Recentemente, os lasers de pulsos ultracurtos têm sido avaliados para o preparo dos tecidos duros dentais devido à sua habilidade de reduzir os efeitos térmicos resultantes da irradiação. O objetivo deste estudo foi avaliar a efetividade de união de 3 sistemas adesivos à dentina preparada com o laser de femtossegundos (10-15 s). Para isso, 60 terceiros molares foram preparados com o laser de femtossegundos (1.450 nm; 0,3W; 100.000Hz) ou ponta diamantada, divididos em 3 subgrupos (n=10) restaurados utilizando o adesivo condicione e lave de 3 passos Optibond FL (OFL; Kerr), o autocondicionante de 2 passos Clearfil SE (CSE; Kuraray) ou o autocondicionante de 1 passo G-aenial Bond (GAB; GC). Após 1 semana de armazenamento em água, os dentes foram seccionados (1,0x1,0 mm) e testados imediatamente e após 6 meses de armazenamento. Vinte e quatro amostras adicionais foram preparadas com o laser ou ponta diamantanda conforme descrito acima. Seis amostras foram seccionadas em espécimes menores e aleatoriamente preparados para observação das características morfológicas da superfície (n=3) e subsuperfície (n=3) em Microscópio Eletrônico de Varredura (MEV) (n=3) e Microscopia Eletrônica de Transmissão (MET) (n=3). As outras 18 amostras foram restauradas com os sistemas adesivos supramencionados, seccionados em espécimes menores e distribuídos para avaliação da interface adesiva em MEV (n=3) e padrão de nanoinfiltração após 1 semana (n=2) e 6 meses (n=2) em MET. O modelo linear de efeitos mistos (=0,05) revelou um efeito significante dos fatores adesivo, armazenagem e a interação preparo x armazenagem na resistência de união. Todos os adesivos apresentaram uma redução significante da resistência de união após 6 meses de armazenamento (p<0,0001) para ambos os tipos de preparo. Com relação ao sistema adesivo, a única diferença verificada foi o maior valor de resistência de união do GAB quando aplicado sobre as superfícies irradiadas (56,71±10,72 MPa) quando comparadas com as preparadas com ponta diamantada (43,14±14,93 MPa) após 1 semana de armazenamento. A análise de fratura revelou fraturas mistas, adesivas e coesivas em dentina para ambos os métodos de preparo com um discreto aumento do número de fraturas mistas após 6 meses de armazenamento exceto para o GAB, que apresentou principalmente fraturas adesivas e mistas. A análise em MEV revelou uma fina camada de debris sobre a superfície da dentina irradiada e a hibridização com todos os sistemas adesivos resultou num íntimo contado da interface adesiva com o substrato. A análise em MET da subsuperfície irradiada revelou fibrilas colágenas preservadas. A análise da interface adesiva revelou um aumento dos depósitos de prata na camada híbrida para todos os adesivos, após 6 meses de armazenamento, independentemente do tipo de preparo. Apenas o GAB apresentou maiores depósitos de prata após 1 semana de armazenamento para as superfícies preparadas com ponta diamantada. A irradiação com o laser de femtossegundos não reduziu a receptividade da dentina aos sistemas adesivos, resultando em valores de resistência de união similares aos obtidos com a ponta diamantada; além de uma ótima interação do substrato com os sistemas adesivos e deposições de prata similares àquelas obtidas com a ponta diamantada. / Recently, the applicability of ultrashort pulsed lasers has been studied for dental hard-tissue irradiation because of its reduced residual thermal damage. The aim of this study was to determine the bonding effectiveness of 3 contemporary adhesive systems to dentin prepared by femtosecond (10-15 sec) laser-irradiation. For this, 60 third molars were prepared either by the femtosecond laser (1450 nm; 0.3W; 100,000Hz) or by bur, randomly divided into 3 subgroups (n=10) and restored with a composite using either the 3-step etch-and-rinse adhesive Optibond FL (OFL; Kerr), the 2-step self-etch adhesive Clearfil SE (CSE; Kuraray) or the 1-step self-etch adhesive G-aenial Bond (GAB; GC). After 1-week water storage, the teeth were sectioned (1.0x1.0 mm) and half of the specimens were tested until failure using a micro-tensile bond-strength (TBS) approach. The other half was stored in water and tested after 6 months. Twenty-four additional dentin samples were exposed to the diamond bur and the laser, following the same abovementioned parameters. Three samples of each treatment were sectioned in smaller specimens in order to be characterized for surface (n=3) and cross-sectional morphological analysis using Scanning Electron Microscopy (SEM) (n=3) and Transmission Electron Microscopy (TEM) (n=3). The other eighteen samples were hybridized with the abovementioned adhesive systems, sectioned in smaller samples and distributed for evaluation of the interface under SEM (n=3) and nanoleakage distribution for 1 week (n=2) and 6 months (n=2) under TEM. Linear mixed effect model (=0.05) revealed a significant effect of the factors adhesive, storage and the interaction of preparation x storage on the TBS. All adhesives presented a significant reduction of the bond strength after 6-month storage (p<0.0001) for both preparation methods. Regarding the adhesive system, the only difference found was a significantly higher TBS of GAB to laser-irradiated (56.71±10.72 MPa) than to bur-cut dentin (43.14±14.93 MPa) after 1-week water storage. Fracture analysis showed mixed, adhesive and cohesive failures in dentin similarly for both preparation methods with a slightly increase of the mixed failures after 6-months water storage for OFL and CSE, but not for GAB that presented mainly adhesive and mixed failures. SEM disclosed a thin layer of debris on the laser-irradiated dentin surface and the hybridization with all adhesive systems resulted in a very tight interface. TEM analysis of the irradiated subsurface revealed collagen fibrils preserved and for the nanoleakage evaluation an increase of silver deposits at hybrid layer for all adhesives testes after 6-months water storage, irrespective of the preparation methods. Only the GAB presented great silver deposits even after 1-week water storage for the bur-cut preparation method. Femtosecond laser irradiation did not reduce the bonding receptiveness of dentin resulting in similar values obtained with the preparation by bur. Additionally it led to a great interaction with different adhesive systems and silver deposits comparable to those obtained with the bur-cut preparation method.

