Bond Strength of Dental Adhesive Systems Irradiated with Ionizing Radiation

Purpose: The aim of the present paper was to determine the effect of different types of ionizing radiation on the bond strength of three different dentin adhesive systems. Materials and Methods: One hundred twenty specimens of 60 human teeth (protocol number: 032/2007) sectioned mesiodistally were divided into 3 groups according to the adhesives systems used: SB (Adper Single Bond Plus), CB (Clearfil SE Bond) and AP (Adper Prompt Self-Etch). The adhesives were applied on dentin and photo-activated using LED (Lec 1000, MMoptics, 1000 mW/cm(2)). Customized elastomer molds (0.5 mm thickness) with three orifices of 1.2 mm diameter were placed onto the bonding areas and filled with composite resin (Filtek Z-250), which was photo-activated for 20 s. Each group was subdivided into 4 Subgroups for application of the different types of ionizing radiation: ultraviolet radiation (UV), diagnostic x-ray radiation (DX), therapeutic x-ray radiation (TX) and without irradiation (control group, CG). Microshear tests were carried out (Instron, model 4411), and afterwards the modes of failure were evaluated by optical and scanning electron microscope and classified using 5 scores: adhesive failure, mixed failures with 3 significance levels, and cohesive failure. The results of the shear bond strength test were submitted to ANOVA with Tukey`s test and Dunnett`s test, and the data from the failure pattern evaluation were analyzed with the Mann Whitney test (p = 0.05). Results: No change in bond strength of CB and AP was observed after application of the different radiation types, only SB showed increase in bond strength after UV (p = 0.0267) irradiation. The UV also changed the failure patterns of SB (p = 0.0001). Conclusion: The radio-induced changes did not cause degradation of the restorations, which means that they can be exposed to these types of ionizing radiation without weakening the bond strength.

FT-IR spectroscopy assessment of aesthetic dental materials irradiated with low-dose therapeutic ionizing radiation

The aim of the present study was to evaluate the effects of low-dose therapeutic ionizing radiation on different aesthetic dental materials. Forty five specimens (n = 45) of three different aesthetic restorative materials were prepared and randomly divided into five groups: G1 (control group); G2, G3, G4, G5 experimental groups irradiated respectively with 0.25, 0.50, 0.75, and 1.00 Gy of gamma radiation by the (60)Co teletherapy machine. Chemical analyses were performed using a FT-IR Nicolet 520 spectrophotometer with reflectance diffuse technique. Even a minimal exposition at ionizing radiation in therapeutic doses can provide chemical changes on light-cured composite resins. The three studied restorative materials showed changes after exposure at gamma radiation, however the increase of the radiation dose did not contribute to an increase in this effect.

Shear strength of the bond to primary dentin: influence of Er:YAG laser irradiation distance

The aim of this study was to assess in vitro the influence of Er:YAG laser irradiation distance on the shear strength of the bond between an adhesive restorative system and primary dentin. A total of 60 crowns of primary molars were embedded in acrylic resin and mechanically ground to expose a flat dentin surface and were randomly assigned to six groups (n = 10). The control group was etched with 37% phosphoric acid. The remaining five groups were irradiated (80 mJ, 2 Hz) at different irradiation distances (11, 12, 16, 17 and 20 mm), followed by acid etching. An adhesive agent (Single Bond) was applied to the bonding sites, and resin cylinders (Filtek Z250) were prepared. The shear bond strength tests were performed in a universal testing machine (0.5 mm/min). Data were submitted to statistical analysis using one-way ANOVA and the Kruskal-Wallis test (p < 0.05). The mean shear bond strengths were: 7.32 +/- 3.83, 5.07 +/- 2.62, 6.49 +/- 1.64, 7.71 +/- 0.66, 7.33 +/- 0.02, and 9.65 +/- 2.41 MPa in the control group and the groups irradiated at 11, 12, 16, 17, and 20 mm, respectively. The differences between the bond strengths in groups II and IV and between the bond strengths in groups II and VI were statistically significant (p < 0.05). Increasing the laser irradiation distance resulted in increasing shear strength of the bond to primary dentin.

