Anatomy of Permanent‎ ‎Mandibular‎ First‎ Molars in a Selected Iranian Population Using ‎Cone-beam Computed Tomography.

Introduction

Proper‎ knowledge‎ of‎ the‎ internal‎ anatomy‎ of‎ root‎ canals‎ is‎ crucial‎ for‎ a‎ successful‎ endodontic‎ treatment‎ which‎ relies‎ on‎ appropriate‎ cleaning‎ and‎ shaping‎ [1, 2].‎ Since‎ mandibular‎ first‎ molars‎ emerge‎ very‎ early‎ in‎ the‎ mouth‎ and‎ have‎ complex‎ surfaces,‎ they‎ are‎ one‎ of‎ the‎ teeth‎ most‎ requiring‎ root‎ canal‎ therapy;‎ and‎ therefore‎ the‎ knowledge‎ of‎ their‎ root‎ canal‎ anatomy‎ is‎ important‎ [2, 3].‎ These‎ teeth‎ usually‎ have‎ three‎ canals‎ within‎ two‎ roots‎ although‎ they‎ can‎ change‎ due‎ to‎ ethnicity‎ or‎ normal‎ variations‎ [4-7].‎ ‎

Since‎ ethnic‎ background‎ can‎ affect‎ root‎ anatomy‎ of‎ mandibular‎ first‎ molars,‎ it‎ is‎ important‎ to‎ document‎ properties‎ of‎ these‎ teeth‎ in‎ various‎ populations.‎ However,‎ studies‎ on‎ Iranians‎ are‎‎ few and controversial [2, 3, 8-11].‎ Many‎ aspects‎ of‎ anatomic‎ features‎ are‎ not‎ usually covered‎ by‎ them (such as modifications of Vertucci classification which is not covered in many studies worldwide).‎ Many of older‎ studies‎ have‎ used‎ conventional‎ or‎ 2D‎ radiography‎ techniques‎ that‎ can be‎ less‎ accurate‎ than‎ 3D‎ radiography techniques [12]. Nevertheless, recent studies have mainly used cone‎-beam‎ computed‎ tomography‎ (CBCT) due to its numerous advantages [8-11].‎

This study evaluated number and shape of roots and canals of permanent mandibular first molars using CBCT images of an Iranian sample population.

Materials and Methods

This‎ in‎ vivo‎ study‎ was‎ performed‎ on‎ CBCT‎ images‎ of‎ patients‎ aged‎ 20‎ to‎ 60‎ years‎‎ who‎ had‎ attended‎ two‎ centers in Tehran‎.‎ All‎ CBCTs‎ had‎ been‎ retrospectively‎ taken‎ solely‎ for‎ clinical‎ purposes.‎ No‎‎ x-ray‎ was‎ emitted‎ to‎ patients‎ for‎ this‎ study,‎ and‎ study‎ ethics‎ were‎ approved‎ by‎ the research‎ committee‎ of‎ Azad University of Medical Sciences, Dental branch, Tehran, Iran (#14859).‎ All‎ CBCTs‎ had‎ been‎ taken‎ with‎ the‎ same‎ unit‎ (NewTom,‎ GiANO,‎ Verona,‎ Italy);‎ with similar field‎ of‎ view‎ (8×5 cm),‎ focal‎ size‎ (0.3‎ mm),‎ current (12 mA),‎ peak kilovoltage‎ (85 kVp), and time (0.4‎ sec).‎ Inclusion‎ criteria‎ were‎ availability‎ of‎ both‎ mandibular‎ first‎ molars‎ and in‎ each‎ patient,‎ full‎ patient‎ information was obtained. Exclusion criteria were‎ resorption, ‎previous‎ endodontic‎ treatment,‎ open‎ apex,‎ agenesis,‎ fractures,‎ or‎ pathologies.‎ A‎ total‎ of‎ 312‎ images of first‎ molars‎ from‎ 156‎ patients‎ were‎ included.‎

