Abstract
Objective
Handling (stickiness, adaptability) of a dental composite does strongly influence quality and success of a dental restoration. The purpose was to develop an in vitro test, which allows for evaluating adaptability and stickiness.
Methods
15 dentists were asked for providing individual assessment (school scores 1–6) of five dental composites addressing adaptability and stickiness. Composites were applied with a dental plugger ( d = 1.8 mm) in a class I cavity (human tooth 17). The tooth was fixed on a force gauge for simultaneous determination of application forces with varying storage (6/25 °C) and application temperatures (6/25 °C). On basis of these data tensile tests were performed with a dental plugger (application force 1 N/2 N; v = 35 mm/min) on PMMA- or human tooth plates. Composite was dosed onto the tip of the plugger and applied. Application and unplugging was performed once and unplugging forces (UF) and length of the adhesive flags (LAF) were determined at different storage (6/25 °C) and application temperatures (25/37 °C). Unplugging work (UW) was calculated from area of UF and LAF data.
Results
The individual assessment revealed significantly different temperature-dependent application forces between 0.58 N and 2.23 N. Adaptability was assessed between 2.1 and 2.8 school scores. Stickiness varied significantly between the materials (scores: 2–3.2). UW differed significantly between the materials with values between 3.20 N mm and 37.83 N mm. Between PMMA substrate or tooth slides and between 1 N or 2 N application force only small UW differences were found.
Significance
The presented in vitro unplugging work allows for an in vitro estimation of the handling parameters adaptability and stickiness.
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Introduction
Light curing dental composites are state of the art for clinical restorations. The development of these composites is strongly orientated on clinical requirements. Therefore various materials with different viscosities, application forms and with optimized properties are available . Nevertheless the clinical success of a composite is strongly influenced by handling opportunities. For example insufficient condensation may result in voids or porosities and may reduce stability, marginal integrity or wear resistance. Because handling may not be fully described by individual parameters like stiffness, viscosity (rheology) , adhesive behavior, visco-elastic behavior or the filler components , it is practise to ask dentists for their distinct impression of unset composites. Parameters are the ease to adapt a composite in the cavity (adaptability), how the composite sticks to the cavity or instrument (stickiness) or how firm the composite appears (firmness). Often a high number of dentists is questioned, which results in high expenditure and costs. Therefore, a standardized laboratory test seems necessary, which allows for estimating handling of composites. Already performed tests are tensile tests or profilometry, examining the influence of different speed, testing temperatures or different substrate surfaces. Work for probe separation, maximum force or coefficients of variation were defined as parameters for characterization of composite properties, temperature influence and unplugging speed. Partly the length of the adhesive flag was determined by polymerizing the material during tensile testing . But in conclusion no test seems available representing the clinical situation. Therefore, the idea was to ask a representative number of dentists for the evaluation of different composites and relate these results to in vitro tensile tests. Clinical parameters such as human tooth tissue, storage conditions or cavity temperatures should be considered. Undetermined application force should be evaluated.
The hypothesis of this investigation was that unplugging work might provide an opportunity for evaluating adaptability and stickiness of dental composites. The purpose of this study was to develop a simplified test, which allows for standardizing adaptability and stickiness.
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