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PubMed2003

Characterization of hydrocarbon-degrading microbial populations in contaminated and pristine Alpine soils.

Biodegradation of petroleum hydrocarbons in cold environments, including Alpine soils, is a result of indigenous cold-adapted microorganisms able to degrade these contaminants. In the present study, the prevalence of seven genotypes involved in the degradation of n-alkanes (Pseudomonas putida GPo1 alkB; Acinetobacter spp. alkM; Rhodococcus spp. alkB1, and Rhodococcus spp. alkB2), aromatic hydrocarbons (P. putida xylE), and polycyclic aromatic hydrocarbons (P. putida ndoB and Mycobacterium sp. strain PYR-1 nidA) was determined in 12 oil-contaminated (428 to 30,644 mg of total petroleum hydrocarbons [TPH]/kg of soil) and 8 pristine Alpine soils from Tyrol (Austria) by PCR hybridization analyses of total soil community DNA, using oligonucleotide primers and DNA probes specific for each genotype. The soils investigated were also analyzed for various physical, chemical, and microbiological parameters, and statistical correlations between all parameters were determined. Genotypes containing genes from gram-negative bacteria (P. putida alkB, xylE, and ndoB and Acinetobacter alkM) were detected to a significantly higher percentage in the contaminated (50 to 75%) than in the pristine (0 to 12.5%) soils, indicating that these organisms had been enriched in soils following contamination. There was a highly significant positive correlation (P < 0.001) between the level of contamination and the number of genotypes containing genes from P. putida and Acinetobacter sp. but no significant correlation between the TPH content and the number of genotypes containing genes from gram-positive bacteria (Rhodococcus alkB1 and alkB2 and Mycobacterium nidA). These genotypes were detected at a high frequency in both contaminated (41.7 to 75%) and pristine (37.5 to 50%) soils, indicating that they are already present in substantial numbers before a contamination event. No correlation was found between the prevalence of hydrocarbon-degradative genotypes and biological activities (respiration, fluorescein diacetate hydrolysis, lipase activity) or numbers of culturable hydrocarbon-degrading soil microorganisms; there also was no correlation between the numbers of hydrocarbon degraders and the contamination level. The measured biological activities showed significant positive correlation with each other, with the organic matter content, and partially with the TPH content and a significant negative correlation with the soil dry-mass content (P < 0.05 to 0.001).

Altitude↗

PubMed1984

Contamination of cultures processed with the isolator lysis-centrifugation blood culture tube.

Overall contamination (on- plus off-streak) of the Isolator (Du Pont Co.) blood culture tube (23%) was greater than that of a conventional broth blood culture bottle (0.6%) or that of a biphasic blood culture bottle (1.3%). To determine the source of this contamination, Isolator cultures of blood from 59 healthy volunteers and of sterile broth from 60 vials were made. A total of 37% of the blood cultures and 22% of the broth cultures were contaminated (P = 0.06). Staphylococcus epidermidis-contaminated cultures represented 31 and 10% of the blood and broth cultures, respectively (P = 0.06). Contamination of plates processed on a bench top, in front of horizontal laminar flow, and in a biological safety cabinet with vertical laminar flow were compared. Processing plates in a biological safety cabinet resulted in a significant reduction in the number of contaminated plates (P less than 0.05). The contamination rate for 7,874 Isolator blood cultures processed in the biological safety cabinet was significantly decreased to 6.7% on-streak (9.3% on- plus off-streak). Contamination of Isolator-processed blood cultures originated from the laboratory and the patient. The former can be reduced by inoculating plates in a vertical laminar flow biological safety cabinet and by maintaining adequate quality control of media. The latter may be unavoidable.

Bacteriological Techniques↗

PubMed1986

Contamination of lung lymph following standard and modified procedures in sheep.

