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Abstract Background Hunter–Schreger bands (HSB) are optical phenomena observed on tooth surfaces under polarized light, resulting from the intersection of enamel prisms. Anthropological studies demonstrate the prevalence of HSB in large mammals, contributing to enamel resistance. Historically, John Hunter and Schreger depicted HSB in dental literature. In dentistry, HSB play a role in non-carious cervical lesions (NCCL) and internal dental perikymata, suggesting their potential for personal identification. Personal identification, crucial in both daily and professional life, involves biometric characteristics, such as fingerprints or facial recognition. The need for non-invasive, rapid, and user-friendly methods has prompted the exploration of using HSB dental images for personal identification. The review aimed to consolidate studies employing HSB for personal identification. Methods The scoping review was carried out strictly following the PRISMA–ScR checklist; the search was carried out on tree databases (PubMed, Scopus, Science Direct,) and a register (Cochrane library). Results The research produced a number of bibliographic sources totaling 410. With the removal of duplicates, 334 were obtained; potentially eligible articles amounted to 14, of which only 4 fully complied with the criteria of eligibility. Conclusions From the data in the literature, we can assert that HSB could be used in personal identification, as they are characteristics that are difficult to change and easily detectable.

Enamel prism is the main microstructural unit of mammalian enamel which composed of hundreds of bioapatite nanocrystals. Prism structure plays a key role in the excellent mechanical performance of dental enamel during millions of chewing cycles without significant remodeling. Thus, quantitative understanding of prism architecture is of utmost importance for biomechanical materials design. To characterize enamel prism orientation quantitatively, a novel image processing method has been developed. Our method is based on scanning electron microscopy images of etched enamel surface and consists of an ellipse fitting procedure, which provides a numerical approximation of prism shape and orientation in the studied cross section. The obtained analytical data allow to construct color coded orientation maps, which provide quick and useful insight into the microstructure of enamel. Besides striking visualization, orientation maps allow to extract and plot the rich information on the azimuthal and inclination angles of the prisms as function of location. Numerical data on prism arrangement can be analyzed using statistical tools over large areas, which paves the way towards quantifying comparative investigation of prism arrangement either in dentistry research or evolution biology. The application of the method is demonstrated for a distal–mesial cross‐section of sound human tooth enamel. Highlights: Scanning electron microscopy images of etched enamel surface are analyzed using ellipse fitting.Geometrical parameters of the fitted ellipses provide numerical data of thousands of prisms.Prism arrangement is visualized on color coded orientation maps and analyzed using statistical tools. [ABSTRACT FROM AUTHOR]

Beavers (Castor) stand out among mammals for their unique capacity to fell trees using their large, ever-growing incisors. This routine consumption of resistant fodder induces prodigious wear in the lower incisors, despite this blunting effect the incisors maintain a remarkably sharp cutting edge. Notably, the enamel edges of their incisors show a highly complex two-part microstructure of which the biomechanical import is unknown. Here, using fracture analysis, nanoindentation, and wear testing on North American beaver (C. canadensis) incisors we test the microstructure's possible contribution to maintaining incisal sharpness. Although comparable in hardness, the inner enamel preferentially fails and readily wears at 2.5 times the rate of the outer enamel. The outer microstructure redirects all fractures in parallel, decreasing fracture coalescence. Conversely, the inner microstructure facilitates crack coalescence increasing the wear rate by isolating layers of enamel prisms that readily fragment. Together these two architectures form a microstructurally driven self-sharpening mechanism contained entirely within the thin enamel shell. Our results demonstrate that enamel microstructures exposed at the occlusal surface can markedly influence both enamel crest shape and surface texture in wearing dentitions. The methods introduced here open the door to exploring the biomechanical functionality and evolution of enamel microstructures throughout Mammalia. Enamel microstructure varies significantly with the diversity of diets, bite forces, and tooth shapes exhibited by mammals. However, minimal micromechanical exploration of microstructures outside of humans, leaves our understanding of biomechanical functions in a nascent stage. Using biologically informed mechanical testing, we demonstrate that the complex two-part microstructure that comprises the cutting edge of beaver incisors facilitates self-sharpening of the enamel edge. This previously unrecognized mechanism provides critical maintenance to the shape of the incisal edge ensuring continued functionality despite extreme wear incurred during feeding. More broadly, we show how the architecture of prisms and the surrounding interprismatic matrix dictate the propagation of fractures through enamel fabrics and how the pairing of enamel fabrics can result in biologically advantageous functions. [Display omitted] [ABSTRACT FROM AUTHOR]

