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Primary mandibular central incisors usually emerge first, at about 6 to 10 months of age. Eruption timing varies, but the mandibular central incisor pair is the earliest primary dentition to appear.
Enamel is approximately 96% mineral by weight, and that mineral is mainly hydroxyapatite. Its high mineral content gives enamel its hardness and radiopacity.
Reactionary dentin is tertiary dentin produced by surviving odontoblasts after a mild stimulus. It is deposited at the pulp-dentin interface and tends to be less regular than primary dentin.
Oblique fibers run from cementum apically to alveolar bone and are oriented to resist axial or intrusive loading. They are the most numerous principal fiber group in the periodontal ligament.
Bicarbonate is the major buffer in saliva and helps neutralize acids produced by plaque bacteria. Its concentration rises with salivary flow rate, improving buffering after stimulation.
Streptococcus mutans adheres to the acquired pellicle, produces glucans from sucrose, and is highly acidogenic. These traits make it a key initiator of smooth-surface caries.
Topical fluoride promotes remineralization and reduces demineralization by forming fluorapatite and inhibiting bacterial acid production. These effects occur at the tooth-plaque interface.
The established gingival lesion is dominated by plasma cells and lymphocytes, reflecting a chronic humoral immune response. Neutrophils are more prominent in the early acute response.
A typical maxillary first molar has four main cusps: mesiobuccal, distobuccal, mesiolingual, and distolingual. The cusp of Carabelli, when present, is an accessory fifth cusp.
In canine guidance, the working-side canine contacts during lateral movement and discludes the posterior teeth on both sides. This reduces lateral forces on posterior teeth.
The acquired pellicle forms rapidly as salivary glycoproteins adsorb to the enamel surface. It is not mineralized and serves as a substrate for bacterial adhesion.
Calculus is mineralized dental plaque, with calcium phosphate salts deposited among the organic matrix and microorganisms. Supragingival calculus is generally less dense than subgingival calculus.
Osteoclasts are multinucleated cells that resorb bone by secreting acid and proteolytic enzymes. In periodontitis, inflammatory cytokines promote osteoclast activity and alveolar bone loss.
The mandibular division of the trigeminal nerve supplies sensation to mandibular teeth and associated tissues. The maxillary division supplies the upper teeth, while the ophthalmic division supplies the upper face and eye region.
Epinephrine is a vasoconstrictor that reduces local blood flow, slowing anesthetic absorption and prolonging its effect. It also improves hemostasis in the injection area.
Vitamin C is required for hydroxylation of proline and lysine during collagen synthesis. Deficiency can cause defective collagen, gingival bleeding, and delayed wound healing.
Hemostasis and clot formation occur immediately after surgery and provide the provisional matrix for healing. Epithelialization, granulation tissue, and collagen deposition follow in later phases.
Secretory IgA is the main immunoglobulin in saliva and mucosal secretions. It inhibits microbial adhesion and neutralizes antigens at mucosal surfaces.
The enamel organ arises from oral ectoderm, and ameloblasts differentiate from this epithelial source. Dentin and pulp, by contrast, arise largely from neural crest-derived ectomesenchyme.
Dens invaginatus results from infolding of the enamel organ before mineralization, producing a channel lined by enamel and dentin. It commonly affects maxillary lateral incisors.
Porphyromonas gingivalis is one of the red complex organisms strongly associated with chronic periodontitis. It produces proteases and virulence factors that promote tissue destruction.
Enamel demineralization begins near pH 5.5 when plaque acids lower the local pH. This critical value varies with calcium and phosphate concentrations but is commonly taught as 5.5.
Acellular extrinsic fiber cementum covers the cervical and middle portions of the root and contains Sharpey fibers for periodontal ligament attachment. Cellular cementum is more prominent apically.
The temporomandibular joint is a synovial joint with a fibrocartilaginous articular disk that divides it into upper and lower compartments. It permits both hinge and gliding movements.
Nonselective beta-blockers block beta-adrenergic receptors and can blunt the cardiovascular effects of epinephrine. This interaction may also produce an exaggerated pressor response from unopposed alpha stimulation.
A complete primary dentition contains five teeth per quadrant - two incisors, one canine, and two molars - for a total of 20. The permanent dentition replaces these and adds premolars and third molars to reach 32 teeth. A count above 20 in a young child suggests supernumerary or permanent teeth have erupted.
The mineral phase of all calcified dental and skeletal tissues is predominantly hydroxyapatite, a crystalline calcium phosphate. Its structure allows substitution of ions such as fluoride and carbonate, which alters solubility. Calcium carbonate and calcium oxalate are not the main mineral of these tissues.
The parotid glands are large serous glands that supply roughly half of the saliva produced under stimulation. At rest, the submandibular glands provide the largest resting volume. Sublingual and minor glands contribute comparatively small amounts at all flow rates.
Vitamin D is hydroxylated to calcitriol, which increases intestinal absorption of calcium and phosphate and supports mineralization of developing dental tissues. Deficiency during odontogenesis can produce enamel hypoplasia and poorly mineralized dentin. The other listed vitamins are not directly responsible for calcium absorption.
The periodontal ligament is a dense connective tissue whose principal fiber bundles insert into cementum on one side and alveolar bone on the other. This arrangement suspends the tooth in its socket and converts occlusal load into tension on bone. Cementum is produced by cementoblasts, and the pulp receives blood from separate vessels entering through the apical foramen.
In health the gingival sulcus is a shallow crevice measuring roughly 1 to 3 mm with light probing force. Depths of 4 mm or more usually indicate attachment loss or gingival enlargement and should be interpreted together with bleeding and clinical attachment level. Sulci shallower than 1 mm are not characteristic of a healthy adult periodontium.
