Magister Scientiae Dentium - MSc(Dent) / Statement of the problem: Fibre reinforcement of polymethyl methacrylate (PMMA) denture base material is known to improve the strength, as well as the fatigue behavior, of the material. The powder liquid (P/L) ratio of PMMA is often changed to modify the handling properties of the material. Little is known about the effect of this deviation from manufacturer’s guidelines on the fatigue behaviour of the fibre reinforced product. Purpose: This study compared the flexural strength (FS) of PMMA reinforced with glass fibre using different P/L ratios, before and after cyclic loading. Methods and materials: Three groups, with 50 glass fibre reinforced (everStick nonimpregnated fibers) heat-cured PMMA resin (Vertex Rapid Simplified) specimens each, were prepared using a custom-made template (dimensions 10x9x50mm). Each group had a different P/L ratio: the control group (100%) had the manufacturer’s recommended ratio; the 90% and 80% groups had reduced P/L ratios (by weight).Twenty five specimens from each group were subjected to a 3-point bending compression test using a universal testing machine. The remaining 25 specimens from each group were subjected to cyclic loading (104 cycles) before compression testing. The (FS) was calculated using the highest force (Fmax) before specimen failure. Flexural strength was calculated using the equation: FS=3WL/2bd2. Within each group, median FS values before and after cyclic loading were compared by means of a non-parametric analysis of variance. The Aligned Ranks Transform method was used for the analysis. Statistical significance was set at p=0.05. Results: The Fmax (N) of the control (100%), 90% and 80% groups fatigued and unfatigued were 100%: 1665 (fat), 1465 (unfat); 90%: 1679 (fat), 1548 (unfat) and 80%: 1585 (fat), 1467 (unfit) respectively. There was no significant interaction between Mix ratio and Fatigue state, and the 80% mix had a significantly higher mean than either the 90% or 100% mix (with differences of about 0.3 units for both). The Fatigued state had a higher mean than the Un- fatigued state by about 6.0 units. Using FS (MPa) it was found that the fatigued 80% mix specimens had the highest value. The FS MPa of the control (100%), 90% and 80% groups fatigued and un-fatigued were 64.3, 60.6; 66.9, 65.6 and 70.2, 69.3 respectively. The fact that fatiguing strengthened the specimens merits further research. When observing the broken specimens it was found that there was a complete debonding of the fibres and the PMMA. Conclusion and clinical relevance: a) Fibre: The benefit of using glass fibre bundles to reinforce prostheses fabricated using heat cured PMMA is questionable due to problems with bonding between the fibre bundles and the heat cured PMMA resin. b) Fatiguing: An average person chews 107 times during a 3 year period. A limited period of average masticatory forces should not have a detrimental effect on prostheses made from heat cured PMMA resin. c) Mix ratio: Within the normal parameters of laboratory techniques the mix ratio of PMMA resin had no significance on the fracture resistance of the prostheses. Due to the high cost of the fibres used for the reinforcement and the limited success and insignificant results achieved in this study, this researcher cannot recommend using Stickbond or Stick fibers for the reinforcement of dentures made with heat cured PMMA resin.

