Surface pH of resin-modified glass polyalkenoate (ionomer) cements

The recently developed group of materials known as light-activated, or resin-modified, glass polyalkenoate (ionomer) cements have been produced in response to clinical demands for a command set cavity base material. This study monitored the surface pH of three commercially available resin-modified glass ionomer cements over a 60-min period following either mixing alone or mixing followed by a 30-s exposure to a curing lamp. The results indicate that each material behaves in a unique manner. For all materials and conditions the pH reached after a 60-min period was significantly (P < 0.001) higher than the initial value. Light curing the materials significantly increased (P < 0.01) the surface pH of two of the materials (Baseline VLC and Vitrebond) as compared to the same materials in the uncured state. In the case of XR-Ionomer, however, no significant (P > 0.05) effect of light curing upon the surface pH was apparent. The precise clinical consequences of a low surface pH are unclear but may be an aetiological factor in postoperative pulpal sensitivity. It is therefore recommended that a sublining of a proprietary calcium hydroxide lining material should be placed routinely beneath these materials and every effort made to ensure effective light curing.