A confecção de infra-estruturas metálicas em reabilitações orais, envolvem processos criteriosos principalmente no que concerne ao processo de fundição e soldagem das mesmas. O objetivo deste trabalho foi avaliar a resistência à tração de peças fundidas em monobloco com três diferentes métodos de soldagem: solda convencional (maçarico), solda a laser e solda TIG (tungstênio Inerte Gás). Oitenta padrões de plástico pré-fabricados (vinte para cada grupo) foram fundidos em liga de Ni-Cr, sendo o grupo controle (monobloco) unido previamente à fundição. Após, os corpos-de-prova do grupo teste foram divididos aleatoriamente para posterior soldagem e teste de resistência, realizado em uma máquina de ensaios mecânicos (Kratos). Os resultados médios (MPa) foram: monobloco 784,08, solda laser 588,42, solda convencional 366,80 e solda TIG 319,78. Os dados foram submetidos á analise estatística ANOVA e teste de Tukey (p,0,05), sendo que o grupo controle (monobloco) apresentou valores de resistência estatisticamente superior a todos os do grupo teste. Entre as peças soldadas, a solda laser apresentou valores de resistência estatisticamente superior em relação aos grupos (convencional e TIG), os quais não diferiram estatisticamente entre si. Concluí-se que apesar de ter havido diferenças estatísticas entre os grupos, os três métodos de soldagem podem ser indicadas pelos resultados altamente satisfatórios. / The development of metallic prosthetic framework in oral rehabilitation, involves critical processes specially related to casting and welding. The objective of this work was to evaluate the tensile strength of cast plates (monobloc) with three different welding methods: conventional welding (torch), laser welding and TIG welding (tungsten inert gas). Eighty pre fabricated plastic patterns (twenty for each group), were welded in Ni-Cr alloy, being the control group (monobloc) jointed previously to welding. The specimens of the test group were randomly divided for posterior welding and tensile strength test, which were performed in an universal testing machine (Kratos). The mean values (Mpa) were: monobloc (control) - 785.08, laser welding - 588.42, conventional welding - 366.80 and TIG 319.78. Data were analyzed by One-way ANOVA and Tukey test (p.0.05). The control group (monobloc) presented tensile strength values statistically superior compared to all test groups. Between the welded patterns, the laser welding presented tensile strength values statistically superior compared to the other welding groups (conventional and TIG), which did not show any statistically difference between them. Therefore, it can be concluded that despite of the statistical difference between the groups, the three welding methods can be indicated by the highly satisfactory results.

Orientador: Regina Maria Puppin Rontani / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-25T23:49:08Z (GMT). No. of bitstreams: 1 Barbosa-Martins_LuizFilipe_M.pdf: 3917283 bytes, checksum: d231cd8d8bf786295bf13e87744334d8 (MD5) Previous issue date: 2014 / Resumo: O objetivo deste estudo foi avaliar o efeito dos agentes remineralizadores Fluoreto de Sódio (NaF) a 0,2%, MI Paste¿ e Curodont¿ Repair sobre a dentina desmineralizada e diferentes sistemas adesivos (Adper¿ single Bond 2 (SB) (3M ESPE, St. Paul, MN, USA) e Clearfil¿ SE Bond (CSE) (Kuraray Co., Tokyo, Japan), por meio da avaliação da resistência da união à microtração. A amostra consistiu de 60 terceiros molares livres de cárie. A superfície dentinária foi exposta por meio de disco diamantado e polidas com lixas de carboneto de silício e congelados em solução tampão fosfato até o uso. Os dentes foram aleatoriamente distribuídos em 10 grupos (n=6) de acordo com o tratamento da superfície dentinária: 1. DH/SB - Dentina hígida; 2. DH/CSE - Dentina hígida; 3. DD/SB ¿ Dentina Desmineralizada; 4. DD/CSE ¿ Dentina Desmineralizada; 5. DR/SB - NaF a 0,2% por 1min; 6. DR/SB - NaF a 0,2% por 1min; 7. DR/SB - MI Paste¿ por 1 min; 8. DR/CSE - MI Paste¿ por 1 min; 9. DR/SB - Curodont¿ Repair; 10. DR/CSE - Curodont¿ Repair. Em 48 dentes a superfície dentinária foi submetida a aplicação de gel ácido (6% de carboximetilcelulose e ácido lático 0,1M com solução concentrada de KOH em pH5,0), simulando a dentina afetada por cárie. O procedimento adesivo/restaurador foi realizado foi realizado de acordo com os grupos experimentais, respeitando-se a aplicação do agente remineralizador e blocos de 4mm de altura de compósito foram construídos (Filtek Z350XT) e estocados em água deionizada por 24h, sendo seccionados em palitos (1mm2 - área secção), perpendicularmente a área de união, sendo submetidos ao teste de µTBS em 1,0mm/min e carga de 50kgF. Os sítios de fratura foram avaliados em MEV (50x e 150x). Os dados de µTBS (MPa) foram submetidos à ANOVA-two way e ao teste de Tukey (p<0,05). Os maiores valores de resistência de união a microtração foram obtidos quando a dentina desmineralizada foi tratada com MI Paste e Sistema CSE que não diferiram daqueles obtidos quando a dentina desmineralizada foi tratada com MI Paste/SB e Curodont Repair/SB e os menores valores foram obtidos para o mesmo adesivo quando utilizado o Curodent Repair, que não diferiram da dentina desmineralizada tratada com ambos sistemas adesivos. O tipo de fratura variou de acordo com o sistema adesivo e tratamento da dentina, sendo observados maiores percentuais de fratura Coesiva no compósito para a dentina hígida/SB, dentina hígida/CSE, Adesiva para a dentina desmineralizada/SB, dentina desmineralizada tratada com Curodont Repair/CSE, Mista para a dentina desmineralizada/NaF/SB, dentina desmineralizada/MI Paste/SB, dentina desmineralizada/Curodont Repair/SB, Coesiva na dentina para a dentina desmineralizada/MIPaste/CSE. Com base nos resultados obtidos e dentro dos limites do presente estudo pôde-se concluir que a utilização de agentes remineralizadores na dentina mostra-se uma alternativa favorável, em curto prazo, aos procedimentos adesivos. Quando utilizados o sistema adesivo Adper¿ Single Bond 2 associado ao tratamento da superfície desmineralizada com Curodont¿ Repair ou MI Paste¿ ou ainda Clearfil¿ SE Bond associado a MI Paste¿ foram observados os maiores valores de resistência da união resina/dentina / Abstract: The purpose of this study was to evaluate the effect of remineralizing agents such as sodium fluoride (NaF) at 0.2%, MI Paste¿ or Curodont¿ Repair on demineralized dentin and different adhesive systems (Adper ¿ Single Bond 2 (SB) (3M ESPE, St. Paul, MN, USA) and (Clearfil ¿ SE Bond (CSE) ( Kuraray Co., Tokyo, Japan) for the microtensile bond strength (µTBS). Sixty human third molars with mid-coronal portion of dentin exposed were randomized in 10 groups (n=6) according to factors studied (substrate): 1. SD/SB ¿ Sound Dentin; 2. SD/CSE - Sound Dentin; 3. DD/SB ¿ Demineralized Dentin; 4. DD/CSE - Demineralized Dentin; 5. RD/SB - Dentin Remineralized with 0.2% NaF for 1 min; 6. RD/CSE - Dentin Remineralized with 0.2% NaF for 1 min; 7. RD/SB - Dentin Remineralized with MI Paste¿ for 1min; 8. RD/CSE - Dentin remineralized with MI Paste¿ for 1min; 9. RD/SB ¿ Dentin remineralized with Curodont¿ Repair - for 5min; and 10. RD/CSE ¿ Dentin remineralized with Curodont¿ Repair - for 5min. Before dentin treatment and bond procedures it was acid gel applied (6% carboxymethylcellulose and 0.1 M lactic acid with KOH concentrated solution at pH 5.0) on 48 molars producing a simulated caries-affected dentin. Adhesive/restorative procedure was performed constructing composite (Filtek Z350XT) blocks with 4 mm height. They were stored in deionized water for 24 hours, sectioned in beams (1mm2) and submitted to ?TBS test at 1.0 mm/min and load of 50kgf. SEM (50x and 150x) evaluated the types of fracture. µTBS data (MPa) were submitted to two - way ANOVA and Tukey tests (p<0.05). It was found an interaction between the factors studied (p<0.01). The highest values of the microtensile bond strength were obtained when the demineralized dentin was treated with MI Paste¿ and adhesive system CSE did not differ from those obtained when the