YY/T 0127.7-2017Biological evaluation of medical devices used in dentistry - Part 7: Pulp and dentine usage test (English PDF)

7.2 Tooth Preparation

7.2.1 Cavity preparation

Remove all tooth stones and soft mucinous deposits on the surface of teeth. Take 3% (volume fraction) hydrogen peroxide to clean and sterilize the surface of teeth, then, use disinfectant that contains iodine or chlorhexidine to sterilize the teeth. Under sufficient vapor spray, take sharp drill to prepare a necessary number of V-type cavities on the buccal side of the teeth or the lip side. The thickness of residual dentine on the bottom of all the cavities shall be < 1 mm, and preferably < 0.5 mm. However, the endodontic pulp shall not be exposed. Experimental filling materials require a different operation. Other than this, all cavities shall be rinsed with water, and dried with absorbent cotton.

Note 1. if animals manifest apparent gingival inflammation, remove all tooth stones and soft mucinous deposits on the surface of teeth several days before cavity preparation; repeat the step of cleaning if necessary, till the inflammation is under control.

Note 2. during cavity preparation, impedance measuring instrument that has been calibrated can be adopted, for example, apical instrument, to assist in the estimation of the thickness of the residual dentine.

7.2.2 Material preparation

Prepare experimental materials in accordance with product specification. If product specification requires the application of cavity lining material or treatment agent (for example, dentine glue), these operations can be added in accordance with the manufacturer's instruction.

7.2.3 Cavity filling

In accordance with the principle of random allocation, experimental materials shall be utilized to fill at least 7 cavities, negative control materials shall be utilized to fill at least 4 cavities in each experimental cycle. If necessary (refer to the note below), there shall be 4 positive control cavities in each experimental cycle.

Note. if laboratory possesses previous positive control database, it is unnecessary to conduct another positive control experiment, unless positive reaction needs to be verified.

7.2.4 Postoperative observation and nursing

Slight inflammation. the structure of dental pulp tissue that passes dentinal tubule and adjoins cavity bottom is normal, inflammatory cells are dispersed Moderate inflammation. the structure of dental pulp tissue that passes dentinal tubule and adjoins cavity bottom is still normal, small-scale lesions of concentrated inflammatory cells exist Severe inflammation. the structure of dental pulp tissue that passes dentinal tubule and adjoins cavity bottom is abnormal, inflammatory cells infiltrate extensively Abscess is formed, or extensive inflammatory cells infiltrate to tissue area except from dental pulp tissue that adjoins dentinal tubule on cavity bottom During the evaluation of each section, record the minimum thickness of residual dentine, including the measurement of the distance from cavity bottom to endodontic pulp - (early stage) dentine interface and the distance along dentinal tubule from the vertical angle. The latter refers to when the plane section is not completely consistent with dentinal tubule, namely, each dentinal tubule in this area fails to stretch from cavity bottom to pulp - (early stage) dentine interface, then, the basic direction of dental tubule shall be complied with during the measurement. Calculate inflammatory response index in each experimental cycle, namely, add the grading score of each section together, then, divide it by the total number of sections being observed.

In experimental data, experimental materials (including lining materials and treatment agents recommended by manufacturers), and results of negative control and positive control shall be listed out respectively. Cavity that's filled with positive control materials can adopt previous data that's acquired under the same experimental conditions. In addition, record the number of cavity bottoms or side walls with bacteria in experimental materials and control materials in each experimental cycle. In accordance with the above-mentioned grading standard, measurable maximum thickness range of residual dentine and observed bacterial microleakage amount, determine inflammatory response index of experimental materials in each experimental cycle.

7.5 Odontoblast Survival Analysis (optional)

In terms of odontoblast survival analysis in tissue formation, select at least 5 sections that are distributed in equal intervals along cavity bottom. Conduct H-E staining, select distinguishable cells with visibility of the whole pulp on cavity bottom - (early stage) dentine interface, then, observe under amplified times. Use cell counter to calculate the number of odontoblasts with integral formation that's contained within the unit length of the whole pulp on cavity bottom - (early stage) dentine interface. This interface refers to the position that links up cavity bottom through dentinal tubule, as it is shown in Figure 1.