Ultrasonic Root-End Preparation Part 1: SEM Analysis

By Gutmann JL, Saunders WP, Nguyen L, Guo IY, Saunders EM.

Date: 01/1994
Journal: IEJ


Determine the degree of superficial debris and smear layer present on the dentinal walls of root-end cavity preparations, using three techniques.


  • N= 60 extracted premolars
  • Teeth were accessed, instrumented, and obturated with gutta percha. Root ends were resected at a 45 degree angle.
  • Teeth were separated into 3 groups.
  • Group 1: Retroprep with 010 round bur.
  • Group 2: Preparation same as group 1 with 10% citric acid and 3% ferric chloride rinse.
  • Group 3: Retroprep with Ultrasonic. All teeth were sectioned longitudinally and evaluated w/ SEM.


  • Greater amounts of superficial debris were present in both bur preparations compared to ultrasonics.
  • The least amount of smear layer on a specimen was observed in the bur group with citric acid treatment.
  • No technique effectively removed the smear layer from the coronal third of the prep.

Clinical Significance:

Root end preparation with ultrasonics produced less debris overall. Treatment with citric acid prior to retrograde fill may remove the smear layer and may allow for improved adaptation of restorative material.