UNIVERSIDADE ESTADUAL PAULISTA

“JÚLIO DE MESQUITA FILHO”

Instituto de Ciência e Tecnologia

Campus de São José dos Campos

SYSTEMATIC REVIEW DOI: https://doi.org/10.4322/bds.2023.e4065

Braz Dent Sci 2023 Oct/Dec; 26 (4): e4065

Morphological alterations of the apical foramen after foraminal enlargement:

a systematic review of

ex vivo

studies

Alterações morfológicas do forame apical após ampliação foraminal: uma revisão sistemática de estudos

ex vivo

Isabella Figueiredo Assis MACEDO1 , Alexandre Henrique dos REIS-PRADO1 , Gabriela da Costa FERREIRA1 ,

Gustavo Oliveira CAMPOS1 , Isabella da Costa FERREIRA1 , Francine BENETTI1 , Isabella Faria da Cunha PEIXOTO1 ,

Warley Luciano Fonseca TAVARES1 , Ana Cecília Diniz VIANA1 

1 - Universidade Federal de Minas Gerais, Faculdade de Odontologia, Departamento de Odontologia Restauradora. Belo Horizonte, MG, Brazil.

How to cite: Macedo IFA, Reis-Prado AH, Ferreira GC, Campos GO, Ferreira IC, Benetti F, et al. Morphological alterations of the apical foramen

after foraminal enlargement: a systematic review of

ex vivo

studies. Braz Dent Sci. 2023;26(4):e4065. https://doi.org/10.4322/bds.2023.e4065

ABSTRACT

Foraminal enlargement has been recommended to optimize the disinfection of infected root canals, although some authors

still claim that the foramen should be kept in its original shape and position. This study aimed to evaluate morphological

alterations of apical foramen after foraminal enlargement through a systematic review. An electronic search was conducted

until April 2022. E

x vivo

studies evaluating inuence of foraminal enlargement in the morphologic changes of apical foramen

were included. Studies without a control group or available full text were excluded. Foraminal deformation and area increase

were considered as primary outcomes. Risk-of-bias assessment was performed according to a modied Joanna Briggs

Institute’s Checklist. From 702 studies retrieved, ve were eligible. Most studies used single-rooted teeth, and rotary systems

for instrumentation ranging from – 2 mm to + 1 mm to the apex. All studies found increased major foramen deformation

after foraminal enlargement. Among four studies that evaluated foraminal area, all found increased area after foraminal

enlargement. Insufcient data for touched/untouched walls by instruments and dentinal microcrack formation was observed.

A low risk of bias was found. Foraminal enlargement during root canal preparation seems to increase deformation and major

apical foramen area. Future investigations with standardized methodologies are encouraged.

KEYWORDS

Apical foramen; Endodontics; Root canal preparation; Root canal therapy; Tooth apex.

RESUMO

A ampliação foraminal tem sido recomendada para otimizar a desinfecção de canais radiculares infectados, embora

alguns autores ainda armem que o forame deve ser mantido em sua forma e posição originais. Este estudo teve como

objetivo avaliar alterações morfológicas do forame apical após ampliação foraminal por meio de uma revisão sistemática.

Uma busca eletrônica foi realizada até abril de 2022. Foram incluídos estudos

ex vivo

que avaliaram a inuência da

ampliação foraminal nas alterações morfológicas do forame apical. Foram excluídos estudos sem grupo controle ou com

texto completo indisponível. A deformação foraminal e o aumento da área foram considerados desfechos primários.

A avaliação do risco de viés foi realizada de acordo com uma lista de vericação modicada do Instituto Joanna Briggs.

Dos 702 registros recuperados, cinco foram elegíveis. A maioria dos estudos utilizou dentes unirradiculares e sistemas

rotatórios para instrumentação, com comprimento de trabalho variando de – 2 mm a + 1 mm até o ápice. Todos os

estudos encontraram aumento da deformação do forame maior após ampliação foraminal. Dos quatro estudos que

avaliaram a área foraminal, todos encontraram aumento de área após alargamento foraminal. Foram observados dados

insucientes para paredes tocadas/intocadas pelos instrumentos e formação de microssuras dentinárias. Um baixo risco

de viés foi encontrado. A ampliação foraminal durante o preparo do canal radicular parece aumentar a deformação e a

área do forame apical. Futuras investigações com metodologias padronizadas são incentivadas.

PALAVRAS-CHAVE

Ápice dentário; Endodontia; Preparo de canal radicular; Tratamento do canal radicular; Forame apical.

Braz Dent Sci 2023 Oct/Dec; 26 (4): e4065

Macedo IFA et al.