demineralized dentin was treated with MI Paste/SB and Curodont Repair/SB and minors values were obtained for the same adhesive used when the Curodont¿ Repair, which did not differ from demineralized dentin treated with both adhesive systems. The type of fracture varied according to the adhesive system and treatment of dentin, the highest percentages of cohesive/composite fracture is observed in to sound dentin/SB, sound dentin/CSE; demineralized dentin/SB and demineralized dentin treated with Curodont¿ Repair/SB for adhesive; mixed for demineralized dentin treated with NaF/SB, demineralized dentin treated with MI Paste¿/SB, demineralized dentin/Curodont Repair/SB; cohesive/dentin to demineralized dentin/MIPaste/CSE. Based on the results obtained and the limits of this study it was concluded that the use of agents in dentin remineralizadores shown a favorable alternative in the short term, the bonding procedures. When used Adper¿ Single Bond system 2 associated with the treatment of demineralized surface Curodont¿ Repair or MI Paste¿ or Clearfil¿ SE MI Paste¿ associated with the highest values of resistance of resin/dentin were observed / Mestrado / Odontopediatria / Mestre em Odontologia

Orientador: Maria Filomena Rocha Lima Huhtala / Banca: Eduardo Bresciani / Banca: João Maurício Ferraz da Silva / Banca: Caio Gorgulho Zanet / Banca: Rogério de Lima Romeiro / Resumo: O objetivo desse estudo in vitro foi avaliar a resistência adesiva, rugosidade superficial, ângulo de contato e o espectro infravermelho da zircônia, após diferentes tratamentos de superfície. Para isso, blocos (n=9) de zircônia Y-TZP (e.max ZirCad - Ivoclar, Schann, Liechtenstein) foram seccionados em 39 fatias (12 x 11x 3 mm) divididas em grupos de acordo com cada teste. Para resistência adesiva, 20 fatias foram divididos em: 2 grupos controle; JAT, jateamento com óxido de alumínio e sílica + primer (Monobond Plus - Ivoclar, Schann, Liechtenstein); HFP, condicionamento com ácido fluorídrico 10% + primer, e 3 experimentais: PL, plasma (Plasma Não Térmico de Superfície - modelo SAP); PLP, plasma + primer; HFPLP, ácido fluorídrico + plasma + primer. Cada fatia de zircônia foi cimentada (Multilink N - Ivoclair, Schann, Liechtenstein) a um bloco pré-polimerizado de resina composta. Após a cimentação os espécimes foram seccionados, e 48 palitos com área adesiva de 1 mm2 foram obtidos em cada grupo para o ensaio de microtração (μTBS). Quatro outras fatias foram submetidas à análise de rugosidade superficial e 12 fatias submetidas à análise do ângulo de contato, após os seguintes tratamentos de superfície: sem tratamento (AV), aplicação de ácido fluorídrico a 10% (AHF), aplicação de plasma (AP) e jateamento (AJ), sendo que para o ângulo de contato foram feitas medições imediatamente após o tratamento, após 12 e 24 horas. Os resultados foram submetidos à análise estatística Anova e ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The purpose of this in vito study was to evaluate zirconia bond strength, surface roughness, contact angle and to mesure infrared spectrum after different surface treatments. Y-TZP zirconium (e.max ZirCAD - Ivoclair, Schann, Liechtenstein) blocks (n=9) were sliced into 36 discs (12 x 11 x 3 mm) and divided (n=4) into surface treatment groups as following: two control groups: JAT, airborneparticle abrasion and HFP, 10% hydrofluoric acid etching + primer (Monobond Plus - Ivoclair, Schann, Liechtenstein)application,and three experimental groups: PL, non-thermal plasma (Surface Non-Thermal Plasma SAP model) application; PLP non-thermal plasma + primer application, and HFPLP, 10% hydrofluoric acid etching + non-thermal plasma + primer application. Each zirconia disk was cemented (Multilink N - Ivoclair, Schann, Liechtenstein) to a pre-polymerized resin block (Filtek Z350 - 3M, St Paul, MN, USA). After cementation the specimens were sectioned and 48 sticks with adhesive area of 1 mm2 obtained from each group for micro-tensile testing (µTBS). Four discs were submitted to surface roughness analysis and 12 discs to contact