| 1281 Flow Characteristics of Flowable Composites and Resin Cements | ||
|
D.L. HADLEY, J.M. CARTER, C.N. BROOKS, and P.C. MOON, Virginia Commonwealth University, Richmond, USA OBJECTIVES: To develop a parallel plate viscometer for measurement of the viscosities of 5 commercial flowable composites and 4 resin cements. METHODS: Experimental conditions were designed such that the weighed 0.5g sample filled the space between the plates (18 mm dia) and exuded from between them when a fixed load (1N)was applied for 30s. A direct current differential transducer (DCDT) and an X-T potentiometric chart recorder were used for data collection. Plate separation h, when plotted as h-2 against time was linear in accordance with the first of Stefan's equations. All tests were started with an h value of approximately 1mm. RESULTS: There was a mean correlation of 0.995 for the straight line plots for the 45 tests made. Viscosities ranged over two orders of magnitude. Flowable composites, Starflow,Versaflow,Flow-It ALC, Filtek Flow and Aelite Flow LV gave mean values from 268 to 740 Poise (P) or 26.8-74 Pa.s. Resin cements, Calibra, Variolink II and Nexus 2 gave much larger values, from to 3530 to 7250 P. In contrast, Lute-It, a resin cement, gave a value of 295 P. Although each sample of every material showed excellent obeyance of Stefan's equation, there were large variances within some sample groups (n=3). We attributed this partly to separation or settling of the filler particles inside the syringe, due to storage. Often, the first-extruded material appeared different to later-extruded material. Another contribution could be that dynaphoresis was occurring during dispensing, where the liquid resin flowed faster than the filler particles, causing some separation of the mixtures. CONCLUSIONS: Stefan's first equation was obeyed for all the materials tested under the conditions of the parallel plate test. Viscosities of flowable composites and resin cement samples varied, presumably due to hydrodynamic effects during dispensation or whilst settling in the syringe. | ||
| Seq #163 - Other Ceramics and Cements 3:45 PM-5:00 PM, Friday, 14 March 2003 Henry B. Gonzalez Convention Center Exhibit Hall C | ||
|
Back to the Dental Materials: III - Ceramics and Cements Program
| ||