¹General Practitioner, Ministry of Health, Baish General Hospital, Jazan, Saudi Arabia

²General Practitioner, Ministry of Health, Alsahaleel Primary Health Care, Jazan, Saudi Arabia

³General Practitioner, Ministry of Health, Albadi and Algarafi Primary Health Care, Jazan, Saudi Arabia

⁴Intern Department, College of Dentistry, Jazan University, Jazan, Saudi Arabia

⁵Postgraduate Students, Sanaa University, Sana’a, Republic of Yemen

⁶General Practitioner, Ministry of Health, Samtah General Hospital, Samtah, Jazan, Saudi Arabia

⁶Department of Prosthetic Dental Science, College of Dentistry, Jazan University, Jazan, Saudi Arabia

Corresponding author email: drmoaleem2014@gmail.com

Article Publishing History

INTRODUCTION

All root canal treatments (RCTs) rely on knowledge of the tooth morphology, and three-dimensional imaging of root canal systems (Castellucci., 2015; Bansal et al., 2018). It has been reported that the shape and number of roots and canals differ among genders and populations (Al‑Fouzan et al., 2012; Mirhosseini et al., 2017; Saati et al., 2018; Mashyakhy., 2019; Valenti-Obino et al., 2019; Baxter et al., 2020; Ghabbani et al., 2020). Therefore, it is important to be familiar with differences in the tooth outlines and characteristic features among ethnicities. Such knowledge can aid in the location and negotiation of canals (Arslan et al., 2015; Zhengyan et al., 2016; Verma et al., 2017; Martins et al., 2018; Martínez et al., 2018; Popovic et al., 2018; Shemesh et al.,2018).

A study classified the cross‑sectional root canal configurations of mandibular teeth as round, oval, long oval, flattened, or irregular (Castellucci 2015). Whoever the majority of permanent of maxillary or mandibular incisors have one root and one canal; however, a small percentage may have a second canal, lateral canal, or apical deltas (Saati et al., 2018). The root canal systems of incisors do not consist of a single canal running uniformly from the orifice of the pulp champers to the apex. In fact, the root canal systems of incisors can be complex due to the splitting and reunion of the canals during its passage to the end of the roots (Vertucci., 1984; Saini et al., 1990; Altunsoy et al., 2014; Razumova et al., 2018; Mashyakhy and Gambarini., 2019; Pan et al., 2019). The root canal systems of incisors open apically into the periodontium through apical and lateral foramens. During its passage, the root canal presents a variety of configurations, differing among tooth types, genders, and populations (Mirhosseini et al., 2017; Martínez et al., 2018; Popovic et al., 2018; Mashyakhy and Gambarini., 2019). Recently, Neelakantan et al (2010) and  Przesmycka and Tomczyk (2016) have compared the efficacy of various methods for visualizing the canal and root morphology. These authors concluded that CBCT is accurate, high-resolution, and can be useful for detailed quantitative and qualitative descriptions of the RC anatomy, (Neelakantan et al., 2010; Filpo–Perez et al., 2015; Przesmycka and Tomczyk., 2016; Martinsa et al., 2020).                    

Some reviews have noted high global rates of a second canal in the anterior central and lateral incisors (20.4% and 25.3%), respectively (Martinsa et al., 2020), while some studies have reported greatly varying numbers of canals and canal types among the same teeth (Ahmad., 2015; Ahmed and Hashem., 2016; Bansal et al., 2018; Martins et al., 2019). All the published reviews that we identified have noted that knowledge of these preoperative variables could help clinicians anticipate more complex RC anatomic configurations, thus minimizing the possibility of lost canals during treatment. Investigators use various morphological characteristics to classify root canal systems e.g., the number of canals from orifice to apex, the sum of roots and number of canals in each root, or the number of isthmuses (Vertucci., 1984; Bansal et al., 2018), but the most widely used is Vertucci’s classification, which classifies root canal systems into eight types.

Variations in the morphology of the canals and roots of maxillary and mandibular central or lateral incisor teeth have been noted in in vivo and in vitro studies (Vertucci., 1984; Saini et al., 1990; Caliskan et al., 1995; Al‑Quadah and Awawdeh; 2006; Weng et al., 2009; Al‑Fouzan et al., 2012; Aminsobhani et al., 2013; Altunsoy et al., 2014; Lin et al., 2014; Zhao et al., 2014; Arslan et al., 2015; Zhengyan et al., 2016; da Silva et al., 2016; Martins et al., 2017; Verma et al., 2017; Mirhosseini et al., 2017; Saati et al., 2018; Martins et al., 2018; Martínez et al., 2018; Popovic et al., 2018; Shemesh et al., 2018; Razumova et al., 2018; Mashyakhy M., 2019; Valenti-Obino et al., 2019; Mashyakhy and Gambarini., 2019; Pan et al., 2019; Bourzgui and Akarslan., 2020; Ghabbani et al., 2020; Baxter et al., 2020) (Table 1), and in case reports (Hwang and Min., 2005; Al-Madi., 2020) (Table 2).

