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Laser irradiation after adhesive and before polymerization
Lasers Laser irradiation after adhesive and before polymerization Background.—The use of laser irradiation to modify hard tissues permits various responses between the tooth and restorative materials. Among the properties affected are permeability, microhardness, and resistance to acid attack. When Nd:YAG laser irradiation is applied before the adhesive procedure, bond strength with the resin composite is reduced because irradiation depletes the number of dentinal tubules present. This approach is not recommended. The results that occur when laser irradiation is applied over the adhesive and before polymerization are largely unexplored. Methods.—The 12 sound molars used for the investigation were sectioned transversely and abraded to remove occlusal enamel. In the adhesive procedure, acid etching of the surfaces was accomplished with use of 35% phosphoric acid for 15 seconds. The dentin was washed, then 2 layers of a 1-bottle adhesive were applied and air dried for 5 seconds. The Nd:YAG laser irradiation was accomplished before polymerization of the adhesive. After irradiation, the adhesive underwent 20 seconds of photopolymerization with a Visiolux 2 apparatus. The teeth were divided into groups depending on the amount of energy density deposited at the tooth surface (L5, L10, and L50 for laser energy densities of 5, 10, and 50 J/cm2), with nonirradiated halves serving as controls (L0). All teeth received applications of resin composite (Filtek Z-250) to build up a resin block about 5 mm above the teeth. The restored teeth were sliced using a diamond wheel saw to produce prismatic samples; 1 half had dentin and the other half had resin composite. Bond strength measurements were analyzed using 1-way analysis of variance and least significant difference assessments. Results.—The L5 group had the greatest microtensile values, which were statistically significantly greater than the other groups. The L50 group had the lowest mean microtensile value and differed significantly from the
other groups. All samples fractured at the interfacial region, with propagation along the dentin, adhesive, or composite. Deeper infiltration of the adhesive agent in the dentinal tubules was noted in L5 teeth compared with the controls. Discussion.— The use of laser irradiation before bonding produces tissue depleted of the dentinal tubules, complicating adhesive infiltration and micromechanical retention. In teeth filled using an adhesive technique, use of the laser for caries removal is also not advisable. Dentin irradiation with the Nd:YAG laser after applying the adhesive but before polymerization may influence microtensile bonding strength. The use of low energy densities, such as 5 J/cm2, heats the dentin and permits better penetration of the adhesive and resulting higher bond strengths. When the energy density is too high, bond strength is reduced.
Clinical Significance.—Laser irradiation before bonding leads to blockage of dentinal tubules, reducing adhesive penetration and micromechanical retention. As such, laser use for caries removal is contraindicated if bonded restorations are planned. However, use of lowenergy laser to warm the dentin after etching and adhesive application but before photopolymerizing increased adhesive penetration and thus increased bond strength.
Franke M, Taylor AW, Lago A, et al: Influence of Nd-YAG laser irradiation on an adhesive restorative procedure. Oper Dent 31:604-609, 2006 Reprints available from M Franke, Caixa Postal 476, 88040-900 Floriano´polis, SC, Brazil; e-mail: [email protected]
Laser frenectomy Background.—The folds of mucous membranes attaching the lips and cheeks to the alveolar mucosa and/ or gingiva and underlying periosteum are called frenums and can cause problems. If the frenum encroaches on the gingival margin, plaque removal may be inhibited. Tension on the frenum can open the sulcus so that plaque
176
Dental Abstracts
accumulates and effective toothbrushing is difficult. Surgical removal of the frenum can be required. Frenectomy can be accomplished conventionally using scalpels and periodontal knives or by using a soft tissue laser. These 2 methods were compared in terms of pain experienced postoperatively.
other groups. All samples fractured at the interfacial region, with propagation along the dentin, adhesive, or composite. Deeper infiltration of the adhesive agent in the dentinal tubules was noted in L5 teeth compared with the controls. Discussion.— The use of laser irradiation before bonding produces tissue depleted of the dentinal tubules, complicating adhesive infiltration and micromechanical retention. In teeth filled using an adhesive technique, use of the laser for caries removal is also not advisable. Dentin irradiation with the Nd:YAG laser after applying the adhesive but before polymerization may influence microtensile bonding strength. The use of low energy densities, such as 5 J/cm2, heats the dentin and permits better penetration of the adhesive and resulting higher bond strengths. When the energy density is too high, bond strength is reduced.
Clinical Significance.—Laser irradiation before bonding leads to blockage of dentinal tubules, reducing adhesive penetration and micromechanical retention. As such, laser use for caries removal is contraindicated if bonded restorations are planned. However, use of lowenergy laser to warm the dentin after etching and adhesive application but before photopolymerizing increased adhesive penetration and thus increased bond strength.
Franke M, Taylor AW, Lago A, et al: Influence of Nd-YAG laser irradiation on an adhesive restorative procedure. Oper Dent 31:604-609, 2006 Reprints available from M Franke, Caixa Postal 476, 88040-900 Floriano´polis, SC, Brazil; e-mail: [email protected]
Laser frenectomy Background.—The folds of mucous membranes attaching the lips and cheeks to the alveolar mucosa and/ or gingiva and underlying periosteum are called frenums and can cause problems. If the frenum encroaches on the gingival margin, plaque removal may be inhibited. Tension on the frenum can open the sulcus so that plaque
176
Dental Abstracts
accumulates and effective toothbrushing is difficult. Surgical removal of the frenum can be required. Frenectomy can be accomplished conventionally using scalpels and periodontal knives or by using a soft tissue laser. These 2 methods were compared in terms of pain experienced postoperatively.