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

The use of sealants and sealant restorations has increased considerabl y over the past 10 years, and with it increased the problem of detecti ng secondary caries and marginal (micro)leakage. It was the purpose of this study to investigate the validity of electrical conductance meas urements (ECMs) in diagnosing marginal leakage into dentine of sealant s and sealant restorations. Ninety extracted premolar teeth were divid ed into three groups. Initial ECMs, denoted 'baseline ECMs', were cond ucted in all three groups by placing the probe tip of an Electronic Ca ries Monitor in the occlusal fissure which was filled with a dentifric e. The ECMs were divided by the area, yielding ECM/mm(2) values. In gr oup A 30 teeth were treated to receive 'nonleaking sealants'. In the 3 0 teeth of group B a narrow groove was cut at the occlusal surface rea ching the dentine and restored by the application of a sealant without etching of the adjacent enamel to create a high probability of margin al leakage. The samples in group C received the same treatment as thos e in group B, but in this group the enamel was etched to reduce the pr obability of marginal leakage. The ECMs subsequently conducted were de noted 'sealed/restored ECMs'. Teeth in groups B and C were thermocycle d 700 times (4-67 degrees C) to provoke leakage, after which ECMs were conducted (denoted 'ECMs after thermocycling'). The teeth were immers ed in fuchsin for 24 h and cut along the fissure system to validate ma rginal leakage. The electrical conductance decreased significantly fro m 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, incr eased significantly after thermocycling (p < 0.05) only in group C. Th e sensitivities of ECMs per unit area and ECMs were 0.98 and 1.00, res pectively, 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 sign ificant difference between the areas under both curves (p > 0.05), den oting 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 .