The sheep lung lymph fistula preparation of Staub et al. is reported to be contaminated by systemic lymph. The published estimates of contamination range from 5% (awake sheep) to 60% (anesthetized sheep). In view of these conflicting estimates, we investigated the pre- and postoperative contaminating sources, morphological and functional consequences of the proposed contamination reducing modifications, and base-line lung lymph flow in awake sheep following standard and modified cannulation procedures. Our morphological observations are not compatible with the higher estimates of contamination (25-60%). Evidence of lymph leakage from cauterized lymphatics was found. The lymphatics that appear after diaphragmatic cautery and partial resection of caudal mediastinal lymph node were found to constitute "new" contaminating sources. The lymph flow data from base-line and increased vascular pressure conditions were consistent with the reported low estimates of contamination (5%). We propose simple modifications of the standard procedure of Staub et al. which may be nearly as effective in reducing contamination by extrapulmonary lymph as the more invasive and/or traumatic modifications.

Animals↗

PubMed1989

Problems in assessing the risks of mixtures of contaminants in drinking water.

In conducting risk assessments on drinking water contaminants, the U.S. Environmental Protection Agency (EPA) attempts to evaluate all available toxicity data to develop Health Advisory (HA) and Maximum Contaminant Level Goal (MCLG) values. The EPA often has grappled with the issues surrounding the toxicity of chemical mixtures, including radioactive contaminants, nitrate/nitrite, and trihalomethanes (THMs). In evaluating the toxicity of chemical mixtures, the EPA's immediate concern is whether the individual HA values and MCLGs are protecting public health when multiple contaminants are present in drinking water. Potential toxic interactions between drinking water contaminants are difficult to predict because experimental studies are generally performed only at high doses relative to environmental levels. Although the contamination of drinking water involves mixtures of contaminants, drinking water regulations are generally based on an assessment of the risks of individual contaminants. This paper discusses three issues of major concern to the EPA: the synergistic effects of solvent mixtures, vehicle effects in laboratory studies, and setting standards for essential trace nutrients where the absorption and/or toxicity are affected by an individual's nutritional status or other dietary components.

Animals↗

PubMed1996

Impaired immunity in harbour seals (Phoca vitulina) exposed to bioaccumulated environmental contaminants: review of a long-term feeding study.

Mass mortalities among seals and dolphins inhabiting contaminated marine regions have led to speculation about a possible involvement of immunosuppression associated with environmental pollution. To evaluate whether contaminants at ambient environmental levels can affect immune function of seals, we carried out an immunotoxicological study under semifield conditions. Two groups of 11 harbour seals (Phoca vitulina) originating from a relatively uncontaminated area were fed herring from either the highly polluted Baltic Sea or the relatively uncontaminated Atlantic Ocean. Changes in immune function were monitored over a 2 1/2-year period. The seals that were fed contaminated Baltic herring developed significantly higher body burdens of potentially immunotoxic organochlorines and displayed impaired immune responses as demonstrated by suppression of natural killer cell activity and specific T-cell responses. During a 2-week fasting experiment performed at the end of the feeding study, mobilization of organochlorines from the blubber did not lead to a strong increase of contaminant levels in the blood, and no enhancement of the existing immunosuppression was observed. These results demonstrate that chronic exposure to environmental contaminants accumulated through the food chain affects immune function in harbour seals, whereas short-term fasting periods, which are normal for seals, do not seem to pose an additional risk. The seals of this study were not exposed perinatally to high levels of environmental chemicals, and body burdens of organochlorines measured near the end of the study were lower than those generally observed in free-ranging seals inhabiting many contaminated regions. Therefore, it may be expected that environmental contaminants adversely affect immune function of free-ranging seals inhabiting contaminated regions at least as seriously as observed in these studies.

Animal Feed↗

PubMed1998

Impact of organochlorine contamination on levels of sex hormones and external morphology of common snapping turtles (Chelydra serpentina serpentina) in Ontario, Canada.

