Laser-tissue interactions

The aims of this paper are to briefly describe laser physics, the types of lasers currently available for use on soft tissues focusing primarily on CO2 and Nd:YAG laser energies, the histological effects of lasers on oral tissues, laser safety, the clinical applications of lasers on oral soft tissues, and future directions. Of the two types of lasers currently available for dental applications, both the CO2 and Nd:YAG lasers can be used for frenectomies, ablation of lesions, incisional and excisional biopsies, gingivectomies, gingivoplasties, soft tissue tuberosity reductions, operculum removal, coagulation of graft donor sites, and certain crown lengthening procedures. The advantages of lasers include a relatively bloodless surgical and post-surgical course, minimal swelling and scarring, coagulation, vaporization, and cutting, minimal or no suturing, reduction in surgical time, and, in a majority of cases, much less or no post-surgical pain. CO2 lasers, compared to Nd:YAG are faster for most procedures, with less depth of tissue penetration and a well-documented history. There have been recent reports on the use of the Nd:YAG laser for periodontal scaling, gingival curettage, and root desensitization, but further research needs to be conducted. Both the CO2 and the Nd:YAG laser have limited use in conventional flap therapy.

Current Status of Lasers in Soft Tissue Dental Surgery

Phonomicrosurgical treatment of premalignant vocal fold epithelium and microinvasive cancer combines principles of surgical oncology with advanced laryngoscopic microsurgical-techniques. This treatment is guided by mucosal-wave theory of voice production and strives not only to cure the disease but also to achieve optimal vocal function. Surgical techniques developed during the past two centuries have improved methods for vocal fold visualization, tissue retrieval, and tissue evaluation. Examination of the evolution of these surgical techniques reveals the incomplete convergence of laryngoscopic surgical theory with both the concept of premalignancy and the anatomical-physiological principles of voice production. This historical review, which helps to explain the lack of consensus about current treatment options, led to a series of four investigations. They were conducted with the aim of developing a laryngoscopic (phonomicrosurgical) management approach for improving the treatment of premalignant and microinvasive vocal fold epithelium. In the first of four investigations, 42 patients (each of whom had a significant smoking history) underwent microlaryngoscopic biopsy of 52 vocal fold lesions. These lesions, which were suspicious for atypia or malignancy and were confined to the musculomembranous vocal fold, were mapped according to surface involvement and depth of penetration. Review of the maps revealed that 27 of the 52 lesions involved only the superior/ventricular surface. For these patients, the entire layered vocal fold structure could potentially be preserved on the medial/vocalizing surface. Twenty-five of the 52 lesions involved both the superior/ventricular surface and the medial/vocalizing surface. No lesion involved only the medial surface. These data suggest that (in smokers) geographic localization of keratotic and erythroplastic lesions on the superior/ventricular surface of the musculomembranous vocal fold are likely to contain atypia. This characteristic facilitates the appropriate selection of patients for biopsy and may spare individuals, who have lesions resulting from hyperfunctional dysphonia and/or gastroesophageal reflux, from unnecessary biopsy. These two disorders typically result in pathology on the medial and/or posterior glottal surfaces. In order to determine whether a directed biopsy or an excisional biopsy approach is preferable for obtaining an accurate diagnosis, all specimens underwent whole-mount sectioning for three-dimensional histopathological analysis. Keratosis was noted: without atypia in 14; with atypia in 27; and with carcinoma in 11. The severity of the atypia usually varied throughout each specimen. The surface appearance of the lesion was not a reliable prognosticator of the severity of dysplasia either between patients or in different areas of the same lesion; therefore, excisional biopsy and whole-mount, multiple-section histopathological analysis were necessary for obtaining an accurate diagnosis.(ABSTRACT TRUNCATED AT 400 WORDS)

Premalignant epithelium and microinvasive cancer of the vocal fold: The evolution of phonomicrosurgical management

Since the introduction of the CO2 laser coupled to the Zeiss operating microscope in 1969, it has become apparent that this instrument is without equal for the carefully controlled removal of small laryngeal lesions. It has now also been shown experimentally and with some clinical confirmation that by using the CO2 laser transorally all of the standard types of partial and excisional laryngeal surgery may be accomplished with minimal morbidity and without the use of tracheotomy. The major exception is that replacement of soft tissue is not possible. Therefore, procedures that remove sufficient amounts of soft tissue to compromise the sphincter function of the larynx should not be done transorally with the CO2 laser.

Transoral laryngeal surgery using the CO2 laser: laboratory experiments and clinical experience.

Summary The conventional management of certain problems in the aerodigestive tract has been either inconvenient or ineffective. Seventy-five cases have been treated with the continuous wave CO 2 laser in an attempt to identify the advantages and limitations of laser surgery. It has been found that the CO 2 laser provides a practical method of tissue ablation or excision which can be carried out with excellent control. The laser beam is directed with a handpiece in the oral cavity, with the surgical microscopic laser attachment in the nose, pharynx, and larynx, and with the endoscope-bronchoscope assembly in the tracheobronchial tree. Laser surgery appears to be most valuable when precise surgery is needed to preserve function.

Laser surgery in the aerodigestive tract

In experiments on dogs, a focused beam from a continuous wave surgical carbon dioxide laser integrated with an operating microscope was used selectively to evaporate predetermined amounts of normal vocal cord tissue through a laryngoscope. This mode of tissue removal was precise, rapid and practically bloodless. Microscopic laryngoscopy examinations and histological work-up one, two and three weeks postoperatively indicated normal healing similar to that of clean surgical wounds.

Geza J. Jako

Papers

Laser surgery of the vocal cords. An experimental study with carbon dioxide lasers on dogs.

The posterior bony ear canal wall and the antrum threshold angle in conservative middle ear surgery

Postaural versus endaural exposure in tympanoplasty.