The nature and tissue distribution of non-collagenous bone proteins synthesized by adult rat bone marrow cells, induced to differentiate in the presence of dexamethasone (DEX) and beta-glycerophosphate (beta-GP), was studied in vitro to determine the potential role of these proteins in bone formation. Northern hybridization analysis revealed a strong induction of bone sialoprotein (BSP) and osteocalcin in DEX-treated cultures, whereas the constitutive expression of secreted phosphoprotein I (SPP-1), type I collagen, SPARC, and alkaline phosphatase was stimulated 6-, 5-, 3-, and 2.5-told, respectively. Metabolic labeling of proteins showed that the sialoproteins (SPP-1 and BSP) were mostly secreted into the culture medium in the non-mineralizing (-beta-GP) cultures, but were the predominant non-collagenous proteins associated with the hydroxyapatite of the bone nodules in mineralizing cultures (+ beta-GP). Extraction of the tissue matrix with 4 M GuHCl and digestion of the demineralized tissue matrix with bacterial collagenase revealed that some BSP was also associated non-covalently and covalently with the collagenous matrix. SPP-1 was present in two distinct, 44 kDa and 55 kDa, forms in the conditioned medium of all cultures and was preferentially associated with the hydroxyapatite in the mineralizing cultures. In comparison, SPARC was abundant in culture media but could not be detected in de-mineralizing extracts of the mineralized tissue. Radiolabeling with [35SO4] demonstrated that both SPP-1 and BSP synthesized by bone cells are sulfated, and that a 35 kDa protein and some proteoglycan were covalently associated with the collagenous matrix in +DEX cultures. Labeling with [32PO4] was essentially confined to the sialoproteins; the 44 kDa SPP-1 incorporating significantly more [32PO4] than the 55 kDa SPP-1 and the BSP. These studies demonstrate that BSP and osteocalcin are only expressed in differentiated osteoblasts and that most of the major non-collagenous bone proteins associate with the bone mineral. However, some novel proteins together with some of the BSP are associated with the collagenous matrix where they can influence hydroxyapatite formation.

Osteopontin (OPN) is a prominent bone matrix protein that is synthesized by osteoblastic cells. To elucidate the function of OPN in bone we studied the regulated expression of the rat OPN protein during bone formation in vivo and in vitro. OPN mRNA is expressed by preosteoblastic cells early in bone formation, but the highest expression is observed in mature osteoblasts at sites of bone remodelling. A low-phosphorylated, 55-kDa form of OPN is produced by the preosteoblastic cells, whereas osteoblasts produce a highly phosphorylated, 44-kDa protein; the two forms of OPN corresponding to pp69 and pp62 in transformed rat cells. The synthesis of the 55-kDa OPN correlates with the formation of a 'cement' matrix that is synthesized prior to bone deposition, whereas the 44-kDa OPN synthesized by osteoblasts associates rapidly with hydroxyapatite, possibly regulating crystal growth, and may also provide a substratum for osteoclast attachment. Expression of OPN mRNA is upregulated by growth and differentiation factors (PDGF, EGF, TGF-beta and BMP-7/OP-1) and by mechanical stress, which promote bone formation, as well as by osteotropic hormones (retinoic acid and vitamin D3), which can promote bone resorption and remodelling. However, OPN mRNA is down-regulated by bisphosphonates, which abrogate bone resorption. Regulation of OPN expression is, therefore, consistent with a multiplicity of functions for OPN that involve specific structural motifs in both the synthesis and resorption of bone.

Objectives: To investigate the predictability of arch expansion using Invisalign. Materials and Methods: Sixty-four adult white patients were selected to be part of this retrospective study. Pre-and posttreatment digital models created from an iTero scan were obtained from a single orthodontist practitioner. Digital models from Clincheck were also obtained from Align Technology. Linear values of upper and lower arch widths were measured for canines, premolars, and first molars at two different points: lingual gingival margins and cusp tips. A paired ttest was used to compare expansion planned on Clincheck with the posttreatment measurements. Variance ratio tests were used to determine if a larger change planned was associated with larger error.

