Resorption

Hydroxyapatite (HA)-coated implants with porous-coated and grit-blasted surface textures were inserted bilaterally in a paired design into the medial femoral condyles of eight dogs for 16 weeks. The implants were weight-loaded and initially subjected to controlled micromotion of 500 ixm during each gait cycle. Histology revealed that five implants in each group had bony anchorage, and the remaining implants were surrounded by fibrous tissue. Push-out testing showed no difference in shear stiffness and strength, while energy absorption for porous-coated implants was increased significantly by threefold. The HA coating delaminated on grit-blasted implants during push-out testing, whereas porous-coated implants predominantly failed at the HA-tissue interface. Coverage, surface area, volume, and thickness of the HA coating were significantly reduced in vivo for porous-coated and grit-blasted implants. In conclusion, a plasma-sprayed porous-coated implant surface seems to give better fixation not only of the HA-coating to the implant surface but also of the implant to the surrounding tissues in comparison to a grit-blasted implant surface. The HA coating was reduced more on fibrous-anchored than on bony-anchored implants, suggesting that micromotion accelerates resorption of HA. Resorbed HA coating was replaced by more bone on porous-coated implants than on grit-blasted implants, which suggests that fixation of porous-coated implants will be durable.

The clinical use of plasma-sprayed hydroxyapatite (HA) coatings on metal implants has aroused as many controversies as interests over the last decade. Although faster and stronger fixation and more bone growth have been revealed, the performance of HA-coated implants has been doubted. This article will initially address the fundamentals of the material selection, design, and processing of the HA coating and show how the coating microstructure and properties can be a good predictor of the expected behavior in the body. Further discussion will clarify the major concerns with the clinical use of HA coatings and introduce a comprehensive review concerning the outcomes experienced with respect to clinical practice over the past 5 years. A reflection on the results indicates that HA coatings can promote earlier and stronger fixation but exhibit a durability that can be related to the coating quality. Specific relationships between coating quality and clinical performance are being established as characterization methods disclose more information about the coating. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 570–592, 2001

Polycyclic aromatic hydrocarbons (PAHs) are released into the environment as a result of incomplete fossil fuel combustion from industrial furnaces, woodburning stoves, and automobile exhaust fumes; however, the primary source of human exposure to these compounds is cigarette smoke. Embryonic and fetal loss after treatment with high doses of PAHs have been well documented in animal studies; however, few studies have addressed the reproductive consequences of long-term, low-level exposure to these chemicals. We previously reported that low doses of PAHs administered to ICR mice over a period of 9 weeks prior to conception resulted in early embryonic resorptions, whereby treated dams lost approximately 50% of their litter. During the course of these studies, we observed greater numbers of infiltrating uterine natural killer (uNK) cells into the placenta of PAH-exposed conceptuses. While exposure to high levels of PAHs has been shown to be immunosuppressive, increasing evidence suggests that chronic, low-dose exposure to PAHs may stimulate immune cells. Thus, we hypothesized that low-dose, chronic PAH exposure in our mouse model is mediating embryonic resorption by hyperstimulating maternal immune cells. In this review of the literature, we outline the rationale of our argument and present preliminary data, focussing upon PAH-mediated alterations in uNK cell dynamics and how these changes may be linked to early embryonic resorptions.

In this study, we evaluated the influence of intrusion mechanics with accentuated and reversed curve of Spee on root resorption of the maxillary and mandibular incisors. Methods: A sample of 60 patients with Class I and Class II Division 1 malocclusions having nonextraction treatment was divided into 2 groups with the following characteristics: group 1 comprised 30 deepbite patients, treated with accentuated and reversed curve of Spee intrusion mechanics, with an initial mean age of 12.8 Ϯ 1.23 years (range, 10.01-15.32 years), and group 2 comprised 30 patients with normal overbite treated without intrusion mechanics, with an initial mean age of 12.87 Ϯ 1.43 years (range, 10.02-15.36 years). Pretreatment and posttreatment periapical radiographs were used to evaluate root resorption. The groups were compared by using the Mann-Whitney U test. Correlation between root resorption and tooth movement was investigated with the Spearman correlation coefficient. Results: The deepbite group treated with accentuated and reversed curve of Spee had statistically greater root resorption (1.87) than the normal overbite group (1.54), at P ϭ .017. Changes in overbite and vertical displacements of the maxillary central incisor apices had significant correlations to root resorption (r ϭ 0.30, P ϭ .019; r ϭ 0.27, P ϭ .037, respectively). Conclusions: Accentuating and reversing the curve of Spee in the archwires to correct deep overbite causes more root resorption than nonintrusive mechanics. (Am J Orthod Dentofacial Orthop 2008;133:261-8)

The purposes of this retrospective study were to investigate the apical root resorption of maxillary incisors in orthodontic patients with en-masse maxillary anterior retraction and intrusion with miniscrews and the factors disposing a patient to apical root resorption. Methods: Fifty adult patients with maxillary protrusion were included; 30 were treated with miniscrews and extraction of the maxillary first premolars (group I), and 20 were treated with extraction of the maxillary first premolars (group II). For each patient, periapical films of the maxillary incisors and lateral cephalometric radiographs were taken before and after treatment to evaluate apical root resorption and cephalometric measurements. The intergroup differences were analyzed with the Student t test and the correlations between apical root resorption and cephalometric measurements were analyzed by the Pearson correlation. Results: The apical root resorption values were 16.0% to 20.0% (2.5-2.8 mm) in group I and 13.4% to 14.4% (2.1-2.3 mm) of the original root length in group II. Group I had significantly more severe Class II jaw discrepancy (ANB, 7.1 6 1.9 ) than did group II (ANB, 3.2 6 2.9 ). The amount of maxillary en-masse anterior retraction (8.2 6 2.4 mm), the duration of treatment (28.3 6 7.3 months), and apical root resorption of maxillary lateral incisors were significantly greater in group I than in group II. Apical root resorption of the maxillary central incisors was significantly correlated to the duration of treatment but not to the amount of enmasse retraction, intrusion, or palatal tipping of maxillary incisors. Conclusions: Miniscrew anchorage allows for more maxillary en-masse anterior retraction in patients with severe Class II cases. But the time needed for the greater amount of maxillary en-masse anterior retraction with miniscrew anchorage is longer and might dispose the patient to more apical root resorption. (Am J Orthod Dentofacial Orthop 2010;137:207-12)

Purpose: The aim of this randomized clinical trial was to compare the potential of deproteinized bovine bone added to autologous bone or corticocancellous allograft block with or without the addition of recombinant human platelet-derived growth factor-BB (rhPDGF-BB) to regenerate mandibular atrophic ridges.

