The Effect of Different Surface Treatment Protocols on the Shear Bond Strength to Repressed Lithium Disilicate Glass Ceramics / Efeito de diferentes protocolos de tratamento de superfície na resistência ao cisalhamento de vitrocerâmica de dissilicato de lítio reprensado

Objective: The present study aimed to evaluate the effect of repressing and different surface treatment protocols on the shear bond strength of lithium disilicate glass-ceramics. Material and Methods: A total of 52 lithium disilicate glass-ceramic discs (IPS emax Press, Ivoclar Vivadent) were fabricated using the heat-press technique. The discs were divided into two groups; group (P): discs fabricated from new e.max ingots (n=26), group (R): discs fabricated from reused e.max buttons (n=26). Each group was subdivided into subgroup (E): discs were etched with hydrofluoric acid (9.5%) (n=13), subgroup (S): discs were air-abraded with 110 µm alumina particles. All specimens were subjected to X-ray Diffraction analysis, Scanning Electron Microscope, Energy Dispersive X-Ray, Thermo-Cycling, and Shear Bond Strength Testing. Results: Repressed Etched subgroup (RE) recorded the statistically highest shear bond strength value, followed by the Pressed Etched subgroup (PE), while the statistically lowest shear bond strength value was recorded for the Pressed Air-Abraded subgroup (PS) and Repressed Air-Abraded subgroup (RS). Conclusion: Repressing the leftover buttons for the construction of new lithium disilicate glass-ceramic restorations has no adverse effect on the bond strength of the resin cement to the ceramic. Hydrofluoric acid surface treatment improves the shear bond strength and durability of resin cement bond to both pressed and repressed lithium disilicate glass-ceramic. Air-abrasion cannot be considered as a reliable surface treatment when bonding to lithium disilicate glass-ceramics. (AU)

Objetivo: O presente estudo teve como objetivo avaliar o efeito da reprensagem e de diferentes protocolos de tratamento de superfície na resistência ao cisalhamento de vitrocerâmica de dissilicato de lítio. Materiais e Métodos: Um total de 52 discos de vitrocerâmica de dissilicato de lítio (IPS emax Press, Ivoclar Vivadent) foram fabricadas usando a técnica de prensagem quente. Os discos foram divididos em dois grupos: grupo (P): discos fabricados a partir de novo lingotes de e-max (n=26), grupo (R): discos fabricados a partir de botões de emax reutilizados (n=26). Cada grupo foi subdividido em subgrupo (E): discos condicionados com ácido fluorídrico (9,5%) (n=13), subgrupo (S) discos foram abrasivos com partícula 110 µm de alumínio. Todos os espécimes foram submetidos a analise de difração de raio-x, microscópio eletrônico de varredura, raio-x de energia dispersiva, termociclagem e teste de resistência de cisalhamento. Resultados: O subgrupo Reprensado-condicionado (RE) registrou o valor estatisticamente mais alta em relação a resistência ao cisalhamento, seguido pelo subgrupo Prensado-condicionado (PE), enquanto o valor estatisticamente mais baixo de resistência ao cisalhamento foi o subgrupo Prensado-Jateado (OS) e o subgrupo Reprensado-Jateado (RS). Conclusão: A reprensagem dos botões restantes para a construção de novas restaurações vitrocarâmicas de dissilicato de lítio não apresentou efeitos adversos na resistência de unicãp do cimento resinoso à cerâmica. O tratamento de superfície com ácido fluorídrico melhora a resistência ao cisalhamento e a durabilidade do cimento resinoso para vitrocerâmica de dissilicato de lítio prensada e reprimida. A abrasão por ar não pode ser considerada um tratamento de superfície confiável quanto a colagem da vitrocerâmica de dissilicato de lítio (AU)

Effect of Thermo-Mechanical Aging and Repressing on Fracture Resistance of Lithium Disilicate Crowns / Efeito do envelhecimento termomecânico e reprensagem na resistência à fratura de coroas de dissilicato de lítio

Objective: The recycling of heat pressed lithium disilicate glass-ceramic leftover material has been reported to be done by dental laboratories. The effect of this procedure on the fracture resistance of single crowns is unknown, especially when it is functioning inside the oral cavity with subsequent exposure to temperature changes and cycles of mastication. Material and Methods: A total of 28 lithium disilicate glass-ceramic crowns (IPS emax Press) were constructed and randomly assigned into two groups (n = 14); Group (P): Included crowns fabricated from new e.max ingots. Group (R): Included crowns fabricated from repressed e.max buttons. Specimens of each group were divided into two equal subgroups (n = 7) according to whether the aging of specimens will be performed or not before fracture resistance testing. Subgroup (N), samples were subjected to fracture resistance without thermo-mechanical aging, while subgroup (A), samples were subjected to thermo-cycling and cyclic loading before being subjected to fracture strength testing. Different methods; SEM, XRD, EDAX were used to characterize the properties of lithium disilicate glass-ceramics before and after repressing. Results: The highest statistically significant fracture resistance value was recorded for the subgroup (RN) repressed/non-aged, followed by the subgroup repressed/aged (RA), while the lowest statistically significant mean value was recorded for the subgroup pressed/aged (PA). There was no significant difference between pressed/non-aged (PN) and repressed/aged (RA) subgroups. Conclusion: Repressing of leftover buttons may increase the fracture resistance of IPS emax Press crowns. Thermo-mechanical aging may negatively affect the fracture resistance of IPS emax Press crowns, yet Repressing may decrease this effect. Clinical implications:This is a novel approach that targets a point of research that has not been investigated before. It elaborates how repressing may decrease the effect of aging and increase the fracture resistance of lithium disilicate crowns. Thus, recycling of lithium disilicate glass ceramics might decrease its failure and prolong their serviceability (AU)