Influence of Er,Cr : YSGG laser treatment on the microtensile bond strength of adhesives to dentin

Purpose: In light of the concept of minimally invasive dentistry, erbium lasers have been considered as an alternative technique to the use of diamond burs for cavity preparation. The purpose of this study was to assess the bonding effectiveness of adhesives to Er,Cr:YSGG laser-irradiated dentin using irradiation settings specific for cavity preparation. Materials and Methods: Fifty-four midcoronal dentin surfaces, obtained from sound human molars, were irradiated with an Er,Cr:YSGG laser or prepared with a diamond bur using a high-speed turbine. One etch-and-rinse (Optibond FL/Kerr) and three self-etching adhesives (Adper Prompt L-Pop/3M ESPE, Clearfil SE Bond/Kuraray, and Clearfil S-3 Bond/Kuraray) were used to bond the composite to dentin. The microtensile bond strength (mu TBS) was determined after 24 h of storage in water at 37 degrees C. The Kruskal-Wallis test was used to determine pairwise statistical differences (p < 0.05). Prepared dentin surfaces, adhesive interfaces, and failure patterns were analyzed using a stereo microscope and Field-emission gun Scanning Electron Microscopy (Feg-SEM). Results: Significantly lower mu TBS was observed to laser-irradiated than to bur-cut dentin (p < 0.05), irrespective of the adhesive employed. Feg-SEM photomicrographs of lased dentin revealed an imbricate patterned substrate and the presence of microcracks at the dentin surface. Conclusion: Morphological alterations produced by Er,Cr:YSGG laser-irradiation adversely influence the bonding effectiveness of adhesives to dentin. Keywords: dentin, adhesion, adhesives, laser, ErCr:YSGG.

In vitro analysis of human tooth pulp chamber temperature after low-intensity laser therapy at different power outputs

In vitro studies have provided conflicting evidence of temperature changes in the tooth pulp chamber after low-level laser irradiation of the tooth surface. The present study was an in vitro evaluation of temperature increases in the human tooth pulp chamber after diode laser irradiation (GaAlAs, lambda = 808 nm) using different power densities. Twelve human teeth (three incisors, three canines, three premolars and three molars) were sectioned in the cervical third of the root and enlarged for the introduction of a thermocouple into the pulp chamber. The teeth were irradiated with 417 mW, 207 mW and 78 mW power outputs for 30 s on the vestibular surface approximately 2 mm from the cervical line of the crown. The highest average increase in temperature (5.6A degrees C) was observed in incisors irradiated with 417 mW. None of the teeth (incisors, canines, premolars or molars) irradiated with 207 mW showed temperature increases higher than 5.5A degrees C that could potentially be harmful to pulp tissue. Teeth irradiated with 78 mW showed lower temperature increases. The study showed that diode laser irradiation with a wavelength of 808 nm at 417 mW power output increased the pulp chamber temperature of certain groups of teeth, especially incisors and premolars, to critical threshold values for the dental pulp (5.5A degrees C). Thus, this study serves as a warning to clinicians that ""more"" is not necessarily ""better"".

Influence of pulse repetition rate of Er : YAG laser and dentin depth on tensile bond strength of dentin-resin interface

The study evaluated the in vitro influence of pulse-repetition rate of Er:YAG laser and dentin depth on tensile bond strength of dentin-resin interface. Dentin surfaces of buccal or lingual surfaces from human third molars were submitted to tensile test in different depths (superficial, 1.0 and 1.5 mm) of the same dental area, using the same sample. Surface treatments were acid conditioning solely (control) and Er:YAG laser irradiation (80 mJ) followed by acid conditioning, with different pulse-repetition rates (1, 2, 3, or 4 Hz). Single bond/Z-250 system was used. The samples were stored in distilled water at 37 degrees C for 24 h, and then the first test (superficial dentine) was performed. The bond failures were analyzed. Following, the specimens were identified, grounded until 1.0- and 1.5-mm depths, submitted again to the treatments and to the second and, after that, to third-bond tests on a similar procedure and failure analysis. ANOVA and Tukey test demonstrated a significant difference (p < 0.001) for treatment and treatment X depth interaction (p < 0.05). The tested depths did not show influence (p > 0.05) on the bond strength of dentin-resin interface. It may be concluded that Er:YAG laser with 1, 2, 3, or 4 Hz combined with acid conditioning did not increase the resin tensile bond strength to dentin, regardless of dentin depth. (C) 2007 Wiley Periodicals, Inc.

