Chipping, notching, or V-shaped defects specifically at the gum line are a common concern that prompts a dental visit. This damage occurs at the cervical margin, the narrow area where the tooth meets the gum tissue. The defects are not typically caused by the bacteria responsible for cavities, meaning they fall under the clinical classification of Non-Carious Cervical Lesions (NCCLs). These lesions represent a loss of hard tooth structure due to mechanical or chemical processes rather than decay.
Understanding Non-Carious Cervical Lesions
NCCLs are fundamentally classified by the primary force responsible for the loss of tooth material at the gum line. The three distinct types that often result in a chipped appearance are Abfraction, Abrasion, and Erosion. Abfraction lesions are often characterized by a deep, sharp, wedge-shaped notch with defined internal and external angles. Abrasion, conversely, usually presents as a smooth, rounded, or polished V-shaped groove near the gum line. Erosion causes a more generalized, smooth loss of surface structure, sometimes appearing cupped or saucer-shaped, which can then make the teeth more susceptible to chipping from other forces.
The Role of Mechanical Stress and Force
The specific type of damage known as Abfraction is caused by internal, biomechanical forces transmitted through the tooth structure. When teeth are subjected to excessive occlusal loading—the force of biting and chewing—the tooth flexes slightly, especially at the gum line. This area, known as the cementoenamel junction, has thinner enamel and is the most vulnerable point for stress concentration. The constant, cyclic flexing of the tooth causes microscopic pieces of the rigid enamel and dentin to break away.
The primary drivers of these damaging forces are parafunctional habits, most notably bruxism, which involves clenching and grinding of the teeth. Bruxism can generate forces significantly greater than those used during normal chewing, leading to high tensile and shear stress at the cervical margin. Malocclusion, or a misaligned bite, also contributes by directing non-axial forces—forces not parallel to the tooth’s long axis—onto certain teeth. These side-to-side forces create maximum flexure and stress, which accelerates the microfracturing process that results in the characteristic wedge-shaped Abfraction lesion.
External Wear and Chemical Factors
The other two major causes of gum line damage, Abrasion and Erosion, result from external forces and chemical interactions, respectively. Abrasion is the physical wearing away of tooth structure by friction from a foreign object. The most frequent cause of abrasion is overly aggressive or improper horizontal toothbrushing, particularly with a hard-bristled brush or highly abrasive toothpaste. This habit physically scrapes away the softer cementum covering the root surface, which is exposed when the gums recede, creating a characteristic V-shaped groove.
Erosion, in contrast, involves the chemical dissolution of the tooth structure by acid, without the involvement of bacteria. This process can stem from extrinsic sources, such as the frequent consumption of highly acidic foods and drinks like citrus fruits, soda, or vinegar. Acids soften the enamel and dentin, making the tooth structure significantly more susceptible to physical wear from chewing or even light brushing. Intrinsic acid sources, such as chronic gastric reflux (GERD) or conditions involving frequent vomiting, expose the teeth to stomach acid, which can rapidly demineralize the enamel.
Professional Treatment and Long-Term Management
The initial professional treatment for these lesions often involves restoration to cover the exposed dentin, reduce sensitivity, and restore the tooth’s structural integrity. Dentists typically use tooth-colored materials like composite resin or glass ionomer to fill the defect. These restorative materials help protect the inner tooth from further wear and minimize the painful sensitivity that occurs when the dentin tubules are exposed to temperature changes.
Successful long-term management, however, depends entirely on identifying and eliminating the root cause of the damage. If the issue is determined to be Abfraction, a dentist may recommend an occlusal adjustment to modify heavy bite contacts or prescribe a custom-fitted night guard to manage the forces from bruxism. For lesions caused by Abrasion, the management strategy involves correcting improper brushing technique, switching to a soft-bristled brush, and avoiding highly abrasive toothpastes. If the cause is Erosion, treatment focuses on dietary counseling to reduce acid intake or medical referral to manage conditions like GERD. Restoring the physical defect without controlling the underlying cause will often result in the restoration failing or a new lesion developing nearby.