8-day marrow cultures stimulated by parathyroid hormone (PTH; 10 nM) or forskolin (FSK; 1 microM). Furthermore, CBX (100 microM) significantly inhibited prostaglandin E2 (PGE2; 10 microM) and 1,25(OH)2-vitamin D3 stimulated osteoclast differentiation in the mouse bone marrow cultures. Consequently, quantitative real-time polymerase chain reaction (PCR) analysis demonstrated that CBX downregulated the expression of osteoclast phenotypic markers, but without having any significant effects on RANK, RANKL, and osteoprotegerin (OPG) mRNA expression. However, the results demonstrated that CBX significantly inhibits RANKL-stimulated (100 ng/ml) osteoclastogenesis in the mouse bone marrow cultures. Taken together, our results suggests that gap junctional diffusion of messenger molecules interacts with signaling pathways downstream RANKL in osteoclast differentiation. Further studies are required to define the precise mechanisms and molecular targets involved., (Copyright 2006 Wiley-Liss, Inc.)

The effects of cystatin C and other cysteine proteinase inhibitors on osteoclast formation and differentiation have been investigated. Cystatin C decreased osteoclast formation stimulated by parathyroid hormone (PTH), 1,25(OH)2-vitamin D3 or interleukin-6 (IL-6) (in the presence of its soluble receptor) as assessed by the number of tartrate-resistant acid phosphatase (TRAP+) multinucleated cells in mouse bone marrow cultures. The inhibitory effect was associated with decreased mRNA expression for the calcitonin receptor as well as decreased number of specific binding sites for 125I-calcitonin, and without any effect on the mRNA expression of receptor activator of nuclear factor kappaB (NF-kappaB) ligand (RANKL). Similarly, the cysteine proteinase inhibitors leupeptin, E-64 and benzyloxycarbonyl-Phe-Ala-diazomethane (Z-FA-CHN2) decreased PTH-stimulated formation of TRAP+ multinucleated cells and binding of 125I-calcitonin. A peptidyl derivative synthesized to mimic part of the proteinase-binding site of cystatin C (benzyloxycarbonyl-Arg-Leu-Val-Gly-diazomethane, or Z-RLVG-CHN2) also decreased PTH-stimulated osteoclast formation. In a 9-day culture, addition of cystatin C during the last 5 days was sufficient to cause substantial inhibition of osteoclast formation. Cystatin C-induced decrease of osteoclast formation was associated with enhanced number of F4/80-positive macrophages and increased mRNA expression of the macrophage receptor c-fms in the bone marrow culture. Osteoclast formation in mouse bone marrow cultures as well as in mouse spleen cell cultures, stimulated by macrophage colony-stimulating factor (M-CSF) and RANKL was also decreased by different cysteine proteinase inhibitors. In addition, cystatin C inhibited M-CSF/RANKL induction of calcitonin receptor mRNA in spleen cell cultures. The inhibitory effect by cystatin C in spleen cells was associated with decreased mRNA expression of RANK and the transcription factor NFAT2. It is concluded that cysteine proteinase inhibitors decrease formation of osteoclasts by interfering at a late stage of pre-osteoclast differentiation.