angle analysis, after the following surface treatments: no treatment (AV), 10% hydrofluoric acid etching (AHF), non-thermal plasma application (AP); and airborne- particle abrasion (AJ). The results were submitted to ANOVA and Tukey's test (p < 0.05). Zirconia surface chemical bonds spectrum was determined in infrared spectroscopy for three specimens after the conditions: no treatment; airborne- particle abrasion and hydrofluoric acid etching + non-thermal plasma application. The results showed no statistically significant differences between the groups JAT and HFPLP, but these two groups were statistically superior to HFP, PL and PLP. Airborne- particle abrasion resulted in a significant increase of surface roughness compared to the other groups...(Resumo completo, clicar acesso eletrônico abaixo) / Doutor

Orientador: Paulo José Paupitz Gonçalves / Banca: Marcos Silveira / Banca: Carlos de Marqui Junior / Resumo: Um sistema de tensegrity é composto por dois tipos de elementos, elementos de tração e compressão, os quais promovem a estabilidade estrutural do sistema, neste trabalho as partes de tração são cabos (cabos de aço), e as partes compressivas são barras de aço. Uma característica atrativa de uma estrutura de tensegridade é a capacidade de ser retrátil, por esta razão, é interessante para aplicações espaciais devido ao pequeno volume que ocupa um possível transporte para uma estação espacial. Em geral, essas estruturas podem ser grandes com muitas células repetitivas. Neste trabalho, estuda-se uma estrutura de tensegrity composta por dez células periódicas de barras e cabos. O modelo matemático, obtido pelo método dos elementos finitos, é validado experimentalmente considerando o caso de uma célula estrutural. Para tornar o sistema adaptável à excitação externa, um dos cabos de aço na célula elementar é substituído por um fio de liga de memória de forma (SMA) que permite que as características dinâmicas do sistema sejam alteradas de acordo com uma corrente elétrica aplicada no SMA, para que através do efeito Joule a liga seja aquecida. Diferentes configurações para a colocação do cabo SMA são estudadas com o objetivo de reduzir as amplitudes de vibração para uma excitação de força harmônica. / Abstract: A tensegrity system is composed by two types of elements, tensile and compressive parts, which promotes the structural stability of the system, in this case the tensile parts are cables (steel cables), and the compressive parts are bars, in this work made of steel. An attractive characteristic of a tensegrity structure is the capability to be deployable, for this reason, is interesting for space applications due to the small volume that it occupies in a possible transport to a station outside the Earth. In general, these structures can be large with many repetitive cells. In this work, a tensegrity boom structure consisting of ten periodic cells made of bars and cables is studied. The mathematical model, obtained by finite element method is validated experimentally considering the case of one structural cell. In order to make the system adaptable to external excitation, one of the steel cables in the elementary cell is replaced by a SMA (shape memory alloy) wire (Nitinol) allowing the dynamics characteristics of the system to be changed according to an electrical current applied to the SMA, to heat the alloy through Joule effect. Different configurations for placing the SMA cable are studied with the objective of reducing the vibration amplitudes for harmonic force excitation. / Mestre