However, only a few of those studies were original research by Saini et al., 1990; Al‑Fouzan et al., 2012; Mashyakhy M., 2019; Mashyakhy and Gambarini., 2019; Ghabbani et al., 2020, or case reports by Al-Nazhan., 1991; Alenazy et al., 2019; Al-Madi., 2020, conducted in Saudi Arabia. Here we summarize the published Saudi studies and investigate the number of canals and root morphology of maxillary and mandibular anterior teeth and making comparisons with the global data in relation to the original researches or case reports.

Search Methodology: All peer-reviewed original research articles or case reports for maxillary and/or mandibular central and lateral incisors from 1980 to 2020 addressing root or root canal morphology of permanent teeth were included in this review. A systematic literature review was carried out using the PubMed, Science Direct, Scopus, Evidence-Based Dentistry, and Journal of Evidence-Based Dental Practice databases. The search terms used were: “root canal morphology”, “root morphology”, “case report for anterior maxillary and mandibular teeth”, and “Saudi Arabian population”. All irrelevant or duplicate articles were excluded; the full texts of whole original researches or case reports were screened and saved in a single folder. In addition, all volumes or issues of the Saudi Dental Journal and Saudi Endodontic Journal were manually investigated for related topics. Lastly, the article reference lists were checked for further eligible articles.

Data Collections Original Researches: A total of 29 original research studies (18 mandibular teeth, seven maxillary teeth, four both teeth) were identified. Nineteen of the maxillary teeth studies were clinical studies that used CBCT, and three were laboratory studies using the clearing technique. Seven of the mandibular teeth studies used CBCT and a single study used radiograph, while the other three used the clearing technique. Three of the studies were original Saudi research involving mandibular teeth (Al‑Fouzan et al., 2012; Mashyakhy., 2019; Ghabbani et al., 2020), were done in Al Madinah Al Munawara, Jazan, and Riyadh, respectively.

Also, two Saudi studies, done in Riyadh and Jazan (Saini et al., 1990; Mashyakhy and Gambarini., 2019), involved maxillary teeth. The author names, the year the study was conducted, country, sample size, type of tooth, genders, and anatomical features and finding are given in Table 1. Also, significant differences were recorded when comparing genders, sides, types of teeth, bilateral symmetry, and techniques used. The anatomical features and finding in relation to Vertucci’s classification were investigated, including the number of roots, number of root canals and their configurations, and other radiographical or anatomical findings.

Few studies in the peer-reviewed literature have investigated the canal and root configuration of the maxillary arches (Table 1). A single Saudi study was carried-out by Mashyakhy and Gambarini., 2019 among a subpopulation in Jazan city, and they found that all maxillary central and lateral incisors were Vertucci’s classification Type I. Another earlier study, published earlier, investigated shovel-shaped and dens invaginates in maxillary central incisors (Saini et al., 1990). Other international studies (Russian, Chinese, and Portuguese participants) reported the same percentages (100%) for their maxillary central and lateral incisors samples, and most of them were Vertucci’s classification Type I (Martins et al., 2017; Razumova et al., 2018; Bourzgui and Akarslan., 2020). Other studies conducted in American, China, and Turkey (Vertucci., 1984; Caliskan et al., 1995; Weng et al., 2009 Altunsoy et al., 2014) reported Type I and Type III rates of 78.05% to 99.5%, respectively, for maxillary incisors. Vertucci’s classification Type V was recorded in 1–4.88% of patients from China, Turkey, and Brazil (Weng et al., 2009; Altunsoy et al., 2014; da Silva et al., 2016).

