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Dentition

Dentition refers to the development, arrangement, type, and number of teeth in the mouth of vertebrates, encompassing structures that evolved as elements of the dermal skeleton in jawed species for functions such as feeding, grasping, and sensory detection.^[1] In vertebrates, teeth typically consist of hard tissues including enamel or enameloid covering a core of dentin surrounding a pulp cavity with vascular and neural elements, with origins tracing back to odontodes—small, tooth-like dermal structures—predating the evolution of jaws in early forms like thelodonts and anaspids.^[1] Vertebrate dentitions vary widely by lineage, classified by morphology (e.g., homodont, with uniform teeth, as in many fish and reptiles; heterodont, with specialized types like incisors, canines, premolars, and molars, typical in mammals), and by replacement pattern (e.g., monophyodont in most reptiles with a single set; diphyodont in mammals with deciduous and permanent generations; polyphyodont in fish and some reptiles with continuous replacement).^[2] Evolutionarily, teeth likely arose through ectodermal invasion into the oropharyngeal cavity, interacting with neural crest-derived mesenchyme, with pharyngeal denticles representing an ancestral "inside-out" component later integrated into oral dentitions as jaws formed.^[1] In mammals, including humans, dentition is predominantly heterodont and diphyodont, adapting to diverse diets through specialized tooth forms: incisors for cutting, canines for tearing, premolars for crushing, and molars for grinding.^[3] Human primary (deciduous) dentition comprises 20 teeth—8 incisors, 4 canines, and 8 molars—that erupt between approximately 6 months and 3 years of age, providing initial masticatory function before replacement by the permanent set.^[4] The permanent human dentition includes 32 teeth (excluding third molars in some individuals)—8 incisors, 4 canines, 8 premolars, and 12 molars—per quadrant formula of I:2/2, C:1/1, P:2/2, M:3/3, erupting from around 6 years through adolescence, supporting advanced mastication, speech articulation, and facial structure maintenance.^[3] Anomalies in dentition, such as supernumerary teeth or agenesis, can affect occlusion and overall oral health,^[5] while comparative studies across vertebrates reveal evolutionary adaptations like hypsodont (high-crowned) teeth in herbivores for abrasive diets^[6] or acrodont (fused to jaw) forms in some lizards.^[7] Overall, dentition exemplifies modular developmental genetics, with conserved pathways like those involving BMP, FGF, and Wnt signaling patterning tooth identity and succession across species.^[1]

Fundamentals

Definition and Scope

Dentition refers to the complete set of teeth in an organism, encompassing their number, type, arrangement within the jaws, and overall condition.^[8] This biological feature is essential for functions such as feeding, defense, and sensory perception, varying widely across species in morphology and replacement patterns.^[9] The term "dentition" derives from the Latin dentitio, meaning "teething" or the process of tooth eruption, with early uses in English dating to the 17th century.^[10] While primarily associated with vertebrates—where teeth are typically mineralized structures anchored to the maxilla and mandible—analogous feeding apparatuses exist in certain invertebrates, such as the radula of mollusks, a chitinous ribbon bearing rows of microscopic teeth for scraping food.^[11] In mammals, dentition is generally diphyodont, featuring two generations of teeth: the primary (deciduous) set, which emerges during infancy and is later shed, and the permanent set that develops afterward to support adult functions.^[3] This distinction highlights the adaptive replacement mechanism unique to many mammals, allowing for larger, more durable teeth suited to mature dietary needs.^[12]

Terminology

In the study of dentition, key terms describe the morphological and developmental variations in teeth across vertebrates. Heterodont dentition refers to a condition where teeth differ in shape and function within the same jaw, typically featuring specialized types such as incisors for cutting, canines for tearing, premolars for crushing, and molars for grinding; this arrangement is characteristic of most mammals, including humans. The term derives from the Greek words heteros (different) and odous (tooth). In contrast, homodont dentition involves teeth that are uniform in shape and primarily conical, suited for grasping or piercing, as seen in many non-mammalian vertebrates like reptiles and most fish. This uniformity derives from Greek homos (same) and odous (tooth).^[2]^[13]^[14] Developmental terminology further classifies dentition based on replacement patterns. Diphyodont describes animals that develop two successive sets of teeth: a primary (deciduous) set replaced by a permanent set, a pattern prevalent in mammals to accommodate growth. The term originates from Greek di- (two), phyein (to produce), and odous (tooth), with first use around 1854 in scientific literature. Conversely, polyphyodont dentition involves continuous replacement of teeth throughout life, often in multiple generations, as observed in sharks, reptiles, and some fish, allowing adaptation to wear or injury. This derives from Greek poly- (many), phyein (to produce), and odous (tooth). Monophyodont dentition refers to animals that develop only one set of teeth with no replacement, common in certain reptiles and some other vertebrates. The term derives from Greek mono- (one), phyein (to produce), and odous (tooth).^[15]^[16]^[2] Tooth positions are standardized terms denoting specific locations and roles in the dental arch. Incisors are the anterior chisel-shaped teeth used for biting and cutting food, with eight in human adults (four maxillary, four mandibular). Canines, also called cuspids, are the pointed teeth adjacent to incisors, adapted for tearing, totaling four in humans. Premolars, or bicuspids, are posterior to canines and feature flattened surfaces for crushing and grinding, numbering eight in adults. Molars are the largest posterior teeth, designed for thorough mastication, with twelve in human adults including wisdom teeth. These positions are organized into four quadrants: the upper right (quadrant 1), upper left (quadrant 2), lower left (quadrant 3), and lower right (quadrant 4), dividing the mouth for precise identification.^[17]^[18]^[19] Notation systems facilitate consistent communication in dental practice and research, particularly for humans. The FDI World Dental Federation numbering system, adopted internationally and approved by the World Health Organization, uses a two-digit format: the first digit indicates the quadrant (1 for upper right, 2 for upper left, 3 for lower left, 4 for lower right), and the second specifies the tooth position from 1 (central incisor) to 8 (third molar) in permanent dentition, or from 1 (central incisor) to 5 (second molar) in primary dentition using quadrants 5-8. In the United States, the Universal Numbering System employs sequential numbers from 1 to 32 for permanent teeth, starting at the upper right third molar (1), proceeding clockwise to the upper left third molar (16), then counterclockwise from the lower left third molar (17) to the lower right third molar (32); primary teeth use letters A-T in a similar clockwise pattern.^[20]^[21]^[22] Related terms address alignment and attachment. Occlusion denotes the alignment and contact of upper and lower teeth during jaw closure or function, encompassing static (centric) and dynamic (chewing) relations essential for mastication and speech. Malocclusion refers to misalignment of teeth or jaws, such as overbite or crossbite, which can impair function or aesthetics and often requires orthodontic intervention. Ankylosis describes the abnormal fusion of a tooth's root (cementum or dentin) directly to the alveolar bone, eliminating the periodontal ligament and potentially causing eruption failure or occlusal issues.^[23]^[24]^[25]