Syftet med projektet var att undersöka hur homogeniserings förhållanden (tryck antal passager och därmed energiinsatsen) vid framställning av MFC (mikrofibrillär cellulosa), från enzymatiskt förbehandlade pappersmassafibrer påverkar hållfastheten av papper förstärkt med MFC. Arbetsgivaren för projektet var Innventia och det laborativa arbetet har utförts i deras lokaler. Fördelen med att använda MFC som tillsats i papper är att arket blir starkare [1]. Detta medför att en mindre mängd material kan användas till ett material med liknande styrkeegenskaper. Vid Innventia används för närvarande en homogenisator för att delaminera (sönderdela) cellulosafibrer till fibriller och fibrillaggregat och därmed producera MFC. Homogenisatorn kan köras vid olika tryck, samt att cellulosafibrerna/MFC kan låtas passera genom homogenisatorn en eller flera gånger. Beroende på tillvägagångssättet varierar produktionsenergin mycket och egenskaperna på den producerade MFC varierar. För att få en så energieffektiv metod som möjligt är det av stor vikt att finna vilken metod som genererar en MFC lämpad för styrkegivning i pappersark. Beroende på hur mycket MFC som tillsätts till arket kan arkets egenskaper variera. Därför är även detta en mycket viktig aspekt att ta hänsyn till då dubbla mängden tillsatt MFC direkt motsvarar dubbla mängden tillförd energi. För att få en jämn dispergering av massafibrer och inbunden MFC utfördes retentionsförsök för att bestämma vilken koncentration C-PAM 1510 som ansågs lämplig att använda vid arkningen för samtliga MFC prover. C-PAM 1510 är en positiv laddad polymer som binder in MFC till massafibrerna [2]. Maskinen som användes för retentionsförsöken är BDDJ (Britt Dynamic Drainage Jar) och syftar till att se hur mycket MFC som retenderar med massafibrerna. Arkningen utfördes enligt ISO 5269-1 med riktvärde att producera ark om 80g/m2 för vidare fysikaliska tester, bland annat dragprovning, densitet och reell ytvikt. Halten C-PAM 1510 som användes under arkningsförsöken bestämdes till 0,15 %. Det fanns ingen säkerställd skillnad i arkstyrka för de olika MFC proverna som testades, förutom prov ett. Prov ett gav en betydande högre mätvärdesvariation vid dragprovningen (figur 8) jämfört med de övriga proverna och får ses extremt påverkad av något. Detta var inte heller ett prov som påverkade slutsatsen. Därav har prov ett utelämnats i diagram. Prov nummer 5 ansågs bäst lämpad som styrkeadditiv i papper. Resultaten kan dock ha påverkats av föroreningar i kranvattnet. Järnjoner och partiklar i varierande koncentrationer hade en påverkan av dispergeringen av fibrer i pappersark. / The goal with the project was to investigate how homogenization conditions (pressure, number of passes and thereby energy consumption) at production of MFC (microfibrillated cellulose), from enzymatic pretreated paper mass fibers affects the strength of paper enhanced with MFC. The employer of the project is Innventia and the laboratory work was conducted in their facilities. The advantage of using MFC as an enhancer in paper is that the paper becomes stronger and more durable [1]. This leads to a decreasing use of material for a paper with similar strength properties as ordinary paper. At Innventia they presently use a homogenisator to delaminate (break apart) cellulose fibers to fibrils and fibril aggregates and thereby produce MFC. The homogenisator can be operated at different pressures and also the cellulose fibers/MFC can pass through one or several times. Depending on the method the energy consumption will greatly vary and so will also the properties of the produced MFC. To make the process as energy efficient as possible it is of most importance to find the best method of production for a MFC suitable as an enhancer in paper. Depending on how much MFC is added to the paper, the papers properties will vary. Therefore this aspect is also important to consider, because if the added MFC doubles, the energy does too. To make an even dispersion of the pulp fibers and adsorbed MFC, retention experiments were conducted to determine which concentration of C-PAM 1510 was most suitable to use during the sheet forming for every MFC sample. C-PAM 1510 is a positively charge polymer that can bind MFC to cellulose fibers [2]. The machine used for the retention experiments was BDDJ (Britt Dynamic Drainage Jar) aiming to determine how much MFC retain in the paper mass. The sheet forming was conducted accordingly to ISO 5269-1 and 80g/m2 sheets where produced for further physical testing, among other things, tensile