Extent Of Resorption Research Articles

Bar Attachement Retained Mandibular Complete Denture

The complete mandibular prosthesis constitutes a challenge for the practitioner. Unfavorable anatomo-physiological factors, including the small bearing surface and the extent of resorption, often compromise prosthetic retention. The exploitation of residual roots as a support for the conjunction bar constitutes an excellent additional mechanical means of retention. This prosthetic alternative considerably improves the comfort and masticatory coefficient of the patient on condition that the imperatives of root conservation as well as the clinical and laboratory implementation techniques are respected.

In-vitro analysis of resorption processes following high hydrostatic pressure treatment of human trabecular bone

The present study focused on the investigation of the resorption behavior of high hydrostatic pressure (HHP) treated bone allografts in vitro by analyzing the differentiation and activity of osteoclast precursors. HHP is known to be an efficient method for devitalization of bone grafts and a gentle alternative compared to conventional processing. While bone resorption is part of the physiological fracture healing, highly processed allografts are prone to excessive degradation, which ultimately leads to graft failure. The influence of HHP treatment on the extent of resorption was analyzed in bone blocks cultivated with peripheral blood mononuclear cells (PBMCs). Data on gene and protein expression as well as histological alterations were obtained. The present study showed that an application of 500 MPa led to significant osteoclastic differentiation and activity which was observed already after 8 h of incubation. Whereas a treatment of 250 MPa resulted also in the differentiation of PBMCs, osteoclastic activity was similar to the untreated control. Thus, the pressure level of HHP is crucial for the extent of degradation processes. Based on our results a treatment with 500 MPa might not be suitable for allografts intended for subsequent clinical applications. This study provides a basis for further experiments including in vivo studies which should focus on the equilibrium of bone formation and bone resorption.

Osteoclast-mediated resorption primes the skeleton for successful integration during axolotl limb regeneration.

Early events during axolotl limb regeneration include an immune response and the formation of a wound epithelium. These events are linked to a clearance of damaged tissue prior to blastema formation and regeneration of the missing structures. Here, we report the resorption of calcified skeletal tissue as an active, cell-driven, and highly regulated event. This process, carried out by osteoclasts, is essential for a successful integration of the newly formed skeleton. Indeed, the extent of resorption is directly correlated with the integration efficiency, and treatment with zoledronic acid resulted in osteoclast function inhibition and failed tissue integration. Moreover, we identified the wound epithelium as a regulator of skeletal resorption, likely releasing signals involved in recruitment/differentiation of osteoclasts. Finally, we reported a correlation between resorption and blastema formation, particularly, a coordination of resorption with cartilage condensation. In sum, our results identify resorption as a major event upon amputation, playing a critical role in the overall process of skeletal regeneration.

Diagnostic Accuracy of Periapical Radiography in Detection and Measurement of the External Root Resorption in Primary Molars: A Single-Blind Prospective Clinical Study

Introduction Identifying the external root resorption plays an important role in treatment planning for deciduous teeth. Although proper accuracy of digital radiography in the diagnosis of external root resorption has been established in permanent dentition, it cannot be at all generalized to the primary root being superimposed by the succeeding permanent teeth. Interestingly, no study has assessed this in primary teeth yet. Thus, this study was undertaken for the first time. Methods This was a single-blind prospective clinical diagnostic study performed on 501 observations (observed by 3 observers) pertaining to 167 roots of 45 maxillary/mandibular primary molars (in 6–8-year-old patients) which were indicated for extraction and did have succeeding permanent teeth. Digital parallel periapical radiographs were taken before dental extraction using a PSP sensor. Radiographs were printed and examined by two pediatric dentists. After the extraction, the extent of resorption was directly measured, twice, by third and fourth observers blinded to radiographic estimates. Radiographic errors and absolute errors (mm) were calculated. Various parameters were analyzed statistically. Results Of the roots, 56.3% were really resorbed with (mean = 5.01 ± 2.10 mm). First/second observers failed to identify 19.6% and 38.3% of roots, respectively. Average errors were −0.77 ± 2.31 and 0.14 ± 2.19 mm in girls and boys, respectively (P=0.043, t-test). The factors “side, jaw, tooth type, and root type” did not affect errors (P > 0.05). Average absolute errors were 1.79 ± 1.47 mm (significantly above zero, P < 0.0005). No evaluated factor affected it (P > 0.1). Actual lesion sizes correlated with errors (Pearson R = 0.682, P < 0.0005) but not with absolute errors (P=0.464). Conclusion Although many deciduous roots might be missed, digital radiography might still provide rather a good accuracy in diagnosis and measurement of external root resorption up to about 1.8 mm absolute error. Observers might overestimate resorption sizes in girls and in cases with actual lesions smaller than 3 mm. Size of the lesion can influence the direction of error (shortening/elongation), but not its directionless magnitude.