Morphological alterations of the apical foramen after foraminal enlargement: a systematic review of ex vivo studies

Macedo IFA et al. Morphological alterations of the apical foramen after foraminal

enlargement: a systematic review of ex vivo studies

INTRODUCTION

Chemical-mechanical preparation is an

important step in endodontic treatment, which aims

to eliminate microorganisms and their products from

the root canal system in order to promote repair of

periradicular tissues. In addition, this procedure

aims at removing necrotic pulp tissue that can serve

as a substrate for reinfection [1-3]. To achieve an

effective chemical-mechanical preparation of the

root canal system, the determination of an adequate

working length (WL) is essential. Instrumentation

below the appropriate WL can leave remnants

of necrotic tissue [2,4], in which can maintain

endodontic infection. Conversely, instrumentation

beyond the apical foramen might exacerbate

the inflammatory response in the periodontal

tissue [5-7] and result in apical extrusion of debris

and lling materials [8].

Traditionally, it was recommended that root

canal instrumentation should be restricted to the

interior of the dentinal canal. In practice, a WL

of 0.5 mm to 1 mm short of the radiographic

apex is considered acceptable, although it might

be not possible to exactly determine the location

of the cementum-dentin junction [9]. While

some authors suggest that the penetration of

an endodontic instrument through the apical

foramen is necessary for an adequate root canal

cleaning due to the presence of necrotic tissue

occupying the apical portion [10-12], other point

out the importance of avoiding the excessive

removal of apical dentin and cementum [6,13].

Hence, a consensus among studies regarding the

most ideal WL has not been reached yet [6,9,14].

Additionally, assessment of the most

appropriate apical foramen enlargement should

be considered, to enhance root canals cleaning and

disinfection, minimizing concerns associated with

this procedure, such as foramen deviation [15,16],

dentinal microcracks [15,17], extrusion of

microorganisms beyond the apex [18] and lling

materials [8]. According to some studies [16,19]

foraminal enlargement can be conducted by

expanding the foramen at least three diameters

(of the ISO standard for endodontic instruments)

larger than the initial apical le (IAF) (rst le

that binds canal walls in the WL), even although

the actual canal diameter determination, by

the IAF, is imprecise [20]. However, there is no

well-dened protocol for performing foraminal

enlargement in the literature, neither in relation

to how much to expand, nor to the ideal WL.

At this point, it’s important to distinguish

between apical patency and foraminal enlargement.

Apical patency maintains access to the apical

foramen using a smaller instrument [14], while

foraminal enlargement, focus of our study, cleans

and disinfects the foraminal region for optimal

healing [11,12]. The objective of the present study

was to evaluate, through a systematic review, if the

foraminal enlargement increases morphological

alterations of the apical foramen, through the

assessment of

ex vivo

studies.

MATERIAL & METHODS

Protocol

The present systematic review was reported

according to the Preferred Reporting Items for

Systematic Reviews and Meta-Analyses (PRISMA)

checklist [21]. A research protocol was registered

in the Open Science Framework (OSF) register

(https://osf.io/bxmt9).

Eligibility criteria

The inclusion criteria were: (1) studies

that evaluated morphological alterations of

the foramen using WL at the major foramen,

and (2) studies that evaluated morphological

alterations of the foramen using WL beyond

the foramen. Exclusion criteria were as follows:

(1) studies without a comparison group with

WL short of the foramen; (2) case report

studies; (3) studies for which the full text was

unavailable; (4) studies that assessed only the

secondary outcomes. There were no restrictions

on the language and date of publication.

The population, intervention, comparison,

outcome, and study design (PICOS) format

was used to address the following research

question: “Does foraminal enlargement inuence

morphologic changes of the apical foramen?”

The study population was extracted human

teeth submitted to root canal preparation.

The intervention explored was root canal

preparation with foraminal enlargement; the

comparison used was root canal preparation

without foraminal enlargement, when WL was

set short of the foramen. The primary outcomes

evaluated were the deformation and area of

the apical foramen. Secondary outcomes were

touched or untouched areas by the instruments

and dentinal microcrack formation. The eligible

study design was

ex vivo

studies.

Braz Dent Sci 2023 Oct/Dec; 26 (4): e4065

Macedo IFA et al.

Morphological alterations of the apical foramen after foraminal enlargement: a systematic review of ex vivo studies

Macedo IFA et al. Morphological alterations of the apical foramen after foraminal

enlargement: a systematic review of ex vivo studies

Search strategy and sources of information

Electronic searches were conducted in

PubMed/MEDLINE, Scopus, Web of Science,

SciELO, Embase and Cochrane Library databases

up to April 2022. Grey literature was consulted

through Google Scholar, and manual searches

were carried out in the reference list of the eligible

articles. The search strategy used a combination of

keywords and Medical Subject Heading (MeSH)

terms associated with the Boolean operators ‘AND’

and ‘OR’ as shown in Table I.

