3D mapping of the irrigated areas of the root canal space using micro-computed tomography.

OBJECTIVES: The aim of this study was to introduce a methodology to map irrigant spreadability within the root canal space using micro-computed tomography (micro-CT). MATERIALS AND METHODS: Mandibular molars presenting Vertucci's types I and II canal configurations were selected, and four scans using isotropic resolution of 19.5 µm were accomplished per tooth: prior to treatment (S1), after glide path (S2) and after root canal preparation (S3 and S4). A contrast solution (CS) was used to irrigate the canals at stages S2 and S4. The touched and untouched surface areas of the canals, the volume of irrigant-free areas and the percentage volume occupied by the CS were calculated. Density, surface tension and the spread pattern of the CS and 2.5% NaOCl were also evaluated. RESULTS: In the type I mesial root, there was an increase in the percentage volume of free-irrigated areas from S2 to S4 preparation steps, whilst in the distal roots and type II mesial root, a decrease of irrigant-free areas was observed. The use of CS allowed the quantification of the touched surface area and the volume of the root canal occupied by the irrigating solution. Density (g/mL) and surface tension (mN/m) of the CS and 2.5% NaOCl were 1.39 and 47.5, and 1.03 and 56.2, respectively. Besides, a similar spread pattern of the CS and 2.5% NaOCl in a simulated root canal environment was observed. CONCLUSIONS: This study introduced a new methodology for mapping the irrigating solution in the different stages of the root canal preparation and proved useful for in situ volumetric quantification and qualitative evaluation of irrigation spreading and irrigant-free areas. CLINICAL RELEVANCE: Micro-computed tomographic technology may provide a comprehensive knowledge of the flush effectiveness by different irrigants and delivery systems in order to predict the optimal cleaning and disinfection conditions of the root canal space.

Influence of laser irradiation on pits and fissures: an in situ study.

OBJECTIVE: The aim of this in situ study was to analyze the influence of the Er:YAG, Nd:YAG, and CO(2) lasers on the enamel acid resistance of pits and fissures. BACKGROUND DATA: The laser tissue interaction has been studied as a method of preventing occlusal caries. METHODS: Thirteen volunteers wore palatal acrylic appliances containing human occlusal enamel blocks that were divided into four groups (G1, control; G2, Er:YAG; G3, Nd:YAG; G4, CO(2)). Each palatal acrylic appliance was used in the four studied groups and was used for 14 consecutive days. A sucrose solution was applied to the specimens six times per day. The specimens were then sectioned in half, and a microhardness test was applied. The other halves were analyzed using polarized light microscopy to measure the caries-like lesion areas, and a morphological analysis was conducted using a scanning electron microscope (SEM). RESULTS: For the statistical analysis of the data obtained from the microhardness test (Knoop hardness number. [KHN]) (α=5%), Fisher's exact test was performed, and the group means were as follows: G1, 247±71; G2, 258±70; G3, 272±73; and G4, 298±56. The results demonstrated that the control group was significantly different from G3 and G4, which presented higher microhardness values. The Wilcoxon signed-rank test was used to analyze the data obtained from the caries-lesion area measurements (mm(2)) (α=5%) (G1, 0.01±1.08; G2, 0.13±0.18; G3, 0.05±0.17; and G4, 0.09±0.22). The results no showed significant differences among the groups in this analysis. CONCLUSIONS: Based on the results from the present study, it may be concluded that the CO(2) and Nd:YAG lasers increased the enamel acid resistance in pits and fissures.

Macroscopic description of teeth of Azara's agouti (Dasyprocta azarae) / Caracterização macroscópica dos dentes de cutias (Dasyprocta azarae)

The teeth of Azara's agouti (Dasyprocta azarae) were described macroscopically in order to provide biological data on one of the largest wild rodents of the Americas. Radiography was taken on six heads and the teeth were described. Enamel surrounds the coronal dentin, projects to the roots and is present as parallel inner laminae in buccolingual direction. The dentin is located among the enamel laminae and surrounds the pulp horns. The cementum is located internally to the enamel laminae. On the lingual surface, the cementum and dentin are the outer elements.