Table 1. Summary of clinical and laboratory morphological studies of roots and canals number, and canals’ configuration of mandibular and maxillary anterior teeth conducted on SA and worldwide countries

Researcher (S), Year/Country	Tooth Type & Sample Size	Anatomical Features & %, general finding Tooth Type/       Vertucci Classification Type (N       %)                                              Two  Gender        I           II           III           IV           V         VI   VII   Others  canals	Sig ↔ Teeth, Gender & Bilateral symmetry, Male: Female %	Technique type
Mandibular teeth
Ghabbani et al, 2020/KSA, Al‑Madinah Al‑Munawara3	812   MN 816   MN   406 Patient	Central   24.6%   0.00%    21.5%    1.2%      2.4%            1.0% Lateral    25.6%   0.00%    20.6%    1.2%      7.1%            1.6% Total       50.3%   0.00%    42.3%    0.2%      5.3%,           1.6% Males     45.2%    0.00%   46.9%    0.00%     6%,              1.7% Female   64.8%    0.00%   29.4%,   0.9%,      3.3%            1.4% Saudi      48.7%,   0.00%   44.1%    0.00%     5.3%            1.7% No-Saudi 52.8%,   0.00%   39.4%    0.6%,      5.4%            1.5%	SD ↔ Type Teeth   SD ↔ Genders Low Symmetry   SD↔Saudi& Non-Saudi Male 300/ Females 106	CBCT
Mashyakhy M, 2019/ KSA, Jazan4	410 MN 412 MN	Central   73.7%    0.00%   26.3%                                                     26.3% Lateral    69.2%    0.00%   29.8%   0.00%     1.0%                          30.8% Male       67.3%    0.00%   32.7%                                                     32.7% Female   79.4%    0.00%   20.6%                                                     20.6%	SD ↔ Canal, Side, Type NSD- Gender Moderate Symmetry Male 48% Female 52%	CBCT
Al‑Fouzan et al, 2012/KSA, Riyadh5	40 MN 40 MN	Central   70%       0.00%    30% Lateral    70%       0.00%    30%	Very High symmetry	In-Vitro, clearing dye injection
Baxter et al, 2020/ Germany6	MN MN 302 Image 1,208 teeth	Central   76.4%    22.3%     0.00%     0.7%       1.2%                       22.6% Lateral   76.3%    21.4%     0.00%     0.00%    1.0%                        24.3% Total      76.4%    21.7%     0.00%     0.00%    1.1%,     0.8%	NSD ↔ Teeth, Age SD ↔ Genders High Symmetry Male 116 / Female 186	CBCT
Mirhosseini et al, 2019/ Iran7	330 MN 331 MN 180 Image	Central   76.1%   0.00%   15.8%        0.6%      7.6%                       23.9% Lateral    65.0%   0.6%     15.7%        0.9%)    17.9%                     35.0%	SD ↔ Tooth Type   Low Symmetry	CBCT
Pan et al, 2019/ Malaysia19	408 MN 400 MN 208 Image	Central    94.9%   0.00%   1.0%        0.00%     4.2% Lateral     87.8%   0.00%   3.8%        0.3%       8.3%	NSD↔ Gender& Side Low Symmetry Male43.3 /Female56.7	CBCT
Valenti-Obino et al, 2019/Italy8	487 MN 491 MN	Central    55.0%    34.3%   9.3%       0.6%      0.8%                           45% Lateral     57.0%    35.7%   6.9%       0.0%      0.4%                          43%	NSD↔ Teeth Type High Symmetry	CBCT
Razumova et al, 2018/ Russia20	510 MN 510 MN	Central    99.4%    0.00%    0.6% Lateral     99.2%    0.8%     0.0%	High Symmetry	CBCT
Saati et al, 2018/Iran9	207 MN 86   MN 270 Image	Central    54.5%    0.00%   34.2%    0.00%    11.3% Lateral     56.5%    0.00%   26.1%    0.00%    17.4% 1 root with 1 canal, CI; 84.5% and LI; 78.2%	NSD ↔Teeth Type NSD ↔ Gender High symmetry	CPCT