Background: An enamel rod is the basic unit of tooth enamel measuring 4 μm wide to 8 μm high and is tightly packed, highly organized mass of hydroxyapatite crystals, which are hexagonal in shape and provide rigidity to the rods and strengthen the enamel. In cross section, it is best compared to a keyhole with the top, or head, oriented toward the crown of the tooth and the bottom, or tail, oriented toward the root of the tooth. Enamel rods are found in rows along the tooth. The arrangement of crystals within each enamel rod is highly complex and gives rise to Hunter–Schreger Bands. This article presents enamel rods in Hunter–Schreger Bands under light microscopy and polarized microscopy which has rarely been reported with additional note on incipient lesion visualized under polarized microscopy. Aim: 1. To visualize enamel rods in Hunter–Schreger Bands under light microscopy and polarized microscopy. 2. Visualization of Zones of enamel in incipient lesion under polarized microscopy. Materials and Methods: Two ground sections were prepared. One normal (without lesion) and the other one was having incipient lesion (white spot). Normal tooth was visualized under light and polarized microscopy under x4,x10,x40,x100 under a light microscope, Leica research microscope (Leica application suite [LES]core version 3.8) of Leica research microscope (Model No. DM1000 LED, Leica Microsystems GmbH Ernst-Leitz-Stra e17–37 | 35,578 Wetzlar [Germany]) and tooth with incipient lesion was visualized under polarized microscopy. Conclusion: Basic mechanism of Hunter Schreger bands can be studied at light microscopy. Zones of enamel in incipient lesion too, was clearly evident under polarized microscopy.

Multiple behavioral and biomechanical analyses have demonstrated that capuchin monkeys (Cebus and Sapajus) are specialized for breaking down hard‐object foods as compared to other cebid monkeys. In addition to a complex suite of craniodental adaptations, it has specifically been demonstrated that capuchins possess highly complex dental enamel, with extensive Hunter–Schreger banding and other decussation, that likely serve as an adaptation to resist crack propagation during hard‐object feeding. Furthermore, it has been demonstrated that robust capuchins (Sapajus spp., formerly Cebus apella) demonstrate further adaptation for hard‐object feeding than other capuchins, routinely breaking down extremely mechanically challenging foods. However, there has been no comparison of dental enamel complexity in robust versus gracile capuchins, to assess whether the dental enamel in Sapajus follows this same pattern of further specialization. Therefore, this study compares dental enamel complexity in images of dental thin sections from a sample of robust versus gracile capuchins using image compression ratio (ICR) analysis. ICR is a variable that correlates with enamel complexity, such that higher ICR values are indicative of increased complexity in the form of enamel decussation. We found no significant difference between robust and gracile capuchins when assessing all teeth in our sample together, however, we did find that robust capuchins have significantly higher ICR values than gracile capuchins for canine teeth, specifically. Our results support prior studies suggesting that robust capuchins are specialized to generate increased masticatory loads with their anterior dentition, specifically, as compared to gracile species. Research Highlights: Robust capuchins (Sapajus) capuchins are differentiated in part from gracile capuchins (Cebus) by increasing specialization in durophagy.Image compression ratio analysis (ICR) demonstrates that Sapajus canines are more complex than Cebus, likely due to this specialization. [ABSTRACT FROM AUTHOR]

Enamel microstructure is studied here in Toxodon sp., a notoungulate from the Pleistocene of South America. The material includes 13 specimens from outcrops in São Paulo and Rio Grande do Sul states, Brazil. Analyses of ground sections of upper and lower incisors, premolars, molars, and deciduous premolars by scanning electron microscopy reveal Schmelzmuster with three enamel types: modified radial enamel (MRE), associated with the enamel-dentine junction (EDJ); Hunter-Schreger bands (HSB), an intermediary layer with decussating prisms; and radial enamel (RE), a layer placed next to the outer enamel surface. Microstructural features vary in each tooth category, on the buccal and lingual sides, as well as in the different regions of each tooth. The proportion of RE increases in the occlusal area of I2, which commonly exhibits intense wear, and may be related to abrasion resistance. HSB thickness ranges from 6 to 20 prisms, with the thickest portions placed in areas with intense masticatory loads. The most concentrated packing densities of HSB in the upper incisors and lower premolars suggest these teeth bore the greatest biomechanical demands. Incisors and cheek teeth show differentiation of Schmelzmuster, suggesting dental antagonistic contact areas, as well as leading and trailing edges. Deciduous premolars exhibit enamel in the early stages of development, and a neonatal line is observed almost parallel to the EDJ, possibly related to biological stress during birth. The EDJ is scalloped in all dental categories, with varying sizes and shapes. Larger and more pronounced scallops are observed in I2, i3, p4, and in the enamel folds of the upper and lower cheek teeth, associated with microstructural features indicative of greater biomechanical demands. Microstructural enamel findings presented here corroborate morphological trends in the dentition of Notoungulata related to hypsodonty, providing greater resistance to the consumption of abrasive diets in these euhypsodont-toothed herbivores. [ABSTRACT FROM AUTHOR]

