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At least 1,099 records · Page 61Linked to original sources
PubMed2002

[A study of tarnish induced by Streptococcus sobrinus serotype g on Co-Cr, Ni-Cr and casting titanium alloys].

OBJECTIVE: The objective of this study was to investigate the tarnish induced by Streptococcus sobrinus serotype g on Co-Cr, Ni-Cr and casting titanium alloys. METHODS: Co-Cr, Ni-Co and casting titanium alloys were respectively machined into a size of 10 mm x 10 mm x 1 mm in tablets, and totally 90 specimens with 30 of each were prepared for the test. The 30 specimens of each alloy were randomly and equally divided into three subgroups, including the blank control group, the media control group and the inoculated media group. Under the aerobic condition, the surfaces of the sucrose agar media were inoculated with Streptococcus sobrinus serotype g. The labeled sterile specimens were placed on the surface of the media for 10 weeks. The specimens were changed to a new sucrose media with bacteria each week. The specimens were removed after 10 weeks of incubation, immersed in 0.05% glutaraldehyde solution to eliminate AaY4, rinsed with distilled water. After 2 weeks, the specimens were removed and observed visually or examined by MINOLTA CR-100 color apparatus. RESULTS: Compared with the blank control, the control media without bacteria did not influence the alloy specimens (P > 0.05). Streptococcus sobrinus serotype g caused tarnish on specimens. There was significant difference between the control media group and the blank control group with inoculated media group on all the specimens (P < 0.05). CONCLUSION: Streptococcus sobrinus serotype g affects the color of Co-Cr, Ni-Cr and casting titanium alloys, but the color does not change from yellow-green range to red-yellow range.

Chromium Alloys↗
PubMed1989

Correlation between the degree of deformation of the stone die and the amount of the master die undercut. Part 1. Single tooth die.

In order to investigate the deformation the stone die depending on the amount of undercut, 5 kinds of undercut master dies were used to take impressions using 3 kinds of impression materials (addition type silicone rubber, polysulfide rubber, alginate). The stone dies were measured for dimensional changes in shape as projected to a two-dimensional plane by means of a newly devised apparatus. The results showed that deformation of the stone dies increased, in general, in proportion to the amount of undercut of the master die. The stone dies obtained from addition type silicone rubber impression material tend to be less deformed. In the case of the polysulfide rubber impression, the deformation was very small in stone dies in the case of non-undercut master dies, but it was very large in the case of undercut master dies. The alginate impression materials gave results with wider variations.

Alginates↗
PubMed1998

Immunocytochemical and immunochemical study of enamelins, using antibodies against porcine 89-kDa enamelin and its N-terminal synthetic peptide, in porcine tooth germs.

Enamelins comprise an important family of the enamel matrix proteins. Porcine tooth germs were investigated immunochemically and immunocytochemically using two antibodies: a polyclonal antibody raised against the porcine 89-kDa enamelin (89 E) and an affinity purified anti-peptide antibody against the porcine enamelin amino-terminus (EN). Immunochemical analysis of layers of immature enamel from the matrix formation stage detected immunopositive protein bands ranging from 10 kDa to 155 kDa in the outer layer enamel sample irrespective of the antibodies used. In contrast, the middle and inner enamel layer mainly contained lower molecular weight enamelins. In immunocytochemical analyses of the differentiation stage, 89 E stained enamel matrix islands around mineralized collagen fibrils of dentin, while EN stained both enamel matrix islands and stippled material. At the matrix formation stage, both antibodies intensely stained enamel prisms located in the outer layer. In the inner layer, 89 E moderately stained enamel matrix homogeneously, while EN primarily stained the prism sheath. The intense immunoreaction over the surface layer of enamel matrix at the matrix formation stage, following staining with 89 E and EN, disappeared by the end of the transition stage and the early maturation stage, respectively. The Golgi apparatus and secretory granules in the ameloblasts from the late differentiation stage to the transition stage were immunostained by both antibodies. These results suggest that expression of enamelin continues from late differentiation to the transition stage and the cleavage of N-terminal region of enamelin occurs soon after secretion. Some enamelin degradation products, which apparently have no affinity for hydroxyapatite crystals, concentrate in the prism sheaths during enamel maturation.

Amino Acid Sequence↗
PubMed1989

[Error sources in recording three-dimensional mandibular movements. An in vitro study using the V-type stereognathograph].