A reader of the JBMR informed the editors about concern regarding a possible duplicate image in Fig. 3 in Richard and colleagues. (1) In consultation with the Committee on Publication Ethics (COPE) guidelines, the editors sought an explanation from the authors for this possible panel duplication. In Richard and colleagues, (1) the authors acknowledge an error made in presenting the images in Fig. 3B, with an image and a partial enlargement appearing in two panels, but were unable to ascertain the source of the duplication. The authors provided an alternate version of Fig. 3 (below). The authors note that osteoid was determined with von Kossa staining (shown in Fig. 3A) as well as with the Fig. 3. ERRATUM

Background: Animal and human researches have shown that immediate implant placement into extraction sockets failed to prevent socket dimensional changes following tooth extraction. It has been suggested that a minimal width of 1–2 mm of buccal bone is necessary to maintain a stable vertical dimension of the alveolar crest.Aim: To determine the dimensions of the bony wall at extraction sites in the esthetic zone (anterior teeth and premolars in the maxilla) and relate it to immediate implant placement.Methods: As part of an ongoing prospective randomized-controlled multicenter clinical study on immediate implant placement, the width of the buccal and palatal bony walls was recorded at 93 extraction sites.Results: The mean width of the buccal and palatal bony walls was 1 and 1.2 mm, respectively (P<0.05). For the anterior sites (canine to canine), the mean width of the buccal bony wall was 0.8 mm. For the posterior (premolar) sites, it was 1.1 mm (P<0.05). In the anterior sites, 87% of the buccal bony walls had a width ≤1 mm and 3% of the walls were 2 mm wide. In the posterior sites, the corresponding values were 59% and 9%, respectively.Conclusions: If the criterion of a minimal buccal bone width of 2 mm to maintain a stable buccal bony wall is valid, only a limited number of sites in the anterior maxilla display such a clinical situation. The data suggested that in the majority of extraction sites in the anterior maxilla, thin (≤1 mm) buccal walls were present. This, in turn, means that in most clinical situations encountered, augmentation procedures are needed to achieve adequate bony contours around the implant.To cite this article: Huynh-Ba G, Pjetursson BE, Sanz M, Cecchinato D, Ferrus J, Lindhe J, Lang NP. Analysis of the socket bone wall dimensions in the upper maxilla in relation to immediate implant placement. Clin. Oral Impl. Res. 21, 2010; 37–42.

Our aim was to comparatively investigate the amount of external apical root resorption (EARR) between conventional and passive self-ligating brackets. Methods: Ninety-six patients were selected from a pool of patients satisfying the following inclusion criteria: no evidence of resorption on the pretreatment panoramic radiographs; no contributing history of trauma; no dilacerations of lateral incisor roots, maxillary anodontia, and impacted canines; complete root formation at the start of treatment; intact and caries-free maxillary incisors; and no endodontically treated incisors. Patients received treatment with either a passive self-ligating bracket system or a conventional edgewise appliance, both with a 0.022-in slot. EARR of the maxillary incisors was evaluated on panoramic radiographs, taken before and after orthodontic treatment measured in millimeters. Distortion of measurements caused by panoramic radiographs was investigated by using a calibrated periodontal probe attached to the lateral incisor, and the extent of magnification was estimated to be 14%. Statistical comparisons of EARR between appliance type, age, sex, extraction treatment, and duration of treatment were investigated with univariate and multivariate regression modeling. Results: Overall, no difference was found in the amount of EARR between appliance systems. Age, sex, and extraction treatment were not reliable predictors of EARR, but a positive association between EARR and duration of treatment was observed. Conclusions: No difference should be expected for root resorption between conventional and passive self-ligating brackets. (Am J Orthod Dentofacial Orthop 2008;134:646-51) Private practice, Corfu, Greece.

Background: The purpose of this study was to compare the tensile strengths of commonly used sutures over a 2-week period under simulated oral conditions. Methods: Three suture materials (chromic gut [CG], polyglactin [PG], and polyglactin-fast absorbing [PG-FA]) were used in 4-0 and 5-0 gauges. After pretensioning, 252 suture samples (42 of each material and gauge) were used. A biologic simulation was created in vitro by mixing 9 ml sterile human saliva and human serum in a 1:1 ratio in a petri dish maintained at a pH of 7.4 to 8.1 at 37°C. All samples were tested preimmersion and 1 hour and 1, 3, 7, 10, and 14 days postimmersion. The tensile strength was assessed using a microtensile tester, and the maximum load required to cause suture breakage was determined. The point of breakage in the samples and the samples themselves were also assessed. Results: During the first 24 hours of immersion, all 4-0 and 5-0 samples of CG and PG maintained their initial level of tensile strength; PG-FA 5-0 decreased in strength, which was statistically significant (P = 0.001). Between days 1 and 3, the tensile strength of PG and PG-FA decreased significantly, with PG-FA 5-0 showing a greater and more precipitous decrease than PG-FA 4-0; the tensile strength of CG changed little during this time. After 7 days of immersion, PG 4-0 had significantly greater tensile strength than CG, and both were significantly greater than that of PG-FA. By day 10, CG and PG had statistically greater strength (P = 0.01) than PG-FA, and values were similar for the 4-0 and 5-0 gauge materials. All samples of PG-FA 5-0 and most samples of the PG-FA 4-0 exhibited 0.00 N strength (i.e., they had disintegrated) at the 10-and 14-day periods of evaluation. Conclusions: 4-0 sutures are stronger and have greater tensile strength than 5-0 sutures. CG seems to sustain its strength better than PG and PG-FA after 2 weeks. PG-FA may not be a desirable suture if tensile strength is required after 10 days. Appropriately designed clinical studies are necessary to confirm this finding in an in vivo environment.

Bone remodeling during tooth movement is regulated by local and systemic factors. Two regulators of bone metabolism are growth hormone (GH) and insulin-like growth factor-I (IGF-I). Their effects are mediated via binding to GH receptor (GHR) and IGF-I receptor (IGF-IR) in target tissues. Corticosteroids may affect the activity of these growth factors. This study examined the effect of prednisolone on GHR and IGF-IR expression in dental tissues following orthodontic tooth movement. The corticosteroid-treated group (N ϭ 6) was administered prednisolone (1 mg/kg) daily and the control group (N ϭ 6) received equivalent volumes of saline. An orthodontic force (30 g) was applied to the maxillary first molar. Animals were sacrificed 12 days postappliance insertion. Sagittal sections of the first molar were stained for GHR and IGF-IR immunoreactivity. GHR and IGF-IR cell counts were elevated following appliance-treatment. Orthodontic tooth movement appeared to up-regulate GHR and IGF-IR immunoreactivity, but this up-regulation was reduced following prednisolone treatment. The suppression of GHR and IGF-I immunoreactivity in steroid-treated animals infers the mechanism whereby bone resorption and deposition, necessary for orthodontic tooth movement, may be inhibited by prednisolone. However, at 12 days postappliance insertion, no difference in orthodontic tooth movement was observed following lowdose prednisolone treatment. (Angle Orthod 2001;71:486-493.) FIGURE 3. Mean GHR cell counts along the alveolar bone and root surfaces and PDL. (Mean values and standard deviations). SAP compared with NAP, P Ͻ .05, except for the root surface on the mesial aspect.

