Analysis of Marginal Adaptation of Porcelain Laminate Veneers Produced by Computer-Aided Design/Computer-Assisted Manufacturing Technology: A Preliminary In Vitro Study.

PURPOSE: To analyze the marginal adaptation of computer-aided design/computer-assisted manufactured (CAD/CAM) porcelain laminate veneers. MATERIALS AND METHODS: A total of 25 three-dimensional (3D) machine-milled laminate veneers were divided into five groups of five each according to fabrication material (E-max; Empress; Lava Ultimate; Suprinity; and Vita Mark II) and cemented in 25 prepared acrylic central incisors. Digital microscopy images (×7.5 magnification) were analyzed for gaps in the mesial/distal surfaces of the prepared tooth and in the cervical, medial, and incisal thirds. RESULTS AND CONCLUSION: All CAD/CAM laminate veneers except for Empress and Suprinity in the middle and incisal thirds showed good results (ie, gaps < 120 µm in the cervical, middle, and incisal thirds).

Assessment of the mechanical properties of glass ionomer cements for orthodontic cementation

OBJECTIVE: To evaluate the mechanical properties of three glass ionomers cements (GICs) used for band cementation in Orthodontics. METHODS: Two conventional glass ionomers (Ketac Cem Easy mix/3M-ESPE and Meron/Voco) and one resin modified glass ionomer (Multi-cure Glass ionomer/3M-Unitek) were selected. For the compressive strength and diametral tensile strength tests, 12 specimens were made of each material. For the microhardness test 15 specimens were made of each material and for the shear bond strength tests 45 bovine permanent incisors were used mounted in a self-cure acrylic resin. Then, band segments with a welded bracket were cemented on the buccal surface of the crowns. For the mechanical tests of compressive and diametral tensile strength and shear bond strength a universal testing machine was used with a crosshead speed of 1,0 mm/min and for the Vickers microhardness analysis tests a Microdurometer was used with 200 g of load during 15 seconds. The results were submitted to statistical analysis through ANOVA complemented by Tukey's test at a significance level of 5%. RESULTS: The results shown that the Multi-Cure Glass Ionomer presented higher diametral tensile strength (p < 0.01) and compressive strength greater than conventional GICs (p = 0.08). Moreover, Ketac Cem showed significant less microhardness (p < 0.01). CONCLUSION: The resin-modified glass ionomer cement showed high mechanical properties, compared to the conventional glass ionomer cements, which had few differences between them.

OBJETIVO: avaliar as propriedades mecânicas de três cimentos de ionômero de vidro (CIVs) utilizados para cimentação de anéis ortodônticos. MÉTODOS: foram utilizados dois CIVs convencionais (Ketac Cem Easy mix/3M-ESPE e Meron/Voco) e um CIV modificado por resina (Multi-Cure Glass ionomer/3M-Unitek). Para os testes de resistência à compressão e tração diametral, foram confeccionados 12 corpos de prova de cada material. Para os testes de microdureza, foram confeccionados 15 corpos de prova de cada material; para os testes de resistência de união ao cisalhamento, foram utilizados 45 dentes bovinos incluídos em resina acrílica, sobre os quais foi cimentada uma lâmina de anel ortodôntico com braquete soldado a ela para a realização dos ensaios. Para os testes de compressão, tração diametral e cisalhamento, foi utilizada uma máquina universal de ensaios a uma velocidade de 1mm/min; para os testes de microdureza Vickers, foi utilizado um microdurômetro com 200g de carga durante 15 segundos. Os resultados foram submetidos à análise estatística ANOVA, complementada pelo teste de Tukey ao nível de significância de 5%. RESULTADOS: os resultados demonstraram que o Multi-Cure Glass Ionomer apresentou resistência à tração diametral significativamente maior (p < 0,01) e maior resistência à compressão (p = 0,08) em relação aos CIVs convencionais. Além disso, o Ketac Cem apresentou microdureza significativamente maior que os demais materiais (p < 0,01). CONCLUSÃO: o CIV modificado por resina apresentou propriedades mecânicas superiores às dos CIVs convencionais, que, por sua vez, apresentaram poucas diferenças entre si.

Influence of ultrasound and diamond burs treatments on microtensile bond strength.

