Evaluating the effect of preheating on resin composites in pit-and-fissure caries treatments with a digital intraoral scanner.

Abstract

To evaluate the effect of preheating on the microleakage and surface hardness of resin composites in the treatment of pit-and-fissure caries with various widths,as measured by an intraoral scanner. A total of 153L-shaped cavities with different widths (1mm, 1.6mm and 2mm) were prepared on the buccal or palatal/lingual surfaces of human molars. The cavities were measured in three dimensions by a TRIOS scanner and then filled with various resins (room temperature Z350 flowable resin and room temperature and 60℃ Z350 universal resin). Microleakage and gap formation at 2 sites were evaluated by stereomicroscopy and scanning electron microscope. Resin samples were prepared, and the top surface Vickers hardness (VHNtop) of all samples was measured at 1day and 30 days postirradiation. No difference were observed in the 3D scans for the cavities sizes among groups with the same width. For the 1mm-wide cavity, the lowest microleakage was obtained with the flowable group; for the 1.6mm-wide cavity, the nonpreheating universal group showed the highest microleakage at site 1, and the preheating group exhibited lower microleakage than that of the nonpreheating universal group at site 2; and for the 2mm-wide cavity, the preheating group presented lower microleakage at site 2. The gap formations were consistent with the microleakage degrees. The preheating group exhibited the highest VHNtop at 1day and 30 days postirradiation. A digital intraoral scanner could be used to scan the cavities in three dimensions. Preheating technology could reduce the microleakage of Z350 universal resin and enhance its surface hardness.