Healing Process of Skin after CO2 Laser Ablation at Low Irradiance: A Comparison of Continuous-Wave and Pulsed Mode

Tissue Responses and Wound Healing following Laser Scleral Microporation for Presbyopia Therapy

Purpose

To investigate the postoperative inflammatory and wound-healing responses after laser scleral microporation for presbyopia.

Methods

Thirty porcine eyes were used for the optimization of laser intensities first. Six monkeys (12 eyes) received scleral microporation with an erbium yttrium aluminum garnet (Er:YAG) laser, and half of the eyes received concurrent subconjunctival collagen gel to modulate wound-healing response. The intraocular pressure (IOP) and the laser ablation depth were evaluated. The animals were euthanized at 1, 6, and 9 months postoperatively. The limbal areas and scleras were harvested for histologic analysis and immunofluorescence of markers for inflammation (CD11b and CD45), wound healing (CD90, tenascin-C, fibronectin, and HSP47), wound contraction (α-smooth muscle actin [α-SMA]), vascular response (CD31), nerve injury (GAP43), and limbal stem cells (P63 and telomerase).

Results

In the nonhuman primate study, there was a significant reduction in IOP after the procedure. Overall, the ablation depth was 76.6% to 81.2% at 1 month and slightly decreased to 71.5% to 72.7% at 9 months. Coagulative necrosis around the micropores, as well as expression of CD11b, CD45, tenascin, fibronectin, HSP47, and GAP43, was distinct at 1 month but subsided with time. Collagen gel treatment significantly suppressed the upregulation of CD11b, CD45, fibronectin, and tenascin-C. The expression of CD90, α-SMA, and CD31 was minimal in all eyes.

Conclusions

The study demonstrated the course of inflammatory and wound-healing responses following laser scleral microporation. The tissue responses were small and self-limited, resolved with time, and were suppressed by concurrent collagen treatment. It provides a useful understanding of this new procedure.

Translational Relevance

The results would be helpful in the laser parameter modification to improve the long-term treatment stability.

Different laser wavelengths comparison in the second-stage implant surgery: an ex vivo study

The implant surgery consists of two distinct techniques, the transmucosal, also known as "one-stage" and the "two-stage" technique. Lasers represent a possible aid in implant dentistry, especially in the two-stage technique and its main characteristics are represented by a decreased trauma to bone and soft tissues, a reduction of pain as well as a reduction of the risk of postoperative infections. The aim of this study was to analyze in an animal model the thermal elevation induced by four different laser wavelengths (diode, Nd:YAG, Er:YAG, KTP) during the implant uncovering. Four pig jaws were used to carry out this study. Five implants were placed in each anatomical specimen for a total of 20 fixtures. Four wavelengths (532, 810, 1,064 and 2,940 nm) were used to uncover the implants. Two thermocouples were used to measure temperature changes during laser irradiation at bone level, peri-implant tissues and on the fixture surface The thermocouples were connected with two probes of 1.5 mm in diameter, in order to simultaneously recording two temperature variations. Surface temperature was also checked during all procedures with a thermal camera (Thermovision A 800, Flyr Systems, Stockolm, Sweden) connected to a PC. The mean temperatures of each specimen (five fixtures) were calculated (TM1, mean temperature at the beginning; TM2, mean peak temperature). Furthermore, a record of the temperature at 1 min after the end of the surgical procedure was taken (mean: TM3). All the recorded values were statistically evaluated by one-way analysis of variance (ANOVA). The thermocouples recorded a lower increase in temperature for Er:YAG and KTP laser; Nd:YAG and diode laser produced similar increases characterized by higher values. The thermo-camera pointed out the lower increase for Er:YAG and higher for diode laser. KTP laser resulted faster in uncovering implants and diode laser was the one that needed more time. This ex vivo study showed that laser utilization with the recommended parameters gives no risks of dangerous thermal elevation to the tissues and implants.