Martins et al, 2018, China and Portugal10	240 MX Asian White 937 MX Asian                     White	Central   99.6%    0.00%    0.4%      0.00%     0.0% Central   72.6%    2.40%    0.8%      0.00%     0.3%        VII; 0.5% Lateral    95.0%    2.90%    0.8%      0.00%     1.3% Lateral    70.1%    6.10%    23.1%    0.00%     0.2%         VII; 0.3%	SD ↔Ethnics   Moderate Symmetry	CBCT
Martínez et al, 2018/ Belgium & Chile11	MN Belgium Chile MN Belgium Chile	Central   60.50%   0.58%   32.18%  0.00%    4.02%  VII; 0.58%, X; 1.15% Central   59.65%   0.58%   37.44%  0.00%    1.75%   VII; 000%  X; 0.58% Lateral    77.8%     2.92%   19.3%    0.00%     0.00% Lateral    79.12%   1.10%   19.8%    0.00%     0.00%	SD ↔ Ethnics Moderate Symmetry   345 Belgium / 353 Chile	CBCT
Popovic et al, 2018/ Serbia12	296MN/Male Female 294MN /Male Female 902 Teeth	Central   68.7%     7.2%     22.0%     0.00%     1.2% Central   78.5%     1.5%     20.0%     0.00%     0.00% Lateral    72.0%     4.7%     22.0%     0.00%     1.2% Lateral    75.4%     4.9%     13.8%     1.5%      3.1% Total      73.3%,    5.1%    20.0%       0.4%,      0.00%        Others 1.4%	NSD↔ Tooth Type SD ↔ Gender Moderate symmetry	CBCT
Shemesh et al, 2018/ Israel13	MN     Male Female MN    Male Female	Central   51.2%,    5.77%   39.15%   1.24%    0.62%           1.87% Central   65.8%     2.65%   29.6%     0.5%       0.5%            0.85% Lateral    56.96%   5.51%   35.83%   0.46%    0.00%           1.53% Lateral    66.5%     3.39%   29.24%   0.46%    0.11%           0.23% Bilateral incidence more than 1 root canal in C; 69.8% & L 68.7%	NSD↔ Tooth Type SD↔ Genders Moderate symmetry   Male 653/ Females 855	CBCT
Verma et al, 2017/ India14	400 MN 400 MN 200 Image 800 Teeth	Central   68.3%    11.0%    15.3%     1.8%       3.8%              Males 15.2% Lateral    65.0%    13.3%    5.3%       3.0%       3.5%         Females 20.4% One root with one canal in 66.5% of Man Two canals 33.5% both right C & L, 30% for left C & 36.5% for left L	SD ↔ Side SD ↔ Gender Moderate Symmetry 103 Male /97Females	CBCT
Zhengyan et al., 2016/ China15	MN MN 9646 Image	Central   96.3%    0.2%     2.7%        0.1%     0.75%             3.8% Lateral    89.4%    1.1%     7.7%        0.3%     0.70% IX; 0.3% 10.8%	SD↔ Tooth Type&Side SD ↔ Gender & Age Low Symmetry Males 923 / Female 802	CBCT
Arslan et al, 2015/ Turkey16	184 MN/Male 190MN/Female   374 Image 101 Patient	Central   51.9%    4.3%    41.6%    0.00%     0.5%             1.6% Central   52.9%    2.6%    42.3%    0.00%     1.6%             0.5% Lateral    37.2%    5.2%    55.2%    0.00%     1.7%            0.6% Lateral    65.3%    2.0%    30.7%    0.00%     0.5%            1.5% Males more complex canal configuration than females.	SD ↔ Gender Low Symmetry     54 Females &47 Males	CBCT
Altunsoy et al, 2014/ Turkey21	MN     / Male     Female MN/     Male Female 1582 Central 1603 Lateral	Central   80.7%   0.6%     1.3%       4.2%       13.1% Central   88.2      0.3%      0.3%      4.3%        7.0% Lateral   76.7%    1.6%     1.4%      5.9%        14.4% Lateral   83.7%    1.0%     0.6%      4.9%        9.8%                     ↑in males	SD ↔ Gender   Moderate Symmetry     410 Male /417 Female	CBCT
