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Enamel is the most highly mineralized tissue in the body, with roughly 96% inorganic content by weight, and that mineral is overwhelmingly carbonated hydroxyapatite. Octacalcium phosphate and amorphous calcium phosphate act as transient precursors during mineralization but are not the stable end product.
Dentin matrix is approximately 90% type I collagen, which forms the scaffold for apatite deposition along and between the fibrils. Type III collagen appears in small amounts, particularly in mantle dentin and in reparative tissue.
The parotid is a purely serous gland, producing a watery, enzyme-rich secretion. The submandibular gland is mixed but predominantly serous, while the sublingual and most minor glands are predominantly mucous.
The mandibular division (V3) is the only mixed branch of the trigeminal nerve, carrying general sensation from the lower face plus motor fibers to the muscles of mastication and several suprahyoid muscles. The ophthalmic and maxillary divisions are purely sensory.
Oblique fibers run from the root surface coronally to insert into bone, converting vertical occlusal force into tension and compressing the apical region. This arrangement makes them the principal load-bearing group.
Cellular cementum contains cementocytes trapped in lacunae within the matrix, whereas acellular cementum has no entrapped cells. Both types are collagenous, are formed by cementoblasts, and anchor Sharpey fibers.
Glucosyltransferase cleaves sucrose and links the glucose moieties into glucans that promote bacterial adhesion and plaque matrix formation. This is why frequent sucrose exposure favors cariogenic biofilm development.
Enamel hydroxyapatite dissolves when plaque fluid pH drops below about 5.5, which is why the Stephan curve drop after sugar exposure is clinically important. Root surfaces, with less mineral content, demineralize at a higher pH of about 6.2 to 6.7.
Calculus forms when plaque biofilm undergoes mineralization by calcium and phosphate from saliva and crevicular fluid. Because it is a mineralized plaque deposit, it retains a porous surface that favors further plaque accumulation rather than acting as a primary irritant itself.
Osteoclasts are multinucleated cells formed by fusion of hematopoietic precursors of the monocyte–macrophage lineage. This origin, plus their requirement for RANKL signaling, distinguishes them from bone-forming osteoblasts.
Lining mucosa covers flexible, non–load-bearing oral surfaces and is nonkeratinized or thinly parakeratinized. Masticatory mucosa is keratinized and covers the gingiva and hard palate, whereas specialized mucosa refers to the dorsum of the tongue.
Bicarbonate concentration rises sharply with salivary flow rate, making it the dominant buffer of stimulated saliva. At low resting flow, phosphate and protein buffers play a proportionally larger role.
Secretory IgA is produced by plasma cells near salivary ducts and acquires its secretory component during transepithelial transport, making it the major mucosal antibody in saliva. It inhibits bacterial adhesion without triggering strong inflammatory responses.
The lateral pterygoid pulls the condyle and disc forward, producing protrusion and assisting in opening. The masseter, medial pterygoid, and temporalis are primarily elevator muscles that close the jaw.
Special taste fibers from the anterior tongue travel with the chorda tympani branch of the facial nerve, which joins the lingual nerve to reach the tongue. General sensation from the same region is carried by the lingual nerve itself, which is a branch of V3.
Neutrophils are the first leukocytes to emigrate from postcapillary venules in acute inflammation, arriving within minutes to hours. Macrophages and lymphocytes follow later or dominate chronic lesions, and plasma cells characterize established chronic inflammation.
In acidified bacterial cells, fluoride enters as hydrogen fluoride and releases fluoride ion that inhibits enolase, a key glycolytic enzyme, thereby reducing acid production. This antibacterial effect supplements fluoride's remineralization and crystal-stability actions.
Aggregatibacter actinomycetemcomitans produces leukotoxin and other virulence factors and is strongly linked to the localized aggressive pattern of rapid attachment loss around first molars and incisors in adolescents. Streptococcus mutans drives caries, while Veillonella and Actinomyces are associated with other plaque communities.