Study selection

Study selection was carried out independently

by two reviewers (I.F.A.M. and G.C.F.), in a

two-step process. Duplicates were identied and

removed using Mendeley Desktop software (version

1.19.8, Elsevier Inc. New York, US). In step 1, the

reviewers appraised titles and abstracts of the

records retrieved from the searches. In step 2, a

full-text assessment of the remaining studies was

performed by the authors. Studies complied with

the eligibility criteria were included in this review.

Table I - Search strategy used for the electronic databases

DATABASE SEARCH STRATEGY

Medline through PubMed

(http://www.ncbi.nlm.nih.gov/pubmed)

(“apical enlargement”[All Fields] OR “apical preparation”[All Fields] OR “apical expansion”[All Fields] OR

“apical widening”[All Fields] OR “apical debridement”[All Fields] OR “foraminal enlargement”[All Fields] OR

“foraminal expansion”[All Fields] OR “foraminal widening”[All Fields] OR “foraminal debridement”[All Fields])

AND (“endodontal”[All Fields] OR “endodontic”[All Fields] OR “endodontical”[All Fields] OR “endodontically”

[All Fields] OR “endodontics”[MeSH Terms] OR “endodontics”[All Fields] OR (“instrumentation”[MeSH

Subheading] OR “instrumentation”[All Fields] OR “instrumentation s”[All Fields] OR “instrumentational”

[All Fields] OR “instrumentations”[All Fields] OR “instrumention”[All Fields]) OR “root canal instrumentation”

[All Fields] OR “root canal preparation”[All Fields] OR “root canal therapy”[All Fields] OR “root canal

treatment”[All Fields]) AND (“morpholog*”[All Fields] OR “geometr*”[All Fields] OR (“alter”[All Fields] OR

“alterated”[All Fields] OR “alteration”[All Fields] OR “alterations”[All Fields] OR “altered”[All Fields] OR

“altering”[All Fields] OR “alters”[All Fields]) OR (“change”[All Fields] OR “changed”[All Fields] OR “changes”

[All Fields] OR “changing”[All Fields] OR “changings”[All Fields]) OR “apical transportation”[All Fields] OR

(“abnormalities”[MeSH Subheading] OR “abnormalities”[All Fields] OR “deformities”[All Fields] OR “congenital

abnormalities”[MeSH Terms] OR (“congenital”[All Fields] AND “abnormalities”[All Fields]) OR “congenital

abnormalities”[All Fields] OR “deformity”[All Fields] OR “deform”[All Fields] OR “deformabilities”[All Fields] OR

“deformability”[All Fields] OR “deformable”[All Fields] OR “deformably”[All Fields] OR “deformation”[All Fields]

OR “deformational”[All Fields] OR “deformations”[All Fields] OR “deformative”[All Fields] OR “deformed”[All

Fields] OR “deforming”[All Fields] OR “deforms”[All Fields]) OR “apical displacement”[All Fields] OR (“crack

cocaine”[MeSH Terms] OR (“crack”[All Fields] AND “cocaine”[All Fields]) OR “crack cocaine”[All Fields] OR

“crack”[All Fields] OR “crack s”[All Fields] OR “cracked”[All Fields] OR “cracking”[All Fields] OR “crackings”

[All Fields] OR “cracks”[All Fields]) OR “micro*”[All Fields] OR (“struct equ modeling”[Journal] OR “scan electron

microsc”[Journal] OR “sem”[All Fields]))

Scopus

(http://www.scopus.com/)

TITLE-ABS-KEY ((“apical enlargement” OR “apical preparation” OR “apical expansion” OR “apical widening”

OR “apical debridement” OR “foraminal enlargement” OR “foraminal expansion” OR “foraminal widening” OR

“foraminal debridement”) AND (endodontic OR instrumentation OR “root canal instrumentation” OR “root canal

preparation” OR “root canal therapy” OR “root canal treatment”) AND (morpholog* OR geometr* OR alteration

OR change OR “apical transportation” OR deformation OR “apical displacement” OR crack OR micro* OR sem))

Cochrane

(https://www.cochranelibrary.com/)

(“apical enlargement” OR “apical preparation” OR “apical expansion” OR “apical widening” OR “apical

debridement” OR “foraminal enlargement” OR “foraminal expansion” OR ” foraminal widening” OR “foraminal

debridement”) AND (endodontic OR instrumentation OR “root canal instrumentation” OR “root canal

preparation” OR “root canal therapy” OR “root canal treatment”) AND (morpholog* OR geometr* OR alteration

OR change OR “apical transportation” OR deformation OR “apical displacement” OR crack OR micro* OR SEM)

in Title Abstract Keyword

Web of Science

(https://clarivate.com/webofsciencegroup/

solutions/web-of-science-core-collection/)

