Extracellular matrix in healing CO2 laser incision wound

Comparison of oral mucosal biopsies done using scalpel and diode lasers: A vivo study

Background:

As dental lasers are becoming more popular in the branch of oral medicine for its various advantages and applications, this study was carried out to evaluate better mode of obtaining oral biopsies which is a common and inevitable procedure for providing final diagnosis in majority of conditions.

Methodology:

In this study, a total of 60 patients who required biopsy for final diagnosis of oral mucosal lesions as part of diagnosis in department of Oral Medicine were selected, out of which 30 were subjected to scalpel biopsies and 30 patients were subjected to diode laser biopsies. A 980 nm Zolar plus diode laser was used for the study. Out of 30 patients who were subjected to laser biopsies, 3W continuous mode settings were used for 15 patients and 3W pulsed mode was used for 15 patients. The specimens were sent to Department of Oral Pathology for histopathological evaluation to provide the final diagnosis. The time taken for each patient, volume of local anesthesia, during operative, postoperative pain scale, and co-relation of provisional and final diagnosis was noted for comparison purpose and the pathologist comments, peripheral tissue damage and artifact's for each slide were noted.

Results:

The study results showed the postoperative pain was comparatively less in diodlaser than scalpel, the lasers were patient friendly as the heammorage was negligible when compared to scalpel and suturing was not required. The pulsed mode in diode laser was advantageous over continuous mode when amount of thermal damage and postoperative pain score was compared.

Conclusion:

The results showed that oral biopsies can be made better using diode lasers, by having thorough knowledge on the device.

Diode Laser Ear Piercing: A Novel Technique

Earlobe piercing is a common office room procedure done by a plastic surgeon. Various methods of ear piercing have been described. In this article, we describe a novel method of laser ear piercing using the diode laser. An 18-year-old female patient underwent an ear piercing using a diode laser with a power of 2.0 W in continuous mode after topical local anaesthetic and pre-cooling. The diode laser was fast, safe, easy to use and highly effective way of ear piercing. The advantages we noticed while using the diode laser over conventional methods were more precision, minimal trauma with less chances of hypertrophy and keloids, no bleeding with coagulation effect of laser, less time taken compared to conventional method and less chance of infection due to thermal heat effect of laser.

Excision of Mucocele Using Diode Laser in Lower Lip

Mucoceles are nonneoplastic cystic lesions of major and minor salivary glands which result from the accumulation of mucus. These lesions are most commonly seen in children. Though usually these lesions can be treated by local surgical excision, in our case, to avoid intraoperative surgical complications like bleeding and edema and to enable better healing, excision was done using a diode laser in the wavelength of 940 nm.

Periodontal and peri-implant wound healing following laser therapy

Laser irradiation has numerous favorable characteristics, such as ablation or vaporization, hemostasis, biostimulation (photobiomodulation) and microbial inhibition and destruction, which induce various beneficial therapeutic effects and biological responses. Therefore, the use of lasers is considered effective and suitable for treating a variety of inflammatory and infectious oral conditions. The CO2 , neodymium-doped yttrium-aluminium-garnet (Nd:YAG) and diode lasers have mainly been used for periodontal soft-tissue management. With development of the erbium-doped yttrium-aluminium-garnet (Er:YAG) and erbium, chromium-doped yttrium-scandium-gallium-garnet (Er,Cr:YSGG) lasers, which can be applied not only on soft tissues but also on dental hard tissues, the application of lasers dramatically expanded from periodontal soft-tissue management to hard-tissue treatment. Currently, various periodontal tissues (such as gingiva, tooth roots and bone tissue), as well as titanium implant surfaces, can be treated with lasers, and a variety of dental laser systems are being employed for the management of periodontal and peri-implant diseases. In periodontics, mechanical therapy has conventionally been the mainstream of treatment; however, complete bacterial eradication and/or optimal wound healing may not be necessarily achieved with conventional mechanical therapy alone. Consequently, in addition to chemotherapy consisting of antibiotics and anti-inflammatory agents, phototherapy using lasers and light-emitting diodes has been gradually integrated with mechanical therapy to enhance subsequent wound healing by achieving thorough debridement, decontamination and tissue stimulation. With increasing evidence of benefits, therapies with low- and high-level lasers play an important role in wound healing/tissue regeneration in the treatment of periodontal and peri-implant diseases. This article discusses the outcomes of laser therapy in soft-tissue management, periodontal nonsurgical and surgical treatment, osseous surgery and peri-implant treatment, focusing on postoperative wound healing of periodontal and peri-implant tissues, based on scientific evidence from currently available basic and clinical studies, as well as on case reports.