Objective: To assess the healing process after flap or flapless surgery in immediate implant placement.Material and Methods: This study was carried out on five Beagle dogs. Four implants were placed in the lower jaw in each dog immediately after tooth extraction. Flap surgery was performed before the extraction on one side (control), and flapless on the contrary (test). After 3 months of healing, the dogs were sacrificed and prepared for histological analysis.Results: Ten implants were placed in each group. Two failed (one of each group). The percentage of bone–implant contact was very similar in both groups: 64.8% and 65.1% for the flap and the flapless group, respectively. The difference between the mean distance from the peri-implant mucosa margin to the first bone–implant contact at the buccal aspect was statistically significant between both groups (3.02 mm. flapless and 3.69 mm. flap group). The mean first bone–implant contact at the buccal aspect was located in relation to the sand-blasted and acid-etched level at 0.82 mm for the flapless group and 1.33 mm for the flap group. This difference was not statistically significant.Conclusion: Flapless immediate implant surgery produces a significant reduction in the vestibular biologic width and a minor reduction in buccal bone plate resorption.

Objectives: Around dental implants exists a ''biologic width'' of few millimeters that have to be preserved in order to not have adverse effect on soft and hard tissues around implant. Because the minimum distance between adjacent implants has not been determined yet, we therefore, decided to perform a retrospective study on a series of spiral family implants (SFIs) to verify the minimum inter-implants' distance that has an impact on crestal bone resorption. Materials and Methods: Fifty-nine implants were investigated with a mean follow-up of 14 months. Implant diameter was 3.75, 4.2, 5 and 6 mm in 11 (18.6%), 29 (49.2%), 17 (28.8%) and 2 (3.4%) SFIs. Implant length was shorter than 13 mm, equal to 13 mm and 16 mm in 23 (39%), 23 (39%) and 13 (22%) SFIs. Implants were inserted to replace 13 incisors (22%), 7 cuspids (11.9%), 30 premolars (50.8%) and 9 molars (15.3%). Twenty-seven fixtures were inserted in post-extractive sockets and the remaining 32 in healed bone; 36 (61%) were immediately loaded. In addition to the above mentioned implant-related factors, several host-and surgery-factors were investigated. Independent samples T-test, univariate and multivariate analysis were used to detect those variables associated with the clinical outcome.

An ammonia/water mixture can be used as an efficient working fluid in industrial-type heat recovery heat pumps and heat transformers. Several configurations of such systems are possible depending on the availability of the waste (thermal) and primary (thermal or electrical) energy sources. This article presents the configurations, the main thermodynamic and hydraulic parameters, and some design guidelines and operating experiences of a medium-temperature, ammonia/water-based compression/re-sorption heat recovery system for district domestic hot water production. In-field experiments have proven the advantages of the concept and its applicability limits in a particular economical environment, while hot water was produced at 55 C with industrial cooling water at 36 C as a waste heat source.

Early embryonic resorption or fetal loss is known to occur occasionally in captive elephants; however, this has mostly been reported anecdotally. The present study documents the case of a 24-year-old, multiparous Asian elephant cow that suffered embryonic death and resorption at around 18 weeks of gestation. From ovulation onwards, this female was sonographically examined 58 times. Blood was collected twice weekly for progestagen determination via enzyme immunoassay. On Day 42 after ovulation, a small quantity of fluid was detected in the uterine horn, which typically indicates the presence of a developing conceptus. Repeated inspections followed what appeared to be a normal pregnancy until Day 116. However, on Day 124, signs of embryonic life were absent. Progestagen concentrations started declining two weeks later, reaching baseline levels one month after embryonic death. Retrospectively, ultrasound examination revealed several abnormalities in the uterine horn. Besides an existin...

Hydroxyapatite (HA)-coated implants with porous-coated and grit-blasted surface textures were inserted bilaterally in a paired design into the medial femoral condyles of eight dogs for 16 weeks. The implants were weight-loaded and initially subjected to controlled micromotion of 500 ixm during each gait cycle. Histology revealed that five implants in each group had bony anchorage, and the remaining implants were surrounded by fibrous tissue. Push-out testing showed no difference in shear stiffness and strength, while energy absorption for porous-coated implants was increased significantly by threefold. The HA coating delaminated on grit-blasted implants during push-out testing, whereas porous-coated implants predominantly failed at the HA-tissue interface. Coverage, surface area, volume, and thickness of the HA coating were significantly reduced in vivo for porous-coated and grit-blasted implants. In conclusion, a plasma-sprayed porous-coated implant surface seems to give better fixation not only of the HA-coating to the implant surface but also of the implant to the surrounding tissues in comparison to a grit-blasted implant surface. The HA coating was reduced more on fibrous-anchored than on bony-anchored implants, suggesting that micromotion accelerates resorption of HA. Resorbed HA coating was replaced by more bone on porous-coated implants than on grit-blasted implants, which suggests that fixation of porous-coated implants will be durable.

The clinical use of plasma-sprayed hydroxyapatite (HA) coatings on metal implants has aroused as many controversies as interests over the last decade. Although faster and stronger fixation and more bone growth have been revealed, the performance of HA-coated implants has been doubted. This article will initially address the fundamentals of the material selection, design, and processing of the HA coating and show how the coating microstructure and properties can be a good predictor of the expected behavior in the body. Further discussion will clarify the major concerns with the clinical use of HA coatings and introduce a comprehensive review concerning the outcomes experienced with respect to clinical practice over the past 5 years. A reflection on the results indicates that HA coatings can promote earlier and stronger fixation but exhibit a durability that can be related to the coating quality. Specific relationships between coating quality and clinical performance are being established as characterization methods disclose more information about the coating. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 570–592, 2001

Ericoid mycorrhizal fungi (ERM) are ubiquitous in cultivated cranberry beds, but no prior studies have used 15 N natural abundance measurements to track ERM influence on nitrogen (N) cycling in these agroecosystems. Cranberries (Vaccinium macrocarpon) evolved in low-nutrient peat bogs, and ERM symbioses often occur in nutrient-poor environments where N is limiting. We investigated ERM symbiosis, resorption rates, as well as leaf litter quality and decomposition to infer N conservation strategies in cultivated cranberry plants. We expected moderate to high resorption rates and low leaf litter decomposition rates. We also expected to find evidence of ERM fungi mediating N uptake. Resorption rates (35.7 AE 3.5% [s.e.]) were moderate, and the resulting cranberry leaf litter had high C:N ratios (56.9 AE 0.02). Decomposition was slow with 57 AE 2% of initial leaf litter mass remaining at the end of 2.5 years. The negative d 15 N values of cranberry leaves (À2.61 AE 0.27&) and positive d 15 N values of cranberry roots (1.04 AE 0.35&) suggest that N uptake was mediated by ERM fungi as 14 N is preferred over 15 N during transfer from mycorrhizal fungi to host plant. We demonstrated that even in this intensively managed and fertilized agroecosystem, cranberry plants retain N conservation strategies observed in wildland cranberry ecosystems, namely high resorption efficiencies, low-quality leaf litter, and active ERM symbiosis. This study has management implications, since current nutrient plans mainly focus on inorganic N fertilizer regulation and do not recognize the role of ERM fungi in mediating N uptake.

