Nylon Brush Research Articles

Experimental Investigation of Contamination Removal from Slider Bar Surface by Using Various Cleaning Methods

The rapid advancements in various current technologies and the constant trend in miniaturizing of components have created a need for higher cleanliness levels. Contamination in the level of monolayers can drastically alter surface properties such as wettability, adhesion, optical or electrical characteristics. To select an effective cleaning method the three essential factors to be considered such as cleaning chemistry, the scrubbing method and other process parameters. This study investigates the effectiveness of brush cleaning, ultrasonic cleaning and combination of brush and ultrasonic cleaning on removal of contamination, surface defects and brush life time. In this study, the cleaning efficiency was compared for the parts cleaned with ultrasonics, nylon brush, Poly Vinyl Alcohol (PVA) brush and combination of ultrasonics and nylon brush. The life time of brush was studied for both nylon and PVA brush. The techniques used to identify the contamination are SEM, EDX and optical microscope. The microscopic result indicates that the removal efficiency was high for the parts cleaned with ultrasonics (90.5%) and PVA brush (90.2%) as compared to Nylon brush (77.4%). This is due to the fact that for PVA brush the fluid was being pumped in and out of brush pores (during compression and elastic recovery of the brush), carries the contamination away from the surface and also the contact area between the contamination surface and brush was more. From Liquid Particle Count (LPC) analysis, the >0.3 mic particle counts is almost two times lower for parts cleaned with ultrasonics as compared to parts cleaned with brushes. This indicates that 58/132 kHz washing followed by 470 kHz DI rinsing effectively removes sub- micron particles from the surface compared to brush cleaning. The defects caused by brushes on the surface of the slider bar is almost 1% for nylon brush cleaning, 0.4% for PVA brush cleaning and 0% for ultrasonic cleaning. From experimental study, it can be seen that the life time of PVA brush was shorter than Nylon brush by 75 times. The contamination increased after 50th run for PVA brush and after 700th run for nylon brush. This is due to the fact that after brush damage (after 50th run for PVA and 700th run for nylon) the brush can not effectively remove the contamination and also re-deposition of contamination from brush.

Induction of tracheal stenosis in a rabbit model—endoscopic versus open technique

To evaluate and compare open versus endoscopic methods of inducing tracheal stenosis in the New Zealand white rabbit model. Prospective randomized control, pilot study. Fifteen New Zealand white rabbits were used in the study. Induction of tracheal stenosis was performed through an open incision in 6 rabbits, an endoscopic approach was utilized in 8 rabbits, and 1 rabbit served as the control. The open approach was performed by brushing the tracheal mucosa 10 times through an anterior tracheotomy with a nylon brush. The endoscopic method was achieved using a rigid bronchoscope and at a measured distance below the cricoid cartilage, passing the same nylon brush four times in each of four quadrants. Repeat endoscopies for evaluation of stenosis progression were performed at 2 and 3 weeks on all rabbits. In the open group, we observed no stenosis with one mortality as a result of gastroenteritis due to antibiotic use. In the endoscopic group, all animals achieved some degree of stenosis by 14 days, with a mean airway narrowing of 43%. The two deaths in the endoscopic group occurred in the immediate postoperative period secondary to laryngeal edema. The endoscopic procedure was 5 minutes in duration. The endoscopic technique is an effective method of achieving circumferential tracheal stenosis in the rabbit model. Advantages include simple instrumentation, an endoscopic approach, potential for decreased costs, and more reliable results.