Recent research has suggested that contaminants in the environment may influence sex differentiation and reproductive endocrine function in wildlife. Concentrations of organochlorine contaminants (total polychlorinated biphenyls, pesticides) were higher in the blood plasma of snapping turtles from contaminated sites than in those from reference sites. The ratio of the precloacal length to the posterior lobe of the plastron (PPR) is sexually dimorphic in snapping turtles. There were significant reductions in the PPR at three contaminated sites versus two reference sites. The magnitude of the response was such that a significantly higher proportion of PPRs of males from a contaminated site (Cootes Paradise) overlapped with those of females than PPRs of males from a reference site (Lake Sasajewun). Observers can incorrectly identify the sex of turtles at the contaminated site based on secondary sexual characteristics alone. Unlike the changes to the morphology, there were few changes in 17 beta-estradiol or testosterone levels, and where differences occurred, there was more variation among reference sites than between the reference and contaminated sites. Our results suggest that environmental contaminants may affect sexually dimorphic morphology in snapping turtles without affecting circulating testosterone or estrogen levels in the adults.

Animals↗

PubMed2006

Pathogen and biological contamination management: the road ahead.

Multiplication of certified pathogen-free stock plants in vitro makes an important contribution to the production of disease-free planting material for vegetatively propagated crops. Meristem culture is extensively used to eliminate pathogens and contaminants from microbially contaminated plants prior to micropropagation. The approach to pathogen and contamination management differs. It is essential to avoid the release of pathogen-contaminated microplants and to ensure this the plant pathogen-testing guidelines and protocols issued by the Food and Agriculture Organisation (FAO) and its regional representative organizations should be followed. Where in vitro methods are used to eliminate pathogens, the progeny plants should be established in vivo under quarantine conditions and tested under FAO guidelines before being used as stock plants for in vitro multiplication. At establishment of microplants in vitro (stage 1), cultures should be culture-indexed for the presence of microbial contaminants. If pathogen-and contaminant-free cultures are established, then the risk is that of managing laboratory contamination by common environmental microorganisms based on Hazard Analysis Critical Control Points (HACCP) principles. International plant health certification organizations are conservative and rely on established pathogen indexing protocols. They are reluctant to accept DNA-based tests and do not accept testing of in vitro cultures. Given that in time both of these restrictions may be relaxed, micropropagators may look forward to availing more of diagnostic service providers using polymerase chain reaction-based multiplex assays for pathogen-indexing and advances in diagnostic kits for environmental microorganisms in support of laboratory contamination management; with the caveat that molecular tests for pathogens may continue to require confirmation by inoculation of indicator plant species.

Biomarkers↗

PubMed2007

Plant availability of zinc and copper in soil after contamination with brass foundry filter dust: effect of four years of aging.

We investigated the effect of 4 yr of aging of a noncalcareous soil contaminated with filter dust from a brass foundry (80% w/w ZnO, 15% w/w Cu0.6Zn0.4) on the chemical extractability of Zn and Cu and their uptake by barley (Hordeum vulgare L.), pea (Pisum sativum L.), and sunflower (Helianthus annus L.). Pot experiments were conducted with the freshly contaminated soil (2250 mg kg-1 Zn; 503 mg kg-1 Cu), with the contaminated soil aged for 4 yr in the field (1811 mg kg-1 Zn; 385 mg kg-1 Cu), and with the uncontaminated control soil (136 mg kg-1 Zn; 32 mg kg-1 Cu). In comparison with the uncontaminated soil, the growth of barley and pea was clearly reduced in both contaminated soils, while toxicity symptoms did not systematically vary from the freshly contaminated to the 4 yr aged soil. The sunflower did not grow in the contaminated soils. The slow oxidative dissolution of the brass platelets led to an increase in the solubility and the plant uptake of Cu from the freshly contaminated to the 4 yr aged soil. In an earlier study, we found that the fine-grained ZnO dissolved in the field soil within 9 mo and that about half of the released Zn was incorporated into a layered double hydroxide phase and about half was adsorbed to the soil matrix. These changes in Zn speciation did not lead to a reduction of the Zn contents in the shoots and roots of barley and pea grown in the aged soil as compared with the freshly contaminated soil.

