Ionic Exchange from Glass-ionomer with Ultrasonic Excitation for Tunnel Restoration

Objectives: This study investigated mineral exchange and surface hardness changes of the demineralized tooth surface using glass-ionomer cement with ultrasonic excitation in tunnel restoration.

Materials and methods: Fifty four extracted, intact permanent premolar teeth were used in this study. Artificial caries were produced on both sides of external proximal surfaces using 4% carboxymethylcellulose gel (pH 4.8, at 37oC) for 5 weeks. Closed tunnel cavity was prepared on both mesial and distal of tooth prior to be restored with glas-ionomer cement (Ketac silver, 3M ESPE). Only on, internal distal cavity was softened by phosphoric acid 37 % (5 mins) before restoration. The specimens were managed into 3 groups: restoration with GI excited using ultrasonic for 10seconds (U-GIC), GI without ultrasonic excitation (GIC) and Group 3 without any restoration (N-GIC). Simulating dentinal fluid was done by injecting Lactated Ringer's solution into pulp chamber and apical sealed with wax. All specimens were kept in deionised water (37oC). Microhardness measurements were performed on tooth surface around restoration at commencing time. Energy dispersive X-Ray spectrometer (EDS) was used to identify mineral content of each area. Hardness values were analyzed with two way ANOVA and a Tukey test.

Results: There were no significant differences in surface hardness of tooth surfaces around the mesial tunnel restoration when compared to their control at 1,7,36 days. However, tooth surface (U-GIC, GIC) around the distal tunnel restoration were found a significant increase hardness values at 7, 36 days. Various elements from glass-ionomer cement were found in the tooth structure interface following using this material.

Conclusion: Applying of ultrasonic to glass-ionomer cement in tunnel restoration not only increase surface hardness of material but also increase hardness of demineralized lesion. Glass-ionomer cement could provide ionic exchange phenomenon to the tooth surface surrounding.