Application of Spectrophotometry and Ion Chromatography for Monitoring the Chemical Stability of Dental Ceramics in an Acid Solution

Korozijski procesi dentalnih slitina dobro su znani. Za razliku od njih malo se zna o koroziji dentalne keramike i zato je svrha ove studije bila raščlamba kemijske stabilnosti dviju vrsta keramike u agresivnome kiselome mediju. Uzorci konvencionalne glinične keramike napečeni su na Co-Cr i Ni-Cr slitinu, a uzorak hidrotermalne keramike na visoko plemenitu zlatnu slitinu. Uzorci su bili pohranjeni u otopinu 10-3 mol/L HCl-a na 50°C 6 mjeseci. Otopine su analizirane nakon 1., 2., 3., i 6. mjeseca. Ioni Na+, K+, Ca2+ i Mg2+ bili su određeni ionskom kromatografijom (IC), a kvantitativne vrijednosti izlučenih Si4+ i Al3+ spektrofotometrijskom metodom. Gubitak težine uzoraka mjeren je analitičkom vagom, a promjena pH otopina pH-metrom. Rezultati su pokazali da je najjača eluacija iona u prva tri mjeseca, te da je izlučivanje bilo znatno manje nakon toga razdoblja iz svih uzoraka. Najznačajnije izlučivanje iona i gubitak težine pokazao je uzorak s hidrotermalnom keramikom. U svim su otopinama nastale promjene u pH vrijednosti, a stabilizirale su se nakon 3. mjeseca od početka istraživanja. Zaključak je da zubna keramika nije kemijski stabilna u kiselome mediju.The corrosive process of dental alloys is very well known, although little information is available on the corrosion of dental ceramics. The aim of this study was the analysis of the chemical stability of two dental ceramics in an aggressive acid medium. Two samples of feldspathic ceramic fused to Co-Cr and Ni-Cr alloy and a sample of hydrothermal ceramic fused to high-noble gold alloy were deposited in 10-3 mol/L HCl at 50°C during six months. The solutions were analysed after one, two, three and six months. The determination of Na+, K+, Ca2+ and Mg2+ was performed by ion chromatography (IC), the quantities of the eluted Si4+ and Al3+ were determined by spectrophotometric method and the weight loss of each sample was measured by an analytical scale. The changes of the pH values were determined by means of a pH meter. The results showed that most ions were eluted after the first three months, while after that period of time elution was significantly lower in each sample. The sample with hydrothermal ceramic showed the most significant elution and the highest weight loss. The pH values changed in each leachate sample, but stabilised after the 3rd month of the investigation. It can be concluded that dental ceramics are not stable in an acid medium