The measurement of degradation and wear of three glass ionomers following peroxide bleaching

Summary Objectives. To investigate, for three glass ionomer dental materials, the effects of a hydrogen peroxide solution on the elution of key elements, and the effects of a novel 6% hydrogen peroxide tooth whitening gel on subsequent wear rates with a toothpaste slurry. Methods. Discs specimens of three glass ionomers (ChemFlex, Fuji II and Ketac-Fil) were prepared. One set of discs was exposed to either 6% hydrogen peroxide in phosphate buffer, phosphate buffer, water, a carbonated beverage or 38% orthophosphoric acid for 60 min. The ions eluted from the discs were determined by inductively coupled plasma—optical emmision spectroscopy. A second set of discs were conditioned with either a 6% hydrogen peroxide gel (30 min), water (30 min), a carbonated beverage (2 min) or 38% orthophosphoric acid gel (2 min) followed by a three-body abrasive wear treatment (2 min) with a toothpaste slurry. Changes in height of the samples were measured with a digital comparitor. The conditioning and abrasive cycles were repeated thirteen times. Results. For the elution study, the solutions gave only minor release of sodium except orthophosphoric acid which showed increased elution levels of aluminium, silicon and sodium ions. For the wear study, the orthophosphoric acid gave the highest level of wear whilst for the other treatments there were no statistical significant differences in the level of wear (one-way ANOVA). Conclusions. A 6% hydrogen peroxide solution did not cause significant dissolution, and a novel 6% hydrogen peroxide tooth whitening gel did not significantly increase the three-body wear rate of any of the materials tested.