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Dr. Fleur A. Blethen

Dr. Fleur A. Blethen

Empathy, tenacity, and perseverance are keys to this clinician’s flourishing practice  What can you tell us about your background? I was born and raised in Seattle, Washington, and lived there until I was 13 years old. My family relocated...

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Dr. Ernest Reeh, Practice Profile

Dr. Ernest Reeh, Practice Profile

Focus on patients, family, academics, and endodontics What can you tell us about your background? I have a bachelor’s degree in chemistry with a minor in business. I was accepted off of the alternate list for dental school and then attained...

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Practice Profile - Dr. Anthony Horalek

Practice Profile - Dr. Anthony Horalek

Practice Profile | Dr. Anthony Horalek: The art and science of endodontics.

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Clinical Articles

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GuttaCore® system: a step forward in the evolution of endodontics

GuttaCore® system: a step forward in the evolution of endodontics

Dr. Andrei Zoryan dispels some of the common myths surrounding carrier-based obturation Carrier-based gutta percha Carrier-based obturation (such as Thermafil®, GT® obturator, ProTaper® obturator [Dentsply Tulsa Dental Specialties]) is one...

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Endodontic retreatment of a lower right first molar with WaveOne®

Endodontic retreatment of a lower right first molar with WaveOne®

Dr. David C. Baker uses a technique that facilitates quick and predictable results Patient history The patient is a 34-year-old female who was referred by a local colleague. She had broken her lower right first molar and complained of some general...

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The Laschal FXP set incorporates transferred oscillation technology

Background There are other ultrasonic devices on the market that depend upon direct contact with a separated file to loosen and remove. However, it is absolutely impossible to restrict the contact of the tip to the file remnant itself. The vibrations...

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Practice Management

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Superior customer service

Superior customer service

Dr. Roger Levin presents the 10 top ways to help create a perfect dental team With the changes brought on by the economy, top companies are bringing in the best resources they can find to evaluate where their organizations stand. They want to know...

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Office Matters: Hard-piped filtered water system vs. self-contained bottled water system

John Bednar helps avert problems coming down the pipe If your office currently has a hard-piped filtered water system, now is a good time to consider if and when you should change to a self-contained bottled water system. A hard-piped filtered water...

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Secrets to financial and personal freedom for endodontists

Secrets to financial and personal freedom for endodontists

In part 1 of his series, Dr. Ace Goerig offers the first steps to becoming debt-free I was presenting at a recent AAE national meeting with over 200 endodontists in the room, and I asked the question, “How many of you are completely debt-free?” ...

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kleinman_front

In vitro comparison of the push-out bond strength of three endodontic sealers with and without amoxicillin

Drs. Brian S. Kleinman and David W. Berzins report the results of their recent study

Abstract
The purpose of this in vitro study was to compare the push-out bond strengths of three endodontic sealers with and without amoxicillin. Methods: Thirty single-rooted extracted human teeth were used for this study. Each tooth was instrumented and irrigated with 5.25% NaOCl and 17% EDTA. The teeth were then divided into six test groups. Group 1-gutta percha (GP)/AH Plus®(Dentsply Maillefer); group 1A-GP/AH Plus® with 10% by weight amoxicillin; group 2-GP/Pulp Canal SealerTM EWT (Extended Working Time; SybronEndo); group 2A-GP/Pulp Canal SealerTM EWT with amoxicillin; group 3-Resilon®/RealSealTM SE (self-etch) (SybronEndo); and group 3A-Resilon®/RealSealTM SE with amoxicillin. After the sealer was set, the entire root was sectioned into 1-mm thick slices. A push-out bond strength test was performed using a universal testing machine. The Mann Whiney and Student’s t-test were used to compare the sealer bond strength within the specific sealer test groups overall and within each sealer at apical, middle, and coronal root levels. Results: There was no significant difference between test groups within each sealer, Group 1 vs. Group 1A (p=.85), Group 2 vs. Group 2A (p=.59) or Group 3 vs. Group 3A (p=.52). There was no significant difference (p > .05) in push-out bond strength within each sealer with or without amoxicillin at the same root level. Conclusion: The addition of 10% by weight of amoxicillin does not significantly (p > .05) change the overall push-out bond strength of GP/AH Plus®, GP/Pulp Canal Sealer EWTTM, and Resilon®/RealSealTM SE or when compared at the apical, middle, and coronal tooth level.

