Proposes that use of a pinion-shaped cutter@ instead of a hob@ causes differences in tooth root geometry. Asserts that these differences lead to different stress concentrations in the tooth root. Uses the Singularity Method for both types of product to calculate@ exactly@ tooth root stresses. Discusses differences in both approaches. Proves that it is possible to calculate stress concentration using the stress parameter 2?Fn/sFn (on 30??angent).