(“apical enlargement” OR “apical preparation” OR “apical expansion” OR “apical widening” OR

“apical debridement” OR “foraminal enlargement” OR “foraminal expansion” OR “foraminal widening” OR

“foraminal debridement”) AND (endodontic OR instrumentation OR “root canal instrumentation” OR “root canal

preparation” OR “root canal therapy” OR “root canal treatment”) AND (morpholog* OR geometr* OR alteration

OR change OR “apical transportation” OR deformation OR “apical displacement” OR crack OR micro* OR SEM)

(All Fields)

Embase

(https://www.embase.com)

(‘apical enlargement’ OR ‘apical preparation’ OR ‘apical expansion’ OR ‘apical widening’ OR ‘apical debridement’

OR ‘foraminal enlargement’ OR ‘foraminal expansion’ OR ‘foraminal widening’ OR ‘foraminal debridement’)

AND (endodontic OR ‘instrumentation’/exp OR instrumentation OR ‘root canal instrumentation’ OR ‘root canal

preparation’/exp OR ‘root canal preparation’ OR ‘root canal therapy’/exp OR ‘root canal therapy’ OR ‘root canal

treatment’) AND (morpholog* OR geometr* OR alteration OR ‘change’/exp OR change OR ‘apical transportation’ OR

‘deformation’/exp OR deformation OR ‘apical displacement’ OR ‘crack’/exp OR crack OR micro* OR ‘sem’/exp OR sem)

Scielo

(https://scielo.org/en/)

(“apical enlargement” OR “apical preparation” OR “apical expansion” OR “apical widening” OR “apical

debridement” OR “foraminal enlargement” OR “foraminal expansion” OR ” foraminal widening” OR “foraminal

debridement”) AND (endodontic OR instrumentation OR “root canal instrumentation” OR “root canal

preparation” OR “root canal therapy” OR “root canal treatment”) AND (morpholog* OR geometr* OR alteration

OR change OR “apical transportation” OR deformation OR “apical displacement” OR crack OR micro* OR SEM)

Google Scholar

(https://scholar.google.com/)

(“foraminal enlargement” OR “foramen enlargement” OR “foraminal debridement” OR “foraminal widening”)

AND (endodontic OR “root canal therapy”) AND (morpholog* OR alteration OR “apical transportation” OR

deformation OR micro* OR SEM)

Braz Dent Sci 2023 Oct/Dec; 26 (4): e4065

Macedo IFA et al.

Morphological alterations of the apical foramen after foraminal enlargement: a systematic review of ex vivo studies

Macedo IFA et al. Morphological alterations of the apical foramen after foraminal

enlargement: a systematic review of ex vivo studies

Discrepancies were resolved through discussion,

and when necessary, a third reviewer (A.H.R.P.)

was consulted. Cohen’s kappa coefficient for

inter-investigator agreement during studies’

selection was assessed [22].

Data extraction

One reviewer (I.F.A.M.) collected data from

the included studies using a guided data extraction

form in a Microsoft Excel spreadsheet. The following

data were retrieved: rst author’s last name, year

of publication, teeth used, sample size, groups, and

experimental protocol. Data were also collected on

the analysis concerning evaluation methods and the

main ndings of the study. Unavailable data were

classied as “not informed”. Subsequently, a second

author (A.C.D.V.) revised the data.

Critical appraisal of studies

The risk of bias of the selected studies was

independently assessed by two reviewers (I.F.A.M

and G.O.C.), in compliance with a modied version

of the Joanna Briggs Institute Critical Appraisal

Checklist for Experimental Studies (JBI) [23-25].

The items included in the checklist were: clearly

stated aim, justication of sample size, sample

randomization, blind treatment allocation,

baseline equivalence of control and treatment

groups, possibility of comparison between control

and treatment groups, clear description of

root canal preparation, measurement method,

measurement standardization, and statistical

analysis. Each item was assessed on a two-point

scale: 0,

not reported or reported inadequately

; 1,

reported and adequate

. Doubts and discrepancies

between investigators were discussed to reach a

consensus, and when necessary, a third investigator

(A.H.R.P.) was consulted.

RESULTS

Study selection

Figure 1 shows de owchart of the selection

process the studies. A total of 702 studies

were found after searching the databases and

through manual search in the references lists.

After the rst screening (Step 1), twenty-eight

studies were selected and submitted to a

full-text reading (Step 2). Then, 23 studies were

excluded [15,26-47] with reasons being available

in Figure 1. Finally, ve studies were included in

the qualitative analysis [16,48-51].

Figure 1 - Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) ﬂowchart.

Braz Dent Sci 2023 Oct/Dec; 26 (4): e4065

Macedo IFA et al.