Lichen amyloidosis induced on the upper back by long‐term friction with a nylon towel

Primary localized cutaneous amyloidosis can take several clinical forms. In Asia, macular amyloidosis caused by prolonged friction from a rough nylon towel or brush is common, and macular amyloidosis and lichen amyloidosis occasionally occur together, as so-called biphasic amyloidosis. We report herein the case of an 83-year-old Japanese man with lichen amyloidosis caused by prolonged nylon towel friction. This patient presented with unique symmetrical papular lesions on the upper back and shoulders. Lesions comprised slightly shiny, brownish, fine uniform papules approximately 0.5 mm in diameter, showing a partially linear, annular or rippled arrangement. Although this case was caused by prolonged nylon towel friction, no coexisting macular lesions could be found. To the best of our knowledge, this represents the first case of lichen amyloidosis induced by nylon towel friction in the absence of the macular amyloidosis that is usually observed in such cases. We instructed the patient to stop the habit of nylon towel rubbing and prescribed a topical steroid ointment and cepharanthine. After 6 months of treatment, papular lesions became clearly flatter.

R453 – Cryoballoon Dilation of Tracheal Stenosis

Problem The endoscopic management of tracheal stenosis remains ineffective, despite advances in dilation and resection techniques. The vascular literature reveals improved patency rates of stenosis with cryodilation compared to balloon angioplasty. The proposed mechanism is a decrease in collagen deposition with cryotherapy. Similarly, tracheal cryotherapy maintains the cartilaginous framework of the airway while minimizing collagen deposition. The objective of this study is to compare collagen deposition in tracheal injuries dilated with room temperature versus subfreezing temperature balloons. Methods Six New Zealand White rabbits underwent endoscopic tracheal injury with a nylon brush. At 3 weeks post injury, dilation was performed by a balloon inflated with either room temperature saline (n=3), or nitrous oxide to −10 °C, (n=3). Rabbits were sacrificed at 2 and 4 weeks post dilation. Segments of injured trachea were histologically examined for collagen and graded as none, mild, moderate, or severe. Results Collagen deposition at 2 weeks post dilation was graded as moderate to severe in all specimens. In the 4 week post dilation tracheas, marked differences in collagen deposition were noted. While the trachea dilated at room temperature was graded as moderate to severe, the cryoballoon dilated trachea showed minimal to no collagen deposition. Despite the observed differences in collagen deposition, sub-mucosal thickness differed between specimens by an average of 0.2 mm. Conclusion This preliminary study suggests that dilation with balloon cryotherapy decreases collagen deposition in the injured airway. Significance Long-term patency of immature tracheal stenosis may be improved with the addition of subfreezing temperatures to endoscopic dilation techniques. Support A grant was provided by Boston Scientific, Inc. in the form of money and supplies.

Upstream passage of inanga Galaxias maculatus and redfin bullies Gobiomorphus huttoni over artificial ramps

The effects of surface type and slope on fish passage over artificial ramps were evaluated for two small diadromous fish species native to New Zealand: the redfin bully Gobiomorphus huttoni and adult and juvenile inanga Galaxias maculatus. Surfaces tested include smooth plastic, sand, gravel (limestone chips 5–20 mm), nylon brush and two plastic moulded cores of ground drainage products Cordrain® and Miradrain®. Slopes of 15° (1:3·7), 30° (1:1·7) and 45° (1:1) were assessed. Slope was the greatest factor influencing successful passage, with the lowest gradient tested (15°) providing the highest passage for both fish species. Most ramps at 45° only allowed the passage of redfin bullies, these fish being capable of ‘climbing’ the wetted margin of the ramps. Because of this climbing ability, redfin bullies were not as affected by the ramp surface, as inanga. Nevertheless, the smooth plastic surface, which resulted in the highest water velocities over the ramps, was un‐passable by either species at slopes >15°. Gravel, the nylon brush and the two plastic moulds provided high passage rates for inanga at gradients of 15 and 30°. At a slope of 45°, Miradrain® was the only surface inanga could pass. Overall, Miradrain® produced the most successful passage for both inanga and redfin bullies, but to maximize passage, slope should not be >15° and a wetted margin is essential for climbing species.