Technology of Lasers and Their Applications in Oral Surgery: Literature Review

The word “Laser” is an acronym for “Light Amplification by Stimulated Emission of Radiation”. Recent advances in laser technology have brought a kind of revolution in dentistry. The purpose of this article is to provide an overview of clinical application of lasers in oral medicine and especially in oral surgery, including their advantages, disadvantages and safety.

CO(2) Laser Surgery and Prosthetic Management for the Treatment of Epulis Fissuratum

The aim of this study was to present a case report of the surgical removal of hyperplasia in the oral cavity, using carbon dioxide (CO(2)) laser radiation and rehabilitation with a complete denture. Epulis fissuratum occurs in complete denture patients, because a constant irritative action induces the mucosa to grow under poorly fitting dentures. These lesions must be removed, and to avoid a relapse, new complete dentures should be made to maintain healthy surgical tissues. The clinical sequence presented in this case shows a completely edentulous patient with epulis fissuratum on the lower alveolar ridge extending to the vestibular sulcus of the anterior region of mandible. Immediate complete dentures were made prior to the lesion removal with CO(2) laser radiation, providing satisfactory results in oral function and tissue health.

Different air-water spray regulations affect the healing of Er,Cr:YSGG laser incisions

Surgeries performed with high-intensity laser devices may be improved with accurate protocols, including the air-water spray regulation. Thus, this study sought to investigate the healing process of wounds made on the dorsum of rat tongues using an Er,Cr:YSGG laser device with different air-water spray regulations. The incisions were made on the dorsum of Wistar rat tongues using an Er,Cr:YSGG laser with three different air-water spray regulations (100/0%, 50/50%, 11/7%). Scalpel incisions functioned as controls. The sacrifices occurred between 0 and 14 days after surgery. Morphological, histological, and immunohistochemical (fibronectin and type III collagen) analysis of the wounds were performed. The air-water spray regulation influenced wound healing and the inflammatory response, especially in the earlier stages. Incisions performed using the 100/0% air/water spray regulation had the worst results, expressing a greater amount of fibronectin and type III collagen. The 50/50% air/water spray regulation brought in a non-clear surgical field and poor laser interaction with the tissue. The 11/7% air/water spray regulation showed the best clinical results and less pronounced histological events. According to the results encountered, the air-water spray should be regulated to improve surgery.

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.

Laser surgery as a treatment for oral leukoplakia

Various treatment procedures for oral leukoplakia have been reported. However, after some treatments, oral leukoplakia show recurrence and/or malignant transformation, even following complete resection. Furthermore, patients with oral leukoplakia may develop new lesions in other oral cavity locations. Laser surgery for oral mucosal lesions has been reported to have many advantages, and it is widely used in the treatment of oral leukoplakia. In previous studies, recurrence and malignant transformation from the lesion have occasionally been observed following laser surgery. We reviewed the records of oral leukoplakia patients treated with laser surgery to assess its clinical usefulness. It has been reported that the rate of recurrence was 7.7-38.1%, while malignant transformation was 2.6-9% for oral leukoplakia treated with laser surgery. In the present study, there was 29.3% recurrence and 1.2% malignant transformation after laser surgery. This was similar to previous findings. This suggests that non-homogeneous leukoplakia on nonkeratinized epithelia, i.e. the tongue mucosa has a high risk for malignant transformation, so lesions should be excised after detecting abnormal epithelia using vital tissue staining. The wound healing process after laser surgery was satisfactory and no significant complications were observed. Management of oral leukoplakia prevents not only recurrence and malignant transformation, but also postoperative dysfunction: laser surgery is an excellent procedure that is able to overcome these problems.

Clinical comparison between conventional suture and vaporization with carbon dioxide laser in rat's skin

OBJECTIVE

This study compares wound healing efficiency on a rat's skin when the incision was closed with a conventional suture versus vaporized with a CO2 laser.

MATERIALS AND METHODS

In this study, 24 rats were used, and two longitudinal incisions were made with a conventional scalpel in the dorsum of each rat. The left incision was sutured with nylon thread, and the right incision was closed by vaporization with a defocused CO2 laser in continuous mode with an 8-watt power density. Clinical photographs were taken immediately after the procedure, 24 h later, and after 3, 7, 14, and 21 days, documenting the healing of the incision.

RESULTS

The results showed that there was an initial delay in wound repair in the vaporized incision as compared to the scalpel incision, but after 21 days, both incisions showed the same clinical characteristics. However, the vaporized incision showed no trauma of the tissue, as opposed to the sutured incision, and no hemorrhagic complications.

CONCLUSION

These results suggest that the CO2 laser can eventually replace the use of sutures.