Dental Anatomy

Tooth Types and Functions

In mammals, dentition is characterized by heterodonty, where teeth are differentiated into distinct types adapted for specific functions in food processing.^[6] The primary tooth types include incisors, canines, premolars, and molars, each contributing to the mechanical breakdown of food during mastication.^[26] Incisors are chisel-shaped front teeth located at the anterior of the dental arcade, primarily functioning to cut and shear food items such as vegetation or flesh.^[26] Canines, positioned lateral to the incisors, are conical and pointed, specialized for tearing and grasping prey or tough fibrous materials.^[27] Premolars, situated between canines and molars, feature broader crowns with one or more cusps and serve to crush, shear, or slice food, aiding in initial grinding.^[26] Molars, the posterior teeth, have large, flat occlusal surfaces with multiple cusps and are dedicated to grinding and pulverizing food into smaller particles for efficient swallowing and digestion.^[26] These tooth types collectively initiate digestion by mechanically reducing food particle size, increasing surface area for enzymatic action in the gastrointestinal tract.^[28] Tooth enamel, the outermost covering, provides durability with a hardness of 5 on the Mohs scale, enabling resistance to wear during repeated occlusal contacts.^[29] Beyond mastication, teeth serve secondary roles in some mammals, such as grooming; for instance, incisors and specialized tooth combs in primates and hyraxes are used to comb fur and remove parasites.^[30]^[31] Morphological variations in tooth shape reflect dietary adaptations across mammals. Cusps, the raised projections on occlusal surfaces, enhance shearing efficiency in carnivores with sharp, blade-like arrangements for slicing meat, while herbivores exhibit low, rounded cusps or flat lophs for grinding abrasive plant matter.^[32] Fissures, the grooves between cusps, facilitate food trapping and trituration, with deeper patterns in omnivores promoting versatile processing.^[33] Cingula, enamel shelves encircling the tooth base, provide structural reinforcement and additional cutting edges, particularly in early mammals adapted to mixed diets.^[34] These features evolve to optimize fracture mechanics against specific food toughness, as seen in the multi-cusped molars of folivores versus the simplified forms in insectivores.^[35]

Tooth Structure and Development

The tooth consists of four primary layers, each with distinct histological features and origins. Enamel, the outermost layer covering the crown, is ectodermal in origin and acellular, composed primarily of hydroxyapatite crystals arranged in rods that provide hardness but no regenerative capacity.^[36] Dentin, forming the bulk of the tooth beneath the enamel, is mesodermal and tubular, consisting of about 70% mineral content with odontoblast processes extending through dentinal tubules that convey sensitivity to the pulp.^[36] Cementum, a mesodermal layer covering the root surface, resembles bone in structure with embedded cementocytes and facilitates attachment to the periodontal ligament.^[36] At the core lies the pulp, a mesodermal vascularized connective tissue housing nerves, blood vessels, and odontoblasts that supports dentin formation and vitality.^[36] Tooth development, or odontogenesis, unfolds through sequential embryogenic stages beginning around the 6th week of intrauterine life. In the bud stage, epithelial thickenings from the dental lamina protrude into the underlying mesenchyme, initiating tooth germ formation under mesenchymal signaling.^[37] The cap stage follows, where the enamel organ assumes a cap-like shape, differentiating the inner enamel epithelium into ameloblasts and inducing the dental papilla and follicle for hard tissue deposition.^[37] During the bell stage, the enamel organ fully envelops the dental papilla, establishing the crown's final shape through epithelial-mesenchymal interactions, with the stellate reticulum and stratum intermedium supporting ameloblast function.^[37] Amelogenesis and dentinogenesis are interdependent processes that produce the mineralized tissues. Dentinogenesis begins first, as inner enamel epithelium induces dental papilla cells to differentiate into odontoblasts, which secrete predentin that mineralizes into dentin via calcospherites coalescing into structured layers.^[37] Amelogenesis then proceeds, with ameloblasts secreting an enamel matrix through Tomes' processes at the amelodentinal junction, followed by mineralization into hydroxyapatite prisms that mature as ameloblasts regress.^[37] Eruption involves coordinated bone remodeling to guide the tooth into the oral cavity. The periodontal ligament plays a key role in the supraosseous phase by generating propulsive forces through collagen fiber shortening and cross-linking, facilitating occlusal movement.^[38] Alveolar bone resorption, driven by osteoclasts activated by the dental follicle, creates the intraosseous pathway superior to the crown, while bone apposition occurs apically to maintain position.^[38] Developmental abnormalities can disrupt these processes, leading to structural defects. Amelogenesis imperfecta arises from genetic mutations affecting enamel formation, resulting in hypoplastic or hypomineralized enamel that is thin, discolored, and prone to wear across all teeth.^[39] Dentinogenesis imperfecta, caused by mutations in genes like DSPP, impairs dentin development, producing opaque, weakened teeth with obliterated pulp chambers and increased fracture risk.^[40]