Preparos para retentores intra-radiculares mais conservadores evitam desgaste desnecessário da estrutura dentinária, requer menos cimento e podem melhorar a retenção adesiva do pino. Assim o objetivo deste estudo foi avaliar a espessura de cimento ea resistência adesiva de pinos de fibra de vidro cônicos em preparo para retentor intra-radicular realizados com uma ponta ultrassônica desenvolvida. Trinta incisivos laterais superiores foram preparados com limas reciprocantes Wave One Gold (Dentsply Sirona, Ballaigues, Suiça) e aleatoriamente divididos em 2 grupos (n=15) de acordo com a técnica de preparo para pino: grupo US foram preparados com uma ponta ultrassônica desenvolvida, e grupo WP (controle) com a broca recomendada pelo fabricante do pino. Os pinos de fibra de vidro cônicos WhitePost DC 0.5 (FGM, Joinville, SC, Brasil) foram cimentados utilizando cimento resinoso dual nos terços cervical e médio do canal radicular. Isto posto, todos os espécimes foram seccionados transversalmente em três seções (cervical, média e apical do pino) para análise da área de cimento resinoso ao redor do pino que foi calculada através do programa AutoCAD, em seguida, para avaliar a resistência adesiva, o teste de cisalhamento por extrusão foi aplicado através de uma maquina de ensaio universal numa velocidade média de 0.5 mm/min até o deslocamento do conjunto restaurador intra-radicular e o tipo de falha avaliado por estereomicroscopia. A comparação entre grupos e entre terços da área de cimento e resistência adesiva foram analisadas pelo teste t independente e Anova com Tukey; e os tipos de falha entre os grupos por Mann-Whitney, todos com nível de significância de 5%. No grupo ultrassônico foi observado a menor quantidade de cimento (p<0.05) e a resistência adesiva nos diferentes grupos e terços se manifestou maior somente no terço apical do grupo ultrassônico (p<0.05). Falha adesiva entre cimento e dentina foi a mais prevalente do terço cervical e apical do grupo US e cervical de grupo WP. Falha adesiva entre cimento e pino foi a mais prevalente nos demais terços. Conclui-se que o preparo para retentor com a ponta ultrassônica desenvolvida requer menor quantidade de cimento e influencia na melhor resistência de união no terço apical do pino de fibra de vidro. / Conservative post space preparations for intra-radicular retainers prevent unnecessary desgaste of the dentin structure, require less cement and improve bond strength of the post. The aim of this study was to evaluate the influence of resin cement thickness and bond strength of prefabricated glass fiber circular postin post space preparations with an ultrasonic tip developed. Thirtymaxillarylateral incisors were prepared with Wave One Gold reciprocating files (Dentsply Sirona, Ballaigues, Switzerland) and randomly divided into 2 groups (n=15) according to the post preparation technique: gruoup US was prepared with an ultrasonic tip developed and group WP (control) with the drill recommended by the post fabricant. Every glass fiber posts WhitePost DC 0.5 (FGM, Joinville, SC, Brazil) was cemented using dual polymerizing resin cement in the cervical and middle thirdof the root canal. After that, every specimen was sectioned transversally into three sections(cervical, middle and apical of the post) and the resin cement thickness area was calculated with AutoCAD program, the bond strength test was done with an universal testing machineat medium velocity 0.5 mm/min and the failure pattern after the test was analyzed with stereomicroscopy. Datas obtained were analyzed statistically using Student\'s t-Test, ANOVA,andTukey\'s test. The comparison of failure modes between the groups in the different thirds was done using Mann-Whitney test, All of those at a 5% significance. Ultrasonic group presented thinnest layer of cement in all thirds (p<0,05), which also obtained a higher bond strength only in apical third (p<0,05). Adhesive failurebetween cement and dentinwas the most prevalent of the cervical and apical third of G1 and cervical of G2.Adhesive failure between cement and post was the most prevalent in the others thirds. It can be concluded that the postpreparation with the ultrasonic tip developed provides a smaller thickness of resin cement that influenced thebond strength in the apical third of the glass fiber post.