All‎ measurements‎ were‎ done‎ by‎ the‎ same‎ dentist‎ trained‎ by‎ a‎ maxillofacial‎ radiologist,‎ using‎ NTT Viewer software program (NTT Software Corporation, Yokohama, Japan).‎ CBCT‎ images‎ were‎ examined‎ in‎ coronal,‎ sagittal,‎ and‎ mainly‎ axial‎ dimensions (Figure 1).‎ Evaluated‎ parameters‎ were‎ number‎ of‎ roots,‎ number‎ of‎ canals‎ in‎ each‎ root‎ and‎ in‎ each‎ tooth,‎ and shapes‎ of‎ canals‎ according‎ to‎ the Vertucci‎ classification‎ [13]‎ and‎ its‎ modifications‎ [14-17].‎ Vertucci‎ classes‎ can‎ be‎ summarized‎ based‎ on‎ the‎ number‎ of‎ canals‎ from‎ coronal‎ to‎ apical‎ portions‎ of‎ the‎ root:‎ type‎ I‎ (coronal‎ canals:‎ 1,‎ apical‎ canals:1‎ [1-1]),‎ type‎ II‎ (2-1),‎ type‎ III‎ (1-2-1),‎ type‎ IV‎ (2-2),‎ type‎ V‎ (1-2),‎ type‎ VI‎ (2-1-2),‎ type‎ VII‎ (1-2-1-2),‎ type‎ VIII‎ (3-3),‎ type‎ IX‎ (3-1),‎ type‎ X‎ (3-1-2-1),‎ type‎ XI‎ (4-2),‎ type‎ XII‎ (3-2),‎ type‎ XIII‎ (2-3),‎ type‎ XIV‎ (4-4),‎ type‎ XV‎ (5-4),‎ type‎ XVI‎ (1-3),‎ type‎ XVII‎ (1-2-3-2),‎ type‎ XVIII‎ (1-2-3),‎ type‎ XIV‎ (3-1-2),‎ type‎ XX‎ (2-3-1),‎ type‎ XXI‎ (2-3-2),‎ type‎ XXII‎ (3-2-1),‎ and‎ type‎ XXIII‎ (3-2-3). Schematic diagrams of Vertucci classes and certain modifications observed are presented in Figure 2.

Figure 1

Examples of transverse CBCT sections

Figure 2

Schematic diagrams representing canals within a root [black columns drawn together from top (coronal) to bottom (apical)], arranged as all Vertucci classes (top row) and as certain Vertucci modifications that were observed in this sample of mandibular first molars (bottom row)

Descriptive‎ statistics‎ were‎ calculated. Groups were compared using the chi-square of Statistical Package for Social Science (SPSS, version 24.0, SPSS, Chicago, IL, USA)‎.‎ The level‎ of‎ significance‎ was predetermined as 0.05.

Results

The observer was calibrated through repeating the diagnosis of cases (especially more difficult cases) under the supervision of a dental anatomist and an endodontist. Of‎ 156‎ enrolled‎ patients,‎ 79‎ were‎ males‎ and‎ 77‎ were‎ females.‎ Patients’‎ average‎ age‎ was‎ 35.58‎±‎11.17‎ years.‎ Of‎ patients,‎ 101‎ (64.7%)‎ were aged‎ between‎ 20‎ and‎ 39‎ years‎ old,‎ while‎ 55‎ (35.3%) were‎ between‎ 40‎ and‎ 60‎ years‎ old.

