Spring 2005

Scientific Article

An In Vitro Assessment of Iodoform Gutta Percha
Submitted by Kirk Huffaker, 3rd year student member of Case Western Reserve University

The purpose of this experiment was to
test the ability of a commercially available iodoform gutta percha, to resist infiltration of E. faecalis using a microleakage model.

Seventy extracted single-rooted teeth were sectioned to a canal length of 12 mm. The canals were prepared and autoc/aved. Thirty roots were obturated laterally with iodoform gutta percha and another thirty with regular gutta percha. The roots were then painted, except for the apical 2mm, to seal any accessory canals and then suspended in sterile BHI broth. An innoculum of E. faecalis suspension was placed at the coronal end of each root, incubated and replenished daily. The apical broth was observed for turbidity, indicating bacterial microleakage.

Samples were observed for thirty-two days and data was analyzed to compare microleakage between the two groups. The results showed no significant difference between the iodoform and regular gutta percha samples (p>.05).

This experiment showed that the iodoform gutta percha did not delay microleakage of E. faecalis any better than regular gutta percha.

In 1993, Smith et al. conducted a study of 823 teeth that had received root canal
therapy and found that there was an 84.3% success rate, meaning that more than 15% of the cases treated required treatment I Since that time there have been other studies that have produced similar findings. 2,3 The sobering fact is that endodontic therapy fails 10-20% of the time.

Root Canal Therapy (RCT) fails when bacteria recolonize inside of the obturated canal. Eventually, these colonies travel to the apex where they produce canal breakdown and inflammation with its resulting sequela. Studies have demonstrated the significance of the gram positive, facultative anaerobe Enterococcus faecalis, in endodontic therapy failure.4.5.6

With RCT failing 10-20% of the time and the cause of failure being reinfection of the canal, the question arises, would obturating the canal with a material that inhibits bacterial growth improve the success rate of endodontic therapy?

Since the early 1900's, the material of choice for endodontic obturation has been Gutta Percha. By itself, Gutta Percha has shown to exhibit some antimicrobial activity due to its Zinc content. Recently, Medicated Gutta Percha (MGP) containing iodoform (triiodomethane) have arrived on the market suggesting that it has an increased antimicrobial activity7 and may have a place in mainstream endodontic therapy.

The purpose of this study was to compare the abilities of MGP and standard gutta percha points in resisting infiltration of E. faecalis using a microleakage model.

Materials and Methods

Seventy extracted, single-rooted teeth were decoronated, leaving 12 mm of apical root. Roots were then observed under the surgical microscope to obtain actual working lengths within 0.5 mm. The canals were prepared to an apical size of 40 using .06 taper Profiles. After autoclaving, thirty roots were obturated laterally with iodoform gutta percha and another thirty with regular gutta percha.

The remaining ten roots were used for positive and negative controls. Penrose tubing was attached to the cervical 5 mm of the roots and then bonded with cyanoacrylate to the root surface. Orthodontic wire was then twisted tightly around the bonded penrose tubing so as to not allow apical movement of any bacteria except through the root canal itself. The roots were then painted with fingernail polish, except for the apical 2 mm, to seal off any accessory canals. The apical 2 mm of the samples was to be suspended in Gill broth inside of 2 mm vials. To accomplish this, holes of the same diameter as the penrose tubing were drilled into the caps of the vials. The tubing was then pulled through the hole and the area immediately surrounding the tubing was sealed off with cyanoacrylate. A sterile cotton point was inoculated with a suspensio E. faecalis and placed at the coronal end of each root inside of the penrose tubing. The samples were then incubated and replenished with a new innoculum daily. The apical broth was observed for turbidity, indicating bacterial microleakage.

Results

Samples were observed for thirty days and data was analyzed using a proportionality z-test to compare microleakage between the two groups. The results showed no significant difference between the iodoform and regular gutta percha samples (p>.05). It took an average of 16.8 days for the E. faecalis to travel the length of the root samples containing regular gutta percha and 19.8 days for the samples containing medicated gutta percha. Results of a two sample t-test showed that the three day difference in results was not significant (p>.05) due to a large standard error. Seventy days after initial inoculation and incubation there was still no significant difference between the two groups of root samples.