O objetivo deste estudo foi avaliar a resistência de união, a penetração e a adaptação à dentina radicular de cimentos obturadores à base de resina epóxica e de silicato de cálcio com e sem ativação sônica e ultrassônica. Raízes de caninos superiores com 16 mm de comprimento foram submetidas a preparo biomecânico com instrumentos rotatórios de níquel titânio sob irrigação constante com NaOCl 2,5% e irrigação final com EDTA 17%. As raízes foram distribuídas em grupos de acordo com os cimentos obturadores: AH Plus e MTA Fillapex. Cada grupo foi subdividido em função da ativação do cimento obturador (n=13): sem ativação; ativação sônica por 30 segundos; ativação ultrassônica por 30 segundos. Em cada subgrupo, a manipulação dos cimentos obturadores foi realizada de acordo com as instruções dos fabricantes para 10 espécimes, para os 3 espécimes restantes, o cimento foi acrescido de Rodamina B 0,1% previamente à manipulação. A obturação foi realizada de acordo com o protocolo de cada subgrupo em relação ao cimento e ativação, utilizando-se a técnica de condensação lateral. Após três vezes os tempos de endurecimento dos cimentos, os espécimes foram seccionados obtendo-se 3 slices de 1,0 mm de espessura de cada terço radicular. Dois slices de cada terço foram submetidos ao teste de push-out e o padrão de falha foi determinado. O terceiro slice de cada terço radicular foi submetido à análise qualitativa da adaptação do cimento à dentina radicular e presença de vazios, por meio de microscopia confocal de varredura a laser. Nos espécimes em que o cimento foi acrescido de Rodamina B 0,1%, avaliou-se a penetração do cimento na dentina radicular por microscopia confocal de varredura a laser com fluorescência. Os dados foram analisados por testes estatísticos paramétricos e não-paramétricos. O cimento AH Plus (2,58±1,21) apresentou maior resistência de união comparado ao MTA Fillapex (1,45±0,71) (p<0,122). A ativação ultrassônica (2,64±1,44) propiciou maior resistência de união comparada aos grupos sem ativação (1,58±0,73) (p<0,0001) e com ativação sônica (1,83±0,85) (p<0,0001), não havendo diferença entre estes (p=0,3303). O terço cervical apresentou maior resistência de união (2,48±1,49) comparado ao médio (2,08±0,94) (p=0,0003) e apical (1,48±0,58) (p<0,001). Para o cimento MTA Fillapex houve predomínio de falhas adesivas mistas em todos os grupos, enquanto que para o cimento AH Plus houve predomínio de falhas adesivas mistas para os grupos sem ativação e ativação ultrassônica e falhas adesivas mistas e adesivas ao material obturador para o grupo de ativação sônica. A ativação ultrassônica promoveu, independente do cimento obturador, maior número, densidade e extensão de tags, com massa obturadora mais homogênea e adaptada às paredes do canal radicular. A ativação sônica, por sua vez, apresentou número, densidade e extensão de tags similares ao grupo sem ativação, no entanto a massa obturadora apresentou desadaptações e formação de bolhas. A ativação ultrassônica impactou na maior resistência de união, penetração, densidade e extensão de tags e melhor adaptação do cimento a dentina radicular, ao contrário da ativação sônica que não aumentou a resistência de união e penetração de tags e proporcionou maior desadaptação e inclusão de vazios na massa obturadora. / The aim of this study was to evaluate the bond strength, penetration and adaptation to the root dentin sealers based on epoxy resin and calcium silicate with and without sonic and ultrasonic activation. Maxillary canine roots with 16 mm length were submitted to biomechanical preparation with nickel titanium rotary files, under constant irrigation with 2.5% NaOCl and final irrigation with 17% EDTA. The roots were divided into groups according to the sealers: AH Plus and MTA Fillapex. Each group was subdivided based on sealer activation (n = 13): no activation; sonic activations (30 seconds); ultrasonic activation (30 seconds). In each subgroup, the sealer manipulation was performed according to the manufacturers instructions for 10 specimens, for the 3 remaining specimens, the Rhodamine B 0.1% was incorpored to the sealer prior to manipulation. The root canal filling was performed according to the protocol of each group relative to the sealer and activation, using the lateral condensation technique. After three times the sealer setting times, the specimens were sectioned and obtained 3 slices of 1.0 mm thickness of each root third. Two slices of each third were submitted to the push-out test and the failure pattern was determined. The third slice of each root third was submitted to qualitative analysis of sealer and root dentin adaptation and the presence of voids, by means of confocal laser scanning microscopy. In specimens in which Rhodamine B 0.1% was added in the sealer was evaluated the sealer penetration in root dentin by confocal laser scanning fluorescence. The data were analyzed using parametric and nonparametric statistical tests. The AH Plus (2.58 ± 1.21) showed higher bond strength compared to MTA Fillapex (1.45 ± 