https://orcid.org/0000-0003-4973-2686
ABSTRACT
The study aimed to radiographically assess the characteristics of pulp stones (PS) and pulp canal obliteration (PCO) in teeth and examined their associations with various dental parameters such as caries, restorations, periodontal status, and age. This cross-sectional observational study was conducted at the Faculty of Dentistry, King Abdulaziz University between September 2022, and May 2023, involved 101 patients exhibiting 402 teeth with PS or PCO. Data were collected from periapical and bitewing radiographs, and analyzed by two calibrated dentists. Multiple dental parameters were assessed, including caries level, presence and level of restorations, periodontal condition, and age of the patient. The study population consisted of 62 females and 39 males, with an age range of 18–65 years. Inter- and intra-examiner reliability were high (Kappa = 0.88 and 0.98 respectively). PS were more commonly found in molars (81.2%), while PCO were presented in only 115 teeth (23%). Age significantly affected the type of calcification (p < 0.001), with PS more common in the 20–30 age group and PCO more common in individuals over 40. Presence of caries was significantly associated with the type of calcification (p = 0.013), but restoration was not. The majority of teeth with PS (76%) or PCO (93%) had healthy periodontium. Around 40% of teeth with PCO showed signs of periapical changes, a finding significantly different from those with PS (p < 0.001). Pulp calcifications were significantly associated with various dental parameters, including caries presence, age, and periodontal status. The findings provide crucial insights into the epidemiology and aetiology of pulp calcifications.
1. Introduction
Pulp calcifications were first identified as dental pulp nodules by Norman and Johnson in 1921, where terminology was refined later to ‘denticles’ [Citation1]. Currently, this calcification process is comprehensively investigated in endodontic literature and classified as pulp stones (PS) or pulp canal obliteration (PCO) [Citation2].
Pulp Stones, represent the localized accumulation of mineralized tissue within the pulp. These calcified formations been identified in carious or non-carious, deciduous or permanent, as well as unerupted teeth [Citation3]. PS can be classified into two groups according to the cell types that form them: Pulp stones formed by terminally differentiated odontoblasts are called true denticles, while pulp stones formed by pulp stem cells (odontoblast-like cells) are called false denticles [Citation4]. PS may either be unattached freely within the pulp tissue or attached to, or incorporated within, the dentinal layer [Citation5]. Their dimensions range from microscopic particles to sizable agglomerations that can effectively occlude the entire pulp chamber [Citation5]. Although more prevalent in the coronal pulp, instances in the radicular pulp have also been reported [Citation6]. Clinically, pulp stones tend to be asymptomatic and are often incidentally identified through standard radiological assessments [Citation7].
Pulp canal obliteration is characterized by the radiographic narrowing or complete obliteration of the root canal space, often accompanied by a yellowish discoloration of the clinical crown [Citation8]. This phenomenon is notably prevalent in teeth that have sustained traumatic injuries, mostly remaining asymptomatic; and are often incidentally discovered during routine clinical or radiological evaluations [Citation9].
The prevalence of PS and PCO has been extensively documented in the endodontic literature, albeit variations in results. Regarding PS, their prevalence ranged from 5% up to 22% [Citation10–13], with most studies averaged as 10% [Citation14–17]. When examined histologically, PS were histologically evident in 87.2% of the samples, while radiographic evidence of PS was limited to merely 14% [Citation18].
The reported prevalence of PCO incidentally when examining radiographic records was reported as 4.7% [Citation19]. The incidence escalates substantially in the context of dental trauma ranging from 16% to 27% [Citation9,Citation20], and can reach up to 56.9% [Citation9] especially in immature roots at the time of the trauma [Citation21].
The etiological factors contributing to PCO and PS revealed associations with a range of variables including dental trauma, age, and caries for PCO, as well as systemic or genetic conditions for PS [Citation22]. For PCO, dental trauma is commonly implicated, but other factors such as age and the presence of dental caries have also been reported [Citation8]. On the other hand, PS have been documented in individuals suffering from specific systemic or genetic disorders like dentine dysplasia, dentinogenesis imperfecta, Van der Woude syndrome, and renal diseases [Citation22]. Interestingly, a recent pilot study suggests that patients with cardiovascular disease exhibited a higher incidence of pulp stones in teeth with non-inflamed pulps, as compared to individuals with no history of cardiovascular diseases [Citation23]. Contradictorily, other research has failed to establish a definitive relationship between pulp stones and systemic diseases [Citation24].
