Taiwan Dentist Licensing Examination key terms

A tightly packed column of hydroxyapatite crystals running from the dentinoenamel junction toward the tooth surface, forming the basic structural unit of enamel. Rod direction and decussation influence how enamel resists chewing forces and how caries spreads.

The process by which ameloblasts secrete and mineralize enamel matrix, beginning at the dentinoenamel junction and proceeding outward. It occurs only before tooth eruption, so enamel cannot regenerate after destruction.

The scalloped boundary where enamel meets dentin at the crown. Its uneven contour increases mechanical interlocking between the two tissues and affects the pattern of caries progression and cavity preparation margins.

Microscopic channels radiating through dentin from the pulp to the dentinoenamel or cementoenamel junction, containing odontoblast processes and fluid. Their diameter and density explain dentin sensitivity and the rapid pulpal spread of caries.

A defensive pulpal response in which mineral is deposited inside dentinal tubules beneath an advancing lesion, narrowing or blocking them. This reduces dentin permeability and slows the progress of caries toward the pulp.

Tertiary dentin formed by surviving primary odontoblasts in response to a mild stimulus such as slow caries or attrition. It increases the distance between the irritant and the pulp, protecting pulp vitality.

A fibrous connective tissue occupying the space between the tooth root and alveolar bone, containing collagen bundles, vessels, and nerve endings. It suspends the tooth, transmits occlusal force, and provides proprioception.

A thin mineralized tissue covering the root surface that anchors periodontal ligament fibers. It is avascular and continues to be deposited throughout life, which allows adaptive changes in attachment.

A nonkeratinized epithelial layer attached to the tooth surface at the base of the gingival sulcus, forming the epithelial seal. Its permeability and rapid turnover make it the first barrier breached in periodontal disease.

A pathologically deepened gingival sulcus caused by apical migration of the junctional epithelium and loss of connective tissue attachment. Its depth and bleeding on probing are key clinical indicators of active periodontal disease.

The distance from the cementoenamel junction to the base of the gingival sulcus or pocket, measured clinically. Unlike probing depth, it reflects cumulative attachment loss and is the standard measure of periodontal destruction over time.

A microcrystalline debris layer of cut dentin and enamel created by rotary instrumentation, occluding tubules and sealing the surface. It affects bonding, permeability, and bacterial penetration, so its removal or modification is a deliberate clinical choice.

Application of acid, usually phosphoric acid, to enamel or dentin to dissolve mineral and create microporosity for resin infiltration. On enamel it produces a classic frosted appearance and is essential for durable micromechanical retention.

The zone formed when resin monomers infiltrate acid-demineralized dentin and polymerize around exposed collagen fibers. Its quality depends on moisture control and complete resin penetration, and it is central to dentin bonding durability.

Volume reduction that occurs as resin composite monomers convert to polymer and pack closer together. If shrinkage stress exceeds bond strength, marginal gaps, postoperative sensitivity, or cuspal deflection can result.

Building a restoration in thin layers of material rather than one bulk increment. In composites it reduces polymerization shrinkage stress and improves adaptation and light-curing depth; in amalgam it controls condensation and carving.

The ratio of bonded to unbonded surface area in a cavity preparation. A high ratio restricts flow during shrinkage and raises stress at the bond, guiding decisions about layering and cavity design.

An electric current generated when two dissimilar metals in saliva contact each other, producing a sharp pain or metallic taste. It is a classic reason to avoid adjacent restorations of different metallic materials.

A metallic restorative material made by mixing silver-tin-copper alloy powder with mercury. It is strong and technique-tolerant but nonadhesive, so it requires mechanical retention and adequate remaining tooth structure.

A metal such as gold, platinum, or palladium that resists oxidation and corrosion in the oral environment. High noble content in casting alloys improves biocompatibility, castability, and marginal stability.

A crown design in which ceramic is fired onto a cast metal substructure. The metal provides strength and fit while porcelain provides esthetics, but the metal-ceramic bond and opaque layer limit light transmission.

The accuracy with which a restoration's edge adapts to the prepared tooth finish line. Poor fit permits microleakage, plaque accumulation, and cement washout, and is assessed clinically with explorers and radiographs.

