The effect of aging on composite-to-composite repair strength

The development of new aesthetic materials enables the dentist to treat patients based on the concept of minimal invasive dentistry. The concept of minimal invasive dentistry, which involves preservation of tooth structure by repair of existing restorations through relayering (composite-to-composite-bonding). Improvements of composite resins and problems occurring in composite restorations due to the influence of dynamic oral conditions are described. A composite restoration ages over time and failure frequently occurs. The success of relayering depends on the strength of composite-to-composite bonding. The first aim of this study was to find the best model for simulating intra-oral aging of composite resins. The second aim was to determine the best possible conditioning method for composite-to-composite repair based on the bond strength analyses.
In this study, the composites were aged by four aging conditions: 1) Thermocycling (5000x, 5-55ºC), 2) Storage in water at 37ºC for six months, or 3) Immersion in citric-acid at 37ºC, pH 3 for one week and a non-aged control, 4) Exposed to oral biofilm in vitro. To reflect what actually occurs in the oral environment, in situ studies were carried out to forward a “gold standard” for comparison of results from in vitro aging methods. Based on the “gold standard” (intra-oral aging), it is concluded that exposure to biofilm in vitro is the best method to simulate intra-oral aging.
Composite-to-composite repair can be done either on the fresh or aged composite resins. In this study, two surface conditioning, namely intermediate adhesive resin and silica coating were applied on the microhybrid, nanohybrid and nanofilled composite resins. Intermediate adhesive resin (IAR-application) conditioning did not improve the composite-to-composite immediate repair strength. Silica coating and silanization followed by its corresponding IAR (SC-application), strongly increased repair bond strengths and provided exclusively cohesive failures in the substrate in all composite resins. Repair bond-strengths in aged composite resins after IAR-application were always lower in non-aged ones, while SC-application led to higher bond strengths than IAR-application after aging conditions. In addition, SC-application led to more cohesive failures than after IAR-application, regardless the aging method. Consequently it is argued that in general SC-application is the best conditioning method to be used in relayering of composite restorations.

	Titel en inhoud
	Hoofdstuk 1
	Hoofdstuk 2 (Embargo t/m 28-06-2011)
	Hoofdstuk 3 (Embargo t/m 28-06-2011)
	Hoofdstuk 4
	Hoofdstuk 5 (Embargo t/m 28-06-2011)
	Hoofdstuk 6
	Hoofdstuk 7
	Hoofdstuk 8
	Nederlandse samenvatting
	Engelse samenvatting
	Dankwoord
	Curriculum vitae
	Volledige dissertatie (Embargo t/m 28-06-2011)

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