Myofibroblasts in healing laser excision wounds

BACKGROUND AND OBJECTIVE

The lack of myofibroblasts, cells responsible for wound contraction, has been suggested to be the underlying factor to the clinically observed minimal contraction in CO2 laser wounds. However, the histologic background to this phenomenon in laser excisions has not been thoroughly clarified. Therefore, we analyzed the expression of myofibroblasts in healing laser excisions and control excisions made by scalpel.

STUDY DESIGN/MATERIALS AND METHODS

CO2 laser (continuous wave, 5 W) or scalpel excision wounds were created in the dorsal tongue mucosa of 144 rats. Sixteen additional rats were kept as untreated controls. Specimens from the tongues were cut at 16 different healing time points and fixed in 10% formalin. Immunohistochemical stainings with monoclonal antibodies to vimentin and to alpha-smooth muscle actin were done to determine microscopically the contractile type of myofibroblasts.

RESULTS

The maximum amount of myofibroblasts was almost three times higher in scalpel than in laser excisions. The peak value was reached at 4 days in laser and at 3 days in scalpel wounds. The increase reverted to normal levels at 14 days in laser and at 6 days in scalpel wounds, respectively.

CONCLUSION

Myofibroblasts appeared and disappeared slower in laser wounds. There were clearly fewer myofibroblasts in CO2 laser than in corresponding scalpel excisions known to heal by contraction. The lack of contractile myofibroblasts, therefore, is suggested as the reason for the minimal degree of contraction in CO2 laser excision wounds.

Er:YAG laser skin resurfacing using repetitive long-pulse exposure and cryogen spray cooling: I. Histological study

BACKGROUND AND OBJECTIVE

To evaluate histologically the characteristics of repetitive Er:YAG laser exposure of skin in combination with cryogen spray cooling (CSC), and its potential as a method of laser skin resurfacing.

STUDY DESIGN/MATERIALS AND METHODS

Rat skin was irradiated in vivo with sequences of 10 Er:YAG laser pulses (repetition rate 20 Hz, pulse duration 150 or 550 micros, single-pulse fluence 1.3-5.2 J/cm(2)). In some examples, CSC was applied to reduce epidermal injury. Histologic evaluation was performed 1 hour, 1 day, 5 days, and 4 weeks post-irradiation.

RESULTS

A sequence of ten 550-micros pulses with fluences around 2 J/cm(2) resulted in acute dermal collagen coagulation to a depth of approximately 250 microm, without complete epidermal ablation. CSC improved epidermal preservation, but also diminished the coagulation depth. Four weeks after irradiation, neo-collagen formation was observed to depths in excess of 100 microm.

CONCLUSIONS

Dermal collagen coagulation and neo-collagen formation to depths similar to those observed after CO(2) laser resurfacing can be achieved without complete ablation of the epidermis by rapidly stacking long Er:YAG laser pulses. Application of CSC does not offer significant epidermal protection for a given dermal coagulation depth.

Healing of laser incisions in rat dermis: comparisons of the carbon dioxide laser under manual and computer control and the scalpel

BACKGROUND AND OBJECTIVE

The Computer-Assisted Surgical Techniques (CAST) program was researched to decrease lateral tissue damage and improve wound healing subsequent to laser incision. CAST differs from the traditional laser because it makes the incision in a discontinuous manner, allowing tissue to cool during the incision process.

STUDY DESIGN/MATERIAL AND METHODS

The transient temperature changes in the tissue adjacent to the incision were measured with a thermocouple in a rat model. The subsequent wound healing was studied with histology and tensiometry.

RESULTS

The thermal measurements demonstrated that all CAST settings were cooler than the continuous mode of laser incision. However, histology and tensiometric studies showed mixed results.

CONCLUSION

This research demonstrates that CAST can be used in future surgical applications with no delay in wound healing as compared to the manually controlled laser. However, this study also finds no decrease in the wound healing time when using the CAST program.

A preliminary study of healing of superpulsed carbon dioxide laser incisions in the hard palate of monkeys

BACKGROUND AND OBJECTIVE

Prior studies of laser wound healing using different animal models have shown a delayed tissue response after carbon dioxide (CO2) laser application. This article reports on the preliminary findings of healing of superpulsed CO2 laser and scalpel incisions in the hard palate of monkeys.

STUDY DESIGN/MATERIALS AND METHODS

Twelve parallel incisions using a superpulsed, continuous wave CO2 laser and a scalpel were performed in the hard palate of each of two adult monkeys at 3, 7, and 14 days time schedules. Power levels of 2.0, 4.0, and 6.0 Watts were used for the laser incisions. Wounds were harvested, fixed in 10% formalsaline for at least 48 hours and processed routinely. Each specimen was embedded in paraffin wax at 90 degrees to the surface epithelium and 5 microm thick sections prepared for staining with haematoxylin and eosin, Periodic acid Schiff and Masson-trichrome at a step-serial interval of 100 microm. Sections were evaluated independently.

