The condition known as a collapsed bite is referred to by dentists as a loss of the vertical dimension of occlusion (VDO). This progressive reduction in the height of the bite affects the stability and function of the jaw joints, muscles, and remaining teeth. Addressing the loss of VDO is important for restoring comfortable function and mitigating the long-term deterioration of the chewing apparatus. Successful repair requires an accurate diagnosis followed by a carefully planned, multi-stage treatment process.
Understanding Vertical Dimension Collapse
Vertical Dimension of Occlusion (VDO) is the specific measurement of the distance between the upper and lower jaws when the teeth are fully closed and in maximum contact. The loss of VDO describes the reduction of this vertical height, causing the jaws to close further than they should.
This loss of height occurs because the structures that maintain the distance—the teeth—have been worn down or removed. When the teeth no longer provide the necessary support, the space between the jaws shrinks.
The reduction in VDO disrupts the natural alignment and balance of the entire chewing system. This change places unnatural stress on the temporomandibular joints (TMJs) and the surrounding muscles. The jaw is forced into a position that can lead to chronic discomfort and difficulty with speaking and eating.
Identifying Common Symptoms and Contributing Factors
Common Symptoms
Patients frequently notice physical changes and discomforts that signal a reduction in VDO. A common visual change is the shortening of the lower third of the face, which can make the chin appear closer to the nose. This facial compression often leads to increased wrinkles around the mouth and a tendency for the lips to look thinner or folded inward.
Another frequent sign is the chronic cracking or chapping at the corners of the mouth, known as angular cheilitis, caused by the excessive folding of the skin. Internally, the patient may experience muscular pain, chronic headaches, or symptoms related to the jaw joint, such as clicking, popping, or generalized tenderness. Difficulty chewing and biting the cheeks or tongue more often are also reported.
Contributing Factors
The primary factors contributing to VDO loss are the progressive wearing down or the absence of posterior teeth. Excessive teeth grinding, known as bruxism, gradually erodes the enamel and dentin, shortening the crowns of the teeth and reducing the overall vertical support.
The loss of back teeth, such as molars and premolars, removes the foundational support structures for the bite. Without these posterior teeth to bear the load of chewing, the remaining front teeth and the jaw joint are subjected to excessive forces, accelerating the collapse. Furthermore, failing dental restorations or extensive tooth decay can compromise the structural integrity of the teeth, leading to their eventual breakdown and VDO loss.
Clinical Procedures for Accurate Measurement
The professional diagnosis of VDO loss involves a precise clinical assessment to confirm the reduction and determine the appropriate height for restoration. Dentists first establish the patient’s Resting Vertical Dimension (RVD), which is the height of the face when the jaw muscles are fully relaxed. This is typically measured using a ruler or specialized caliper between two marked facial points.
From the RVD, the dentist determines the Interocclusal Rest Space (IRS), often called the freeway space. This is the small, natural gap that exists between the upper and lower teeth when the jaw is at rest. The normal IRS is typically between two and four millimeters in the premolar region.
The VDO is calculated by subtracting the IRS from the RVD. If the existing VDO is too small, the IRS will be larger than normal, indicating that the patient’s teeth are over-closing. Dentists employ techniques like phonetic tests, asking the patient to repeat specific sounds like “M” or “S” to observe the closest speaking space, which helps confirm a comfortable and functional vertical dimension.
Advanced diagnostic tools, including face bows and articulated study models, are used to accurately replicate the patient’s jaw movements and relationships outside the mouth. Imaging, such as lateral cephalometric radiographs, provides a view of the skeletal relationship and helps confirm the severity of the collapse. This comprehensive data allows the dental team to plan a precise and stable restoration.
Restoring the Bite Treatment Options
Phased Treatment Approach
Restoring a collapsed bite focuses on re-establishing the lost vertical dimension and stabilizing the jaw relationship through a phased approach. Treatment typically begins with a reversible phase to test the new vertical position before any irreversible changes are made.
A temporary appliance, often a removable splint or orthotic, is fabricated to hold the jaw at the proposed, increased VDO. The patient wears this appliance for a period of time to allow the jaw muscles and joints to adapt to the new position. This trial period confirms that the restored height is comfortable, stable, and does not induce pain or discomfort.
Permanent Restoration Methods
Once the new VDO is confirmed to be stable, the dentist moves to the permanent restorative phase, which aims to build up the height of the teeth. The most common restorative methods involve placing crowns or onlays on the posterior teeth to increase their height and provide new structural support. These restorations are precisely sculpted to meet the opposing teeth at the confirmed vertical dimension.
In cases of generalized wear, the treatment may require full-coverage crowns or porcelain veneers on nearly all teeth in both the upper and lower arches. This extensive approach, known as full-mouth reconstruction, uniformly distributes the chewing forces across the entire dentition at the new vertical position. Restorative materials like ceramics and composite resins are used to add the necessary height and structural integrity.
Other treatment components include:
- Overlay Removable Partial Dentures (ORPDs): These appliances fit over the remaining natural teeth, acting as a removable fixed prosthesis to quickly provide the necessary vertical support. While fixed restorations are generally preferred for long-term stability, ORPDs can serve as a permanent solution or an interim option.
- Orthodontic Therapy: Braces or clear aligners can reposition the teeth and create the necessary space to place the final restorations.
- Orthognathic Surgery: In the most severe cases involving skeletal discrepancies, surgery may be combined with restorative and orthodontic phases to achieve a stable and functional bite.