The repeatability of human dentine permeability measurement in vitro.

OBJECTIVE: The aim of this study was to determine the repeatability of apparatus designed to assess dentine permeability at two different pressures. METHOD: Forty-five human coronal tooth portions were prepared and permeability was measured at two separate time points, 5h apart, at 14 cm H2O pressure and then at 100 cm H2O pressure. Repeatability was determined using the limits of agreement (LOA) method. RESULTS: The results showed equal mean permeability of 0.6 microl at both time 1 and time 2 at 14 cm H2O pressure, and 2.7 and 2.5 microl at time 1 and time 2, respectively, at 100 cm H2O pressure. At 14 cm H2O pressure, the LOA were (-0.4, 0.4)microl and at 100 cm H2O pressure the LOA were (-0.2, 0.6)microl. CONCLUSION: Although repeatability measurement at 14 cm H2O pressure appeared to be acceptable, the higher permeability values at 100 cm H2O pressure may make the latter the pressure of choice despite the small bias.

The permeability of natural dentine caries before and after restoration: An in vitro study.

OBJECTIVES: The objectives of this experiment were to determine in vitro the permeability of teeth exhibiting a range of natural dentine caries and the effects of caries excavation and subsequent restoration on the dentine permeability of extracted teeth. METHODS: Forty-five human permanent molars with obvious occlusal caries were selected and coronal dentine permeability was measured before (baseline) and after caries excavation, as well as after acid etching the prepared cavity and finally, after restoration. RESULTS: The small permeability values for all teeth made statistical testing between the different stages of specimen preparation both meaningless and inappropriate. An alternative means of examining the data was to calculate the percentage of teeth which had exhibited permeability values greater than zero at each of the four specimen preparation stages. The percentage of teeth with permeability greater than zero remained unchanged before and after cavity preparation (23%). Removal of the smear layer, however, increased substantially the percentage of teeth demonstrating permeability greater than zero, to 72%. None of the restored teeth demonstrated measurable permeability. CONCLUSION: The teeth chosen exhibited a range of dentine caries and, surprisingly, demonstrated either low or no measurable permeability. This experiment highlighted the need for more investigation into the quality of carious-affected dentine and the properties of the smear layer produced from such dentine.