Understanding the anatomical variability of maxillary molars is critical in endodontic and surgical dental procedures. Typically, these molars exhibit a three-root configuration—one palatal and two buccal roots. However, anatomical anomalies such as additional roots or canals are well documented and can contribute to treatment failure if overlooked. One of the rarest yet clinically significant anomalies is the occurrence of four-rooted maxillary molars, which pose challenges in diagnosis, instrumentation, and treatment planning during endodontic therapy and extractions [1].

With the advent of cone-beam computed tomography (CBCT), detailed imaging of dental root anatomy has become more accessible and accurate, allowing better identification of unusual anatomical presentations [2]. A systematic review by Magnucki and Mietling determined that the global incidence of four-rooted maxillary first molars is approximately 0.047%, based on a meta-analysis of over 26,000 teeth [1]. These four-rooted molars most often present with two palatal and two buccal roots, deviating from the standard anatomical norm and complicating routine clinical protocols [3-5]. Several studies from different populations have documented this rare anatomical variant. In a northwestern Chinese population, Gu et al. identified four-rooted maxillary molars using CBCT, demonstrating the role of imaging in detecting such anomalies [5]. Similarly, Alghali et al. reported a 0.53% incidence of four-rooted maxillary second molars among Malaysian Mongoloids, and observed that the presence of two palatal roots often results in larger mesiodistal crown dimensions [6]. These findings suggest a regional and ethnic component to the prevalence of this anomaly and support the need for population-based studies. Failure to recognize and treat all root canals—especially in teeth with supernumerary roots—can lead to endodontic failure due to persistent microbial infection. Ghasemi et al. emphasized the importance of thorough knowledge of root anatomy in the success of root canal therapy and the prevention of post-treatment complications [7]. Aydın also showed that specific crown morphologies may be predictive of underlying root complexity, which can be useful in preliminary radiographic assessments [8]. More recently, Martins et al. conducted a multicenter cross-sectional meta-analysis and confirmed the presence of four-rooted maxillary molars across multiple populations, noting that these cases are often underreported due to inadequate imaging or clinician oversight [10]. Thus, proper identification through advanced imaging and an awareness of root variation is essential for clinical success [14,15].

This article presents findings from an observational study conducted on extracted maxillary molars to identify and document the incidence of four-rooted configurations, particularly among second molars. The objective is to contribute to the existing literature and improve clinical awareness of this rare anatomical variation.

Study Design and Setting

This was an retrospective, descriptive study conducted using archived data and specimens of extracted maxillary molars from the Department of Dentistry, Nalanda Medical College & Hospital, Agamkuan, Patna, Bihar. The study aimed to assess the prevalence and morphological features of four-rooted maxillary molars using a sample of extracted teeth.

Sample Selection

Archived carious extracted permanent maxillary molars with complete root formation (n=180) from departmental records. Only molars with complete root formation, intact structure, and proper documentation were included. Teeth with complete root formation, intact morphology, and without signs of resorption or fractures were included in the study. Teeth with incomplete roots, iatrogenic damage during extraction were excluded.

Cleaning and Storage

All extracted teeth were washed with normal saline and stored in 10% formalin for disinfection and preservation. The external debris and calculus were removed using ultrasonic scalers. The teeth were then individually coded for documentation and anonymization purposes.

Examination Procedure

The archived teeth were examined in 2025 by three independent examiners:

1. A postgraduate specialist in Conservative Dentistry and Endodontics.
2. A postgraduate specialist in Pedodontics.
3. A postgraduate specialist in Prosthodontics

Visual and tactile inspection was carried out under good illumination. Each examiner independently recorded the number of roots without knowing the findings of the other two examiners to minimize bias. Discrepancies, if any, were resolved by consensus discussion.

Data Recording and Classification

The number of roots was documented for each molar, and any specimen found with four distinct roots was subjected to further documentation of:

• Root distribution (e.g., number of palatal and buccal roots).
• Morphological description (size, shape, and divergence).

Teeth were photographed using a digital camera under standardized lighting conditions for archival and comparative analysis.

Statistical Analysis

All data were entered into Microsoft Excel 2019 and analyzed descriptively. The frequency and percentage of four-rooted molars were calculated. Inter-examiner reliability for root number identification was measured using Cohen’s Kappa coefficient. Due to the low expected frequency of four-rooted cases, inferential statistics were not applied.

A total of 180 extracted permanent maxillary molars were analyzed for root morphology. The most common finding was the presence of three roots, observed in the vast majority of specimens. Only one molar (0.56%) was found to have four roots, and no cases of single-rooted molars were identified.

Table 1: Distribution of Number of Roots in Maxillary Molars

Among the 180 extracted maxillary molars examined, the predominant root configuration observed was the classic three-rooted form, accounting for 91.67% (n=165) of all specimens. A smaller subset of teeth (7.78%, n=14) displayed two-rooted anatomy, predominantly in maxillary second molars with fused buccal roots. Notably, only one tooth (0.56%) exhibited a four-rooted configuration, highlighting the extreme rarity of this anatomical variation within the studied population.