Early repair tissue contains fine, randomly oriented type III collagen that is progressively degraded and replaced by stronger type I collagen during maturation and remodeling. This shift increases tensile strength as the scar matures.
The anterior mandibular teeth and midline lower lip drain first to the submental nodes, which lie beneath the chin, before passing to submandibular and deep cervical nodes. The submandibular nodes collect the posterior mandibular teeth and most of the maxillary dentition.
The posterior superior alveolar arteries arise from the maxillary artery and enter the posterior maxilla to supply the molar pulps and sinus lining. The facial, lingual, and ascending pharyngeal arteries supply other regions of the head and neck.
The epithelial cells of the junctional epithelium adhere to enamel or cementum by hemidesmosomes facing an internal basal lamina. This attachment forms the epithelial seal that separates the oral environment from the connective tissue.
In healthy sulci, fluid enters as a transudate from gingival capillaries; with inflammation, increased permeability makes it an exudate containing cells, immunoglobulins, and enzymes. Its volume and composition are therefore used as indicators of periodontal inflammation.
The alveolar bone proper is bundle bone because extrinsic Sharpey fibers of the periodontal ligament insert directly into it. This dense, perforated plate lines the socket and appears as a thin radiopaque line, the lamina dura.
The mandibular first molar erupts at about 6 years, generally preceding or coinciding with the mandibular central incisor, and is often called the six-year molar. Because it erupts distal to the primary dentition, it is frequently mistaken for a primary tooth.
Ameloblasts are the specialized epithelial cells of the inner enamel epithelium that secrete the enamel matrix before mineralizing and then retract. Odontoblasts form dentin, cementoblasts form cementum, and fibroblasts produce connective tissue collagen.
Mature enamel is approximately 96% mineral by weight, and that mineral is principally hydroxyapatite. Enamel contains almost no collagen, little water, and only trace organic material after maturation.
The parotid gland contains only serous acini and is therefore a pure serous gland. The submandibular gland is mixed but predominantly serous, and the sublingual gland is mixed but predominantly mucous.
Oblique fibers run from the alveolar bone obliquely to the root and constitute the largest fiber group; their orientation converts axial occlusal force into tension on the ligament. Alveolar crest, horizontal, and interradicular fibers resist other directional loads or are limited to multirooted teeth.
Vitamin C is required for hydroxylation of proline and lysine during collagen synthesis, so deficiency weakens collagen and produces capillary fragility and impaired healing. Vitamin D, K, and B12 deficiencies produce different clinical pictures such as rickets, bleeding diathesis, and megaloblastic anemia.
The acquired pellicle is a thin, acellular film formed by selective adsorption of salivary glycoproteins and other macromolecules onto the tooth surface. Bacterial polysaccharides form the plaque matrix, epithelial cells are not a structural component, and calcium salts form calculus.
The mandibular division of the trigeminal nerve carries motor fibers to the masseter, temporalis, medial pterygoid, lateral pterygoid, mylohyoid, and anterior digastric. The facial nerve supplies muscles of facial expression, the hypoglossal nerve supplies the tongue, and the glossopharyngeal nerve supplies the stylopharyngeus and pharyngeal sensation.
Enamel is approximately 96% mineral by weight, exceeding dentin, cementum, and bone, each of which contains substantially more organic matrix and water. This high mineral content gives enamel its hardness and brittleness.
Hertwig's epithelial root sheath is a collar of epithelial cells that proliferates from the cervical loop and guides the pattern, number, and shape of roots before inducing odontoblast differentiation. Crown mineralization and the dental papilla arise earlier from other structures.
Secondary dentin is deposited by odontoblasts at a slow, regular rate after root completion and continues throughout the life of the tooth, gradually reducing pulp chamber size. Reparative or tertiary dentin forms in response to injury, and dentin is produced by odontoblasts rather than ameloblasts.