test, density and basis weight. The C-PAM 1510 concentration used during the sheeting was determined to 0,15 %. There was no big difference for tensile strength compared to the different MFC samples, except sample one. Sample one had significant higher coefficient of variation compared to the other samples (figure 8) during tensile strength test, probably due to a high influence of some interference. The exclusion of sample one did not affect the overall result. Therefore sample one was excluded from diagrams. Sample number 5 was considered to be the best strength enhancing additive for paper. The results may have been influenced by impurities in the tap water and should be considered. Iron ions and particles in various concentrations did have an effect of the dispersion of fibers in paper.

Indiana University-Purdue University Indianapolis (IUPUI) / Microabrasion with PREMA Compound (Premier Dental Product Co., King of Prussia, Penn.) has been advocated for the removal of superficial enamel stains. This procedure eliminates stains by removing a microscopic layer of enamel. The objective of this study was to determine whether the use of PREMA microabrasion prior to orthodontic bonding affects the tensile bond strength of an adhesive precoated stainless steel orthodontic bracket. Sixty noncarious extracted human premolar teeth were randomly divided into three groups of 20 and stored in 3-percent buffered formalin solution. Group I was a control group that was etched and bonded in the usual manner. Group II received PREMA Compound microabrasion immediately prior to bonding. Group III received PREMA microabrasion followed by a six-week storage period prior to bonding. After bonding, specimens were thermocycled and stored in distilled water at 37 °C for 14 days. The specimens were then loaded to failure in the tensile mode of an Instron testing machine (Instron Corp., Canton, Mass.). A stress-breaking apparatus was utilized to minimize all forces other than tensile. The data was statistically analyzed using one-way analysis of variance at the 0.05 level. No statistically significant differences were found among the three groups. From these results it was concluded that microabrasion with PREMA did not affect bond strength. Enamel microabrasion can be provided prior to orthodontic treatment without any detriment to bracket bond strength.

Dovetail joints are commonly seen in a furniture frame construction because of their unique configuration and strength. The tensile strength of dovetail joints was experimentally and analytically investigated using fracture mechanics method in this study. Experimental results of the investigation of effects of geometry factors on the tensile strength of dovetail joints in southern yellow pine and red oak indicated that the tensile strength of red oak joints was about 2 times higher than the one of southern yellow pine joints. Statistical analysis results indicated that the tail angle and tenon length of dovetail joints had significant influences on their tensile strength, and the tenon width was not a significant factor on the joint tensile strength. The fracture behaviors of southern yellow pine and red oak materials were investigated in the radial-longitudinal crack propagation system using a compact tension test method. Effects of wood specific gravity on fracture toughness for two wood species were studied in terms of their three growth ring combinations; earlywood, earlywood and latewood interface, and latewood. Regression analysis results indicated that the fracture toughness of two evaluated wood species can be predicted based on their specific gravity values. Statistical analyses indicated that the latewood yielded the significantly higher fracture toughness value, followed by earlywood and latewood interface, then earlywood for both wood species. Proposed prediction equations for tensile strengths of dovetail joints based on fracture toughness values of wooden materials used for frame construction were validated experimentally.

No description available.

