Dose-related tissue effects of the CO2 and noncontact Nd:YAG lasers in the canine glottis

Objectives: The CO₂ laser is the standard for control of recurrent respiratory papillomatosis because of its predictable action on laryngeal tissue. The noncontact neodymium:yttrium aluminum garnet (Nd:YAG) 1064-nm laser is generally not used in the larynx owing to the lack of data on its tissue effects, and its potential lack of safety in the larynx. Combined Nd:YAG and CO₂ laser treatments have been used safely in the tracheobronchial tree to eradicate recurrent respiratory papillomas. The objectives of this study were to describe and evaluate a method for applying the noncontact Nd:YAG laser to the larynx, to compare the tissue effects of the Nd:YAG, CO₂, and combined Nd:YAG and CO₂ lasers in the canine larynx, and to extrapolate canine tissue data to the human. Methods: The CO₂, Nd:YAG, and combined Nd:YAG/CO₂ lasers were applied to the glottis in four mongrel dogs. Laryngectomy was performed and the tissue was examined histologically. The nature and degree of tissue injury were analyzed relative to laser type and energy data. Results: In the canine larynx, the CO₂ laser vaporized the surface epithelium and caused varying degrees of edema and necrosis of the lamina propria. The Nd:YAG laser did not cause ulceration but did show a greater degree of thermal damage to the lamina propria. Combined Nd:YAG/CO₂ applications resulted in separation of the perimysial fibers from the muscle fibers of the vocalis muscle. Conclusion: These findings suggest that the noncontact Nd:YAG laser can be applied in a controlled fashion to the canine larynx at appropriate power densities. Anatomical differences between human and canine larynges are considered. Extrapolation to humans is proposed. Key Words: Laser, larynx, tissue effects, papillomatosis.     

A prospective randomised controlled trial of Nd:YAG laser photocoagulation versus liquid paraffin plus antiseptic cream in the treatment of recurrent epistaxis

Clin. Otolaryngol. 2012, 37 , 271–275 Objectives: To evaluate the efficacy of Nd:YAG laser photocoagulation with that of liquid paraffin plus antiseptic cream in the management of recurrent epistaxis. Design: Prospective clinical study. Eighty consecutive patients with histories of recurrent epistaxis were randomly assigned to receive treatment in an outpatient setting consisting of either a combination of liquid paraffin plus antiseptic cream (group 1) or Nd:YAG laser photocoagulation (group 2). Setting: University‐affiliated teaching hospital. Participants: Eighty consecutive patients who suffered from recurrent anterior epistaxis presented to the Otolaryngology Department at the Eye and ENT Hospital, Fudan University between February 2011 and June 2011. Main outcome measures: The following outcome measures were assessed: bleeding intensity, bleeding frequency 4 and 12 weeks after treatment (0 = no bleeding, 1 = reduced bleeding, 2 = the same, 3 = worse), participant’s perception of discomfort during the management (grade 0–10, where 10 is the worst pain) and complications. Results: At 12 weeks, 85% of laser patients versus 40% of control patients had no reported bleeding. The outcome score at 4 weeks after treatment showed no significant difference between the two groups (P = 0.130, P > 0.05); however, the outcome score at 12 weeks after treatment showed a significant difference between the two groups (P = 0.000, P < 0.01). The median and mean ± sd pain levels experienced were 5.0 and 5.2 ± 2.2. Both groups had no complications. Conclusions: It can be concluded that Nd:YAG laser photocoagulation is a preferable therapy in the treatment of recurrent epistaxis, especially in terms of long‐lasting efficacy. The level of pain associated with the procedure was tolerated. It is a simple, easy, safe and rapid therapy, which can be performed in an office setting.     

