CONTROLLING DENTIN PENETRATION IN COMPUTER MICROLEAKAGE TRACER MAPPING

Objectives. Microleakage tracer penetration tests in dentine with simp le sectioning are often confounded by dentine tubule penetration into the interface, leaching of water soluble tracers on wet sectioning, la ck of standardized cavity dimensions affecting stresses, inadequate se ctioning missing important tracer regions and airlocks obstructing tra cer entry. The present aim was to create high resolution maps of stain ed interfaces without these confounding factors.Methods: Ten intact ex tracted permanent upper central incisors were horizontally sectioned t hrough the upper root, one third of the root length from the mid-bucca l enamel limit. A dentine-bonded resin composite (Scotchbond MP, Z100, 3M) restoration was placed in a cylindrical cavity milled centrally i n the root face of the coronal portion of five teeth. Tubules were ang led at a mean of 12.5+/-4.8 degrees to the root face, and travelled ap proximately radially from the interface, such that tubule penetration was directed sufficiently radially outward to be distinguished from ve rtical interface penetration. Waterfast silver nitrate staining was ap plied with initial vacuum at 30 mmHg. A precision grinding machine ser ially removed approximately 100 mu m increments of the tooth until no tracer remained, and computer image analysis data for the 18 revealed surfaces were used to construct detailed interface tracer maps. Result s: Control specimen tubule penetration was directed sufficiently radia lly outward to permit tubule penetration to be isolated from vertical interface penetration in test specimens, and ignored. Interface penetr ation ranged from approximately 0.3 to 1.6 mm in depth, and 0.90 to 5. 09 mm(2) in area. Conclusions: This method provided quantitative stand ardized high resolution mapping of interface tracer penetration, uncon founded by dentine penetration. None of the interfaces was fully seale d. (C) 1997 Elsevier Science Ltd.