New classification for pulp chamber floor anatomy of human molars.

Comprehensive knowledge of the entire root canal system is an essential prerequisite for successful routine endodontic treatments. The internal and external morphological configurations of roots and root canals are quite complex. Thus, several classifications have been put forth by researchers to appropriately understand the distinguishable features of root and root canal systems of multirooted teeth. Until now, the researchers have proposed new classification systems for a thorough understanding of the root canal systems, mainly concentrating on the root canal anatomy and anomalies. Moreover, with the advent of newer digital imaging systems, these classifications are more reproducible and relevant. They have further gained importance for the clinicians by acting as an aid in decision-making based on evidence-based dentistry. However, these classifications are primarily focused on the root canals, but none have assessed the anatomy of the pulp chamber floor. This review article delineates a novel Pawar and Singh molar pulp chamber floor classification© for the anatomy of maxillary and mandibular molars to ease the clinician's skills and further increase the prevailing literature for the benefit of researchers. Copyright:

INTRODUCTION

The word “endodontics” is derived from two Greek words; Endo meaning “inside” and Odonto meaning “tooth.” This is the branch of dentistry concerned with the study of pulp and periapical diseases and treatment.[1] Endodontic treatment is commonly referred to as root canal treatment which involves the removal of the infected pulp and periapical tissues, followed by the preparation of the root canal so that it can be sealed with an appropriate and best biocompatible material.[1] The basis of this surgical procedure is a series of approaches starting with the biomechanical tooth preparation, followed by microbial cleaning and control and complete obturation of the prepared root canal area.[2] However, the accessibility to the root canal orifices and precise de-roofing of the pulp chamber are important aspects for the success of these procedures. Otherwise, the entire procedure becomes time-consuming.[3] The first and foremost step is the access cavity preparation which involves thorough clinical preparation and allows clear access to the root canal orifices, thus facilitating straight-line access to the apical foramen, gaining authorized control over techniques of instrumentation, and further promoting the ability for perfect obturation.[4]

Barrett has stated that the study of pulp cavity morphology is the most complex among all the phases of anatomic systems.[5] The anatomy of the root canal has always been a topic of interest among the researchers – The vitality of pulp and its reaction with the periapical tissue for the basis of endodontics. The distinguishing line between the endodontic zone and the conservative zone is significant in the treatment and is based on precise pulp space detection. The exact knowledge of root canal anatomy, specifically locating position and the number of orifices on floors of the pulp chamber, is important in allowing the clinician to perfectly have straight-line access to the apex. Most of the focus is on the visual inspection of the root canal orifices and then proceeding with the instrumentation. If they are not visible, then the clinician might extend the coronal preparation which might cause perforation and loss of unnecessary tooth structure.[367] Thus, it is proposed that the anatomy of the pulp chamber floor plays a significant role in determining the access and evaluating the success of finding the extra canals in the tooth if there are any.[78910] Pulp space primarily comprises two parts: pulp chamber, which refers to the portion inside of the crown, while the pulp canal is the one which lies within the boundaries of the root. The pulp chamber is one single cavity, and it has varied dimensions according to the morphology of the crown and the basic structure of the roots. In cases of multirooted teeth, the pulp chamber depth generally depends on the position of furcation, and this might be extending beyond the structure of the anatomical crown.[11] While studying the anatomic morphology of the pulp chamber and its floor, it has been found that they possess peculiar characteristics. Moreover, it is rightly said that a well-designed access cavity is desirable for a successful endodontic result.[12]

Previous literature studies have focused on the importance of studying the pulp chamber floor anatomy. One such study conducted by Kaptan et al.,[13] on the pulp chamber floor of maxillary and mandibular molars, states that the access cavity has to be made in rhomboidal shape rather than the conventional triangular shape in case of maxillary molars, while in mandibular molars, it should be rectangular. Radiographs only allow us with a limited vision of the configurations of the canals, its degree of curvature in different planes, and whether the canals in a single root are separate or they merge. The degree of curvatures of the canal and the pulp chamber anatomy have been observed in the past, but there is no relevant information regarding the location of orifices of the single-rooted and multirooted teeth that could give us some prediction of the morphology of such canals.[14] Till recent times, the literature regarding the anatomy of the pulp chamber is very general and hardly specific enough to appropriately determine the orifice location and number. Short communications and clinical discussions of the case-based scenarios in the classroom have classically presented generalizations about the approximate number of canals in various teeth. Nevertheless, while considering an individual tooth, the mean number of canals is of less significance. Similarly, the representation of the location of canal orifices is being put forward in a nonsystematic manner. Essentially, most of the treatment decision is based on the visual inspection of the clinician. However, locating orifices might be difficult in the cases of heavily restored teeth, advanced caries with less tooth structure, or in retreatment cases wherein there is gouging by previous accessing. All of these cases appear as a challenge to the clinician, and the solution to this in the research article and textbook holds very little value as such.