Laser-assisted surgery with different wavelengths: a preliminary ex vivo study on thermal increase and histological evaluation

Since the introduction of laser in clinical practice, different wavelengths have been used for oral surgery on the basis of the different characteristics and affinities of each one. The aim of this study was a comparison of different laser wavelengths in relation to both thermal increase and "histological quality" in a model of soft tissue surgery procedures. Thermal evaluation was realized, during laser-assisted surgery excision performed on a bovine tongue, by a thermal camera device to evaluate thermal increase on the surface of the sample and with four thermocouples to evaluate thermal increase on the depth of the specimen; temperature was recorded before starting surgical procedure and at the peak of every excision. The quality of excision, in terms of tissue damage and regularity, was realized by two blind examiners on the basis of established criteria. The highest superficial thermal increase was recorded for Superpulse 5-W CO2 laser, the lowest one for Er:YAG laser. The highest in depth thermal increase was recorded for 5 W Diode laser, the lowest one for Er:YAG laser. The best quality of incision was obtained with a 3-W CO2 laser and 3-W diode laser; epithelial, stromal, and vascular damages were evaluated with different degrees for all the used wavelengths with the best result, in terms of "tissue respect," for Er:YAG laser. In all the surgical procedures performed, thermal increase was evaluated until the end of the procedure; at remaining tissue level, thermal decrease was evaluable in the few seconds after surgery. The Er:YAG laser was the device with a lower influence on thermal increase; CO2 and diode lasers revealed a good histological quality. Further studies may be necessary to test the reliability of laser devices for the excision of all the types of specimens needing histological evaluation and diagnosis.

Effect of CO₂ laser irradiation on wound healing of exposed rat pulp

This study examined the effects of direct pulp capping treatment using super-pulsed CO₂ laser preirradiation on the wound healing process of exposed rat pulp on days 1, 3, 7, 14, and 28 postoperatively. Group 1 was irradiated with a CO₂ laser and directly capped with a self-etching adhesive system. The laser was operated in super-pulse mode (pulse duration, 200 μs; interval, 5800 μs; 0.003 J/pulse). The irradiation conditions were a power output of 0.5 W, an irradiation time of 3 s, and repeat mode (10 ms of irradiation at 10-ms intervals for a total beam exposure time of 1.5 s), defocused beam diameter of 0.74 mm (approximately 20 mm from the exposed pulp surface), energy density of 0.698 J/cm² per pulse, total applied energy of 0.75 J, and an activated air-cooling system. Group 2 was capped with the self-etching adhesive system. Group 3 was capped with commercially available calcium hydroxide, and the self-etching adhesive system was applied to the cavity. The following parameters were evaluated: pulp tissue disorganization, inflammatory cell infiltration, reparative dentin formation, and bacterial penetration. The results were statistically analyzed using the Kruskal-Wallis test for differences among the groups at each observation period (P < 0.05). There were no significant differences among the experimental groups in any parameters at any postoperative period (P > 0.05). CO₂ laser irradiation was effective in arresting hemorrhaging but showed a tendency to delay reparative dentin formation compared with the application of calcium hydroxide.

Removal of oral lichen planus by CO2 laser

The aim of this case report is to present a histologically diagnosed oral lichen planus excised by the CO2 laser. Oral lichen planus is a chronic inflammatory mucocutaneous disease of unknown etiology. Different treatments have been used to manage this condition. A 46 year-old female was referred to the Laser Clinic of the Dental School of the Federal University of Bahia to excise a lesion characterized by white patches on the oral mucosa, which was causing pain and burning sensation and had not respond to treatment with triamcinolone and corticosteroids for 3 months. CO2 laser was used to remove the lesion and the conclusive histopathological diagnosis was oral lichen planus. The patient was followed up over 1year with no signs of lesion recurrence. The use of the CO2 laser was found to be useful and effective to treat lichen planus.

Surgical treatment of oral lymphangiomas with CO2 laser: report of two uncommon cases

This paper reports the treatment of oral lymphangiomas with carbon dioxide CO2 Laser. Lymphangiomas are rare congenital lymphatic malformations. These lesions are most frequently diagnosed during childhood, are most commonly located in the head and neck region, and are extremely rare in the oral cavity. Oral lymphangiomas are of complex treatment due to the difficulty in performing a complete excision. CO2 laser is the most often used laser in the oral cavity due to its affinity with water and high absorption by the oral mucosa. Several benefits of the use of CO2 laser have been reported for surgical oral procedures. The cases reported herein were biopsy-proven lymphangiomas of the oral cavity. The surgical procedures were carried out under local anesthesia and a focused CO2 laser beam (l10.600 nm, f ~2 mm, CW/RSP) was used. At the end of the surgery, the laser beam was used on a defocused mode to promote better hemostasis. Neither sutures nor dressings were used after surgery. No medication and only mouthwashes were prescribed to all patients on the postoperative period. There were no postsurgical complaints from the patients and no relapses of the conditions were observed after follow-up periods of 12 and 18 months. The use of CO2 laser was practical, easy to carry out and effective on the treatment of oral lymphangiomas, with no lesion recurrence.

