Analysis of the surface characteristics and mineralization status of feline teeth using scanning electron microscopy

Microspatial distribution of trace elements in feline dental hard tissues: early life exposure to essential and toxic elements

Introduction

Trace elements play a key role in dental tissue development, as dental hard tissues accumulate both essential and toxic trace elements during mineralization. Characterization of the spatial accumulation pattern of trace elements may provide insight into exposure to toxic elements over time and to the nature of disease processes affecting the hard dental tissues. Here, we present the first report of the use of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to map the microspatial distribution of multiple trace elements, essential and toxic, across feline dental hard tissues.

Methods

Eleven teeth were extracted from 8 cats. Nine teeth were from 7 cats diagnosed with idiopathic tooth resorption on intraoral radiographs prior to extraction. Two teeth were included from a cadaver that had no signs of tooth resorption on intraoral radiographs. The normal dental tissue was analyzed from each sample using LA-ICP-MS to map the microspatial distribution of essential and toxic trace elements across feline enamel, dentin, and cementum.

Results

Results showed a higher accumulation of barium and strontium in coronal dentin as compared to root dentin. The timing of the accumulation mirrors nursing timelines seen in teeth from human and non-human primates, consistent with barium and strontium being sourced from maternal milk. Results also showed a higher uptake of lead in the coronal dentin, suggesting this lead exposure was likely passed from mother to offspring.

Discussion

This work characterizes a baseline for elemental distribution in feline teeth linked to early life exposure to toxic elements such as lead and provides a framework for future studies investigating long-term environmental exposures to trace elements, essential and toxic, and their involvement in feline systemic and dental diseases.

Microcracks on the Rat Root Surface Induced by Orthodontic Force, Crack Extension Simulation, and Proteomics Study

Root resorption is a common complication during orthodontic treatment. Microcracks occur on the root surface after an orthodontic force is applied and may be related to the root resorption caused by the orthodontic process. However, the mechanisms underlying root resorption induced by microcracks remain unclear. In this study, a rat orthodontic model was used to investigate the biological mechanisms of root resorption caused by microcracks. First, the first molar was loaded with 0.5-N orthodontic force for 7 days, and microcracks were observed on the root apex surface using a scanning electron microscope. Second, to describe the mechanical principle resulting in microcracks, a finite element model of rat orthodontics was established, which showed that a maximum stress on the root apex can cause microcrack extension. Third, after 7 days of loading in vivo, histological observation revealed that root resorption occurred in the stress concentration area and cementoclasts appeared in the resorption cavity. Finally, proteomics analysis of the root apex area, excluding the periodontal ligament, revealed that the NOX2, Aifm1, and MAPK signaling pathways were involved in the root resorption process. Microcrack extension on the root surface increases calcium ion concentrations, alters the proteins related to root resorption, and promotes cementoclast formation.

Morphology of the Cementoenamel Junction in Permanent Teeth of Dogs: A Scanning Electron Microscopic Study

In human teeth, the cementoenamel junction (CEJ) can have different morphologies, known as Choquet cases or types: in type 1, the cementum overlaps the enamel; in type 2, the enamel overlaps the cementum; in type 3, the relationship between the cementum and enamel is edge-to-edge; and in type 4, there is a gap between the enamel and the cementum, with exposed dentin. Since little is known on the morphology of the CEJ in animals, the aim of this study was to characterize the structure of the CEJ of dog teeth by SEM. We studied 82 permanent teeth extracted from 4 dogs of similar size, aged from 7 months to 2 years. Teeth were grouped according to their size, sectioned and prepared for SEM. The teeth evaluated showed the 4 CEJ types. Type 3 was the most prevalent, being present, either alone or in combination, in 90.79% of the samples, followed by type 4 (present in 31.58% of the samples). Of the samples, 65.13% showed only one type, while 34.87% presented a combination of them. Types 3 and 4 were the only ones present alone (in 55.92% and 9.21% of the samples respectively), whereas the combinations between types 3 and 4 (20.40%) and types 1 and 3 (9.87%) were the most frequent. In all combinations, type 3 was predominant. The CEJ of the dogs evaluated showed a high degree of variability in the different types of teeth, within a same tooth, within the dentition of a single individual, and among individuals.

Root surface microcracks induced by orthodontic force as a potential primary indicator of root resorption

Root resorption is closely related to orthodontic force and affects orthodontic treatment with high incidence; however, the mechanism governing this effect is unclear. Microcracks are associated with bone resorption and may also play an important role in root resorption. This study aimed to assess the occurrence of microcracks on the root surface induced by orthodontic force, analyze the association between force and microcrack development, and propose potential measures to reduce microcracks. Different loads (0.5, 1, or 2 N) were applied between the left first molar and anterior teeth for different durations (1, 3, 7, or 14 days) in a rabbit model. The first molar was dissected and its surface was examined using scanning electron microscopy (SEM), which revealed the presence of microcracks on the compressed side of the root apices. The number, width, and length of microcracks were all positively correlated with the load magnitude and duration. The breaking strength of the root apex was tested by using a digital force tester. In addition, a finite element (FE) model was used to analyze the stress at the root apices and the crack propagation on the root surfaces. FE analysis calculated that the regions of maximum stress at the root apices were consistent with the microcrack regions observed via SEM. These results imply that orthodontic force can directly induce the occurrence and development of microcrack, and may contribute to further root resorption. Therefore, an appropriate interval and direction of orthodontic force may help reduce microcracks and prevent root resorption.