Unlabelled: PAR-2 is expressed by osteoblasts and activated by proteases present during inflammation. PAR-2 activation inhibited osteoclast differentiation induced by hormones and cytokines in mouse bone marrow cultures and may protect bone from uncontrolled resorption., Introduction: Protease-activated receptor-2 (PAR-2), which is expressed by osteoblasts, is activated specifically by a small number of proteases, including mast cell tryptase and factor Xa. PAR-2 is also activated by a peptide (RAP) that corresponds to the "tethered ligand" created by cleavage of the receptor's extracellular domain. The effect of activating PAR-2 on osteoclast differentiation was investigated., Materials and Methods: Mouse bone marrow cultures have been used to investigate the effect of PAR-2 activation on osteoclast differentiation induced by parathyroid hormone (PTH), 1,25 dihydroxyvitamin D3 [1,25(OH)2D3], and interleukin-11 (IL-11). Expression of PAR-2 by mouse bone marrow, mouse bone marrow stromal cell-enriched cultures, and the RAW264.7 osteoclastogenic cell line was demonstrated by RT-PCR., Results: RAP was shown to inhibit osteoclast differentiation induced by PTH, 1,25(OH)2D3, or IL-11. Semiquantitative RT-PCR was used to investigate expression of mediators of osteoclast differentiation induced by PTH, 1,25(OH)2D3, or IL-11 in mouse bone marrow cultures and primary calvarial osteoblast cultures treated simultaneously with RAP. In bone marrow and osteoblast cultures treated with PTH, 1,25(OH)2D3, or IL-11, RAP inhibited expression of RANKL and significantly suppressed the ratio of RANKL:osteoprotegerin expression. Activation of PAR-2 led to reduced expression of prostaglandin G/H synthase-2 in bone marrow cultures treated with PTH, 1,25(OH)2D3, or IL-11. RAP inhibited PTH- or 1,25(OH)2D3-induced expression of IL-6 in bone marrow cultures. RAP had no effect on osteoclast differentiation in RANKL-treated RAW264.7 cells., Conclusion: These observations indicate that PAR-2 activation inhibits osteoclast differentiation by acting on cells of the osteoblast lineage to modulate multiple mediators of the effects of PTH, 1,25(OH)2D3, and IL-11. Therefore, the role of PAR-2 in bone may be to protect it from uncontrolled resorption by limiting levels of osteoclast differentiation.

Several studies have demonstrated that connexin 43 (Cx43) mediates signals important for osteoblast function and osteogenesis. The role of gap junctional communication in bone resorption is less clear. We have investigated the expression of Cx43 mRNA in osteoclasts and bone resorption cultures and furthermore, the functional importance of gap junctional communication in bone resorption. RT-PCR analysis demonstrated Cx43 mRNA expression in mouse bone marrow cultures and in osteoclasts microisolated from the marrow cultures. Cx43 mRNA was also expressed in bone resorption cultures with osteoclasts and osteoblasts/stromal cells incubated for 48h on devitalized bone slices. An up-regulation of Cx43 mRNA was detected in parathyroid (PTH)-stimulated (0.1 nM) bone resorption. Two inhibitors of gap junction communication, 18alpha-glycyrrhetinic acid (30 microM) and oleamide (100 microM), significantly inhibited PTH- and 1,25-(OH)(2)D(3)-stimulated osteoclastic pit formation. In conclusion, our data indicate a functional role for gap junction communication in bone resorption.

Skeletal tissue contains a network of nerve fibers expressing several neuropeptides, including vasoactive intestinal peptide (VIP) and the related peptide pituitary adenylate cyclase activating peptide (PACAP). These peptides have been demonstrated to regulate osteoclast formation and osteoclast activity. Using atomic force microscopy and by analysing changes of the intracellular calcium concentrations, we have recently demonstrated that multinucleated rat osteoclasts have cell membrane binding sites recognising VIP and PACAP. In the present study, we have further studied the expression of VIP receptor subtypes in mouse bone marrow cultures and isolated osteoclasts. A micromanipulation technique was used to isolate pure populations of osteoclasts formed in PTH-stimulated mouse bone marrow cultures. By reverse transcriptase polymerase chain reaction (RT-PCR), we studied the expression of mRNA for VIP-1, VIP-2, and PACAP receptors. The purity of the microisolated osteoclasts was determined by studying the expression of specific mRNA associated with the phenotypic trait of osteoclasts or osteoblasts/stromal cells. In this study, we show that mouse osteoclasts express VIP-1 and PACAP, but not VIP-2, receptor mRNA., (Copyright 2000 Academic Press.)

