Lasers in Medical Science

In otorhinolaryngology, dermatology and reconstructive surgery biomaterials as implants and a variety of lasers are used. Laser light applied near to an implant could have the risk to damage these materials. Therefore, their resistance exposed to laser light is of interest. A diode laser emitting at 940 nm and a CO2 laser were used to investigate its effects to the biomaterials Bioverit®, Medpor® and Palacos®, and in addition, an excised implant containing Medpor® and nasal turbinate tissue, excised and fixed in formalin. The macro- and microscopic changes of the material, temperature development during laser energy application in dependency to distance of fibre and material, time of exposure and applied power were investigated. Interaction of diode laser light with Bioverit® (0 mm distance, 360 s, 10 W, 3,600 J) resulted in minimal microscopic effects in direct contact of with the fibre. Using Medpor® (1 mm, 10s, 10 W, 100 J) resulted in melting and perforation. In the case of Palacos® (0.6 mm, 10s, 10 W, 100 J), melting occurred creating a flat excavation. The effect to Medpor® in nasal turbinate (1–2 mm, 10s, 10 W, 100 J) showed tissue denaturation and carbonisation and creation of a hole. The interaction of the CO2 laser with Bioverit® (3 cm, 0.5, 1 and 5 s, 2, 10 or 20 W) induced melting and discolouring resulting finally in a perforating hole. Depending on the material, first damage starts 10 s after an impact of 100 J (threshold value). So interaction between laser energy and biomaterials occurs. This should be carefully considered during clinical laser treatments especially nearby implants.

This study aimed to histologically and radiographically evaluate the effectiveness of low-intensity laser irradiation of different wavelengths (660 or 808 nm) as an adjunct to scaling and root planing in the treatment of experimental periodontitis in rats. Periodontitis was induced by placing a ligature around the mandibular first molar of the rats. In total, 40 Wistar rats were randomly divided into five groups (n = 8 each): control (CG), periodontal disease (PD), scaling and root planing (SRP), SRP + 660 nm laser (GL660) and SRP + 808 nm laser (GL808). Groups with laser use received radiation at 6 points in the first molar. The animals were euthanized at baseline and at 7 and 14 days after the interventions. Mandibles were surgically removed for histomorphometric and radiographic assessment of periodontal tissues. The GL660 group showed lesser bone loss than the PD group (P < 0.05) and greater alveolar bone margin after 14 days, indicating a better long-term treatment response (P < 0.05). These findings suggest that SRP with the 660 nm laser as an adjunct results in more favorable radiographic and histological responses than the 808 nm laser.

Six sensitizers [haematoporphyrin derivative (HPD), Photofrin II, themeta-, ortho- andpara- isomers of the tetra(hydroxyphenyl)porphyrins (m-, o-, andp-THPP) and the potassium salt ofp-THPP (K-p-THPP)] were compared in their ability to sensitize mouse skeletal muscle and tumours. Muscle damage was measured as percentage weight increase due to oedema 4h after illumination and as percentage cross-sectional area necrosis at 48h. These results were compared with those that had previously been obtained for depth of necrosis in subcutaneous tumours. All the photosensitizers damaged both tumours and skeletal muscle. Acost (muscle damage) vsbenefit (subcutaneous tumour necrosis) analysis of the results showed thatm-THPP was the most tumour selective sensitizer of those studied. In the long-term, muscle healed by regeneration and some fibrosis with full return of function.

To investigate the effect of pulsing on neodymium-YAG laser-induced hyperthermia we have exposed rat liver to low-power Nd-YAG laser light delivered via an interstitially inserted fibre. This was either continuous wave excitation or pulsed excitation at 10 or 40 Hz (pulse duration 100μs) with an average power of 1W and exposure durations of 400 s. No differences were seen with respect to overall diameter of the histological damage, diameter of the central cavitation, or intrahepatic temperatures, as measured by an embedded array of microthermocouples. We conclude that with 100-μs pulses, within the range of parameters studied, the pulsing rate does not influence the nature or the extent of damage seen after low-power interstitial Nd-YAG laser hyperthermia.