Morphological alterations of the apical foramen after foraminal enlargement: a systematic review of ex vivo studies

Macedo IFA et al. Morphological alterations of the apical foramen after foraminal

enlargement: a systematic review of ex vivo studies

The assessed Cohen’s kappa coefcient for

inter-investigator agreement during the studies’

selection was, equal to 0.917 for Pubmed, 0.922

for Scopus, 0.867 for Web of Science, 1.000 for the

Cochrane Library, 0.905 for Embase, and 0.955 for

Google Scholar. These values indicated an almost

perfect level of agreement between reviewers

during the selection of studies according to the

scale of Landis and Koch [22].

Characteristics of the included studies

Table II summarizes the main characteristics

and results of the selected studies. All evaluations

were performed in extracted human teeth, especially

molars, with different root curvatures, such as

straight root canal [51], mild [16], and moderate

to severe degree of curvature [50]. Two studies did

not report root curvature of evaluated teeth [48,49].

Table II - Characteristics and main results of included

ex vivo

studies

Author/ Year Teeth used n Groups

Estimated

ﬁnal FD

according

to MAF

nominal

diameter

(mm)*

Outcomes/

Analysis Main results

Souzaetal., 2021

[48]

Human

mandibular

premolars

G1: Largo #2, Hero (#20/.06), GG drills (#5, #4, #3, #2),

Mtwo (#40/.04), WL = +1 mm; G2 (control): Largo #2,

Hero (#20/.06), GG (#5, #4, #3, #2), Mtwo (#40/.04),

WL = -1 mm.

G1: 0.44 Foraminal area

and foraminal

transportation using

SEM.

Foraminal enlargement

increased foraminal area

and increased foraminal

transportation

For all groups, irrigation was performed with 2% CHX gel,

0.9% saline solution, 17% EDTA.

G2: n/a

Marin, 2019

[49]

Single-rooted

human teeth;

FD ≤ 0.40 mm

G1 (control): PDL (#25/.06 and #40/.05), WL = -1 mm;

G2: PDL (#25/.06, #40/.05 and Glide Path ﬁle #45/.01),

WL = 0.0; G3: PDL (#25/.06, #40/.05 and Glide Path ﬁle

#45/.01), WL = +1 mm; G4: PDL (#25/.06, #40/.05 and

Glide Path ﬁle #50/.01), WL = 0.0; G5: PDL (#25/.06,

#40/.05 and Glide Path ﬁle #50/.01), WL = +1 mm.

G1: ≤ 0.40

Foraminal area

and foraminal

transportation using

SEM

Foraminal enlargement

increased foramen

area compared to

instrumentation 1 mm

short of the foramen

(control); it increased

foraminal transportation

compared to control

G2: 0.45

G3: 0.46

G4: 0.50

For all groups, irrigation was performed with 2.5%

NaOCl and 17% EDTA G5: 0.51

Schmidt, 2019

[50]

MB and

ML canals

of human

mandibular

molars

(curvature <30º)

G1 (control): R25 (#25/.08) WL = -1 mm, K #10 at

foramen; G2: R25 WL = -1 mm, FF (#20, #25 or #30) at

foramen; G3: PDS (#25/.01, #30/.10, #25/.06, #25/.08),

WL = 0.0; G4: R25, WL = 0.0; G5: PDS (#25/.01, #30/.10,

#25/.06, #25/.08), WL = +1 mm; G6: R25, WL = +1 mm.

G2: 0.20,

0.25 or 0.30 Foraminal area,

perimeter, and

untouched

cementum wall using

a stereomicroscope,

and apical

transportation using

μ-CT

Foraminal enlargement

increased foraminal

area and deviation;

instrumentation 1 mm

beyond the foramen

did not inﬂuence

untouched cementum

walls compared to

instrumentation 1 mm

short of apical foramen

G3: 0.25

G4: 0.25

G5: 0.33

For all groups, irrigation was performed with 2.5%

NaOCl G6: 0.33

Silvaetal., 2016

[16]

Palatal roots of

human molars

(curvature ≤ 5°)

For all groups, instrumentation in cervical and middle

thirds was performed with K3 ﬁles (#25/.10, #25/.08)

and apical third with IAF + 3 with a .06 taper.