The presence of a network of peptidergic nerve fibers in the skeleton, expressing several neuropeptides including vasoactive intestinal peptide (VIP), has been demonstrated. This observation, together with our findings in vitro showing that VIP can regulate the activities of osteoblasts and osteoclasts as well as the recruitment of osteoclasts, has suggested the existence of a neuro-osteogenic interplay in bone metabolism. In the present study, the effects of VIP and pituitary adenylate cyclase-activating polypeptide (PACAP), two members of the VIP/secretin/glucagon superfamily, on osteoclast formation and mRNA expression of three key regulatory proteins involved in osteoclast formation have been investigated. VIP, PACAP-27, and PACAP-38, at concentrations of 10(-6) M, all significantly inhibited formation of tartrate-resistant acid phosphatase-positive multinuclear cells (TRAP + MNC) in mouse bone marrow cultures stimulated by 1, 25(OH)(2)-vitamin D3 (D3; 10(-8) M). By using semiquantitative RT-PCR, it was found that D3 upregulated the mRNA expressions of receptor activator of NF-kappaB ligand (RANKL) and receptor activator of NF-kappaB (RANK), whereas the expression of osteoprotegerin (OPG) was downregulated in mouse bone marrow cultures stimulated by D3 for 7 days. Both VIP and PACAP-38 decreased the stimulatory effects of D3 on RANKL and RANK expression, whereas the inhibitory effect of D3 on OPG expression was reversed by VIP and PACAP-38. These observations indicate that the inhibitory effects of VIP and PACAP on osteoclast recruitment are due to regulation of the expression of key proteins involved in later stages of osteoclast differentiation., (Copyright 2000 Academic Press.)

Prostaglandins are involved in force-induced orthodontic tooth movement. Bradykinin (BK) and thrombin are known to cause a significant time- and concentration-dependent burst of prostanoid biosynthesis in cultured human periodontal-ligament (PDL) cells. The aim now was to investigate interactive effects between interleukin 1 alpha, -beta (IL-1 alpha, -1 beta), tumour necrosis factor-alpha,-beta (TNF-alpha, -beta) and BK or thrombin on prostaglandin biosynthesis in human PDL cells. IL-1 alpha and -1 beta produced time- and concentration-dependent stimulation of prostanoid biosynthesis [prostaglandin (PG)E2 and 6-keto-PGF1alpha]. Synergistic stimulation of prostanoid biosynthesis was demonstrated when BK or thrombin were added together with IL-1 alpha or -1 beta. BK and IL-1 beta both significantly stimulated the release of [3H]arachidonic acid. No synergistic effect on [3H]arachidonic acid release was seen when BK and IL-1 beta were added simultaneously. These data suggest that the synergistic effect of BK and IL-1 beta on prostanoid biosynthesis is not due to interactions at the receptor level nor to enhanced release of arachidonic acid, but may be due to increased activity of cyclo-oxygenase. Also, TNF-alpha and -beta produced a concentration-dependent stimulation of PGE2 formation in cultured human PDL cells. Synergistic effects of BK and thrombin were demonstrated when PGE2 production was stimulated in combination with TNF-beta. In addition, a synergistic effect on the PGE2 response to IL-1 alpha or -1 beta was demonstrated when added in combination with TNF-alpha. These experiments demonstrate synergistic interactions between BK, thrombin, IL-1 and TNF on prostaglandin biosynthesis in cultured human PDL cells. The findings suggest that inflammatory mediators may act in concert in stimulating prostanoid production in response to pro-inflammatory stimuli. As an inflammatory reaction is seen in the periodontal ligament when teeth are orthodontically treated, this synergistic interaction may be of importance in force-induced tooth movement.

The thyroid hormones, thyroxine (T4) and triiodothyronine (T3), were found to enhance both neonatal mouse calvarial bone resorption and pit formation on bovine slices by isolated rat osteoclasts. Dosage-dependent release of 45Ca from mouse calvarial bones was observed after 120 hr of culture with 10(-6)-10(-8) MT4 and 10(-6)-10(-10) M T3. Maximum treatment/control ratios of 45Ca release were recorded for 10(-7) M T4 and 10(-8) MT3. Inhibition of 45Ca release stimulated by 10(-8) M T3 was observed in the presence of 30 nM salmon calcitonin at 48 hr and 120 hr of culture with no indication of "escape" by T3-treated bones. In contrast, stimulation of 45Ca release from mouse calvarial bones by 10(-7) MT4 and 10(-8) MT3 was not inhibited by 10(-6) M indomethacin. Formation of PGE2 and PGI2 (evaluated by measuring 6-keto-PGF1alpha) by mouse calvariae was also not increased by 10(-8) MT3 after 120 hr of culture. Furthermore, no increases in cAMP formation were observed in calvarial bone cultures after either 10 min or 24 hr of exposure to 10(-8) MT3. However, significant inhibition of 45Ca release stimulated by 10(-8) M T3 was found at 120 hr in the presence of 10(-3) M hydroxyurea. When isolated rat osteoclasts were cultured in the presence of 10(-7) MT3, a 1.4-fold stimulation of pit number was observed. Pit formation was not affected by addition of 10(-6) M indomethacin to either the control or T3-treated cultures. These data suggest that the stimulation of bone resorption in neonatal mouse calvariae and activation of isolated rat osteoclasts by the thyroid hormones is not related to either prostaglandin or cAMP formation. In mouse calvariae, the effect on bone resorption of the thyroid hormones is dependent on increased cellular replication, perhaps of osteoclast precursors, or other bone cells involved in the resorptive process.