RESULTS

According to the clinical findings we showed a wound closure in all of the wounds (laser and scalpel incisions) at 3, 7, and 14 days of healing. Histologically, we showed that laser incisions at three and seven days demonstrated an increased, power setting-dependent tissue necrosis and marked inflammatory response with minimal organization compared to scalpel incisions. At 14 days both types of incisions exhibited complete wound healing of the epithelium and connective tissue.

DISCUSSION AND CONCLUSIONS

According to these preliminary results, superpulsed CO2 laser tends to produce more pronounced changes (due to tissue thermal damage) with corresponding greater inflammatory reaction and delay in tissue organization only initially.

The versatile contact Nd:YAG laser in head and neck surgery: an in vivo and clinical analysis

OBJECTIVE

Lasers have been used in otolaryngology as a surgical instrument for more than 25 years, and the CO2 laser has emerged as the most widely employed surgical laser in use today. However, recent technological advances have made the Nd:YAG laser a challenger as an effective photothermal surgical tool.

STUDY DESIGN AND METHODS

This is a two-part study. Tissue injury and healing profiles after application of both the CO2 and Nd:YAG lasers are compared using an in vivo rat tongue model. A prospective clinical review based on the experience of 327 operative cases spanning a 7-year interval using the Nd:YAG laser, highlighting its various applications and associated complications, is detailed.

RESULTS

Comparable tissue and healing effects were noted with both lasers in the in vivo rat tongue model with no statistical differences. The clinical application of the laser showed wide versatility in the head and neck with a complication rate of 3%.

CONCLUSION

The Nd:YAG laser has proved equivalent in tissue damage and healing to the CO2 laser. The Nd:YAG laser has proved itself to be an excellent and perhaps superior laser for use in head and neck surgery.

Comparison of carbon dioxide laser, erbium:YAG laser, dermabrasion, and dermatome: a study of thermal damage, wound contraction, and wound healing in a live pig model: implications for skin resurfacing

BACKGROUND

Advances in laser technology allow for precise tissue removal and minimal thermal damage. However, mechanisms for cosmetic improvement have not been determined. Investigators have suggested that ablation, collagen shrinkage, and new collagen deposition all contribute to the clinical outcome.

OBJECTIVE

In a live farm pig, we examined gross and microscopic effects of thermal and mechanical ablation devices to characterize immediate and long-term mechanisms in skin rejuvenation.

METHODS

Two CO(2) lasers, an erbium:YAG laser, a dermabrader, and a dermatome were used to treat flank skin in a farm pig. There were 14 different treatment groups based on device type and working parameters. One to five sites were treated for each group. Wound surface areas were measured before treatment, immediately after treatment, and 7, 17, 23, 30, and 60 days thereafter. Biopsies were performed immediately after irradiation and 2, 7, 17, and 60 days after treatment.

RESULTS

For the CO(2) laser-induced wounds, surface area measurements showed that immediate and final wound contraction tended to increase with initial residual thermal damage (RTD) for a range of values, above which immediate contraction remained relatively constant. Although there was no immediate wound contraction with mechanical ablation devices, long-term wound contraction in the dermatome and dermabrasion sites increased with depth of ablation. The erbium:YAG laser sites healed in a manner similar to that of mechanically induced wounds. Wound contraction profiles over time were dependent on depth of RTD and depth of ablation. Sixty days postoperatively, histologic examination showed varying degrees of fibroplasia. Overall, there was greater compaction and horizontal orientation of collagen fibers in those wounds with more than 70 microm of dermal RTD. Grossly, all wounds were similar after 60 days, with the exception of the deep dermabrasion sites, at which clinical scarring was observed.

CONCLUSION

Our results show that CO(2) laser resurfacing produces short- and long-term wound contraction that is greater than that induced by purely ablative methods for the same total depth of injury. The erbium laser produced wound contraction profiles similar to those produced by mechanical wounding. The data suggest that initial collagen contraction and thermal damage modulate wound healing.

Histologic study of oral mucosa wound healing: a comparison of a 6.0- to 6.8-micrometer pulsed laser and a carbon dioxide laser

Incisional wound healing in the canine oral mucosa was histologically monitored at 3, 7, and 14 days after incision. Healing was compared from a scalpel, a carbon dioxide (CO2) laser at 10.6 microm, and the Vanderbilt free-electron laser tuned to 6.0, 6.45, and 6.8 microm. A significant delay in wound healing was observed when incisions were made with the CO2 laser, probably attributable to the excess thermal damage caused by the continuous-wave laser beam. When using the short pulsed, free-electron laser, a much smaller delay comparable to the scalpel wound healing was observed. This smaller delay tended to decrease with increasing tissue absorption. The results emphasize the greater importance of laser pulse duration rather than wavelength in relation to the subsequent wound healing.