OBJECTIVE: To compare surface treatments with CVDentUS ultrasound tips (UT) and KGSorensen diamond burs (DB) on etched (e) and non-etched (n/e) dentin. The microtensile bond strength (µTBS) was measured and fractography was assessed by scanning electron microscope (SEM). MATERIALS AND METHODS: Sixteen molars were divided into four groups of four teeth each according to treatment (DB-n/e; DB-e; UT-n/e; UT-e). The teeth were restored, sectioned into samples for µTBS (n=40) and tested on a EMIC DL-2000 universal machine (0.5 mm/min) and analyzed by SEM for fracture classification. STATISTICAL ANALYSIS: For analysis of the data on µTBS, the two-way ANOVA, using treatment and acid etching as fixed factor, and the Tukey test were used (α=0.05). To failures classification in cohesive in dentin (CD); cohesive in composite resin (CC); cohesive interfacial on base or top of hybrid layer (CBT); cohesive in adhesive (CA); mixed (M); interfacial on smear layer (S) the Fisher's exact test (α=0.05) was performed. RESULTS: The mean values of µTBS (in MPa) in the different groups were as follows: UT-e: 45.31 ± 8.16; DB-e: 34.04 ± 9.29; UT-n/e: 15.17 ± 3.71; and DB-n/e: 9.86 ± 3.80. On analysis of the SEM micrographs, the DB-n/e group showed total obstruction of dentinal tubules; the UT-n/e group showed partial desobstruction of dentinal tubules and irregular surface; the DB-e group showed complete desobstruction of dentinal tubules; and the UT-e group showed complete desobstruction of dentinal tubules and irregular surface. CONCLUSION: The combination of ultrasound treatment and acid etching provides high values of µTBS. An association exists between CA/CC failures and the UT method, CBT failure and the DB method, CBT/CC failures and etching, S failure and non-etching.

Cytotoxicity of esthetic, metallic, and nickel-free orthodontic brackets: cellular behavior and viability.

INTRODUCTION: In this study, we evaluated the cellular viability of various esthetic, metallic, and nickel-free orthodontic brackets. METHODS: The sample was divided into 11 groups (n = 8): cellular control, negative control, positive control, metallic, polycarbonate, 2 types of monocrystalline ceramic, 3 types of nickel free, and polycrystalline ceramic brackets. Cell culture (NIH/3T3-mice fibroblasts) was added to the plates of 96 wells containing the specimens and incubated in 5% carbon dioxide at 37°C for 24 hours. Cytotoxicity was analyzed qualitatively and quantitatively. Cell growth was analyzed with an inverted light microscope, photomicrographs were obtained, and the results were recorded as response rates based on modifications of the parameters of Stanford according to the size of diffusion halo of toxic substances. Cell viability was analyzed (MTT assay); a microplate reader recorded the cell viability through the mitochondrial activity in a length of 570 nm. The values were statistically analyzed. RESULTS: All tested brackets had higher cytotoxicity values than did the negative control (P <0.05), with the exception Rematitan and Equilibrium (both, Dentaurum, Ispringen, Germany) (P >0.05), suggesting low toxicity effects. The values showed that only polycarbonate brackets were similar (P >0.05) to the positive control, suggesting high toxicity. CONCLUSIONS: The brackets demonstrated different ranges of cytotoxicity; nickel-free brackets had better biocompatibility than the others. On the other hand, polycarbonate brackets were made of a highly cytotoxic material for the cells analyzed.

Evaluation of inorganic particles of composite resins with nanofiller content.

The purposes of this study were evaluate by energy dispersed X-ray (EDS) and scanning electron microscopy (SEM) the inorganic particles of three nanofilled composite resins, comparing particles sizes, shape and composition, and the filler weight content by thermogravimetric analyzes (TGA). Three composite resins classified as nanofilled were selected to this study: Esthet-X; Grandio; Filtek Supreme XT. The shade was standardized (A2) for enamel (E) or dentin (D). Ten samples with 20 mg (±10 mg) of each composite resin were submitted to thermogravimetric analyzes (TGA) in order to record the filler weight content (wt%). The amount of inorganic phase ranged from 75.75 to 87 wt%, to Esthet-X (D) and Grandio (D), respectively. The filler composition was analyzed by energy dispersed X-ray (EDS), and the size and shape were evaluated by scanning electron microscopy (SEM). The filler average size (µm) obtained by SEM were: Esthet-X (E) 1.16; Esthet-X (D) 1.39; Filtek Supreme XT (E) 0.6 (nanocluster); Filtek Supreme XT (D) 1.14 (nanocluster); Grandio (E) 2.05 and Grandio (D) 3.1. Silica (SiO2), Ba and Al were observed through EDS. The shape of Esthet-X and Grandio fillers showed similar characteristics with high quantity of irregular inorganic particles and heterogeneous filler. However, Filtek Supreme XT showed spherical and regular particles with homogeneous distribution and sizes. Based in the analysis of nanofilled composites inorganic phase, inconsistencies of weight content, composition, shape and size can be stated between the literature and manufacturer's instructions.