Table‎ 1‎ summarizes‎ the number‎ of‎ canals.‎ Among‎ 312‎ assessed‎ teeth,‎ 16‎ (5.2%)‎ bilateral‎ teeth‎ in‎ 8‎ patients‎ had‎ 3‎ roots;‎ in‎ all‎ these‎ cases,‎ the‎ third‎ root‎ was‎ distolingual.‎ All‎ other‎ teeth‎ had‎ 2‎ roots.‎ Mesial‎ roots‎ had‎ mostly‎ 2‎ canals‎ and‎ in‎ few‎ cases‎ 3‎ canals‎ (Table‎ 1).‎ Distal‎ roots‎ showed‎ a‎ rather‎ similar‎ distribution‎ of‎ 1‎ and‎ 2‎ canals,‎ in‎ addition‎ to‎ very‎ few‎ 3‎ canals‎ (Table‎ 1).‎ All‎ distolingual‎ roots‎ contained‎ only‎ 1‎ canal.‎ Overall,‎ number‎ of‎ canals‎ ranged‎ between‎ 3‎ and‎ 6.‎ Of‎ 312‎ teeth,‎ 39.7%‎ had‎ 3‎ canals,‎ 45.2%‎ had‎ 4‎ canals,‎ 13.8%‎ had‎ 5‎ canals,‎ and‎ 1.3%‎ had‎ 6‎ canals.‎ All‎ 6-canaled‎ teeth‎ were‎ 3-rooted.‎ There were no significant differences between males and females, in terms of number of roots (P=0.137), number of canals in mesial (P=0.453) or distal roots (P=0.328), and total number of canals (P=0.138).

Table‎ 1

Distribution‎ (%)‎ of‎ canal‎ number‎ in‎ roots‎ of‎ mandibular‎ first‎ molars across mesial, distal, and distolingual roots

	Canal ‎ number
Root	1	2	3
Mesial	-	271‎ (86.9%)	41‎ (13.1%)
Distal	136‎ (43.6%)	165‎ (52.9%)	11‎ (3.5%)
Distolingual	16‎ (100%)	-	-

Tables‎ 3‎ and‎ 4‎ present‎ Vertucci‎ classes‎ and‎ Vertucci‎ modifications.‎ In‎ mesial‎ roots,‎ the‎ most‎ common‎ classes‎ were‎ type‎ IV‎ followed‎ by‎ II.‎ In‎ distal‎ roots,‎ the‎ most‎ common‎ class‎ was‎ type‎ I‎ (Tables‎ 2‎ and‎ 3, Figure 2).‎ The Chi-square did not show significant differences between males and females in terms of Vertucci classes in the mesial root (P=0.211) or distal root (P=0.205).

Table‎ 2

Distribution‎ of‎ canal‎ types‎ according‎ to‎ Vertucci‎ classes (I to VIII) in mesial and distal roots of mandibular first molars

		I	II	III	IV ‎	IV ‎	V	VI	VII	VIII
Mesial root	N	–	66	20	125	125	13	27	10	–
	%	–	21.1	6.4	40.0	40.0	4.1	8.6	3.2	–
Distal root	N	136	15	55	–	–	47	–	31	–
	%	43.6	4.8	17.6	–	–	15.0	–	9.9	–

Table‎ 3

Distribution‎ of‎ canal‎ types‎ according‎ to‎ Vertucci‎ modifications (IX to XXIII) in mesial and distal roots of mandibular first molars. Modification with all-empty cells are removed from the table

		X	XII	XIII	XVI	XVII	XX	XXI	XXII
Mesial root	N	10	9	4	–	7	13	8	–
	%	3.2	2.9	1.3	–	2.2	4.2	2.5	–
Distal root	N	17	–	3	4	–	–	–	4
	%	5.4	–	0.9	1.3	–	–	–	1.3

Discussion

The‎ findings‎ of‎ the present‎ study‎ showed‎ that‎ only‎ 5.2%‎ of‎ first‎ molars‎ had‎ three‎ roots.‎ Our‎ results‎ were‎ similar‎ to‎ other‎ Iranian‎ studies‎ reporting‎ prevalence‎ of‎ third‎ root‎s ranging‎ between‎ zero‎ and‎ 3.9%‎ [2, 8-11].‎ Also‎ our‎ findings‎ were‎ consistent‎ with‎ studies‎ on‎ Jordan‎ [14],‎ India‎ [18],‎ Turkey‎ [19, 20]‎ and‎ Sudan‎ [21].‎ However,‎ they‎ were‎ not‎ in‎ line‎ with‎ results‎ from‎ South‎ Korea‎ [22]‎ and‎ Burma‎ [7].‎ It‎ seems‎ that‎ presence‎ of‎ distolingual‎ roots‎ might‎ depend‎ on‎ ethnicity, and results‎ in‎ Asians‎ indicate‎ a‎ rather‎ high‎ prevalence‎ of‎ the‎ third‎ root‎ (Table‎ 4)‎ [4-7, 22, 23].

