LASERS ON FACIAL REJUVENESCENCE

Received on 15/02/2009
Approved on 25/02/2009
We declare no conflict of interest.

Abstract

The 10,600-nm CO 2 and 2940-nm Erbium lasers were the first ones used for rejuvenescence, with surprising results due to their ability stimulate collagen. Since they are ablative lasers, the postoperative period is difficult and prolonged, and with important complications. To minimize those undesirable effects, non-ablative lasers with different wavelengths were introduced (840 nm, 1320 nm, long pulse 1640 nm, among others), with a very mild postoperative period, but with a very limited capacity to promote neocollagenesis. New studies were responsible for non-ablative fractional lasers (1440 nm, 1540 nm, and 1550 nm) with a different action: they promote dermal-epidermal coagulation columns, have a moderate postoperative period, and a reasonable capacity to stimulate collagen fibers with a negligible risk of side effects. However, they are very limited in severe photoaging. To fill this gap, new fractional 10,600-nm CO2 and 2940-nm Erbium lasers were introduced. This reduced the incidence of side effects, but also reduced the final effect, which is not as good when compared with the same, non-fractional, lasers. They represent a good option for the treatment of severe photoaging.

INTRODUCTION

Since the discovery of selective photothermolysis by Anderson and Parrish,¹ lasers have been used on skin rejuvenescence, and they were introduced in Brazil in the 1990s. First generation non-fractional 10600-nm CO₂ ² and 2940-nm Erbium³ lasers were the first to be used. Results were encouraging, but since they cause complete ablation of the epidermis both present, postoperatively, all possible complications of the total exposure of the dermis.⁴ The Erbium laser is somewhat milder and has a lower but still significant incidence of side effects.⁵ Since it is such an aggressive procedure, it often causes personal and familiar problems for the patient. All those technical difficulties led to a slow decrease in their use after a period of great excitement.

In an attempt to improve the effects of collagen stimulation, non-ablative skin resurfacing,6 using lasers with deeper dermal penetration and that do not cause epidermal ablation,⁷ was developed. The 800- to 1450-nm diode laser and long-pulse (1064 nm) Nd:YAG laser were used but their results were inferior to what was expected.

Investigation of new wavelengths absorbed by water led to the discovery of non-ablative fractional lasers8 (1440 to 1565 nm). It represented a revolution in those techniques: collagen is stimulated through columns of dermal-epidermal coagulation without epidermal ablation, the postoperative (PO) period lasts only 2 to 3 days, and it has better results than pulsating light and the non-ablative (non-fractional) lasers described above.⁹ Despite this discovery, the effects of skin rejuvenescence with advanced photoaging are still mild. Non-ablative fractional lasers require several sessions and are highly costly.

Thus, to achieve similar results of traditional ablative resurfacing and the safety of non-ablative fractional lasers, new equipment, with lasers more capable of stimulating collagen, was developed: the 10600-nm CO₂ and 2940-nm Erbium lasers with a huge modification: fractionation of those rays.^9-11 Therefore, in fractional ablation, only part of the epidermis, a higher or smaller proportion, is removed in a controlled manner, according to the desired results. The postoperative period became more tolerable, and the incidence of side effects decreased; however, the results are also inferior to the non-fractional CO₂ and Erbium lasers. Currently, fractional ablative lasers represent the most adequate technique for the treatment of moderate to severe photoaging with a medium intensity PO period.

ABLATIVE LASERS

CO₂ lasers
Carbon dioxide laser emits a 10600-nm wavelength, which is strongly absorbed by tissue water (Figure 1). Penetration depends on the water content and is independent of melanin and hemoglobin contents, and it has a water absorption coefficient of 800/cm.¹ It has a mean pulse duration below 1 millisecond, with a tissue penetration of about 20 µm.⁵

In general, lasers work by heat production: small increases in temperature produce biostimulation; elevations from 60°C to 85°C cause coagulation, above 85°C produce carbonization, and vaporization occurs with temperatures close to 100°C.