SEM analysis of enamel surface treated by Er : YAG laser: Influence of irradiation distance

Background: Depending on the distance of laser tip to dental surface a specific morphological pattern should be expected. However, there have been limited reports that correlate the Er:YAG irradiation distance with dental morphology. Purpose: To assess the influence of Er:YAG laser irradiation distance on enamel morphology, by means of scanning electron microscopy (SEM). Methods: Sixty human third molars were employed to obtain discs (congruent to 1 mm thick) that were randomly assigned to six groups (n = 10). Five groups received Er:YAG laser irradiation (80 mJ/2 Hz) for 20 s, according to the irradiation distance: 11, 12, 14, 16, or 17 mm. and the control group was treated with 37% phosphoric acid for 15 s. The laser-irradiated discs were bisected. One hemi-disc was separated for superficial analysis without subsequent acid etching, and the other one, received the phosphoric acid for 15 s. Samples were prepared for SEM. Results: Laser irradiation at 11 and 12 min provided an evident ablation of enamel, with evident fissures and some fused areas. At 14, 16 and 17 mm the superficial topography was flatter than in the other distances. The subsequent acid etching on the lased-surface partially removed the disorganized tissue. Conclusions: Er:YAG laser in defocused mode promoted slight morphological alterations and seems more suitable for enamel conditioning than focused irradiation. The application of phosphoric acid on lased-enamel surface, regardless of the irradiation distance, decreased the superficial irregularities.

Effect of blood contamination on the shear bond strength at resin/dentin interface in primary teeth

Purpose: To assess in vitro the shear bond strength at the resin/dentin interface in primary teeth after contamination with fresh human blood. Methods: 75 crowns of primary molars were embedded in acrylic resin and mechanically ground to expose a flat dentin surface. The specimens were randomly assigned to five groups (n=15), according to the surface treatment. Group I (control) had no blood contamination. The other groups were blood-contaminated and subjected to different post-contamination protocols: in Group 2, the surfaces were rinsed with water; in Group 3, the surfaces were air-dried; in Group 4, the surfaces were rinsed and air-dried; and in Group 5, no post-contamination treatment was done. In all groups, a 3-mm dentin bonding site was demarcated, Single Bond adhesive system was applied and resin composite cylinders were bonded. After 24 hours in distilled water, shear bond strength was tested at a crosshead speed of 0.5 mm/minute. Results: Means (in MPa) were: Group 1: 7.1 (+/- 4.2); Group 2: 4.0 (+/- 1.8); Group 3: 0.9 (+/- 0.7); Group 4: 3.9 (+/- 2.2) and Group 5: 1.3 (+/- 1.5). Data were analyzed statistically by the Kruskal-Wallis test at 5% significance level. Groups 2 and 4 were similar to each other (P > 0.05) and both ware similar to Group 1 (P > 0.05). These groups (2, 3 and 4) had statistically significantly higher bond strengths than Groups 3 and 5 (P < 0.05). Blood contamination negatively affected the shear bond strength to primary tooth dentin. Among the blood-contaminated groups, water-rinsed specimens had higher bond strengths than those that were exclusively air-dried or not submitted to any post-contamination protocol before adhesive application.

Bond durability in erbium:yttrium-aluminum-garnet laser-irradiated enamel

This study sought to evaluate the influence of thermocycling and water storage on the microtensile bond strength of composite resin bonded to erbium:yttrium-aluminum-garnet (Er:YAG)-irradiated and bur-prepared enamel. Eighty bovine incisors were selected and sectioned. Specimens were ground to produce a flat enamel surface. Samples were randomly assigned according to cavity preparation device: (I) Er:YAG laser and (II) high-speed turbine, and were subsequently restored with composite resin. They were subdivided according to the duration of water storage (WS)/number of thermocycles (TCs): 24 h WS/no TCs; 7 days WS/500 TCs; 1 month WS/2,000 TCs; 6 months WS/12,000 TCs. The teeth were sectioned into 1.0 mm(2)-thick slabs and subjected to tensile stress in a universal testing machine. Data were submitted to two-way analysis of variance (ANOVA) and Tukey`s test at a 0.05 significance level. The different periods of water storage and thermocycling did not influence the microtensile bond strength (A mu TBS) values in the Er:YAG laser-prepared groups. In bur-prepared enamel, the group submitted to 12,000 TCs/6 months` WS (IID) showed a significant decrease in bond strength values when compared to the group stored in water for 24 h and not submitted to thermocycling (IIA), but values were statistically similar to those obtained in all Er:YAG laser groups and in the bur- prepared groups degraded with 500 TCs/1 week WS (IIB) or 2,000 TCs/1 month WS (IIC). It may be concluded that adhesion of an etch-and-rinse adhesive to Er:YAG laser-irradiated enamel was not affected by the methods used to simulate degradation of the adhesive interface and was similar to adhesion in the bur-prepared groups in all periods of water storage and thermocycling.