The authors report their experience with two recent improvements in the treatment of port-wine stains. Firstly, the frequency-doubled Nd-YAG laser producing a 532 nm wavelength. This wavelength corresponds to greater absorption by haemoglobin (15–20% more than with the argon laser beam) and so is more selectively absorbed by angiomatous tissue. This gives better clinical results and the classic side effects of the argon laser are eliminated (with the frequency-doubled Nd-YAG, there is no damage to hair or to healthy non-angiomatous skin). Treatment is thus made easier, as shownn in our series of 79 patients who received 92 treatment sessions over a period of 14 months. In addition, an automatic device makes it possible to use the beam on a continuous mode scanning contiguous sections (Multiscan). With this automatic apparatus, treatment becomes uniform because the variations inherent to the use of a hand piece are eliminated. Extensive port-wine stains can also be treated in a single session instead of the multiple sessions which were previously necessary. An interval of 5–6 months should elapse before treating the residual part of the portwine stain, situated deeper in the dermis, which should be considered as a new port-wine stain. The association of the 532 nm wavelength and the automatic, scanning device makes it possible to use fluences of only 8–15 J cm−2. This is explained by the dynamic nature of this treatment and distinguishes it from static treatments requiring higher fluences. Treatment of port-wine stains is thus improved for the ultimate benefit of the patients suffering from this disfigurement.

Functional chronic constipation (FCC) is a disorder caused by low fiber consumption, lack of fluid intake, lack of mobility, or side effects of medications. The objective of this study was to compare the effects of laser acupuncture and the commonly used osmotic laxative, lactulose (as the control), both combined with behavioral therapy and dietary modification, on children with FCC in a randomized controlled trial (RCT). Forty children were randomly chosen, aged 5–15 years with FCC, and randomized into two equal groups (gender ratio (50% male; 50% female), mean ± SD weight (24.2 ± 6.27 kg and 25.7 ± 7.47 kg for groups A and B, respectively)). Study group (group A): used laser acupuncture (650 nm), 30 mW, 0.15 cm2 spot size, 90 s per acupuncture point (ST25, ST36, ST37, BL25, and LI11). Control group (group B): lactulose syrup (1 to 3 mL/kg/day) orally, in divided doses 3 times weekly for 4 weeks, and behavioral training for both groups. Evaluations were conducted before and after the study to assess the efficacy of the therapy. Median value frequency significantly increased in groups A and B post-treatment (4 (6.75–3) and 3 (3.75–2), respectively) compared to pre-treatment (2 (2–1) and 2 (2–0.25), respectively) (p = 0.0001), in favor of group A (p = 0.01). Significant improvement of stool consistency according to Bristol stool scale (BSS) in groups A and B (p = 0.0001), (p = 0.002) respectively in favor of group A (p = 0.03). T-test, Fisher, and Wilcoxon signed rank tests were conducted to compare groups. Non-invasive, painless laser acupuncture therapy can be considered as an alternative therapy for patients with FCC.

The purpose was to investigate the effect of daylight-intensity blue light on F. solani isolated from the cornea of patients with fungal keratitis. Spore suspensions of 5 F. solani strains (one standard strain and 4 clinical corneal isolates) were prepared in 6-well plates. Blue light groups were irradiated by a light-emitting diode (LED) device with a peak wavelength of 454 nm at 0.5 mW/cm2 for 0 to 48 h, while the controls were maintained in darkness. Hyphal morphology in the 6-well plates was recorded at 0, 12, 24, 36, 48 h. One hundred microliters of spore suspensions of each strain at these five time points was transferred to SGA plates and cultured for 36 h at 29 °C; the number of colonies formed was counted as a measure of conidia quality and viability. Blue light has dual effects on F. solani. The hyphal length of F. solani exposed to blue light was significantly shorter than that of the control (P < 0.01), indicating that fungal growth was inhibited. Meanwhile, instead of reducing the viability of spores, blue light significantly enhanced the conidia quality and viability after at least 24 h irradiation. Daylight-intensity blue light exposure will inhibit the hyphal growth of F. solani but promote conidiation, which would be more harmful to fungal keratitis. Eliminating the influence of blue light for these patients should be taken into account.