Os dentes de cutias (Dasyprocta azarae) foram descritos macroscopicamente para fornecer informações sobre um dos maiores roedores das Américas. Radiografias foram realizadas em seis cabeças, e os dentes foram descritos. O esmalte envolve a dentina coronal e se projeta até a raiz e é presente como lâminas dispostas paralelamente em direção vestíbulolingual. A dentina é localizada entre as lâminas do esmalte e envolve os cornos pulpares. O cemento é localizado internamente às lâminas de esmalte. Na superfície lingual, o cemento e a dentina são os elementos mais externos.

In vitro assessment of laser efficiency for caries prevention in pits and fissures.

This study aimed to assess the in vitro efficacy of the lasers Er:YAG, Nd:YAG, and CO(2) operating in the low energy mode for caries prevention in pits and fissures. Forty-five caries-free enamel occlusal sections were randomly divided into three groups: G1 - Er:YAG (80 mJ/2 Hz); G2 - Nd:YAG Laser (1 W and 10 Hz); and G3 - CO(2) Laser (0.4 W and 20 Hz). After surface treatment, the samples were submitted to challenge with acid consisting of a 10-day immersion in demineralizing (6 h) and remineralizing solution (18 h). Next, enamel demineralization was quantitatively evaluated by subsurface microhardness test and polarized-light microscopy (PLM, mm(2)) and qualitatively assessed by scanning electron microscopy. The Wilcoxon test was used for comparison of each group with its own control. ANOVA (α = 5%) was employed for comparison among groups, and Fisher's LSD multiple comparison test was applied, to check the difference in means. Concerning the microhardness analyses, statistical difference between control, and experimental areas was only detected for the CO(2) group. Experimental values were higher than the controls. As for PLM analyses, smaller demineralized areas were measured for G2 (Nd:YAG) and G3 (CO(2)) compared with the control areas. In conclusion, the present findings suggest that the CO(2) laser should be selected in order to increase the enamel resistance to acid in pits and fissures.

Avaliação da microinfltração coronária de três materiais utilizados na restauração provisória da cavidade endodôntica: estudo in vitro. / Coronal leakage of three materials used for temporary restoration of endodontic access cavities: an in vitro study

O objetivo deste trabalho foi avaliar a capacidade seladora de um material restaurador provisório, Villevie, e de uma resina composta, Tetric Ceram, associada a dois tipos de sistema adesivos, XENO III e Single Bond. Quarenta incisivos inferiores unirradiculares foram distribuídos em três grupos de dez dentes cada e cinco dentes para cada grupo controle, positivo e negativo. Os espécimes, após a cirurgia de acesso, foram preparados por meio de sistema de instrumentação rotatória e irrigados com água destilada e deionizada. A porção externa dos dentes foi impermeabilizada até 2 mm aquém da margem externa da cirurgia de acesso. Colocou-se no interior do canal radicular um cone de papel seguido de uma pensa de algodão impregnados com solução alcoólica de dimetilglioxima 1%. A cavidade endodôntica foi selada de acordo com os seguintes grupos: GA- sistema adesivo autocondicionante XENO III + resina composta; GB- sistema adesivo Single Bond + resina composta; e GC- selador provisório. Os espécimes foram imersos em recipientes contendo solução de sulfato de níquel 5% e submetidos à ciclagem térmica por 72h. Os testes de Kruskal-Wallis e Dunn foram utilizados para análise dos resultados com nível de 5% de signifcância. O menor nível de microinfltração foi observado no grupo do restaurador provisório (GC), com diferença estatística signifcante em relação aos demais grupos (P<0,001). Os grupos A e B mostraram-se semelhantes ao controle positivo (P>0,05), com os maiores índices de microinfltração. Concluiu-se que nenhum dos materiais avaliados foi capaz de impedir a microinfltração coronária.