Table 2: Laterality and Tooth Type of Four-Rooted Molar

The only four-rooted molar identified in this study was a left-sided maxillary second molar. It presented a 2-palatal + 1 mesiobuccal + 1 distobuccal root configuration. This morphology was unusual due to the presence of two clearly separated palatal roots, a feature more commonly associated with first molars or rare bilateral anomalies. The specimen did not display root fusion, and all roots appeared well separated on gross inspection.

Table 3: Examiner-wise Agreement on Root Identification

All three examiners — an Endodontist, one Pedodontist and one Prosthodontist — correctly identified the number of roots for all 180 teeth, including the four-rooted molar. The inter-examiner agreement was perfect (Cohen’s Kappa = 1.00), indicating strong reliability and consistency in root number assessment using visual and tactile inspection methods. This reinforces the validity of the observational findings and supports the role of experienced clinicians in detecting rare anatomical variants without advanced imaging tools.

.Table 1. Distribution of Number of Roots in Maxillary Molars (n = 180)

Table 2. Laterality and Tooth Type of Four-Rooted Molar

The single four-rooted molar identified was a left-sided maxillary second molar, with two palatal roots, one mesiobuccal, and one distobuccal root.

Table 3. Examiner-wise Agreement on Root Identification (n = 180)

All three examiners correctly identified the four-rooted case, showing perfect inter-observer agreement (Kappa = 1.0).

Maxillary molars are known for their complex and variable root canal anatomy, posing significant challenges in both endodontic and surgical treatments. While three-rooted maxillary molars are considered the anatomical normal, deviations from this standard—particularly the occurrence of a four-rooted molar—are exceedingly rare. In this retrospective study, only one case (0.56%) among 180 extracted maxillary molars exhibited a four-root configuration. This observation aligns with the low prevalence reported in the literature, where studies indicate a global incidence ranging from 0.04% to 0.5%, depending on the population and imaging modalities used [1].

A prominent multicenter study by Martins et al. revealed that four-rooted maxillary molars, although uncommon, have been documented globally, with prevalence affected by ethnicity, gender, and tooth type [10]. Similarly, Allawi et al. reported in their CBCT-based Syrian population analysis that the maxillary first molars exhibited multiple anatomical configurations, although no four-rooted cases were noted, highlighting the rarity of such presentations even in well-imaged cohorts [11]. In our study, the four-rooted molar was a left-sided maxillary second molar with two palatal and two buccal roots. This specific root configuration corresponds with that described by Fry et al., who emphasized that anatomical anomalies—especially those involving additional palatal roots—may significantly alter the proximity of the molar roots to critical anatomical structures like the maxillary sinus and the floor of the orbit [12]. While CBCT is the gold standard for detecting such configurations, this case was successfully identified through gross morphological inspection, suggesting that, in resource-limited settings, trained visual and tactile examination can still yield reliable anatomical assessments.

Root morphology also shows regional and ethnic variation. Pei et al., in a CBCT analysis of a Chinese population, documented a consistent relationship between the maxillary posterior molar roots and the maxillary sinus, particularly in molars with multiple palatal roots [13]. Similarly, Olczak and Pawlicka’s Polish population study found rare instances of four-rooted molars, underscoring that such anomalies are not exclusive to any single demographic group [14]. These findings stress the importance of population-specific anatomical databases for clinical planning and educational purposes. Anatomical classification schemes, such as the one proposed by Ghasemi et al., have attempted to standardize the categorization of maxillary second molar root morphologies into types based on the number and orientation of roots [7]. However, configurations with two palatal roots do not consistently fit into existing classifications, suggesting a need for newer schemes that incorporate rarer anatomical variants. In the present study, the identified molar may fall under a Type IV variant, but its distinct palatal bifurcation may warrant a unique subclassification.

The clinical relevance of identifying a four-rooted molar cannot be overstated. Failure to detect an extra root can result in untreated canals, incomplete debridement, and persistent periapical pathology, as emphasized by Madfa et al. in their CBCT study of Saudi populations [15]. Their data reinforce that while three roots are expected, vigilant clinical examination and radiographic assessment are essential—especially in cases where symptoms persist after initial treatment. In our study, the root morphology was confirmed by three independent examiners with complete agreement (Cohen’s kappa = 1.00), further validating the visual diagnostic approach when CBCT is not feasible.

Another noteworthy aspect of this study is that the four-rooted molar was found among second molars, which are typically associated with more frequent root fusion and simpler anatomy compared to first molars. This reinforces the importance of not dismissing second molars as “simple” cases, as anatomical variations can occur unpredictably. Lin et al. found a low but notable incidence of palatal root duplication in Taiwanese patients, again confirming the necessity for thorough pre-operative exploration [16].

This retrospective study identified a rare case of a four-rooted maxillary second molar among 180 extracted specimens, with a prevalence of 0.56%. The molar exhibited two palatal and two buccal roots, a highly uncommon anatomical configuration. Accurate identification was achieved through visual inspection by trained examiners, demonstrating the value of clinical expertise even in the absence of advanced imaging. Recognizing such variations is crucial to prevent endodontic failures and surgical complications. Greater awareness and documentation of rare root morphologies can enhance diagnostic accuracy and guide effective treatment planning in routine dental practice.

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