0.71) (p <0.122). The ultrasonic activation (2.64 ± 1.44) provided higher bond strength compared to no activation groups (1.58 ± 0.73) (p <0.0001) and sonic activation (1.83 ± 0.85) (p <0.0001), with no difference between them (p = 0.3303). The cervical third showed higher bond strength (2.48 ± 1.49) compared to the middle (2.08 ± 0.94) (p = 0.0003) and apical thirds (1.48 ± 0.58) (P < 0.001). For the MTA Fillapex there was a predominance of mixed adhesive failures in all groups, whereas for AH Plus there was a predominance of mixed adhesive failures for groups without activation and ultrasonic activation and mixed adhesive failures and adhesives to the filling material for the sonic activation group. Ultrasonic activation promoted, regardless of the sealer, the greater number, density and length tags with more homogenous and adapted root canal filling to the root canal walls. On the other hand, the sonic activation, presented number, density and length of tags similar to the group without activation, however the root canal filling showed mismatches and blistering. Ultrasonic activation impacted the highest bond strength, penetration, density and length tags and better adaptation of the sealer root dentin, unlike the sonic activation that not increased bond strength and penetration tags and provided greater mismatch and the inclusion of voids in the root canal filling.

Submitted by SBI Biblioteca Digital (sbi.bibliotecadigital@puc-campinas.edu.br) on 2017-02-21T18:17:11Z No. of bitstreams: 1 Diana Roberta Pereira Grandizoli.pdf: 22186247 bytes, checksum: eda73530f877f7998ed73ea7c0033e18 (MD5) / Made available in DSpace on 2017-02-21T18:17:11Z (GMT). No. of bitstreams: 1 Diana Roberta Pereira Grandizoli.pdf: 22186247 bytes, checksum: eda73530f877f7998ed73ea7c0033e18 (MD5) Previous issue date: 2016-12-19 / The present study sought to evaluate the influence of protease inhibitors on the bond strength of a self-etch adhesive system during hybrid layer formation in caries-affected dentin. The occlusal thirds of 80 permanent third molars were ground down to flat dentin surfaces. Dentinal caries were induced artificially by the microbial method. Groups were divided as follows: G1 (n=20), application of Clearfil SE Bond adhesive system (CL) alone; G2 (n=20), pretreatment with 2% chlorhexidine (CLX)+CL; G3 (n=20), pretreatment with sodium bicarbonate (BIC)+CL; G4 (n = 20), BI +CLX+CL. Bond strength was assessed immediately and at 6 months. Composite resin (Z350) build-ups were made on the dentin surfaces, and beam-shaped specimens with a cross-sectional area of 1 mm? were obtained. Microtensile bond strength testing was performed. Only adhesive or mixed-mode fractures were taken into account for calculation of bond strength. The results were submitted to the Kruskal-Wallis test (Student-Newman-Keuls). There was no significant difference on bond strength between the control, bicarbonate and chlorhexidine groups in the immediate test (p> 0.05). After 6 months, adhesive resistance fell for all groups. The control group had higher bond strength (p <0.05). The predominant fracture was of the adhesive type independent of the period evaluated. It can be concluded that after six months, there was decrease on bond strength for all groups. This reduction was greater in the groups in which the inhibitors were used / O objetivo desse trabalho foi avaliar a influ?ncia do bicarbonato de s?dio na resist?ncia adesiva durante a hibridiza??o da dentina cariada utilizando o sistema adesivo autocondicionante. Foram selecionados 80 terceiros molares permanentes, feita a remo??o do ter?o oclusal e superf?cies dentin?rias planas foram obtidas. A les?o de c?rie dentin?ria foi confeccionada atrav?s do m?todo microbiol?gico. Os grupos foram: G1 (n=20): aplica??o do sistema adesivo Clearfil (CL), G2 (n=20): aplica??o de clorexidina 2% (CLX) + CL, G3 (n=20): aplica??o de bicarbonato de s?dio (BI) + CL, G4 (n=20): BI + CLX + CL. A resist?ncia adesiva foi avaliada imediatamente e ap?s seis meses. Um bloco de resina composta Z350 foi constru?do em dentina. Cada bloco dente/adesivo/resina foi seccionado com disco diamantado acoplado ? m?quina de corte em planos paralelos obtendo-se corpos de prova em forma de palito, com ?rea de sec??o transversal de 1 mm?. Foi realizado teste de resist?ncia de uni?o por meio do teste de microtra??o. Foi considerada apenas fratura adesiva/mista para c?lculo da resist?ncia de uni?o. Os resultados foram submetidos aos teste de Kruskal-Wallis (Student-Newman-Keuls). N?o houve diferen?a significante na resist?ncia de uni?o entre os grupos controle, bicarbonato e clorexidina no teste imediato (p>0.05). Ap?s 6 meses, houve queda da resist?ncia adesiva para todos os grupos. O grupo controle apresentou maior resist?ncia de uni?o (p<0.05). A fratura predominante foi do tipo adesiva independente do per?odo avaliado. Pode-se concluir que ap?s seis meses, houve diminui??o na for?a de uni?o para todos os grupos. Essa redu??o apresentou-se maior nos grupos em que os inibidores foram utilizados.