The purpose of this study was to evaluate the sealing capacity of a temporary restorative material (Villevie) and a composite resin, Tetric Ceram, associated with two adhesive systems (XENO III and Single Bond). Forty single-rooted mandibular incisors were distributed into three experimental groups of 10 teeth each, and two control groups (positive and negative) of 5 teeth each. After preparation of the access cavities, the canals were instrumented with a rotary system and irrigated with distilled deionized water. The external surfaces of the teeth were rendered water-proof up to 2 mm from the external margins of the access cavities. A paper point and a coton mesh impregnated with an alcoholic 1% dimethylglyoxime were placed inside the root canals, and the endodontic access cavities were sealed according to the following groups: GA- XENO III self-etch adhesive system + composite resin; GB- Single Bond etch-and-rinse adhesive system + composite resin; and GC- temporary restorative material. The specimens were immersed in receptacles containing a 5% nickel sulfate solution and subjected to a thermal cycling regimen during 72 h. The Kruskal-Wallis and Dunn's tests were used for statistical analysis of the results at 5% signifcance level. The group restored with the temporary restorative material (GC) presented statistically signifcant less coronal leakage than the other groups (p<0.001). GA and GB were statistically similar to the positive control (p>0.05), showing the highest levels of coronal leakage. None of the tested materials was able to prevent the occurrence of coronal leakage.

Avaliação do efeito do EDTA, CDTA e EGTA sobre a microdureza da dentina radicular humana: estudo in vitro. / valuation of the effect of EDTA, CDTA and EGTA on the microhardness of human root dentine: in vitro study.

Objetivo: Estudou-se a ação das soluções de EDTA 17%, CDTA 17% e EGTA 17% sobre a microdureza da dentina radicular. Material e métodos: Foram utilizados cinco dentes incisivos centrais superiores humanos, recém-extraídos, os quais tiveram suas coroas seccionadas na junção cemento-esmalte e posteriormente desprezadas. As raízes foram incluídas em acrílico de rápida polimerização, adaptadas à máquina de corte e seccionadas transversalmente de um em um milímetro. O primeiro corte foi desprezado e o segundo dividido em quatro quadrantes. Cada quarto de dentina foi colocado sobre um disco de resina acrílica, obtendo-se quatro corpos-de-prova para cada raiz. Cinqüenta microlitros da solução a ser testada foram depositados sobre o corpo-de-prova por meio de uma pipeta micrométrica, permanecendo por cinco minutos. A medição da microdureza da dentina foi obtida em um aparelho de dureza Vickers com peso de cinqüenta gramas de carga e tempo de quinze segundos de aplicação. Resultados: Após análise estatística, os resultados mostraram que todas as soluções testadas foram efetivas quanto à redução da microdureza dentinária, mas estatisticamente diferentes entre si (p<0.05). A solução de EGTA 17% promoveu maior redução, seguida pela solução de CDTA 17%. A solução de EDTA 17% foi a menos efetiva. Conclusão: Pode-se concluir que as soluções quelantes testadas no experimento foram efetivas quanto à redução da microdureza dentinária.

Objective: In this work the action of 17 % EDTA solution, CDTA 17 % solution and EGTA 17% solution had been studied on human radicular dentin microhardness. Material and methods: Five freshly extracted human maxillary incisors were transversely sectioned at the cement-enamel junction; the crowns were discarded. The roots were embedded in blocks of resin polymerization rapidly, which were adaptated in the cut machine and seccionated transversely in 1 to 1 milimeter. The first cut was discarded and the second divided into four quadrants. Each quarter of dentin was placed on a disc of acrilic resin, resulting in four samples for each root. Fifty microliters of the tested solutions were deposited on the specimen using a micrometer pipete, staying for five minutes. The measurement of dentin microhardness was in a unit of Vickers hardness with 50 grams of weight and load time of 15 s of application. Results: After statistical analysis, results showed that all solutions were efective in reducting dentin microhardness, but statistically diferent from each other (p<0.05). The 17 % EGTA solution was more efective, followed by 17 % CDTA solution. 17 % EDTA solution was the less efective. Conclusion: It was possible to conclude that all the chelants solutions were efective in reduction of the radicular dentin microhardness.

Influence of the irradiation distance and the use of cooling to increase enamel-acid resistance with Er:YAG laser.

