Biomedical subjects

J A Sorensen

Publications and source records attributed to J A Sorensen.

At least 19 recordsLinked to original sources

PubMed2006

Rollover protection on New York tractors and farmers' readiness for change.

Tractor overturns contribute significantly to fatalities in New York State agriculture. On-site inspections a decade ago indicated that approximately 60% of tractors were without effective rollover protection. Our objectives were: to describe the current prevalence and distribution of rollover protective structures (ROPS) on New York farm tractors, to identify characteristics associated with the absence of ROPS, to explore segmenting the New York farm community on readiness for ROPS retrofitting, and to identify demographic characteristics that might assist in this segmenting. A random selection of 644 livestock, dairy, fruit, cash crop, vegetable, and organic farms were contacted for a telephone survey. Of 562 farms (87%) participating, 102 (18.1%) had all tractors equipped with ROPS and 138 (24.6%) had none. A disproportionate number of livestock, cash crop, and organic operations had no ROPS. Rates of ROPS-equipped tractors correlated directly with farm size and annual hours of tractor operation. Older farmers had a lower proportion of ROPS tractors. The presence of a child operator did not affect the proportion of ROPS tractors. After weighting the sample, the total number of non-ROPS tractors in New York is estimated at more than 80,000. In addition to providing key farm demographics, the survey enabled placement of farmers on a "stage of change" continuum related to readiness for retrofitting. Three-quarters of New York farmers are in the "precontemplation" stage of change relative to ROPS retrofitting, and this varies little by size of operation, age of farmer, or the presence of child tractor operators. Stage of change may relate to hours of tractor operation (p = 0.05) and does relate to commodity (p = 0.003) due primarily to the higher proportion of crop farmers in the earliest stage of change. The goal of retrofitting all New York farm tractors with ROPS appears nearly as daunting as it did a decade ago.

Accidents, Occupational↗

PubMed2006

Risk perceptions, barriers, and motivators to tractor ROPS retrofitting in the New York state farm community.

The prevalence of tractor rollovers among agricultural workers has made the retrofitting of tractors with rollover protective structures (ROPS) and seat belts a public health priority for agricultural health and safety specialists. To address this concern, the New York Center for Agricultural Medicine and Health (NYCAMH) developed a seven-question survey, designed to assess perceptions of risk as well as potential motivators and barriers to retrofitting. Data from 465 phone surveys were gathered from New York State farmers representing various commodities and farm sizes. Analysis of responses to three qualitative questions contained in the survey indicated that most farmers in New York understand the importance of ROPS but lack the proper motivation to consider retrofitting. It appears that more convenient safety strategies, cost, and age of the tractor compete with a farmer's initiative to retrofit. In addition, survey responses illustrate that although many farmers believe ROPS are important in a general sense, many believe that this safety measure is not necessary for them in particular. Frequent motivators to retrofitting are concerns about safety, although the authors conclude that a more thorough analysis of these "general safety concerns" in qualitative interviews is important.

Accident Prevention↗

PubMed2005

Estimating farmworker population size in New York State using a minimum labor demand method.

Assessment of health needs and services for hand-harvest farmworkers requires reliable population estimates. In New York State, the only publicly available source for these is the Department of Labor (DOL). However, published production data exist that may enable estimation of minimum labor demand (MLD) for hand-harvest labor. Our objective was to develop an estimation process for minimum labor demand (MLD) for hand-harvested crops in NYS and contrast the results with DOL estimates. Four crop strata (below ground, ground, bush/vine, and orchard) were identified. MLD (measured in worker-seasons) was estimated by dividing the total annual harvest hours required for each crop stratum by the total hours worked by one worker in a season for that crop stratum. The MLD estimate of the total number of worker seasons combined for all strata (14,121) was higher than that of the DOL (8,230). Harvest acreage was unavailable for 21% of the 991 county-crop combinations studied; therefore, data were imputed from other sources. Within these strata, the greatest difference was found for ground crops, where the DOL count was 28% of the size of the MLD estimate. DOL and MLD estimates were closest in orchard crops (DOL 109% of MLD). Publicly available data provide a potentially valuable source of informationfor estimation of the MLD. Use of these methods implies that the DOL may substantially underestimate the size of this population. Differences seen between the two methods were sensitive to the crop type. County-level farm surveys to verify MLD estimation factors would enhance the method's accuracy.

Agriculture↗

PubMed1999

A prospective clinical evaluation of electronically mixed polyvinyl siloxane impression materials: results from the prosthetic "SuperStudy"--a consumer evaluation.

