Amalgam type, adhesive system, and storage period as influencing factors on microleakage of amalgam restorations

The penetration of oral fluids and bacteria at the interface between the preparation walls and amalgam restorations, known as marginal microleakage, continues to be a problem in restorative dentistry. Microleakage may result in secondary caries and the irritation of the pulp.

This study evaluated the effect of amalgam type, adhesive system, and storage period on microleakage of amalgam restorations.

Eighty human premolars and molars were divided randomly into 8 equal groups of 10 teeth each. A combination of 2 different types of amalgam alloys (Spherodon and Nogama-2) and 2 bonding agents (Resinomer and High-Q-Bond) were used to restore Class V preparations. After thermocycling for 750 cycles (4 degrees C and 60 degrees C for 1-minute dwell times), the teeth were stored in a corrosive solution (modified Fusayama solution). The mean depth of fuchsin dye penetration was evaluated after an immersion period of 14 days and 180 days. The data were analyzed with a 3-way analysis of variance model and Wilcoxon paired signed rank test (alpha=.05). Main effects (aging time, amalgam, and adhesive), as well as possible interactions, were included in the model.

Significant differences were found in all analyzed combinations. The 3-way interaction between time, restoration, and adhesive was significant (P=.04 and P=.015 for the cervical and occlusal margin, respectively). After long-term storage, dye penetration values decreased in all groups and reached a lower level compared with short-term storage (range of 0.42 mm to 0.83 mm versus 0.61 mm to 3.6 mm for the long and short term, respectively).

An adhesive bonding agent may affect microleakage in the short term. However, in the long term the effect of the adhesive does not appear to be the dominant factor in reducing microleakage around amalgam restorations.