OBJECTIVES: The aim of this study was to assess the influence of irradiation distance and the use of cooling in the Er:YAG laser efficacy in preventing enamel demineralization. METHODS: 84 enamel blocks were randomly assigned to seven groups (n=12): G1: control group - no treatment, G2-G7: experimental groups treated with Er:YAG laser (80mJ/2Hz) at different irradiation distances with or without cooling: G2: 4mm/2mL; G3: 4mm/no cooling; G4: 8mm/2mL; G5: 8mm/no cooling; G6: 16mm/2mL; G7: 16mm/no cooling. The samples were submitted to an in vitro pH cycles for 14 days. Next, the specimens were sectioned in sections of 80-100microm in thickness and the demineralization patterns of prepared slices were assessed using a polarized light microscope. Three samples from each group were analyzed with scanning electronic microscopy. Analysis of variance and the Fisher test were performed for the statistical analysis of the data obtained from the caries-lesion-depth measurements (CLDM) (alpha=5%). RESULTS: The control group (CLDM=0.67mm) was statistically different from group 2 (CLDM=0.42mm), which presented a smaller lesion depth, and group 6 (0.91mm), which presented a greater lesion depth. The results of groups 3 (CLDM=0.74mm), 4 (CLDM=0.70mm), 5 (CLDM=0.67mm) and 7 (CLDM=0.89mm) presented statistical similarity. The scanning electronic microscopy analysis showed ablation areas in the samples from groups 4, 5, 6 and 7, and a slightly demineralized area in group 2. CONCLUSIONS: It was possible to conclude that Er:YAG laser was efficient in preventing enamel demineralization at a 4-mm irradiation distance using cooling.

Comparative study of physico-chemical properties of MTA-based and Portland cements.

The purpose of this investigation was to evaluate the physicochemical properties of gray and white structural and nonstructural Portland cement, gray and white ProRoot MTA and MTA BIO. The water/powder ratio, setting time, solubility and pH (hydrogen-ion potential) changes of the materials were evaluated. Tests followed specification #57 from the American National Standard Institute/American Dental Association (2000) for endodontic sealing materials and pH was determined by a digital pH meter. The test results were statistically analyzed by variance analyses for global comparison and by the complementary Tukey's test for pairwise comparisons (5%). Considering the water/powder ratio, no significant difference (p > 0.05) was observed among the cements. MTA BIO (33.10 +/- 2.30) had the lowest setting time (p < 0.05), gray ProRoot MTA (10.10 +/- 2.70) had the highest (p < 0.05). White nonstructural Portland cement (2.55 +/- 0.08) had the highest solubility (p < 0.05), while gray ProRoot MTA (1.03 +/- 0.12) had the lowest (p < 0.05), although all materials showed solubility values in compliance to ANSI/ADA. No difference (p > 0.05) was observed among materials when considering pH evaluation. The pH levels were highly alkaline immediately after immersion in solution, remaining stable throughout the test period. The authors conclude that the cements had similar water/powder proportions. MTA BIO had the shortest setting time and gray ProRoot MTA had the lowest solubility. All cements had similar behavior in the pH analysis.

First detection of lead in black paper from intraoral film: an environmental concern.

Lead (Pb) contamination in the black paper that recovers intraoral films (BKP) has been investigated. BKP samples were collected from the Radiology Clinics of the Dental School of Ribeirão Preto, University of São Paulo, Brazil. For sake of comparison, four different methods were used. The results revealed the presence of high lead levels, well above the maximum limit allowed by the legislation. Pb contamination levels achieved after the following treatments: paper digestion in nitric acid, microwave treatment, DIN38414-54 method and TCLP method were 997 microg g(-1), 189 microg g(-1), 20.8 microg g(-1), and 54.0 microg g(-1), respectively. Flame atomic absorption spectrometry (FAAS) and inductively coupled plasma mass spectrometry (ICP-MS) were employed for lead determination according to the protocols of the applied methods. Lead contamination in used BKP was confirmed by scanning electron microscopy coupled with energy dispersive X-ray microanalysis (SEM-EDS). All the SEM imaging was carried out in the secondary electron mode (SE) and backscattered-electron mode (QBSD) following punctual X-ray fluorescence spectra. Soil contamination derived from this product revealed the urgent need of addressing this problem. These elevated Pb levels, show that a preliminary treatment of BKP is mandatory before it is disposed into the common trash. The high lead content of this material makes its direct dumping into the environment unwise.

Influence of cavity preparation with Er:YAG Laser on enamel adjacent to restorations submitted to cariogenic challenge in situ: a polarized light microscopic analysis.