The instrument-induced measurement errors in V-type stereognatography have been analyzed. An optical bench was used as a measurement apparatus. In measuring not too small movement distances, the linearity errors remained within acceptable limits. The variations in linearity due to calibration errors were almost negligible. In practical applications, the stereognatography proved to be insensitive to external factors such as type of illumination, room temperature and voltage fluctuations. Factors affecting the effectiveness of the projection error correction system, such as tilting of the filter, different sites of measurement of the six optoelectronic canals, and mandibular protrusion during mediotrusive movements, might be reduced by slight modifications of the measurement system.

Cephalometry↗
PubMedDate not supplied

[The electrical excitability of the neuroreceptor apparatus of the pulp in the intact teeth of patients with chronic alcoholism].

The aim of the study was to develop rapid methods for tentative diagnosis of chronic alcoholism. For this purpose 50 patients, male and female ones, suffering from chronic alcoholism were examined for electroexcitability of their intact teeth pulp nerve receptor system. Initial examination revealed reduced the threshold of tooth pulp electroexcitability as against the control. Drastic variations in electroexcitability values of neighbouring teeth were noted. The parameter studied was found perverted in 52 percent of the alcoholics. This characteristic improved by the patient's discharge from hospital, though in the majority of cases the regularities cited above persisted.

Adult↗
PubMed1994

Apical dentin permeability and microleakage associated with root end resection and retrograde filling.

This study evaluated the apical leakage associated with various depths of retrograde fillings placed in root apices which had been resected at one of three different angles. Leakage was assessed with a hydraulic conductance apparatus. Teeth were divided into groups corresponding to the angle of apical resection (0, 30, and 45 degrees to the long axis of the root) and apical leakage was determined following incremental increases in the depth of the retrograde filling (Ketac Silver). Increasing the depth of the retrograde filling significantly decreased apical leakage; there was also a significant increase in leakage as the amount of bevel increased. Both the permeability of resected apical dentin and microleakage around the retrograde filling material had a significant influence on apical leakage.

Apicoectomy↗
PubMed1979

Functional state, bite force and postural muscle activity in patients with osseointegrated oral implant bridges.

The function of the masticatory system of 13 women, aged 42-59 years, with osseointegrated oral implant bridges (OIB) made within the last seven years was compared with that of 10 matched dentate controls by means of a questionnaire, clinical examination, bite force measurements and electromyographic recordings of biting and of postural muscle activity. Both groups were satisfied with their masticatory capacity according to the questionnaire. The clinically determined state of the masticatory system, as judged from the clinical dysfunction index, was normal in both groups. Three levels of bite force 1) gentle biting, 2) biting as when chewing and 3) maximal biting, were recorded with a bite force apparatus and electromyographically. There was no statistically significant difference between the groups at any level of bite force for any of the methods of registration. Nor was there any difference of the two groups in the activity of the masticatory muscles with the mandible in the postural position. It is concluded that patients with osseointegrated oral implant bridges have a masticatory muscle function equal to or approaching that of patients with natural teeth, or with tooth-supported bridges, with the same number of chewing units as the OIB-patients.

Adult↗
PubMed2001

Solvent action of sodium hypochlorite on bovine pulp and physico-chemical properties of resulting liquid.

The solvent effect of 4 concentrations of sodium hypochlorite (0.5, 1.0, 2.5, and 5.0%) on bovine pulp tissue and the level of residual chlorine, pH and surface tension before and after dissolution were studied in vitro. A fragment of bovine pulp was submersed in sodium hypochlorite that circulated in an apparatus with a peristaltic pump and Luer Lok syringe. The higher the concentration of sodium hypochlorite the faster the dissolution of the pulp tissue. All concentrations of sodium hypochlorite reduced the pH and the surface tension and the higher concentrations of the solution had the least consumption of chlorine during tissue dissolution. Thus this study indicated that residual chlorine was directly proportional to concentration in the process of pulp tissue dissolution and that there was residual chlorine at all concentrations used.

Animals↗
PubMed2000

Bacterial leakage in coronally unsealed root canals obturated with 3 different techniques.