Remodeling of the rat gingiva induced by CO2 laser coagulation mode

BACKGROUND AND OBJECTIVES

This study was conducted to clarify the morphologic characteristics and subsequent repair process of coagulation necrosis produced by pulsed CO(2) laser irradiation with relatively low fluence, and thereby to evaluate the clinical efficacy of this irradiation mode.

STUDY DESIGN/MATERIALS AND METHODS

Wounding of rat gingiva to produce coagulation necrosis was done with a CO(2) laser with a fluence of 326 J/cm(2). The structural characteristics of the wound and subsequent repair process were examined by means of histology, immunohistochemistry, and electron microscopy.

RESULTS

At 6 hours after irradiation, the cells in the laser wound appeared histologically intact but had lost the immunoreactivity to antibodies against Hsp47 and exhibited various ultrastructural signs of cell death. This wound area was lined by Hsp70-positive cells. At 1-day post-irradiation, the uptake of BrdU rapidly increased in the adjacent epithelium and connective tissue. The re-epithelization commenced at 1 day and was completed by 7 days. The necrotic tissue gradually became integrated within the newly formed connective tissue and the original contour of the gingiva was retained during the repair process. The repair process of the laser-induced wound progressed more rapidly than that of a scalpel-made wound.

CONCLUSIONS

The present study suggests that the coagulation necrosis produced by the low fluence pulsed CO(2) laser does not disturb the repair process but promotes its steady progress and subsequent tissue remodeling. This laser mode will pave the way for more conservative and minimally invasive surgery for treating a wide variety of oral soft tissue disorders.

Comparison of carbon dioxide laser and scalpel for breast lumpectomy: a randomized controlled trial

OBJECTIVE

To investigate whether the CO2 laser is superior to conventional surgical techniques for minor breast surgery in a randomized clinical trial.

BACKGROUND DATA

It has been suggested in the literature that application of CO2 laser in breast surgery might be superior to conventional surgery in some aspects.

PATIENTS AND METHODS

Sixty women whose breast masses were suitable for excisional biopsy were randomly allocated to laser and control (conventional surgical technique with scalpel) groups. Perioperative and postoperative variables were recorded and analyzed.

RESULTS

The patients' ages ranged from 16-63 y. There were no significant differences between the two groups in total operative time (17.4 min with laser and 17.5 min with scalpel). There was a significant decrease in the required dose of lidocaine in the laser group (9.3 mL) compared to the scalpel group (12.4 mL; p = 0.01). In addition, hemorrhage was significantly lower in the laser group (6.6 mL) compared to the control group (11.9 mL; p = 0.006). There was no difference in the grade of the scar or postoperative pain between the two groups.

CONCLUSION

Use of the CO2 laser in breast mass biopsy has some advantages, including a lower requirement for local anesthetic and a lower rate of intraoperative bleeding. Furthermore, using the laser does not prolong the operative time.

Use of the CO(2) laser on orthodontic patients suffering from gingival hyperplasia

OBJECTIVE

The present study aimed to assess the effect of the use of the CO(2) laser on the treatment of gingival hyperplasia in orthodontic patients wearing fixed appliances.

BACKGROUND DATA

Gingival hyperplasia is a condition very frequent in patients undergoing fixed orthodontic treatment. Amongst the treatments available for this is the use of surgical lasers.

METHODS

Ten patients entered this study and signed an informed consent. Seventy-five anterior teeth with gingival hyperplasia were selected for laser surgery. Prior to surgery, the length of the crowns were measured using a digital caliper, and depth of the pocket was probed. The hyperplasic gingival was removed with a CO(2) laser under local anesthesia. Immediately after surgery, measurement of the length of the crowns and probing were carried out and were repeated.

RESULTS

The results were statistically analyzed and significant differences were detected regarding the length of the crown (p = 0.000) and depth of the gingival sulcus (p = 0.000).

CONCLUSION

It is concluded that the use of the CO(2) laser was effective in the treatment of gingival hyperplasia.