Mechanical descaling of wire rod using reverse bending and brushing

Wire rods are covered with an oxide layer, which must be removed before wire drawing. This paper presents an investigation of mechanical descaling by reverse bending and brushing as replacement for pickling. Steel grades studied were low carbon steel and silicon chromium steel. Brushing was done with steel brushes and nylon brushes with SiC. The amount of scale remaining after reverse bending of the low carbon steel depended on the roller diameter. After brushing traces of scale remained in valleys on the surface. Surface damage was observed after brushing with steel brushes but not after SiC–nylon brushing. Silicon chromium alloyed steel was not possible to clean by bending and brushing with the roller diameters studied. The electrical energy required for the mechanical descaling of low C steel may be estimated to be 7 kWh/tonne with SiC–nylon brushes and 14 kWh/tonne with steel brushes.

Rabbit Model of Airway Stenosis Induced by Scraping of the Tracheal Mucosa

Prolonged endotracheal intubation in children often induces intractable airway stenosis. The aim of the present study was to establish a new model of airway stenosis for developing an effective method of treatment. The rabbit trachea was annularly incised, and the tracheal mucosa was scraped with a nylon brush. The trachea was then closed. Nine days after scraping, the trachea was microscopically examined. All of the examined rabbits showed tracheal stenosis, ranging from 22% to 82% in diameter and from 48% to 97% in cross-sectional area. The stenotic lesion was confined within the scraped region, not including the sutured region. Histologic examination showed inflammation in the stenotic lesion with submucosal hyperplasia caused by proliferation of fibroblasts and thickening of collagen fibers. This method can be easily carried out and assures induction of airway stenosis. This model may be useful for developing methods for treating airway stenosis in the early stage.

Quantification of diatoms in biofilms: Standardisation of methods

Benthic diatoms, which often dominate marine biofilms are mostly pennate along with a few centric species that have an attached mode of life. Even though the range of diatoms in biofilms is diverse, their ecology is poorly understood because of the difficulty in sampling and enumeration. Scraping or brushing are the traditional methods used for removal of diatoms from biofilms developed on solid substrata. The method of removal is the most critical step in enumerating the biofilm diatom community structure. In this study, a nylon brush and ceramic scraper were used as tools for the removal of diatoms from 1 – 4-day-old biofilms developed on fibreglass coupons and glass microscope slides. Standardisation of methods showed that the sample volume used in the analyses had the least influence on the quantification, whereas the method of removal was critical. The nylon brush was more efficient at recovering diatoms compared to a ceramic scraper. Direct microscopic enumeration of the community in the case of glass slides indicated that scraping resulted in between 30–50% underestimation. Heterogeneity in diatom community structure between replicate samples is one possible reason for such underestimation.

Efficiency and countereffects of cleaning treatment on limestone surfaces—investigation on the Corfu Venetian Fortress

Surface alterations of the original limestone and the efficiency of several cleaning methods were investigated on the Corfu Venetian Fortress facade. Black crusts of gypsum dendrites and loose depositions or black-grey calcareous encrustations in combination with biological decay were identified as main decay processes. The cleaning treatments, chosen according to their acting on the stone surface, were: sepiolite for solvent action, ammonium bicarbonate for exchange action, EDTA for the chemical chelating action, hydrogen peroxide for chemical action on biological species and nylon brushes for physical action. Each cleaning method's efficiency and counteractions were evaluated by laboratory examinations concerning the morphology and the composition of the surface with SEM observations and X-ray microanalysis, before and after treatment and during ageing tests in sulphur dioxide and humidity atmosphere. The used methodology creates a sound basis for the evaluation and proper selection of a cleaning method, which should be highly efficient and with limited counteractions to the stone.

