The rediscovery of a neglected part of care. Palliative care is one of the main tasks in nursing

The dimensional accuracy, surface hardness and reproduction of surface detail of stone casts produced from alginate impressions treated with 4.65% sodium hypochlorite, were investigated. To test dimensional accuracy, a Reflex Microscope was used to compare casts from 10 untreated impressions with casts from 10 impressions immersed in the solution for 30 mins. Surface detail and hardness were investigated on casts produced from impressions of a master stainless steel plate with 10 micro-indentations of increasing size. Surface detail of the casts were assessed by observation and surface hardness by a Vickers Hardness Machine. The dimensional accuracy test showed no significant differences between the experimental and control groups. Surface detail was unaffected after immersion of up to 10 mins. Surface hardness decreased linearly with respect to immersion time, when this was greater than 5 mins.     

Clinical significance of surface activation of silicone impression materials

OBJECTIVES: Surface activation of silicone impression materials enhances impression accuracy as well as the quality of stone casts. This study examined the relation between impression quality and the hydrophilicity of silicone impression materials used in a two-stage putty and wash technique. METHODS: The study included 14 silicone impression materials with and without surface activation. The contact angles of the light body materials were measured using deionised water. Free surface energies were calculated. A total of 140 impressions of wet intact permanent molar teeth were examined for definition of the gingival sulcus reproduction and then classified in a quality ranking. The percentage of the sulcus reproduction ability of each material was calculated from the sulcus depths of cross-sectioned resin casts from the impressions and clinically measured sulcus depths. RESULTS: Free surface energies (mJ/m2) of hydrophobic materials (contact angle > 90 degrees) ranged from 16.8 to 26.8 mJ/m2. Surface activated materials (contact angle < 90 degrees) exhibited free surface energies from 38.1 to 55.7 mJ/m2. Not all materials described as surface activated showed hydrophilic properties. Medians of impression quality ranking ranged from 1.75 (best) to 13.25 (worst), mean sulcus reproduction ranged from 30 to 52%. Significant differences (P < 0.05) in quality ranking and sulcus reproduction were found between certain materials but correlations were found neither between sulcus reproduction and free surface energy nor between quality ranking and free surface energy. CONCLUSIONS: For clinical impression recording, surface activation seems to be of minor relevance, at least in the two-stage putty and wash technique investigated and is superimposed by other material properties.     

A technique for developing a master cast with previously made dies

This article describes a technique for preparing final working casts to be used in the laboratory phase of restorative treatment. The goal is to produce accurate working casts that have stable dies which are easily removed from the base and reliably replaced. Most casts with removable dies are made from a single master impression. However, individual dies are sometimes made previously from individual tooth (preparation) impressions. In such cases, transfer copings are required to relate the dies and produce the final working cast. Hollow plastic casting sprues are used as temporary dowels in this technique until a transfer coping pickup impression has been made. After the dies are seated and secured in the transfer coping pickup impression, the plastic casting sprues are replaced with conventional brass dowel pins. This technique ensures well-placed dowel pins that will facilitate easy and accurate withdrawal and replacement of the dies.     

Accuracy, detail reproduction, and hardness of gypsum casts produced from silicone impressions treated with glow discharge

Plasma treatment has been reported to improve the wettability of silicone impression materials. This study investigated whether plasma treatment of silicone impressions influenced the linear dimensional accuracy, detail reproducibility, and surface hardness of models produced from a type IV dental die stone. Five silicone impressions materials were used in this study. Linear dimensional accuracy and detail reproduction were tested according to ISO standards. Surface hardness was evaluated with a Vickers hardness test. The results indicated that plasma-treated impressions from Xantopren and Provil silicone impression materials had significantly smaller dimensional change than their respective controls, and the other materials were not influenced. The detail reproduction was superior in casts produced from plasma-treated impressions from President silicone. Surface hardness was not influenced by the treatment. Plasma treatment of silicone impressions has no negative influence on the tested physical properties of die stone models.     

