ABSTRACT
It is important to know the location of the center of resistance (CR) to control tooth movement. In this study, photoelastic techniques were used to determine the center of resistance. The photoelastic model included the anterior 4 maxillary teeth, which were interconnected firmly with 6 mm of space between lateral incisors and canines. Determination of the CR for the anterior arch segment was based on considerations of a wide variety of load conditions that generated the more uniform stresses in the supporting alveolar bone simulant. For the arch having the anterior 4 teeth connected, the CR was located within the mid-sagittal plane, 6-mm apical and 4-mm posterior to a line perpendicular to the occlusal plane from the labial alveolar crest of the central incisor.
Subject(s)
Dental Arch/physiology , Dental Stress Analysis , Maxilla/physiology , Birefringence , Elasticity , Humans , Incisor , Light , Models, Dental , Palate , Stress, MechanicalABSTRACT
Prostaglandins (PGs) are well known to be important local factors in regulating bone formation and resorption. PGE2 is a potent stimulator of bone resorption because of enhancing osteoclast formation by its indirect action through stromal cells. However, the direct action of PGE2 on functionally mature osteoclasts is still controversial. In this study using highly purified rabbit mature osteoclasts, we examined the direct effect of PGE2 on osteoclastic bone-resorbing activity and its mechanism. PGE2 inhibited resorption pit formation on a dentine slice by the purified osteoclasts in a dose- and time-dependent manner. The inhibitory effect appeared as early as 4 hours after the PGE2 addition. Forskolin and 12-0-tetradecanoyl phorbol-13-acetate (TPA), respective activators of adenylate cyclase and protein kinase C, also decreased the osteoclastic bone-resorbing activity. PGE2 increased the content of intracellular cAMP in a dose range effective for the inhibition of bone resorption, whereas the prostanoid did not alter the intracellular level of inositol triphosphate. The inhibition of osteoclastic bone resorption by PGE2 was amplified and diminished by a cAMP phosphodiesterase inhibitor (isobutyl methylxanthine) and a protein kinase A inhibitor (Rp-cAMP), respectively. Of four different subtypes of PGE2 receptors (EPs), EP4 mRNA was predominantly expressed in isolated osteoclasts, whereas the other types of EP mRNA were detected in only small amounts. These results suggest that the PGE2 inhibitory effect was mediated by an adenylate cyclase system coupled with EP4. This possible association of PGE2 with EP4 in mature osteoclasts was supported by the finding that a specific agonist of EP4 (AE-604) inhibited the bone-resorbing activity and elevated the intracellular cAMP content. However, butaprost, a selective EP2 agonist, also mimicked the PGE2 effects on isolated osteoclasts although EP2 mRNA expression was minimal. In conclusion, PGE2 directly inhibits bone-resorbing activity of functionally mature osteoclasts by activation of the adenylate cyclase system, perhaps mainly through EP4.
Subject(s)
Bone Resorption/metabolism , Dinoprostone/metabolism , Osteoclasts/metabolism , Receptors, Prostaglandin E/metabolism , Adenylyl Cyclases/metabolism , Animals , Cells, Cultured , Dinoprostone/pharmacology , Gene Expression/drug effects , Osteoclasts/cytology , Osteoclasts/drug effects , Protein Kinase C/metabolism , Rabbits , Receptors, Prostaglandin E/genetics , Receptors, Prostaglandin E, EP4 SubtypeABSTRACT
We examined human pineal concretions and found them to exhibit a multi-layered concentric structure consisting of irregularly spaced dense and sparse zones containing fine crystals. The hydroxyapatite crystallites were shown to be irregularly outlined plate forms (measuring 11-70 nm in their longest dimension and 2-10 nm in thickness). At the center of each crystallite a central dark line was observed by means of high resolution electron microscopy. The structure and size of the crystals were similar to those of dentin and bone. The ground surface of the concretions was observed metallurgically by means of an electron probe microanalyzer (EPMA). The surface zones of the concretions contained a higher concentration of zinc, which seems to play an important role during the mineralization process, whereas calcium and phosphorus exhibited higher concentrations at the center.
Subject(s)
Pineal Gland/pathology , Pineal Gland/ultrastructure , Aged , Aged, 80 and over , Calcium/analysis , Electron Probe Microanalysis/methods , Female , Humans , Male , Microscopy, Electron/methods , Microscopy, Electron, Scanning/methods , Middle Aged , Zinc/analysisABSTRACT
The presence of adrenergic nerve fibers was demonstrated ultrastructurally in the human periodontal ligament obtained from extracted premolar teeth from 8 young patients. The nerve endings were located close to arterioles. The results suggest that they seem to control blood flow in the human periodontal ligament.
Subject(s)
Adrenergic Fibers/ultrastructure , Periodontal Ligament/innervation , Periodontal Ligament/ultrastructure , Adolescent , Arterioles/ultrastructure , Axons/ultrastructure , Bicuspid , Child , Female , Humans , Male , Microcirculation , Microscopy, Electron , Norepinephrine , Periodontal Ligament/blood supplyABSTRACT
The treatment of a skeletal Class III open bite malocclusion with Turner's syndrome is described. Although the patient had a negative overbite of 9 mm, a positive overbite of 2 mm was obtained through treatment, without any tooth extractions; however, an excessive vertical growth of the anterior regions was noted.
Subject(s)
Malocclusion, Angle Class III/therapy , Malocclusion/therapy , Tooth Movement Techniques/methods , Turner Syndrome/therapy , Cephalometry , Child , Female , Humans , Malocclusion, Angle Class III/etiology , Mouth Breathing , Speech Disorders/etiology , Speech Disorders/therapy , Tooth Movement Techniques/instrumentation , Turner Syndrome/complicationsABSTRACT
Changes in the bone tissue and the blood vessels in the rat alveolus induced by feeding with a high protein low calcium diet for 7 days were observed by means of light microscopy and scanning electron microscopy. Almost no difference was observed between the control group and the experimental group in the rat femur. However, in the alveolar bone resorption was observed with the appearance of osteoclasts and the enlargement of osteocyte lacunae. The blood vessels in bone marrow spaces showed alternation of their form from straight to slightly ortuous, diverged more frequently and, as a whole, formed a large loop. The vessels ran up and down adjacent to the side wall of the alveolar bone. In the interalveolar septum, ladder-shaped trabeculae and vessels running along them were observed. The present study clearly shows that a high protein low calcium diet affects the alveolar bone in rats, even when given for a short period of 7 days.