CO2激光与掺钕钇铝石榴石激光治疗声门型喉癌手术并发症的比较研究

目的 比较CO2和掺钕钇铝石榴石(Nd:YAG)两种激光治疗声门型喉癌的手术并发症的发生率,并探讨减少并发症的有效方法.方法 采用回顾性分析1999年1月1日至2008年12月31日在北京大学第一医院耳鼻咽喉头颈外科接受支撑喉镜下CO2和Nd:YAG激光治疗的83例患者的临床资料,比较两组并发症的发生率.CO2激光治疗组32例,其中原位癌2例,T1N0M021例,T2N0M0 8例,T3N0M0 1例,采用非接触式脉冲激光;Nd:YAG激光治疗组51例,原位癌3例,T1N0M0 36例,T1N2M0 3例,T2N0M0 9例,采用光纤接触式激光.结果 CO2激光并发症共4例(12.5%),其中喉软骨膜炎1例(3.1%),舌体麻木1例(3.1%),门齿松动1例(3.1%),皮下气肿1例(3.1%);Nd:YAG激光并发症27例(52.9%),其中术后出血2例(3.9%),呼吸困难5例(9.8%),喉软骨膜炎7例(13.7%),肺部感染4例(7.8%),舌体麻木2例(3.9%),咽颈瘘1例(2.0%),声带固定4例(7.8%),喉狭窄2例(3.9%).结论 Nd:YAG激光较CO2激光更易发生手术并发症,少数并发症需要紧急处理,通过适当预防措施可以减轻并发症,避免严重后果.     

Management of epistaxis in hereditary hemorrhagic telangiectasia by Nd:YAG laser and quality of life assessment using the HR-QoL questionnaire

The purpose of this study was to describe the results of Nd:YAG laser application in hereditary hemorrhagic telangiectasia (HHT) patients and to measure the Health-Related Quality of Life (HR-QoL) in patients with HHT before and after Nd:YAG laser application in a prospective, clinical trial at a university hospital. Twenty-seven consecutive patients with HHT and mild to moderate degrees of epistaxis were followed-up for 2 years after Nd:YAG laser treatments. Recurrence of epistaxis after Nd:YAG laser application and measurement of HR-QoL using the International Quality of Life Assessment questionnaire, version 1.1 (IQOLA 1.1), was found. Eight patients (30%) received only one Nd:YAG laser treatment, 15 (56%) had a recurrence and received a second treatment and 4 (14%) had two recurrences and received three Nd:YAG laser treatments. HR-QoL was improved 2 years after the first Nd:YAG laser application in both its Physical Health Dimension (47.5±2.9 vs. 38.1±2.3 before treatment, P <0.05) and Mental Health Dimension (45.1±2.7 vs. 39.6±2.4 before treatment, P <0.05). Although no curative treatment for HHT exists, Nd:YAG laser treatment seems to constitute a simple and efficient method of epistaxis control, resulting in a significant improvement in quality of life.     

Effects of the autonomic nervous system function on the course of postoperative period in surgical removal of vocal cords polyps with Nd:YAG-laser

The study of the effects of autonomic nervous system (ANS) function on the course of the postoperative period after removal of the vocal cord polyps with Nd:YAG laser has shown that laryngeal operations with utilization of Nd:YAG laser accelerate normalization of structural-functional condition of the vocal cords in patients with adequate autonomic support by 25-40 days compared to those with inadequate ANS function.     

Usefulness of ND:YAG laser in head and neck surgery

Nd:YAG laser is widely used in surgery as well as in otolaryngology and head and neck surgery for 25 years. This type of laser is characterized by low absorption in water and haemoglobin, deep penetration to the tissue and high ability for vessels coagulation. The laser light can be guided with glassfiber and can be focussed with handpices and micromanipulators. These characteristics make Nd:YAG laser very useful surgical instrument, especially in ORL and head and neck surgery. One institution's experiences, based on 300 operations with Nd:YAG laser are presented and discussed. Main indications to Nd:YAG laser operations in our material were: malignant neoplasms of oral cavity, pharynx and larynx, papillomas and haemangiomas of mucosa of upper respiratory tract, tracheal stenoses, scars of the larynx after partial laryngectomies and snoring and sleep apnoea syndrome. In our opinion, Nd:YAG laser has high usefulness in treatment of malignant and benign head and neck neoplasms, as well as in laryngeal scars and treatment of snoring. In cases of post intubation tracheal stenoses and in cases of post strumectomy bilateral paralysis of larynx the treatment results were not satisfactory. High usefulness of Nd:YAG laser results from very good coagulation ability and wide possibility of transmission of laser light with glassfiber.     