Marginal accuracy of indirect provisional restorations fabricated on poly(vinyl siloxane) models

Indirect interim restorations have been traditionally fabricated on stone casts. Recently, flexible models fabricated from poly(vinyl siloxane) impression material have been suggested in place of stone casts. This study compared the marginal accuracy of indirect single-unit provisional restorations fabricated on stone casts with units made on poly(vinyl siloxane) impression material models. The mean marginal discrepancy of provisional restorations was compared for restorations fabricated from stone, low-viscosity poly(vinyl siloxane), and medium-viscosity poly(vinyl siloxane). Ten restorations were also fabricated directly on a master metal model (control). The mean marginal discrepancies were: control = 0.161 mm; stone model = 0.180 mm; low-viscosity poly(vinyl siloxane) = 0.245 mm; and medium-viscosity poly(vinyl siloxane) = 0.157 mm. The mean marginal discrepancy for the low-viscosity poly(vinyl siloxane) models was significantly higher than the other three groups. No significant difference was found between the control, stone cast, and medium-viscosity poly(vinyl siloxane) model groups.     

An in vivo study of a clinical surfactant used with poly(vinyl siloxane) impression materials

The aim of this study was to determine whether the use of a topical surfactant (Hydrosystem), designed for clinical use, improved the quality of the impression surface of two poly(vinyl siloxane) materials used in vivo. Before impressions were taken, Hydrosystem was applied to the maxillary left or right premolar teeth, allocated at random, in 50 subjects. The untreated side acted as a control for each subject. The impressions were examined for quality of reproduction and number of surface defects. Hydrosystem was found to significantly improve the quality of reproduction.     

Subtle neurological deficits and psychopathological findings in substance-abusing homeless and non-homeless veterans

PROBLEM: In vitro studies have demonstrated microfractures in resected roots after root end cavity preparation with ultrasonic tips. Such microfractures are of concern; however, they may be artifacts. OBJECTIVES: To assess the incidence of microfractures after ultrasonic root end cavity preparation in situ. STUDY DESIGN: Fifty-two roots in two cadavers were endodontically treated, the soft tissues excised, and the root ends exposed and resected. The resected root surfaces were replicated with polyvinylsiloxane impressions. Root end cavities were prepared with ultrasonic tips, then impressed a second time. The roots were retrieved; 25 were processed for direct SEM examination as were both the impressions of each root. The specimens were examined by stereomicroscope and scanning electron microscope. RESULTS: In the impressions, the resected and prepared surfaces appeared irregular, but none demonstrated microfractures. In contrast, 15 retrieved roots showed microfractures. CONCLUSIONS: Ultrasonic root end cavity preparation in situ did not cause root microfractures, and the impression technique could be clinically usable with minor modifications.     

The influence of the impression tray on the accuracy of impressions for crown and bridge work--an investigation and review

OBJECTIVE: To evaluate the accuracy of working casts for crown and bridge restorations made from twin mix putty/wash silicone elastomeric impression materials using different types of stock tray. DESIGN: A master cast was made from ivorine teeth in a mandibular model. Three teeth were prepared for full crown restorations to simulate a single unit and a three unit bridge. Impressions were taken using four different types of impression tray and two different viscosities of silicone putty, together with a wash. Full metal crowns were constructed and seated on duplicate master casts and measurements made of the marginal discrepancies. SETTING: The work was carried out in a dental technology laboratory in a university department of restorative dentistry in 1995/1996. RESULTS: Metal and rigid plastic impression trays showed the least discrepancy (about 50 microns), the latter slightly greater with the normal putty than the soft one. Impressions taken with flexible plastic trays produced considerable discrepancy with both putties, approximately 210 microns and 180 microns respectively. CONCLUSIONS: Metal and rigid plastic stock trays give greater accuracy in the putty/wash silicone twin mix impression technique compared with flexible plastic ones for crown and bridge work. Those using the latter should be aware of their shortcoming in this respect.     

