Iran Dental Residency Entrance Exam key terms

A developmental jaw cyst lined by parakeratinized stratified squamous epithelium with a corrugated surface and palisaded basal layer. It grows along bone with minimal expansion, has a high recurrence rate, and is associated with PTCH1 mutations and nevoid basal cell carcinoma syndrome.

A benign but locally aggressive odontogenic epithelial tumor, most often in the posterior mandible, showing islands of odontogenic epithelium with reverse polarity and stellate reticulum-like centers. It is commonly solid/multicystic and requires wide resection to prevent recurrence.

A hamartomatous odontogenic lesion composed of enamel, dentin, cementum, and pulp, classified as compound when tooth-like structures form and complex when a disorganized mass forms. It is the most common odontogenic tumor and often blocks eruption of adjacent teeth.

An anucleate, pale eosinophilic epithelial cell seen in calcifying odontogenic cysts and ghost cell odontogenic tumors. The cells may undergo calcification and are a diagnostic hallmark of these lesions.

An inherited autosomal dominant defect of dentin formation, with opalescent blue-brown teeth, bulbous crowns, obliterated pulp chambers, and rapid wear. It occurs alone or as part of osteogenesis imperfecta.

A group of hereditary defects affecting enamel formation, classified as hypoplastic, hypomaturation, or hypocalcified types. Enamel is thin, soft, or discolored, and the condition may be autosomal dominant, recessive, or X-linked.

A malignant neoplasm of oral stratified squamous epithelium, strongly linked to tobacco and alcohol, often presenting as an indurated nonhealing ulcer. Prognosis depends on stage, depth of invasion, and nodal metastasis.

A predominantly white mucosal plaque that cannot be clinically or pathologically classified as any other disease. It is a clinical diagnosis of exclusion and carries a variable risk of dysplasia and malignant transformation.

Disordered epithelial maturation with cytologic atypia, including altered nuclear-cytoplasmic ratio, hyperchromatism, and loss of polarity. It is graded mild, moderate, or severe and represents a premalignant change.

Physiologic or pathologic wearing of tooth structure caused by tooth-to-tooth contact during mastication or parafunction. It produces flattened, polished wear facets on occlusal and incisal surfaces and may expose dentin.

Irreversible loss of dental hard tissue by chemical dissolution from acids of intrinsic or extrinsic origin, without bacterial involvement. It produces smooth, cupped, or scooped lesions, often on palatal and cervical surfaces.

Pathologic wearing of tooth structure by mechanical friction from foreign objects such as toothbrushes or abrasive dentifrices. Lesions are typically wedge-shaped and located at the cervical margin.

An intraoral radiograph showing the crowns of maxillary and mandibular posterior teeth on one image. It is used mainly to detect interproximal caries and to assess alveolar crest bone levels.

An intraoral radiograph that shows the entire tooth including the root apex and surrounding periapical bone. It is used to detect apical pathosis, root fractures, and root resorption, and to evaluate endodontic treatment.

A three-dimensional imaging technique using a cone-shaped X-ray beam and flat detector to reconstruct volumetric data of the maxillofacial region. It provides high spatial resolution with lower dose than medical CT for evaluating bone, impactions, and root canals.

A standardized scale of radiodensity used in computed tomography, where water is zero and air is about minus 1000. It allows objective comparison of tissue densities and is used to characterize lesions and bone quality.

An intraoral radiograph taken with the film or sensor parallel to the occlusal plane, showing a wide view of the dental arch and floor of the mouth or palate. It is useful for localizing sialoliths, impacted teeth, and root fragments.

A calcified concretion within a salivary gland or duct, most common in the submandibular gland. It causes recurrent painful swelling, especially at mealtimes, and is often visible on occlusal or panoramic radiographs.

The subjective sensation of dry mouth, which may result from reduced salivary flow, medications, Sjogren syndrome, or radiotherapy. It increases caries risk, dysphagia, and oral candidiasis.

An opportunistic fungal infection of oral mucosa caused mainly by Candida albicans, presenting as removable white plaques, erythema, or angular cheilitis. It is associated with immunosuppression, antibiotics, and denture wear.

A chronic immune-mediated mucocutaneous disease producing white reticular striae, erosions, or plaques on oral mucosa. The erosive form is painful and requires biopsy and long-term follow-up because of a small malignant potential.

The distance from a coronal reference point to the apical constriction or intended apical limit of root canal preparation. It is determined by radiographs and electronic apex locators to avoid over- or under-instrumentation.

A device that measures electrical impedance between the endodontic file and the periodontium to locate the apical constriction. It provides reliable working length determination even in the presence of blood or exudate.

The narrowest point of the root canal near the cementodentinal junction, where pulp tissue transitions to periodontal tissue. It is the ideal apical limit for instrumentation and obturation.

A microcrystalline layer of dentin debris and organic material created on canal walls by instrumentation. It reduces dentin permeability and bacterial penetration but may harbor bacteria, so removal with chelating agents is often recommended.

The most widely used endodontic irrigant, with antimicrobial and tissue-dissolving properties. It is used at concentrations of 0.5 to 5.25 percent and can cause severe tissue damage if extruded beyond the apex.

A chelating irrigant used in endodontics to remove the smear layer and demineralize the superficial dentin wall. It is typically used in low concentration as a final rinse after sodium hypochlorite.

The distance from the cementoenamel junction to the base of the periodontal pocket, reflecting the amount of periodontal support lost. It is the key measure for staging periodontitis.

The distance from the gingival margin to the base of the sulcus or pocket, measured with a periodontal probe. It is interpreted together with gingival margin position and attachment loss.