Table‎ 4

Summary‎ of‎ reports‎ on‎ number‎ of‎ roots

Author /Country	Method	Sample size	Number ‎ of ‎ roots
			1	2	3
Kim‎ et‎ al. /South‎ Korea [22]	CBCT‎ (in‎ vivo)	1952	0.67%	73%	25%
Abella‎ et‎ al. [4]	review‎ of‎ literature‎ of‎ 45‎ articles	19056	-	-	14%‎ (Range‎ 0*‎ to‎ 29%)
Zhang‎ et‎ al./China [23]	CBCT‎ (in‎ vivo)	232	0.4%	70%	29%
DePablo‎ et‎ al./Spain [5]	review‎ of‎ literature‎ of‎ 41‎ articles	18787			13%‎ (Range‎ 0‎ to‎ 32%)
Demirbuga‎ et‎ al./Turkey [20]	CBCT‎ (in‎ vitro)	1748	0.85%	95.8%	2%
Chourasia‎ et‎ al./India [18]	in ‎ vitro‎ (clearing‎ technique)	150		94.6%	5.3%
Garg‎ et‎ al./India [24]	in ‎ vitro‎ (periapical‎ radiography)	1054			6%
Al-Qudah,‎ Awawdeh/Jordan [14]	in ‎ vitro‎ (clearing‎ technique)	330		96%	4%
Ahmed‎ et‎ al./Sudan [21]	in ‎ vitro‎ (clearing‎ technique)	100		94%	3%
Mirzaie et‎ al./Iran [11]	CBCT‎ (in‎ vivo)	66		100%
Ballullaya‎ et‎ al. [6]	review‎ of‎ literature‎ of‎ 97‎ articles				Range:‎ 3-35%
Gulabivala‎ et‎ al./Myanmar [7]	in ‎ vitro‎ (clearing‎ technique)	139		90%	10%
Nur‎ et‎ al./Turkey [19]	CBCT‎ (in‎ vivo)	966	0.3%	99.2%	0.5%
Zafar‎ et‎ al./Saudi‎ Arabia [25]	CBCT‎ (in‎ vitro)	100		100%
Arjmand‎ et‎ al./Iran [10]	CBCT‎ (in‎ vivo)	121		97.5%	2.5%
Masoudi‎ et‎ al./Iran [9]	CBCT‎ (in‎ vivo)	129		96.1%	3.9%
Akhlaghi‎ et‎ al./Iran [2]	in ‎ vitro‎ (clearing‎ technique)	150		69.7%	3.3%

In ‎ studies ‎ from ‎ Iran, ‎ Uganda, ‎ Pakistan, ‎ Turkey, ‎ Kuwait ‎ and ‎ Spain, ‎ no ‎ three-root ‎ teeth ‎ had ‎ been ‎ observed

