PubMed Health⌕ Search

Biomedical subjects

R D Davis

Publications and source records attributed to R D Davis.

At least 145 records · Page 8Linked to original sources
PubMed1971

Studies on the inhibition of clearance of organic dyes by Saramycetin.

1. Saramycetin, a polypeptide antifungal antibiotic has been found to retard the clearance of sulphobromophthalein (BSP) in man. An explanation for this observation was sought in several lower species.2. Doses of Saramycetin without effect on the other standard tests of hepatic function or on hepatic morphology profoundly altered the disposition of BSP and several other dyes in mice and dogs.3. Saramycetin strongly inhibited the hepatic enzyme which conjugates BSP to reduced glutathione, provoked a regurgitation of BSP from the liver into the bloodstream, and was anticholeretic in the dog.4. These diverse actions of Saramycetin may, in concert, explain the altered clearance of BSP. It is suggested that low doses of Saramycetin exert a pharmacological effect on certain hepatic excretory processes, whereas high doses are toxic.

Animals↗
PubMedDate not supplied

Fracture strength of Class 2 amalgams with various cavity-lining materials.

UNLABELLED: This in vitro study compared the fracture resistance of class 2 amalgam restorations placed over seven materials: three resin-modified glass-ionomer cements (Fuji II LC, Vitrebond, and Vitremer), one polyacid-modified composite resin (VariGlass VLC), two conventional glass-ionomer cements (Ketac-Bond and GlasIonomer Cement), and one calcium-hydroxide material (Dycal). Eighty maxillary molars with flattened occlusal surfaces were divided into 14 experimental groups and two control (no liner) groups. One standardized class 2 amalgam cavity preparation was completed per tooth. Lining materials standardized at a thickness of 0.5 mm were placed in the approximal box portion of 10 test specimens per experimental group. Spherical amalgam was hand condensed into each cavity preparation. At 1 hour and again at 7 days, five samples from each group were fractured in compression using an Instron Universal Testing Machine. The force was directed at 10 degrees to the long axis of the tooth, 2.0 mm inside the approximal portion of the restoration. Results were analyzed using a two-way ANOVA for time and material. No statistically significant differences were found among the materials and controls at either time interval tested (P > 0.05). A statistically significant difference was found (P < 0.05) when comparing 1-hour and 7-day strengths. The 7-day specimens were more resistant to fracture than the 1-hour specimens. CONCLUSION: The fracture resistance of amalgam restorations was not affected by the presence of a material 0.5 mm thick placed in the approximal box when 3 mm of bulk of amalgam remained over it.

Acrylic Resins↗
PubMedDate not supplied

Effect of saliva contamination on the bond of dentin to resin-modified glass-ionomer cement.

This in vitro study compared the shear bond strength of a resin-modified glass-ionomer restorative material (Fuji II LC) bonded to saliva-contaminated dentin versus non-contaminated dentin. Seventy-five extracted human molar teeth were randomly divided into five groups of 15 samples each. The dentin was treated with 10% polyacrylic acid for 20 seconds, rinsed, and dried. The acid-treated dentin surfaces in Groups 1-4 were contaminated with saliva. In Group 1, the saliva was air thinned. In Groups 2-4, saliva was dried completely with compressed air. The saliva-contaminated dentin in Group 3 was rinsed and dried. The saliva-contaminated dentin in Group 4 was rinsed, dried, treated with 10% polyacrylic acid, and dried. Specimens in Group 5 received no contamination. The resin-modified glass-ionomer cement restorative material was mixed and applied to the dentin surfaces. Following placement of the restorative material and 7 days of storage, the specimens were thermo-cycled 300 times. Using the Instron Universal Testing Machine, a shear force was applied to the restorative material. Shear bond strength values were compared among the groups using a one-way ANOVA and Student-Neuman-Keuls Multiple Range Test (alpha = 0.05). The non-contaminated specimens (Group 5) were significantly stronger than the contaminated specimens (Groups 1-4). There were no significant differences in bond strength among the groups containing contaminated specimens. Salivary contamination occurring after dentin etching significantly reduced the bond strength of the resin-modified glass-ionomer restorative material to dentin. Neither rinsing nor rinsing and re-etching resulted in bond strengths as great as to non-contaminated dentin.

Analysis of Variance↗
PubMedDate not supplied

Cuspal reinforcement in endodontically treated molars.