Human Dentition

Dental Formula

The dental formula is a standardized notation system used to summarize the number and arrangement of teeth in the human dentition by type and position.^[8] It specifies the count of incisors (I), canines (C), premolars (P), and molars (M) present in one half of the upper jaw (maxilla) over the corresponding half of the lower jaw (mandible), with the total number of teeth obtained by multiplying the formula by two to reflect bilateral symmetry.^[41] This method provides a concise representation of the dentition's composition without detailing individual tooth positions or eruption timing.^[8] To calculate the dental formula, teeth are counted per quadrant—dividing the mouth into four sections (upper right, upper left, lower right, lower left)—focusing on one quadrant for the notation.^[41] For example, in the permanent human dentition, each quadrant contains 2 incisors, 1 canine, 2 premolars, and 3 molars, yielding the formula I 2.C 1.P 2.M 3 × 2, or equivalently 2.1.2.3 × 2, for a total of 32 teeth.^[8] The deciduous (primary) dentition follows a similar process but with 2 incisors, 1 canine, 0 premolars, and 2 molars per quadrant, resulting in 2.1.0.2 × 2, or 20 teeth total.^[41] This counting assumes typical symmetry and serves as a reference for normal development across the four tooth types: incisors for incision, canines for puncture, premolars for crushing, and molars for grinding.^[8] Notation variations exist between textual and graphical formats. The standard textual dental formula uses a dotted or slashed sequence, such as 2/2 1/1 2/2 3/3 for permanent dentition, separating upper and lower counts with a line.^[41] In contrast, Palmer's graphical method employs quadrant symbols (e.g., ┐ for upper right, └ for lower left) combined with numbers (1-8 for permanent teeth, starting from the midline) to denote specific teeth, facilitating detailed charting rather than summary representation.^[42] In clinical dentistry, the dental formula provides a foundational framework for identifying and documenting anomalies, such as agenesis (congenital absence of teeth, altering the count in affected categories) or supernumerary teeth (extra teeth beyond the standard formula).^[8] Dentists use it to systematically record deviations during examinations, aiding in diagnosis, treatment planning, and communication of cases like hypodontia or hyperdontia.^[43] This application underscores its role in forensic and orthodontic contexts, where deviations from the norm inform broader health assessments.^[8]

Eruption Sequence and Naming

In human primary dentition, teeth begin erupting around 6 months of age, with the mandibular central incisors typically emerging first between 6 and 10 months.^[44]^[45] The sequence generally follows mandibular central incisors, maxillary central incisors, lateral incisors, first molars, canines, and second molars, resulting in a full set of 20 primary teeth by approximately 2 to 3 years of age.^[46]^[47] Permanent dentition commences with the eruption of the first molars around 6 years of age, followed by central incisors (6-8 years), lateral incisors and first premolars (8-9 years), canines and second premolars (10-12 years), second molars (11-13 years), and third molars (wisdom teeth) between 17 and 25 years.^[38] Females generally experience earlier eruption than males across most permanent teeth, with differences of several months observed in timing.^[47]^[48] Standard naming conventions facilitate precise identification of teeth, with the Fédération Dentaire Internationale (FDI) system—also known as the ISO 3950 notation—employing a two-digit code where the first digit denotes the quadrant (1 for upper right, 2 for upper left, 3 for lower left, 4 for lower right) and the second indicates the tooth position from 1 (central incisor) to 8 (third molar); for example, tooth 11 refers to the upper right central incisor.^[49]^[50] This contrasts with the American Universal Numbering System, which sequentially numbers permanent teeth from 1 to 32 starting at the upper right third molar and proceeding clockwise, leading to discrepancies in international communication and documentation.^[51]^[52] Several factors influence the eruption sequence and timing, including genetics, which determine baseline patterns; nutrition, where deficiencies such as in calcium or vitamins can delay emergence; and pathologies like endocrine disorders or systemic conditions that may postpone or alter the process.^[53]^[54]^[55]