OBJECTIVE: The purpose of this in vitro study was to evaluate the coronal leakage of microorganisms from saliva into root canals filled by 3 obturation techniques. STUDY DESIGN: Obturated canals were mounted in an apparatus and then exposed to human saliva. The number of days required for the entire contamination of the root canal was recorded. Evaluation was carried out for 60 days. RESULTS: Regardless of the technique used, a significant number of specimens were contaminated after 30 and 60 days. No significant differences were detected among the techniques (P >.05). CONCLUSIONS: Results indicated that none of the techniques tested could predictably produce a coronal bacteria-tight seal of the root canal after direct saliva challenge.

Dental Leakage↗
PubMed1979

A laser instrument for measuring tooth movements.

An improved apparatus has been constructed which is based upon the laser reflexion method and is used in a highly accurate direct technique of measuring tooth movement without contact. The possibility of making clinical investigations of tooth movements with the equipment has been investigated by testing its various components. The most critical part of the system is the repositioning of the patient, which has been done with an accuracy of +/- 20 micron. The reflected pattern used during 3 months of experiments was the same. The instrument can be used for measurements down to 50 micron.

Adult↗
PubMed1981

Ultrastructural location of Streptococcus mutans and Streptococcus sanguis antigens in carious human dentine.

The ultrastructural localization of bacterial antigens of Streptococcus sanguis and of the various serotypes a,b,c,d,e,f and g of Streptococcus mutans was studied in human carious dentine using the indirect peroxidase-antiperoxidase method with appropriate controls. No positive staining was seen in adjacent normal dentine. In the inner dentine underlying the cytoplasm of fibroblasts and Schwann cells of unmyelinated nerve fibrils. In sclerosed tubules, or on the plasmalemma of the odontoblast process or on both structures. Only in the odontoblast, facing the carious cone, were dense stainings noted in vacuoles of various sizes located in the Golgi apparatus in juxta-nuclear position and in their odontoblast processes. In pulpal regions, underlying the carious cone, dense vacuoles were also observed in the cytoplasm of fibroblasts and Schwann cells of unmyelinated nerve fibrils. In sclerosed tubules, electron dense deposits were noted in the lumen and the walls of the calcified tubules. In the outer carious dentine, invaded by micro-organisms, positive antigenic stainings were observed in the cell wall and capsular material of a great number of micro-organisms as well as in the interbacterial matrix.

Antigens, Bacterial↗
PubMed1997

[Study for searching equilibrium point in dentulous hemimandibulectomy patients].

Occlusal registration for prosthodontic rehabilitation in dentulous hemimandibulectomy patient has various difficulties due to mandibular instability. The purpose of this study was to find the occlusal contact position for remaining dentition to stabilize the hemiresected mandible during clenching. Three hemimandibulectomized subjects without surgical bony construction were selected and custom-made Gothic-arch typed apparatus was fabricated. Mandibular movements during clenching were recorded with jaw movement tracking device with six degrees of freedom. The results were as follows: 1. The direction of the mandibular rotation around each coordinate axis in 3-dimensional space during clenching was constant in each subject, regardless of stylus position. 2. The most stable points on the hemimandibules during clenching did not necessarily correspond to the mid-portion of the remaining dentition of the mandible. 3. When referred to the maxillary arch, the point was lined up within the distal half of the second premolar and the mesial third of the first molar in mid-sagittal plane along the long axis of the remaining dentition. 4. Rotational axis during clenching existed on the horizontal plane. 5. It was assumed that the most stable point of the mandible in a hemimandibulectomy patient may be useful in interocclusal registration in clinical dental practice.

Carcinoma, Squamous Cell↗
PubMed1996

Extracellular matrix in tooth cementum and mantle dentin: localization of osteopontin and other noncollagenous proteins, plasma proteins, and glycoconjugates by electron microscopy.

