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Biomedical subjects

J H Hembree

Publications and source records attributed to J H Hembree.

At least 73 records · Page 4Linked to original sources
PubMed1978

Film thickness of cements beneath complete crowns.

The results showed that Durelon, EBAC, zinc phosphate, Epoxylite CBA, and Fynal had thinner film thicknesses than EBA and Fluro-Thin. In addition, venting of a crown resulted in lower film thicknesses with all cements except Fynal and EBAC. No significant differences occurred with these two cements whether the crown was vented or not. Obviously many other factors besides film thickness, such as toxicity, strength, and solubility, have to be considered before selecting a cement for clinical use. When only film thickness is to be considered, all of the cements in the study could be recommended for the cementation of crowns with the exception of EBA and Fluoro-Thin.

Cementation↗
PubMed1978

The bactericidal potential of various endodontic materials for primary teeth.

An in vitro study of the bactericidal or bacteriostatic effects of several pulp therapy compounds and their components on selected bacterial commonly isolated from infected primary teeth was undertaken. It was determined that zinc oxide had no inhibitory effects on E. coli, Staph. aureus, and Strep. viridans; however, the addition of eugenol to this system retarded the growth of only the grampositive organisms. The inclusion of zinc acetate as a setting accelerator inhibited both gram-positive and gram-negative bacteria. Also the inhibitory effects on these three organisms could be greatly enhanced by the addition of formocresol or paraformaldehyde to the zinc oxide--eugenol--zinc acetate system. It was also noted that Sargenti's N-2 paste was apparently no more effective in retarding growth of these organisms than the mixtures. Only the lead tetroxide and hydorcortisone present in the N-2 paste was toxic to the Staph. aureus but not to E. coli or to Strep. viridans. The other heavy metals in N-2 apparently have no antibacterial activity in the manner in which they were tested. This evidence suggests, but is not conclusive, that zinc oxide--eugenol--zinc acetate, with or without formaldehyde-containing compounds, may be effective in the elimination of bacteria from pulpotomized primary teeth. Therefore, the addition of highly cytotoxic chemicals which will remain sealed in a root canal and be active for extended periods of time may not be necessary for successful treatment.

Anti-Bacterial Agents↗
PubMed1978

Microleakage of several class V anterior restorative materials: a laboratory study.

The study was designed to evaluate the marginal leakage of abraded gingival areas in extracted teeth using five anterior composite resin acid-etch restorative materials and a glass ionomer cement, ASPA. In using three of the composite resin restorative materials, Simulate, Cervident, and Concise, there was a layer of unfilled resin between the etched tooth surface and the composite resin. Restodent and Enamelite were placed directly on the etched tooth surface. The results of the study indicate that there is a significantly greater degree of marginal leakage at the gingival margin than there is at the occlusal or incisal margin of composite restorations. In addition, greater marginal leakage was observed in those restorations where no layer of unfilled resin was placed between the etched tooth surface and the composite resin. The glass ionomer cement showed no marginal leakage at intervals of one day, three months, and six months; however, a small amount of leakage was observed at the incisal or occlusal and gingival margins at a year on half of the autoradiographs. A study has been initiated to determine leakage patterns around composite resin restorations placed in teeth with naturally occurring cervical erosion or abrasion.

Acrylic Resins↗
PubMed1976

Preventing enamel decalcification during orthodontic treatment.

One hundred thirty-two extracted premolar teeth were selected and divided into four equal groups. The first group of thirty-three teeth received a topical application of acidulated phosphate fluoride; the second group, a topical application of stannous fluoride; the third group, an application of a polymeric adhesive coating; the fourth group was left untreated to serve as a control. On each tooth a loosely fitted orthodontic band was cemented to place. After cementation, the band was broken to simulate a loose orthodontic band in vivo. The four groups of teeth were simultaneously immersed in a decalcifying gelatin and were left undisturbed for 11 weeks. The teeth were then removed and a record was made of the decalcification produced. A chi-square test was used to compare the teeth in each group to those in every other group. Compared to a control group of teeth, those teeth treated with polymeric adhesive coating, acidulated phosphate fluoride, or stannous fluoride produced a statistically significant reduction in decalcification of the tooth surfaces beneath loose orthodontic bands. For a one-application technique, the polymeric adhesive coating provided more protection against decalcification of teeth under loose orthondontic bands than did either acidulated phosphate fluoride or stannous flouride.