Evaluation of mechanical properties on three nanofilled composites.

The purpose of this study was to evaluate the mechanical behavior of three composites with nanoparticles Filtek Z350 XT (3M ESPE), Esthet X (Dentsply), Grandio (Voco) in enamel and body shades (A2) trough nanohardness, elastic modulus, compressive strength test, flexural strength test, diametral tensile strength, flexural modulus, weight filler content and Knoop microhardness. One sample of each material was submitted to nanohardness and elastic modulus. Five values of ten indentations were considered valids inside confidence intereval. Ten samples of each material were submitted to compressive strength, flexural strength and diametral tensile strength test at universal testing machine. The flexural modulus test was calculated based on flexural strength results. Ten samples of each group were submitted to knoop microhardness test. The results were submitted to ANOVA and Tukey statistical tests. The highest inorganic weight filler content for Grandio was registered after the organic mould decomposition. After statistical analysis Grandio showed the highest averages for nanohardness, elastic modulus, flexural modulus and knoop microhardness. For diametral tensile strength Grandio and Filtek Z350 XT obtained the highest averages. The tested composite resins ranged similar medias statistically for compressive strength. For flexural strength Filtek Z350 XT and Esthet X showed the highest averages. The results suggest that the weight filler content, the filler size and shape and the contact surface between nanofillers and organic phase has direct relation with composite resins with nanoparticles mechanical properties. Further studies should be carried out to improve the knowledge of composites with nanoparticles mechanical behavior.

Development of glass ionomer cement modified with seashell powder as a scaffold material for bone formation / Desenvolvimento de cimento de ionômero de vidro modificado com pó de conchas como material estrutural para formação óssea

PURPOSE: The present study examined the possibility of modifying the structural properties of glass ionomer cement by adding seashells to form a possible 'scaffold' material for cases of bone formation. METHODS: White and black seashells were ground into a fine, homogeneous powder. To analyze their composition, the seashell samples were submitted to EDX and X-Ray diffraction. The ground seashells were mixed with the glass ionomer cement at either 1, 5 or 10 percent concentrations (in weight). Samples without any seashells were used as the control group. Solutions and GIC samples were analyzed for pH measurement. The structural and superficial analysis of samples was performed by using scanning electron microscopy (SEM). RESULTS: There was no difference in pH values among the tested solutions with different seashell concentrations (1, 5 and 10 percent). In the GIC samples with the shells, the pH values were close to 7.0. The EDX and X-Ray diffraction showed calcium carbonate (CaCO3) peaks for the shell samples. The superficial SEM analysis demonstrated that the samples containing seashells had framework formations in their structures. CONCLUSION: Although there is a need for biocompatibility and cellular cytotoxicity testing in vitro, as well as in vivo evaluation, seashells could be used in glass ionomer cement aiming at the development of a 'scaffold' material for bone grafting or osseointegration.

OBJETIVO: Este estudo examinou a possibilidade de modificar as propriedades estruturais do cimento de ionômero de vidro (CIV) pela adição de conchas para formar um material estrutural, com objetivo de uso em casos de formação óssea. METODOLOGIA: Conchas de cor branca e preta foram transformadas em um pó fino e homogêneo e sua composição foi analisada por EDX e difração por RX. O pó de concha foi misturado a CIV nas concentrações de 1, 5 ou 10 por cento (em peso) para a confecção das amostras. Amostras sem pó de concha foram usadas como grupo controle. Foram realizadas medições de pH de soluções do pó de conchas e das amostras de CIV. A análise estrutural e superficial das amostras foi realizada por microscopia eletrônica de varredura (MEV). RESULTADOS: Não houve diferença de pH entre as soluções testadas com diferentes concentrações de pó de concha (1, 5 ou 10 por cento). Nas amostras de CIV com conchas, os valores de pH foram próximos a 7,0. Os métodos de EDX e difração por RX mostraram picos de carbonato de cálcio (CaCO3) para as amostras com conchas. A análise por MEV demonstrou que as amostras com pó de conchas tinham formações estruturais diferentes do controle. CONCLUSÃO: Embora haja necessidade de testes de biocompatibilidade e citotoxicidade celular, assim como avaliação in vivo, as conchas poderiam ser utilizadas como material de modificação estrutural do cimento de ionômero de vidro em casos de material para enxerto ósseo ou osseointegração.

