Association of Remaining Dentin Thickness to the Degree of Inflammation in Coronal Pulp of Primary Molars

INTRODUCTION

Pulpal therapy in primary teeth is based on the validation of inflammatory changes in the pulp.^[1] There is scant literature available to support the signs, symptoms, and histopathological status of the inflamed coronal pulp, thus indicating the need for this study.^[2] Preservation of the primary dentition until its natural, expected exfoliation is critical in the child’s orofacial development because it retains arch length, essential for mastication, speech development, increases aesthetics, and therefore maintains an optimal oral environment.^[3]

The pulp is a highly specialised connective tissue that resides in a rigid environment, has complex blood circulation, and is abundant in cellular and neurological components required for the immunological function and sensation of the tooth. In the early stages of pulp inflammation, there are unexplored treatment possibilities, as current research focuses on how vascular reactions can be controlled and manipulated in a compromised dental pulp.^[4]

Remaining dentin thickness (RDT) serves as an excellent barrier for the pulp against pathological and iatrogenic damage. Due to the heterogeneity of the individual tooth morphology, pulp chamber calcification, and degree of reparative dentin formation, determining the residual dentin thickness is tricky, and the clinician is uncertain of the proximity of the pulp chamber during tooth preparation.^[5]

The RDT has an impact on the vitality of pulp. The decrease in RDT leads to the reduced number of odontoblasts, impacts the severity of pulpal inflammation by permitting easy penetrance of the bacteria.^[6] Reduced thickness of measured RDT is suggestive of prophylactic endodontic therapy in circumstances where the pulp’s future is uncertain.^[5]

As dentin permeability can be diminished by dentinal sclerosis and reparative dentine development, the pulp response is also influenced by the thickness and degree of calcification of the remaining dentin.^[7] A careful interpretation of the extent of carious lesion may help in determining the severity of the pulp inflammation and, as a result, establishing the appropriate endodontic treatment.

It is not feasible to adequately measure the pulpal inflammatory condition and severity in decayed primary molars, both of which are important criteria in determining the prognosis of primary teeth.^[7]

However, there is an increasing consensus that the remaining dentin thickness (the depth of undamaged hard tissue between the caries lesion and the pulp border) is a reliable predictor of potential pulpal reactions.^[8]

This study aims to associate the radiographic estimation of RDT to the degree of inflammatory changes in the coronal pulp of decayed primary molars and aid the clinician in formulating the appropriate treatment plan.

MATERIAL AND METHODS

Procedure and estimation of RDT

Pre-operative digital radiographs were taken, and RDT was measured using the SOPRO Imaging software. [Figure 1] The identified teeth received formocresol or chitosan (Axiostat®) pulpotomy. The required anaesthetic procedures were followed, and isolation was done with a rubber dam. After complete caries removal, coronal access was obtained with a high-speed bur with water spray to expose the pulp chamber and coronal pulp was amputated with a sterile spoon excavator, colour of the bleeding was observed, haemostasis was then obtained with a moistened cotton pellet and the pulp chamber was then filled with a thick mix of zinc oxide Eugenol.^[10]

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Figure 1:

Estimation of remaining dentin thickness using SOPRO software. Dark patches seen on the proximal surfaces of the primary molars are carious lesions.

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RESULTS

The study included 25 children from Mangalore South who reported to the Department of Pediatric and Preventive Dentistry, A B Shetty Memorial Institute of Dental Sciences, of which 25 primary molars whose pulpal status required the pulpotomy procedure.

Children with the mean age of 6.15 years [range = 4-9 years] participated in the study. The age and gender distribution did not show statistical significance for primary pulpal inflammation or RDT.

Pre-operative digital radiographs were taken, and Table 1 shows the measured values of RDT on the digital radiographs using SOPRO Imaging software. Post-histological reporting of the excavated coronal pulp, the observed degree of pulpal inflammation was noted.

The association between the measured RDT values with the degree of pulpal inflammation was then histologically assessed and evaluated using Duggal’s Classification system.^[11]

Out of 25 coronal pulp samples, 2 samples were reported to be insufficient by the pathologist, hence were not included in the study [Table 2].

Table 2 shows the association of RDT measured pre-operatively (ranging from <0.5 to 1.5mm) with the degree of pulpal inflammation after histological examination. There was no statistically significant association between RDT and the inflammatory status of coronal pulp (p >0.05).

DISCUSSION

Dental caries is one of the most common chronic disorders in children globally. It is a bacterial infection that causes tooth demineralisation and destruction of the hard tissues. The severity ranges from clinically evident early demineralisation to extensive cavitation leading to pulpal exposure.^[12]

The fundamental goal of pulp interventions is to preserve the tooth’s integrity and the health of its supporting tissues. The pulp of the primary teeth can be affected by caries, restorative procedures, and trauma. Endodontic therapy for primary teeth is classified into two types: vital pulp therapy (VPT) and non-vital pulp therapy treatment.^[3,13]

For reversible pulpitis, vital pulp therapy is the treatment of choice in both primary and permanent teeth to maintain pulp vitality and function. Pulpotomy is one of the most widely accepted approaches for treating cariously involved coronal pulp in primary teeth. The prime objectives of VPT in deciduous teeth are to cure pulpal injuries and to preserve the vitality of the radicular pulp, thereby maintaining the teeth as a natural space maintainer till the normal exfoliation period.^[3] The accuracy of pulpal inflammation is critical for the success of treatment, and advanced caries propagation involving more than half of the RDT is often linked with varying degrees of pulpal inflammation.^[14]

