摘要:

The efficacy of autoclaving high-speed dental handpieces was tested in two types of downward displacement steam sterilizers (instrument autoclaves), commonly used in the dentist's office. Eight series of experiments were performed with various sterilization schedules. Lubrication oils with or without antimicrobial agent were used in four of the series. Each handpiece was inoculated with 1 ml of a suspension containing equal amounts of saliva and spores ofBacillus stearothermophilus(approx. 106spores/ml). Neither sterilization at 120—124°C for 20 min nor at 134—136°C for 10 min resulted in complete inactivation of the spores in series in which the instruments were tested without oil or with oil containing no antimicrobial agent. However, when the handpieces were lubricated with oil containing isopropanol and formaldehyde and the schedule 134—136°C/10 min was used, no growth was observed. The results indicate that instrument autoclaves with built-in programs of 120—124°C/20 min and 134—136°C/10 min could have insufficient capacity to sterilize lubricated or unlubricated dental handpieces. The use of oils containing an antimicrobial agent can overcome this problem.

ISSN:0001-6357    

DOI:10.3109/00016358309162342

出版商:Taylor&Francis    

年代:1983

数据来源: Taylor

摘要:

The polishability of some amalgam products was studied by determining the roughness (Rs) of metallographically polished specimens. The surface porosity of the specimens was also measured and was found to be closely correlated with the roughness. Two manipulative variables, condensation pressure and primary (precondensation) mercury content, were examined with respect to their effect on porosity and polishability. For the condensation pressures 14 and 20 MPa no differences could be observed in the effect on the surface properties studied. The primary mercury content was varied in three steps—the normal, recommended level and 5% more and less than this. For those products having a recommended precondensation mercury content of 50% or less, the 5% decrease in mercury resulted in a pronounced increase in porosity and Rs. The results indicate that polishability is for some products markedly improved by avoiding a dry mix.

ISSN:0001-6357    

DOI:10.3109/00016358309162343

出版商:Taylor&Francis    

年代:1983

数据来源: Taylor

摘要:

The microvasculature of the subodontoblastic region in the human dental pulp was studied, using freeze-fracturing. This technique allows an analysis of the fine structure of the vascular endothelium with special reference to the membrane structure. The blood capillaries were noted to be of the non-fenestrated or continuous type, although a few fenestrated vessels were observed. The endothelial plasmalemma often exhibited bundles of fibrillar structures, presumably myofilaments. There was a relatively large number of micropinocytotic vesicles and the interendothelial spaces were closed juxtaluminally by tight junctions (zonulae occludentes). The junctions appeared mostly as two to four strands, seen as ridges or grooves on the cell membrane. Thin-walled, irregular, tissue channels lacking the typical, blood-vessel configuration were disclosed. These vessels were believed to represent lymphatics.

ISSN:0001-6357    

DOI:10.3109/00016358309162344

出版商:Taylor&Francis    

年代:1983

数据来源: Taylor

摘要:

Oral tardive dyskinesia may develop due to neuroleptic therapy as a drug-induced disorder of the dopaminergic system of the brain. Long-term treatment with a neuroleptic drug impairing dopaminergic neurotransmission in the rat brain augments oral dyskinetic responses to dopaminergic agonists like apomorphine. In the present experiments, rats were pretreated daily with haloperidol for 3 weeks to cause a‘chronic’blockade in the striatal dopamine receptors. After a withdrawal period of 3 and 6 days, oral sensory stimulation was applied. On the following day the same groups were given apomorphine, and the oral stimulation was repeated. The rats pretreated daily with haloperidol had significantly higher dyskinesia scores than the rats pretreated with saline. The main observation with these sensitized rats was an increase in the frequency and intensity of experimental bruxism caused by oral sensory stimulation alone. Sensory impulses are known to cause release of dopamine in the nigrostriatal system. The combination of oral sensory stimulation and central dopaminergic supersensitivity in the rat can be regarded as an animal model for oral symptoms in human dyskinesia.

ISSN:0001-6357    

DOI:10.3109/00016358309162345

出版商:Taylor&Francis    

年代:1983

数据来源: Taylor

摘要:

Several physical properties were measured for two zinc phosphate and three polycarboxylate cements. The specimens were tested in compression 24 h after they had been made. Two series of specimens were examined. In one series the cement powders were given a correct treatment, protected from atmospheric humidity. In the other series the powders were exposed for 1 week to ambient conditions with the temperature varying between 20°and 24°C and the relative humidity between 40% and 59%. The zinc phosphate cements were characterized by high values of modulus of elasticity and by plastic deformations less than 0.2%. The polycarboxylate cements were more flexible and also exhibited large plastic deformations. Compared with the zinc phosphate cements, therefore, the polycarboxylate cements had high values of resilience and toughness. The storing of cement powders exposed to atmospheric humidity for 1 week did not change the measured properties of the polycarboxylate cements. However, both strength and resilience were significantly reduced for one phosphate cement.

