The impact of sorption, buffering, and proteins on leaching of organic and inorganic substances from dental resin core material.

Dental core materials are resin-based polymers that act as support for overlying dental restorations. Interaction with aqueous media, such as saliva in the oral cavity or serum in the pulp chamber, can cause leaching of substances from core materials. These substances can potentially have serious effects to tissues. The purpose of this study was to delineate the factors that cause leaching and to quantitate both organic and inorganic substances that leach from core materials. Two core materials and one control material were stored in distilled water, artificial saliva, buffered artificial saliva, or artificial serum for 30 days at 37 degrees C. The materials were examined for changes in appearance and chemical composition, with a surface precipitate appearing on specimens stored in artificial saliva. The pH of the media was monitored and increased for all conditions. Organic eluants, triethyleneglycol dimethacrylate (TEGDMA), and camporquinone (CQ) were identified and measured in all media with high pressure liquid chromatography. Silicon, calcium, phosphate, and potassium were measured in the media using inductively coupled plasma optical emission spectroscopy. These results show that sorption, buffering, and the presence of proteins have an impact on the quantity of eluants that are leached from dental core materials.

An in situ interproximal model for studying the effect of fluoride on enamel.

This crossover study determined the ability of an interproximal, intra-oral model to demonstrate a fluoride dose response to 0-, 250- and 1,100-ppm fluoride (sodium fluoride) dentifrices with respect to fluoride uptake into, and remineralization of, incipient subsurface enamel lesions. Following a 1 week 'lead in' period during which 30 panelists were randomly assigned to use one of the products, two enamel specimens with artificial carious lesions were mounted into a specially designed functional partial denture worn by each panelist. Panelists continued to brush three times daily with their test dentifrice for 4 weeks, after which the specimens were removed and analyzed for fluoride uptake and remineralization. The procedure was repeated until each panelist had followed all three treatment regimens. Fluoride analyses were performed using a microdrill biopsy technique, and mineral content changes were determined by transverse microradiography. Fluoride uptake data were significantly different (p < 0.01) for all three products with the effect of 1,100 ppm F > 250 ppm F > placebo. The 1,100 ppm F dentifrice also effected significantly greater remineralization (p < 0.01) than did the 250-ppm-F or placebo dentifrices. Relative efficacy of the three fluoride dentifrices tested in this study was similar to that established in a clinical trial, and, therefore, supports the use of this model for in situ studies of the effects of fluoride-containing products on enamel lesions.

An in vitro model for studying the efficacy of fluoride dentifrices in preventing root caries.

This investigation tested and validated an in vitro model for studying the effects of fluoride on human dentin mineral content and fluoride uptake. Four studies examined the effects of different concentrations of fluoride, established dose-response profiles with NaF and Na2PO3F, and tested commercial dentifrices. A 7- or 14-day cyclic treatment regimen involved four 1-min exposures of sound human dentin specimens to the treatment agents, a 4-hour acid challenge period, and 20 h in human saliva daily. Mineral content was analyzed by image analysis microradiography and fluoride assays were performed using a microdrill biopsy technique. Data from these studies established the ability of the in vitro model to provide reproducible results, to demonstrate significant dose-related differences in the effects of both NaF- and Na2PO3F-containing treatments on dentin fluoride uptake and demineralization, and to detect a fluoride-induced reduction in dentin caries, relative to a nonfluoride control, similar to results established in a clinical trial.