Enamel-dentine Junction Research Articles

Distinguishing Traditional and Internal Craze Lines in Human Enamel

Objectives: This study aims to introduce and differentiate between traditional craze lines and a newly identified type of line in enamel, termed an “internal craze line.” This novel classification enhances diagnostic precision and carries significant clinical implications for treatment strategies. The goal is to provide a clear description of these two types of lines, discuss their unique clinical implications, and highlight their differing appearances and staining characteristics, contributing to improved understanding and management of enamel anomalies. Method and materials: Four extracted teeth exhibiting visible and internal craze lines were selected and examined using a stereo microscope to observe the structural characteristics of the lines. Cross-sections of the coronal parts of the teeth were prepared to document the differences between traditional craze lines (extending from the dentin-enamel junction [DEJ] to the enamel surface) and internal craze lines (originating at the DEJ but terminating midway through the enamel). Additionally, intraoral observations were conducted under high magnification to identify the visual differences between the two types of lines, noting that traditional craze lines can be stained while internal craze lines cannot. Results: Microscopic examination revealed two distinct types of lines: traditional craze lines extending from the DEJ to the enamel surface and internal craze lines terminating within the enamel. Intraoral observations confirmed that these lines could be distinguished under high magnification. Traditional craze lines appear as continuous lines reaching the enamel surface and can be stained, whereas internal craze lines are shorter, do not extend to the surface, and cannot be stained. Conclusion: The identification of internal craze lines presents significant clinical implications. Differentiating between traditional and internal craze lines can enhance diagnostic accuracy and inform treatment decisions. Recognizing internal craze lines might indicate different etiologies or risk profiles compared to traditional craze lines, influencing preventive and therapeutic strategies in dental practice. Further research is needed to explore the prevalence, causes, and long-term impacts of internal craze lines.

Molar enamel–dentine junction shape of Pliobates cataloniae and other Iberian pliopithecoids

The phylogenetic relationships of the small-bodied catarrhine Pliobates cataloniae (∼11.6 Ma, NE Iberian Peninsula) have been controversial since its original description. However, the recent report of additional dentognathic remains has supported its crouzeliid pliopithecoid status. Based on the available hypodigm, the molar enamel–dentine junction (EDJ) shape of P. cataloniae is compared with that of other pliopithecoids from the same basin as well as both extinct and extant hominoids to further evaluate its pliopithecoid affinities. We also quantitatively compare the EDJ shape among these taxa by means of landmark-based three-dimensional geometric morphometrics using principal component analysis (PCA), canonical variate analysis, and between-group PCA. Permutation tests are performed to test whether Pliobates variation exceeds that of extant hominoid genera. Results indicate that Pliobates is similar in molar EDJ shape to other pliopithecoids, particularly crouzeliids. The variation displayed by Pliobates upper molars is less marked at the EDJ level than at the outer enamel surface, probably owing to differential enamel wear and intraspecific differences in enamel thickness. Multivariate analyses of EDJ shape show that all pliopithecoids (including Pliobates) cluster together in the PCAs, canonical variate analyses, and between-group PCAs and occupy a different portion of the morphospaces from extinct and extant hominoids. Posterior and typicality probabilities strongly support the classification of Pliobates as a pliopithecoid, wheras permutation tests fail to reject the single-genus hypothesis for the P. cataloniae hypodigm. We conclude that P. cataloniae is a crouzeliid pliopithecoid, as recently supported by cladistic analyses of craniodental characters, and that previous cladistic results that supported a stem hominoid status are attributable to postcranial convergences with crown hominoids. Our results further highlight the potential of three-dimensional geometric morphometrics analyses of the EDJ shape for better informing fossil primate alpha-taxonomy by means of quantitatively testing hypotheses about tooth shape variation.

Management of preeruptive intracoronal radiolucency (PEIR): a case series with up to 8 years follow-up.