Comparative Dentition

Mammalian Variations

Mammalian dentition exhibits significant variations in tooth number, arrangement, and morphology, reflecting adaptations to diverse diets and lifestyles. The primitive dental formula for placental mammals, representing the ancestral condition, is 3 incisors, 1 canine, 4 premolars, and 3 molars per quadrant in both the upper and lower jaws (3.1.4.3/3.1.4.3), totaling 44 teeth.^[56] This formula has undergone reductions in many lineages; for example, carnivores like dogs display a modified formula of 3.1.4.2/3.1.4.3, with fewer upper molars to accommodate shearing carnassials for meat processing.^[6] In contrast, humans exhibit further reduction to 2.1.2.3/2.1.2.3 as a reference point for comparative heterodonty.^[57] Tooth replacement patterns also vary among mammals, with most species being diphyodont, featuring two successive generations: deciduous teeth replaced by permanent ones, as seen in humans and many other therians.^[58] However, monotremes, such as the platypus and echidna, lack functional adult dentition; the platypus has temporary teeth in juveniles that are resorbed before adulthood, while echidnas have no teeth and use grinding pads, adaptations linked to their specialized diets.^[59] Some mammals, including certain rodents and lagomorphs, further modify this by having continuously erupting teeth to compensate for heavy wear. Dietary influences drive key morphological adaptations in crown height and structure. Grazing mammals, such as horses, typically have hypsodont (high-crowned) teeth with extended roots and continuous eruption, allowing prolonged use against abrasive forage like grasses.^[6] In contrast, browsing species like deer possess brachydont (low-crowned) teeth suited to softer vegetation, with crowns that do not exceed root length and limited eruption.^[60] These differences enhance occlusal efficiency and durability tailored to feeding ecology. Specialized dental features further illustrate mammalian diversity. Rodents feature ever-growing incisors driven by persistent stem cells at the cervical loop, enabling gnawing through hard materials without wear-down.^[61] Elephants possess elongated tusks as modified upper incisors, composed primarily of dentin and used for foraging, defense, and manipulation, growing continuously throughout life.^[62] Among cetaceans, odontocetes (toothed whales) have evolved numerous simple, conical teeth—often peg-like and homodont—for grasping slippery prey like fish and squid, with tooth counts varying widely from dozens to hundreds per jaw.^[63]

Non-Mammalian Dentition

Non-mammalian dentition is characterized by polyphyodonty, where teeth are continuously replaced throughout life, and homodonty, in which teeth are generally uniform in shape and function across the jaw, contrasting with the diphyodont replacement and heterodonty typical of mammals.^[64]^[65] This arrangement supports diverse feeding strategies in vertebrates such as fish, amphibians, reptiles, and birds, with teeth often adapted for grasping, piercing, or grinding rather than specialized occlusion.^[66] In reptiles, dentition varies by implantation mode and replacement dynamics, with polyphyodonty enabling lifelong tooth renewal to maintain functionality. Acrodont teeth, fused directly to the crest of the jawbone, are prevalent in lizards such as agamids and chameleons, providing a stable anchorage but limiting individual tooth mobility and replacement.^[67] Pleurodont teeth, attached to the medial or lateral surface of the jaw, occur in snakes and many lizards, allowing for more flexible eruption and continuous substitution as worn teeth are shed lingually.^[68] This side-fused structure facilitates the resorption and regeneration cycles characteristic of reptilian polyphyodonty, where successional teeth develop asynchronously to ensure uninterrupted feeding capability.^[69] Fish exhibit highly diverse dentition adapted to aquatic environments, often featuring homodont arrangements of simple, conical teeth distributed across multiple jaw elements, including pharyngeal arches. Pharyngeal teeth, located on the gill arches, process food after initial capture by oral teeth and vary from crushing forms in herbivorous species to pointed types in carnivores.^[70] Cardiform teeth, small and comb-like in rows, aid in raking and holding slippery prey, as seen in gars and many predatory teleosts.^[71] Villiform teeth, resembling dense brushes of fine points, function similarly for grasping and piercing, enhancing grip on evasive aquatic organisms in species like catfishes and perches.^[72] Polyphyodont replacement in fish ensures rapid turnover, with teeth forming in lingual successional rows that migrate occlusally as predecessors are lost.^[64] Birds represent a notable exception among non-mammalian vertebrates, having completely lost teeth during their evolution, with the rhamphotheca—a keratinous sheath—replacing dentition as the primary feeding structure.^[73] This edentulous condition, achieved by the suppression of odontogenic pathways, allows for lightweight skulls optimized for flight, while the beak's horny covering enables diverse functions from cracking seeds to tearing flesh.^[74] Fossil evidence from Mesozoic avialans, such as Archaeopteryx, reveals ancestral toothed dentitions with conical, recurved teeth suited for carnivory, indicating that tooth loss occurred multiple times within bird lineages but was irreversible in modern forms.^[75] Amphibians display varied dentition, with frogs featuring pedicellate teeth that consist of a calcified base fused to the jaw and a separate, often bicuspid crown connected by an unmineralized zone, facilitating individual tooth replacement.^[76] This two-part structure predominates on the upper jaw bones—premaxillae, maxillae, and vomers—serving to grasp and hold prey during ingestion, while the labile crown design supports polyphyodonty through periodic shedding.^[77] In contrast, salamanders retain more uniform, homodont teeth across both jaws, and caecilians possess robust, recurved teeth for burrowing and predation, though tooth loss has evolved independently over 20 times in anuran lineages.^[77]