G1 (control): WL= -1 mm; G2: WL = 0.0; G3: WL = +1 mm. n/a

Foraminal area,

transportation using

SEM images

Foraminal enlargement

increased cementum

removal, and

instrumentation + 1mm

beyond the foramen led to

greater foraminal deviation

For all groups, irrigation was performed with 2% CHX,

saline solution and 17% EDTA

Liuetal., 2013

[51]

Human

mandibular

incisors with

straight roots

G1: GG drills (#2 and #1), K3 rotary ﬁles

(#35/.04 up to #25/.06), WL = - 2 mm; G2: GG

drills (#2 and #1), K3 rotary ﬁles (#35/.04 -

#25/.06), WL = -1 mm; G3: GG drills (#2 and #1),

K3 rotary ﬁles (#35/.04 - #25/.06), WL = 0.0; G4:

GG drills (#2 and #1), K3 rotary ﬁles (#35/.04

- #25/.06), WL = +1 mm; G5: GG drills (#2 and

#1), ProTaper (SX up to F3), WL= -2 mm; G6:

GG drills (#2 and #1), ProTaper (SX up to F3), WL = -1 mm;

G7: GG drills (#2 and #1), ProTaper (SX up to F3),

WL = 0.0 mm; G8: GG drills (#2 and #1), ProTaper

(SX up to F3), WL = +1 mm; G9: GG drills (#2 and #1),

Flex HF (20-35, SB: 40-50), WL = -2 mm; G10: GG drills

(#2 and #1), Flex HF (20-35, SB: 40-50), WL = -1 mm;

G11: GG drills (#2 and #1), Flex HF (20-35, SB: 40-50),

WL = 0.0 mm; G12: GG drills (#2 and #1), Flex HF

(20-35, SB: 40-50), WL = +1 mm. For all groups, irrigation

was performed with 2% NaOCl

G1: n/a

Dentinal

detachments and

apical cracks using

stereomicroscope

Foraminal enlargement

increased dentinal

detachments and

cracks than controls,

especially when using

mechanized ﬁles

G2: n/a

G3: 0.35

G4: 0.39

G5: n/a

G6: n/a

G7: 0.30

G8: 0.39

G9: n/a

G10: n/a

G11: 0.35

G12: 0.40

The symbol < indicates ‘less than’, ≤ indicates ‘less than or equal to’, ≅ indicates ‘approximately equal to’, mm: millimeters. CHX:

chlorhexidine, μ-CT: micro-computed tomography, EDTA: ethylenediaminetetraacetic acid, FD: foraminal diameter, FF: Flexoﬁle, G: group,

GG: Gates-Glidden, HF: hand ﬁles, IAF: initial apical ﬁle (ﬁrst ﬁle that binds the foramen), MAF: master apical ﬁle (larger ﬁle used to enlarge

apical region), MB: mesiobuccal, ML: mesiolingual, n/a: not applicable, NaOCl: sodium hypochlorite, PDL: ProDesign Logic, PDS: ProDesign

S, SB: step-back, SEM: scanning electron microscopy, WL: working length. *This column refers to the ﬁnal FD, considering the determined WL

and ﬁle tip and taper described by the manufacturers.

Braz Dent Sci 2023 Oct/Dec; 26 (4): e4065

Macedo IFA et al.

Morphological alterations of the apical foramen after foraminal enlargement: a systematic review of ex vivo studies

Macedo IFA et al. Morphological alterations of the apical foramen after foraminal

enlargement: a systematic review of ex vivo studies

Regarding the instrumentation protocol,

one study used rotary and reciprocating systems

in their experimental groups [50], while the

other four used only rotary systems for foraminal

enlargement [16,48,49,51]. Two studies also

used hand-les in their groups [50,51]. Most

studies had groups with WL that ranged

between – 1 mm and + 1 mm from the

apex [16,48-50]. Additionally, one study had

groups ranging between – 2 mm and + 1 mm

from the apical foramen [51].

Deformation and area of the apical foramen

Foraminal deformation was mostly assessed

using scanning electron microscopy (SEM).

Out of the ve studies that evaluated foraminal

deformation or transportation after foraminal

enlargement, three presented descriptive results

based on qualitative analysis of images [16,48,51].

Other two studies presented results through

measurement and numerical parameters [49,50].

The five studies observed that foraminal

instrumentation led to higher deformation compared

to control groups, in which instrumentation

occurred short of the apical foramen [16,48-51].

Comparing the foraminal deviation when WL was

determined at the foramen or beyond it, two studies

did not observe a statistically signicant difference

among the experimental groups [50,51]. Other two

studies observed that WL beyond the foramen led

to more cases of foraminal deviation compared to

WL at the foramen [16,49].

Four studies evaluated the increase in

foraminal area after foraminal instrumentation,

and comparing with the control groups, in

general, foraminal enlargement increased

foraminal area [16,48-50]. Regarding the different

experimental WL, one study did not observe

signicative difference when the same le systems

were used [50]. One study observed that the

#45.01 (WL=0) group had a lower average wear

during foraminal enlargement compared to the

other experimental groups (#45.01 WL= +1;

#50.01 WL = 0, WL = +1) [49].