Effect of different bleaching systems on the ultrastructure of bovine dentin

The aim of this study was to evaluate in vitro the effect of different in-office bleaching systems on the surface morphology of bovine dentin. Thirty tooth fragments measuring 4 x 4mm, containing enamel and dentin, were obtained from the crowns of extracted bovine incisors. Samples were subjected to simulated intracoronal bleaching techniques using conventional (Opalescence Endo (R) and Whiteness Super Endo (R)) and light-activated systems (Opalescence Xtra (R) and Whiteness HP Maxx (R)). Controls were treated with either sodium perborate mixed with 10% hydrogen peroxide or no bleaching agent. The samples were observed under SEM and the recorded images were evaluated for topographic alterations. The ultrastructural alterations of dentin observed in this study varied greatly between groups according to the products used. Higher pH products (Whiteness HP Maxx (R) and Opalescence Xtra (R)) associated with in-office techniques yielded better maintenance of dentin ultrastructure. Apparently, both low pH and hydrogen peroxide oxidation play a role in altering the ultrastructure of dentin during internal dental bleaching. The use of alkaline products with reduced time of application (in-office techniques) may decrease such morphological alterations.

Adhesion to Er : YAG laser-prepared dentin after long-term water storage and thermocycling

This in vitro study evaluated the microtensile bond strength of a resin composite to Er:YAG-prepared dentin after long-term storage and thermocycling. Eighty bovine incisors were selected and their roots removed. The crowns were ground to expose superficial dentin. The samples were randomly divided according to cavity preparation method (I-Er:YAG laser and II-carbide bur). Subsequently, an etch & rinse adhesive system was applied and the samples were restored with a resin composite. The samples were subdivided according to time of water storage (WS)/number of thermocycles (TC) performed: A) 24 hours WS/no TC; B) 7 days WS/500 TC; C) 1 month WS/2,000 TC; D) 6 months WS/12,000 TC. The teeth were sectioned in sticks with a cross-sectional area of 1.0-mm(2), which were loaded in tension in a universal testing machine. The data were subjected to two-way ANOVA, Scheffe and Fisher`s tests at a 5% level. In general, the bur-prepared group displayed higher microtensile bond strength values than the laser-treated group. Based on one-month water storage and 2,000 thermocycles, the performance of the tested adhesive system to Er:YAG-laser irradiated dentin was negatively affected (Group IC), while adhesion of the bur-prepared group decreased only within six months of water storage combined with 12,000 thermocycles (Group IID). It may be concluded that adhesion to the Er:YAG laser cavity preparation was more affected by the methods used for simulating degradation of the adhesive interface.

Influence of dentin cavity surface finishing on micro-tensile bond strength of adhesives

The current trend toward minimal-invasive dentistry has introduced innovative techniques for cavity preparation. Chemical vapor deposition (CVD) and laser-irradiation technology have been employed as an alternative to the common use of regular burs in high-speed turbines. Objectives. The purpose of this study was to assess the influence of alternative techniques for cavity preparation on the bonding effectiveness of different adhesives to dentin, and to evaluate the morphological characteristics of dentin prepared with those techniques. Methods. One etch&rinse adhesive (OptiBond FL, Kerr) and three self-etch systems (Adper Prompt L-Pop, 3M ESPE; Clearfil SE Bond, Kuraray; Clearfil S3 Bond, Kuraray) were applied on dentin prepared with a regular bur in a turbine, with a CVD bur in a turbine, with a CVD tip in ultrasound and with an ErCr:YSGG laser. The micro-tensile bond strength (mu TBS) was determined after storage in water for 24 h at 37 degrees C, and morphological evaluation was performed by means of field -emission -gun scanning electron microscopy (Feg-SEM). Results. Feg-SEM evaluation revealed different morphological features on the dentin surface after the usage of both the conventional and alternative techniques for cavity preparation, more specifically regarding smear-layer thickness and surface roughness. CVD bur-cut, CVD ultra-sonoabraded and laser-irradiated dentin resulted in lower mu TBSs than conventionally bur-cut dentin, irrespective of the adhesive employed. Significance. The techniques, such as CVD diamond-bur cutting, CVD diamond ultra-sonoabrasion and laser-irradiation, used for cavity preparation may affect the bonding effectiveness of adhesives to dentin, irrespective of their acidity or approach. (C) 2007 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

