Crystallographic properties of a series of synthetic hydroxyapatites

The crystallographic properties of hydroxyapatites synthesized at temperatures of 200 degrees C, 500 degrees C, 900 degrees C and 1250 degrees C, designated HAP200, HAP500, HAP900 and HAP1250, respectively, were studied using X-ray powder diffraction. Values of a-axis length for the hydroxyapatites ranged from 9.406 A to 9.416 A, which were smaller than the corresponding value for stoichimetric hydroxyapatite, a = 9.418 A. Generally, the a-axis length decreased with the synthesis temperature, except for HAP500 which showed the smallest value. Crystallinity of the hydroxyapatites, measured by X-ray diffraction peak broadening as full width at the half-maximum value (FWHM), increased with the synthesis temperature, although HAP500 showed a decrease. These results suggest that the synthetic hydroxyapatites contained some carbonate ions, probably at the A-site of the apatite structure, and that the structure was depleted of carbonate ions at about 500 degrees C.     

Protective efficacy of active and passive immunizations against experimental infection with Bacteroides gingivalis in ligated hamsters

The protective efficacy of immunization against Bacteroides gingivalis infection was examined in hamsters. Whole cells or extracted hemagglutinin of B. gingivalis 381 was injected with incomplete Freund adjuvant into the inguinal regions of hamsters. Two weeks after the rats received a booster injection, cotton threads were tied coronally to the gingival margins of the mandibular first molars, and then a streptomycin-resistant B. gingivalis 381R' strain was inoculated into the rats' oral cavities. The subcutaneous immunizations resulted in slight reductions in the numbers of B. gingivalis on the ligature threads compared with the sham-immunized group. Peroral administration of whole cells of B. gingivalis to hamsters elicited salivary immunoglobulin responses, but no reduction of B. gingivalis 381R' colonization was found in this group. Repeated passive immunizations with rabbit antiserum to B. gingivalis into the oral cavities of the hamsters resulted in a reduction in the number of organisms in the periodontal region.     

Analysis of brain activity during clenching by fMRI

It has been considered difficult to obtain satisfactory functional magnetic resonance images (fMRI) during jaw movements because the head motion during jaw movements makes artefacts on the images. To avoid these artefacts, we chose clenching task and larger pixels to allow some head motion of the subjects. Further the study discarded all data from subjects whom the head was evaluated to move more than 0.3 mm. The study examined 10 healthy right-handed volunteers with echo-planar magnetic resonance (MR) imaging and functional MR signal intensity changes could be obtained in all subjects. However, in the analysis of each pixel of individuals, three different types of pixels were established. It was determined that the pixels that synchronized positively with the task on/off and where signal intensity increase was below 10% expressed the real brain activity. Pixels showing the real brain activity were found in the sensory, motor and pre-motor cortexes in both hemispheres in all subjects, and also in the insula region of two subjects. No pixels were found in the striatum and supplementary motor areas. From the above careful consideration and individual analysis of each pixel, it was concluded that brain activity during the clenching task could be obtained by fMRI.     

Effect of serotonin (5-HT) on trigeminal rhythmic activities generated in in vitro brainstem block preparations

We used rat isolated brainstem block preparations to analyze the functional roles of serotonin receptors in the generation of trigeminal rhythmic activities. We previously reported that trigeminal rhythmic activities could be induced by some pharmacological applications in an isolated brainstem preparation with a rostral boundary at the border between the inferior and superior colliculus, and a caudal border at the level of the rostral facial nucleus. However, the same stimulation did not induce trigeminal rhythmic activities in a whole brainstem block preparation with the same rostral boundary and a caudal border at the obex level. In the present study, both the 5-HT(1A) phthalimido-butyl-piperazine, and the 5-HT(2C) agonist, 1-2,5-dimethoxy-4-iodophenyl-2-aminopropane, combined with N-methyl-D,L-aspartate and bicuculline, elicited trigeminal rhythmic activities in a whole brainstem block preparation. Our results suggest that serotonin has both facilitation and inhibition effects on the generation of trigeminal rhythmic activities in an isolated brainstem block preparation in vitro.     

Fabrication of a digitally scanned, custom-shaped abutment: a clinical report

A procedure for the creation of a custom, anatomic implant abutment copy milled with digitally scanned information has been described. The definitive restoration was a custom-machined abutment with a ceramic crown that had an aluminous oxide core.     

