Reagin Orthodontics

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Orthodontics Terms and Definitions


Cross bites in the back teeth usually result from a constricted upper jaw or unusually wide lower jaw. A narrow upper jaw will often force a patient to move their lower jaw forward or to the side when closing into a stable bite. When in this position, the lower teeth are located outside the upper teeth.

This problem could lead to:

  • An incorrect position for the lower jaw
  • Accompanying facial asymmetry
  • Uneven wear of teeth


Crowding of the teeth is the most common issue associated with the need for orthodontic care. Although many factors contribute to crowding, the problem is usually a discrepancy between space available in each jaw and the size of the teeth.

This problem could lead to:

  • An aesthetically unpleasing smile
  • Poor alignment of teeth
  • Periodontal problems
  • An increased risk of dental decay due to difficulty in maintaining proper oral hygiene


Excessive vertical overlap of incisor teeth, called “overbite,” is generally found in association with a discrepancy between the length of the upper and lower jaws.

This problem could lead to:

  • Excessive eruption of either the upper and lower incisors or both
  • Excessive display of gum tissue
  • Lip protrusion or entrapment
  • Biting the roof of the mouth


A lack of vertical overlap of the incisor teeth can usually be traced to jaw disharmony or persistent habits (e.g., digit-sucking habits and posturing of the tongue between the front teeth) or excessive vertical growth of one or both jaws. Early assessment and intervention are critical to success.

This problem could lead to:

  • Increased wear on posterior teeth
  • Dysfunctional chewing
  • Trauma where the teeth of the lower jaw meet with the corresponding teeth of the upper jaw


Spaces between teeth are another common problem associated with the need for orthodontic care. Like crowding, spacing may be related to a tooth-to-jaw size disharmony. Gum tissue attachments called “frenae” are also a common cause of spacing between the front teeth.

This problem could lead to:

  • Atypical or unusually narrow teeth
  • Missing teeth
  • Impacted teeth


The dental midline is the line between the two upper front teeth and the lower front teeth and it plays a significant role in orthodontic treatment. Changes in the dental midline can occur due to extra or missing teeth, skeletal asymmetries, or shifting due to the premature loss of primary dentition.

This problem could lead to:

  • A bit that does not match correctly
  • Improper jaw and dental function
  • An aesthetically unpleasing smile


An underbite is a condition in which the lower jaw and teeth protrude or extend forward and in front of the upper jaw. Underbites can be caused by several factors including genetics, abnormalities in the upper and lower jaw, and abnormalities in the upper and lower tooth positions.

This problem could lead to:

  • Jaw and joint pain
  • Increased wear and tear on enamel
  • Difficulty biting into certain foods (ex: lettuce in a sandwich or cheese off a pizza)
  • Changes in the structure and appearance of the face
  • Interference of speech
  • Abnormal alignment of the teeth


Overjet is the distance the upper front teeth protrude in front of the lower front teeth. Excessive overjet can be caused by thumb or finger habits, deficient growth of the lower jaw, improper tooth inclination or differences in the length of the upper and lower arches.

This problem could lead to:

  • Low self-esteem and social insecurities
  • Issues with biting and chewing
  • Trauma to the upper front teeth
  • Premature wear of the back teeth
  • Reduced airway space


Impacted teeth are teeth that do not erupt into the dental arch within their expected developmental window. Wisdom teeth, canines, and second premolars are the most common teeth to become impacted. Teeth become impacted for several reasons including lack of space to erupt, improper angulation in the bone, adjacent teeth shape and size, and narrow jaws. Early assessment and intervention can help reduce the risk of some impactions.

This problem could lead to:

  • Damage to other nearby teeth
  • Infection or cystic formations near the impaction
  • Discomfort in the mouth
  • Improper bite and alignment due to teeth that have not erupted