Alveolar Bone Defect

Alveolar bone defects are gaps or loss in the bone that holds and supports your teeth, which can result from various causes including gum disease, tooth loss, birth defects, or trauma, and often require specialized treatment to restore the bone and prevent further dental complications.

Table of contents

• What Is the Alveolar Bone
• Causes of Alveolar Bone Defects
• Types of Alveolar Bone Defects
• Effects and Complications
• Diagnosis
• Treatment Options

What Is the Alveolar Bone

The alveolar bone (also called the alveolar process) is the portion of your jaw bones that contains the tooth sockets. In your mouth, this includes both the upper jaw bone (maxilla) and the lower jaw bone (mandible).^[1] The alveolar bone is covered by gums and serves as the foundation that holds and supports your teeth.^[5]

The alveolar bone is connected to your teeth through a structure called the periodontal ligament, which is attached by tough fibers known as Sharpey’s fibers. These fibers connect the bone to the outer covering of the tooth root called cementum.^[1] To maintain healthy teeth, the foundation supporting them must be healthy as well.

Like other bones in your body, the alveolar bone is living tissue that constantly changes. It is repeatedly broken down by cells called osteoclasts and rebuilt by cells called osteogenic cells. This means that old bone is constantly being removed and replaced by new bone.^[1]

Causes of Alveolar Bone Defects

Alveolar bone defects can develop from several different causes. Understanding what leads to bone loss can help in preventing and treating these conditions.

The most common cause of alveolar bone defects is periodontal disease (also known as gum disease). In periodontal diseases, the alveolar bone around the teeth is absorbed, and as the disease progresses, the alveolar bone shrinks gradually.^[1] When bacteria and inflammation affect the gums, they can spread to the supporting bone structures, leading to bone destruction.

Tooth loss is another major cause of alveolar bone defects. The most common form of dental bone loss occurs from losing a tooth. While teeth themselves are not made of bone, losing a tooth can lead to deterioration of the jawbone. With healthy teeth, chewing stimulates the jawbone daily. However, if you lose a tooth, the section of jaw above or beneath the gap begins to recede.^[3]

Some people are born with alveolar bone defects as part of conditions like cleft lip and palate. These are considered the most common congenital craniofacial anomalies. People with a cleft lip and palate can have a cleft defect of the alveolus, where there is a gap in the alveolar bone.^[7] The size, shape, height, and width of these defects can vary considerably among patients.^[6]

Other causes include trauma, tumor resection, and certain jaw abnormalities. Studies have shown that different types of jaw alignment problems (called malocclusions) are associated with varying degrees of alveolar bone defects. Research found that patients with Class II and Class III malocclusions had higher rates of bone defects compared to those with normal jaw alignment.^[2]

Types of Alveolar Bone Defects

Alveolar bone defects can take different forms depending on their location and how the bone has been lost or damaged.

One type is called dehiscence, which appears as a gap or opening in the bone. Studies evaluating jaw abnormalities found that Class II malocclusions showed a 64.47% prevalence of dehiscence, while Class III malocclusions showed 58.43%, compared to only 32.96% in patients with normal jaw alignment.^[2]

Another type is called fenestration, which refers to a window-like opening in the bone surface. The research showed no significant difference in the prevalence of fenestration among different jaw alignment types.^[2]

Vertical bone loss occurs when the height of the bone decreases, often creating what is called an infrabony pocket (a pocket that extends below the normal level of the bone). This type is frequently seen in periodontal disease.^[3]

Alveolar bone expansion (also called alveolar osteitis) is a different condition where the bone actually thickens rather than shrinks. This occurs when there is chronic infection involving the bone tissue, leading to both bone destruction and bone formation. The bone formation can sometimes be extensive and may result in a hard mass of tissue that causes bulging, usually on the cheek side of the tooth.^[3] This condition is more frequently seen in cats than dogs when it comes to veterinary medicine, though it can occur in humans as well.

Effects and Complications

Alveolar bone defects can lead to numerous problems that affect both the health and appearance of your teeth and mouth.