Polyvinyl siloxane (PVS) impression materials incorporating a polyether carbosilane wetting agent and mixed with an electronic mixing system (Pentamix) were clinically compared with traditionally delivered (i.e., automixed) PVS impression materials during routine use by 1,505 general and specialized dental practitioners evaluating more than 30,000 impressions. Each study participant selected 20 patients and used standard tooth-preparation procedures appropriate to the therapy required, supplied specific data on each case, and ultimately evaluated the marginal detail, fit, and success of the final restorations. The areas requiring evaluation upon completion of the final restorations were ranked between "excellent," "good," "poor," and "remake needed," among users of the PVS materials with the electronic mixing system. About 80% of the respondents rated the Pentamix system as easier to mix and deliver than the gun or hand-mixed systems and two thirds said it was faster to mix. The system also received high scores for hygienic delivery, ease of mixing, and clean-up.

Consumer Behavior↗

PubMed1998

IPS Empress crown system: three-year clinical trial results.

The IPS Empress system is a highly esthetic hot pressed glass ceramic material for fabrication of single crowns. Adhesive cementation of the system not only contributes to the esthetics but is necessary for increased strength of the crown. The purpose of this prospective clinical trials was to evaluate the longevity of 75 adhesively cemented Empress full crowns. An additional aim was to assess the adhesive cementation methodology and potential side effects. At the three-year point, one molar crown fractured for a 1.3 percent failure rate. The resin cementation technique that was employed exhibited a low incidence of microleakage with few clinical side effects. There was a 5.6 percent incidence of post-cementation sensitivity, with all symptoms subsiding by eight weeks. None of the crowns in the study required endodontic therapy.

Adolescent↗

PubMed1998

In-Ceram fixed partial dentures: three-year clinical trial results.

In-Ceram is a sintered, high-alumina-content, glass-infiltrated ceramic core material reported to have sufficient strength for all-ceramic fixed partial dentures. While Vita/Vident recommends that In-Ceram should be used only for anterior FPDs, the purpose of this study was to push the sintered alumina material to its limits by testing posterior FPDs with premolar and molar pontics. This prospective clinical trial tested the longevity of 61 three-unit In-Ceram alumina FPDs. The failed specimens were analyzed to determine factors contributing to failure. The abutment teeth were prepared for full crown retainers with shoulder margins and 1.3 mm of axial reduction. All FPDs were cemented with an encapsulated glass ionomer. None of the patients reported postcementation sensitivity. During the three-year period, seven FPDs fractured through the connector area. By location of the pontic, failure rates were 0 percent for anteriors, 11 percent for premolars and 24 percent for molars. Based on the results of this clinical study at the three-year point, In-Ceram alumina can be reliably utilized for anterior FPDs as indicated by a 100 percent success rate. The findings do not support the use of In-Ceram alumina for posterior FPDs as was advised by the porcelain manufacturer. Glass ionomer cement can be predictably used to cement In-Ceram FPDs with few clinical side effects. Because of a technological malfunction, this article could not be presented with the others on ceramic restorations that appeared in the February issue.

Aluminum Oxide↗

PubMed1997

A clinical trial of all-ceramic crown restorations: status, fall 1995.

Although porcelain-fused-to-metal (PFM) restorations are the most widely used full-coverage crown restoration systems, their inherent properties make the achievement of natural aesthetic restorations an elusive task. In contrast, the all-ceramic system (IPS Empress, Ivoclar North America, Amherst, NY) offers excellent translucency and vitality, without the opacity associated with PFM restorations. Its vitality is further enhanced by an adhesive resin cementation method that conducts the color of the underlying tooth structure. This article reports the status of a 5-year investigation, initiated in 1992, of the clinical performance of the IPS Empress all-ceramic system and the resin cementation system used with it.

Adolescent↗

PubMed1996

Relative gap formation adjacent to ceramic inlays with combinations of resin cements and dentin bonding agents.

This study investigated the effect of combining dentin bonding agents (DBAs) with various resin cements on contraction gap formation at the cavity floor of resin-cemented ceramic inlays. Cylindrical dentin cavities were pretreated with one of five DBAs before luting of ceramic inlays with one of four dualcuring resin cements. Measurements of cross sections showed that mean gap widths were reduced from 46% to 93% compared with control specimens prepared without a DBA. The extent of the gap reduction was dependent on the type of bonding agent and resin cement. Although none of the resin cement-dentin bonding agent combinations tested were able to completely eliminate development of interfacial contraction gaps, some combinations produced considerable reductions in gap size.

