Reverse Bite (Crossbite): Understanding Causes, Symptoms, and Treatment

What is Reverse Bite?

A "reverse bite," also known as a crossbite, is a form of dental malocclusion where one or more upper teeth bite inside or behind the opposing lower teeth when the jaws are closed, rather than the normal alignment where upper teeth slightly overlap the lower teeth.

Understanding Malocclusion

Malocclusion, derived from Latin words meaning "bad bite," refers to any deviation from a normal occlusion, where the upper teeth correctly overlap the lower teeth and the cusps of the molars interlock precisely. It's a common condition that can range from minor cosmetic concerns to significant functional impairments. Malocclusions are broadly categorized by the relationship between the upper and lower jaws and teeth, including overbites (Class II), underbites (Class III), open bites, and crossbites, with the reverse bite falling under the latter category.

What Exactly is a Reverse Bite?

A reverse bite specifically describes a situation where the normal relationship of teeth is inverted. It can manifest in two primary forms:

• Anterior Reverse Bite (Anterior Crossbite): This occurs when one or more of the upper front teeth (incisors or canines) bite behind the lower front teeth. Instead of the upper teeth slightly overlapping the lower teeth, they are positioned inside the lower arch. This can involve a single tooth or several teeth.
• Posterior Reverse Bite (Posterior Crossbite): In this type, one or more upper back teeth (premolars or molars) bite inside the lower back teeth. Normally, the cusps of the upper back teeth fit outside the lower back teeth. A posterior crossbite can be unilateral (affecting one side of the mouth) or bilateral (affecting both sides).

It's important to distinguish a localized reverse bite (crossbite) from a full Underbite (Class III Malocclusion). While an underbite involves all upper front teeth biting behind the lower ones, it's a more severe skeletal condition where the entire lower jaw is positioned significantly forward relative to the upper jaw. A reverse bite, or crossbite, can be a dental issue involving just a few misaligned teeth, or it can be a component of a broader skeletal discrepancy like an underbite.

Causes of Reverse Bite

The development of a reverse bite can be attributed to a combination of genetic, developmental, and environmental factors:

• Genetic Factors: Inherited jaw size and shape discrepancies are common contributors. If one parent has a small upper jaw or a large lower jaw, their child may inherit similar characteristics, predisposing them to a reverse bite.
• Developmental Issues:
  • Discrepancies in Jaw Growth: Uneven growth rates between the upper and lower jaws during childhood can lead to misalignment.
  • Dental Arch Width Discrepancies: A narrow upper jaw relative to the lower jaw is a frequent cause of posterior crossbites.
• Early Childhood Habits:
  • Prolonged Thumb-Sucking or Pacifier Use: These habits can exert pressure on developing teeth and jaws, potentially pushing the upper front teeth inward or narrowing the upper arch.
  • Tongue Thrusting: An abnormal swallowing pattern where the tongue pushes against the front teeth can contribute to anterior crossbites.
• Dental Factors:
  • Premature Loss of Primary (Baby) Teeth: If baby teeth are lost too early, adjacent teeth may drift into the empty space, preventing permanent teeth from erupting into their correct positions.
  • Crowding or Impaction of Permanent Teeth: Lack of space can force teeth to erupt out of alignment, leading to crossbites.
  • Supernumerary Teeth: Extra teeth can block the proper eruption path of other teeth.
• Trauma: Injuries to the jaw or teeth, especially during childhood, can affect jaw growth or tooth position.

Signs and Symptoms

Individuals with a reverse bite may experience a range of signs and symptoms, varying in severity:

• Visible Misalignment of Teeth: The most obvious sign, where one or more upper teeth are noticeably positioned behind or inside the lower teeth.
• Asymmetrical Jaw Closure: The lower jaw may shift to one side when closing to achieve a comfortable bite, especially in unilateral posterior crossbites. This can lead to facial asymmetry over time.
• Chewing Difficulties: Inefficient mastication due to improper tooth contact, potentially leading to digestive issues.
• Speech Impediments: Difficulty pronouncing certain sounds, such as lisps, particularly with anterior crossbites.
• Jaw Pain and Temporomandibular Joint (TMJ) Dysfunction: Chronic strain on the jaw muscles and TMJs due to compensatory biting patterns can lead to pain, clicking, popping, headaches, or even lockjaw.
• Abnormal Tooth Wear: Specific teeth may experience excessive or uneven wear due to improper contact and friction.
• Increased Risk of Dental Issues: Misaligned teeth are harder to clean effectively, increasing the risk of plaque accumulation, cavities, and gum disease (gingivitis, periodontitis).
• Self-Consciousness: The aesthetic impact of a reverse bite can affect an individual's self-esteem and confidence.