BACKGROUND AND OBJECTIVES: Er:YAG laser has been used for caries removal and cavity preparation, using ablative parameters. Its effect on the margins of restorations submitted to cariogenic challenge has not yet been sufficiently investigated. The aim of this study was to assess the enamel adjacent to restored Er:YAG laser-prepared cavities submitted to cariogenic challenge in situ, under polarized light microscopy. STUDY DESIGN/MATERIALS AND METHODS: Ninety-one enamel slabs were randomly assigned to seven groups (n = 13): I, II, III-Er:YAG laser with 250 mJ, 62.5 J/cm2, combined with 2, 3, and 4 Hz, respectively; IV, V, VI-Er:YAG laser with 350 mJ, 87.5 J/cm(2), combined with 2, 3, and 4 Hz, respectively; VII-High-speed handpiece (control). Cavities were restored and the restorations were polished. The slabs were fixed to intra-oral appliances, worn by 13 volunteers for 14 days. Sucrose solution was applied to each slab six times per day. Samples were removed, cleaned, sectioned and ground to polarized light microscopic analysis. Demineralized area and inhibition zone width were quantitatively assessed. Presence or absence of cracks was also analyzed. Scores for demineralization and inhibition zone were determined. RESULTS: No difference was found among the groups with regard to demineralized area, inhibition zone width, presence or absence of cracks, and demineralization score. Inhibition zone score showed difference among the groups. There was a correlation between the quantitative measures and the scores. CONCLUSION: Er:YAG laser was similar to high-speed handpiece, with regard to alterations in enamel adjacent to restorations submitted to cariogenic challenge in situ. The inhibition zone score might suggest less demineralization at the restoration margin of the irradiated substrates. Correlation between the quantitative measures and scores indicates that score was, in this case, a suitable complementary method for assessment of caries lesion around restorations, under polarized light microscopy.

Influence of Er:YAG laser on microhardness of enamel adjacent to restorations submitted to cariogenic challenge in situ.

OBJECTIVE: This study assessed the effect of the Er:YAG laser on enamel adjacent to restorations submitted to cariogenic challenge in situ, by microhardness analysis. BACKGROUND DATA: The influence of Er:YAG laser energy on secondary caries formation has been investigated in vitro. However, no research involving demineralization around cavities prepared with the Er:YAG laser under intra-oral conditions has yet been described. MATERIALS AND METHODS: Slabs of enamel were randomly assigned to seven groups (n = 12), according to the cavity preparation technique: groups I, II, and III--Er:YAG laser, 250 mJ, at 2, 3, and 4 Hz, respectively; groups IV, V, and VI--350 mJ, at 2, 3, and 4 Hz, respectively; group VII--high-speed handpiece (control). Cavities were restored and the specimens were fixed in intra-oral appliances and worn by 12 volunteers for 14 d. Sucrose solution was applied to each slab 6 times/d. Samples were removed, sectioned, and examined for microhardness at 100, 200, and 300 microm (factor distance), and 30, 60, and 90 microm (factor depth), from the restoration and enamel surface, respectively. RESULTS: Analysis of variance according to a split-plot model showed no difference among the cavity preparation techniques, among distances, or among depths, as well as no difference in the interaction between the factors of cavity preparation and distance. A significant difference was found in the interaction of cavity preparation and depth (p < 0.0001), as identified by contrast technique. CONCLUSION: The results revealed that the Er:YAG laser did not differ from conventional cavity preparation with regard to enamel microhardness.

Adhesion of a self-etching system to dental substrate prepared by Er:YAG laser or air abrasion.