Wedge turbinectomy: a new combined photocoagulative Nd:YAG laser technique

OBJECTIVES: To demonstrate that Nd:YAG laser photocoagulation using a combination of interstitial and contact approaches in the surgical treatment of inferior turbinate hypertrophy yields improved results in terms of postoperative nasal patency, complications, and relapse. STUDY DESIGN: A group of 121 patients with symptoms of nasal obstruction due to hypertrophied inferior turbinates were treated between January 1994 and December 1997 at the Otolaryngology-Head and Neck Surgery Unit of the Main Military Hospital of Rome using the wedge turbinectomy, a new endonasal laser technique. METHODS: This is a combined photocoagulative procedure performed under local anesthesia. In the first surgical step we perform interstitial photocoagulation using Nd:YAG laser and in the second step we use a contact approach, making two strips of photocoagulated mucosa running side by side from the tail to the head of turbinate. RESULTS: At 1-year follow-up, the complication rate in all our patients treated with this laser technique was very low and we achieved a steady improvement in nasal patency in 104 patients (85.9%). The relapse rate was approximately 14%, but we observed that 65% of the patients who experienced long-term failure were affected by allergic rhinitis. CONCLUSIONS: An accurate preoperative evaluation of the cause of the turbinate hypertrophy is fundamental to achieving better results after laser turbinectomy and reducing the risk of relapse.     

Videoendolaryngeal surgery in primary local laryngeal amyloidosis with involvement of the upper third of the trachea: case report

Laryngeal amyloidosis is a rare pathology (0.5-1% of all benign laryngeal newgrowths). Five patients with local laryngeal and tracheal amyloidosis were successfully diagnosed and treated endoscopically in the endoscopic department of the P.A. Herzen Moscow Research Cancer Institute in 1987-2007. Videoendolaryngeal operations were performed with application of Nd:YAG laser, argon-plasma coagulation and their combination. The patients were followed up for 15 years maximum. Two most interesting cases of primary local laryngeal amyloidosis with involvement of the upper third of the trachea are presented. Foreign and domestic literature data on diagnosis and treatment of respiratory amyloidosis are reviewed.     

Ergebnisse einer In-vitro-Studie und erster klinischer Anwendung eines kombinierten Ho:YAG-/Nd:YAG-Lasers

BACKGROUND AND OBJECTIVE: A combined Ho:YAG/Nd:YAG laser produces light with properties similar to the beams of the mainly coagulating Nd:YAG laser and the cutting CO2 laser alone. PATIENTS/METHODS: The combined laser was tested in vitro on pig tissue. Additionally, we used this new combined tool for enoral operations. RESULTS: An effect of the pulsed Ho:YAG laser was explosive-like tissue disruption and sprinkling of fragments. Simultaneous use of the Nd:YAG laser resulted in an enlarged zone of coagulation. Clinically, the laser-assisted intervention was inferior to the classic operational methods. CONCLUSIONS: Comparing the established CO2 laser and the Ho:YAG laser, the latter showed only the advantage of delivery via a flexible fiber. Sprinkling of tissue fragments and wide incisions are oncologically problematic. We conclude that this new tool is of minor value for otorhinolaryngologists and head and neck surgeons.     