Cementation↗

PubMed1996

Relative gap formation of resin-cemented ceramic inlays and dentin bonding agents.

The effect of dentin bonding agents (DBAs) on contraction gap formation at the cavity floor of resin-cemented ceramic inlays was investigated. Cylindrical dentin cavities were pretreated with one of 12 DBAs before luting of ceramic inlays with a dual-curing resin cement. Measurements of cross sections revealed that mean gap widths were reduced between 21% and 80% compared with control specimens prepared without a DBA. The extent of the gap reduction depended on the type of bonding agent. None of the dentin bonding agents tested were able to completely eliminate development of interfacial gaps.

Cementation↗

PubMed1996

A clinical trial of all-ceramic crown restorations: status, fall 1995.

Adolescent↗

PubMed1995

Ceramic inlay movement during polymerization of resin luting cements.

In cavities with no support for inlays, polymerization contraction of the resin cement may move the ceramic inlay axially. The purpose of this study was to determine the velocity and extent of such movement. Cylindrical ceramic inlays were placed in dentin cavities filled with one of four commercially available resin composite cements. An initial standardized 200-microns-thick cement film was created. The movement of the ceramic inlay during polymerization of one of the resin cements was measured by a dial gauge. The velocity of the inlay movement decreased exponentially with time and with a velocity constant of 0.09 min-1. The majority of the movement occurred within the first 12 min after photopolymerization and probably continued for several days, reaching an estimated value of 5.8 microns. After 1-2 d of water storage, 1-2-microns contraction gaps at the cavity floors were observed microscopically for every cement used. It is concluded that in cavities without support for the inlay, about 2/3 of the resin cement contraction results in movement of the inlay and about 1/3 results in formation of gaps at the cavity floors.

Analysis of Variance↗

PubMed1995

Interfacial gaps of resin cemented ceramic inlays.

A method was developed for measuring presence, location and extent of interfacial contraction gaps of resin-cemented ceramic inlays in dentin cavities. Cylindrical ceramic inlays were cemented using one of 12 commercially available resin composite cements to make a film thickness of 200-microns. Cross-sections revealed absence of marginal gaps but contraction gaps occurred at all dentin-cement interfaces at the cavity floors and ranged from 1.6 to 7.1 microns. This was equivalent to 0.8-3.5% of the cement film thickness and was 3-10 times greater than the wall-to-wall contraction in percent observed when resin composites are used as filling materials in 3-5 mm butt-joint dentin cavities. The results support the theory that contraction gaps developing adjacent to thin films of resin cements reach a size equivalent to the cement film thickness multiplied by the volumetric polymerization shrinkage of the cement.

Adhesiveness↗

PubMed1995

Failure of all-ceramic fixed partial dentures in vitro and in vivo: analysis and modeling.

Hertzian cone cracks visible at the loading site of 20 all-ceramic fixed partial dentures (FPDs), tested in vitro, led to the hypotheses that failure was due to the propagation of localized contact damage crack systems (Hertzian stress state) and that such damage was an unlikely clinical failure mode. Fractographic analysis of the 20 laboratory-failed and nine clinically-failed all-ceramic FPDs allowed for definitive testing of these hypotheses and a comparison between in vitro and in vivo failure behavior. In all cases, failure occurred in the FPD connectors (none from contact damage), with approximately 70 to 78% originating from the interface between the core and veneer ceramics. The coincidence between failure origins provides strong evidence that the in vitro test modeled aspects of structural behavior having clinical importance. The fractographic observations, coupled with the in vitro failure load data, furnished very specific boundary conditions which were applied to constrain mathematical models of FPD connector failure. Finite element analysis (FEA) of the laboratory FPDs found that maximum principal tensile stresses would occur at locations consistent with the fractographic observations only if: (1) there were appropriate elastic moduli differences between the ceramics; and (2) a small amount of abutment rotation was allowed. Weibull failure probability (Pf) calculations, incorporating FEA stress profiles, very closely replicated the laboratory failure distribution only when: (1) the veneer ceramic was much weaker than the core ceramic; and (2) the Weibull modulus of the core-veneer interface was much lower than that for the free veneer surface (i.e., the interface is of lower quality with regard to defects).(ABSTRACT TRUNCATED AT 250 WORDS)

Ceramics↗

PubMed1994

Experimental localization of intestinal uptake sites for metals (Cd, Hg, Zn, Se) in vivo in mice.