Lin et al, 2014/ China30	706 MN 706 MN   353 Image	Central   89.1 %   2.4 %   6.2%      1.7 %        0.6 % Lateral    74.5 %   3.7 %   19.3%    2.1 %        0.4   Type III incisors were most prevalent, followed by types II, IV & V	SD↔ Tooth Type SD ↔ Gender High Symmetry Male 163 / Females 190	CBCT
Zhao et al., 2014/ China31	866 Patients   4 674 MN	All Centrals and Laterals were with a single root.                 Central 6.7% Type III canal most prevalent                                                 Lateral 7.4% Two root canals 9.8% in 31-40 years in Cs, & 21.5% (31-40 years) in Ls	SD↔ Tooth type SD ↔Age Groups Moderate Symmetry	CBCT
Aminsobhani et al, 2013/ Iran32	632 MN 614 MN 400 Image	Central   72.7%    11.3%     4.7%     7.7%      3.6%                         27.3% Lateral    70.6%    7.10%     3.7%    15.4%     3.2%                        29.4% Root Length; MANC (21.3±0.10) MANL (21. 9± 0.13 mm).	NSD ↔ Gender High Symmetry Males 620/Females 626	CBCT
AlOudah&Awadeh, 2006 / Jordan33	450 Extracted Teeth	73.8%    26.2% 8.7% had two separate apical foramina.		In-Vitro, staining & tooth‐clearing
Vertucci FJ, 1984/ USA22	100 MN 100 MN	Central   70%      5%        22%       0.00%        3% Lateral    75%      5%        18%       0.00%        2%	Moderate Symmetry	In-Vitro Clearing method
Maxillary teeth
Mashyakhy & Gambarini, 2019 / KSA, Jazan17	184 MX 200 MX	Central   100% Lateral    100%	NSD ↔ Gender Very High Symmetry Male 52.1/Females 47.9	CBCT
Saini et al, 1990/ KSA, Riyadh18	1980 MX 1980 MX	Teeth with Shovel-shaped incisors were Central   Cs- Type I;0.90%, II; 3.73%, III; 3.25%, IV; 7.8% Lateral    Ls- Type I; 1.96%, II; 6.81%, III; 1.21%, IV:10% Teeth with Type II Dens invaginatus; Centrals 4.48% Laterals 11.11%	NS ↔ Genders Measured Shovel-shaped incisors Dens –  invaginatus	Radiograph
Martins et al, 2018/ China & Portugal10	240 MX 937 MX	Central   Asian 100% and White 100% Lateral    Asian 100% and White 100%	SD ↔Ethnics	CBCT
Pan et al, 2019/ Malaysia19	347 MX 362 MX 208 Image	Central   94.9%      5.1% Lateral    87.85      12.3%	NSD ↔ Gender NSD ↔ Side High Symmetry	CBCT
Razumova et al, 2018/Russia20	510 MX 510 MX	Central   100% Lateral    100%	High Symmetry	CBCT
Martins et al, 2017/Portugal35	827 MX 902 MX	Central   100% Lateral    100%	Very High Symmetry	CBCT
de Silva et al, 2016/ Brazil36	200 MX 200 MX	Central   98%         1.0%       0.00%    0.00%         1.0% Lateral    96%         3.5%       0.00%     0.00%        0.5%	Moderate Symmetry	CBCT
Altunsoy et al, 2014/ Turkey21	MX   Male   MX   Female	Central   99.5%      0.00%     0.4%      0.00%          0.1%      Male Higher Lateral    99.7%      0.00%     0.00%    0.00%         0.3% Central   96.7%      1.3%       0.7%       0.00%         1.3%         Female/Lesser Lateral    98.3%      0.7%       0.00%     0.5%            0.5%	SD ↔ Gender Moderate Symmetry   Male 410 /Females 417	CBCT
Weng et al, 2009/ China37	71 MX 70 MX	Central   95.8%      4.2%        0.00%    0.00%         0.00% Lateral    91.4%      2.9%       1.40%     0.00%         4.3%	Moderate Symmetry	Clearing method with dye
Caliskan et al, 1995/ Turkey38	100 MX 100 MX	Central   100% Lateral    78.05%    2.44%     14.63%   0.00%       4.88%	Moderate Symmetry	Clearing technique
Vertucci FJ, 1984/ USA22	100 MX 100 MX	Central   100% Lateral    100% 24 lateral canals in MAXC; 1% cervical, 6% medial, 93% apical	Very High Symmetry	In-Vitro Clearing