Temporal changes in the distribution and number of macrophage-lineage cells in the periodontal membrane of the rat molar in response to experimental tooth movement

In order to evaluate the possible role of macrophages in the remodelling of periodontal tissue in response to tooth movement, temporal changes in the number and distribution of macrophage-lineage cells in the periodontal membrane of the rat molar tooth after experimental tooth movement were examined immunohistochemically using four anti-rat monoclonal antibodies: ED1 (anti-monocyte/macrophage-lineage cells and dendritic cells), ED2 (anti-resident macrophages), KI-M2R (anti-tissue macrophages), and OX6 (anti-class II molecules). The right maxillary first molar tooth of Wistar rats was moved mesially by a closed-coil spring for 1, 3, 5, or 7 days. Sham-treated rats wearing an inactivated appliance for each experimental period and entirely untreated rats were used as controls. Alternate horizontal serial cryostat sections were cut and incubated with antibodies to ED1, ED2, KI-M2R, and OX6. In addition, cells immunopositive for each monoclonal antibody in the periodontal membrane during tooth movement were analysed on the tension and pressure sides. In the control rats, large numbers of cells positively stained with each monoclonal antibody were distributed throughout the periodontal membrane surrounding the distobuccal root. At 1 day after experimental tooth movement, the number of immunopositive cells obtained with all four monoclonal antibodies decreased as compared with those of the control on the mesial/pressure side. During the later experimental time periods, ED1- and OX6-positive cells in the periodontal membrane of this side were significantly increased in number compared with controls, whereas the density and distribution pattern of cells positive with ED2 or KI-M2R remained unchanged. On the mesial/pressure side, which underwent hyalinization, a marked accumulation of OX6- and ED1-reactive cells, but not of ED2- or KI-M2R-reactive cells, was frequently observed in the area of the hyalinized tissue at 5-7 days after the start of tooth movement. On the distal/tension side, no particular change in the distribution of immunopositive cells obtained with any antibody was detected throughout the experimental periods, with the exception that there was a significant increase in the number of ED1-positive cells and in of OX6-positive cells at 1 and 7 days, respectively, after the start of tooth movement. These results suggest that after the start of tooth movement OX6- and ED1-positive cells, which are mostly exudative macrophages, but not ED2- and KI-M2R-positive cells, i.e., resident macrophages, may be actively engaged in bone resorption and the remodelling of tissues on the pressure side of the periodontal membrane.     

Adhesion of N-methacryloyl-omega-amino acid primers to collagen analyzed by 13C NMR

Previously, we reported that the strength of the interaction between N-methacryloyl-omega-amino acid (NMomegaA) primers and dentinal collagen exhibited a strong correlation with the bond strength of the resin to etched dentin. To determine the pertinent functional groups of the amino acid residues in the dentinal collagen, to which the amide and/or the carboxylic acid groups of the NMomegaAs are adsorbed, we used 13C NMR techniques--primarily through the observation of spin-lattice relaxation times, Ti--to investigate the adsorption characteristics resulting from the interaction of NMomegaAs with a model oligopeptide for collagen, (PPG)5. The addition of NMomegaAs to a collagenous solution resulted in a decrease in the T1 values of the carbonyl carbons attributed to the carboxylic acid of the C-terminal Gly and to the third amide of the N-terminal Pro residues in the (PPG)5 molecule, thus reflecting the formation of hydrogen-bonded interactions.     

Tooth-implant supported fixed prostheses: a retrospective multicenter study

PURPOSE: The purpose of this retrospective multicenter study on implants combined with natural teeth was to investigate the implant survival rate and loss of marginal bone, as well as indications and complications pertinent to this form of implant therapy. MATERIALS AND METHODS: The study comprised 185 implants in 111 patients from six different clinics in Sweden. Gathering of data, which were taken from patient records, followed a strict protocol. The registrations included indications for treatment, failure of implants, radiographs from baseline and follow-up, and information on complications. RESULTS: The cumulative implant survival was found to be 95.4% (standard error 4.5%) up to 3 years of follow-up. The marginal bone level at baseline was lower in the maxilla compared with the mandible (P = .015), but any further loss did not differ between the jaws. The most severe complication other than loss of osseointegration (6/185) or periimplant infections (4/183) was intrusion of the abutment teeth, which occurred in 5% of the cases. In all instances, the intrusion was seen in constructions with nonrigid forms of connection between the implants and teeth. CONCLUSION: The tooth-implant supported prosthesis using the Br?nemark system is in the short term an equally predictable treatment as the completely implant-supported prosthesis concerning implant survival and loss of marginal bone. When combining implants and teeth, a rigid form of connection should be used to prevent tooth intrusion.