CDT key terms

A slight compression built into the back edge of a maxillary denture base that presses the soft palate tissue just enough to close the space, so air cannot leak under the denture and break the suction.

The space in the mouth where the tongue pushes one way and the cheeks and lips push the other with equal force. Denture teeth set in this zone are not tipped by those muscles.

Contacts between upper and lower teeth on both sides at the same time, in the front and back, as the jaw slides sideways or forward. It helps stop a denture from tipping during chewing.

The amount of jaw separation when the upper and lower teeth or wax rims first touch in closing. Setting it too wide causes soreness; too narrow gives a collapsed, aged look.

Shaping the rim of a custom tray with a material that sets while the patient moves the lips, tongue and cheeks, so the impression records the full depth of the sulcus.

Gradual loss of bone and gum tissue where teeth were removed. It is fastest in the first year after extraction and continues slowly, so dentures need relining or remaking over time.

The surface inside the mouth that the denture base rests on and that carries the chewing load, mainly the hard palate and the residual ridge.

A four-class system for partly edentulous arches, based on where the toothless gaps sit relative to the remaining natural teeth rather than on how many teeth are missing.

Practical rules for applying the Kennedy classes when an arch is not straightforward, for example deciding which gap counts first and when a gap changes the class.

A shallow prepared hollow, usually on an occlusal or lingual surface, into which a rest of the partial denture fits so biting force travels down the long axis of the tooth.

The widest bulge around a tooth crown, marked by a surveyor. Its position tells the designer where a clasp can be rigid and where it must be flexible to engage an undercut.

Flat, parallel surfaces prepared on the sides of teeth that touch the metal framework. They steer the partial denture along one path of insertion and help resist tipping.

The part of a partial denture framework that joins the left and right sides, such as a lingual bar or palatal plate, and spreads the load across the arch.

A rest placed on a tooth away from the saddle that stops the denture base from lifting when the other end is pushed down, working like a lever counterweight.

A second, corrected impression of the toothless ridge taken with the metal framework seated and the tissue gently loaded, so the denture base fits the ridge in function.

The shape of a prepared tooth, mainly its taper and surface area, that keeps the crown from being lifted off along the path of insertion.

The shape of a prepared tooth that prevents the crown from rocking or twisting under sideways forces, helped by a wide seat and a gentle taper.

The edge on a prepared tooth where the crown or bridge margin sits. Its shape, position and smoothness affect how well the restoration fits and how healthy the gum stays.

A ring of sound tooth or core material that surrounds the preparation just above the margin, bracing the tooth and lowering the risk of root fracture under a crown.

A copy of one prepared tooth, usually poured in stone from an impression, on which the crown or bridge is built and its fit checked.

The false tooth in a fixed bridge that fills the gap left by a missing tooth. Its underside shape is chosen to be easy to clean and kind to the gum.

A bridge in which the false tooth is held from one end only. The single abutment has to carry a tipping load, so case selection matters.

The one direction a crown, bridge or partial denture must travel to seat fully, set by the taper of preparations and the position of undercuts.

A restoration with a cast metal core covered by fired porcelain. The metal supplies strength and the porcelain supplies tooth-like colour and shape.

How closely a metal and the porcelain fired onto it expand and shrink at the same rate. A close match prevents cracking and peeling as the restoration cools.

A crystal that forms in dental feldspathic porcelain. Its amount changes how much the porcelain expands, which lets manufacturers match it to the alloy it will cover.

A very strong oxide ceramic used for bridge frameworks and full-contour crowns. It resists fracture well but is relatively opaque, so shading needs care.

A glass-ceramic full of fine needle-shaped crystals. It combines high strength with good appearance, which is why it is popular for single crowns and veneers.

A liquid painted on a silica-based ceramic before cementing. One end attaches to the glass, the other to the resin cement, forming a chemical bond across the joint.

A gel applied to glass-containing ceramic to dissolve part of the glass and leave a pitted surface. Resin cement then flows into the pits and grips mechanically.

The resistance that stops teeth you want to stay put from moving while others are being moved. It can come from other teeth, the palate, the head or tiny implants.

Tracing and measuring set points on a side-view skull radiograph to describe how the jaws and teeth relate, and to plan or judge orthodontic treatment.

An angle built from points at the deepest part of the upper and lower jaw fronts and at the bridge of the nose. It shows whether the upper jaw sits ahead of the lower.

The inwards or outwards lean built into a bracket slot that tips a tooth root toward or away from the lip. It controls root position, not just crown position.

The gentle upward curve of the biting surfaces from front teeth to back teeth seen from the side. A deep curve has to be levelled during treatment.

The spare room on each side of the arch because the primary molars are wider than the premolars that replace them. It can be used to relieve crowding.

The tendency of teeth to drift back toward their old crooked positions after braces come off. Retainers are worn to hold the result while the surrounding tissues settle.

A removable brace that changes how the jaws and muscles work, guiding growth and moving teeth, often used in growing patients with a Class II pattern.