Preparation and Measurement of Artificial Enamel Lesions, a Four-Laboratory Ring Test

Abstract

Transversal microradiography is the most widely accepted method used to study changes in mineral content profiles. In spite of its widespread use, relatively little information is available on its validity and reproducibility. Following the recommendation of the Consensus Conference on Intraoral Model Systems, this study was designed to explore reproducibility of lesion analysis within a laboratory and comparability of analysis among various laboratories. Incipient enamel lesions were produced by four research groups using both a common (‘standard’) and a local (‘preferred’) protocol. Sections were produced by each group and allocated to ‘mixed’ bags of specimens, which were analysed by the groups. With the chosen scheme some sections were analysed six times by the same group (as an internal reference standard) while others were analysed by all four groups. The data for the mineral content profiles were expressed as the integrated mineral loss (IML) value and lesion depth. The results showed the lesions produced with the standard protocol to be in the range 2,000–3,000 vol% mineral × μm for IML. The IML of the lesions produced with the preferred protocol varied between 1,800 and 6,300 vol% mineral × μm. Variation in IML values could be attributed to the biological variation between lesions, but also to time (of microradiograph production) and measurement effects, calibration of the magnification of the specimens, and the parameters used in the algorithm to calculate IML. Some of these parameters also affected the lesion depth. It is advised to standardise (or at least report) the method of calculation of IML, and to include a reference lesion between analyses in a longitudinal study as an internal standard. With the data produced, it was calculated that the number of lesions required to differentiate between preventive treatments varied substantially among laboratories. The recommendations given will improve the power of the screening methods for caries-preventive agents for which microradiography is an essential analytical method.

Monitoring remineralization of enamel subsurface lesions by optical coherence tomography

“…Second, subsurface lesions were then formed on the remaining surface using the two-layer demineralization method with 8% methylcellulose gel (Methocel MC; Fluka, Everett, Washington) and 0.1 M lactate buffer (pH 4.6) at 37°C for 14 days. 27 The ratio of gel to lactate buffer was 3:5, respectively. After demineralization, the blocks were sterilized by ethylene oxide gas sterilizer (Steri-Gas; 3M, St. Paul, Minnesota).…”

An approach to normalizing micro-CT depth profiles of mineral density for monitoring enamel remineralization progress

“…After the lesion formation, the specimens were remineralized for 4 weeks at 37˚C in a remineralization solution (20 mL per specimen) containing 1.5 mM CaCl2, 0.9 mM KH2PO4, 130 mM KCl and 20 mM HEPES (pH 7.0) 10 . The solution was renewed every week ( Fig.…”

The effects of lesion baseline characteristics and different Sr:Ca ratios in plaque fluid-like solutions on caries lesion de- and remineralization

“…Lesion protocols were chosen based on preliminary studies. MeC have been employed in many previous studies, 4,16 whereas CMC and SOLN were chosen to represent lesions with more pronounced although similar surface layers, yet different degrees of lesion body mineralization (Table 2). While there is no consensus among researchers with regards to what constitutes a suitable in vitro caries lesion, the three chosen protocols are representative of the broad spectrum of available laboratory lesions.…”

“…In vitro incipient caries lesions were prepared using the following three methods as (unpublished) pilot studies revealed significant differences in the resulting lesions' mineral distributions: For MeC, the method used by ''Laboratory D'' as described by ten Cate et al 16 Lesions were created at 20 ml gel and/or 20 ml solution per specimen and at 37 8C.…”