A clinical approach strategy for the diagnosis, treatment and evaluation of external cervical resorption.

To propose a clinical approach strategy on the diagnosis, treatment and evaluation of external cervical tooth resorption (ECR) cases. To investigate and discuss the outcome of this approach. A clinical approach strategy on ECR was developed based on a retrospective observation study of 542 teeth. Forty-seven teeth were excluded due to lack of clinical/radiographical information, and 182 were immediately extracted. This approach had three steps: diagnosis, treatment planning and evaluation. During diagnosis, the medical, dental history and clinical/radiographical characteristics were evaluated. Depending on the resorption extent, ECR cases were categorized into four classes according to Heithersay's classification. During treatment planning, a treatment decision flowchart was prepared based on four main decisive criteria: probing feasibility, pain, location and extent of resorption (class), and existence of bone-like tissue. Three treatment options were applied: (a) extraction, (b) monitoring or (c) conservative treatment by external, internal or combination of internal-external treatments. During evaluation, assessment of ECR progression, tooth survival and other factors like aesthetics and periodontal attachment were performed. Descriptive statistical analysis of the outcome for up to 10years (for the overall clinical approach and for each individual treatment decision), was carried out with OriginLabs OriginPro 9 and Microsoft Excel 365. A three-step strategy was developed on how to deal with ECR cases. Indicative examples of each treatment decision were presented and discussed. The overall survival rate of this strategy was 84.6% (3years), 70.3% (5years), 42.7% (8years) and 28.6% (10years). Higher survival rate was observed for external treatment decision than for internal. The success of each treatment decision depended on the extent of the resorption (class). The success of a treatment decision should be based on the long-term outcome, as a different evolution can be observed with time. A clinical approach strategy was introduced on ECR pathosis. This strategy was not solely based on ECR class, as other important decisive criteria were considered. This step-wise approach, has a 70.3% survival rate with a mean of 5years. This work will hopefully provide an incentive for a broader collaboration, to potentially establish a universally accepted ECR treatment strategy.

Nanocomposites based on apatitic tricalcium phosphate and autofibrin

Nanocomposites based on apatitic tricalcium phosphate in an autofibrin matrix were obtained by precipitation at a Ca/P ratio of 1.50, pH 9 and a maturation time from 30 min to 7–14 days. The resorbability of nanocomposites was determined by the composition of calcium phosphates, which, during long-term maturation, formed as the calcium-deficient hydroxyapatite with a Ca/P ratio of 1.66, whereas biopolymer matrix favored the formation of more soluble calcium phosphates with a Ca/P ratio of 1.53–1.59. It was found that the fibrin clot stabilized, along with apatitic tricalcium phosphate, the phase of amorphous calcium phosphate, which after 800 °C was transformed into resorbable α-tricalcium phosphate. Citrated plasma inhibited the conversion of apatitic tricalcium phosphate into stoichiometric hydroxyapatite, which also facilitated the formation of resorbable β-tricalcium phosphate after 800 °C. The combined effect of the maturation time and the biopolymer matrix determined the composition, physicochemical and morphological properties of nanocomposites and the possibililty to control its extent of resorption

Regional differences in microarchitecture and mineralization of the atrophic edentulous mandible: A microcomputed tomography study

