Effect of pH Cycling Frequency on Glass–Ceramic Corrosion

Abstract

The effect of pH changes on the chemical durability of dental glass–ceramic materials was evaluated using weight loss and ion release levels. The hypothesis that increased pH changes will exhibit greater corrosion was investigated. The ion concentration was analyzed using inductively coupled plasma atomic emission spectrometer (ICP). The surface compositions were investigated using X-ray photoelectron spectroscopy (XPS). The surface morphologies were examined using scanning electron microscopy (SEM). Dental glass–ceramics were tested in constant immersion, 3-day cycling, and 1-day cycling with pH 10, pH 2, and pH 7 for 3, 15, and 30 days. The 1-d cycling group demonstrated the highest levels of weight loss compared with 3-d cycling and constant immersion. For the ion release, Si4+ and Ca2+ had the highest rates of release in 1-d cycling, whereas the Al3+ release rate with constant pH 2 was highest. The alteration/passivation layer that was formed on the surface of disks possibly prevented further dissolution of pH 10 corroded disks. XPS analysis demonstrated different surface compositions of corroded disks in pH 10 and pH 2. Si4+, K+, Na+, Al3+, and Ca2+ were detected on the surface of corroded pH 10 disks, whereas a Si4+ and P5+-rich surface formed on corroded pH 2 disks. SEM results demonstrated rougher surfaces for corroded disks in cycling conditions and pH 2 constant immersion. In conclusion, increased pH changes significantly promote the corrosion of dental glass–ceramic materials.

Fracture of Lithia Disilicate Ceramics under Different Environmental Conditions

“…However, the strengths of the specimens exposed to pH cycling were about 50% less than the reference strengths. This agrees with earlier findings of the effect of pH cycling versus constant exposure on chemical durability [ 2 , 18 ]. These studies demonstrated that the increased frequency of pH changes significantly enhanced the corrosion of the glass-ceramic specimens.…”

“…Studies have demonstrated the significant surface degradation that occurs when ceramics are immersed in pH 2, 7 and 10 independently [ 1 ]. Other studies demonstrated that the effects on the surface are more deleterious when pH 2, 7 and 10 are cycled, that is, when samples are immersed in alternating pH solutions [ 2 , 18 ]. The researchers proposed a mechanism that occurs in glass-ceramics when pH environments are alternated, which is not only limited to ionic exchange but extends to dissolution of the silicon bonds and cleavage of the whole material.…”

Evaluation of surface changes in glass-ceramics submitted to artificial aging by simulated brushing

“…Previous studies evaluated the deterioration of glass ceramics by constant immersion in the solution for pH change. In these studies, the groups showed mass loss at different pHs (Esquivel-Upshaw et al, 2013;Esquivel-Upshaw et al, 2018;Hsu et al, 2020). The present work reveals an initial tendency of mass loss, which is evident in the low-abrasion EMX group, corroborating the findings of Hsu and collaborators (2020), who observed a loss of Si4+, K+, Na+, Al3+, and Ca2+ ions at pH 10, the same EMX toothpaste pH.…”

Effect of different surface treatments and thermomechanical aging on the ion elution of CAD-CAM materials

“…However, increasing the frequency of pH changes was reported to promote corrosion in glass-ceramics and increase the amount of Si elution compared with immersion in a constant pH environment. 20,21 Si, O, Ti, and Zr, the predominant elements of materials used in the present study, were not detected. These elements are present as chemical compounds formed with each other, which may explain this finding.…”

“…12 The chemical degradation and ion release of ceramics immersed in solutions has been investigated, 6,11,12,18,19 and they are also subjected to cyclic immersion. 20,21 However, the authors are unaware of studies on the effect of 2-body wear on the ion elution of monolithic CAD-CAM ceramics. The purpose of this in vitro study was to investigate the effect of surface treatment (glazed or polished) and thermomechanical aging on the ion elution of CAD-CAM materials before and after 2-body wear simulation.…”