Case Reports: Twenty-nine clinical case reports are listed in Table 2: 25 cases involving maxillary teeth and four cases including mandibular teeth. Among these, three cases were related to Saudi patients (Al-Nazhan S., 1991; Alenazy et al., 2019; Al-Madi EM., 2020). Most of the maxillary case reports were central incisors teeth ‘’21 of 25 in the maxilla’’; nine cases were males and 14 females; and 14 cases were on the left side. Most canals were Vertucci’s classification Type IV in both arches, and most of the teeth had two roots. Relatively few cases relating to the mandibular arch have been published. The following information’s were gathered: the author(s) name, time of publication of the case report, place of documentations, gender, type and side of involved tooth/teeth, number of canals, roots or canal configuration according to Vertucci’s classification, and special finding associated with the treated case, if any. Figure 1 shows a radiograph of a treated case for male on the left lateral incisor maxillary tooth and other mandibular case for a female patient on the left central incisor tooth.

Table 2. Summary of previous case reports of Maxillary and Mandibular central and lateral incisors with variations as gender, tooth type, side, and canal morphology according to Vertucci’s Classification

Maxillary Teeth
Author (s) & Year Publication	Country	Gender	Tooth type	Vertucci’s Classification	Canal (s)	Root (s)	Special findings
Present Case	Figure 1 (A-C)	Male	Lateral, left	V	1	2	Non – Vital
Al-Madi et al, 202039	Saudi Arabia	Female	Central, left	IV	2	2	Re-treatment
Al-Nazhan S, 199140	Saudi Arabia	Female	Central, left	IV	2	2	Enamel Hypoplasia
Buonvivere & Buonvivere, 201942	Italy	Female	Lateral, left	VIII	1	3	Non-vital
Elbay et al, 201643	Turkey	Female	Central, right Lateral, right	IV IV	2 2	2 2	Non-vital
Sharma et al, 201444	India	Male	Central, right	V	1	2	Crown dilaceration
Krishnamurti et al,201245	India	Female	Central, right	———–	2	1	Root resorption
Kottoor & Murugesan, 201246	India	Male	Lateral, left	——-	1	4	Non-vital
Nabavizadeh et al,201047	Iran	Male	Central, left	IV	2	2	Non-vital
Gondim et al, 200948	Brazil	Male	Central, right		2	3	———
Shokouhinejad et al, 200949	Iran	Female	Central, left Lateral, left	V V	1 1	2 2	Non-vital
Rodrigues & Silva, 200950	Brazil	Female	Central, right	IV	2	2	Non-vital
Sheikh-Nezami MM, 200751	Iran	Male	Central, right		1	3	Non-vital
Sponchiado et al, 200652	Brazil	Female	Central, left	IV	2	2	———
Lin et al, 200653	China	Female	Central, right	IV	2	2	————-
Benenati FW, 200654	——–	——	Central, left	IV	2	2	Non-vital
Khojastehpour & Khaya, 200555	Iran	Female	Central, left	IV	2	2	Non-vital
Zaitoun &Mackie, 200456]	United Kingdom	Female	Central, right	VIII	1	3	Non-vital
Genovese & Marsico,200357	Italy	Female	Central, right	IV	2	2	Non-vital
Cimilli & Kartal, 200258	Turkey	Male	Central, left	IV	2	2	Fusion of roots
Cabo-Valle & Gonzalez-Gonzalez, 200159	Spain	Female	Central, right	IV	2	2	Non-vital
Mangani & Ruddle, 199460	Italy	Female	Central, right		1	4	Dens invaginatus
Lambruschini & Camps, 199361	France	Male	Central, right	IV	2	2	——–
Hososmi et al, 198962	Japan	Male	Central, right		2	3	Gemination
Mader & Konzelman, 198063	United States America	Male	Central, left	IV	2	2	—–
Sinai & Lustbader, 198064	United States America	——–	Central, right	IV	2	2	Incomplete apical formation
Mandibular Teeth
Present Case	Figure 1 (D-E)	Female	Central, left	V	2	1	Re-treatment
Al Enazay et al., 201941	Saudi Arabia	Female	Central, left Lateral, left Central, right Lateral, right	V III III IV	1 1 1 2	2 1 1 2	Re-treatment
Hwang & Min, 200565	South Korea	——-	Central, right Central, left Lateral, left	IV IV IV	2 2 2	2 2 2	Re-treatments
Kabak & Abbott, 200766	Belarusia	Male	Central, right Lateral, right Lateral, left	II II V	2 2 1	2 2 2	Non -vital
Guan  et al., 200967	China	——–	Central, left Lateral, left Central, right Lateral, right	IV IV IV IV	2 2 2 2	2 2 2 2	———-

Figure 1: Maxillary left lateral incisor with preapical pathosis (A), teeth after RCT for lateral with two canals (B), follow-up after
18 months (c). Mandibular left lateral incisor with incomplete RCT (D), tooth after RCT with two root canals (E).

DISCUSSION

Knowledge of tooth morphology is main basis for science of RCT. Today, root apex is not the only area in RCT science but the idea of three-dimensional RC filling implies that although working length and maintaining it is more important, access to all complications of canal inside is also crucial in order to RC filling (Castelucci., 2015; Bansal et al., 2018). Worldwide, the maxillary and mandibular central and lateral incisors are among the most likely teeth to require RCT (Castelucci., 2015; Filpo–Perez et al., 2015; Ahmed and Hashem., 2016; Martinsa et al., 2020; Baruwa et al., 2020).