Preeruptive intracoronal radiolucency (PEIR) is a rare dental anomaly often incidentally detected during routine radiographic examinations. This condition manifests as a radiolucent lesion beneath the enamel-dentin junction of unerupted teeth, particularly in mandibular molars, posing diagnostic and management challenges due to its asymptomatic nature. The treatment of PEIR depends on the extent of the lesion and the degree of pulp involvement. Case series: This case series reports on four patients with progressive PEIR. In Cases 1 and 2, lesions were incidentally discovered in panoramic radiographs during orthodontic planning (mandibular permanent second molars), and additional surgical exposure to access the lesion was required as teeth were only partially erupted. Interestingly, in Case 3, the PEIR was not visible in earlier radiographs though the crown of the tooth was already mineralized (mandibular permanent second molar). For Case 4, the tooth presented with symptoms of reversible pulpitis (mandibular permanent first molar). All lesions were treated with indirect pulp capping using biocompat-ible material. The patients were followed up for a period of up to 8 years to evaluate treatment success. Indirect pulp capping and restorations were found to be successful in all four cases in the last follow-up: 1 year (Case 2), 1.4 years (Case 4), 1.5 years (Case 1), and 8 years (Case 3). Conclusion: This case series demonstrates the effectiveness of early intervention via surgical exposure and indirect pulp capping and restoration for managing severe cases of PEIR. However, further research with larger samples and long follow-up is necessary.

Testing the patterning cascade model of cusp development in Macaca fascicularis mandibular molars

ObjectiveMolar crown configuration plays an important role in systematics, and functional and comparative morphology. In particular, the number of cusps on primate molars is often used to identify fossil species and infer their phylogenetic relationships. However, this variability deserves renewed consideration as a number of studies now highlight important developmental mechanisms that may be responsible for the presence of molar cusps in some mammalian taxa. Experimental studies of rodent molars suggest that cusps form under a morphodynamic, patterning cascade model of development (PCM) that involve the iterative formation of enamel knots. This model posits that the size, shape and location of the first-forming cusps determines the presence and positioning of later-forming cusps. DesignHere we test whether variation in accessory cusp presence in 13 Macaca fascicularis mandibular second molars (M2s) is consistent with predictions of the PCM. Using micro-CT, we imaged these M2s and employed geometric morphometrics to examine whether shape variation in the enamel-dentine junction (EDJ) correlates with accessory cusp presence. ResultsWe find that accessory cusp patterning in macaque M2s is broadly consistent with the PCM. Molars with accessory cusps were larger in size and possessed shorter relative cusp heights compared to molars without accessory cusps. Peripheral cusp formation was also associated with more centrally positioned primary cusps, as predicted by the PCM. ConclusionsWhile these results demonstrate that a patterning cascade model is broadly appropriate for interpreting cusp variation in Macaca fascicularis molars, it does not explain all manifestations of accessory cusp expression in this sample.

Influence of adhesive systems containing different functional monomers on the longevity of bond strength at different dentin depths

This study evaluated the influence of adhesive systems containing different functional monomers on the longevity of bond strength (BS) to superficial (SD) and deep dentin (DD). Thirty molars were sectioned longitudinally, to obtain regions of SD (closest to the dentin-enamel junction) and DD (closest to the pulp chamber). Adhesive systems were applied (n = 10): Clearfil SE Bond (containing 10-MDP), FL-Bond II (containing 4-MET) and OptiBond Universal (containing GPDM). Microcylinders were made of resin composite (Filtek Z250) in SD and DD. After 24 h or 180 days of storage in Simulated Body Fluid (SBF) solution, BS tests were carried out. The fracture mode was evaluated by scores. ANOVA showed that there was no statistically significant difference between the adhesives in terms of BS (p = 0.5156). There was no significant difference between storage times for the three adhesive systems (p = 0.4703). There was a significant interaction between storage time and dentin depth (p = 0.0175), and in the time interval of 24 h, irrespective of the adhesive system, BS was significantly higher in SD than in DD (p < 0.05). In the time interval of 24 h, there was a significant association between the adhesive and the type of failure in SD (p = 0.0085) (Fisher's Exact test). Under these conditions, only OptiBond Universal showed cohesive failures in dentin (10 %) and mixed failures (15 %). After 180 days of storage, the percentages of early failures in deep dentin were 25.0 % (OptiBond Universal), 16.7 % (Clearfil SE Bond) and 0.0 % (FL-Bond II), with a significant difference between adhesives regarding early failures (p = 0.0410). The adhesive systems showed similar BS at different dentin depths over time, irrespective of the composition of functional monomers. FL Bond II was the only adhesive system that did not show early failures mode in DD within 180 days.