Introduction
The primary objective of nonsurgical endodontic therapy is the thorough chemomechanical cleaning and shaping of the canal system followed by complete three-dimensional obturation.1 Non-healing endodontic lesions are caused by the persistence of bacteria and bacterial byproducts in the root canal system.2,3 Bacteria may be present from the incomplete cleaning and shaping of the system or due to leakage from the oral cavity. Three-dimensional obturation of the radicular space is essential to long-term success.4 This prevents both the leakage of bacteria and their byproducts into the periapical tissues and entombs any bacteria and byproducts not removed during cleaning and shaping of the canal system. Traditionally, obturation has been accomplished with the use of an endodontic sealer and gutta percha. More recently, resin-based sealers and resin-based obturation materials have been introduced as an alternative for endodontic obturation.5,6 Regardless of the obturation system used, failures do occur due to bacteria remaining in the root canal system.7 One recently introduced strategy to address the bacterial etiology of endodontic failure is the use of endodontic sealers with an added antibiotic.8,9
An ideal endodontic sealer would exhibit antimicrobial properties.10 Baer et al9 showed that the addition of amoxicillin to endodontic sealers is effective in eradicating E. faecalis for at least 7 days after mixing. The addition of amoxicillin to endodontic sealers could change their ability to seal the canal system. One model used to determine the sealing ability of an endodontic sealer is to test the micro push-out bond strength.11-14
The purpose of this in vitro study was to compare the push-out bond strengths of three endodontic sealers with and without embedded amoxicillin. The null hypothesis tested was that there is no significant difference in the push-out bond strength within specific sealers with and without amoxicillin overall, or when compared at the same tooth level (apical, middle, coronal). The alternative hypothesis is that the addition of amoxicillin will decrease the push-out bond strength of the tested sealers.

fig2_kleinmanMaterials and methods
Thirty single-rooted extracted human teeth were used in this study. All teeth were initially disinfected by immersion in 5.25% sodium hypochlorite for 6 hours followed by storage in sterile saline. Each tooth was decoronated, and working length (WL) was established by passing a 15 K-file (Dentsply Maillefer) to the apex as observed under 4.8× magnification and subtracting 1 mm. The canals were instrumented using RaCe™ 35 (.08) and 40 (.10) (Brasseler USA) in the coronal and middle thirds and EndoSequence® nickel-titanium rotary instruments (Brasseler USA) in the apical third. The canals were instrumented to a final apical size of 40 (.06) using no less than 6 mL of 5.25% sodium hypochlorite to irrigate. A final rinse of 6 mL of 17% EDTA over a 1-minute time period was accomplished. The canal was then dried with paper points, and the teeth were randomly assigned to one of the six obturation groups:

  • Group 1: gutta-percha and AH Plus® (AHP).
  • Group 1A: gutta-percha and AH Plus® with the addition of amoxicillin
  • Group 2: gutta percha and Pulp Canal SealerTM EWT
  • Group 2A: gutta percha and Pulp Canal SealerTM EWT with the addition of amoxicillin
  • Group 3: Resilon® and RealSeal® SE (RS) sealer
  • Group 3A: Resilon® and RealSeal® SE with the addition of amoxicillin.

Each obturation group consisted of five roots obturated using the specified gutta-percha or Resilon® and sealer combination, using a warm vertical-compaction technique. Each plain sealer was mixed and used according to the manufacturer’s instructions. The sealers with amoxicillin were mixed initially according to manufacturer’s instructions followed by the addition of 10% by weight of crushed amoxicillin (TEVA Pharmaceuticals) as described by Baer.9 The coronal aspect of each root was sealed with 1 mm of Fuji IXTM glass ionomer (GC Corporation).
The obturated roots were stored at 37°C in 100% humidity for 14 days to allow for the sealer to set. The roots were then sectioned perpendicular to the long axis into 1-mm thick slices by using an IsoMet® saw (Buehler Ltd.) with water lubrication. Slices from all six groups were collected from the apical, middle, and coronal thirds. Slices containing filling material of a noncircular shape were discarded to avoid non-uniform stress distribution during testing and inaccurate measurements. The thickness of each disk, at the filling material dentin interface, was determined using a digital caliper to the nearest 0.01 mm. The diameter of the filling material within each disk was determined using a digital caliper under 4.8× magnification. One of five plungers that most closely matched the diameter of the filling material without contacting dentin was connected to a universal testing machine (Instron Corporation). A vertical load was applied to the obturation material in an apical to coronal direction at the rate of 0.5 mm/min (Figure 1).  Failure of bond was determined when a sharp decline was observed on a load versus time curve plotted in real time. The bond strength, expressed in MPa, was calculated by dividing the maximum load in Newtons by the area of the bonded interface. The area of the bonded interface was calculated using the formula, area = 2π r * h, where π is the constant 3.14, and r and h are the measured radius and height in millimeters of the filling material.
The Mann Whiney test was used to determine if there was an overall difference in bond strength between matched obturation groups (Group 1 and 1A, Group 2 and 2A, and Group 3 and 3A) with and without amoxicillin, regardless of tooth level. Analysis was also completed to compare matched obturation groups with and without amoxicillin at the apical, middle, and coronal levels of the root using either the independent samples, t-test, or the Mann-Whitney test (for non-normally distributed fig1samples).