ObjectiveThe aim of the present study was to assess mineralization and trabecular microarchitecture in atrophic edentulous mandibles and to identify regional differences and relations with the extent of resorption. MethodsCortical and trabecular bone volumes in anterior, premolar and molar regions of 10 edentulous cadaveric mandibles (5 males and 5 females; mean age ± SD: 85.4 ± 8.3 years) were assessed by microcomputed tomography. Mandibular height and Cawood & Howell classes were recorded. Concerning trabecular volumes, bone mineral density (BMD), bone volume fraction, trabecular tissue volume fraction, connectivity density, trabecular number, trabecular thickness, trabecular separation, degree of anisotropy, and structural model index were measured; concerning cortical volumes porosity, BMD and cortical thickness were measured. ResultsIn molar regions, the bone volume fraction and trabecular number were lower, whereas trabecular separation, degree of anisotropy and cortical BMD were higher compared to anterior regions. In premolar regions, mandibular height correlated negatively with trabecular number (Spearman’s correlation r = 0.73, p = 0.017) and connectivity density (Spearman’s correlation r = 0.82, p = 0.004), and correlated positively with trabecular separation (Spearman’s correlation r = − 0.65, p = 0.04). Cortical BMD was higher at bucco-inferior cortex of molar and inferior border of premolar region and lower at anterior cranial buccal and lingual surface. ConclusionsIn the premolar region, increased resorption coincides with local impairment of trabecular bone quality. Cortical bone BMD is higher in areas with highest strains and lower in areas with most mandibular resorption. Trabecular bone volume and quality is superior in the anterior region of the edentulous mandible, which might explain improved primary stability of dental implants in this region.

Bone resorption in autologous cryopreserved cranioplasty: quantitative evaluation, semiquantitative score and clinical significance.

Changes after reimplantation of the autologous bone have been largely described. However, the rate and the extent of resorption in cranial grafts have not been clearly defined. Aim of our study is to evaluate the bone flap resorption (BFR) after cryopreservation. We retrospectively reviewed 27 patients, aged 18years or older, subjected to cranioplasty (CP) adopting autologous cryopreserved flap. The BFR was derived from the percentage of decrease in flap volume (BFR%), comparing the first post-operative computed tomography (CT) and the last one available (performed at least 1year after surgery). We also proposed a semiquantitative scoring system, based on CT, to define a clinically workable BFR classification. After a mean ± SE follow-up of 32.5 ± 2.4months, the bone flap volume decreased significantly (p < 0.0001). The mean BFR% was 31.7 ± 3.8% and correlated with CT-score (p < 0.001). Three BFR classes were described: mild (14.8% of cases) consisting in minimal bone remodelling, CT-score ≤ 6, mean BFR% = 3.5 ± 0.7%; moderate (51.9% of cases) corresponding to satisfactory cerebral protection, CT-score < 13, mean BFR% = 25.6 ± 2.2%; severe (33.3% of cases) consisting in loss of cerebral protection, CT-score ≥ 13, mean BFR% = 54.2 ± 3.9%. Females had higher BFR% than males (p = 0.022). BFR classes and new reconstructive surgery were not related (p = 0.58). BFR was moderate or severe in 85.2% of re-implanted cryopreserved flaps. The proposed CT-score is an easy and reproducible tool to define resorption extent.

Morphological Changes of the Root Apex in Permanent Teeth with Failed Endodontic Treatment.

To determine the number, shape and diameter of apical foramina as well as changes in root apex morphology of permanent teeth with failed endodontic treatment. Clinical records were collected for teeth diagnosed with posttreatment periapical periodontitis that subsequently underwent endodontic microsurgery. Resected root apices were examined with stereomicroscopy. The number, shape and diameter of apical foramina were recorded. Scanning electron microscopy (SEM) was used to investigate the presence and extent of apical external root resorption and evaluate how it was influenced by sex, age, tooth position, periapical radiolucency size and periapical lesion biopsy results. External root resorption was classified according to site (periforaminal or foraminal), and the extent of resorption was graded as 0, 1, 2 or 3. A total of 112 teeth with 112 apices were examined. The mean diameter of the main apical foramina was 420.78 µm. The apical foramen was most commonly irregularly shaped (68.39%). The incidence of multiple foramina was 48.21%. SEM revealed that 96.43% of apices had periforaminal resorption (PR) and 94.64% had foraminal resorption (FR). The existence and extent of external root resorption were not correlated with sex, age, tooth position, periapical radiolucency size or periapical lesion biopsy results (P > 0.05). Apical foramina of permanent teeth with failed endodontic treatment were commonly irregularly shaped, with a mean diameter of approximately 420 µm. Nearly half of the samples had multiple foramina. There was a high prevalence of apical external root resorption. A relationship may exist between morphological changes in the root apex and treatment failure.