Changes in the structure of hard tissues of the lower third molars at different stages of eruption according to IR spectroscopy data

The structure of the hard tissues of the lower third molars (enamel, dentin, enamel-dentin junction) at different stages of eruption in the presence/absence of connective tissue dysplasia as a factor that can affect not only odontogenesis, but also teething was analyzed using infrared (IR) spectroscopy. A technique for deconvolution of IR spectra of hard dental tissues has been developed. It has been established that the differences between the stages of eruption are due to changes in the mineral component (phosphate ions) for all dental tissues, while for the enamel-dentin junction an important contribution is made by fluctuations in the methyl and methylene groups of organic compounds, for dentin the contribution of collagen absorption bands is shown. The differences between the stages of tooth eruption increase in the following order: dentin, enamel-dentin junction, enamel. It can be assumed that in the early stages of tooth formation, it is with the participation of collagen proteins that changes in the structure of dentin occur, which subsequently causes changes in the enamel-dentin junction and enamel. Changes in the enamel are subtler and appear only with additional processing of the IR spectra using mathematical methods.

Characterizing the microstructures of mammalian enamel by synchrotron phase contrast microCT

The enamel of mammalian teeth is a highly mineralized tissue that must endure a lifetime of cyclic contact and is inspiring the development of next-generation engineering materials. Attempts to implement enamel-inspired structures in synthetic materials have had limited success, largely due to the absence of a detailed understanding of its microstructure. The present work used synchrotron phase-contrast microCT imaging to evaluate the three-dimensional microstructure of enamel from four mammals including Lion, Gray Wolf, Snow Leopard, and Black Bear. Quantitative results of image analysis revealed that the decussation pattern of enamel consists of discrete diazone (D) and parazone (P) bands of rods organized with stacking arrangement of D+/P/D-/P in all mammals evaluated; the D+ and D- refer to distinct diazone bands with juxtaposed rod orientations from the reference plane. Furthermore, the rod orientations in the bands can be described in terms of two principal angles, defined here as the pitch and yaw. While the pitch angle increases from the outer enamel to a maximum (up to ≈ 40°) near the dentin enamel junction, minimal spatial variations are observed in yaw across the enamel thickness. There are clear differences in the decussation parameters of enamel across species that are interpreted here with respect to the structural demands placed on their teeth. The rod pitch and band width of enamel are identified as important design parameters and appear to be correlated with the bite force quotient of the four mammals evaluated. Statement of significanceThe multi-functionality of tooth enamel requires both hardness and resistance to fracture, properties that are generally mutually exclusive. Ubiquitous to all mammalian teeth, the enamel is expected to have undergone adaptations in microstructure to accommodate the differences in diet, body size and bite force across animals. For the first time, we compare the complex three-dimensional microstructure of enamel from teeth of multiple mammalian species using synchrotron micro-computed tomography. The findings provide new understanding of the “design” of mammalian enamel microstructures, as well as how specific parameters associated with the decussation of rods appear to be engineered to modulate its fracture resistance.

Sexual dimorphism in the enamel-dentine junction (EDJ) of permanent canines of European modern humans.

Dental anthropological investigations into sexual dimorphism have conventionally concentrated on evaluating the dimensions and configuration of the enamel cap of canines. However, the morphology of the crown dentine surface can be closely linked to that of the enamel surface. This link can facilitate examination of crown morphology even when the enamel surface is slightly worn. Here, we determine if the morphology of the enamel-dentine junction (EDJ) differs within (maxillary vs. mandibular) and between a sample of male (n = 26) and female (n = 21) contemporary human permanent canines from Europe. The morphological data of the EDJ were gathered employing a template comprising 96 landmarks and sliding semilandmarks. Subsequently, the data underwent analysis through form space principal component analysis following Procrustes registration, utilizing standard 3D geometric morphometric techniques. Significant differences in the morphology of the EDJ were observed between the sexes, particularly concerning the overall shape of the crown, the symmetry of the mesial and distal edges, and the development of the distal accessory ridge. Sex differences in the morphology of the EDJ could relate in part to retention of the canine-premolar honing complex in males. Our results indicate that analyses of the permanent canine EDJ may potentially provide a novel method for estimating the sex of adult and nonadult skeletons.

