Background: The aim of this study was to assess the influence of externally applied 'command set' methods on the microleakage of several glass ionomer cements (GICs). Methods: Four different restorative GICs were cured using three different methods: standard curing (SC), ultrasonic excitation (UC) and by an external heat source (HC). Different conditioning agents (10% polyacrylic and 10% citric acid) were used. The sample comprised 180 teeth with 360 Class V restorations placed on the lingual and vestibular tooth surface. After thermocycling, the teeth were immersed in a dye solution for 24 hours, embedded in acrylic resin, sectioned and evaluated. Oberholtzer criteria were used for margin evaluation. Data were analysed using three-way ANOVA. Results: The heat cured GIC showed statistically significant better marginal adaptation compared to the other tested groups (SC, UC) (p < 0.001). GICs in groups with HC and conditioned cavities had lower microleakage scores. The highly viscous material Fuji IX GP Fast in the HC and conditioned cavities group demonstrated the best marginal adaptation. The other three products reacted similarly to heating treatment. Leakage at the enamel margins was significantly lower than the cementum ⁄ dentine margins (p < 0.001). Conclusions: Heating the GIC during setting decreased microleakage, improved marginal adaptation of the GIC restoration and is suitable for clinical practice.

Under clinical conditions, conventional glass-ionomer dental cements can be cured by application of heat from dental cure lamps, which causes acceleration in the setting. In order for this to be successful, such heat must be able to spread sufficiently through the cement to enhance cure, but not transmit heat so effectively that the underlying dental pulp of the tooth is damaged. The current study was aimed at measuring heat transfer properties of modern restorative glass-ionomers to determine the extent to which they meet these twin requirements. Three commercial glass ionomer cements (Ionofil Molar, Ketac Molar and Equia™ Fill) were used in association with three different light emitting diode cure lamps designed for clinical use. In addition, for each cement, one set of specimens was allowed to cure without application of a lamp. Temperature changes were measured at three different depths (2, 3 and 4 mm) after cure times of 20, 40 and 60 s. The difference among the tested groups was evaluated by ANOVA (P < 0.05) and post hoc Newman-Keuls test. All brands of glass-ionomer showed a small inherent setting exotherm in the absence of heat irradiation, but much greater temperature increases when exposed to the cure lamp. However, temperature rises did not exceed 12.9 °C. Application of the cure lamp led to the establishment of a temperature gradient throughout each specimen. Differences were typically significant (P < 0.05) and did not reflect the nominal power of the lamps, because those lamps have variable cooling systems, and are designed to optimize light output, not heating effect. Because the thermal conductivity of glass-ionomers is low, temperature rises at 4 mm depths were much lower than at 2 mm. At no time did the temperature rise sufficiently to cause concern about potential damage to the pulp.

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