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Biomedical subjects

R A Hatch

Publications and source records attributed to R A Hatch.

At least 19 recordsLinked to original sources
PubMed1998

Alginate lyase promotes diffusion of aminoglycosides through the extracellular polysaccharide of mucoid Pseudomonas aeruginosa.

We demonstrated that a 2% suspension of Pseudomonas aeruginosa alginate completely blocked the diffusion of gentamicin and tobramycin, but not that of carbenicillin, illustrating how alginate production can help protect P. aeruginosa growing within alginate microcolonies in patients with cystic fibrosis (CF) from the effects of aminoglycosides. This aminoglycoside diffusion barrier was degraded with a semipurified preparation of P. aeruginosa alginate lyase, suggesting that this enzyme deserves consideration as an adjunctive agent for CF patients colonized by mucoid strains of P. aeruginosa.

Alginates↗
PubMed1992

A preliminary test of the replicability of a computerized occlusal analysis system.

A system for computerized occlusal analysis was tested in a laboratory. The investigation focused on the ability of the system to replicate results when sensors were used five times under a series of three levels of load that were applied to the occlusion. Also compared were the effects of zero mm immediate side shift and 0.2 mm immediate side shift on the research model. Results showed that there were both statistically significant differences (p less than or equal to 0.05 level) and nonsignificant differences scattered among the data derived from both articulator treatments.

Bite Force↗
PubMed1992

Change in occlusal height resulting from placement of pit and fissure sealants.

This in-vitro study was done to identify the amount of change in occlusal height resulting from standard sealant application technique and to determine whether this change was uniform for both a filled and an unfilled sealant material. Twelve dental hygienists experienced in sealant technique each applied 10 filled sealants and 10 unfilled sealants in standardized artificial teeth mounted in a dentiform and mannikin setup in a dental unit. The teeth were measured with a digital caliper before and after sealant placement. Measurements were from a predetermined point at the apical area of the teeth to the depth of the central fossa. For the sample of 240 teeth, the mean sealant thickness was 0.43 +/- 0.20 mm. When the data for the filled and unfilled sealants were examined separately, the means were 0.47 +/- 0.23 mm and 0.38 +/- 0.16 mm, respectively. A t-test indicated a significant difference at p < 0.001. Analysis of variance revealed significant interoperator differences in sealant thickness (p < 0.01).

Analysis of Variance↗
PubMed1992

Occlusal discrepancies after sealant therapy.

To date there has been no evidence concerning the need for adjusting the occlusion after sealant placement. Thus, this study investigated the occlusal effects of filled and unfilled sealants. For each of 18 subjects a sealant was applied and the occlusion monitored for 1 week. Each participant received a filled and an unfilled sealant for the specified period. With the filled sealant, nearly all subjects experienced a perceptable occlusal change and most were unable to abrade the interferences to a comfort level. These results indicate that the occlusion should be routinely verified and, if necessary, adjusted immediately after placement of a filled sealant.

Acrylic Resins↗
PubMed1991

Computerized occlusal analysis: an evaluation of the sensors.

Dentists traditionally depend on their experiences to evaluate occlusion. A computerized system, that enables an objective analysis of dental occlusion has been developed and is currently available. A key component of the system is the disposable sensor. This research tested the sensors' validity and reliability in detection of known interceptive occlusal contact and discovered that the sensors were valid when used just twice.

Analysis of Variance↗
PubMed1989

Complement activation and C3 binding by serum-sensitive and serum-resistant strains of Pseudomonas aeruginosa.

The relationship among complement consumption, C3 deposition, and C3 fragmentation pattern was compared for serum-sensitive (Sers) and serum-resistant (Serr) strains of Pseudomonas aeruginosa. The Sers strains, which were mucoid strains derived from patients with cystic fibrosis, had lipopolysaccharide deficient in O-antigen side chains. These organisms generally activated much less complement per organism than their Serr counterparts, characterized by the presence of lipopolysaccharide with long lipopolysaccharide O side chains. Surprisingly, however, although the Serr strains consumed more total hemolytic complement, less C3 was deposited onto the surface of these strains than onto that of the Sers strains. Maximal C3 binding required the participation of both the classical and alternative complement pathways, although classical complement pathway involvement was more important for Serr strains. Finally, while more than half of the C3 deposited on most Sers strains was in the form of C3b, most of the C3 on the Serr strains was in the form of iC3b, indicating a more rapid and extensive conversion of C3b to iC3b on the surface of these strains. Limited complement activation by Sers mucoid strains of P. aeruginosa may confer a selective survival advantage to these organisms in colonizing the airways of patients with cystic fibrosis.

Adult↗
PubMed1988

Contamination of local anesthetic cartridges with acrylic monomer.