Histological evaluation of the repair process of replanted rat teeth after storage in resveratrol dissolved in dimethyl sulphoxide.

The storage media is directly related to the prognosis of avulsed teeth, with resveratrol drawing attention due to its antioxidant and anti-inflammatory proprieties. The aim of this study was to evaluate the repair process in rat teeth following delayed replantation after storage in resveratrol (R) dissolved in dimethyl sulphoxide (DMSO). The upper right central incisors of 36 rats were divided into 4 groups. In group I, the teeth were extracted and immediately replanted. Group II teeth were stored in 50mL R+DMSO (0.0512g/mL), whereas group III teeth were stored in 50mL pure DMSO, both for a period of 60minutes. The teeth of group IV were stored dry for 60minutes. The teeth of groups II, III and IV were then replanted, and the animals were euthanized after 60days. Longitudinal histological cuts were HE stained for histomorphometric analysis of the periodontal ligament, alveolar bone, cementum and dentin. The analysis of HE stained histological sections showed the following statistical differences: the acute inflammatory process in the epithelial insertion was less prominent in group II than in group III; the organization of the periodontal ligament was better in group I, while the intensity and extension of acute inflammation in the periodontal ligament were better in group I, and worse in group III; the chronic inflammatory infiltrate was less in groups I and IV, and the depth and extent of resorption, as well as the repair of root resorption, were better in group I. Storage in R+DMSO solution did not inhibit root resorption after delayed replantation in rat teeth. It is concluded that pure DMSO is not a suitable transport medium for avulsed teeth.

Nonsurgical management of horizontal root fracture associated external root resorption and internal root resorption

Horizontal root fractures, which frequently affect the upper incisors, usually result from a frontal impact. As a result, combined injuries occur in dental tissues such as the pulp, dentin, cementum, periodontal ligament, and alveolar bone. Internal root canal inflammatory resorption involves a progressive loss of intraradicular dentin without adjunctive deposition of hard tissues adjacent to the resorptive sites. It is frequently associated with chronic pulpal inflammation, and bacteria might be identified from the granulation tissues when the lesion is progressive to the extent that it is identifiable with routine radiographs. With the advancement in technology, it is imperative to use modern diagnostic tools such as cone beam computed tomography and radiovisuography to diagnose and confirm the presence and extent of resorptions and fractures and their exact location. This case report presents a rare case having internal root resorption and horizontal root fracture with external inflammatory root resorption both which were treated successfully following guidelines by International Association of Dental Traumatology by nonsurgical treatment with 1 year follow-up.

Osteoimmunological mechanisms involved in orthodontically and bacterially induced periodontal stress

Orthodontic tooth movement is known to cause sterile inflammation of the periodontal ligament (PDL). It may also be accompanied by pathological effects of external apical root resorption, with interindividual differences in the incidence and extent of resorption. An involvement of autoimmunological mechanisms is currently under discussion. This study aimed to improve our understanding of similarities between the inflammatory mechanisms underlying the pathophysiology of periodontitis and root resorption. Human PDL cells were stimulated with interleukin (IL)-1β/IL-17A/IFN-γ, or left non-stimulated. Their potential for phagocytosis was then evaluated by incubation with dextran or E. coli or S. aureus particles, followed by flow cytometric and immunohistochemical analysis. Real-time polymerase chain reaction (PCR) was used to analyze receptor activator of NF-κB ligand (RANKL) and osteoprotegerin (OPG) expression in PDL cells. Verification was obtained in vivo by studying IL-17A, RANKL, and OPG expression in biopsies of inflamed periodontal tissues and in biopsies of rat maxillae with mechanically induced root resorption. Statistical analysis included Wilcoxon's rank sum test to analyze gene expression data and one-way ANOVA in conjunction with Tukey's post hoc test to analyze flow cytometric data. PDL cells phagocytosed foreign particles under both inflammatory and non-inflammatory conditions. Furthermore, IL-17A significantly downregulated RANKL expression while significantly upregulating OPG expression in PDL cells. These immunomodulatory cytokines were also demonstrable in both inflammatorily altered periodontal tissues and root resorption lacunae, while the incidence of IL-7A was strikingly variable in resorption areas. PDL cells were demonstrated to effect phagocytosis and to express immunomodulatory molecules, which proves their capability of participating in periodontal osteoimmunological processes. The development of root resorption and periodontitis appears to be governed by similar pathophysiological mechanisms.