Saliva with different concentrations of enzyme with esterolytic activity, and its effect on the immediate and long-term bond strength of adhesive systems to dentin

The present study evaluated whether different concentrations of albumin would influence the immediate or long-term bond strength of adhesive systems to dentin. Human third molars (N = 90) were sectioned at the dentin-enamel junction to obtain middle dentin occlusal surfaces. After sectioning into discs, the molars were restored with resin composite (Filtek Z250, 3 M/ESPE) by using an etch-and-rinse (Adper Scotchbond Multi-Purpose, 3 M/ESPE) or a self-etch (Clearfil SE Bond, Kuraray) adhesive system. The specimens were then sectioned into beams and stored in artificial saliva containing albumin in regular (100 μg/mL; SA100) or elevated (700 μg/mL; SA700) concentration—both concentrations simulated the range in which this enzyme may be present clinically, depending on the patient's periodontal condition. Beams from the control group (CO) were kept in artificial saliva with no addition of albumin. Half of the beams from each group were stored for 24 h, and the remainder, for 12 months. Then, the microtensile bond strength test was performed, and the failure mode was analyzed (adhesive, cohesive, or mixed). Bond strength data were submitted to the generalized linear model, followed by the Tukey tests, and failure modes were compared using chi-square tests (α = 5%). There were no significant interactions, but there was a significant effect between the albumin concentration (p = 0.015) and the time factor (p = 0.016). The beams stored in SA700 had significantly lower bond strength in comparison with the CO beams, regardless of the adhesive system. At 12 months, the bond strength decreased significantly for all groups. SA700 caused a significant increase in the adhesive failures after 12 months (p = 0.005). It was concluded that the bond strength of both adhesive systems was impaired by the albumin concentration aging.

Variation in enamel prism size in primate molars

ObjectiveThis study examines whether larger enamel prism diameters accommodate a greater enamel volume from the enamel-dentine junction (EDJ) to the outer-enamel surface (OES) in primate molars, and how prism size relates to enamel thickness and crown location. DesignWe assessed variation in enamel prism diameter in relation to crown location and enamel thickness in catarrhine lower molars (n = 14 species) and one platyrrhine. Prism diameter and enamel thickness were recorded in four locations (lingual lateral; lingual cuspal; buccal cuspal; buccal lateral), using a buccal-lingual section through the centre of the mesial cusps. Ten prism diameter readings were collected at inner (near the EDJ), outer (near the OES) and middle (between the two locations) enamel for each location. ResultsMean prism diameter values for each species were similar (range: 4.06 µm to 5.81 µm). Prism diameter enlarged from inner to outer enamel, suggesting larger prisms help accommodate the increase in enamel volume from the EDJ to the OES. Average prism diameter does not associate with enamel thickness. Instead, cuspal positions had significantly smaller prism diameter at the EDJ than lateral positions, and larger prism sizes at the OES, leading to an overall similar prism diameter mean for all positions (Lingual lateral: 5.11 µm; Lingual cuspal: 5.04 µm; Buccal cuspal: 4.78 µm; Buccal lateral: 4.99 µm). ConclusionsOur study revealed consistent average enamel prism diameters in various crown locations of lower primate molars, potentially contributing to the mechanical integrity and functional optimization of enamel in primates.

Stereolithography-manufactured zirconia substrate with bionic-patterned surface microstructure for enhancing bond strength to porcelain veneer

The bond strength between the zirconia substrates and porcelain materials has been extensively investigated, and sandblasting is one of the most effective methods for increasing the bond strength between zirconia and porcelain. However, it also introduces microcracks and pollution, which have a negative impact on the final mechanical properties of zirconia restorations. To increase the mechanical chimaerism of zirconia/veneer structures nondestructively, in this study we developed a novel surface design called a bionic-patterned surface microstructure (BSM) using stereolithography (SLA) technology. Inspired by the dentin–enamel junction model, the microstructure includes a cylinder and pit. Among all the specimens, both computer numerical control (CNC) zirconia with sandblasting and SLA zirconia with BSM showed higher bond strengths than the CNC group (P < 0.001), and the BSM groups showed improved bonding properties (P < 0.001). No significant differences were observed between the cylindrical and pit BSM at the same height/depth (P = 0.493), and for BSM of the same type, the bond strength increased with increasing height/depth (P < 0.001). Zirconia with BSM thus had superior bond strength to porcelain veneers. The height/depth of the BSM had a positive effect on the bonding strength, whereas the type had no effect.

