Seymour Hoffman

Scanning Electron Microscope Studies of Dental Enamel

The capability of the scanning electron microscope (SEM) was evaluated for ultrastructural studies of dental enamel. Sound, acid-etched, and EDTA-treated enamel samples were examined, It was found that acid causes demineralization of prism cores, whereas EDTA attacks their peripheral boundaries. The scanning electron microscope appears to be exceptionally well suited for studying sound and experimentally treated dental structures.

Demineralization Studies of Fluoride-Treated Enamel Using Scanning Electron Microscopy

Enamel was treated with topical stannous fluoride and demineralized with an acetate buffer for varying periods. A scanning electron microscope comparison of the surface alterations revealed that stannous fluoride inhibited surface alterations when challenged by the acid. Evidence suggested that fluoride plays a role in the remineralization of repair of slightly etched enamel surfaces.

Scanning Electron Microscopy of Dental Enamel

The image capabilities of the scanning electron microscope (SEM) enable simple and direct observations of the ultramicroscopic structure of dental tissues that are not possible with the conventional electron microscope. The SEM depth of field is stated to be 500 times that of the optical microscope, and its resolution is ten times greater. These features are augmented by a wide range of magnifications ( X 50 to X 100,000). Specimens can be observed directly within a few minutes after being mounted, without complicated technics of tissue preparations and delays from faulty replicas. Suitably prepared whole specimens are mounted on a small pedestal, placed in a vacuum evaporator, and coated with a vaporized gold-palladium alloy to a thickness of about 200 Angstroms. The image is formed on a 105-X 105-mm cathode ray tube located on one section of the control panel of the microscope. A duplicate viewer is located on the second control panel for photomicrography. Low-power scanning examinations of specimen surfaces can be quickly accomplished, and areas of interest can be charted. More detailed studies can be performed at increasingly higher magnifications.

Scanning Electron Microscope Studies of Dextranase-Treated Plaque Streptococci

The in vitro effects of dextranase on extracellular polysaccharide-producing streptococci grown on autoclaved enamel samples were evaluated by scanning electron microscopy. This enzyme was found to be highly effective in dispersing both strains of streptococci when compared with controls.

Variations in Surface Resistance to Enamel Etching

Scanning electron microscopy of clinically sound enamel samples demonstrated two distinct types of perikymata patterns: undulating, and overlapping. When treated with a buffered acetate solution (pH 4.0), the overlapping perikymata were more susceptible to demineralization than the undulating perikymata. Furthermore, in erupted teeth the overlapping forms seemed to be confined primarily to the cervical third of the crown, and in unerupted and partially erupted teeth they were distributed more widely.

Antiplaque Potential of Topical Stannous Fluoride

Sterile enamel samples treated by topical application of 10% stannous fluoride were incubated with S mutans and S sanguis respectively and with a mixed culture to which L casei had been added. The results were compared with sterile nonfluoridated enamel samples subjected to the same procedures. The parameters compared were postincubation pH values, bacterial concentrations on the surfaces, and enamel surface alterations. Stannous fluoride treated samples consistently yielded higher pH readings than nonfluoridated samples; the concentration of microorganisms adhering to the surfaces was conspicuously reduced on the pretreated enamel when compared by scanning electron microscopy to untreated samples, as were enamel surface alterations. These findings lend support to other recent investigations which have shown that fluorides act in several ways to inhibit cariogenesis in addition to reducing hydroxyapatite solubility.