Patrícia Moreira de Freitas

Bond Strength of Adhesive Systems to Er,Cr:YSGG Laser-Irradiated Dentin

OBJECTIVEnThe purpose of this study was to evaluate the effects of Er,Cr:YSGG laser irradiation and different adhesive procedures on bond strength of two bonding agents to dentin.nnnBACKGROUND DATAnStudies have shown that laser-irradiated dentinal tissue yields lower bond strengths than does nonirradiated dentin. In this study, different treatment methods of laser irradiating dentin were studied to enhance the bond strength of bonding agents to nonirradiated dentin.nnnMETHODSnThird molars were wet ground with SiC until the occlusal flat dentin surface was exposed, and the teeth were randomly assigned to six groups (n=5). A two-step self-etching primer (Clearfil SE Bond, G1) and a two-step etch-and-rinse adhesive (Single Bond Plus, G2) were applied to the nonirradiated dentin surface according to manufacturers instructions, as control groups. In G3 and G4, the same adhesives were applied after Er,Cr:YSGG laser irradiation, whereas in G5 and G6 adhesives were applied after Er,Cr:YSGG laser irradiation, phosphoric acid etching, and NaOCl deproteinization of etched dentin. The Er,Cr:YSGG laser worked at 2.78??m and the repetition rate was fixed at 20?Hz. Composite blocks were built on bonded surfaces and the teeth were stored for 24?h at 37?C. Restored teeth were vertically and serially sectioned to obtain bonded specimens for the bond strength test. Data were analyzed by two-way ANOVA and Tukey test (?=5%).nnnRESULTSnLaser irradiation reduced bond strengths for the two adhesives, regardless of acid etching and deproteinization of dentin post-irradiation (p<0.05). The self-etching primer system showed higher bond strengths to laser irradiated dentin than did Single Bond Plus (p<0.05). The adhesive systems applied to normal dentin yielded higher bond strengths than when they were applied to laser irradiated dentin (p<0.05).nnnCONCLUSIONSnThe self-etching primer seemed to be less affected by dentin irradiation with Er,Cr:YSGG laser. The additional etching and NaOCl solution did not overcome the effects of laser irradiation on dentin.

Shear bond strength after dentin bleaching with 10% carbamide peroxide agents

This in vitro study evaluated the shear bond strength (SBS) of dentin treated with two 10% carbamide peroxide bleaching agents 15 days after bleaching and storage in artificial saliva. Dentin fragments were randomly divided into 3 groups (n = 20) for the treatment with the two different bleaching agents (Rembrandt 10% or Opalescence 10%) or with a placebo agent, applied to the tooth surface for 8 hours a day. During the remaining time, the specimens were stored in artificial saliva. After 42 days, the fragments were stored in artificial saliva for 14 days. Another group (n = 20) was exposed to distilled and deionized water for 56 days. An adhesive system and microhybrid composite resin were used to prepare specimens for the SBS test. SBS tests were performed and the fractured surfaces were visually examined using a stereoscope at 30 x magnification. The analysis of variance (ANOVA) and SIDAK tests showed higher SBS values for dentin treated with Opalescence 10% than for dentin treated with Rembrandt 10% or placebo. Groups treated with Rembrandt 10%, Opalescence 10% or placebo did not differ from the group treated with distilled and deionized water. Ten percent carbamide peroxide agents or a placebo agent caused no differences in SBS of dentin after 15 days of storage in artificial saliva.

