Influencia da radiação ionizante em compositos odontologicos, ionomero de vidro e ceramica

Orientador: Frab Norberto BoscoloDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de PiracicabaResumo: A influência da radiação ionizante proveniente de exames radiográficos de diagnóstico ou tratamento radioterápico em materiais como compósitos odontológicos, ionômero de vidro e cerâmica é pouco conhecida. Procurando uma maior compreensão da influência da radiação ionizante no comportamento químico, em escala molecular, dos materiais restauradores estéticos usados na Odontologia, o objetivo neste estudo foi avaliar à ação da radiação aplicada com o aumento de dose e determinar quais possíveis alterações ocorreram na estruturas químicas destes materiais restauradores. Foram confeccionados 25 corpos de prova de cada material, seguindo as recomendações do fabricante e após o período de estabilização dos materiais, foram aplicadas as doses fracionadas de 0,25Gy. Os corpos de prova foram separados em 5 grupos, dentre eles o grupo G1, controle não irradiado, e os grupos G2, G3, G4 e G5, que receberam as doses de 0,25Gy; 0,50Gy; 0,75Gy; e 1,00Gy respectivamente de radiação gama de Cobalto 60. Após um mês da radiação, os corpos de prova foram secos e triturados para a análise espectrométrica. O método usado foi a espectrometria de FTIR com refletância difusa. De acordo com a metodologia empregada e os resultados obtidos, foi possível observar que a radiação ionizante interagiu com todos os materiais odontológicos estudados os quais apresentaram padrão de modificação não linear com aumento da dose de radiação. Vários grupos funcionais se apresentaram susceptíveis, tanto na fração orgânica como na fração inorgânica. Ocorreram alterações na estrutura química de todos materiais irradiados apresentando flutuações quantitativas dos grupos funcionaisAbstract: The influence of the ionizing radiation from diagnosis radiographic exams or radiotherapy treatment in dental materials as resin composite, glass ionomer and ceramic dental is not wide known. Trying a better understanding about the ionizing radiation influence in the chemical behavior, in molecular scale, of the esthetics restoration materials used in the dentistry, our aim with this study was to evaluate the radiation action using a different dose to determine which possible alterations in the chemical structures happened. Twenty-five specimens of each material were performed, following the manufacturer's recommendations, after the materials stabilization period, 0.25Gy fractional doses gamma radiation 60Co were applied. The specimens were separated in 5 groups; group G1, control group not irradiated, and the groups G2, G3, G4 and G5 irradiated with 0.25Gy; 0.50Gy; 0.75Gy; and 1.00Gy respectively. One month after radiation applying, the specimens were dried and triturated for spectrometric analysis. The used method was FTIR spectrometric with diffuse reflectance. According to used methodology and the obtained results, it was possible to observe that the ionizing radiation interacted with all this studied dental materials, which had non lineal pattern of modification with radiation dose increase. Several functional groups are susceptible, as well as in the organic fraction and in the inorganic fraction. All the irradiated materials had alterations in the chemical structure presenting quantitative fluctuation of the functional groupsMestradoRadiologia OdontologicaMestre em Radiologia Odontológic

Investigation of bond strength of dental adhesive systems irradiated with ionizing radiations