Risk factors associated with external apical root resorption of the maxillary incisors: a 15-year retrospective study

Abstract Aim: To determine the possible risk factors for external apical resorption (EARR) of the maxillary incisors. Methods: Panoramic radiographs of 132 orthodontic patients with a mean age of 16.9 ± 3.6 years were selected from two practice centres in Tehran. The radiographs were taken between 1990 and 2005 and 63.6% of the subjects were female. Mean, standard deviation and distribution of EARR for various variables were assessed. Prevalence significance, as well as differences between frequency distributions of clinical EARR (≥ 1.2 mm) between genders, treatment plans (extraction/ non-extraction), initial overjet and overbite magnitude, and incisor types (centrals/laterals) were evaluated by the chi-squared test. The mean resorption rates on central and lateral incisors were compared using the independent-samples t-test. Associations between EARR with the age, duration of treatment, pretreatment overjet and overbite were assessed by the Pearson’s correlation test. The reliability of the method was determined by remeasuring 117 randomly selected incisors and determining the associations between both sets of measurements with the Pearson’s correlation coefficients. Results: The prevalence of EARR, and clinical EARR (≥ 1.2 mm) were 91.8% and 44.78% respectively. The average of EARR was 1.377 ± 1.214 mm, or 8.165 ± 8.021% of pretreatment root lengths. The prevalence of clinical EARR was significantly higher in extraction cases, cases with greater initial overjet and on lateral incisors. Using the t-test, significant differences (p &lt; 0.05) were observed between the extent of resorption between genders (higher in females), treatment plans (higher in extraction cases) and incisor types (greater on lateral incisors). Longer treatment times and excessive initial overjet were correlated with higher EARR levels (p &lt; 0.05, r &lt; 0.2). Conclusions: Factors related to premolar extraction, initial ovejet size, treatment time and being female may be correlated with higher EARR. Clinically significant resorption did not occur more in females.

Urinary excretion of deoxypyridinoline increases after gastrointestinal surgery

Objective We investigated the effect of gastrointestinal surgery on bone metabolism with special reference to nutrition status and the systemic inflammatory response (SIR). Methods We assessed bone resorption by measuring the urinary excretion of deoxypyridinoline (D-Pyr), a specific marker that reflects the amount of degraded collagen. Twenty patients who underwent gastrectomy or colectomy were enrolled in this study. Daily energy intake, nitrogen, calcium, and phosphate balances, and urinary D-Pyr were examined preoperatively and for 14 days after the operation. The nutritional risk index and prealbumin were measured for nutrition assessment, and SIR was evaluated daily based on scorings of body temperature, pulse rate, respiratory rate, and white blood cell number according to our criteria. Results Urinary D-Pyr excretion had already increased on postoperative day 1 and continued to increase until postoperative day 14. The amounts of postoperative urinary excretion of D-Pyr correlated positively with the SIR scores and the amount of urinary excretion of cortisol, one of the stress-response hormones, and inversely with pre- and postoperative nutritional risk indices. In addition, the patients who experienced complications during the postoperative period excreted larger amounts of D-Pyr. Conclusions Because the amount of excreted D-Pyr reflects the loss of the bone matrix, these results may indicate that bone resorption increases after gastrointestinal surgery. The extent of resorption was parallel to the degree of SIR and nutrition status.

Apical root resorption after lingual orthodontic therapy.