Relationship between filler content and selected mechanical properties of six microhybrid composites / Relação entre o conteúdo de carga e propriedades mecânicas de seis resinas compostas microhíbridas

PURPOSE: The purpose of this study was to evaluate the influence of filler weight content on selected mechanical properties of six microhybrid composite resins. METHODS: Compressive strength, elastic modulus, Vickers microhardness (VHN), and weight filler content were evaluated in the following dental composites: Admira (AD), Charisma (CH), InTen-S (IN), Tetric Ceram (TC), Point 4 (P4), and Z250 (Z2). RESULTS: Mean values for compressive strength (MPa) ranged from P4 76.60 to Z2 222.33. The elastic moduli (GPa) ranged from IN 2.56 to Z2 4.59. Microhardness VHN ranged from P4 50.53 to Z2 87.88. Filler weight content (Wt percent) ranged from IN 72.51 to TC 79.56. Significant differences were found between the composites (ANOVA/Tukey's, P<0.05). CONCLUSION: Z2 had the highest compressive strength; Z2 and TC showed the highest elastic modulus, VHN and filler weight content. Weight filler content had a strong influence on mechanical properties (0.78

OBJETIVO: O objetivo deste estudo foi avaliar a influência do conteudo de carga, em peso, de seis resinas compostas microhíbrida sobre determinadas propriedades mecânicas. METODOLOGIA: A resistência à compressão, módulo de elasticidade, microdureza Vickers (VHN) e conteúdo de carga de peso foram avaliados nas seguintes resinas compostas: Admira (AD), Charisma (CH), InTen-S (IN), Tetric Ceram (TC), Point 4 (P4) e Z250 (Z2). RESULTADOS: Os valores médios de resistência à compressão (MPa) variaram de P4 76,60 a Z2 222,33. Os módulos de elasticidade (GPa) variou de IN 2,56 a Z2 4,59. A microdureza VHN variou de P4 50,53 a Z2 87,88. O conteúdo de carga em peso (Wt por cento) variou de IN 72,51 a TC 79,56. Foram encontradas diferenças significativas entre as resinas compostas (ANOVA/Tukey's, P<0,05). CONCLUSÃO: A resina Z2 teve a maior resistência à compressão; Z2 e TC apresentaram maiores módulo de elasticidade, VHN e conteúdo de carga em peso. O conteúdo de carga em peso teve uma forte influência nas propriedades mecânicas avaliadas (0,78

Análise in vitro do alívio interno de coroas totais após a utilização de espaçadores para troqueis / In vitro analysis of the internal relief of full crowns after the use of die spacers

OBJETIVO: Avaliar o alívio interno de coroas totais após a utilização de espaçadores para troqueis. MÉTODOS: Foram confeccionadas 20 coroas metálicas, em níquel-cromo, divididas em quatro grupos de cinco coroas de acordo com o número de camadas de espaçador empregadas. Cada coroa foi submetida à medição do espaço interno, formado entre as suas paredes internas e a parede externa do troquel mestre metálico. Para a medição, uma silicona de adição ultraleve foi injetada no interior das coroas. As amostras assim obtidas foram seccionadas ao meio no sentido ocluso-cervical de modo a obter duas metades, as quais foram escaneadas em alta resolução juntamente com um paquímetro. As imagens obtidas foram levadas ao software Image Tool 3.0 para medição do alívio interno obtido em dois pontos equidistantes em cada uma das paredes axiais e na parede oclusal. Os valores médios obtidos em micrômetros (µm) para condição de alívio nas diferentes paredes foram submetidos à análise estatística através da análise de variância, teste de Tukey e teste t de Student. RESULTADOS: À medida que se aumenta o número de camadas de espaçador aumenta também o alívio interno obtido. O Grupo 4 demonstrou uma espessura elevada na parede oclusal, a qual foi equivalente ao Grupo 2 e explicada pelo não escoamento do material para moldagem no interior da coroa. CONCLUSÃO: A aplicação de espaçadores para troqueis antes da ceroplastia permite ao operador obter fundições com alívio interno controlado, como condição para obter espaço suficiente para o agente cimentante.