Mechanical brush-catheter abrasion method for the isolation and culture of human umbilical vein endothelial cells. First in vitro results

Mechanical brush-catheter abrasion method for the isolation and culture of human umbilical vein endothelial cells. First in vitro results. To determine the value of a nylon brush (Cragg thrombolytic catheter system) with regard to the isolation and culture of viable human vascular umbilical vein endothelial cells (HUVEC). Fresh human umbilical cords were collected after a maximum of 6 - 8 h post delivery. They were stored in sterile tubes till further preparation. After predilation the umbilical cord veins, a 6 French brush catheter was inserted, expanded, and removed by hand using rotating movements. The nylon brush was shaken out in cell medium containing serum proteins by a connected motor drive. After repeating these procedures, the detached endothelial cells were centrifugated and resuspended. The cell numbers were assessed and cell viability controlled. The endothelial cell (EC) viability depended on the umbilical cord's age and was the highest (29.8 +/- 11.4 %) within 3 h after delivery. The brush abrasion (3.32 x 10(5) +/- 52016 viable EC/10 cm vein segment) enabled us to culture these cells under different cell concentrations. They grew to confluence after 2 - 3 weeks. The brush-catheter abrasion is an effective method for collecting viable human endothelial cells in vitro.

Comparison of the Mechanical Thrombectomy Efficacy of the Amplatz Thrombectomy Device and the Cragg Thrombolytic Brush In Vitro

To determine the efficacy of thrombectomy (without thrombolytic agents) for the Amplatz thrombectomy device (ATD) and the Cragg thrombolytic brush catheter (CBC) in vitro. Thrombectomy was performed with the ATD or CBC (6F) in a flow model. Embolus sizes, weight, remaining thrombus, and activation time were evaluated. No significant difference in the activation time was found. The CBC produced significantly less embolism (3.3% vs. 0.03% in the 5-mm and 89% vs. 0.5% in the 7-mm model), but also much more thrombus remained in the system than with the ATD (1% vs. 41% in the 5-mm and 0.1% vs. 62% in the 7-mm model). The ATD can remove almost all thrombus (99%), whereas the CBC removes only up to 60%, producing fewer emboli than the ATD. This might be due to the lower rotational speed of the CBC compared with the ATD, which is 20 times greater. The soft nylon brush offers less resistance and shear force toward the thrombus than the stainless-steel impeller of the ATD. Because of the large amount of remaining thrombus, the CBC should not be used without lytic agents.

422 ナイロンブラシを用いた鏡面加工法(OS12 研削・砥粒加工)

422 ナイロンブラシを用いた鏡面加工法(OS12 研削・砥粒加工)

Pharmacology of sensory stimulation-evoked increases in frontal cortical acetylcholine release

Recent research has demonstrated that a variety of sensory stimuli can increase acetylcholine release in the frontal cortex of rats. The aim of the present experiments was to investigate the pharmacological regulation of sensory stimulation-induced increases in the activity of basal forebrain cholinergic neurons. To this end, the effects of agonists and antagonists at a variety of neurotransmitter receptors on basal and tactile stimulation-evoked increases in frontal cortical acetylcholine release were studied using in vivo brain microdialysis. Tactile stimulation, produced by gently stroking the rat's neck with a nylon brush for 20 min, significantly increased frontal cortical acetylcholine release by more than 100% above baseline. The noradrenergic α 2 agonist clonidine (0.1 or 0.2 mg/kg) and α 1 antagonist prazosin (1 mg/kg) failed to affect basal cortical acetylcholine release; however, both compounds significantly reduced the increases evoked by sensory stimulation. In contrast, the α 2 antagonist yohimbine (3 mg/kg) increased basal cortical acetylcholine release, thereby preventing meaningful investigation of its effects on tactile stimulation-evoked increases. The benzodiazepine agonist diazepam (5 mg/kg) reduced, and the GABA A receptor antagonist picrotoxin (2 mg/kg) increased basal cortical acetylcholine release; in addition, diazepam attenuated the increases in cortical acetylcholine release evoked by tactile stimulation. While dopaminergic D 1 (SCH 23390, 0.15 mg/kg) and D 2 (raclopride, 1 mg/kg) receptor antagonists did not by themselves significantly influence the increases evoked by tactile stimulation, their co-administration produced a significant reduction. The opioid receptor antagonist naltrexone (1.5 mg/kg) failed to affect either basal or tactile stimulation-evoked increases in acetylcholine overflow. Finally, the non-competitive N-methyl- d-aspartate receptor antagonist, dizocilpine maleate (MK-801; 0.025 and 0.05 mg/kg) increased basal cortical acetylcholine release. These results confirm that cortically projecting cholinergic neurons are activated by sensory stimuli, and indicate that the increases in cortical acetylcholine release produced by tactile stimulation are inhibited by stimulation of α 2 or blockade of α 1 noradrenergic receptors, and by enhanced GABAergic transmission. In addition, simultaneous blockade of dopamine D 1 and D 2 receptors appears necessary to achieve a significant reduction of sensory stimulation-evoked acetylcholine release in the frontal cortex. The results are consistent with the hypothesis that cortical acetylcholine release is a component of the neurochemistry of arousal and/or attention and indicate that this is modulated by GABAergic, noradrenergic and dopaminergic systems. In contrast, endogenous opioid actions do not appear to be involved.

