Pulpal status of human primary molars with coexisting caries and physiological root resorption

Changes in Pulp and Roots of Deciduous Teeth during Different Stages of Physiologic Resorption: A Histologic Study

Background

Resorption of primary teeth and eruption of permanent teeth involves a complex series of changes. The cellular and histological changes occurring during the process of resorption vary stagewise. The knowledge of the changes occurring in the pulp of deciduous teeth would provide information about the resorptive process.

Aim

To evaluate the histologic changes of the pulp of deciduous teeth related to different stages of physiologic root resorption.

Study setting and design

To establish the cause and effect relationship, a contrived histologic study design was planned.

Materials and methods

A total of 60 extracted deciduous incisors, canines, and molars were included in the study. The remaining root length (RRL) was determined based on the standardized photographs. The teeth were then grouped into three based on the percentage of RRL. The teeth were subjected to decalcification with 5% nitric acid, following which histological processing was performed.

Statistical analysis

The present study being a qualitative study design, descriptively explains the histologic findings, and no statistical tests have been applied.

Results

During the initial stages of resorption, there were no histological alterations noted in the pulp, particularly in the cervical 3rd, with the cellular structure relatively maintained. As the resorption progresses, reversal lines were evident, indicating a process of repair occurring simultaneously during the process of resorption. With further advancement, the repair is overtaken by the resorption indicated by the presence of resorptive cells. Neovascularization and an increase in immune cells are also evident in advanced stages.

Conclusion

The pulp exhibits progressive changes as the resorption continues from stage I to stage III. The changes vary from a smaller number of immune cells and odontoclasts in stage I to increasing number of the same as resorption progresses.

How to cite this article

Murthy P, Bhojraj N, Hegde U. Changes in Pulp and Roots of Deciduous Teeth during Different Stages of Physiologic Resorption: A Histologic Study. Int J Clin Pediatr Dent 2023;16(3):437-443.

Improving radiographic diagnosis of pulpo-periodontal complications in primary molars by training: Application in education and clinical research

INTRODUCTION

The objective of this study was to assess an original learning intervention to train students and paediatric dentistry teachers in radiographic diagnostic accuracy of pulpo-periodontal complications in primary molars.

MATERIALS AND METHODS

The learning intervention was based on 250 different randomly ordered radiographs of primary molars within three quizzes (A, B and C) for 5 sessions (S): quiz A (50 X-rays), B and C (100 X-rays) were, respectively, completed in S1 to assess the extent of agreement with 5 experts' diagnoses, in S2 and S3 (B at days 8 and 23) and in S4 and S5 (C at days 90 and 105). During S1 and at the end of S3 and S5, the participants (48 students and 16 teachers) were informed of correct diagnoses. A satisfaction questionnaire was completed by all the students. Alongside the descriptive analyses, generalised linear mixed model (GLMM) analyses assessed the odds of participants' correct diagnosis over the study duration.

RESULTS

At S1, the odds of diagnostic accuracy among students were significantly lower than those among the teachers. After receiving feedback at S1, GLMM analyses showed that among all the participants, accuracy improved over time with the odds of correct diagnoses higher in S2-5 than in S1; and there were similar increases across sessions between teachers and students, except in S3, where the improvement among teachers tended to be greater than that among the students. All students were satisfied though one-third reported that quizzes with 100 radiographs felt too long.

CONCLUSION

The online case-based learning was a good training format for dental education.

Advances in the Study of the Mechanisms of Physiological Root Resorption in Deciduous Teeth

Physiological root resorption of deciduous teeth is a complex physiological process that is essential for the normal replacement of deciduous teeth and permanent teeth in clinical practice, but its importance is often overlooked due to the presence of permanent teeth. This physiological process includes not only the resorption of hard tissues of deciduous teeth, such as dentin and cementum, but also the elimination of soft tissues, such as pulp and periodontal ligament (PDL). However, the mechanisms of physiological root resorption are not yet clear. In this article, the advances of research on the mechanisms related to physiological root resorption will be reviewed in two main aspects: hard tissues and soft tissues of deciduous teeth, specifically in relation to the effects of inflammatory microenvironment and mechanical stress on the resorption of hard tissues, the repair of hard tissues, and the elimination and the histological events of soft tissues.