OBJECTIVE: This research evaluated the internal relief in full crowns after the use of die spacers. METHODS: Twenty nickel-chromium crowns were made and divided into four groups of five crowns each, according to the number of die spacer layers used .The space between the inside walls and outside walls of the metal master die of each crown was measured. The measurement was done by injecting a very light-bodied addition silicone inside the crowns. The resulting samples were cut in half along the occlusal cervical plane and the halves were scanned in high resolution together with a slide caliper. The resulting images were transferred to the Image Tool 3.0 software for measuring the internal relief obtained from two equidistant points on each axial wall and on the occlusal wall. The relief means in micrometers in the different walls were statistically analyzed by analysis of variance, Tukey test and Student's t-test. RESULTS: As the number of spacer layers increases, so does internal relief. The occlusal wall of Group 4 was very thick, equivalent to that of Group 2, which is explained by the impression material not flowing inside the crown. CONCLUSION: The application of die spacers before waxing allows the operator to obtain casts with controlled internal reliefs, making room for the cement.

Effect of conditioner on microtensile bond strength of self-adhesive resin cements to dentin.

OBJECTIVE: Evaluate, in vitro, the microtensile bond strength (µTBS) of RelyX ARC conventional resin cement and RelyX Unicem and Maxcem self-adhesive resin cements to dentin, and the influence of polyacrylic acid pretreatment on the µTBS. MATERIAL AND METHODS: Flat dentin surfaces were obtained in 15 third molars which were randomly divided into 5 groups: Group 1 - RelyX ARC (control); Group 2 - RelyX Unicem; Group 3 - Maxcem Elite; Group 4 - 22.5% polyacrylic acid and RelyX Unicem; Group 5 - 22.5% polyacrylic acid and Maxcem Elite. A block of composite resin was built over the resin cements. The samples were sectioned to obtain beams, and 20 specimens for each group were submitted to µTBS on a universal testing machine. Failure modes were analyzed by scanning electron microscopy. RESULTS: According to ANOVA and Tukey test, the highest µTBS mean (MPa) was obtained with RelyX ARC (21.38), which did not differ statistically from Maxcem Elite with polyacrylic acid pretreatment (19.22) and RelyX Unicem with polyacrylic acid pretreatment (17.75) (p>0.05). The latter two groups did not differ statistically from RelyX Unicem (16.98) (p>0.05). The lowest mean was obtained for Maxcem Elite (6.43), which differed statistically from the other groups (p<0.05). All failures were adhesive for Maxcem Elite without polyacrylic acid pretreatment, and mixed failures were predominant in the other groups. CONCLUSIONS: RelyX ARC achieved higher µTBS to dentin in comparison to the self-adhesive resin cements. Polyacrylic acid pretreatment was effective in improving the µTBS of Maxcem Elite, but did not influence the µTBS for RelyX Unicem.

Stress distribution of an internal connection implant prostheses set: a 3D finite element analysis.

OBJECTIVE: This study evaluated the stress distribution by loads, under a internal connection implant system with two sort of abutment screws and prosthetic crown models at ten observation points. MATERIALS AND METHOD: The analysis were made in two models with internal butt joint, and with gold and titanium screw, respectively. The load was 382N with 90 masculine to the occlusal surface and 15 masculine to the implant axis at 4 and 6 mm from the implant center. RESULTS: In both models, a large amount of stress was located around the implant neck and little stress was concentrated along the abutment screw. CONCLUSION: The simulations made suggest that the internal connection protects the abutment screw from the accumulated stresses; however, it exposes the implant walls to these stresses.

Cytotoxicity of silver solder employed in orthodontics.

OBJECTIVE: To test the null hypothesis that the silver soldering employed in orthodontics is not cytotoxic for fibroblasts. MATERIALS AND METHODS: This in vitro study was performed using a culture of mice fibroblasts (lineage NIH/3T3), divided into four groups (n = 10 each): control, negative control (stainless steel archwire), positive control (amalgam disks), and test group (silver soldering). After cell culture in complete Dulbecco modified eagle medium and achievement of confluence in 80%, the suspension was added to the plates of 24 wells containing the specimens and incubated in an oven at 37 degrees C for 24 hours. The plates were analyzed on an inverted light microscope, photomicrographs were obtained, and the results were recorded as response rates based on modifications of the parameters of Stanford according to the size of the diffusion halo of the toxic substance and quantity of cell lysis. RESULTS: The results revealed a maximum response rate for the silver soldering group, as well as severe inhibition of cell proliferation and growth, more round cells with mostly darkened and granular aspects, suggesting lysis with cell death. A similar response was seen in the positive control group. CONCLUSION: The hypothesis is rejected. The silver soldering used in orthodontics represents a highly cytotoxic material for the cells analyzed.