Orientador: Frab Norberto BoscoloTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de PiracicabaResumo: No presente estudo, materiais adesivos com diferentes modos de aplicação foram submetidos à ação de radiações ionizantes de diferentes energias com o objetivo de verificar a resistência adesiva após irradiação, por meio do ensaio de microcisalhamento, avaliando o padrão de fratura, considerando se as radiações utilizadas podem ser agentes externos capazes de causar degradação da união adesiva. Após aprovação do projeto pelo comitê de ética em pesquisa (protocolo:032/2007), 60 dentes humanos tiveram as coroas seccionadas no sentido mesiodistal, e incluídas em bloco de resina epóxi. As coroas foram lixadas para exposição da dentina média obtendo 120 corpos de provas. Os corpos de prova foram divididos em 3 grupos (n=40), de acordo com os sistemas adesivos usados: SB (Adper ¿ Single Bond Plus), CB (Clearfil¿ SE Bond) e AP (Adper¿ Prompt¿ Self-Etch). Os adesivos foram aplicados em dentina e fotoativados usando LED (Lec 1000, MMoptics, 1000mW/cm2). Sobre as áreas adesivas foram colocados moldes de elastômero (0,5mm de espessura por 1,2mm de diâmetro) com três orifícios que foram preenchidos com resina composta (Filtek¿ Z-250) fotoativada por 20s. Cada grupo foi subdividido em 4 (n=10): GC= grupo controle que não foi irradiado; UV= grupo irradiado com ultravioleta; RXD= grupo irradiado com raios-X de energia para o diagnóstico; e RXT= grupo irradiado com raios-X de energia para terapia. Após irradiação foram realizados testes de microcisalhamento (Instron Inc., modelo 4411) para a avaliação da resistência adesiva, e em seguida foram avaliados os modos da fratura das amostras, classificando-os com 5 escores: 1- fratura adesiva; 2- fratura mista com 75% de exposição dentinária, 3 -fratura mista com 50% de exposição dentinária, fratura mista com 25% de exposição dentinária, e fratura coesiva. Os resultados foram submetidos à ANOVA com os testes de Tukey, Dunnett, Kruskal-Wallis e Dunn ( =0,05). As diferentes radiações ionizantes não causaram alterações na resistência da união dos adesivos CB e AP; somente o adesivo SB exibiu aumento na resistência da união após a exposição com UV (p=0,0267). A UV também alterou os padrões de fratura do adesivo SB (p=0,0000). As alterações na resistência da união adesiva e no padrão de fratura não foram degradantes, mas dependeram tanto da energia das radiações ionizantes como do modo de aplicação dos adesivos. Assim as radiações ionizantes não podem ser consideradas como agentes externos capazes de causar degradação nos materiais adesivos estudadosAbstract: In the present study, adhesive materials with different application types were exposed to ionizing radiations of varying energy with the objective to verify by means of microshear and failure mode test the bond strength after irradiation trying to determine whether the used radiations could be external agents able to degrade the adhesive bond. After approbation of this project by the Ethical Committee for Human Research (protocol number 032/2007), 60 human teeth had its crowns sectioned mesio-distally and then were included into block of epoxy resin. The crowns were sanded to show the medium dentin and to obtain 120 specimens. The specimens were divided into 3 groups (n=40), according to the adhesive systems used: SB (Adper¿ Single Bond Plus), CB (Clearfil¿ SE Bond) and AP (Adper¿ Prompt¿ Self-Etch). The adhesives were applied on dentin and photo-activated using LED (Lec 1000, MMoptics, 1000mW/cm2). Onto the bonding areas were placed customized elastomer molds (0.5 mm-thickness by 1.2mm-diameter) with three orifices which were filled with composite resin (Filtek¿ Z-250) photoactivated during 20s. Each group was subdivided into 4 subgroups (n=10): GC=control group without irradiation; UV=group irradiated with ultraviolet radiation; RXD=group irradiated with diagnostic radiation-X; RXT=group irradiated with therapeutic radiation-X. After irradiation the microshear tests were carried out (Instron Inc., model 4411) to evaluate the adhesive bond, and afterwards the modes of failure of the specimens were evaluated and classified using 5 scores: 1=adhesive failure, 2=mixed failure with 75% dentin exposed; 3=mixed failure with 50% dentin exposed; 4=mixed failure with 25% dentin exposed; 5=cohesive failure. The results were submitted to ANOVA by the Tukey, Dunnett, Kruskal-Wallis and Dunn test ( =0.05). No changes in bond strength of CB and AP were observed after application of the different radiations; only SB showed an increase in bond strength after UV (p=0.0267) irradiation. UV also changed the failure patterns in SB (p=0.0000). The changes in the adhesive bond and in the mode of failure did not show degradation, but were dependent of both the energy of ionizing radiation and the way of adhesive application. Thus, the ionizing radiation cannot be considered an external agent able to cause degradation in the studied adhesive materialsDoutoradoRadiologia OdontologicaDoutor em Radiologia Odontológic

Prevalence of C-shaped root canal in a Brazilian subpopulation: a cone-beam computed tomography analysis

The aim of this study was to use cone-beam computed tomography (CBCT) images to evaluate the prevalence and configurations of C-shaped canals in permanent mandibular second molars among members of a Brazilian subpopulation. CBCT exams of 214 patients (406 teeth) were evaluated for: presence of C-shaped root canals, number of canals and direction of the root grooves (buccal or lingual). Of the 214 CBCT images examined, 192 showed intact bilateral molars, which were used to analyze the distribution of unilateral and bilateral occurrences of C-shaped canals. The prevalence of these canals was correlated with gender and age, and the number of canals was correlated with the direction of the root grooves using the chi-squared test (α = 0.05). The prevalence of C-shaped canals was 15.3%. This prevalence did not differ with gender or age. Most of the C-shaped molars had three (43.5%) or two (37.1%) canals; 69.4% of the C-shaped canals were grooved in the buccal direction; 68.3% of the C-shaped cases were unilateral. In conclusion, there was a significant prevalence of C-shaped canals in the mandibular second molars of the population studied; the C-shaped canal system varied in configuration, with a higher prevalence of three and two canals and unilateral occurrence; CBCT is a useful tool for endodontic diagnosis and treatment.The aim of this study was to use cone-beam computed tomography (CBCT) images to evaluate the prevalence and configurations of C-shaped canals in permanent mandibular second molars among members of a Brazilian subpopulation. CBCT exams of 214 patients (406 teeth) were evaluated for: presence of C-shaped root canals, number of canals and direction of the root grooves (buccal or lingual). Of the 214 CBCT images examined, 192 showed intact bilateral molars, which were used to analyze the distribution of unilateral and bilateral occurrences of C-shaped canals. The prevalence of these canals was correlated with gender and age, and the number of canals was correlated with the direction of the root grooves using the chi-squared test (α = 0.05). The prevalence of C-shaped canals was 15.3%. This prevalence did not differ with gender or age. Most of the C-shaped molars had three (43.5%) or two (37.1%) canals; 69.4% of the C-shaped canals were grooved in the buccal direction; 68.3% of the C-shaped cases were unilateral. In conclusion, there was a significant prevalence of C-shaped canals in the mandibular second molars of the population studied; the C-shaped canal system varied in configuration, with a higher prevalence of three and two canals and unilateral occurrence; CBCT is a useful tool for endodontic diagnosis and treatment281394