The facial nerve, cranial nerve VII, supplies the muscles of facial expression, including the orbicularis oris and buccinator that position the lips and cheeks during chewing. The trigeminal nerve carries sensation from the face and oral cavity but does not provide this motor supply. The hypoglossal and glossopharyngeal nerves serve the tongue musculature and pharyngeal sensation.
Community water fluoridation is maintained at approximately 0.7 mg/L, or ppm, fluoride, a level that reduces caries while limiting the risk of fluorosis. Concentrations near 2 ppm exceed the recommended level and can produce enamel fluorosis. Concentrations far below 0.7 ppm provide little cariostatic benefit.
Streptococcus sanguinis and related oral streptococci attach first to salivary proteins of the acquired pellicle and form the initial layer of biofilm. Their presence creates binding sites that allow bridging organisms and later anaerobes to colonize. Porphyromonas gingivalis, Treponema denticola, and lactobacilli appear later in biofilm maturation.
Lactobacillus species are acidogenic and highly acid-tolerant, so they thrive in the low-pH environment of an advancing lesion and are associated with dentinal progression. They are generally regarded as secondary invaders rather than initiators of the lesion. Streptococcus sanguinis is an early plaque colonizer, and Veillonella and Fusobacterium are not the principal acid producers in dentinal caries.
Phenytoin is a classic cause of drug-induced fibrous gingival enlargement, affecting a substantial proportion of long-term users. The mechanism involves fibroblast proliferation and increased collagen synthesis, and plaque control influences the severity. Metformin, atorvastatin, and levothyroxine are not associated with this effect.
Tetracyclines chelate calcium and are incorporated directly into enamel, dentin, and bone during mineralization. The drug fluoresces under ultraviolet light and darkens with light exposure, producing yellow-brown intrinsic staining. The other processes do not require the drug to be present at the time of mineral deposition.
Bicarbonate concentration rises with salivary flow rate and becomes the dominant buffer of stimulated whole saliva, protecting enamel against acid challenges. Phosphate contributes more at low flow rates, and urea-derived ammonia plays only a minor buffering role in most individuals. Protein buffers contribute little to overall salivary buffering capacity.
Gingival crevicular fluid is a serum-derived transudate whose volume increases as inflammation raises vascular permeability in the gingival connective tissue. Flow rises measurably within days of plaque accumulation, even before clinical attachment loss. Measuring the flow can therefore indicate the presence of active gingival inflammation.
Junctional epithelial cells attach to the tooth by hemidesmosomes anchored to an internal basal lamina, forming the epithelial attachment. Collagen fiber bundles inserting into cementum belong to the connective tissue attachment, which is a separate structure. Desmosomes and gap junctions connect epithelial cells to one another rather than to the tooth.
Parathyroid hormone responds to low serum calcium by stimulating osteoclastic bone resorption and by increasing renal tubular reabsorption of calcium. It also promotes phosphate excretion and activates vitamin D to enhance intestinal calcium absorption. It does not lower serum calcium or suppress resorption.
Plaque bacteria ferment sucrose rapidly, driving plaque pH down to about 5.0 or lower within 5 to 20 minutes of the challenge. Salivary buffering and remineralization then restore pH toward neutrality over the following 30 to 60 minutes. This rapid fall and slow recovery is the basis of the Stephan curve.
Rising progesterone and estrogen during pregnancy alter gingival vasculature and modulate the inflammatory response, exaggerating the reaction to plaque. The condition usually resolves after delivery as hormone levels return to baseline. Diet and hygiene changes are secondary contributors, and the condition is not explained by changes in pathogen counts.
Amide anesthetics are metabolized mainly by hepatic microsomal enzymes, which is why severe liver disease can prolong their effect. Ester anesthetics such as procaine and benzocaine are hydrolyzed in plasma by pseudocholinesterase. The kidney excretes metabolites rather than the parent amide compound.
Actinomyces viscosus and other Actinomyces species colonize exposed cementum and dentin and are the organisms most consistently associated with root caries. Streptococcus mutans is linked primarily to coronal caries initiation. Veillonella and Campylobacter are not the principal pathogens of root surface lesions.
The pKa governs the equilibrium between the charged and uncharged forms of the drug at tissue pH, and only the uncharged base crosses the nerve membrane. A lower pKa relative to tissue pH yields more base and a faster onset. Lipid solubility governs potency and protein binding influences duration, not the fraction of diffusible base.
Peritubular, or intratubular, dentin forms a highly mineralized cuff lining each tubule and contains far less collagen than the surrounding intertubular matrix. The odontoblast process occupying the tubule lumen is cellular and not mineralized. The dentinoenamel junction is a boundary zone between two tissues rather than a structure within a tubule.
Lactoperoxidase catalyzes the oxidation of salivary thiocyanate by hydrogen peroxide to hypothiocyanite, which damages bacterial membranes and interferes with glycolysis. Iron sequestration is the mechanism of lactoferrin rather than lactoperoxidase. Peptidoglycan hydrolysis and DNA cleavage are carried out by lysozyme and DNase respectively.
Five percent sodium fluoride varnish contains about 2.26% fluoride ion, which equals roughly 22,600 ppm. It is applied in small quantities and sets on the tooth surface to release fluoride over time. A 5,000 ppm product is a prescription high-fluoride dentifrice, and 1,000 to 1,500 ppm products are standard over-the-counter dentifrices.
Nicotine and other tobacco constituents cause vasoconstriction and blunt the vascular inflammatory response, so a smoker's gingiva may bleed little despite advanced destruction. Smokers also show impaired neutrophil function and poorer healing, so their disease is often more severe than bleeding scores suggest. Bleeding is therefore a less reliable screening indicator in smokers.