Fracture strength of endodontically treated molars transfixed horizontally by a fiber glass post.

PURPOSE: To assess the effect of a horizontally transfixed fiber glass post placed between buccal and palatal surfaces, on the fracture strength of endodontically treated molar teeth with MOD cavities, either restored with resin-based composite, or not. METHODS: 75 sound maxillary human third molars were extracted, embedded in acrylic resin blocks and randomly assigned to five groups (n=15). Group A (sound teeth), (control) and Groups B, C, D and E, which were subjected to the following procedures after endodontic treatment: GB--(MOD+Endo), GC--(MOD+Endo+Post), GD--MOD and composite restoration (MOD+Endo+CR), GE--(MOD+Endo+Post+CR). The specimens were stored in distilled water at 37 degrees C for 24 hours. Later, a compressive force was applied by means of a universal testing machine at 1 mm/minute speed, parallel to the long axis of the teeth until fracture occurred. RESULTS: The means of the results (N) followed by the same letter represent no statistical difference by ANOVA and Tukey (P<0.05): GA = 4289.8 (+/- 1128.9)a, GB = 549.6 (+/- 120.7)b, GC = 1474.8 (+/- 338.1)c, GD = 1224.7 (+/- 236.0)c, GE = 2645.4 (+/- 675.1)d. In the analysis of qualitative variables, there was a tendency to cusp fracture in all groups except for Group C. The fiber glass post transfixed horizontally in a MOD cavity significantly increased the fracture resistance of the teeth restored with resin composite.

Influence of chisel width on shear bond strength of composite to enamel / Influência da largura do cinzel sobre a resistência ao cisalhamento da união esmalte/resina composta

Purpose: To evaluate the effect of chisel width on shear bond strength of composite to dental enamel. Methods: Sixty crowns of bovine incisors were embedded in acrylic resin, and their enamel surfaces were flattened and etched with 35% phosphoric acid. Single Bond (3M/ESPE) adhesive system and Z-250 (3M/ESPE) composite were used to build a cylindrical-shaped restoration perpendicular to the conditioned enamel flat surface. Specimens were divided into four groups and subjected to the shear bond strength testing using a chisel-shaped shearing blade with a 0.5, 1.0, 2.0, or 3.0 mm-width blunt edge in a universal testing machine at crosshead speed of 0.5 mm/min. Data on shear bond strength were analyzed by ANOVA and Duncan's test (á=0.05). Results: Shear bond strength means for the experimental groups were: 0.5 mm - 19.66 MPa; 1 mm - 18.78 MPa; 2 mm - 16.77 MPa; 3 mm - 16.06 MPa. Bond strength was significantly different between the groups tested with chisels of 0.5 and 3 mm-width (P=0.045) showing an inverse relationship between shear bond strength and chisel width. Conclusion: The results suggest that shear bond strength varies as a function of chisel width.

Objetivo: Avaliar a influência de diferentes larguras de cinzel sobre a resistência de união ao cisalhamento na interface esmalte dental/resina composta. Metodologia: As coroas de 60 dentes incisivos bovinos foram incluídas em resina acrílica e as superfícies vestibulares de esmalte foram planificadas e condicionadas com ácido fosfórico a 35 %. O sistema adesivo Single Bond (3M/ESPE) e de resina composta Z-250 (3M/ESPE) foram utilizados para fabricar restaurações cilíndricas de resina composta perpendiculares à superfície plana do esmalte condicionado. Para o teste de cisalhamento, os espécimes foram submetidos ao ensaio mecânico com cinzéis de 0,5 mm, 1,0 mm, 2,0 mm ou 3,0 mm de largura da parte ativa romba, em uma máquina de ensaio universal à velocidade de 0,5 mm/min. Os dados obtidos foram analisados por análise de variância e teste de Duncan ao nível de significância de 5 %. Resultados: As médias de resistência de união ao cisalhamento dos grupos testados foram: 0,5 mm - 19,66 MPa; 1,0 mm -18,78 MPa; 2,0 mm - 16,77 MPa; 3,0 mm - 16,06 MPa. Houve diferença estatisticamente significativa entre os grupos de 0,5 e 3,0 mm (P=0,045), com uma relação inversa entre resistência de união ao cisalhamento e largura do cinzel. Conclusão: Os resultados sugerem que a resistência de união ao cisalhamento sofre influência da largura do cinzel utilizado no ensaio.

