Smear Layer Morphology of Instrumented Root Surface after Exposure to Demineralizing Solution

Aims: The present study evaluates the modification of smear layer produced on root surface by instrumentation with curette, bur and ultrasonic handpiece after storing in demineralising cariogenous solution. Methods: 18 Extracted human incisors were cleaned and divided into two groups: 1) instrumented (20 strokes) with a curette 7/8 (Hu-Friedy, USA) (n=6) 2) instrumented with ultrasonic handpiece (Castellini) (n=6) 3) burred with a diamond bur(Intensiv, USA) (n=6). Half of the specimen of the three groups were selected randomly and stored in demineralising cariogenic solution (pH= 4.5) for 3 days. The remaining samples were used as control. All samples were fixed in 4% glutaraldeyde in 0.2 M sodium-cacodylate buffer, dehydrated in graded alcohol, air dried, gold sputtered and observed with SEM (Jeol, 5200, Japan). Results: Group 1) control samples showed the presence of a multilayered smear layer. Smear layer was completely dissolved and collagen fibers were exposed after demineralization. The root surface of control samples of group 2) was free from smear layer with exposed collagen fibers. Collagen fibers were collapsed after demineralization. In group 3) control samples a thick smear layer was detected with presence of grooves and streaking produced by the action of the bur. After demineralization smear layer was partially dissolved with exposed dentinal tubules in limited areas. Conclusions: Root smear layer produced by conventional root planing may be easily removed by a short time storage in demineralising solution. Ultrasonic instrumentation dissolved smear layer and exposed fibers. Bur instrumentation could produce modification of the ultrastructural morphology of root surface. Exposed dentin could be affected by the demineralising effect of low pH.