Very limited focus has been put on this aspect, and no research has been conducted on the pulp chamber floor anatomy in any population. If there are variations in root canal anatomy in various populations, there can be a change of difference in the pulp chamber floor too. With this concept, a novel classification has been proposed in this study to observe the anatomy of the coronal pulp chamber, certain specific, consistent landmarks or configurations which exist, and whether they are quantifiable. If these landmarks are present, then they will act as a guide for locating orifices in a more systematic and with higher certainty. Furthermore, this novel classification of the anatomy of the pulp chamber floor can act as a guide for conducting future research studies.

THE RATIONALE FOR A NOVEL CLASSIFICATION SYSTEM

The majority of the failures in root canal treatment attribute to the inability to locate the extra canals, debride them, and fill them necessarily. Numerous researches are describing the anatomies of maxillary and mandibular permanent molars' root canals.[1516] These are multirooted teeth and have multiple canals. Since they have multiple canals, the in-depth knowledge of the coronal pulp chamber floor of the teeth is of utmost significance.[17] If the clinician is not aware of the chamber floor and its varied shapes, then the chances of missing root canals are high. The variability in the pulp chamber and root canals of maxillary and mandibular molar teeth can be attributed to many factors. The canal morphology of teeth is complex.[1819] Variations may occur due to age,[18] gender,[20] different races, and ethnic backgrounds of the population studied.[212223] Walton and Torabinejad in 1996[18] and Ash and Nelson in 2003[19] have noted that understanding the intricate pulpal configurations is necessary and desirable for the clinicians for the success of their treatments, otherwise the whole and sole cause of the failure may be the missed extra canal in the tooth. In 2004, Krasner and Rankow[3] conducted a study on 500 extracted teeth and observed the pulp chamber floor anatomy in all of these teeth. They formed new laws and guidelines for appropriate location of the root canal orifice in the pulp chamber.

A complete clinical and radiographic investigation of tooth angulation sulcus, occlusion, coronal clefts, cusp position, and restorations is essential before access preparation is begun. The clinician must be able to visualize before tooth entry the most expected location of the pulp chamber as well as canal orifice position.[24] During endodontic therapy, thorough knowledge and comprehension of pulp space morphology and its routine anatomic variation assist a clinician in attaining a successful outcome. Complications may occur like a perforation in the floor of the pulp chamber, incomplete de-roofing, iatrogenic pulp exposure during cavity preparation, dentinal gouging, and missed canals during the endodontic procedure. All this can be minimized by following a certain framework of the anatomy of the pulp chamber floor. This acts as a roadmap for understanding the location of the anatomical landmarks in the teeth and dictates an ideal access cavity preparation while exposing all the possible pulp canal orifices and with the little loss of intact tooth structure. These landmarks particularly include the roof and floor of the pulp chamber, the cementoenamel junction (CEJ), the central groove of the central fossa, and the furcation.[25]

Krasner and Rankow[3] have focused importantly on the knowledge of the laws of orifice locations, which guides the clinicians from causing lateral crown perforations, during cavity preparations. They have reinforced the law of centrality, which states that the pulp chamber is always centrally located at the level of CEJ. Hence, the clinician can always use CEJ as a peculiar target regardless of the nonanatomic structure of the clinical crown or presence of any restoration. CEJ can act as a reliable and relevant landmark for the location of the pulp chamber even though the crown is present at an obtuse angle to the root. Furthermore, the occlusal anatomy of the tooth might not have relevance to the position of the underlying pulp chamber, even after the restoration of a tooth.