Modern baleen whales have no adult teeth, whereas dolphins and porpoises have a homodont and polydont dentition, with simplified enamel microstructure. However, archaic cetaceans (archaeocetes and early mysticetes and odontocetes) had a complex and ornamented dentition, with complex enamel microstructure as in terrestrial mammals. This study describes the morphology of teeth and enamel microstructure in two fossil cetaceans from Antarctica: a basilosaurid archaeocete from the La Meseta Formation (middle Eocene); and Llanocetus sp. from the Submeseta Formation (late Eocene), one of the oldest mysticetes known. The two teeth analyzed were lower premolars, with transversely compressed triangular crowns composed of a main cusp and accessory denticles. The enamel microstructure of the basilosaurid and Llanocetus sp. is prismatic with Hunter-Schreger bands (HSB) and an outer zone of radial enamel. In the basilosaurid, the enamel is relatively thin and measures 150–180 μm, whereas in Llanocetus sp. it is considerably thicker, measuring 830–890 μm in the cusp area and 350–380 μm near the crown base. This is one of the thickest enamel layers among cetaceans, extinct and living. Structures resembling enamel tufts and lamellae were observed in both fossils at the enamel-dentine junction (EDJ) and extending along the thickness of the enamel layer, respectively. The presence of HSB and biomechanical reinforcing structures such as tufts and lamellae suggests prominent occlusal loads during feeding, consistent with raptorial feeding habits. Despite the simplification or absence of teeth in modern cetaceans, their ancestors had complex posterior teeth typical of most mammals, with a moderately thick enamel layer with prominent HSB. [ABSTRACT FROM AUTHOR]

We investigate the enamel microstructure of 37 isolated rodent incisors from several late middle Eocene and late Oligocene localities of Contamana (Loreto Department, Peruvian Amazonia), and from the early Oligocene TAR-01 locality (Shapaja, San Martín Department, Peruvian Amazonia). All incisors show an enamel internal portion with multiserial Hunter-Schreger Bands (HSB). The late middle Eocene localities of Contamana yield incisors with subtypes 1, 1–2, and 2 of multiserial HSB; TAR-01 yielded incisors with subtypes 1–2, 2, 2–3, and 3 of multiserial HSB; and the late Oligocene localities of Contamana, incisors with subtypes 1–2, 2, and 2–3 of multiserial HSB. Based on our current knowledge of the South American and African rodent fossil records and given the primitiveness of the Eocene caviomorph faunas, it may be expected that the hystricognath pioneer(s) who have colonized South America from Africa sometime during the middle Eocene, most probably had incisors that displayed a multiserial enamel with an interprismatic matrix arrangement characterizing the subtype 1 (or subtype 1 + the subtype 2 and/or the transitional 1–2) of multiserial HSB. In contrast, the derived subtypes 2–3 and 3 conditions were subsequently achieved but likely rapidly, as evidenced by its record as early as the ?late Eocene/early Oligocene (e.g., Santa Rosa, Shapaja, and La Cantera), and seemingly evolved iteratively but only in the Octodontoidea clade. [ABSTRACT FROM AUTHOR]

The dentition of Cambaytherium was investigated in terms of dental wear, tooth replacement and enamel microstructure. The postcanine tooth row shows a significant wear gradient, with flattened premolars and anterior molars at a time when the last molars are only little worn. This wear gradient, which is more intensive in Cambaytherium thewissi than in Cambaytherium gracilis, and the resulting flattened occlusal surfaces, may indicate a preference for a durophagous diet. The tooth replacement (known only in C. thewissi) shows an early eruption of the permanent premolars. They are in function before the third molars are fully erupted. During the dominant phase I of the chewing cycle the jaw movement is very steep, almost orthal, with a slight mesiolingual direction and changes into a horizontal movement during phase II. The enamel microstructure shows Hunter-Schreger-bands (HSB) in the inner zone of the enamel. In some teeth the transverse orientation of the HSB is modified into a zig-zag pattern, possibly an additional indicator of a durophagous diet. [ABSTRACT FROM AUTHOR]

