NZ Dental Technician REX key terms

The contact relationship between the upper and lower teeth when the jaw is fully closed and the condyles sit in their most retruded, unstrained position. It guides how denture teeth are arranged to give stable, even contact.

The position of the mandible where the upper and lower teeth have their greatest number of contacts, regardless of condyle position. It may differ from centric occlusion and is recorded before designing occlusal schemes.

The distance measured between two fixed facial points, such as the base of the nose and the chin, when the teeth or occlusion rims are in contact. It sets the height at which dentures or restorations are built.

The gap between the upper and lower occlusal surfaces when the jaw is in its resting posture. It is usually a few millimetres and helps the technician judge whether a proposed vertical dimension is physiologically acceptable.

The anterior-to-posterior curvature of the occlusal plane, seen from the side, formed by the buccal cusps and incisal edges. It influences occlusal balance and the arrangement of posterior denture teeth.

The anteroposterior and mediolateral curvature built into the occlusal surfaces of a complete denture to maintain simultaneous contact during jaw movement. It is developed by tilting posterior teeth and setting them to a curved plane.

An occlusal arrangement in which contacts occur on both sides of the arch simultaneously during eccentric jaw movement. It is used in complete dentures to reduce tipping forces and improve stability during chewing.

A clinically recorded jaw relationship in which the condyles are in their most anterior, superior position against the articular eminences. It is a reproducible reference used when constructing complete dentures and complex restorations.

A registration that relates the maxillary dental arch to the temporomandibular joints and the hinge axis. It is transferred to an articulator so casts can be mounted in a position that mimics the patient's anatomy.

A mechanical device that holds dental casts and reproduces jaw movements using adjustable condylar guidance and incisal guidance settings. It is used to build occlusal contacts that approximate the patient's functional movements.

The progressive loss of bone and soft tissue height and width of the alveolar ridge after tooth extraction. It affects denture support and often requires relining or remaking a prosthesis over time.

A raised, rounded ridge placed on the palatal surface of a maxillary denture near the junction of the hard and soft palate. It compresses soft tissue to improve the peripheral seal and retention.

The process of shaping the denture base periphery using softened impression material and functional movements of the patient's tissues. It records the reflection of the vestibule so the finished base obtains an effective seal.

The design of the denture border so that it reaches the functional depth of the vestibule and covers the maximum support area without impinging on moving tissues. Correct extension improves retention and distributes load.

The rigid part of a removable partial denture that joins the components on each side of the arch and distributes forces to the teeth and tissues. Common designs include palatal plates and lingual bars.

A prepared or natural surface on a tooth, shaped to receive a rest and direct occlusal forces along the long axis of the tooth. It provides support and helps prevent the partial denture from settling.

A design feature in a removable partial denture that allows some movement between the tooth-supported and tissue-supported parts. It aims to reduce torque on abutment teeth when the denture base is loaded.

The part of a clasp assembly that contacts the tooth on the side opposite the retentive arm. It stabilises the clasp and helps ensure the retentive tip engages the tooth during insertion and removal.

The mechanical reinforcement gained when a crown extends around a vertical wall of sound tooth structure, surrounding the core. A minimum height of this wall helps resist fracture of the restored tooth.

Material placed in a badly broken-down tooth to replace missing structure and provide a shaped foundation for a crown or bridge. It is often retained by posts or remaining walls and must resist functional loads.

The shape of a prepared tooth surface that resists removal of the restoration along its path of insertion. It is achieved with near-parallel walls, minimal taper, and features that create mechanical resistance.

The shape of a tooth preparation that enables the restoration and tooth to withstand occlusal forces without fracture or displacement. Adequate bulk, rounded internal angles and reduced unsupported enamel all contribute.

The direction in which a restoration or removable prosthesis is placed onto its supporting structures. It must be planned so that rigid parts of a framework do not bind against teeth during seating.

The location chosen for the edge of a crown or veneer relative to the gingival tissue, such as supragingival, equigingival or subgingival. The choice affects plaque control, aesthetics and impression accuracy.

The junction between a prepared tooth and the gingival tissue, or the design of the restoration edge at that point. Common designs include chamfer, shoulder and knife-edge, each suited to different materials.

The process of analysing a dental cast with a parallelometer to identify undercuts, survey lines and the best path of insertion for a partial denture framework. It guides clasp and rest placement.

The technique of building a restoration by applying and firing successive layers of porcelain over a core or coping. It allows control of shade, translucency and contour to match adjacent teeth.