Evolutionary and Applied Aspects

Evolutionary History

The evolutionary origins of dentition trace back to the early vertebrates in the Cambrian period, approximately 500 million years ago, where conodonts represent some of the earliest known dental elements. These microscopic, tooth-like structures, composed of dentine and enamel, are thought to have functioned in feeding or sensory roles within the oral cavity of ancient chordates.^[78] The development of true teeth is believed to have evolved from external skin denticles, or odontodes, which were dermal structures providing protection and possibly sensory functions in primitive fish-like vertebrates; over time, these odontodes internalized and specialized within the mouth, marking a key transition from exoskeletal armor to oral dentition.^[1] A significant advancement occurred in the archosaur lineage during the late Permian to early Triassic, around 250 million years ago, with the evolution of thecodont implantation, where teeth became deeply socketed in the jawbones for enhanced stability during biting and tearing. This adaptation is characteristic of early archosaurs and their descendants, including crocodilians, which retain it today. However, teeth were subsequently lost in several archosaur groups, notably birds and some reptiles like turtles, likely due to shifts toward beak-like structures for efficient processing of food without the need for replaceable dentition; non-mammalian polyphyodonty, involving continuous tooth replacement, persisted in many reptilian lineages.^[79]^[80] Among extinct archosaurs, dinosaurs exhibited remarkable dental diversity adapted to their ecological niches. Theropod dinosaurs, such as Tyrannosaurus rex, displayed heterodont dentition with conical, recurved teeth featuring serrated edges akin to carnassial blades, enabling them to slice through flesh efficiently. In contrast, herbivorous ornithischians, including hadrosaurs and ceratopsians, evolved complex dental batteries comprising hundreds of tightly packed, self-sharpening teeth that formed grinding surfaces for processing tough plant material, representing a pinnacle of dental specialization in Mesozoic reptiles.^[81]^[82] The post-Triassic radiation of mammals, beginning around 200 million years ago, saw the refinement of heterodonty, with distinct incisors, canines, premolars, and molars enabling specialized functions like cutting, piercing, and grinding to support increasingly varied diets in terrestrial environments. This dental complexity arose from synapsid ancestors and contributed to mammalian diversification by facilitating efficient resource exploitation.^[83]^[84]

Archaeological and Forensic Uses

Dentition analysis plays a crucial role in archaeology by providing insights into the age, diet, health, and population affiliations of ancient human remains. Through examination of tooth eruption, wear patterns, and morphological traits, researchers reconstruct aspects of prehistoric lifeways, such as subsistence strategies and social structures. In forensics, dental evidence facilitates victim identification and crime scene analysis, leveraging unique tooth characteristics and preserved biological material for legal purposes.^[85] Age estimation in archaeological contexts often relies on tooth eruption sequences for subadults and wear patterns for adults, with methods like the Gustafson technique assessing regressive changes such as secondary dentin deposition, cementum apposition, root resorption, and dentin translucency to predict age at death. Developed in 1949, Gustafson's method scores these features on a scale to estimate adult ages with reasonable accuracy, particularly when combined with histological analysis, and has been validated in studies of known-age samples from various populations. In forensic applications, these techniques help determine the biological profile of unidentified remains, aiding in narrowing search parameters for missing persons.^[86]^[87]^[85] Dietary reconstruction from ancient teeth employs dental microwear analysis, which examines microscopic pits and scratches on enamel surfaces to infer food types; for instance, large pits suggest tough, abrasive foods like meat or seeds, while fine scratches indicate grassy or leafy vegetation. This approach has revealed shifts from hunter-gatherer to agricultural diets in Neolithic populations, as seen in European skeletal samples where microwear patterns correlate with increased grain consumption. Complementing microwear, stable isotope analysis of tooth enamel measures ratios of carbon (δ¹³C) and nitrogen (δ¹⁵N) to determine trophic levels and plant sources; elevated δ¹⁵N values indicate higher protein intake from animal sources, while δ¹³C distinguishes C₃ (e.g., wheat, trees) from C₄ (e.g., maize, millet) pathways, enabling paleodietary profiling in contexts like ancient Egyptian or Andean remains.^[88]^[89]^[90]^[91] Tooth morphology aids in estimating ancestry and population affinity in bioarchaeological studies by analyzing non-metric traits like shovel-shaped incisors or Carabelli's cusp, which vary systematically across groups and reflect genetic heritage. For example, multivariate statistical models applied to dental phenotypes from prehistoric European sites have traced migration patterns and admixture events over millennia. Pathological evidence, such as abscesses from untreated caries or periodontal disease, appears frequently in prehistoric skulls, indicating poor oral hygiene and dietary stressors; a two-million-year-old Paranthropus robustus specimen from South Africa showed maxillary abscesses linked to heavy wear from abrasive foods. Trepanation, an ancient cranial surgery sometimes associated with relieving dental-related headaches or infections, is evidenced in healed skull perforations from Iron Age Iranian remains, where proximity to abscessed teeth suggests therapeutic intent.^[92]^[93]^[94]^[95] In forensic odontology, bite mark analysis compares class characteristics (e.g., arch width, tooth alignment) and individual traits (e.g., unique fractures or spacing) from impressions on skin, food, or objects to suspect dentitions, though its reliability is debated due to tissue distortion. Successful applications include linking bites to perpetrators in assault cases, as documented in American Board of Forensic Odontology guidelines. Additionally, DNA extraction from dental pulp provides high-quality genetic material for identification, even in degraded remains; pulp's protected location within dentin and enamel yields sufficient nuclear DNA for STR profiling, as demonstrated in disaster victim identification efforts where teeth survived incineration.^[96]^[97]^[98]^[99]