Dental enamel is formed by rod‐like structures, the enamel prisms. Groups of prisms are packed together in successive horizontal layers of alternating directions, known as Hunter‐Schreger bands (HSBs). HSBs are the major microstructural characteristic of mammalian enamel. The pattern of HSBs can vary among mammalian species and this variability may provide relevant information regarding the species life history and taxon identification. In human HSBs can be used as a biometric‐based parameter for personal identification in automated systems. The analysis of HSBs has been hampered by technical difficulties. The low contrast between light and dark bands and variations in light intensity may hinder the observation of HSBs in digital images. This article describes a simple and efficient computational procedure that greatly enhances the contrast and minimizes the differences in the intensity of illumination in HSBs images. Its use can significantly increase the quality and the number of HSBs that can be recorded in intact teeth. Improving the quality of images of enamel microstructure in intact teeth.Enhancing the contrast of Hunter‐Schreger bands observed in enamel of intact teeth.Increasing the area of Hunter‐Schreger bands observed in enamel of intact teeth. [ABSTRACT FROM AUTHOR]

In most mammalian species enamel prisms are regularly arranged in layers of alternating directions forming an angle of approximately 90°. These successive layers of prisms are known as Hunter-Schreger bands (HSBs). The analysis of HSBs may provide valuable information regarding the species life history, taxon and personal identification, with evident applicability in physical anthropology and forensics. Obtaining good quality digital images of HSBs in intact specimens is not always a feasible task. The major problems are the low contrast of images; the reflection of incident light, which may create areas of intense shine in digital images; and the abrupt decrease in the degree of illumination that occurs after light crosses the vertical cracks, frequently present in enamel. We show here that the area of intense shine can be minimized by a polarizing filter coupled to the camera objective, and the filling of enamel cracks with corn oil can reduce refraction of light in enamel cracks. These procedures can significantly increase the quality and the area of HSBs that can be recorded in intact teeth. [ABSTRACT FROM AUTHOR]

Hunter-Schreger Bands (HSB), are light and dark bands, which can be seen in the enamel due to the different curvature of the enamel prisms, they are widely mentioned in studies, both dental and anthropological, but are not reflected in Terminologia Histologica. The aim of the present work was to carry out an analysis of the HSB term, in order to propose it as a new histological term, and thus be able to be included in Terminologia Histologica by the Federative International Program for Anatomical Terminology (FIPAT). After the analysis in study texts and scientific publications, we propose in replacement of the term HSB, for two terms: diazone prismatica (diá of Greek διá 'through' and of Greek zon(e) ζωνη 'strip', 'zone of the earth') and parazone prismatica (pará &#π945;ρá gr. 'along' and from the Greek zon(e) ζωνη 'strip', 'zone of the earth'), thus defining the most descriptive and noneponymous terms, as the International Terminology says. Propose new terms that are more in agreement with those indicated by the International Federation of Associations of Anatomists (IFAA) and the own terminology, presents great answers; A term is not only a word that refers to a morphological structure, but also a unit of language, which unites the morphological community in a single language. So we propose that the term sea included by the FIPAT in the next discussions. [ABSTRACT FROM AUTHOR]

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In the field of dentistry, the murine incisor has long been considered as an outstanding model to study amelogenesis. However, it clearly appears that enamel from wild type mouse incisors and molars presents several structural differences. In incisor, exclusively radial enamel is observed. In molars, enamel displays a high level of complexity since the inner part is lamellar whereas the outer enamel shows radial and tangential structures. Recently, the serotonin 2B receptor (5-HT2BR) was shown to be involved in ameloblast function and enamel mineralization. The incisors from 5HT2BR knockout (KO) mice exhibit mineralization defects mostly in the outer maturation zone and porous matrix network in the inner zone. In the molars, the mutation affects both secretory and maturation stages of amelogenesis since pronounced alterations concern overall enamel structures. Molars from 5HT2BR KO mice display reduction in enamel thickness, alterations of inner enamel architecture including defects in Hunter-Schreger Bands arrangements, and altered maturation of the outer radial enamel. Differences of enamel structure were also observed between incisor and molar from other KO mice depleted for genes encoding enamel extracellular matrix proteins. Thus, upon mutation, enamel analysis based exclusively on incisor defects would be biased. In view of the functional relationship between enamel structure and tooth morphogenesis, identification of molecular actors involved in amelogenesis requires comparative studies between mice molars and incisors. [ABSTRACT FROM AUTHOR]

