Attrition of primary enamel against primary enamel

Purpose: This study determined the average amount of natural attrition produced in deciduous and permanent teeth over a 4 year equivalent using an in-vitro model.;Materials and Methods: A total of 32 human teeth were used as specimens. After bucco-lingual sectioning of 8 human primary teeth and 8 human permanent teeth, they were cast in acrylic blocks with the area presenting the most intact and flat enamel surface exposed (worn teeth). Antagonists were created using cusps sectioned from another 8 human primary teeth and another 8 human permanent teeth and mounted on stylus tips (wearing teeth). The specimens were distributed into two groups, primary and permanent teeth, scanned via CAD-CAM, and cycled 800,000 times in the Leinfelder style in-vitro wear-test apparatus with a mixture of PMMA beads and deionized water. Specimens were cleaned, scanned using CAD-CAM, and wear measured via E4D's Compare software. Maximum depth (z-axis), width (x-axis), and length (y-axis) were determined on the specimens. Data was analyzed and the x (width) and z-values (depth) submitted to t-test for independent samples and the y-axis (length), which did not follow a normal distribution, submitted to Mann-Whitney U test.;Results: For primary worn teeth (flat surfaces), the average x-axis (width) wear was 1287 microns, y-axis (length) wear was 1767 microns, and z-axis (depth) was 113 microns. For primary wearing teeth (cusp tips), the average x-axis (width) was 1371 microns, y-axis (length) was 1188 microns, and z-axis (depth) was 123 microns. For permanent worn teeth (flat surfaces), the average x-axis (width) was 902 microns, y-axis (length) was 720 microns, and z-axis (depth) was 20.5 microns. For permanent wearing teeth (cups tips), the average x-axis (width) was 2133 microns, y-axis (length) was 1054 microns, and z-axis (depth) was 260 microns. The worn primary teeth (flat surfaces) wore significantly more in all axes than the permanent worn teeth. The wearing permanent teeth (cusp tips) wore significantly more than the primary wearing teeth in the x-axis (width) and the z-axis (depth) with no significant difference in the y-axes.;Conclusion: Although enamel wear is documented in both groups, the amount of in-vitro wear was statistically greater among primary enamel than permanent enamel with respect to worn (flat) surfaces.