Every tooth exhibits quite a variation in the anatomical configuration of pulp space. Majority of the cases show a difference in the morphology of maxillary first molars and are the reason for treatment complications.[26] As reported by Burns, maxillary first molar is the posterior tooth which is minimally apprehended and frequently treated. The first study of the root canal anatomy was done by Okumura[27] and Singh and Pawar.[28] He studied the tooth specimens by injecting a transparent dye to visualize the canal morphology and canal configurations and thus proposed a simple classification of the root canal. Another method studied by Pineda and Kuttler[22] involves the use of radiographs to study the anatomy of the root canal. The combination of two methods was applied by Weine et al.,[6] wherein radiographic methods and sectioning of the tooth both were used to accurately classify the configurations of root canal within a single root, further dividing into three types. These types were dependent on the pattern of division of the main root canal, from the pulp chamber orifice to its course along the root apex. Later, a classification system established on the evaluation of 200 maxillary second premolars, wherein the pulp cavity staining was done with a dye, was described by Vertucci et al.[29] and Gulabiwala's modification.[30] They were able to identify a total of eight accurate configurations. This classification of the root canal systems was much more complex as compared to the classification given by Weine et al. Hence, this newer modification was later added to the original classification system of Weine.[31]

Vertucci[32] concluded that the use of both staining and radiographic methods helps keep an intact root of a tooth specimen which is rendered transparent by the process of decalcification. Furthermore, the radiographic examination allows the investigator to visualize more peculiarly, almost all of the ramifications and divisions of root canals. Other studies conducted by Kulild and Peters,[33] Sperber and Moreau,[34] and Hartwell and Bellizzi[10] have appropriately noted that a second canal present frequently in the mesiobuccal-2 (MB-2) root of maxillary molars is at times difficult to clinically locate. This presence of the MB-2 canal has to be confirmed with the radiographic and clinical evaluations of the operator. Similar is the case in mandibular molars. Overall, the results of various clinical studies assessing the root canal configuration of mandibular molars have suggested the presence of a second canal in the distal root.

Concerning the studies conducted in the Indian context, Singh and Pawar[35] described that in comparison with other races, the prevalence of MB2 canals is higher among the Indian teeth. Hence, this can be attributed to a racial characteristic, as the incidence is found to be greater in Japanese, European, Caucasian, and Far Eastern races. Their findings discovered that African Ugandans, Brazilians, and Mexicans have a similar root canal morphology as that of the Indian molar teeth. Thus, racial differences can be appreciated well. About the mandibular second molars, a study conducted by Pawar et al.[36] fortifies that there is a racial predisposition while classifying the root canal morphology. In cases of the Indian population, there is a higher prevalence of c-shaped canals with fused roots when compared to the Korean or Chinese population. Moreover, the mesial roots show evidence of a larger variety of configurations of the root canal, which is of clinical importance.

Cimilli et al.[14] assessed the interorifical distance of MB and mesiolingual (ML) orifice and noted the relationship between the degree of curvature of root canal in the first mandibular molars. Kaptan et al.[13] reported in their study that the pulp chamber floor anatomy to locate the extra canals dictates the endodontic cavity preparation in the posterior teeth. They noted that very few samples presented triangular coronal pulp anatomy, which is generally referred to as normal anatomy, while most of the samples presented rhomboidal anatomy.[28] Thus, following the regular conventional triangular-shaped cavity preparation is not sufficient to locate the extra canal in cases of maxillary and mandibular molars. Thus, they mentioned that the shape of the access cavity is required to be changed to rhomboidal shape in cases of maxillary molars and a rectangular shape in cases of mandibular molars.

Hence, the in-depth exploration of the anatomy of the coronal pulp chamber floor is a necessity in the times of decision-making based on evidence-based dentistry. Thus, the morphological configurations of the pulp chamber floor have been contemplated to be the determining component for the endodontic access cavity, which is the first and the most important step of endodontic therapy. Lacunae in the knowledge of the coronal pulp chamber anatomy of the tooth being treated lead to failure of locating all the canals present in the complex teeth (molars). As stated previously, diminutive studies have been embossed regarding the significance of pulp chamber floor anatomy in the success of root canal treatment. Thus, this novel can help in identifying and distinguishing the shape for an endodontic access cavity shapes for the teeth studied while treating the population.

