Runny or not?

When designing resin composite materials, manufacturers have to balance, among other things, the degree of filler loading, filler particle size and resin viscosity, given that these are factors in the viscosity/runniness of the material, although viscosity-modifying resins can also be added. Given that a more and more frequently asked question (FAQ) at my presentations on posterior composite is – ‘is it sinful to heat composite before placement of a restoration, and/or, should I be buying a composite heater’, it is my feeling that the practice of heating composite is increasing. Here I must make full disclosure and acquaint readers with my personal view on viscosity of resin composites – I like them to maintain their shape, ie be sculptable, and by this I mean that I like them to stay exactly where they are placed after shaping. Why? For posterior composite restorations, if at all possible, I look at the shape of the (sound) tooth or the previous restoration and, if that has been functioning well from an occlusion viewpoint, I then try to remember its shape and replicate that in my final restoration. This is important, because if the restoration initially is overcontoured/too high/too bulbous, then it will take (patient's and clinician's) time shaping the restoration to a correct shape with a turbine and/or discs. Not good for either the patient or the clinician. For treatment of tooth wear with additive composite at an increased occlusal vertical dimension, use of a sculptable composite, which stays where it is placed, facilitates freehand placement of the restorations, without the need for a putty matrix. Martin Kelleher is obviously also in this camp, given that a technique tip that he provided in the second of his two excellent McNamara's Fallacies papers on the restoration of worn teeth¹ was to keep the resin composite material in the fridge until the clinician is ready to use it, in order to make it more sculptable!