Effect of therapeutic dose X rays on mechanical and chemical properties of esthetic dental materials

The aim of this study was to investigate the influence of therapeutic dose X rays on the microhardness (MH) and degree of conversion (DC) of two different esthetic restorative dental materials. The materials were photo-activated with a LED light-curing unit using three cure-times: 5, 20 and 40 seconds. The photo-activation was carried out in two distinct periods: before and after irradiation with doses of 5, 35 and 70 Gy, from a 6 MV X rays beam. In accordance with the methodology used, it was conclude that a therapeutic dose does not have a detrimental effect on the photoinitiator molecules, because the photo-activation occurred after they were irradiated. When the irradiation was applied before photo-activation, the materials showed MH improvement, but when photo-activation was performed after irradiation, there was less improvement. However, there was no correlation between MH and DC. Thus, a therapeutic dose applied to cured material can promote linking and breaking of chain bonds in a non-linear way.FUNCAM

Effect of therapeutic dose X rays on mechanical and chemical properties of esthetic dental materials

The aim of this study was to investigate the influence of therapeutic dose X rays on the microhardness (MH) and degree of conversion (DC) of two different esthetic restorative dental materials. The materials were photo-activated with a LED light-curing unit using three cure-times: 5, 20 and 40 seconds. The photo-activation was carried out in two distinct periods: before and after irradiation with doses of 5, 35 and 70 Gy, from a 6 MV X rays beam. In accordance with the methodology used, it was conclude that a therapeutic dose does not have a detrimental effect on the photoinitiator molecules, because the photo-activation occurred after they were irradiated. When the irradiation was applied before photo-activation, the materials showed MH improvement, but when photo-activation was performed after irradiation, there was less improvement. However, there was no correlation between MH and DC. Thus, a therapeutic dose applied to cured material can promote linking and breaking of chain bonds in a non-linear way.113313318FUNCAM

Silver Nanoparticles in Dental Biomaterials

Silver has been used in medicine for centuries because of its antimicrobial properties. More recently, silver nanoparticles have been synthesized and incorporated into several biomaterials, since their small size provides great antimicrobial effect, at low filler level. Hence, these nanoparticles have been applied in dentistry, in order to prevent or reduce biofilm formation over dental materials surfaces. This review aims to discuss the current progress in this field, highlighting aspects regarding silver nanoparticles incorporation, such as antimicrobial potential, mechanical properties, cytotoxicity, and long-term effectiveness. We also emphasize the need for more studies to determine the optimal concentration of silver nanoparticle and its release over time

Bond strength of dental adhesive systems irradiated with ionizing radiation

The aim of the present paper was to determine the effect of different types of ionizing radiation on the bond strength of three different dentin adhesive systems.\ud Materials and Methods: One hundred twenty specimens of 60 human teeth (protocol number: 032/2007) sectioned mesiodistally were divided into 3 groups according to the adhesives systems used: SB (Adper Single Bond Plus), CB (Clearfil SE Bond) and AP (Adper Prompt Self-Etch). The adhesives were applied on dentin and photo-activated using LED (Lec 1000, MMoptics, 1000 mW/cm2). Customized elastomer molds (0.5 mm thickness) with three orifices of 1.2 mm diameter were placed onto the bonding areas and filled with composite resin (Filtek Z-250), which was photoactivated for 20 s. Each group was subdivided into 4 subgroups for application of the different types of ionizing radiation: ultraviolet radiation (UV), diagnostic x-ray radiation (DX), therapeutic x-ray radiation (TX) and without irradiation (control group, CG). Microshear tests were carried out (Instron, model 4411), and afterwards the modes of failure were evaluated by optical and scanning electron microscope and classified using 5 scores: adhesive failure, mixed failures with 3 significance levels, and cohesive failure. The results of the shear bond strength test were submitted to ANOVA with Tukey's test and Dunnett's test, and the data from the failure pattern evaluation were analyzed with the Mann Whitney test (p = 0.05).\ud Results: No change in bond strength of CB and AP was observed after application of the different radiation types, only SB showed increase in bond strength after UV (p = 0.0267) irradiation. The UV also changed the failure patterns of SB (p = 0.0001).\ud Conclusion: The radio-induced changes did not cause degradation of the restorations, which means that they can be exposed to these types of ionizing radiation without weakening the bond strength