ISSN:0001-6357    

DOI:10.3109/00016358309162346

出版商:Taylor&Francis    

年代:1983

数据来源: Taylor

摘要:

Ground sections of deciduous teeth from 64 infants with birth weights below 2000 g and from 43 healthy full-term infants were examined in polarized light and by microradiography. The deciduous enamel displayed various changes, which were more frequent and pronounced in the low-birth-weight group. The main findings were diffuse areas of increased porosity and distinct subsurface lesions in the postnatal enamel. Five teeth with enamel hypoplasia from the low-birth-weight group were also examined. The hypoplasias were all located along the neonatal line. The postnatal enamel seemed to be more susceptible to disturbances in the mineralization than the prenatal enamel. The subsurface lesions showed an arrest in the very late stages of enamel maturation, which frequently occurred in the cervical deciduous enamel. Enamel hypoplasia is considered to be a result of severe neonatal hypocalcemia.

ISSN:0001-6357    

DOI:10.3109/00016358309162347

出版商:Taylor&Francis    

年代:1983

数据来源: Taylor

摘要:

A dental alloy consisting of Ag-Pd-Cu-Au has been annealed at various temperatures and subsequently quenched to produce a solid solution before a hardening heat treatment. The phases present were studied by means of X-ray diffraction measurements. As in conventional Au-Ag-Cu alloys, an equilibrium of two FCC (face-centered cubic) phases existed up to the solid solution annealing temperature, which is considerably higher in the present alloy (900°C). However, even a rapid quench from 900°C caused a small amount of decomposition of the matrix. The X-ray diffractogram indicated that this new phase is CuPd with a CsCl(B2) superstructure. The greatest hardness after age-hardening at 350°C was achieved with a proper prerequisite solid-solution annealing.

ISSN:0001-6357    

DOI:10.3109/00016358309162348

出版商:Taylor&Francis    

年代:1983

数据来源: Taylor

摘要:

The responses of intradental sensory nerves to hyperosmotic solutions of sucrose (4 M) and calcium chloride (6 M) applied in dentinal cavities were studied in anesthetized cats. Nerve impulse activity was recorded from canine teeth after application of the test solutions in shallow and deep cavities. In shallow cavities (thickness of remaining dentin, about 500μm) sucrose and calcium chloride caused an immediate and transient excitation of the nerves in 3 out of 15 teeth and in 8 of 12 teeth, respectively. Treatment of such cavities with lactic acid (1 M) increased the frequency of nerve responses to 100%. When applied in deep cavities (thickness of remaining dentin, 0—50μm), sucrose induced a burst of impulses followed by continuous nerve activity, whereas calcium chloride decreased the nerve excitability. Our results support the hypothesis that solutions exerting an effective osmotic pressure excite the intradental nerves by an indirect mechanism when applied on the dentin and that they exert a direct effect on nerves when in contact with the pulp. In addition, it is suggested that acids produced in carious dentin may facilitate the induction of pain by hyperosmotic stimuli.

ISSN:0001-6357    

DOI:10.3109/00016358309162349

出版商:Taylor&Francis    

年代:1983

数据来源: Taylor

摘要:

The effect of toothbrushing, using tap water, pumice, or dentifrice, on five resins—-two microfiller resins, one composite resin with both large and microfiller particles, one composite resin introduced as a filling material for posterior teeth, and one conventional composite resin—-was studied by scanning electron microscopy. Brushing with water had almost no effect on the unfinished specimens. When the unfinished and finished specimens of the large filler-containing materials were brushed with toothpaste or pumice, rough surface characteristics were obtained. After the finishing and toothbrushing procedures only one of the microfiller materials showed very smooth surface characteristics. The microfiller materials may be finished with successively finer devices to smooth surfaces that will stay smooth after toothbrushing, whereas finishing the large filler-containing resin materials does not lead to a lasting smooth surface.

ISSN:0001-6357    

DOI:10.3109/00016358309162350

出版商:Taylor&Francis    

年代:1983

数据来源: Taylor