Fluorescent probes for cancer detection

Histological evaluation of artifacts in tongue tissue produced by the CO2 laser and the electrotome

OBJECTIVE

The purpose of this study was to investigate the clinical usefulness of laser surgery in pathologic diagnosis following excisional biopsy of human oral mucosa by CO(2) laser and electrotome.

BACKGROUND DATA

When performing pathologic diagnosis and microscopic analysis of specimens excised by the CO(2) laser, there have been concerns about thermal denaturation of the excisional margin that may prevent diagnosis.

MATERIALS AND METHODS

Thirty tongue tissue samples from humans that were surgically resected using a CO(2) laser (continuous wave mode for 10 cases and pulse wave mode for 10 cases) and an electrotome (10 cases) were formalin-fixed and paraffin-embedded. These preserved specimens were then cut into thick sections and subjected to hematoxylin and eosin staining followed by microscopic assessment.

RESULTS

Despite the differences between the CO(2) laser and electrotome methods, similar thermal denaturation, such as carbonization, vacuolar degeneration, and elongation of nuclei, were observed at the excisional margins for both methods. Use of the CO(2) laser, particularly in pulse wave mode, reduced the amount of thermal denaturation significantly (p < 0.01) compared to the electrotome.

CONCLUSION

These results indicate that the CO(2) laser is better than the electrotome as a means of making excisions for performing pathologic diagnosis.

Evaluation of Patient Perceptions After Frenectomy Operations: A Comparison of Carbon Dioxide Laser and Scalpel Techniques

BACKGROUND

A frenum that encroaches on the margin of the gingiva may interfere with plaque removal and cause tension. Frenectomy is the complete removal of the frenum that can be made by scalpels or with soft tissue lasers. The aim of this article was to compare the degree of postoperative pain, such as discomfort and functional complications (eating and speech), experienced by patients after two frenectomy operation techniques.

METHODS

Forty patients requiring frenectomy were randomly assigned to have treatment either with a conventional technique or with a carbon dioxide (CO2) laser. The postoperative pain and functional complication ratings of each patient were recorded using a visual analog scale on days 1 and 7.

RESULTS

The results indicated patients treated with the CO2 laser had less postoperative pain and fewer functional complications (speaking and chewing) (P <0.0001 each) and required fewer analgesics (P <0.001) compared to patients treated with the conventional technique.

CONCLUSIONS

This clinical study indicates that CO2 laser treatment used for frenectomy operations provides better patient perception in terms of postoperative pain and function than that obtained by the scalpel technique. Considering the above advantages, when used correctly, the CO2 laser offers a safe, effective, acceptable, and impressive alternative for frenectomy operations.

Management of oral leukoplakia by laser surgery: relation between recurrence and malignant transformation and clinicopathological features

OBJECTIVE

The aim of the present study was to assess the clinical usefulness of laser surgery for oral leukoplakia.

BACKGROUND

Recurrence and/or malignanT transformation of oral leukoplakia have occasionally been observed following laser surgery. It is reported that the rate of recurrence was 7.7-38.1%, while malignant transformation was 2.6-9%.

MATERIALS AND METHODS

A total of 154 oral leukoplakias from 116 patients were treated in our department. Comparisons with the rate of recurrence, malignant transformation and clinical futures, epithelial dysplasia, location, and treatment procedure were examined. To evaluate recurrence and malignant transformation, the cases were restricted to those with a minimum follow-up of 6 months.

RESULTS

A total of 97 lesions fulfilled this criterion. The rate of recurrence had no association with the location or the epithelial dysplasia, although it differed with the treatment procedure. The rate of recurrence in laser surgery was approximately 29%. Malignant transformation was observed in four of 97 lesions. They were observed in 13.6% of tongue cases and 1.8% of gingival cases. Three of four lesions were treated with excision surgery, and the remaining one treated with laser vaporization. Only 1.2% malignant transformation in laser surgery was revealed.

CONCLUSION

Laser excision is suitable for leukoplakia cases on non-keratinized epithelia (i.e., the tongue and buccal mucosa), while laser vaporization is suitable for the gingival cases. Management of oral leukoplakia prevents not only recurrence and malignant transformation, but also postoperative dysfunction. We believe that laser surgery is an excellent procedure.

Determination of energy density threshold for laser ablation of bacteria. An in vitro study

The Nd:YAG and CO2 lasers have been shown to be bactericidal at relative low energy densities. However, at energy densities exceeding 120 J/cm2 (CO2) and 200 J/cm2 (Nd:YAG), laser irradiation also causes irreparable root surface damage. The purpose of this study was to determine, in vitro, the energy density threshold at which microbial ablation could be achieved while inflicting the least amount of damage to the root surfaces of human teeth. Pairs of Escherichia coli colonies cultured on broth agar were treated with a CO2 laser using a pulsed waveform at approximate energy densities ranging from 3 to 110 J/cm2. One of each colony-pair was then examined by scanning electron microscopy (SEM) and the other subcultured for viable microbes. Roots of extracted teeth were lightly scaled and treated by CO2 laser, again with pulsed beam using approximate energy densities of 3 to 110 J/cm2: and examined by SEM. Regardless of the level of energy density, residual bacteria could be subcultured from all laser treated microbial colonies. The inability of the laser to completely obliterate microbial colonies was likely due to: depth of energy penetration, difficulty in precisely overlapping beam focal spots, irregular beam profile, and presence of microbes at the periphery of the beam focal spot. The threshold energy density for bacterial obliteration was determined to be 11 J/cm2 and that for root damage was 41 J/cm2. Root damage was evident by charring, crater formation, melt-down and resolidification surface mineral, and increasing surface porosity. The results of this in vitro study indicate that when used at an energy density between 11 and 41 J/cm2 the CO2 laser may destroy microbial colonies without inflicting undue damage to the tooth root surface.