Although pulp calcifications are known to be associated with a variety of factors such as aging, systemic diseases, dental caries, and trauma. Nonetheless, the literature currently offers limited insight into the relationship between pulp calcifications and other dental parameters, including periodontal status, caries level, presence, and level of restorations. Given this, the objective of this study was to radiographically assess the characteristics of distinct types of pulp calcification and to investigate their correlation with these various dental parameters.
2. Materials and methods
2.1. Data collection
The study received ethical approval from the institutional ethics committee before commencing the research (Reference number: 331-11-21). The present cross-sectional observational study took place at the Faculty of Dentistry, King Abdulaziz University. In the period between September 2022 and May 2023, the radiographic images of patients attending dental clinics were scanned. In case of the presence of any type of calcification in at least one tooth, patients were approached while in their dental visit. Inclusion criteria were patients above 18 years old, with evidence of PS or PCO in at least one tooth, patient accepting to participate in the study. Exclusion criteria included patients under 18 years old, and with inadequate quality radiographs. Demographic variables such as age and gender were recorded, and detailed medical histories were obtained, history of trauma, and any mouth habits were documented. Clinical examination included recording of teeth mobility, pocket depths discoloration, and crown status ().
Figure 1. Schematic diagram of the research methodology.
3. Radiographic examination
Periapical and bitewing radiographs were taken as part of dental treatment with size #1 or #2 digital plates using FOCUSTM Intraoral X-ray unit (KaVo Dental, Charlotte, NC, USA). Exposure parameters were set at kVp = 70 and mA = 7, with an average exposure time of 1 s. The Gendex DenOptix Digital Imaging System (Gendex, York, PA, USA) was utilized for image viewing in a dimmed room. The radiographs were evaluated independently by two experienced dentists to identify the presence of pulp stones and pulp canal obliteration and other parameters. In case of any differences in their diagnoses, it was resolved through discussion and reached a consensus.
A tooth was classified as having a pulp stone when a definite radiopaque mass was observed in the pulp space, while pulp canal obliteration was determined based on narrowing or complete closure of the root canal space seen on conventional radiograph. The location, size, and number of PS as well as location, extent of PCO were noted. Moreover, the status of the teeth including tooth number, caries presence and depth, restoration presence and depth, bone level, periapical pathology, and other tooth characteristics were also assessed and recorded. Both examiners underwent calibration, where they evaluated 50 images of calcified teeth that were not part of the current study. To prevent examiner fatigue, the viewing sessions were divided into multiple periods throughout the day, and the images were randomly ordered. To assess intra-examiner reliability, the same 50 images were re-evaluated in a separate session conducted at least two weeks apart.
4. Statistical analysis
Data were analyzed using the SPSS IBM program (Statistical Package for the Social Sciences 22.0). The significance level was set at 5% (α = 0.05). Inter- and intra-examiner reliability were assessed using Cohen’s Kappa correlation coefficient. Descriptive statistics, such as frequencies and percentages, were used to summarize the data on pulp stones, pulp canal obliteration. Chi-square tests or Fisher’s exact tests were employed to examine the associations between type of calcification and included variables.
5. Results
A total of 402 teeth exhibiting PS or PCO were included in this study, representing 101 patients with various dental conditions. The age range of the patients was 18 to 65 years, with a mean age of 33.2 years. The sample consisted of 62 females and 39 males. Inter- and intra-examiner reliability measures demonstrated strong agreement, with 0.88 and 0.98 kappa values respectively.
Among the radiographs assessed, PS were observed in 387 teeth, representing 76.9% among examined calcified teeth. The majority of PS were found within the pulp chamber of molar teeth; 81.2% of teeth with PS were in molars, with a smaller proportion located in premolars and anterior teeth. Pulp canal obliteration was detected in 115 teeth, 23% among calcified teeth as presented in (). The degree of calcification varied, ranging from partial to complete obliteration of the root canal space with a slightly greater prevalence of partial obliteration; in which 44.8% of teeth exhibiting PCO were completely obliterated (). Around 60–70% of teeth with PS, PCO or both were associated with intact teeth ().
