Master apical file size – smaller or larger: a systematic review of healing outcomes

© Ramaiah University of Applied Sciences
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Faculty of Dental Sciences
Master apical file size – smaller or
larger: a systematic review of healing
outcomes
Aminoshariae A, Kulild JC , International endodontic
journal. 2015 Jul;48(7):639-47.

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Introduction
Byström & Sundqvist (1981) - cultured 15 teeth with necrotic pulps after instrumentation
accompanied with saline irrigation, a 100- to 1000-fold reduction in the bacterial counts,
yet no teeth cultured bacteria-free after the first appointment
To eliminate microorganisms and pathologic debris from the root canal system (Kakehashi et al.
1969) and to prevent its reinfection (Nair 2004)
Gutierrez & Garcia (1968) - Root canal systems are often improperly cleaned and shaped

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Chemomechanical preparation with supplemental irrigation devices promotes higher
microbial reduction but is not able to render the canals bacteria-free
(Dalton et al. 1998, Shuping et al. 2000, Sum et al. 2005, Alves et al. 2011, Paiva et al. 2012, Saini et al. 2013)
In a quest for the optimal methodology to eliminate contaminants from the root canal
system, size of apical preparation may be important in achieving that outcome
(Ørstavik et al. 1991, Parris et al. 1994, Wu & Wesselink 1995, Shuping et al. 2000, Card et al. 2002, Rollison et al. 2002,
Saini et al. 2012)
It is unclear, where the binding occurred and, if in fact, it reflected the true pre instrumented apical diameter
of the root canal system
(Wu et al. 2002, Jou et al. 2004, Dillon & Amita 2012)

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• Baugh & Wallace 2005 - A thorough search of the literature failed to show what an optimal apical
preparation diameter might be and it still remains a subject of uncertainty’
• Ørstavik et al. 1991, McGurkin-Smith et al. 2005, Siqueira et al. 2008 - Creating a “larger” apical
preparation followed by a one-week dressing of calcium hydroxide
• Ram 1977, Salzgeber & Brilliant 1977, Chow 1983, Shuping et al. 2000, Card et al. 2002, Rollison et al.
2002, Usman et al. 2004, Bierenkrant et al. 2008, Siqueira et al. 2008 - Enlarging the canal terminus to a
predetermined size beyond 35 or 40
• Tan & Messer 2002, Darda et al. 2009, Saini et al. 2012, Souza et al. 2012 - Enlarging the canal three
sizes larger than the first apical binding file would be adequate
• Wu et al. (2002)- the first file to bind in the apical root canal system did not necessarily reflect the true
apical diameter at the proposed working length, because the apical anatomy is often irregularly shaped
and not a round configuration

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• Wu et al. 2002 –Three sizes larger than the first binding file does not ensure removal of the inner layer of dentine
from all apical root canal walls or all infected necrotic pulp tissue
• Albrecht et al. 2004 - Taper is more important in instrumentation than the final apical size of the canal
• Siqueira et al. 1999 - Both taper and diameter are equally important in chemo-mechanical instrumentation of the
root canal system
• Parris et al. 1994, Yared & Dagher 1994, Card et al. 2002, McGurkin-Smith et al. 2005, Saini et al. 2012, Souza et al.
2012 - Clinical outcome of various master apical sizes, and despite conflicting claims, the ideal apical size remains a
mystery in any individual root canal systems within individual teeth in separate roots

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the goals of this study were
1. To identify and locate E. faecalis in each clinical case using in vivo
DNA fingerprints from the saliva, pulp chambers, and
root canals of endodontically treated teeth with apical periodontitis
using 2 molecular methods; and
3. To determine the diversity and similarity of genotypes present within
the oral cavity.
Aim Of Study
To determine in patients undergoing
root canal treatment, whether apical
enlargement affected the healing
outcome

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The protocol for this systematic review was developed following established guidelines
(Bader 2004), and a well-defined review question was developed using the PICO
framework
In patients with restorable teeth that have had persistent periapical pathosis and/or
clinical symptoms, is there an optimal apical enlargement which would result in better
microbial reduction?
Materials and Methods