Nd:YAG laser treatment of the lower turbinates with contact in hyperreflexic and allergic rhinopathy]

BACKGROUND: Nasal obstruction caused by mucosal swelling due to hyperreflectory or allergic rhinitis is a very frequent disorder. We would like to report about our first results (ENT department, University of G?ttingen) in the reduction of hyperplastic inferior turbinates by Nd:YAG Laser treatment. PATIENTS AND METHOD: One hundred seventeen patients with nasal obstruction were treated by Nd:YAG laser between October 1993 and February 1997. We used the laser in "contact mode" and all outpatients were under local anaesthesia. Follow-up was possible in 83 cases. A subjective scale was used to evaluate our results. One quarter of the patients suffered from an allergic rhinitis. RESULTS: For 80% the nasal airflow was increased. Sixty percent had excellent or good results without any nasal obstruction after therapy. The patients with allergic rhinitis performed as well as the patients with hyperreflectory rhinopathy. This improvement appeared as early as four weeks after treatment and was permanent in 37 of 40 cases with long-term observation of at least one year. Side effects: 14% reported a dry nasal mucosa for two weeks; 31% had a bloody nasal secretion for two days after treatment, but did not bleed. Fifteen percent complained of pain during the procedure. CONCLUSION: The reduction of the inferior turbinates by Nd:YAG laser is an effective treatment of equal value in symptomatic therapy of the hyperplastic turbinates due to hyperreflectory and allergic rhinopathy. Seventy-three percent of these patients would like to be treated in this way again if necessary.     

Microinvasive Nd:YAG laser therapy of early glottic carcinoma and its effect on soluble interleukin-2 receptor, interleukin-2, and natural killer cells

OBJECTIVE: To investigate the effectiveness of microinvasive Nd:YAG laser therapy in human glottic Tis and T1 carcinomas, as well as its effect on the cellular immune function of the tumor-bearing hosts. STUDY DESIGN: We treated 34 patients with microinvasive Nd:YAG laser therapy and evaluated its effect on the cellular immune function of the host. METHODS: Thirty-four patients with glottic Tis or T1 squamous cell carcinoma were treated with fiberoptic laryngoscopic Nd:YAG laser surgery. Both before and after therapy, serum levels of soluble interleukin-2 receptor (SIL-2R) and interleukin-2 (IL-2), as well as natural killer (NK) cell activity, were determined by means of double-antibody sandwich technique, tritiated thymidine-deoxyribonucleoside incorporation, and iodine 125-uridine-deoxyribonucleoside release technique, respectively. RESULTS: All 34 patients tolerated the procedure well. A 3- to 7-year follow-up in a subgroup of 27 patients resulted in an estimated cure rate of 85.2% (23 of 27 patients). In all 27 patients with a regular follow-up, a subjective improvement of phonation was noted after therapy to various degrees. In 74% (20 of 27 patients), voice and speech subjectively recovered to almost normal levels. The post-therapy serum levels of SIL-2R were significantly declined (P <.001), whereas those of IL-2 and the NK activity were significantly elevated (P <.001) as compared with those detected before therapy. CONCLUSIONS: Therapy with fiberoptic laryngoscopic Nd:YAG laser surgery is simple, safe, effective and only minimally invasive for patients with glottic Tis or T1 carcinoma. At the same time, it has an immunoenhancing effect on its host.     

鼻咽癌局部复发或残留病灶的Nd：YAG激光手术挽救治疗

目的 探讨Nd:YAG激光手术挽救治疗鼻咽癌放射治疗后鼻咽局部复发或残留的可行性和临床疗效。方法在鼻内镜下经鼻腔Nd:YAG激光,对35例鼻咽癌经根治性放射治疗后鼻咽局部复发或残留病灶进行治疗。手术在局麻下进行,在鼻内镜直视下,激光功率调整在50W左右,YAG激光光纤经同侧或对侧鼻腔导入鼻咽部,气化切除肿瘤病灶。部分患者术后接受了再放射治疗,放射剂量20-60Gy不等。结果 手术均顺利完成。术后3年、5年生存率分别为51.4%、30.3%。结论 鼻内镜下Nd:YAG激光挽救手术是治疗鼻咽癌放射治疗后鼻咽局部复发或残留的有效手段,丰富了鼻咽癌放射治疗失败后的外科治疗手段。术后是否再需放射治疗,视具体情况决定。     