Osteoclasts are the primary mediators of pathological bone resorption in many conditions in which micro-environmental hypoxia is associated with disease progression. However, effects of hypoxia on human osteoclast activity have not been reported. Mature human osteoclasts were differentiated from peripheral blood or obtained from giant cell tumour of bone. Osteoclasts were exposed to a constant hypoxic environment and then assessed for parameters including resorption (toluidine blue staining of dentine slices), membrane integrity (trypan blue exclusion), apoptosis (TUNEL, DAPI), and osteolysis-associated enzyme activity (TRAP, cathepsin K). 24 h exposure to 2% O 2 produced a 2.5-fold increase in resorption associated with increased TRAP and cathepsin K enzyme activity. Hypoxia-Inducible Factor-1α (HIF-1α) siRNA completely ablated the hypoxic increase in osteoclast resorption. 24 h at 2% O 2 also increased the number of osteoclasts with compromised membrane integrity from 6% to 21%, with no change in the total osteoclast number or the proportion of late-stage apoptotic cells. Transient reoxygenation returned the percentage of trypan blue-positive cells to normoxic levels, suggesting that osteoclasts can recover from the early stages of cell death. Repeated over an extended period, hypoxia/reoxygenation enhanced osteoclast differentiation at this pO 2 . These data suggest that in diseased bone, where the pO 2 may fall to ≤2% O 2 , a delicate balance between hypoxia-induced osteoclast activation and hypoxia-induced osteoclast apoptosis mediates pathological bone resorption.

Aim: Receptor activator of NF-kB ligand (RANKL) and osteoprotegerin (OPG) are a system of molecules that regulate bone resorption. This study aims to compare the levels of RANKL, OPG and their relative ratio in gingival crevicular fluid (GCF) of healthy and periodontal disease subjects. Material and Methods: GCF was obtained from healthy (n 5 21), gingivitis (n 5 22), chronic periodontitis (n 5 28), generalized aggressive periodontitis (n 5 25) and chronic periodontitis subjects under immunosuppressant therapy (n 5 11). RANKL and OPG concentrations in GCF were measured by enzyme-linked immunosorbent assays. Results: RANKL levels were low in health and gingivitis groups, but increased in all three forms of periodontitis. OPG levels were higher in health than all three periodontitis, or gingivitis groups. There were no differences in RANKL and OPG levels between chronic and generalized aggressive periodontitis groups, whereas these were lower in the immunosuppressed chronic periodontitis group. The RANKL/ OPG ratio was significantly elevated in all three periodontitis forms, compared with health or gingivitis, and positively correlated to probing pocket depth and clinical attachment level. Conclusion: GCF RANKL and OPG levels were oppositely regulated in periodontitis, but not gingivitis, resulting in an enhanced RANKL/OPG ratio. This ratio was similar in all three periodontitis groups and may therefore predict disease occurrence.

To investigate effects of green-leaf nutrient status on senesced-leaf nutrient concentrations and resorption efficiency, we developed a database of nitrogen (N) and phosphorus (P) concentrations in green and senesced leaves from 92 published studies. We fit power functions (i.e., [nutrient] sen ϭ A [nutrient] ) separately for N and P. The database B gr encompassed 297 perennial species of different life-forms. Across these divergent species and conditions, a major control on senesced-leaf nutrient concentration was green-leaf nutrient status; nutrient concentrations in senesced leaves were positively associated with green-leaf nutrient concentrations (r 2 values from 51% to 84%). Within-species variation as well as species differences contributed to the overall variation in nutrient concentrations. Moreover, N and P resorption efficiency decreased, respectively, with increased N and P green-leaf status; fitted power functions indicated that a disproportionate amount of nutrient remained in senesced leaves of higher green-leaf nutrient status. Functional relationships between nutrient concentrations in senesced and green leaves were indistinguishable for evergreen and deciduous species, but evergreens tended to have lower concentrations in both senesced and green leaves. General relationships (across species and environments) between senesced-and green-leaf nutrient concentrations and broad, intraspecific variation in nutrient concentrations suggest that variation in resorption efficiency and proficiency could be a result (and not necessarily a cause) of species sorting across fertility gradients.

The resorption of nutrients (C, N and P) from senescent leaves of six seagrass species from nine different locations in tropical (Indonesia and Kenya), Mediterranean (Spain) and temperate (The Netherlands) regions has been investigated. Resorption was quantitatively assessed by calculating the difference in nutrient content between the leaves with the highest content, and the oldest leaves. In order to do so, the leaves were classified according to their age. The nutrient contents of leaves of a given age category were calculated by multiplying the measured nutrient concentration in this age category with its corresponding modelled leaf biomass. N-and P-concentrations declined during ageing and senescence of the leaves in all of the investigated situations but two. The decline in concentration varied up to 58% for N and up to 66% for P. The C-concentration declined on three of the investigated occasions and varied up to 24%. Despite a decline in concentration, the leaf C-content did not change, indicating no resorption of carbon. The efficiency of N-resorption from intact seagrass leaves varied between 3.8 and 29% (average: 15%), while the efficiency of phosphorus resorption varied between 0 and 51% (average: 21%). The resorption efficiency was not significantly different in seagrasses with a relatively high and a relatively low nutrient concentration, although within-species comparisons showed that in some cases resorption efficiency was positively related to the nutrient concentration of the leaves. Premature loss of leaves and leaf fragments (by e.g. herbivory) may substantially interfere with the resorption process. In Indonesian seagrasses we estimated that as a result of fragmentation and premature detachment only between 56 and 77% of the physiological resorption potential actually was realised. It is concluded that internal resorption may play a role in the nutrient dynamics of seagrass plants, but that its quantitative importance probably is limited. Nutrient resorption from senescent seagrass leaves may reduce the nutrient requirements for seagrass leaf production by approximately 10% for nitrogen and 15% for phosphorus.