Usually, there is just one canal in the anteriors incisors (Vertucci., 1984; Altunsoy et al., 2014; Razumova et al., 2018; Mashyakhy and Gambarini., 2019; Pan et al., 2019). However, a second canal or other variations do occur (Al‑Quadah and Awawdeh., 2006; Aminsobhani et al., 2013; Arslan et al., 2015; Zhengyan et al., 2016; Verma et al., 2017; Saati et al., 2018; Martins et al., 2018; Martínez et al., 2018; Popovic et al., 2018; Shemesh et al., 2018; Ghabbani et al., 2020). Anteriors incisors are the smallest human permanent teeth; incisors have complex roots and canals, especially mandibular incisors. Incisors can be single-rooted, have double roots or canals, a lateral branch of a root canal, apical ramification, or apical furcation; this variability can complicate RCT (Hwang and Min., 2005; Kabak and Abbott., 2007; Guan et al., 2009; Elbay et al., 2016; Alenazy et al., 2019; Buonvivere & Buonvivere., 2019).

Here we review local and international studies and describe the numbers of canals and root morphology of maxillary and mandibular anterior teeth.Starting in the 20^th century, the outside and inner structure of the maxillary and mandibular anterior teeth have been evaluated using in vivo and in vitro techniques. The in vivo techniques include clinical evaluation during RCT, retrospective assessment of patients’ files, and radiographic analysis using conventional and advanced radiographic methods, such as CBCT. The in vitro techniques include root sectioning, canal staining, tooth clearing, microscopic and radiographic examinations using traditional or conventional x-rays, and 3-D techniques, such as micro-computed to be as high as 70% (Al‑Fouzan et al., 2012; Mashyakhy., 2019),and similar rates have been reported in the US, Turkey, Iran, Portugal, and Germany, (Vertucci., 1984; Altunsoy et al., 2014; Mirhosseini et al., 2017; Martins et al., 2018; Baxter et al., 2020). The frequency of Vertucci’s Type III in mandibular lateral incisors was recorded as 20–30% in Saudi studies by Al‑Fouzan et al., 2012; Mashyakhy., 2019; Ghabbani et al., 2020; and similar findings were reported by (Satti et al., 2018) in Iran, (Martins et al., 2018) among patients from China and Portugal, and Turkish patients by (Arslan et al., 2015), and less than 20% amongst patients from Iran, Belgium & Chile, and Germany (Mirhosseini et al., 2017; Martínez et al., 2018; Baxter et al., 2020).

Local studies in Saudi Arabia have reported that around 30% of mandibular teeth had two canals (Al‑Fouzan et al., 2012; Mashyakhy., 2019; Ghabbani et al., 2020). This is well supported by Ahmed et al., 2015. who reported that the two-canal configuration is the most common accessory anatomical variation in single-rooted mandibular anteriors (Ahmed and Hashem., 2016). This is in line with other studies conducted in, Iran, India, Serbia, and Germany (Mirhosseini et al., 2017; Verma et al., 2017; Popovic et al., 2018; Baxter et al., 2020) but a higher percentage was detected in Turkey, Israel, and Italy (Arslan et al., 2015; Shemesh et al., 2018; Valenti-Obino et al., 2019). Also, two canals were more common amongst females than males (Verma et al., 2017), but this trend was reversed in a Turkish population (Altunsoy et al., 2014). Finally, mandibular lateral incisors with two canals were more than central incisors among a Chinese population (Zhao et al., 2014). Vertucci’s classification Type IV was the least common in all studies, and Type V was present in small percentages within the screened patients in most of the studies (Table 1).

The root canal morphology can change over time. Changes due to normal physiological aging usually occur because of secondary dentine deposition (Johnstone and Parashos., 2015). A recent study has reported high variability in root canal morphology of mandibular anterior incisors. Vertucci’s classification Type VII was detected in a local study conducted in Al Madinah Al Munawara (Ghabbani et al., 2020). Also, a similar canal Type was reported in those studies that included participants from Turkey, China, Portugal, Belgium, Chile, and Israel (Arslan et al., 2015, Martins et al., 2018; Martínez et al., 2018; Shemesh et al., 2018;). Other variations were shown in the form of Types IX and X in China and Belgium (0.58–1.15%, respectively), and in China alone (10.8%) (Weng et al., 2009; Bourzgui and Akarslan., 2020).

