The attempts to improve the appearance of the skin and to repair skin changes by exfoliation, dates back to the beginning of recorded time. The ancient Egyptians used salt, animal oils and alabaster to improve skin appearance. Sulphur, mustard and limestone were also applied. The Turks used fire to singe the skin and exfoliate it. The basic concept with all these methods is to wound the skin in a controlled and regenerative manner for aesthetic improvement.
The use of the C02 laser for exfoliation began in the 1980’s. The initial work was met with caution because of the difficulty to control the thermal damage to the underlying dermis. The ideal C02 laser for cutaneous surgery should incise or vaporize tissue rapidly and effectively coagulates blood vessels and most importantly, allow for rapid, normal healing. The development of a computer pattern generator (CPG) for use with ultrapulse C02 laser, effectively ablates tissue with minimal thermal conduction to the underlying and surrounding tissue.
Every now and then, more advanced lasers are introduced onto the market. The manufacturing companies are competing to produce the most accurate and safest laser that controls the exfoliation depth and thermal damage, in order to reduce the post laser prolonged erythema and possible scarring. This chapter will discuss the principles of laser resurfacing regardless of the kind of laser machine that is being used.
The skin is divided into two distinct layers, the epidermis and the dermis. The epidermis is primarily composed of keratinocytes, which form tight intracellular bridges and act as an impermeable barrier. The dermis is divided into papillary and reticular layers. The papillary dermis is immediately beneath the epidermis and is composed of loosely arranged collagen matrix, blood vessels and fibrocytes. Beneath the papillary dermis lies the reticular dermis, composed of compact collagen with minimal fibrocytes. Extending from the surface of the skin to deep reticular dermis are the adnexal structures. These dermal appendages are lined by epithelium and serve as the focal points for epidermal regeneration after either chemical or mechanical exfoliation. It is vital and essential to preserve these structures for rapid healing. Damage to the deep reticular dermis will result in the loss of the adnexal structures with prolonged healing and scar formation. This architectural hierarchy must be understood as it applies to surgical exfoliation, which is needed to obtain consistent results without complications.
With age and sun damage, multiple changes occur throughout the different layers of the skin. The epidermis can develop textural and pigment irregularities. The result is superficial actinic keratosis, superficial dyschromias and fine wrinkling. Photoaging causes the dermis to become thickened with elastosis and accumulation of amorphous ground substance. The collagen bundles become fragmented and irregularly aligned. The result is deep pigment irregularities associated with deep wrinkling. These skin changes are ideal to treat by exfoliation. By removing the damaged layers of the skin, new healthy skin is allowed to regenerate with reorganization of the underlying collagen matrix. Ideally, this results in uniform skin texture and quality and decreased wrinkling.
The CPG with untrapulse C02 laser provides more controlled precise and selective means of tissue exfoliation with more reliable and improved results. The histological depths of exfoliation is proportional to erythema and rhytid resolution. Minimal treatment means
Fig. 18 – 18. Illustrations of the layers of the skin showing the colour effects and the exfoliation depth by repeated passes.
minimal improvement and rapid healing, while excessive treatment means delayed healing, prolonged erythema, dyschromia and scarring. The exfoliation depths differ according to the types of laser being used (Sharplan, Luxor, Coherent) and according to the number of laser passes in each sitting. (Fig. 18 – 18)
- Luxon nova scan, 6 watts, 2 passes = exfoliation
depths of 100 µm
- Shaplan silk touch (18mm spot, 20 watts, 2 passes) = exfoliation depths of 160µm.
The exfoliation depths at the first pass is about 50-80Âµm according to the type of laser being used. Each single laser pass causes exfoliation and thermal damage (coagulative necrosis). By repeated passes one sees less tissue exfoliation and an increasing amount of thermal damage.
The average exfoliation with the first pass in depths of 70Âµm (50-80 Âµm), while the average of thermal coagulation is 20Âµm. A second pass increases exfoliation by 20Âµm, while the zone of thermal coagulation increased to 65Âµm. The third pass increases exfoliation by 10Âµm with the zone of coagulation up to 145Âµm.