Aim To test an electrical device for determining root canal length in primary teeth in vitro, and to compare it with the radiographic length measurement. Methodology Two examiners determined the root canal length of 24 extracted maxillary primary incisors (12 with visible root resorption and 12 without) using an electrical root canal meter (Tri Auto ZX, Morita, Dietzenbach, Germany). The instrument was left in the root canal after the second examination and a radiograph was taken. The whole tooth was cleared by immersion in methylsalicylate and subsequently photographed. Both radiographs and photographs of cleared teeth were measured and compared with the electronic measurements. Results The evaluation of the radiographs showed a mean distance between the instrument tips and apices of 0.60 (± 0.41) mm; evaluation of the cleared teeth showed an equivalent distance of 0.62 (± 0.40) mm. The mean distance between instrument tip and acceptable working length (determined with the clearing method) was 0.26 (± 0.24) mm in teeth without resorption and 0.29 (± 0.30) mm in teeth with resorption. Conclusion The presence of resorption in primary teeth did not affect the accuracy of electrical measurement of root canal length in vitro. The application of this method in primary teeth should be evaluated further.

The purposes of this retrospective study were to investigate the apical root resorption of maxillary incisors in orthodontic patients with en-masse maxillary anterior retraction and intrusion with miniscrews and the factors disposing a patient to apical root resorption. Methods: Fifty adult patients with maxillary protrusion were included; 30 were treated with miniscrews and extraction of the maxillary first premolars (group I), and 20 were treated with extraction of the maxillary first premolars (group II). For each patient, periapical films of the maxillary incisors and lateral cephalometric radiographs were taken before and after treatment to evaluate apical root resorption and cephalometric measurements. The intergroup differences were analyzed with the Student t test and the correlations between apical root resorption and cephalometric measurements were analyzed by the Pearson correlation. Results: The apical root resorption values were 16.0% to 20.0% (2.5-2.8 mm) in group I and 13.4% to 14.4% (2.1-2.3 mm) of the original root length in group II. Group I had significantly more severe Class II jaw discrepancy (ANB, 7.1 6 1.9 ) than did group II (ANB, 3.2 6 2.9 ). The amount of maxillary en-masse anterior retraction (8.2 6 2.4 mm), the duration of treatment (28.3 6 7.3 months), and apical root resorption of maxillary lateral incisors were significantly greater in group I than in group II. Apical root resorption of the maxillary central incisors was significantly correlated to the duration of treatment but not to the amount of enmasse retraction, intrusion, or palatal tipping of maxillary incisors. Conclusions: Miniscrew anchorage allows for more maxillary en-masse anterior retraction in patients with severe Class II cases. But the time needed for the greater amount of maxillary en-masse anterior retraction with miniscrew anchorage is longer and might dispose the patient to more apical root resorption. (Am J Orthod Dentofacial Orthop 2010;137:207-12)

To examine a potential role for phytoestrogens in postmenopausal bone loss, the oophorectomized (OOX) rat model has been used in three studies to investigate the effects of the phytoestrogens coumestrol, zearalanol and a mixture of isoflavones on estrogen-dependent bone loss. In the studies of coumestrol and zearalanol, the rats were allocated to a control group, a phytoestrogen-treated group (1.5 mmol coumestrol or 3.1 mmol zearalanol twice per week, intramuscular) or, in the coumestrol study, an estrogen-treated group (28.1 nmol, intramuscular). In the isoflavone study, the rats were allocated to a control group, an estrogen treated group or a treatment group that received 131.25 mg of phytoestrogens per week incorporated into the nonpurified rat diet. Bone mineral density was measured globally and at the spine and femur at base line and 6 wk post-oophorectomy. In the coumestrol study, blood and urine samples were collected. Compared with the control group, rats receiving coumestrol and zearalanol had significantly reduced bone loss at all sites measured. The estrogen-treated group had significantly greater bone density than the control and the coumestrol-treated groups in the spine and global measurements. Coumestrol reduced urine calcium excretion and the bone resorption markers pyridinoline and deoxypyridinoline after 1 wk of treatment. Oral isoflavone phytoestrogens had no effect on oophorectomized rats including bone loss at the dose used. Thus, for the first time, the bioactivity of coumestrol and zearalanol in preventing bone loss has been demonstrated in a well-recognized model of postmenopausal bone loss. J. Nutr. 127: 1795Nutr. 127: -1799Nutr. 127: , 1997.

It is well established that chronic excess of glucocorticoids has negative effects on bone and collagen turnover, and that secondary osteoporosis is a known clinical complication of endogenous Cushing's syndrome (CS). The aim of the present study was to evaluate bone dimension and bone mineral content in relation to biochemical markers of bone and collagen turnover, in a consecutive series of 23 patients with endogenous CS (18 with pituitary adenoma and 5 with adrenal tumor; 17 women, 6 men; mean age 39.7 Ϯ 2.8 (S.E.M.) and 44.3 Ϯ 3.1 years respectively), compared with 23 age-, sex-and body mass index-matched healthy controls.

The uncoupling of osteoblastic and osteoclastic activity is central to disorders such as osteoporosis, osteolytic malignancies, and periodontitis. Numerous studies have shown explicit functions for bone morphogenetic proteins (BMPs) in skeletogenesis. Their signaling activity has been shown in various contexts to be regulated by extracellular proteins, including Twisted gastrulation (TWSG1). However, experimental paradigms determining the effects of BMP regulators on bone remodeling are limited. In this study, we assessed the role of TWSG1 in postnatal bone homeostasis. Twsg1-deficient (Twsg1 2/2) mice developed osteopenia that could not be explained by defective osteoblast function, because mineral apposition rate and differentiation markers were not significantly different compared with wildtype (WT) mice. Instead, we discovered a striking enhancement of osteoclastogenesis in Twsg1 2/2 mice, leading to increased bone resorption with resultant osteopenia. Enhanced osteoclastogenesis in Twsg1 2/2 mice was caused by increased cell fusion, differentiation, and function of osteoclasts. Furthermore, RANKL-mediated osteoclastogenesis and phosphorylated Smad1/5/8 levels were enhanced when WT osteoclasts were treated with recombinant BMP2, suggesting direct regulation of osteoclast differentiation by BMPs. Increase in detectable levels of phosphorylated Smad 1/5/8 was noted in osteoclasts from Twsg1 2/2 mice compared with WT mice. Furthermore, the enhanced osteoclastogenesis in Twsg1 2/2 mice was reversed in vitro in a dose-dependent manner with exposure to Noggin, a BMP antagonist, strongly suggesting that the enhanced osteoclastogenesis in Twsg1 mutants is attributable to increased BMP signaling. Thus, we present a novel and previously uncharacterized role for TWSG1 in inhibiting osteoclastogenesis through regulation of BMP activity.

