Reaction of the human dental pulp to silver amalgam restorations. The modifying effect of treatment with calcium hydroxide

Pulp exposure after stepwise versus direct complete excavation of deep carious lesions in young posterior permanent teeth

The aim was to assess the prevalence of pulp exposure after stepwise versus direct complete excavation of permanent posterior teeth with deep carious lesions. The material, representing 116 patients aged 6-16 yrs (mean = 10.2 yrs), consisted of 127 teeth with radiographs revealing carious lesions to such a depth that pulp exposure could be expected if direct complete excavation was performed. Teeth with clinical symptoms, other than transient pain shortly before treatment, were not accepted. The teeth were randomly selected for either treatment procedure. Stepwise excavation implied removal of the bulk of carious tissue and application of calcium hydroxide, followed by sealing of the cavity with zinc-oxide eugenol cement. After a period of 8-24 weeks the rest of the carious dentin was removed and the cavity sealed with calcium hydroxide, zinc-oxide-eugenol (ZOE) and a restorative material. Direct complete excavation entailed removal of all carious dentin followed by sealing as mentioned above. In case of pulp exposure, pulp treatment was performed. The pulp was exposed in 40 of the teeth treated by direct complete excavation. The corresponding figure for those treated by stepwise excavation was 17.5%. The difference was statistically significant. The teeth with no pulp exposure after direct or stepwise excavation showed normal clinical and radiographic conditions at the last check-up (mean = 43 months).

Characterization of an in vitro dentin barrier test using a standard toxicant

To characterize a new artificial pulp chamber using bovine dentin, the influence of different phenol concentrations on the cell reaction was evaluated. Bovine dentin slices of 100, 200, 300, 500, and 700 microns were cleaned, sterilized, and mounted between two 5-mm-thick glass plates with a borehole of 5 mm in diameter. L-929 mouse fibroblasts were seeded into the "pulpal" part of the device and incubated for 24 h. Different concentrations of a phenol solution as a standard toxicant were applied to a sterile cotton pellet in the "cavity" side of the device. After incubation for 24 h, the cytotoxic reaction was evaluated by cell counting after vital staining with fluorescein diacetate and related to the negative control. A dependency of the cytotoxic reaction on the concentration of the standard toxicant and on the thickness of the dentin slice was demonstrated. The simple dentin barrier test using bovine dentin may be a suitable alternative to other more complicated procedures using human dentin.

Reactions of the dental pulp to microbial provocation of calcium hydroxide treated dentin

The purpose of the present study was to determine whether treatment of dentin with calcium hydroxide reduces pulp irritation caused by microbial products. The experiment was carried out in three young monkeys. Cavities were prepared on the buccal tooth surface deep into dentin of 62 teeth. Calcium hydroxyde mixed with distilled water was placed in one group of cavities. A set of control cavities received treatment with saline soaked filter-paper discs. The calcium hydroxide dressing and the saline discs were separated from the oral cavity for a period of 14 or 60 d by a Teflon disc and a layer of zinc oxide-eugenol cement. At the end of these periods the content of each cavity was removed and substituted by lyophilized material from cultivated plaque bacteria. After 3 d of exposure the monkeys were killed and the teeth subjected to histologic treatment. Assessments made in the light microscope revealed that pulps subjacent to calcium hydroxide-treated dentin in the majority of cases showed no or only slight infiltrates of inflammatory cells. In controls, 13 out of 22 pulps showed severe inflammatory cell infiltrates or total pulp tissue necrosis. It was concluded that treatment of dentin with calcium hydroxide may reduce the possibility for bacterial components to cause pulp tissue damage.