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Zörgiebel, Julius (2014): Langzeitliche Untersuchung der Veränderungen mechanischer Eigenschaften traditioneller und innovativer Glasionomerzemente unter labor- und klinisch simulierten Bedingungen, Evaluation of a conventional glass ionomer cement with new zinc formulation: effect of coating, aging and storage agents: an in vitro study on the maturation of conventional glass ionomer cements and their interface to dentin. Dissertation, LMU München: Medizinische Fakultät
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Abstract

Objective: the study focused on a recently launched conventional glass ionomer cement (GIC) with a particular chemical formulation of both, filler and acrylic liquid, by analysing its mechanical behaviour in comparison to three conventional GICs. Furthermore, the effect of resin coating and storage conditions was evaluated. Materials and methods: Three commercially available GICs were chosen: Riva Self Cure (SDI), Fuji IX Fast (GC) and Fuji IX GP Extra/Equia (GC). Additionally a new developed zinc containing GIC - ChemFil Rock (Dentsply) - was tested. Mechanical properties were determined at macro- {flexural strength (FS) and modulus of elasticity (Eflexural)} and micro-scale {Vickers hardness (VH) and indentation modulus (E)} after storing coated and uncoated specimens in artificial saliva and distilled water for 7 and 30 days. Results: ChemFil Rock revealed the highest FS, but the lowest VH and E. The micro-mechanical properties of the analysed GICs did neither benefit from the new zinc formulation, nor from resin coating. A resin coating is nevertheless a valuable support for GIC fillings, since it offers the absence of visible surface defects like crazing and voids and thus it led to significant improvements in flexural strength. This statement is also valid for Chemfil Rock, contrary to manufacture recommendation. The impact of storage agent and storage duration on the measured properties was low. Conclusions: The new development (ChemFil Rock) might represent a promising approach regarding longevity of GIC fillings in molar regions, due to the high flexural strength and the absence of visible surface defects like crazing and voids. Clinical Relevance: All GICs should receive surface protection in order to perform their maximum in stability

Abstract

Objective: To investigate the influence of long-term storage (till one year) and coating on the variation of micro-mechanical properties of four conventional restorative glass ionomer cements (GICs) within 3.5-mm deep class I cavities. Materials and methods: Four commercially available GICs (Riva Self Cure (SDI), ChemFil Rock (Dentsply), Fuji IX Fast and Fuji IX GP Extra/Equia (GC)) were applied in 100 teeth. In each tooth, two similar 3.5 mm deep Class I cavities were prepared and filled with the GICs, with and without resin coating. The samples were stored in artificial saliva at 37°C for 1 week, 1 month, 3 months, 6 months and 1 year. The variation in mechanical properties (indentation modulus (E) and Vickers hardness (HV)) were determined in 100µm steps starting from the filling surface, through the intermediate layer in-between dentine and GIC and ending 100µm in dentin. Results: HV and E were highly influenced by the material but less by aging duration and resin coating. The depth of measurement has no influence on HV. HV shows a gentle increase over the one year storage period. A ca. 300µm GIC zone at the areas close to dentin with weaker properties as those measured in dentin or GIC was identified in all fillings, irrespective of the presence of coating, and at all storage periods. The thickness of this zone is stronger influenced by storage than by material-type, while coating showed no influence. Filler morphology or dimension were similar to upper parts of the GIC filling, however the amount of low cations was higher. Conclusion: This study has shown that class I GIC restorations are unlikely featuring constant mechanical properties throughout the cavity, regardless of conditions such as aging and coating