Phytoestrogens, which have structural similarity to 17beta-estradiol, have been reported to act as agonists/antagonists of estrogen in animals and humans. Estrogen is known to have an important role in maintaining bone mass, because the concentration of serum estrogen decreases after menopause and the estrogen deficiency causes bone loss. In this study, we investigated the effects of coumestrol and other phytoestrogens on osteoclast differentiation using estrogen receptor alpha-transfected RAW264.7 (RAW264.7-ERalpha) cells. When the cells were cultured with the receptor activator of nuclear factor kappa B-ligand (RANKL), both formation of tartrate-resistant acid phosphatase (TRAP) positive multinucleated cells and TRAP activity were increased compared with control cells that were cultured in the absence of RANKL. Coumestrol decreased RANKL-induced formation of TRAP-positive multinucleated cells and TRAP activity dose-dependently. RANKL-stimulated RAW264.7-ERalpha cells formed resorp...

Boron (B) is an essential micronutrient, whose deficiency is common in boreal forests. Our aim was to investigate the effects of the B supply on the retranslocation of micro-and macro nutrients in seedlings of Betula pendula Roth. One-year-old seedlings were grown under three different levels of B: 0%, 30% and 100% of the standard level for complete nutrient solution. Half of the seedlings were harvested after summer period and another half when leaves abscised. Boron was not resorbed in significant amounts from senescing birch leaves prior to abscission. The only micronutrients resorbed were Zn and Ni. Three macronutrients, N, P, and S, were resorbed efficiently from senescing leaves and accumulated into the stems. The resorption of nutrients was the mostly pronounced in B0 seedlings and minimal in B30 seedlings, which, however, showed the highest accumulation of nutrients during autumn period at least partly independently from the resorption from senescing leaves. Boron was shown to be an immobile element in silver birch seedlings that was not withdrawn from senescing leaves prior to abscission. This may increase the B availability for other tree species but also increase the potential for its leaching.

The clinical use of plasma-sprayed hydroxyapatite (HA) coatings on metal implants has aroused as many controversies as interests over the last decade. Although faster and stronger fixation and more bone growth have been revealed, the performance of HA-coated implants has been doubted. This article will initially address the fundamentals of the material selection, design, and processing of the HA coating and show how the coating microstructure and properties can be a good predictor of the expected behavior in the body. Further discussion will clarify the major concerns with the clinical use of HA coatings and introduce a comprehensive review concerning the outcomes experienced with respect to clinical practice over the past 5 years. A reflection on the results indicates that HA coatings can promote earlier and stronger fixation but exhibit a durability that can be related to the coating quality. Specific relationships between coating quality and clinical performance are being established as characterization methods disclose more information about the coating. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 570–592, 2001

Introduction: TREM2 (triggering receptor expressed in myeloid cells-2) associates with the signaling adapter DAP12 in osteoclasts (OCs). Genetic mutation or deletion of either the TYROBP (DAP12) or TREM2 gene is associated with the human disorder of brain and bone, Nasu-Hakola disease. We and others recently showed the critical requirement for immunoreceptor tyrosinebased activation motif (ITAM) signals through DAP12 and the Fc Receptor gamma chain (FcR gamma) during OC development. Here, we further define the role of TREM2 in OC differentiation and describe a role for TREM2 in OC migration and bone resorption. Materials and Methods: We generated monoclonal anti-mouse TREM2 antibodies (mAb), analyzed preosteoclasts and mature OCs for TREM2 surface expression, and determined the effect of antibody ligation on in vitro OC differentiation, resorption, and migration. TREM2 RNA interference (RNAi) was used to disrupt expression of TREM2 in pre-osteoclasts. Results: Using flow cytometry, our studies reveal that TREM2 is weakly expressed on C57BL/6 bone marrow macrophages (BMMs) and is upregulated during culture with RANKL and macrophage-colony stimulating factor (M-CSF). The expression of TREM2 is unaltered in DAP12-deficient OCs. Using C57BL/6 BMMs or RAW264.7 precursors, anti-TREM2 mAb treatment with RANKL and M-CSF enhances the formation of multinuclear TRACP(+) OCs compared with control mAb treatment. In contrast, these agents have no effect on DAP12-deficient precursors. Monoclonal Ab blockade of TREM2 on OCs generated from C57BL/6 BMMs results in decreased resorption of artificial calcium-phosphate substrate and dentine. Reduction of TREM2 expression in RAW264.7 cells by RNAi results in loss of OC formation in response to RANKL and M-CSF. Anti-TREM2 cross-linking enhances migration of C57BL/6 OCs and RAW246.7 OCs in response to M-CSF. Conclusions: Our studies indicate that eScholarship provides open access, scholarly publishing services to the University of California and delivers a dynamic research platform to scholars worldwide. the TREM2 receptor regulates OC multinucleation as well as resorption and migration of mature OCs. Thus, TREM2-DAP12 signals regulate both OC formation and function.

The clinical use of plasma-sprayed hydroxyapatite (HA) coatings on metal implants has aroused as many controversies as interests over the last decade. Although faster and stronger fixation and more bone growth have been revealed, the performance of HA-coated implants has been doubted. This article will initially address the fundamentals of the material selection, design, and processing of the HA coating and show how the coating microstructure and properties can be a good predictor of the expected behavior in the body. Further discussion will clarify the major concerns with the clinical use of HA coatings and introduce a comprehensive review concerning the outcomes experienced with respect to clinical practice over the past 5 years. A reflection on the results indicates that HA coatings can promote earlier and stronger fixation but exhibit a durability that can be related to the coating quality. Specific relationships between coating quality and clinical performance are being established as characterization methods disclose more information about the coating. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 570–592, 2001

Some tropical N2-fixing trees exhibit specific characteristics for phosphorus (P) acquisition and utilisation that contrast with the large nitrogen (N) fluxes in their litterfall. To investigate differences in N and P cycling in N2-fixing plantations, litterfall and fresh leaf quality of a N2-fixing Acacia mangium plantation were compared with that of a non-N2-fixing Swietenia macrophylla plantation and a coniferous Araucaria cunninghamii plantation. The N concentration in the A. mangium litterfall was higher than that in the litterfall of the two other species, whereas the P concentration in the A. mangium leaf litterfall was 0.16 mg g–1, which was only 12–22% of that of the other species. The P concentration in the reproductive parts of A. mangium was markedly higher (16.1 mg g–1) than those in the other fractions. The N:P ratio was higher in the leaf fall (81) compared to the fresh leaves (29) of A. mangium, in contrast to the N:P ratios in the leaf samples of the other two species. An analysis of a global litterfall dataset of tropical plantations indicated that N:P ratios in litterfall were significantly higher in N2-fixers than in non-N2-fixers, and those of A. mangium were high among species in the N2-fixer group. These results indicated that A. mangium efficiently retranslocated P in contrast to very large N cycling, under field conditions. These differences may be related to other physiological characteristics of A. mangium.