Prevention of pharyngocutaneous fistulas by means of laser-weld techniques

Although much has been written on methods of dealing with pharyngocutaneous fistulas once they have formed, there are few reports of methods of preventing fistula formation from occurring. We examined the use of laser-weld techniques with the neodymium:yttrium aluminum garnet (Nd:YAG) and diode lasers to seal pharyngotomy closures. Laser-weld techniques have been used successfully in many other tissues, but reports documenting use in the upper aerodigestive tract are minimal. Indocyanine-green dye-enhanced collagen and fibrinogen were studied as laser solder materials for the diode laser. Twenty-nine experimental animals were studied. Neither the Nd:YAG nor the diode laser was successful in preventing fistula formation. Tensiometric studies documented significant strength of the laser welds ex vivo, but this finding was not clinically significant.     

Laser and cisplatinum for treatment of human squamous cell carcinoma

Objective: Interstitial laser therapy (ILT) with the neodynuumiyttrium-aluminum-garnet (Nd:YAG) (1064 nm) laser via fiberoptics is becoming a more precise, minimally invasive alternative for thermoablation of unresectable or recurrent head and neck neoplasms, but recurrence is often seen at the margin. Combining intratumor chemotherapy with interstitial laser should be most effective using drugs activated by thermal energy. The objective of the current study was to test intratumor cisplatinum (cis-diaminedichloroplatinum [CDDP]) injections given in conjunction with laser therapy as an experimental approach for improved treatment of squamous cell carcinoma (SCC). Methods: Human SCC tumors were grown as subcutaneous transplants in nude mice and injected with CDDP (0.4 to 1.2 mg/g) in water or in collagen-based gel carrier with epinephrine (epi-gel) followed by ILT via 0.6-mm fiberoptics coupled to an Nd:YAG laser (1064 nm/180 J). Results: Tumors injected with CDDP epi-gel exhibited a partial response with two- to fourfold tumor delay compared with aqueous drug or untreated SCC transplants during 10 weeks' follow-up. Combined drug and laser therapy significantly (P < .01) decreased tumor volume, with recurrence in only 25% of animals tested compared with 78% tumor regrowth after ILT alone. Conclusion: These initial results suggest that laser chemotherapy may become an effective treatment for advanced head and neck cancer.     

Ultrasound-Guided Interstitial Nd: YAG Laser Treatment of Voluminous Hemangiomas and Vascular Malformations in 92 Patients

In many cases voluminous vascular anomalies of the head and neck region are still treated with conventional surgery, although neodymium:yttrium-aluminum-garnet (Nd:YAG) laser therapy offers a valuable treatment alternative. Ninety-two patients with voluminous hemangiomas and vascular malformations were treated with interstitial Nd:YAG laser therapy (power density, 1300 to 3300 W/cm²), partly complemented by a noncontact-mode Nd:YAG laser light application (energy density, 1000 to 2500 J/cm²). The vascular tumors had a diameter of more than 3 cm in at least two dimensions. Treatment was carried out under ultrasound and manual control. Nearly 60% of the patients (n = 55) showed a complete clinical regression. Thirty-three patients (35.8%) had a partial regression and were satisfied with the treatment outcome. Four patients were treated unsuccessfully with the laser, and three of them subsequently underwent conventional surgery. Only nine of the 92 patients (9.8%) showed cosmetic or functional impairments. The results of this first consecutive series study with a retrospective clinical evaluation of the interstitial Nd:YAG laser therapy of voluminous hemangiomas and vascular malformations in a large patient group demonstrate a high effectiveness of this novel therapy modality.     

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.     