Longterm comparison of soft palate scars after UPPP made by CO(2), contact Nd-YAG or combined CO (2) and Nd-YAG laser beams

C0(2) laser, contact Nd-YAG laser and Combolaser (combined CO(2) and Nd-YAG laser beam) vary distinctively in the way they interact with target tissue. To study the quality of mature scars produced by these lasers, the ultrastructure and amount of collagen in soft palate scars after 60 uvulopalatopharyngoplasty (UPPP) operations were analysed. The CO(2) laser was used in 19, contact Nd-YAG in 21 and Combolaser in 20 operations. At a clinical follow-up examination carried out, on average, 51 (range 34-74) months postoperatively, a specimen was obtained from the soft palate scar for collagen analysis. Postoperative complaints of the patients were acknowledged. No differences between the laser groups were observed concerning the gross appearance of the scars or the amount and ultrastructure of collagen. Neither the frequency nor the quality of post-operative symptoms showed any differences between the lasers. Although the initial tissue effects are different, long-term remodelling produces nearly identical soft palate scars after the use of CO(2), contact Nd-YAG and Combolaser beams.

Wound healing and soft tissue effects of CO2, contact Nd: YAG and combined CO2-Nd: YAG laser beams on rabbit trachea

Rabbit trachea was used as an experimental model to study tissue effects and healing of full-thickness tracheal lesions produced by CO2, contact Nd: YAG and combined, coaxial CO2-Nd: YAG (Combo) laser beams. Two power settings (10 W and 16 W) were used with CO2 and contact Nd: YAG lasers. Three different CO2/Nd:YAG power ratios (1:1, 1:2 and 1:4) and power settings (12 W 15 W and 16 W) were used with the Combolaser. Histological specimens for light and transmission electron microscopy were prepared immediately and 1, 3, 5, 7, 14 and 21 days postoperatively. The wound with the most precise and fastest healing was produced by contact Nd: YAG laser. CO2 laser produced a moderate amount of charring and the largest amount of coagulated tissue with a slightly prolonged healing period. In the acute phase, tissue defects produced by the Combolaser with power ratios 1:1 and 1:2 resembled the CO2 laser lesions but with slightly less charring. The power ratio 1:4 diminished the cutting properties of the beam considerably. During the healing period the Combolaser produced the most intensive inflammation and granulation tissue formation resulting in delayed regeneration of the lesion. In transmission electron micrographs the most severe damage to chondrocytes was seen after using the Combolaser. These findings indicate that the Combolaser produces deeper tissue damage than CO2 or contact Nd:YAG laser. However, the Combolaser appears to be suitable for tracheobronchial operations, owing to its good simultaneous cutting and haemostatic properties.

A Comparison of Mucosal Incisions Made by Scalpel, CO2 Laser, Electrocautery, and Constant-Voltage Electrocautery

This study compares the histologic effects of scalpel, CO2 laser, electrosurgery, and constant-voltage electrosurgery incisions on the mucosal tissue of swine. Tissue studies comparing the CO2 laser with the scalpel and electrosurgery have been done. However, a gross and histologic comparison of the effects of all three techniques on oral mucosal tissue has not been reported. A swine model of both tongue and buccal mucosa was used to compare the scalpel, CO2 laser, electrosurgery unit, and constant-voltage electrosurgery unit in an effort to assess their value in oral surgery. Tissue samples of tongue and buccal mucosal incisions and excisions were histologically examined at 0, 3, 7, 14, 28, and 42 days after surgery to evaluate tissue damage and wound healing properties induced by the four instruments. The instruments were also evaluated for performance and ease of use. On subjective evaluation of ease of use, constant-voltage electrosurgery scored highest ( p < 0.05) on a scale of 0 to 4, followed by the CO2 laser. Speed of incisions and excisions, measured in seconds, was fastest with the scalpel ( p < 0.001) and electrosurgery unit ( p < 0.05). The amount of bleeding, as evaluated on a scale of 0 to 4, was least for electrosurgery ( p < 0.001) and CO2 laser ( p < 0.001). Histologic damage, as expected, was least with a scalpel. The extent of epithelial damage lateral to the wound edge and the extent of collagen denaturation were the lowest with the scalpel ( p < 0.001), followed by constant-voltage electrosurgery. The wounds created by all four instruments displayed intact epithelium by 4 weeks, and granulation tissue peaked at 4 weeks with all methods except constant-voltage electrosurgery, where granulation tissue was still prevalent at week 6. Constant-voltage electrosurgery and the CO2 laser provided the best combination of ease of use, hemostasis, and lack of tissue injury among the instruments compared. Incisions and excisions made with constant-voltage electrosurgery required less time than those made with the laser, but constant-voltage electrosurgery wounds also had significantly more granulation tissue in later weeks of the study, suggesting that wound healing may be delayed.

