Modifications of bur design does not include which of the following?
As the effectiveness of small burs has increased, they have replaced larger burs in many procedures.
Three other major trends in bur design are discernible:

Reduced use of crosscuts
Extended heads on fissure burs
Rounding of sharp tip angles. 

Crosscuts are needed on fissure burs to obtain adequate cutting effectiveness at low speeds, but they are not needed at high speeds. Because crosscut burs used at high speeds tend to produce unduly rough surfaces, many of the crosscut sizes originally developed for lowspeed use have been replaced by noncrosscut instruments of the same dimension for high-speed use.
Ref: Sturdevant's art and science of operative dentistry. 4th edition page 333
Increased use of crosscuts
Extended heads on fissure burs
Rounding of sharp tip angles
Small diameter sizes