A novel type of precast, prestressed concrete structural element is being implemented in load-bearing systems in buildings. These structural elements combine the use of high-performance, self-consolidating concrete (HPSCC) and non-corroding carbon fibre reinforced polymer (CFRP) prestressing tendons; this produces highly optimized, slender structural elements with excellent serviceability and (presumed) extended service lives. More widely, the use of new construction techniques, innovative materials, and ground-breaking designs is increasingly commonplace in today's rapidly evolving building construction industry. However, the performance of these and other structural elements in fire is in general not well known and must be understood before these can be used with confidence in load-bearing applications where structural fire resistance is a concern. Structural fire testing has traditionally relied on the use of the standard fire resistance test (i.e. furnace test) for assuring regulatory compliance of structural elements and assemblies, and in many cases also for developing the scientific understanding of structural response to fire. Conceived in the early 1900s and fundamentally unchanged since then, the standard testing procedure is characterized by its high cost and low repeatability. A novel test method, the Heat-Transfer Rate Inducing System (H-TRIS), resulting from a mental shift associated with controlling the thermal exposure not by temperature (e.g. temperature measured by thermocouples) but rather by the time-history of incident heat flux, was conceived, developed, and validated within the scope of the work presented in this thesis. H-TRIS allows for experimental studies to be carried out with high repeatability, imposing rationally quantifiable thermal exposure, all at low economic and temporal cost. The research presented in this thesis fundamentally seeks to examine and understand the behaviour of CFRP prestressed HPSCC structural elements in fire, with emphasis placed on undesired 'premature' failure mechanisms linked to the occurrence of heat-induced concrete spalling and/or loss of bond between the pretensioned CFRP tendons and the concrete. Results from fire resistance tests presented herein show that, although compliant with testing standards, temperature distributions inside furnaces (5 to 10% deviation) appear to influence the occurrence of heat-induced concrete spalling for specimens tested simultaneously during a single test; fair comparison of test results is therefore questionable if thermal exposure variability is not explicitly considered. In line with the aims of the research presented in this thesis, H-TRIS is used to carry out multiple comprehensive studies on the occurrence of concrete spalling and bond behaviour of CFRP tendons; imposing a quantified, reproducible and rational thermal exposure. Test results led to the conclusion that a "one size fits all" approach for mitigating the risk of heat-induced concrete spalling (e.g. prescribed dose of polypropylene (PP) fibres included in fresh concrete), appears to be ineffective and inappropriate in some of the conditions examined. This work demonstrates that PP fibre cross section and individual fibre length can have an influence on the risk of spalling for the HPSCC mixes tested herein. The testing presented herein has convincingly shown, for the first time using multiple repeated tests under tightly controlled thermal and mechanical conditions, that spalling depends not only on the thermal gradients in concrete during heating but also on the size and restraint conditions of the tested specimen. Furthermore, observations from large scale standard fire resistance tests showed that loss of bond strength of pretensioned CFRP tendons occurred at a 'critical' temperature of the tendons in the heated region, irrespective of the temperature of the tendons at the prestress transfer length, in unheated overhangs. This contradicts conventional wisdom for the structural fire safety design of concrete elements pretensioned with CFRP, in which a minimum unheated overhang is generally prescribed. Overall, the research studies presented in this thesis showed that a rational and practical understanding of the behaviour of CFRP prestressed HPSCC structural elements during real fires is unlikely to be achieved only by performing additional standard fire resistance tests. Hence, H-TRIS presents an opportunity to help promote an industry-wide move away from the contemporary pass/fail and costly furnace testing environment. Recommendations for further research to achieve the above goal are provided.