Submitted by JÚLIO HEBER SILVA (julioheber@yahoo.com.br) on 2017-05-03T17:14:13Z No. of bitstreams: 3 Tese - Amanda Vessoni Barbosa Kasuya - 2017-1-50.pdf: 15013683 bytes, checksum: f8924a9fa740c813552a7c3316dba183 (MD5) Tese - Amanda Vessoni Barbosa Kasuya - 2017-51-111.pdf: 15359599 bytes, checksum: ea14f282d1609854707110f304682486 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Rejected by Luciana Ferreira (lucgeral@gmail.com), reason: olhe no guia a forma de nomear arquivos divididos on 2017-05-04T11:04:01Z (GMT) / Submitted by JÚLIO HEBER SILVA (julioheber@yahoo.com.br) on 2017-05-04T17:04:01Z No. of bitstreams: 3 Tese - Amanda Vessoni Barbosa Kasuya - 2017- Parte 1.pdf: 15013683 bytes, checksum: f8924a9fa740c813552a7c3316dba183 (MD5) Tese - Amanda Vessoni Barbosa Kasuya - 2017- Parte 2.pdf: 15359599 bytes, checksum: ea14f282d1609854707110f304682486 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Rejected by Luciana Ferreira (lucgeral@gmail.com), reason: No guia está registrado: - Quando o arquivo tiver que ser dividido, por ser grande, cada um deve ser renomeado da mesma forma, adicionando a indicação da parte, entre parênteses, no final. Exemplos: “Tese - João Alves da Silva - 2015 (1)”, “Tese - João Alves da Silva - 2015 (2)”. on 2017-05-05T12:44:32Z (GMT) / Submitted by JÚLIO HEBER SILVA (julioheber@yahoo.com.br) on 2017-05-05T16:53:52Z No. of bitstreams: 3 Tese - Amanda Vessoni Barbosa Kasuya - 2017- Parte 1.pdf: 15013683 bytes, checksum: f8924a9fa740c813552a7c3316dba183 (MD5) Tese - Amanda Vessoni Barbosa Kasuya - 2017- Parte 2.pdf: 15359599 bytes, checksum: ea14f282d1609854707110f304682486 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Rejected by Erika Demachki (erikademachki@gmail.com), reason: on 2017-05-05T17:13:14Z (GMT) / Submitted by JÚLIO HEBER SILVA (julioheber@yahoo.com.br) on 2017-05-05T17:15:42Z No. of bitstreams: 3 Tese - Amanda Vessoni Barbosa Kasuya - 2017 (1).pdf: 15013683 bytes, checksum: f8924a9fa740c813552a7c3316dba183 (MD5) Tese - Amanda Vessoni Barbosa Kasuya - 2017 (2).pdf: 15359599 bytes, checksum: ea14f282d1609854707110f304682486 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-05-08T15:51:39Z (GMT) No. of bitstreams: 3 Tese - Amanda Vessoni Barbosa Kasuya - 2017 (1).pdf: 15013683 bytes, checksum: f8924a9fa740c813552a7c3316dba183 (MD5) Tese - Amanda Vessoni Barbosa Kasuya - 2017 (2).pdf: 15359599 bytes, checksum: ea14f282d1609854707110f304682486 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-05-08T15:51:39Z (GMT). No. of bitstreams: 3 Tese - Amanda Vessoni Barbosa Kasuya - 2017 (1).pdf: 15013683 bytes, checksum: f8924a9fa740c813552a7c3316dba183 (MD5) Tese - Amanda Vessoni Barbosa Kasuya - 2017 (2).pdf: 15359599 bytes, checksum: ea14f282d1609854707110f304682486 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-03-02 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The objectives of this work were to evaluate the stress distribution (SD), fracture resistance (RF), adhesive strength (AS) and their respective fracture patterns of weekeaned bovine roots, rehabilitated with customized pins with different resinous materials. In addition, the objective of this study was to evaluate the polymerization depth of the resinous materials by Knoop microhardness method (MH). Eight experimental groups were established (n = 10 for FR and AS; n = 5 for MH), with the factor under study: 1. The post type (industrialized glass fiber post relined (I) and personalized post (P), 2. the relining material only for industrialized glass fiber post (experimental composite (e) and composite resin (R)); 3. the material used only for personalized post (experimental composite (e) and bulk fill resin (b), and 4. the amount of remaining dentin (root embrittlement inner wear, in lengths of 5 mm or 10 mm). One hundred and forty bovine roots of similar size were selected and restored according to the group to which they belonged. For FR, Pperiodontal and alveolar bone were simulated and the specimens were placed in an Instron 5965 machine at a 135 ° angle to the long axis and loaded at a constant velocity of 0.5 mm/min in compression until the fracture. The fracture pattern was classified as: F1- crown; F2- root; F3- crown/root; F4- fracture with displacement of the crown/post. For AS, the specimens were sectioned in slices of 1 mm perpendicular to their long axis. Each specimen was placed in a test machine to received the load in the apical-coronal direction, at a constant velocity of 0.5mm / min, pushing the pin through the largest side of the sample until fracture. The