Protective Buffer Capacity of Restorative Dental Materials In Vitro

Objectives: Restored teeth are exposed to acids in their oral environment. The aim of this study was to determine the buffer capacity of typical and experimental dental materials during a carious and intrinsic erosive attack.
Methods: Samples with a small cavity (130 µl) were milled out of composites (Quixfil¹, Ceram X Mono¹, Filtek Supreme², Apa Fill 3³), a compomer (Dyract eXtra¹), a giomer (Beautifil flow⁴), a pulp capping liner (Thera Cal⁵) and an experimental dual-curing composite containing a bismuth-doped bioactive glass⁶ using CEREC MCXL (Sirona) to create a standardized surface. 80 µl of acid (lactate with a pH 4.5 or hydrochloride acid with a pH 2.6) was added. The pH changes were measured over a period of 12 min using a calibrated pH-electrode (In Lab nano, Mettler Toledo).

¹Dentsply, ²3M ESPE,³Cumdente, ⁴Shofu, ⁵Bisco, ⁶smartodont
Results: After the HCl acid attack composite materials had no relevant buffer capacity, while compomers and giomers showed some buffering effect (p<0.05). The experimental bioactive glass-containing composite buffered most effectively (pH >9) and performed similar to the positive control group (liner). Following the lactate acid attack smaller pH-changes were measured as compared to the HCl. The experimental bioactive glass composite was again significantly more reactive than all other materials except for the positive control group. The buffering ability of the other dental materials was weaker; however, after 12 min, a neutral pH was induced by the majority of the tested materials.
Conclusions: While typical composites showed only limited reaction, compomers and giomers demonstrated effective buffering capacity against HCl. The behavior of the experimental bioactive glass composite demonstrates an interesting perspective in the development of protective properties of dental materials. Although a neutralization of the lactate attack could be achieved, it remains questionable, if it is clinically sufficient.