A strong ceramic material based on zirconium dioxide, often used for crowns, bridges and implant frameworks. Its strength and translucency depend on composition and processing, and it requires careful sintering control.

A measure of how much a material expands per unit length for each degree of temperature rise. Mismatch between a metal framework and its veneering ceramic can cause cracking or chipping during firing and cooling.

The reduction in volume that occurs when a resin-based material sets by chemical reaction. It can create gaps at interfaces and stresses in restorations, and is influenced by filler content and curing method.

The proportion of reactive groups in a resin that have reacted during curing. A higher value generally means better mechanical properties and less residual monomer, and it depends on light exposure and initiator systems.

Unreacted liquid molecules left in a cured acrylic or resin material. High levels can reduce strength, cause tissue irritation and affect dimensional stability, so processing and curing must be controlled.

A polymer material, usually polymethyl methacrylate, used to form the base of removable dentures. It is processed by heat or chemical curing and must balance strength, fit and colour stability.

A hydrocolloid impression material mixed with water and used to record the shape of teeth and soft tissues. It sets by a gelation reaction and must be poured promptly because it loses water and changes dimension.

The ability of a material or impression to retain its shape and size over time and under changing conditions. It determines how long an impression or record can be stored before it distorts.

An individually made impression tray, usually of light-cured or chemically cured resin, built on a study cast. It carries a controlled thickness of impression material and improves accuracy for final impressions.

The set of practices, including hand hygiene, personal protective equipment, cleaning and sterilisation, that reduce the spread of microorganisms in the laboratory. It applies to all items entering or leaving the lab.

Basic infection control measures applied to all patients and materials regardless of known infection status. They include hand hygiene, gloves, eye protection and safe handling of sharps and contaminated items.

A process that destroys all microorganisms, including bacterial spores, on an item. In the laboratory it applies to instruments and heat-stable items, and its effectiveness is monitored by indicators and records.

The reduction of pathogenic microorganisms on surfaces or items, but not necessarily spores. It is used for impressions, prostheses and equipment that cannot withstand sterilisation, following validated procedures and contact times.

Any chemical or material in the laboratory that can harm health, such as monomers, acids, solvents or dusts. It must be identified, labelled, stored and handled according to safety data sheets and local regulations.

A document supplied with a hazardous substance that describes its hazards, safe handling, first aid and disposal. It must be available to workers and used to inform risk assessments and training.

An engineering control that captures dust, vapour or fumes at the point of generation and removes them from the work area. It is important when grinding, polishing or mixing volatile materials.

Clothing and equipment worn to protect the worker from hazards, such as gloves, masks, eye protection and aprons. It is a last line of defence and must be selected, fitted and maintained correctly.

Agreement given by a patient after receiving clear information about a proposed procedure, its risks, benefits and alternatives. In laboratory work it underpins the authority to handle patient information and materials.

The obligation to protect personal and health information from unauthorised access, use or disclosure. It covers patient records, photographs and digital scans, and requires secure storage and appropriate sharing.

The range of tasks and responsibilities a dental technician is trained and permitted to perform. Working outside it can endanger patients and may breach registration or employment requirements.

A practice that recognises power imbalances and the cultural identity of patients, and works to avoid diminishing, demeaning or disempowering them. In New Zealand it includes responsiveness to Māori values and expectations.

The planned activities and checks used to ensure that products and processes consistently meet defined standards. It includes documentation, calibration, audits and corrective action when problems are found.

The operational checks performed during production to verify that a specific item or process meets its requirements. Examples include measuring fit, checking occlusion and testing material properties.

The ability to trace a finished appliance back to its materials, batch numbers, dates and the people involved in its production. It supports recalls, complaint investigation and compliance with laboratory records.

The use of intraoral or laboratory scanners, design software and manufacturing units such as mills or printers to produce dental restorations. It changes how records, designs and physical models are handled.

Computer-aided design and computer-aided manufacturing, used to design a restoration digitally and then produce it by milling or printing. Accuracy depends on scan quality, design parameters and machine calibration.

A device that captures the shape of teeth and soft tissues directly in the mouth as a digital model. Its output replaces a conventional impression and must be checked for completeness before design.

A device that applies controlled force to teeth or jaws to guide movement or growth. It may be removable or fixed, and its design must balance force levels, anchorage and patient comfort.

The resistance to unwanted tooth movement that provides a base against which active orthodontic forces act. It can be gained from other teeth, the palate, extraoral structures or temporary anchorage devices.

The process of filling an impression with gypsum or another model material to produce a positive replica of the teeth and tissues. Correct mixing, vibration and setting time are needed to avoid bubbles and distortion.