Argon and Nd:YAG Lasers for Caries Prevention in Enamel

OBJECTIVEnThe aim of this study was to investigate the effect of Nd:YAG and argon laser irradiations on enamel demineralization after two different models to induce artificial caries.nnnBACKGROUND DATAnIt is believed that the use of the high-intensity laser on the dental structure can lead to a more acid-resistant surface.nnnMATERIALS AND METHODSnTwenty-one extracted human third molars were sectioned into tooth quarters. The quarters were distributed in three groups: Group I (control), untreated; Group II, Nd:YAG laser (60 mJ, 15 pps, 47.77 J/cm(2), 30 sec); and Group III, argon laser (250 mW, 12 J/cm(2), 48 sec). Tooth quarters from each group were subjected to two different demineralization models: cycle 1, a 14 day demineralization (pH 4.5; 6 h) and remineralization (pH 7.0; 18 h) solutions, 37 °C and cycle 2, 48 h in demineralization solution (pH 4.5). Samples were prepared in slices (60-100 μm thick) to be evaluated under polarized light microscopy. Demineralization areas were measured (mm(2)) (n=11). Data were analyzed by ANOVA and Tukeys test (p<0.05).nnnRESULTSnMeans followed by different letters are significantly different: 0.25 A (control, cycle 48 h); 0.18 AB (control, cycle 14 days); 0.17 AB (Nd:YAG, cycle 14 days); 0.14 BC (argon, cycle 48 h); 0.09 BC (Nd:YAG, cycle 48 h), and 0.06 C (argon, cycle 14 days).nnnCONCLUSIONSnThe argon laser was more effective for caries preventive treatment than Nd:YAG laser, showing a smaller demineralization area in enamel.

Influence of Cavity Preparation with Er,Cr:YSGG Laser and Restorative Materials on In Situ Secondary Caries Development

OBJECTIVEnThe aim of this study was to evaluate the influence of cavity preparation and restorative materials containing fluorides in the prevention of secondary caries lesion development in situ.nnnMETHODSnA total of 120 blocks obtained from human teeth were divided into two groups and standardized cavities were prepared using diamond burs (DB) or Er,Cr:YSGG-laser [20u2009Hz, 4.0W, 55% water, 65% air (LA)]. They were divided into three subgroups according to the restorative material (n=20): glass-ionomer cement (GI), resin modified glass-ionomer (RM) or composite resin (CR). Blocks were fixed in palatal intra-oral appliances worn in situ by 20 human volunteers, who dropped 20% sucrose solution eight times daily. After 21 days, blocks were removed and restorations were cross-sectioned to evaluate microhardness [Knoop hardness number (KHN)] underneath enamel surface from 30 to 200u2009μm. Factors cavity preparation, restorative materials, and depth were evaluated by three way ANOVA, followed by Tukey test (p<0.05).nnnRESULTSnThe results showed lower microhardness in cavities prepared with DB than in cavities prepared with LA. At 30u2009μm, there were no statistical significant differences with regard to cavity preparation or restorative materials factors. In depth evaluation, the enamel microhardness progressively increased as a function of depth for the GI groups. In the groups prepared with LA at 60u2009μm/90u2009μm, there were no significant differences between GI and RM materials, whose microhardnesses were significantly higher than that of CR.nnnCONCLUSIONSnCavity preparation using Er,Cr:YSGG laser increases caries resistance of enamel walls, and reduce caries lesion depth development regardless of fluoride presence in the restorative material. CR showed higher caries lesion development than GI, and RM showed intermediate results.

Lasers in Dentistry: Guide for Clinical Practice

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Laser Phototherapy (660 nm) Can Be Beneficial for Reducing Gingival Inflammation in Prosthodontics

Among the new technologies developed, low power lasers have enabled new approaches to provide conservative treatment. Low power lasers act at cellular level, resulting in reduced pain, modulating inflammation, and improved tissue healing. Clinical application of the low power laser requires specific knowledge concerning laser interaction with biological tissue so that the correct irradiation protocol can be established. The present case report describes the clinical steps involved in an indirect composite resin restoration performed in a 31-year-old patient, in whom low power laser was used for soft tissue biomodulation. Laser therapy was applied with a semiconductor laser 660u2009nm, spot size of 0.028u2009cm2, energy density of 35.7u2009J/cm2, mean power of 100u2009mW, and energy per point as 1u2009J, in contact mode, on a total of 2 points (mesial and distal), totaling 2u2009J of energy. The therapy with low power laser can contribute positively to the success of an indirect restorative treatment.

