Basic physics of laser interaction with vital tissue.

It is essential for any practitioner who uses lasers in their clinical practice to understand the basic physics of lasers. It is this knowledge that allows for an educated assessment of the clinical outcomes that lasers produce in our patients. It is also this understanding that provides a scientific basis for the visual feedback the clinician uses to vary parameters as needed to get the desired clinical results. It is the intent of this paper to discuss the very basic reasons why lasers affect tissues the way they do, and to synthesize the plethora of information dental practitioners are seeing regularly in dental journals.

In vivo imaging of oral mucositis in an animal model using optical coherence tomography and optical Doppler tomography.

PURPOSE: To assess noninvasive optical coherence tomography (OCT) and optical Doppler tomography (ODT) for early detection and evaluation of chemotherapy-induced oral mucositis. EXPERIMENTAL DESIGN: Cheek pouches of 10 Syrian golden hamsters were imaged using OCT/ODT during development of chemotherapy-induced mucositis. I.p. injections of 5-fluorouracil and mechanical irritation induced oral lesions. At 2, 4, 7, and 11 days, one hamster was sacrificed and processed for histopathology. OCT images were visually examined; ODT results were semiquantified. Imaging data were compared with histologic findings. RESULTS: During the development of mucositis, OCT/ODT identified the following events: (a) change in epithelial thickness (beginning on day 2), (b) loss of surface keratinized layer continuity (beginning on day 4), (c) loss of epithelial (day 4 onwards) and submucosal integrity (day 7 onwards), (d) changes in axial blood flow velocity (increased on days 2 and 4; decreased on day 7), and (e) changes in blood vessel size (diameter doubled on day 2; quadrupled on day 4; unchanged on day 7). The semiquantitative imaging-based scoring system identified the severity of mucositis as defined by histopathology. The combination of imaging criteria used allowed for the detection of early, intermediate, and late mucositic changes. Imaging data gave higher scores compared with clinical scores early on, suggesting that the imaging-based diagnostic scoring was more sensitive to early mucositic change than the clinical scoring system. Once mucositis was established, imaging and clinical scores converged. CONCLUSION: OCT/ODT identified chemotherapy-induced oral changes before their clinical manifestation, and the proposed scoring system for oral mucositis was validated for the semiquantification of mucositic change.

Histologic analysis of the effect on dental pulp of a 9.6-microm CO(2) laser.

BACKGROUND AND OBJECTIVE: Both patients and dentists would like a replacement of the dental drill. During the last decade, lasers have been investigated as a possible replacement. For lasers to be accepted, studies must show that their effect on the dental pulpal tissues is equal to or less noxious than those effects caused by the dental handpiece (drill). STUDY DESIGN/MATERIALS AND METHODS: In this study, two laser systems were used; the first was a breadboard CO(2) laser and the second a prototype clinical CO(2) laser system both emitted 60-micros-long pulses of 9.6-microm radiation. On the delivery system of both lasers, a scanner moved the focussed beam in a circular pattern and a water spray system served to cool the ablation site. Both lasers were used to create holes of similar dimensions in canine teeth. The treated teeth were then restored and harvested at either 4 days or 4 weeks. The teeth were decalcified, sectioned, and stained for examination via light microscopy. RESULTS: The histologic examination revealed normal pulpal tissues in the canine teeth treated with both CO(2) lasers. Some histologic sections showed an increase in the predentin layer, 28 days after laser treatment. While many histologic sections showed normal pulpal architecture following handpiece treatment, some sections showed total disruption of the normal pulpal histology. CONCLUSIONS: Histologic evaluation revealed that the lasers produced no noticeable damage to the dental pulpal tissue and appear to be a safe method for removing dental hard tissues. From this study, it appears that 9.6 microm CO(2) laser does not cause damage to the dental pulpal tissues in dogs.