Histological changes in elastic components of soft palate scars after CO2 and contact Nd:YAG laser incisions in the dog as an experimental model

Soft palate stiffening operations--often with CO2 or contact Nd:YAG lasers--have been used recently to treat patients with pronounced snoring. Differences in soft palate scars formed after CO2 and contact Nd:YAG laser incisions were studied in an animal model to determine which of these lasers produces a more rigid scar and consequently might be more effective for a soft palate stiffening operation. Six mongrel dogs were placed in each laser group, after which either the CO2 or Nd:YAG laser was used to make a 1.5-cm-long soft palate incision. The scars produced were then excised and studied histologically 4 weeks postoperatively. Special attention was paid to collagen density and elastin fibers in the scar tissue. After contact Nd:YAG laser incisions scar tissue was found to contain densely aligned collagen fibers and practically no elastin fibers. CO2 laser incisions produced significantly different scars: irregularly arranged collagen fibers with some elastin fibers also inside the scar tissue. Differences in the shapes of the scars and wound contractions were also found that were only seen after contact laser incisions. These findings suggest that the contact Nd:YAG laser might be more effective for soft palate stiffening operations.

Thermal injury patterns and tensile strength of canine oral mucosa after carbon dioxide laser incisions

The amount of collateral damage in laser surgery is affected by the precision of the beam delivery. To test a new control system, the authors of this study produced surgical incisions in the canine oral mucosa and then documented histologic and tensile strength changes during the wound healing process. The incisions were made by three different methods: scalpel, manually controlled carbon dioxide (CO2) laser, and computer-controlled C02 laser. Both types of laser incisions took longer to heal than the scalpel incisions. The laser incisions were accompanied by a zone of thermal damage lateral to the incision. With the computer-controlled laser incision, the area of thermal damage was reduced, the laser-induced delay in wound healing was less, and tensile strength was relatively greater. The data indicate that surgical performance is improved by critical beam control.

High magnification in situ viewing of wound healing in oral mucosa

Microscope endoscopy is a technique which allows high resolution, non-invasive examination of soft tissues. This study employed microscope endoscopy to examine the process of healing following exposure of the oral mucosa to carbon dioxide laser radiation. On the wound boundaries, cellular debris and the laser-induced char layer were shed as epithelial migration occurred. Wounds healed by secondary intention, with complete epithelial closure by 72 hours. A marked vascular response was evident from 6 to 48 hours following wounding, a time period coincident with the known pattern of blood vessel activation and infiltration of the wound site by leukocytes. The use of microscope endoscopy as an adjunct to biopsy and other invasive diagnostic methods in the assessment and follow-up of soft tissue pathology may have value in clinical practice.

A comparative histological study of wound healing following Nd:YAG laser with different energy parameters and conventional surgical incision in rat skin

Wound healing following the use of Nd:YAG laser with different frequencies and energy parameters (20 pps and 1.75 W/30 pps and 3.0 W), and the conventional scalpel incision were studied over a period of 4, 7, 14, 21, and 28 days in the rat skin. The low-energy laser wounds could not be significantly differentiated from the conventional incisions although less damage and inflammatory reaction, increased matrix production, and only a little wound contraction could be demonstrated. In the high-energy lased tissues extensive damage and an increased inflammatory reaction were present. The low-energy Nd:YAG and scalpel incisions established a normal wound healing without scar tissue formation compared to the high-energy Nd:YAG, where the necrosis was higher.

Lasers in dentistry

Since the development of the ruby laser by Maiman in 1960, there has been great interest among dental practitioners, scientists, and patients to use this tool to make dental treatment more pleasant. Oral soft tissue uses are becoming more common in dental offices. The possible multiple uses of lasers in dentistry, beyond soft tissue surgery and dental composite curing, unfortunately, have not yet been realized clinically. These include replacement of the dental drill with a laser, laser dental decay prevention, and laser decay detection. The essential question is whether a laser can provide equal or improved treatment over conventional care. Safe use of lasers also must be the underlying goal of proposed or future laser therapy. With the availability and future development of different laser wavelengths and methods of pulsing, much interest is developing in this growing field. This article reviews the role of lasers in dentistry since the early 1960s, summarizes some research reports from the last few years, and proposes what the authors feel the future may hold for lasers in dentistry.