Lasers in Esthetic Dentistry: Soft Tissue Photobiomodulation, Hard Tissue Decontamination, and Ceramics Conditioning

The increasing concern and the search for conservative dental treatments have resulted in the development of several new technologies. Low and high power lasers can be cited as one of these new technologies. Low power lasers act at cellular level leading to pain reduction, modulation of inflammation, and improvement of tissue healing. High power lasers act by increasing temperature and have the potential to promote microbial reduction and ablation of hard and soft tissues. The clinical application of both low and high power lasers requires specific knowledge concerning laser interaction with biological tissues, so that the correct irradiation protocol can be established. The present case report describes the clinical steps of two metal-ceramic crowns development in a 60-year-old patient. Three different laser wavelengths were applied throughout the treatment with different purposes: Nd:YAG laser (1,064u2009nm) for dentin decontamination, diode (660u2009nm) for soft tissue biomodulation, and Er:YAG laser (2,940u2009nm) for inner ceramic surface conditioning. Lasers were successfully applied in the present case report as coadjutant in the treatment. This coadjutant technology can be a potential tool to assist treatment to reach the final success.

Laser phototherapy for Stevens-Johnson syndrome: a case report.

BACKGROUND AND OBJECTIVEnStevens-Johnson syndrome (SJS) is a life-threatening dermatosis characterized by epidermal sloughing and stomatitis. We report the case of a 7-year-old boy in whom laser phototherapy (LPT) was highly effective in reversing the effects of an initial episode of SJS that had apparently developed in association with treatment with phenobarbital for a seizure disorder. The patient was first seen in the intensive care unit (ICU) of our institution with fever, cutaneous lesions on his extremities, trunk, face, and neck; mucosal involvement of his genitalia and eyes (conjunctivitis); ulcerative intraoral lesions; and swollen, crusted, and bleeding lips. He reported severe pain at the sites of his intraoral and skin lesions and was unable to eat, speak, swallow, or open his mouth.nnnMATERIALS AND METHODSnTrying to prevent and minimize secondary infections, gastric problems, pain, and other complications, the patient was given clindamycin, ranitidine, dipyrone, diphenhydramine (Benadryl) drops, and morphine. In addition, he was instructed to use bicarbonate solution and Ketoconazole (Xylogel) in the oral cavity. Because of the lack of progress of the patient, the LPT was selected.nnnRESULTSnAt 5 days after the initial session of LPT, the patient was able to eat gelatin, and on the following day, the number and severity of his intraoral lesions and his labial crusting and swelling had diminished. By 6 days after his initial session of LPT, most of the patients intraoral lesions had disappeared, and the few that remained were painless; the patient was able to eat solid food by himself and was removed from the ICU. Ten sessions of LPT were conducted in the hospital. The patient underwent three further and consecutive sessions at the School of Dentistry, when complete healing of his oral lesions was observed.nnnCONCLUSIONnThe outcome in this case suggests that LPT may be a new adjuvant modality for SJS complications.

Evaluation of enamel mineral loss around cavities prepared by the Er,Cr:YSGG laser and restored with different materials

The aim of this study was to evaluate the enamel demineralization around cavities prepared by Er,Cr:YSGG laser (2780 nm) and restored with different materials after an acid challenge. The human dental enamel samples were randomly divided in 12 groups (n=10): G1- high-speed drill (HD); G2- Er,Cr:YSGG laser L (3 W, 20 Hz, 53.05 J/cm2)(air 65% - water 55%); G3– L (4 W, 20 Hz, 70.74 J/cm2); G4– L (5 W, 20 Hz, 88.43 J/cm2). Each group was divided in subgroups: 1- glass ionomer cement (GIC), 2- resin modified GIC (RMGIC), 3- composite resin (C). Samples were submitted to an acid challenge (4.8 pH) for7 days. The calcium ion contend (ppm/mm2) from demineralizing solutions were analyzed by atomic emission spectrometry. ANOVA and LSD tests were performed (α=5%). The significant lower average values of calcium loss were observed on G2 + GIC, G2 + RMGIC, G1 + RMGIC (p<0.05); the significant higher values were observed on G1 + C, G4 +GIC, G4 + C (p<0.05). The composite resin showed higher calcium loss than RMGIC and GIC (p<0.05). The lased cavities using lower fluence (53.05J/cm2) showed significant reduced demineralization than higher fluences (70.74 and 88.43J/cm2) (p<0.05). Neither the techniques nor the restorative materials used were able to avoid the enamel demineralization. The findings of this in vitro study suggest that the Er,Cr:YSGG lased cavities restored with GIC or RMGIC or conventional drill cavities with RMGIC were effective on reducing the demineralization around restorations, showing an important potential in preventing secondary caries.