The intestinal uptake process consists of two separable steps: transport over the luminal membrane into epithelial cytoplasm and transport over the basolateral membrane into serosal fluid. A compound's residence time in mucosal epithelial cytoplasm depends on rates of the two transport processes and, if the rate of the second step is low, on the rate of mucosal sloughing. Using gamma-emitting metal isotopes, in vivo labeling profiles of the intestinal tract were obtained from mice eating their normal diet. The results pertain to processes in the functioning, undisturbed intestinal tract. Single-dose chase experiments indicated that intestinal uptake processes were in fact studied. The labeling profiles varied considerably for different metals. Thus, Cd++ was absorbed mainly in duodenum and early jejunum, while Zn++ was taken up in jejunum and ileum. The uptake profile of Hg++ indicated most rapid uptake in proximal jejunum. Selenomethionine labeled the entire intestinal tract, most rapidly the duodenum, the following intestinal segments were labeled with falling rate. This experimental method is rapid and simple. Further studies aim at developing a quantitative model suited for studying interactions between essential and toxic metals at the level of intestinal metabolism.

Animals↗

PubMed1993

Identification of the gastrointestinal absorption site for cadmium chloride in vivo.

Most models for the study of the mechanism of intestinal absorption of Cadmium (Cd) have been using intestinal tissue in vitro or in situ. The in vivo experiments reported in this article were performed in an attempt to localize the site for gastrointestinal absorption of cadmium chloride during natural physiological conditions by oral exposure of mice to 109Cd-labelled CdCl2. Independent of exposure via drinking water or oral administration of a single dose, Cd was primarily deposited in the most proximal duodenum. Thus the present study as well as others indicate that absorption takes place in the proximal part of the intestine. Absorbed Cd is initially transported to the liver and deposited before being redistributed and accumulated in the kidneys. In this experimental model, dietary tetraethylthiuram disulfide exposure was shown to change the intestinal labelling profile and increase the whole-body retention as well as the intestinal deposition of Cd.

Administration, Oral↗

PubMed1992

Marginal fidelity and microleakage of porcelain veneers made by two techniques.

This study evaluated the marginal fidelity and microleakage of porcelain veneers made with the platinum foil and refractory die techniques. Maxillary incisors, matched for size and amount of enamel, were prepared with 0.5 mm uniform intraenamel reduction. The indirectly made veneers were etched, treated with silane, and luted with a composite resin, and the margins were finished and polished. The restored teeth were stored in 37 degrees C water, thermocycled 1000 times, stained with silver nitrate, embedded, sectioned buccolingually and mesiodistally, and measured at x250 magnification. The platinum foil veneers had significantly better vertical marginal fidelity but significantly more overcontouring than had the refractory die veneers. Universal microleakage at the tooth-composite resin interface and negligible microleakage at the porcelain-composite resin interface were observed. No relationship was found between the amount of vertical marginal opening and the amount of microleakage.

Acid Etching, Dental↗

PubMed1992

Microleakage of new crown and fixed partial denture luting agents.

This study measured the in vitro microleakage of conventional and new FPD luting agents. Standardized preparations were made on 42 freshly extracted premolars. Facial and lingual chamfer margins were placed in enamel, mesial and distal in dentin and cementum, and castings were made in Rexillium III alloy and were then cemented with a standardized technique. Six groups of seven samples were tested, (1) polycarboxylate, (2) zinc phosphate, (3) glass ionomer, (4) Den-Mat Thin Film cement, (5) Panavia Ex, and (6) Den-Mat Thin Film cement with Tenure. The ranking of groups for stain ingress was from the greatest (1) to the least (6). A one-way analysis of variance and Tukey-Student range analysis revealed significantly similar groups, p less than 0.05:(1,2,3,4) (5,6).

Adhesives↗

PubMed1992

Marginal fidelity of four methods of swaged metal matrix crown fabrication.

The swaged metal matrix provides a method for rapidly making a metal substructure for ceramic crowns. This study determined the vertical and horizontal marginal fidelity of swaged metal substrate crowns made with four methods. No significant difference in vertical or horizontal marginal fidelity was found for metal margin crowns formed with either a plastic spacer or a paint-on die spacer. The vertical marginal fidelity was significantly better in crowns made with a metal margin (37 microns) than in crowns made with a porcelain facial margin (62 microns), and the latter were significantly better than crowns made with a 360-degrees porcelain margin (86 microns). Crowns made with all four methods were overcontoured by 46 to 82 microns. The 360-degrees porcelain margin was technically more difficult and time-consuming to make.

Analysis of Variance↗