IL-1beta and TNF-alpha regulate IL-6-type cytokines in gingival fibroblasts

Interleukin-6 (IL-6)-type cytokines are pleiotropic molecules capable of stimulating bone resorption and expressed by numerous cell types. In the present study, we tested the hypothesis that gingival fibroblasts may exert local osteotropic effects through production of IL-6 and related cytokines. IL-6-type cytokine expression and regulation by IL-1beta and tumor necrosis factor-alpha (TNF-alpha) were studied in fibroblasts from the non-inflamed gingiva of healthy individuals. Constitutive mRNA expression of IL-6, IL-11, and leukemia inhibitory factor (LIF), but not of oncostatin M (OSM), was demonstrated, as was concentration-dependent stimulation of IL-6 and LIF mRNA and of protein by IL-1beta and TNF-alpha. IL-11 mRNA and protein were concentration-dependently stimulated by IL-1beta. The signaling pathway involved in IL-6 and LIF mRNA stimulation involved MAP kinases, but not NF-kappaB. The findings support the view that resident cells may influence the pathogenesis of periodontal disease through osteotropic IL-6-type cytokine production mediated by activation of MAP kinases. Abbreviations: IL-1alpha (interleukin-1alpha); IL-1beta (interleukin-1beta); IL-6 (interleukin-6); IL-11 (interleukin-11); LIF (leukemia inhibitory factor); OSM (oncostatin M); alpha(1)-coll. I (alpha(1)-collagen I); ALP (alkaline phosphatase); BMP-2 (bone morphogenetic protein-2); OC (osteocalcin); BSP (bone sialoprotein); TNFR I (tumor necrosis factor receptor I); TNFR II (tumor necrosis factor receptor II); IL-1R1 (interleukin-1 receptor 1); GAPDH (glyceraldehyde-3-phosphate dehydrogenase); RPL13A (ribosomal protein L13A); mRNA (messenger ribonucleic acid); cDNA (complementary deoxyribonucleic acid); PCR (polymerase chain-reaction); BCA (bicinchoninic acid); ELISA (enzyme-linked immunosorbent assay); alpha-MEM (alpha modification of Minimum Essential Medium); and FCS (fetal calf serum).     

Is there a lower threshold value of bone density for early loading protocols of dental implants?

This clinical study aimed to determine the bone density in dental implant recipient sites using computerized tomography (CT) and to establish a lower threshold value of bone density for early loading protocols. The study group was composed of 100 early loaded implants in 42 patients. A total of four groups were established according to the loading time and implant sites. The bone density of each recipient site for implant placement was determined using CT. The maximum insertion torque values were recorded with torque controlling machine. Implant stability measurements were performed with resonance frequency analyser. The bone density values varied from 528 to 1231 HU. It was found that mean bone density, insertion torque and resonance frequency analysis values were 887 +/- 180 HU, 41.2 +/- 6 Ncm, and 73.7 +/- 4 ISQ, respectively. Strong correlations were found between these three parameters. CT may be a useful tool for assessing the bone density of recipient areas before implant placement, and the early loading of dental implants may be possible in the implant sites where bone density is over 528 HU.     

Effect of Compromised Cortical Bone on Implant Load Distribution

Purpose: To investigate photoelastically the difference in load distribution of dental implants with different implant neck designs in intact and compromised bone. Materials and Methods: Composite photoelastic models were fabricated using two different resins to simulate trabecular bone and a 1‐mm thick layer of cortical bone. The following parallel‐sided, threaded implants were centrally located in individual models representing intact and compromised cortical bone: Straumann (4.1‐mm diameter × 12‐mm length), AstraTech (4.0‐mm diameter × 13‐mm length), and 3i (3.75‐mm diameter × 13‐mm length). The compromised cortical bone condition was simulated by contaminating a 1‐mm neck portion with Vaseline to impair the implant–resin interface. Vertical and oblique static loads were applied on the abutments, and the resulting stresses were monitored photoelastically and recorded photograhphically. Results: For the fully intact condition, the highest stresses were observed around the crest and apical region for all implant designs under vertical and inclined loads. There were no appreciable differences in magnitude or distribution between implant types. With compromised cortical bone, for all designs and load directions, higher stresses in the supporting structures were observed. Increased stresses were noted especially at the cortical bone–trabecular bone interface. Somewhat lower stress levels were observed with the 3i implant. Conclusions: The condition of implant–cortical bone contact has considerable influence on stress distribution. A compromised cortical bone condition caused higher level stresses for all implant designs tested.     

Processing of ameloblastin by MMP-20

Ameloblastin (AMBN) cleavage products are the most abundant non-amelogenin proteins in the enamel matrix of developing teeth. AMBN N-terminal cleavage products accumulate in the sheath space between enamel rods, while AMBN C-terminal products localize within rods. We tested the hypothesis that MMP-20 is the protease that cleaves AMBN. Glycosylated recombinant porcine AMBN (rpAMBN) was expressed in human kidney 293F cells, and recombinant porcine enamelysin (rpMMP-20) was expressed in bacteria. The purified proteins were incubated together at an enzyme:substrate ratio of 1:100. N-terminal sequencing of AMBN digestion products determined that rpMMP-20 cleaved rpAMBN after Pro(2), Gln(130), Gln(139), Arg(170), and Ala(222). This shows that MMP-20 generates the 23-kDa AMBN starting at Tyr(223), as well as the 17-kDa (Val(1)-Arg(170)) and 15-kDa (Val(1)-Gln(130)) AMBN cleavage products that concentrate in the sheath space during the secretory stage. We conclude that MMP-20 processes ameloblastin in vitro and in vivo.     

Osteochondroma of the mandibular condyle. Case report and its management.

1. A case of osteochondroma of the temporomandibular joint simulating a unilateral condylar hyperplasia is presented. 2. The need to divide the zygomatic arch to facilitate removal of large tumors is noted. 3. The removal of the growth resulted in normal functioning of the jaws with the disappearance of the features of unilateral hyperplasia. 4. Occlusal grinding is often necessary to correct the compensatory occlusal adjustment that occurs with the rotation of the mandible in these lesions. 5. The possibility of the presence of a tumor must be kept in mind when patients present with symptoms of unilateral condylar hyperplasia.