RDT is the thickness of the healthy dentine between the pulpal floor and the roof of the pulp chamber. Several methods have been tested to determine the RDT beneath carious lesions. These include electrical resistance^[15] and the Prepometer^[16] but the measurement on a radiograph is the most easily available approach to the dental practitioner. According to Jesse et al. and Kooistra et al., the measurement of RDT on histological sections is always considered to be the gold standard.^[17,18] Since measurements were calibrated with a grid, the recordings were accurate and repeatable, as tested by the principal investigator using the same procedure within a short time. The caries depth was calculated as a percentage of whole dentin thickness, as previously reported.^[8]

Digital radiography, because of its numerous advantages, including the ability to change and enhance images with suitable software, has become a viable alternative to conventional radiography. Daudibertiers et al. stated that improving the contrast in digital radiographs allows better visualisation of the carious lesion.^[19]

Everett and Fixott,^[20] and Krithika et al.^[21] proposed the use of a millimetre grid superimposed on the film as a method of evaluating the depth of carious lesions or the RDT. In the current study, the lead investigator measured RDT on the digital radiograph. This was repeatable and less time-consuming where a millimetre grid was superimposed using the SOPRO Imaging Software and RDT was measured [Figure 1]

The literature states that histological investigation can accurately assess the pathological state of the pulp. Duggal et al. established that pulp inflammation can develop at an early stage of proximal caries attack, and that pulp inflammation is generally substantial once proximal caries involvement manifests clinically with marginal ridge breakdown and when restorative treatments are done it results in a failure leading to re-treatment of the affected tooth.^[11]

The effectiveness of vital pulp therapy is largely dependent on the accurate assessment of pulp condition. Diagnosis of pulp pathology can be challenging, particularly in very young children, when a clear pain history and response to vitality tests may be less accurate. Furthermore, investigations have failed to demonstrate a substantial relationship between histological inflammatory alterations in the pulp and reported pain history, reactions to sensitivity tests and percussion, or even radiographs.^[8]

Duggal et al.^[11] reported caries-related pulpal inflammation in primary teeth and proposed a classification based on inflammatory responses in each layer of the pulp, which was used because the classification is based on objective, reproducible observations and, more significantly, gives clinically useful data regarding the amount of inflammatory dissemination across the coronal pulp. However, the limitation of this scoring system was that it did not furnish the pulpal inflammatory status, determining whether the observed pulpal inflammation was reversible or irreversible.

The participants in the present study reported with history of pain and food lodgement as their chief complaint and with the absence of any physiological mobility, swelling, sinus, or fistula. In the current study, out of 25 pulpotomised teeth, the coronal samples of 23 teeth were evaluated histologically and the observations recorded. Two samples could not be examined as the tissue was insufficient for histological examination.

Thorough histological examination showed a Class III degree of pulpal inflammation in 21 coronal pulp samples and Class IV in two [Table 1].

Table 2 enumerates the association between measured RDT to various degrees of pulpal inflammation reported post-histological examination, and it was statistically insignificant. However, the observed class III and IV degrees of inflammation in 91.3% and 8.7 % of the pulpally involved teeth, respectively, in the current study, is of great clinical value. This enables the clinician to understand that as the RDT decreases, the degree of inflammation is widespread in the primary pulp. The extensive nature of the inflammation calls for a more aggressive approach rather than conserving the radicular pulp.

In the current study, histological observations indicate the presence of mild, moderate, and chronic inflammatory components, such as lymphocytes, fibroblasts, and extravasated RBCs. The degenerative changes reported were necrotic pulp material with minimal cellularity and few dystrophic calcifications. The objective of the present study is to ascertain if there is a significant association between the clinical and radiographic RDT and the inflammatory status of the coronal pulp, and although the findings of the study were not statistically significant, the clinical, radiographic, histopathological, and RDT correlations add value to a robust treatment plan.

Despite the limitations of this study, which include radiographic measurements, RDT is not the singular factor to be considered for predicting the inflammatory status of the pulp; rather, as an adjunct, it will strongly complement the clinician’s subjective reporting and will aid in treatment planning. However, the clinician’s experience in deciding whether to preserve the vitality of radicular pulp in the event of deep cavities remains crucial to the success of vital pulp therapy procedures, and we can conclude that the RDT may serve as an additional indicator and predictor for successful pulpotomies.^[7]

The limitations of the study include the requirement of a larger sample size, more efficient radiological reading methods for measuring RDT, and precise assessment of the nature of the remaining dentin and the colour of bleeding under microscopic levels to offer a satisfactory result to our hypothesis and can be considered as the future recommendations for upcoming studies.

CONCLUSION

The present study evaluated the association between remaining dentin thickness (RDT) in decayed primary molars and coronal pulp inflammation. The findings suggest that RDT alone is insufficient to determine pulpal inflammation. A comprehensive diagnosis requires both clinical and radiographic assessments to guide appropriate treatment. Additionally, subjective and objective parameters must complement RDT for an accurate evaluation of pulpal status in primary teeth.