Dental Pathology of the Iberian Lynx (Lynx pardinus), Part II: Periodontal Disease, Tooth Resorption, and Oral Neoplasia

The Iberian lynx is an endangered felid that has been subject to an intensive, ongoing conservation program to save it from extinction. Identification of dental pathologies could play an important role in the survival of this endangered species. The prevalence of periodontal bone loss, tooth resorption, and oral neoplasia was evaluated in this species. Skulls of 88 adult specimens of the Iberian lynx ( Lynx pardinus) from the Doñana Biological Station (EBD-CSIC), Seville, Spain, were examined macroscopically and full-mouth dental radiographs of all specimens were performed. Different stages of periodontal disease were identified in 81.3% of teeth. Approximately two-thirds (64.8%) of the specimens examined had at least 1 tooth affected by stage 3 or 4 periodontal disease. Maxillary and mandibular incisor teeth accounted for a majority (59.4%) of teeth affected by stage 3 or 4 periodontal disease. Tooth resorption affected 12 teeth (0.63% of evaluated teeth) in 6 skull specimens (6.8% of skulls evaluated). Five of the teeth with resorptive lesions were detected on 1 skull specimen. Six teeth (50%) of those affected by tooth resorption were incisor teeth. Only 1 (1.1%) adult specimen showed signs of oral neoplasia. Our study concluded that there is a high prevalence of periodontal disease that could lead to impaired hunting ability, as well as may represent a threat to overall health and subsequent survival of this endangered species. The extremely low prevalence of tooth resorption in L pardinus could open new pathways in the discovery on the pathogenesis of tooth resorption in felids.

Structure-Function Correlative Microscopy of Peritubular and Intertubular Dentine

Peritubular dentine (PTD) and intertubular dentine (ITD) were investigated by 3D correlative Focused Ion Beam (FIB)-Scanning Electron Microscopy (SEM)-Energy Dispersive Spectroscopy (EDS) tomography, tapping mode Atomic Force Microscopy (AFM) and scattering-type Scanning Near-Field Optical Microscopy (s-SNOM) mapping. The brighter appearance of PTD in 3D SEM-Backscattered-Electron (BSE) imaging mode and the corresponding higher grey value indicate a greater mineral concentration in PTD (~160) compared to ITD (~152). However, the 3D FIB-SEM-EDS reconstruction and high resolution, quantitative 2D map of the Ca/P ratio (~1.8) fail to distinguish between PTD and ITD. This has been further confirmed using nanoscale 2D AFM map, which clearly visualised biopolymers and hydroxyapatite (HAp) crystallites with larger mean crystallite size in ITD (32 ± 8 nm) than that in PTD (22 ± 3 nm). Correlative microscopy reveals that the principal difference between PTD and ITD arises primarily from the nanoscale packing density of the crystallites bonded together by thin biopolymer, with moderate contribution from the chemical composition difference. The structural difference results in the mechanical properties variation that is described by the parabolic stiffness-volume fraction correlation function introduced here. The obtained results benefit a microstructure-based mechano-chemical model to simulate the chemical etching process that can occur in human dental caries and some of its treatments.

Morphology and age-related changes in calcospherites of human teeth: an ultrastructural study

BACKGROUND

Dentine has been examined extensively for age-related physiological changes, but there are limited data on age-related changes at ultrastructural level of dentine.

AIM

The present study aimed to examine age-related ultrastructural changes in calcospherites of human dentine under the scanning electron microscope.

MATERIALS AND METHODS

Thirty single rooted teeth of North Western adult Indians (18-75 years) were collected from the Department of Oral Health Sciences, PGIMER, Chandigarh. Labiolingual sections were prepared and morphology of calcospherites was studied at different locations (coronal, cervical, midroot and apical) of the tooth.

RESULTS

Morphologically, four types (I [small, unfused and discrete], II [partially fused and globular], III [large, completely fused] and IV [structureless]) of calcospherites were seen in the sample. With advancing age, type I calcospherites approached neighbouring crystals and changed their form to type II, which ultimately coalesced and transformed to type III. Results revealed that among different age groups (young, middle and old), calcospherites of only type I, II and III showed statistically significant differences in their shapes using Pearson's Chi-square test. Statistically non-significant differences were obtained in the shapes at different locations of the tooth.