In the case of the CO₂ laser, vaporization occurs when the laser reaches the skin, by rapidly heating the water (Figure 2A), leading to its boiling point. This phenomenon generates ablation, which represents the tissue renewal responsible for ablative resurfacing.^2,4 Moreover, this reaction is exothermic, i.e., it releases heat, which spreads through adjacent cells, generating a residual thermal effect. This heat transference is probably responsible for collagen denaturation. Collagen denaturation contributes to tissue contraction (frequently visible to the naked eye during the procedure) and the improvement of rhytides and flaccidity that occurs after the procedure; besides, this phenomenon can also induce a tissue reaction that generates neocollagenosis in the six months that follow the procedure. Summarizing, CO₂ laser produces skin rejuvenescence through ablation (removal of damaged skin), collagen contraction, and neocollagenosis.

Best indications: Severe photoaging, treating hyperpigmented lesions, improving actinic keratoses, and causing collagen contraction.¹⁴

Technical advantages: Better results after a single session.

Disadvantages and limitations: Since it is a very aggressive technique, it has a long and uncomfortable PO period, with a relative high risk of scar formation.^2,4 It should not be performed during the times of highest solar radiation, which is not always feasible in some specific regions in Brazil.

Step-by-step technique
1 month before: The use of sunscreen, retinoic and glycolic acids or C vitamin are recommended, and the use of hydroquinone is controversial.¹²

The day before: The use of a systemic antiviral drug is always mandatory to prevent facial herpes simplex , and the use of prophylactic antifungal drugs and antibiotics is controversial.

Procedure: Since it is a very painful procedure, several resources to minimize pain should be used: topical anesthesia should be initiated 1 hour before the session, along with oral sedatives and analgesics. Usually, depending on the level of patient anxiety, general anesthesia or sedation is indicated. Smoke aspirator must be used during the procedure, which should only be initiated after careful cleaning of the skin, eliminating any residue of the anesthetic cream. Plexus block is very useful in the malar and supralabial regions. Cooling of the skin with cold air between discharges (to avoid interfering with the smoke aspirator) relieves considerably the burning sensation produced by the CO₂ laser.

After the procedure: The patient should remain in a cold room with a cold mask and cold air directed to the face; if necessary, an oral analgesic should be prescribed. The patient should only leave the office after relief of the pain. Wet-dressings with NS are used for cleaning, as well as a cicatrizing ointment and a systemic antiviral agent should be continued until complete reepitelization. During this period, the patient should be seen by the physician daily or every other day. Systemic antibiotics and antifungals should be prescribed immediately at the first sign of bacterial or candida infection. Light-emitting diode (LED) produces light with anti-inflammatory and cicatrizing effects13 that can be used postoperatively. The patient should be instructed to avoid direct sun exposure for at least 6 months after the procedure.

Expected results: Results are very exuberant after only one session, but this is an invasive technique and the patient has a social impediment for 30 days, and the skin remains photosensitive and erythematous for up to 6 months.

Standardized photographic documentation before and after the procedure is necessary for CO₂ laser ablation and other laser procedures to safeguard the physician and show the results to the patient. An Informed Consent should also be obtained.

The Erbium: YAG laser was the second laser developed for ablative resurfacing. It emits a 2940-nm wavelength ray in the infrared spectrum that is close to the peak water absorption (water absorption coefficient = 12000)⁵ (Figure 1). This laser has a depth of penetration limited to 1 to 3 µm of tissue per J/cm2, while the CO₂ laser reaches 20 to 30 µm. The residual thermal effect is also much lower with the Er:YAG laser. This causes a more precise skin ablation with minimal tissue damage (estimated value of 10 to 40 µm).⁵ Bleeding, an inconvenient of this laser, occurs during the procedure.

