Effects of sandblasting of prosthetic abutment surfaces on the tensile strength of cement-retained crowns, using a cementing technique: an in vitro study

Objective: The tensile strength effects on the sandblasting of the abutment associated with a cementing technique are not well documented. The objective of this study is to analyze the tensile strength of prosthetic crowns cemented on standard and sandblasted abutments, using a cementing technique. Methods: Experimental groups were formed according to ce­menting technique (control and practice abutment technique) and prosthetic abutment roughness (standard and sandblas­ted), totaling forty specimens. The crowns were cemented with Zinc Phosphate cement. Statistical analysis was conducted with an α at 0.05. Results: Considering the cementation techniques analysis, there were no statistically significant differen­ces between the groups, with mean tensile strength values of 157.83±22.16 N for the control technique, and 159.95±46.40 N for the practice abutment technique on the standard surface. Result analysis of the control technique (626.23±34.80 N) and practice abutment technique (642.62±94.00 N) indicated no significant differences on the sandblasted surface. Consi­dering the surface roughness analysis, significant differences were observed, with values of 157.83±22.16 N for the control technique/standard surface group and 626.23±34.80 N for the control technique/sandblasted surface group. Significant differences were observed in the practice abutment technique/standard surface group with 159.95±46.40 N values, compa­red to the 642.62±94.00 N value for the practice abutment technique/sandblasted group. Conclusions: The practice abut­ment cementing technique showed no significant differences with the control technique, regarding to the tensile strength, in the two surfaces (standard and sandblasted) used in the study. The sandblasting of prosthetic abutments led to a signifi­cant increase on the tensile strength considering the two studied cementation techniques.Objetivos: Os efeitos de resistência à tração no jateamento do pilar associado a uma técnica de cimentação não estão bem documentados. O objetivo deste estudo é analisar a resistência à tração de coroas protéticas cimentadas em munhões padrões e asperizados, utilizando uma técnica de cimentação. Métodos: Os grupos experimentais foram formados de acordo com a técnica de cimentação (técnica de controle e prática de pilares) e a rugosidade do pilar protético (padrão e asperizado), totalizando quarenta espécimes. As coroas foram cimentadas com cimento de fosfato de zinco. A análise estatística foi conduzida a um valor de α=0,05. Resultados: Na análise das técnicas de cimentação não houve diferenças estatisticamente significativas entre os grupos, com valores médios de resistência à tração de 157,83±22,16 N para a técnica controle e 159,95±46,40 N para a técnica practice abutment na superfície padrão. A análise dos resultados na técnica controle (626,23±34,80 N) e na técnica practice abutment (642,62±94,00 N), na superfície jateada, também não indicaram diferenças significativas. Na análise da rugosidade da superfície, observaram-se diferenças significativas, com valores de 157,83±22,16 N para o grupo técnica controle/superfície padrão e 626,23±34,80 N para o grupo técnica controle/superfície asperizada. Foram observadas diferenças significativas no grupo técnica Practice abutment/ superfície padrão com valores de 159,95±46,40 N comparado com o grupo técnica Practice abutment/grupo jateado, com valores de 642,62±94,00 N. Conclusões: A técnica de cimentação Practice abutment não mostrou diferenças significativas com a técnica controle, em relação à resistência à tração, nas duas superfícies (padrão e asperizada) usadas no estudo. O jateamento dos munhões protéticos levou a um aumento significativo da resistência à tração nas duas técnicas de cimentação estudadas

The marginal adaptation of main all ceramic systems

Nos últimos anos pudemos observar um aumento na qualidade e na quantidade de restaurações de cerâmica pura. Este aumento se deve principalmente à superioridade estética que estas restaurações apresentam quando comparadas com as restaurações convencionais com base metálica. No entanto, é sabido que além do fator estético, a resistência e a adaptação marginal são, também, requisitos fundamentais para a longevidade e o sucesso das restaurações fixas. Diante disso, o objetivo desse trabalho foi realizar uma análise da literatura sobre a adaptação marginal dos principais sistemas de cerâmica pura. Após a avaliação dos trabalhos concluímos que a alta qualidade de adaptação marginal das restaurações é essencial para a saúde do órgão dentário e dos tecidos periodontais; e que em apenas dois trabalhos analisados, algumas restaurações de cerâmica pura não alcançaram alta qualidade de assentamento marginal, e, portanto, não estavam dentro dos limites de aceitabilidade clínica de 120µm.In the last years we could notice an increase in quality and quantity of all ceramic restorations. The main cause of this is relationed to the great esthetics superiority of this restorations comparing to conventional restorations with metallic base. Is known that beyond the esthetic factor, resistance and marginal adaptation are also fundamental requirements to the longevity and success of fixed restorations. The aim of this study was analyse the literature about marginal adaptation of main all ceramic systems. After studies valuation, we can conclude that the high quality of marginal adaptation is essential to tooth organ and periodontal tissues health; and in only two studies, some all ceramic restorations didn’t achieve a high quality of marginal adaptation, therefore, weren’t within the established clinical acceptability of 120µm