UNLABELLED: This in vitro study compared the ability of horizontal pins and a dental adhesive to reinforce the facial cusps of endodontically treated mandibular molars. Seventy-two mandibular molars were divided into six groups and mounted in acrylic blocks (n = 12). In Groups 1-5 standardized endodontic access and instrumentation in the coronal one-third of each root canal were completed. In Groups 1-4 the lingual cusps were reduced, leaving the buccal cusps intact. The facial cusps of the teeth in each group received one of the following modes of reinforcement: Group 1--no reinforcement; Group 2--dentin adhesive (Amalgambond Plus); Group 3--two horizontal TMS Minim pins; Group 4--two horizontal TMS Minim pins and Amalgambond Plus. Teeth in Group 5 were prepared for and restored with a complete cuspal coverage amalgam restoration using four vertical TMS Minim pins. Group 6 consisted of intact natural teeth. Using an Instron Universal Testing Machine, the lingual slope of the facial cusp of each specimen was loaded to failure using a compressive force applied at an angle 60 degrees to the long axis of the tooth. The mean fracture strengths for all groups were analyzed using a one-way ANOVA and Student-Newman-Keuls multiple range test (alpha = 0.05). Fracture patterns and modes of failure were also evaluated. RESULTS: The intact teeth (Group 6) were significantly more fracture resistant than all other groups, with the exception of Group 4 (combination of pins and adhesive). Group 1 (non-reinforced teeth) was significantly weaker than all other groups. Groups 2-4 (specimens with reinforced cusps) were not significantly different from each other. The use of horizontal pins or a combination of horizontal pins plus dentin adhesive for cuspal reinforcement resulted in significantly more teeth demonstrating favorable fracture patterns than did the use of adhesives alone. CONCLUSION: The buccal cusps of endodontically treated mandibular molars reinforced with a combination of horizontal pins and dentin adhesive were not significantly weaker than intact teeth. Of the restored teeth, those which had buccal cusps reinforced with horizontal pins and those treated with complete cuspal coverage amalgam restorations exhibited the most favorable restorative prognosis following cusp fracture.

Chi-Square Distribution↗
PubMedDate not supplied

Systemic effects of an intraosseous injection of 2% lidocaine with 1:100,000 epinephrine.

The effect of a mandibular intraosseous injection of 2% lidocaine with 1:100,000 epinephrine on the heart rate and blood pressure of 20 volunteer patients was examined. Changes in blood pressure from preoperative levels were minimal and did not vary significantly at any time of measurement. The only statistically significant change in heart rate occurred immediately after the intraosseous injection (an increase of 12 beats per minute). In young healthy adults, the intraosseous injection of 1.5 mL of 2% lidocaine with 1:100,000 epinephrine resulted in a slight transient elevation in heart rate but had no significant effect on systolic or diastolic blood pressure.

Adult↗
PubMedDate not supplied

Reduction of bacteria-containing spray produced during ultrasonic scaling.

Bacteria-containing spray (including both aerosols and splatter) has been shown to be a potential source of contagion in the dental environment. Bacterial air contamination increases during dental treatment; this is especially true during ultrasonic scaling procedures. This in vivo investigation evaluated the amount of bacteria-containing spray produced during ultrasonic scaling of 15 patients when using a suction-type aerosol reduction device (ARD) and/or a preoperative 0.12% chlorhexidine gluconate (CHX) antimicrobial rinse. When the study protocol was followed, the use of either an ARD or a CHX rinse produced significant bacterial reductions during ultrasonic scaling compared to the control. The use of an ARD produced the greatest bacterial reductions. Combining the ARD and the CHX rinse was no more effective than the use of an ARD alone.

Adult↗
PubMedDate not supplied

The effect of eugenol-containing and eugenol-free temporary cements on microleakage in resin bonded restorations.

Eugenol is known to have a detrimental effect on both composite resin and dentin bonding agents. The purpose of this in vitro investigation was to compare the microleakage among groups of resin-luted inlays when the cavity preparations were pretreated with a eugenol-containing temporary cement, a eugenol-free temporary cement, or no temporary cement. Class 5 inlay preparations (20 per group) were completed in extracted human molars. Following the fabrication of composite resin inlays, the preparations were filled with either a eugenol-based temporary cement, a eugenol-free temporary cement, or no cement. After removal of the cement from the cavity preparations and application of a dentin bonding agent, the composite inlays were luted with a resin cement, thermocycled, stained, sectioned, and evaluated for microleakage under a stereomicroscope. None of the groups exhibited significant leakage at the enamel margins. Both of the groups treated with temporary cement leaked at the nonenamel margins significantly more than the control (no cement) group. No significant difference in leakage was demonstrated between the groups treated with the eugenol-containing and the eugenol-free temporary cements.

Analysis of Variance↗