Manual and mechanical stripping-induced enamel roughness and elemental composition in vivo

Interproximal enamel reduction (IPR) is routinely used in orthodontics to generate small to moderate amounts of space within the dental arch. Aim of this ex vivo study was to evaluate the effect of two different IPR systems on the enamel surface's waviness, roughness, and elemental composition after 6 months of intraoral exposure.

Fifteen orthodontic extraction patients were included in the present study. The 39 healthy premolars, which were scheduled to be extracted, were subjected to IPR at least 6 months before their extraction. IPR was performed on their mesial side with two different methods: (1) instrumented method with the Ortho-Strips system (on handpiece) and (2) manually with the Intensiv ProxoStrip (strips)-each with four different grits for contouring, finishing, and polishing. The distal side of each premolar served as its own internal control. Treated and untreated tooth surfaces were evaluated by optical profilometry, Raman, and scanning electron microscope/X-ray energy-dispersive (EDX) analyses. Data were analysed with descriptive statistics and generalized linear models at alpha = 5%.

Both IPR methods significantly reduced the waviness of the enamel surface (P < 0.001), with manual IPR leading to smaller waviness reductions than the instrumented IPR (P ≤ 0.001). On the other side, both IPR methods led to a significant increase in enamel surface roughness (P < 0.001), with no significant differences between IPR methods. EDX and Raman analyses did not demonstrate any alterations on elemental composition of enamel after at least 6 months of intraoral exposure.

Both stripping systems led to a flatter but rougher enamel surface. Further polishing is needed to restore the initial enamel smoothness. The elemental composition of the stripped enamel returns to the baseline level after 6 months of intraoral exposure.