Apical root resorptions are among the undesirable side effects of orthodontic therapy. The aim of the present study was to investigate radiologically whether and to what extent resorptions occur in patients treated solely with a fixed lingual appliance, as well as the pathogenetic relevance of the extent and direction of the therapeutically induced apical movement. The collective comprised 33 female and seven male patients with a mean age of 24.2 +/- 8.4 years. Permanent lower premolars were extracted in five, and permanent upper premolars in 22 patients. In total, 456 upper and lower incisors and canines were assessed. In order to evaluate the relative change in root length and the sagittal and vertical apical movements, pre- and posttherapeutic panoramic radiographs and/or lateral cephalograms were analyzed. After completion of orthodontic treatment the mean root length was 96.3%, corresponding to a resorption rate of 3.7%. The resorption rates of teeth 11, 12 and 21 differed significantly from those of teeth 31, 32 and 43. Upper incisors presented increased mean resorption rates < or = 10%. Only 18% of the 456 teeth analyzed were affected by pronounced resorptions > 10%. 82% of the teeth were resorption-free. A patient-related evaluation revealed that 26 of the 40 patients had no resorptions > 20%, while 14 had between one and four affected teeth. No significant relationship between extent of resorption and parameters such as age, gender, active treatment time, Angle class, or extent and direction of apical movement was recorded. The results suggest that lingual orthodontic therapy resulted in only slight root resorptions. Pronounced root shortenings were observed in some patients whose individual predisposition may constitute the main risk factor for the occurrence of root resorptions.

Estimation of volume referent bone turnover in the otic capsule after sequential point labeling.

Using fluorochrome labeling and a newly validated method for bone turnover estimation, we determined absolute values for canine perilabyrinthine bone remodeling. The overall capsular bone turnover was found to be 2.1% per year, compared to 13.9% per year for the neighboring cranial bones and 7.4% per year for the humerus compacta. This gross 2.1% per year conceals a vast range, from 0.13% per year for the innermost perilymphatic zone, through a centrifugal increment toward 8% to 10% per year in the periphery. The underlying individual bone remodeling units exhibit a similar centrifugal pattern in numerical density and size. These findings indicate an inhibition of remodeling, seemingly emanating from the perilymphatic spaces, and affecting both the activation of osteoclasts and the extent of resorption by the osteoclasts. These values satisfactorily explain the preservation of such fetal remnants as the globuli ossei, the interglobular spaces, and the skein bone. In humans, local ineffective inhibition of bone resorption may play a role in the initiation of otosclerosis.

Weekly administration of alendronate: Rationale and plan for clinical assessment

This paper describes the rationale and supporting data for once-weekly dosing of alendronate. Alendronate sodium, a bisphosphonate that potently inhibits bone resorption, has been shown to increase bone mass and substantially reduce the incidence of osteoporotic fractures, including fractures of the hip. The standard regimen of daily administration has generally been well tolerated. However, weekly administration may provide greater convenience to patients without compromising efficacy or tolerability. The pharmacokinetics of alendronate and bone remodeling theory predict similar efficacy for weekly and daily administration if the cumulative dose is the same. Bone resorption in individual remodeling units normally proceeds for approximately 2 weeks; alendronate inhibits the rate and extent of resorption. Because the half-life of residence on bone surfaces is several weeks, weekly administration of alendronate should inhibit bone resorption to an overall extent similar to that of daily dosing, thereby producing similar effects on bone mass and strength. Animal studies demonstrate that both weekly and daily parenteral administration of alendronate effectively increase bone mass and strength, but confirmation of efficacy is needed for weekly oral dosing in humans. Although daily bisphosphonates (alendronate and risedronate) elicited esophageal irritation in a canine model of gastroesophageal reflux, weekly dosing with alendronate at a higher unit dose did not. Thus, the lower frequency of weekly dosing with a higher unit dose may actually reduce the risk of upper gastrointestinal irritation compared with daily administration of a lower dose. Current safety and efficacy data justify further investigation of once-weekly dosing of alendronate. Two positive-control, double-blind, randomized trials of osteoporosis treatment and prevention are currently being performed to assess the comparability of weekly, biweekly, and daily dosing of alendronate with regard to effects on bone density, safety, and tolerability.