In‎ this‎ study,‎ prevalence‎ of‎ three‎ and‎ four‎ canals‎ in‎ each‎ tooth‎ were‎ rather‎ similar.‎ This‎ finding‎ was‎ comparable‎ to‎ results‎ of‎ Kim‎ et‎ al‎. [22],‎ Zhang‎ et‎ al‎.‎ [23],‎ Al-Qudah‎ and‎ Awadeh‎ [14]‎ who‎ reported‎ similar‎ prevalence‎ of‎ three‎ and‎ four‎ canals,‎ but was‎ in‎ contrast‎ to‎ observations‎ of‎ Demirbuga‎ et‎ al‎. [20], Chourasia‎ et‎ al‎. [18],‎ Ballullaya‎ et‎ al‎. [6],‎ Nur‎ [19] and‎ Masoudi‎ [9]‎ who‎ reported‎ a‎ considerably‎ greater‎ prevalence‎ of‎ 3-canaled‎ roots‎ compared‎ to‎ 4-canaled‎ roots. Three-canaled‎ roots‎ can‎ be‎ problematic‎ in‎ endodontic‎ treatments.‎ This‎ research‎ showed‎ prevalence‎ of‎ 3-canaled‎ roots‎ about‎ 13%‎ in‎ mesial‎ roots‎ and‎ 3.5%‎ in‎ distal‎ roots;‎ this‎ was‎ consistent‎ with‎ findings‎ of‎ Al-Qudah‎ and‎ Awawdeh‎ [14],‎ De‎ Pablo‎ et‎ al‎. [5]‎ regarding‎ mesial‎ roots‎ and‎ Ahmed‎ et‎ al‎. [21]‎ regarding‎ distal‎ root.‎ However,‎ our‎ result‎ was‎ not‎ in‎ line‎ with‎ other‎ reports,‎ which‎ might‎ be‎ due‎ to‎ differences‎ in‎ ethnicity‎ or‎ methodologies.‎ In‎ this‎ study,‎ most‎ of‎ mesial‎ roots‎ had‎ 2‎ canals‎ but‎ about‎ 13%‎ of‎ them‎ had‎ 3‎ canals.‎ This‎ was‎ similar‎ to‎ other‎ studies‎ stating‎ that‎ 2-canaled‎ roots‎ are‎ much‎ more‎ prevalent‎ (summarized‎ in‎ Table‎ 5).‎ In‎ distal‎ roots,‎ similar‎ prevalence‎ of‎ one‎ or‎ two‎ canals‎ were‎ observed‎ in‎ this‎ study‎ (with‎ very‎ few‎ cases‎ of‎ three‎ canals).‎ Such‎ a‎ high‎ frequency‎ of‎ two‎ canals‎ in‎ this‎ root‎ was‎ similar‎ to‎ studies‎ of‎ Ahmed‎ et‎ al‎. [21],‎ Arjmand‎ et‎ al‎. [10],‎ and‎ Al-Qudah‎ and‎ Awadeh‎ [14].‎ All‎ distolingual‎ roots‎ were‎ single-rooted‎ as‎ what‎ was‎ reported‎ by‎ Akhlaghi‎ et‎ al‎.‎ [2].‎

Table‎ 5

Summary‎ of‎ reports‎ on‎ number‎ of‎ canals

Author /Country	Method	Sample size	Number ‎ of ‎ canals
			Overall	Mesial root	Distal root
Kim ‎ et‎ al‎. /South‎ Korea [22]	CBCT ‎ ( in ‎ vivo )	1952	48.6%‎ three‎,‎ 49.2%‎ four‎	-	-
Zhang ‎ et‎ al‎. /China [23]	CBCT ‎ ( in ‎ vivo )	232	53%‎ three-,‎ 43%‎ four-	95%‎ two-canal
De Pablo ‎ et‎ al‎. /Spain [5]	review ‎ of ‎ literature ‎ of ‎ 41 ‎ articles	18787	61%‎ three-,‎ 35.7%‎ four-	94.4%‎ two‎,‎ 2.3%‎ three‎	63%:‎ single-canal
Demirbuga ‎ et‎ al‎. /Turkey [20]	in ‎ vitro ‎ (CBCT)	1748	79.9%‎ three-,‎ 15.4‎ %%‎ four-	-	-
Chourasia ‎ et‎ al‎. /India [18]	in ‎ vitro ‎ (clearing ‎ technique)	150	64%‎ three‎,‎ 36%‎ four‎
Al-Qudah, ‎ Awawdeh/Jordan [14]	in ‎ vitro ‎ (clearing ‎ technique)	330	49%‎ three-,‎ 46%‎ four-	93%‎ two-,‎ 6%‎ three-	54%‎ single‎ 45%‎ two‎ s
Ahmed ‎ et‎ al‎. /Sudan [21]	in ‎ vitro ‎ (clearing ‎ technique)	100		86%‎ two	59%‎ two-,‎ 38%‎ single‎,‎ 3%‎ three-
Mirzaie ‎ et‎ al‎. /Iran [11]	CBCT ‎ ( in ‎ vivo )	66	63%‎ three-,‎ 37%‎ four-
Ballullaya ‎ et‎ al‎. [6]	review ‎ of ‎ literature ‎ of ‎ 97 ‎ articles		35%‎ four-	Three‎ canals:‎ Range‎ 0.95‎ to‎ 15%
Nur ‎ et‎ al‎. /Turkey [19]	CBCT ‎ ( in ‎ vivo )	966	63%‎ three-,‎ 37%‎ four-	96.8%‎ two ,‎ 0.2%‎ three‎,‎ 3%‎ single‎
De Pablo ‎ et‎ al‎. /Spain [5]	CBCT ‎ ( in ‎ vitro )	53	41.5%‎ three‎,‎ 29.4%‎ four‎,‎ 28.3%‎ five‎	96.8%‎ two ‎,‎ 0.2%‎ three‎,‎ 3%‎ single‎
Zafar ‎ et‎ al‎. /Saudi‎ Arabia [25]	CBCT ‎ ( in ‎ vitro )	100		95.5%‎ two ‎	20%‎ double‎,‎ 80%‎ single‎
Arjmand ‎ et‎ al‎. /Iran [10]	CBCT ‎ ( in ‎ vivo )	121		92.5%‎ two ‎	58.6%‎ single‎,‎ 37.2%‎ double‎
Masoudi ‎ et‎ al‎.‎ /Iran [9]	CBCT ‎ ( in ‎ vivo )	129	72.1%‎ three‎,‎ 24.8%‎ four‎,‎ 1.6%‎ five‎		74.7%‎ single‎
Akhlaghi ‎ et‎ al./Iran [2]	in ‎ vitro ‎ (clearing ‎ technique)	150		100%‎ two	61.3%‎ single‎,‎ 38.7%‎ double‎