Copper↗

PubMed2003

Accidental injuries and cutaneous contaminations during general surgical operations in a Nigerian teaching hospital.

OBJECTIVE: To determine the prevalence of accidental injuries and body contaminations among the operating personnel during general surgical operation, those involved, the circumstances surrounding the injuries or body contaminations and the factors affecting the prevalence in a unit of a teaching hospital in Nigeria. DESIGN: Patients operated for general surgical conditions in a unit of a Teaching Hospital Complex during a period of two years (1997-1998) were studied. A proforma was designed to enter personal biodata, preoperative and intra-postoperative clinical information of all the patients. SETTING: Wesley Guild Hospital a unit of teaching hospital complex serving the large agrarian rural and semi-urban Nigerians. PATIENTS: Five hundred and eighty nine consecutive general surgical patients. All types of general surgical operations were included, emergency or elective, major or minor, carried out during the day or at night. INTERVENTION: All the patients were operated and operating personnel observed for sharp injuries and body contamination. MAIN OUTCOME MEASURES: Incidence of sharp injuries and cutaneous contamination and personnel at risk determined. RESULTS: Operating personnel sustained 62 sharp injuries (10.5%), these were caused by suture needle in 57 cases (92.0%), towel clips in three (4.8%), knife cut in two (3.2%). Operating physicians sustained 56 cases of sharp injuries (90.3%) and Scrub Nurses in six (9.7 %). Self-inflicted sharp injuries in 49 (79 %) and in 12 cases (21%) injuries were inflicted by the surgeons or their assistants. Left hand was injured in 39 cases (63%) and right in 23 (37%). Cutaneous or mucosa membrane contamination with blood or body fluid occurred in 232 cases (39.4 %). These were made up of wet gown contamination in 124(53.5 %), glove failure in 72(31%) and splashing of blood or fluids into the face or eyes in 36 cases (15.5 %). Contamination occurred in more than one operating personnel in more than half of the cases. Operating surgeons were affected in 211 cases (91%). The risks of accidental injuries and blood and body fluid contamination were significant, if the duration of the operation was more than one hour, among the operating surgeons and if the operation was major (p<0.05). CONCLUSION: This study has demonstrated that cutaneous, percutaneous, and mucous membrane exposure to patients blood and body fluids are common events during general surgical operations. Most accidental injuries were due to solid suture needle-sticks, mostly injured personnel were the primary operating surgeons, injuries occurred predominantly on the left hand. This may poses a significant risk of infection with blood borne pathogens when operating on infected patients.

Adolescent↗

PubMed1999

Effects of blood contamination of cerebrospinal fluid on western blot analysis for detection of antibodies against Sarcocystis neurona and on albumin quotient and immunoglobulin G index in horses.

OBJECTIVE: To determine effects of blood contamination on western blot (WB) analysis of CSF samples for detection of anti-Sarcocystis neurona antibodies, and on CSF albumin and IgG concentrations, albumin quotient (AQ), and IgG index in horses. DESIGN: Prospective in vitro study. SAMPLES: Blood with various degrees of immunoreactivity against S neurona was collected from 12 healthy horses. Cerebrospinal fluid without immunoreactivity against S neurona was harvested from 4 recently euthanatized horses. PROCEDURE: Blood was serially diluted with pooled nonimmunoreactive CSF so that final dilutions corresponded to 10(-3) to 100 microliters of blood/ml CSF, and WB analysis was performed on contaminated CSF samples. Number of RBC, albumin and IgG concentrations, AQ, and IgG index were also determined. RESULTS: Antibodies against S neurona were detected in CSF contaminated with 10(-3) microliters of strongly immunoreactive blood/ml. In CSF samples contaminated with 10 microliters of blood/ml, AQ remained within reference range. Volume of blood required to increase IgG index varied among blood samples and was primarily influenced by serum IgG concentrations. Number of RBC in contaminated samples was correlated with volume of blood added, but not with degree of immunoreactivity detected in contaminated CSF samples. CONCLUSIONS AND CLINICAL RELEVANCE: During collection of CSF from horses, contamination with blood may introduce serum antibodies against S neurona at concentrations sufficient for detection by WB analysis, thus yielding false-positive results. When blood is moderately or strongly immunoreactive, the amount of contaminating albumin may be small enough as to not increase AQ above reference range. In these cases, AQ and IgG index should be interpreted with caution.

