Prevalence of dens invaginatus and palatogingival groove in North India: A cone-beam computed tomography-based study.

Aim: The aim of this study was to study the prevalence of dens invaginatus (DI) and palatogingival groove (PGG) in maxillary lateral incisors, and the occurrence of apical periodontitis in association with these anomalies in North Indian population. Methodology: Maxillary lateral incisors in 163 cone-beam computed tomography scans were assessed to determine the presence of DI and PGG. Anomalies identified were then classified as per Oehler's and Gu's classification, respectively. Their side and gender predilection and association with apical and lateral radiolucency was also studied. Statistical Analysis: Descriptive data were reported as percentages. Chi-square analysis was used to determine the association with gender and side predilection.
Results: DI was present in 13.5% of the scans, while PGG was present in 7.3% of the scans. No significant gender and side predilection was observed. 6.67% of lateral incisors with DI and 25% of lateral incisors with PGG had an associated apical radiolucency. 33.33% of lateral incisors with PGG had an associated lateral radiolucency. Conclusions: There is a high prevalence of DI and PGG in maxillary lateral incisors. Copyright:

INTRODUCTION

Developmental anomalies predispose the tooth to pulpal and periradicular diseases and pose significant challenges to the root canal treatment.[1] By affecting thickness and mineralization of hard tissues of tooth, altering pulpal volume, creating inaccessible areas to routine oral hygiene measures thereby providing a safe niche for microorganisms, and adding complexity to endodontic intervention, developmental anomalies influence the disease progression and affect treatment outcomes.[2]

Two such common developmental anomalies that result in distorted relation of enamel, dentin, cementum, and periodontal ligament are dens invaginatus (DI) and palatogingival groove (PGG). Both of these entities are frequently encountered in clinical practice of endodontics and periodontology and have known predilection for maxillary lateral incisors.[34]

DI, also known as dens in dente, is reported to have a prevalence of 0.3% to 10%.[3] There also exists preponderance for symmetry-presence on one side of arch increases the likelihood of existence on other side also.[3] In Indian population, the prevalence of DI in maxillary lateral incisors has been reported to be 2.4%.[5]

PGG is a developmental aberration that occurs near cingulum of a tooth and extends along the root to varying lengths, altering the pulp cavity configuration and affecting enamel, dentine, and cementum thickness.[1] Occasionally, pulp cavity may communicate with periodontal space.[1] Sometimes, the groove may be so deep that a bifurcation and a small additional proximal root may also be present. The prevalence of PGGs has been reported to range from 0.5% to 9.58% in previous studies.[46789]

There have been many studies done across the countries documenting the prevalence of DI and PGG in different regions and ethnicities.[5810] Nevertheless, given the implications these entities have on treatment outcomes, there always exists a scope to supplement the available literature by utilizing advanced diagnostics instruments and employing different population cohorts.

Three-dimensional cone-beam computed tomography (CBCT) is a noninvasive diagnostic tool that helps provide three-dimensional anatomical configuration thereby facilitating diagnosis, classification, and treatment planning and improving treatment outcomes. Literature is sparse on utilization of this diagnostic tool to assess the prevalence of these two entities.[101112] Therefore, this study was planned to study the prevalence of DI and PGG in maxillary lateral incisors, their classification based on the extent of invagination, and the occurrence of apical periodontitis in association with these entities in Indian population.

METHODOLOGY

This retrospective study was done by the department of dentistry in collaboration with a maxillofacial radiological diagnostic center after obtaining approval from Institutional Ethics Committee (Registration number KCGMC/IEC/2020/15). The sample size was calculated using Daniel's formula with Z value as 1.96, value of expected prevalence as 20%, which was the maximum prevalence for either anomaly among previously reported literature, and precision as 5%. Based on these, the sample size needed to estimate the prevalence of DI or PGG was 246 teeth.

1062 CBCT scans taken from January 2017 to December 2020 for reasons such as implants, impaction, and large pathologies were screened for inclusion criteria, i.e., high quality scans with voxel size not more than 0.4 mm3 and involving bilateral permanent maxillary lateral incisors with complete root formation. No images were taken with specific intent to be used in this study. Maxillary lateral incisors with incomplete root formation, crown or root fractures, restorative or endodontic treatment, crowns, orthodontic brackets, and any other factors which may interfere with assessment were excluded from the study. Low-quality images, such as those with scattering or insufficient accuracy of bony borders in the anterior region and patient movement artifacts were also excluded. A total of 163 scans were found matching the inclusion criteria.

The CBCT machine used in this study was Newtom Giano (QR, Verona, Italy). It had a tube voltage of 90 kVp, pulsed beam current of 1–10 mA, and an automatic adjustment to exposure time according to the area of scan. The image acquisition was performed by an experienced maxillofacial radiologist according to the manufacturer's recommended protocol. Images were examined using the scanner's proprietary software (Newtom NNT Analysis software).