Results
Five teeth were prepared for each test group. Nine slices were obtained from each tooth. The mean push-out bond strengths of each group were: Group 1, 4.66±3.22 MPa; Group 1A, 4.34±2.50 MPa; Group 2, 2.13±2.01 MPa; Group 2A, 2.00±2.03 MPa; Group 3, 2.49±2.25 MPa; and, Group 3A, 2.18±2.08 MPa. There was no significant difference between test groups within each sealer: Group 1 vs. Group 1A (p=.85), Group 2 vs. Group 2A (p=.59), or Group 3 vs. Group 3A (p=.52). There was no significant difference (p > .05) in push-out bond strength within each sealer with or without amoxicillin at the same root level (Figure 2).

Discussion
Antibiotics are commonly used systemically in endodontics.15 The local application of antibiotics to the root canal system and periapical tissues may be a more effective method of delivery.16 Two recent studies8,9 have expounded on the concept of endodontic sealers for local antibiotic delivery. Baer et al9 showed that endodontic sealers with added amoxicillin not only demonstrated inhibition of bacterial cell growth initially, but also demonstrated inhibition after 7 days of sealer set. However, the addition of amoxicillin may change the properties of the endodontic sealers. A pilot study was conducted to compare film thickness, dimensional change, and solubility of AHP, EWT, and RS with and without amoxicillin according to ISO standards. The results of this pilot study suggested further testing of sealers with added amoxicillin should be conducted to more closely mimic the clinical environment.
The push-out bond strength test is one way to evaluate the effectiveness of an endodontic obturation material or technique. Other methods of testing include bacterial leakage, fluid filtration, and dye penetration testing.17 While each method of in vitro testing seeks to replicate the clinical environment, the correlation between leakage studies and clinical success has been questioned.17-21 The push-out model has been used extensively to evaluate the dentin obturation interface, but its relevance has also been called into question.22 There is no evidence that any of these testing methods is the best for measuring the clinical effectiveness of an endodontic obturation material or technique.
The results of this study are in agreement with the results of many other studies comparing the bond strength of gutta percha and Resilon® to dentin using different sealers.11-14 Generally, these studies have shown gutta percha and AHP to have higher bond strengths than Resilon® and gutta percha EWT obturation systems. The current study made no attempt to compare push-out bond strengths between different sealers with amoxicillin. The well-established differences in the bond strengths between plain sealers11-14 suggest any differences in push-out bond strength found between different sealers with added amoxicillin would be due to the inherent differences in the plain sealers’ push-out bond strength.
The present study demonstrated that the highest mean bond strengths were found at the apical segment of each test group. This could be due to pooling of sealer at the apical segment as evident by the extrusion of sealer through the apex during obturation.  Each tooth was prepared so tug-back was felt when placing the master cone. This demonstrates a tight fit that could influence push-out bond strength.   
The apical segments exhibited the highest standard deviation. This may be due to the small diameter of the obturation material found near the apex. Attempts were made to match the diameter of the plunger used in the push-out testing to the diameter of the filling material to eliminate the plunger touching the wall of the canal. All the slices were examined under 4.8× magnification after push-out. If evidence was found that the canal wall was touched, the sample was discarded. It is possible that errors in sample elimination occurred. The middle and coronal slices were more easily aligned with the push-out plungers, minimizing the need to discard slices. The overall standard deviations in this study ranged from 57% to 101% of the mean push-out bond strength. This is comparable to other push-out studies11-14 that demonstrate standard deviations that range from 31%-127% of the mean push-out bond strength.
This study represents a step in the process of evaluating the effectiveness of endodontic sealers as a vehicle for the local delivery of antibiotics. While this study demonstrates the push-out bond strength is not significantly (p > 0.05) decreased by adding amoxicillin, further clinical testing should be completed to explore the clinical effectiveness of sealers with added amoxicillin.

Conclusion
In conclusion, this study demonstrated that the addition of 10% by weight of amoxicillin does not significantly (p > .05) change the overall push-out bond strength of GP/AHP, GP/EWT, and Resilon®/RS, or when compared at the apical, middle, and coronal tooth level. Therefore the null hypothesis is accepted, and the alternative hypothesis is rejected.

Acknowledgement
The authors would like to thank Jessica Pruszynski, PhD, from the Medical College of Wisconsin, for statistical analyses.

