The Pulp Stones: Morphological Analysis in Scanning Electron Microscopy and Spectroscopic Chemical Quantification

Background and objectives: Pulp stones are hard tissue structures formed in the pulp of permanent and deciduous teeth. Few studies have evaluated their morphology and chemical composition. However, their formation, composition, configuration and role played in overall health status are still unclear. Clinically, they may be symptomatic; technically, they impede access during endodontic therapy, increasing the risk of treatment errors. Thus, this study aimed to morphologically analyze pulp stones and present their chemical quantification, identifying their main chemical elements. It also correlates the results with their possible induction mechanisms. Materials and Methods: Seven pulp nodules were collected from molar teeth needing endodontic treatment. The morphology of the stones was analyzed by scanning electron microscopy (SEM), and their chemical composition was determined by X-ray dispersive energy spectroscopy (EDX). Results: These structures varied considerably in shape, size and topography. The site of the stones in the pulp cavity was the factor that most affected the morphology. The majority of the stones found in the pulp chambers presented nodular morphology, while those in the root canals presented a diffuse shape, resembling root canal anatomy. The topography of the nodules showed heterogeneous relief, revealing smooth and compact areas contrasting with the rugged and porous ones. The chemical composition varied depending on the location of the nodule in the pulp cavity and the relief of the analyzed area. Radicular stones presented considerably lower calcium and phosphorus content than coronary nodules. Conclusions: The high cellularity rate of the coronal pulp predisposes this region to nodular mineralizations around injured cells. The presence of larger caliber vascular bundles and higher collagen fiber content in radicular pulp determines a diffuse morphological pattern in this region. Understanding the morphology and chemical composition of the pulp stones allows future translational pathways towards the prevention or treatment of such conditions.

Multiple Idiopathic Internal Root Resorption in an Adolescent: A Case R Multiple Idiopathic Internal Root Resorption in an Adolescent: A Case Report

Internal root resorption (IRR) refers to a slow or rapid progressive resorption process that occurs in the pulp cavity of the tooth or the dentin of the root. IRR occurs as result of odontoclast action; in many cases, the pulp tissue exhibits chronic inflammation, and odontoblasts and predentin do not appear on the dentin wall near the pulp. Exact predisposing factors have not been clearly elucidated; therefore, it is difficult to identify reliable data on the prevalence of IRR because of its scarce occurrence and pathology. Reports have indicated that IRR is more common in the primary than in the permanent teeth. This case report discusses a 17-year-old girl with multiple idiopathic internal root resorptions of anterior permanent teeth in a short period of a time and its management.

Follow Up on Simple (Closed) Extraction of Fractured Maxillary Canine Teeth in Domestic Ferrets (Mustela putorius furo)

Fractured canine teeth (especially maxillary canine teeth) are common in domestic ferrets (Mustela putorius furo). We evaluated (detailed oral/dental and radiographic examination under general anesthesia) 18 domestic ferrets affected by 23 complicated crown fractures of periodontally healthy permanent maxillary canine teeth over a 2-year period. Average age of the ferrets at the time of diagnosis was 2.6 years. Only three teeth were discolored on clinical examination. Out of 23 teeth, 22 were radiographically evaluated. No radiographic evidence of endodontic disease was observed in 11/22 canine teeth. Inflammatory root resorption was observed in 5/22, periapical lucency in 5/22 teeth, apical widening of periodontal ligament space in 6/22 teeth, and failure of the pulp cavity to narrow in 3/22 teeth. All animals were treated by simple (closed) extraction of the affected teeth. Histological examination of eight teeth was performed. Pulp appeared histologically vital in five (3/5 showed no radiographic evidence of endodontic disease), pulpitis was diagnosed in two (both without radiographic evidence of endodontic disease) and pulp necrosis in one case (dental radiographs revealed apical widening of periodontal ligament space and failure of the pulp cavity to narrow). All extraction sites healed uneventfully by the 2-week recheck examination. Long-term follow-up revealed development of post-extraction upper lip entrapment with mandibular canine tooth in eight out of 18 ferrets, which appeared clinically irrelevant. According to clients seven out of 18 ferrets showed an improved quality of life. Simple tooth extractions are warranted in ferrets affected by complicated crown fracture of the periodontally healthy permanent maxillary canine teeth.

Age-dependent decrease in dental pulp cavity volume as a feature for age assessment: a comparative in vitro study using 9.4-T UTE-MRI and CBCT 3D imaging