Confidentiality of data was maintained by recording data with identity number in place of names. The electronic data files were stored only in a password-protected electronic database.

Data collection format included the identity number, age, and gender of the patients. The evaluation of maxillary lateral incisors was done in all the three planes (coronal, sagittal, and axial) [Figure 1]. Scans were looked for the presence of DI and PGG by two experienced endodontists (VK, MA), and the anomalies were classified according to their extent into the root. Images were re-evaluated by the two endodontists together, with an interval of 2 weeks between evaluations. In case of disagreements, an experienced oral radiologist (lumbar puncture) was consulted to perform a third evaluation and a final consensus was reached. The diagnosis of PGG was confirmed by presence a v-shaped defect in otherwise continuous margins in axial sections of the roots of maxillary anterior teeth [Figure 2]. The continuity of this groove was traced as the sections were moved from coronal to apical and accordingly, classification of grooves was done. For classification of PGG, Gu's classification[13] was used, which classifies the PGG into three types: type I, the groove is short (not beyond the coronal third of the root); Type II, the groove is long (beyond the coronal third of the root) but shallow, corresponding to a normal or simple root canal; and Type III, the groove is long (beyond the coronal third of the root) and deep, corresponding to a complex root canal system.

Figure 1

Cone beam computed tomography images showing dens invaginatus in left maxillary lateral incisor in axial, coronal and transverse sections

Figure 2

Cone beam computed tomography images showing palatogingival groove in right maxillary lateral incisor in coronal and apical third of the root

DI was identified in sagittal and axial sections as an invagination lined by an opaque lining, representing the enamel-lined sac. For the classification of DI, Oehler's classification[14] was used, which classifies DI into three types: Type I, the invagination confined within the crown of the tooth and does not extend beyond level of the external amelo-cemental junction; type II, the enamel-lined invagination invades into the root but remains confined within it as a blind sac, there may, however, be a communication with the pulp; and type III, the invagination penetrates through the root and opens apically or laterally at a foramen.

SPSS software, version 19.0 (IBM Corporation, Armonk, NY, USA) was used for analytical statistics. The primary outcome was the prevalence of PGG and DI in maxillary lateral incisors. Predictive variables were gender and left and right side. Descriptive data were reported as percentages. Intra-rater and inter-rater reliability were measured using kappa statistics. Chi-square analysis was done to determine the association with gender and side of the arch. P < 0.05 was considered statistically significant.

RESULTS

Of the total 163 scans, 96 (58.9%) were male patients and 67 (41.1%) were female patients. Out of these, DI in maxillary lateral incisors was found in 22 patients making the person prevalence for lateral incisors to be 13.5%. Among these scans, 14 (63.64%) had unilateral dens, while 8 (36.36%) had bilateral dens, making a total of 30 lateral incisors with DI. Thus, the total tooth prevalence of DI among maxillary lateral incisors studied was 9.20% [Table 1]. Three maxillary central incisors and one maxillary canine also had DI in the studied population, making the overall tooth prevalence of DI among maxillary anterior teeth to be 3.47%. 23 (67.65%) teeth were classified as Oehler's Type I, and 7 teeth (32.35%) with Oehlers Type II [Table 2]. No Type III DI was found among the studied cases.

Table 1

Analysis of gender and side predilection of dens invaginatus and palatogingival groove in maxillary lateral incisors in North Indian population

	Number of teeth	Tooth prevalence of the anomaly, n (%)	P
Dens invaginatus
Gender
Female (n=67)	134	11 (8.21)	0.627
Male (n=96)	192	19 (9.89)
Side
Right	163	14 (8.59)	0.358
Left	163	16 (9.82)
Total	326	30 (9.2)
Palatogingival groove
Gender
Female (n=67)	134	8 (5.97)	0.062
Male (n=96)	192	4 (2.08)
Side
Right	163	8 (4.90)	0.645
Left	163	4 (2.45)
Total	326	(3.68)

Table 2

Classification of DI by Oehlers classification12 and PGG by Gu’s classification11

	Type 1	Type 2	Type 3	Total
DI (Oehler’s classification)	23 (67.65%)	11 (32.35%)	0	34
PGG (Gu’s classification)	7 (58.3%)	2 (16.67%)	(25%)	12

PGG was found in 12 scans making person prevalence to be 7.36%, out of which 4 (33.33%) were on the left side and 8 (66.67%) were on the right side. Out of 12 grooves, one was present on mesial aspect, 4 on distal aspect, while 7 were on mid-palatal aspect. No case of bilateral PGG was found among the studied population, making the tooth prevalence among maxillary lateral incisors to be 3.68% [Table 1]. As per Gu's classification, 58.3% of these PGG were type I groove, 16.67% were type II, and 25% were Type III. One scan had PGG on the right side while DI on the left side. The intra-rater reliability and inter-rater reliability was more than 0.8 for both DI and PGG.