The enamel microstructure in molars ofArsinoitheriumis reinvestigated and a new modification of radial enamel (RE), ‘arsinoitheriid radial enamel (ARE)’, is defined. It is characterised by alternating stripes with different organisation of the interprismatic matrix but no prism decussation. Recognition of this new subtype leads to a reinterpretation of structure previously identified as modified radial enamel and of Hunter–Schreger bands inArsinoitherium.The newly differentiated ARE ofArsinoitheriumis more derived in relation to corresponding microstructures ofPalaeoamasiaandCrivadiatherium. A careful reinvestigation of RE in other Paenungulata will be required to provide additional data bearing on phylogenetic reconstruction. The enamel ofPhenacolophusargues against inclusion of this genus in the Embrithopoda. [ABSTRACT FROM PUBLISHER]

Harichane Y, Dimitrova-Nakov S, Marchadier A, Collet C, Baudry A, Vidal C, Kamoun-Goldrat A, Kellermann O, Goldberg M. Enamel alterations in serotonin 2B receptor knockout mice. Eur J Oral Sci 2011; 119 (Suppl. 1): 177-184. © 2011 Eur J Oral Sci The role of the serotonin 2B receptor (5-HT2BR) in enamel formation and mineralization was explored in adult 5HT2BR knockout (KO) mice compared with wild-type (WT) mice. In the molar, quantitative data obtained by micro-computed tomography imaging showed that the overall volume of the enamel layer was firmly reduced in KO mice. Defective mineralization was ascertained by energy-dispersive X-ray microanalysis. We also observed, using scanning electron microscopy, that parazones in the KO mice included two or three helicoidally twisted rods within Hunter-Schreger bands, instead of a single rod, as found in the WT mice. Minor disturbances were also detected in the incisors of KO mice. Structural modifications, thinner enamel crystallites, and porosities observed in KO mice indicate that the 5-HT2BR-mediated signaling pathways as part of the enamel formation process. These data provide a basis for evaluating the role of 5-HT2BR in ameloblast functions. Defects observed in the mineralization and structure of enamel in KO mice highlight that the 5-HT2BR interferes with the mechanisms directing amelogenesis. [ABSTRACT FROM AUTHOR]

Hunter-Schreger Bands (HSBs) are an optical phenomenon visualised when a cut or fractured enamel surface is viewed under reflected light. These bands demonstrate the synchronous decussation of individual or groups of enamel prisms. While the role of HSB patterns has been investigated in comparative anatomical studies, until recently there has been little consideration of HSB patterns in human teeth. The aim of this paper is to consider the significance of HSB patterns in the human dentition and in relation to clinical dentistry. It is concluded that within the human dentition, HSB patterns have evolved to optimise resistance to attrition, abrasion and tooth fracture. It appears that certain aspects of HSB packing densities and distributions have beneficial roles in enamel bonding. Hunter-Schreger Band patterns seem to passively facilitate conditions such as abfraction and cracked tooth syndrome. [ABSTRACT FROM AUTHOR]

Using light microscopy, we examined Hunter-Schreger Band (HSB) patterns on the axial and occlusal/incisal surfaces of 160 human teeth, sectioned in both the buccolingual and mesiodistal planes. We found regional variations in HSB packing densities (number of HSBs per mm of amelodentinal junction length) and patterns throughout the crown of each class of tooth (maxillary and mandibular: incisor, canine, premolar, and molar) examined. HSB packing densities were greatest in areas where functional and occlusal loads are greatest, such as the occlusal surfaces of posterior teeth and the incisal regions of incisors and canines. From this it is possible to infer that the behaviour of ameloblasts forming enamel prisms during amelogenesis is guided by genetic/evolutionary controls that act to increase the fracture and wear resistance of human tooth enamel. It is suggested that HSB packing densities and patterns are important in modern clinical dental treatments, such as the bonding of adhesive restorations to enamel, and in the development of conditions, such as abfraction and cracked tooth syndrome. [ABSTRACT FROM AUTHOR]

