A Haas expander is a fixed orthodontic appliance designed to widen the upper jaw (maxilla). It uses a small screw connected to bands on back teeth and an acrylic pad that rests against the palate. It is most commonly used to correct a narrow upper arch and certain bite problems. It is typically placed in children and adolescents, though case selection varies by clinician and case.

A hyrax expander is a fixed orthodontic appliance used to widen the upper jaw (maxilla). It includes a small central screw connected to bands or attachments on upper back teeth. It is most commonly used to correct a narrow upper arch and related bite problems. It is typically placed by orthodontists and sometimes by other trained dental clinicians.

RPE is a shorthand term used in some dental settings for a resin-based preventive enamel material. It most often refers to a light-cured resin sealant or very flowable resin composite placed on tooth enamel. RPE is commonly used on the chewing surfaces of back teeth where deep grooves can trap plaque and food. Terminology can vary by clinician and region, and RPE may be documented differently in clinical notes.

rapid palatal expansion is an orthodontic method used to widen a narrow upper jaw (maxilla). It uses a fixed appliance with an expansion screw that applies outward pressure to the upper teeth and palate. It is most commonly used in growing patients to correct transverse (side-to-side) jaw width problems. It can be part of a broader orthodontic plan before braces or aligners.

palatal expansion is an orthodontic approach used to widen the upper jaw (maxilla). It is most often done with a dental appliance called an expander that applies gentle outward pressure. It is commonly used in growing patients to correct a narrow upper arch and related bite problems. In some adults, expansion may still be possible, but the method and predictability vary by clinician and case.

arch expansion is an orthodontic approach that increases the width (and sometimes the length) of the dental arch. It is used to create space for teeth, improve how the upper and lower teeth fit together, and support stable alignment. It can be done with braces, clear aligners, or expansion appliances (devices) that apply controlled forces. In some patients, it also involves orthopedic changes to the upper jaw, depending on age and anatomy.

arch perimeter is a measurement of the available space along the curve of the dental arch. It describes how much “room” the jaw and dental arch provide for teeth to sit in alignment. Dentists and orthodontists use it most often in orthodontic diagnosis and space analysis. It is typically measured on dental models or digital scans of the teeth.

arch length is a measurement of the size of a dental arch (the curved line of teeth in the upper or lower jaw). It describes how much space is available along the arch to accommodate the teeth. It is commonly used in orthodontics and pediatric dentistry to evaluate crowding, spacing, and treatment needs. It can be measured on dental models, photographs, or digital scans during diagnostic records.

arch form is the overall shape and curvature of the dental arch (the arc made by the teeth) in the upper or lower jaw. It describes how wide, narrow, tapered, or rounded the arch looks when viewed from above. arch form is commonly used in orthodontics, restorative dentistry, and prosthodontics to plan how teeth should be aligned or rebuilt. It is also used in digital dentistry and lab work when designing aligners, braces, dentures, or smile designs.

An open coil spring is a small orthodontic spring made from coiled wire with visible spaces between the coils. It is commonly placed on an archwire between braces brackets or tubes. Its plain purpose is to create or maintain space between teeth during orthodontic treatment. It is most often used in fixed braces, and sometimes in combination with other orthodontic appliances.