Orientador: Josimeri Hebling / Resumo: Objetivo: Avaliar a estabilidade mecânica e a atividade proteolítica de interfaces produzidas pela apliação de um adesivo convencional simplificado sobre a dentina biomodificada e seca. Métodos: Superfícies planas de dentina coronária foram criadas em 64 molares hígidos. Os dentes foram divididos em 4 grupos de acordo com a solução aplicada sobre a dentina condicionada: extrato de semente de uva 5% (GSE), glutaraldeído 5% (GD), Gluma Desensitizer ou água (controle). As soluções foram aplicadas por 60s seguido de lavagem e secagem com papel absorvente. Os dentes foram então subdivididos em dois grupos, nos quais a dentina condicionada foi mantida úmida ou foi seca com ar por 60s. O adesivo Optibond foi aplicado e em seguida foi construído um cilindro de resina. Decorridas 24h, os dentes foram cortados em espécimes (0,81 mm2 ), submetidos ao ensaio de microtração imediatamente ou após 12 meses de envelhecimento. Os mesmos procedimentos adesivos foram realizados em 32 dentes adicionais. Esses dentes foram seccionados em fatias de 0,5 mm de espessura, preparadas para os ensaios de nanoinfiltração e zimografia in situ (EnzChek). Os dados de resistência de união foram submetidos aos testes de ANOVA e Tukey (p<0,05), e os ensaios de nanoinfiltração e zimografia in situ foram apresentados descritivamente. Resultados: Redução significante da resistência de união imediata (ca. 65%) e aumento da atividade proteolítica e nanoilfiltração foi observado em interfaces produzidas sobre a dent... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Objective: To evaluate the mechanical stability and the proteolytic activity of bonds created by a one-step, etch-and-rinse adhesive applied to cross-linked and air-dried etched dentin. Methods: Flat coronal dentin surfaces were produced in 64 sound molars. The teeth were divided into 4 groups according to the solution applied on the etched dentin: 5% grape seed extract, 5% glutaraldehyde, Gluma Desensitizer or deionized water (control). Solutions were applied for 60s followed by rinse and blot drying. Then, the teeth were separated into two subgroups: the etched dentin was kept moist or air dried for 60s. Optibond was applied followed by a composite resin buildup. After 24h, the teeth were cut into beams (0.81 mm²) which were microtensile tested immediately or after 12mo of storage. Additional teeth (n=32) were bonded as described and cut into 0.5 mm-thick slabs. The slabs were prepared for nanoleakage and in situ zymography analyses (EnzChek). Bond strength data were submitted to ANOVA and Tukey tests (p<0.05) while nanoleakage and zymography data were descriptively reported. Results: Significant reduction in bond strength (ca. 65%) and increase of the proteolytic activity was seen when the etched dentin was air-dried without previous biomodification. Conversely, bond strengths did not differ from those produced on wet dentin when collagen was cross-linked before air-drying, irrespective of the solution. For both moist and air-dried etched dentin, collagen cross-linking res... (Complete abstract click electronic access below) / Mestre

O objetivo desde estudo foi avaliar a eficiência de remoção de smear layer e a influência da resistência de união de cimentos de silicato de cálcio de um novo inserto ultrassônico para agitação do irrigante em preparos retrógrados. Metodologia Foram selecionados 112 caninos unirradiculados, que foram formatados e obturados de forma convencional com a subsequente ressecção apical. Seguidamente, foram conformados 4 grupos de avaliação, ultra-som/solução salina; convencional/solução salina; ultra-som/EDTA17% e convencional/EDTA17%. Para analisar a remoção do smear layer, 72 espécimes foram divididos em 4 grupos (n=18), e retroprepararados utilizando uma ponta ultrassônica. Os espécimes foram clivados, obtendo-se dois segmentos iguais (mesial e distal). Os segmentos retrocavitários foram observados através da microscopia eletrônica de varredura (MEV), a partir de três regiões representativas a 250x, obtendo-se imagens correspondentes à pré-irrigação. Posteriormente, foram executados os protocolos de irrigação e novamente obtidas imagens representativas da pós-irrigação. Para o teste de push-out, 40 dentes alocados em 4 grupos (n=10) foram empregados, conforme os diferentes protocolos de irrigação previamente mencionados. Os espécimes foram retrobturados e a obtenção dos corpos-de-prova realizada a partir de um novo seccionamento apical de 2mm±0.1 de cada espécime. A resistência de união foi determinada por meio de uma máquina de ensaios mecânicos e o tipo de falha foi determinado por meio de MEV. Os dados foram comparados por meio dos testes de Kruskal-Wallis e Dunn para a remoção de smear layer e ANOVA e Tukey no teste de push-out. Resultados O grupo ultrassom/EDTA17% removeu significativamente uma maior quantidade do smear layer, observando-se uma maior porcentagem de túbulos dentinários abertos em comparação com os outros grupos (P < 0.05). Na resistência de união, o grupo ultrasom/ EDTA17% mostrou os maiores valores na resistência de união (6.42±0.69) seguido pelos grupos convencional/EDTA17%, ultra-som/solução salina e convencional/solução salina respectivamente (P < 0.05). O padrão de falha adesivo foi o mais predominante, enquanto que no grupo ultrassom/EDTA17% foi preponderantemente mista (8/10). Conclusões O novo inserto ultrassônico para ativação do irrigante promoveu uma maior remoção de smear layer além de favorecer maior resistência de união do material retrobturador às paredes dentinárias em preparos retrógrados, principalmente se associado ao EDTA17%. / To evaluate the smear layer removal capacity and its influence on the bond strength of a calcium silicate-based