Maxillary Permanent First Premolars With Three Canals: Incidence Analysis Using Cone Beam Computerized Tomographic Techniques.

AIM: This study aimed to analyze incidence of three canals in human permanent maxillary first premolar teeth using cone beam tomographic techniques.
MATERIALS AND METHODS: The samples were divided into three groups namely Group (GP) I (single rooted [n = 255]), GP II (two rooted [n = 326]), and GP III (three rooted [n = 8)]. The teeth were processed, mounted in arches, coded, and subjected to cone beam tomographic scanning. Incidence of three canals was evaluated by cone beam tomography, compared, and statistically analyzed.
RESULTS: The percentage of incidence of three canals in human permanent maxillary first premolar teeth was 1.7% and there was no statistically significant difference of incidence of three canals between studies using cone beam and non-cone beam methodologies.
CONCLUSION: Clinicians should be aware of the variations they may encounter when endodontically treating a maxillary first permanent premolar and should apply this knowledge in a clinical scenario systematically.

INTRODUCTION

Awareness of the normal internal anatomy of the teeth and its variations is essential.[1] Maxillary permanent first premolars have root and canal configuration that is variable and the prevalence of three canals is low. These variations can possibly lead to failures of therapy and adequate anticipation and knowledge of these variations ensures long-term success.[2] This also necessitates special clinical assessment, radiographic interpretation, access modifications, and canal preparation methods.[34] Cone beam tomography is a useful recent diagnostic methodology that provides additional information compared to conventional intraoral radiography regarding the tooth and the surrounding structures. The presence of a third canal is often missed and when successfully identified it is difficult to biomechanically prepare. The incidence of a third canal has been widely reported in maxillary first premolars. Three canals have been reported with an incidence of 5% in maxillary first premolars.[5] Operator training is essential to successfully manage these anatomical challenges. This study aimed to analyze incidence of three canals in permanent maxillary first premolars using cone beam computed tomographic techniques.

MATERIALS AND METHODS

Maxillary permanent first premolar teeth were collected after extraction, cleansed, and stored. The samples were visualized under a magnifying loupe with illumination for presence of intact occlusal and root morphology and selected as per accepted criteria.[6] They were then analyzed using digital radiography and those teeth with canal calcifications and open apices were discarded. A total of 589 teeth (n = 589) were selected, divided into two groups namely Group I (single-rooted maxillary first premolars [n = 255]), Group II (two-rooted maxillary first premolars [n = 326]), and Group III (three-rooted maxillary first premolars [n = 8]) based on their morphological characteristics [Chart 1]. The teeth belonging to respective groups were mounted on a wax occlusal rim, numerically coded with markings so that they were visible during the image analysis procedure, and stored for further analysis. They were then mounted on the cone beam tomography machine and imaging process was performed. Imaging scan was performed in such a way that occlusal surfaces of both the arches face each other with a layer of wax in between them. The presence of three canals was assessed by individually analyzing the samples three dimensionally. The groupwise data observed on the incidence of three canals were recorded and compared statistically, and the results were tabulated. The results were compared with that of previous studies on the prevalence of three canals performed using cone beam techniques. The results of studies on the prevalence of three canals carried out using non-cone beam methodologies were tabulated and compared with those that used cone beam techniques.

Chart 1

Incidence – Number of roots

RESULTS

The percentage of incidence of three canals in human permanent maxillary first premolar teeth in this study done using cone beam tomographic analysis was 1.7% [Table 1; Figures 1 and 2]. On a statistical comparison and analysis of the results of the incidence of three canals obtained in this study with that of other studies performed using cone beam tomographic techniques [Table 2], the results were found to be statistically on par with that of other studies (P > 0.05). On a statistical comparison between studies done using cone beam tomography techniques and studies using other techniques on the incidence of three canals in maxillary first premolars, no significant difference was found (P > 0.05) [Table 3]. Two single rooted maxillary first premolars with three canal configuration were found [Figure 3 and 4].