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Sep 9, 2022 · It is the highly mineralized and the hardest tissue in the human body (number 5 on the Mohs scale), with low organic content and porosity [1].Missing: authoritative | Show results with:authoritative
[28]
Differentiation of teeth in an individual | Animal Diversity Web
In many species, incisors are used as pincers for grasping or picking, both in feeding and in grooming. ... Molars -- The most posterior teeth in the jaws of most ...
[29]
Function of the mandibular tooth comb in living and extinct mammals
Feb 12, 1981 · One of the principal functions of the tooth comb in primates is to comb the fur, and we present here indirect evidence that condylarths used this structure in ...
[30]
On the evolutionary advantage of multi-cusped teeth - PubMed Central
Many mammals feature postcanine teeth with enamel-covered cusps. Such cusps are useful in breaking down food while also shielding the soft dentine–pulp interior ...Missing: cingula | Show results with:cingula
[31]
The Diversity of Cheek Teeth
Keep an eye on how the main cusps are changed as mammals adapt to different feeding styles and food consistencies. A zalambdodont upper molar is characterized ...Missing: adaptations fissures
[32]
Modeling the effects of cingula structure on strain patterns and ...
Oct 19, 2010 · The mammalian cingulum is a shelf of enamel, which rings the base of the molar crown (fully or partially). Certain nonmammalian cynodonts ...
[33]
Mammalian dental diversity: an evolutionary template for ... - Frontiers
The number of teeth present in each tooth class varies among mammals and is not only important as a taxonomic consideration but also as a functional adaptation.
[34]
Early development of the human dentition revisited - PubMed Central
In general, the basic function of dentition is grasping and crushing food, which is supported by the extreme hardness of tooth tissues and by an appropriate ...
[35]
Histology, Tooth - StatPearls - NCBI Bookshelf - NIH
Jun 26, 2023 · The enamel covers coronal dentin, while the radicular dentin is covered with cementum. Cementum is similar to bone in structure and ...
[36]
Embryology, Teeth - StatPearls - NCBI Bookshelf
The different layers of tooth i.e., enamel, dentin, pulp, and cementum, play different roles—enamel functions to protect the dentin.
[37]
Anatomy, Head and Neck, Tooth Eruption - StatPearls - NCBI
Sep 20, 2023 · Tooth eruption results from bone remodeling processes involving bone formation and resorption mechanisms. ... The periodontal ligament is ...
[38]
Amelogenesis imperfecta - PMC - PubMed Central
Apr 4, 2007 · AI is a developmental condition of the dental enamel (characterised by hypoplasia and/or hypomineralisation) that shows autosomal dominant, autosomal recessive ...
[39]
Dentinogenesis imperfecta - Genetics - MedlinePlus
Jun 1, 2017 · Dentinogenesis imperfecta is a disorder of tooth development. This condition causes the teeth to be discolored (most often a blue-gray or yellow-brown color) ...Missing: amelogenesis | Show results with:amelogenesis
[40]
DENTAL FORMULAE - Provet
The dental formula for different species are as follows where I = incisors, C = canines, P = premolars and M = molars.Missing: authoritative | Show results with:authoritative
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Palmer notation | Radiology Reference Article | Radiopaedia.org
Aug 22, 2019 · Permanent teeth · central incisor = 1 · lateral incisor = 2 · canine/cuspid = 3 · 1st premolar/bicuspid = 4 · 2nd premolar/bicuspid = 5 · 1st molar = ...Missing: formula | Show results with:formula
[42]
Comparison of the dental anomaly frequency in patients with and ...
Therefore, the clinical implications of patterns of associated dental anomalies are important, since early detection of a single dental anomaly (such as the ...
[43]
Eruption Charts | MouthHealthy - Oral Health Information from the ADA
They also help give your face its shape and form. At birth people usually have 20 baby (primary) teeth, which start to come in (erupt) at about 6 months of age.
[44]
Teething (Teething Syndrome): Symptoms & Tooth Eruption Chart
When do all of the primary teeth erupt and fall out? ; Central incisor, 8 to 12 months. 6 to 7 years. ; Lateral incisor, 9 to 13 months. 7 to 8 years. ; Canine ( ...Missing: sequence | Show results with:sequence
[45]
Eruption Timing and Sequence of Primary Teeth in a Sample of ...
The typical order of tooth emergence is: central incisor, lateral incisor, first molar, canine, and second molar in the maxillary and mandibular arch [14,15].
[46]
Anatomy and Development of the Mouth and Teeth
The primary teeth begin to come in between the ages of 6 and 12 months. Most of the primary teeth (baby teeth) will have erupted by 33 months.
[47]
Eruption Chronology in Children: A Cross-sectional Study - PMC
The purpose of this study is to determine the appropriate reference standard for eruption timing of primary teeth in infants and preschool children of ...
[48]
Fédération Dentaire Internationale (FDI) notation - Radiopaedia.org
Mar 19, 2019 · The system uses a two number system for the location and naming of each tooth. On this page: Article: Permanent teeth; Deciduous teeth; See ...
[49]
Proposed Revision of FDI's 2-Digit Dental Numbering System - PMC
The FDI 2-digit system enhances accuracy in distinguishing between the right and left sides of the mouth as well as between upper and lower dental arches.
[50]