 

Dr. Kleinman is in private practice at Northern Arizona Endodontics in Prescott, Arizona. He completed course work for his Bachelors of Science degree at Yavapai College and Arizona State University, and his dental training at the University of Colorado School of Dental Medicine in 2009. He received his Certificate in Endodontics and Masters of Science from the Marquette University School of Dental Medicine in May 2011. Dr. Kleinman has presented dental materials research at AADR and AAE meetings in 2009 and 2011. He is a member of the American Dental Association and the American Association of Endodontists.

David Berzins, PhD, BS, is an Associate Professor and the Graduate Program Director for Dental Biomaterials at the Marquette University School of Dentistry. He graduated with a BS in Materials Science & Engineering from Case Western Reserve University and a PhD in Biomedical Engineering from Tulane University. He is a member of the Academy of Dental Materials, as well as the American and International Associations for Dental Research (AADR/IADR).

 

References

1. Schilder H (1967) Filling root canals in three dimensions. Dent Clin North Am 1:723-744.

2. Kakehashi S, Stanley HR, Fitzgerald RJ (1965) The effects of surgical exposures of dental pulps in germ-free and conventional laboratory rats. Oral Surg Oral Med Oral Path 20:340-349.

3. Lin LM, Skribner JE, Gaengler P (1992) Factors associated with endodontic treatment failures. J Endod 18:625-627.

4. Cohen S, Heargraves KM (2006) Pathways of the Pulp, 9th edition. Mosby: St Louis, MO.

5. Teixeira FB, Trope M (2004) Gutta-percha: the end of an era? Alpha Omegan 97:16-22.

6. Teixeira FB, Teixeira ECN, Thompson J, et al (2004) Dentinal bonding reaches the root canal system. J Esthet Restor Dent 16:348-354.

7. Siqueira JF Jr (2001) Aetiology of root canal treatment failure and why well-treated teeth can fail. Int Endod J 34:1-10.

8. Hoelscher AA, Bahcall JK, Maki J (2006) In vitro evaluation of antimicrobial effects of a root canal sealer-antibiotic combination against enterococcus faecalis. J Endod 32:145-147.

9. Baer J, Maki JS (2010) In vitro evaluation of the antimicrobial effect of three endodontic sealers mixed with amoxicillin. J Endod 36:1170-1173.

10. Grossman L (1988) Endodontic practice, 11th edition. Lea & Febiger: Philadelphia, PA.

11. Skidmore LJ, Berzins DW, Bahcall JK (2006) An in vitro comparison of the intraradicular dentin bond strength of resilon and gutta-percha. J Endod 32:963-966.

12. Sly MM, Moore BK, Platt JA, et al (2007) Push-out bond strength of a new endodontic obturation system (Resilon/Epiphany). J Endod 33:160–162.

13. Fisher MA, Berzins DW, Bahcall JK (2007) An in vitro comparison of bond strength of various obturation materials to root canal dentin using a push-out test design. J Endod 33:856-858.

14. Stiegemeier D, Baumgartner JC, Ferracane J (2010) Comparison of push-out bond strengths of resilon with three different sealers. J Endod 36:318-321.

15. Yingling NM, Byrne BE, Hartwell GR (2002) Antibiotic use by members of the American Association of Endodontists in the year 2000: report of a national survey. J Endod 28:396-404.

16. Mohammadi A, Abbott PV (2009) On the local applications of antibiotics and antibiotic based agents in endodontics and dental traumatology. Int Endod J 42:555-567.

17. Wu MK, Wesselink PR (1993) Endodontic leakage studies reconsidered. Part 1. Methodology, application and relevance. Int Endod J 26:37-43.

18. Schuurs AH, Wu MK, Wesselink PR, et al (1993) Endodontic leakage studies reconsidered. Part II. Statistical aspects. Int Endod J 24:44-52.

19. Wu MK, DeGee AJ, Wesselnk PR, et al (1993) Fluid transport and bacterial penetration along root canal fillings. Int Endod J 26:203-208.

20. Oliver CM, Abbott PV (2001) Correlation between clinical success and apical dye penetration. Int Endod J 34:637-644.

21. Susini G, Pommel L, About I, et al (2006) Lack of correlation between ex vivo apical dye penetration and presence of apical radiolucencies. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 102:el9-e23.

22. Sudsangiam S, Van Noort R (1999) Do dentin bond strength tests serve a useful purpose? J Adhes Dent 1:57-67.

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There remains a growing belief among clinicians that obturation is to blame for endodontic failures. This notion has more recently fallen under scrutiny as researchers have discovered that the most thorough obturation can only reflect the quality of the cleaning and shaping of the canal. In fact, a number of researchers point to the thorough use of irrigants — making sure that the debris and irrigant itself are lifted completely out of the canal, not forced out the apex — as the most important determinant in the long-term success of an endodontic procedure.

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