Influence of irradiation by a novel CO2 9.3-μm short-pulsed laser on sealant bond strength

Abstract

The objective of this in vitro study was to evaluate whether irradiation of enamel with a novel CO 9.3-μm short-pulsed laser using energies that enhance caries resistance influences the shear bond strength of composite resin sealants to the irradiated enamel. Seventy bovine and 240 human enamel samples were irradiated with a 9.3-μm carbon dioxide laser (Solea, Convergent Dental, Inc., Natick, MA) with four different laser energies known to enhance caries resistance or ablate enamel (pulse duration from 3 μs at 1.6 mJ/pulse to 43 μs at 14.9 mJ/pulse with fluences between 3.3 and 30.4 J/cm, pulse repetition rate between 4.1 and 41.3 Hz, beam diameter of 0.25 mm and 1-mm spiral pattern, and focus distance of 4-15 mm). Irradiation was performed "freehand" or using a computerized, motor-driven stage. Enamel etching was achieved with 37% phosphoric acid (Scotchbond Universal etchant, 3M ESPE, St. Paul, MN). As bonding agent, Adper Single Bond Plus was used followed by placing Z250 Filtek Supreme flowable composite resin (both 3M ESPE). After 24 h water storage, a single-plane shear bond test was performed (UltraTester, Ultradent Products, Inc., South Jordan, UT). All laser-irradiated samples showed equal or higher bond strength than non-laser-treated controls. The highest shear bond strength values were observed with the 3-μs pulse duration/0.25-mm laser pattern (mean ± SD = 31.90 ± 2.50 MPa), representing a significant 27.4% bond strength increase over the controls (25.04 ± 2.80 MPa, P ≤ 0.0001). Two other caries-preventive irradiation (3 μs/1 mm and 7 μs/0.25 mm) and one ablative pattern (23 μs/0.25 mm) achieved significantly increased bond strength compared to the controls. Bovine enamel also showed in all test groups increased shear bond strength over the controls. Computerized motor-driven stage irradiation did not show superior bond strength values over the clinically more relevant freehand irradiation. Enamel that is made caries-resistant with CO 9.3-μm short-pulsed laser irradiation showed at least equal or significantly higher shear bond strength to pit and fissure sealants than non-laser-irradiated enamel. The risk of a sealant failure due to CO 9.3-μm short-pulsed laser irradiation appears reduced. If additional laser ablation is required before placing a sealant, the CO 9.3-μm enamel laser-cut showed equivalent or superior bond strength to a flowable sealant.

Pit and Fissure Sealants—A Comprehensive Review

“…Differences of the fissure morphologies are visualized in Figure 1 . Long-term success of the resin-based materials might also be influenced by the use of a bonding system [ 10 , 48 , 49 ] and various pretreatment strategies such as laser irradiation [ 50 ], air abrasion of the tooth surface [ 51 ], or preheating of the sealing material [ 52 ].…”

Influence of Laser and Ozone Pretreatment on the Shear Bond Strength of Fissure Sealants: An In Vitro Comparative Study

“…In contrast, other studies have reported enhanced bond strength or no effect on enamel bond strength with the use of laser technology. 46,47 This is possibly because of the use of different energy levels and application modes.…”

Effects of 9,300 nm Carbon Dioxide Laser on Dental Hard Tissue: A Concise Review

“…Sub-ablative irradiation on an enamel surface before etch-and-rinse could increase the shear bond strength of composite resin to enamel. 38 However, compared to etch-and-rinse, ablative irradiation before etching cannot enhance shear bond strength of enamel to resin. [38][39][40] The high irradiation energy causes thermal damage to enamel.…”

“…38 However, compared to etch-and-rinse, ablative irradiation before etching cannot enhance shear bond strength of enamel to resin. [38][39][40] The high irradiation energy causes thermal damage to enamel. Large white asperities can be formed on the enamel surface when ablated with high energy.…”