The objectives of this research were to evaluate the sensitivity of indirect tensile strength (ITS) test results to stabilizer type, stabilizer concentration, and curing time for multiple clayey soils with varying plasticity indices (PIs), identify cases in which an ITS of 30 psi can be obtained, and create a general linear model that predicts ITS. The scope of work included laboratory testing of three clayey soils sampled from Monticello, Utah; Bloomington, Indiana; and San Antonio, Texas. Each soil was tested using two stabilizers, cement or lime, at three concentrations, and two replicate samples were prepared for each combination. ITS testing was performed on two specimens of each combination at curing times of both 7 days and 28 days, for a total of 72 tests. The procedures outlined in this study include soil characterization, determination of moisture-density relationships, Eades and Grim testing, soil preparation, soil compaction, ITS testing, and statistical analysis. Regarding stabilizer type, treatment with cement consistently yielded higher ITS values than treatment with lime. Regarding stabilization concentration, ITS consistently increased with increasing concentrations of cement for all three soils; however, the effect of lime concentration depended on the PI of the soil, where increasing ITS values were only apparent with higher PI values. Regarding curing time, the ITS values corresponding to 28 days were generally higher than those corresponding to 7 days. Differences in ITS among the soils were largely attributable to differences in PI, which can influence pozzolanic reactivity. A cement or lime concentration that was equal to or 2% above the lime concentration indicated by the Eades and Grim test was typically required for a minimum 28-day ITS value of 30 psi to be attained. For the model developed to predict ITS, the significant predictor variables included PI, stabilizer type, actual stabilizer concentration, and curing time, as well as the two-way interactions between PI and stabilizer type, PI and actual stabilizer concentration, PI and curing time, and stabilizer type and actual stabilizer concentration. Overall, the model has an R2 value of 0.943 and an adjusted R2 value of 0.936. The model is best suited for soils having a fines content greater than 50%, a PI greater than 20, and a soluble sulfate concentration less than 3000 ppm.

Indiana University-Purdue University Indianapolis (IUPUI) / The search for an orthodontic bonding adhesive that has chemical adhesion to enamel and releases fluoride into the oral environment has led to experimentation with glass ionomer cements. This study compared the tensile bond strength of eight different orthodontic bracket base designs in vitro and assessed the amount of adhesive remaining on the bracket pad after debonding. Each bracket base design included in this study had unique characteristics warranting their inclusion. The groups contained brackets with 60, 80, and 100 gauge mesh pads; 100 gauge mesh sandblasted pads; perforated metal bases; Micro-Lock™ photo-etched bases; Dyna-Lock™ integral bracket/bases; and ceramic silane-coated bracket pads. Groups contained 20 to 22 specimens that were bonded to bovine incisor teeth embedded in a self-curing acrylic block that could be held in the testing machine. Pre-encapsulated glass ionomer cement (Ketac-Fil™) was the experimental adhesive. The adhesive was mixed according to the manufacturer's instructions in a dental amalgamator. The specimens were thermocycled between water oaths of 15°C and 55°C. The specimens spent 30 seconds in each bath for a total of 2,500 cycles and were stored in a humidor until debonding. After 14 days, the specimens were subjected to a tensile force using an Instron mechanical testing machine until failure occurred. The Micro-Loc™ photo-etched base had significantly higher mean tensile bond strength (p<0.05) than all other brackets tested. The ceramic brackets were unable to be tested due to the extremely weak bond strength which did not allow preparation of the samples for debonding. Following debonding, the percentage of adhesive remaining attached to the bracket base was determined using a grid in the ocular of a light microscope. In general, the site of bond failure involved the base/adhesive interface. The Dyna-Lock™ integral bracket/base and 80 gauge mesh base had a greater mean percent of adhesive remaining attached to the base. (Dyna-Lock™ 45 percent and 80 gauge mesh 43 percent vs. all other < 20 percent.) The results indicate that the bracket base design can influence the bond strength when GIC is used as an orthodontic adhesive and suggests that development of GIC with increased fracture toughness might increase bond strength.