Secondary outcomes

Two studies evaluated the amount of

untouched cementum walls after instrumentation

using a stereomicroscope [50] or SEM [16]

and showed that the percentage of all touched

cementum walls were similar when instrumentation

was performed at the foramen or 1 mm beyond.

The occurrence of dentinal microcracks were

evaluated in only one study using a stereomicroscope.

Instrumentation short of the foramen caused less

cracks than WL = 0 or +1 mm [51].

Critical appraisal of included studies

Table III and Figure 2 summarize the results

of the risk of bias assessment by using the JBI

tool. All the included articles showed a clearly

stated aim, baseline equivalence of control and

treatment groups, clear root canal preparation

protocol, measurement standardization, reliable

measurement method, and adequate statistical

approach. However, a high risk of bias was

noticed for some domains, including justication

of sample size, sample randomization and blind

treatment allocation.

ynthesis of results

Meta-analysis was not performed due to wide

variations in methods for assessment, anatomical

variation of samples, NiTi systems and protocols

used for root canal preparation among the

included

ex vivo

studies. In addition, a lack of

available data was observed for some evaluated

outcomes.

DISCUSSION

This systematic review primarily investigated

the morphological changes of the major apical

foramen after foraminal enlargement with data

from ve

ex vivo

studies. All studies demonstrated

increased foraminal deformation and area, though

one study did not measure the latter parameter.

Besides the different WL considered for

foraminal enlargement in the literature, such

as instrumentation at the major foramen [43]

or beyond [41,48], the size of the endodontic

instrument used during instrumentation is also

an important consideration. In this procedure, the

endodontic instrument diameter must guarantee

the preparation of the cemental canal [16,49].

Clinically, a common practice is to rstly estimate

the apical foraminal size, known as the IAF, and

subsequently, choose the instrument that will be

used for foraminal enlargement [16]. The chosen

IAF is normally smaller than the actual size of the

foramen [20], from that, one possibility to determine

how much to enlarge, in terms of instrument

diameter, is increasing apical enlargement to three

ISO diameters larger than IAF [16].

Braz Dent Sci 2023 Oct/Dec; 26 (4): e4065

Macedo IFA et al.

Morphological alterations of the apical foramen after foraminal enlargement: a systematic review of ex vivo studies

Macedo IFA et al. Morphological alterations of the apical foramen after foraminal

enlargement: a systematic review of ex vivo studies

Table III - Critical appraisal of included studies

Quality criteria

Was the aim of the study clearly stated?

Was the sample size justiﬁed?

Was the assignment to treatment groups truly random?

Were those assessing the outcomes blind to the treatment allocation?

Were control and treatment groups comparable at entry?

Were groups treated identically other than for the named interventions?

Was root canal preparation clearly described?

Were outcomes measured in the same way for all groups?

Were outcomes measured in a reliable way?

Was appropriate statistical analysis used?

Total score

Souzaetal., 2021 [48] 1 1 1 1 1 1 1 1 1 1 10

Marin, 2019 [49] 1 0 0 0 1 1 1 1 1 1 7

Schmidt, 2019 [50] 1 0 0 0 1 1 1 1 1 1 7

Silvaetal., 2016 [16] 1 0 0 1 1 1 1 1 1 1 8

Liuetal., 2013 [51] 1 0 0 0 1 1 1 1 1 1 7

0, not reported or reported but inadequate; 1, reported and adequate.

Figure 2 - Assessment of the risk of bias in the included studies according to the percentage of the scores attributed to each evaluated study.

Braz Dent Sci 2023 Oct/Dec; 26 (4): e4065

Macedo IFA et al.

Morphological alterations of the apical foramen after foraminal enlargement: a systematic review of ex vivo studies

Macedo IFA et al. Morphological alterations of the apical foramen after foraminal

enlargement: a systematic review of ex vivo studies

The four studies, of the five included,

that evaluated foraminal area after foraminal

enlargement, observed that this procedure increased

foraminal area, as expected. It demonstrates that

foraminal enlargement really happened within

the parameter used by the authors [16,48-50].

Some articles point out the importance of

performing foraminal enlargement for microbial

reduction [12,52] as it was associated with a greater

reduction in the amount of bacteria within root canals

and better periapical healing compared to root canal

preparation without foraminal enlargement. On the

other way, foraminal enlargement may increase

amount of apically extruded debris and irrigants

to the periapical area [53]. Although it would

be expected to see an increase in the prepared

cemental walls when using the same instrument

at the level of the foramen or 1 mm beyond, some

articles in this study did not observe a signicant

difference in these parameter [16,50]. Surprisingly,

one study showed that over-instrumentation,

regardless of kinematics, did not differ signicantly

from instrumentation short of the foramen while

keeping it patent [50].

