Experimental approaches to assess the effect of composition of abrasives in the cause of dental microwear

Abstract

Dental microwear is used to investigate feeding ecology. Animals ingest geological material in addition to food. The full effect of geological abrasives on tooth wear is unknown. To evaluate mineralogical abrasives as tooth wear agents, rats were fed food manufactured with quartz silt, diatomaceous earth, and calcium carbonate. Rats were assigned to treatments and fed for 15 days. Molars were scanned with a Sensofar Plu Neox confocal microscope and evaluated using ISO-25178-2 parameters and traditional microwear variables using light microscopy. Using a pellet-diet as the control, all treatments had influence on microwear and discriminant function analyses indicated that unique surface textures had been produced. ISO variables with high discriminatory values were correlated to scratch and pit frequencies, but more ISO parameters identified changes associated with numbers of scratches than changes associated with pits. The microwear changes associated with the abrasive inclusions were co-dependent on the type of diet that the abrasives had been added to. The abrasives had less effect with pellets but produced more modified and more differentiated microwear when added to the transgenic dough. Although abrasives produce distinctive surface textures, some knowledge of the properties of food with the abrasives is needed to identify the abrasive agent.

Keywords: abrasives; dental microwear; experimental animals; surface metrology.

Figure 1.

Outline of basic research design where rats were fed seven experimental diets and compared with a control diet composed of standard pellet chow.

Figure 2.

(a) Upper molar row showing targeted area of analysis on the right upper second molar; (b) colour topography map with colour Z scale; (c) greyscale photo simulation of the same surface.

Figure 3.

Greyscale photo simulations for each feeding treatment. The shown images display numbers of pits and scratches that are near the mean for each treatment (figure 4) are roughly representative of the average surfaces of each feeding treatment.

Figure 4.

Box and whisker plots of individual ISO parameters for each feeding treatment. Asterisk denotes significant differences from other feeding treatments according to Tukey's post hoc tests (table 2). Only those parameters with significant results are included. Green boxes are pellet diets, blue boxes are dough diets.

Figure 5.

Means and standard errors of TS (total scratches) and TP (total pits).

Figure 6.

Pearson correlation coefficients comparing TS (total scratches) and TP (total pits) with ISO parameters.

Figure 7.

Outlines of areas occupied by the eight feeding treatments on discriminant functions one (x-axis) and two (y-axis) for three discriminant function analyses involving the TM data, ISO data, and total evidence analysis where ISO and TM data are combined. These results are based on the analysis of raw data. Expanded plots with individual data points are in the electronic supplementary material.

Figure 8.

Absolute values of canonical loadings of ISO variables based on total evidence analysis of raw data versus Pearson correlation coefficients with TM variables (a) narrow scratches (NS) for DF1, and (b) large pits (LP).

Figure 9.

Total discriminatory power of each variable resulting from the total evidence analysis of raw data where ISO and TM data are combined.