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Week of September 18, 2002

 

 


Title:   In situ antimicrobial effectiveness of chlorhexidine and calcium hydroxide: gel and paste versus Gutta percha points.

Author: Barthel C.R. et al

  Journal: JOE, Vol 28, (6), June 2002

Reviewed by: Pranav Vohra, D.M.D.

Purpose:  To determine the antimicrobial effectiveness of either calcium hydroxide ( Ca(OH)2)paste, Ca(OH)2 containing GP points, chlorhexidine (CHX) gel or CHX paste without any other chemo-mechanical debridement.

Materials &Methods: 

  • 75 single rooted teeth with crowns cut at CEJ and PDL removed were instrumented to size 60, 1.0 mm from apex. Smear layer was removed with 15% EDTA using an ultrasonic handpiece for 20secs.
  • Teeth were sterilized , accessed and placed in the oral cavity of volunteers for 1 week.
  • At one-week paper point samples were taken and bacterial sampling performed.
  • Then the antimicrobial agents were placed in the teeth and after sealing the access with resin, they were incubated in 1ml saline for 1 week.
  • The teeth were divided into six groups: 
    1) CHX
    2) Ca(OH)2 mixed with saline
    3) CHX containing GP
    4) Ca(OH)2 containing GP
    5) Positive control with thioglycolate broth
    6) Tooth with sealed access serving as negative control.
  • After a week, the Ca(OH)2 was neutralized with citric acid and CHX with a specific solution.
  • The teeth were then sealed with a paper point containing thioglycolate broth to check for recolonization.
  • Statistical analysis of the results was performed.

Results: 

  • Negative control showed no bacterial growth.
  • Samples with the CHX gel and Ca(OH)2 paste showed fewer bacteria than the CHX-GP and Ca(OH)2 -GP groups.
  • After neutralizing the antimicrobial agents, re-growth of bacteria in some samples was seen.

Discussion: The paste form of Ca(OH)2 and CHX gel showed better antimicrobial action than either one placed in conjunction with GP.

 

 

 


Title:  Apical leakage of five root canal sealers after one year of storage

Author:  Miletic, I., Ribaric, S., Karlovic, Z., et al

Journal:  JOE 28(6)431-432

Reviewed by:  M. Pallante, D.M.D.

Purpose:  To compare the sealing quality of five root canal sealers after the specimens were stored in saline for one year.

Materials and Methods:

            Tested sealers were: AH26, AHplus, Diaket, Apexit, Ketac-Endo

  • Canals from 60 human teeth were enlarged with a gates glidden and flared using a step-back technique.
  • 10 specimens were used with each sealer. 
  • Smear Layer was removed. 
  • Lateral condensation was used with gutta percha and the corresponding sealer. 
  • Sealing ability was measured by the movement of an air bubble under pressure.
  • A measurement was performed 2 weeks after sealing and then specimens were stored in saline for one year. 

Results:   Apexit showed significantly more leakage than AHplus and KetacEndo.  AH26 and Diaket leakage was not significantly different than AHplus and KetacEndo.

Discussion:   This study claims that the fluid transport model used in the leakage study is superior to other methods such as dye leakage because it is more sensitive in detecting voids and it is more reproducible.  Also, the samples are not destroyed.  Authors stress the point that microleakage studies must be repeated after long periods of time because the relative differences between the materials change over time which has a clinical relevance.

 

 

 


Title:  Cyclic fatigue of endodontic nickel titanium rotary instruments:  static and dynamic tests

Author:  Li, Uei-Ming

Journal:  JOE, vol. 28(6):448, June 2002

Reviewer:  Alison Morrison, D.M.D.

Purpose: The purpose of this investigation was to evaluate the cyclic fatigue of 0.04 ProFile nickel titanium (NiTi) rotary instruments operating at different rational speeds and varied distances of pecking motion in metal blocks that simulate curved canals.

Materials and Methods: 150 size 25 0.04 taper Profile NiTi rotary files were introduced into metal blocks with variable slope at 200, 300, 400 rpm using a contra-angle hand piece and an Instron motor.   The curvature of a rotary instrument was produced when worked against a sloped metal block.   The hand piece and motor were activated until the instruments were broken in two different modes, static (constant pressure) and dynamic pecking (cyclical pressure) motion.  The time to fracture was measured in seconds and the files were examined using SEM.

Results:  The time required to fracture an instrument decreased as the angle of curvature or RPM increased.  When the pecking distance increased the time to failure also increased.  These results showed that a pecking motion may be a crucial factor in preventing the breakage of NiTi rotary instruments.

Conclusion:   To prevent breakage of a NiTi file, appropriate rotational speeds and a continuous pecking motion in the root canals are recommended.

 

 

 

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