Mid infrared optical parametric oscillator (OPO) as a viable alternative to tissue ablation with the free electron laser (FEL)

BACKGROUND AND OBJECTIVES

Investigations with a Mark-III free electron laser, tuned to 6.45 microm in wavelength have demonstrated minimal collateral damage and high ablation yield in ocular and neural tissues. While the use of mid-IR light produced by the free electron laser (FEL) has shown much promise for surgical applications, further advances are limited due the high costs of its use. Further investigation and widespread clinical use of six-micron radiation requires the development of an alternative laser source. In this research, we compared a Mark-III FEL and an Er:YAG pumped ZGP-OPO with respect to the effect of pulse duration on ablation efficiency and thermal damage on porcine cornea.

STUDY DESIGN/MATERIALS AND METHODS

A five by seven grid of craters was made about the center of each cornea. Craters were made with a 60-microm spotsize with a 500-microm spacing. Ablation craters were made using 50 pulses per crater at approximately three times the ablation threshold (for water). Histological analysis was used to determine crater depth and thermal damage.

RESULTS

The average zone of thermal damage at 6.1 microm was found to be 4.1 microm for the optical parametric oscillator (OPO) and 5.4 microm for the FEL. At 6.45 microm, the damaged zone was 7.2 microm for the OPO and 7.2 microm for the FEL. At 6.73 microm, the damaged zone was 6.3 microm for the OPO and 7.6 microm+/-0.3 microm for the FEL.

CONCLUSIONS

The OPO caused similar or significantly less thermal damage in porcine cornea when compared with the FEL while generating significantly deeper craters. We determined that the ZGP-OPO has much promise as a bench-top replacement for the FEL for soft tissue ablation.

Fiber-Guided CO2 Laser Surgery in an Animal Model

OBJECTIVE

This study tested a newly developed flexible fiber for CO(2) laser surgery.

BACKGROUND DATA

The lack of a flexible delivery system with the current CO(2) laser has limited its surgical application. We conducted in vitro and in vivo studies by using the skin tissue model of animals to test a new laser fiber system.

METHODS

In an in vitro study, the acute thermal effect of laser surgery using this new fiber was tested and compared on fresh porcine skin at 3.0-5.0-W laser power and at 0.3-0.5-mm spot size. In the in vivo experiments, the healing process of the skin incisions and wounds was followed microscopically in 16 rats, at post-operative days 2, 6, 12, and 21 after the laser surgery with 3.0-W power and 0.5-mm spot size.

RESULTS

The results from the in vitro tissue showed limited thermal damage to neighboring tissue. In the in vivo study, there was rapid postoperative healing.

CONCLUSION

Our findings indicate that this fiber system, at least with the laser parameters used in this study, appears to be an effective and feasible alternative for CO(2) laser surgery. It has great potential for development of office-based surgery under local anesthesia.

Controlling thermal damage of incisions using diamond, copper, and sapphire heat-conducting templates with and without cooling

INTRODUCTION

We investigated the reduction of thermal damage to the surrounding tissue when laser incisions were made with and without using thermal conducting templates at room temperature and cooled to 5 degrees C.

STUDY DESIGN/MATERIALS AND METHODS

We used the Vanderbilt free-electron laser (FEL) at 5.4, 6.1, 6.45, and 7.7 microns. We also used a conventional continuous wave (CW) carbon dioxide laser at 10.6 microns. Incisions were made on 5x10 mm pieces of human breast skin (in vitro) and analyzed with histology. Computer morphometrics were used to measure the amount of thermal damage.

RESULTS

All templates produced a statistically significant reduction in the thermal damage. Additionally, we showed that cooling the templates made a statistically significant greater reduction in the thermal damage. The cooled diamond template reduced the thermal damage from the FEL to 28% of the damage observed without a template. The same cooled template reduced the thermal damage from the CO(2) laser to 56% of the damage observed without a template. Lesser reductions were observed with the copper template and even less with the sapphire template. The sapphire template reduced the thermal damage to 39 and 67% of the damage observed without a template for the FEL and the CO(2) laser, respectively.

CONCLUSION

These results indicate that unwanted lateral thermal damage from laser incisions can be reduced with cooled thermally conductive templates with the best results obtained with the diamond template, which is also the best thermal conductor.