Influence of Nd:YAG laser irradiation on microtensile bond strength of adhesive systems to sound or carious dentin.

OBJECTIVE: To evaluate the microtensile bond strength of 2 adhesive systems (Adper Single Bond Plus [3M ESPE] and Clearfil SE Bond [Kuraray]) to carious or normal dentin, with or without previous treatment with Nd:YAG laser or Nd:YAG laser associated with fluoride. METHOD AND MATERIALS: Dentin surfaces of 60 human third molars were exposed. Teeth were divided into 12 groups; groups 1 to 6 were submitted to pH cycling for artificial caries, and groups 7 to 12 remained with normal dentin. Dentin surfaces received 3 treatments: laser Nd:YAG irradiation (60 mJ, 15 Hz, and 0.9 W) for 1 minute; laser Nd:YAG irradiation associated with fluoride in gel; and no treatment (controls). In experimental groups, adhesive systems were applied in accordance with the manufacturers' instructions, and a composite resin block (Filtek Z250, 3M ESPE) was made incrementally for the microtensile bond strength test. The teeth were sectioned serially in both x and y directions, and sticks were submitted to microtensile bond strength testing in a universal testing machine. RESULTS: According to ANOVA and Tukey (P < .05), the highest mean bond strengths were obtained in groups of normal dentin treated with Clearfil SE Bond (40.65 MPa) and Single Bond (34.2 MPa). The presence of carious dentin significantly decreased the mean bond strengths of the 2 adhesive systems whether or not they were previously laser irradiated. Nevertheless, Clearfil SE Bond presented the best microtensile bond strength on an irradiated surface. Moreover, laser irradiation associated with fluoride also decreased the bond strength values of the 2 adhesive systems. CONCLUSION: After excavating a cavity with caries-affected dentin, the use of Nd:YAG laser followed by a self-etching adhesive system is the best clinical choice when considering bond strength, compared with the total etching- based system and laser.

Creating three-dimensional tooth models from tomographic images.

UNLABELLED: The use of Finite Element Analysis (FEA) is becoming very frequent in Dentistry. However, most of the three-dimensional models presented by the literature for teeth are limited in terms of geometry. Discrepancy in shape and dimensions can cause wrong results to occur. Sharp cusps and faceted contour can produce stress concentrations, which are incoherent with the reality. AIM: The aim of this study was the processing of tomographic images in order to develop an advanced three-dimensional reconstruction of the anatomy of a molar tooth and the integration of the resulting solid with commercially available CAD/CAE software. METHODS: Computed tomographic images were obtained from 0.5 mm thick slices of mandibular molar and transferred to commercial cad software. Once the point cloud data have been generated, the work on these points started to get to the solid model of the tooth with Pro/Engineer software. RESULTS: The obtained tooth model showed very accurate shape and dimensions, as it was obtained from real tooth data with error of 0.0 to -0.8 mm. CONCLUSION: The methodology presented was efficient for creating a biomodel of a tooth from tomographic images that realistically represented its anatomy.

Surface modification of In-Ceram Zirconia ceramic by Nd:YAG laser, Rocatec system, or aluminum oxide sandblasting and its bond strength to a resin cement.

OBJECTIVE: The purpose of this study was to evaluate the effect of different surface treatments on bond strength between In-Ceram Zirconia ceramic and Panavia Fluoro Cement. BACKGROUND DATA: Although several surface treatments have been used on In-Ceram Zirconia, no study has been conducted to investigate the effect of the Nd:YAG laser. MATERIALS AND METHODS: Nine In-Ceram Zirconia blocks (10 x 10 x 6 mm) received three different surface treatments (n = 3 per group): group 1-Al2O3 sandblasting + silane; group 2-Al2O3 sandblasting + Rocatec Plus + silane; and group 3-Al2O3 sandblasting + Nd:YAG laser + silane. Resin cement was applied and light-cured, followed by the application of composite resin. The blocks were sectioned to obtain square rods with a cross-sectional dimension of 1.0 mm2 (n = 12 per group). Microtensile bond strength (muTBS) was recorded using a universal testing machine at a cross-head speed of 0.5 mm/min and expressed in megapascals (MPa). RESULTS: All groups yielded statistically significantly different muTBS mean values: group 1 (11.81 +/- 3.12 MPa); group 2 (15.75 +/- 4.45 MPa); group 3 (18.70 +/- 5.14 MPa) (ANOVA and Tukey's test; alpha = 0.05). CONCLUSION: Nd:YAG laser irradiation is an effective surface treatment for bonding between In-Ceram Zirconia and Panavia Fluoro Cement.

