Class I Malocclusion Classification, Diagnosis & Management

Description

The modern definition of malocclusion refers to a misalignment of the upper and/or lower teeth that is measurable enough to interfere with the person’s ability to bite properly. Dentists make a professional diagnosis of malocclusion by assessing the size and shape of teeth, the position of teeth when the mouth is closed, and, in some cases, the architecture of supporting skeletal structures. Normal alignment of teeth involves the upper teeth resting slightly over or in front of the lower teeth, with molar points corresponding with the grooves of oppositional molars.

The most common types of malocclusion are overbites and underbites. Overbites occur when teeth 6 through 11 (incisors and canines) jut out and over the bottom teeth. Underbites usually involve teeth 21 through 28 (1st bicuspid, canine, lateral and central incisors) that extend farther in front of the upper teeth when the mouth is biting or closed.

Causes of Malocclusions

Malocclusions can occur in baby teeth or permanent teeth. Excessive use of pacifiers, thumb sucking, or tongue thrusting in children from one to three years old may force baby teeth and, eventually, permanent teeth to erupt in overbite positions. Early loss of baby teeth, the eruption of extra teeth (hyperdontia), or having abnormally shaped teeth could promote an underbite or overbite.

Class III malocclusions are believed to emerge from the interaction of environmental factors and genetic susceptibility. Recent studies indicate that chromosomal loci 1p36 and 12q23, and 12q13 harbor genes increase the risk for Class III malocclusion in individuals carrying these genetic markers.

Dentoalveolar and Skeletal Malocclusion

Dentoalveolar malocclusions specify improper bite parameters between the lower and upper teeth. A dentoalveolar malocclusion also exclusively refers to bite misalignment due to crooked or otherwise incorrectly positioned teeth.

Skeletal malocclusions implicate a distorted shape and/or size of the jawbones causing the malocclusion. If the development of the mandibular or maxillary bone support is abnormal, teeth will likely be mispositioned, crowded, or crooked. Skeletal malocclusions are typically diagnosed in neonatal infants and often accompany tongue deformities, cleft palate, or other skeletal abnormalities

Class I Malocclusion

When an overlap (upper teeth rest over the lower teeth while biting down) exists but the bite is normal or near-normal, the patient may be diagnosed with a Class I malocclusion. Subtypes of Class I malocclusions include:

Class I, Type I: upper and/or lower teeth are angled towards the tongue.

Class I, Type II: a narrow arch accompanied by overlap and the lower teeth leaning towards the tongue.

Class I, Type III: teeth crowding and angling of the upper front teeth towards the tongue.

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