Controlled Spawning of the Neon Tetra

Abstract The neon tetra Paracheirodon innesi is one of the most valuable species in the ornamental fish trade. Most neon tetras available in the United States are imported from Southeast Asia, where they are farm raised, or from South America, where they are collected from the wild. In this study, we describe a method for artificially breeding the neon tetra that can be adapted to domestic commercial production. Broodfish pairs were routinely spawned in acidified, soft water at 25°C (pH, 5.5–6.5, adjusted with phosphoric acid; total alkalinity, 3.2 mg/L, and total hardness, 6.0 mg/L, as CaCO3). The water was also conditioned with humic acids (0.04%). A spawning substrate (nylon brush) was available for egg deposition. Fish reared in the laboratory had a significantly higher number of larvae (82 larvae/female) than broodstock collected from the wild or cultured abroad (28 larvae/female). The domestic population reached sexual maturity at 5–6 months of age, and broodfish pairs produced an average of 82 larvae every 2 weeks over a period of 1 year. Rotifers and boiled egg yolk were the first larval feeds. Thereafter, fish were fed nauplii of brine shrimp Artemia sp., shaved cattle liver, and formulated diets. At approximately 1 month of age, larvae obtained their adult body coloration. The described method can be adapted for domestic commercial production of neon tetras.

The influence of weight of ryegrass per unit area and treatment at and after mowing on rate of drying

The rates of drying of perennial ryegrass, subjected to different treatments at mowing and after mowing, were assessed in the field by weight change of grass fresh weight in wire‐mesh trays over 3·5 d (76 h). In a 5 × 3 × 3 factorial experimental design, the effects of five weights of grass per unit area [1·5, 3, 6, 12 and 24 kg fresh material (FM) m−2], three treatments at mowing (no treatment, mower‐conditioned, flail‐treated) and three treatments after mowing (no treatment, inverted, mixed) were examined. The experiment was replicated twice on 16 occasions in 1992 at the Agricultural Research Institute of Northern Ireland. This gave a total of thirty‐two replicates per treatment. The trays were weighed at 2‐h intervals from 09.00 to 17.00 h each day. Data sets were restricted to rain‐free days and also to the first day after mowing (day 1). On day 1, grass weight per unit area was a major factor dictating drying; reducing the grass weight per unit area of unconditioned grass from 6 to 3 kg FM m−2 increased grass drying rate by 47%. There was no significant (P > 0·05) benefit over the untreated grass on day 1 from mixing or turning mower‐conditioned or the unconditioned grass. Mixing of the flail‐treated grass improved drying rate significantly (P > 0·001) over the control. Over the whole 76‐h period, the relative benefit from either mower conditioning or flail treatment over no treatment was dependent upon both grass weight per unit area and initial dry‐matter (DM) concentration. At higher initial DM concentrations (>150 g kg−1) and lower grass weights (<6 kg FM m−2) both mower conditioning using a nylon brush type conditioner and intensive conditioning by flail treatment gave substantial increases in drying over no treatment. Moisture regain of grass exposed to overnight dew was small. Rain had a much greater effect than dew on subsequent moisture regain. Unconditioned grass at 12 kg m−2 retained 82% less water following rainfall than unconditioned grass at 3 kg m−2.