[PDF] Introduction of New Tooth Notation Systems in Comparison with ...
Apr 15, 2022 · As far as the FDI numbering system is concerned, there is a world of difference between tooth number 32 and tooth number 23 [4]. Page 3 ...
[51]
[PDF] Universal Tooth Designation System –Value Set – Version 1
Aug 1, 2022 · Permanent teeth are numbered 1-32, starting with the third molar (1) on the right side of the upper arch, following around the arch to the ...
[52]
Nutritional Status is Associated with Permanent Tooth Eruption in a ...
Studies have shown that calcium, vitamin D, vitamin B, and ascorbic acid deficiency may be related to different forms of periodontal disease. Malnutrition/ ...Missing: pathologies | Show results with:pathologies
[53]
Maternal and early life factors of tooth emergence patterns and ... - NIH
These include weight and length at the time of birth,7 and in early fetal life, maternal smoking8, 9 and malnutrition.Missing: pathologies | Show results with:pathologies
[54]
Tooth eruption disorders associated with systemic and genetic ...
Apr 20, 2017 · They result from the combination of two factors: on the one hand, the movements made by the germ itself, Page 4 Choukroune C. Tooth eruption ...Missing: nutrition | Show results with:nutrition
[55]
Morphoregulation of teeth: modulating the number, size, shape and ...
The primitive placental mammals have a dental formula of 3.1. 4.3./3.1. 4.3. Some rodents, mice, for example, have the dental formula, 1.0.
[56]
Lab
Look at the beaver and coyote skulls and see if you can determine the dental formula for each species. Although you will not be expected to memorize the dental ...
[57]
[PDF] Tissue Mechanical Forces and Evolutionary Developmental ... - UCSF
Oct 6, 2018 · [76,77] e) Most extant mammals have diphyodont tooth replacement, while some have evolved monophyodont dentitions (no replacement) or edentulism ...
[58]
An Evo-Devo perspective on ever-growing teeth in mammals ... - NIH
Aug 28, 2014 · During tooth evolution, the transition from a brachydont to a hypsodont tooth is thought to have led to the formation of the hypselodont tooth.
[59]
Continuously growing rodent molars result from a predictable ...
We examined evolution of the continuous growth (hypselodonty) of rodent molar teeth, which is fuelled by the presence of dental stem cells.
[60]
Asian elephant | Smithsonian's National Zoo and Conservation ...
Tusks are modified upper incisors that grow throughout an individual's life at a rate of several inches per year. They are composed of ivory, a material similar ...
[61]
Whales, Dolphins, and Porpoises: Cetaceans - Alaska Sea Grant
Odontocetes have various numbers of identical conical or spade-shaped teeth that are used to strain or grasp prey, primarily fish and squid.
[62]
Mapping the milestones in tooth regeneration: Current trends and ...
Evolutionary biology Many non-mammalian vertebrates are polyphyodonts and have cyclical rounds of tooth regeneration throughout life e.g. – in an adult cichlid ...
[63]
[PDF] Indeterminate Growth: Could It Represent the Ancestral Condition?
(A) Homodonty: all teeth in a row the same shape (many fishes, amphibians, reptiles). (B). Heterodonty: teeth different shapes in a row (e.g., the incisors, ...
[64]
A Curriculum Vitae of Teeth: Evolution, Generation, Regeneration
Teeth can be classified into three types, based on where they are formed: jaw, mouth and pharyngeal. The close relationship between past and present teeth can ...
[65]
The developmental origins of heterodonty and acrodonty as ...
Dec 17, 2021 · Phenotypic diversity and implantation mode in lepidosaurian dentitions. Lepidosaurian reptiles, including Squamata (lizard and snakes) and ...
[66]
X-ray microtomography imaging of craniofacial hard tissues in ...
Mar 7, 2022 · (A) In Timon lepidus, the most common appearance of reptilian tooth-bone interface is presented with typical asymmetrical pleurodont teeth.
[67]
Resilience of the replacing dentition in adult reptiles - PMC
Reptiles have much greater capacity for tooth replacement than mammals. Indeed, the interesting features of the replacing reptilian dentition have been studied ...
[68]
Pharyngeal teeth of the freshwater drum (Aplodinotus grunniens) a ...
Freshwater drum have three types of pharyngeal teeth: cardiform, villiform, and molariform. Molariform teeth are dominant in fish 265 mm long.
[69]
Amazing Diversity in Fish Dentition | OSU Bio Museum
May 13, 2016 · Gar – rows of small villiform teeth for capturing and holding fishes in their elongated jaws while they manipulate the fish to a headfirst ...
[70]
Tooth Types & Patches – Discover Fishes
Mar 27, 2018 · This picture shows three common types of teeth that can be found in many of the different species of bony fish.Missing: definition | Show results with:definition<|control11|><|separator|>
[71]
[PDF] Meredith_pages 1..6 - ResearchGate
Dec 11, 2014 · Instead of teeth, modern birds use a horny beak (rhamphotheca) and part of their digestive tract (muscular gizzard) to grind up and process food ...
[72]
Loss of teeth and enamel in tetrapods: fossil record, genetic data ...
Tooth loss in birds and the famous hen's teeth. Fossil and living birds constitute the Avialae (sensu Gauthier, 1986) (Fig. 2).
[73]
Macroevolutionary dynamics of dentition in Mesozoic birds reveal no ...
Mar 19, 2021 · We show that patterns of avialan tooth loss adhere to Dollo's law and suggest that the exclusive survival of toothless birds to the present represents lineage- ...