fracture pattern was classified as: F1- cohesive of the pin and/or reline material; F2- cohesive of dentin; F3- adhesive of pin/reline material; F4 - Adhesive bonding cement/ eline material and F5 - mixed. For MH, the specimens were sectioned parallel to their long axis. The tests were performed with a Knoop penetrator under a static charge of 50 grams per 10 seconds. MH was calculated as the average value for each third. Finally, the finite element method was used to analyze the DT. 3D virtual models representative of each experimental group were created and analyzed under von Mises equivalent stresses criterion, simulating loading of 100N at a 45o angle with the long axis. The experimental composite proved to be an alternative for the rehabilitation of weakened roots when used to create personalized posts or when used as a relining material, with FR values similar to the traditional technique, but with more favorable stress distributions. Moreover, it presented excellent adhesive strength to the dentin structure, being comparable to conventional composite resin and bulk fill resin. The bulk fill resin resulted in low values of fracture resistance associated with the fracture and displacement of post/crown. Lower microhardness values were observed in the apical third for bulk fill resin. / Os objetivos deste trabalho foram avaliar a distribuição de tensões (DT), resistência à fratura (RF), resistência adesiva (RA) e seus respectivos padrões de fratura de raízes bovinas fragilizadas, reabilitadas com pinos personalizados com diferentes materiais resinosos. Além disso, objetivou-se avaliar a profundidade de polimerização dos materiais resinosos por meio do método de microdureza Knoop (MD). Oito grupos experimentais foram criados (n=10 para RF e RA; n=5 para MD), tendo como fator em estudo: 1. o tipo de pino utilizado (pino de fibra de vidro industrializado reembasado (I) e pino personalizado (P)); 2. o material de reembasamento apenas para os pinos industrializados (compósito experimental (e) e resina composta (r)); 3. o material utilizado para confecção apenas dos pinos personalizados (compósito experimental (e) e resina bulk fill (b)); e 4. a quantidade de dentina remanescente (fragilização radicular por desgaste interno nos comprimentos de 5 mm ou 10 mm). Cento e quarenta raízes bovinas com dimensões semelhantes foram selecionadas e restauradas de acordo com o grupo ao qual pertenciam. Para RF, ligamento periodontal e osso alveolar foram simulados e os espécimes posicionados em máquina Instron 5965, em um ângulo de 135° em relação ao longo eixo do dente de modo que recebessem carregamento à velocidade constante de 0,5mm/min em compressão até a fratura. Em seguida, o padrão de fratura foi classificado em: F1- coroa; F2- raiz; F3- coroa/raiz; F4- fratura com deslocamento do conjunto coroa/pino. Para RA, os espécimes foram seccionados em fatias 1 mm perpendicularmente ao seu longo eixo. Cada espécime foi posicionado em máquina de ensaio de modo que recebessem a carga no sentido apical-coronal, à velocidade constante de 0,5mm/min, empurrando o pino através do maior lado da amostra até a fratura. O padrão de fratura foi classificado em: F1 - coesiva do pino e/ou material de reembasamento; F2 - coesiva da dentina; F3 - adesiva pino/material de reembasmento; F4 - adesiva material de reembasamento/cimento e F5 – mista. Para MD, os espécimes foram seccionados paralelamente ao seu longo eixo. Os testes foram realizados com um penetrador Knoop sob uma carga estática de 50 gramas por 10 segundos. MD foi calculada como o valor médio para cada terço. E por fim, o método de elementos finitos foi empregado para analisar a DT. Modelos virtuais 3D representativos de cada grupo experimental foram criados e analisados sob critério de tensões equivalentes de von Mises, simulando carregamento de 100N em um ângulo de 45o com o longo eixo. O compósito experimental demostrou ser uma alternativa para a reabilitação de raízes fragilizadas quando utilizado para criar pinos personalizados ou quando utilizado como material de reembasamento de pinos, com valores de resistência à fratura semelhantes à técnica tradicional porém, com distribuição de tensões mais favoráveis. Além disso, apresentou excelente resistência adesiva à estrutura dentinária, sendo comparável à resina composta convencional e à resina bulk fill. Já a resina bulk fill resultou em baixos valores de resistência à fratura associado ao deslocamento do conjunto pino/coroa protética. Valores de microdureza inferiores foram observados no terço apical para a bulk fill.