The purpose of this study was to assess the microtensile bond strength of a self-etching adhesive system to enamel and dentin prepared by Er:YAG laser irradiation or air abrasion, as well as to evaluate the adhesive interfaces by scanning electron microscopy (SEM). For microtensile bond strength test, 80 third molars were randomly assigned to five groups: Group I, carbide bur, control (CB); II, air abrasion with standard tip (ST); III, air abrasion with supersonic tip (SP); IV, Er:YAG laser 250 mJ/4 Hz (L250); V, Er:YAG laser 300 mJ/4 Hz (L300). Each group was divided into two subgroups (n = 8) (enamel, E and dentin, D). E and D surfaces were treated with the self-etching system Adper Prompt L-Pop and composite buildups were done with Filtek Z-250. Sticks with a cross-sectional area of 0.8 mm(2) (+/-0.2 mm(2)) were obtained and the bond strength tests were performed. Data were submitted to ANOVA and Tukey's test. For morphological analysis, disks of 30 third molars were restored, sectioned and prepared for SEM. Dentin presented the highest values of adhesion, differing from enamel. Laser and air-abrasion preparations were similar to enamel. Dentin air-abrasion with standard tip group showed higher bond strength results than Er:YAG-laser groups, however, air-abrasion and Er:YAG laser groups were similar to control group. SEM micrographs revealed that, for both enamel and dentin, the air-abrasion and laser preparations presented irregular adhesive interfaces, different from the ones prepared by rotary instrument. It was concluded that cavity preparations accomplished by both Er:YAG laser energies and air abrasion tips did not positively influence the adhesion to enamel and dentin.

Assessment of thermal alteration during class V cavity preparation using the Er:YAG laser.

OBJECTIVE: The aim of this study was to evaluate in vitro the pulp thermal alterations during class V cavity preparations using the Er:YAG laser and high-speed water flow. MATERIALS AND METHODS: Forty human teeth were selected and prepared for the thermocouple adaptation in the pulp chamber. The specimens were assigned to four groups: (1) laser 300 mJ/3 Hz, (2) laser 300 mJ/4 Hz, (3) high-speed 9 mL/min water flow, and (4) high-speed 100 mL/min water flow. The temperature was measured before the beginning and at the end of the preparation, as well as during the procedures. The groups were analyzed by scanning electron microscopy. RESULT: Data analysis disclosed temperature reduction at high-speed drilling with the high-speed total water flow group, and these values were statistically different from the other groups. The results of the 9-mL/min water flow group were similar to those of the 300-mJ/3-Hz group and different from the 300-mJ/4-Hz laser group. CONCLUSION: The laser promoted a greater increase in temperature only when compared with high-speed handpiece and water flow rate of 100 mL/min.

Influence of Er:YAG laser on cavity preparation and surface treatment in microleakage of composite resin restorations.

OBJECTIVE: The purpose of this study was to assess microleakage on class V cavities prepared by Er:YAG laser with varying surface treatment. BACKGROUND DATA: There has been little reported research on microleakage at cavities prepared and treated with Er:YAG laser. METHODS: Fifty preparations using Er:YAG laser or a highspeed handpiece were developed. The surface treatment was performed as follows: Er:YAG laser (group 1); 35% phosphoric acid (group 2); laser + acid (group 3); finishing with low-speed + laser + acid (group 4); conventional preparation developed with a high-speed handpiece + acid (group 5--control). The samples were restored with Single Bond/Z250, thermocycled, isolated, and immersed in a 50% AgNO(3) solution. The restorations were sectioned, and the microleakage was measured in milimeters using a specific computer software. Data were analyzed employing ANOVAand Tukey test. RESULTS: Statistical analysis showed that group 5 (G5) obtained the lowest results of microleakage (22.05%), and it was statistically similar (p > 0.05) to G1 (37.7%) and different (p < 0.05) from the other groups (G2 = 50.4%; G3 = 43%; G4 = 44.2%). The occlusal margins (22.62%) demonstrated less microleakage (p < 0.05) than the cervical margins (56.32%). CONCLUSION: The use of Er:YAG laser for cavity preparation and surface treatment negatively influenced the marginal sealing of composite resin restorations.

Morphologic evaluation of the radicular dentine irradiated with Nd:YAG laser under different parameters and angles of incidence.