Discussion

Antimicrobial chemicals such as iodoform have been added to gutta percha points with the intent that it will retard the growth of bacteria inside the obturated root canal, above that which the non-medicated gutta percha can do. Martin 7 in his 1999 article, promoted the use of gutta percha points containing iodoform as an inhibitor of obligate and facultative anaerobic bacteria. Our results did not show that its inhibitor of obligate and facultative anaerobic bacteria. Our results did not show that its inhibitory characteristics are superior to non-medicated gutta percha. These results were supported by the Shur 8 study which also failed to show that iodoform containing gutta percha points had a greater inhibitory effect on bacterial growth.

One possible explanation for this is found in the patent for the Medicated Gutta Percha point which says that iodoform is leached from the gutta percha in the presence of saliva. 9 The infected root canals in this study were never exposed to saliva, possibly allowing the iodoform to not properly leach out of the gutta percha point.

The species of bacteria used to infect the canals may have also influenced our results.

Silver, 10 showed that MGP had no inhibitory effect on E. faecalis but it did inhibit the growth of S. sanguis. This could explain the lack of bacterial inhibition by MGP in the current results, since the canals in our study were inoculated with E. faecalis.

In other studies 11, 12 the average time for observed turbidity (apical microleakage) of root samples was comparable with the current results.

In conclusion, this experiment showed that the iodoform containing gutta percha did not delay micro leakage of E. faecalis any better than regular gutta percha. According to these results, iodoform gutta percha may not present any advantage over regula~ gutta percha in delaying micro leakage in vitro. In vivo studies, however, are needed to substantiate this claim.

References

1. Smith CS, Setcchell DJ, Harty FJ Factors influencing the success of conventional root canal therapy - a five-year retrospective study. International Endodontic Journal 1993 Nov; 26(6): 321-33.

2. Kojima K. Inamoto K, Nagamatsu K, Hara A, Morita I, Nagasaki H, Nakamura H. Success rate of endodontic treatment of teeth with vital and nonvital pulps. A meta-analysis. Oral Surg Oral Med Oral Pathol Oral Radio Endodo. 2004 Jan; 97(1): 95-9.

3. Field JW, Gutman HL, Solomon ES, Rakusin H. A clinical radiographic retrospective assessment of the success rate of single-visit root canal treatment. International Endodontic Journal 2004 Jan; 37(1): 70-82.

4. Sundqvist G, Figdor D, Persson S, Sjogren U. Microbiologic analysis of teeth with failed endodontic treatment and the outcome of conservative retreatment. Oral Surg Oral Med Oral Pathol Oral Radio Endodo. 1998 Jan; 85(1): 86-93.

5. Siquiera JF Jr, Rocas IN. Polymerase chain reaction-based analysis of microorganisms associated with failed endodontic treatment. Oral Surg Oral Med Oral Pathol Oral Radio Endodo. 2004 Jan; 97(1): 85-94.

6. Pinhiero ET, Gomes BP, Ferraz CC, Teixeira FB, Zaia AA, Souza FJ. Microorganisms from canals of
root-filled teeth with periapical lesions. International Endodontic Journal 2003 Jan; 36(1): 1-11.

7. Martin H, Martin TR. Iodoform gutta-percha: MGP, a new endodontic paradigm. Dentistry Today
1999; 18(4).

8. Shur A, Sedgley C, Fenno J. The antimicrobial efficacy of 'MGP' gutta-percha. International
Endodontic Journal 1. Sep 2003; 36(9), 616.

9. Martin H. AntibioticlMedicated gutta percha point. Patent #6,602,516: 11 Nov 1999.

10. Silver GK, Taylor TL, SimonJHS. Antimicrobial effect of iodoform gutta-percha cones on Streptococcus sanguis and Enterococcus faecalis. New Zealand Endodontic Journal. 2000; 26, 1-3.

11. Torabinejad M, Ung B, Kettering JD. JOE> 1990; 16:566.

12. Gulabivala K. Sayed AA, Wilson M. The effect of retrograde cavity design on micro leakage of amalgam fillings. Int Endodo J 1995 Jul; 28(4):204-12.

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