Dental morphology in Homo habilis and its implications for the evolution of early Homo

The phylogenetic position of Homo habilis is central to debates over the origin and early evolution of the genus Homo. A large portion of the species hypodigm consists of dental remains, but they have only been studied at the often worn enamel surface. We investigate the morphology of the H. habilis enamel-dentine junction (EDJ), which is preserved in cases of moderate tooth wear and known to carry a strong taxonomic signal. Geometric morphometrics is used to characterise dentine crown shape and size across the entire mandibular and maxillary tooth rows, compared with a broad comparative sample (n = 712). We find that EDJ morphology in H. habilis is for the most part remarkably primitive, supporting the hypothesis that the H. habilis hypodigm has more in common with Australopithecus than later Homo. Additionally, the chronologically younger specimen OH 16 displays a suite of derived features; its inclusion in H. habilis leads to excessive levels of variation.

Radiographic evaluation of enamel thickness of permanent teeth: relevance and applicability.

This descriptive observational study aimed to determine clinically relevant and applicable data of enamel thickness (ETH), considering the mesio-distal differences of anterior and posterior permanent teeth and their relationships. The sample consisted of right-sided standardized radiographs of 34 individuals (21 females and 13 males), aged between 13 and 24 (average 16) years, with all permanent teeth intact and without crowding. Four periapical and four interproximal radiographs were obtained and digitized. ETH measurements (mesial to distal contact points at the dentin-enamel junction) were performed after correction for radiographic image magnification. The Students' t-test was applied to the differences between paired means, with the Pearson correlation to evaluate the correlation between them. The mesial and distal ETH increased from the anterior to the posterior teeth. Incisor ETH ranged between 0.60 and 0.84 mm. Canines, premolars, and molars were more than 1.0 mm thick, and molar enamel reached values between 1.26 and 1.44 mm. Distal ETH was significantly greater than the mesial ETH, and progressively thicker from the anterior to posterior teeth. Interproximal reduction (IPR) of the lower central and upper lateral incisors should be avoided, reduced, or performed on their distal surfaces. There is a positive and significant correlation between ETH and the mesial and distal surfaces of the teeth. Periapical radiographs and evaluation of the remaining ETH are necessary in cases of retreatment. The location and number of tooth size discrepancies should be considered in treatment planning and appropriately compensated with IPR.

Developmental process of the modern house shrew's molars: implications for the evolution of the tribosphenic molar in Mesozoic mammals.

Phylogenetically, the tribosphenic molars-prototypes of multi-cusped cheek teeth in marsupial and placental mammals-are derived from the single-cusped conical teeth of reptiles through the addition of cusps. Ontogenetically, mammalian molars are formed through the interface between the dental epithelium and mesenchyme (future enamel-dentin junction), becoming geometrically complex by adding epithelial signaling centers, called enamel knots, which determine future cusp positions. To reevaluate cusp homologies in Mesozoic mammals from an ontogenetic perspective, this study tracked molar development in a living placental mammal species, the house shrew (Suncus murinus), whose molars are morphologically the least derived from tribosphenic prototypes. The development of shrew molars proceeded as if it replayed the evolutionary process of tribosphenic molars. The first formed enamel knots gave rise to the evolutionarily oldest cusps-upper paracone and lower protoconid. The order of formation of other enamel knots and their location in development seemed to trace the order of cusp appearance in evolution. The parallel relationship between ontogeny and phylogeny of mammalian molars, if any, suggests that a change in the timing between developmental events rather than a change in the morphogenetic mechanism itself, should have been a major causal factor for the evolutionary transformation of tooth morphology.