Person prevalence of DI was slightly more in males (14.6%) than females (11.9%), however, the association with gender was not statistically significant by Chi-square tests (P = 0.627). Similarly, person prevalence of PGG was more in females (11.9%) as compared to males (4.2%), with difference being statistically insignificant (P = 0.062).

A periapical radiolucency was found in 6.67% of the teeth with DI. However, the association was not statistically significant (P = 0.135). 25% of the teeth with PGG, on the other hand, were associated with a periapical radiolucency, and 33.33% with a lateral radiolucency, with a statistically significant association (P = 0.000 and P = 0.005, respectively).

DISCUSSION

An accurate preoperative assessment of tooth anatomy and its common variations is a sine qua non for successful treatment outcomes. Both of the entities studied in the current research have fairly common occurrence and pose daunting challenges to predictable treatment outcomes.

There have been repeated attempts to measure their prevalence utilizing varied means such as careful clinical examination, microscopic examination of extracted teeth, and two-dimensional radiography. These means have helped establish the approximate prevalence of DI and PGG. However, there exist some limitations in the above-mentioned methodologies to elucidate the prevalence of DI and PGG with precision. Clinical examination alone for diagnosis of PGG is limited by overlying gingival tissues and alveolar bone and is unable to confirm the presence of periapical pathology. Extracted teeth examination cannot yield any information over the periapical pathology, or unilateral/bilateral pattern, and suffers from sampling bias as most anterior teeth are extracted due to periodontal reasons. Two-dimensional radiographic examination, though is crucial in establishing the presence of associated periapical pathology, does not allow accurate examination of these two entities. Cone-beam computed tomography, however, is an excellent tool capable of providing details as good as those obtained with in vitro methods, along with the advantages of clinical studies. It has been used as an extremely helpful tool in numerous case reports for assessing the morphological details of teeth with DI and PGG and to aid in endodontic management.[1516]

The prevalence of DI in the studied lateral incisors of this study was 13.5%. Published literature shows a wide variation in prevalence in various regions and done by various methods. Five teams of researchers, who used only panoramic radiographs to assess the prevalence of DI reported the person prevalence to be in the range of 0.17%–3.8%,[1718192021] while those using a combination of panoramic radiography with either clinical examination or periapical radiography reported the same to be 2.5%–12%. Capar et al.[22] in 2015 compared the presence of DI by using CBCT and panoramic images rendered from CBCT images. They reported the DI person prevalence to be 10.7% in CBCT images, while only 3% in the CBCT rendered panoramic images. This finding corroborates our study where the use of CBCT resulted in a higher prevalence of 13.5%, as compared to the previous studies. The accurate representation of external and internal anatomy by CBCT must have attributed to high diagnostic frequency of DI using CBCT.

The person prevalence of PGG in the present study was 7.36%, while the prevalence reported in published literature ranges from 0.5% to 9.58%.[46789] In the present study, as high as 25% of the teeth affected by PGG had associated periapical radiolucency, and 33.33% of the teeth had a lateral radiolucency. A significant association between PGG and poor periodontal health has already been established,[7] where 26% of the teeth with PGG had periodontal pocket depth of >4 mm. Further, it may also be noted that in this study not all the teeth with PGG exhibited bone loss, as was also emphasized by Everett and Kramer[9] that not every instance of grooved lateral incisor leads to periodontal breakdown.

The present study demonstrated no gender predilection in the prevalence of DI. This is in accordance with work by Kfir et al.[23] and Cakici et al.,[24] however, differs from the results of Gündüz et al.[25] and Haghanifar et al.,[21] who reported more prevalence in women, and from Chen et al.,[26] and Colak et al.[17] who reported more prevalence in men. In the present study, 36.36% of the scans had bilateral DI. Previous reports have reported bilateral DI in 25%,[17] 24.5%,[27] 63.53%,[26] 82%,[10] and 64%.[11] We noticed no gender predilection in PGG also and the same has also been reported previously.[7]

An important issue related to CBCT based studies is that the risk from radiation exposure should outweigh the benefit. This was not a concern in the present study, however, as only preexisting CBCT records were re-evaluated rather than taking new scans specifically for purpose of the study. This, however, may add a selection bias, as the individuals with these anomalies may more likely have periradicular disease, and more likely to get the CBCT scan done, thus may present an inflated prevalence rate.

Limitations

This study investigated CBCT scans from only one radiological center; hence limited representation remains an issue. Moreover, only high-resolution scans were selected and teeth with obturated canals, crowns, and image artifacts were not analyzed, so under-representation of the sample might exist in this study.

CONCLUSIONS

There is high prevalence of DI and PGG in maxillary lateral incisors. These anomalies, especially PGG, have high degree of association with asymptomatic apical and lateral periodontitis. Hence, a routine screening for these anomalies should be an integral part of oral health checkup as well as diagnostic workup before endodontic treatment.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.