High-power diode laser in the disinfection in depth of the root canal dentin

Objective. The objective of this study was to evaluate the disinfection degree of dentine caused by the use of diode laser after biomechanical procedures. Study design. Thirty teeth were sectioned and roots were autoclaved and incubated for 4 weeks with a suspension of Enterococcus faecalis. The specimens were randomly divided into 3 groups (n = 10): G1, instrumented with rotary files, irrigated with 0.5% sodium hypochlorite and 17% EDTA-T, and then irradiated by 830-nm diode laser at 3 W; G2, the same procedures as G1 but without laser irradiation; and G3, irrigation with saline solution (control). Dentin samples of each third were collected with carbide burs and aliquots were sowed to count viable cells. Results. The disinfection degree achieved was 100% in G1 and 98.39% in G2, when compared to the control group (G3). Conclusion. Diode laser irradiation provided increased disinfection of the deep radicular dentin in the parameters and samples tested.

Comparative Histopathological Analysis of Human Pulps after Class I Cavity Preparation with a High-Speed Air-Turbine Handpiece or Er:YAG Laser

The purpose of this study was to comparatively evaluate the response of human pulps after cavity preparation with different devices. Deep class I cavities were prepared in sound mandibular premolars using either a high-speed air-turbine handpiece (Group 1) or an Er: YAG laser (Group 2). Following total acid etching and the application of an adhesive system, all cavities were restored with composite resin. Fifteen days after the clinical procedure, the teeth were extracted and processed for analysis under optical microscopy. In Group 1 in which the average for the remaining dentin thickness (RDT) between the cavity floor and the coronal pulp was 909.5 mu m, a discrete inflammatory response occurred in only one specimen with an RDT of 214 mu m. However, tissue disorganization occurred in most specimens. In Group 2 (average RDT = 935.2 mu m), the discrete inflammatory pulp response was observed in only one specimen (average RDT = 413 mu m). It may be concluded that the high-speed air-turbine handpiece caused greater structural alterations in the pulp, although without inducing inflammatory processes.

Increased Viability of Odontoblast-Like Cells Subjected to Low-Level Laser Irradiation

Studies have shown that the increase of cell metabolism depends on the low level laser therapy (LLLT) parameters used to irradiate the cells. However, the optimal laser dose to up-regulate pulp cell activity remains unknown. Consequently, the aim of this study was to evaluate the metabolic response of odontoblast-like cells (MDPC-23) exposed to different LLLT doses. Cells at 20000 cells/cm(2) were seeded in 24-well plates using plain culture medium (DMEM) and were incubated in a humidified incubator with 5% CO(2) at 37 degrees C. After 24 h, the culture medium was replaced by fresh DMEM supplemented with 5% (stress by nutritional deficit) or 10% fetal bovine serum (FBS). The cells were exposed to different laser doses from a near infrared diode laser prototype designed to provide a uniform irradiation of the wells. The experimental groups were: G1: 1.5 J/cm(2) + 5% FBS; G2: 1.5 J/cm(2) + 10% FBS; G3: 5 J/cm(2) + 5% FBS; G4: 5 J/cm(2) + 10% FBS; G5: 19 J/cm(2) + 5% FBS; G6: 19 J/cm(2) + 10% FBS. LLLT was performed in 3 consecutive irradiation cycles with a 24-hour interval. Non-irradiated cells cultured in DMEM supplemented with either 5 or 10% FBS served as control groups. The analysis of the metabolic response was performed by the MTT assay 3 h after the last irradiation. G1 presented an increase in SDH enzyme activity and differed significantly (Mann-Whitney test, p < 0.05) from the other groups. Analysis by scanning electron microscopy showed normal cell morphology in all groups. Under the tested conditions, LLLT stimulated the metabolic activity of MDPC-23 cultured in DMEM supplemented with 5% FBS and exposed to a laser dose of 1.5 J/cm(2). These findings are relevant for further studies on the action of near infrared lasers on cells with odontoblast phenotype.