Experimental validation of mechanical oscillating IPR system

BACKGROUND: Interproximal enamel reduction (IPR) is a clinical procedure which involves reduction and anatomic recontouring of interproximal surfaces of enamel as a method of gaining space. The biological effects related to this clinical procedure have long been discussed. Thus, the aim of this study was to evaluate the enamel reduction efficiency and the effects on enamel surfaces of the oscillating mechanical system for interproximal enamel reduction (IPR). METHODS: Fifteen complete oscillating IPR sequences included one opener (0.1 mm), two metallic strips for active IPR phase (0.2 and 0.3 mm), three resin strips for active and initial polishing phases (0.4 and 0.5 mm), and one resin strip for polishing phase (0.15 mm). Sequences were selected and tested on fifteen freshly extracted teeth by means of tribological tests with alternative dry -sliding motion (Linear Reciprocating Tribometer; C.S.M. Instruments, Peseaux, Switzerland). A 3D analysis of treated surfaces was performed by using a TayMap software. Then, enamel surfaces were qualitatively evaluated before and after the tribological analysis, with a FEI Quanta 200 (FEI, Hillsboro, OR, USA) in high vacuum at 30.00 kV. Images were acquired at a 30x, 100x and 300x magnification. RESULTS: Minimum surface irregularities were observed on all treated enamel surfaces when compared with untreated ones. The 3D analysis showed a uniform wear pattern after tribological tests. Meanwhile, the SEM analysis revealed smooth and regular wear lines on treated surfaces after the entire mechanical IPR sequence. The macroscopic irregularities illustrated can be considered similar to those of untreated surfaces. CONCLUSIONS: The adoption of a standardized oscillating IPR sequence allows an efficient reduction of the interproximal enamel, leaving regular and harmonious surfaces. Adequate polishing procedures should always be performed at the end of active IPR phases in order to guarantee a good long-term prognosis and proper respect of biological structures.