To characterize the bone-like tissue produced by rat bone marrow cells (RBMC) from young adult femurs, the synthesis of bone proteins and the expression of their mRNA were studied in vitro. RBMC plated at a density of 5 x 10(3) cells/cm2 and grown in the presence of 10(-8) M dexamethasone (Dex) and 10 mM beta-glycerophosphate (beta-GP) produced mineralized bone nodules, which were first evident at day 3 and increased markedly to day 13. However, in the absence of dexamethasone, few mineralized nodules were observed. The formation of mineralized nodules was reflected by the uptake of 45Ca, which also increased markedly to day 13. Analysis of bone protein expression by Northern and slot-blot hybridizations revealed an increase in mRNA levels of collagen type I (Col I), osteonectin/SPARC (ON), alkaline phosphatase (ALP), osteopontin (OPN), bone sialoprotein (BSP), and osteocalcin (OC) during the formation of mineralized nodules. Whereas the Col I, ON, ALP, and OPN mRNAs were expressed before the formation of mineralized nodules was evident and were also expressed at various levels in the absence of Dex, the expression of BSP and OC mRNA was induced in the bone-forming cultures. The expression of BSP mRNA was correlated temporally with bone tissue formation, reaching maximal levels on day 16. In contrast, OC mRNA was expressed later and, following induction, increased over the 28 day culture period. Production of matrix proteins during the rapid formation of the bone tissue appeared to reflect the levels of the respective mRNAs. However, whereas some of the collagen and almost all of the SPARC were secreted into the culture medium, virtually all of the OPN and most of the BSP were extracted from the mineralized tissue matrix with EDTA. Some OPN and BSP were present in the medium, especially early in the culture, and a significant amount of BSP was also found associated with the collagenous tissue matrix. These studies point to the importance of Col I, ALP, OPN, and BSP, but not ON or OC, in the initial formation of bone tissue.

No abstract

Short free-standing dental implants with a sintered porous surface used for implant fixation are a predictable and effective means of retaining a mandibular overdenture in patients with advanced mandibular ridge resorption.

Purpose. The immunological mechanisms of peri-implant crestal bone loss have, hitherto, not been elucidated. We hypothesized that bacterial products from the microgap cause upregulation of cytokines in otherwise healthy peri-implant cells, which results in osteoclast formation and, ultimately, in bone resorption. Materials and Methods. We used RT-PCR and ELISA to assay mediators of osteoclastogenesis in rat and human macrophages (r-and hMO); bone marrow derived stromal cells (r-and hBMCs); and human gingival fibroblasts (hGF)—with or without stimulation by LPS. TRAP positive multinucleate cells were assessed for their resorptive ability. Results. We show that IL-1α, IL-1β, and IL-6 were expressed by all examined cell types, and TNF-α was upregulated in hGF. Secretion of IL-1α and IL-1β proteins was stimulated in hMO by LPS, and IL-6 protein secretion was highly stimulated in hBMCs and hGF. Both LPS and RANKL stimulated macrophages to form osteoclast-like TRAP positive cells, which resorbed calcium phosphate substrates. Conclusion. Taken together, the results of our study support the hypothesis that bacterial endotoxins upregulate enhanced mediators of osteoclastogenesis in resident cells found in the healthy peri-implant compartment and that the local synergistic action of cytokines secreted by such cells results in the genesis of resorptively active osteoclasts.

This report is an update on a group of 46 clinical trial patients who each received 3 free-standing Endopore dental implants placed using a 2-stage surgical approach in the anterior mandible. After an initial healing interval of 10 weeks, the implants were used in each case to retain an over-denture, and at the time of the report, all patients had passed 5 years of continuous function. The 5-year cumulative "survival" rate based on a life table analysis was 93.4% and this remained unchanged after 6 years. The 5-year "success rate" was 83.3% when assessed qualitatively with the published criteria of others using a four-field table analysis categorizing every implant in the study as one of "Grade 1 Success", "survival", "unaccounted for" or "failure". Modified periodontal parameters verified continued peri-implant soft tissue health. No implant still in function had more than 1.8 mm cumulative bone loss during the first 5 years of function. These results provide clear evidence that Endopore implants despite their short lengths function at least as well as other dental implant designs used in much longer lengths.