We examined the effect of calcitonin in cultured mouse calvarial bones after prestimulation with different activators of adenylyl cyclase. Calcitonin (100 ng/ml), added after 48 h of culture, inhibited bone resorption (assessed as release of 45Ca from prelabeled bones cultured for 96-144 h) stimulated with parathyroid hormone (PTH, 10 nM; 0-144 h) or the adenylyl cyclase stimulator forskolin (2 microM; 0-144 h). However, no effect of calcitonin was demonstrated when bone resorption was prestimulated with the adenylyl cyclase stimulator cholera toxin, at and above 1 ng/ml, at any time point studied. In contrast, two other types of inhibitors of bone resorption in vitro, the carbonic anhydrase inhibitor acetazolamide (10 microM) and the aminobisphosphonate AHPrBP (10 microM), significantly inhibited cholera toxin-stimulated bone resorption. No cyclic AMP response to calcitonin was seen after preculture for 48 h with cholera toxin (0.1-100 ng/ml), although bones precultured in basic medium, in the absence or presence of forskolin, were still able to respond to calcitonin with elevation of cyclic AMP. Binding studies with [125I]calcitonin demonstrated that the preculture with cholera toxin did not affect the binding of calcitonin to the receptor. In summary, our data show that cholera toxin pretreatment makes calvarial bones insensitive to calcitonin-induced inhibition of bone resorption as a result of an interaction with cholera toxin at the level of calcitonin receptor-linked signal transduction. We suggest that the interaction, distal to the calcitonin receptor, is caused by the irreversible activation of Gs produced by cholera toxin.(ABSTRACT TRUNCATED AT 250 WORDS)

Previous reports have demonstrated the importance of prostaglandin formation in orthodontic tooth movement, but the mechanisms involved in the activation of prostaglandin biosynthesis in the periodontal ligament (PDL) are still unclear. There is, however, evidence that inflammatory reactions appear after application of orthodontic forces. In the present study, the effect of bradykinin (BK) and thrombin, two inflammatory mediators, on prostanoid biosynthesis in human PDL-cells was investigated. BK and thrombin caused a time-dependent burst of prostaglandin E2 (PGE2) formation (maximal effect after 2-5 min). The stimulatory actions of BK and thrombin on PGE2 biosynthesis were dose-dependent; seen in PDL-cells isolated from four different patients and abolished by the non-steroidal anti-inflammatory drug indomethacin. BK and thrombin also dose-dependently stimulated the biosynthesis of PGI2. BK agonists, with affinity to the B2 subtype of BK receptors, caused a significant increase of PGE2 biosynthesis in human PDL-cells. In contrast, BK agonists with affinity to BK-B1 receptors did not cause a burst of PGE2 biosynthesis. BK and BK-B2 receptor agonists as well as thrombin, but not BK-B1 receptor agonists, also significantly increased [3H] release in human PDL-cells prelabelled with [3H]-arachidonic acid, indicating that BK and thrombin stimulate prostanoid biosynthesis, at least partly, due to activation of phospholipase A2. These data show that BK via BK-B2 receptors, as well as thrombin, have the capacity to stimulate arachidonic acid release and subsequent prostanoid biosynthesis in human PDL-cells and thus may be implicated in the tissue reactions involved in orthodontic tooth movement.