Objectives. It was the aim of this study to determine thermal and histologic events resulting from soft tissue incision with three C02 lasers: one emitting light energy via a hollow waveguide at 9.3 #m; the others emitting light energy at 10.6/~m, one via a hollow waveguide, the other through an articulated arm delivery system. Study design. Thirty standardized incisions were made in the oral mucosa of pig's mandibles with three different lasers at actual power levels of 1,4, and 12 W. Thermal events were recorded with thermocouples, and a histologic examination was performed to determine vertical and horizontal tissue damage as well as incision depth and width.Results. Thermal and histologic results were related to parameters andbeam characteristics rather than wavelength. Conclusion. In addition to wavelength, many variables can contribute to the surgical characteristics of a laser.(ORAL SURG ORAL MED ORAL PATHOL ORAL RADIOL IENDOD 1995;79:685-91)
Dentin was visualized using a new fluorescence technique and confocal laser scanning microscopy. Thirty extracted human teeth showing no clinical signs of caries were investigated. All teeth were horizontally sectioned to approximately 200 m thickness and sections were subjected to different pretreatment conditions as follows: vacuum only, ultrasonication only, sodium hypochlorite only, sodium hypochlorite and vacuum, sodium hypochlorite and ultrasonication, and a combination of sodium hypochlorite, vacuum, and ultrasonication. Some samples were left untreated to serve as control. Following pretreatment, rhodamine 123 fluorescent dye was used for staining at concentrations ranging from 10 Ϫ3 to 10 Ϫ7 M for 1 to 24 h at pH 6.0, 6.5, or 7.4. Optical staining occurred at pH 7.4 and concentrations у 10 Ϫ5 M over 3 h or longer. Surface images obtained using confocal laser scanning microscopy were similar to those observed by scanning electron microscopy without the need for sample-altering conventional scanning electron microscope preparation techniques. Subsurface imaging to a depth of approximately 60 m was achieved using confocal laser microscope techniques. This fluorescence technique offers a useful new alternative for visualization and quantification of dentin.
We have proposed and experimentally demonstrated a new configuration of laser Doppler flowmetry for dental pulpal blood flow measurements. To date, the vitality ofa tooth can be determined only by subjective thermal or electric tests, which are of questionable reliability and may induce pain in patient. Non-invasive techniques for determining pulpal vascular reactions to injury, treatment, and medication are in great demand. The laser Doppler flowmetry technique is non-invasive; however, clinical studies have shown that when used to measure pulpal blood flow the conventional back-scattering Doppler method suffers from low signal-to-noise ratio (SNR) and unreliable flux readings rendering it impossible to calibrate. A simplified theoretical model indicates that by using a forward scattered geometry the detected signal has a much higher SNR and can be calibrated. The forward scattered signal is readily detectable due to the fact that teeth are relatively thin organs with moderate optical loss. A preliminary experiment comparing forward scattered detection with conventional back-scattered detection was carried out using an extracted human molar. The results validated the findings of the simple theoretical model and clearly showed the utility of the forward scattering geometry. The back-scattering method had readings that fluctuated by as much as 187% in response to small changes in sensor position relative to the tooth. The forward scattered method had consistent readings (within 10%) that were independent ofthe sensor position, a signal-to-noise ratio that was at least 5.6 times higher than the back-scattering method, and a linear response to flow rate.