OBJECTIVE: The aim of this research was to evaluate, under the scanning electron microscope, the role of different parameters and angles of incidence of the Nd:YAG laser on the morphology of the radicular dentine. BACKGROUND DATA: Irradiation of dentine with Nd:YAG laser removes smear layer and promotes its fusion and recrystallization, thus decreasing permeability. METHODS: Forty-eight human maxillary canines were randomly divided in four groups of 12 teeth each, according to the following parameters of irradiation: 1 Wand 10 Hz; 1 Wand 20 Hz; 3 Wand 10 Hz; 3 Wand 20 Hz. Two teeth of each group were split longitudinally and the laser was applied perpendicularly to the root canal. Specimens were observed under the SEM, and the morphological alterations in dentine were recorded. RESULTS: The increase of power and frequency of the laser produced more structures that characterize the irradiation of dentine by Nd:YAG laser, such as globular formations, melting and glazing, and ebullitions. Such structures were especially frequent when 3 Wand 20 pps were used as parameters. The removal of the smear layer produced root canals with more dentinal tubules visible under the SEM. CONCLUSIONS: The increase in power and frequency of the Nd:YAG laser irradiation produced more visible morphological alterations than the lower settings. The removal of the smear layer increased the number of visible dentinal tubule openings.

Shear bond strength to enamel of primary teeth irradiated with varying Er:YAG laser energies and SEM examination of the surface morphology: an in vitro study.

OBJECTIVE: This study aimed to assess in vitro the influence of Er:YAG laser energy on the shear bond strength of a total-etch adhesive system to lased enamel of primary teeth, and to observe by SEM the morphological appearance of laser-ablated enamel surfaces. MATERIALS AND METHODS: For the SBS test, primary canines were assigned to four groups (n = 12): a control (G1) and three groups irradiated with different Er:YAG laser energies- 60 mJ/2 Hz (G2), 80 mJ/2 Hz (G3), and 100 mJ/2 Hz (G4). In all groups, enamel surfaces were acidetched, Single Bond was applied, and resin cylinders were fabricated from Z250 resin. Bond strength was tested in shear (0.5 mm/min). For morphological analysis, 21 specimens were irradiated using the same energies, with or without acid-etching, and observed by SEM. RESULTS: SBS means, in MPa, were: G1-14.28 (+/-3.24); G2-18.48 (+/-4.58); G3-17.82 (+/-4.38); G4-16.59 (+/-5.40). Overall, Er:YAG laser ablation of primary teeth enamel, prior to the adhesive protocol, influenced the shear bond strength. Bond strengths recorded after irradiation with energies of 60 and 80 mJ were statistically similar among them (p > 0.05), and both were superior to those yielded by the acid-etched control group (p < 0.05). No significant difference (p < 0.05) was found between bond strengths recorded for control specimens and those irradiated with 100 mJ. SEM analysis revealed that the increase of laser energy resulted in increasingly uneven and microroughened surfaces, regardless of acid-etching association. CONCLUSIONS: The favorable results of the present study suggest that Er:YAG laser irradiation may be a viable approach for the preparation and treatment of primary teeth enamel prior to the placement of adhesive restorative systems.

Influence of the use of Er:YAG laser for cavity preparation and surface treatment in microleakage of resin-modified glass ionomer restorations.

This study quantitatively assessed the amount of microleakage on Class V cavities prepared by Er:YAG laser and high-speed handpiece, varying the surface treatment and restoring with a resin-modified glass ionomer cement. Fifty cavities were prepared using either an Er:YAG laser device or a carbide bur at high speed. The surface treatment was performed as follows: Er:YAG laser irradiation (G1); 40% polyacrylic acid (G2); laser + acid (G3); finishing with low speed + laser + acid (G4); conventional bur preparation + acid (G5-control). The samples were restored with Fuji II LC, thermocycled, isolated and immersed in a 50% AgNO3 solution. The restorations were serially sectioned and the extent of dye penetration was measured in milimeters using specific computer software. Data were analyzed by two-way ANOVA and Tukey test. The lowest degree of microleakage was observed for G5, which was statistically similar (p>0.05) to G4 but different (p<0.05) from all the other experiental groups. Lesser microleakage was observed at the occlusal margins than at the cervical margins (p<0.05). It may be concluded that the use of Er:YAG laser for cavity preparation and surface treatment negatively affected the marginal sealing of resin-modified glass ionomer restorations.

Comparative study of the dentin/adhesive systems interface after treatment with Er:YAG laser and acid etching using scanning electron microscope.

