Previous studies have established that root sensitivity is due in part to open dentinal tubules at the root surface. The purpose of this study was to longitudinally evaluate the occlusion of dentinal tubules by various clinical procedures including scaling and root planing and the application of potassium oxalate. A model was developed to evaluate dentinal surfaces in vivo. Six 2 mm x 3 mm sections were taken from the roots of extracted teeth immediately below the CEJ. One half of the treated dentin samples from each donor was incorporated into the removable denture worn by the donor and the other half served as baseline. The dentin samples were evaluated at 1 week by scanning electron microscopy. At day zero no open tubules were observed in any of the samples due to the presence of a smear layer or oxalate crystals. Evaluation of root planed samples revealed that by 7 days the tubules had re-opened. The samples which had been treated with potassium oxalate showed few oxalate crystals by 7 days revealing open tubules. Control samples were etched with EDTA and evaluated in the same manner. Although the number of tubules did not significantly change in the EDTA etched control samples, the diameter of the tubules dramatically decreased by 4 weeks. It can be concluded that the creation of a smear layer or application of oxalates to occlude dentinal tubules to reduce sensitivity are relatively short-lived. These procedures may provide patient comfort prior to natural occlusion of the tubules.