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Biomedical subjects

R D Norman

Publications and source records attributed to R D Norman.

At least 19 recordsLinked to original sources
PubMed1991

Five-year findings of a multiclinical trial for a posterior composite.

This paper reports the 5-year findings of a multiclinical (n = 11) trial of a posterior composite restorative. The overall findings, based on data collected from 649 (68 per cent) of the 958 restorations originally included in the study, indicate that the material evaluated satisfies established clinical requirements for posterior composites over periods of up to 5 years. Deviations in the reporting of certain elements of the data appear to have been related to local variations in method.

Acid Etching, Dental↗
PubMed1991

A 14-year clinical assessment of 12 amalgam alloys.

After 14 years, 40 patients from an in vitro/in vivo study of 12 amalgam alloys were evaluated. All these patients had been attending private practitioners over the past 10 years, and the clinical evaluation revealed that 320 restorations were intact and 47 (12.8%) had been lost. The majority (75.0%) of the lost restorations were lost to crown placement or the replacement with another amalgam restoration. The six high-copper alloys exhibited better clinical performance, in both loss rate and fracture at the margins, than did traditional low-copper materials. Fracture at the margins was a better predictor of the loss of a restoration than were mechanical properties.

Copper↗
PubMed1990

A 5-year study comparing a posterior composite resin and an amalgam.

Eighty class I and class II light-cured posterior composite resin restorations were compared with 43 class I and class II amalgam restorations during a 5-year period after placement. The results of this clinical study showed that both materials were satisfactory during the time period and that the only significant statistical differences are a poorer marginal integrity for the amalgam and a greater wear rate for the composite resin.

Adult↗
PubMed1990

13-year clinical assessment of 10 amalgam alloys.

The first commercial high-copper amalgam was developed in the mid-1960's. In 1975, a study to evaluate in vivo/in vitro performance of nine of these new alloys was initiated at Indiana University. These nine high-copper amalgams plus a traditional amalgam were tested for four laboratory properties and their gamma-2 content, and were clinically assessed for fracture at the margins. Originally, 60 restorations of each material were placed in patients and then recalled at six, 12, and 24 months. Recently, 13 years post-operatively, approximately one-third of the original patients were located. These patients were given a clinical exam, and photographs were taken of their restorations. From these recall data, the mean loss of all restorations at 13 years was 11.3%. The alloys Cupralloy, Tytin, and Dispersalloy had the lowest loss rates. The evaluation of the fracture at the margins (ridit means) indicates that there are five groups of alloys with some overlap between groups. The alloys Cupralloy, Indiloy, Dispersalloy, and Phasealloy exhibited the least fracture at the margins. The gamma-2-containing alloys--Optaloy II, Micro II, Velvalloy, and Aristaloy CR--showed the greatest rate of fracture at the margins. A correlation matrix of the ridit means at different years, the loss of restorations at 13 years, and the mechanical properties indicate that the early (one- and two-year) fracture at the margins predicts the 13-year results. Mechanical properties, however, do not predict the clinical performance of the materials at 13 years.

Copper↗
PubMed1990

Mechanical properties of metal-ceramic alloys at high temperature.

Four alloys used for the construction of porcelain-fused-to-metal restorations were tested at high temperatures (1000 degrees C) so that loss of properties could be ascertained. In addition, thin flat plates of metal (30 x 11 x 1 mm) with a 9-mm recess and a metal thickness of 0.35 mm were processed for porcelain application and distortion measured at 15 points along the surface prior to and following each firing cycle. Yield and ultimate tensile strengths and elongation were determined on specimens at room temperature and at 1000 degrees C. None of the alloys tested showed a great amount of distortion during the various firing cycles, yet they showed increased change with each successive heating. The greatest distortion occurred with Jelenko "O" alloy. When the mechanical properties were compared, there was a marked loss of both yield and ultimate strength values for each alloy (Jelenko "O"-Y.S., 95.64%, U.T.S., 96.22%; Olympia--Y.S., 95.08%, U.T.S., 96.76%; Tempo--Y.S., 91.23%, U.T.S., 93.46%; Biobond II--Y.S., 83.72%, U.T.S., 86.21%). Percent elongation increased by 272% with Biobond II and 370% with Jelenko "O", whereas Tempo and Olympia increased by 120 and 155%. It is apparent that the palladium-based alloy and the nickel-chromium-based alloy have higher mechanical properties at the temperature where porcelain will be applied.

Dental Alloys↗
PubMed1990

A 12-year clinical evaluation of two composite resins.

Two composite resin materials were clinically evaluated after 12 years in vivo. Although the Class III restorations did not have the benefit of acid etching and bevels, all 32 restorations in the nine patients who were located were intact, and none needed to be replaced. Stain was the most prominent problem, both at the margins and on the surface of the restorations. Neither wear or marginal integrity appeared to be a problem.

Color↗
PubMed1980

Fluoride distribution in teeth using a silicate model.

The fluoride determinations were done on enamel biopsies taken before and after restoration of extracted teeth with silicate cement. Two sites, one near the restoration and one 3 mm or more away from the restoration, were assayed. No difference was noted in pre- and post-restoration biopsies when teeth were restored with a fluoride-free silicate. Post-restoration biopsies at sites near and away from the restoration were significantly higher in fluoride as compared to pre-restoration biopsies when the teeth were restored with a fluoride-containing silicate.

Dental Cements↗
PubMed1978

A comparison of pin-retained amalgam and composite resin cores.

The 24 hour tensile loads required to separate the core material and dentin produced the following results: 1. No statistical difference was found between the tensile strength of retained amalgam and composite resin core materials. 2. Generally, no statistical difference was found between the retentive ability of three and four pins. 3. No statistical difference was found between the retentive ability of regular pins and minim pins if three or more pins were employed. 4. As the number of regular pins was increased beyond three, and when four minim pins were used, there was a very significant increase in dentin fracture.

Composite Resins↗
PubMed1977

An evaluation of silicophosphate as an orthodontic cement.

In a laboratory and clinical evluation, when used for the cementation of orthodontic bands, a zinc silicophosphate cement has proved to be comparable to zinc phosphate cement in its bond strength to enamel. This was demonstrated in laboratory tests by higher values being required to break the mechanical bond and in the clinical study by the slightly smaller percentage of bands which became loose during orthodontic treatment. In both the laboratory and clinical studies it was found that silicophosphate remained attached to the enamel in higher percentages after a band had become loose. It also was found that the remaining cement was often quite difficult to remove from the enamel. Probably the greatest advantage of using silicophosphate is that no decalcification of enamel was found under bands which had become loose during orthodontic treatment. This may be attributable to the higher bond strength and/or the presence of fluoride in the cement. Further clinical studies of this nature appear warranted.

Dental Bonding↗