The global efficacy of the Er:YAG laser is comparable to the CO₂ laser, but, in most comparative studies, the results of the latter are considered to be superior. However, the Er:YAG laser induces faster cicatrization with fewer side effects.⁵

Best indications: Moderate facial aging, treating pigmented lesions, and improving scars. It is indicated for patients who want to rejuvenate without the risks of the side effects caused by the CO₂ laser.

Technical advantages:session Visible results after a single session.

Disadvantages and limitations: In cases of severe photoaging, the treatment has to be repeated. The risk of side effects is not negligible, but it is lower when compared with the CO₂ laser.

Step-by-step technique

1 month before: Similar to that of the CO₂ laser.

The day before: The use of an oral antiviral drug is mandatory in the presence of a history of facial herpes simplex.

Procedure: The skin should be cleaned and the smoke aspirator used; usually, only a topical anesthetic is necessary; occasionally, sedation or general anesthesia is necessary.

After the procedure: The conduct is the same as the prior laser but, with the Er:YAG laser, pain and inflammation are less severe.

Expected results: Results are highly satisfactory for moderate photoaging; in cases of severe photoaging, complimentary sessions are indicated.

NON-ABLATIVE LASERS

The main wavelength of this group is a long pulse of 1064 nm. The main cromophores are melanin, hemoglobin, and water. The interaction of the laser with those structures results in a deep thermal effect, since water absorption by cromophores is small when compared with other wavelengths (Figure 1). Thus, heating of the surface and diffusion to the superficial and medium dermis (which affects up to 5 mm) occur (Figure 2B). Through the correct combination of pulse duration and fluency, the best results in collagen remodeling can be achieved, since more diffuse and uniform heating of the tissue water occurs. The use of pulse duration in the order of milliseconds induces good effects on the treatment of flaccidity, fine rhytides, and acne scars. Two wavelengths, 532- and 1064-nm, can also be combined with synergistic effects.14 A pulse of very short duration (nanoseconds = Q-switched) with a wavelength of 1064 nm has also been used in dermatology as a form of non-ablative treatment of photoaging. It has an extremely limited potential, although low fluencies can induce neoformation of collagen, with little or no side effects.¹⁴

Other wavelengths can also be used.
The 900- to 980-nm low fluency diode laser has been shown to be effective in the shortening of collagen fibers, besides promoting collagen denaturation and neocollagenesis.¹⁵

The 1320-nm Nd:YAG laser, for its turn, operates in the band of absorption by water and it does not compete with other cromophores, therefore avoiding the adverse effects of skin pigmentation. Light absorption by the water in the tissue leads to dissipation of the thermal energy through the entire area being treated, and heating can reach up to 2 mm deep.16 The use of this laser involves epidermal protection mechanisms by using a cryogen spray before, during, and after triggering the pulse (CoolTouch®, Roseville, CA, USA). The use of this laser without proper epidermal cooling has shown higher chances of hyperpigmentation and punctual scars.17 Best results are achieved with multiple passings of the laser beam and target temperatures between 45 and 48°C. Heating above 48°C implicates on a higher risk of scar formation. Summarizing, improvement of fine, non-expression wrinkles and acne scars is seen more often.

The 1450-nm diode laser operates in the infrared band, and it is capable of reaching up to 500 µm deep. It works with low fluency and requires epidermal cooling to avoid scars and dispigmentation. In general, it induces good responses in the treatment of fine rhytides after several treatment sessions. Its use in the treatment of active acne was approved by the FDA since it induces atrophy of sebaceous glands. Some authors prefer to use it in the treatment of acne scars and sebaceous hyperplasia.¹⁸

Best indications: Mild to moderate facial aging without the need of collagen contraction.

Technical vantages: It does not keep the patient away from his/hers usual activities and it is associated with a low risk of side effects.

Disadvantages and limitations: It has variable results, which depend on individual reaction. Permanent scars after the use of higher energies have been reported. Some devices have consumable components which are costly both for the physician and patient.

Step-by-step technique:

1 month before: The use of sunscreen is mandatory, and topical treatment is recommendable.