Table 1. The distribution of pulp stones according to dental arches, sex, and location and teeth characteristics.
Table 2. Description of PCO and PS among examined teeth (n = 402); within the sample a total of 100 teeth exhibiting both PS and PCO.
A significant difference was noted within the type of calcification and age group. Teeth exhibiting both PCO and PS were greatest among patients above 40 years old. While PS exclusively were noted most among patients between 20 and 30 years old (Fisher exact test, p < 0.001).
The majority of examined teeth with PS, PCO, or both did not show any history of trauma (approximately 97–99% of all teeth). Among teeth exhibiting PS, or PCO a small proportion (ranging from 5 to 10%) were reported to have a history of orthodontic teeth movement, as stated by the patients, and approximately 6 to 19% of teeth with calcification were associated with mouth habits, especially clenching ().
Figure 2. Radiographic images showing pulp stone and pulp canal obliteration associated with different dental parameters.
Of the teeth exhibiting PS, 77% had no caries, while 23% showed radiographic and clinical evidence of caries. In the case of PCO, 46.7% of the affected teeth had no caries. Among teeth presented with both PCO and PS, the absence of caries was noted in 81%. Statistical analysis revealed a significant association between the type of calcification with the presence of caries level (Fisher exact test, p = 0.013) ().
Figure 3. Distribution of teeth exhibiting pulp canal obliteration (PCO), pulp stones (PS), and combined calcification types in relation to main clinical and historical factors, including oral habits, orthodontic tooth movement, and trauma history.
Upon classifying the caries level radiographically as shallow, and deep, it was observed that the level of caries was almost equally distributed in cases with PS, but greater evidence of deep caries in cases presented with PCO, or with both PS and PCO ().
The presence and level of restoration did not exhibit a significant difference in relation to the type of calcification. Among all examined teeth, nearly half of the teeth in each calcification group had a restoration. It was observed that deep restorations were more common among teeth exhibiting PCO, or both PCO and PS.
A tooth with a healthy periodontium was categorized in case of absence of bone loss, pocket depths is 2-3 mm, normal physiological mobility, intact lamina dura. Intact and healthy periodontium was observed in the majority of teeth with PS (76%), or PCO (93%).
Among examined teeth, 330 had available periapical radiographs. Majority of teeth with PS or both PS, PCO did not show signs of periapical pathosis. On the other hand, around 6 teeth (40%) of teeth with PCO solely had sort of periapical changes (widening of PDL and LD or periapical lesion). Compared to teeth with PS, or both, a significant difference was noted (Fisher exact test, p < 0.001).
6. Discussion
The objective of this investigation was to assess the radiographic features of distinct varieties of pulp calcifications, PS and PCO, and their associations with multiple dental metrics. A comprehensive evaluation was conducted on 402 teeth from 101 subjects, presenting with radiographic evidence of calcifications. Notably, high inter-examiner and intra-examiner kappa values (0.88 and 0.98, respectively) attest to the methodological consistency and reliability of our findings.
Our analysis demonstrated a significant predilection of PS for molar teeth in which 80% of examined teeth with PS were molars, corroborating previously published research. In particular, first molars showed a higher prevalence of PS than second molars and maxillary first molars more than mandibular [Citation11,Citation15,Citation16]. Contradictory reports exist regarding the incidence of pulp stones between genders. This study reported no significant gender-based differences, which is consistent with previous studies [Citation11–13]. While other studies indicate a higher prevalence in females [Citation24,Citation25].
Our data showed age-specific trends for PS and PCO occurrences. PS were predominantly observed in adults aged 20–30 years, whereas PCO was most prevalent in individuals over the age of 40, aligning with previous studies that have identified age as an influential factor in the occurrence of PCO [Citation11,Citation15]. Moreover, Cone Beam Computed Tomography analyses revealed that the only significant predictor for the manifestation of PCO was age, particularly in those above 60 years [Citation19]. It is established that the accumulation of secondary and tertiary dentin intensifies with advancing age, leading to a reduction in the dimensions of the pulp canal space and pulp chamber [Citation26].