cement of a new ultrasonic tip for irrigant agitation in rootend cavity preparations. Methods: One hundred and twelve maxillary and mandibular canines were chemomechanically instrumented, root filled and the root apexes resected. Specimens were randomly distributed into 4 experimental groups: ultrasonic/saline solution; conventional/ saline solution; ultrasonic/EDTA 17% and conventional/EDTA solution 17%. The analysis of the smear layer removal employed seventy-four specimens divided into 4 groups (n=18), and the retrograde cavities were prepared using an ultrasonic tip. Next, the specimens were split longitudinally and obtained two halves (mesial and distal). Scanning electron microscopy (SEM) was used to examine and score the internal surfaces for dentinal tubule opening before and after to perform the irrigation protocols. Images were taken at three representative areas with a magnification of 250x. The push-out test employed forty specimens allocated in four groups (n=10), according to the different irrigation protocols previously described. The specimens were retrofilled, sectioned perpendicularly and obtained apical slices at 2mm±0.1 from the apex. Each disc/dentin/retrofilling material was placed in a testing machine for the bond strength measurement and the failure mode was observed by SEM. The smear layer removal data were analysed and compared using Kruskal-Wallis and Dunn. Push-out data were analysed using ANOVA and Tukey\'s test. Results The ultrasonic/EDTA 17% group removed the smear later more effectively, and showed the best tubule opening condition than the others three groups. (P < 0.05). Ultrasonic/EDTA 17% group demonstrated the highest mean bond strength values (6.42±0.69) compared with conventional/EDTA, ultrasonic/saline solution and conventional/saline solution, respectively (P < 0.05). Most failure modes were predominantly adhesive (55%), whereas in the ultrasonic/EDTA 17% group was mixed (80%). Conclusion The new ultrasonic tip for irrigant agitation showed higher percentage of smear layer removal and improved the push-out bond strength of the retrograde root filling to the root-end dentine surfaces, mainly when associated to EDTA 17%.

Masonry is a layered composite consisting of mortar and the masonry unit. Perfect bond between the masonry unit and the mortar is essential for the masonry to perform as one single entity in order to resist the stresses due to various loading conditions. Nature of stresses developed in the masonry unit and the mortar and the failure pattern of masonry subjected to compression greatly depends upon the relative stiffness of the masonry unit and the mortar. The thesis is focused on (a) some issues pertaining to masonry unit – mortar bond strength and its influence on masonry compressive strength, and (b) developing a finite element (FE) model to predict the compressive strength of masonry. Importance of masonry bond strength and masonry behaviour is highlighted in chapter 1. Characteristics of masonry units and mortars used in the investigations are presented in Chapter 2. Two types of soil-cement blocks with widely varying strength and elastic properties and cement-lime mortars of two different proportions were used in the investigations. Results of stress-strain relationships and other characteristics were determined for the blocks as well as for mortars. Block-mortar combinations were selected to have block modulus to mortar modulus ratio of <1.0, ~1.0 and >1.0. Different artificial methods of enhancing the shear bond strength of masonry couplets have been discussed in chapter 3. Shear bond strength of the masonry couplets was determined through a modified direct shear box test apparatus. Without altering the block and mortar properties, bond strength values for three block-mortar combinations were generated through experiments. Effect of pre-compression on shear bond strength has also been examined for certain block-mortar combinations. Considering five different bond strength values and three block-mortar combinations, compressive strength and stress-strain characteristics of masonry was obtained through the tests on masonry prisms. A detailed discussion on influence of shear bond strength on masonry compressive strength is presented. Major conclusions of the investigation are: (a) without altering the block and mortar characteristics shear bond strength can be enhanced considerably through the manipulation of surface texture and surface coatings, (b) masonry compressive strength increases linearly as the shear bond strength increases only for the combination of masonry unit modulus less than that of mortar modulus, (c) masonry compressive strength is not sensitive to bond strength variation when the modulus of masonry unit is larger than that of the mortar. Chapter 4 is dedicated to the development of a 3D FE model to predict the masonry compressive strength. Literature review of empirical methods/formulae and some failure theories developed to predict masonry strength are presented. Existing FE models for masonry dealing with both macro and micro modelling approaches are reviewed. The proposed FE model considers (a) 3D non-linear analysis combined with a failure theory, (b) uses multi-linear stress-strain relationships to model the non-linear stress-strain behaviour of masonry materials, (c) adopting Willam-Warnke’s five parameter failure theory developed for modelling the tri-axial behaviour of concrete, and (d) application of orthotropic constitutive equations based on smeared crack approach. The predicted values of masonry compressive strength are compared with experimental values as well as those predicted from other failure theories. The thesis ends with a summary of conclusions in chapter 5.