The evidence presented shows that both methyl methacrylate and ethyl methacrylate monomers can diffuse through the rubber bulb of a dropper dispenser-style bottle. Methyl methacrylate is substantially more efficient in this regard than is ethyl methacrylate, which leads to the loss of these products into the environment immediately around the dropper bottle. If a dropper bottle of these agents is stored in a confined space such as a storage tub along with certain local anesthetic cartridges, the monomer vapor can enter the cartridge and contaminate its contents. A combination of methyl methacrylate in the presence of 2% lidocaine with 1:100,000 epinephrine appears to be the most reactive of the combinations tested. Local anesthetic cartridges should not be stored in a confined space with dropper bottles containing either methyl methacrylate or ethyl methacrylate monomers.

Anesthetics, Local↗
PubMed1986

Tissue displacement methods in fixed prosthodontics.

The various methods to accomplish gingival displacement have been described. The techniques have been noted and their relative advantages and disadvantages summarized. The practicing dentist can use this review to make better informed decisions regarding the method he or she chooses for the treatment of a particular patient.

Crowns↗
PubMed1986

Interalar width as a guide in denture tooth selection.

This study was undertaken to determine the relationship of the IAW, measured between at the widest dimension of the alae of the nose, and two other measurements of maxillary anterior teeth. The other measurements, both of which are significant in the selection and arrangement of artificial teeth used in complete dentures, were the ICTW and the ARCD measured from the distal surface of the maxillary canine on one side of the arch to the distal surface of the canine on the opposite side of the arch. No distinction was made between either the sex or the age of the subjects. The mean ICTW of 35.35 mm was 3% greater than the mean IAW of 34.28 mm. The mean ARCD of 44.85 mm was 31% greater than the mean IAW of 34.28 mm. This mean ARCD compares favorably (less than 1 mm difference) with a constructed ARCD of 45.8 mm from a tooth dimension study by Shillingburg et al. The ARCD was 44.85 mm. This measurement had not been made in the previous study examining the relationship of interalar distance to ICTW. When the IAW was plotted against the intercanine cusp tip width, a fairly strong correlation coefficient of 0.413 was exhibited. A weaker but definite correlation coefficient of 0.217 was observed when the interalar width plotted against the circumferential arc distance from distal surface to distal surface of the maxillary canines.

Adolescent↗
PubMed1985

Impression material thickness in stock and custom trays.

This study did not examine the accuracy of the resultant impressions. Rather, the impression material thickness in impressions made using both the highly advocated custom acrylic resin tray and in the highly used manufactured stock tray was examined. Comparison between the material thickness at the prepared tooth area revealed a mean difference in material thickness of less than 1 mm. The question of the significance of this difference remains to be answered. If the difference is not significant in the success of the impression and the resultant casting, then there are several advantages in using the manufactured stock tray; the first is economy. The average cost of a custom acrylic full arch impression tray is $3.65, compared with an average cost of slightly over $0.30 for the stock tray. The second advantage is the convenience factor. Making a custom tray requires planning, study models, laboratory time, curing interval, and finishing time. In contrast, the stock tray can be selected, adapted, and used in a single visit for both anticipated and unanticipated situations. If the difference in material thickness is significant, the custom tray is indicated. However, attention to detail in making and inserting the tray in the mouth must be observed to maximize the benefits of the custom tray.

Acrylic Resins↗
PubMed1983

The serum sensitivity, colonial morphology, serogroup specificity, and outer membrane protein of Pseudomonas aeruginosa strains isolated from several clinical sites.

Ninety-three strains of Pseudomonas aeruginosa, isolated from 68 patients hospitalized with respiratory tract infections, burns, urinary tract infections, and other illnesses, were examined for: 1) sensitivity to the bactericidal activity of fresh normal human serum (FHS); 2) colonial morphology; 3) serogroup designation; and 4) outer membrane protein (OMP) profile. The purpose of this study was to determine if there was any relationship between any of these microbial characteristics and the propensity of this microorganism to infect a specific clinical site or tissue. The results of this study can be summarized as follows: 1) slime-producing strains were generally more serum-sensitive than non-slime producers, although serum sensitivity was not related to slime production per se; 2) CF strains were much more serum-sensitive than non-CF strains; 3) the clinical isolation site appeared to be the predominant determinant of a strain's sensitivity to FHS; 4) the ability of P. aeruginosa to colonize/infect a specific clinical site or resist the bactericidal activity of FHS was generally unrelated to serogroup specificity; and 5) whereas the OMP profile of a particular strain does not appear to correlate with its response to the bactericidal effect of FHS, it does appear to be related to its clinical isolation site.

Adult↗
PubMed1980

Impression materials and techniques used for cast restorations in eight states.

In a survey of dentists practicing in eight states, it was found that polysulfide is used by 35.8% of them for cast restorations. Polyether and hydrocolloid are the second most used materials; silicone putty/reline and double mix standard silicone follow. Epinephrine cord was chosen for gingival retraction by 73.3% of the respondents. Nonepinephrine cord is used by 23.5% of the dentists who responded.

Administration, Topical↗