BACKGROUND: Noncollagenous proteins (NCPs) are considered to have multiple functions related to the formation, turnover, and repair of the collagen-based mineralized tissues. Collectively, they comprise a class of generally acidic, mineral-binding proteins showing extensive posttranslational modifications, including glycosylation, phosphorylation, and sulfation. METHODS. We have used colloidal-gold immunocytochemistry and lectin-gold cytochemistry, together with transmission electron microscopy, to examine the organic matrix composition of tooth cementum and the subjacent mantle dentin in rodent molar teeth. Molars were processed for immunocytochemistry using antibodies against osteopontin (OPN), osteocalcin (OC), bone sialoprotein (BSP), bone acidic glycoprotein-75 (BAG-75), albumin (ALB), and alpha 2HS-glycoprotein (alpha 2HS-GP), or for glycoconjugate cytochemistry using lectin-gold complexes. RESULTS: Ultrastructurally, at the advancing root edge in developing molars, OPN and BSP initially were associated with small calcification foci in the mantle dentin. With progressing mineralization, OC and alpha 2HS-GP appeared diffusely distributed throughout the calcified mantle dentin, and diminished as a gradient toward the circumpulpal dentin. Immediately following disruption of Hertwig's epithelial root sheath, cementum deposition commenced at the root surface occasionally with the appearance of a cement line rich in OPN. Cementum matrix proper contained abundant OPN, BSP, OC, and alpha 2HS-GP, but no or little BAG-75 or ALB. Protein immunolabeling, as well as lectin labeling for beta-D-galactose and N-acetyl-neuraminic acid and/or N-glycolyl-neuraminic acid, both being prominent sugars of certain NCPs, was primarily concentrated between, and at the surface of, collagen fibrils in acellular extrinsic fiber cementum. OPN, BSP, OC, and alpha 2HS-GP were also prominent components of cellular cementum and of Sharpey's fibers. In cellular cementum, laminae limitantes sometimes present delimiting cementocyte lacunae and cell process-containing canaliculi were also rich in OPN. Along the root surface, occasional cementoblasts exhibited intracellular labeling for OPN over the Golgi apparatus and secretory granules. CONCLUSIONS: We have identified OPN, BSP, OC, and alpha 2HS-GP as being prominent organic constituents of both mantle dentin and acellular and cellular cementum, and, have elucidated the details of their distribution at the ultrastructural level. The temporal appearance and spatial distribution of these organic moieties in the teeth root are similar to those seen during bone formation and are consistent with proposals that certain NCPs may be involved in regulating calcification and/or participating in cell-matrix and matrix-matrix/mineral adhesion events.

Animals↗
PubMed1992

Investigation into the behavior of symmetrically and asymmetrically activated face-bows.

The distal and lateral forces and also the couples (in a transverse plane) delivered by the inner terminals of a face-bow have been derived analytically according to the complementary (strain) energy method for various face-bow configurations on the assumption that the terminals are rigidly held by the molar tubes and that the external forces acting are in the plane of the inner bow. The results of the theory have been checked experimentally with a specially designed apparatus in which two mild steel transducer pegs that carry three pairs of strain gauges were used to measure the force system delivered by the inner bow under a range of loading, both symmetrical and asymmetrical. Good agreement with the theory was obtained, confirming the validity of the theoretical analysis. It is concluded that force systems are dependent on bow geometry and that with increasing asymmetry of the external loading transference of the distal load to the power-arm side is accompanied by a shift of lateral force and couple to the opposite side.

Dental Stress Analysis↗
PubMed1978

[Concept and testing of the Tübingen immediate implant].

This introductory communication deals with the functional-anatomical, biophysical and neurophysiological considerations which led to the construction of an aluminium oxide immediate implant from a stepped cylindrical body. This intra-osseous implant differs in essential constructional features from the implant shapes known up to now; it endeavours to make use of the architecture of the natural gingival fibre apparatus for the placing of the mucosal cuff. Its surface was maximalised towards the bone, leaving out surface structures which could produce pressure points. The enlargement of surface compared with the root of the corresponding natural tooth amounts to 65 to 100% varying according to the shape of the implant. Descriptions are given of the concept of testing experimental implants, the physical and chemical characterisation of surfaces, animal-experimental steps, clinical tests including legal problems posed and the control system created with the view to large scale clinical trials.

Aluminum Oxide↗
PubMed1984

Cranial morphology of Australopithecus afarensis: a comparative study based on a composite reconstruction of the adult skull.