Plaque, calculus and altered cementum removal by scaling and root planing is a fundamental procedure in periodontal treatment. However, the residual smear layer contains cytotoxic and inflammatory mediators which adversely affect healing. Chemical smear layer removal is also problematic.In previous investigations effective smear layer removal was achieved using long pulsed irradiation at 1.06u. However, laser irradiation was not adequate as an alternative to scaling and root planing procedures and concurrent temperature rises exceeded thermal thresholds for pulpal and periodontal safety. It was the aim of this study to determine whether nanosecond pulsed irradiation at l.06u could he used as an alternative or an adjunct to scaling and root planing. 60 freshly extracted teeth were divided as follows: 5 control, 5 root planed only, 25 irradiated only, 25 root planed and irradiated. Irradiation was performed at fluences of ().5-2.7J/cm2, total energy densities of 12-30() J/cm2, frequencies of 2-l() Hz using the Medlite (Continuum) laser. Irradiation-induced thermal events were recorded using a thermocouple within the root canal and a thermal camera to monitor surface temperatures. SEM demonstrated effective smear layer removal with minimal microstructural effects. Surface temperatures increased minimally (<3C) at all parameters, intrapulpal temperature rises remained below 4 C at 2 and 5 Hz, F
The objective of this study was to evaluate CO2 laser surgical treatment of pulpal exposures in canine patients. 17 permanent teeth with exposures of 48h were randomly allocated to receive either (a) localized laser pulp surgery to remove all compromised soft tissues or (b) localized pulp surgery using a large round sterile bur under sterile saline irrigation. Single laser pulses were used at O.Ols pulse duration, l.Os pulse interval, a spot size of 0.004cm2 and an energy density of 276J/cm2 . Exposures were dressed with CaOH and Glass ionomer. Clinical and radiographic evaluations were performed by one blinded clinician 4, 12, 24 and 52 weeks after treatment using standard scales of O-(-1).15/17 laser-treated teeth assessed over 1 year post-treatment remained clinically and radiographically healthy.
These investigations were performed to determine thermal, histological and incisional effects in soft tissue of laser irradiation at 9.3um. Specifically, the consequences of varying pulse duration, interval and frequency, peak and average powers and energy densities were studied.In fresh pig's jaws, 6 standardised incisions, 3cm in length, were made per parameter using a template and motorised jig. Incisions were made at various standardised anatomical sites, and surface thennal events monitored using an IR camera. Laser parameters investigated: power: 1-11W, duty cycle: 10-90%, Pulse duration: 1-200ms, at gated continuous wave (Cw). Superpulse and OptiPuls& modes with 300us pulses were also investigated. Incision width and depth as well as collateral tissue effects were assessed statistically. They were directly related to the parameters used. Ease of incision and effects on underlying bone were also parameter-related. INTRODUCTIONOver the past 25 years, areas of routine CO' laser use in oro-facial surgery have progressed to include frenectomies, periodontal surgery, tumor resections and excision of lesions such as hyperplasias, papillomas, hemangiomas, lymphangiomas and mucoceles. Clinical and laboratory investigations have consistently confirmed the advantages of this tool: precision, minimal iniraoperative hemorrhage, sterilization of the surgical area and healing with minimal scarring, postoperative pain and swelling (1-5).The C02 laser emits light energy which is strongly absorbed by water, and therefore also by tissues with a high water content, such as the oral soft tissues. The absorbed energy causes vaporization of the intra-and exiracellular fluid and destruction of the cell membranes at the focal point (6,7), producing zones of incision or ablation. The energy applied to the target tissues will also affect, to a varying degree, adjacent or underlying tissue structures. The extent of collateral damage is related to the absorption characteristics of light in the tissues, and the laser parameters used. At a given wavelength, longer pulse durations will tend to result in higher levels of coagulation and necrosis in collateral structures, as they allow thermal energy to accumulate and penetrate to a greater extent than short, transient pulses. For clinical applications, the zone of thennal damage to adjacent structures should ideally be kept to a minimum, as it may impede wound healing, graft take, and reduce wound tensile strength, especially if it is extensive. Furthermore, laser-induced temperature increases can threaten the vitality of adjoining structures such as teeth, pulp or periodontium. Conversely, very short pulse durations may hinder haemostasis and reduce ease of incision or ablation; attempts at compensating for this phenomenon by increasing pulse frequency can result in an exacerbation of thermal effects.In the CO lasers traditionally available to clinical dentistry, light at lO.6u is delivered by means of an articulated arm or a hollow waveguide and a handpiece to the surgical site....
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