The quantification of tertiary dentine formation in response to materials commonly placed in deep cavities in general...

To determine the rate of formation of tertiary dentine in dogs' teeth, in response to five commonly used lining materials. Also, to record the resulting differences in quality of the formed dentine.

Representatives of five types of materials commonly used in general practice in the UK were placed in deep standardised cavities with a remaining dentine thickness of 400-500 microns, and sealed to the cavo-surface with zinc oxide-eugenol. The daily rate of tertiary dentine formed in response to each material was measured over a period of 119 days using a tetracycline staining method. A concomitant study to show the quality of the formed dentine was undertaken using the same materials and experimental conditions.

There was a significant difference between the rates of tertiary dentine formation for all materials except zinc oxide-eugenol and Ledermix paste. For each material there was a increased rate of tertiary dentine formation in the second period (29-49 days) compared to the first period (0-28 days). This is considered to be due, in part, to a lag period when damaged odontoblasts are differentiating from mesenchymal elements. The rate of tertiary dentine formation in response to all the test materials was always greater than that of normal physiological dentine formation in unprepared teeth. Qualitatively, there was difference in the formed tertiary dentine beneath each material. All the materials caused odontoblast destruction, altered ground substance production and alterations in the calcification process.

None of the materials routinely used at present can be considered to be 'ideal' as odontoblast destruction, altered ground substance production and altered calcification occur beneath zinc oxide-eugenol preparations, calcium hydroxide preparations as well as in response to corticosteroid-containing materials such as Ledermix paste and cement.