A classification of periodontitis severity and extent based mainly on clinical attachment loss, radiographic bone loss, tooth loss, and complexity factors. Stages I to IV guide prognosis and treatment planning.

A surgical periodontal procedure using barrier membranes to exclude gingival epithelium and connective tissue from a defect, allowing slower periodontal ligament and bone cells to repopulate. It is used for intrabony and furcation defects.

Direct structural and functional connection between living bone and the surface of a load-bearing implant without intervening fibrous tissue. It depends on primary stability, biocompatible material, and controlled loading.

The protective effect of a circumferential band of dentin, at least 1.5 to 2 mm in height, surrounding a tooth preparation and retained by a crown. It resists lever forces and reduces root fracture risk.

A foundation restoration placed in a prepared root canal to retain a coronal restoration when insufficient tooth structure remains. The post provides retention, while the core replaces missing coronal dentin.

The accuracy with which a restoration fits the prepared tooth margin, minimizing the gap and cement film thickness. Poor adaptation increases plaque accumulation, microleakage, and caries risk.

An occlusal arrangement in complete dentures in which contacts occur bilaterally and simultaneously in centric relation and are maintained during eccentric movements. It improves stability and distributes forces.

A maxillomandibular relationship in which the condyles articulate with the thinnest avascular portion of their disks, independent of tooth contact. It is a reproducible reference position used in prosthodontics and occlusal diagnosis.

The distance between selected maxillary and mandibular landmarks when the teeth or occlusion rims are in maximum intercuspation. It is a key parameter in complete denture construction and full-mouth rehabilitation.

Measurement of skeletal and dental relationships on a standardized lateral head radiograph, using angular and linear values to assess growth, jaw position, and treatment change. It is fundamental to orthodontic diagnosis and treatment planning.

Resistance to unwanted tooth movement, provided by teeth, bone, or extraoral and skeletal devices during orthodontic treatment. It is classified as maximum, moderate, or minimum depending on the planned tooth movement.

Evaluation of a patient's remaining growth potential using cervical vertebral maturation, hand-wrist radiographs, or midpalatal suture status. It guides timing of growth modification and orthognathic surgery.

Removal of the coronal pulp while preserving vital radicular pulp tissue, usually performed in primary molars with deep caries. Success depends on achieving hemostasis and a bacteria-tight restoration.

Complete removal of coronal and radicular pulp tissue followed by canal obturation, typically with a resorbable paste in primary teeth. It is indicated when radicular pulp is irreversibly inflamed or infected.

A preformed metal crown used to restore extensively damaged primary molars and sometimes permanent teeth. It provides durable full-coverage protection and is cemented after minimal tooth preparation.

Local anesthetic injection into soft tissue near the terminal nerve endings to block sensation in a limited area. It is commonly used in the maxilla and for mandibular primary teeth.

A mandibular nerve block depositing anesthetic near the inferior alveolar nerve before it enters the mandibular foramen. It anesthetizes mandibular teeth on one side, along with lip and chin sensation.

The fascial space between the medial pterygoid muscle and the mandibular ramus, containing the inferior alveolar and lingual nerves. It is the target region for the classic inferior alveolar nerve block.

A rapidly spreading bilateral cellulitis of the submandibular and sublingual spaces, often of odontogenic origin, causing board-like swelling and airway threat. It requires urgent airway management and surgical drainage.

Exposed irradiated bone that fails to heal for at least three months without evidence of tumor recurrence, occurring after high-dose radiotherapy. It is managed with conservative care, antibiotics, and sometimes hyperbaric oxygen or resection.

Exposed bone in the maxillofacial region persisting for more than eight weeks in a patient receiving or previously treated with antiresorptive or antiangiogenic drugs, without radiotherapy history. It is often triggered by extraction.

A rapid, transient reversal of membrane potential produced by sequential sodium influx and potassium efflux in excitable cells. It propagates along axons and triggers neurotransmitter release at synapses.

The steady electrical potential difference across a cell membrane at rest, typically about minus 70 millivolts in neurons, maintained mainly by potassium permeability and the sodium-potassium pump. It sets the baseline for excitation.

Reversible blockade of voltage-gated sodium channels in nerve membranes, preventing depolarization and impulse conduction. Unmyelinated and small fibers are blocked first, producing loss of pain before touch and motor function.

The quantitative study of reaction rates catalyzed by enzymes, including Michaelis-Menten behavior, Km, and Vmax. It explains substrate affinity, inhibition types, and effects of pH and temperature.

Reversible enzyme inhibition in which an inhibitor resembling the substrate binds the active site, raising apparent Km while leaving Vmax unchanged. It can be overcome by increasing substrate concentration.

The cytoplasmic pathway converting glucose to pyruvate with net production of two ATP and two NADH molecules. Under anaerobic conditions pyruvate is reduced to lactate, regenerating NAD for continued glycolysis.

The mitochondrial cycle that oxidizes acetyl coenzyme A to carbon dioxide, generating NADH, FADH2, and GTP. It is the central pathway linking carbohydrate, fat, and protein metabolism to oxidative phosphorylation.

A group of plasma proteins activated in cascade fashion to opsonize microbes, promote inflammation, and form membrane attack complexes. It bridges innate and adaptive immunity and is activated by classical, lectin, or alternative pathways.

A glycoprotein antibody produced by plasma cells, composed of two heavy and two light chains with variable antigen-binding sites. Classes IgA, IgD, IgE, IgG, and IgM differ in effector function and distribution.