Indented lines on the skin represent a physical depression or furrow resulting from external pressure or internal structural change. The question of whether these lines disappear depends entirely on the skin’s viscoelastic properties—its ability to stretch and return to its original shape. Skin that is young and well-hydrated behaves more elastically, snapping back quickly when pressure is removed. Conversely, when the underlying support structure of the skin is compromised by damage or volume loss, the indentation becomes a permanent feature.
The Mechanism of Temporary Indentations
Temporary indentations occur when external force mechanically strains the skin tissue without causing lasting damage to the dermal layer. The skin, behaving as a viscoelastic material, temporarily displaces interstitial fluid and stretches its elastic fibers in response to this pressure. Common examples include the marks left by tight clothing seams, watch straps, or the creases known as “sleep lines” from resting the face against a pillow.
Once the mechanical pressure is released, the skin’s inherent elasticity and the quick re-entry of fluid into the compressed area allow the surface to rebound and flatten. The speed of this recovery is directly related to the condition of the skin’s structural proteins, collagen and elastin, and its hydration level. In younger adults, the recovery from a mechanical depression often takes only a few minutes.
In contrast, studies have observed that the recovery time for mechanically depressed skin can dramatically increase with age, sometimes taking upwards of 24 hours to fully resolve. This delay is a visual manifestation of reduced skin resilience, which is caused by the natural degradation of the elastic network and a general decrease in tissue hydration over time. The temporary nature of these marks is defined by the fact that the underlying fibers remain intact, merely stretched, allowing for eventual, complete recovery.
Structural Indentations: Scars, Stretch Marks, and Atrophy
Indentations that do not go away are characterized by a lasting alteration or deficit in the skin’s structural components, primarily in the middle layer, the dermis, or the subcutaneous tissue below it. These permanent depressions signal that the tissue’s natural healing or maintenance processes have failed to fully restore the original volume and architecture. The depth and permanence of the line are determined by the extent of this structural deficit.
Atrophic scars are a common form of persistent indentation, resulting from the body’s inability to produce enough new connective tissue during the healing of a wound, such as severe acne or a deep injury. This insufficient tissue repair leads to a sunken, pitted appearance because the surface skin lacks adequate underlying support. These scars are classified by shape, including deep icepick scars, broad boxcar scars, and wider rolling scars, all anchored by a deficit of collagen.
Stretch marks, medically termed striae distensae, represent a form of dermal scarring caused by rapid or excessive stretching of the skin, such as during pregnancy or growth spurts. This rapid extension causes microscopic tears in the dermis, leading to the breakdown of the extracellular matrix and a disruption of the collagen and elastin fiber bundles. The resulting depressed lines are structurally distinct from normal skin, showing features like epidermal atrophy and disorganized collagen fibers.
Another source of permanent indentation is age-related atrophy, or volume loss, which affects the subcutaneous fat layer beneath the dermis. As people age, there is a distinct redistribution of adipose tissue, often involving a loss of fat from peripheral areas like the face and limbs. This loss of underlying cushion leads to the caving-in effect seen in sunken cheeks and deep folds, as the overlying skin is no longer supported. This atrophy can also be localized and medically induced, such as the lipoatrophy sometimes seen following certain injections, which results in a distinct, persistent depression at the injection site.
Addressing Persistent Indentations: Treatment Options
Treatments for persistent indentations focus on either rebuilding the missing structural components or physically restoring the lost volume. The goal is to stimulate the body’s healing response to generate new support structure beneath the depressed area.
Collagen Stimulation
One primary approach is collagen stimulation, which encourages the body to produce new structural proteins within the dermis. Procedures like microneedling, often called collagen induction therapy, create controlled micro-injuries to trigger a wound-healing cascade that generates new collagen and elastin fibers. Laser resurfacing techniques, such as fractional ablative lasers, remove damaged tissue layers to stimulate the growth of a healthier, smoother skin surface.
Volume Restoration and Subcision
Another effective strategy involves volume restoration to physically lift the depressed area. Injectable dermal fillers, particularly those containing hyaluronic acid, provide immediate volume to raise the base of atrophic scars or deep folds. For scars that are tethered down by fibrous bands of tissue, a minor procedure called subcision is performed to break these connections, allowing the indentation to rise and encouraging new collagen formation to maintain the correction.
Long-Term Improvement
For a more gradual, long-term improvement, specialized collagen-stimulating fillers, such as poly-L-lactic acid, are injected to trigger a sustained biological response. These materials work by creating a scaffold that prompts the surrounding tissue to generate its own collagen over several months, resulting in a subtle, enduring volume increase. Topical retinoids, derived from Vitamin A, are also utilized to support this process by increasing cell turnover and promoting collagen synthesis, leading to minor improvement in the appearance of shallower indentations over time.