The reinforcement gained when a cast restoration encircles a collar of sound tooth structure at the cervical margin. A continuous ferrule of adequate height reduces root fracture risk in endodontically treated teeth.

A foundation restoration in which a post is placed in the root canal and a core is built up to support a crown. The post retains the core but does not strengthen the root, so remaining tooth structure matters most.

The distance from a coronal reference point to the apical limit of instrumentation, usually the apical constriction. Accurate determination prevents short obturation and minimizes extrusion of irrigants or debris.

The narrowest point of the root canal near the apical foramen, where the canal meets the periodontal tissues. It is the biological target for cleaning and obturation because it limits material extrusion.

Use of a chlorine-releasing solution to dissolve necrotic tissue and kill microorganisms inside the root canal system. It requires careful needle control because accidental extrusion can cause severe tissue injury.

A microcrystalline debris layer of cut dentin and enamel created by rotary instrumentation, occluding tubules and sealing the surface. It affects bonding, permeability, and bacterial penetration, so its removal or modification is a deliberate clinical choice.

A maxillomandibular relationship in which the condyles are seated in their most anterior-superior position against the articular eminences, independent of tooth contact. It is a reproducible reference for recording occlusion and designing complete dentures.

The complete interdigitation of upper and lower teeth when the mandible is fully closed, regardless of condylar position. It is the habitual biting position and may or may not coincide with centric relation.

An arrangement of artificial teeth in complete dentures where contacts occur bilaterally and simultaneously in excursions as well as at centric. It stabilizes the denture bases and reduces tipping forces during function.

The stage of a patient's bone development, often assessed from hand-wrist or cervical vertebral radiographs. It predicts remaining facial growth and thus the timing of orthodontic or orthopedic intervention.

Measurement of angular and linear relationships of craniofacial structures on a standardized lateral head radiograph. It quantifies skeletal and dental discrepancies and is used to plan treatment and evaluate change.

Orthopedic or functional treatment intended to alter the direction or amount of craniofacial growth in a growing patient, for example by advancing the mandible. Success depends on remaining growth potential and patient cooperation.

Resistance to unwanted tooth movement that provides a base from which other teeth can be moved. It is conserved through mechanics, appliance design, or skeletal devices, and its loss limits achievable correction.

Death of irradiated bone, most often the mandible, occurring months to years after radiotherapy for head and neck cancer. Poor vascularity makes it chronic and progressive, and invasive dental procedures in the field increase risk.

Exposed bone in the jaws that fails to heal in a patient taking or previously taking antiresorptive drugs, often after extraction. Prevention emphasizes oral health before therapy and conservative surgical management.

An infection of bone and marrow, in the jaws usually spreading from a necrotic tooth or periodontal lesion. It presents with pain, swelling, and sometimes a radiolucent mottled pattern, and requires drainage plus antibiotics.

A rapidly spreading bilateral cellulitis of the submandibular, sublingual, and submental spaces that can elevate the tongue and obstruct the airway. It is a surgical and airway emergency requiring urgent drainage and intravenous antibiotics.

A malignant tumor of stratified squamous epithelium and the most common oral malignancy. It often presents as a nonhealing ulcer or indurated mass, so any persistent oral lesion warrants biopsy.

The lowest concentration of an antimicrobial agent that prevents visible growth of a standard bacterial inoculum. It guides drug selection and dosing and is interpreted against susceptibility breakpoints.

Administration of antibiotics before a procedure to prevent infection in susceptible patients, such as those with certain cardiac conditions or prostheses. It is reserved for defined high-risk groups because routine use promotes resistance.

A structured community of microorganisms embedded in a self-produced matrix and attached to a surface. In the mouth it forms dental plaque, which resists rinsing and antibiotics and drives caries and periodontal disease.

A process that destroys all microorganisms, including bacterial spores, on an instrument or surface. In dentistry it is typically achieved by autoclaving after cleaning, and it is distinguished from disinfection by its sporicidal endpoint.

Infection-control practices applied to all patients regardless of diagnosis, including hand hygiene, gloves, eye protection, and safe sharps handling. They assume every body fluid may transmit infection and replace diagnosis-based precautions.

A patient's voluntary agreement to treatment after receiving adequate information about its nature, risks, benefits, and alternatives. It requires decision-making capacity and must be documented, reflecting respect for patient autonomy.