Early morphological and immunological alterations in the spleen during magnesium deficiency in the rat

PURPOSE: Materials used to fabricate the most dimensionally accurate implant casts have not been identified experimentally. The purpose of this investigation was to examine the dimensional accuracy of implant casts fabricated with different materials. Measurements of linear horizontal dimensional change and strain produced on a master framework were evaluated and correlated. MATERIALS AND METHODS: A master framework was fabricated to fit an aluminum five-implant model. Forty polyether implant impressions of the aluminium model were randomly grouped and poured in either Vel-mix, Die Keen, Resin Rock, or Low Fusing Alloy. A digital veneer caliper was used to measure linear distance between the most distal abutments on each of the experimental implant casts and the master model. In addition, strain values were recorded from strain gauges bonded in the mesiodistal axis of the framework, which was secured by prosthetic retaining screws torqued to 10 Ncm. RESULTS: A one-way ANOVA showed a significant difference among the four die materials in dimensional change of the experimental casts (p = .0001). A post-hoc Duncan's multiple-range test (p < .05) showed that casts fabricated with Low Fusing Alloy had the least linear dimensional change from the master cast, but the material exhibited the greatest dimensional variability. A MANOVA (Wilks' Lambda) showed significant differences in strain on the framework based upon die material (p = .015). A post-hoc Duncan's multiple-range test (p < .05) showed that Resin Rock casts induced significantly less strain on the framework than the other materials. Negligible correlation was found between the linear horizontal dimensional change and the total absolute strain on the framework. CONCLUSION: Experimental implant casts made of Resin Rock minimized strain on the master framework and decreased the amount of framework distortion on casts of this material. Low Fusing Alloy yielded accurate casts, but highly variable linear dimensional changes in the horizontal dimension may preclude its clinical benefit.     

Transmission electron microscope specimen preparation of Zn powders using the focused ion beam lift-out technique

Particles of Zn powder have been studied to show that high-quality scanning electron microscope (SEM) and transmission electron microscope (TEM) specimens can be rapidly produced from a site-specific region on a chosen particle by the focused ion beam (FIB) lift-out technique. A TEM specimen approximately 20-μm long by 5-μm wide was milled to electron transparency, extracted from the bulk particle, and micromanipulated onto a carbon coated copper mesh TEM grid. Using the FIB lift-out method, we were able to prepare a site-specific TEM specimen from a difficult material in under 3 hours. The TEM analysis of the lift-out specimen revealed a large amount of thin area free from characteristic signs of damage that may be observed as a result of conventional argon ion milling. The overall microstructure of the specimen prepared by the FIB lift-out method was consistent with samples prepared by conventional metallographic methods. A grain size of ∼10 to 20 μm was observed in all specimens by both TEM and SEM analysis. Light optical microscopy revealed the presence of internal voids in ∼10 to 20 pct of all particles. The SEM analysis showed the voids to extend over ∼70 pct of the particle volume in some cases.     

Combined bronchoalveolar-vascular casting of the canine lung

Canine bronchoalveolar and vascular corrosion casts were prepared using unfixed tissue and Dow-Corning Room Temperature Vulcanizing Silastic 734. The casts were observed using stereo light microscopy and scanning electron microscopy. The casts show the relationship between the vasculature and airway and demonstrate intricate microanatomical details. Also, microvasculature filling was enhanced using unfixed tissue as compared to my previously described technique using fixed tissue. Prewashing the microvasculature with cold phosphate buffered saline appeared to facilitate microvascular filling with silicone rubber. The described method is useful for rapidly making durable models for studying the normal respiratory airway and microvasculature. It should be useful in future studies of diseased pulmonary tissue as well as other normal and diseased tissues where microanatomical relationships between microvasculature and adjacent luminal structures are relevant.     