Table 1

Presence of three canals—Overall

Author	Year	Type of Study	Three Canal	Sample Size	Population
Cairns et al.[22]	1973	In vitro	0–6%	100	White Americans
Vertucci and Gegauff[5]	1979	In vitro	5%	400	White Americans
Hartwell et al.[23]	1985	In vivo	3.3%	514	United States
Sieraski et al.[12]	1989	In vitro	5–6%	400	North American
Zaatar et al.[24]	1997	In vitro	3.8%	79	Kuwaiti
Kartal et al.[25]	1998	In vitro	1.66%	600	Turkish
Chaparro et al.[26]	1999	In vitro	3.3%	150	Andalusian
Sert et al.[27]	2004	In vitro	3%	200	Turkey
Dehua et al.[28]	2004	In vitro	0.6%	326	Chinese
Lipski et al.[29]	2005	In vitro	9.2%	142	Polish
Javidi et al.[21]	2008	In vivo	0.5–6%	3
Awawdeh et al.[30]	2008	In vitro	1.5%	600	Jordan
Ateih MA et al.[31]	2008	In vitro	1.2%	246	Saudi
Ng’ang’a et al.[32]	2010	In vitro	11.7%	155	Kenyan
Tian YY et al.[33]	2012	In vivo	1%	300	Chinese
Özcan et al.[34]	2012	In vitro	1.5%	653	Turkish
Ok et al.[35]	2014	In vivo	1.01%	1379	Turkish
Gupta et al.[36]	2015	In vitro	0.4%	250	North Indian
Abella et al.[37]	2015	In vivo	2.6%	430	Spanish
Stošić et al.[38]	2016	In vitro	3.4%	41	Serbian
Celikten et al.[39]	2016	In vivo	0.9%	437	Turkish Cypriot
Martins et al.[40]	2017	In vivo	0.7%	690	Caucasian
Burklein et al.[41]	2017	In vivo	2.0%	644	German
Banga et al.[42]	2018	In vitro	2.32%	246	South Indian
Senan et al.[43]	2018	In vitro	0.66%	75	North Indian
Nazeer et al.[44]	2018	In vivo	0.5%	114	Pakistani
Alquediari et al.[45]	2018	In vivo	2.1%	334	Saudi
De Lima et al.[46]	2018	In vivo	1.6%	496	Brazilian
Popović et al.[47]	2018	In vivo	5.4%	129	Serbian
Dinakar et al.[48]	2018	In vitro	2.32%	225	South Indian
Present study	2018	In vitro	1.7%	589	South Indian
Overall average		31	2.78%

Figure 1

Incidence—CBCT studies. CBCT = cone beam computerised tomography

Figure 2

Incidence—non-CBCT studies

Table 2

Presence of three canals—CBCT studies

Author	Year	Incidence (%)	Sample Size	Population
Tian YY et al.[33]	2012	1	300	Chinese
Ok.E et al.[35]	2014	1.01	1379	Turkish
Abella et al.[37]	2015	2.6	430	Spanish
Celikten et al.[39]	2016	0.9	437	Turkish Cypriot
Martins et al.[40]	2017	0.7	690	Caucasian
Burklein et al.[41]	2017	2.0	644	German
Nazeer et al.[44]	2018	0.5	114	Pakistani
Alquediari et al.[45]	2018	2.1	334	Saudi
De Lima et al.[46]	2018	1.6	496	Brazilian
Popović et al.[47]	2018	5.4	129	Serbian
Present study	2018	1.7	589	South Indian
Overall average	11	1.77

Table 3

Presence of three canals—non-CBCT studies

Author	Year	Study Type	Incidence	Sample Size	Population
Cairns et al.[22]	1973	Radiography	0–6%,	100	White Americans
Vertucci and Gegauff[5]	1979	Dye injection	5%	400	White Americans
Belizzi et al.[23]	1985	Radiography	3.3%	514
Sieraski et al.[12]	1989	Radiography	5–6%	400	North American
Zaatar et al.[24]	1997	Radiography	3.8%	79	Kuwaiti
Kartal et al.[25]	1998	Clearing technique	1.66%	600	Turkish
Chaparro et al.[26]	1999	Cross-sectioning	3.3%	150	Andalusian
Sert et al.[27]	2004	Clearing technique	3%	200	Turkey
Dehua et al.[28]	2004	Clearing technique	0.6%	326	Chinese
Lipski et al.[29]	2005	Radiography	9.2%	142	Polish
Javidi et al.[21]	2008	Radiography	0.5–6%	3
Awawdeh et al.[30]	2008	Clearing technique	1.5%	600	Jordan
Ateih MA et al.[31]	2008	Clearing technique	1.2%	246	Saudi
Ng’ang’a et al.[32]	2010	Clearing technique	11.7%	155	Kenyan
Ozcan et al.[34]	2012	Visual examination and digital radiography	1.5%	653	Turkish
Gupta et al.[36]	2015	Clearing technique	0.4%	250	North Indian
Stošić et al.[38]	2016	Longitudinal sectioning	3.4%	41	Serbian
Dinakar et al.[48]	2018	Clearing technique	2.32%	225	South Indian
Banga et al.[42]	2018	Clearing technique	2.32%	246	South Indian
Senan et al.[43]	2018	Dye injection	0.66%	75	North Indian
Overall Average		20	3.33%

Figure 3

Sample 1—three canals configuration (3-2-1)

Figure 4

Sample 2—three canals configuration (4-2-1)

DISCUSSION

Two distinct types of three canal maxillary premolars presentations, namely, two-rooted three canal and three-rooted three canal teeth, are found to be present.[7] The maxillary first premolar presenting with three canals, namely, mesiobuccal, distobuccal, and palatal, is similar to maxillary first molars. They are referred to as ridiculous, radiculous, or small molars. The incidence of three canal maxillary first permanent premolar has been reported to be between 0.5% and 11.7% as reported by various studies. The incidence of three canals has also been reported from different population groups.[89] In this study of human maxillary permanent first premolar teeth, the percentage of incidence of three canals in maxillary first premolars is “1.7%”.