Effects of Nd:YAG laser on wound healing processes: clinical and immunohistochemical findings in rat skin

BACKGROUND AND OBJECTIVE

The clinical effects of the Nd:YAG laser in the rat skin as well as alterations of the extracellular matrix during healing were presented in this study.

STUDY DESIGN/MATERIAL AND METHODS

This study evaluated the clinical effects of the Nd:YAG laser used with different energy parameters (low energy: 1.75 W and 20 pps/high energy: 3.0 W and 30 pps) in a duration 20-40 s in rat skin. Control incisions were performed with a scalpel blade. Rat skin incisions were examined over a period of 28 days by clinical photographs as well as by using immunohistochemical techniques in order to find the distribution and the amount of the extracellular matrix fibrillar components, i.e., collagen types I and III.

RESULTS

Low energy laser treatment caused a rapid wound healing without scar tissue formation (compared to the high energy laser group) and clinical signs of scar tissue formation (compared to control incisions with the conventional scalpel). During the study period, the laser-induced lesions healed through reparative synthesis of the matrix proteins, which led to filling of the tissue defects. The regenerative processes were similar in the low-energy laser group and in the control incisions. In the high-energy lased tissues, we observed a delayed replacement of the defects by newly formed extracellular matrix proteins.

CONCLUSIONS

This study showed a slower wound healing in the high-energy lased tissues. A similar healing in the low-energy lased tissues and in the incisions with the conventional scalpel was observed. The differences in the distribution of matrix proteins during healing and the coagulation of the tissues, which were exposed to low-energy laser treatment, might be the explanation for the minimal scarring, contraction, and pigmentation of the lased tissues as compared to conventional incisions.

Healing of incisions in the tongue: a comparison of results with milliwatt carbon dioxide laser tissue welding versus suture repair

The healing of carbon dioxide laser weld closures produced by two commercial instruments of differing design were compared. Healing after laser welding was also compared to healing following conventional suture closure. Healing was evaluated histologically and by measurement of tensile strength over time. No histologic differences were found between closures produced by different lasers; however, in all cases suture closure resulted in slower healing times consistent with a foreign body reaction prolonging the healing process. Tensile strength measurements were performed at intervals over the first 21 days after the operation. Laser repair was found to be equivalent to or stronger than suture repair at every interval measured. The clinical use of the carbon dioxide laser for tissue welding of oral injuries should be investigated further, since it appears to be a good alternative to suture repair.

Healing of rat mouth mucosa after irradiation with CO2, Nd:YAG, and CO2-Nd:YAG combination lasers

The healing process of wounds made by a combination laser was studied in 90 rats. The laser system enabled both separate and combined use of CO2 and Nd:YAG laser irradiations. The laser wounds and the control excision wounds made by alligator forceps appeared on both sides of the tongue. Specimens from the wound sites were taken immediately, 6 h, and 1, 2, 4, 7, 11, 21, 28, and 42 days after surgery. The wound-healing process was studied by macroscopic evaluation before preparing the specimens for light microscopy. Some differences were noted in the wound-healing process among the three groups into which the experimental animals were divided. Tissue coagulation damage was most extensive in the Nd:YAG laser sites, where it was observed in its full extent 4 days after surgery. Epithelial cells were seen to begin to proliferate in all the wounds 6 h after surgery. Re-epithelialization was completed by between 7 (CO2) and 21 days (Nd:YAG) at all the wound sites. The inflammatory cell infiltration was more prominent in the Nd:YAG and the CO2-Nd:YAG combination laser wounds than in the CO2 and excision wounds during healing. Tissue regeneration occurred faster with less contraction in the combination CO2-Nd:YAG wounds than in Nd:YAG wounds. The best macroscopic healing result was seen in the CO2 wound sites. The combination laser was effective both at cutting and at coagulating tissue. Combining the CO2 and Nd:YAG laser irradiation into one beam resulted in a greater incision depth than what could have been expected from using the two lasers separately.

Profile of hyaluronidase activity distinguishes carbon dioxide laser from scalpel wound healing

Hyaluronic acid plays a key role in the process of wound repair. Deposition of this glycosaminoglycan polymer is in turn controlled by levels of the enzyme hyaluronidase. Hyaluronidase activity was examined in a rat incisional skin wound model comparing laser and scalpel wounds. A polyacrylamide gel electrophoresis (PAGE) hyaluronic acid substrate assay was used to detect differences in the rates of appearance, and level, of hyaluronidase activity in wound homogenates. The hyaluronidase activity in laser wounds appeared earlier, had a bimodal distribution, and increased to a higher level than that in scalpel wounds. The origin of hyaluronidase is not clear, but control of its appearance and modulation of its activity may be a more complex process than previously assumed.