In regards PS, the relationship with age presents a complex picture, with varying evidence from multiple studies. While some research has indicated an increased prevalence of PS with advancing age [Citation25], other studies have posited a contrary viewpoint [Citation27], suggesting that PS are statistically more prevalent in a younger demographic compared to older individuals, aligning with our findings. Additionally, some studies, reported no significant association between the prevalence of PS and age [Citation12]. This varying evidence underscores the need for further research to elucidate the relationship between age and the occurrence of PS.
Earlier research has indicated that among patients experiencing malocclusion and currently undergoing orthodontic interventions, 4.2% displayed the presence of pulp stones [Citation28]. Further, other investigations have suggested potential association between the occurrence of pulp stones and factors such as orthodontic treatment and traumatic occlusion [Citation29]. Similarly, PCO is generally understood to frequently result from traumatic events [Citation30]. Contrary to these findings, This study revealed a decreased prevalence of a history of trauma among teeth displaying calcification. Two critical factors warrant caution in interpreting these results. Firstly, the data on historical trauma and orthodontic treatments were reliant upon patient recall, a method subject to inherent limitations such as potential underreporting or unreliability. Secondly, the absence of a definitive correlation between PCO and a history of trauma should not be misconstrued as evidence for the absence of a causal relationship. While it is evident that the incidence of PCO surges following traumatic dental injuries, the presence of PCO in a tooth does not invariably indicate a past traumatic experience.
Additionally, our research highlighted a meaningful relationship between the type of calcification and the presence of dental caries. Teeth with PS, or both types of calcifications exhibited a stronger association with caries than those with PCO. While the majority of teeth in our study with either type of calcifications were intact – approximately 60–70%—this suggests that pulp calcification can take place even when the tooth remains structurally sound. Trowbridge’s study noted that pulp responses to carious lesions could induce calcific alterations, a finding corroborated by subsequent research [Citation10,Citation15,Citation31]. However, dystrophic calcification has been observed even in teeth free from caries or restorations, indicating that sporadic calcification can occur irrespective of dental disease [Citation25,Citation26,Citation32]. This implies that while canal calcification is generally a physiological process, certain factors, such as caries, may accelerate this process [Citation33].
Previous studies have indicated that 9% to 16% of teeth with PCO eventually develop pulp necrosis and periapical rarefaction [Citation30,Citation34]. Significantly, all instances of pulpal necrosis were closely linked to teeth that had sustained severe injuries, such as intrusion, extrusion, and lateral luxation, and those with mature roots formation [Citation20,Citation21,Citation35]. But further studies have also found that no variables were notably correlated with the occurrence of periapical pathology in teeth manifesting PCO [Citation19,Citation34]. These are consistent with our data, which demonstrated that teeth manifesting PCO exhibited a higher prevalence of periapical pathosis relative to teeth characterized by PS or a concurrent presentation of both PCO and PS. This increased incidence is likely attributable to the notion that the isolated presence of PCO in a tooth may be associated with traumatic injuries.
Although our study has shed light on several important correlations and findings of interest, it’s important to acknowledge its limitations. The study’s cross-sectional nature and focus on patients already receiving dental care restricted its scope. Future investigations could benefit from employing longitudinal designs, incorporating a broader and more diverse sample population, and possibly examining additional biochemical indicators.
7. Conclusion
The present study offers meaningful contributions to the understanding of radiographic features of pulp calcification and their interplay with various dental conditions. The types of pulp calcification change with age and have a significant link to the presence of caries. To corroborate these findings and delve deeper into the underlying mechanisms, additional research is warranted.
Author contributions
Conception and design: Ruaa Alamoudi and Shatha Zahran; data acquisition, analysis, and interpretation: Ruaa Alamoudi and Shatha Zahran; drafted the manuscript: Ruaa Alamoudi and Shatha Zahran; revised the manuscript: Ruaa Alamoudi and Shatha Zahran
Acknowledgments
We extend our sincere thanks to Dr. Fatimah M. Alzayer and Dr. Rawabi A. Alotaibi for their contributions in radiographic evaluation for this study.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Data availability statement
All data generated or analysed during this study are included in this article. Further enquiries can be directed to the corresponding author.
Additional information
Funding
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