Procedure: Since it is less painful, anesthetic ointments and/or prior cooling of the skin are enough.

After the procedure: There are no specific recommendations.

Expected results: Results are progressive, and multiple sessions are necessary.

NON-ABLATIVE FRACTIONAL LASERS

They include lasers that use 1440-, 1540-, 1550-, and 1565-nm rays. Since they are well absorbed by the water, promotion of collagen synthesis and remodeling represent its main indication.¹⁹

These are lasers with specific characteristics:
1 – The tip of the laser releases rays whose energy is measured in millijoules.

2 – The rays promote coagulation columns in the skin, keeping the local epidermis intact; in other words, they do not promote its ablation (Figure 2C). In this column, a process of reconstitution of the coagulated area begins, in the dermal-epidermal direction, after a few hours, lasting 14 days. Coagulated fractions of collagen, pigments, and blood vessels are eliminated through the epidermis.²⁰

3 – The penetration of the rays varies according to their fluency. The release of higher energy levels has deeper effects and causes greater collagenosis, allowing modulation of the desired result.²⁵

4 – Although melanin and hemoglobin are not targets of this laser, some of the pigments and/or blood vessels coagulate when they are hit by the beam at the moment of skin penetration. Thus, even indirectly, superficial epidermal and dermal pigments are removed, as well as some of the smaller blood vessels. The 1550- and 1540-nm (Table 1) are used more often in Brazil, and there are a few differences between them. In the 1540-nm laser (Erbium glass rod laser), the rays are released in a static mode, similar to a “rubber stamp”, in 10-100 msec pulses. It has 2 tips, one with a more superficial action (15 mm) and other deeper (10 mm). Fluencies used vary from 20 to 100 ml/cm2. They are capable of causing medium thermal damage, 333-µm wide and 1-mm deep, when used in high fluencies. In the 1550-nm laser (Erbium glass laser), the beams are released in a dynamic manner through a tip (two sizes available) closely associated with the handpiece. The treatment is initiated only when it is moved over the skin. This device allows the automatic control of the beam density and the width and depth of coagulation columns.

Best indications: Mild photoaging is the main indication, since this technique has a limited capability of neocollagenesis. A second indication includes the removal of superficial epidermal and dermal pigments.

Vantages of the technique: It is performed with a high level of safety and few side effects.

Step-by-step technique
The use of topical anesthesia is necessary. The procedure is less painful with the 1540-nm laser, which is applied (“rubber stamp”) in small segments, with 2 to 4 passings with overlapping of the tip. Thus, the whole area can be treated. For example, the face is divided in 8 areas, completing the treatment in one area before beginning another. The 1550-nm laser allows higher speeds and it is also applied in small areas, with a total number of passings that is calculated by the device according to the desired effect. In both cases, subtle face edema and intense erythema occur at the end of the treatment, lasting 2 to 3 days. Since they are non-ablative, make up can be used immediately after the treatment to conceal the erythema. Extreme care should be taken with sun exposure for at least 30 days. The technique can be used in any area of the skin. Although its indication is questionable, it is one of the few techniques that can reduce the dermal-epidermal pigments of melasma;22 however, it does not interfere with its evolution.

The 1440-nm YAG laser, which has just been recently introduced in Brazil, has similar effects. It has a lower dermal penetration, but the speed of the firings, which reduces the total treatment time, is its main advantage. More recently, devices that combine the 1440-nm with the 1320-nm,23 whose indications are similar to the 1550- and 1540-nm lasers, have been used.

Disadvantages/limitations: Since approximately 15 to 20% of the skin is treated in each session, 4 to 5 procedures are necessary to achieve the desired objective. They are expensive, and some devices have consumable components. For patients with melasma or increased tendency for hyperpigmentation, the procedure should not be performed during summer months with extreme ultraviolet indexes. Although rare, hyperpigmentation is the most important side effect.

