Orthodontic Malocclusion: Crossbites, Crowding, and Treatment Approaches

Orthodontic Malocclusion: Crossbites, Crowding, and Treatment Approaches

Types of Crossbite

A crossbite occurs when the upper teeth fit inside the lower teeth. It can be classified based on its origin:

• Dentoalveolar Crossbite

  Also known as compressed, inclined, or altered crossbite. In this type, the dental arch is narrowed even though the skeletal width is correct. If the base of the palatal vault is wide, but the dentoalveolar process leans inward, the crossbite is DENTAL, caused by a distortion of the dental arch itself.

• Basal Crossbite

  Also known as compression, inclined, or symmetric crossbite. If the palatal vault is narrow and the maxillary teeth lean outward but are nevertheless in crossbite, the crossbite is SKELETAL. There can be dental compensations for skeletal deformity.

Clark's Twin Block Appliance

The Clark's Twin Block appliance is a widely used functional appliance in orthodontics:

• It can be used as a removable or fixed functional appliance (FA).
• The twin block appliance consists of individual maxillary and mandibular plates with ramps that guide the mandible forward as the patient closes down.
• The maxillary and mandibular portions are configured so that the interaction of the two parts controls how much the mandible is postured forward and how much the jaws are separated vertically.
• It is similar to the Herbst appliance in that pressure against the teeth, rather than the mucosa, is employed to bring the jaw forward.

Orthodontic Treatment for Teenagers with Unknown Growth

When treating a teenager whose remaining growth potential is unknown, the following treatment approaches may be considered:

• Growth Modification (if growth is present)

  Attempt to modify any remaining growth using anterior appliances:

  • Headgear
  • Functional appliances

  Inform the patient that if this phase is not successful, a second surgical phase may be necessary.

• Surgical Phase

  This involves fixed appliances before and after the surgery to improve the skeletal vertical and sagittal relationship of the jaws.

• Orthodontic Camouflage

  This approach aims to mask skeletal discrepancies through dental movements:

  • Extractions: This closes the occlusion and decreases the vertical dimension. Posterior extractions are generally more effective.

Van der Linden Classification of Crowding

This classification categorizes different types of dental crowding:

• Type A (Too Much Space)

  • Diastemas in the upper arch
  • Lingual inclination of central and lateral incisors
  • Increased overbite
  • Lower incisors are retruded and crowded

• Type B (Lack of Space)

  • Crowding in the upper arch
  • Central incisors are retroclined
  • Lateral incisors are buccally inclined due to lack of space

• Type C (More Severe Lack of Space)

  • More crowded than Type B
  • Retroclined central incisors
  • Lateral incisors erupt in the canine's place
  • Canines erupt high in the arch

Types of Orthodontic Crowding and Etiological Factors

Dental crowding can be categorized into different types based on its origin and timing:

• Primary Crowding

  Caused by a negative Tooth Size Arch Length Discrepancy (TSALD), macrodontia (large teeth), small arches, or a combination of these factors.

• Secondary Crowding

  Results from premature loss of primary teeth (leading to mesial migration, ectopic premolar eruption, and crowding) or oral habits (such as oral breathing or thumb sucking).

• Tertiary Crowding

  Characterized by loss of alignment and worsening of crowding, typically occurring between 18-25 years old. Contributing factors include lack of tooth wear, third molar pressure, and late mandibular growth.