Influence of different access cavity sizes on the direction of stress distribution in endodontically treated uniradicular maxillary premolar

Objective: This study aimed to evaluate the influence of different access cavity sizes on the stress distribution in an endodontically treated maxillary premolar model compared to an intact one using finite element analysis (FEA). Materials and Methods: The distributions of maximum and minimum principal stress were calculated. In the intact tooth, the maximum principal stress was located in the enamel-dentine junction and the minimum principal stress was in the cervical area. Results: In large-sized access, the maximum principal stress (tensile) increased by 41% compared to the contracted access model. This tensile strength was concentrated on interface tooth/restoration. Medium-sized access caused an increase of 27% of the minimum principal stress(compressive strength) on the apical region compared to the contracted access cavity. There was also an increase of 15% of the maximum principal stress (tensile strength) when comparing medium and minimum-sized cavities. Conclusion: The endodontic access cavity design modified the value and the direction of principal stress distribution of endodontically treated uniradicular maxillary premolar compared to the natural one.

The Distribution and Biogenic Origins of Zinc in the Mineralised Tooth Tissues of Modern and Fossil Hominoids: Implications for Life History, Diet and Taphonomy.

Zinc is incorporated into enamel, dentine and cementum during tooth growth. This work aimed to distinguish between the processes underlying Zn incorporation and Zn distribution. These include different mineralisation processes, the physiological events around birth, Zn ingestion with diet, exposure to the oral environment during life and diagenetic changes to fossil teeth post-mortem. Synchrotron X-ray Fluorescence (SXRF) was used to map zinc distribution across longitudinal polished ground sections of both deciduous and permanent modern human, great ape and fossil hominoid teeth. Higher resolution fluorescence intensity maps were used to image Zn in surface enamel, secondary dentine and cementum, and at the neonatal line (NNL) and enamel-dentine-junction (EDJ) in deciduous teeth. Secondary dentine was consistently Zn-rich, but the highest concentrations of Zn (range 197-1743 ppm) were found in cuspal, mid-lateral and cervical surface enamel and were similar in unerupted teeth never exposed to the oral environment. Zinc was identified at the NNL and EDJ in both modern and fossil deciduous teeth. In fossil specimens, diagenetic changes were identified in various trace element distributions but only demineralisation appeared to markedly alter Zn distribution. Zinc appears to be tenacious and stable in fossil tooth tissues, especially in enamel, over millions of years.

Deciphering load attenuation mechanisms of the dentin-enamel junction: Insights from a viscoelastic constitutive model.

A considerable material discontinuity between the enamel and dentin might jeopardize the tooth's mechanical durability over time without the attenuation of the dentin-enamel junction (DEJ). However, the critical loading transmission mechanism at the DEJ remains understudied. This study aimed to define the extent and effective width of the DEJ, along with its mechanical competence. The presence of DEJ interphase layer was identified using a motif analysis based on the ion beam-transmission electron microscopy coupled with nanoindentation modulus mapping. For each region, nanoindentation load-displacement curves were recorded and mathematically analyzed using an appropriate viscoelastic constitutive model. The time-course of indenter penetration (creep) behavior of the tooth tissues can be mathematically approximated by the Kelvin-Voigt model in series, which determined the visco-contribution to the overall mechanical responses. Therefore, the elastic-plastic contribution can be distinguished from the overall mechanical responses of the tooth after subtracting the visco-contributions. During the loading period, the enamel behavior was dominated by elastic-plastic responses, while both the dentin and DEJ showed pronounced viscoelastic responses. The instantaneous modulus of the DEJ, which was measured by eliminating viscoelastic behavior from the raw load-displacement curve, was almost double that of the dentin. The DEJ was stiffer than the dentin, but it exhibited large viscoelastic motion even at the initial loading stage. This study revealed that the load attenuation competence of the DEJ, which involves extra energy expenditure, is mainly associated with its viscoelasticity. The mathematical analysis proposed here, performed on the nanoindentation creep behavior, could potentially augment the existing knowledge on hard-tissue biomechanics. STATEMENT OF SIGNIFICANCE: In this study, we undertake a rigorous mechanical characterization of the dentin-enamel junction (DEJ) using an advanced nanoindentation technique coupled with a pertinent viscoelastic constitutive model. Our approach unveils the substantial viscoelastic contribution of the DEJ during the initial indentation loading phase and offers an elaborate delineation of the DEJ interphase layer through sophisticated image analysis. These insights significantly augment our understanding of tooth durability. Importantly, our innovative mathematical analysis of creep behavior introduces a novel approach with profound implications for future research in the expansive field of hard-tissue biomechanics. The pioneering methodologies and findings presented in this work hold substantial potential to invigorate progress in biomaterials research and fuel further explorations into the functionality of biological tissues.