Resistance to fracture of direct restorations with cuspal coverage in upper endodontically treated bicuspids

Endodontically treated teeth are considered more susceptible to fracture because of the loss of tooth structure. The aim of this study was to evaluate the increase of resistance to fracture of upper bicuspids that underwent endodontic access and were restored with composite resin, with cuspal coverage. Forty extracted human maxillary premolars were divided in 4 groups: I - intact teeth; II - teeth with endodontic access and MOD preparation, restored with composite resin, without cuspal coverage; III - teeth with endodontic access, MOD preparation and occlusal reduction, restored with composite resin, with cuspal coverage; IV - teeth with endodontic access and MOD preparation, without any restoration. The test specimens were submitted to compression test up to their fracture. The test of Tukey and the ANOVA analysis were used to compare and test the results. The teeth from group III (with cuspal coverage) presented with significantly greater resistance to fracture, when compared with those from groups II (restored without cuspal coverage) and IV (not restored). The composite restoration with cuspal coverage can be considered an alternative for endodontically treated premolars.Dentes tratados endodonticamente são considerados mais susceptíveis à fratura em função da perda de estrutura dentária. Este estudo teve como objetivo avaliar o aumento da resistência à fratura de pré-molares superiores que receberam acesso endodôntico e foram restaurados em resina composta com cobertura de cúspide. Foram utilizados 40 pré-molares superiores humanos extraídos, que foram divididos em 4 grupos: I - dentes hígidos; II - dentes com acesso endodôntico, com preparo MOD, restaurados em resina composta, sem cobertura de cúspide; III - dentes com acesso endodôntico, com preparo MOD e redução de cúspide, restaurados em resina composta, com cobertura de cúspide; IV - dentes com acesso endodôntico, com preparo MOD, sem receber restauração. Os corpos-de-prova foram submetidos a teste de compressão até a fratura e os resultados foram submetidos a análise de variância e comparados através do teste de Tukey, podendo-se concluir que os dentes do grupo III (restaurados com cobertura de cúspide) apresentaram maior resistência à fratura, com valores significativos, em relação aos dentes do grupo II (restaurados sem cobertura de cúspide) e IV (só preparo cavitário sem restauração). A restauração em resina composta direta com cobertura de cúspide pode ser considerada uma alternativa restauradora para dentes pré-molares submetidos à terapia endodôntica

Manganese accumulation and its relation to "eucalyptus shoot blight in the Vale do Rio Doce"

Eucalyptus Shoot Blight in the Vale do Rio Doce (ESBVRD) is an anomaly that leads to reduced growth and, in more extreme cases, to death of eucalyptus plants. Initially diagnosed in plantations in the region of the Vale do Rio Doce, in the State of Minas Gerais, Brazil, this problem has also been found in plantations in other regions of the country and even in other countries. Although the symptoms of this anomaly are well-known, its causes are not yet understood. The aim of this study was to evaluate the cause-effect relationship between accumulation of manganese (Mn) in eucalyptus clones and ESBVRD. Characterization of the environment in areas of greater occurrence of this problem in regard to soil, climate and fluctuation of the water table was undertaken in eucalyptus plantations of the Celulose Nipo-brasileira S.A. (Cenibra) company in the region of the Vale do Rio Doce. Plant tissues were sampled in two situations. In the first situation, diagnosis occurred in the initial phase of the anomaly in clones with differentiated tolerance to the problem; in the second situation, diagnosis was made in a single clone, considered to be sensitive, in two time periods - in the phase with the strong presence of symptoms and in the recovery phase, in areas of occurrence and in areas of escape from the problem. The most ESBVRD-sensitive clone showed much higher (4.8 times higher) leaf Mn contents than more tolerant clones. In plants with the anomaly, Mn leaf contents were greater than 3,070 mg kg-1, much greater than the quantity found in those without the anomaly (734 mg kg-1). In the period in which the symptoms began to wane, there was a sharp decline in leaf Mn contents, from 2,194 to 847 mg kg-1. Manganese content in the above ground part and plant litter (44.4 g ha-1) in the area of occurrence of the anomaly was three times greater than that found in these same components (14.1 g ha-1) in the area of absence of the symptom. Based on the evidence found, such as the existence of environmental conditions favorable to high Mn availability to the plants in the areas of greatest incidence of ESBVRD, greater uptake of Mn in sensitive clones and in plants with symptoms, and a synchronism between the intensity of symptoms of ESBVRD and leaf Mn contents, it may be inferred that temporary excess of Mn in eucalyptus plants is closely related to ESBVRD