title: Composite resin's adhesive resistance to dentin: influence of Er:YAG laser focal distance variation.
abstract: The aim of this study was to analyze in vitro the influence of Er:YAG laser focal distance variation on tensile bond strength of a composite resin to dentin. Although there are several studies using the Er:YAG laser for dentin treatment, there is a lack of available literature related to the Er:YAG laser focal distance variation. Sixty vestibular and lingual dentin surfaces from extracted human third molars, kept in a 0.4% azide sodium solution, were ground and assigned to six groups. The control group was conditioned with 35% phosphoric acid (CA). In the lased groups, the dentin surface treatment was performed by irradiation with Er:YAG laser (80 mJ/2 Hz), varying the focal distance (11, 12, 14, 16, and 17 mm), followed by acid etching. The Single Bond/Filtek Z250 (3M) resinous system was used for the specimen manufacture. The tensile bond strength tests were performed in a Universal Testing Machine with 50 kgf load cell and 0.5 mm/min cross head speed. The averages in MPa were: CA: 18.03 (+/-2.09); 11 mm; 9.92 (+/-3.34); 12 mm: 9.49 (+/-2.29); 14 mm: 10.99 (+/-3.45); 16 mm: 10.56 (+/-1.93); and 17 mm: 17.05 (+/-2.31). It was concluded that the application of Er:YAG laser in a defocused mode (17 mm) associated with acid etching was similar to the treatment of acid solely. Er:YAG laser irradiation in a focused (12 mm) and a defocused (11, 14, and 16 mm) mode coupled with acid conditioning produced the lowest values of adhesion.
authors.affiliation: Ribeirão Preto School of Dentistry, University of São Paulo, São Paulo, Brazil. nelsoncorona@uol.com.br
authors.forename: Silmara Aparecida Milori
authors.initials: SA
authors.lastname: Corona
authors.forename: Juliana Abdallah
authors.initials: JA
authors.lastname: Atoui
authors.forename: Daniela Thomazatti
authors.initials: DT
authors.lastname: Chimello
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Borsatto
authors.forename: Jesus Djalma
authors.initials: JD
authors.lastname: Pecora
authors.forename: Regina Guenka Palma
authors.initials: RG
authors.lastname: Dibb
mesh_terms: D000134:Acid Etching, Dental; D000268:Adhesiveness; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry / Q000528:radiation effects*; D003188:Composite Resins / Q000737:chemistry / Q000528:radiation effects*; D001840:Dental Bonding; D003763:Dental Leakage / Q000517:prevention & control; D003793:Dental Restoration, Permanent; D017220:Dentin-Bonding Agents / Q000737:chemistry / Q000528:radiation effects*; D006801:Humans; D066298:In Vitro Techniques; D007834:Lasers; D008422:Materials Testing; D008963:Molar; D013718:Tensile Strength
chemical_list: D003188:Composite Resins; D017220:Dentin-Bonding Agents; C115612:single bond; D017438:Bisphenol A-Glycidyl Methacrylate