Expected results: After the first session, one can see a very subtle improvement. Effects become more visible after the 2nd and 3rd sessions. Changes in skin color and texture, and total or partial reduction of more superficial rhytids are seen. Pigments of melanin show the same evolution.

It can also be used in patients with severe photoaging who are not willing to undergo ablative techniques; however, in this case, the results are subtle.

Ablative Fractional CO₂
As discussed previously, facial rejuvenescence through ablative skin resurfacing with CO₂ is extremely effective.2 However, this procedure is usually very painful, requires a long period of PO intensive care, and the individual cannot engage in his/her personal activities. It also has a considerable percentage of side effects, such as: infections, long-term pigmentation changes, erythema, and scars.⁵

Fractional ablative laser was introduced in 2006 aiming at obtaining a technique as effective as CO₂ ablative lasers in wrinkle removal, and as safe as non-ablative fractioned resurfacing.¹² Besides, light fractioning allows achieving deeper planes more safely (Figure 2D), since part of the stem cells are preserved.

Best indications: Facial aging in need of collagen contraction, pigmented lesions, and actinic keratoses.²⁴

Technical advantages: Results are visible after a single session. Most modern devices have mechanisms to adjust the energy level, column concentration, speed, and size and format of the area treated with the laser beam.

Disadvantages and limitations: A relatively aggressive technique, with a moderate risk of side effects.⁹

Step-by-step technique
1 month before: The conduct is similar to CO₂ and Erbium:YAG ablative lasers.

The day before: The use of a systemic antiviral agent is mandatory in the presence of a history of facial herpes simplex.

Procedure: This is a moderately painful procedure; topical anesthesia should be initiated 1 hour before treatment, along with oral analgesics. Smoke aspirator should be used during the procedure and cold air cooling between the discharges relieves the burning sensation.

After the procedure: The conduct is similar to that of the CO₂ laser but one should notice that, with fractional lasers, pain and inflammation are less severe.

Expected results: Highly satisfactory, but this is a moderately invasive procedure and the patient cannot socialize for 4 to 7 days. Results are inferior to those obtained with non-fractional ablation, especially regarding the depth of the wrinkles, and the procedure should be repeated once or twice, until the expected results are achieved.

Fractional Erbium
The 2940-nm Erbium:YAG laser has the advantages and disadvantages mentioned before. With light fractionation and the change in the duration of the pulse, it was possible to increase its penetration.

More modern equipment have double pulse duration: short, for more superficial ablative resurfacing, and longer duration, for greater coagulation and deeper targets; it is also possible to use both pulses simultaneously. With those modifications, ablation can reach 1 mm.¹⁰

Best indications: Moderate facial aging in patients who cannot spare the time for recovery.

Technical advantages: Results are visible after a single session, with low risk of side effects.
It is associated with less pain than CO₂ lasers. More modern devices have mechanisms to adjust the energy, concentration of ablation columns, variable pulse duration, and size of the area treated per each laser beam.

Disadvantages and limitations: It is necessary to repeat the treatment.

Step-by-step technique

1 month before: The conduct is similar to ablative CO₂ and Erbium:YAG lasers.

The day before the procedure: The use of a systemic antiviral agent is mandatory in case of a history of facial herpes simplex.

Procedure: Topical anesthetic 1 hour before the procedure and smoke aspirator.

After the procedure: The conduct is similar to that of fractional CO₂ laser.

Expected results: Satisfactory, but complimentary sessions are necessary.

CONCLUSION

Rejuvenation treatments evolved considerably in the last two decades, pioneering the use of more aggressive lasers for ablative resurfacing with CO₂ and Er:YAG lasers. With the need for less aggressive treatments, we went to the generation of non-ablative lasers and, more recently, fractional laser was another huge development in rejuvenation techniques.

However, evolution continues and the ideal technology should eliminate blemishes, blood vessels, rhytides, and flaccidity in only one session, without pain and the risk of side effects, and with a low cost, which does not exist yet.

In table 1 we find the main laser and intensed pulsed light equipments on facial rejuvenescence.

References

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