Unusual anatomical configurations must be routinely assessed during clinical evaluation, radiographic assessment, and during endodontic treatment procedure. The occurrence of three canals with separate foramina in maxillary first premolar has been shown to be of very low percentage. It has also been documented as practically nonexistent in Asian populations.[10]

Good quality radiographs are mandatory for accurate detection of canals especially when analyzing the anatomic details of the root not clearly visible or distinct.[11] Disappearing or suddenly narrowing root canals should be taken into consideration during preoperative radiographic examination. If the path of the root canal cannot be traced, straightens, or broadens abruptly, the likelihood of an additional canal in the same or additional root should be suspected. This is because the additional canal is superimposed on the first one because of the two-dimensional nature of the radiographic image.[12] When an intraoral radiograph shows an instrument within the canal as eccentric in the roots, the possibility of presence of multiple roots should be considered.[13] Therefore a radiograph of good quality using paralleling radiographic technique with a cone shift in the right direction will provide additional insight into the internal anatomy of the root canal. Three-dimensional analysis methodologies such as cone beam tomography will surely help identify the variant anatomical configurations without fail. Where three root canals are present, the buccal orifices are not well defined on visual inspection. Use and correct directional placement of the endodontic explorer, use of magnification, or a small size file is necessary to identify the canals.[1415]

In certain instances, the two buccal canals arise from a narrow common main canal that extends from the pulp chamber and this creates an “S”-shaped shape of the canal that leads to restriction of instrumentation as it is difficult to confirm to that shape. This situation can be effectively managed by troughing for a depth of 1–2 mm in an apical direction and between the two buccal canals. This is similar to the preflaring technique in endodontics during intracanal preparation and “S”-shaped canal shape is straightened out, rendering apical instrumentation more easier and effective. This is carried out after the access preparation. Buccal canals that are narrow should be enlarged carefully and any excess removal of radicular dentin will result in a strip perforation. The safest technique is using a small endodontic file till the full working length. Using step back flaring, reverse flaring, and reverse filing as deemed appropriate after which the canal obturation is carried out. The common root morphology seen in maxillary first permanent premolar when three canals are present is three separate roots, each consisting of a single canal classified as the mesiobuccal, distobuccal, and the palatal.[16] The proper identification of variations in curvature and length of roots allows the operator to adjust his canal preparation technique, thereby avoiding iatrogenic complications.[17] These three-rooted maxillary first premolars resemble the adjacent molars and are therefore sometimes called “radiculous.” There are various methods by which the third canal can be identified using intraoral radiography. Though three-dimensional, the cone beam tomographic investigation cannot be used routinely because of economic and radiation-exposure concerns. The maxillary first premolar routinely has two canals. The presence of a third hidden canal should be searched during access if the pulp chamber appears too large in the mesiodistal plane on the intraoral radiograph. Access cavity outline is determined by the anatomical size and shape of the pulp chamber and the location of the root canal orifices. A modification in the access preparation with a T-shaped access outline helps in the identification of the third canal. This access modification procedure allows for an easy straight line accessibility to the canal system. If a third canal is suspected, the outline is extended by making a ditch cut at the bucco proximal angles from the buccal canal entrance to the cavosurface angle.[17] The buccal orifices may be close to each other and difficult to locate in three-canalled teeth. One may encounter an obstruction and a deflection to the buccal or the lingual side before further exploration of the canal while using a small file. The canal entrance will take an ovoid shape in the buccopalatal direction if there is a bifurcation of the canals in the middle third.[18] The crucial factors in correct diagnosis and easy negotiation are proper tactile feel technique and adequate precurving of the file.

CONCLUSION

In addition to having adequate knowledge on the variations of the root canal anatomy, periapical radiographs from different angles, careful examination of the pulp chamber floor, and use of dental operation microscope during the procedure are also important factors that contribute to successful identification of additional roots and canals.[19] The incidence of three-canalled maxillary first premolars bilaterally has also been reported. It is therefore recommended to look for a similar anatomic variation in the contralateral and opposing teeth during preliminary assessment of canal anatomy.[2021]

This study was carried out using cone beam tomographic analysis. On a statistical comparison and analysis of the results of the incidence of three canals obtained in this study with that of other studies performed using cone beam tomographic techniques [Table 2; Figure 3], the results were found to be statistically on par with that of other studies (P > 0.05). On a statistical comparison between the studies carried out using cone beam tomography technique and the studies carried out using other techniques [Table 3; Figure 4] on the incidence of three canals in maxillary first premolars, no significant difference was found (P > 0.05).

Dealing with maxillary premolars that have three canals during endodontic therapy is challenging. Clinicians should be aware of the variations of anatomy they may encounter when endodontically treating a maxillary first permanent premolar. They should apply this knowledge in a clinical scenario systematically on a case-wise basis. Awareness that they can encounter a third root canal even when three roots are not present, as also recognizing the presence of a third root preoperatively and making suitable modifications to endodontic treatment procedure, will go a long way in achieving successful treatment outcomes. In the maxillary first premolar due to anatomical factors even when the third canal is identified, preparation is a challenge and the operator should sufficiently be trained to handle these clinical skill levels.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.