CONCLUSIONS

Results showed that calcospherites get fused as age advances. There is a change in the shape of calcospherites based on the location of the tooth.

Multiple idiopathic cervical root resorption: a case report

AIM

To report a severe and rare case of multiple idiopathic cervical root resorption (MICRR) in an adult female.

SUMMARY

A healthy 27-year-old Chinese female, with no significant associated factors, presented with MICRR. Resorption progressed quickly and lesions varied in severity, involving 29 teeth and leading to the loss of 23 teeth over a period of only 3 years. The inner surface of the crown showed extensive areas with worm-eaten lacunar resorption, and the resorptive lesions had abundant lysosomes throughout their cytoplasm. Further, heavy deposits of reaction products were shown in variously sized lysosomes.

Oral examination in the cat: a systematic approach

PRACTICAL RELEVANCE

Oral examination in the cat is a process of observing both normal and abnormal, and should be an integral part of any wellness examination as well as a response to any specific complaint(s). The basis for an accurate diagnosis is meticulous attention to detail. It is essential that the clinician performs a whole body examination prior to examining the head and neck region.

STAGES OF EXAMINATION

A thorough oral examination involves four stages. The first stage is to review the current oral problem(s) by asking questions and listening carefully to the owner's responses; gaining a thorough medical/dental history may shed more light on the current problem(s). The second stage is an extraoral physical examination to visualise and palpate the head and neck regions in the awake patient. In the third stage the clinician performs an intraoral examination in the awake patient, before proceeding to the final stage, which is an extraoral and intraoral examination under general anaesthesia.

AIM

This article describes a systematic approach to the oral examination, based on these four stages. The aim of this process is not only to facilitate the making and recording of observations, but also to help avoid missing important clues that may aid in reaching a diagnosis. Common tooth pathologies in the feline patient are also briefly reviewed, paving the way for accompanying articles in this two-part Special Issue, which will provide further insight into these pathologies and discuss management approaches.

Tooth Resorption in the Swedish Eurasion Lynx (Lynx Lynx)

The etiology of tooth resorption in the domestic cat remains unknown. The high prevalence and progressive nature of the disease complicates defining healthy control groups. In order to evaluate the possible influence of various life style changes on the prevalence of tooth resorption, healthy control groups are a prerequisite. This paper presents a prevalence study for tooth resorption in a free-ranging wild felidae population. Skulls from 46 free-ranging Eurasian lynx (Lynx lynx) were examined. The age of the animals had previously been estimated based on cementum annuli in the maxillary right canine tooth. The dental examination included both dental probing and radiographic imaging. Complicated fractures of the canine teeth were found in 9/46 (19.5 %) skulls. In one fractured canine, apical root resorption and periapical lucency was detected. The root resorption was attributed to inflammatory resorption as a consequence of the initial dental trauma and necrotic pulp. No signs of tooth resorption were found in the remaining teeth. Supernumerary roots were detected in 18/46 skulls (39.1 %). Supernumerary “peg” teeth caudal to the mandibular first molar tooth were detected in 6/46 (13.0 %) skulls. Although further studies on dental ultra-structure are needed, the Swedish Eurasian lynx may, in the future, be useful as a healthy comparative model for studies on the etiopathogenesis of tooth resorption in the domestic cat.

Identifying early osteoclastic resorptive lesions in feline teeth: a model for understanding the origin of multiple idiopathic root resorption

BACKGROUND AND OBJECTIVE

Domestic cats commonly suffer from external osteoclastic tooth resorption, a disease with many similarities to human multiple idiopathic root resorption. In both diseases, it is unclear whether anatomical features of the tooth surface are associated with a predisposition for resorptive lesions. The aim of the present study was to investigate the origin and progression of early feline osteoclastic resorptive lesions in teeth exhibiting no clinical signs of disease.

MATERIAL AND METHODS

The entire surfaces of 138 teeth from 13 adult cats were analysed using back-scattered electron microscopy. The distribution of lesions was assessed by tooth type, location and between individuals.

RESULTS

Seventy-three (53%) teeth showed at least one resorptive lesion. Eleven (85%) cats had lesions, and there was a significant association between increasing age and incidence of resorptive lesions. The highest frequency occurred in mandibular molars (82%). On average, there were 3.5 lesions per tooth. Fifty-two (38%) teeth featured resorptive lesions at the cemento-enamel junction. Twenty-three per cent of teeth with resorptive lesions showed evidence of repair of lesions that was limited to the root surface. There was no evidence of repair of resorptive lesions at the cemento-enamel junction.

CONCLUSION

Resorption is prevalent without evidence of clinical disease, and occurred at younger ages than previously reported. It can initiate anywhere on the root surface, but lack of repair of lesions at the cemento-enamel junction indicates that mechanisms of replacement are absent or compromised in this region. Whereas resorption of the root may undergo repair, resorption at the cervix may progress to clinically evident lesions.