Health and Functional Implications

Beyond cosmetic concerns, an untreated reverse bite can lead to significant health and functional problems:

• Compromised Oral Function: Impaired ability to chew food efficiently, which can impact digestion and nutrient absorption. Speech clarity can also be affected.
• Dental Damage: Accelerated wear and tear on specific teeth, leading to enamel erosion, sensitivity, and increased risk of fractures. It can also cause gum recession around affected teeth.
• Musculoskeletal Issues: Chronic jaw strain can lead to temporomandibular joint disorders (TMD/TMJ), characterized by pain in the jaw joint, headaches, neck pain, and even shoulder discomfort. The compensatory shifting of the jaw can also contribute to facial muscle imbalances.
• Psychosocial Impact: For many, the visible misalignment of teeth can lead to self-consciousness, anxiety, and reluctance to smile or speak confidently.

Diagnosis

Diagnosis of a reverse bite typically involves a comprehensive evaluation by a dentist or orthodontist:

• Clinical Examination: A thorough visual inspection of the teeth, jaws, and facial structure, assessing how the teeth come together.
• Dental Impressions: Molds of the teeth are taken to create plaster models, allowing the orthodontist to study the bite in detail from all angles.
• Radiographic Imaging:
  • Panoramic X-rays: Provide a broad view of the entire mouth, including all teeth (erupted and unerupted) and the jawbones.
  • Cephalometric X-rays: Lateral (side-profile) X-rays of the head, used to analyze the relationship between the jaws, teeth, and facial bones, crucial for identifying skeletal discrepancies.
  • 3D Cone Beam CT (CBCT) Scans: Provide detailed three-dimensional images for complex cases, offering precise anatomical information.

Treatment Options

The treatment approach for a reverse bite depends on its severity, the patient's age, and whether it's a dental or skeletal issue. Early intervention is often key, especially in children.

• Early Orthodontic Intervention (Childhood):
  • Palatal Expanders: For posterior crossbites caused by a narrow upper jaw, these appliances gradually widen the upper arch.
  • Removable Appliances: Simple plates or appliances can be used to move individual teeth into correct alignment.
  • Habit Correction: Addressing habits like thumb-sucking or tongue thrusting with specific appliances or myofunctional therapy.
• Adolescent and Adult Orthodontics:
  • Braces: Traditional metal, ceramic, or lingual (placed on the inside of teeth) braces are highly effective in repositioning teeth and correcting bite discrepancies.
  • Clear Aligners (e.g., Invisalign): A series of custom-made, removable clear trays that gradually shift teeth into place. Suitable for many, but not all, crossbite cases.
• Dental Restorations: For very minor crossbites, or as a refinement after orthodontic treatment, dental bonding, crowns, or veneers might be used to reshape teeth for better occlusion.
• Orthognathic Surgery (Jaw Surgery): For severe skeletal reverse bites (underbites) where the jaw bones themselves are misaligned, surgical correction may be necessary. This is typically performed by an oral and maxillofacial surgeon in conjunction with orthodontic treatment.
• Myofunctional Therapy: A program of exercises designed to correct improper tongue and facial muscle function, often used in conjunction with orthodontic treatment to address underlying functional issues.

Prevention and Management

While some cases of reverse bite are genetically predisposed, certain measures can help in prevention or early management:

• Regular Dental Check-ups: Routine visits to the dentist from an early age allow for early detection of developing bite problems.
• Addressing Oral Habits: Discouraging prolonged thumb-sucking, pacifier use, or bottle feeding beyond appropriate ages (typically by age 2-4) can help prevent dental and jaw development issues.
• Good Oral Hygiene: Regardless of bite alignment, maintaining excellent oral hygiene is crucial to prevent cavities and gum disease, which can be exacerbated by malocclusion.
• Orthodontic Consultation: An orthodontic evaluation is recommended for children around age 7, or earlier if a specific concern arises, as this is often the ideal time for interceptive treatment to guide jaw growth and tooth eruption.

Understanding the "reverse bite" involves recognizing its specific manifestations, the underlying causes, and the potential impact on oral health and overall well-being. Early diagnosis and appropriate treatment are crucial for correcting the bite, improving function, alleviating symptoms, and enhancing both oral health and quality of life.