NOVEL CLASSIFICATION SYSTEM

Considering the lacunae in literature, it is the need of the hour to describe appropriately the primary classification of pulp chamber floor anatomy that can act as a framework for the clinicians. Hence, this review reports a novel classification for maxillary and mandibular molars. The location of orifices, the shape of the orifice, the shape of the pulp chamber floor, the presence of developmental lines, and pulp stones have been taken into consideration while developing this classification. All these factors ultimately are responsible for predicting the anatomy of the pulp chamber floor. It has slight variations in maxillary molars as compared to the mandibular molars. This difference can be attributed to the primary morphological structure differentiation of the two. Hence, the aim was to develop a novel classification system of the pulp chamber floor anatomy of molars to ease the clinician's/operator's skills. The objectives targeted were as follows: (i) to assess the variations in the anatomy of pulp chamber floor of maxillary and mandibular molars, (ii) to establish a pulpal anatomical classification based on individual tooth type, and (iii) to assist the researchers/students/clinicians to excel in their clinical expertise and have a higher success rate of endodontic treatments.

THE PAWAR AND SINGH MOLAR PULP CHAMBER FLOOR CLASSIFICATION©

The described classification is copyrighted by the Copyright Office Government of India (Reg. No.: L-95492/2020; dated October 07, 2020). The classification of maxillary molars involves the description of the shape of the pulp chamber floor, primarily divided into four classes: K, Y, I, and others [Figure 1]. Depending on the location and number of the canal orifices and number of canals present in a single root, forming a peculiar alphabetical letter, the classification is devised as follows:

Figure 1

A schematic presentation of the Pawar and Singh molar pulp chamber floor classification© for maxillary molar teeth (K, Y, and I)

K – in maxillary molars with the presence of four canal orifices: MB, MB-2, distobuccal, and palatal, a line joining the distobuccal and palatal and another two lines radiating from the center of this line to MB and MB-2 would form an alphabetical letter “K”

Y – in maxillary molars having three canal orifices: MB, distobuccal, and palatal, when a line is formed joining all three canals in the center of the access cavity, it resembles the alphabetical letter “Y”

I – in maxillary molars with the presence of two canal orifices: buccal and palatal, a line can be joining both the canals resembling the alphabetical letter “I”

Others – include all those cases other than the abovementioned.

The classification of mandibular molars involves the description of the shape of the pulp chamber floor, primarily divided into five classes: H, Y, I, and others [Figure 2]. Depending on the location and number of the canal orifices and number of canals present in a single root, forming a peculiar alphabetical letter, the classification is devised as follows:

Figure 2

A schematic presentation of the Pawar and Singh molar pulp chamber floor classification© for mandibular molar teeth (H, Y, and I)

H – in mandibular molars with the presence of four canal orifices: MB, ML, distobuccal, and distolingual, two lines drawn joining the mesial and distal canals and a line joining the center of these lines resemble letter “H” (following the chamber floor anatomy)

Y– in mandibular molars with the presence of three canal orifices: MB, ML, and distal, a line joining all three canals in the center of the access cavity resembles letter “Y.” If there are four canal orifices: MB, ML, distobuccal, and distolingual (placed close to each other), a line mesial and distal canals and a line joining the center of these lines resemble the letter “Y”

I – in mandibular molars with the presence of two canal orifices: mesial and distal, a line joining both the canals resembles the letter “I”

Others – include all those cases other than the abovementioned.

The Pawar and Singh molar pulp chamber floor classification© was applied to the cut specimen of the maxillary [Figure 3] and mandibular molars [Figure 4].

Figure 3

Representative images of the pulp chamber floor of maxillary teeth on application of the Pawar and Singh classification

Figure 4

Representative images of the pulp chamber floor of mandibular teeth on application of the Pawar and Singh classification

CONCLUSIONS

The Pawar and Singh molar pulp chamber floor classification© will make it easier and act as an adjunct for the operators aiding in having a bird's eye view of the entire root canal system, combining the pulp chamber floor anatomy and the root and root canal configurations. Furthermore, future research studies can be conducted for testing the diagnostic reliability and accuracy of this classification.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.