Cytopathology of the Nasal Mucosa in Smokers: A Possible Biomarker of Air Pollution?

In our search for an easy, reliable, and inexpensive screening method to assess the toxic effects of air pollution and the attendant cancer risk on the respiratory tract, we investigated to what extent brush cytology of the nasal mucosa satisfies these demands. Using brush cytology, we examined the nasal mucosa of 60 cigarette smokers and compared the cytopathologic findings with those of 60 nonsmokers. All subjects were healthy male office workers with no nasal disorders. Mucosal cells were obtained from the maxillo-turbinal region with a small nylon brush, subsequently processed by Papanicolaou staining on a glass slide, and examined “blinded” by cytopathologists. The cytologic findings were normal in 46 of the nonsmokers, with simple squamous cell metaplasia detectable in the remaining 14 of this group. However, in the group of cigarette smokers, 52 showed unequivocal dysplasia of various degrees, whereas merely eight showed only metaplasia. Dividing the smokers into two groups based on pack/years of cigarette consumption revealed that the severity of dysplasia (mild or moderate) correlated well with the pack/years (P = 0.0001). As yet, no significant relation between smoking habits and the incidence of nasal sinus squamous cell carcinomas has been demonstrated in contrast to the established relationship between smoking and carcinomas of the larynx and lungs. Nevertheless, it is conceivable that cytopathologic changes in the nasal mucosa could act as a biomarker reflecting similar changes in the lower respiratory tract.

The ecology of intertidal algal crusts: variation within a functional group

Encrusting marine algae are found at all depths in the photic zone from polar to tropical seas worldwide, yet little is known about their ecology. Crusts (including red, brown, and green algae as well as lichens and Cyanobacteria) tend to predominate in areas of high disturbance (e.g. from herbivores or sand scour) or high stress ( = low potential productivity, e.g. high on the shore). Patterns of crust and herbivore distribution and abundance were quantified in the intertidal zone in Washington state, and then the two environmental parameters predicted to be critical to among-crust variation in survival were manipulated: disturbance potential by varying abundances of herbivores, or by eliminating herbivores and artificially disturbing crusts with nylon and steel brushes; productivity potential by transplanting crusts along an environmental gradient from the high to the low intertidal zone and onto a submerged raft. Within-functional-group variation among crusts was studied by transplanting eight species (varying in calcification, thickness, tightness of construction, and other characters), and measuring their survival and growth over 2–3 yr in the different environments. Crusts varied widely in their responses to both disturbance and productivity potential. In general, thick, calcified, or very tightly constructed crusts withstood being steel-brushed at regular intervals. Nylon brushing sometimes actually benefitted these crusts relative to the controls (unbrushed but cleaned monthly), probably because of the reduction in fouling. In contrast, thinner or more loosely-constructed species showed poor survival when steel-brushed and often suffered significant losses even when nylon-brushed. Most crusts tended to do best in habitats having higher productivity potential (lower intertidal zone), showing mortality or reduced growth when transplanted into more stressful areas, although two species were healthiest under “stressful” conditions, i.e. desiccated or submerged in high pools. Experiments in the laboratory with herbivores (littorinid snails, limpets, and a chiton) demonstrated that they did not always consume the species that are mechanically easiest to remove (as indicated by the steel brushing experiments). Three species were avoided, including a brown known to contain high concentrations of phenolics, a blue-green crust, and a lichen with a blue-green phycobiont. All crusts grew very slowly, even in their optimal habitats; the fastest species grew laterally at < 20 mm/yr, and the slowest measurable at < 0.5 mm/yr. Some species showed no lateral growth over 2 yr. This low ability to sequester space, and their two-dimensional growth form, means that crusts often rely on grazers or other disturbance to keep from being overgrown. In other cases, they grow in areas where desiccation or low light levels apparently eliminate other algal forms. Crusts survive disturbance by either resisting it (through calcification or toughness), tolerating it (by being thick or regenerating rapidly), or avoiding it (by having an opportunistic life history, living in refugia such as crevices or high tidepools, or being unpalatable). Their life histories are highly variable, allowing them to exploit habitats in different ways. For example, in the mid intertidal zone in Washington the three dominant crust species include: (1) a fast-growing, frequently-recruiting brown ( Ralfsia pacifica Hollenberg) that senesces after several years and sloughs away; (2) a fast-growing but rarely-recruiting red (“Petrocelis”) that lives for decades; and (3) a very slow-growing and rarely-recruiting red [ Hildenbrandia rubra (Sommerfelt) Meneghini] that persists even when overgrown, and regenerates following disturbance. These diverse morphologies and life history strategies help make this morphology an ecological success.