Albumins↗

PubMed2000

Bond strength of brackets cemented with light-cured glass-ionomer cements to contaminated enamel.

PURPOSE: To examine the effect of contamination on the bond strength of orthodontic brackets cemented with either a commercial (Fuji Ortho LC) or an experimental light-cured glass-ionomer cement to enamel, and the effect of etching times on the bond strength. MATERIALS & METHODS: Simulated metal brackets were applied with the cements to bond polished and etched (37% phosphoric acid) bovine enamel with and without contamination by water, human saliva, and blood. After 1-day water immersion, the shear bond strengths were measured. The fractured surfaces were examined using SEM. Additional tests were conducted on: (1) the Knoop hardness of the contaminated cements, (2) the HEMA composition of the cements, (3) the viscosity of the cements, and (4) the intensity of transmitted visible light through the contaminants. The results were compared by ANOVA and Duncan's tests at P=0.05. RESULTS: Water and saliva reduced the bond strength to polished and etched enamel, except for the bond strength of Fuji Ortho LC to polished enamel. The blood contamination produced poor bond strengths to polished and etched enamel. The experimental cement showed higher bond strengths to polished enamel with water and saliva contamination than Fuji Ortho LC. The bond strength of the experimental cement to etched enamel with and without contamination were comparable to those of Fuji Ortho LC. SEM micrographs revealed that the specimens exhibiting high bond strengths to polished and etched enamel mainly had cement-enamel interface failure and cement-metal mesh interface failure, respectively. Fuji Ortho LC had higher HEMA concentration than the experimental cement. The highest viscosity was measured with blood, followed by saliva and water. Blood contamination, showing the highest attenuation of the light intensity, reduced Knoop hardness of the experimental cement and Fuji Ortho LC.

Acid Etching, Dental↗

PubMed2002

Is contaminated groundwater an important cause of viral gastroenteritis in the United States?

The large volume of human sewage discharged into the ground has raised concerns about contamination of underground water supplies and possible human health risks. Few groundwater outbreaks reported in the United States, however, have been linked to enteric viruses. Studies on the occurrence of groundwater enteric viruses have detected viruses in groundwater, but many of these studies selected high-risk wells for testing. The results likely overestimated the occurrence of virus contamination in groundwater as well as the resulting public-health risks. This study found only limited evidence for viral contamination of groundwater in the absence of bacterial indicators of sewage contamination. From current studies of virus contamination in groundwater, the authors could not identify a sufficient population with evidence of exposure convincing enough to make an epidemiological investigation feasible and thus were unable to epidemiologically evaluate health risks that may be associated with viral contamination of groundwater. To better estimate the potential health risks, surveys should look at the occurrence of groundwater virus contamination in water that does not have bacterial indicators of sewage contamination and in water that has not been adequately disinfected. These surveys should include groundwater from a wide range of geological conditions.

Environmental Exposure↗

PubMed2002

Genetic and physiological responses of flounder (Platichthys flesus) populations to chemical contamination in estuaries.