[74]
[PDF] the Tree of Life - Utexas
Most adult amphibians have teeth that are pedicellate and bicuspid, or modified from this condition. Pedicellate teeth have a zone of reduced mineralization ...
[75]
Rampant tooth loss across 200 million years of frog evolution - PMC
Jun 1, 2021 · We demonstrate that dentition is invariably present in caecilians and salamanders, but teeth have been lost completely more than 20 times in frogs.
[76]
The origin of vertebrate teeth and evolution of sensory exoskeletons
May 21, 2025 · These patterns of convergence and innervation reveal that dentine evolved as a sensory tissue in the exoskeleton of early vertebrates, a ...
[77]
Archosauria
... teeth set in sockets (called thecodont tooth implantation), and a modified ankle joint. The ancestral archosaurs probably originated some 250 million years ...
[78]
The Development of Archosaurian First-Generation Teeth in a ...
Feb 21, 2006 · In addition, teeth have been independently lost several times within nonavialan theropods, avialans, and chelonians; this loss is correlated ...
[79]
Dental features in theropods - Palaeontologia Electronica
Theropod dental features include 34 qualitative characters and 145 quantitative characters, with crown ornamentations, enamel texture, and microstructure being ...
[80]
Chew on This: Two new studies reveal secrets of early dinosaur and ...
Nov 7, 2018 · Ornithischian (“bird-hipped”) dinosaurs developed an incredible diversity of teeth, including the complex dental batteries of derived ...Missing: heterodont | Show results with:heterodont
[81]
Dental ontogeny in extinct synapsids reveals a complex evolutionary ...
Nov 7, 2018 · Heterochrony has played a prominent role in the diversification of mammalian teeth, including evolutionary changes to eruption timing and the ...
[82]
On the earliest evolution of the mammaliaform teeth, jaw joint ... - NIH
Jul 19, 2024 · Mammals are characterized by having heterodont teeth, of which most of the check teeth are supported by divided roots and display diverse morphologies.
[83]
Age-at-Death Estimation by Dental Means as a Part of the Skeletal ...
Jun 13, 2023 · Age-at-death estimation by dental means is performed by forensic odontologists and forensic anthropologists in their daily casework tasks. Both ...
[84]
Age estimation from physiological changes of teeth - PubMed Central
Conclusion: The present study concludes that Gustafson's method is a reliable method for age estimation with some proposed modifications.
[85]
Evolution of dental age estimation methods in adults over the years ...
Nov 17, 2021 · It was Gustafson, who for the first time considered the histological method for dental age estimation in adults. The histological methods were ...
[86]
Dental microwear as a diet indicator in the seventeenth-century ...
Jul 23, 2020 · The dental microwear analysis (DMA) focuses on diet reconstructions, being able to provide proxy indicators of some events regarding ...
[87]
Integrating buccal and occlusal dental microwear with isotope ...
Mar 29, 2021 · Dental microwear and stable isotope analyses have been shown to be successful techniques for paleodietary reconstruction of ancient populations ...
[88]
Tooth enamel nitrogen isotope composition records trophic position
Apr 7, 2023 · Tooth enamel nitrogen and carbon isotopes clearly record diet and trophic level in modern African mammals. We observed an average difference in ...
[89]
Stable isotopes in fossil hominin tooth enamel suggest a ... - NIH
The primary distinction in application of stable carbon isotopes to hominin diets is the difference in 13C/12C (expressed as δ13C) between C3 and C4 plants.
[90]
Dental ancestry estimation in a 1500 years old human skeleton from ...
This study demonstrates a modern approach to estimating ancestry from dental morphology in bioarcheological and forensic contexts.
[91]
Reconstructing human population history from dental phenotypes
Oct 2, 2017 · In archaeological and paleontological studies, dental phenotypic data are often used to estimate biological relatedness among past human groups, ...
[92]
[PDF] Dental abscesses on the maxilla of a two million-year-old early ...
Apr 1, 2019 · Abscesses and other periapical lesions are found in abundance in recent archeological samples, yet are scarce in the fossil hominin record.Missing: trepanation | Show results with:trepanation
[93]
An unprecedented case of cranial surgery in Longobard Italy (6th ...
Dental abscesses and ante-mortem tooth loss likely indicate poor oral health ... Prehistoric and early historic trepanation. Diseases in Antiquity. In ...
[94]
Full article: Forensic Odontology and Bite Mark Analysis
May 12, 2023 · Bite mark assessment involves assessing whether a mark is caused by a bite (see Figure 1) and/or assessing if an individual person or animal “biter” made the ...
[95]
Bite Marks - Forensic Dentistry - Dentalcare.com
A bite mark is known as the registration of the cutting edges of teeth on a substance caused by a jaw closing.
[96]
Dental DNA fingerprinting in identification of human remains - NIH
As dental pulp is surrounded by dentin and enamel, which forms dental armor, it offers the best source of DNA for reliable genetic type in forensic science.
[97]
DNA identification from dental pulp and cementum - PubMed
Oct 14, 2023 · We report on two methods of DNA isolation that minimizes destruction of the tooth when accessing the DNA within pulp and cementum.