Application of neural networks for compliant tool polishing operations

The purpose of this research is to develop a strategy for automating polishing operations using filamentary brushes. In the first stage of the research, the experiments using the Taguchi system of experimental design are performed to identify the effects of various polishing parameters on the surface finish. It is observed that an abrasive impregnated filamentary brush improves the surface finish more substantially than a nylon brush. In addition, an interaction between brush type and rotational speed, and an interaction between brush rotational speed with brush depth, and type of brush with use of lubricant have been identified. In the second stage of the research, the experimental results are utilized to investigate an applicability of using neural networks in predicting and controlling polishing operations. It is shown that neural networks with one hidden layer learn faster than the two hidden layer designs. The neural network trained to predict the surface finish for a given set of polishing parameters performed with an average percent error between 1%–2%. However, the neural network designed to determine the levels of polishing parameters for a desired surface finish did not perform as well.

An assessment of cleaning and sampling methods for food-contact surfaces in premises preparing and selling high-risk foods

The performance of agar-contact plates and an alginate-swab method for sampling food surfaces before and after cleaning was compared. Contact plates were more convenient, and were at least as sensitive as the swabbing method. To assess cleaning efficiency repeated sampling was carried out in selected premises, and several cleaning methods were introduced for trial periods. Some surfaces, notably wood and polypropylene, were particularly difficult to clean. For these scrubbing with a nylon brush was the best method. Other surfaces were more easily cleaned, and generally the methods introduced as part of this study were better than the original method used in the premises. Paper proved to be unpopular, and cleaning solutions applied with it did no better than those cleaned with a multiuse cloth kept soaking in a detergent and hypochlorite solution.

Determination of adhesive bond strength to dentine. A new method

Specimens for the determination of adhesive bond strength to dentine were prepared using suitable surfaces of freshly extracted teeth from 15 patients who were having immediate dentures fitted. As soon as possible after extraction, shallow cavities were cut into the dentine to a depth of 1 mm using a high-speed round bur (diameter 4.2 mm) under water coolant. The cavities were restored using dentine bonding agents and single increments of light activated composite resin. The restored teeth were cut down to approximately 5 mm in diameter and 3 mm thick and were either placed in previously prepared sites in the buccal or occlusal surfaces of their respective dentures or in containers of tap water. Patients were instructed to remove their dentures only for cleaning with a soft nylon brush and toilet soap, while the laboratory specimens were stored at ambient temperature. After one week, the tensile force needed to dislodge each restoration from its cavity was determined using a universal testing machine. Previously reported laboratory methods for bond strength determination have usually employed a flat dentine surface. However, this study more closely resembled the clinical situation in that the smear layer was produced by a rotary cutting instrument, and the effects of polymerization shrinkage when curing the composite resin were simulated. Furthermore, it was easier to confine the bonding agent to the desired dentine surface.