The Pliocene hominid species Australopithecus afarensis is represented by cranial, dental, and mandibular remains from Hadar, Ethiopia, and Laetoli, Tanzania. These fossils provide important information about the cranial anatomy of the earliest known hominids. Because complete crania or skulls are not known, we produced a composite reconstruction of an adult male skull based on 13 specimens from the Hadar Formation. The reconstruction serves as a testable hypothesis regarding functional relationships in the A. afarensis skull and is the basis for the comparative study presented here. We examine six major aspects of cranial and mandibular anatomy. We combine our results with those of White et al. (1981) in a discussion of alternate hypotheses of early hominid phylogeny. In the cranium, jaws, and teeth A. afarensis exhibits a morphological pattern that we interpret as primitive for the Hominidae. Homo habilis retains a number of these primitive features for which A. africanus, A. robustus, and A. boisei share derived character states, particularly in the masticatory apparatus. Homo and "robust" species of Australopithecus share a suite of derived cranial base features. These shared traits may relate to upper facial orthognathium which is also common to these taxa and are probably indicative of parallelism rather than a close phylogenetic relationship. The cranial base characteristics of A.L. 333-45 do not, contrary to Olson's (1981) claims, provide evidence for an A. afarensis--"robust" Australopithecus sister group. When the range of mastoid variation in extant African pongids and A. afarensis is examined thoroughly, the Pliocene hominid appears to retain a primitive, rather than derived, morphology.

Adult↗
PubMed2003

Evaluation of friction of stainless steel and esthetic self-ligating brackets in various bracket-archwire combinations.

This study measured and compared the level of frictional resistance generated between stainless steel self-ligating brackets (Damon SL II, SDS Ormco, Glendora, Calif), polycarbonate self-ligating brackets (Oyster, Gestenco International, Göthenburg, Sweden), and conventional stainless steel brackets (Victory Series, 3M Unitek, Monrovia, Calif), and 3 different orthodontic wire alloys: stainless steel (Stainless Steel, SDS Ormco), nickel-titanium (Ni-Ti, SDS Ormco), and beta-titanium (TMA, SDS Ormco). All brackets had a.022-in slot, whereas the orthodontic wire alloys were tested in 3 different sections:.016,.017 x.025, and.019 x 0.025 in. Each of the 27 bracket and archwire combinations was tested 10 times, and each test was performed with a new bracket-wire sample. Both static and kinetic friction were measured on a custom-designed apparatus. All data were statistically analyzed (Kruskal-Wallis and Mann Whitney U tests). Stainless steel self-ligating brackets generated significantly lower static and kinetic frictional forces than both conventional stainless steel and polycarbonate self-ligating brackets, which showed no significant differences between them. Beta-titanium archwires had higher frictional resistances than stainless steel and nickel-titanium archwires. No significant differences were found between stainless steel and nickel-titanium archwires. All brackets showed higher static and kinetic frictional forces as the wire size increased.

Dental Alloys↗
PubMed1989

Histologic evaluation of new attachment apparatus formation in humans. Part III.

There is still controversy as to the role of bone grafting materials in the formation of a new attachment apparatus and component tissues (bone, cementum, and periodontal ligament). The purpose of this study was to compare the healing of intrabony defects with and without the placement of decalcified freeze-dried bone allograft (DFDBA) in a nonsubmerged environment in humans. The most apical level of calculus on the root served as a histologic reference point to delineate root surfaces exposed to the oral environment and to measure new attachment apparatus and new component tissue formation. Free gingival grafts were placed over grafted and nongrafted defects to retard epithelial migration. Biopsies were obtained at 6 months and regeneration was evaluated histometrically. Data from 12 patients with 32 grafted and 25 nongrafted defects were submitted for statistical analysis. Results indicate that in nongrafted defects, a long junctional epithelium formed along the entire length of exposed root surfaces and often extended apical to the calculus reference notch. Free gingival grafts did not enhance regeneration of a new attachment apparatus, new cementum, new connective tissue, or new bone in nongrafted defects. The formation of a new attachment apparatus was observed when intrabony defects were grafted with DFDBA (x1.21 mm); significantly more new attachment apparatus (P less than .005), new cementum (P less than .005), new connective tissue (P less than .05), and new bone (P less than .0001) formed in intrabony defects grafted with DFDBA than in nongrafted defects. There was a greater chance for regeneration of a new attachment apparatus and component tissues in grafted defects than in nongrafted defects. New cellular cementum formed on old cementum and dentin but more often formed over both in the same defect). The periodontal ligament was more frequently oriented perpendicular to the root; there was greater loss in alveolar crest height in nongrafted than grafted defects (P less than .05); and extensive root resorption, ankylosis, and pulp death were not observed in grafted or nongrafted defects.

Analysis of Variance↗