In most cases, the lost alveolar bone does not return to its original form even after periodontal disease is cured. The gum covers the tooth surface to match the shape of the reduced bone, exposing more of the tooth surface than before. This makes the teeth look longer, leaves gaps between the teeth, and in some cases causes tooth sensitivity or pain.^[1]

As bone loss progresses, teeth can become loose and mobile. When there is a cleft of the alveolus (gap in the bone), teeth near it may erupt in the wrong place or may not erupt at all. Sometimes, teeth near a cleft may be absent, have an unusual shape, or there can be extra teeth.^[7]

If there is a hole connecting the mouth with the nose (called a fistula), food and fluid can leak into the nose from the mouth. Air can also leak through the fistula, which can make speech sound nasal.^[7]

Bone defects can also complicate dental implant placement. The presence and quality of alveolar bone is vital for successful implant placement, which has become an indispensable treatment method in dentistry and an important option for replacing missing teeth.^[1]

Diagnosis

Proper diagnosis of alveolar bone defects requires both physical examination and imaging techniques to assess the extent and nature of bone loss.

During an oral examination, a dentist will look for several signs. These include thickening of the alveolar bone and gums, inflammation of the gums (gingivitis), gum recession, and increased pocket depth when probing around teeth. Tooth mobility may also be detected. Generally, the larger the bone defect, the more advanced the associated dental disease.^[3]

Dental radiographs (X-rays) are essential for visualizing bone defects that cannot be seen during visual examination alone. On intra-oral dental radiographs, the alveolar margin will appear thickened and more radiolucent (less dense). Large lesions may have a mottled appearance with rough and large trabeculae (the internal structure of bone). Vertical alveolar bone loss is usually visible with a widening of the adjacent periodontal ligament space.^[3]

Cone-beam computed tomography (CBCT) scans provide three-dimensional assessment of alveolar bone. These scans allow clinicians to evaluate the shape, height, and width of bone defects more accurately than traditional X-rays.^[6] CBCT images can be used to create 3D surface models that help in planning treatment and assessing the severity of defects.^[2]

Advanced diagnostic approaches now include using artificial intelligence to classify the severity of alveolar bone defects. These automated classification systems can analyze 3D surface models from CBCT scans to determine the severity of bone defects, particularly in patients with cleft lip and palate.^[6]

Treatment Options

Treatment for alveolar bone defects aims to regenerate lost bone and restore the supporting structures of teeth. The approach depends on the cause, size, and location of the defect.

Bone grafting is a common treatment where bone material is placed in an area where there is not enough bone. An alveolar bone graft fills the gap in the bone with bone taken from elsewhere in the body or from other sources.^[7] For patients with cleft lip and palate, bone grafting of the alveolar cleft is an essential part of the treatment protocol as it promotes alveolar bone continuity on the cleft side.^[6] This procedure is normally done when children are between 8 and 10 years old, depending mainly on how quickly their teeth are developing.^[7]

Several types of grafting materials are available. Autogenous bone (bone from the same person) is considered the best option based on current evidence. Recently, using extracted teeth to create bone graft material has gained attention. Demineralized dentin matrix (DDM) from extracted teeth can be used because tooth components are very similar to alveolar bone components. Both dentin and bone are composed of 65% inorganic and 35% organic substances.^[10] Studies show that DDM grafts appear to be a feasible alternative to other biomaterials used for alveolar bone preservation.^[9]

Regenerative procedures can help regenerate the supporting tissues of teeth destroyed by periodontal diseases and restore teeth to their original healthy state as much as possible. Previously, the only treatment for periodontal diseases was to stop the disease from progressing further before teeth fell out, and restoration to the original condition was almost impossible.^[1]

Bone augmentation methods have contributed remarkably to expanding treatment options. Various advances in materials science have made these techniques possible. With improvements in implant material properties, implant therapy has become an indispensable treatment method in dentistry.^[1]

Emerging treatments include the use of medications that promote bone formation. Research has shown that sclerostin antibody, which works by blocking a protein that inhibits bone formation, can stimulate bone and cemental regeneration around teeth when given systemically.^[13]

Future treatments may involve induced pluripotent stem cell (iPS) technology for regenerating periodontal tissues, including alveolar bone. This technology is expected to be applied in the treatment of diseases such as tooth loss and periodontitis.^[1]