Regarding deformation of the apical foramen,

most studies used SEM images for evaluation, in

which a magnication ranging from

50 to

100

was reported [16,48,49]. Photomicrographs were

analysed with the aid of a software to perform

measurements and comparisons after different

instrumentation moments. SEM allows increasing

measurement accuracy and is a viable method

when analysing a large sample [43], meanwhile

it requires a device to standardize the acquisition

of the consecutive images [48]. All studies

concluded that instrumentation at the major

foramen or beyond the apex promoted foraminal

deformations [16,48-51]. Instruments with #25

tip size already showed to be able to cause apical

transportation when instrumentation reached

foramen or was beyond it, in comparison to

WL = -1 mm plus patency with #10 SS le [50].

The occurrence of foraminal deformation

or transportation may negatively impact in

the quality of obturation [8,54] and one of the

major concerns regarding performing foraminal

widening is the possibility of increased risk of

endodontic sealer extrusion. The possibility for

overow of lling materials into the perirradicular

tissues [8] can increase the risk of tissue irritation

or delayed healing. Conversely, two included

studies demonstrated that sealing ability is not

affected by over-instrumentation [16,48].

Regarding shape analysis, few data were

found. One study demonstrated that original oval

foramens turned into more circular shape. The use of

instruments with greater tip size and reduced taper

may provide greater exibility than larger taper les,

in which may reduce irregular deformation [49].

Only one study evaluated the occurrence

of dentinal microcracks showing that foraminal

enlargement increased the occurrence of this

outcome [51].

A modied JBI critical appraisal tool assessed

study quality, revealing methodological limitations

in sample size justication, randomization, and

blinding across most included studies. Enhanced,

standardized evaluations considering anatomical

variations are needed for robust evidence. Despite

this, many studies exhibited low bias risk and

adequate reporting, contributing to overall high-

quality evidence.

Laboratory studies commonly exhibit

methodological heterogeneity [55]. This review

found variability in instrumentation protocol,

instrument tip and taper sizes, working length

determination, and root canal curvature.

Inconsistent methodologies hampered comparisons

between studies. Additionally, only

ex vivo

models

using extracted human teeth were selected,

which must be considered when interpreting the

ndings and making assumptions to the clinical

setting. It is important to emphasize that it is only

through

ex vivo

studies that the selected outcomes

can be analysed more precisely, since, clinically,

microscopy or microtomography, for example,

cannot be performed in clinical studies. However,

future clinical research should delve into long-term

consequences of foraminal enlargement.

CONCLUSION

This review showed that foraminal enlargement,

whether performed at the apical foramen or beyond

it, causes both an increase in foraminal area and

its deformation. It was not possible to conclude if

there is a conservative, but effective, protocol for

foraminal enlargement due to great methodological

heterogeneity of studies. Well-designed evaluations

with standardized methodologies are necessary.

Clinicians must weigh benefits (e.g., bacterial

reduction) against possible risks of the foraminal

deformation (e.g., material leakage, debris and

irrigating solution extrusion) when choosing

foraminal enlargement, considering individual cases.

Braz Dent Sci 2023 Oct/Dec; 26 (4): e4065

Macedo IFA et al.

Morphological alterations of the apical foramen after foraminal enlargement: a systematic review of ex vivo studies

Macedo IFA et al. Morphological alterations of the apical foramen after foraminal

enlargement: a systematic review of ex vivo studies

Author’s Contributions

IFAM: Conceptualization, Investigation, Data

Curation, Formal Analysis, Writing – Original Draft

Preparation. AHRP: Methodology, Software, Formal

Analysis, Writing – Original Draft Preparation.

GCF: Investigation, Formal Analysis, Visualization.

GOC: Investigation, Formal Analysis, Visualization.

ICF: Conceptualization, Validation, Visualization.

FB: Methodology, Resources, Supervision and

Validation. IFCP: Resources, Supervision and

Validation. WLFT: Conceptualization, Writing –

Review & Editing, Project Administration. ACDV:

Conceptualization, Investigation, Formal Analysis,

Resources, Supervision, Writing – Review &

Editing, Project Administration.

Conict of Interest

No conicts of interest declared concerning

the publication of this article.

Funding

This research was partially financed by

Fundação de Amparo à Pesquisa do Estado de

Minas Gerais - FAPEMIG - #340

Regulatory Statement

A regulatory statement is not applicable as this

is a systematic review study conducted through an

electronic database search.

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Ana Cecília Diniz Viana

(Corresponding address)

Universidade Federal de Minas Gerais, Faculdade de Odontologia, Departamento de

Odontologia Restauradora, Belo Horizonte, MG, Brazil.

Email: acdviana@ufmg.br Date submitted: 2023 Sept 25

Accept submission: 2023 Nov 21