Dental Malocclusions and Tooth Number Anomalies

Tooth Number Anomalies: Agenesis and Hyperdontia

Tooth number is determined by excess or defect. When referring to missing teeth, the term is agenesis. Conversely, having more teeth is known as supernumerary or hyperdontia. Heredity plays a significant role in these anomalies.

Impact of Premature Tooth Loss

Premature tooth loss can alter the perimeter and symmetry of the dental arch. This can be caused by caries, root resorption, and iatrogenic factors. If a tooth is lost, a space maintainer or eruption guide is necessary to keep the antagonist in normal occlusion.

Consequences in Permanent Dentition

In the case of permanent dentition, loss involves:

• Shortening of the arch
• Tilting of adjacent teeth during eruption
• Deviation of the dental midline

Iatrogenic factors resulting in periodontal inflammation can cause premature contact, leading to mandibular deviation and increased masticatory loads on the tooth, which can result in the loss of that tooth.

Periodontal Alterations and Malocclusion

Active and untreated periodontal disease can cause tooth loss due to the large destruction of support structures. This destruction leads to the development of a malocclusion.

Angle's Classification of Malocclusion

Class 1 Malocclusion or Normocclusion

This represents a normal anteroposterior relationship between the superior and inferior jaws. The mesiobuccal cusp of the first superior molar occludes in the middle vestibular fossa of the first inferior molar. Additionally, the vertex of the superior canine occludes in the embrasure between the inferior canine and the first inferior premolar.

Etiology of Class 1 Malocclusion

• General Factors: Genetics (discrepancy between tooth and jaw size leading to crowding).
• Evolution: Changes in dental and jaw size.
• Diet: Soft, processed foods leading to muscle hypofunctionalism.
• Local Factors: Supernumerary teeth causing crowding or asymmetry, and dental loss leading to mesial migration and alterations of shape, size, and number.

Clinical Features

Features include a normal skeletal relationship, normal molar and canine positions, a straight or harmonious profile, and specific dental problems.

Class 1 Malocclusion with Vertical Problems

This involves an alteration in the normal vertical bite (typically 2mm).

• Open Bite: Often caused by finger sucking, atypical swallowing, or tongue interposition. Treatment focuses on correcting the habit and is limited to the anterior dental arch.
• Deep Bite: Occurs at the level of the front incisors. It can be caused by the premature loss of temporary canines, leading to the lingual displacement of inferior incisors. This may involve inferior anterior crowding, extruded incisor positions with increased length, or the intrusion of the posterior segment.