Are encapsulated anterior glass-ionomer restoratives better than their hand-mixed equivalents?

The crushing truth about glass ionomer restoratives: Exposing the standard of the standard

“…For GI restoratives the reported standard deviation of the mean CFS is routinely 15% or less [20][21][22][23][24]. Employing power law statistics [44][45] (at a 95% power level) informs us that 20 or more samples is sufficient to show statistically significant CFS differences where standard deviations of groups are similar and the differences between groups is 15% (or more) of the mean CFS [20][21][22][23][24].…”

“…In the current statistical analysis the differences in the CFS data between the three GI restoratives was not of interest, as the reported CFS for GI restoratives vary in accordance with the dental literature [20][21][22][23][24][25][26][27][28][29][30][31][32][33]. As a result, the CFS data for each GI restorative was analysed individually, using three three-way ANOVAs (operator × mixing regime × batch) such that differences between the materials would not influence the analyses.…”

“…Encapsulated GI restoratives were employed in the current study as they offer significant advantages over their hand-mixed equivalents [20][21], by eliminating operator induced variability in the powder to liquid mixing ratios [22] and by standardising the mixing regime [20][21][23][24]. M a n u s c r i p t Prior to the commencement of testing, each operator manufactured and tested ten preliminary batches of five specimens to learn the specimen preparation technique.…”

“…To minimise air entrapment the nozzle of the capsule was positioned to one side of the unfilled cylindrical split-mould and the plastic mass extruded slowly to provide laminar flow [20][21]. The filled mould was covered with a second acetate strip and isolated from the surrounding environment with a glass slab.…”

“…During this time only a limited number of investigators have adopted alternative and potentially more valid strength determination methods for GIs in which the failure mode is reproducible [11][12][13][14][15][16][17][18][19]. In contrast, a significant body of evidence has been presented for GIs [20][21][22][23][24][25][26][27][28][29][30][31][32][33] which could account for the lack of reliability of the CFS test method observed in the 1990 test-house variability study [8]. It has been demonstrated that the proportioning of constituents [20][21][22]24,[37][38], mixing technique [20][21][23][24] and mould design [20][21][22][23][24][26][27][28][29][30][31][32]…”