Calcium Metabolism Disorders↗
PubMed1976

Shear strength of orthodontic direct-bonding adhesives.

A total of 210 double-width stainless steel edgewise brackets with retentive lip bases were bonded to bovine incisors with seven commercially available direct-bonding materials. Ten samples for each of the seven direct-bonding materials were tested for shear strength using the Instron Universal Testing Instrument. The samples were tested after 1 day, 1 month, and 3 months of immersion in 30 per cent physiologic saline solution. The mean shear strength of each direct-bonding material at each time interval was compared statistically to the mean shear strength of each of the materials at each time interval with a matched 1 test. The same test was used to determine whether there had been a significant change in mean shear strength from start to finish of testing for each material. One product showed a significantly better mean shear strength than any other material at each test interval. The remaining materials were grouped in middle or low ranges, depending upon their final mean shear strengths and degrees of nonsignificance when compared to each other.

Acrylic Resins↗
PubMed1976

In vivo evaluation of marginal leakage of four inlay cements.

Marginal leakage was demonstrated in all the inlays at all time intervals with all cements by the use of the isotope Ca45. Gross marginal leakage was observed in all inlays luted with the cyanoacrylate cement at all time intervals. The setting time of this cement is very short, making it difficult to completely seat the inlay before the cement sets. The results of this study indicate that the cyanoacrylate cement is not a satisfactory luting medium for Class V inlays. Inlays cemented with EBA demonstrated leakage patterns similar to those of inlays seated with polycarboxylate and zinc phosphate cements in the specimens taken at 72 hours. In the 3 month and 6 month specimens, greater marginal leakage was seen with EBA cement than with polycarboxylate and zinc phosphate cements. Leakage patterns associated with polycarboxylate and zinc phosphate cements were very similar at all time intervals. The polycarboxylate and zinc phosphate cements showed less marginal leakage than the other two cements at 3 months and 6 months. The results of this study indicate that inlays cemented with polycarboxylate cement and zinc phosphate cement exhibit significantly less marginal leakage than the cyanoacrylate cement and EBA cement over a 6 month period of time.

Animals↗
PubMed1976

The bond strengths of resin systems to etched enamel.

This study was undertaken to compare the resin-enamel bond strengths of seven anterior restorative resins using the acid-etch technique. Six of the materials (Restodent, Enamelite, Smile, Nuva-System, Concise, and Adaptic) were composite resins. Only one, Sevriton, was an unfilled resin. Of the seven, only Sevriton and Smile were not designed for the acid-etch technique. Of the materials tested, Sevriton and Enamelite had the weakest bonds. There was no significant difference in the bond strength among Nuva-System, Smile, and Restodent; the bonds of all these were stronger than those of Sevriton and Enamelite. Concise showed a significantly greater bond strength than all the other materials in the study except Adaptic and the Nuva-System. The resin-enamel bond strength of Adaptic was of a greater magnitude than that of all other test materials.

Acrylic Resins↗
PubMed1976

Leakage of different root canal sealants.

One hundred five single-rooted teeth were prepared and filled with ten commercially available root canal paste sealers. Five teeth were filled with only gutta-percha points, fifty teeth were filled with a particular cement alone, and the rest of the teeth were filled with a particular cement in conjunction with gutta-percha points. It was found that the gutta-percha point alone is not sufficient for sealing the periapical foramen; nor are N2 (Sargenti), Riebler's paste, and the iodoform paste. In general, it was found that the combination of gutta-percha and cement is more effective in sealing the periapical foramen. Polycarboxylate cement used in this investigation, although it does not meet all the requirements of a good root canal sealant, was found to yield promising results.

Dental Cements↗