Objetivo: A reutilização de material residual de vitrocerâmicas de dissilicato de lítio prensadas a quente tem sido realizada pelos laboratórios de prótese. O efeito deste procedimento na resistência à fratura de coroas unitárias é desconhecido, especialmente quando estão em função na cavidade oral com subsequente exposição às variações de temperatura e ciclos mastigatórios. Material e Métodos: Vinte e oito coroas de dissilicato de lítio (IPS e.max Press) foram confeccionadas e divididas aleatoriamente em dois grupos (n = 14); Grupo (P): Incluiu coroas fabricadas de pastilhas novas de e.max; Grupo (R): Incluiu coroas fabricadas de e.max reprensado. As amostras de cada grupo foram divididas em dois subgrupos iguais (n = 7) de acordo com a realização de envelhecimento dos espécimes antes do teste de resistência à fratura. As amostras do subgrupo (N) foram submetidas ao teste de resistência à fratura sem envelhecimento termomecânico, enquanto as amostras do subgrupo (A) foram submetidas ao envelhecimento termomecânico antes do teste de resistência à fratura. Diferentes métodos (MEV, DRX e EDS) foram usados para caracterizar as propriedades da cerâmica de dissilicato de lítio antes e depois da reprensagem. Resultados: O maior valor de resistência à fratura estatisticamente significativo foi do subgrupo (RN) reprensado/não envelhecido, seguido pelo subgrupo reprensado/envelhecido (RA), enquanto o menor valor médio estatisticamente significativo foi do subgrupo prensado/envelhecido (PA). Não houve diferença estatística entre os subgrupos prensado/não envelhecido (PN) e reprensado/envelhecido (RA). Conclusão: A reprensagem de material residual pode aumentar a resistência à fratura de coroas de IPS e.max Press. O envelhecimento termomecânico pode afetar negativamente na resistência à fratura deste material, enquanto a reprensagem pode diminuir este efeito. Relevância clínica: Esta é uma nova abordagem que busca estudar um tema que não havia sido investigado anteriormente. Este estudo demonstrou como a reprensagem pode diminuir o efeito do envelhecimento e aumentar a resistência à fratura de coroas de dissilicato de lítio. Assim, a reutilização de vitrocerâmicas de dissilicato de lítio pode diminuir o risco à falha e aumentar o tempo de vida útil (AU)

An in-vitro wear study of human enamel opposing heat-pressed ceramics / 대한치과보철학회지

PURPOSE: The purpose of this study was to compare the wear characteristics of human enamel opposing 2 heat-pressed ceramics (e.max Press and Empress Esthetic), conventional feldspathic porcelain (Ceramco 3) and type III gold alloy. MATERIAL AND METHODS: Intact cusps of extracted premolars were used for enamel specimens. Five disk samples were made for each of two heat-pressed ceramics groups, conventional feldspathic porcelain group and type III gold alloy group. Wear tests were conducted in distilled water using a pin-on-disk tribometer. The amount of enamel wear was determined by weighing the enamel specimens before and after wear tests, and the weight was converted to volumes by average density. The wear tracks were analyzed by scanning electron microscopy and surface profilometer to elucidate the wear characteristics. RESULTS: 1. Ceramco 3 led to the greatest amount of enamel wear followed by Empress Esthetic, e.max Press and type III gold alloy. However, there was no significant difference between Ceramco 3 and Empress Esthetic (P > .05), and there were also no significant differences among Empress Esthetic, e.max Press and type III gold alloy (P > .05). 2. The average surface roughness of e.max Press after wear test was smallest followed by Empress Esthetic and Ceramco 3, but there was no significant difference between Empress Esthetic and Ceramco 3 (P > .05). 3. There were no significant differences among the depth of wear tracks of all the groups (P > .05). The group that showed the largest width of wear track was Ceramco 3 followed by Empress Esthetic, e.max Press and type III gold alloy. However, there was no significant difference between e.max Press and Empress Esthetic (P > .05), and there was also no significant difference between Empress Esthetic and Ceramco 3 (P > .05). CONCLUSION: Within the limits of this study, heat-pressed ceramics were not more abrasive than conventional feldspathic porcelain.