The rhytid resolution needs at least an exfoliation depth of 100Âµm. and an increase in exfoliation depth requires more passes which will lead to prolonged post laser erythema and possible dyschromia.
The post laser biopsy changes resembling that of young patients:
- Collagen contraction: This is not achieved by chemical peel or dermabrasion.
- Increase compaction of collagen fibres in the upper papillary dermis.
- Re-aligment of collagen fibres more parallel to the surface.
- Re-aligment of elastin fibres parallel to the surface.
The collagen fibre shrinks to approximately one third of the original length with the thermal energy causing tightening of the skin.
The knowledge of the settings of the laser to be used and the depth of exfoliation is vital to avoid injury to adnexal structure and hyperthropic scars:
- Pink colour indicates epidermal level.
- Greyish colour indicates upper papillary dermis.
- Chamois yellow indicates deeper papillary dermis.
Thin epidermic regions should be dealt with severe caution, danger areas are:
- Turning edge of the mandible
- Lateral temporal region
- Nasal malar junction Vermillion border
- Neck, chest and back
- Rhytids: fine or deep
- Actinic keratosis, solar keratoses
- Dyschromia, solar lentigos, freckles
- Acne scars
- Traumatic scars
- Smallpox, warts
Classification of patient skin type:
Type I – Light skin:
Blue or green eyes
Type II – Light skin:
Type III – Medium skin:
Brown hair and eyes
Type IV – Medium to dark skin:
Brown to black hair and eyes
Type V – Dark skin :
Black hair and eyes
Type VI – Black skin:
Black hair and eyes
Most importantly, that patients with skin type III, V, or VI have a tendency to hyperpigmentation which could be temporary or permanent. Special selection, preoperative preparation and long postoperative care is mandatory in these patients.
DYSCHROMIA: Solar lentigos and freckles, indicative of significant sun exposure, it lies in the epidermis. With the first pass, the epidermis along with these pigmentations is vaporized away. Although refreckling will occur with subsequent sun exposure, good photoprotection will inhibit this process.
RHYTIDS: Fine rhytids respond best and usually completely clear, whereas deep, coarse rhytids may only be softened. Tightening of the skin occurs wherever the laser is used; the more surface that is treated, the greater the overall tightening effect. Skin tightening leads to the softening of the facial folds. The deeper rhytids require more passes and will take longer to re-epithelialize and have more erythema. Rhytids that appear to arise from muscular action will still be subject to those same forces and have a higher chance to recur.
ACNE SCARS: Shallow, dish-shaped acne scars are most amenable to resurfacing, whereas deeper “ice pick” scars may still be present although less noticeable. White fibrotic scars and stellate acne scars will not be removed, although the surrounding undulations should be less prominent. Similar to rhytids, the more area resurfaced, the more tightening that will occur and further aid the textural improvement seen. In addition, scars soften with time as more remodelling of collagen occurs and, unlike rhytid formation, the muscular forces are not an issue.
OTHER IMPERFECTIONS: Solar elastosis can be improved with resurfacing as well. Clumped, degenerated collagen and elastin fibers can be vaporized, allowing new collagen to form and take its place. Actinic keratosis, solar-induced premalignant lesions, will also be removed with resurfacing, although extension down the follicular ostia may allow recurrence. Sebaceous hyperplasia and intradermal nevi can also be levelled and made more cosmetically appealing.
INFORMED CONSENT: A thorough explanation of the procedures and the postoperative course often reduces the patient’s fear. Anticipation of an adequate recovery time will help patients plan their schedules and minimize frustration with the postoperative phase. A typical postoperative course and possible complications should be explained, such as erythema, pigmentation, irritation, dryness, infection and possible scarring. A written confirmation of this understanding should be signed by the patient ; it is best to have this done at the first consultation visit.
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