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Biomedical subjects

K M Phillips

Publications and source records attributed to K M Phillips.

42 records · Page 3Linked to original sources
PubMedDate not supplied

Load fatigue of compromised teeth: a comparison of 3 luting cements.

PURPOSE: This study compared the number of cycles to failure of central incisors restored with full cast crowns and then cemented with 3 different luting cements. MATERIALS AND METHODS: Fifteen human maxillary central incisors received cast post-and-core restorations. These were cemented with zinc phosphate. The teeth were then divided into 3 groups of 5 samples each. Each tooth had a ferrule length of 1.0 mm and was prepared for a full crown. A waxing jig was used to standardize the load application point on all waxed crowns. Complete cast crowns were cemented to the compromised teeth using 3 different luting cements: a zinc phosphate cement (control group), a resin-modified glass-ionomer cement, and a resin cement with a dentin bonding agent. A fatigue load of 1.5 kg was applied at a rate of 72 cycles per minute until failure of the cement layer occurred between the crown and the tooth (preliminary failure). The independent variable was the number of load cycles required to create preliminary failure. An electrical resistance strain gauge was used to provide evidence of preliminary failure. RESULTS AND CONCLUSION: The resin cement samples had a significantly higher number of load cycles to preliminary failure than both the zinc phosphate and the resin-modified glass ionomer (P < or = 0.05). There was no significant difference between the zinc phosphate and the resin-modified glass-ionomer cements.

Analysis of Variance↗
PubMedDate not supplied

Accuracy of electronic implant torque controllers following time in clinical service.

Tightening of the screws in implant-supported restorations has been reported to be problematic, in that if the applied torque is too low, screw loosening occurs. If the torque is too high, then screw fracture can take place. Thus, accuracy of the torque driver is of the utmost importance. This study evaluated 4 new electronic torque drivers (controls) and 10 test electronic torque drivers, which had been in clinical service for a minimum of 5 years. Torque values of the test drivers were measured and were compared with the control values using a 1-way analysis of variance. Torque delivery accuracy was measured using a technique that simulated the clinical situation. In vivo, the torque driver turns the screw until the selected tightening torque is reached. In this laboratory experiment, an implant, along with an attached abutment and abutment gold screw, was held firmly in a Tohnichi torque gauge. Calibration accuracy for the Tohnichi is +/- 3% of the scale value. During torque measurement, the gold screw turned a minimum of 180 degrees before contact was made between the screw and abutment. Three torque values (10, 20, and 32 N-cm) were evaluated, at both high- and low-speed settings. The recorded torque measurements indicated that the 10 test electronic torque drivers maintained a torque delivery accuracy equivalent to the 4 new (unused) units. Judging from the torque output values obtained from the 10 test units, the clinical use of the electronic torque driver suggests that accuracy did not change significantly over the 5-year period of clinical service.

Analysis of Variance↗
PubMedDate not supplied

Fine tuning a bile-enzymatic-gravimetric total dietary fiber method.

A recently proposed bile-enzymatic-gravimetric total dietary fiber (TDF) method was modified and the new procedure was compared with the original method, the traditional AOAC enzymatic-gravimetric determination (AOAC Official Method 985.29), and another simplified AOAC procedure by analyzing several diet composites, including National Institute of Standards and Technology 1548 total diet reference material. The original and modified bile-enzymatic-gravimetric procedures also were compared by analyzing 9 food samples from a collaborative study of the original method. The modified method consistently yielded values about 10% lower than the original method but closer to reference values and to values from AOAC Official Method 985.29, suggesting results that are more in line with accepted TDF standard methodology. Our modified method was used to analyze 180 fresh-frozen diet composites with TDF values ranging from 0.6 to 3.2 g/100 g wet weight. Samples were from 2 multicenter feeding studies sponsored by the National Heart, Lung and Blood Institute: DELTA (Dietary Effects on Lipoproteins and Thrombogenic Activity) and DASH (Dietary Approaches to Stop Hypertension). The mean relative standard deviation (RSD) for duplicate analyses was 1.1%. For 40 assays of a quality control diet composite over 9 months, the standard deviation was 0.1 g/100 g wet weight (4.9% RSD), indicating the method's excellent precision for routine use.

Diet↗
PubMedDate not supplied

Effect of seeds on bile-enzymatic-gravimetric analysis of total dietary fiber.

Dietary fiber sometimes is defined chemically as nonstarch polysaccharides plus lignin or as other specific chemical entities. Analysis of dietary fiber according to a chemical definition typically involves gas chromatography, which allows separation and quantitation of chemical constituents that are added to arrive at a dietary fiber value. Other definitions of fiber are broader, defining it to be whatever is not digested in the alimentary tract. Analytically, this definition translates into the gravimetric sum of the material remaining after a series of enzymatic and chemical treatments that simulate in vivo digestion. Various methods reflect the gravimetric definition, which might include as dietary fiber some protein, resistant starch, and even lipids that are not digested by particular assay conditions. We used a recently proposed bile-enzymatic-gravimetric assay for total dietary fiber on commonly consumed seeds (hulled and unhulled sesame, caraway, and poppy) and visually found these seeds to be undigested. We then determined the impact of the undigested seeds on measured dietary fiber content by spiking homogenized daily menus with 5% by weight of these seeds and calculating recoveries with 2 assumptions: seeds are 100% fiber because they are not digested, and the fiber content of seeds is as determined by assay. Calculated recoveries were very different depending on which assumption was made (71-90% or 99-109%, respectively), and the difference was closely related to the seed's protein content.

Bile↗