Biomedical subjects
Publications and source records attributed to R L Cooley.
Five new visible light-curing cavity liners/bascs that contain fluoride were evaluated for fluoride release over a 17-week period. Fluoride was released from all the materials, but the level of fluoride release decreased significantly (P less than .01) over the test period. There was also a statistically significant (P less than .05) difference among the materials in the amount of fluoride released.
A fluoride-containing sealant (FluroShield) was evaluated in vitro and compared to a sealant without fluoride (Helio-Seal). Both materials were applied to the occlusal surface of extracted teeth and microscopically evaluated for their ability to penetrate pits and fissures. Additional specimens were subjected to dye immersion and evaluated for resistance to microleakage. Disc-shaped samples of the fluoride-containing sealant were immersed in distilled water and analyzed daily for seven days for fluoride release. All specimens of FluroShield released fluoride during the evaluation period, but there were differences between the materials in resistance to microleakage.
All dental restoratives exhibit some microleakage. Recent studies disclosed that oxalate salts were superior to Copalite varnish in reducing dentinal permeability, but inferior in reducing microleakage. This study compared the effectiveness of a potassium oxalate solution (DDS) with three other cavity liners (Copalite, Cavi-Line, Prisma Universal Bond) and a no-liner control in reducing microleakage under amalgam restorations. Under the conditions of this study, DDS solution was significantly effective in reducing microleakage under amalgam restorations.
The effect of the glass-mm, and 3 mm thicknesses were placed over glass-ionomer bases, and the microhardness of the external surface was compared with that of controls without a base. A significant reduction in surface hardness (p less than 0.05) was determined only for the 1-mm test specimens.
A new resin dentin adhesive consisting of a primer (phosphonate dimethacrylate) and bonding agent (phosphonated BIS-GMA) was evaluated with bond strength tests, marginal microleakage studies, and SEM examination. The mean bond strength to dentin was 15.6 +/- 3.7 MPa. Microleakage studies found no marginal leakage at the enamel cavosurface margin and very minimal microleakage at the dentin/cementum margins. SEM examination showed that the primer was very effective in modifying the smear layer.
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Two commercial orthodontic adhesives containing fluoride were evaluated in vitro for fluoride release. Fluoride release is critical in preventing both decalcification around orthodontic brackets and the formation of white spot lesions. A paste-type adhesive composite resin and a glass ionomer luting agent were compared to a glass ionomer restorative material to determine fluoride release. The composite resin adhesive released minimal fluoride for only three days and then ceased. The glass ionomer adhesive released fluoride at a similar rate to the glass ionomer restorative material with fluoride release still evident at three months.
This study evaluated the Max 017 retentive pin (.019 in./.48 mm) and its twist drill (.017 in./.43 mm) along with the Max 021 pin (.024 in., .61 mm) and its twist drill (.021 in./.53 mm), in relation to shoulder stop position, space between the end of the pin and the end of the channel and the development of cracks in dentin adjacent to pin channels. A total of 20 non-carious human molar teeth were used, 10 for each size pin. Four pins were placed in each tooth for a total of 40 of each size pin. An air turbine contra-angle was used at 1,200 rpm to prepare all channels and seat all pins. Results showed that with the 017 pins, only 14 pins out of 40 (35%) were completely seated with the shoulder stop against dentin, while the 021 pins had 36 out of 38 (95%) of the shoulder stops completely seated. There was a significant difference in the two groups. Cracks were seen adjacent to only one pin. Space between the end of the pin and the end of the channel for the 017 pins whose shoulder stops were seated was an average of .55 mm, while the 021 pins had an average of .14 mm.
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The repair bond strength of three different brands of glass-ionomer restorative was tested over time. In this laboratory study, immediate repair of glass ionomer was possible with all three brands; however, over time the repair bond strengths decreased at different rates for the different materials.
A liquid solution of an oxalate bonding system containing NTG-GMA and PMDM has become commercially available. The bond strength of this oxalate adhesive (Tenure Solution) to dentin was determined by bonding composite resin cylinders to extracted teeth. The bond strengths obtained in this study are compared to the bond strengths obtained in earlier studies with the first and second generation oxalate adhesives whose components were supplied as powders and required mixing. The oxalate solutions developed significantly higher bond strengths than the original powder type systems.
The effects of an air-powder abrasive instrument on porcelain were evaluated. Sample disks made from two commercial porcelains and three porcelain stains were treated for 30 seconds with this instrument. Although there was no visible change in the stain or glaze of the samples, scanning electron microscopy revealed severe pitting of all of the Vita porcelain/Vita stain samples, moderate pitting of all of the Vita porcelain/Ceramco stain samples, and no pitting or effects on Willceram porcelain/Crystar stain samples. It is recommended that the air-powder abrasive instrument be used cautiously or not at all on porcelain restorations, especially those with staining and/or specific characterizations. Pitting of the surface could be a result of this treatment.
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