We sampled and analyzed European flounder (Platichthys flesus) from two highly contaminated estuaries (Seine and Loire, France) and one moderately contaminated estuary (reference site: Ster, France). Significant and convergent modifications of the allelic frequencies for the loci phosphoglucomutase (PGM), glucose phosphate isomerase 2 (GPI-2), mannose phosphate isomerase (MPI), and aspartate aminotransferase (AAT-2) were evident for fish in the contaminated sites versus fish from the reference site. Back-calculation from otoliths showed that the average growth rate of fish between the first and the second winter was greater at the reference site (approximately 150 mm/year) than at the contaminated sites (approximately 100 mm/year). Flounder from the reference site also had a higher condition factor (somatic wt/(fish length)3) compared to fish from the two contaminated sites. However, the observed pattern of growth rate and condition factor might be biased by particular environmental conditions other than contaminants and must be confirmed by more extensive study. Flow cytometry analysis of fish blood revealed a significant difference in the frequency of abnormal profiles for fish from the Seine (20%) versus from the Ster (3%). We interpret this result as a marked genotoxic effect of contaminants on fish in the Seine system. Some genotypes, such as PGM 85/85, appeared to be linked to the measured components of fitness, particularly to DNA integrity. Thus, these genotypes might be considered to be more tolerant to pollutants. The frequency of the PGM 85 allele was clearly elevated in flounder from the more contaminated sites, compared to flounder from the reference site.

Adaptation, Physiological↗

PubMed2003

The day of contamination.

OBJECTIVE: We present 3 cases of suspected radioisotope urinary contamination that occurred on a single day. Because net clearance is via the kidneys, the injected dose is excreted in patients' urine. It is important to recognize the patterns of urinary contamination to avoid reporting false-positive abnormalities. MATERIALS AND METHODS: (99m)Tc-Medronate was administered intravenously and whole-body bone scans and spot views were obtained 2-3 h later. RESULTS: Two cases of urinary contamination were confirmed, and the third case was false-positive with a urinary collection leg bag seen in an orthogonal view. CONCLUSION: We believe that urinary contamination is probably the most common type of contamination. There are distinct urinary contamination patterns among male and female patients. It is unusual to find so many cases of contamination on a single day in our institution. Few statistics are widely available on the number or percentages of contamination for specific radiopharmaceuticals.

Adult↗

PubMedDate not supplied

Use of a bonding agent to reduce sealant sensitivity to moisture contamination: an in vitro study.

Moisture contamination of etched enamel during application of sealant is the most frequently cited reason for sealant failure. In preliminary studies, a dentin bonding agent (Scotchbond Dual Cure, 3M, St. Paul, MN) has been shown to bond adequately to etched enamel after salivary contamination. This study investigated bond strength in vitro, when a bonding agent was used beneath sealants under varied conditions of contamination. Five hundred bovine incisor crowns were separated randomly into eight groups. The enamel samples, etched for 60 sec with a 37% phosphoric acid gel, were contaminated with: 1) fresh whole saliva, air dried, 2) fresh whole saliva, left wet, or 3) moisture from a humidity chamber. All contamination conditions were tested for sealant bond strength with and without the bonding agent as an intermediate layer under the sealant. As controls, both sealant and bonding agent under sealant also were applied to clean etched enamel. Bond strength was measured using a universal testing machine. Data were analyzed using a two-way ANOVA. Under conditions of humidity or intact saliva, sealant alone showed significant reduction in bond strength (P less than 0.001). Bonding agent under sealant on wet contamination yielded bond strengths equivalent to the bond strength obtained when sealant was bonded directly to clean, etched enamel. Bonding agent used without contamination yielded bond strengths significantly greater than the bond strength obtained when using sealant alone without contamination (P less than 0.001). When the saliva was air dried onto the surface, there was no significant difference in bond strengths whether or not a bonding agent was used under the sealant.

Acid Etching, Dental↗

PubMed2004

Microbial contamination of femoral head allografts.

