Statement of the Problem: to compare the efficacy of photodynamic therapy (PDT) compared to widely accepted smear layer removal protocol is not well established.
Purpose: To evaluate the effect of PDT on smear layer removal from human root canal compared to combined use of irrigation solutions (sodium hypochlorite (NaOCl) and ethylene diamine tetra acetic acid (EDTA)) by scanning electron microscopy (SEM).
Materials and Method: Straight roots from 48 extracted human maxillary incisors and canines were selected and decoronated. Instrumentation was completed with RaCe rotary system and normal saline irrigation between files. Then roots were randomly divided into 3 groups (n=16). Group 1 was the control group to confirm smear layer formation. In group 2 the canals were irrigated with 2ml of 2.5% NaOCl solution for 10 minutes and 2ml of 17% EDTA solution for 1 minute. In group 3 PDT with methylene blue and diode laser (625nm, 150 mW, for 5 minutes) was the final procedure for smear layer removal. All the specimens were sectioned into two halves, gold coated and analyzed under SEM. The smear layer in the coronal, middle and apical thirds, were evaluated and scored by two examiners independently. Statistical analysis was done using Chi-square test.
Results: It was observed that the NaOCl+EDTA removed the smear layer significantly better than PDT in the coronal and apical thirds (P <0.05) whereas PDT was unable to remove the smear layer in none of the root areas. At the apical thirds, there was no significant difference between NaOCl+EDTA and PDT (P <0.05). Both procedures were unable to remove smear layer from radicular dentine of this area.
Conclusion: According to the results of this in-vitro study, the use of PDT alone is not recommended to remove smear layer. Combined application of NaOCl and EDTA, is ineffective in removing smear layer of apical third, despite efficacy in the coronal and middle regions.