Compared to the mandibular arch, relatively few studies have addressed maxillary anteriors (Vertucci., 1984; Caliskan et al., 1995; Weng et al., 2009; Altunsoy et al., 2014; da Silva et al., 2016; Martins et al., 2017; Razumova et al., 2018; Mashyakhy and Gambarini., 2019; Pan et al., 2019; Bourzgui and Akarslan., 2020). Both central and lateral maxillary teeth typically start with a single canal and end in a single root. Rates of up to 100% Vertucci’s Classification Type I have been reported, including in a single local Saudi study (Mashyakhy and Gambarini., 2019), and studies carried out in Russia, America, China, Portugal, and Turkey (Vertucci., 1984; Caliskan et al., 1995; Martins et al., 2017; Razumova et al., 2018; Bourzgui and Akarslan., 2020), but lower rates have been reported amongst central maxillary teeth in studies conducted in China, Brazil, and Malaysia (Weng et al., 2009; da Silva et al., 2016; Pan et al., 2019). On the other hand, a rate of 78–91%; Weng et al., 2009 was recorded for maxillary lateral incisors in Turkey, China, and Malaysia (Caliskan et al., 1995; Pan et al., 2019;). Few studies reported a moderate percentage of two canals in maxillary anteriors or incisors, with lower rates than in mandibular teeth. Vertucci’s classification Type III and IV were relatively rare. In a study conducted by Altunosy et al., 2014 among a Turkish population, the authors reported that two canals were more common in males than females; another study reported significant differences in canal number and configuration when comparing populations from China and Portugal (Bourzgui and Akarslan., 2020).

In this review, we conducted a gender comparison in relation to the number of canals, the number of root canals, and root canal configurations (according to Vertucci’s classification). Both studies among Jazanian publications showed no significant differences between gender (Mashyakhy., 2019; Mashyakhy and Gambarini., 2019), while a study conducted in Al Madinah Al Munawara by Ghabbani et al., 2020 showed a significant difference between genders. This could be explained by the uniform sample of the population in Jazan, and mixed populations in the study conducted by Ghabbani et al., 2020 and both studies conducted in Turkey by Altunsoy et al., 2014 and Arslan et al., 2015, while no significant differences were recorded in Malaysia in both arches Pan et al., 2019, or both Iranian studies by Aminsobhani et al., 2013; Saati et al., 2018).

The bilateral symmetry between sides in relation to the type of teeth and canals configurations as well as root numbers, Al-Fouzan et al., 2012 reported a high or typical symmetry between the extracted mandibular teeth in relation to the number of canals and canal configurations. This is consistent with studies conducted in Europe ‘Italy and Germany’’ (Valenti-Obino et al., 2019; Baxter et al., 2020), Asia ‘’China and Iran’’ (Lin et al., 2014; Saati et al., 2018), and the US (Vertucci., 1984), which have also reported high symmetry, which might be related to the racial type and uniform sample types. Mashyakhy M., 2019, Mashyakhy and Gambrini., 2019 reported moderate bilateral asymmetries in central and lateral maxillary and mandibular incisors in relation to some canals and canals configurations. This finding is similar to those from other countries, such as studies conducted in India, China, Portugal, Belgium, Serbia, and Israel (Verma et al., 2017; Martins et al., 2018; Martínez et al., 2018; Popovic et al., 2018; Shemesh et al., 2018). anteriors (Ahmed and Hashem., 2016). Due to the wide morphological variance of the root and root canal system in human anterior teeth, dental general practitioners and specialists should be aware of such anatomical variations, thereby decreasing the risk of failure because of inadequate debridement of inaccessible or undetected parts of the RCS. Recently developed diagnostic devices, the latest endodontic (and periodontal) techniques, and improvements in RCT biomaterials and machines are likely to improve RCT outcomes for patients (Ahmed and Hashem., 2016).

CONCLUSION

From this review the concluding remarks can be drown; The Saudi data and data gathered internationally in relation to canal number, root canal configuration was largely consistent. Type I Vertucci’s classification of canal configuration is the most common type in both arches, followed by Type III. Variations are frequent in the mandibular teeth. Other types of Vertucci’s classification were present in all populations, but at lower rates. The bilateral symmetry of canal and root numbers and configuration vary across populations and genders. All reported cases describing maxillary teeth included only a single tooth, while most of the cases involving mandibular anterior teeth described an unusual canal configuration or root canal number. Dentists should be familiar with the variations in canal numbers and configuration. Also, dentists should know how to use at least read the output of new technologies for visualizing root canal systems.

Conflicts of interest: The authors declare that there are no conflicts of interests.

Funding: We did not receive any fund for this project.

Ethical approval: Ethical approval was obtained from College of Dentistry, Jazan University, # CODJU-2007F date Septamber 15/ 2020.

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