Evaluation of shear bond strength and interfacial micromorphology of direct restorations in primary and permanent teeth--an in vitro study.

This in vitro study sought to evaluate the bond strength and interfacial morphology of composite restorations in primary and permanent teeth that utilized different adhesive systems. In this study, 180 samples (n = 15 per subgroup) were submitted to shear bond strength tests while 72 samples were analyzed with scanning electron microscopy (n = 6 per subgroup). Fifty-four blocks of permanent enamel, 54 blocks of permanent dentin, 54 blocks of primary enamel, and 54 blocks of primary dentin were randomly assigned to three groups for bonding. All of the blocks received a resin composite restoration made with a matrix after the application of the dental bonding systems, according to the manufacturer's instructions. The shear bond strength test found no statistical differences among the tissues or the adhesive systems used. However, a difference in quality of the interfacial seal was observed when Single Bond restorations were compared to restorations bonded with AdheSE and Prompt-L-Pop. The Single Bond system formed an authentic hybrid layer that can ensure adequate adhesion. The other adhesive systems showed an interface with inadequate sealing and even with no sealing. The self-etching systems must be used with caution in composite restorations because the quality of the hybrid layer formed is as important as the bond strength when determining the efficacy of the adhesive.

Influência do método de polimerização na microdureza de compósitos microhíbridos armazenados em água destilada / Influence of curing method on the micro hardness of microhybrid composites immersed in distilled water

O objetivo do presente estudo é comparar e avaliar a microdureza Vickers de um compósito restaurador microhíbrido ativado por dois tipos de unidades polimerizadoras e armazenados em água destilada. Trinta espécimes foram feitos com resina Charisma B1, para cada um dos regimes de polimerização: fotopolimerização por luz halógena, fotopolimerização por LED e fotopolimerização mais ciclo adicional em autoclave. Foram feitas duas leituras de microdureza Vickers por corpo de prova em 1 dia, 7 dias e 14 dias de imersões. O ciclo adicional de polimerização mostrou uma tendência de aumentar os valores de microdureza dos compósitos restauradores, não mostrando diferenças estatisticamente significantes entre LED e Luz Halógena (p > 0,05).

The purpose of this study is to evaluate and compare the Vickers microhardness of one microhybrid composite polymerized with different sources and stored in distilled water for up to 14 days. Thirty samples have been prepared with Charisma composite, shade B1, for each polymerization method: halogen light photopolymerization, LED photopolymerization, photopolymerization plus post-cured cycles in autoclave. Two readings of Vichers micro hardness have been done in each sample on 24h, 7days and 14 days of storage. The post curing method tended to improve the microhardness, but it was not statistically different from halogen or LED curing methods (p > 0.05). After 7 days, the hardness values were higher than the first day, but statistically not different to 14 days (p < 0.05). Post-cured samples in autoclave had an improved mean value, however, without differing from those of the LED and halogen.

Development of a device to measure bracket debonding force in vivo.

The purposes of this study were to develop a device to measure bracket debonding force in vivo and to evaluate, in vitro, the bond strength obtained with the device and with tensile and shear bond strength (SBS) tests performed in a universal testing machine. The device was developed using polypropylene pliers (3M Unitek). The basic principle consisted of measuring the applied force to debond, using two strain gauges (Kyowa) bonded to the region of major deformation of the plier handles. The crowns of 75 bovine incisors were embedded in acrylic resin and orthodontic brackets were bonded to the facial surface with Transbond XT (3M Unitek). In group A (n = 25) debonding was carried out with the device, while tensile bond strength testing was performed in group B (n = 25) and SBS testing in group C (n = 25). A universal testing machine (EMIC-DL-2,000) was used for these last two groups. According to analysis of variance and Tukey's test (alpha = 0.05), the mean bond strength for group C (7.71 MPa) was statistically higher than for groups A (2.98 MPa) and B (2.69 MPa). Groups A and B were not statistically different. The device was shown to be feasible to obtain in vivo bond strength values for orthodontic brackets, and that the bond strength values were dependent on the method and direction of debonding.