Fermentable carbohydrate is rapidly metabolized by plaque bacteria to organic acids, causing pH to fall within minutes to a minimum and then recover over roughly 30 to 60 minutes as buffers and clearance act and acid production slows. Even in patients with good oral hygiene, a similar curve occurs, though from a different baseline.
Parathyroid hormone increases serum calcium by promoting renal calcium reabsorption, stimulating renal production of active vitamin D, and increasing osteoclast-mediated resorption, largely through signaling from osteoblasts. It enhances rather than inhibits calcium reabsorption and promotes phosphate excretion.
Interleukin-1 beta is a proinflammatory cytokine that upregulates RANKL and other mediators, driving osteoclast differentiation and bone loss in periodontitis. Interferon gamma and transforming growth factor beta generally exert immunomodulatory or antifibrotic effects, and immunoglobulin A is an antibody rather than a cytokine.
The red complex comprises Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia, organisms strongly associated with advanced periodontitis. Fusobacterium nucleatum acts as a bridging organism, while Aggregatibacter actinomycetemcomitans is linked to aggressive periodontitis and Capnocytophaga species are associated with other clinical conditions.
Epinephrine constricts local vessels, slowing systemic absorption so more anesthetic remains at the nerve and duration increases, while reduced blood flow also improves hemostasis. Slower absorption lowers rather than raises systemic toxicity, and onset depends mainly on the anesthetic's pKa and diffusion.
Wharton's duct travels in the floor of the mouth and opens at the sublingual caruncle lateral to the lingual frenum. The parotid duct opens at the parotid papilla, and the palatine and incisive foramina transmit nerves and vessels.
The masseter elevates the mandible and, with the temporalis and medial pterygoid, provides the closing force of mastication. The anterior digastric and lateral pterygoid assist depression and protrusion, and the platysma is a muscle of facial expression.
Attached gingiva is covered by parakeratinized or orthokeratinized stratified squamous epithelium, which provides a protective surface against masticatory friction. Nonkeratinized epithelium lines the sulcular and alveolar mucosa, and the other epithelial types listed occur elsewhere in the body.
Hyperglycemia impairs neutrophil chemotaxis and phagocytosis while forming advanced glycation end products that promote inflammation and microvascular damage, increasing periodontal destruction. Salivary flow is typically reduced and crevicular glucose is increased in poorly controlled diabetes.
The maxillary artery arises from the external carotid artery and gives off branches such as the inferior alveolar, posterior superior alveolar, and greater palatine arteries. The internal carotid supplies intracranial structures, while the facial and lingual arteries are separate branches of the external carotid.
RANKL, expressed by osteoblasts and stromal cells, binds the RANK receptor on osteoclast precursors to promote their differentiation, fusion, and activation; osteoprotegerin is a decoy receptor that neutralizes RANKL. In periodontitis, inflammatory cytokines increase RANKL relative to osteoprotegerin.
Mandibular incisors often lie labially with a thin buccal bony plate and a narrow band of attached gingiva, so even mild inflammation or brushing trauma can lead to attachment loss and recession. Thick bone and broad keratinized tissue are protective, and all teeth are supported by periodontal ligament fibers.
The mylohyoid arises from the mylohyoid line of the mandible and forms the floor of the mouth, separating the sublingual space above from the submandibular space below. This relationship explains the spread of oral infections between these spaces.
The greater palatine nerve emerges from the greater palatine foramen and supplies the posterior hard palate and palatal gingiva. The nasopalatine nerve supplies the anterior hard palate, the lesser palatine nerve supplies the soft palate, and the anterior superior alveolar nerve supplies maxillary anterior teeth.
Fluoride incorporated during remineralization forms fluorapatite, which has lower solubility than hydroxyapatite and is more resistant to acid challenge. It also enhances calcium and phosphate precipitation and inhibits demineralization, but it does not remove calcium or chelate it.