Evaluation of secondary dentin formation is generally suitable for age assessment. We investigated the potential of modern magnetic resonance imaging (MRI) technology to visualize the dental pulp in direct comparison with cone beam computed tomography (CBCT). To this end, we examined 32 extracted human teeth (teeth 11–48 [FDI]) using 9.4-T ultrashort echo time (UTE)-MRI and CBCT (methods). 3D reconstruction was performed via both manual and semi-automatic segmentation (settings) for both methods in two runs by one examiner. Nine teeth were also examined by a second examiner. We evaluated the agreement between examiners, scan methods, and settings. CBCT was able to determine the pulp volume for all teeth. This was not possible for two teeth on MRI due to MRI artifacts. The mean pulp volume estimated by CBCT was consistently higher (~ 43%) with greater variability. With lower variability in its measurements, evaluation of pulp volume using the MRI method exhibited greater sensitivity to differences between settings (p = 0.016) and between examiners (p = 0.009). The interactions of single-rooted teeth and multi-rooted teeth and method or setting were not found to be significant. For examiner agreement, the mean pulp volumes were similar with overlapping measurements (ICC > 0.995). Suitable for use in age assessment is 9.4-T UTE-MRI with good reliability and lower variation than CBCT. For MRI, manual segmentation is necessary due to a more detailed representation of the interior of the pulp cavity. Since determination of pulp volume is expected to be systematically larger using CBCT, method-specific reference values are indispensable for practical age assessment procedures. The results should be verified under in vivo conditions in the future.

Comparison of diagnosis of cracked tooth using contrast-enhanced CBCT and micro-CT

Objectives: To evaluate the diagnostic accuracy using sodium iodide (NaI) and dimethyl sulfoxide (DMSO) as contrast agent in cone beam computed tomography (CBCT) scanning, and compare this with micro-CT. Methods: 18 teeth were cracked artificially by soaking them cyclically in liquid nitrogen and hot water. After pre-treatment with artificial saliva, the teeth were scanned in four modes: CBCT routine scanning without contrast agent (RS); CBCT with meglumine diatrizoate (MD) as contrast agent (ES1); CBCT with NaI + DMSO as contrast agent (ES2); and micro-CT (mCT). The number of crack lines was evaluated in all four modes. Depth of crack lines and number of cracks presented from the occlusal surface to the pulp cavity (Np) in ES2 and micro-CT images were evaluated. Results: There were 63 crack lines in all 18 teeth. 45 crack lines were visible on ES2 images as against four on the RS and ES1 images (p<0.05) and 37 on micro-CT images (p>0.05). Further, 34 crack lines could be observed on both ES2 and micro-CT images, and the average depth presented on ES2 images was 4.56 ± 0.88 mm and 3.89 ± 1.08 mm on micro-CT images (p<0.05). More crack lines could be detected from the occlusal surface to the pulp cavity on ES2 images than on micro-CT images (22 vs 11). Conclusion: CBCT with NaI +DMSO as the contrast agent was equivalent to micro-CT for number of crack lines and better for depth of crack lines. NaI + DMSO could be a potential CBCT contrast agent to improve diagnostic accuracy for cracked tooth.

Refined tooth and pulp segmentation using U-Net in CBCT image

Objectives The aim of this study was extracting any single tooth from a CBCT scan and performing tooth and pulp cavity segmentation to visualize and to have knowledge of internal anatomy relationships before undertaking endodontic therapy. Methods: We propose a two-phase deep learning solution for accurate tooth and pulp cavity segmentation. First, the single tooth bounding box is extracted automatically for both single-rooted tooth (ST) and multirooted tooth (MT). It is achieved by using the Region Proposal Network (RPN) with Feature Pyramid Network (FPN) method from the perspective of panorama. Second, U-Net model is iteratively performed for refined tooth and pulp segmentation against two types of tooth ST and MT, respectively. In light of rough data and annotation problems for dental pulp, we design a loss function with a smoothness penalty in the network. Furthermore, the multi-view data enhancement is proposed to solve the small data challenge and morphology structural problems. Results: The experimental results show that the proposed method can obtain an average dice 95.7% for ST, 96.2% for MT and 88.6% for pulp of ST, 87.6% for pulp of MT. Conclusions This study proposed a two-phase deep learning solution for fast and accurately extracting any single tooth from a CBCT scan and performing accurate tooth and pulp cavity segmentation. The 3D reconstruction results can completely show the morphology of teeth and pulps, it also provides valuable data for further research and clinical practice.

Estimation of the Age and Reproductive Performance of Wild-Born and Escaped Mink (Neovison vison) Caught in the Wild in Denmark

The feral mink population in Denmark consists of two groups of animals: mink born in the wild and mink that have recently escaped from farms. The aims of this study were to: (1) estimate the reproductive performance and mortality of the Danish mink born in the wild (wild-born) and mink escaped from farms (captive-born); (2) discuss the likelihood of a self-sustaining population of wild-born mink in Denmark; and (3) model the relationship between the pulp cavity width and the age of mink. During 2018, 247 wild caught mink were sent for necropsy at the Danish National Veterinary Institute. Based on body length, 112 were determined as captive-born and 96 as wild-born. The mean litter size ± SE of wild-born females was 7.6 ± 0.9 (range: 5–11 kits) and for captive-born females 5.9 ± 0.9 (range: 1–10 kits). The relationship between age (in months) of mink and pulp cavity width was highly significant. Individuals with a pulp cavity width of >35% were younger than one year. Based on fecundity, the turnover of the mink population was estimated to be 66%, and the yearly mortality was estimated at 69%. Hence, the population is slightly declining. In conclusion, a feral reproducing mink population in Denmark persists without a continuous influx of captive-born mink from farms.