VALIDITY OF ELECTRICAL CONDUCTANCE MEASUREMENTS IN EVALUATING THE MARGINAL INTEGRITY OF SEALANT RESTORATIONS

The use of sealants and sealant restorations has increased considerably over the past 10 years, and with it increased the problem of detecting secondary caries and marginal (micro)leakage. It was the purpose of this study to investigate the validity of electrical conductance measurements (ECMs) in diagnosing marginal leakage into dentine of sealants and sealant restorations. Ninety extracted premolar teeth were divided into three groups. Initial ECMs, denoted 'baseline ECMs', were conducted in all three groups by placing the probe tip of an Electronic Caries Monitor in the occlusal fissure which was filled with a dentifrice. The ECMs were divided by the area, yielding ECM/mm(2) values. In group A 30 teeth were treated to receive 'nonleaking sealants'. In the 30 teeth of group B a narrow groove was cut at the occlusal surface reaching the dentine and restored by the application of a sealant without etching of the adjacent enamel to create a high probability of marginal leakage. The samples in group C received the same treatment as those in group B, but in this group the enamel was etched to reduce the probability of marginal leakage. The ECMs subsequently conducted were denoted 'sealed/restored ECMs'. Teeth in groups B and C were thermocycled 700 times (4-67 degrees C) to provoke leakage, after which ECMs were conducted (denoted 'ECMs after thermocycling'). The teeth were immersed in fuchsin for 24 h and cut along the fissure system to validate marginal leakage. The electrical conductance decreased significantly from baseline to the sealed/restored stage in all groups (p < 0.05). The electrical conductance per unit area increased in groups B and C after thermocycling. The electrical conductance, irrespective of area, increased significantly after thermocycling (p < 0.05) only in group C. The sensitivities of ECMs per unit area and ECMs were 0.98 and 1.00, respectively, and the specificities were 0.77 and 0.79, respectively. The areas under the receiver operating characteristic curves of ECMs per unit area and ECMs were 0.94 and 0.96, respectively. There was no significant difference between the areas under both curves (p > 0.05), denoting that ECMs need not necessarily be expressed relative to the area of the electrode. It was concluded that marginal leakage into dentin of sealants and sealant restorations can be accurately detected by ECM.