An asymmetrical gingival margin occurs when the gum line is lower on one side compared to the other. This common clinical finding can manifest as gum recession, where the tissue pulls away and makes teeth appear longer, or as localized gingival overgrowth, where the tissue appears bulky or swollen. This unevenness is a physical sign that an underlying process is affecting one area of the mouth more than others. Understanding the specific factors causing this unilateral change is the first step toward correcting the issue and restoring a balanced, healthy gum line.
Localized Habits and Mechanical Stress
Physical forces applied unevenly to the mouth are a frequent cause of a lower or receding gum line on one side. The most common mechanical culprit is an overly aggressive brushing technique, often occurring on the side opposite a person’s dominant hand. A right-handed person may brush the left side of their mouth too hard, leading to recession in that quadrant as the gum tissue is physically abraded.
The force from habitual clenching or grinding (bruxism) can also be distributed unevenly across the dental arch. This excessive pressure places stress on the periodontal ligament and supporting bone, especially if the bite is not perfectly aligned. This localized stress contributes to the breakdown of tissue attachment, leading to recession marks on teeth that bear the brunt of the force. Localized trauma from sharp foods, fingernail biting, or the consistent pressure of a poorly fitting dental appliance can also injure the gum tissue. Such single-point trauma disrupts the gingival attachment, causing it to migrate away from the crown of the tooth, only in the injured area.
Asymmetrical Gum Disease and Inflammation
A localized infection or inflammatory response is a significant cause when a gum line appears lower due to swelling or true recession. Gum disease, which begins as gingivitis and can progress to periodontitis, does not always affect the entire mouth uniformly. Patients often maintain better hygiene on accessible areas, while a back quadrant or one side receives inadequate cleaning.
This differential hygiene results in asymmetrical plaque accumulation, allowing bacterial colonies to thrive and trigger a localized inflammatory response. In early gingivitis, this inflammation causes the gums to become red, swollen, and bulky, making the tissue appear lower or overgrown relative to healthy tissue. If untreated, periodontitis develops, causing the detachment of the gum from the tooth root and destruction of the underlying bone.
This localized bone loss is often the reason for one-sided recession, as the gum tissue follows the contour of the supporting bone. The resulting periodontal pockets will be measurable only in the affected, lower quadrant. The continuous presence of calculus and plaque in this area sustains the infection, leading to a progressive and unilateral loss of the gingival margin.
Structural Factors Affecting Gum Height
Asymmetry in the gum line can result from anatomical features or previous dental work, not just habits or infection. The natural thickness of the gum tissue, known as the gingival biotype, varies among individuals; a thin biotype is more vulnerable to recession from mechanical or inflammatory stress. If one side naturally has thinner tissue, it will recede first, creating an uneven appearance.
Misaligned teeth (malocclusion) can predispose certain areas to an uneven gum line. A tooth that is tipped or protrudes often has a thinner plate of supporting bone, making the overlying gum tissue prone to recession. Furthermore, the frenum, the band of tissue connecting the lip or cheek to the gum, can be attached too close to the gingival margin on one side. A high-pulling frenum creates constant, localized tension that tugs the gum tissue away, causing recession in that specific spot.
Dental alterations can also introduce asymmetry. A crown, filling, or veneer that does not fit perfectly can irritate the surrounding gum tissue. Restorations with rough or overhanging margins trap plaque and perpetually inflame the gum, causing localized swelling or recession only around the poorly adapted restoration.
Next Steps for Evaluation and Care
A professional dental examination is necessary to determine the specific cause of an asymmetrical gum line, whether mechanical, infectious, or structural. The dentist or periodontist will perform a thorough assessment, including periodontal probing, which measures the depth of the space between the tooth and the gum. Disease-related asymmetry will show deeper probing depths only in the affected quadrant.
Dental X-rays check for asymmetrical bone loss, as the gum tissue level is closely tied to the height of the underlying bone. If gum disease is found, treatment involves professional deep cleaning procedures, such as scaling and root planing, to remove calculus and bacteria. For cases caused by mechanical stress, the treatment focuses on identifying and correcting the habit, including instruction on proper, gentle brushing techniques.
If the gum line is uneven due to significant recession or structural issues, surgical treatments may be recommended. Gum contouring (gingivectomy) removes excess tissue to create symmetry. Soft tissue grafting covers exposed roots and restores the gum line. These interventions improve appearance, reduce sensitivity, and enhance long-term oral health.