To investigate the microstructure, elemental composition and mechanical properties of polar bear teeth. Incisors, canines and fourth premolar teeth of two subadult male museum specimens were analysed. Teeth were measured, photographed, embedded in Epoxy resin, sectioned, polished and etched for scanning electron microscope (SEM) imaging, elemental composition and nanomechanical testing analyses. The thickness of enamel ranged from 350-430 µm in canines, 220–330 µm in incisors and 320–510 µm in premolars. SEM images showed distinct transversely-oriented undulating Hunter Schreger bands from the enamel-dentine junction (EDJ) to the outer enamel surface. Enamel prisms had a hexagonal shape, with open prism sheaths. Prisms measured 6–8 µm in diameter. The EDJ was straight with no evidence of scalloping. Larger tubules adjacent to the EDJ were observed in the mantle dentine zone. Enamel Hardness and Elastic modulus values were higher in premolars (6.9 GPa and 269 GPa), followed by canines (6.5 GPa and 230 GPa) and incisors (4.9 GPa and 187 GPa). Dentine Hardness and Elastic modulus values were higher in canines. CaO and P 2 O 5 were the components with higher oxide weight percentage in both enamel and dentine. Understanding the microstructure, elemental composition and mechanical properties of polar bear teeth can help elucidate the biology and functional morphology of this globally threatened species and could be used as a proxy for studies with fossil ursids. • This study concerned teeth in the polar bear Ursus maritimus • Enamel thickness greater in canines (350–430 µm) followed by incisors and premolars • Enamel is composed of transversely-oriented undulating Hunter-Schreger bands • Higher Hardness and Elastic modulus in premolars, followed by canines and incisors • Tooth microstructure and properties linked to biology and functional morphology [ABSTRACT FROM AUTHOR]

Many living primates that feed on hard food have been observed to have thick-enameled molars. Among platyrrhine primates, members of the tribe Pitheciini (Cacajao, Chiropotes, and Pithecia) are the most specialized seed and nut predators, and Cebus apella also includes exceptionally hard foods in its diet. To examine the hypothesized relationship between thick enamel and hard-object feeding, we sectioned small samples of molars from the platyrrhine primates Aotus trivergatus, Ateles paniscus, Callicebus moloch, Cebus apella, Cacajao calvus, Chiropotes satanas, Pithecia monachus, and Pithecia pithecia. We measured relative enamel thickness and examined enamel microstructure, paying special attention to the development of prism decussation and its optical manifestation, Hunter-Schreger Bands (HSB). Cebus apella has thick enamel with well-defined but sinuous HSB overlain by a substantial layer of radial prisms. Aotus and Callicebus have thin enamel consisting primarily of radial enamel with no HSB, Ateles has thin enamel with moderately developed HSB and an outer layer of radial prisms, and the thin enamel of the pitheciins (Cacajao, Chiropotes, and Pithecia) has extremely well-defined HSB. Among platyrrhines, two groups that feed on hard objects process these hard foods in different ways. Cebus apella masticates hard and brittle seeds with its thick-enameled cheek teeth. Pitheciin sclerocarpic foragers open hard husks with their canines but chew relatively soft and pliable seeds with their molars. These results reveal that thick enamel per se is not a prerequisite for hard object feeding. The Miocene hominoid Kenyapithecus may have included hard objects in its diet, but its thick-enameled molars indicate that its feeding adaptations differed from those of the pitheciins. The morphology of both the anterior and posterior dentition, including enamel thickness and microstructure, should be taken into consideration when inferring the dietary regime of fossil species. [Copyright &y& Elsevier]

It is well recognized that enamel microanatomy in mammals reflects biomechanical demands placed upon teeth, as determined by mechanical properties of species' diets, use of teeth as weapons, and so forth. However, there are limited options for researchers wishing to perform large-scale comparisons of enamel microstructure with adaptive questions in mind. This is because to date there has been no efficient method for quantification and statistical analysis of enamel complexity. Our study proposes to apply a method previously developed for quantification of 3D tooth cusp morphology to the problem of quantifying microstructural enamel complexity. Here, we use image compression ratio (ICR) as a proxy variable for enamel complexity in 2D enamel photomicrographs taken using circularly polarized transmitted light microscopy. ICR describes the relationship between a digital image captured in an uncompressed file format and the identical image that has had its file size compressed using computer algorithms; more complex images receive less compression. In our analyses, ICR analysis is able to distinguish between images of teeth with simple, radial enamel and teeth with complex decussating enamel. Moreover, our results show a significant correlation between ICR and enamel complexity ranks assigned via visual assessment. Therefore, our results demonstrate that ICR analysis provides a viable methodology for efficient comparison of overall enamel complexity among dental samples. Anat Rec, 302:2279-2286, 2019. © 2019 American Association for Anatomy., (© 2019 American Association for Anatomy.)