At 4 and 8 weeks , between treatment analyses found the test dentifrice to be significantly better than the negative control dentifrice in relieving dentin hypersensitivity for all measures ( Schiff : P < 0.0001 at 4 and 8 weeks ; VAS score : P = 0.0003 at 4 weeks , P < 0.0001 at 8 weeks ; tactile threshold : P = 0.0138 at 4 weeks , P < 0.0001 at 8 weeks ) .