In Vivo Effect of β2-Microglobulin on Bone Resorption

β2-Microglobulin (β2-M) deposits have been found in the destructive bone lesions associated with dialysis-related amyloidosis. To examine whether β2-M can cause bone resorption in vivo, doses of (β2-M alone were compared with parathyroid hormone (PTH), aluminum, and vehicle alone. Eleven injections of 10 δg each were made over a period of 56 hours into the subcutaneous tissue overlying the occipital region of mice. Using a computerized image analysis system we measured (1) periosteal and inner bone length, (2) bone marrow interface length, and (3) the extent of resorption along these surfaces expressed as percentage of total length. Injections of either (β2-M or PTH were associated with 22% ± 4% and 25% ± 4% resorption of periosteal surface, respectively, and 15.9% ± 2% and 19.9% ± 5% resorption of marrow bone surfaces, respectively, compared with control. In contrast, aluminum did not increase bone resorption over controls. The simultaneous injection of calcitonin, an osteoclast inhibitor, with β2-M or PTH did not increase periosteal resorption over controls. The resorption of inner bone surface was similar in all groups. These studies show that β2-M and PTH cause bone resorption in the bone surfaces proximate to the site of injection. This suggests that β2-M may contribute to the development of the bone cysts in dialysis-related amyloidosis.

Bone acidic glycoprotein 75 inhibits resorption activity of isolated rat and chicken osteoclasts

Matrix protein effects on the differentiated activity of osteoclasts were examined in order to understand the functional significance of bone protein interactions with osteoclasts. Bone acidic glycoprotein 75 (BAG 75) from rat calvariae inhibited the resorption of bone by isolated rat osteoclasts with IC50 = 1 nM compared to IC50 = 10 nM for chicken osteoclasts. By contrast, other phosphoproteins similarly isolated from bone were less effective in inhibiting resorption with IC50 = 100 nM osteopontin and IC50 greater than 100 nM bone sialoprotein. Likewise, RGD-containing matrix proteins vitronectin, thrombospondin, and fibronectin all displayed IC50 greater than or equal to 100 nM. Mechanistically, 10 nM BAG 75 marginally slowed, but did not block, the association of bone particles with chicken osteoclasts compared with osteopontin or control media. Pretreatment of osteoclasts with 50 nM BAG 75 had no effect on subsequent bone resorption; however, pretreatment of bone with BAG 75 before incubation with osteoclasts reduced the extent of resorption by 55%. These data suggest that a BAG 75/bone surface complex, rather than BAG 75 alone, represents the inhibitory form. Consistent with this hypothesis, direct binding studies provided no evidence of specific, high-affinity receptors on osteoclasts for BAG 75, nor was an excess of BAG 75 (100 nM) able to compete with 0.3 nM sechistatin for osteoclastic avB3-like receptors. However, BAG 75 displayed cooperative binding to tissue fragments and bone particles at concentrations greater than 10 nM, suggesting that BAG 75 self-associates into higher-order species on bone surfaces. Electron microscopy confirmed the time-dependent polymerization of BAG 75 into interconnecting filaments. These data suggest a novel, inhibitory activity for surface-bound BAG 75 on bone resorption that does not appear to involve the osteoclastic avB3-like integrin.

Bone Biopsy in the Horse: 3. Normal Histomorphometric Data According to Age and Sex

Histomorphometrical analysis of bone biopsies from the wing of ilium in 35 clinically normal horses are reported according to age. The biopsies were collected from 20 mixed-bred foals (mean age 6 +/- 1 months) and 15 older horses (mean age 73 +/- 62 months). No gender differences were found in the group of foals examined, but a significant difference (p less than 0.001) in a number of the primary measurements occurred between them and the older horses. The parameters which altered with age were the extent of osteoid surface (OS/BS), the extent of resorption (erosion) surface (ES/BS), the osteoid thickness (O. Th), the mineral appositional rate (MAR), which corresponds to the rate of matrix mineralisation and, if no mineralisation defects exist reflects the amount of bone laid down per day, and the extent of labelled surfaces (MS/BS). These data indicate a much greater rate of bone remodelling in the foals. This was also reflected in a number of the derived parameters (i.e. the extent of quiescent surfaces [QS/BS] and the activation frequency [Ac.f]).