Response of associated oral soft tissues when exposed to Argon laser during polymerization of dental resins

Dentine bond strength of a composite resin polymerized with conventional light and argon laser

The use of argon laser (488 nm) has been suggested as a new alternative for polymerizing adhesive materials. This study aimed to evaluate the tensile bond strength of a microfilled composite (A110, 3M) inserted by incremental technique (3 increments of 1 mm) and by single increment (3 mm) polymerized by argon laser for 10, 20 and 30 seconds and halogen light for 40 seconds. Eighty (8 groups of 10 teeth) freshly extracted bovine teeth were stored in a freezer in distilled water for one week. The crowns were cross-sectioned from the roots. Pulpectomy was performed and the pulp chambers were sealed with wax. The buccal surfaces of the teeth were ground with wet sandpaper (grains: 120, 400, and 600) to expose the surface dentin, and the teeth were then included in acrylic resin. A metal device was used to fix each sample and a black propylene matrix25 (3 mm high with an internal millimetric delimitation) was used to insert the material according to the groups studied. The polymerization intervals were of 10, 20 and 30 seconds for the laser polymerization and 40 seconds for the conventional polymerization. Tensile tests were performed by a Universal Testing Machine 4442 (Instron) at a speed of 0.5 mm/min and 500 N load. According to the methodology used, the incremental technique increased bond strength values. There was no difference between the studied polymerization techniques when resin was filled in 3 increments.

Polymerization of dental composite resins using plasma light

Five visible light-cured composite resins used as restoration or adhesive materials in dentistry, were irradiated with high energy plasma light (1300 mW/cm2), and contraction, rate of contraction, irradiation-induced temperature were analysed. A comparison was carried out with the same materials irradiated with a conventional halogen light (400 mW/cm2). The exposure to the photoactivating lights was either continuously or sequentially in three or more intervals with 10 min between intervals. Comparing the lengths of exposure of both lights, which induced the same contraction in a given material, it was found that the exposure length to the plasma light was greatly reduced, when compared with the exposure length of the halogen light (1:10). Frequently, the final contraction of plasma-irradiated materials was lower, whereas the rate of contraction, as indicated by the linear dimensional variation curves obtained by laser beam scanning method, did not show significant differences between the two lights. The temperature increase induced by plasma light on the material did not exceed the temperature induced by conventional light.