The purpose of this study was to determine the effects of bone sialoprotein (BSP) overexpression in bone metabolism in vivo by using a homozygous transgenic mouse line that constitutively overexpresses mouse BSP cDNA driven by the cytomegalovirus (CMV) promoter. CMV-BSP transgenic (TG) mice and wildtype mice were weighed, and their length, BMD, and trabecular bone volume were measured. Serum levels of RANKL, osteocalcin, osteoprotegerin (OPG), TRACP5b, and PTH were determined. Bone histomorphometry, von Kossa staining, RT-PCR analysis, Western blot, MTS assay, in vitro mineralization assay, and TRACP staining were also performed to delineate phenotypes of this transgenic mouse line. Compared with wildtype mice, adult TG mice exhibit mild dwarfism, lower values of BMD, and lower trabecular bone volume. TG mice serum contained increased calcium levels and decreased PTH levels, whereas the levels of phosphorus and magnesium were within normal limits. TG mice serum also exhibited lower levels of osteoblast differentiation markers and higher levels of markers, indicating osteoclastic activity and bone resorption. H&E staining, TRACP staining, and bone histomorphometry showed that adult TG bones were thinner and the number of giant osteoclasts in TG mice was higher, whereas there were no significant alterations in osteoblast numbers between TG mice and WT mice. Furthermore, the vertical length of the hypertrophic zone in TG mice was slightly enlarged. Moreover, ex vivo experiments indicated that overexpression of BSP decreased osteoblast population and increased osteoclastic activity. Partly because of its effects in enhancing osteoclastic activity and decreasing osteoblast population, BSP overexpression leads to an uncoupling of bone formation and resorption, which in turn results in osteopenia and mild dwarfism in mice. These findings are expected to help the development of therapies to metabolic bone diseases characterized by high serum level of BSP.

Nutrient resorption efficiency of woody plants, litterfall and nutrient fluxes were investigated in a burned and an unburned cerrado plot between October 1997 and September 1999. A large experiment (Fire Project, Brasília, Brazil) on the effects of prescribed burnings was initiated in 1992. Cerrado plots were delimited and subjected to different fire regimes. Seasonal trend of litterfall was similar in both plots but the production in the burned plot was 42.2 g m −2 y −1 before the fourth prescribed fire (September 1998) and decreased by 22% 1 y after burning while in the unburned plot it was around 230 g m −2 y −1 . Although nutrient concentrations in leaf litter were higher in the burned plot, the nutrient fluxes were 60-80% lower than in the unburned plot. Nutrient use efficiency (ecosystem level) was 4373 for P and 137 for N. Measured resorption efficiency for 10 cerrado species ranged from 14.5 to 37.2% for N and from 40 to 70.4% for P and in general, there were no differences between plots. N is in short supply, partly because of fire history, but the results, both at ecosystem and species levels (mean N/P in fresh leaves was 18), indicated a stronger limitation by P than by N.

Celiac disease is an autoimmune disorder characterized by atrophy of the intestine villi triggered by ingestion of gluten in genetically susceptible individuals. The association between celiac disease and low BMD has been recognized, but the mechanisms of disturbance are poorly understood. We show imbalance of cytokines relevant to bone metabolism in celiac patients' sera and the direct effect of these sera on in vitro bone cell activity.

Nutrient resorption from senescing plant tissues is an important determinant of the fitness of plant populations in nutrient-poor ecosystems, because it makes plants less dependent on current nutrient uptake. Moreover, it can have significant ''afterlife'' effects through its impact on litter chemistry and litter decomposability. Little is known about the effects of climate change on nutrient resorption. We studied the effects of climate change treatments (including winter snow addition, and spring and/or summer warming) on nutrient resorption of four dominant species in a nutrient-poor subarctic peatland. These species were Betula nana (woody deciduous), Vaccinium uliginosum (woody deciduous), Calamagrostis lapponica (graminoid) and Rubus chamaemorus (forb). After five years of treatments both mature and senesced leaf N concentrations showed a small but significant overall reduction in response to the climate treatments. However, the effects were species-specific. For exam-ple, in the controls the N concentration in senesced leaves of Calamagrostis (3.0±0.2 mg N g -1 ) was about four times lower than for Rubus (11.2±0.2 mg N g -1 ). There were no significant treatment effects on N resorption efficiency (% of the N pool in mature leaves that is resorbed during senescence). The nitrogen resorption efficiency of Calamagrostis (about 80%) was higher than in the other three species (about 60%). Thus, climate change has only a minor impact on nutrient resorption parameters. However, given the substantial interspecific differences in these parameters, substantial changes in plant-soil feedbacks may be expected as a result of the observed changes in the species composition of high-latitude vegetation. These changes are species-specific and thus difficult to predict.

A method was devised, from a pilot study, for transplanting a root-treated tooth with an intact periodontium into a newly prepared socket to assess whether the prognosis for transplantation procedures could be improved. Five male vervet monkeys were used for the definitive study. The mandibular central incisors were extracted from each monkey and the sockets were allowed to heal for 5 weeks. Thereafter a window of gingiva overlying each of these healed receptor sites was removed and the sockets were prepared with tapered burs. The distal root of the mandibular second molar was used as the transplant tooth and the distal root of the first molar as the control tooth. The transplant tooth was removed, together with surrounding alveolar bone which was then trimmed to a thickness of approximately 1 mm. The control tooth was extracted with root forceps. After transplantation, the teeth were splinted to the adjacent incisors for 3 weeks. After 8 weeks the healing process was examined histo...

Bone resorption stimulated by elevated serum 1,25-(OH)2-vitainin D concentrations in healthy men. We evaluated whether calcitriol administration to healthy men stimulates bone resorption. We compared serum 1,25-(0H)2-D concentrations, Ca and P04 balances, and urinary hydroxyproline excretion rates in four healthy men adapted to a low Ca diet providing only 4.0 0.2 so mmoles Calday to those in four healthy men eating a comparable diet 4.2 0.9 mmoles Ca/day) during the chronic oral administration of calcitriol. 0.75 jsg every 6 hr. Serum 1,25-(0H)2-D levels averaged 94 16 p during the control studies and 209 35 pM during calcitriol administration. Net intestinal Ca absorption averaged 0.5 0.3 mmoles/day during control and 1.8 0.5 mmoles/ day during calcitriol (P < 0.005), but urinary Ca excretion averaged 8.7 2.0 mmoles/day during calcitriol as compared to 2.9 1.4 mmoles/ day during control (P < 0.005). Thus, mean Ca balance, which averaged -2.4 1.2 mmoles/day during control, was more negative during calcitriol at -6.3 2.4 mmo!es/day (P < 0.05). Average daily P04 balances averaged +7.7 1.5 mmoles/day during control but only tended to be negative during calcitriol at -1 1 5.4 mmoles/day, (NS). Urinary hydroxyproline excretion averaged 0.26 0.03 mmoles/day during control and 0.49 0.06 during calcitriol (P < 0.001). We conclude that elevated serum l.25-(OH)2-D concentrations in healthy men eating low Ca diets stimulate bone resorption.