Evaluation of factors affecting the accuracy of impressions using quantitative surface analysis

Impression material goes from a plastic to an elastic state during setting. Movement of the impression and excessive seating pressure during this transition can cause distortion in the impressions. The purpose of this study is to determine if the impression distortion is related to movement during setting or to distortion of the putty phase in the two-step impressioning technique. A master model of a maxillary quadrant of teeth was impressed using four different procedures: 1) one-step technique without movement (1S-NM); 2) one-step technique with movement (1S-M); 3) two-step technique without movement (2S-NM); and 4) two-step technique with movement (2S-M). An artificial oral environment and surface analysis technique of the Minnesota Dental Research Center for Biomaterials and Biomechanics were used to produce the impressions and measure their accuracy. A digitized image of the first premolar of the master model was aligned with a digitized image of the first premolar of each epoxy model using AnSur. The root mean squared difference (RMS) between the aligned images is a measure of the distortion. The corresponding RMS values for the different methods were: 1S-NM = 23.7 +/- 9.21; 1S-M = 20.4 +/- 3.9; 2S-NM = 20.5 +/- 7.7; 2S-M = 21.3 +/- 4.4. Statistical analysis using a two-way analysis of variance showed no difference at the 0.05 level of significance. Pairwise comparison using the Tukey method showed that neither technique (one-step vs two-step) nor movement is a significant factor. These results showed that low seating pressure will not cause any greater distortions in the two-step impression technique than in the one-step technique, and minor movement during the setting of the impression material will no cause distortion.     

Latent fingerprints on cartridges and expended cartridge casings

The effects of time and detonation on latent fingerprints from cartridges and cartridge castings were explored. Time alone did not appear to seriously degrade latent fingerprint quality over the three-week period of experimental trials. The greatest effect of detonation seemed to stem from hot gaseous blowback on the external surface of the cartridge casings. Nickel-plated casings, because of their greater chemical resistance and more polished surface, were found less satisfactory as a substrate for latent impressions than brass casings. An interesting technique for development and permanent preservation of latent fingerprint impressions on castridge casings was also described.     

Improved impression cytology techniques for the immunopathological diagnosis of superficial viral infections

BACKGROUND: For epidemiological and therapeutic reasons early diagnosis of superficial viral infections is crucial. Conventional microbiological techniques are expensive, time consuming, and not sufficiently sensitive. In this study impression cytology techniques were evaluated to analyse their diagnostic potential in viral infections of the ocular surface. METHOD: A Biopore membrane device instead of the original impression cytology technique was used to allow better quality and handling of the specimens. The impressions were processed, using monoclonal antibodies and immunoperoxidase or immunofluorescence techniques to assess the presence of herpes simplex virus, varicella zoster virus, or adenovirus antigens. Ocular surface specimens from healthy individuals (n = 10) and from patients with suspected viral surface disease (n = 19) were studied. Infected and non-infected cell cultures served as controls. RESULTS: This modified technique of impression cytology allowed the collection of large conjunctival and corneal epithelial cell layers with excellent morphology. Immunocytological staining of these samples provided diagnostic results for all three viruses in patients with viral surface disease. CONCLUSIONS: The use of Biopore membrane devices for the collection of ocular surface epithelia offers new diagnostic possibilities for external eye diseases. Immunopathological methods that are applied directly on these membrane devices can provide virological results within 1-4 hours. This contributes considerably to the clinical management of patients with infectious diseases of the ocular surface.     

Neonatal nucleated red blood cell and lymphocyte counts in fetal brain injury

STATEMENT OF PROBLEM: Flexible die materials have been introduced to facilitate the fabrication of indirect provisional or definitive restorations in 1 appointment. PURPOSE: This study compared the surface detail reproduction of 7 potential flexible die materials when used in combination with 7 elastomeric impression materials. METHODS: Surface detail reproduction of 17 impression material/flexible die material systems was compared with a control system containing an elastomeric impression material and a Type IV dental stone. Test dies of each system were prepared in a random order with the American Dental Association apparatus for testing detail reproduction, compatibility, and dimensional stability. RESULTS: One flexible die system had better surface detail reproduction than the control stone die, other systems had similar or worse reproduction. Surface detail reproduction was adversely affected when a separator was required between the impression and flexible die material. CONCLUSIONS: Impregum F die material with Extrude Light impression material produced better surface detail reproduction than the control dies. Impregum F impressions were incompatible with Blu-Mousse, Impregum F, or Imprint die materials. Polyvinyl siloxane impressions were incompatible with polyvinyl siloxane dies unless a separator was used. When a separator was used, the surface detail reproduction was not as good as the control die system or the Extrude Light impression material/Impregum F die material combination.     