BACKGROUND AND OBJECTIVES: To assess dentin/adhesive systems interface after dentin conditioning with Er:YAG laser. STUDY DESIGN/MATERIALS AND METHODS: Twenty-four dentin half-disks were assigned to 3 groups: All Bond 2 (AB); Optibond Solo Plus (OP); and Clearfil Liner Bond 2V (CL), which were divided into three sub-groups, according to dentin surface treatment: Er:YAG laser; Er:YAG laser plus acid; acid solely. After the adhesive protocol, specimens were embedded in resin, sectioned, and prepared for SEM analysis. Each area was examined under 1,500x magnification to assess the hybrid layer. RESULTS: Acid conditioning provided to AB and OP thick and homogeneous hybrid layer, as well as conical and uniform tags. The same pattern was observed for CL. In general, dentin treatment with laser, even when associated to acid, promoted irregular and thin hybrid layer, as well as scarce and thin tags. CONCLUSIONS: Er:YAG laser influenced the adhesive systems interface, hampering hybrid layer formation.

Bond strength to dentin of primary teeth irradiated with varying Er:YAG laser energies and SEM examination of the surface morphology.

BACKGROUND AND OBJECTIVES: This study aimed to assess in vitro the influence of Er:YAG laser energy on the shear bond strength of a total-etch adhesive to lased dentin of primary teeth, and observe under SEM the morphological appearance of laser-ablated dentin surfaces. STUDY DESIGN/MATERIALS AND METHODS: For SBS, specimens were irradiated with the energies 60 mJ/2 Hz (G2), 80 mJ/2 Hz (G3), 100 mJ/2 Hz (G4). Control (G1) was not irradiated. Dentin surfaces were acid-etched, Single Bond adhesive (3 M) was applied, and resin cylinders were fabricated from Z250 resin (3 M). Bond strength was tested in shear (0.5 mm/min). For morphological analysis, specimens were irradiated using the same energies, either or not acid-etched, and observed by SEM. RESULTS AND CONCLUSIONS: SBS means, in MPa, were: G1-17.89(+/-4.75); G2-12.34(+/-4.85); G3-10.30(+/-3.67); G4-10.41(+/-4.20). Overall, Er:YAG laser irradiation of primary teeth dentin, prior to the adhesive protocol, adversely affected bond strength. Furthermore, it was noticed that even though there was no significant difference among the Er:YAG laser-treated groups, the increase of laser energy resulted in increasingly cratered surfaces, regardless of acid-etching association.

Effects of Er:YAG and Nd:YAG laser irradiation on radicular dentine permeability using different irrigating solutions.

BACKGROUND AND OBJECTIVES: To evaluate the effect of Er:YAG and Nd:YAG laser on radicular dentine permeability when using distilled and deionized water and 1% NaClO as irrigating solutions. STUDY DESIGN/MATERIALS AND METHODS: Thirty human maxillary canines were divided randomly into six groups. The root canals were instrumented with K files and the step-back technique. Group I, irrigation with distilled and deionized water; Group II, irrigation with 1% NaClO; Group III, irrigation with distilled and deionized water and Er:YAG laser application (140 mJ input, 61 mJ output 15 Hz, 300 pulses, and 42 J); Group IV, irrigation with 1% NaClO and Er:YAG laser application (same parameters as Group III); Group V, irrigation with distilled and deionized water and Nd:YAG laser application (150 mJ, 15 Hz, 2,25 W); Group VI, irrigation with 1% NaClO and Nd:YAG laser application (same parameters as Group V). During laser application the teeth were always filled with the irrigating solution. The tip was withdrawn gently in helicoidal movement from the apex to the cervical portion. The teeth were processed for histochemical evaluation. RESULTS: The Tukey test showed that the cervical and middle thirds were statistically similar (P > 0.05) and significantly greater than the apical third (P < 0.05). The Scheffé test showed significantly greater dentine permeability in root canals in which water and Er:YAG laser were used and were significantly different from the other treatments (P < 0.05). CONCLUSIONS: The use of distilled and deionized water and Er:YAG laser showed the greater increase of dentine permeability. The use of 1% NaClO with Nd:YAG laser, distilled, and deionized water with Nd:YAG laser and the use of water increased dentine permeability less than the other groups. The use of 1% NaClO with and without Er:YAG laser application were positioned intermediately among the treatments.