The‎ most‎ common‎ types‎ of‎ canal‎ which‎ were‎ found‎ in‎ mesial‎ roots‎ of‎ this‎ study‎ were‎ Vertucci classes IV‎ (40%),‎ II‎ (21.1%)‎ and‎ VI (8.1%),‎ while‎ about‎ 16%‎ of‎ cases‎ were‎ Vertucci‎ modifications.‎ Higher‎ prevalence‎ of‎ type‎ IV‎ followed‎ by‎ type‎ II‎ was‎ seen‎ in‎ most‎ other‎ studies‎ [2, 8] except‎ those‎ reported by Zafar‎ et‎ al‎. [24]‎ and‎ Masoudi‎ et‎ al‎. [9]‎ (Table‎ 7).‎ In‎ distal‎ roots,‎ most‎ common‎ Vertucci‎ types‎ were‎ I‎ (43.6%),‎ III‎ (17.6%),‎ and‎ V‎ (15%);‎ about‎ 9%‎ of‎ cases‎ were‎ Vertucci‎ modifications‎ (Table‎ 6).‎ This‎ was‎ consistent‎ with‎ studies‎ of‎ Zafar‎ et‎ al‎. (37),‎ Arjamand‎ et‎ al‎. [10],‎ and‎ Masoudi‎ et‎ al‎. [9].‎ Although‎ Vertucci‎ classes‎ can‎ simplify‎ reports,‎ they are not‎ sufficient‎ to‎ cover‎ all‎ complexities‎ of‎ root‎ canal‎ structures which were‎ observed‎ in‎ this‎ study‎ and‎ few‎ others‎ that‎ have‎ evaluated‎ Vertucci‎ modifications‎ [7, 14].‎ Sometimes,‎ real‎ canals‎ are‎ much‎ more‎ irregular‎ to‎ be‎ easily‎ categorized‎ into‎ one‎ of‎ Vertucci‎ classes‎ or‎ modifications.‎ Differences‎ might‎ be‎ attributed‎ to‎ ethnicity‎.‎

Table‎ 6

Summary‎ of‎ reports‎ on‎ Vertucci‎ types‎ and‎ modifications‎ (all‎ reported‎ values‎ in‎ percent)