Comparison of nerve fibers in the deciduous first and second molar teeth: an in vitro study

INTRODUCTION

Sensory nerves of the tooth pulp have been evolved in both deciduous and permanent teeth for conducting possible damages to the teeth. Although it has been reported that the deciduous tooth's pulp is histologically similar to permanent teeth, the difference in the density of nerves between the first and second deciduous molars has been reported in no studies.

AIM

The aim of the study was to investigate the histological assay of pulpal nerves and assess the relationship between diameter and density of nerve fibres in the first and second deciduous molar teeth.

MATERIALS AND METHODS

In this in vitro study, 15 deciduous first and 16 deciduous second extracted from molar teeth belonging to children aged from 5 to 8 years were studied. After fixation, the decalcified teeth were sectioned and then stained with silver solution and calcitonin gene-related peptide (CGRP) antibody. The mean diameter of myelinated fibres, un-myelinated fibres, and density of peripheral network fibres of dental pulp were examined.

RESULTS

The results showed that the mean diameter of myelinated and non-myelinated fibres and density of nerve fibres were significantly more in the second molars (4.269, 2.328 µm, 2.6 fibres per unit area) compared to the first molar teeth (3.793, 2.093 µm, 1.8 fibres per unit area) (P < 0.032, 0.019, 0.003, respectively). An important finding in this study, which is reported for the first time, is the presence of fatty cells (adipocytes) in pulp tissue of some of the first deciduous molars as well as the second molars.

CONCLUSIONS

Based on the results of the current study, differences between nerve fibres of first and second molar teeth are significant. It could be concluded that the less sensitivity to pain of the first deciduous molars compared with the second deciduous molars, is due to the lower nerve density of this tooth.

Immunocytochemical characterization of primary teeth pulp stem cells from three stages of resorption in serum-free medium

BACKGROUND/AIMS

Dental pulp stem cells from primary teeth cultured in serum-free conditions may have clinical use for the repair and regeneration of teeth as well as other complex tissues and organs. The aim of this study was to test the change in the stem cell markers expression/ stem cell population in human primary pulp cells at the different stages of root resorption.

METHODS

Caries-free human primary canines at defined stages of physiological root resorption were included (n = 9). In vitro cultures were established in xeno-free, serum-free Essential 8™ medium with human truncated vitronectin for cell attachment. An embryonic stem cell line (GENEA002) was used as a positive control. The expression of embryonic stem cell markers (Oct4, Nanog and Sox2), neural crest stem cell markers (nestin and Dlx2) and mesenchymal stem cell surface markers (CD90, CD73 and CD105) were investigated by immunocytochemistry. Mesenchymal stem cell markers CD105, CD73 and CD90 and haematopoietic markers: CD45, CD34, CD11b, CD19 and HLA-DR were quantified with flow cytometry.

RESULTS

The early neural progenitor markers nestin and Dlx2 were detected in most serum-free cultured dental pulp stem cells, regardless of the tooth resorption stage from which they were harvested. Only isolated cells were found that expressed the embryonic stem cell transcription factors Oct4A, Nanog and Sox2, and in the late stages of resorption, no Oct4A was detected. The majority expressed the mesenchymal stem cell markers CD90, CD73 and CD105. Flow cytometry found positive signals for CD90 > 97.3%, CD73 > 99.6% and CD105 > 82.5%, with no detectable differences between resorption stages.

CONCLUSIONS

This study identified populations of dental pulp cells in vitro with markers characteristically associated with embryonic stem cells, neural crest-derived cells and mesenchymal stem cells. Flow cytometry found CD105 expressed at lower levels than CD90 and CD73. The consistency of stem cell marker expression in cells cultured from teeth at different resorption stages suggests that pre-exfoliated primary teeth that are free of caries may provide a convenient source of multipotent stem cells for use in regenerative medicine.