Pre-eruptive intracoronal resorption: case report

This case describes the presentation of pre-eruptive intracoronal resorption affecting multiple permanent teeth in an 11-year-old female child. Pre-eruptive intracoronal resorption is a lesion that is often located within the dentine, adjacent to the enamel–dentine junction in the occlusal face of the tooth crown. Histological reports have shown the presence of resorptive cells in these lesions. Previous literature presents cases usually affecting a single tooth, in this case 10 permanent teeth were found to be affected. Clinicians should be aware of this diagnosis and its treatment modalities to ensure appropriate management is carried out. CPD/Clinical Relevance: This case highlights pre-eruptive intracoronal resorption for clinicians based in both primary and secondary care settings

Remineralizing potential of the biomimetic P11-4 self-assembling peptide on noncavitated caries lesions: A retrospective cohort study evaluating semistandardized before-and-after radiographs

BackgroundSelf-assembling peptide (SAP) P11-4 was introduced to treat initial caries lesions by means of guiding hydroxyapatite regeneration within the lesion. The objective of this study was to assess its effectiveness in a practical clinical setting. MethodsCaries lesions in permanent teeth treated with monomeric and polymeric SAP P11-4 from May 2015 through October 2020 were retrospectively analyzed at lesion and child levels by means of bite-wing radiography for changes in stage and cavitation and restoration. ResultsTwo hundred and nineteen children aged 10 through 19 years with a total of 405 proximal lesions in posterior teeth were followed from 0.4 through 5.5 years (median, 7 months; interquartile range, 6-19 months). Regression occurred in 37% of stage RA1 (radiolucency in the outer one-half of enamel) (95% CI, 31% to 44%), 38% of stage RA2 (radiolucency in the inner one-half of enamel plus or minus the enamel–dentin junction) (95% CI, 30% to 45%), and 40% of stage RA3 (radiolucency limited to the outer one-third of dentin) (95% CI, 16% to 68%) lesions. The proportion of lesions with no cavitation was 0.96 (95% CI, 0.94 to 0.98) after 1 year and 0.91 (95% CI, 0.88 to 0.95) after 2 years. ConclusionsReal-world clinical data indicate that SAP P11-4 can lead to recovery and a healthier tooth stage. Practical ImplicationsSAP P11-4 is a safe treatment for initial caries lesions in permanent teeth that remineralizes in the deepest zone of the lesion and can be introduced easily into routine dental practice.

Variation in enamel mechanical properties throughout the crown in catarrhine primates

Enamel mechanical properties vary across molar crowns, but the relationship among mechanical properties, tooth function, and phylogeny are not well understood. Fifteen primate lower molars representing fourteen taxa (catarrhine, n = 13; platyrrhine, n = 1) were sectioned in the lingual–buccal plane through the mesial cusps. Gradients of enamel mechanical properties, specifically hardness and elastic modulus, were quantified using nanoindentation from inner (near the enamel-dentine junction), through middle, to outer enamel (near the outer enamel surface) at five positions (buccal lateral, buccal cuspal, occlusal middle, lingual cuspal, lingual lateral). Cuspal positions had higher mechanical property values than lateral positions. Middle enamel had higher mean hardness and elastic modulus values than inner and outer locations in all five crown positions. Functionally, the thicker-enameled buccal cusps of lower molars did not show evidence of increased resistance to failure; instead, lingual cusps—which show higher rates of fracture—had higher average mechanical property values, with no significant differences observed between sides. Preliminary phylogenetic results suggest there is relatively little phylogenetic signal in gradients of mechanical properties through the enamel or across the crown. There appears to be common mechanical property patterns across molar crowns in Catarrhini and potentially among primates more broadly. These results may allow more precise interpretations of dental biomechanics and processes resulting in mechanical failure of enamel in primates, such as wear and fracture.