Author /Country	Method	Size	Mesial ‎ root	Distal ‎ root	Vertucci ‎ modifications
Kim ‎ et‎ al‎. /South‎ Korea [22]	CBCT ( in vivo ) ‎	1952	IV‎ 71‎‎ II‎ 20‎	I‎ 66‎‎‎ II‎ 19‎‎ IV‎ 12	0.35%
Zhang ‎ et‎ al‎. /China [23]	CBCT ( in vivo ) ‎	232	IV‎ 81‎‎ V‎ 15‎	-	-
De Pablo et ‎ al ‎ . /Spain [5]	review ‎ of ‎ literature ‎ of ‎ 41 ‎ articles	18781	IV‎ 52.3‎‎‎ II‎ 35‎	I‎ 63‎‎ II‎ 14‎‎ IV‎ 12.4‎
Demirbuga ‎ et‎ al‎. /Turkey [20]	CBCT ‎ ( in ‎ vitro )	1748	IV‎ 68 II‎ 30‎	I‎ 82‎‎ II‎ 6‎‎ IV‎ 5.6‎
Chourasia ‎ et‎ al‎. /India [18]	in ‎ vitro ‎ (clearing ‎ technique) ‎	150	IV‎ 54 II‎ 36.6‎	I‎ 65.3 II‎ 20.6‎‎‎ IV‎ 9.3
Al-Qudah, ‎ Awawdeh/Jordan [14]	in ‎ vitro ‎ (clearing ‎ technique)	330	IV‎ 53‎‎‎ II‎ 36‎	I‎ 54‎‎‎ II 17‎‎‎ V‎ 11 IV‎ 9‎	Mesial root: 5.7% Distal root: 1.7%
Ahmed ‎ et‎ al‎. /Sudan [21]	in ‎ vitro ‎ (clearing ‎ technique)	100	IV‎ 73‎‎‎ II‎ 14‎	I‎ 38 II 28‎‎‎ V‎ 22‎‎
Gulabivala ‎ et‎ al‎. /Myanmar [7]	in ‎ vitro ‎ (clearing ‎ technique)	139	IV‎ 38.1‎‎‎ II 28.8‎‎‎ V‎ 6.5‎	I‎ 92.9	Mesial: 12.9% Distal: 10%
Faraz ‎ et‎ al‎. [26]	in ‎ vitro ‎ (clearing ‎ technique)	123	IV‎ 70.7 II‎ 26.8‎	I‎ 65.8‎‎‎ II 14.6‎‎‎ V‎ 19.5‎
Nur ‎ et‎ al‎. /Turkey [19]	CBCT ( in vivo ) ‎	966	IV‎ 92‎‎‎ II‎ 5‎	I‎ 60‎‎‎ II 12IV‎ 20‎‎‎ V‎ 7
Zafar ‎ et‎ al‎. /Saudi‎ Arabia [25]	CBCT ( in vitro ) ‎	100	II‎ 30IV‎ 27.5‎‎ III‎ 20‎‎ V‎ 12.5‎	I‎ 58.6‎‎ II‎ 20.3III 16.9‎‎
Arjmand ‎ et‎ al‎. /Iran [10]	CBCT ( in vivo ) ‎	121	IV‎ 65.3 II‎ 27.2‎	I‎ 47.2 III 18.9
Masoudi ‎ et‎ al‎. /Iran [9]	CBCT ( in vivo ) ‎	129	II‎ 62.1IV‎ 29.5‎‎	I‎ 74.7‎‎ III 18.6‎‎ II 17.8
Akhlaghi ‎ et‎ al‎. /Iran [2]	in ‎ vitro ‎ (clearing ‎ technique)	150	IV‎ 55.3‎‎‎ II 41.3 VIII‎ 2.7	I‎ 61.2 II‎ 26.6IV‎ 9.4‎	‎

Conclusion

In this population, there were 3 to 6 canals per tooth (mostly 4 and 3 canals).‎ Males and females might be similar regarding number of roots, or number of canals in each root, or number of canals in each tooth. The most frequent Vertucci classes in mesial and distal roots were IV‎ (followed‎ by‎ II) and I‎, respectively without a significant sex dimorphism.