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Faculty of Dental Sciences©M. S. Ramaiah University of Applied Sciences
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Inclusion criteria
1. In vivo human investigations from peer-reviewed
journals published in English from January 1950
to July 2014 which reported microbial reduction
2. A comparison between different MAFS
3. The sample size was identified
4. The effect of enlargement on microbial reduction
was measured as a primary objective
5. Quantitative results were reported
Inclusion And Exclusion Criteria
Exclusion criteria
Studies that did not meet the
above inclusion criteria, studies
that used predetermined file size
with no comparison(s), laboratory
studies, animal studies and studies
that only discussed other
antimicrobial protocols

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RESULTS

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Current systematic review may be divided into three schools of thought:
Investigators who suggested
(1)Ørstavik et al. 1991, Dalton et al. 1998, Shuping et al. 2000, McGurkin-Smith et al.
2005 - Apical enlargement significantly reduced microbial flora
(2) Card et al. 2002 - There was a tendency towards more microbial reduction beyond
size 60 MAFS
(3) Yared & Bou Dagher 1994a,b, Nair et al. 2005 - Apical enlargement had no significant
effect in microbial reduction
Discussion

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• Ørstavik et al. 1991, Dalton et al. 1998, Shuping et al. 2000, McGurkin-Smith et al. 2005 - Apical
enlargement significantly reduced microbial reduction used 1 week of Ca(OH)2 dressing in addition
to apical enlargement ,enlargement of the canals was the sole reason, and there was a decrease in
bacteria between the samples
• Card et al. (2002) - enlarged the canals to size 60 as the MAFS and sampled the canals for microbes
before using Ca(OH)2 medication
• Yared & Bou Dagher 1994a,b, Nair et al. 2005 - Enlargement of apical preparations had no influence
on bacterial reduction compared MAFS 25 or MAFS 40
• Direct comparisons cannot be made because of differences in methodologies used in the individual
investigations, use of 1% NaOCl and 5% NaOCl and one visit vs two visits with Ca(OH)2 medication
• Other factors - antimicrobial solution (Shuping et al. 2000), delivery system(Kahn et al. 1995), canal
configuration (isthmus, curvature, etc.) (Card et al. 2002), intracanal medicament(Ørstavik et al.
1991), apical patency (Vera et al. 2011), taper (Albrecht et al. 2004) and microbial root canal
sampling technique (Sathorn et al. 2007).

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• Strindberg 1956, Kerekes & Tronstad 1979 - Despite much interest and research in this area, a
recommended MAFS remains a controversial topic. The articles published in the era before NiTi
rotary instrumentation advocated a higher healing rate where the MAFS was kept as small as
possible
• Bier et al. 2009 - There is a legitimate concern regarding the potential fracturing of teeth
instrumented to sizes above 40
• The question remaining is how large is ‘large enough’ to significantly reduce bioburden within the
RCS to allow for healing to occur in an immunologically competent patient?
• The answer may be that because the adequate removal of bacteria is not predictable using current
techniques as evidenced by the inadequate results from all the reported investigations to eliminate
microbes, the reliance on medications and chemomechanical debridement becomes more critical
• Bystr€om & Sundqvist 1981, , Wu & Wesselink 1995, Dalton et al. 1998, Shuping et al. 2000 - it is
virtually impossible to render canals bacteria-free

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• A Cochrane systematic review (Figini et al. 2008) and a systematic review with meta-analysis (Sathorn
et al. 2005) have reported that there is no significant differences in healing outcomes comparing
single or multiple visits.
• Importance of stringent application of all chemomechanical measures is to
- Treat teeth with infected canals
- Decrease the bioburden
- Reduce the microbial load to the lowest possible level

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Five of the seven articles concluded that canal enlargement reduced bioburden in the root canal
system
Two articles reported no difference in canals enlarged to either size 25 MAFS or 40 MAFS
Contemporary chemomechanical debridement techniques with canal enlargement techniques
do not eliminate bacteria during root canal treatment at any size.
Conclusion

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Future studies : the file sizes, the type of teeth used and if there are various types of
teeth how the MAF was determined and adapted to the morphology of that particular
root, irrigation solution used, size and type of needle and how far the needle
penetrated the canal, the volume of irrigation solution used in the various groups

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Master apical file size – smaller or larger: a systematic review of healing outcomes

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