Improvement of longitudinal resolution by deblurring technique in helical CT of the head and neck

Patients for cataract surgery in India routinely undergo preoperative syringing to rule out chronic dacryocystitis. We determined the sensitivity and specificity of the clinical test of regurgitation on pressure over the lacrimal sac (ROPLAS) as a screening test for chronic dacryocystitis and compared it to syringing. 621 consecutive outpatients who needed syringing for various reasons (including 318 who had routine syringing prior to cataract surgery) were examined in a masked manner for regurgitation on pressure over the lacrimal sac. They then underwent syringing by a trained (masked) observer. The sensitivity and specificity of ROPLAS were 93.2% and 99.3%, respectively. Using a 6.6% prevalence of chronic dacryocystitis (the prevalence in our cataract population), the negative predictive value of the test was 99.5%. In the presence of regurgitation of pressure over the sac, the high specificity of ROPLAS confirms chronic dacryocystitis. In view of the opportunity costs, when ROPLAS is negative, preoperative syringing in cataract is perhaps unnecessary, unless the findings are equivocal or the index of suspicion for chronic dacryocystitis is very high.     

When not to syringe an ear

This article reviews the potential hazards of ear syringing and the Accident Compensation Corporation Medical Misadventure Unit's experience of alleged iatrogenic injury over a 17-month period. Syringing claims account for about 25% of the total claims received by the ACC ENT Medical Misadventure Committee. Forty-seven claims were accepted as either mishap or error, and 63 claims were declined. Perforation of the drum was by far the commonest injury resulting in significant disability. Severe iatrogenic otitis externa accounted for most of the remainder. Practice nurses had syringed the ears of approximately two-thirds of the claimants with significant disability. The contraindications to ear syringing are listed and discussed. The correct technique, with a few "do and don't" pointers, is briefly reviewed. Management of the unintentional injury is discussed.     

The quality of impressions for crowns and bridges received at commercial dental laboratories

OBJECTIVE: To determine the quality of impressions for crown and bridge work made in general dental practice. DESIGN AND SETTING: All impressions for crown and bridge work which had been sent to four commercial dental laboratories in the UK were assessed by two examiners, each laboratory being visited on two occasions. MATERIALS AND METHODS: 290 cases which had been received by the laboratories on the days of the visits were assessed for a number of factors related to quality. There was no selection or rejection--all impressions received were examined. RESULTS: Flexible plastic trays were used for the majority of working impressions for crown and bridge work in general dental practice (72%), many had been re-used (> 13%), defects in the recording of the prepared teeth were common, and cross infection control was not routine. CONCLUSIONS: Quality standards for impressions for crown and bridge work in general dental practice in the UK are a cause for concern if the sample of cases seen in this study is typical.     

Changes in microvascularization of some rat organs following soman poisoning

Vascularization of some organs of rat following soman (O-pinacolyl methylphosphonofluoridate) intoxication was studied using scanning electron microscopy. Corrosion casts were prepared with commercially available methyl metacrylate monomer which was partly polymerized, supplemented with catalyst and accelerator and injected into the prewashed and fixed vascular bed. The obtained corrosion casts were sectioned and trimmed using a stereoscopic light microscope. Microvascular casts of normal organs', bed pattern were studied under scanning electron microscope and compared with vascularization patterns after soman poisoning. Changes in the vascular bed architecture of kidneys, brain, adrenal glands and thymus were described.     

Evaluation of intranasal zinc sulfate treatment on olfactory discrimination in rats

The effects of intranasal syringing with 5% zinc sulfate were assessed in rats trained in a wind-tunnel olfactometer to detect the presence of an odor or to discriminate odors of graded intensities. The syringing produced a severe but brief interference in olfactory performance. Full recovery of detection performance occurred within 72 hr after treatment. Initial recovery of odor intensity discrimination occurred in 2-8 days and full recovery within 8-10 days. These results suggest that intranasal syringing with ZnSO4 is not an adequate control for the effects of anosmia produced by olfactory bulbectomy.