Laser disruption of biofilm

Objectives/Hypothesis: To demonstrate the capability of a fiber‐based Q‐switched Nd:YAG laser (ARCLaser, Nuremberg, Germany and Valam, Orangeburg, NY) to disrupt biofilm. Study Design: Biofilms were grown in broth for 72 hours prior to the experiment. A clinical otorrhea isolate from Pseudomonas aeruginosa was used. Biofilms were placed in MatTek culture plates, on stainless steel screws, tympanostomy tubes, and polyethylene terephthalate (PET) sutures. Methods: Culture plates, stainless steel screws, tympanostomy tubes, and PET sutures were used for the laser disruption of biofilm experiments. Q‐switched Nd:YAG laser pulses were delivered on biofilms using shockwave probes originally designed for cataract surgery. The thin laser fiber tip was targeted against a titanium target, creating the production of plasma and resulting in a shockwave effect. Results: Biofilm areas were imaged before, during, and after laser application using a confocal microscope. The biofilm was imaged growing on the glass/plastic step of the plates, in the grooves of the threads of the screws, over the tympanostomy tube, and on the PET suture. During laser treatment, a time‐lapse function was used to capture the results. As a result of laser‐generated shockwaves, the biofilm was initially seen to oscillate and eventually break off with individual pulses. Large and small pieces of biofilm were totally and instantly removed from the surface to which they were attached in a matter of a few seconds. Conclusions: We were able to effectively disrupt Pseudomonas aeruginosa biofilms in vitro using a miniature Q‐switched Nd:YAG laser, thin fibers, and special probes that generated plasma formation and a resulting shockwave effect. This laser technology has the ability to generate a powerful stress wave sufficient to disrupt biofilm without any ill effect to the underlying host structure.     

Technique, utility, and safety of awake tracheoplasty using combined laser and balloon dilation

OBJECTIVES: Laryngotracheostenosis (LTS) is a condition in which the airway is narrowed between the vocal cords and the carina. We seek to examine whether flexible bronchoscopy with neodymium-doped yttrium aluminum garnet (Nd:YAG) laser incision and balloon dilation tracheoplasty is a practical choice in the management of patients with subglottic or tracheal stenosis. METHODS: A retrospective chart review was performed at a tertiary care hospital. All subjects with laryngotracheostenosis treated between January 1, 2000, and April 2005 who underwent endoscopic Nd:YAG laser incision and balloon dilation tracheoplasty performed using topical anesthesia and intravenous sedation were included. RESULTS: A total of 18 patients comprised the study and 36 procedures were performed without complication. Only one procedure was required by eight subjects, while five subjects required two procedures, three subjects had three procedures, one subject had four procedures, and one subject had five procedures until an adequate stable airway was obtained. The average follow-up was 22 months (range 3-55 months). The average body mass index (BMI) was 32.0 kg/m (range = 20.8-42.2 kg/m) and 11 of the 18 subjects (61.1%) were categorized as obese or morbidly obese by BMI criteria. CONCLUSION: Combined Nd:YAG laser incision and balloon dilation in an awake, spontaneously breathing patient is a safe and effective management tool in the treatment of laryngotracheostenosis. This technique may be particularly beneficial in patients who are at increased risk for general anesthesia such as those with morbid obesity or who have had a history of airway problems during anesthesia.     

Flexible Nd:YAG laser palliation of obstructive tracheal metastatic malignancies.

Flexible Nd:YAG endoscopic laser surgery may become an effective new modality for palliation in patients with obstructive endotracheal metastatic malignancies. We report the results of the treatment of two patients with severely obstructing intraluminal tracheal metastatic melanoma and medullary thyroid carcinoma, using the neodymium-YAG laser via the flexible fiberoptic bronchoscope. Both patients complained of significant dyspnea, orthopnea, cough, and hemoptysis and were not candidates for rigid bronchoscopy because of underlying medical contraindications and anatomical problems. Multiple treatment sessions were used with treatment intervals of 1 to 2 weeks. All treatments were performed in the operating room under sedation, without intubation, with topical lidocaine and standard superior laryngeal nerve block. Successful relief of airway obstruction with complete regression of the endotracheal masses was achieved and no recurrences were seen after 9 months' follow-up. Flexible Nd:YAG laser bronchoscopy offered an alternative for the relief of obstructing endotracheal or bronchial malignancies in patients in whom the rigid bronchoscope could not be passed. it seemed to prolong survival in selected cases, and provided definite improvement in quality of life.     

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.