Distribution of tenascin in healing incision, excision and laser wounds

The distribution of the extracellular matrix glycoprotein, tenascin, was studied in normal mucosa and during healing of scalpel incised or excised and CO2 laser-wounded rat tongue dorsal mucosa in 51 male Sprague-Dawley rats over a period of 21 days. A polyclonal antibody specific for tenascin was applied in indirect immunofluorescence microscopy. In normal mucosa tenascin was sparsely distributed in a discontinuous manner at the tips of the connective tissue papillae in association with the basement membrane (BM) and in the walls of the capillaries. In all the healing wounds there was a marked increase in the distribution of tenascin, particularly close to the BMs at the wound edges beneath the proliferating and migrating epithelium, and later on during healing in the regenerating connective tissue (CT) area. This expression subsided later on during healing. Laser surgery did not alter the ability of fibroblasts to synthesize tenascin. The transient expression of tenascin in the BMs and CT of the healing wounds suggests that this protein could play an important role in providing ideal conditions for cell movement, and in the deposition and organization of other extracellular matrix (ECM) glycoproteins during tissue repair.

Minimizing risk of infection using a carbon dioxide laser

The carbon dioxide laser is a surgical device increasingly important to dentistry. The advantages of laser use in the treatment of oral disease have been well documented. Such benefits include bloodless incisions, accurate tissue destruction, reduced pain, minimal swelling, excellent hemostasis, and limited postoperative tissue morbidity. Little information exists currently regarding laser use in the management of medically complex patients, most notably patients with infectious diseases. This article reports the use of the carbon dioxide laser for reducing the risks of disease transmission in the surgical management of an human immunodeficiency virus (HIV) seropositive patient.

Fibronectins in healing incision, excision and laser wounds

The distribution of extracellular matrix (ECM) glycoproteins, fibronectins (FNs), was studied in healing scalpel incision, excision and laser wounds of rat tongue dorsal mucosa over a healing period of 42 days by indirect immunofluorescence microscopy using mono- and polyclonal antibodies. A monoclonal antibody (Mab) DH1 was used to detect extradomain-A containing cellular fibronectin (ED-AcFN), and a polyclonal antiserum was utilized to recognize all forms of FNs. In normal tissue ED-AcFN was confined only to the endothelia of larger blood vessels whereas in healing wounds abundant immunoreactive deposits were found in regenerating connective tissue and endothelia of capillaries. The increased content of FNs revealed with both antibodies subsided later on during healing. The results suggest that the locally produced ED-AcFN is essential for tissue regeneration and plays a distinct functional role during wound healing. Laser treatment did not affect the ability of wound fibroblasts to synthesize and deposit cFN. The results provide further evidence that certain embryonic characteristics are seen in regenerating tissue.

Oral focal epithelial hyperplasia removed with CO2 laser

A case of oral focal epithelial hyperplasia (FEH) treated with CO2 laser surgery is presented. Histological diagnosis is discussed. The association of human papillomavirus (HPV) type 32 with the lesions is demonstrated with DNA in situ hybridization technique. Laser surgery is suggested as a treatment of choice.

The effect of carbon dioxide laser on wound contraction and epithelial regeneration in rabbits

This study was undertaken to compare objectively healing rates (in rabbits) of wounds caused by CO2 laser with those caused by scalpel. The rates of contraction and epithelialisation of standard wounds were determined with daily measurement of wound area from the time of wounding until the wound had healed. Our results demonstrate significant delays in both wound contraction (p = 0.0001) and epithelialisation (p = 0.0001) for CO2 laser-created wounds when compared to those seen in scalpel-created wounds. Normal epithelial regenerative capacities were demonstrated in the laser group despite the slow onset of epithelial migration. The appearance of the healed areas appeared comparable for both modalities.

Myofibroblasts in healing laser wounds of rat tongue mucosa

The distribution of myofibroblasts was studied in healing laser incisions compared with scalpel-incision and excision wounds in dorsal tongue mucosa and excision wounds in back skin. Myofibroblasts (m-f-b) were visualized by staining with NBD-phallacidin, a fluorescent probe specific for F-actin, and by electron microscopy. Few, randomly-orientated m-f-b were found in laser wounds over 28 days. Neither m-f-b nor contraction were seen in the scalpel-incisions. No contraction was observed in the laser wounds whereas an organized network of m-f-b with substantial contraction occurred in excision wounds. It is suggested that lack of contraction in laser wounds is partially due to the fewness of m-f-b. The residual connective tissue matrix resisting the laser treatment also seems to play a role in preventing the wound contraction.