Post-mitotic odontoblasts in health, disease, and regeneration

OBJECTIVE

Description of the odontoblast lifecycle, an overview of the known complex molecular interactions that occur when the health of the dental pulp is challenged and the current and future management strategies on vital and non-vital teeth.

METHODS

A literature search of the electronic databases included MEDLINE (1966-April 2019), CINAHL (1982-April 2019), EMBASE and EMBASE Classic (1947-April 2019), and hand searches of references retrieved were undertaken using the following MESH terms 'odontoblast*', 'inflammation', 'dental pulp*', 'wound healing' and 'regenerative medicine'.

RESULTS

Odontoblasts have a sensory and mechano-transduction role so as to detect external stimuli that challenge the dental pulp. On detection, odontoblasts stimulate the innate immunity by activating defence mechanisms key in the healing and repair mechanisms of the tooth. A better understanding of the role of odontoblasts within the dental pulp complex will allow an opportunity for biological management to remove the cause of the insult to the dental pulp, modulate the inflammatory process, and promote the healing and repair capabilities of the tooth. Current strategies include use of conventional dental pulp medicaments while newer methods include bioactive molecules, epigenetic modifications and tissue engineering.

CONCLUSION

Regenerative medicine methods are in their infancy and experimental stages at best. This review highlights the future direction of dental caries management and consequently research.

Association of S100 calcium-binding protein A12, receptor for advanced glycation endproducts, and nuclear factor-κB expression with inflammation in pulp tissues from tooth caries

AIM

S100 calcium-binding protein A1 (S100A12) is a pro-inflammatory molecule which is secreted during inflammation and induces chemotaxis and the production of pro-inflammatory cytokines via interaction with receptor for advanced glycation endproducts (RAGE) and subsequent, activation of nuclear factor-κB (NF-κB). The present study was designed to determine the expression levels of S100A12, RAGE, and NF-κB in the inflamed pulp of carried teeth.

METHODS

In the present study, mRNA from 50 inflamed pulp and 50 healthy pulp were used for expression studies using real-time polymerase chain reaction. The expression levels of S100A12, RAGE, and NF-κB were compared between inflamed and healthy tissues.

RESULTS

The results revealed that the expression of S100A12, but not of RAGE or NF-κB, was significantly decreased in inflamed pulp when compared to healthy pulp. mRNA levels of RAGE were also increased in the inflamed pulp taken from men when compared with women.

CONCLUSION

The results suggest that S100A12 does not participate in the induction of inflammation in dental pulp. However, RAGE can participate in the inflammation in the pulp of males.

Axonal Degeneration in Dental Pulp Precedes Human Primary Teeth Exfoliation

The dental pulp in human primary teeth is densely innervated by a plethora of nerve endings at the coronal pulp-dentin interface. This study analyzed how the physiological root resorption (PRR) process affects dental pulp innervation before exfoliation of primary teeth. Forty-four primary canine teeth, classified into 3 defined PRR stages (early, middle, and advanced) were fixed and demineralized. Longitudinal cryosections of each tooth were stained for immunohistochemical and quantitative analysis of dental pulp nerve fibers and associated components with confocal and electron microscopy. During PRR, axonal degeneration was prominent and progressive in a Wallerian-like scheme, comprising nerve fiber bundles and nerve endings within the coronal and root pulp. Neurofilament fragmentation increased significantly during PRR progression and was accompanied by myelin degradation and a progressive loss of myelinated axons. Myelin sheath degradation involved activation of autophagic activity by Schwann cells to remove myelin debris. These cells expressed a sequence of responses comprising dedifferentiation, proliferative activity, GAP-43 overexpression, and Büngner band formation. During the advanced PRR stage, increased immune cell recruitment within the dental pulp and major histocompatibility complex (MHC) class II upregulation by Schwann cells characterized an inflammatory condition associated with the denervation process in preexfoliative primary teeth. The ensuing loss of dental pulp axons is likely to be responsible for the progressive reduction of sensory function of the dental pulp during preexfoliative stages.