A dental filling is a common procedure used to restore a tooth damaged by decay or trauma. Dentists classify these defects to determine the appropriate treatment approach. The Class 5 filling addresses lesions found on the smooth surfaces of the tooth near the gumline. This unique location and diverse causes require particular attention during diagnosis and restoration.
Context and Location of Class 5 Cavities
The designation “Class 5” originates from the G.V. Black classification system, which categorizes dental defects based on their location. A Class 5 lesion occurs on the cervical third of the tooth, situated near the gumline on the facial (cheek side) or lingual (tongue side) surfaces of any tooth. These defects often present as shallow, crescent-shaped, or wedge-shaped depressions near the cementoenamel junction (CEJ).
Because this area is close to the soft tissue and often involves the root surface (dentin or cementum), these lesions can cause heightened sensitivity. Exposed dentin contains microscopic tubules leading directly to the pulp, allowing stimuli to trigger pain. Restoring these lesions helps seal the exposed dentin, alleviating sensitivity and preventing further loss of tooth structure. Repair is also important for aesthetic reasons, especially when visible on the front teeth.
Factors That Cause Gumline Wear
Class 5 lesions are unique because they are frequently non-carious, meaning they result from wear rather than bacterial decay. The causes of this gumline wear are often multifactorial, involving mechanical, chemical, and biomechanical forces. Dentists differentiate between abrasion, erosion, and abfraction to determine the underlying cause and prevent recurrence.
Abrasion involves the loss of tooth structure due to mechanical friction from outside agents. A common example is aggressive horizontal toothbrushing using a hard-bristled brush or abrasive toothpaste. This mechanical action scrapes away the softer tooth structure near the gumline, especially if the enamel has been weakened.
Erosion is the loss of tooth structure caused by chemical dissolution, primarily from acids. Intrinsic acids (like those from chronic acid reflux or frequent vomiting) or extrinsic acids (from a diet high in citrus fruits or carbonated drinks) can soften the tooth surface. This chemical softening makes the area more susceptible to mechanical wear, often leading to a combined abrasion-erosion defect.
A third factor, known as abfraction, describes the loss of tooth structure resulting from occlusal stress. Heavy biting forces, such as those from clenching or grinding (bruxism), cause the tooth to flex slightly at the cervical third. This repeated flexing concentrates stress at the CEJ, leading to microfractures and a characteristic wedge-shaped defect.
Filling Materials and Restoration Procedure
Once a Class 5 lesion is diagnosed, the goal of restoration is to stop the defect’s progression, reduce sensitivity, and restore the tooth’s contour. Material selection is important due to the challenging location, which is often difficult to keep completely dry. The two most common materials used are composite resin and glass ionomer cement.
Composite resin, a tooth-colored plastic material, is frequently chosen for its excellent aesthetics and strong bond to enamel. Its use requires meticulous moisture control and a multi-step procedure involving etching and bonding agents to ensure long-term retention. Since the Class 5 area often involves dentin and cementum near the gums, which are less predictable to bond to than enamel, retention can be a challenge.
Glass Ionomer Cement (GIC) and its hybrid variant, Resin-Modified Glass Ionomer Cement (RMGIC), are often preferred in Class 5 restorations. These materials chemically bond to the tooth structure and are more tolerant of moisture than composite resin, which is advantageous near the gumline. They also release fluoride, which helps prevent further decay. The restoration procedure involves cleaning the lesion, applying the material, and then curing it to harden it.