OBJECTIVE: To study the incidence of microbial contamination at the bone bank of the United Christian Hospital. DESIGN. Retrospective study. SETTING: Regional hospital, Hong Kong. PATIENTS: A total of 151 patients (33 men and 118 women) who underwent hip arthroplasty surgery and from whom femoral head allografts were retrieved between January 1994 and March 2000; and 81 patients in whom allografts were implanted. MAIN OUTCOME MEASURES: Bone biopsies were taken from the femoral head and used to detect any microbial contamination that might have occurred during removal and after storage. The rates of infection among recipients and donors were also assessed. RESULTS: Of the 151 allografts, 94 non-contaminated allografts were implanted by the end of the study. Fourteen (9.3%) heads showed positive culture results after retrieval and were discarded. Four (4.3%) of the 94 stored allografts that were implanted tested positive for microbial growth, but the recipients of these allografts did not develop any clinical infection. Three (3.2%) had wound infections after implantation of the stored allografts although the grafts had previously been tested negative for any microbial contamination. CONCLUSION: Our centre has a low allograft contamination rate. The wound infection rate among recipients was also low. The culture of a bone biopsy sample is a reliable method to detect contamination of bone grafts. However, the contamination rate among stored allografts should prompt orthopaedics departments to review allograft handling procedures, so as to minimise the chance of contamination.

Anti-Bacterial Agents↗

PubMed1992

Soil contamination with Ascaris lumbricoides eggs as an indicator of environmental hygiene in urban areas of north-east Brazil.

The objective of this study was to detect the pathways of transmission of Ascaris lumbricoides eggs in low-income households of two Brazilian cities. An inexpensive flotation technique for egg isolation was applied for the determination of soil contamination in 227 households. The median contamination levels were 0.8 (indoor), 0.3 (backyard) and 0.6 (defaecation site) eggs per gram soil. The contamination levels showed no significant correlation with the presence or quality of latrines or flush toilets. Houses with flush toilets were found to be sources of faecal contamination of the neighbourhood due to the absence of an adequate sewage system. Households with small children were more often contaminated than those without. The keeping of pigs was correlated with an increased yard contamination. The faecal egg excretion showed a significant correlation with the soil contamination in the backyard. Embryonated eggs, which represent the 'older' eggs, constituted 37% of all eggs. In the dry season significantly fewer Ascaris eggs were found in the soil than during the rainy season. The usefulness of the soil contamination with Ascaris lumbricoides eggs as an indicator of the efficacy of hygiene programmes is discussed.

Animals↗

PubMed2005

SEM analysis of internal adaptation of adhesive restorations after contamination with saliva.

PURPOSE: This study tested the null hypothesis that different treatments of saliva-contaminated substrate would not affect microgap formation at the dentin walls of bonded restorations. MATERIALS AND METHODS: Forty freshly extracted human molars received standardized Class V preparations on buccal and lingual surfaces. The specimens were assigned to four experimental groups (n = 20): [G1] no contamination (control group), [G2] saliva contamination (10 s) after etching followed by 5 s air stream; [G3] saliva contamination after etching and rinsed for 10 s; and [G4] re-etching for 10 s after saliva contamination. All specimens were restored with a one-bottle adhesive (Single Bond, 3M ESPE) and microhybrid composite resin (Filtek Z250, 3M ESPE) according to the manufacturer's instructions. The specimens were thermocycled, sectioned through the center of the restoration, and then processed for SEM. Microgaps were measured at the axial wall at 1500X magnification. The data were submitted to Kruskal-Wallis nonparametric statistical analysis at p < 0.05. RESULTS: The data revealed that different groups resulted in a statistically significant difference (p < 0.01) in gap formation. Air drying [G2] and rinsing [G3] the saliva-contaminated dentin resulted in similar microgap values (p > 0.05). However, re-etching the dentin after saliva contamination [G4] increased microgap formation (p < 0.05) when compared with the groups G1 and G2. Although air drying and rinsing produced results comparable to noncontaminated dentin, the presence of microgaps was not completely eliminated. CONCLUSION: Contaminated saliva did not prevent hybrid layer formation; however, it did reduce the adaptation of the restorative material to bonded surfaces.

Acid Etching, Dental↗