In this thesis different mechanical properties for shotcrete (sprayed concrete) such as compression strength, bond strength, bending tensile strength, elastic modulus, free and restrained shrinkage as a function of its age was investigated. One of the main issues was to investigate the difference between ordinary cast concrete and shotcrete. Reliable material data for young and hardening shotcrete is scarce which in the past have made such comparisons difficult. Also, less accurate data representative for cast concrete has often been used in numerical modelling and design analyses. The focus of the project has particularly been on the properties bond strength and restrained shrinkage for which two new testing methods has been developed and evaluated. Microstructural studies have also been performed as a complement to the bond strength testing. The bond to rock is one of the most important properties for shotcrete used as rock reinforcement. During the very first time after spraying the physical properties and the bond to the rock depend on the set accelerator and the micro structure that is formed. The investigation of early age bond strength of shotcrete is of great importance both from a production perspective and a safety perspective. The newly developed method was tested and evaluated and proved that it can be used for bond strength testing already from a couple of hours after shotcreting. The bond, or adhesion, depends on several factors such as texture of the rock, the type of accelerator, application technique, etc. In this work the development of the microstructure in the interfacial transition zone (ITZ) and strength of the bond was investigated. The results show that the bond strength is related to the hydration process, i.e. the strength gain of the shotcrete. The early development of the ITZ was here studied using a scanning electron microscope (SEM) making it possible to observe changes over time, before and after proper cement hydration. Restrained shrinkage cracking of shotcrete, especially in the case of shotcrete sprayed on soft drains that are parts of a tunnel lining not continuously bonded to the rock, can be detrimental for the sustainability of an infrastructure tunnel system. Maintenance and repair costs can be high over time. It is shown that the developed test method realistically captures the behaviour of shotcrete drains on hard rock in situ. The method can be used in the evaluation of different technical solutions for avoiding or minimizing shrinkage cracks in shotcreted soft drains. It can also be used to assess the performance of shotcrete fully bonded to a rock surface, with respect to the ability to prevent cracking or to distribute possible shrinkage damage into several fine cracks instead of one wide. / <p>QC 20140526</p>

The main objective of the project was to establish a fracture-mechanics energy-based approach for the design of structural adhesive joints under cyclic loading. This required understanding how an adhesive system behaved near its fatigue threshold, and how the key factors affected this behavior in a fresh undegraded joint. The investigated factors were mode ratio (phase angle), substrate material, surface treatment and surface roughness (both affecting the bond strength), bondline thickness and load ratio. It was first required to understand how the adhesive system behaved under quasi-static loading by examining a fracture mechanics-based design approach for adhesive systems with different substrate materials and geometries. Experiments were initially performed to characterize the strength of aluminum and steel adhesive systems based on the fracture envelope, critical strain energy release rate as a function of the mode ratio. Ultimate failure loads of aluminum and steel adhesive joints, having different overlap end conditions and different geometries were then experimentally measured. These values were compared with the failure loads extracted from the fracture envelope. Considering the toughening behavior of the adhesive in the fracture mechanics analyses, a very good agreement (average of 6%) was achieved between the predictions and experiments for all types of overlap end conditions and geometries. Different fatigue threshold testing approaches, which are commonly used in the literature or suggested by the ASTM standard, were evaluated for the cracked and intact fillet joints. Based on the experimental and analytical studies, the most appropriate technique for fatigue testing and characterization of adhesive systems was suggested. Comparing the mixed-mode near-threshold behavior of different adhesive systems with the fracture behavior and fatigue mode-I and mixed-mode high crack growth rates showed the high sensitivity of the mixed-mode near-threshold fatigue to the subtle changes in the interfacial bond strength. In order to make a baseline for the design of adhesive joints under cyclic loading, similar to the previous fracture tests and following the energy-based approach, fatigue behavior was characterized as a function of the loading mode ratio for aluminum and steel adhesive joints. The effect of substrate material, surface treatment, bondline thickness, surface roughness and fatigue testing load ratio on the near-threshold fatigue behavior of adhesives joints was evaluated experimentally. The experimental observations were then explained using finite element modeling. To generalize the conclusions, the majority of experiments and studies covered a broad range of crack growth rates, as low as fatigue threshold and as high as 10-2 mm/cycle. Having understood the significant testing and design parameters, an adhesive system can be designed based on a safe cyclic load that produces an insignificant (for automotive industry) or reasonably low but known crack growth rate (for aerospace industry).