Absorptive hypercalciuria (AH), a common stone-forming condition characterized biochemically by intestinal hyperabsorption of calcium and hypercalciuria may be associated with bone loss. In AH type I (AH-1), hypercalciuria persists despite restriction in dietary calcium intake. We therefore hypothesized that the skeleton may contribute to the hypercalciuria in this subgroup of patients. Histomorphometric analysis of iliac crest biopsies were performed on nine stone-formers with AH-1 and on nine matched normal subjects. After stabilization on a stone-prevention diet, calcium homeostasis in the stone formers was then evaluated on inpatient constant metabolic diet before and after short-term blockade of bone resorption by alendronate (10 mg daily, 17 days total). Compared with controls, the stone-formers had lower indices of bone formation (osteoblast surface/bone surface 1.872.1 vs 3.071.5%, P ¼ 0.04; wall thickness 35.876.9 vs 47.277.6%, P ¼ 0.001) and relatively higher bone resorption (osteoclast surface/bone surface 0.470.2 vs 0.270.2%, P ¼ 0.05). In the stone-formers, a short-term course of alendronate treatment corrected fasting urinary calcium (0.1470.06 to 0.0670.04 mg Ca/mg Cr, P ¼ 0.001) and marginally reduced 24-h urinary calcium by 48 mg/day (P ¼ 0.06). Increased intestinal calcium absorption and hypercalciuria persisted, but estimated calcium balance improved (P ¼ 0.007). Our results suggest that the hypercalciuria of AH-1 originates primarily from intestinal hyperabsorption of calcium, but bone resorption in excess of bone formation may contribute.

We studied the effects of intravenous alendronate on disease activity in 36 patients with active Paget's disease of bone. Alendronate was administered to 3 groups of 12 patients at doses of 2.5'5, and 10 mg intravenously daily for 5 consecutive days. The patients were matched for disease activity. Symptomatic improvement was seen in at least 10 patients in each treatment group. Alendronate induced a dose-dependent suppression of biochemical indices of bone turnover in all patients. A significant reduction in the mean fasting urinary excretion of hydroxyproline occurred within 2 days of starting treatment, reaching a nadir at 2-4 weeks, which was most marked in patients receiving 10 mg of alendronate (p < 0.05). There was a slower fall in serum alkaline phosphatase activity with maximal suppression occurring 3 months after the start of treatment. The degree of suppression was least for those receiving 2.5 mg of alendronate (p C 0.05) but no difference in response was observed for the other dosages. The duration of response was also dose-related. A significant fall in the serum calcium and urinary excretion of calcium occurred from the second day of treatment but returned to pretreatment values by 4 months. A transient fall in the mean lymphocyte count was observed, which was similar for each group. This was associated with a short-lived fever in 3 patients receiving 10 mg, in 4 patients receiving 5 mg, and in 2 patients receiving 2.5 mg. We conclude that intravenous alendronate, 5-10 mg/day for 5 days, induces a more complete suppression of bone resorption than the lower dose and provides durable long-term control of Paget's

Background/Purpose: The aim of this study was to analyze the cytotoxicity of strontium ranelate (SR) on human periodontal ligament fibroblasts (PDL cells) in vitro. Methods: PDL cells were obtained from healthy human third molars and cultured in Dulbecco's Modified Eagle's Medium. The experimental groups were: G1, cultures treated with fresh medium (control); and G2, G3, G4 and G5: treated with SR at 20, 10, 5 and 2.5 mg/mL, respectively. The experimental times were 1, 6, 12 and 24 hours (short-term) for viability, and 2, 4, 6 and 8 days (long-term) for cell survival. The cells were counted using a hemocytometer. Data were then analyzed by one-way ANOVA and Tukey's tests (p < 0.05). Results: Cultures treated with the highest SR concentrations (G2 and G3) had significantly lower cell viability and cell numbers (p < 0.05) than those in G1, G4 and G5. SR at 2.5 mg/mL was non-cytotoxic to PDL cells. Conclusion: SR was non-toxic at appropriate concentrations. Preclinical tests are needed to further assess its safety and effectiveness for tooth resorption prior to clinical use. [J Formos Med Assoc 2008;107(8): 609-615]

Objective: To assess the healing process after flap or flapless surgery in immediate implant placement.Material and Methods: This study was carried out on five Beagle dogs. Four implants were placed in the lower jaw in each dog immediately after tooth extraction. Flap surgery was performed before the extraction on one side (control), and flapless on the contrary (test). After 3 months of healing, the dogs were sacrificed and prepared for histological analysis.Results: Ten implants were placed in each group. Two failed (one of each group). The percentage of bone–implant contact was very similar in both groups: 64.8% and 65.1% for the flap and the flapless group, respectively. The difference between the mean distance from the peri-implant mucosa margin to the first bone–implant contact at the buccal aspect was statistically significant between both groups (3.02 mm. flapless and 3.69 mm. flap group). The mean first bone–implant contact at the buccal aspect was located in relation to the sand-blasted and acid-etched level at 0.82 mm for the flapless group and 1.33 mm for the flap group. This difference was not statistically significant.Conclusion: Flapless immediate implant surgery produces a significant reduction in the vestibular biologic width and a minor reduction in buccal bone plate resorption.

Premature bone resorption and remodeling by osteoclasts can limit the longevity of implant fixation and recovery time. Orally administered bisphosphonates (BPs) have been used to inhibit osteoclast action at the implant/ bone interface. Ideally, these should be delivered at the interface with the osteoblast-active hydroxyapatite (HA) for maximum effect. This investigation introduces a novel BP loading technique to achieve improved BP release from a simulated body fluid-grown HA (SBF-HA) with the aim of improving implant fixation. A solution co-precipitation technique incorporates the BP (pamidronate) into a thin SBF-HA coating. Surface analysis, using X-ray photoelectron spec-troscopy (XPS), of the resultant coating was employed to confirm the presence of the adsorbed BP on the surface of SBF-HA. XPS analysis was also used to determine the optimal adsorption process. Osteoclast cell culture experiments confirmed the biological effectiveness of BP adsorption and proved that the pamidronate was biologically active, causing both decreased osteoclast numbers and decreased resorption.