Abfraction Lesions: What Causes Those Notches at the Gum Line

An abfraction lesion is a wedge-shaped or notch-shaped defect that develops at the cervical area of a tooth, the region where the crown meets the root at and just below the gum line. The defect is in the tooth structure itself, not in the gum tissue. The notch is typically sharp-edged and well-defined, with a hard, glossy floor, and it is found on the buccal (cheek-facing) surface of the tooth rather than on the chewing surface or between teeth.

The term 'abfraction' was coined in 1991 by John Grippo to describe a specific mechanism of tooth structure loss involving occlusal stress and flexion. It joins the family of non-carious cervical lesions (NCCLs), a group of defects at the gum line that includes abrasion (wear from mechanical cleaning), erosion (chemical dissolution from acids), and attrition (wear from tooth-to-tooth contact). In practice, many cervical lesions result from a combination of these mechanisms rather than a single cause, which is why the diagnosis and treatment approach requires evaluating all contributing factors.

Abfraction lesions are not rare. They are found in ten to twenty percent of adults in some studies, and their prevalence increases with age. They are most commonly observed on premolars (the teeth at the corners of the mouth where lateral bite forces concentrate), but they can affect any tooth. A single tooth with a heavy bite contact that absorbs disproportionate force is at higher risk than teeth with balanced occlusal loading.

The abfraction hypothesis proposes that off-axis occlusal loading causes the tooth to flex. When a force is applied to the crown of a tooth from the side rather than directly along the long axis of the root, the entire tooth bends slightly. This flexion creates tensile stress on one side and compressive stress on the other. The weakest structural point is at the cervical region near the cemento-enamel junction (CEJ), where the enamel is thinnest. Repeated cycles of flexion cause the hydroxyapatite crystals in the enamel to fatigue and separate at this location, creating the characteristic notch.

Supporting evidence for the flexion mechanism comes from finite element analysis (computational stress modeling), which shows stress concentration at the cervical region when lateral forces are applied to tooth models. Electron microscopy studies have identified microcracks in enamel prisms at the cervical area consistent with fatigue fracture. Clinical observations note that abfraction lesions tend to be deepest on teeth with the most pronounced occlusal interferences and in patients with parafunctional habits like bruxism and clenching.

However, the force-flexion theory remains somewhat controversial in the literature. The main criticism is that experimental studies have not consistently demonstrated tooth flexion of sufficient magnitude to cause the observed lesion, and that the prevalence of abfraction lesions does not always correlate cleanly with occlusal load distribution in clinical populations. Some researchers argue that what is called abfraction may more often represent a combination of erosion and abrasion at a site that is already thinned and weakened by dietary acids, with the occlusal load playing a contributing but not primary role.

Distinguishing abfraction from erosion and abrasion guides treatment planning. Erosion creates a smooth, scooped, or cupped defect with a wider, more rounded profile. It is caused by acid dissolving the tooth surface, whether from dietary sources (frequent citrus, carbonated beverages, vinegar-based foods), gastric acid (reflux, bulimia), or occupational acid exposure. Erosion affects surfaces broadly, including the chewing surfaces and palatal surfaces of upper front teeth in gastric acid cases, and has a characteristic glazed appearance.

Abrasion is caused by mechanical wear from an external agent, most commonly a toothbrush, and produces a horizontal notch or groove with a smooth, polished floor. It is found on the buccal surfaces of teeth, similar to abfraction, but tends to span multiple teeth in a horizontal band at the same height rather than occurring at an isolated tooth. The distribution corresponds to where the toothbrush is being applied with excess pressure.

A true abfraction lesion (if one accepts the force mechanism) should be found on a tooth with identifiable occlusal overload or parafunctional habits, with a sharp, wedge-shaped defect, hard and glossy floor, and a distribution limited to the most heavily loaded teeth. In clinical practice, most cervical lesions have features of more than one mechanism: a patient may have slight erosion from a soft drink habit that softens the enamel, combined with brushing abrasion that removes the softened surface, combined with occlusal stress that concentrates in that already-thinned region. The three mechanisms act synergistically.

Many abfraction lesions are asymptomatic, discovered incidentally during examination. When symptoms are present, the most common is sensitivity to cold, sweet substances, or cold air. The sensitivity occurs because the lesion exposes dentin, the inner layer of the tooth beneath enamel, whose tubules connect directly to the nerve of the tooth. Once dentin is exposed at the cervical area, temperature changes and osmotic stimuli can trigger sharp, brief pain. This is the same mechanism as dentinal hypersensitivity from gum recession.

In deeper lesions, sensitivity may be present to touch: brushing the area or running a fingernail over the defect may trigger pain. This is a sign that the lesion has progressed and may be approaching the pulp. Very deep cervical lesions, though uncommon, can eventually compromise the nerve of the tooth if not treated, leading to pulpitis (inflammation of the pulp) or eventually pulp death requiring root canal treatment.

Abfraction lesions do not cause visible staining unless secondary decay has begun in the defect. The hard, glossy floor of an abfraction lesion is not carious tissue. When the floor of a cervical notch feels soft, sticky to a dental explorer, or appears discolored, caries has superimposed on the structural defect. This changes the treatment from monitoring or bonding to caries removal and restoration.

Treatment depends on the severity of the lesion, the presence of symptoms, and whether active progression is occurring. Small, asymptomatic lesions with no sensitivity and no decay do not require immediate restorative treatment. Monitoring with photographs and measurements at recall visits establishes a baseline and allows detection of progression. In the meantime, addressing the contributing factors (diet acidic content, brushing technique, occlusal habits) may slow or arrest the lesion.

Desensitizing treatments are appropriate for lesions causing cold sensitivity. Fluoride varnish applied at professional visits, desensitizing toothpaste containing potassium nitrate or stannous fluoride, and in-office bonding agents applied to the exposed dentin can all provide relief by occluding (blocking) the dentin tubules. For persistent sensitivity, a tooth-colored composite resin restoration bonded into the defect provides both desensitization and structural reinforcement. The bonded restoration also eliminates the mechanical stress concentration at the notch base, which may slow further development.

Addressing the occlusal component is important for preventing recurrence of restored lesions. If an identifiable occlusal interference is loading the affected tooth disproportionately, an equilibration (selective reshaping of the bite) can redistribute force more evenly. For patients who brux or clench, a custom night guard reduces the force delivered to the dentition during sleep, which is typically when the heaviest parafunction occurs. Without addressing the force component, composite restorations placed in abfraction lesions may debond at higher rates than expected because the flexion that created the lesion continues to cycle stress at the restoration margin.

Any noticeable notch or groove at the gum line of a tooth, whether symptomatic or not, is worth having evaluated. The clinical assessment includes probing to measure the dimensions of the defect, checking for soft carious tissue, assessing the tooth's response to cold and percussion, examining the occlusal contacts with articulating paper, and reviewing the bite for lateral interferences. Radiographs help evaluate the remaining thickness of dentin overlying the pulp in deeper lesions.

If you have been experiencing sensitivity at the gum line for more than a few weeks that does not improve with desensitizing toothpaste, that is a reasonable trigger to schedule an evaluation. Sensitivity that is severe, prolonged after the stimulus is removed, or present to heat as well as cold suggests pulpal involvement beyond simple dentin sensitivity and needs assessment sooner rather than later.

Patients who grind or clench their teeth and have visible wear on the biting surfaces should also have their cervical areas examined specifically for abfraction lesions, because the same parafunctional forces that cause wear on the chewing surfaces may be contributing to cervical lesions simultaneously. An occlusal evaluation that addresses both issues together is more comprehensive than treating each finding in isolation.